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Changes in Involved and Uninvolved Limb Function During Rehabilitation After Anterior Cruciate Ligament Reconstruction: Implications for Limb Symmetry Index Measures Eric Rohman, J. Tyler Steubs and Marc Tompkins Am J Sports Med published online March 31, 2015 DOI: 10.1177/0363546515576127 The online version of this article can be found at: http://ajs.sagepub.com/content/early/2015/03/31/0363546515576127
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Changes in Involved and Uninvolved Limb Function During Rehabilitation After Anterior Cruciate Ligament Reconstruction Implications for Limb Symmetry Index Measures Eric Rohman,* MD, J. Tyler Steubs,* MD, and Marc Tompkins,*yz MD Investigation performed at TRIA Orthopaedic Center, Bloomington, Minnesota, USA Background: Functional testing is used to assess anterior cruciate ligament (ACL) reconstruction rehabilitation, with the goal of symmetric ability. The pattern of change in the uninvolved limb’s function during rehabilitation is not established. Hypotheses: (1) Involved and uninvolved limb ability increases during rehabilitation, but the uninvolved limb ability increases to a lesser degree. (2) Hop tests will show larger initial asymmetry and will improve the most with rehabilitation. Study Design: Cohort study; Level of evidence, 3. Methods: This was a retrospective case series of 122 patients who underwent ACL reconstruction at our ambulatory surgery center and received multiple postoperative Standard Functional Tests (SFTs) between October 2009 and October 2013. Ten of the 12 individual tests within the SFT battery were analyzed. The patients’ earliest and latest SFTs were compared for changes in Limb Symmetry Index (LSI) and absolute function in each limb. We also analyzed the subgroup with SFTs (n = 38) at both 4 and 6 months postoperatively. Results: In all patients with multiple SFTs, involved limb performance increased in all tests except eyes-closed stork. Uninvolved limb performance increased in 4 SFT component tests and decreased in none. LSI significantly improved in 6 tests, all of which also showed involved limb improvement that was significant. Of these 6 tests, 5 showed initial LSI below 90%: single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop. Retro step-up and single-leg hop showed LSI improvements greater than 10 percentage points. In patients with 4- and 6-month data, involved limb performance increased in all tests except single-leg triple hop. Uninvolved limb performance increased in 5 SFT component tests and decreased in none. LSI significantly improved in 4 tests, all of which had initial LSI below 90%, and showed involved limb improvement that was significant. Retro step-up, single-leg hop, and crossover triple hop showed LSI improvements greater than 10 percentage points. Conclusion: During ACL reconstruction rehabilitation, LSI improvements indicated absolute increases in involved limb ability and were not attributable to uninvolved limb deterioration. The single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop are suggested as highly useful tests, since all showed initial LSI below 90%, with significant LSI improvement after rehabilitation. Keywords: ACL physical therapy/rehabilitation; functional test; limb symmetry index; ACL reconstruction
Anterior cruciate ligament tears are a common injury in active individuals. Return to play is a primary goal of
surgical intervention, yet the criteria for athletic clearance have been inconsistent historically and may not accurately predict readiness to perform.7,12,22,32,36,37 Standard Functional Tests (SFTs) have been developed as a more accurate measure of patient ability and readiness to return to play.18,31,36 Multiple tests exist in this category, all of which combine complex kinetic chain motions to better simulate sport-related demands and evaluate neuromuscular control. The single-leg hop test has been evaluated extensively and is capable of detecting functional limitations up to 54 weeks postoperatively, with good test-retest reliability.14,19,22,28,29 Other investigators have recommended a 4-test battery consisting of a singleleg hop, a crossover triple hop, a single-leg triple hop,
z Address correspondence to Marc Tompkins, MD, Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue S, Suite R200, Minneapolis, MN 55454, USA (e-mail: tompkinsm@hotmail .com). *Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA. y TRIA Orthopaedic Center, Bloomington, Minnesota, USA. The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.
The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546515576127 Ó 2015 The Author(s)
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and a timed hop. This test battery has shown predictive value for a patient’s subjective ability for up to 2 years postoperatively, as measured by the International Knee Documentation Committee (IKDC) form.3,9,12,30 Strength testing also has a role in rehabilitation assessment, as well as other functional tests such as single-leg squat and retro step-up. No universally accepted protocol of functional testing exists, and multiple groups have developed unique functional test batteries for assessment. During rehabilitation, the injured limb’s SFT performance is typically compared with that of the uninjured limb as a reference, yielding a measure known as the Limb Symmetry Index (LSI). This is preferable to the use of arbitrary single-limb performance levels, both because patients inherently differ in ability and because in biomechanical testing, limb symmetry is associated with better rates of return to play and lower rates of reinjury.17,25,27 Investigators in the literature support the use of LSI thresholds ranging from 80% to 90% before recommending return to play; previous studies have established that 93% of normal individuals have greater than 85% LSI for single-leg hop, and 100% have LSI greater than 80%.1,2,5,6,33 However, the effects of postoperative rehabilitation on the uninvolved limb are not fully understood in regard to functional testing. Postoperative rehabilitation entails a unique activity regimen for patients, which could plausibly cause incidental changes in the uninvolved limb. Physical therapy programs focus on the injured limb, yet many exercises involve the uninjured side as well—for instance, double leg jumps and Russian hamstring raises. In addition, the patient undergoes motor learning during each assessment, since both limbs are tested. Therefore, uninvolved limb ability may increase over subsequent SFTs. Previous research on this theory is inconclusive, with one study showing no significant change in uninvolved limb ability in hop test–naı¨ve subjects who underwent multiple assessments in a 5-day period.16 A subsequent study, however, showed increased uninvolved limb performance with repeat testing in all 4 hop tests, which the authors attributed to motor learning.29 Other functional tests in wide use, such as the single-leg squat and the retro step-up, have not been studied in this regard. Some studies that involved strength testing even suggested that the uninvolved limb’s performance worsens during rehabilitation.10,34 This is conceivable since the postsurgical period likely involves an overall lower level of activity, especially for an athlete.13 While limb symmetry in the SFT is a clearly beneficial goal, if this is achieved due to deterioration in the uninvolved limb, it could diminish the legitimacy of LSI measurements in functional testing.23,27 Therefore, it is especially vital to exclude the possibility that the uninvolved limb’s SFT performance may worsen with rehabilitation. This study aimed to determine the change in SFT performance of both the involved and uninvolved limbs during postoperative rehabilitation and to examine what effect that might have on LSI scores in functional testing. Our study is the largest that we are aware of to examine this effect, and it examines a broader variety of functional tests than the existing literature. We hypothesized that both the
involved limb’s and the uninvolved limbs’ ability would increase, but the uninvolved limb’s ability would increase to a lesser extent than that of the involved limb. We hypothesized that LSI values would therefore increase, indicating a true gain of function. We further hypothesized that within the SFT battery, the 4 hop tests would initially be the most asymmetric and show the most LSI improvement.
METHODS This study was approved by the institutional review board at our institution. A retrospective review was carried out using the medical records for all patients undergoing anterior cruciate ligament (ACL) reconstruction at our ambulatory surgery center from October 2009 to October 2013. All patients who underwent more than one SFT at our institution during postoperative rehabilitation after ACL reconstruction were included. Inclusion was not limited by surgical technique or concurrent procedures. Concurrent procedures included partial meniscectomy (43 patients), meniscal repair (14), chondroplasty (11), removal of hardware (7), plica resection (3), microfracture (3), and loose body removal (2). All patients underwent a standard ACL rehabilitation protocol, and all SFTs were performed at our institution. Patients at our institution underwent an initial SFT when the surgeon and physical therapist thought that the patients could complete the SFT safely. This was performed as early as possible, with a goal of 4 months postoperatively. Clearance for return to play is at the surgeon’s discretion but generally requires 90% LSI performance on all tests and subjective readiness to return to activities. If these goals were not met, the patient was referred for additional physical therapy either at our institution or at another of the patient’s choosing. After the prescribed physical therapy regimen was complete, the patient performed an additional SFT. Further physical therapy was arranged if performance was still inadequate, with additional SFTs after each additional regimen. Our institution’s SFT battery involves 12 functional test exercises, performed in the following order: single-leg anterolateral reach, single-leg anteromedial reach, stork stance (eyes open), stork stance (eyes closed), retro step-up, single-leg squat, single-leg hop, single-leg triple hop, crossover triple hop, timed hop, core plank, and single-leg bridge. For a visual demonstration of our testing battery, please view the online Video Supplement. A detailed text description of these tests is provided in the supplementary material (available in the online version of this article at http://ajsm.sagepub.com/supplemental). This battery of tests is performed under the supervision of physical therapists, after a 5-minute warm-up on a stationary bike. The entire testing protocol takes approximately 40 minutes, and patients are allowed to rest as needed to avoid fatigue. For each component test, patients were given 2 practice trials, followed by 3 testing attempts. The best of the 3 attempts was recorded. Patients were required to maintain balance and proper technique throughout the individual assessments. If patients failed due to improper form, they were allowed one repeat attempt after a verbal cue.
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TABLE 1 Patient Demographicsa Patients With Multiple SFTs (n = 122)
Patients With SFTs at 4 and 6 Months (n = 38)
57 59 12 (10)
60 61 3 (8)
Female, % With concurrent procedures, % Previous ipsilateral ACLR, n (%)
Age at surgery, y Body mass index Total no. of physical therapy sessions All SFTs Time of first SFT, days postoperative Time of last SFT, days postoperative Time between SFTs, days SFTs involving hop tests Time of first SFT, days postoperative Time of last SFT, days postoperative Time between SFTs, days
Mean 6 SD
Median
Range
Mean 6 SD
Median
Range
26 6 11.4 25.3 6 4.1 18.6 6 7.9
22 25 17
12-53 17.5-38.4 6-46
26 6 11.6 25.5 6 3.9 17.7 6 6.7
20 25 16
14-53 18.2-35.5 7-35
119 6 48.3 199 6 65.6 80 6 43
111 183 72
51-260 58-454 7-222
113 6 15.5 181 6 15.4 68 6 16.2
113 182 64
90-146 154-210 36-105
158 6 41.9 240 6 64.4 81 6 44.4
155 234 71
63-260 84-454 18-211
118 6 16.7 182 6 15.4 64 6 16.4
118 182 62
90-146 154-207 36-105
a
ACLR, anterior cruciate ligament reconstruction; SFT, Standard Functional Test.
Individual components of each patient’s SFTs were used for analysis only if the patient completed that component during both recorded SFTs. Core plank measurements were not analyzed as there is no uninvolved limb for comparison. Single-leg bridge was also removed from analysis as the testing procedure does not produce a reliable LSI measurement. Consequently, 10 of the 12 tests in our SFT battery were analyzed in this study. For patients with more than 2 SFTs, the earliest and latest SFTs were used, excluding those performed more than 1 year from surgery. The performance of the injured and uninjured limbs was recorded in absolute terms for each portion of the test. We also calculated the performance of the involved limb as a proportion of the uninvolved limb’s performance, yielding an LSI for each SFT component. We compared the absolute and LSI results of each patient’s earliest and latest SFT, using a 2-tailed paired t test assuming equal variance, with P = .05. An identical analysis was performed on the subgroup of patients with SFTs performed at both the 4-month and 6month postoperative times. SFTs performed between 90 and 150 days postoperatively qualified as a 4-month test, and SFTs performed between 150 and 210 days postoperatively qualified as a 6-month test. Individual components of the SFT were used for analysis for each patient only if that patient completed that component during both SFTs. Again, we compared the absolute results and LSI of each patient’s 4-month and 6-month SFT, using a 2-tailed paired t test assuming equal variance, with P = .05.
(92%), whereas 10 (8%) involved contact to the knee. A total of 102 patients performed only 2 SFTs during their rehabilitation, which reflects our usual practice of obtaining both an ‘‘entry’’ and ‘‘exit’’ SFT with rehabilitation. Sixteen patients performed 3 SFTs, and 4 patients performed 4 SFTs. A description of the patients included in this analysis can be found in Table 1. In the involved limb, absolute changes were seen in single-leg anterolateral reach (from 64.8 cm to 70.4 cm, P \ .001), single-leg anteromedial reach (from 66.8 cm to 72.1 cm, P \ .001), stork stance (from 55.7 s to 59.1 s, P = .031), retro step-up (from 21.4 cm to 28.1 cm, P \ .001), single-leg squat (from 77.7° to 85.9°, P \ .001), single-leg hop (from 111.1 cm to 137.0 cm, P \ .001), crossover triple hop (from 326.5 cm to 389.8 cm, P \ .001), single-leg triple hop (from 359.3 cm to 415.1 cm, P = .006), and timed hop (from 2.77 s to 2.27 s, P \ .001) (Figure 1, Table 2). In the uninvolved limb, absolute changes were seen over multiple SFTs in single-leg anterolateral reach (from 67.1 cm to 71.6 cm, P \ .001), single-leg anteromedial reach (from 69.7 cm to 72.9 cm, P \ .001), retro step-up (from 27.9 cm to 31.8 cm, P \ .001), and timed hop (from 2.31 s to 2.10 s, P = .002) (Figure 2, Table 2). LSI changed significantly for single-leg anteromedial reach (from 96.1% to 99.0%, P \ .001), retro step-up (from 77.0% to 89.5%, P \ .001), single-leg squat (from 88.5% to 96.1%, P \ .001), single-leg hop (from 78.2% to 90.3%, P \ .001), crossover triple hop (from 84.5% to 92.3%, P = .003), and timed hop (from 85.3% to 92.8%, P = .001) (Figure 3, Table 2).
RESULTS Patients With 4-Month and 6-Month SFTs All Patients With Multiple SFTs A total of 122 patients fulfilled our inclusion criteria. The mechanism of injury was noncontact in 112 patients
Thirty-eight patients had SFTs performed at both the 4month and 6-month postoperative times. A description of the patients included in this analysis can be found in Table 1.
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TABLE 2 Functional Test Performance in All Patients With Multiple SFTsa
Single-leg reach anterolateral Involved, cm Uninvolved, cm LSI, % Single-leg reach anteromedial Involved, cm Uninvolved, cm LSI, % Stork–eyes open Involved, s Uninvolved, s LSI, % Stork–eyes closed Involved, s Uninvolved, s LSI, % Retro step-up Involved, cm Uninvolved, cm LSI, % Single-leg squat Involved, deg Uninvolved, deg LSI, % Single-leg hop Involved, cm Uninvolved, cm LSI, % Triple hop distance Involved, cm Uninvolved, cm LSI, % Crossover triple hop Involved, cm Uninvolved, cm LSI, % Timed hop Involved, s Uninvolved, s LSI, %
SFT 1
SFT 2
P Value
64.8 (62.3-67.3) 67.1 (64.6-69.5) 96.7 (95.0-97.6)
70.4 (68.2-72.7) 71.6 (69.4-73.8) 98.4 (97.5-99.3)
\.001 \.001 .063
66.8 (64.6-69.1) 69.7 (67.4-72.1) 96.1 (94.8-97.0)
72.1 (70.2-74.0) 72.9 (71.0-74.9) 99.0 (98.1-99.8)
\.001 \.001 \.001
55.7 (52.5-59.0) 57.6 (55.0-60.3) 96.4 (92.9-97.6)
59.1 (56.4-61.7) 59.7 (57.0-62.4) 99.0 (97.8-100.3)
.031 .068 .136
17.6 (11.5-23.7) 25.8 (17.4-34.1) 99.7 (54.3-121.5)
38.2 (13.3-63.0) 45.5 (19.3-71.6) 87.4 (65.6-109.2)
.119 .153 .628
21.4 (19.9-23.0) 27.9 (26.3-29.5) 77.0 (73.2-79.5)
28.1 (26.3-29.8) 31.8 (29.6-34.0) 89.5 (87.0-92.0)
\.001 \.001 \.001
77.6 (74.9-80.4) 88.2 (85.5-90.8) 88.5 (86.2-91.4)
85.9 (82.7-89.2) 90.9 (87.4-94.3) 96.1 (93.2-99.1)
\.001 .068 \.001
111.1 (99.4-122.8) 140.4 (126.4-154.4) 78.2 (73.3-80.9)
137.0 (126.7-147.2) 152.8 (141.3-164.2) 90.3 (87.5-93.0)
\.001 .056 \.001
359.3 (323.1-395.4) 420.5 (384.8-456.2) 85.9 (78.7-89.6)
415.1 (382.0-448.3) 455.2 (410.9-499.5) 91.6 (87.9-95.4)
.006 .175 .160
326.5 (289.5-363.5) 394.7 (343.0-446.5) 84.5 (79.8-87.4)
389.8 (362.6-416.9) 425.7 (394.3-457.0) 92.3 (89.4-95.1)
\.001 .154 .003
2.77 (2.54-3.00) 2.31 (2.15-2.47) 85.3 (80.9-88.2)
2.27 (2.11-2.43) 2.10 (1.94-2.25) 92.8 (89.9-95.7)
\.001 .002 .001
a Values are reported as mean (95% CI). Bolded text indicates statistically significant difference between groups (P \ .05). LSI, Limb Symmetry Index; SFT, Standard Functional Test.
Absolute changes were seen in the involved limb for single-leg anterolateral reach (from 65.6 cm to 71.7 cm, P \ .001), single-leg anteromedial reach (from 66.9 cm to 72.2 cm, P \ .001), retro step-up (from 22.6 cm to 28.6 cm, P = .007), single-leg squat (from 80.1° to 86.5°, P = .048), single-leg hop (from 112.4 cm to 141.2 cm, P = .028), crossover triple hop (from 329.1 cm to 414.3 cm, P = .025), and timed hop (from 2.42 s to 2.02 s, P = .032). Absolute changes were seen in the uninvolved limb for single-leg anterolateral reach (from 66.9 cm to 73.0 cm, P \ .001), single-leg anteromedial reach (from 68.4 cm to 72.8 cm, P \ .001), retro step-up (from 29.1 cm to 31.7 cm, P = .014), single-leg hop (from 141.4 cm to 153.5 cm, P = .007), and timed hop (from 2.06 s to 1.87 s, P = .042).
LSI changed in retro step-up (from 78.1% to 90.3%, P \ .001), single-leg squat (from 87.1% to 97.0% of the uninvolved limb, P = .020), single-leg hop (from 79.1% to 91.4%, P \ .001), and crossover triple hop (from 80.2% to 92.6%, P = .008).
DISCUSSION Our data indicate that uninvolved limb ability does not decrease during rehabilitation and instead shows improvement in several of the SFT component tests. The involved limb showed greater improvement than the uninvolved limb and showed improvement in more of the individual
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100
*
90
Inial SFT Final SFT
80
Measured Value
70
*
* *
60 50
*
40
*
*
30
*
20
*
10 0
Stork– Single-Leg Single-Leg Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up (sec) (cm) (cm) (sec) (cm)
Single-Leg Squat (deg)
Single-Leg Single-Leg Crossover Timed Hop Triple Hop Triple Hop Hop (dm) (dm) (dm) (sec ×10)
Figure 1. Comparison of involved limb performance during the first Standard Functional Test (SFT) and last SFT, in all patients with multiple SFTs (means and 95% CIs). Some units were converted from centimeters to decimeters for ease of display. *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial.
100
Inial SFT Final SFT
90 80
*
*
Measured Value
70 60 50 40
* *
30 20 10 0
Single-Leg Single-Leg Stork– Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up (cm) (cm) (sec) (sec) (cm)
Single-Leg Squat (deg)
Single-Leg Single-Leg Crossover Timed Hop Triple Hop Triple Hop Hop (dm) (dm) (dm) (sec ×10)
Figure 2. Comparison of uninvolved limb performance during the first Standard Functional Test (SFT) and last SFT in all patients with multiple SFTs (means and 95% CIs). Some units were converted from centimeters to decimeters for ease of display. *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial. tests. This is consistent with previous studies in ACL reconstruction patients, including one from Reid et al,29 who showed early improvements in both limbs, followed by continued improvements in the involved limb only, with corresponding LSI increases. These authors argued that this early effect represents motor learning acquired during the testing itself and that the later LSI increases represent true improvement in the involved limb. In our study, which involved a sizable study population and a long postoperative period, the increased involved limb ability was comparable and consistent with this theory. Perhaps most crucial was that the uninvolved limb ability did not decrease, as this could undermine the legitimacy of LSI testing. Based on these findings, LSI scoring appears
to be an appropriate method of detecting functional improvement and evaluating rehabilitation progress. Of all the tests included in our functional testing protocol, hop tests have received the most attention in previous literature.8,14,28 All 4 of the hop tests in our study showed initial LSI below 90%. Three of the 4 hop tests (single-leg hop, crossover triple hop, and timed hop) showed significant LSI improvement, and all hop tests showed final LSI greater than 90% at an average of 28 weeks. At 8 months postoperatively, Mohammadi et al21 also found most hop test LSIs to be above 90%. In a specific test example, the single-leg hop showed LSI improvements of more than 10 percentage points in our study. Reid et al29 found that LSI increased by 5.3 percentage points in the single-
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150
Inial SFT Final SFT
140
Limb Symmetry Index, %
130 120 110 100
* *
*
*
*
*
90 80 70 60 50
Single-Leg Single-Leg Stork– Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up
Single-Leg Squat
Single-Leg Single-Leg Crossover Hop Triple Hop Triple Hop
Timed Hop
Figure 3. Comparison of the Limb Symmetry Index scores during the first Standard Functional Test (SFT) and last SFT, in all patients with multiple SFTs (means and 95% CIs). *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial. leg hop over 22 weeks. While the minimal clinically important change has not been established for the single-leg hop, our study found even greater LSI increases over a longer time period, and we believe that this result was especially robust. Strong test-retest reliability for these 4 hop tests has been demonstrated by previous authors.11,16,29 We therefore conclude that these tests can provide useful information regarding functional deficits and are appropriate for use in evaluating rehabilitation progress. Our study also identified additional tests in our SFT protocol that showed initial LSI asymmetry and improvement during rehabilitation and may therefore be useful complements to hop testing. The single-leg squat and retro step-up tests showed initial LSI below 90%. Both tests showed significant LSI improvement in both analyses, and single-leg anteromedial reach showed LSI improvements in the larger analysis only. Retro step-up showed LSI improvement of more than 10 percentage points in both analyses. Again, although the minimal clinically important change has not been established, we believe that this robust outcome indicates a high utility for this test in functional evaluation. These 3 additional tests have not been as extensively studied in the literature, and test-retest reliability data are not available. These tests, however, may have high value in a functional testing protocol, especially since they can be performed earlier than hop tests. Regardless of the SFT battery used, our study also provides some general guidance for the use of functional testing during rehabilitation. First, since the uninvolved limb’s abilities may improve during rehabilitation, we recommend that the LSI always be calculated using measurements of both limbs from the same date. LSI calculations based on uninvolved limb ability from a previous date—for instance, a benchmark obtained at the beginning of rehabilitation—will not account for improvements in uninvolved limb ability and may therefore overestimate improvements in the LSI. Second, since many tests showed
improvement beyond 6 months, rehabilitation efforts are likely beneficial even after this time point. Consistent with what we see clinically, many patients are not fully rehabilitated by 6 months and are aided by further physical therapy beyond this time. Persistent LSI asymmetry at 6 months postoperatively can be used as an indication for more intensive rehabilitation regimens and potentially can improve the probability of successful return to play. Recovery from ACL reconstruction can be slow, with only 33% of patients attempting competitive sport by 12 months postoperatively.4,15 Ultimately, only 43% of athletes successfully return to their preinjury level of competition, and upon returning, athletes face a significantly higher chance of contralateral ACL tear (19%) and ipsilateral graft rupture (6%) within 12 months.20,26 To improve these outcomes, rehabilitation regimens are becoming increasingly evidence-based, and many have incorporated functional testing protocols.8,14,24,28,35,38 However, the literature has not yet established a relationship between SFT performance and successful return to play or lower reinjury rates.4 While one previous study found that ACL reconstruction patients with LSI higher than 85% in the single-leg hop and crossover triple hop were more likely to attempt return to play, it did not examine the success of those attempts.4 A different study of 35 nonoperative ACL-deficient patients found no correlation between hop test LSI scores and pain, swelling, or giving way upon return to sport.6 Therefore, although functional testing has found widespread use, future studies need to further examine the correlation between SFT performance and patient outcomes. Our study was limited by its retrospective nature. Although SFTs were performed at the same facility, rehabilitation depends upon the quality of rehabilitation effort, something that was not possible to standardize among patients. Additionally, the postoperative timing of each SFT varied between patients because of the variable rate of progression with the rehabilitation process among patients.
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Although we attempted to standardize SFT timing with our additional 4-month to 6-month analysis, fewer than half of the patients were eligible for inclusion in this more stringent time frame. It also should be noted that although we revealed functional deficits in several SFT components and subsequent improvement, we cannot conclude that this improvement translated into superior outcomes for the patient. Future studies should seek to correlate SFT performance with readiness to return to play and lower reinjury rates.
CONCLUSION During the rehabilitation process after ACL reconstruction, SFT testing successfully detects improvement in both the LSI and the involved limb’s absolute ability. There were some comparatively smaller increases, and no decreases, in the functional ability of the uninvolved limb. An increased LSI therefore reflects a true increase in the involved limb’s function, rather than a spurious result due to a decrease in the ability of the uninvolved limb. Based on our subjects’ initial performance below 90% LSI and subsequent improvement, our study suggests that single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop are highly useful for detecting functional asymmetry and tracking improvement in the involved limb.
ACKNOWLEDGMENT The authors acknowledge TRIA Orthopaedic Center for providing the workspace needed to perform the data collection and analysis for this study. They thank Megan Reams and the staff of TRIA Orthopaedic Center for coordinating and facilitating the logistics of this study and for helping to collect the outcomes data. They also thank Adam Meierbachtol and Amanda LeValley for their assistance creating the online video supplements.
A Video Supplement for this article is available in the online version or at http://ajsm.sagepub.com/supplemental.
REFERENCES 1. Adams D, Logerstedt DS, Hunter-Giordano A, et al. Current concepts for anterior cruciate ligament reconstruction: a criterion-based rehabilitation progression. J Orthop Sports Phys Ther. 2012;42(7):601614. 2. Ageberg E, Roos HP, Silbernagel KG, Thomee R, Roos EM. Knee extension and flexion muscle power after anterior cruciate ligament reconstruction with patellar tendon graft or hamstring tendons graft: a cross-sectional comparison 3 years post surgery. Knee Surg Sports Traumatol Arthrosc. 2009;17(2):162-169. 3. Anderson A, Irrgang J, Kocher M, Mann B, Harrast J. International Knee Documentation Committee. The International Knee Documentation Committee Subjective Knee Evaluation Form: normative data. Am J Sports Med. 2006;34(1):128-135. 4. Ardern CL, Webster KE, Taylor NF, Feller JA. Return to the preinjury level of competitive sport after anterior cruciate ligament reconstruction surgery: two-thirds of patients have not returned by 12 months after surgery. Am J Sports Med. 2011;39(3):538-543.
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5. Asik M, Sen C, Tuncay I. The mid- to long-term results of the anterior cruciate ligament reconstruction with hamstring tendons using transfix technique. Knee Surg Sports Traumatol Arthrosc. 2007;15(8):965-972. 6. Barber SD, Noyes FR, Mangine RE. Quantitative assessment of functional limitations in normal and anterior cruciate ligament-deficient knees. Clin Orthop Relat Res. 1990;255:204-214. 7. Barber-Westin SD, Noyes FR. Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction. Arthroscopy. 2011;27(12):1697-1705. 8. Fitzgerald G, Lephart S, Hwang J, Wainner R. Hop tests as predictors of dynamic knee stability. J Orthop Sports Phys Ther. 2001; 31(10):588-597. 9. Hambly K, Griva K. IKDC or KOOS: which one captures symptoms and disabilities most important to patients who have undergone initial anterior cruciate ligament reconstruction? Am J Sports Med. 2010;38(7):1395-1404. 10. Hiemstra LA, Webber S, MacDonald PB, Kriellaars DJ. Knee strength deficits after hamstring tendon and patellar tendon anterior cruciate ligament reconstruction. Med Sci Sports Exerc. 2000;32(8):14721479. 11. Hopper DM, Goh SC, Wentworth LA, et al. Test-retest reliability of knee rating scales and functional hop tests one year following anterior cruciate ligament reconstruction. Phys Ther Sport. 2002;3:10-18. 12. Irrgang J, Anderson F, Boland A, et al. Development and validation of the International Knee Documentation Committee subjective knee form. Am J Sports Med. 2001;29(5):600-613. 13. Ito Y, Deie M, Adachi N, et al. A prospective study of 3-day versus 2week immobilization period after anterior cruciate ligament reconstruction. Knee. 2007;14(1):34-38. 14. Jarvela T, Kannus P, Latvala K, Jarvinen M. Simple measurements in assessing muscle performance after an ACL reconstruction. Int J Sports Med. 2002;23(3):196-201. 15. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93(11):994-1000. 16. Kramer JF, Nusca D, Fowler P, Webster-Bogaert S. Test-retest reliability of the one-leg hop test following ACL reconstruction. Clin J Sport Med. 1992;2(4):240-243. 17. Kvist J. Rehabilitation following anterior cruciate ligament injury: current recommendations for sports participation. Sports Med. 2004;34(4):269-280. 18. Lephart S, Perrin D, Fu F, Gieck J, McCue F, Irrgang J. Relationship between selected physical characteristics and functional capacity in the anterior cruciate ligament-insufficient athlete. J Orthop Sports Phys Ther. 1992;16(4):174-181. 19. Logerstedt D, Grindem H, Lynch A, et al. Single-legged hop tests as predictors of self-reported knee function after anterior cruciate ligament reconstruction: the Delaware-Oslo ACL cohort study. Am J Sports Med. 2012;40(10):2348-2356. 20. McCullough KA, Phelps KD, Spindler KP, et al. Return to high schooland college-level football after anterior cruciate ligament reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) cohort study. Am J Sports Med. 2012;40(11):2523-2529. 21. Mohammadi F, Salavati M, Akhbari B, Mazaheri M, Mir S, Etemadi Y. Comparison of functional outcome measures after ACL reconstruction in competitive soccer players. J Bone Joint Surg Am. 2013;95(14):1271-1277. 22. Myer GD, Schmitt LC, Brent JL, et al. Utilization of modified NFL combine testing to identify functional deficits in athletes following ACL reconstruction. J Orthop Sports Phys Ther. 2011;41(6):377387. 23. Newton R, Gerber A, Nimphius S, et al. Determination of functional strength imbalance of the lower extremities. J Strength Cond Res. 2006;20(4):971-977. 24. Pairot de Fontenay B, Argaud S, Blache Y, Monteil K. Asymmetries in joint work during multi-joint movement after anterior cruciate ligament reconstruction: a pilot study. Scand J Med Sci Sports. 2014;24(6):e471-476.
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25. Paterno MV, Ford KR, Myer GD, Heyl R, Hewett TE. Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction. Clin J Sport Med. 2007;17(4):258-262. 26. Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of contralateral and ipsilateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction and return to sport. Clin J Sport Med. 2012;22(2):116-121. 27. Paterno MV, Schmidt LC, Ford KR, et al. Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport. Am J Sports Med. 2010;38(10):1968-1978. 28. Petschnig R, Baron R, Albrecht M. The relationship between isokinetic quadriceps strength test and hop tests for distance and onelegged vertical jump test following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther. 1998;28(1):23-31. 29. Reid A, Birmingham T, Stratford P, Alcock G, Giffin J. Hop testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction. Phys Ther. 2007;87(3):337-349. 30. Reinke EK, Spindler KP, Lorring D, et al. Hop tests correlate with IKDC and KOOS at minimum of 2 years after primary ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2011;19(11):1806-1816. 31. Risberg MA, Holm I, Tjomsland O, Lunggren E, Ekeland A. Prospective study of changes in impairments and disabilities after anterior
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cruciate ligament reconstruction. J Orthop Sports Phys Ther. 1999;29(7):400-412. Ross M, Langford B, Whelan P. Test-retest reliability of 4 single-leg horizontal hop tests. J Strength Cond Res. 2002;16(4):617-622. Tadokoro K, Matsui N, Yagi M, Kuroda R, Kurosaka M, Yoshiya S. Evaluation of hamstring strength and tendon regrowth after harvesting for anterior cruciate ligament reconstruction. Am J Sports Med. 2004;32(7):1644-1650. Thomee´ R, Neeter C, Gustavsson A, et al. Variability in leg muscle power and hop performance after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2012;20(6):1143-1151. Van Grinsven S, Van Cingel R, Holla C, Van Loon C. Evidence-based rehabilitation following anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2010;18(8):1128-1144. Wilk KE, Romaniello WT, Soscia SM, Arrigo CA, Andrews JR. The relationship between subjective knee scores, isokinetic testing, and functional testing in the ACL-reconstructed knee. J Orthop Sports Phys Ther. 1994;20(2):60-73. Wright R, Fetzer G. Bracing after ACL reconstruction: a systematic review. Clin Orthop Relat Res. 2007;455:162-168. Wright R, Preston E, Fleming B, et al. A systematic review of anterior cruciate ligament reconstruction rehabilitation, part I: continuous passive motion, early weight bearing, postoperative bracing, and home-based rehabilitation. J Knee Surg. 2008;21(3):217-224.
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Changes in Involved and Uninvolved Limb Function During Rehabilitation After Anterior Cruciate Ligament Reconstruction: Implications for Limb Symmetry Index Measures Eric Rohman, J. Tyler Steubs and Marc Tompkins Am J Sports Med published online March 31, 2015 DOI: 10.1177/0363546515576127 The online version of this article can be found at: http://ajs.sagepub.com/content/early/2015/03/31/0363546515576127
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On behalf of: American Orthopaedic Society for Sports Medicine
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Changes in Involved and Uninvolved Limb Function During Rehabilitation After Anterior Cruciate Ligament Reconstruction Implications for Limb Symmetry Index Measures Eric Rohman,* MD, J. Tyler Steubs,* MD, and Marc Tompkins,*yz MD Investigation performed at TRIA Orthopaedic Center, Bloomington, Minnesota, USA Background: Functional testing is used to assess anterior cruciate ligament (ACL) reconstruction rehabilitation, with the goal of symmetric ability. The pattern of change in the uninvolved limb’s function during rehabilitation is not established. Hypotheses: (1) Involved and uninvolved limb ability increases during rehabilitation, but the uninvolved limb ability increases to a lesser degree. (2) Hop tests will show larger initial asymmetry and will improve the most with rehabilitation. Study Design: Cohort study; Level of evidence, 3. Methods: This was a retrospective case series of 122 patients who underwent ACL reconstruction at our ambulatory surgery center and received multiple postoperative Standard Functional Tests (SFTs) between October 2009 and October 2013. Ten of the 12 individual tests within the SFT battery were analyzed. The patients’ earliest and latest SFTs were compared for changes in Limb Symmetry Index (LSI) and absolute function in each limb. We also analyzed the subgroup with SFTs (n = 38) at both 4 and 6 months postoperatively. Results: In all patients with multiple SFTs, involved limb performance increased in all tests except eyes-closed stork. Uninvolved limb performance increased in 4 SFT component tests and decreased in none. LSI significantly improved in 6 tests, all of which also showed involved limb improvement that was significant. Of these 6 tests, 5 showed initial LSI below 90%: single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop. Retro step-up and single-leg hop showed LSI improvements greater than 10 percentage points. In patients with 4- and 6-month data, involved limb performance increased in all tests except single-leg triple hop. Uninvolved limb performance increased in 5 SFT component tests and decreased in none. LSI significantly improved in 4 tests, all of which had initial LSI below 90%, and showed involved limb improvement that was significant. Retro step-up, single-leg hop, and crossover triple hop showed LSI improvements greater than 10 percentage points. Conclusion: During ACL reconstruction rehabilitation, LSI improvements indicated absolute increases in involved limb ability and were not attributable to uninvolved limb deterioration. The single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop are suggested as highly useful tests, since all showed initial LSI below 90%, with significant LSI improvement after rehabilitation. Keywords: ACL physical therapy/rehabilitation; functional test; limb symmetry index; ACL reconstruction
Anterior cruciate ligament tears are a common injury in active individuals. Return to play is a primary goal of
surgical intervention, yet the criteria for athletic clearance have been inconsistent historically and may not accurately predict readiness to perform.7,12,22,32,36,37 Standard Functional Tests (SFTs) have been developed as a more accurate measure of patient ability and readiness to return to play.18,31,36 Multiple tests exist in this category, all of which combine complex kinetic chain motions to better simulate sport-related demands and evaluate neuromuscular control. The single-leg hop test has been evaluated extensively and is capable of detecting functional limitations up to 54 weeks postoperatively, with good test-retest reliability.14,19,22,28,29 Other investigators have recommended a 4-test battery consisting of a singleleg hop, a crossover triple hop, a single-leg triple hop,
z Address correspondence to Marc Tompkins, MD, Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue S, Suite R200, Minneapolis, MN 55454, USA (e-mail: tompkinsm@hotmail .com). *Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA. y TRIA Orthopaedic Center, Bloomington, Minnesota, USA. The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.
The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546515576127 Ó 2015 The Author(s)
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and a timed hop. This test battery has shown predictive value for a patient’s subjective ability for up to 2 years postoperatively, as measured by the International Knee Documentation Committee (IKDC) form.3,9,12,30 Strength testing also has a role in rehabilitation assessment, as well as other functional tests such as single-leg squat and retro step-up. No universally accepted protocol of functional testing exists, and multiple groups have developed unique functional test batteries for assessment. During rehabilitation, the injured limb’s SFT performance is typically compared with that of the uninjured limb as a reference, yielding a measure known as the Limb Symmetry Index (LSI). This is preferable to the use of arbitrary single-limb performance levels, both because patients inherently differ in ability and because in biomechanical testing, limb symmetry is associated with better rates of return to play and lower rates of reinjury.17,25,27 Investigators in the literature support the use of LSI thresholds ranging from 80% to 90% before recommending return to play; previous studies have established that 93% of normal individuals have greater than 85% LSI for single-leg hop, and 100% have LSI greater than 80%.1,2,5,6,33 However, the effects of postoperative rehabilitation on the uninvolved limb are not fully understood in regard to functional testing. Postoperative rehabilitation entails a unique activity regimen for patients, which could plausibly cause incidental changes in the uninvolved limb. Physical therapy programs focus on the injured limb, yet many exercises involve the uninjured side as well—for instance, double leg jumps and Russian hamstring raises. In addition, the patient undergoes motor learning during each assessment, since both limbs are tested. Therefore, uninvolved limb ability may increase over subsequent SFTs. Previous research on this theory is inconclusive, with one study showing no significant change in uninvolved limb ability in hop test–naı¨ve subjects who underwent multiple assessments in a 5-day period.16 A subsequent study, however, showed increased uninvolved limb performance with repeat testing in all 4 hop tests, which the authors attributed to motor learning.29 Other functional tests in wide use, such as the single-leg squat and the retro step-up, have not been studied in this regard. Some studies that involved strength testing even suggested that the uninvolved limb’s performance worsens during rehabilitation.10,34 This is conceivable since the postsurgical period likely involves an overall lower level of activity, especially for an athlete.13 While limb symmetry in the SFT is a clearly beneficial goal, if this is achieved due to deterioration in the uninvolved limb, it could diminish the legitimacy of LSI measurements in functional testing.23,27 Therefore, it is especially vital to exclude the possibility that the uninvolved limb’s SFT performance may worsen with rehabilitation. This study aimed to determine the change in SFT performance of both the involved and uninvolved limbs during postoperative rehabilitation and to examine what effect that might have on LSI scores in functional testing. Our study is the largest that we are aware of to examine this effect, and it examines a broader variety of functional tests than the existing literature. We hypothesized that both the
involved limb’s and the uninvolved limbs’ ability would increase, but the uninvolved limb’s ability would increase to a lesser extent than that of the involved limb. We hypothesized that LSI values would therefore increase, indicating a true gain of function. We further hypothesized that within the SFT battery, the 4 hop tests would initially be the most asymmetric and show the most LSI improvement.
METHODS This study was approved by the institutional review board at our institution. A retrospective review was carried out using the medical records for all patients undergoing anterior cruciate ligament (ACL) reconstruction at our ambulatory surgery center from October 2009 to October 2013. All patients who underwent more than one SFT at our institution during postoperative rehabilitation after ACL reconstruction were included. Inclusion was not limited by surgical technique or concurrent procedures. Concurrent procedures included partial meniscectomy (43 patients), meniscal repair (14), chondroplasty (11), removal of hardware (7), plica resection (3), microfracture (3), and loose body removal (2). All patients underwent a standard ACL rehabilitation protocol, and all SFTs were performed at our institution. Patients at our institution underwent an initial SFT when the surgeon and physical therapist thought that the patients could complete the SFT safely. This was performed as early as possible, with a goal of 4 months postoperatively. Clearance for return to play is at the surgeon’s discretion but generally requires 90% LSI performance on all tests and subjective readiness to return to activities. If these goals were not met, the patient was referred for additional physical therapy either at our institution or at another of the patient’s choosing. After the prescribed physical therapy regimen was complete, the patient performed an additional SFT. Further physical therapy was arranged if performance was still inadequate, with additional SFTs after each additional regimen. Our institution’s SFT battery involves 12 functional test exercises, performed in the following order: single-leg anterolateral reach, single-leg anteromedial reach, stork stance (eyes open), stork stance (eyes closed), retro step-up, single-leg squat, single-leg hop, single-leg triple hop, crossover triple hop, timed hop, core plank, and single-leg bridge. For a visual demonstration of our testing battery, please view the online Video Supplement. A detailed text description of these tests is provided in the supplementary material (available in the online version of this article at http://ajsm.sagepub.com/supplemental). This battery of tests is performed under the supervision of physical therapists, after a 5-minute warm-up on a stationary bike. The entire testing protocol takes approximately 40 minutes, and patients are allowed to rest as needed to avoid fatigue. For each component test, patients were given 2 practice trials, followed by 3 testing attempts. The best of the 3 attempts was recorded. Patients were required to maintain balance and proper technique throughout the individual assessments. If patients failed due to improper form, they were allowed one repeat attempt after a verbal cue.
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TABLE 1 Patient Demographicsa Patients With Multiple SFTs (n = 122)
Patients With SFTs at 4 and 6 Months (n = 38)
57 59 12 (10)
60 61 3 (8)
Female, % With concurrent procedures, % Previous ipsilateral ACLR, n (%)
Age at surgery, y Body mass index Total no. of physical therapy sessions All SFTs Time of first SFT, days postoperative Time of last SFT, days postoperative Time between SFTs, days SFTs involving hop tests Time of first SFT, days postoperative Time of last SFT, days postoperative Time between SFTs, days
Mean 6 SD
Median
Range
Mean 6 SD
Median
Range
26 6 11.4 25.3 6 4.1 18.6 6 7.9
22 25 17
12-53 17.5-38.4 6-46
26 6 11.6 25.5 6 3.9 17.7 6 6.7
20 25 16
14-53 18.2-35.5 7-35
119 6 48.3 199 6 65.6 80 6 43
111 183 72
51-260 58-454 7-222
113 6 15.5 181 6 15.4 68 6 16.2
113 182 64
90-146 154-210 36-105
158 6 41.9 240 6 64.4 81 6 44.4
155 234 71
63-260 84-454 18-211
118 6 16.7 182 6 15.4 64 6 16.4
118 182 62
90-146 154-207 36-105
a
ACLR, anterior cruciate ligament reconstruction; SFT, Standard Functional Test.
Individual components of each patient’s SFTs were used for analysis only if the patient completed that component during both recorded SFTs. Core plank measurements were not analyzed as there is no uninvolved limb for comparison. Single-leg bridge was also removed from analysis as the testing procedure does not produce a reliable LSI measurement. Consequently, 10 of the 12 tests in our SFT battery were analyzed in this study. For patients with more than 2 SFTs, the earliest and latest SFTs were used, excluding those performed more than 1 year from surgery. The performance of the injured and uninjured limbs was recorded in absolute terms for each portion of the test. We also calculated the performance of the involved limb as a proportion of the uninvolved limb’s performance, yielding an LSI for each SFT component. We compared the absolute and LSI results of each patient’s earliest and latest SFT, using a 2-tailed paired t test assuming equal variance, with P = .05. An identical analysis was performed on the subgroup of patients with SFTs performed at both the 4-month and 6month postoperative times. SFTs performed between 90 and 150 days postoperatively qualified as a 4-month test, and SFTs performed between 150 and 210 days postoperatively qualified as a 6-month test. Individual components of the SFT were used for analysis for each patient only if that patient completed that component during both SFTs. Again, we compared the absolute results and LSI of each patient’s 4-month and 6-month SFT, using a 2-tailed paired t test assuming equal variance, with P = .05.
(92%), whereas 10 (8%) involved contact to the knee. A total of 102 patients performed only 2 SFTs during their rehabilitation, which reflects our usual practice of obtaining both an ‘‘entry’’ and ‘‘exit’’ SFT with rehabilitation. Sixteen patients performed 3 SFTs, and 4 patients performed 4 SFTs. A description of the patients included in this analysis can be found in Table 1. In the involved limb, absolute changes were seen in single-leg anterolateral reach (from 64.8 cm to 70.4 cm, P \ .001), single-leg anteromedial reach (from 66.8 cm to 72.1 cm, P \ .001), stork stance (from 55.7 s to 59.1 s, P = .031), retro step-up (from 21.4 cm to 28.1 cm, P \ .001), single-leg squat (from 77.7° to 85.9°, P \ .001), single-leg hop (from 111.1 cm to 137.0 cm, P \ .001), crossover triple hop (from 326.5 cm to 389.8 cm, P \ .001), single-leg triple hop (from 359.3 cm to 415.1 cm, P = .006), and timed hop (from 2.77 s to 2.27 s, P \ .001) (Figure 1, Table 2). In the uninvolved limb, absolute changes were seen over multiple SFTs in single-leg anterolateral reach (from 67.1 cm to 71.6 cm, P \ .001), single-leg anteromedial reach (from 69.7 cm to 72.9 cm, P \ .001), retro step-up (from 27.9 cm to 31.8 cm, P \ .001), and timed hop (from 2.31 s to 2.10 s, P = .002) (Figure 2, Table 2). LSI changed significantly for single-leg anteromedial reach (from 96.1% to 99.0%, P \ .001), retro step-up (from 77.0% to 89.5%, P \ .001), single-leg squat (from 88.5% to 96.1%, P \ .001), single-leg hop (from 78.2% to 90.3%, P \ .001), crossover triple hop (from 84.5% to 92.3%, P = .003), and timed hop (from 85.3% to 92.8%, P = .001) (Figure 3, Table 2).
RESULTS Patients With 4-Month and 6-Month SFTs All Patients With Multiple SFTs A total of 122 patients fulfilled our inclusion criteria. The mechanism of injury was noncontact in 112 patients
Thirty-eight patients had SFTs performed at both the 4month and 6-month postoperative times. A description of the patients included in this analysis can be found in Table 1.
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TABLE 2 Functional Test Performance in All Patients With Multiple SFTsa
Single-leg reach anterolateral Involved, cm Uninvolved, cm LSI, % Single-leg reach anteromedial Involved, cm Uninvolved, cm LSI, % Stork–eyes open Involved, s Uninvolved, s LSI, % Stork–eyes closed Involved, s Uninvolved, s LSI, % Retro step-up Involved, cm Uninvolved, cm LSI, % Single-leg squat Involved, deg Uninvolved, deg LSI, % Single-leg hop Involved, cm Uninvolved, cm LSI, % Triple hop distance Involved, cm Uninvolved, cm LSI, % Crossover triple hop Involved, cm Uninvolved, cm LSI, % Timed hop Involved, s Uninvolved, s LSI, %
SFT 1
SFT 2
P Value
64.8 (62.3-67.3) 67.1 (64.6-69.5) 96.7 (95.0-97.6)
70.4 (68.2-72.7) 71.6 (69.4-73.8) 98.4 (97.5-99.3)
\.001 \.001 .063
66.8 (64.6-69.1) 69.7 (67.4-72.1) 96.1 (94.8-97.0)
72.1 (70.2-74.0) 72.9 (71.0-74.9) 99.0 (98.1-99.8)
\.001 \.001 \.001
55.7 (52.5-59.0) 57.6 (55.0-60.3) 96.4 (92.9-97.6)
59.1 (56.4-61.7) 59.7 (57.0-62.4) 99.0 (97.8-100.3)
.031 .068 .136
17.6 (11.5-23.7) 25.8 (17.4-34.1) 99.7 (54.3-121.5)
38.2 (13.3-63.0) 45.5 (19.3-71.6) 87.4 (65.6-109.2)
.119 .153 .628
21.4 (19.9-23.0) 27.9 (26.3-29.5) 77.0 (73.2-79.5)
28.1 (26.3-29.8) 31.8 (29.6-34.0) 89.5 (87.0-92.0)
\.001 \.001 \.001
77.6 (74.9-80.4) 88.2 (85.5-90.8) 88.5 (86.2-91.4)
85.9 (82.7-89.2) 90.9 (87.4-94.3) 96.1 (93.2-99.1)
\.001 .068 \.001
111.1 (99.4-122.8) 140.4 (126.4-154.4) 78.2 (73.3-80.9)
137.0 (126.7-147.2) 152.8 (141.3-164.2) 90.3 (87.5-93.0)
\.001 .056 \.001
359.3 (323.1-395.4) 420.5 (384.8-456.2) 85.9 (78.7-89.6)
415.1 (382.0-448.3) 455.2 (410.9-499.5) 91.6 (87.9-95.4)
.006 .175 .160
326.5 (289.5-363.5) 394.7 (343.0-446.5) 84.5 (79.8-87.4)
389.8 (362.6-416.9) 425.7 (394.3-457.0) 92.3 (89.4-95.1)
\.001 .154 .003
2.77 (2.54-3.00) 2.31 (2.15-2.47) 85.3 (80.9-88.2)
2.27 (2.11-2.43) 2.10 (1.94-2.25) 92.8 (89.9-95.7)
\.001 .002 .001
a Values are reported as mean (95% CI). Bolded text indicates statistically significant difference between groups (P \ .05). LSI, Limb Symmetry Index; SFT, Standard Functional Test.
Absolute changes were seen in the involved limb for single-leg anterolateral reach (from 65.6 cm to 71.7 cm, P \ .001), single-leg anteromedial reach (from 66.9 cm to 72.2 cm, P \ .001), retro step-up (from 22.6 cm to 28.6 cm, P = .007), single-leg squat (from 80.1° to 86.5°, P = .048), single-leg hop (from 112.4 cm to 141.2 cm, P = .028), crossover triple hop (from 329.1 cm to 414.3 cm, P = .025), and timed hop (from 2.42 s to 2.02 s, P = .032). Absolute changes were seen in the uninvolved limb for single-leg anterolateral reach (from 66.9 cm to 73.0 cm, P \ .001), single-leg anteromedial reach (from 68.4 cm to 72.8 cm, P \ .001), retro step-up (from 29.1 cm to 31.7 cm, P = .014), single-leg hop (from 141.4 cm to 153.5 cm, P = .007), and timed hop (from 2.06 s to 1.87 s, P = .042).
LSI changed in retro step-up (from 78.1% to 90.3%, P \ .001), single-leg squat (from 87.1% to 97.0% of the uninvolved limb, P = .020), single-leg hop (from 79.1% to 91.4%, P \ .001), and crossover triple hop (from 80.2% to 92.6%, P = .008).
DISCUSSION Our data indicate that uninvolved limb ability does not decrease during rehabilitation and instead shows improvement in several of the SFT component tests. The involved limb showed greater improvement than the uninvolved limb and showed improvement in more of the individual
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100
*
90
Inial SFT Final SFT
80
Measured Value
70
*
* *
60 50
*
40
*
*
30
*
20
*
10 0
Stork– Single-Leg Single-Leg Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up (sec) (cm) (cm) (sec) (cm)
Single-Leg Squat (deg)
Single-Leg Single-Leg Crossover Timed Hop Triple Hop Triple Hop Hop (dm) (dm) (dm) (sec ×10)
Figure 1. Comparison of involved limb performance during the first Standard Functional Test (SFT) and last SFT, in all patients with multiple SFTs (means and 95% CIs). Some units were converted from centimeters to decimeters for ease of display. *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial.
100
Inial SFT Final SFT
90 80
*
*
Measured Value
70 60 50 40
* *
30 20 10 0
Single-Leg Single-Leg Stork– Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up (cm) (cm) (sec) (sec) (cm)
Single-Leg Squat (deg)
Single-Leg Single-Leg Crossover Timed Hop Triple Hop Triple Hop Hop (dm) (dm) (dm) (sec ×10)
Figure 2. Comparison of uninvolved limb performance during the first Standard Functional Test (SFT) and last SFT in all patients with multiple SFTs (means and 95% CIs). Some units were converted from centimeters to decimeters for ease of display. *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial. tests. This is consistent with previous studies in ACL reconstruction patients, including one from Reid et al,29 who showed early improvements in both limbs, followed by continued improvements in the involved limb only, with corresponding LSI increases. These authors argued that this early effect represents motor learning acquired during the testing itself and that the later LSI increases represent true improvement in the involved limb. In our study, which involved a sizable study population and a long postoperative period, the increased involved limb ability was comparable and consistent with this theory. Perhaps most crucial was that the uninvolved limb ability did not decrease, as this could undermine the legitimacy of LSI testing. Based on these findings, LSI scoring appears
to be an appropriate method of detecting functional improvement and evaluating rehabilitation progress. Of all the tests included in our functional testing protocol, hop tests have received the most attention in previous literature.8,14,28 All 4 of the hop tests in our study showed initial LSI below 90%. Three of the 4 hop tests (single-leg hop, crossover triple hop, and timed hop) showed significant LSI improvement, and all hop tests showed final LSI greater than 90% at an average of 28 weeks. At 8 months postoperatively, Mohammadi et al21 also found most hop test LSIs to be above 90%. In a specific test example, the single-leg hop showed LSI improvements of more than 10 percentage points in our study. Reid et al29 found that LSI increased by 5.3 percentage points in the single-
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150
Inial SFT Final SFT
140
Limb Symmetry Index, %
130 120 110 100
* *
*
*
*
*
90 80 70 60 50
Single-Leg Single-Leg Stork– Stork– Retro Reach, AL Reach, AM Eyes Open Eyes Closed Step-up
Single-Leg Squat
Single-Leg Single-Leg Crossover Hop Triple Hop Triple Hop
Timed Hop
Figure 3. Comparison of the Limb Symmetry Index scores during the first Standard Functional Test (SFT) and last SFT, in all patients with multiple SFTs (means and 95% CIs). *Statistically significant change (P \ .05). AL, anterolateral; AM, anteromedial. leg hop over 22 weeks. While the minimal clinically important change has not been established for the single-leg hop, our study found even greater LSI increases over a longer time period, and we believe that this result was especially robust. Strong test-retest reliability for these 4 hop tests has been demonstrated by previous authors.11,16,29 We therefore conclude that these tests can provide useful information regarding functional deficits and are appropriate for use in evaluating rehabilitation progress. Our study also identified additional tests in our SFT protocol that showed initial LSI asymmetry and improvement during rehabilitation and may therefore be useful complements to hop testing. The single-leg squat and retro step-up tests showed initial LSI below 90%. Both tests showed significant LSI improvement in both analyses, and single-leg anteromedial reach showed LSI improvements in the larger analysis only. Retro step-up showed LSI improvement of more than 10 percentage points in both analyses. Again, although the minimal clinically important change has not been established, we believe that this robust outcome indicates a high utility for this test in functional evaluation. These 3 additional tests have not been as extensively studied in the literature, and test-retest reliability data are not available. These tests, however, may have high value in a functional testing protocol, especially since they can be performed earlier than hop tests. Regardless of the SFT battery used, our study also provides some general guidance for the use of functional testing during rehabilitation. First, since the uninvolved limb’s abilities may improve during rehabilitation, we recommend that the LSI always be calculated using measurements of both limbs from the same date. LSI calculations based on uninvolved limb ability from a previous date—for instance, a benchmark obtained at the beginning of rehabilitation—will not account for improvements in uninvolved limb ability and may therefore overestimate improvements in the LSI. Second, since many tests showed
improvement beyond 6 months, rehabilitation efforts are likely beneficial even after this time point. Consistent with what we see clinically, many patients are not fully rehabilitated by 6 months and are aided by further physical therapy beyond this time. Persistent LSI asymmetry at 6 months postoperatively can be used as an indication for more intensive rehabilitation regimens and potentially can improve the probability of successful return to play. Recovery from ACL reconstruction can be slow, with only 33% of patients attempting competitive sport by 12 months postoperatively.4,15 Ultimately, only 43% of athletes successfully return to their preinjury level of competition, and upon returning, athletes face a significantly higher chance of contralateral ACL tear (19%) and ipsilateral graft rupture (6%) within 12 months.20,26 To improve these outcomes, rehabilitation regimens are becoming increasingly evidence-based, and many have incorporated functional testing protocols.8,14,24,28,35,38 However, the literature has not yet established a relationship between SFT performance and successful return to play or lower reinjury rates.4 While one previous study found that ACL reconstruction patients with LSI higher than 85% in the single-leg hop and crossover triple hop were more likely to attempt return to play, it did not examine the success of those attempts.4 A different study of 35 nonoperative ACL-deficient patients found no correlation between hop test LSI scores and pain, swelling, or giving way upon return to sport.6 Therefore, although functional testing has found widespread use, future studies need to further examine the correlation between SFT performance and patient outcomes. Our study was limited by its retrospective nature. Although SFTs were performed at the same facility, rehabilitation depends upon the quality of rehabilitation effort, something that was not possible to standardize among patients. Additionally, the postoperative timing of each SFT varied between patients because of the variable rate of progression with the rehabilitation process among patients.
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Although we attempted to standardize SFT timing with our additional 4-month to 6-month analysis, fewer than half of the patients were eligible for inclusion in this more stringent time frame. It also should be noted that although we revealed functional deficits in several SFT components and subsequent improvement, we cannot conclude that this improvement translated into superior outcomes for the patient. Future studies should seek to correlate SFT performance with readiness to return to play and lower reinjury rates.
CONCLUSION During the rehabilitation process after ACL reconstruction, SFT testing successfully detects improvement in both the LSI and the involved limb’s absolute ability. There were some comparatively smaller increases, and no decreases, in the functional ability of the uninvolved limb. An increased LSI therefore reflects a true increase in the involved limb’s function, rather than a spurious result due to a decrease in the ability of the uninvolved limb. Based on our subjects’ initial performance below 90% LSI and subsequent improvement, our study suggests that single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop are highly useful for detecting functional asymmetry and tracking improvement in the involved limb.
ACKNOWLEDGMENT The authors acknowledge TRIA Orthopaedic Center for providing the workspace needed to perform the data collection and analysis for this study. They thank Megan Reams and the staff of TRIA Orthopaedic Center for coordinating and facilitating the logistics of this study and for helping to collect the outcomes data. They also thank Adam Meierbachtol and Amanda LeValley for their assistance creating the online video supplements.
A Video Supplement for this article is available in the online version or at http://ajsm.sagepub.com/supplemental.
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