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Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study
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Original research
Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study Maria Thorning a , Jonas B. Thorlund a , Ewa M. Roos a,b , Tim V. Wrigley b , Michelle Hall b,∗ a b
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Denmark Centre for Health, Exercise and Sports Medicine, Department of Physiotherapy, School of Health Sciences, The University of Melbourne, Australia
a r t i c l e
i n f o
Article history: Received 18 December 2015 Received in revised form 9 February 2016 Accepted 16 March 2016 Available online xxx Keywords: Braces Biomechanics Knee Arthroscopy Knee osteoarthritis
a b s t r a c t Objectives: Patients undergoing medial arthroscopic partial meniscectomy are at increased risk of developing and/or progressing knee osteoarthritis, with increased medial compartment load being a potential contributor. The aim of this study was to evaluate the immediate effect of a valgus unloader knee brace on knee joint moments in patients following medial arthroscopic partial meniscectomy. Design: Within-participant design. Methods: Twenty-two patients (age 35–55 years) who had undergone medial arthroscopic partial meniscectomy within the previous 8–15 months completed three-dimensional analysis of gait, forward lunge and one-leg rise during two conditions: with and without a valgus unloader knee brace. Outcome measures included the peak and impulse of the knee adduction moment and the peak knee flexion moment. Results: The peak knee flexion moment increased during brace condition for forward lunge (mean difference [95% CI]) 0.54 [0.27–0.82] (Nm/(BW × HT)%), p < 0.001 and one-leg rise (mean difference 0.45 [95% CI 0.08–0.82] (Nm/(BW × HT)%), p = 0.022). No other significant differences were found between conditions in any of the included tasks. Conclusions: A significant effect of the knee brace was detected in terms of an increase in peak knee flexion moment during the more demanding tasks such as forward lunge and one-leg rise. This increase implies enhanced stability of the knee provided by the brace, which may induce increased knee function and knee-related confidence during strenuous tasks. Future research is required to explore the structural implications. © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Osteoarthritis (OA) in the tibiofemoral and patellofemoral compartment is common in patients following arthroscopic partial meniscectomy (APM).1 Despite strong evidence questioning the efficacy of APM to manage symptomatic meniscal tears,2 a large volume of these procedures are performed.3 Thus, investigation into treatments aiming to prevent or delay the development or progression of early OA in this patient population is warranted. The external knee adduction moment (KAM) is an indicator of mediolateral knee joint load distribution where the peak KAM has been positively associated with structural joint change in patients following medial APM.4 Studies from patients with established knee OA also report an association between higher KAM and structural degeneration during gait.5,6 The KAM is
∗ Corresponding author. E-mail address: [email protected] (M. Hall).
predominantly determined by the product of the ground reaction force (GRF) vector and the perpendicular distance of this force to the centre of the joint (i.e. the frontal plane lever arm).7 Increased varus malalignment is thought to increase the frontal plane lever arm and consequently increase the KAM.7 Varus malalignment has been shown to progress over time in patients following medial APM8 and partially account for the increase in KAM during gait.9 Thus, varus malalignment is a potential target for treatments to address in patients following medial APM. Valgus unloader knee braces are a non-surgical treatment strategy for patients with medial compartment knee OA.10 Theoretically, the brace applies an external valgus moment, which plausibly reduces load in the medial tibiofemoral compartment10 and retard structural disease progression.11 According to a recent systematic review, valgus knee bracing can reduce the KAM during walking, with moderate-to-large effects in patients with established medial knee OA.10 A similar effect of valgus bracing could potentially exist in patients following medial APM, although to our knowledge this has not yet been investigated.
http://dx.doi.org/10.1016/j.jsams.2016.03.005 1440-2440/© 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005
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2
In addition to the KAM, the external knee flexion moment (KFM) is of interest. Patients following medial APM reportedly have a higher peak KFM12,13 that appears to increase over time.13 These results are of potential significance as there is an association between higher peak KFM during gait and patellar cartilage volume loss over 2 years in this population.4 Although the mechanisms by which a valgus unloader knee brace would alter the KFM are unclear, it is important to evaluate the immediate effects of bracing on the KFM. Given the association between knee joint moments during gait and structural change, reducing knee joint moments during gait is considered desirable. In addition to gait, we considered more physically demanding tasks appropriate to middle-aged APM patients. The purpose of this study was to test the hypothesis that wearing a valgus unloader knee brace would reduce the peak KAM during gait in middle-aged individuals following APM at high risk of developing or progressing early knee OA. The secondary exploratory aims of this study was to assess the immediate effect of the valgus unloader brace on KAM impulse and the peak KFM during gait, and all three moment parameters (peak KAM, KAM impulse and peak KFM) during a forward lunge and one-leg rise. 2. Methods Participants aged 35–55 years who had undergone an isolated medial APM were recruited from the existing cohort study “Knee Arthroscopy Cohort Southern Denmark” (KACS).14 Exclusion criteria were: major cartilage damage defined as deep visible clefts or bone observed at arthroscopy; co-morbidities affecting lower extremity function; current self-reported back problems; very low activity level (i.e. gait function restricted to indoor walking only); unable to read or understand Danish. Assessment was conducted in the Movement Laboratory at the University of Southern Denmark. Ethical approval was granted from the Regional Scientific Ethics Committee of Southern Denmark. All included participants provided written informed consent. Participants completed the Knee Injury Osteoarthritis Outcome Score (KOOS) prior to testing, to evaluate knee pain and function. The KOOS is a valid and reliable self-reported outcome measure for use in, patients with meniscus injury and cartilage damage.15 Knee pain (for the study knee) was additionally assessed using Numerical Rating Scale (NRS)16 immediately before and after testing, to evaluate if pain changed during the testing session. Furthermore, participants registered the comfort of the brace by a NRS while wearing it during the movement tasks (0 indicate “most comfortable” and 10 indicate “least comfortable”). Static frontal plane knee alignment of the study knee was assessed using an inclinometer as participants stood comfortably upright. This method is reliable (ICC = 0.94) and valid compared to mechanical axis from full-length radiographs (r = 0.80).17 The valgus knee brace tested was the Rebound® Cartilage knee brace (Össur, Reykjavik, Iceland). The brace is a prefabricated based on a 3-point pressure system where a single axis joint on the medial side of the leg connects the thigh and shank segments. Prior to assessment, each participant had the brace fitted on the APM leg by the same physiotherapist (MT). The brace was fitted to each patient by adjusting straps and dials in order to produce a valgus torque without any perceived discomfort. The magnitude of torque applied by the brace was not assessed and unlikely uniform across all participants. Kinematic data were acquired using a Vicon MX motion analysis system (Vicon, Oxford, UK) consisting of 16 cameras operating at 200 Hz. Kinetic data were captured in synchrony at 3000 Hz using two force plates (Advanced Mechanical Technology, Watertown, MA, USA) embedded in the floor. Similar to previous studies, the University of Western Australia seven-segment model was used.18
Reflective markers were attached to the 10th thoracic vertebra, 7th cervical vertebra, manubrium and bilaterally to the anterior superior iliac spines, posterior superior iliac spines, lateral epicondyles, lateral malleoli, first and fifth metatarsal head, fifth metatarsal base and calcaneus; 3-marker triads were attached to each thigh and shin. To determine relative positioning of the knee and ankle joint centres, additional markers were placed at the medial femoral condyles and medial malleoli for a single static trial. The brace did not interfere with marker placement. Hip joint centres were estimated based on the Harrington approach.19 Marker trajectories and GRF were low pass-filtered at 6 Hz. Moments of the lower limb joints were estimated using inverse dynamics BodyBuilder model (Vicon, Oxford, UK). Following standardised instructions and familiarisation, participant performed three tasks, including: (i) gait, (ii) forward lunge and (iii) one-leg rise under two conditions: with a brace and without a brace on the previously meniscectomised knee. The sequence of tasks and conditions were randomised for each participant and an adaption period of at least 5 min was incorporated between conditions. Participants were instructed to perform all tasks at comfortable, self-selected pace while barefoot. Participants performed six gait trials for each condition and were asked to adjust their walking speed if the self-selected walking speed was greater than ±5% different between conditions. For the forward lunge, participants were instructed to stand with feet shoulder width apart and leading with the APM leg step forward onto the force plate until the knee reached 90◦ flexion. Participants were asked to maintain their trunk in an upright position, with hands on their hips and maintain floor contact with contralateral foot throughout the duration of the movement. Participants then returned to the starting position by pushing backwards through extending the knee. The forward lunge distance was standardised between conditions according to leg length. Three forward lunge trials were recorded. For the one-leg rise task, using the APM limb only, participants were instructed to rise from the seat until standing upright and return to the seated position, in a controlled smooth motion. Meanwhile, the non-weight bearing leg was held off the ground by flexing the knee while arms were held across the chest. Seat position was standardised between conditions by marking seat depth and foot placement. Stance phase for the one-leg rise was defined from the period when the GRF reached 100 N to the point when the GRF dropped below 100 N. Three one-leg rise trials were recorded. The moments of interest in the current study were: (1) peak KAM during the first half of stance as the primary outcome, (2) positive KAM impulse during the stance phase as a secondary outcome, (3) peak KFM throughout stance as a secondary outcome. Moments were averaged across trials and expressed as external moments normalised by the product of body weight (N) times body height (m). For this exploratory study, an a priori sample size calculation estimated that 20 participants were required to detect a 7% change in peak KAM during gait with 80% statistical power. The estima√ tion was based upon the smallest detectable (SDC) change SDC/ n (using a SDC of 0.80 Nm/(BW × HT)% based on test–retest data from our laboratory and data from a knee OA sample).20 However, due to equipment failure only 17 participants were available for gait analysis. A subsequent post hoc power analysis confirmed that 17 participants adequately detected a large effect size of 0.8 with 80% statistical power. The difference between conditions was calculated by subtracting the no brace condition-scores from the brace condition-scores. For NRS-pain, the difference was estimated by subtracting the “pre-session” score from the “post-session” score. Student’s paired t-test (parametric test) and Wilcoxon signed rank test (non-parametric test) were used to compare biomechanical variables of interest between conditions, in addition to NRS-pain
Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005
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scores before and after the testing session. The outcomes from Student’s paired t-test are reported since no difference in interpretation was found between the parametric and non-parametric tests-results for any variables, including those not conforming to the Gaussian distribution. Statistical analysis was performed using STATA 13.1 (StataCorp, College Station, Texas, USA) and alpha level of 0.05 was used.
Table 1 Participant characteristics (n = 22).
3. Results Twenty-two patients who had undergone a medial APM within the previous 8–15 months participated in this study. Descriptive characteristics are presented in Table 1. Participants were middleaged, predominantly female, overweight, and had neutral static alignment (Table 1). The majority of meniscal injuries resulted from a non-traumatic incident (Table 1). The KOOS scores indicate on average mild pain during activity, mild other symptoms and functional restriction during daily life. Sport and recreation function and knee related quality of life were, on average moderately affected (Table 1). However according to the NRS, participants reported minimal pain prior to testing (mean 1.27 [95% CI 0.55–2.00]) and immediately following testing (mean 2.00 [95% CI 1.19–2.81], where 0 indicates no pain). Pain increased marginally during the testing session (mean change 0.73 [95% CI 0.27–1.18], p-value = 0.003). During the tasks, participants considered the valgus brace relatively comfortable to wear scoring a mean of 2.82 [95% CI 2.17–3.47] on a NRS, where 0 indicated greatest comfort. The mean (SD) peak KAM, KAM impulse and peak KFM for each of three tasks (gait, forward lunge, one-leg rise) assessed during each condition (brace and no brace) are presented in Table 2. Seventeen of the 22 participants had data available for gait trials. Five were excluded due to malfunction of one of the force plates. Twenty-one participants completed the forward lunge and 16 completed the one-leg rise. Some participants opted not to perform a forward lunge (n = 1) and one-leg rise (n = 6) due to pain, limited functional ability and/or lack of confidence. There were no significant differences between the conditions for our primary outcome, the peak KAM during gait (mean difference −0.07 [95% CI −0.24 to 0.11] (Nm/(BW × HT)%), p = 0.442). Notably, there was large variation in the individual percentage changes in peak KAM between the conditions, which ranged from a decrease of approximately −30% to an increase of 20%, as shown in Fig. 1a. There were no significant differences in KAM impulse or peak KFM between conditions
3
Age, yrs Women, n (%) Body mass index, kg/m2 Time from surgery, mths Varus alignmenta (◦ ) Pain medication use, study knee (yes/no)b
48.6 ± 5.2 15 (68) 28.0 ± 5.3 12 ± 2 0.0 ± 2.4 5/17
KOOS (0–100) Pain Symptoms ADL Sport and recreation QOL
72.2 ± 20.7 71.1 ± 16.3 79.3 ± 17.2 48.2 ± 25.7 47.4 ± 17.6
Symptom onset, n (%) Pain problems arouse slowly Non-traumatic incidentc Traumatic incidentd
5 (23) 12 (54) 5 (23)
Location of tear, n (%) Posterior Mid-body Posterior and mid-body
13 (59) 3 (14) 6 (27)
e
Amount resected from medial meniscii, n (%) <25% 25–50% >50%
14 (74) 4 (21) 1 (5)
Values are reported as mean ± SD, or n (%). Abbreviations: ADL: activities of daily living; KOOS: knee injury osteoarthritis outcome score, ranges from 0 to 100 (100 is the best possible); QOL: knee-related quality of life. a Values below 0◦ indicates varus alignment. b Within past week prior to testing. c i.e. kneeling, sliding, knee rotation, etc. d Sudden onset, i.e. sport, crash, collision, etc. e The amount of meniscus tissue resected was noted by the surgeon during arthroscopy.
during gait (Table 2) with considerable variation also observed for the individual percentage changes (Fig. 1b, c). For the more challenging tasks assessed, there were no significant differences in peak KAM or KAM impulse between brace conditions during forward lunge or one-leg rise. However wearing the brace resulted in a 10% higher peak KFM during forward lunge (mean difference 0.54 [95% CI 0.27–0.82] (Nm/(BW × HT)%), p < 0.001) and an 8% higher peak KFM during a one-leg rise (mean difference 0.45 [95% CI 0.08–0.82] (Nm/(BW × HT)%), p = 0.022) compared to not wearing a brace. Interestingly, as illustrated in Fig. 1d and e, the majority
Table 2 Mean [95% confidence intervals] peak KAM, KAM impulse, peak KFM. Brace [95% CI]
No brace [95% CI]
Mean difference [95% CI] (brace minus no brace)
p-Value
Gait (n = 17) Walking speed (m/s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%) KAM impulse (Nm.s/(BW × HT)%)
1.35 [1.27, 1.44] 2.90 [2.32, 3.48] 2.66 [1.93, 3.39] 0.98 [0.75, 1.21]
1.38 [1.29, 1.47] 2.97 [2.38, 3.55] 2.77 [2.07, 3.46] 0.92 [0.71, 1.13]
−0.03 [−0.02, 0.07] −0.07 [−0.24, 0.11] −0.11 [−0.42, 0.21] 0.06 [−0.01, 0.12]
0.210 0.442 0.489 0.082
Forward lunge (n = 21) Stance phase (s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%)
1.78 [1.49, 2.07] 2.64 [2.01, 3.26] 5.77 [5.00, 6.55]
1.88 [1.61, 2.16] 2.51 [1.92, 3.10] 5.23 [4.43, 6.03]
−0.10 [−0.30, 0.09] 0.12 [−0.07, 0.32] 0.54 [0.27, 0.82]
0.286 0.208 <0.001
One-leg risea (n = 15) Stance phase (s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%) KAM impulse (Nm s/(BW × HT)%)
3.20 [2.93, 3.48] 3.38 [2.74, 4.03] 6.00 [4.74, 7.27] 5.96 [4.75, 7.17]
3.40 [2.86, 3.92] 3.40 [2.70, 4.10] 5.56 [4.32, 6.79] 6.64 [4.73, 8.56]
−0.20[−0.66, 0.27] −0.02 [−0.31, 0.26] 0.45 [0.08, 0.82] −0.68 [−2.00, 0.63]
0.387 0.873 0.022 0.281
Values are reported as mean averaged over number of trials. Abbreviations: KAM: knee adduction moment; KFM: knee flexion moment. Bold indicates statistical significance at p < 0.05. a Data from one participant performing the one-leg rise was excluded; Nm/(BW × HT)%.
Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005
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Individual parcipants
Fig. 1. Percentage change in peak knee adduction moment (a), knee adduction moment impulse (b) and peak knee flexion moment (c) for each participant during gait. Percentage change in peak KFM during forward lunge (d) and one-leg rise (e) for each participant. Negative values indicate a decrease in moment wearing the brace compared to walking without wearing the brace. Positive values indicate an increase in moment wearing the brace compared to walking without wearing the brace.
of participants demonstrated an increase in peak KFM performing a forward lunge (76%) and a one-leg rise (69%) when wearing the knee brace. 4. Discussion The aim of this exploratory study was to examine the immediate effect of a valgus unloader knee brace on joint moments during three functional tasks, in a group of middle-aged patients 12 months following medial APM. While no evidence was found to suggest an immediate effect of the valgus unloader knee brace on peak KAM or KAM impulse for any of the tasks assessed, the immediate effect of wearing the brace demonstrated an increase in peak KFM during a forward lunge (10%) and one-leg rise (8%) compared to performing the task without the brace. We speculate the increase in peak KFM reflects greater knee-related confidence. The peak KAM during gait was selected as the primary outcome given its positive association with medial tibiofemoral cartilage defect onset or progression in patients following medial APM.4 We expected that the immediate effect of the brace would reduce the KAM as the brace is designed to neutralise the frontal knee position which could plausibly reduce the length of the frontal plane lever arm,7 and thereby the KAM. However, contrary to our hypothesis and findings from studies in patients with established knee OA evaluating valgus knee bracing10,21 we observed no immediate effect of wearing the brace in the KAM during gait. Furthermore, no evidence was found to suggest an immediate effect of the brace on the KAM (peak or impulse) during a forward lunge or one-leg rise. Failure to reduce the KAM might be
partially explained by absence of frontal plane varus malalignment in our study sample. On average, patients in this study presented with neutral static alignment, which would theoretically reduce the scope to bring the knee into a neutral position and decrease the KAM. Conversely, the KAM magnitudes presented in the current study are comparable with other APM literature22 as such it is reasonable to speculate that our participants have scope to reduce KAM. Notably, the immediate effect of wearing the brace in the present study yielded quite variable individual responses to the valgus knee brace (Fig. 1). These results indicate that the effect of the brace may be influenced by individual participant characteristics. It is unclear which individual factors mediate the response to valgus knee bracing. However, similar variation has been observed in studies evaluating the immediate effect of lateral wedges on KAM in people with knee OA.23 Previously, authors have reported that various factors including toe angle,24 trunk leak24 and walking speed25 influence KAM magnitude during walking. Although in the present study walking speed was matched with ±5% between conditions for gait, small changes may be in part responsible the individual variation and hence, failure to significantly reduce the KAM. The peak KFM is also of clinical interest, partially because it is known to mediate medial tibiofemoral contact force26 during gait and is associated with patellar cartilage loss in APM patients during gait.4 Previously, valgus bracing in people with established knee OA has found no change in peak KFM during gait.21 Nonetheless, we found that peak KFM significantly increased by 10% and 8% during brace condition compared to not wearing the brace, for the forward lunge and the one-leg rise, respectively. Although the immediate
Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005
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effect of the brace on knee-related confidence or stability was not assessed in this study, knee-related confidence was characterised by a question (Q3) on the quality-of-life subscale of the KOOS questionnaire prior to testing. Fifteen (68%) participants reported on being on average moderately troubled with lack of confidence in the meniscectomised knee (range from mildly to severely troubled). The reported comfort-assessment-score while wearing the brace, was relatively high, we therefore speculate that good comfort may infer greater confidence in knee stability while wearing the brace. Studies in knee OA patients found valgus bracing to increase joint stability27 and knee-related confidence,28 albeit during gait. However, future research is required to confirm our speculation on knee related confidence and determine if superior confidence is unique to valgus bracing. Future research should consider the clinical implications of wearing a valgus knee brace in APM patients. Although the structural implication of increasing the peak KFM should be considered, caution must be used extrapolating these data beyond gait. Indeed, improving knee muscle strengthening may be of particular relevance to APM patients given that knee extensor weakness, a risk factor for the development of knee OA,29 is often present in this population.30 Theoretically, a greater KFM would indicate a greater demand on the knee extensors. Thus, wearing a knee brace may improve knee-related confidence such that, patients are confident in placing a greater demand on the knee extensor muscles. Furthermore, in light of evidence from in vivo studies describing the influence of the KFM on joint contact force,26 it is plausible that changes in peak KFM represent changes in medial contact force even in absence of change in KAM. Strengths of our study include the randomisation of test conditions and order of tasks performed. However, limitations of this study warrant consideration. First, although the KAM is widely used as a surrogate of medial knee joint load5,6 we did not assess knee joint loading in vivo and therefore cannot conclusively determine that the valgus brace did not alter medial joint contact force. Second, although our sample size was adequately powered to detect a large effect (0.80), a clinically meaningful amount of change in peak KAM in APM patients is unknown. Therefore larger samples may detect smaller effects, which may be clinically relevant. Third, all tests were performed during one test session. This excludes an elucidation of how the valgus knee brace influences the structural health over time in patients following medial APM. Fourth, we did not evaluate pain between conditions and tasks, for which reason the effect of the included valgus knee brace on pain is unknown. Fifth, we cannot conclusively confirm the absence of radiographic and/or clinical knee OA. 5. Conclusion Our preliminary findings suggest that the immediate effect of valgus bracing in people following a medial APM increases the peak KFM during challenging tasks including forward lunge and one-leg rise. Alterations in the peak KFM provide the impetus for conducting larger scale studies investigating the implication on physical function and structural change. Practical implications • Valgus bracing does not appear to alter measures of knee joint loading during gait, although individual results vary. • Valgus bracing could be beneficial to meniscectomised patients by providing greater knee-related confidence during demanding activities. • The results may aid development of conservative management of meniscectomised patients.
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Acknowledgements We thank Össur, Reykjavik, Iceland who provided us with the braces and consulting assistance. Össur was not involved in study design, writing or editing this manuscript. MH was supported by a PhD scholarship from a National Health Medical Research Council, Australia program grant (#631717) and an International Travel Grant from the International Society of Biomechanics. Finally, the authors would like to express gratitude to the patients who voluntarily participated in the present study.
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24. Simic M, Hinman RS, Wrigley TV et al. Gait modification strategies for altering medial knee joint load: a systematic review. Arthritis Care Res 2011; 63(3):405–426. 25. Kirtley C, Whittle MW, Jefferson RJ. Influence of walking speed on gait parameters. J Biomed Eng 1985; 7(4):282–288. 26. Walter JP, D’Lima DD, Colwell Jr CW et al. Decreased knee adduction moment does not guarantee decreased medial contact force during gait. J Orthop Res 2010; 28(10):1348–1354. 27. Ramsey DK, Briem K, Axe MJ et al. A mechanical theory for the effectiveness of bracing for medial compartment osteoarthritis of the knee. J Bone Joint Surg Am 2007; 89(11):2398–2407.
28. Hart HF, Crossley KM, Ackland DC et al. Effects of an unloader knee brace on knee-related symptoms and function in people with post-traumatic knee osteoarthritis after anterior cruciate ligament reconstruction. Knee 2015; 23:85–90. 29. Oiestad BE, Juhl CB, Eitzen I et al. Knee extensor muscle weakness is a risk factor for development of knee osteoarthritis. A systematic review and meta-analysis. Osteoarthr Cartil 2015; 23(2):171–177. 30. Hall M, Juhl CB, Lund H et al. Knee extensor muscle strength in middle-aged and older individuals undergoing arthroscopic partial meniscectomy: a systematic review and meta-analysis. Arthritis Care Res 2015; 67:1289–1296.
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Original research
Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study Maria Thorning a , Jonas B. Thorlund a , Ewa M. Roos a,b , Tim V. Wrigley b , Michelle Hall b,∗ a b
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Denmark Centre for Health, Exercise and Sports Medicine, Department of Physiotherapy, School of Health Sciences, The University of Melbourne, Australia
a r t i c l e
i n f o
Article history: Received 18 December 2015 Received in revised form 9 February 2016 Accepted 16 March 2016 Available online xxx Keywords: Braces Biomechanics Knee Arthroscopy Knee osteoarthritis
a b s t r a c t Objectives: Patients undergoing medial arthroscopic partial meniscectomy are at increased risk of developing and/or progressing knee osteoarthritis, with increased medial compartment load being a potential contributor. The aim of this study was to evaluate the immediate effect of a valgus unloader knee brace on knee joint moments in patients following medial arthroscopic partial meniscectomy. Design: Within-participant design. Methods: Twenty-two patients (age 35–55 years) who had undergone medial arthroscopic partial meniscectomy within the previous 8–15 months completed three-dimensional analysis of gait, forward lunge and one-leg rise during two conditions: with and without a valgus unloader knee brace. Outcome measures included the peak and impulse of the knee adduction moment and the peak knee flexion moment. Results: The peak knee flexion moment increased during brace condition for forward lunge (mean difference [95% CI]) 0.54 [0.27–0.82] (Nm/(BW × HT)%), p < 0.001 and one-leg rise (mean difference 0.45 [95% CI 0.08–0.82] (Nm/(BW × HT)%), p = 0.022). No other significant differences were found between conditions in any of the included tasks. Conclusions: A significant effect of the knee brace was detected in terms of an increase in peak knee flexion moment during the more demanding tasks such as forward lunge and one-leg rise. This increase implies enhanced stability of the knee provided by the brace, which may induce increased knee function and knee-related confidence during strenuous tasks. Future research is required to explore the structural implications. © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Osteoarthritis (OA) in the tibiofemoral and patellofemoral compartment is common in patients following arthroscopic partial meniscectomy (APM).1 Despite strong evidence questioning the efficacy of APM to manage symptomatic meniscal tears,2 a large volume of these procedures are performed.3 Thus, investigation into treatments aiming to prevent or delay the development or progression of early OA in this patient population is warranted. The external knee adduction moment (KAM) is an indicator of mediolateral knee joint load distribution where the peak KAM has been positively associated with structural joint change in patients following medial APM.4 Studies from patients with established knee OA also report an association between higher KAM and structural degeneration during gait.5,6 The KAM is
∗ Corresponding author. E-mail address: [email protected] (M. Hall).
predominantly determined by the product of the ground reaction force (GRF) vector and the perpendicular distance of this force to the centre of the joint (i.e. the frontal plane lever arm).7 Increased varus malalignment is thought to increase the frontal plane lever arm and consequently increase the KAM.7 Varus malalignment has been shown to progress over time in patients following medial APM8 and partially account for the increase in KAM during gait.9 Thus, varus malalignment is a potential target for treatments to address in patients following medial APM. Valgus unloader knee braces are a non-surgical treatment strategy for patients with medial compartment knee OA.10 Theoretically, the brace applies an external valgus moment, which plausibly reduces load in the medial tibiofemoral compartment10 and retard structural disease progression.11 According to a recent systematic review, valgus knee bracing can reduce the KAM during walking, with moderate-to-large effects in patients with established medial knee OA.10 A similar effect of valgus bracing could potentially exist in patients following medial APM, although to our knowledge this has not yet been investigated.
http://dx.doi.org/10.1016/j.jsams.2016.03.005 1440-2440/© 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
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2
In addition to the KAM, the external knee flexion moment (KFM) is of interest. Patients following medial APM reportedly have a higher peak KFM12,13 that appears to increase over time.13 These results are of potential significance as there is an association between higher peak KFM during gait and patellar cartilage volume loss over 2 years in this population.4 Although the mechanisms by which a valgus unloader knee brace would alter the KFM are unclear, it is important to evaluate the immediate effects of bracing on the KFM. Given the association between knee joint moments during gait and structural change, reducing knee joint moments during gait is considered desirable. In addition to gait, we considered more physically demanding tasks appropriate to middle-aged APM patients. The purpose of this study was to test the hypothesis that wearing a valgus unloader knee brace would reduce the peak KAM during gait in middle-aged individuals following APM at high risk of developing or progressing early knee OA. The secondary exploratory aims of this study was to assess the immediate effect of the valgus unloader brace on KAM impulse and the peak KFM during gait, and all three moment parameters (peak KAM, KAM impulse and peak KFM) during a forward lunge and one-leg rise. 2. Methods Participants aged 35–55 years who had undergone an isolated medial APM were recruited from the existing cohort study “Knee Arthroscopy Cohort Southern Denmark” (KACS).14 Exclusion criteria were: major cartilage damage defined as deep visible clefts or bone observed at arthroscopy; co-morbidities affecting lower extremity function; current self-reported back problems; very low activity level (i.e. gait function restricted to indoor walking only); unable to read or understand Danish. Assessment was conducted in the Movement Laboratory at the University of Southern Denmark. Ethical approval was granted from the Regional Scientific Ethics Committee of Southern Denmark. All included participants provided written informed consent. Participants completed the Knee Injury Osteoarthritis Outcome Score (KOOS) prior to testing, to evaluate knee pain and function. The KOOS is a valid and reliable self-reported outcome measure for use in, patients with meniscus injury and cartilage damage.15 Knee pain (for the study knee) was additionally assessed using Numerical Rating Scale (NRS)16 immediately before and after testing, to evaluate if pain changed during the testing session. Furthermore, participants registered the comfort of the brace by a NRS while wearing it during the movement tasks (0 indicate “most comfortable” and 10 indicate “least comfortable”). Static frontal plane knee alignment of the study knee was assessed using an inclinometer as participants stood comfortably upright. This method is reliable (ICC = 0.94) and valid compared to mechanical axis from full-length radiographs (r = 0.80).17 The valgus knee brace tested was the Rebound® Cartilage knee brace (Össur, Reykjavik, Iceland). The brace is a prefabricated based on a 3-point pressure system where a single axis joint on the medial side of the leg connects the thigh and shank segments. Prior to assessment, each participant had the brace fitted on the APM leg by the same physiotherapist (MT). The brace was fitted to each patient by adjusting straps and dials in order to produce a valgus torque without any perceived discomfort. The magnitude of torque applied by the brace was not assessed and unlikely uniform across all participants. Kinematic data were acquired using a Vicon MX motion analysis system (Vicon, Oxford, UK) consisting of 16 cameras operating at 200 Hz. Kinetic data were captured in synchrony at 3000 Hz using two force plates (Advanced Mechanical Technology, Watertown, MA, USA) embedded in the floor. Similar to previous studies, the University of Western Australia seven-segment model was used.18
Reflective markers were attached to the 10th thoracic vertebra, 7th cervical vertebra, manubrium and bilaterally to the anterior superior iliac spines, posterior superior iliac spines, lateral epicondyles, lateral malleoli, first and fifth metatarsal head, fifth metatarsal base and calcaneus; 3-marker triads were attached to each thigh and shin. To determine relative positioning of the knee and ankle joint centres, additional markers were placed at the medial femoral condyles and medial malleoli for a single static trial. The brace did not interfere with marker placement. Hip joint centres were estimated based on the Harrington approach.19 Marker trajectories and GRF were low pass-filtered at 6 Hz. Moments of the lower limb joints were estimated using inverse dynamics BodyBuilder model (Vicon, Oxford, UK). Following standardised instructions and familiarisation, participant performed three tasks, including: (i) gait, (ii) forward lunge and (iii) one-leg rise under two conditions: with a brace and without a brace on the previously meniscectomised knee. The sequence of tasks and conditions were randomised for each participant and an adaption period of at least 5 min was incorporated between conditions. Participants were instructed to perform all tasks at comfortable, self-selected pace while barefoot. Participants performed six gait trials for each condition and were asked to adjust their walking speed if the self-selected walking speed was greater than ±5% different between conditions. For the forward lunge, participants were instructed to stand with feet shoulder width apart and leading with the APM leg step forward onto the force plate until the knee reached 90◦ flexion. Participants were asked to maintain their trunk in an upright position, with hands on their hips and maintain floor contact with contralateral foot throughout the duration of the movement. Participants then returned to the starting position by pushing backwards through extending the knee. The forward lunge distance was standardised between conditions according to leg length. Three forward lunge trials were recorded. For the one-leg rise task, using the APM limb only, participants were instructed to rise from the seat until standing upright and return to the seated position, in a controlled smooth motion. Meanwhile, the non-weight bearing leg was held off the ground by flexing the knee while arms were held across the chest. Seat position was standardised between conditions by marking seat depth and foot placement. Stance phase for the one-leg rise was defined from the period when the GRF reached 100 N to the point when the GRF dropped below 100 N. Three one-leg rise trials were recorded. The moments of interest in the current study were: (1) peak KAM during the first half of stance as the primary outcome, (2) positive KAM impulse during the stance phase as a secondary outcome, (3) peak KFM throughout stance as a secondary outcome. Moments were averaged across trials and expressed as external moments normalised by the product of body weight (N) times body height (m). For this exploratory study, an a priori sample size calculation estimated that 20 participants were required to detect a 7% change in peak KAM during gait with 80% statistical power. The estima√ tion was based upon the smallest detectable (SDC) change SDC/ n (using a SDC of 0.80 Nm/(BW × HT)% based on test–retest data from our laboratory and data from a knee OA sample).20 However, due to equipment failure only 17 participants were available for gait analysis. A subsequent post hoc power analysis confirmed that 17 participants adequately detected a large effect size of 0.8 with 80% statistical power. The difference between conditions was calculated by subtracting the no brace condition-scores from the brace condition-scores. For NRS-pain, the difference was estimated by subtracting the “pre-session” score from the “post-session” score. Student’s paired t-test (parametric test) and Wilcoxon signed rank test (non-parametric test) were used to compare biomechanical variables of interest between conditions, in addition to NRS-pain
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scores before and after the testing session. The outcomes from Student’s paired t-test are reported since no difference in interpretation was found between the parametric and non-parametric tests-results for any variables, including those not conforming to the Gaussian distribution. Statistical analysis was performed using STATA 13.1 (StataCorp, College Station, Texas, USA) and alpha level of 0.05 was used.
Table 1 Participant characteristics (n = 22).
3. Results Twenty-two patients who had undergone a medial APM within the previous 8–15 months participated in this study. Descriptive characteristics are presented in Table 1. Participants were middleaged, predominantly female, overweight, and had neutral static alignment (Table 1). The majority of meniscal injuries resulted from a non-traumatic incident (Table 1). The KOOS scores indicate on average mild pain during activity, mild other symptoms and functional restriction during daily life. Sport and recreation function and knee related quality of life were, on average moderately affected (Table 1). However according to the NRS, participants reported minimal pain prior to testing (mean 1.27 [95% CI 0.55–2.00]) and immediately following testing (mean 2.00 [95% CI 1.19–2.81], where 0 indicates no pain). Pain increased marginally during the testing session (mean change 0.73 [95% CI 0.27–1.18], p-value = 0.003). During the tasks, participants considered the valgus brace relatively comfortable to wear scoring a mean of 2.82 [95% CI 2.17–3.47] on a NRS, where 0 indicated greatest comfort. The mean (SD) peak KAM, KAM impulse and peak KFM for each of three tasks (gait, forward lunge, one-leg rise) assessed during each condition (brace and no brace) are presented in Table 2. Seventeen of the 22 participants had data available for gait trials. Five were excluded due to malfunction of one of the force plates. Twenty-one participants completed the forward lunge and 16 completed the one-leg rise. Some participants opted not to perform a forward lunge (n = 1) and one-leg rise (n = 6) due to pain, limited functional ability and/or lack of confidence. There were no significant differences between the conditions for our primary outcome, the peak KAM during gait (mean difference −0.07 [95% CI −0.24 to 0.11] (Nm/(BW × HT)%), p = 0.442). Notably, there was large variation in the individual percentage changes in peak KAM between the conditions, which ranged from a decrease of approximately −30% to an increase of 20%, as shown in Fig. 1a. There were no significant differences in KAM impulse or peak KFM between conditions
3
Age, yrs Women, n (%) Body mass index, kg/m2 Time from surgery, mths Varus alignmenta (◦ ) Pain medication use, study knee (yes/no)b
48.6 ± 5.2 15 (68) 28.0 ± 5.3 12 ± 2 0.0 ± 2.4 5/17
KOOS (0–100) Pain Symptoms ADL Sport and recreation QOL
72.2 ± 20.7 71.1 ± 16.3 79.3 ± 17.2 48.2 ± 25.7 47.4 ± 17.6
Symptom onset, n (%) Pain problems arouse slowly Non-traumatic incidentc Traumatic incidentd
5 (23) 12 (54) 5 (23)
Location of tear, n (%) Posterior Mid-body Posterior and mid-body
13 (59) 3 (14) 6 (27)
e
Amount resected from medial meniscii, n (%) <25% 25–50% >50%
14 (74) 4 (21) 1 (5)
Values are reported as mean ± SD, or n (%). Abbreviations: ADL: activities of daily living; KOOS: knee injury osteoarthritis outcome score, ranges from 0 to 100 (100 is the best possible); QOL: knee-related quality of life. a Values below 0◦ indicates varus alignment. b Within past week prior to testing. c i.e. kneeling, sliding, knee rotation, etc. d Sudden onset, i.e. sport, crash, collision, etc. e The amount of meniscus tissue resected was noted by the surgeon during arthroscopy.
during gait (Table 2) with considerable variation also observed for the individual percentage changes (Fig. 1b, c). For the more challenging tasks assessed, there were no significant differences in peak KAM or KAM impulse between brace conditions during forward lunge or one-leg rise. However wearing the brace resulted in a 10% higher peak KFM during forward lunge (mean difference 0.54 [95% CI 0.27–0.82] (Nm/(BW × HT)%), p < 0.001) and an 8% higher peak KFM during a one-leg rise (mean difference 0.45 [95% CI 0.08–0.82] (Nm/(BW × HT)%), p = 0.022) compared to not wearing a brace. Interestingly, as illustrated in Fig. 1d and e, the majority
Table 2 Mean [95% confidence intervals] peak KAM, KAM impulse, peak KFM. Brace [95% CI]
No brace [95% CI]
Mean difference [95% CI] (brace minus no brace)
p-Value
Gait (n = 17) Walking speed (m/s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%) KAM impulse (Nm.s/(BW × HT)%)
1.35 [1.27, 1.44] 2.90 [2.32, 3.48] 2.66 [1.93, 3.39] 0.98 [0.75, 1.21]
1.38 [1.29, 1.47] 2.97 [2.38, 3.55] 2.77 [2.07, 3.46] 0.92 [0.71, 1.13]
−0.03 [−0.02, 0.07] −0.07 [−0.24, 0.11] −0.11 [−0.42, 0.21] 0.06 [−0.01, 0.12]
0.210 0.442 0.489 0.082
Forward lunge (n = 21) Stance phase (s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%)
1.78 [1.49, 2.07] 2.64 [2.01, 3.26] 5.77 [5.00, 6.55]
1.88 [1.61, 2.16] 2.51 [1.92, 3.10] 5.23 [4.43, 6.03]
−0.10 [−0.30, 0.09] 0.12 [−0.07, 0.32] 0.54 [0.27, 0.82]
0.286 0.208 <0.001
One-leg risea (n = 15) Stance phase (s) Peak KAM (Nm/(BW × HT)%) Peak KFM (Nm/(BW × HT)%) KAM impulse (Nm s/(BW × HT)%)
3.20 [2.93, 3.48] 3.38 [2.74, 4.03] 6.00 [4.74, 7.27] 5.96 [4.75, 7.17]
3.40 [2.86, 3.92] 3.40 [2.70, 4.10] 5.56 [4.32, 6.79] 6.64 [4.73, 8.56]
−0.20[−0.66, 0.27] −0.02 [−0.31, 0.26] 0.45 [0.08, 0.82] −0.68 [−2.00, 0.63]
0.387 0.873 0.022 0.281
Values are reported as mean averaged over number of trials. Abbreviations: KAM: knee adduction moment; KFM: knee flexion moment. Bold indicates statistical significance at p < 0.05. a Data from one participant performing the one-leg rise was excluded; Nm/(BW × HT)%.
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Fig. 1. Percentage change in peak knee adduction moment (a), knee adduction moment impulse (b) and peak knee flexion moment (c) for each participant during gait. Percentage change in peak KFM during forward lunge (d) and one-leg rise (e) for each participant. Negative values indicate a decrease in moment wearing the brace compared to walking without wearing the brace. Positive values indicate an increase in moment wearing the brace compared to walking without wearing the brace.
of participants demonstrated an increase in peak KFM performing a forward lunge (76%) and a one-leg rise (69%) when wearing the knee brace. 4. Discussion The aim of this exploratory study was to examine the immediate effect of a valgus unloader knee brace on joint moments during three functional tasks, in a group of middle-aged patients 12 months following medial APM. While no evidence was found to suggest an immediate effect of the valgus unloader knee brace on peak KAM or KAM impulse for any of the tasks assessed, the immediate effect of wearing the brace demonstrated an increase in peak KFM during a forward lunge (10%) and one-leg rise (8%) compared to performing the task without the brace. We speculate the increase in peak KFM reflects greater knee-related confidence. The peak KAM during gait was selected as the primary outcome given its positive association with medial tibiofemoral cartilage defect onset or progression in patients following medial APM.4 We expected that the immediate effect of the brace would reduce the KAM as the brace is designed to neutralise the frontal knee position which could plausibly reduce the length of the frontal plane lever arm,7 and thereby the KAM. However, contrary to our hypothesis and findings from studies in patients with established knee OA evaluating valgus knee bracing10,21 we observed no immediate effect of wearing the brace in the KAM during gait. Furthermore, no evidence was found to suggest an immediate effect of the brace on the KAM (peak or impulse) during a forward lunge or one-leg rise. Failure to reduce the KAM might be
partially explained by absence of frontal plane varus malalignment in our study sample. On average, patients in this study presented with neutral static alignment, which would theoretically reduce the scope to bring the knee into a neutral position and decrease the KAM. Conversely, the KAM magnitudes presented in the current study are comparable with other APM literature22 as such it is reasonable to speculate that our participants have scope to reduce KAM. Notably, the immediate effect of wearing the brace in the present study yielded quite variable individual responses to the valgus knee brace (Fig. 1). These results indicate that the effect of the brace may be influenced by individual participant characteristics. It is unclear which individual factors mediate the response to valgus knee bracing. However, similar variation has been observed in studies evaluating the immediate effect of lateral wedges on KAM in people with knee OA.23 Previously, authors have reported that various factors including toe angle,24 trunk leak24 and walking speed25 influence KAM magnitude during walking. Although in the present study walking speed was matched with ±5% between conditions for gait, small changes may be in part responsible the individual variation and hence, failure to significantly reduce the KAM. The peak KFM is also of clinical interest, partially because it is known to mediate medial tibiofemoral contact force26 during gait and is associated with patellar cartilage loss in APM patients during gait.4 Previously, valgus bracing in people with established knee OA has found no change in peak KFM during gait.21 Nonetheless, we found that peak KFM significantly increased by 10% and 8% during brace condition compared to not wearing the brace, for the forward lunge and the one-leg rise, respectively. Although the immediate
Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005
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effect of the brace on knee-related confidence or stability was not assessed in this study, knee-related confidence was characterised by a question (Q3) on the quality-of-life subscale of the KOOS questionnaire prior to testing. Fifteen (68%) participants reported on being on average moderately troubled with lack of confidence in the meniscectomised knee (range from mildly to severely troubled). The reported comfort-assessment-score while wearing the brace, was relatively high, we therefore speculate that good comfort may infer greater confidence in knee stability while wearing the brace. Studies in knee OA patients found valgus bracing to increase joint stability27 and knee-related confidence,28 albeit during gait. However, future research is required to confirm our speculation on knee related confidence and determine if superior confidence is unique to valgus bracing. Future research should consider the clinical implications of wearing a valgus knee brace in APM patients. Although the structural implication of increasing the peak KFM should be considered, caution must be used extrapolating these data beyond gait. Indeed, improving knee muscle strengthening may be of particular relevance to APM patients given that knee extensor weakness, a risk factor for the development of knee OA,29 is often present in this population.30 Theoretically, a greater KFM would indicate a greater demand on the knee extensors. Thus, wearing a knee brace may improve knee-related confidence such that, patients are confident in placing a greater demand on the knee extensor muscles. Furthermore, in light of evidence from in vivo studies describing the influence of the KFM on joint contact force,26 it is plausible that changes in peak KFM represent changes in medial contact force even in absence of change in KAM. Strengths of our study include the randomisation of test conditions and order of tasks performed. However, limitations of this study warrant consideration. First, although the KAM is widely used as a surrogate of medial knee joint load5,6 we did not assess knee joint loading in vivo and therefore cannot conclusively determine that the valgus brace did not alter medial joint contact force. Second, although our sample size was adequately powered to detect a large effect (0.80), a clinically meaningful amount of change in peak KAM in APM patients is unknown. Therefore larger samples may detect smaller effects, which may be clinically relevant. Third, all tests were performed during one test session. This excludes an elucidation of how the valgus knee brace influences the structural health over time in patients following medial APM. Fourth, we did not evaluate pain between conditions and tasks, for which reason the effect of the included valgus knee brace on pain is unknown. Fifth, we cannot conclusively confirm the absence of radiographic and/or clinical knee OA. 5. Conclusion Our preliminary findings suggest that the immediate effect of valgus bracing in people following a medial APM increases the peak KFM during challenging tasks including forward lunge and one-leg rise. Alterations in the peak KFM provide the impetus for conducting larger scale studies investigating the implication on physical function and structural change. Practical implications • Valgus bracing does not appear to alter measures of knee joint loading during gait, although individual results vary. • Valgus bracing could be beneficial to meniscectomised patients by providing greater knee-related confidence during demanding activities. • The results may aid development of conservative management of meniscectomised patients.
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Acknowledgements We thank Össur, Reykjavik, Iceland who provided us with the braces and consulting assistance. Össur was not involved in study design, writing or editing this manuscript. MH was supported by a PhD scholarship from a National Health Medical Research Council, Australia program grant (#631717) and an International Travel Grant from the International Society of Biomechanics. Finally, the authors would like to express gratitude to the patients who voluntarily participated in the present study.
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Please cite this article in press as: Thorning M, et al. Immediate effect of valgus bracing on knee joint moments in meniscectomised patients: An exploratory study. J Sci Med Sport (2016), http://dx.doi.org/10.1016/j.jsams.2016.03.005