The Journal of Arthroplasty xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty Joakim Bjerke, MSc a, b, Fredrik Öhberg, PhD c, Kjell G. Nilsson, PhD d, Ann K. Stensdotter, PhD a, b a
Department of Community Medicine & Rehabilitation Physiotherapy, Umeå University, Umeå, Sweden Department of Physiotherapy, School of Health Education & Social Work, Sør-Trøndelag University College, Trondheim, Norway Department of Biomedical Engineering & Informatics, Umeå University Hospital, Umeå, Sweden d Surgical & Perioperative Sciences, Umeå University Hospital, Umeå, Sweden b c
a r t i c l e
i n f o
Article history: Received 14 October 2013 Accepted 27 January 2014 Available online xxxx Keywords: muscular utilization electromyography maximal voluntary contraction kinematics stairs
a b s t r a c t Subjects with total knee arthroplasty (TKA) exhibit decreased quadriceps and hamstring strength. This may bring about greater relative effort or compensatory strategies to reduce knee joint moments in daily activities. To study gait and map out the resource capacity, knee muscle strength was assessed by maximal voluntary concentric contractions, and whole body kinematics and root mean square (RMS) electromyography (EMG) of vastus lateralis and semitendinosus were recorded during stair ascent in 23 unilateral TKA-subjects ~19 months postoperation, and in 23 healthy controls. Muscle strength and gait velocity were lower in the TKA group, but no significant group differences were found in RMS EMG or forward trunk lean. The results suggest that reduced walking velocity sufficiently compensated for reduced knee muscle strength. © 2014 Elsevier Inc. All rights reserved.
Subjects with total knee arthroplasty (TKA) often express decreased ability to execute activities of daily living (ADL), such as negotiating stairs [1-3]. Several studies [2,4-6] show evidence of decreased quadriceps and hamstring strength after TKA compared to the contralateral leg and compared to healthy controls. As quadriceps and hamstring weakness often is persistent years after knee arthroplasty surgery with a reduction of 40% and 35% respectively, compared to healthy age-matched groups [1], it seems important to investigate the implication of these strength deficits on a functional activity such as stair climbing. Studies comparing elderly with younger individuals [7], have shown that quadriceps weakness affected the ability to ascend stairs by requiring a substantially greater effort evidenced by higher relative electromyography (EMG) activity. In a weak muscle more of the total capacity is used, and neural drive has to increase in order to recruit additional motor units [8]. Alternatively or in addition, compensatory strategies may be adopted to reduce the load on weakened muscles. Andriacchi [9] found that TKA patients leaned the trunk forward during stair climbing in order to decrease the knee flexion moment, and thus, reduce the demand on the quadriceps. A similar strategy of compensatory forward lean to reduce quadriceps demand during level gait was described by Li et al [10]; TKA patients showed significantly decreased contribution of normalized quadriceps force in The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.01.033. Reprint requests: Joakim Bjerke, MSc, Sør-Trøndelag University College, N-7004 Trondheim, Norway.
the vertical acceleration and forward deceleration of the center of mass during early stance compared to healthy controls. The same distinctive compensatory pattern of increased forward trunk lean to reduce the quadriceps demand during stair climbing has been found in patients with osteoarthritis (OA) [11]. Furthermore, TKA patients appear to walk significantly slower than controls at self-selected speed 6 months after the surgery [12], maybe due to residual impairments such as pain, reduced range of motion and muscle weakness in the operated knee [13]. Although there is evidence of reduced thigh muscle strength and compensatory strategies in gait on level surface after TKA, no previous studies appear to have assessed the relative muscle effort and movement strategies during stair climbing. As the contralateral leg is likely affected by the reduction in the prosthetic side [14] it may not provide a valid healthy control for the affected limb. It is therefore important to also include an asymptomatic control group. We hypothesized that the TKA group would use relatively more of their maximal muscular capacity in the quadriceps and hamstrings during stair ascent than stronger healthy individuals, and that they would compensate muscle weakness by increased forward lean of the trunk and walk slower. Materials and Methods Participants This cross-sectional study took place in the period of October 2010 to December 2010. It was conducted according to the guidelines of the
0883-5403/0000-0000$36.00/0 – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2014.01.033
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
2
J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
Helsinki declaration, and informed consent was obtained from all participants with detailed information about the study. Ethic approval was granted by the Regional Ethical Review Board. The orthopedic department sent 139 inquiries to subjects who underwent TKA less than two years earlier. Fifty-two TKA patients agreed to participate and 23 subjects met the inclusion criteria and were included in the study. Twenty-three age and gender matched healthy control subjects were recruited from the university and hospital staff. Inclusion criteria for patients was a unilateral TKA with a cemented Duracon prosthesis from Stryker Orthopedics (Howmedica, Rutherford, NJ); a posterior cruciate ligament-retaining prosthesis with fixed platform and without a patella component. The most relevant post-surgical time frame when to test TKA patients was motivated by results from Andriacchi et al [15] who found that 6 months may be insufficient time for recovery of the post-surgical symptoms such as acute pain and swelling that still may have a major impact on gait. Hence, only TKA-subjects who had surgery ≥ one year to b three years ago were included as more of these post-surgical symptoms were expected to be resolved. For all participants, inclusion criteria were b 65 years of age to exclude age-related physical limitations, BMI b 35, no diagnosed neurological or orthopedic conditions (other than TKA). The characteristics of the participants are presented in Table 1. The Staircase The staircase was a free standing module of three steps up and three steps down without banister. The stairs were constructed in accordance with normal stair standards; step height 18 cm and tread length 26 cm. The subjects were asked to climb the stairs in a stepover-step pattern in a self-selected normal and comfortable pace with a total of six trials. The first three trials were performed with the right foot on the first step and the three last trials with the left foot on the first step. Isokinetic Measurements Maximal quadriceps and hamstring strength was measured in an isokinetic dynamometer (Biodex®) following a low intensity 10 min warm-up period on a stationary bike. Three sub-maximal voluntary concentric contractions were performed for familiarization and to potentiate the muscle. To measure peak torque (Nm), a maximal voluntary concentric contraction (MVCC) were performed in a standardized range of motion ranging from 0° to 90° at 60°/s of a total of 5 repetitions for each leg. The highest torque for each leg, normalized to body weight was used. The experimenter gave verbal encouragement during the testing. Electromyography During the stair ascent and isokinetic testing, the EMG was recorded with disposable Ag–AgCl surface electrodes with a measuring area of 95 mm 2 (Ambu® Neuroline 720) bilaterally from vastus lateralis (VL) and semitendinosus (ST). Before the measurement, the skin area was shaved and cleaned with alcohol to reduce the skin–
electrode impedance. The electrodes were attached in a bipolar arrangement along the direction of the muscle fibers with an interelectrode distance of 20 mm, center to center, with adjoining reference electrode placed in recommendation following the SENIAM guidelines [16]. EMG data were collected via an 8-channel portable device (Biomonitor ME6000® T16, Mega Electronics Ltd, Kuopio, Finland), which was strapped around the waist. For the stair ascent, EMG data were transferred telemetrically (WLAN) to QTM (Qualisys Track Manager, 2.6 682, Qualisys, Sweden) for storage. For the isokinetic testing of MVCC, EMG data were transferred via a USB cable and stored in the Megawin 2.3-software (Mega Electronics Ltd, Kuopio, Finland). The recorded EMG signals were both in stair ascent and MVCC pre-amplified 305 times and band-pass filtered between 8 and 500 Hz before digitizing at a sample rate of 1000 Hz using 14bit resolution. For the data analysis the digitized EMG signals were later quantified via a MatLab (The MathWorks, Inc., Natick, MA, USA) script by using moving RMS with a window of 100 ms. To calculate the normalized EMG activity, the peak RMS EMG signal of VL and ST during stair ascent was normalized as percentage of the averaged median RMS EMG signal obtained during the MVCC in knee extension and knee flexion. The median value of each full MVCC curve (from where curve starts to rise to where curve flats out) was calculated and all medians of the curves were then averaged to obtain the values used in the normalization. Median RMS EMG is a more robust measure of MVCC than peak RMS EMG as peak values are sensitive to inconsistent “spikes”. EMG data from dynamic contractions are very much susceptible to motion artifacts [17], thus the peak values could be less trustworthy which motivated the use of median values. Kinematic Measurements Whole body kinematics to assess the angle of forward trunk lean and time to complete the stair ascent, starting from heel off towards the first step and ending with both legs parallel at the uppermost step, was recorded at 100 Hz with an eight-camera system (Oqus, Qualisys, Sweden) and compiled into three dimensional kinematics (Qualisys Track Manager, 2.6 682, Qualisys, Sweden). During the stair ascent, infrared light emitted from the cameras was reflected from 34 spherical 19 mm reflex markers attached to defined anatomical landmarks denoting proximal and distal ends of body segments. Additional 4-marker clusters were placed on thighs and shanks. For the kinematic data analysis, a model based on 50 markers was recorded from a standing trial (Visual 3D Basic/RT, 4.00.20, C-Motion Maryland, USA). The angle of forward trunk lean was defined through the sagittal plane projection of a marker at the origin of the pelvis and the sternal markers. The peak forward trunk angle during stair ascent was noted. Values were averaged for the six trials. Subjects were barefoot and wore tight clothing to ensure that the reflective markers were firmly secured to anatomical landmarks. The camera system was calibrated prior to each session and the global coordinate system was defined as; medio-lateral X, antero-posterior Y, and vertical Z. System precision was measured with an average residual of ≈ 0.5 mm. Statistics
Table 1 Mean (± SD) Subject Demographics. Variable Male/female Age, (years) Body weight, (kg) Height, (cm) BMI, (kg/m2) Pain, NRS
TKA-Group (N = 23)
Control Group (N = 23)
P
11/12 57.6 ± 5.8 88.0 ± 15.1 172 ± 0.1 29.9 ± 5.0 1.4 ± 1.8
10/13 54.7 ± 7.4 74.3 ± 15.5 173 ± 0.1 24.5 ± 3.1 n/a
.767 .151 .004 .556 .000
BMI = body mass index, NRS = numeric rating scale.
Normal distribution of data was inferred by Kolmogorov–Smirnov. Absolute and normalized EMG RMS for VL and ST during stair ascent and absolute values for MVCC and quadriceps and hamstring peak torque/body weight were compared between legs within subjects with paired sample t-test and between subjects with one-way ANOVA. Subject demographics were compared between the groups with one-way ANOVA. The significance level was set at P b 0.05. All statistics were performed using Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA), version 20.
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
3
Table 2 Mean (± SD) EMG (RMS) of Vastus Lateralis and Semitendinosus During Isokinetic MVCC/Stair Ascent, and Forward Lean Thorax and Time Up Stairs. TKA-Group (N =23) Variable Quadriceps peak torque (Nm/bw) Hamstring peak torque (Nm/bw) MVCC, vas lateralis, (μV) MVCC, semitendinosus, (μV) Stair ascent, vas lateralis (μV) Stair ascent, semitendinosus, (μV) Normalized, vas lateralis, (%) Normalized, semitendinosus, (%) Forward lean thorax during stair ascent (°) Time up stairs (s)
Control Group (N = 23)
PROSTHESIS vs Ctrl. (Both Legs Comb.)
Contralateral vs Ctrl. (Both Legs Comb.)
P2
P2
Prosthesis
Contralateral
P1
Non-Dominant
Dominant
P1
1.24 ± 0.40
1.67 ± 0.43
.000
2.00 ± 0.30
2.14 ± 0.40
.009
2.07 ± 0.33
.000
.001
0.92 ± 0.29
0.96 ± 0.32
.121
1.08 ± 0.21
1.14 ± 0.23
.066
1.11 ± 0.21
.015
.068
199.1 ± 108.0 223.2 ± 131.6 111.2 ± 54.4
220.9 ± 107.5 258.3 ± 110.7 132.9 ± 48.4
.114 .124 .034
207.7 ± 81.1 265.3 ± 117.2 109.5 ± 37.1
204.0 ± 64.2 230.8 ± 95.2 151.4 ± 95.8
.832 .388 .027
205.9 ± 61.1 238.2 ± 90.8 130.4 ± 59.8
.807 .681 .274
.582 .535 .890
101.0 ± 61.6
108.1 ± 63.8
.758
134.5 ± 86.8
122.1 ± 70.5
.592
128.3 ± 62.3
.162
.323
68 ± 43
69 ± 31
.873
55 ± 17
77 ± 46
.021
66 ± 28
.846
.777
56 ± 36
46 ± 26
.109
54 ± 29
66 ± 52
.405
62 ± 35
.595
.149
Both Legs Comb.
13.3 ± 4.3
16.3 ± 6.8
.087
2.6 ± 0.5
2.3 ± 0.3
.013
MVCC = maximal voluntary concentric contraction, Nm/bw = newton meter/body weight, μV = micro volt, P1 = Side-to-side differences (t-test), P2 = Group differences (ANOVA).
Results Between and within group differences are found in Table 2. During stair ascent, no differences were found in normalized EMG RMS for VL or ST between the TKA group and the control group. In the TKA group, no side-to-side differences were found in normalized EMG RMS for VL or ST, however in the control group a significantly lower value was found for VL in the non-dominant side compared to the dominant side. Quadriceps peak torque in the TKA group was significantly lower in their prosthetic side compared to the contralateral side and compared to the mean combined sides in the control group. Also the contralateral side in the TKA group produced significantly weaker quadriceps peak torque than the mean combined sides in the control group. The hamstring strength of the prosthetic side was significantly lower than the average of both sides in the control group. The contralateral side, however, produced equal hamstring strength to the average of both sides in the control group. Time to complete the stair ascent showed that the TKA group walked significantly slower than the control group. There was no group difference in forward trunk lean during stair ascent. Discussion The present study showed that the TKA group ascended stairs at a slower self-selected pace than healthy controls. Despite significantly lower quadriceps and hamstring strength in the TKA group, the relative muscular effort was similar to the control group. Kinematics did not reveal increased forward lean of the trunk in the TKA group as a compensation for muscle weakness during stair ascent. Our result is in line with previous studies that have shown a reduction of about 50% in stair climbing velocity one year after TKAsurgery compared to healthy age-matched individuals [1]. In contrast to our results, Hortobágyi et al [7], found that old adults (74 ± 3 years), contrary to young adults (22 ± 2 years), ascended stairs close to their maximal capability as a consequence of muscular weakness. Similar relative muscular effort in both groups in the present study could perhaps be explained by a difference in gait velocity. EMG activity is positively correlated with gait velocity [18,19]. Reduced gait velocity may indicate reduced knee extension moment and therefore also reduced activity in VL, the net effect resulting in similar effort relative to MVCC in both groups. Similarly, Milot et al [20], showed that by slowing gait velocity, utilization of
maximal capacity was reduced. Others have shown reduced knee extension moments and significantly lower force in the vastii and rectus femoris in TKA patients compared to controls during level gait compensated by increased back extension moments [10]. Thus, different strategies may be adopted to compensate for muscle weakness and reduce the relative effort. To enforce differences in effort between groups, standardization of different parameters may be implemented. Hortobágyi et al [7] used a metronome during stair ascent in order to ensure similar overall gait speed. Nevertheless, the angular velocity at the knee joint was still significantly higher in the younger and stronger group than in the older and weaker group. This suggests that switching in the velocity pattern between knee and hip joint is yet another strategy to compensate for muscle weakness at the knee [7]. In spite of lower angular velocity at the knee, the older group still displayed a significantly increased relative effort due to the reduced capability to produce maximal leg strength [7]. The results in the present study suggest that the TKA group managed to compensate muscle weakness with reduced gait velocity, and thus used the same effort as controls relative to maximum capacity. The quadriceps strength in the TKA group was 40% lower in the prosthetic side and 20% lower in the contralateral side compared to controls. The greater strength difference between groups (60%) in the study by Hortobágyi et al [7], may explain why the weaker subjects in that study were unable to compensate muscle weakness. Although the prosthetic side was significantly weaker than the contralateral side, the relative effort in stair ascent was similar in both sides. In contrast, other studies have found greater relative quadriceps muscular effort in the prosthetic leg compared to the contralateral leg in older TKA patients during level gait [21]. However that study did not use EMG normalized to maximal effort for each leg, but compared absolute values between legs during gait only. In the present study, the control group displayed significantly higher proportion of the maximal capacity in the stronger and dominant side during stair ascent. This asymmetry may be explained by limb dominance, suggesting that the dominant side is more active during gait [22,23]. The hypothesis of a compensatory strategy in order to reduce the load on the prosthetic knee with an increased forward trunk lean in the TKA group compared to the control group was rejected. As discussed above, compensation for muscle weakness was apparently achieved by reduced gait velocity and not forward trunk lean. Increased forward trunk lean to reduce the quadriceps demand
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
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J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
during stair climbing has been demonstrated in patients with OA [11]. Notably, OA comes with a great deal of pain which needs to be relieved during weight acceptance [24], which partly may explain this compensation. The TKA group in the present study did not report pain. While Li et al [10] found increased forward trunk lean in TKA patients during level gait, the TKA patients in that study were both older and closer to the time of TKA surgery than the subjects in the present study. In conclusion, the present study offers more information about strategy than utilization of capacity as it is difficult to control the compensatory factors and isolate muscular capacity. Different strategies may be employed to compensate muscle weakness and by controlling or monitoring various factors such as gait velocity, cadence, joint angle velocities, upper body dynamics, and anthropometrics, various compensatory strategies for muscle weakness may be found. Although muscle weakness in the lower extremities may be compensated by different strategies, strength in the lower extremity is positively correlated with gait speed and function in daily life activities [25]. Furthermore, gait speed is also correlated with survival [26] and falls [27]. Therefore, improvement and maintenance of lower extremity strength to improve function in daily life are crucial after TKA surgery. References 1. Walsh M, Woodhouse LJ, Thomas SG, et al. Physical impairments and functional limitations: a comparison of individuals 1 year after total knee arthroplasty with control subjects. Phys Ther 1998;78:248. 2. Bjerke J, Ohberg F, Nilsson KG, et al. Peak knee flexion angles during stair descent in TKA patients. J Arthroplasty 2013 http://dx.doi.org/10.1016/j.arth.2013.07.010. 3. Mizner RL, Snyder-Mackler L. Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplasty. J Orthop Res 2005;23:1083. 4. Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil 2002;83:1432. 5. Silva M, Shepherd EF, Jackson WO, et al. Knee strength after total knee arthroplasty. J Arthroplasty 2003;18:605. 6. Stevens-Lapsley JE, Balter JE, Kohrt WM, et al. Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty. Clin Orthop Relat Res 2010;468:2460. 7. Hortobagyi T, Mizelle C, Beam S, et al. Old adults perform activities of daily living near their maximal capabilities. J Gerontol A Biol Sci Med Sci 2003;58:M453.
8. Hortobagyi TMC, Beam S, DeVita P. Old adults perform activities of daily living near their maximal capabilities. J Gerontol A Biol Sci Med Sci 2003:453. 9. Andriacchi TP. Functional analysis of pre and post-knee surgery: total knee arthroplasty and ACL reconstruction. J Biomech Eng 1993;115:575. 10. Li K, Ackland DC, McClelland JA, et al. Trunk muscle action compensates for reduced quadriceps force during walking after total knee arthroplasty. Gait Posture 2013;38:79. 11. Asay JL, Mundermann A, Andriacchi TP. Adaptive patterns of movement during stair climbing in patients with knee osteoarthritis. J Orthop Res 2009;27:325. 12. Casartelli NC, Item-Glatthorn JF, Bizzini M, et al. Differences in gait characteristics between total hip, knee, and ankle arthroplasty patients: a six-month postoperative comparison. BMC Musculoskelet Disord 2013;14:176. 13. Kauppila AM, Kyllonen E, Mikkonen P, et al. Disability in end-stage knee osteoarthritis. Disabil Rehabil 2009;31:370. 14. Gage WH, Frank JS, Prentice SD, et al. Organization of postural responses following a rotational support surface perturbation, after TKA: sagittal plane rotations. Gait Posture 2007;25:112. 15. Andriacchi TP. Dynamics of pathological motion: applied to the anterior cruciate deficient knee. J Biomech 1990;23(Suppl 1):99. 16. Hermens HJ FB. The state of the art on sensors and sensor placement procedures for surface electromyography: a proposal for sensor placement procedures. Roessingh Research and Development bv 1997. 17. De Luca CJ, Gilmore LD, Kuznetsov M, et al. Filtering the surface EMG signal: movement artifact and baseline noise contamination. J Biomech 2010;43:1573. 18. Sousa AS, Tavares JM. Effect of gait speed on muscle activity patterns and magnitude during stance. Motor Control 2012;16:480. 19. Liikavainio T, Bragge T, Hakkarainen M, et al. Gait and muscle activation changes in men with knee osteoarthritis. Knee 2010;17:69. 20. Milot MH, Nadeau S, Gravel D. Muscular utilization of the plantarflexors, hip flexors and extensors in persons with hemiparesis walking at self-selected and maximal speeds. J Electromyogr Kinesiol 2007;17:184. 21. Lester DK, Shantharam R, Zhang K. Dynamic electromyography after cruciateretaining total knee arthroplasty revealed a threefold quadriceps demand compared with the contralateral normal knee. J Arthroplasty 2013;28:557. 22. Arsenault AB, Winter DA, Marteniuk RG. Bilateralism of EMG profiles in human locomotion. Am J Phys Med 1986;65:1. 23. Ounpuu S, Winter DA. Bilateral electromyographical analysis of the lower limbs during walking in normal adults. Electroencephalogr Clin Neurophysiol 1989;72: 429. 24. Hurwitz DE, Ryals AR, Block JA, et al. Knee pain and joint loading in subjects with osteoarthritis of the knee. J Orthop Res 2000;18:572. 25. Gine-Garriga M, Guerra M, Manini TM, et al. Measuring balance, lower extremity strength and gait in the elderly: construct validation of an instrument. Arch Gerontol Geriat 2010;51:199. 26. Studenski S, Perera S, Patel K, et al. Gait speed and survival in older adults. JAMA 2011;305:50. 27. Quach L, Galica AM, Jones RN, et al. The nonlinear relationship between gait speed and falls: the maintenance of balance, independent living, intellect, and zest in the elderly of Boston study. J Am Geriatr Soc 2011;59:1069.
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty Joakim Bjerke, MSc a, b, Fredrik Öhberg, PhD c, Kjell G. Nilsson, PhD d, Ann K. Stensdotter, PhD a, b a
Department of Community Medicine & Rehabilitation Physiotherapy, Umeå University, Umeå, Sweden Department of Physiotherapy, School of Health Education & Social Work, Sør-Trøndelag University College, Trondheim, Norway Department of Biomedical Engineering & Informatics, Umeå University Hospital, Umeå, Sweden d Surgical & Perioperative Sciences, Umeå University Hospital, Umeå, Sweden b c
a r t i c l e
i n f o
Article history: Received 14 October 2013 Accepted 27 January 2014 Available online xxxx Keywords: muscular utilization electromyography maximal voluntary contraction kinematics stairs
a b s t r a c t Subjects with total knee arthroplasty (TKA) exhibit decreased quadriceps and hamstring strength. This may bring about greater relative effort or compensatory strategies to reduce knee joint moments in daily activities. To study gait and map out the resource capacity, knee muscle strength was assessed by maximal voluntary concentric contractions, and whole body kinematics and root mean square (RMS) electromyography (EMG) of vastus lateralis and semitendinosus were recorded during stair ascent in 23 unilateral TKA-subjects ~19 months postoperation, and in 23 healthy controls. Muscle strength and gait velocity were lower in the TKA group, but no significant group differences were found in RMS EMG or forward trunk lean. The results suggest that reduced walking velocity sufficiently compensated for reduced knee muscle strength. © 2014 Elsevier Inc. All rights reserved.
Subjects with total knee arthroplasty (TKA) often express decreased ability to execute activities of daily living (ADL), such as negotiating stairs [1-3]. Several studies [2,4-6] show evidence of decreased quadriceps and hamstring strength after TKA compared to the contralateral leg and compared to healthy controls. As quadriceps and hamstring weakness often is persistent years after knee arthroplasty surgery with a reduction of 40% and 35% respectively, compared to healthy age-matched groups [1], it seems important to investigate the implication of these strength deficits on a functional activity such as stair climbing. Studies comparing elderly with younger individuals [7], have shown that quadriceps weakness affected the ability to ascend stairs by requiring a substantially greater effort evidenced by higher relative electromyography (EMG) activity. In a weak muscle more of the total capacity is used, and neural drive has to increase in order to recruit additional motor units [8]. Alternatively or in addition, compensatory strategies may be adopted to reduce the load on weakened muscles. Andriacchi [9] found that TKA patients leaned the trunk forward during stair climbing in order to decrease the knee flexion moment, and thus, reduce the demand on the quadriceps. A similar strategy of compensatory forward lean to reduce quadriceps demand during level gait was described by Li et al [10]; TKA patients showed significantly decreased contribution of normalized quadriceps force in The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.01.033. Reprint requests: Joakim Bjerke, MSc, Sør-Trøndelag University College, N-7004 Trondheim, Norway.
the vertical acceleration and forward deceleration of the center of mass during early stance compared to healthy controls. The same distinctive compensatory pattern of increased forward trunk lean to reduce the quadriceps demand during stair climbing has been found in patients with osteoarthritis (OA) [11]. Furthermore, TKA patients appear to walk significantly slower than controls at self-selected speed 6 months after the surgery [12], maybe due to residual impairments such as pain, reduced range of motion and muscle weakness in the operated knee [13]. Although there is evidence of reduced thigh muscle strength and compensatory strategies in gait on level surface after TKA, no previous studies appear to have assessed the relative muscle effort and movement strategies during stair climbing. As the contralateral leg is likely affected by the reduction in the prosthetic side [14] it may not provide a valid healthy control for the affected limb. It is therefore important to also include an asymptomatic control group. We hypothesized that the TKA group would use relatively more of their maximal muscular capacity in the quadriceps and hamstrings during stair ascent than stronger healthy individuals, and that they would compensate muscle weakness by increased forward lean of the trunk and walk slower. Materials and Methods Participants This cross-sectional study took place in the period of October 2010 to December 2010. It was conducted according to the guidelines of the
0883-5403/0000-0000$36.00/0 – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2014.01.033
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
2
J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
Helsinki declaration, and informed consent was obtained from all participants with detailed information about the study. Ethic approval was granted by the Regional Ethical Review Board. The orthopedic department sent 139 inquiries to subjects who underwent TKA less than two years earlier. Fifty-two TKA patients agreed to participate and 23 subjects met the inclusion criteria and were included in the study. Twenty-three age and gender matched healthy control subjects were recruited from the university and hospital staff. Inclusion criteria for patients was a unilateral TKA with a cemented Duracon prosthesis from Stryker Orthopedics (Howmedica, Rutherford, NJ); a posterior cruciate ligament-retaining prosthesis with fixed platform and without a patella component. The most relevant post-surgical time frame when to test TKA patients was motivated by results from Andriacchi et al [15] who found that 6 months may be insufficient time for recovery of the post-surgical symptoms such as acute pain and swelling that still may have a major impact on gait. Hence, only TKA-subjects who had surgery ≥ one year to b three years ago were included as more of these post-surgical symptoms were expected to be resolved. For all participants, inclusion criteria were b 65 years of age to exclude age-related physical limitations, BMI b 35, no diagnosed neurological or orthopedic conditions (other than TKA). The characteristics of the participants are presented in Table 1. The Staircase The staircase was a free standing module of three steps up and three steps down without banister. The stairs were constructed in accordance with normal stair standards; step height 18 cm and tread length 26 cm. The subjects were asked to climb the stairs in a stepover-step pattern in a self-selected normal and comfortable pace with a total of six trials. The first three trials were performed with the right foot on the first step and the three last trials with the left foot on the first step. Isokinetic Measurements Maximal quadriceps and hamstring strength was measured in an isokinetic dynamometer (Biodex®) following a low intensity 10 min warm-up period on a stationary bike. Three sub-maximal voluntary concentric contractions were performed for familiarization and to potentiate the muscle. To measure peak torque (Nm), a maximal voluntary concentric contraction (MVCC) were performed in a standardized range of motion ranging from 0° to 90° at 60°/s of a total of 5 repetitions for each leg. The highest torque for each leg, normalized to body weight was used. The experimenter gave verbal encouragement during the testing. Electromyography During the stair ascent and isokinetic testing, the EMG was recorded with disposable Ag–AgCl surface electrodes with a measuring area of 95 mm 2 (Ambu® Neuroline 720) bilaterally from vastus lateralis (VL) and semitendinosus (ST). Before the measurement, the skin area was shaved and cleaned with alcohol to reduce the skin–
electrode impedance. The electrodes were attached in a bipolar arrangement along the direction of the muscle fibers with an interelectrode distance of 20 mm, center to center, with adjoining reference electrode placed in recommendation following the SENIAM guidelines [16]. EMG data were collected via an 8-channel portable device (Biomonitor ME6000® T16, Mega Electronics Ltd, Kuopio, Finland), which was strapped around the waist. For the stair ascent, EMG data were transferred telemetrically (WLAN) to QTM (Qualisys Track Manager, 2.6 682, Qualisys, Sweden) for storage. For the isokinetic testing of MVCC, EMG data were transferred via a USB cable and stored in the Megawin 2.3-software (Mega Electronics Ltd, Kuopio, Finland). The recorded EMG signals were both in stair ascent and MVCC pre-amplified 305 times and band-pass filtered between 8 and 500 Hz before digitizing at a sample rate of 1000 Hz using 14bit resolution. For the data analysis the digitized EMG signals were later quantified via a MatLab (The MathWorks, Inc., Natick, MA, USA) script by using moving RMS with a window of 100 ms. To calculate the normalized EMG activity, the peak RMS EMG signal of VL and ST during stair ascent was normalized as percentage of the averaged median RMS EMG signal obtained during the MVCC in knee extension and knee flexion. The median value of each full MVCC curve (from where curve starts to rise to where curve flats out) was calculated and all medians of the curves were then averaged to obtain the values used in the normalization. Median RMS EMG is a more robust measure of MVCC than peak RMS EMG as peak values are sensitive to inconsistent “spikes”. EMG data from dynamic contractions are very much susceptible to motion artifacts [17], thus the peak values could be less trustworthy which motivated the use of median values. Kinematic Measurements Whole body kinematics to assess the angle of forward trunk lean and time to complete the stair ascent, starting from heel off towards the first step and ending with both legs parallel at the uppermost step, was recorded at 100 Hz with an eight-camera system (Oqus, Qualisys, Sweden) and compiled into three dimensional kinematics (Qualisys Track Manager, 2.6 682, Qualisys, Sweden). During the stair ascent, infrared light emitted from the cameras was reflected from 34 spherical 19 mm reflex markers attached to defined anatomical landmarks denoting proximal and distal ends of body segments. Additional 4-marker clusters were placed on thighs and shanks. For the kinematic data analysis, a model based on 50 markers was recorded from a standing trial (Visual 3D Basic/RT, 4.00.20, C-Motion Maryland, USA). The angle of forward trunk lean was defined through the sagittal plane projection of a marker at the origin of the pelvis and the sternal markers. The peak forward trunk angle during stair ascent was noted. Values were averaged for the six trials. Subjects were barefoot and wore tight clothing to ensure that the reflective markers were firmly secured to anatomical landmarks. The camera system was calibrated prior to each session and the global coordinate system was defined as; medio-lateral X, antero-posterior Y, and vertical Z. System precision was measured with an average residual of ≈ 0.5 mm. Statistics
Table 1 Mean (± SD) Subject Demographics. Variable Male/female Age, (years) Body weight, (kg) Height, (cm) BMI, (kg/m2) Pain, NRS
TKA-Group (N = 23)
Control Group (N = 23)
P
11/12 57.6 ± 5.8 88.0 ± 15.1 172 ± 0.1 29.9 ± 5.0 1.4 ± 1.8
10/13 54.7 ± 7.4 74.3 ± 15.5 173 ± 0.1 24.5 ± 3.1 n/a
.767 .151 .004 .556 .000
BMI = body mass index, NRS = numeric rating scale.
Normal distribution of data was inferred by Kolmogorov–Smirnov. Absolute and normalized EMG RMS for VL and ST during stair ascent and absolute values for MVCC and quadriceps and hamstring peak torque/body weight were compared between legs within subjects with paired sample t-test and between subjects with one-way ANOVA. Subject demographics were compared between the groups with one-way ANOVA. The significance level was set at P b 0.05. All statistics were performed using Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA), version 20.
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
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Table 2 Mean (± SD) EMG (RMS) of Vastus Lateralis and Semitendinosus During Isokinetic MVCC/Stair Ascent, and Forward Lean Thorax and Time Up Stairs. TKA-Group (N =23) Variable Quadriceps peak torque (Nm/bw) Hamstring peak torque (Nm/bw) MVCC, vas lateralis, (μV) MVCC, semitendinosus, (μV) Stair ascent, vas lateralis (μV) Stair ascent, semitendinosus, (μV) Normalized, vas lateralis, (%) Normalized, semitendinosus, (%) Forward lean thorax during stair ascent (°) Time up stairs (s)
Control Group (N = 23)
PROSTHESIS vs Ctrl. (Both Legs Comb.)
Contralateral vs Ctrl. (Both Legs Comb.)
P2
P2
Prosthesis
Contralateral
P1
Non-Dominant
Dominant
P1
1.24 ± 0.40
1.67 ± 0.43
.000
2.00 ± 0.30
2.14 ± 0.40
.009
2.07 ± 0.33
.000
.001
0.92 ± 0.29
0.96 ± 0.32
.121
1.08 ± 0.21
1.14 ± 0.23
.066
1.11 ± 0.21
.015
.068
199.1 ± 108.0 223.2 ± 131.6 111.2 ± 54.4
220.9 ± 107.5 258.3 ± 110.7 132.9 ± 48.4
.114 .124 .034
207.7 ± 81.1 265.3 ± 117.2 109.5 ± 37.1
204.0 ± 64.2 230.8 ± 95.2 151.4 ± 95.8
.832 .388 .027
205.9 ± 61.1 238.2 ± 90.8 130.4 ± 59.8
.807 .681 .274
.582 .535 .890
101.0 ± 61.6
108.1 ± 63.8
.758
134.5 ± 86.8
122.1 ± 70.5
.592
128.3 ± 62.3
.162
.323
68 ± 43
69 ± 31
.873
55 ± 17
77 ± 46
.021
66 ± 28
.846
.777
56 ± 36
46 ± 26
.109
54 ± 29
66 ± 52
.405
62 ± 35
.595
.149
Both Legs Comb.
13.3 ± 4.3
16.3 ± 6.8
.087
2.6 ± 0.5
2.3 ± 0.3
.013
MVCC = maximal voluntary concentric contraction, Nm/bw = newton meter/body weight, μV = micro volt, P1 = Side-to-side differences (t-test), P2 = Group differences (ANOVA).
Results Between and within group differences are found in Table 2. During stair ascent, no differences were found in normalized EMG RMS for VL or ST between the TKA group and the control group. In the TKA group, no side-to-side differences were found in normalized EMG RMS for VL or ST, however in the control group a significantly lower value was found for VL in the non-dominant side compared to the dominant side. Quadriceps peak torque in the TKA group was significantly lower in their prosthetic side compared to the contralateral side and compared to the mean combined sides in the control group. Also the contralateral side in the TKA group produced significantly weaker quadriceps peak torque than the mean combined sides in the control group. The hamstring strength of the prosthetic side was significantly lower than the average of both sides in the control group. The contralateral side, however, produced equal hamstring strength to the average of both sides in the control group. Time to complete the stair ascent showed that the TKA group walked significantly slower than the control group. There was no group difference in forward trunk lean during stair ascent. Discussion The present study showed that the TKA group ascended stairs at a slower self-selected pace than healthy controls. Despite significantly lower quadriceps and hamstring strength in the TKA group, the relative muscular effort was similar to the control group. Kinematics did not reveal increased forward lean of the trunk in the TKA group as a compensation for muscle weakness during stair ascent. Our result is in line with previous studies that have shown a reduction of about 50% in stair climbing velocity one year after TKAsurgery compared to healthy age-matched individuals [1]. In contrast to our results, Hortobágyi et al [7], found that old adults (74 ± 3 years), contrary to young adults (22 ± 2 years), ascended stairs close to their maximal capability as a consequence of muscular weakness. Similar relative muscular effort in both groups in the present study could perhaps be explained by a difference in gait velocity. EMG activity is positively correlated with gait velocity [18,19]. Reduced gait velocity may indicate reduced knee extension moment and therefore also reduced activity in VL, the net effect resulting in similar effort relative to MVCC in both groups. Similarly, Milot et al [20], showed that by slowing gait velocity, utilization of
maximal capacity was reduced. Others have shown reduced knee extension moments and significantly lower force in the vastii and rectus femoris in TKA patients compared to controls during level gait compensated by increased back extension moments [10]. Thus, different strategies may be adopted to compensate for muscle weakness and reduce the relative effort. To enforce differences in effort between groups, standardization of different parameters may be implemented. Hortobágyi et al [7] used a metronome during stair ascent in order to ensure similar overall gait speed. Nevertheless, the angular velocity at the knee joint was still significantly higher in the younger and stronger group than in the older and weaker group. This suggests that switching in the velocity pattern between knee and hip joint is yet another strategy to compensate for muscle weakness at the knee [7]. In spite of lower angular velocity at the knee, the older group still displayed a significantly increased relative effort due to the reduced capability to produce maximal leg strength [7]. The results in the present study suggest that the TKA group managed to compensate muscle weakness with reduced gait velocity, and thus used the same effort as controls relative to maximum capacity. The quadriceps strength in the TKA group was 40% lower in the prosthetic side and 20% lower in the contralateral side compared to controls. The greater strength difference between groups (60%) in the study by Hortobágyi et al [7], may explain why the weaker subjects in that study were unable to compensate muscle weakness. Although the prosthetic side was significantly weaker than the contralateral side, the relative effort in stair ascent was similar in both sides. In contrast, other studies have found greater relative quadriceps muscular effort in the prosthetic leg compared to the contralateral leg in older TKA patients during level gait [21]. However that study did not use EMG normalized to maximal effort for each leg, but compared absolute values between legs during gait only. In the present study, the control group displayed significantly higher proportion of the maximal capacity in the stronger and dominant side during stair ascent. This asymmetry may be explained by limb dominance, suggesting that the dominant side is more active during gait [22,23]. The hypothesis of a compensatory strategy in order to reduce the load on the prosthetic knee with an increased forward trunk lean in the TKA group compared to the control group was rejected. As discussed above, compensation for muscle weakness was apparently achieved by reduced gait velocity and not forward trunk lean. Increased forward trunk lean to reduce the quadriceps demand
Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
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J. Bjerke et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
during stair climbing has been demonstrated in patients with OA [11]. Notably, OA comes with a great deal of pain which needs to be relieved during weight acceptance [24], which partly may explain this compensation. The TKA group in the present study did not report pain. While Li et al [10] found increased forward trunk lean in TKA patients during level gait, the TKA patients in that study were both older and closer to the time of TKA surgery than the subjects in the present study. In conclusion, the present study offers more information about strategy than utilization of capacity as it is difficult to control the compensatory factors and isolate muscular capacity. Different strategies may be employed to compensate muscle weakness and by controlling or monitoring various factors such as gait velocity, cadence, joint angle velocities, upper body dynamics, and anthropometrics, various compensatory strategies for muscle weakness may be found. Although muscle weakness in the lower extremities may be compensated by different strategies, strength in the lower extremity is positively correlated with gait speed and function in daily life activities [25]. Furthermore, gait speed is also correlated with survival [26] and falls [27]. Therefore, improvement and maintenance of lower extremity strength to improve function in daily life are crucial after TKA surgery. References 1. Walsh M, Woodhouse LJ, Thomas SG, et al. Physical impairments and functional limitations: a comparison of individuals 1 year after total knee arthroplasty with control subjects. Phys Ther 1998;78:248. 2. Bjerke J, Ohberg F, Nilsson KG, et al. Peak knee flexion angles during stair descent in TKA patients. J Arthroplasty 2013 http://dx.doi.org/10.1016/j.arth.2013.07.010. 3. Mizner RL, Snyder-Mackler L. Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplasty. J Orthop Res 2005;23:1083. 4. Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil 2002;83:1432. 5. Silva M, Shepherd EF, Jackson WO, et al. Knee strength after total knee arthroplasty. J Arthroplasty 2003;18:605. 6. Stevens-Lapsley JE, Balter JE, Kohrt WM, et al. Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty. Clin Orthop Relat Res 2010;468:2460. 7. Hortobagyi T, Mizelle C, Beam S, et al. Old adults perform activities of daily living near their maximal capabilities. J Gerontol A Biol Sci Med Sci 2003;58:M453.
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Please cite this article as: Bjerke J, et al, Compensatory Strategies for Muscle Weakness During Stair Ascent in Subjects With Total Knee Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.01.033
