Finite element analysis of the influence of the posterior tibial slope on mobile-bearing unicompartmental knee arthroplasty

BackgroundThe most common modes of failure reported in unicompartmental knee arthroplasty (UKA) in its first two decades were wear on the polyethylene (PE) insert, component loosening, and progressive osteoarthritis in the other compartment. The rates of implant failure due to poor component positioning in patients who have undergone UKA have been reported. However, the effect of the posterior tibial slope on the biomechanical behavior of mobile-bearing Oxford medial UKA remains unknown.MethodsWe applied finite element (FE) analysis to evaluate the effects of the posterior tibial slope in mobile-bearing UKA on the contact stresses in the superior and inferior surfaces of PE inserts and articular cartilage as well as the forces exerted on the anterior cruciate ligament (ACL). Seven FE models for posterior tibial slopes of −1°, 1°, 3°, 5°, 7°, 9°, and 11° were developed and analyzed under normal-level walking conditions based on this approach.ResultsThe maximum contact stresses on both the superior and inferior surfaces of the PE insert decreased as the posterior tibial slope increased. However, the maximum contact stress on the lateral articular cartilage and the force exerted on the ACL increased as the posterior tibial slope increased.ConclusionsIncreasing the tibial slope led to a reduction in the contact stress on the PE insert. However, a high contact stress on the other compartment and increased ACL force can cause progressive osteoarthritis in the other compartment and failure of the ACL.     

What is the relationship between the “Fujisawa point” and postoperative knee valgus angle? A theoretical,computer-based study

BackgroundThe purpose of this study was to determine the relationship between the Fujisawa point and postoperative knee valgus angle and the anatomical factors influencing this relationship.MethodsAn experimental study was conducted including 116 patients with medial compartment knee osteoarthritis undergoing treatment with open-wedge high tibial osteotomy (OWHTO). Each patient received simulated HTO through the Fujisawa point in the picture archiving and communication system (PACS). The preoperative hip-knee-ankle (HKA) angle and lower extremity anatomical parameters were recorded before the computerized HTO simulation. The postoperative knee valgus angle was measured after this procedure. A second simulation HTO was performed to adjust the mechanical axis to the optimal valgus angle (4.5°) and calculate the percentage of the tibial plateau width where the Mikulicz line crossed the knee. The Spearman correlation test and multivariate regression were used for analysis.ResultsThe median preoperative HKA varus angle of this study cohort was 174.1° (170.8, 176.2°). The median knee valgus angle after simulated osteotomy through the Fujisawa point was 2.4° (2.1, 2.7°). The valgus angle was positively correlated with the tibial plateau width (r = 0.23, p = .013) and preoperative HKA angle (r = 0.32, p < .001). Multivariate regression analysis showed that the preoperative HKA angle was a significant contributor to the postoperative valgus angle. When conducting the osteotomy with the optimal valgus angle (4.5°), the percentage of the Mikulicz line passing through the tibial plateau was 71.93% (67–78%).ConclusionsThe preoperative HKA angle affects the postoperative valgus angle after HTO. If the optimal valgus angle of 4.5° is desired, a more lateral position of the Fujisawa point should be targeted during OWHTO, which accounts for approximately 71.9% of the tibial plateau.     

Finite element analysis of unicompartmental knee arthroplasty

Concerns over accelerated damage to the untreated compartment of the knee following unicompartmental knee arthroplasty (UKA), as well as the relatively poor success rates observed for lateral as opposed to the medial arthroplasty, remain issues for attention. Finite element analysis (FEA) was used to assess changes to the kinematics and potential for cartilage damage across the knee joint in response to the implantation of the Oxford Mobile Bearing UKA. FE models of lateral and medial compartment arthroplasty were developed, in addition to a healthy natural knee model, to gauge changes incurred through the arthroplasty. Varus–valgus misalignments were introduced to the femoral components to simulate surgical inaccuracy or over-correction. Boundary conditions from the Stanmore knee simulator during the stance phase of level gait were used. AP translations of the tibia in the medial UKA models were comparable to the behaviour of the natural knee models (±0.6 mm deviation from pre-operative motion). Following lateral UKA, 4.1 mm additional posterior translation of the tibia was recorded than predicted for the natural knee. IE rotations of the medial UKA models were less consistent with the pre-operative knee model than the lateral UKA models (7.7° vs. 3.6° deviation). Varus misalignment of the femoral prosthesis was more influential than valgus for medial UKA kinematics, whereas in lateral UKA, a valgus misalignment of the femoral prosthesis was most influential on the kinematics. Resection of the cartilage in the medial compartment reduced the overall risk of progressive OA in the knee, whereas removing the cartilage from the lateral compartment, and in particular introducing a valgus femoral misalignment, increased the overall risk of progressive OA in the knee. Based on these results, under the conditions tested herein, both medial and lateral UKA can be said to induce kinematics of the knee which could be considered broadly comparable to those of the natural knee, and that even a 10° varus–valgus misalignment of the femoral component may not induce highly irregular kinematics. However, elevated posterior translation of the tibia in lateral UKA and large excursions of the insert may explain the higher incidence of bearing dislocation observed in some clinical studies.     

External rotation of the tibial component should be avoided in lateral unicompartmental knee arthroplasty

BackgroundLateral unicompartmental knee arthroplasty (UKA) leads to good clinical outcomes for isolated lateral osteoarthritis. However, the impact of the tibial component position on postoperative outcomes in lateral UKA is yet to be determined.PurposeThis study investigated the influence of tibial component malposition on clinical outcomes in lateral UKA.MaterialsThis was a retrospective study of 50 knees (mean age 73.5 years) who underwent lateral UKA between September 2013 and January 2019. The Oxford Knee Score (OKS), Knee Society Score – Knee (KSSK), and Knee Society Score – Function (KSSF) were evaluated. The coronal alignment, posterior slope of tibial component, tibial component rotation relative to Akagi’s line (angle α), and femoral anteroposterior (AP) axis (angle β) were measured postoperatively. The average follow up period was 2.3 (range, 1–4.9) years.ResultsClinical scores were significantly improved after lateral UKA. The mean coronal alignment was 0.9° ± 3.2° varus (range, 9.1° varus to 5.5° valgus), the mean posterior slope was 6.8° ± 3.8° (range, 0.8° to 14.8°). The mean α and β angles, were 4.1° ± 5.8° (range, −9.7° to 16.5°) and 6.7° ± 7.1° (range, −7.0° to 20.5°) external rotation. The angle α had significant negative correlations with postoperative OKS (r = −0.36), KSSK (r = −0.28), and KSSF (r = −0.39), and angle β had significant negative correlations with postoperative OKS (r = −0.34) and KSSK (r = −0.46).ConclusionExcessive external rotation of the tibial component could negatively influence the postoperative outcomes of lateral UKA.     

Single photon emission computed tomography in planning unicompartmental knee arthroplasty. A prospective study examining the association between scan findings and intraoperative assessment of osteoarthritis

The aim of this study was to determine the relationship between preoperative single photon emission computed tomography (SPECT) scan findings and intraoperative assessments of knee osteoarthritis (OA) in patients undergoing tibiofemoral unicompartmental knee arthroplasty (UKA). Fifty knees in 46 patients undergoing UKA were investigated preoperatively with a SPECT scan to confirm unicompartmental disease. There were 38 men and 12 women in the cohort with an average age of 63 years (range 44-78). The SPECT scan uptake in each compartment of the knee was graded by a single radiologist and these findings were compared with intraoperative assessments of OA (size and grade of lesion), made by two experienced surgeons, blinded to the scan findings. Significant association was demonstrated between scan findings and OA in all compartments of the knee (p<0.05), and this was strongest in the medial compartment and weakest in the patellofemoral compartment and lateral tibial plateau. We conclude that SPECT scan is a useful imaging modality in the planning of medial tibiofemoral UKA to confirm unicompartmental disease. The lower degree of association between scan findings and OA encountered in the patellofemoral compartments and lateral tibial plateau indicates that greater vigilance should be exercised in the intraoperative assessment of these areas.     

第三代牛津单髁系统在膝关节内侧间室骨性关节炎的应用

目的探讨牛津第三代单髁假体微创单髁置换术治疗膝关节内侧间室骨性关节炎的疗效与技术。方法回顾性分析2005年5月~2011年6月采用微创单髁置换术治疗100例膝关节内侧间室骨性关节炎患者的资料,对患者术前、术后膝关节疼痛及关节活动度进行评估(HSS评分法),并测量术后假体力线,分析假体设计、手术适应证的选择及手术技术。结果 100例术后平均随访36个月(12~75个月),末次随访时膝关节HSS评分和膝关节活动度明显增加,股骨假体力线平均为0.69°内旋±3.18°,0.83°伸直±3.63°,胫骨假体力线平均为0.12°内翻±0.80°,0.39°伸直±1.24°,无假体位置不良、脱位及假体松动等并发症。结论微创单髁置换术治疗膝关节内侧间室骨性关节炎具有很好的疗效,其关键在于手术适应证的选择和手术技术。     

How does asymmetric tibial insert affect tibiofemoral kinematics and contact stresses in total knee Arthroplasty?

BackgroundAsymmetric tibial insert design is expected to restore normal knee kinematics better than symmetric design. A tri-condylar implant has asymmetric and symmetric tibial inserts with a ball-and-socket joint to replace the post-cam mechanism. The purpose of this study was to compare the knee kinematics of the two designs and to measure tibiofemoral contact stresses, including that of the ball-and-socket joint.MethodsUsing a computer simulation, the anteroposterior position and axial rotation of the femoral component were simulated during a weight-bearing deep knee bend for six validated models. Contact forces were simultaneously simulated in the medial, lateral, and ball-and-socket compartments. The relative position and the magnitude and direction of each contact force were applied to aforce/displacement control knee simulator. The contact stresses were measured individually using a pressure sensor.ResultsThe asymmetric tibial insert demonstrated a more posterior position of the femoral component in the lateral compartment during the entire range of motion and greater external rotation of the femoral component, compared to the symmetrical tibial insert. The mean peak contact stress of the medial and lateral compartments was < 9 Mpa, with no significant differences between the two designs except at 0°. The contact stress of the ball-and-socket joint was < 5 MPa.ConclusionsAsymmetry of the tibial insert shows significant kinematic difference and has little influence on the peak contact stress, which is considerably lower than the yield strength of polyethylene. The asymmetric tibial insert can lead to clinical benefits owing to its kinematic and kinetic properties.     

A preliminary modeling investigation into the safe correction zone for high tibial osteotomy

Background

High tibial osteotomy (HTO) re-aligns the weight-bearing axis (WBA) of the lower limb. The surgery reduces medial load (reducing pain and slowing progression of cartilage damage) while avoiding overloading the lateral compartment. The optimal correction has not been established. This study investigated how different WBA re-alignments affected load distribution in the knee, to consider the optimal post-surgery re-alignment.

Clinical results of a valgus high tibial osteotomy for the treatment of osteoarthritis of the knee and the ipsilateral ankle

The treatment of patients with osteoarthritic knees accompanied by ipsilateral osteoarthritic ankles is not well documented. We here report both clinical results and radiographic evaluations of such patients treated using a high tibial osteotomy (HTO). HTO was performed on 16 knees of 10 patients (all women with a mean age; 68years; range 58 to 73years) who had a varus deformity of both their legs as a result of medial compartmental osteoarthritis of their knees. The Hospital for Special Surgery's (HSS score) knee scoring system and the clinical rating system for the ankle-hindfoot by Kitaoka (AOFAS) were used to evaluate the patients clinically before and after HTO. Radiographic findings were measured using antero-posterior one-leg weight bearing radiographs of the whole lower extremity taken before surgery. The mean time of follow-up was 8years (range, 4–10years).

The HSS score improved from 54 to 91 points after HTO and the mean ankle score improved significantly from 54 to 86 points. After HTO also, the alignment of the knees changed from 6° varus to 12° valgus. The decrease of the inclination angle of the tibial axis changed from 10° laterally to − 2° medially and the talar tilt angle improved from 18° to 6° resulting in an improvement of the ankle congruity.

HTO, which can correct the total alignment of the lower extremity, is thus recommended as one of more effective surgical procedures for patients with an ipsilateral osteoarthritis of the knee and ankle.     

Assessment of articular cartilage of the lateral tibial plateau in varus osteoarthritis of the knee

This study describes the soft X-ray examinations of 24 lateral tibial plateaus obtained during total knee arthroplasty for varus osteoarthritis. The average thickness of the articular cartilage was 3.5 min and ranged from 2.1 to 5.0. We considered that 21 out of the 24 lateral tibial plateaus had well preserved articular cartilage. Within the well preserved articular cartilage, bony protuberances of various sizes were found in five cases. All lateral tibial plateaus except one showed osteophyte formation. We considered that 12 of the 24 lateral tibial plateaus had large osteophytes. Ten of these 12 lateral tibial plateaus had well preserved articular cartilage. Large osteophyte formation may not necessarily be a contra-indication of high tibial osteotomy (HTO) or unicompartmental knee arthroplasty (UKA). Cases with a bony protuberance may not be suitable for HTO or UKA, because the overlying articular cartilage is thin and inadequate for supporting load.     

个体化开放楔形胫骨高位截骨治疗内侧间室膝骨关节炎的优势

文题释义：开放楔形胫骨高位截骨：是一种治疗内侧间室膝骨关节炎合并膝内翻的保膝术式。通过胫骨近端内侧切口,在水平面、冠状面双截骨后,进行楔形撑开、钢板固定。其治疗意义在于将内翻的下肢力线转移至相对正常的膝外侧,以缓解内侧症状,延长关节寿命,延缓骨关节炎进展,甚至避免关节假体置换。 个体化力线矫形：根据膝骨关节炎的多阶段性,针对不同退变程度的膝内侧间室,施行不同的力线矫形方案。通过术前规划截骨后的楔形撑开角度或距离,可以将内翻的下肢力线矫正至中线或偏外侧,以达到临床治疗效果。 背景：开放楔形胫骨高位截骨对于内侧间室膝骨关节炎合并膝内翻患者疗效明确,但目前关于力线矫正点的选择仍以Fujisawa点作为参考,个体化力线矫形是否能获得更优越的临床疗效？ 目的：探讨开放楔形胫骨高位截骨术中个体化下肢力线矫形治疗内侧间室膝骨关节炎的短期疗效。 方法：选择2016年6月至2018年5月无锡市人民医院骨科因内侧间室膝骨关节炎行开放楔形胫骨高位截骨治疗的46例患者。根据X射线片、MRI综合评估患膝并划分退变等级(Ⅰ-Ⅲ级),其中Ⅰ,Ⅱ级患者随机分为个体化组及对照组,每组16例;14例Ⅲ级患者作为Fujisawa组。个体化组轻度退变Ⅰ级矫正下肢力线至胫骨平台50%点,中度退变Ⅱ级矫正至胫骨平台外侧55%点;对照组、Fujisawa组均矫正力线至62.5%点。测量评估术后下肢力线,比较术前、术后膝关节活动度、股胫角、胫骨近端内侧角;随访术前及术后3,6,12个月患膝的美国特种外科医院评分、西安大略和麦克马斯特大学骨关节炎指数,比较患者术后综合满意度的自评分。结果与结论：①所有患者均获得12个月随访;②3组下肢力线矫形结果满意,术后膝关节活动度、胫骨近端内侧角较术前明显增加,股胫角明显减少(P < 0.05);③随着随访时间延长,3组患者的美国特种外科医院评分显著增加,西安大略和麦克马斯特大学骨关节炎指数显著减少,组内不同时点差异有显著性意义(P < 0.05);个体化组术后3,6个月美国特种外科医院评分高于对照组,西安大略和麦克马斯特大学骨关节炎指数低于对照组,差异有显著性意义(P < 0.05);个体化组及对照组术后12个月美国特种外科医院评分、西安大略和麦克马斯特大学骨关节炎指数差异无显著性意义(P > 0.05);④所有患者对手术矫形效果满意,个体化组术后综合满意评分高于对照组,差异有显著性意义(P < 0.05);⑤结果表明,个体化开放楔形胫骨高位截骨通过准确地力线矫形,有利于膝关节早期功能恢复,提升患者满意度。 ORCID: 0000-0003-0566-2858(俞颖豪) 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     

个性化3D打印术前模拟与传统截骨在高位胫骨截骨中的应用与比较

文题释义： 高位胫骨截骨：是治疗早期单纯内侧间室膝关节骨关节炎行之有效的术式,包括内侧开放与外侧闭合截骨两种术式。 3D打印技术：是将计算机三维数字成像技术和多层次连续打印技术相结合的一种新兴应用技术,与传统的材料去除加工方法不同的是,它通过分层加工、叠加成型的方式,逐层增加材料来生成3D实体模型。有研究报道3D打印截骨模块可精确指导全膝关节置换及内侧开放高位胫骨截骨术中截骨。 背景：高位胫骨截骨是治疗早期单纯内侧间室膝关节骨关节炎的经典术式,3D打印可用于制作个性化手术工具,课题组已应用3D打印技术辅助高位胫骨截骨治疗膝关节骨关节炎。 目的：对比传统截骨方法,探讨个性化3D打印截骨辅助下外侧闭合楔形高位胫骨截骨联合膝关节清理治疗合并内翻畸形膝关节骨关节炎的优势与不足。 方法：行外侧闭合楔形高位胫骨截骨联合膝关节清理的病例47例,采用随机数字法分成2组：3D打印截骨组21例术中采用个性化3D打印截骨,传统截骨组26例予传统截骨。对比两组的手术时间、术中C形臂透视次数及出血量、术后1个月患侧下肢力线,以及术后1,3,6,12,24个月评估患侧膝关节美国特种外科医院(hospital of special surgery,HSS)评分。研究方案经莆田市第一医院伦理委员会审查批准,参与试验的患病个体对治疗过程完全知情同意。 结果与结论：①术中3D打印截骨模块均与术前模拟卡位相一致;②3D打印截骨组手术时间较传统截骨组明显缩短[(69.71±3.17),(92.92±5.91)min,t=-17.21,P < 0.01];3D打印截骨组术中C形臂透视次数明显少于传统截骨组[(5.71±1.62),(18.15±3.00)次,t=-18.12,P < 0.01];3D打印截骨组出血量显著少于传统截骨组[(275.24±53.82),(507.69±45.19)mL,t=-16.10,P < 0.01];③两组术后1个月患侧下肢力线及术后24个月患侧膝关节HSS评分差异无显著性意义(均P > 0.05);④结果说明,对比传统截骨,在外侧闭合楔形高位胫骨截骨中应用个性化3D打印截骨可明显缩短手术时间,减少术中透视和出血,但二者术后2年随访患者膝关节功能恢复无明显差异。 ORCID: 0000-0001-9766-6164(陈金国) 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     

High tibial osteotomy versus unicompartmental joint replacement in unicompartmental knee joint osteoarthritis: 7-10-year follow-up prospective randomised study.

The clinical outcome of patients treated either by high tibial osteotomy or unicompartmental arthroplasty for medial unicompartmental osteoarthritis of the knee was compared in a prospective randomised study. In total, 32 patients received a high tibial osteotomy (HTO) and 28 patients a unicompartmental arthroplasty (UKA). More intra- and postoperative complications were observed after HTO. Patients were assessed at an average of 2.5 (1.6-5), 4.5 (3.6-7), and 7.5 years (6.6-10) after the operation. Using the Knee Society Score, 71% (15) of patients after osteotomy and 65% (13) after replacement had a knee score of excellent or good 7-10 years postoperatively. The Kaplan-Meier survival analysis 7-10 years postoperatively showed a survivorship of 77% for UKA and 60% for HTO. Although the unicompartmental prosthesis used in this series has not shown promising results, we conclude that with the advanced design of unicompartmental prosthesis today, UKA offers better long-term success.     

Tibial slope and patellar height after opening wedge high tibia osteotomy using autologous tricortical iliac bone graft

Our aim was to evaluate the alteration in angle of posterior slope of the tibia and the degree of patellar height following medial opening wedge high tibia osteotomy(HTO) using autologous tricortical iliac bone graft in 32 consecutive patients. Twenty three females and nine males underwent medial opening wedge high tibia osteotomy (HTO) using autologous tricortical iliac bone graft in 34 knees (33 primary medial compartment osteoarthritis and 1 idiopathic osteonecrosis of medial tibial condyle). The posterior slope of tibia was determined by the proximal tibial anatomical axis. Patellar height was measured by the Insall-Salvati and the Blackburne-Peel ratios. Preoperative and postoperative (last follow up) values of these three parameters were compared. The intra- and interobserver variability of these methods was determined before and after operation. At the end of mean follow up of 3 years this procedure produced no significant change in posterior slope. Pre and postoperative posterior slope were 8.7 degrees+/-3.6 degrees and 8.2 degrees+/-2.8 degrees respectively (P=0.412). Pre and postoperative Insall-Salvati ratios were 0.93+/-0.10 and 1.05+/-0.11 respectively (P<0.001). The Insall-Salvati ratio increased in 94% of patients and patellar ligament length was significantly increased. The distance between the patellar and tibiofemoral joint line decreased in 82% of patients. The mean Blackburne-Peel ratio declined from 0.71+/-0.12 to 0.61+/-0.13 (P<0.001). Twenty six percent of postoperative Blackburne-Peel values satisfied the radiographic criterion for patellar infera (Blackburne-Peel ratio<0.54). There was no difference in the intra-and interobserver variability of measurements either before or after HTO. Opening wedge HTO using autologous tricortical iliac bone graft with internal fixation and early mobilisation prevented change in posterior slope of tibia, lengthened the patellar ligament and elevated the tibiofemoral joint line when the mean ratio of anterior and posterior gap at the osteotomy site was around two-thirds.     

从生物力学角度评价单髁置换术与腓骨截骨术

膝关节单间室骨性关节炎引起的膝内翻是常见病症之一，目前手术方法主要有胫骨高位截骨术、单髁置换术以及最新推广的腓骨截骨术。单髁置换术自开展以来已有60余年历史，相比全膝关节置换术具有可保留膝关节正常运动、手术创伤小、保留骨量多以及术后关节活动度大等优点，故单髁置换术已成为治疗内侧间室骨关节炎一种可靠的治疗方式。腓骨截骨术是一种治疗膝内翻的新治疗手段，具有手术简单、费用低、恢复快等优点，目前正在被大力推广，但其治病机制尚不很清楚。综述单髁置换和腓骨截骨两种临床手术方式，并从生物力学角度推论腓骨截骨术治疗内侧间室骨性关节炎的可能机制，提出腓骨截骨术后外侧收缩肌力下降导致关节合力矩再平衡，故关节接触位置改变、关节接触力下降可能是腓骨截骨术能够缓解疼痛治疗骨性关节炎的原因。     

从生物力学角度评价单髁置换术与腓骨截骨术

膝关节单间室骨性关节炎引起的膝内翻是常见病症之一,目前手术方法主要有胫骨高位截骨术、单髁置换术以及最新推广的腓骨截骨术。单髁置换术自开展以来已有60余年历史,相比全膝关节置换术具有可保留膝关节正常运动、手术创伤小、保留骨量多以及术后关节活动度大等优点,故单髁置换术已成为治疗内侧间室骨关节炎一种可靠的治疗方式。腓骨截骨术是一种治疗膝内翻的新治疗手段,具有手术简单、费用低、恢复快等优点,目前正在被大力推广,但其治病机制尚不很清楚。综述单髁置换和腓骨截骨两种临床手术方式,并从生物力学角度推论腓骨截骨术治疗内侧间室骨性关节炎的可能机制,提出腓骨截骨术后外侧收缩肌力下降导致关节合力矩再平衡,故关节接触位置改变、关节接触力下降可能是腓骨截骨术能够缓解疼痛治疗骨性关节炎的原因。     

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.     

从生物力学角度评价单髁置换术与腓骨截骨术

膝关节单间室骨性关节炎引起的膝内翻是常见病症之一,目前手术方法主要有胫骨高位截骨术、单髁置换术以及最新推广的腓骨截骨术。单髁置换术自开展以来已有60余年历史,相比全膝关节置换术具有可保留膝关节正常运动、手术创伤小、保留骨量多以及术后关节活动度大等优点,故单髁置换术已成为治疗内侧间室骨关节炎一种可靠的治疗方式。腓骨截骨术是一种治疗膝内翻的新治疗手段,具有手术简单、费用低、恢复快等优点,目前正在被大力推广,但其治病机制尚不很清楚。综述单髁置换和腓骨截骨两种临床手术方式,并从生物力学角度推论腓骨截骨术治疗内侧间室骨性关节炎的可能机制,提出腓骨截骨术后外侧收缩肌力下降导致关节合力矩再平衡,故关节接触位置改变、关节接触力下降可能是腓骨截骨术能够缓解疼痛治疗骨性关节炎的原因。     

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.     

Opening- or closing-wedged high tibial osteotomy: a meta-analysis of clinical and radiological outcomes

High tibial osteotomy (HTO) has been advocated for the treatment of isolated medial compartment osteoarthritis of the knee. Debate remains over the superiority of performing a medial opening-wedge or lateral closing-wedge HTO. The purpose of this study was to compare the clinical and radiological outcomes, and complications of patients following opening-wedge compared to closing-wedge HTO. A systematic review was undertaken of published and unpublished literature databases from their inception to May 2010. Twelve papers reporting nine clinical trials were found to be suitable for meta-analysis comparing 324 opening-wedge HTOs to 318 closing-wedge HTOs. There was no difference in the incidence of infection, deep vein thrombosis, peroneal nerve palsy, non-union or revision to knee arthroplasty (p > 0.05). There was however a significantly greater posterior tibial slope and mean angle of correction, reduced patellar height and hip–knee–ankle angle following opening-wedge HTO (p < 0.05). No significant difference was found for any clinical outcome including pain, functional score or complications (p > 0.05).