Different targets of mechanical alignment do not improve knee outcomes after TKA

BackgroundAccurate alignment is a basic principle of TKA surgery, but achieving alignment within this target may not translate into superior outcomes after surgery.PurposeTo assess if neutral TKA mechanical alignment was associated with superior knee outcomes and to examine the effect of various aspects of pre-operative and post-operative alignment on knee function.MethodsAnalysis of a database of 444 TKA patients between June 2009 and October 2016. Knee outcomes (WOMAC, AKSS and knee range of motion) were collected before surgery and during follow-up at a minimum of six months.ResultsAnalysis included 444 TKA patients (62% female, mean age 66 years, mean follow-up 23 months). Deformity varied from 21° varus (mean = 7.9, SD = 2.8) to 17° valgus deformity (mean = 7.7, SD = 2.8). Pre-operatively, 101 (23%) knees were in native neutral mechanical alignment, while 278 (63%) were in varus and 65 (15%) were in valgus. Post-operatively, a group of 365 (82%) TKA were found to be in neutral mechanical alignment and a group of 79 (18%) TKA were noted to be ‘Outliers’ (17 [4%] TKA > 3° varus and 62 [14%] TKA > 3° valgus alignment). Restoration of the target of alignment of 0 ± 3° or 0 ± 1°, did not have better functional outcomes scores, range of motion or prosthesis longevity than those in the outlier range.ConclusionNeutral TKA alignment did not appear to be a significant contributing factor to the improvement in knee function in short-medium term follow-up.     

Baseline varus deformity is associated with increased joint loading and pain of non-operated knee two years after unilateral total knee arthroplasty

Background

The goals of this study were (1) to document the gait pattern of patients with unilateral knee osteoarthritis (OA), (2) to determine the knee adduction moment (KAM) changes in the non-operated knee, and (3) to identify the predictors of change in KAM in the non-operated knee.

Correlation between static limb alignment and peak knee adduction angle during gait is affected by subject pain in medial knee osteoarthritis

BackgroundAlthough increases in knee adduction moment (KAM) and angle (KAA) during gait are considered key pathologies that produce mechanical overload in the medial compartment of knee osteoarthritis (OA), it is unclear how these pathologies are related to subjective pain. The purpose of this study was to examine how subjective pain is related to such pathologies.MethodsGait analysis was performed in 31 participants with medial knee OA. The knees were classified into three groups based on Kellgren–Lawrence (KL) grade: early (0 and 1), moderate (2), and severe (3 and 4). Subjective pain was evaluated by the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index pain score. The knees were classified into low- and high-pain groups based on the pain score.ResultsThe WOMAC pain score did not correlate with either peak KAM or peak KAA. Although a positive correlation between static limb alignment and peak KAA was observed in the low-pain group, it was not observed in the high-pain group. Knee flexion angle at heel strike correlated negatively with the gap between static femorotibial angle and peak KAA in the high-pain group.ConclusionsAlthough a direct correlation between subjective pain and peak KAM or KAA was not observed, our results suggest a compensatory movement in the high-pain group of participants to reduce KAA increases in the early stance phase. Such movements would be one of the reasons why it is difficult to obtain a consistent relationship between subjective pain and load-related parameters.     

The association of external knee adduction moment with biomechanical variables in osteoarthritis: A systematic review

ContextOsteoarthritis (OA) is a musculoskeletal disorder primarily affecting the older population and resulting in chronic pain and disability. Biomechanical variables, associated with OA severity such as external knee adduction moment (KAM) and joint malalignment, may affect the disease process by altering the bone-on-bone forces during gait.ObjectiveTo investigate the association between biomechanical variables and KAM in knee OA.MethodA systematic search for published studies' titles and abstracts was performed on Ovid Medline^®, Cumulative index to Nursing and Allied Health, PREMEDLINE, EBM reviews and SPORTDiscus. Fourteen studies met the inclusion criteria and were considered for the review.ResultsThe magnitude and time course of KAM during gait appeared to be consistent across laboratories and computational methods. Only two of the included studies that compared patients with OA to a control group reported a higher peak KAM for the OA group. Knee adduction moment increased with OA severity and was directly proportional to varus malalignment. Classifying the patients on the basis of disease severity decreased the group variability, permitting the differences to be more detectable.ConclusionsBiomechanical variables such as varus malalignment are associated with KAM and therefore may affect the disease process. These variables should be taken into considerations when developing therapeutic interventions for individuals suffering from knee OA.     

Can total knee arthroplasty restore the correlation between radiographic mechanical axis angle and dynamic coronal plane alignment during gait?

BackgroundTotal knee arthroplasty (TKA) is the treatment of choice for end-stage knee osteoarthritis. Postoperative static knee alignment has been recognized as a key component of successful surgery. A correction toward the kinematics of a native knee is expected after TKA, with an aim for neutral mechanical alignment. The evolution of frontal plane knee kinematics is not well understood.MethodsNineteen patients awaiting TKA were recruited. Three-dimensional knee kinematics during treadmill gait were assessed pre-operatively, 12 months after surgery, and compared to a control group of 17 asymptomatic participants.ResultsMean radiographic mechanical alignment was corrected from 5.4° ± 5.0 (Standard Deviation) varus pre-operatively to 0.1° ± 2.0 (Standard Deviation) valgus postoperatively (P = 0.002). Mean stance coronal plane alignment decreased from 6.7° ± 4.0 (Standard Deviation) varus per-operatively to 2.1° ± 3.8 (Standard Deviation) postoperatively (P = 0.001). Correlation between radiographic mechanical axis angle and dynamic frontal plane alignment during gait, before and after surgery, was weak (pre-operative R = 0.41; postoperative R = 0.13) compared to control (R = 0.88). In the sagittal plane, TKA patients maintained their pre-operative stiff knee gait adaptation. Postoperative transverse plane kinematics suggested restoration of external tibial rotation during swing after TKA compared to control (Pre-operative 3.1°, postoperative 6.8°, control 7.1°, P = 0.05).ConclusionThe lack of correlation between static and dynamic alignment suggests that static radiographic coronal alignment of the knee does not accurately predict dynamic behavior. In the sagittal plane, pre-operative gait adaptations were still present 12 months after surgery, supporting the need for a functional assessment to guide postoperative rehabilitation following TKA.     

胫骨髁外翻截骨术治疗创伤性膝关节炎的早期临床疗效分析

目的 探讨胫骨髁外翻截骨术（TCVO）治疗陈旧性内侧胫骨平台骨折并发创伤性膝关节炎（TKOA）的早期临床疗效。方法 回顾性分析2016年6月至2021年6月于苏州市立医院关节外科接受TCVO手术治疗陈旧性内侧胫骨平台骨折并发TKOA的18例患者的术前及术后相关临床资料,所有患膝均为陈旧性内侧胫骨平台骨折保守治疗后畸形愈合并发膝内翻TKOA。患者发生胫骨平台骨折至TCVO手术治疗的时间为49 ～ 171个月,平均（111.1±33.8）个月;患膝内翻角度为6.81° ～ 14.49°,平均10.95°±2.62°;关节线会聚角（JLCA）为3.58° ～ 8.12°,平均5.95°±1.42°。所有患者于术前及术后3个月拍摄站立位双下肢全长X线片、膝关节正侧位X线片并测量患膝内翻角度、胫骨近端内侧角（MPTA）、JLCA、胫骨平台后倾角（PTS）,评估术前、术后下肢力线以及膝关节对合状态的变化情况。依据术前及术后3、12个月的患膝关节活动度（ROM）、疼痛视觉模拟评分（VAS）、西安大略与麦克马斯特大学（WOMAC）骨关节炎指数、膝关节损伤与骨关节炎评分（KOOS）评估早期临床疗效。结果 18例患者均获得随访,随访时间为14 ～ 65个月,平均随访（27.4±14.4）个月。术后3个月时,患膝内翻角、JLCA均较术前显著降低,差异均具有统计学意义（P＜0.05）;MPTA与术前相比有显著提升,差异有统计学意义（P＜0.05）;PTS与术前相比差异无统计学意义（P＞0.05）。术后3、12个月时,患膝关节ROM、VAS、WOMAC、KOOS评分均较术前有显著好转,差异均具有统计学意义（P＜0.05）。结论 采用TCVO治疗陈旧性内侧胫骨平台骨折并发TKOA可以取得良好的早期临床疗效,有效矫正膝关节内翻畸形,缓解膝关节疼痛及改善膝关节功能。     

膝内翻患者全膝关节置换术后保留轻度内翻对临床效果的影响

目的 评价膝内翻患者全膝关节置换术后保留轻度内翻对临床效果的影响。方法 对2016年3月至2019年11月于武汉大学人民医院因膝内翻膝关节骨性关节炎行TKA治疗的93例（93膝）患者的临床资料进行回顾性分析。其中,男17例,女76例;年龄71 ～ 87岁,平均77岁。按患者术后下肢力线角度将患者分为中立组、轻度内翻组、严重内翻组。用ROM、HSS、AKS评分量表评价患者膝关节功能。结果 患者随访时间15 ～ 47个月,平均（24.4±8.9）个月,ROM术前平均（49.9±6.7）°,术后末次随访中立组、轻度内翻组、严重内翻组分别为平均（111.4±5.3）°、（112.2±5.0）°、（103.1±2.7）°,HSS评分术前平均（52.4±3.0）分,术后末次随访中立组、轻度内翻组、严重内翻组分别为平均（84.2±3.0）分、（87.1±2.6）分、（81.6±1.9）分,AKS功能评分术前平均（49.8±2.8）分,术后末次随访中立组、轻度内翻组、严重内翻组分别为平均（73.2±5.3）分、（80.1±3.0）分、（72.6±1.5）分,AKS活动评分术前平均（60.5±3.7）分,术后末次随访中立组、轻度内翻组、严重内翻组分别为平均（86.0±2.6）分、（89.9±2.0）分、（80.6±2.9）分,三组术后HSS、AKS评分均较术前有所提高,差异有统计学意义。结论 从短期随访来看,膝内翻患者全膝关节置换术后保持3° ～ 6°的轻度内翻会带来更好的临床疗效,但目前还不能判断内翻对齐和翻修率之间是否存在关联。     

全膝关节置换修复膝内翻畸形：胫股角及膝关节活动度随访评价

背景：膝关节内翻畸形施行人工全膝关节置换难度大,涉及面多,包括手术入路、术中截骨、软组织松解顺序、方法及程度、软组织平衡等,目前意见不统一,争议较多。 目的：观察全膝关节置换修复成人膝关节内翻畸形胫股角及膝关节活动度的1年以上随访结果。 方法：2006年6月至2013年6月对31例(35膝)膝内翻畸形采用后稳定型假体进行全膝关节置换,髌骨内侧入路,正确截骨,选择性软组织松解,以恢复膝关节正常力线和软组织平衡,获得膝关节的稳定,置换后采取针对性的康复训练。全膝关节置换前后拍X射线片测量胫股角,置换后定期随访检查膝关节活动度,并进行美国特种外科医院(HSS)评分、美国西部Ontario和McMaster大学骨关节炎指数(WOMAC)评估。 结果与结论：所有患者均获得随访,随访时间为12-96个月,随访方式为门诊复查随访。胫股角由置换前平均内翻17.69°(5°-30°)纠正至置换后的5.66°(2°-8°),膝关节活动度由置换前的74.29°(60°-95°)提高到置换后119.46° (105°-130°);HSS评分由置换前的26.60分(14-42分)提高到置换后89.03分(82-95分),优28膝,良7膝;WOMAC评分由42.83分(28-54分)提高到置换后90.17分(85-95分)。结果经统计学分析提示,所有病例置换后胫股角、膝关节活动度、HSS及WOMAC评分均较置换前显著改善(P < 0.01)。置换后X射线片检查未见假体周围透亮区,关节力线正常,无髌骨低位、髌骨骨折。提示成人膝关节内翻畸形患者全膝关节置换后1年以上随访畸形均得到纠正,功能明显改善,修复效果满意。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

Under-correction of preoperative varus alignment does not lead to a difference in in-vivo bone loading in 3D-SPECT/CT compared to neutral alignment

BackgroundThe aim was to investigate the correlation of bone tracer uptake (BTU) in SPECT/CT and changes in coronal knee alignment after total knee arthroplasty (TKA). We questioned if undercorrection of preoperative varus alignment leads to a difference in BTU compared to neutral alignment.MethodsConsecutive 66 patients who received SPECT/CT before and after TKA were retrospectively included. Adjusted mechanical alignment was the alignment target. The alignment of the knee was measured on 3D-CT by selecting standardized landmarks. Maximum (mean ± SD) and relative BTU (ratio to the reference) were recorded using a previously validated localization scheme (p < 0.05).ResultsIn the native group, 20 knees were aligned (30.3%) in valgus (HKA > 181.5°), 12 (18.2%) in neutral (178.5°-181.5°) and 34 (51.5%) in varus (HKA < 178°). Overall TKA changed the alignment towards neutral. 48.5% remained in the same groups, whereas 50% of native valgus and 33% of varus knees changed to neutral after TKA. In native varus alignment mean BTU was significantly higher in some medial tibial and femoral regions (fem1ia (p = 0.010), fem1ip (p = 0.002), tib1a.mid (p = 0.005), tib1a.tray (p = 0.000), tib1p.tray (p = 0.000)); in native valgus alignment mean BTU was higher in the corresponding lateral tibial and femoral regions (fem2ip (p = 0.001), tib2a.tray (p = 0.011), tib2p.tray (p = 0.002)). After TKA, a significant decrease in femoral and tibial BTU (femoral preoperative BTU 1.64 +/-0.69; femoral postoperative BTU 0.95 +/-0.42; p = 0.000// tibial preoperative BTU 1.65 +/- 0.93; tibial postoperative BTU 1.16 +/- 0.48; p = 0.000) and an increase in patellar BTU was observed (p = 0.025). Native varus alignment correlated with a higher medial BTU decrease medially. Undercorrection of preoperative varus alignment showed no higher BTU after TKA.ConclusionPreoperative varus alignment correlated with a higher decrease in BTU in specific femoral and tibial medial regions. Preoperative valgus alignment correlated with a higher decrease in the corresponding lateral regions. Undercorrection of preoperative varus alignment did not lead to higher bone loading reflected by BTU after TKA.     

Surgical epicondylar axis is not orthogonal to the femoral mechanical knee axis in valgus knees with primary osteoarthritis: Three-dimensional analysis according to knee coronal alignment in 112 patients

BackgroundDuring total knee arthroplasty (TKA), most surgeons align the femoral component along the surgical epicondylar axis (SEA) considering it as orthogonal to the femoral mechanical axis. However, it is still unclear how SEA coronal alignment varies according to the native coronal knee alignment. The main goal of this study was to analyze the SEA orientation according to the native coronal knee morphotype.MethodsA total of 112 patients underwent a three-dimensional (3D) -planning-based TKA. The SEA was then determined by locating the epicondyles on 3D models. The 3D femoral and tibial mechanical axes were marked and the femoral (FMA) and tibial (TMA) mechanical angles were measured. The native HKA angle was measured as FMA + TMA. The SEA orientation angles were measured in the coronal (SEA-α) and axial (SEA-β) plane. SEA orientation was compared between the valgus, neutral, and varus knees.ResultsThe mean SEA-α angle was 90.2 ± 3° and the mean axial SEA-β angle was 92.2 ± 1.3°. The SEA-α angle was significantly higher in the valgus group compared with the neutral group (92.3 ± 2.9°, 90 ± 2.9°, P = 0.0009) whereas there was no significant difference in the SEA-α angle between the varus and the neutral group (89.7 ± 2.3°, 90 ± 2.9°, P = 0.32).ConclusionsIn contrast to the neutral and varus knees, the SEA was not orthogonal to the femoral mechanical axis in patients undergoing TKA for primary osteoarthritis. Our results suggest adapting the coronal alignment of the femoral component during TKA, while maintaining an average 2° valgus in valgus knees. By contrast, with varus and neutral knees, our data support the use of a mechanical alignment.     

The effect of component alignment on clinical outcomes in fixed bearing unicompartmental knee arthroplasty

BackgroundThe aim of this study is to report component alignment in a series of ZUK fixed bearing unicompartmental knee arthroplasty (UKA) implants and compare this to clinical outcomes.MethodsThe radiographs, Knee Society Scores (KSS) and knee flexion of 223 medial UKAs were evaluated. The following alignment parameters were assessed; coronal and sagittal femoral component angle (c-FCA and s-FCA), coronal and sagittal tibia component angle (c-TCA and s-TCA) and the coronal tibiofemoral angle (c-TFA). Each alignment parameter was grouped at consecutive 2.5° intervals, mean KSS and knee flexion was then compared between the interval groups.Results96.4% of femoral components were between 7.5° of varus and valgus and 95.1% between 7.5° extension and 5° flexion. 89.6% of tibial components were between 7.5° of varus and 2.5° valgus and 97.3% between 2.5° and 15° flexion. There was no significant difference between the KSS or knee flexion between any of the incremental groups of component alignment. Mean c-TFA was 0.2 ± 3.0°, 92.4% were between −5° (varus) and 5° (valgus). KSS were significantly greater for two of the increments with slightly more varus. Linear regression analysis showed there was very weak correlation (R² = 0.1933) between c-TFA and c-TCA.ConclusionsThe results of this study show that fixed bearing UKA components are forgiving to accommodate some variation in tibial and femoral component position without effecting clinical outcome scores or knee flexion. Limb alignment matters more than component position and knees with slight varus tibiofemoral alignment have better clinical scores than those with valgus.     

The impact of residual varus alignment following total knee arthroplasty on patient outcome scores in a constitutional varus population

Background

Following a total knee arthroplasty (TKA), restoration of the mechanical axis of the lower limb to a neutral position of 0°?±?3° is generally considered the standard of care. Little is known, however, regarding the impact of realignment defined according to the patient's physiologic anatomy on clinical outcome scores.

Reductions in peak knee abduction moment in three previously studied gait modification strategies

BackgroundFirst peak internal knee abduction moment (KAM) has been associated with knee osteoarthritis. Gait modification including trunk lean, medial knee thrust, and toe-in gait have shown to reduce KAM. Due to heterogeneity between study designs, it remains unclear which strategy is most effective. We compared the effects of these modifications in healthy individuals to determine their effectiveness to reduce KAM, internal knee extension moment (KEM), and medial contact force (MCF).MethodsTwenty healthy individuals volunteered for this study (26.7 ± 4.7 years, 1.75 ± 0.1 m, 73.4 ± 12.4 kg). Using real-time biofeedback, we collected 10 trials for each modification using individualized gait parameters based on participants' baseline mean and standard deviation (SD). Two sizes of each modification were tested: 1–3 SD greater (toe-in and trunk lean) or lesser (knee adduction) than baseline for the first five trials and 3–5 SD greater or lesser than baseline for the last five trials.ResultsA significant main effect was found for KAM and KEM (p < .001). All modifications reduced KAM from baseline by at least five percent; however, only medial knee thrust and small trunk lean resulted in significant KAM reductions. Only medial knee thrust reduced KEM from baseline. MCF was unchanged. Conclusion: Medial knee thrust was superior to trunk lean and toe-in modifications in reducing KAM. Subsequent increases in KEM and variation in individual responses to modification suggests that future interventions should be individualized by type and magnitude to optimize KAM reductions and avoid detrimental effects.     

Longitudinal changes in knee kinematics and moments following knee arthroplasty: A systematic review

BackgroundKnee arthroplasty (KA) is recognized as an effective treatment of knee joint osteoarthritis and up to 90% of patients experience substantial pain relief. There has been no systematic review synthesizing the longitudinal changes in gait following KA. The aims of this systematic review were to determine the effects of KA on (i) frontal plane and (ii) sagittal plane kinematic and kinetic parameters during the stance phase of gait.MethodsMEDLINE (PubMed), CINAHL, SPORTdiscus (EBSCO), and Cochrane Library (Wiley) were searched until April 10th, 2014. 1,765 articles were identified, of which 19 studies describing 3-dimensional gait analysis pre- and post-KA were included. Study quality was evaluated by two reviewers independently using the Downs and Black checklist.FindingsFollowing KA, in the frontal plane, the maximum knee adduction angle and external knee adduction moment (KAM) tended to decrease. In the sagittal plane, findings suggest that the maximum knee flexion moment is increased. From the ten studies that included a healthy reference group, it was unclear whether gait variables returned to normal following KA.InterpretationOverall, it appears that KA results in a decreased peak KAM and maximum knee adduction angles, an increased peak knee flexion moment and inconsistent changes in the peak knee flexion angle. Knowledge gaps remain due to methodological inconsistencies across studies, limited statistical analysis, and largely heterogeneous sample populations. More research is needed to determine whether KA restores gait patterns to normal, or if additional rehabilitation may be needed to optimize gait following surgery for osteoarthritis.     

Effect of walking with a modified gait on activation patterns of the knee spanning muscles in people with medial knee osteoarthritis

ObjectiveTo evaluate muscle activation patterns and co-contraction around the knee in response to walking with modified gait patterns in patients with medial compartment knee-osteoarthritis (KOA).Design40 medial KOA patients walked on an instrumented treadmill. Surface EMG activity from seven knee-spanning muscles (gastrocnemius, hamstrings, quadriceps), kinematics, and ground reaction forces were recorded. Patients received real-time visual feedback on target kinematics to modify their gait pattern towards three different gait modifications: Toe-in, Wider steps, Medial Thrust. The individualized feedback aimed to reduce their first peak knee adduction moment (KAM) by ≥ 10%. Changes in muscle activations and medial/lateral co-contraction index during the loading response phase (10–35% of the gait cycle) were evaluated, for the steps in which ≥ 10% KAM reduction was achieved.ResultsData from 30 patients were included in the analyses; i.e. all who could successfully reduce their KAM in a sufficient number of steps by ≥ 10%. When walking with ≥ 10% KAM reduction, Medial Thrust gait (KAM − 31%) showed increased flexor activation (24%), co-contraction (17%) and knee flexion moment (35%). Isolated wider-step gait also reduced the KAM (− 26%), but to a smaller extent, but without increasing muscle activation amplitudes and co-contraction. Toe-in gait showed the greatest reduction in the KAM (− 35%), but was accompanied by an increased flexor activation of 42% and hence an increased co-contraction index.ConclusionGait modifications that are most effective in reducing the KAM also yield an increase in co-contraction, thereby compromising at least part of the effects on net knee load.     

A non-invasive measurement of the knee contact force using a subject-specific musculoskeletal model to investigate osteotomy

The varus knee has been defined as a Hip-Knee-Ankle alignment of less than 180 degrees. Varus knee alignment increases the load on the medial knee and also the risk of osteoarthritis. High tibial osteotomy has been designed to modify the malalignment of varus knee. The aim of this study was to investigate the osteotomy effects on knee adduction moment (KAM) and contact forces using a musculoskeletal and subject-specific knee model. A patient with varus knee and no symptoms of any other disease or disability participated in this study. The geometry of the multibody knee model has been modified using MR images. The solutions of its finite element model have been used to determine the parameters of the multibody model. The motion data, ground reaction force and kinetic data have been applied to run the subject-specific musculoskeletal model during the stance phase of gait. After osteotomy, the adduction moment decreased, where the maximum values are comparable to other studies. The pattern of KAM did not witness any significant changes. The total and medial contact forces reduced considerably after surgery, but the lateral contact force did not significantly change. The changes in total and medial contact forces and lack of change in lateral contact force could be explained by modification of the gait pattern after surgery.     

Differences between opening versus closing high tibial osteotomy on clinical outcomes and gait analysis

BackgroundHigh tibial osteotomy (HTO) for medial knee osteoarthritis (OA) is mainly performed via two procedures: closing wedge HTO (CW) and opening wedge HTO (OW). In this study, differences between these procedures were assessed by serial clinical evaluation and gait analysis before and after surgery.MethodsTwenty-one patients underwent HTO for medial knee OA in 2011 and 2012, with 12 patients undergoing CW and nine undergoing OW. The severity of OA was classified according to the Kellgren–Lawrence classification. The Japanese Orthopedic Association score for assessment of knee OA (JOA score), the Numeric Rating Scale (NRS), and the femoral tibial angle (FTA) on X-ray were evaluated. For gait analysis, gait speed, varus moment, varus angle and lateral thrust were calculated.ResultsThe JOA score and NRS were improved significantly one year postoperatively in both groups. The FTA was maintained in both groups at one year. Varus angle and varus moment were significantly improved in both groups at each postoperative follow-up, when compared preoperatively. Lateral thrust was significantly improved at three months postoperatively in both groups. However, the significant improvement in lateral thrust had disappeared in the CW group six months postoperatively, whereas it was maintained for at least one year in the OW group.ConclusionsThis study found that clinical outcomes were well maintained after HTO. OW reduced knee varus moment and lateral thrust, whereas CW had little effect on reducing lateral thrust.Level of evidenceLevel IV     

Dynamic alignment and its association with knee adduction moment in medial knee osteoarthritis

Lower limb dynamic alignment represents the limb position during functional loading conditions and obtains valuable information throughout the gait cycle rather than a single instant in time. This study aims to determine whether dynamic alignment is altered in medial knee osteoarthritis (OA) and how dynamic alignment is related to knee adduction moment (KAM). Community-dwelling women (n = 17) with medial OA in at least one knee, according to the American College of Rheumatology criteria and 17 body mass index-matched women without OA were recruited. A three-dimensional motion analysis system was used to collect the gait data at self-selected habitual and maximal speeds. Clinical evaluation of lower extremities, physical function, pain, habitual level of physical activity, quality of life and physical self-efficacy were assessed. Shank adduction angle and shank mean angular velocity were significantly greater in the OA group compared to the controls from heel strike to 30% stance. KAM was not different between the groups (p = 0.542). Dynamic alignment variables were the best predictors of KAM. Health-related quality of life, habitual level of physical activity, lower extremity muscle strength and balance performance were impaired in the OA group compared to the controls. The importance of variables that contribute to dynamic alignment and the contribution of limb alignment to KAM were highlighted in this study. Detection of postural changes such as altered dynamic alignment in early stages of OA will lead to the institution of joint-protective measures including changes in footwear, orthotics, gait re-training, use of assistive devices to reduce weight-bearing loads, strengthening and balance enhancing exercises, better analgesia, or cartilage-preserving pharmacotherapy.     

In vivo kinematic comparison before and after mobile-bearing unicompartmental knee arthroplasty during high-flexion activities

BackgroundMany patients who undergo unicompartmental knee arthroplasty (UKA) have an expectation that their knee flexion would increase following its replacement. Additionally, the survival rate of mobile-bearing UKA (MB-UKA) is high. However, the effect on the patient's kinematics remains unknown. This study aimed to clarify the kinematic effect of MB-UKA knees during high-flexion activities by comparing the in vivo kinematics before and after surgery.MethodsA squatting motion was performed under fluoroscopic surveillance in the sagittal plane before and after MB-UKA. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. The femoral rotation and varus–valgus angle relative to the tibia and anteroposterior (AP) translation of the medial and lateral side of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle were evaluated.ResultsRegarding the varus–valgus angle, the preoperative knees indicated a significant varus alignment compared with the postoperative knees from 10° to 60° of flexion. There were no significant differences in the femoral rotation angle, AP translation, and kinematic pathway before and after MB-UKA in the mid-flexion of the range of motion.ConclusionThere were differences between the varus–valgus knee kinematics before and after MB-UKA, from 10 to 60° of flexion, but no difference from midrange of flexion to deep flexion. In addition, the rotational knee kinematics before and after MB-UKA was not significantly different.