Original Article
139
Medial Patellofemoral Ligament (MPFL) Reconstruction for the Treatment of Patellofemoral Instability Rick P. Csintalan, MD1 L. Daniel Latt, MD, PhD2 Maria Cs Inacio, PhD5 Donald C. Fithian, MD4
Stefan Fornalski, MD3
1 Department of Orthopedics, Southern California Permanente
Medical Group, Orange County, Irvine, California 2 Department of Orthopedic Surgery, University of Arizona, Tuscon, Arizona 3 Department of Orthopedic Surgery, Kaiser Permanente, Irvine, California 4 Department of Orthopedic Surgery, Kaiser Permanente, San Diego, California 5 Department of Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, California
Kian Raiszadeh, MD4
Address for correspondence Rick P. Csintalan, MD, Department of Orthopedics, Southern California Permanente Medical Group, Orange County, 6670 Alton Parkway, Irvine, CA 92618 (e-mail: [email protected]).
Abstract
Keywords
► ► ► ►
patellofemoral instability MPFL reconstruction
Patellofemoral instability can be a disabling problem. Numerous techniques are employed for its treatment. Medial patellofemoral ligament (MPFL) reconstruction in combination with other procedures has been explored by many orthopedic surgeons. The purpose of the study was to determine the effectiveness of isolated MPFL reconstruction in treating the symptoms associated with patellofemoral instability, preventing recurrence of patella dislocation, and returning patients to preinjury level of activity. This is a case series study. We conducted a clinical follow-up study on 56 knees (49 patients) after MPFL reconstruction for recurrent patellar instability with a mean follow-up of 4.3 years (range, 1.1–6.8). A single MPFL reconstruction technique was performed in all cases. Patient outcomes were evaluated using: International Knee Documentation Committee (IKDC) subjective knee form, Tegner activity score, functional hop test, and radiographs. Mean age at time of surgery was 24 years old (range, 13–49). Females comprised 75% of the sample. Mean interval from injury to surgery was 7.2 8.6 years (range, 51 days–37 years). At follow-up, there were no recurrent dislocations reported, patella subluxation in 6 (11%) cases, and radiographic degenerative changes were none to mild in all patients. The series mean IKDC scores at follow-up was 76.3 19.2 (range, 30–99), and Tegner activity scores were 5.6 2.5. MPFL reconstruction is an option for treating the symptoms of patellar instability, preventing recurrent dislocation, and returning patients near to their preinjury level of activity. The level of evidence is IV.
Patellofemoral instability and recurrent dislocation can cause significant functional impairment in young active patients.1 More than 100 different surgical procedures have been described for the treatment of patellar instability. The majority of
proposed procedures treat patellar instability by altering the pull of the extensor mechanism.2 Such techniques provide only indirect stabilization, as they do not address the underlying pathoanatomy. Several studies have identified the medial
received May 13, 2013 accepted after revision September 6, 2013 published online November 13, 2013
Copyright © 2014 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0033-1360652. ISSN 1538-8506.
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J Knee Surg 2014;27:139–146.
MPFL Reconstruction for the Treatment of Patellofemoral Instability patellofemoral ligament (MPFL) as the primary stabilizer against lateral patellar displacement.3–5 MPFL reconstruction is designed to treat the essential lesion in recurrent patellar instability by restoring the passive medial restraint. Several authors have reported on the use of MPFL reconstruction in combination with other procedures.6–10 However, few studies have reported on MPFL reconstruction as an isolated procedure to treat recurrent patellofemoral instability. We have used the MPFL reconstruction as a stand-alone procedure, on patients without significant clinical evidence of malalignment, to treat recurrent patellar instability since 2001. Several trials have reported on the effectiveness of MPFL reconstruction in preventing redislocation,7–17 however, only a few have examined pain relief8,13,17 or return to activity.7,17 The purpose of this study was to determine the effectiveness of MPFL reconstruction in preventing recurrence of patella dislocation and returning patients to their preinjury level of activity. In addition, we hoped to gain insight into the factors associated with recurrent instability after MPFL reconstruction. Our hypotheses were that MPFL reconstruction is effective at preventing recurrent patellar dislocations and at returning patients to preinjury level of activity.
Methods Subjects A series of 110 consecutive patients who had undergone isolated MPFL reconstruction between January 2001 and August 2006 were identified as potential study subjects. All procedures were performed by seven surgeons at three locations. Although the majority of the operations were done by the two senior authors (R.P.C. and D.C.F.), five other surgeons performed one to three cases each. Eighteen patients were excluded because they either had surgery before the MPFL reconstruction or had unrelated subsequent surgery on the same knee that could affect their postoperative examination and outcomes. Twenty-three patients could not be reached and six patients declined to participate. Of the remaining 63 subjects, 4 patients were unable to be consented and 3 became ineligible after enrollment in the study secondary to not meeting the inclusion criteria. Seven patients declined a physical exam and X-rays, and completed subjective questionnaires only. This left 56 knees in 49 patients that were available for both clinical and radiographic follow-up.
Procedure The surgical procedure began with examination under anesthesia to confirm patellar instability. Knee arthroscopy was then performed to assess patellar tracking and mobility, to look for articular cartilage injury or degenerative changes, and to debride unstable chondral flaps. The ipsilateral semitendinosus tendon was harvested in a standard fashion. The graft was trimmed to a length 240 mm and the ends were whipstitched. The graft was then folded in half, a No. 5 suture was placed through the loop, and the folded end was whipstitched for 25 mm. A longitudinal incision, as long as the patella, was made half-way between the midline and the medial border of the The Journal of Knee Surgery
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patella. The medial third of the patella was exposed by subperiosteal dissection. A 4.5-mm drill hole was placed on the medial side of the upper one-third of the patella adjacent to the articular margin and a second hole was drilled on the anterior surface of the patella approximately 8 mm from the medial border. The two drill holes were connected with a curved curette. A second tunnel was created in similar fashion at a point half-way down the length of the patella. A third incision was made just anterior to the palpable ridge connecting the medial femoral epicondyle and the adductor tubercle. A long curved clamp was used to develop the selected interval between layers 2 and 3 from the patellar incision to the medial femoral epicondyle. A Beath pin was then placed at the insertion site of the MPFL near the medial epicondyle, the pin was passed toward the lateral side of the femur. A loop of suture was passed around the Beath pin and through one of the patellar tunnels. The knee was ranged to evaluate isometry and the location of the femoral pin was adjusted accordingly. A 7 mm 25 mm socket was then reamed. The looped end of the graft was then docked into the femoral tunnel and fixed with a 7 mm 23 mm absorbable interference screw. Next, the free ends of the graft were passed through the retinacular interval and then through their patellar tunnels using a curved suture passer. The free graft arms were then folded back and sutured on themselves. The graft was fixed at the greatest length as determined by isometry. Care was taken to not over tension the graft. Patellar mobility and range of motion were checked. Excess graft was removed. The remnant of the native MPFL was sutured to the graft, and the retinaculum was closed over the graft. The wounds were closed in standard fashion. Following surgery, subjects were allowed weight bearing as tolerated in a brace locked in extension. Bracing was continued for 4 weeks during ambulation to prevent falls until adequate quadriceps control was regained.
Clinical Evaluation At 24 months or longer, patients were examined by two sports medicine fellows in training, not involved in the patients’ care, during a return office visit. One exception was a patient with bilateral MPFL reconstructions, who had greater than 2 years follow-up on the first knee, but the more recent knee having only a 14-month follow-up was included in the study. A physical, radiographic, and functional examination were performed during the visit. History was obtained from the patient using a modified version of the 2000 International Knee Documentation Committee (IKDC) knee history form (Appendix A), the modification included evaluation/recording of the medial and lateral patellar glide of the index and opposite knee. Patient-reported outcomes were also collected during this visit, using the 2000 IKDC subjective knee form.18 The level of activity at follow-up was compared with the level of activity before injury using the Tegner activity scale.19
Physical Examination The physical examination was performed according to the IKDC knee examination form.20 It consisted of the assessment
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Functional Testing Function was assessed with the use of the single-leg hop for distance. Subjects were asked to hop as far as they could three times on each leg. The ratio of the average distance hopped on the operated compared with the nonoperated leg was calculated. Performance was assigned to one of four grades: greater than 90, 89 to 76, 75 to 50, or less than 50% of contralateral. Subjects with bilateral surgery were excluded from functional testing.
Radiographic Examination Weight bearing anterior-posterior (AP), lateral, and axial patellofemoral radiographs were obtained. The AP view was made in full extension. The other two views were made with 30 degrees of knee flexion. A true lateral projection of the distal femur was sought such that the condyles overlapped perfectly in the projection. If the distance between the posterior projections of the condyles measured greater than 2 mm, a second attempt was made to obtain a true lateral radiograph. The anteroposterior radiograph was examined for loss of medial or lateral joint space. The lateral radiograph was used to determine loss of anterior or posterior joint space, patellar height (Caton-Deschamps ratio), crossing sign, and prominence. The axial radiograph was evaluated for patellofemoral joint space loss, sulcus angle, congruence angle, and lateral patellofemoral angle of Laurin.22 Femoral tunnel placement was assessed using Schottle radiographic criteria.23
Statistical Analysis Descriptive statistics were used to summarize the series presented. Frequencies and proportions described categorical variables. Means, standard deviations, and ranges described continuous variables.
Results The final study sample consisted of 56 knees in 49 patients. There were 12 male and 37 female subjects. The mechanism of injury, indication for surgery, and number of bilateral cases are shown in ►Table 1. Mean age at surgery was 24 years (range, 13–49 years). Mean interval from injury to surgery was 7.2 8.6 years (range, 51 days–37 years). Clinical and radiographic follow-up was performed at 4.3 1.4 years (range, 1.1–6.8 years) after surgery.
Table 1 Knee history Total sample (N ¼ 56) N
%
Nontraumatic sudden onset
13
23
Nontraumatic gradual onset
2
4
Traumatic noncontact onset
32
57
Traumatic contact onset
9
16
Recurrent instability
52
93
Primary dislocation
1
2
Not reported
3
5
14
25
Mechanism of injury
Indication for surgery
Bilateral surgery
Function and Activity Scores Mean postoperative IKDC scores averaged 76.3 19.2 (range, 30–99). Analysis of the patients with an IKDC score of 70 or below did not correlate with poor femoral tunnel placement, trochlea dysplasia, patellofemoral arthritis, subjective feeling of subluxation, or deficiency of the medial check rein. Postreconstruction Tegner activity scores averaged 5.6 2.5, whereas preinjury scores averaged 6.1 2.7.
Physical Examination Knee flexion angle averaged 135 degrees (range, 110–150 degrees), with four knees flexing to 120 degrees or less. Thigh muscle atrophy was not reported, as thigh circumference difference averaged 0.3 cm (range, 3.5 to þ 5.0 cm), where positive values indicate that the index thigh has a larger circumference. Passive lateral displacement (patellar glide) at 30 degrees of knee flexion averaged 1.6 0.8 quadrants for the operated knee versus 2.0 0.9 quadrants for the nonoperated knee, though this difference was not found to be statistically significantly different. The rest of the physical examination findings are detailed in ►Table 2.
Functional Testing Functional testing was performed in 39 knees, three patients were unable to or refused to perform the one-legged hop test, and 14 knees were excluded because of bilateral surgery. The patients who refused to hop were assigned to the < 50% group. The majority of subjects were able to hop more than 75% of the distance with the index extremity compared with the contralateral extremity.
Radiographic Evaluation Symptoms at Follow-Up No dislocations occurred following reconstruction. Patellar subluxation occurred in six cases (11%). The patients reported their pain at follow-up. Most often the pain was reported to be dull and retropatellar, or medial parapatellar. Catching or locking was reported in 13 knees.
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The measurements obtained from the radiographs are detailed in ►Table 3. Radiographs were not available for one subject. Perfect lateral radiographs with the posterior aspect of the femoral condyles being separated by less than 2 mm were only obtained in 24 cases. Troclear dysplasia was very common, with a crossing sign in 30 knees and The Journal of Knee Surgery
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of: generalized ligamentous laxity,21 limb alignment, difference in thigh circumference, joint effusion, J-sign, crepitus, peripatellar tenderness, range of motion, patellar grind, medial retinacular endpoint with lateral translation at 0 degree knee flexion, and apprehension and patellar glide at 30 degrees of knee flexion.
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Table 2 Physical exam Total Sample (N ¼ 56) Generalized laxity
Alignment
J-sign
%
Tight
1
2
Normal
34
61
Lax
20
36
Normal
40
71
Valgus
15
27
Missing
1
2
Present
20
36
Absent
36
64
None
55
98
Mild
1
2
Peripatellar tenderness
4
7
Patellar grind
18
32
Palpable endpoint
51
91
Effusion
Apprehension (index)
7
13
Apprehension (contralateral)
10
18
None
48
86
Mild
5
9
Moderate
3
5
Harvest site pathology
prominence in 36 knees. Lateral translation and tilting of the patella were also common. The congruence angle was positive (laterally translated) in 33 knees and the lateral patellofemoral angle of Laurin was less than 10 degrees (laterally tilted) in 33 knees. Patella alta (Caton-Deschamps ratio 1.2) was found in only nine knees. Degenerative changes were usually absent or mild. Femoral tunnel placement was found to be too anterior in 27 cases (49%) using the criteria of Schottle.23 No correlation was found between tunnel placement and subjective score.
Complications Complications included one case of painful hardware at the medial epicondyle requiring removal, one case of stiffness required manipulation under anesthesia (MUA), two cases of superficial infection that resolved with oral antibiotics (no surgical intervention was needed), and one case of extensor lag.
Discussion Reconstruction of the MPFL has become increasingly popular since the early 2000s and studies with small sample sizes have evaluated the efficacy of this treatment. The current study evaluated surgical outcomes and complications of the treatment of patellar instability with isolated MPFL reconstruction in a series of 49 patients with 56 knees. Moreover, this study determined the effectiveness of isolated MPFL reconstruction in: (1) preventing recurrent subluxation or dislocation and (2) returning the patient to preinjury level of activity. The Journal of Knee Surgery
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Surgical Outcomes The average postoperative IKDC score observed in the present case series (76.3) compares favorably with the study performed by of Ahmad et al (82.3).11 Similarly, the postoperative examination findings were in agreement with previous reports. Peripatellar tenderness was noted in 4 out of 56 knees in our study. Similarly, Drez et al noted one of the 15 patients evaluated had medial facet tenderness postoperatively.24 In contrast, Christiansen et al reported 43% (19/44) of their series had palpable pain at the medial patellar facet.13 In the present study, the averaged postoperative knee flexion angle was 135 degrees with four knees having 120 degrees or less. Several other studies reported a similar knee flexion loss postoperatively.13,24 Quadriceps atrophy was not observed, in the present study, as a significant problem. A thigh circumference difference averaged 0.3 cm, whereas quadriceps atrophy was reported in some other studies.16,24,25 A positive apprehension test was found in 7 of 56 (13%) operated knees in our series. Some other studies reported similar results,25,26 whereas others showed no patients with a positive postoperative apprehension test.11,24 Christiansen et al reported a postoperative positive apprehension sign in 41% (18/44) of patients.13 Deie et al reported on one patient with a retained apprehension sign which had medial instability postoperatively. Lateral retinacular reconstruction was performed and the apprehension sign disappeared.26 Our average passive lateral displacement (patellar glide) was 1.6 quadrants postoperatively. Comparable results were seen in other studies. Translations of 1.8, 1.6, and 1.25 were recorded after reconstruction.11,27
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Table 3 Radiographic exam Total sample (N ¼ 56)
N (%)
Crossing sign
30 (54%)
Prominence
36 (65%)
Sulcus angle (degrees), mean (SD), range
141 (9), (125–170) 7.5 (16.3), (47–40) 33 (60%)
Lateral patellofemoral angle of Laurin (degrees), mean (SD), range
4.0 (7.7), ( 13–20)
Lateral tilt ( 10 degrees)
17 (31%)
Patella alta (C-D ratio > 1.2)
9 (15%)
Patellofemoral joint space
Medial joint space
Lateral joint space
Femoral tunnel placement
Trochlear dysplasia was seen in 68% of patients in the present study, with a crossing sign in 30 knees and prominence in 36 knees out of 56 knees. In Steiner’s et al series, 36 of 41 knees (88%) had trochlear dysplasia.17 In contrast, Han et al excluded patients with high grade trochlea dysplasia from their series.27 Postoperatively, the sulcus angle, observed in the present study, averaged 141 degrees, and the congruence angle average was 7.5 degrees. Other studies found similar results, reporting congruence angles of 5 to 5.5 degrees on average.24,26 Patella alta was found in only 9 out of 56 knees in the current study. None of the patients had patella alta significant enough to require a distalization of the tibial tubercle. Ahmad et al reported 4 out of 22 patients had patella alta by Insall-Salvati ratios, and 6 had patella alta by Blackburne-Peel ratios.11 Out of 52 patients, 6 had patella alta based on the Insall-Salvati ratio, and 9 had patella alta based on the Blackburne-Peel ratios in the study by Han et al.27
None
35 (64%)
Mild
15 (27%)
Moderate
2 (4%)
Missing
3 (5%)
None
44 (79%)
Mild
8 (15%)
Moderate
2 (4%)
Severe
1 (2%)
None
50 (91%)
Mild
4 (7%)
Moderate
1 (2%)
Severe
0 (0%)
Normal
17 (31%)
Anterior
21 (38%)
anterior/distal
6 (11%)
Distal
8 (15%)
Proximal
3 (5%)
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Congruence angle (degrees), mean (SD), range Lateral patellar tilt (positive congruence angle)
patient required an evacuation of a postoperative hematoma, one patient had a graft advancement after loosening in a motor vehicle accident, and three patients had removal of painful hardware from the medial epicondyle.17 Ronga et al used transverse patellar tunnels, leading to anterior patellar cortex violation (without fracture) along the lateral aspect of the patella in two patients. Two other patients were unable to flex the knee beyond 90 degrees and underwent MUA to restore range of motion. Moreover, they had three patients with recurrent dislocation.16 Christiansen et al reported on five reoperations out of 44 reconstructions. In their study, one patient underwent MUA for knee flexion less than 90 degrees, three underwent symptomatic hardware removal from the medial epicondyle, and one patient had a transverse patellar fracture.13 In contrast, several other studies reported no postoperative complications.11,26,27
Pain Complications and Reoperations In our series, we found only a few postoperative complications. Drez et al reported one case of arthrofibrosis requiring MUA and one case of wound dehiscence that resolved with local wound care.24 Steiner et al had five reoperations: one
In the present study, 63% of patients reported significant pain relief. These results are nearly identical to those of Christiansen et al who found 64% of patients were completely pain free with activities of daily living, and 59% were pain free when engaging in sporting activities.13 The Journal of Knee Surgery
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Recurrent Instability
Strengths
In the present study, no recurrent dislocations occurred during the postoperative period. However, six cases of patellar subluxation (11%) were reported. One other study had similar results to our series,24 and some other studies reported no recurrent patellar dislocations or subluxations.11,17,25–27 In contrast, Ronga et al reported three patients with recurrent patellar instability out of 28 patients. All were male soccer players at the recreational level, and sustained the new episode of patellar dislocation 13 to 22 months after the index procedure.16 Christiansen et al reported 1 patient with a new dislocation 6 months postoperatively, and 3 patients with a sensation of subluxation out of 44 patients.13 The present study did not have enough subjects to assess risk factors for postoperative subluxation or dislocation.
Strengths of this study include the standard technique used by the surgeons. This decreases the variability in results that could be introduced by different techniques by many different surgeons. Isolated MPFL reconstruction was evaluated to determine the procedure’s effectiveness in re-establishing stability of the patellofemoral joint without introducing the effect of other concurrent procedures. The postoperative assessment of the series evaluated was performed by independent observers who were not involved with the patients’ surgery and follow-up care assuring minimal observer bias in the measurements obtained. The number of cases in this study, while small, is one of the largest series of such cases in the United States and can therefore provide some insight of the procedure and outcomes in the population seeking such care.
Function and Return to Activity In the present study, functional testing of a single-leg hop test was performed in 39 knees. Nineteen patients evaluated scored > 90% compared with the contralateral leg, 11 scored between 76 and 89%, 6 scored between 50 and 75%, and 3 scored less than 50%. In comparison, isokinetic strength testing revealed the operative limb was always significantly weaker than the contralateral limb in the study by Ronga et al.16 Christiansen et al study’s subjective patient assessment revealed that 80% of patients felt their knee function had improved.13 In the present study, Tegner activity score averaged 6.1 before injury and 5.6 after reconstruction. Similarly, Drez et al reported a preinjury score of 6.8 and 6.7 postoperatively.24 Steiner et al did not report a preinjury Tegner activity score, but the preoperative score was 3.1, which improved postreconstruction to 5.1.17 Ahmad et al reported a preoperative Tegner score of 3.6, this score improved to 5.6 postoperatively.11 Christiansen et al reported a mean postoperative Tegner activity score of 4.24
Conclusion In conclusion, our study supports the use of MPFL reconstruction in the treatment of episodic lateral patellar instability with no other significant comorbidities. The present study’s results are comparable to other series, had only a few minor complications, had no redislocations, and only 10% of patients reported subluxation events. Based on Tegner score, patients were able to return approximately the same preinjury level. Larger studies are needed to determine the risk factors for redislocation and to determine the effects of patella alta and trochlea dysplasia on outcome. Longer follow-up is needed to determine the risk of developing patellofemoral osteoarthritis.
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Limitations There are several limitations of the current study. First, this was a convenience sample of patients and selection bias could be present. In addition, a large number of eligible patients (42%) declined to enroll in the study and then a few others were subsequently excluded after enrollment due to unrelated complications or declined follow-up examination. Second, our study was retrospective and preoperative assessments are not available for comparison. The progression of IKDC scores could not be evaluated. Moreover, preoperative axial imaging (magnetic resonance imaging or computed tomography) to identify subjects with increased tibial tubercle to trochlear groove offset was not available. Finally, this study had insufficient statistical power to evaluate the effects of trochlear dysplasia or patella alta on outcomes after MPFL reconstruction or to answer questions about factors associated with recurrent dislocation or development of arthrosis. Another limitation was the early learning curve of the surgeons on the potential outcomes of the procedure. Since this initial cohort of patients, we have added intraoperative imaging to more accurately identify the femoral tunnel. The Journal of Knee Surgery
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Appendix A: Modified IKDC 2000 knee history form
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Medial Patellofemoral Ligament (MPFL) Reconstruction for the Treatment of Patellofemoral Instability Rick P. Csintalan, MD1 L. Daniel Latt, MD, PhD2 Maria Cs Inacio, PhD5 Donald C. Fithian, MD4
Stefan Fornalski, MD3
1 Department of Orthopedics, Southern California Permanente
Medical Group, Orange County, Irvine, California 2 Department of Orthopedic Surgery, University of Arizona, Tuscon, Arizona 3 Department of Orthopedic Surgery, Kaiser Permanente, Irvine, California 4 Department of Orthopedic Surgery, Kaiser Permanente, San Diego, California 5 Department of Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, California
Kian Raiszadeh, MD4
Address for correspondence Rick P. Csintalan, MD, Department of Orthopedics, Southern California Permanente Medical Group, Orange County, 6670 Alton Parkway, Irvine, CA 92618 (e-mail: [email protected]).
Abstract
Keywords
► ► ► ►
patellofemoral instability MPFL reconstruction
Patellofemoral instability can be a disabling problem. Numerous techniques are employed for its treatment. Medial patellofemoral ligament (MPFL) reconstruction in combination with other procedures has been explored by many orthopedic surgeons. The purpose of the study was to determine the effectiveness of isolated MPFL reconstruction in treating the symptoms associated with patellofemoral instability, preventing recurrence of patella dislocation, and returning patients to preinjury level of activity. This is a case series study. We conducted a clinical follow-up study on 56 knees (49 patients) after MPFL reconstruction for recurrent patellar instability with a mean follow-up of 4.3 years (range, 1.1–6.8). A single MPFL reconstruction technique was performed in all cases. Patient outcomes were evaluated using: International Knee Documentation Committee (IKDC) subjective knee form, Tegner activity score, functional hop test, and radiographs. Mean age at time of surgery was 24 years old (range, 13–49). Females comprised 75% of the sample. Mean interval from injury to surgery was 7.2 8.6 years (range, 51 days–37 years). At follow-up, there were no recurrent dislocations reported, patella subluxation in 6 (11%) cases, and radiographic degenerative changes were none to mild in all patients. The series mean IKDC scores at follow-up was 76.3 19.2 (range, 30–99), and Tegner activity scores were 5.6 2.5. MPFL reconstruction is an option for treating the symptoms of patellar instability, preventing recurrent dislocation, and returning patients near to their preinjury level of activity. The level of evidence is IV.
Patellofemoral instability and recurrent dislocation can cause significant functional impairment in young active patients.1 More than 100 different surgical procedures have been described for the treatment of patellar instability. The majority of
proposed procedures treat patellar instability by altering the pull of the extensor mechanism.2 Such techniques provide only indirect stabilization, as they do not address the underlying pathoanatomy. Several studies have identified the medial
received May 13, 2013 accepted after revision September 6, 2013 published online November 13, 2013
Copyright © 2014 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0033-1360652. ISSN 1538-8506.
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J Knee Surg 2014;27:139–146.
MPFL Reconstruction for the Treatment of Patellofemoral Instability patellofemoral ligament (MPFL) as the primary stabilizer against lateral patellar displacement.3–5 MPFL reconstruction is designed to treat the essential lesion in recurrent patellar instability by restoring the passive medial restraint. Several authors have reported on the use of MPFL reconstruction in combination with other procedures.6–10 However, few studies have reported on MPFL reconstruction as an isolated procedure to treat recurrent patellofemoral instability. We have used the MPFL reconstruction as a stand-alone procedure, on patients without significant clinical evidence of malalignment, to treat recurrent patellar instability since 2001. Several trials have reported on the effectiveness of MPFL reconstruction in preventing redislocation,7–17 however, only a few have examined pain relief8,13,17 or return to activity.7,17 The purpose of this study was to determine the effectiveness of MPFL reconstruction in preventing recurrence of patella dislocation and returning patients to their preinjury level of activity. In addition, we hoped to gain insight into the factors associated with recurrent instability after MPFL reconstruction. Our hypotheses were that MPFL reconstruction is effective at preventing recurrent patellar dislocations and at returning patients to preinjury level of activity.
Methods Subjects A series of 110 consecutive patients who had undergone isolated MPFL reconstruction between January 2001 and August 2006 were identified as potential study subjects. All procedures were performed by seven surgeons at three locations. Although the majority of the operations were done by the two senior authors (R.P.C. and D.C.F.), five other surgeons performed one to three cases each. Eighteen patients were excluded because they either had surgery before the MPFL reconstruction or had unrelated subsequent surgery on the same knee that could affect their postoperative examination and outcomes. Twenty-three patients could not be reached and six patients declined to participate. Of the remaining 63 subjects, 4 patients were unable to be consented and 3 became ineligible after enrollment in the study secondary to not meeting the inclusion criteria. Seven patients declined a physical exam and X-rays, and completed subjective questionnaires only. This left 56 knees in 49 patients that were available for both clinical and radiographic follow-up.
Procedure The surgical procedure began with examination under anesthesia to confirm patellar instability. Knee arthroscopy was then performed to assess patellar tracking and mobility, to look for articular cartilage injury or degenerative changes, and to debride unstable chondral flaps. The ipsilateral semitendinosus tendon was harvested in a standard fashion. The graft was trimmed to a length 240 mm and the ends were whipstitched. The graft was then folded in half, a No. 5 suture was placed through the loop, and the folded end was whipstitched for 25 mm. A longitudinal incision, as long as the patella, was made half-way between the midline and the medial border of the The Journal of Knee Surgery
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patella. The medial third of the patella was exposed by subperiosteal dissection. A 4.5-mm drill hole was placed on the medial side of the upper one-third of the patella adjacent to the articular margin and a second hole was drilled on the anterior surface of the patella approximately 8 mm from the medial border. The two drill holes were connected with a curved curette. A second tunnel was created in similar fashion at a point half-way down the length of the patella. A third incision was made just anterior to the palpable ridge connecting the medial femoral epicondyle and the adductor tubercle. A long curved clamp was used to develop the selected interval between layers 2 and 3 from the patellar incision to the medial femoral epicondyle. A Beath pin was then placed at the insertion site of the MPFL near the medial epicondyle, the pin was passed toward the lateral side of the femur. A loop of suture was passed around the Beath pin and through one of the patellar tunnels. The knee was ranged to evaluate isometry and the location of the femoral pin was adjusted accordingly. A 7 mm 25 mm socket was then reamed. The looped end of the graft was then docked into the femoral tunnel and fixed with a 7 mm 23 mm absorbable interference screw. Next, the free ends of the graft were passed through the retinacular interval and then through their patellar tunnels using a curved suture passer. The free graft arms were then folded back and sutured on themselves. The graft was fixed at the greatest length as determined by isometry. Care was taken to not over tension the graft. Patellar mobility and range of motion were checked. Excess graft was removed. The remnant of the native MPFL was sutured to the graft, and the retinaculum was closed over the graft. The wounds were closed in standard fashion. Following surgery, subjects were allowed weight bearing as tolerated in a brace locked in extension. Bracing was continued for 4 weeks during ambulation to prevent falls until adequate quadriceps control was regained.
Clinical Evaluation At 24 months or longer, patients were examined by two sports medicine fellows in training, not involved in the patients’ care, during a return office visit. One exception was a patient with bilateral MPFL reconstructions, who had greater than 2 years follow-up on the first knee, but the more recent knee having only a 14-month follow-up was included in the study. A physical, radiographic, and functional examination were performed during the visit. History was obtained from the patient using a modified version of the 2000 International Knee Documentation Committee (IKDC) knee history form (Appendix A), the modification included evaluation/recording of the medial and lateral patellar glide of the index and opposite knee. Patient-reported outcomes were also collected during this visit, using the 2000 IKDC subjective knee form.18 The level of activity at follow-up was compared with the level of activity before injury using the Tegner activity scale.19
Physical Examination The physical examination was performed according to the IKDC knee examination form.20 It consisted of the assessment
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Functional Testing Function was assessed with the use of the single-leg hop for distance. Subjects were asked to hop as far as they could three times on each leg. The ratio of the average distance hopped on the operated compared with the nonoperated leg was calculated. Performance was assigned to one of four grades: greater than 90, 89 to 76, 75 to 50, or less than 50% of contralateral. Subjects with bilateral surgery were excluded from functional testing.
Radiographic Examination Weight bearing anterior-posterior (AP), lateral, and axial patellofemoral radiographs were obtained. The AP view was made in full extension. The other two views were made with 30 degrees of knee flexion. A true lateral projection of the distal femur was sought such that the condyles overlapped perfectly in the projection. If the distance between the posterior projections of the condyles measured greater than 2 mm, a second attempt was made to obtain a true lateral radiograph. The anteroposterior radiograph was examined for loss of medial or lateral joint space. The lateral radiograph was used to determine loss of anterior or posterior joint space, patellar height (Caton-Deschamps ratio), crossing sign, and prominence. The axial radiograph was evaluated for patellofemoral joint space loss, sulcus angle, congruence angle, and lateral patellofemoral angle of Laurin.22 Femoral tunnel placement was assessed using Schottle radiographic criteria.23
Statistical Analysis Descriptive statistics were used to summarize the series presented. Frequencies and proportions described categorical variables. Means, standard deviations, and ranges described continuous variables.
Results The final study sample consisted of 56 knees in 49 patients. There were 12 male and 37 female subjects. The mechanism of injury, indication for surgery, and number of bilateral cases are shown in ►Table 1. Mean age at surgery was 24 years (range, 13–49 years). Mean interval from injury to surgery was 7.2 8.6 years (range, 51 days–37 years). Clinical and radiographic follow-up was performed at 4.3 1.4 years (range, 1.1–6.8 years) after surgery.
Table 1 Knee history Total sample (N ¼ 56) N
%
Nontraumatic sudden onset
13
23
Nontraumatic gradual onset
2
4
Traumatic noncontact onset
32
57
Traumatic contact onset
9
16
Recurrent instability
52
93
Primary dislocation
1
2
Not reported
3
5
14
25
Mechanism of injury
Indication for surgery
Bilateral surgery
Function and Activity Scores Mean postoperative IKDC scores averaged 76.3 19.2 (range, 30–99). Analysis of the patients with an IKDC score of 70 or below did not correlate with poor femoral tunnel placement, trochlea dysplasia, patellofemoral arthritis, subjective feeling of subluxation, or deficiency of the medial check rein. Postreconstruction Tegner activity scores averaged 5.6 2.5, whereas preinjury scores averaged 6.1 2.7.
Physical Examination Knee flexion angle averaged 135 degrees (range, 110–150 degrees), with four knees flexing to 120 degrees or less. Thigh muscle atrophy was not reported, as thigh circumference difference averaged 0.3 cm (range, 3.5 to þ 5.0 cm), where positive values indicate that the index thigh has a larger circumference. Passive lateral displacement (patellar glide) at 30 degrees of knee flexion averaged 1.6 0.8 quadrants for the operated knee versus 2.0 0.9 quadrants for the nonoperated knee, though this difference was not found to be statistically significantly different. The rest of the physical examination findings are detailed in ►Table 2.
Functional Testing Functional testing was performed in 39 knees, three patients were unable to or refused to perform the one-legged hop test, and 14 knees were excluded because of bilateral surgery. The patients who refused to hop were assigned to the < 50% group. The majority of subjects were able to hop more than 75% of the distance with the index extremity compared with the contralateral extremity.
Radiographic Evaluation Symptoms at Follow-Up No dislocations occurred following reconstruction. Patellar subluxation occurred in six cases (11%). The patients reported their pain at follow-up. Most often the pain was reported to be dull and retropatellar, or medial parapatellar. Catching or locking was reported in 13 knees.
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The measurements obtained from the radiographs are detailed in ►Table 3. Radiographs were not available for one subject. Perfect lateral radiographs with the posterior aspect of the femoral condyles being separated by less than 2 mm were only obtained in 24 cases. Troclear dysplasia was very common, with a crossing sign in 30 knees and The Journal of Knee Surgery
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of: generalized ligamentous laxity,21 limb alignment, difference in thigh circumference, joint effusion, J-sign, crepitus, peripatellar tenderness, range of motion, patellar grind, medial retinacular endpoint with lateral translation at 0 degree knee flexion, and apprehension and patellar glide at 30 degrees of knee flexion.
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Table 2 Physical exam Total Sample (N ¼ 56) Generalized laxity
Alignment
J-sign
%
Tight
1
2
Normal
34
61
Lax
20
36
Normal
40
71
Valgus
15
27
Missing
1
2
Present
20
36
Absent
36
64
None
55
98
Mild
1
2
Peripatellar tenderness
4
7
Patellar grind
18
32
Palpable endpoint
51
91
Effusion
Apprehension (index)
7
13
Apprehension (contralateral)
10
18
None
48
86
Mild
5
9
Moderate
3
5
Harvest site pathology
prominence in 36 knees. Lateral translation and tilting of the patella were also common. The congruence angle was positive (laterally translated) in 33 knees and the lateral patellofemoral angle of Laurin was less than 10 degrees (laterally tilted) in 33 knees. Patella alta (Caton-Deschamps ratio 1.2) was found in only nine knees. Degenerative changes were usually absent or mild. Femoral tunnel placement was found to be too anterior in 27 cases (49%) using the criteria of Schottle.23 No correlation was found between tunnel placement and subjective score.
Complications Complications included one case of painful hardware at the medial epicondyle requiring removal, one case of stiffness required manipulation under anesthesia (MUA), two cases of superficial infection that resolved with oral antibiotics (no surgical intervention was needed), and one case of extensor lag.
Discussion Reconstruction of the MPFL has become increasingly popular since the early 2000s and studies with small sample sizes have evaluated the efficacy of this treatment. The current study evaluated surgical outcomes and complications of the treatment of patellar instability with isolated MPFL reconstruction in a series of 49 patients with 56 knees. Moreover, this study determined the effectiveness of isolated MPFL reconstruction in: (1) preventing recurrent subluxation or dislocation and (2) returning the patient to preinjury level of activity. The Journal of Knee Surgery
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Surgical Outcomes The average postoperative IKDC score observed in the present case series (76.3) compares favorably with the study performed by of Ahmad et al (82.3).11 Similarly, the postoperative examination findings were in agreement with previous reports. Peripatellar tenderness was noted in 4 out of 56 knees in our study. Similarly, Drez et al noted one of the 15 patients evaluated had medial facet tenderness postoperatively.24 In contrast, Christiansen et al reported 43% (19/44) of their series had palpable pain at the medial patellar facet.13 In the present study, the averaged postoperative knee flexion angle was 135 degrees with four knees having 120 degrees or less. Several other studies reported a similar knee flexion loss postoperatively.13,24 Quadriceps atrophy was not observed, in the present study, as a significant problem. A thigh circumference difference averaged 0.3 cm, whereas quadriceps atrophy was reported in some other studies.16,24,25 A positive apprehension test was found in 7 of 56 (13%) operated knees in our series. Some other studies reported similar results,25,26 whereas others showed no patients with a positive postoperative apprehension test.11,24 Christiansen et al reported a postoperative positive apprehension sign in 41% (18/44) of patients.13 Deie et al reported on one patient with a retained apprehension sign which had medial instability postoperatively. Lateral retinacular reconstruction was performed and the apprehension sign disappeared.26 Our average passive lateral displacement (patellar glide) was 1.6 quadrants postoperatively. Comparable results were seen in other studies. Translations of 1.8, 1.6, and 1.25 were recorded after reconstruction.11,27
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Table 3 Radiographic exam Total sample (N ¼ 56)
N (%)
Crossing sign
30 (54%)
Prominence
36 (65%)
Sulcus angle (degrees), mean (SD), range
141 (9), (125–170) 7.5 (16.3), (47–40) 33 (60%)
Lateral patellofemoral angle of Laurin (degrees), mean (SD), range
4.0 (7.7), ( 13–20)
Lateral tilt ( 10 degrees)
17 (31%)
Patella alta (C-D ratio > 1.2)
9 (15%)
Patellofemoral joint space
Medial joint space
Lateral joint space
Femoral tunnel placement
Trochlear dysplasia was seen in 68% of patients in the present study, with a crossing sign in 30 knees and prominence in 36 knees out of 56 knees. In Steiner’s et al series, 36 of 41 knees (88%) had trochlear dysplasia.17 In contrast, Han et al excluded patients with high grade trochlea dysplasia from their series.27 Postoperatively, the sulcus angle, observed in the present study, averaged 141 degrees, and the congruence angle average was 7.5 degrees. Other studies found similar results, reporting congruence angles of 5 to 5.5 degrees on average.24,26 Patella alta was found in only 9 out of 56 knees in the current study. None of the patients had patella alta significant enough to require a distalization of the tibial tubercle. Ahmad et al reported 4 out of 22 patients had patella alta by Insall-Salvati ratios, and 6 had patella alta by Blackburne-Peel ratios.11 Out of 52 patients, 6 had patella alta based on the Insall-Salvati ratio, and 9 had patella alta based on the Blackburne-Peel ratios in the study by Han et al.27
None
35 (64%)
Mild
15 (27%)
Moderate
2 (4%)
Missing
3 (5%)
None
44 (79%)
Mild
8 (15%)
Moderate
2 (4%)
Severe
1 (2%)
None
50 (91%)
Mild
4 (7%)
Moderate
1 (2%)
Severe
0 (0%)
Normal
17 (31%)
Anterior
21 (38%)
anterior/distal
6 (11%)
Distal
8 (15%)
Proximal
3 (5%)
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Congruence angle (degrees), mean (SD), range Lateral patellar tilt (positive congruence angle)
patient required an evacuation of a postoperative hematoma, one patient had a graft advancement after loosening in a motor vehicle accident, and three patients had removal of painful hardware from the medial epicondyle.17 Ronga et al used transverse patellar tunnels, leading to anterior patellar cortex violation (without fracture) along the lateral aspect of the patella in two patients. Two other patients were unable to flex the knee beyond 90 degrees and underwent MUA to restore range of motion. Moreover, they had three patients with recurrent dislocation.16 Christiansen et al reported on five reoperations out of 44 reconstructions. In their study, one patient underwent MUA for knee flexion less than 90 degrees, three underwent symptomatic hardware removal from the medial epicondyle, and one patient had a transverse patellar fracture.13 In contrast, several other studies reported no postoperative complications.11,26,27
Pain Complications and Reoperations In our series, we found only a few postoperative complications. Drez et al reported one case of arthrofibrosis requiring MUA and one case of wound dehiscence that resolved with local wound care.24 Steiner et al had five reoperations: one
In the present study, 63% of patients reported significant pain relief. These results are nearly identical to those of Christiansen et al who found 64% of patients were completely pain free with activities of daily living, and 59% were pain free when engaging in sporting activities.13 The Journal of Knee Surgery
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Recurrent Instability
Strengths
In the present study, no recurrent dislocations occurred during the postoperative period. However, six cases of patellar subluxation (11%) were reported. One other study had similar results to our series,24 and some other studies reported no recurrent patellar dislocations or subluxations.11,17,25–27 In contrast, Ronga et al reported three patients with recurrent patellar instability out of 28 patients. All were male soccer players at the recreational level, and sustained the new episode of patellar dislocation 13 to 22 months after the index procedure.16 Christiansen et al reported 1 patient with a new dislocation 6 months postoperatively, and 3 patients with a sensation of subluxation out of 44 patients.13 The present study did not have enough subjects to assess risk factors for postoperative subluxation or dislocation.
Strengths of this study include the standard technique used by the surgeons. This decreases the variability in results that could be introduced by different techniques by many different surgeons. Isolated MPFL reconstruction was evaluated to determine the procedure’s effectiveness in re-establishing stability of the patellofemoral joint without introducing the effect of other concurrent procedures. The postoperative assessment of the series evaluated was performed by independent observers who were not involved with the patients’ surgery and follow-up care assuring minimal observer bias in the measurements obtained. The number of cases in this study, while small, is one of the largest series of such cases in the United States and can therefore provide some insight of the procedure and outcomes in the population seeking such care.
Function and Return to Activity In the present study, functional testing of a single-leg hop test was performed in 39 knees. Nineteen patients evaluated scored > 90% compared with the contralateral leg, 11 scored between 76 and 89%, 6 scored between 50 and 75%, and 3 scored less than 50%. In comparison, isokinetic strength testing revealed the operative limb was always significantly weaker than the contralateral limb in the study by Ronga et al.16 Christiansen et al study’s subjective patient assessment revealed that 80% of patients felt their knee function had improved.13 In the present study, Tegner activity score averaged 6.1 before injury and 5.6 after reconstruction. Similarly, Drez et al reported a preinjury score of 6.8 and 6.7 postoperatively.24 Steiner et al did not report a preinjury Tegner activity score, but the preoperative score was 3.1, which improved postreconstruction to 5.1.17 Ahmad et al reported a preoperative Tegner score of 3.6, this score improved to 5.6 postoperatively.11 Christiansen et al reported a mean postoperative Tegner activity score of 4.24
Conclusion In conclusion, our study supports the use of MPFL reconstruction in the treatment of episodic lateral patellar instability with no other significant comorbidities. The present study’s results are comparable to other series, had only a few minor complications, had no redislocations, and only 10% of patients reported subluxation events. Based on Tegner score, patients were able to return approximately the same preinjury level. Larger studies are needed to determine the risk factors for redislocation and to determine the effects of patella alta and trochlea dysplasia on outcome. Longer follow-up is needed to determine the risk of developing patellofemoral osteoarthritis.
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Limitations There are several limitations of the current study. First, this was a convenience sample of patients and selection bias could be present. In addition, a large number of eligible patients (42%) declined to enroll in the study and then a few others were subsequently excluded after enrollment due to unrelated complications or declined follow-up examination. Second, our study was retrospective and preoperative assessments are not available for comparison. The progression of IKDC scores could not be evaluated. Moreover, preoperative axial imaging (magnetic resonance imaging or computed tomography) to identify subjects with increased tibial tubercle to trochlear groove offset was not available. Finally, this study had insufficient statistical power to evaluate the effects of trochlear dysplasia or patella alta on outcomes after MPFL reconstruction or to answer questions about factors associated with recurrent dislocation or development of arthrosis. Another limitation was the early learning curve of the surgeons on the potential outcomes of the procedure. Since this initial cohort of patients, we have added intraoperative imaging to more accurately identify the femoral tunnel. The Journal of Knee Surgery
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Appendix A: Modified IKDC 2000 knee history form
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