Muscle strength and exercise intensity adaptation to resistance training in older women with knee osteoarthritis and total knee arthroplasty

OBJECTIVES:

To analyze muscle strength and exercise intensity adaptation to resistance training in older women with knee osteoarthritis and total knee arthroplasty.

METHODS:

Twenty-three community-dwelling women were divided into the following groups: older, with knee osteoarthritis and total knee arthroplasty in the contralateral limb (OKG; N = 7); older, without symptomatic osteoarthritis (OG; N = 8); and young and healthy (YG; N = 8). Muscle strength (1-repetition maximum strength test) and exercise intensity progression (workload increases of 5%–10% were made whenever adaptation occurred) were compared before and after 13 weeks of a twice-weekly progressive resistance-training program.

RESULTS:

At baseline, OKG subjects displayed lower muscle strength than those in both the OG and YG. Among OKG subjects, baseline muscle strength was lower in the osteoarthritic leg than in the total arthroplasty leg. Muscle strength improved significantly during follow-up in all groups; however, greater increases were observed in the osteoarthritic leg than in the total knee arthroplasty leg in OKG subjects. Greater increases were also seen in the osteoarthritic leg of OKG than in OG and YG. The greater muscle strength increase in the osteoarthritic leg reduced the interleg difference in muscle strength in OKG subjects, and resulted in similar posttraining muscle strength between OKG and OG in two of the three exercises analyzed. Greater exercise intensity progression was also observed in OKG subjects than in both OG and YG subjects.

CONCLUSIONS:

OKG subjects displayed greater relative muscle strength increases (osteoarthritic leg) than subjects in the YG, and greater relative exercise intensity progression than subjects in both OG and YG. These results suggest that resistance training is an effective method to counteract the lower-extremity strength deficits reported in older women with knee osteoarthritis and total knee arthroplasty.     

Smoking is associated with earlier time to revision of total knee arthroplasty

Background

Smoking is associated with early postoperative complications, increased length of hospital stay, and an increased risk of revision after total knee arthroplasty (TKA). However, the effect of smoking on time to revision TKA is unknown.

膝关节置换修复退行性股骨髁间窝前交叉韧带撞击症的价值

背景：传统上对退行性股骨髁间窝前交叉韧带撞击症采用非手术治疗,但是可造成交叉韧带功能的丧失,引起膝关节不稳等并发症。随着医学技术的发展,越来越多的观点主张对于韧带损伤及合并膝关节其他结构损伤应尽早手术治疗。 目的：探讨膝关节置换对退行性股骨髁间窝前交叉韧带撞击症的修复效果,并与AO空心螺钉内固定对比。 方法：纳入退行性股骨髁间窝前交叉韧带撞击症患者72例,根据随机抽签法分为治疗组与对照组,每组36例。对照组采用切开AO空心螺钉内固定治疗,治疗组采用膝关节置换治疗。治疗后7 d评定患者的修复效果;在治疗前与治疗后7 d根据Lysholm膝关节评分和国际膝关节文献委员会制定的膝关节评估表(IKDC)评分进行膝关节功能评定;治疗后对所有患者进行6个月的随访,调查并发症发生情况。 结果与结论：所有患者均顺利完成手术。治疗后7 d治疗组的疗效优良率为94%,对照组为75%,治疗组明显高于对照组(P < 0.05)。治疗后7 d治疗组的Lysholm评分明显高于治疗前,而IKDC评分明显低于治疗前,对比差异有显著性意义(P < 0.05);同时治疗后7 d治疗组的Lysholm评分和IKDC评分均优于对照组,差异有显著性意义(P < 0.05)。随访6个月,治疗组患者的切口感染、关节腔感染、关节疼痛、深静脉血栓等并发症发生率明显低于对照组(P < 0.05)。提示膝关节置换治疗退行性股骨髁间窝前交叉韧带撞击症能提高近期疗效,有效恢复膝功能,同时减少置换后并发症的发生。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     

A mid-term clinical outcome study of the Advance Medial Pivot knee arthroplasty

The Advance Medial Pivot Total Knee Arthroplasty (Wright Medical Technology, Arlington, Tennessee, USA) has been designed to reproduce modern ideas of knee kinematics. We report a prospective clinical outcome study of 284 arthroplasties in 225 consecutive patients with a mean follow-up of 6.7 years (range 4 to 9 years). For evaluation, both objective and subjective clinical rating systems and serial radiographs were used. At final follow-up, 10 (4.4%) patients (10 knees) only were lost from follow-up and four (1.8%) patients (five knees) had died for reasons unrelated to the surgery with their knees performing well. There was an 82% compliance in the intervals of follow-up evaluation. All patients showed a statistically significant improvement (p = 0.01) in the Knee Society clinical rating system, WOMAC questionnaire, SF-12 questionnaire, and Oxford knee score. The majority of patients (92%) were able to perform age-appropriate activities with a mean knee flexion of 117° (range 85° to 135°) at final follow-up. Survival analysis showed a cumulative success rate of 99.1% at 5 years. Two (0.7%) arthoplasties, in which patient selection and surgical errors were identified, were revised due to aseptic loosening, one due to infection and one due to a traumatic dislocation. This study demonstrates satisfactory mid-term clinical results for this knee design.     

双向锯齿缝线在人工全膝关节置换术中的应用

目的比较用双向锯齿缝线和常规薇乔线缝合人工全膝关节置换术(Total Knee Arthroplasty,TKA)中缝合关节囊的临床疗效及患者对切口愈合满意度的差异性。方法回顾性选取自2013年1月~2013年12月在我院关节外科接受TKA术的符合本研究纳入标准的患者90例(选用双向锯齿线的50例,常规薇乔线缝合的40例)。分别比较俩组之间患者手术时间,术后切口并发症,患者术后1月和3月时的术侧膝关节HSS评分,患者对切口愈合的满意度以及同期的伤口愈合情况。结果双向锯齿线组的患者手术时间较薇乔线缝合组明显缩短,且时间差异有统计学意义(0.05)。而两组之间患者术后切口并发症发生率,患者对伤口愈合满意度及术后同期HSS评分均无明显差异性(0.05)。结论用双向锯齿缝线缝合关节囊较薇乔线缝合相比能够有效缩短缝合时间及手术时间,具有更好的性价比。     

Temporal trends of primary hinge knee arthroplasty and risk factors associated with revision: National Joint Registry data from 2003 to 2018 for 4921 patients

BackgroundThe aim was to describe temporal changes and associated changes in patient demographics and surgical variables, revision rate and factors associated with revision of primary hinge knee arthroplasty (HKA) in the UK.MethodsNational Joint Registry data for England, Wales, Northern Ireland and Isle of Mann was used to examine the temporal trends in patient demographics, surgical factors and indications for primary HKA usage over a 16-year (2003 to 2018) period and associated risk factors for revision.ResultsThere were 4921 patient episodes with a median follow up of 5.5 (range 0 to 16.3) years. The median age was 75years and the majority were female (72.9%). There was a tenfold increase in the use of HKA (p < 0.001), with an increased relative usage in female patients (p = 0.010), but no significant changes in age (p = 0.484) or BMI (p = 0.781). There were 227 revisions performed at a median of 695days. The overall unadjusted probabilities of revision at 1, 5 and 10 years were 1.5% (95% confidence intervals (CI) 1.1to1.8), 4.4% (95%CI 3.7 to 5.0) and 6.4% (95%CI 5.5 to 7.3), respectively. Cox proportional hazard analysis demonstrated younger age (p < 0.01), male sex (hazard ratio (HR) 1.43, p < 0.01), morbid obesity (HR 2.31, p = 0.022) or previous trauma as the indication (HR 1.48, p = 0.025) were associated with an increased risk of revision.ConclusionThere was an increase in the use of HKA with increased uptake among female patients. The revision rate was a 6.4% at 10 years, however, younger age, male sex, morbid obesity or previous trauma were associated with an increased risk of revision.Level of EvidenceIII Retrospective study.     

Knee stabilisation following infected knee arthroplasty with bone loss and extensor mechanism impairment using a modular cemented nail

Infected Total Knee Replacement with significant bone loss and loss of extensor mechanism poses a difficult management problem. Arthrodesis relying on bony union can be difficult to achieve and can result in significant limb shortening. We retrospectively looked at the outcome of seven patients with significant bone loss and extensor mechanism insufficiency following infected TKR who underwent knee stabilisation using a modular cemented nail. The nail relied on the strong coupling mechanism between the modular femoral and tibial components. Pain score improved from a mean of 7.9 pre-operatively to 1.5 post-operatively at a mean follow up of 39.6 months (range 7–68) months. Two patients underwent technically easy revision nailing for recurrent infection and aseptic loosening. The Endo-Model® Knee Fusion Nail (Newsplint, UK/Waldemar Link®, GmbH & Co. KG, Hamburg, Germany) has good early results in terms of pain relief and provides a stable knee in cases with significant bone loss and extensor mechanism insufficiency following an infected TKR thus avoiding an above knee amputation.     

Two-year fixation and ten-year clinical outcomes of total knee arthroplasty inserted with normal-curing bone cement and slow-curing bone cement: A randomized controlled trial in 54 patients

BackgroundThe normal-curing Refobacin® Bone Cement R (RR) and slow-curing Refobacin® Plus Bone Cement (RP) were introduced after discontinuation of the historically most used bone cement, Refobacin®-Palacos® R, in 2005. The aim of this study was to compare total knee arthroplasty component fixation with the two bone cements.Methods54 patients with primary knee osteoarthritis were randomized to either RR (N = 27) or RP (N = 27) bone cement and followed for two years with radiostereometric analysis of tibial and femoral component migration and dual-energy x-ray absorptiometry measured periprosthetic bone mineral density (BMD). Further, patients were followed up at ten years with clinical outcome scores (OKS and KOOS).ResultsAt two-years follow-up, tibial total translation was 0.31 mm (95% CI: 0.19 – 0.42) for the RP group and 0.56 mm (95% CI: 0.45 – 0.67) (p < 0.01) for the RR group. There was continuous tibial component migration from one to two years follow-up (MTPM > 0.2 mm) in 13/27 patients from the RR and in 12/26 patients from the RP group. There was no difference between groups in BMD baseline values or changes during follow-up, as well as no correlation between change in BMD and tibial component migration. At ten-years follow-up, the improvement in the clinical outcome scores was similar between groups. There were no prosthesis related complications during the 10-year follow-up.ConclusionAt two years, tibial total translation was lower in the RP compared with the RR cement group, but BMD changes were similar. At ten years, no components were revised and clinical outcome scores were similar between groups.     

Limited knee extension during gait after total knee arthroplasty is related to a low Oxford Knee Score

BackgroundAfter total knee replacement (TKR) some patients report low self-perceived function, which is clinically measured using patient reported outcome measures (PROMs). However, PROMs, e.g. the Oxford Knee Score (OKS), inherently lack objective parameters of knee function. Biomechanical gait analysis is an objective and reliable measurement to quantitatively assess joint function. Therefore, the aim of this study was to explore the relationship between biomechanical gait parameters and the OKS.MethodsGait analyses were recorded in 37 patients at least one year after primary TKR and in 24 healthy controls. Parameters from this analysis were calculated for hip, knee and ankle joint angles and joint moments in the sagittal and frontal plane including initial contact, early, late stance and swing. For the patients these parameters were expressed as its difference to control values at matched walking speed. Linear regression analyses were performed between the parameters from gait analysis and the OKS, with speed as covariate.ResultsThe difference in knee extension angle at initial contact and late stance between patients and controls was significantly related to the OKS. Per one degree knee extension difference increase, the OKS reduced with 1.0 to 1.6 points. Overall, patients extended their knee less than controls. Neither ankle and hip gait parameters, nor joint moments showed a relation with OKS.ConclusionsAll patients with a submaximal score on the OKS showed limited knee extension during gait, even without a mechanical constraint in knee extension. This could be related to motor control limitations in this patient group.     

Sensitivity of knee soft-tissues to surgical technique in total knee arthroplasty

Restricted range of motion and excessive laxity are both potential complications of total knee arthroplasty (TKA). During TKA surgery, the surgeon is frequently faced with the question of how tightly to implant the prosthesis. The most common method of altering implantation tightness is to vary the thickness of the polyethylene inlay after the bone cuts have been made and the trial components inserted. We have sought to quantify how altering the polyethylene thickness may affect post-operative soft tissue tension for a range of prosthetic designs.Four different prosthetic designs were implanted into fresh-frozen cadaveric knee joints. All four designs were implanted in the standard manner, with a 100 Newton distraction force used to set soft tissue balance. The tibiofemoral force was then recorded at 15° intervals throughout the passive flexion range. After the standard implantation of each prosthesis, the tibial component was raised or lowered to mimic increasing and decreasing the polyethylene thickness by 2 mm and the force measurements repeated.Tibiofemoral force in extension correlated with implantation tightness for all prosthesis designs. Between 15° and 90°of knee flexion, all four designs were insensitive to changes in implantation tightness. Beyond 90° the effect was more notable in rotating platform mobile-bearing and cruciate-retaining prostheses than in posterior-stabilised mobile-bearing designs.The findings of this research may be useful in assisting surgical decision-making during the implantation of TKA prostheses.     

数字化导航模板辅助全膝关节置换的临床应用

目的　探讨临床数字化导航模板辅助全膝关节置换的可行性和准确性。 方法　招募20例（男8例,女12例）膝骨性关节炎患者。采集患者下肢全长MRI扫描数据,利用逆向工程软件对MRI数据进行处理,计算机内设计得到一款与股骨远端和胫骨近端匹配的可定位截骨平面和外旋轴的导航模板,最后通过快速成型机制作模板实物用于临床手术操作。手术由同一位具有关节置换经验的骨科医生行全膝关节置换手术。术前观察导航模板与股骨髁和胫骨平台匹配性,术后通过CT扫描检测截骨的准确性。 结果 导航模板与股骨髁和胫骨平台贴合紧密,无明显移动;所有患者股骨远端和胫骨近端截骨面与下肢机械轴基本垂直,外旋轴定位精确,股骨后髁截骨面与通髁轴保持平行。 结论 数字化导航模板辅助全膝关节置换具有安全可行,手术操作简单,截骨力线准确。     

Prevalence of Osteoporosis in Female Patients with Advanced Knee Osteoarthritis Undergoing Total Knee Arthroplasty

This study sought to demonstrate bone mineral density (BMD) conditions in elderly female patients with knee osteoarthritis (OA) undergoing total knee arthroplasty (TKA). In addition, we sought to determine whether their BMD conditions differ from those of community-based females without knee OA. Finally we sought to determine whether clinical statuses are related to BMD in the knee OA patients. BMD conditions in 347 female patients undergoing TKA and 273 community-based females were evaluated. Additionally, comparative analyses of BMD between age and body mass index-matched knee OA groups (n=212) and the control groups (n=212) were performed. In the pre-matched knee OA group, regression analyses were performed to determine whether preoperative clinical statuses were related to BMD. Considerable prevalence of coexistent osteoporosis (31%) was found in the pre-matched knee OA patients undergoing TKA. We found no significant differences of the BMD T-scores and the prevalence of osteoporosis between the age and body mass index-matched knee OA and control groups. In the pre-matched knee OA patients, poorer preoperative clinical scores were related to poorer BMD T-scores in the proximal femur and/or lumbar spine. Our study suggests that more attention should be paid to identify and treat osteoporosis in elderly female patients with advanced knee OA undergoing TKA.

Graphical Abstract

相似文献   

乌司他丁在全膝关节置换中的应用

背景：乌司他丁是从人尿液中分离纯化提取的广谱胰蛋白酶抑制药。其主要药理机制是抑制溶酶体酶等多种水解酶的过度释放,从而改善组织灌注和微循环。目前关于乌司他丁对全膝关节置换后急慢性疼痛及置换后深静脉血栓发生率的影响报道较少。 目的：观察乌司他丁对应用充气式止血带条件下接受双侧全膝关节置换患者的炎性递质、置换后疼痛、置换后凝血功能、下肢深静脉和浅静脉血栓发生率及置换后肢体功能恢复的影响。 方法：选择接受双侧全膝关节置换的患者72例,随机分为对照组和试验组,各36例。试验组静脉给予乌司他丁,对照组给予等剂量生理盐水。所有患者麻醉镇痛方案及置换后功能康复方案均相同。在不同时间点检测患者炎症指标、凝血指标,观察静息和活动时的疼痛评分及置换后恢复质量评分。根据下肢血管超声检查结果分析置换后血栓形成情况。 结果与结论：试验组部分时间点的炎症因子水平低于对照组(P < 0.05)。试验组置换后4 h的静息疼痛目测类比评分显著低于对照组(P < 0.05)。各时间点两组患者凝血功能指标差异无显著性意义(P > 0.05)。与推入手术室时比较,置换后4,24 h时两组患者纤维蛋白原水平均明显下降,置换后48 h时明显升高(P均 < 0.05);置换后24,48 h时两组活化部分凝血活酶时间均明显延长(P < 0.05);置换后4-48 h时两组D-二聚体表达水平明显升高(P < 0.05)。与对照组相比,试验组血栓条数显著减少,血栓总长度明显短,差异均有显著性意义(P < 0.05)。试验组在置换后4 h、置换后1,3,5,7 d置换后恢复质量评分均高于对照组(P < 0.05)。提示乌司他丁可以减轻全膝关节置换患者的炎性反应,缓解置换后早期的疼痛,减少下肢肌间静脉血栓形成数量,减缓血栓形成的速度,提高患者置换后恢复质量。 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：      

Immunohistochemical analysis of the neural structures of the posterior cruciate ligament in osteoarthritis patients submitted to total knee arthroplasty: an analysis of thirty-four cases

OBJECTIVES:

Many authors recommend posterior cruciate ligament-retaining arthroplasty with the intention to maintain the proprioception properties of this ligament. Preservation of the neuroreceptors and nervous fibers may be essential for retaining the proprioception function of the posterior cruciate ligament. The present study was thus developed to evaluate the presence of neural structures in the posterior cruciate ligament resected during posterior stabilized arthroplasty in osteoarthritis patients. In particular, clinical, radiographic and histological parameters were correlated with the presence or absence of neural structures in the posterior cruciate ligament.

METHODS:

In total, 34 posterior cruciate ligament specimens were stained with hematoxylin-eosin and Gomori trichrome. An immunohistochemical analysis using antibodies against the S100 protein and neurofilaments was also performed. The presence of neural structures was correlated with parameters such as tibiofemoral angulation, histological degeneration of the posterior cruciate ligament, Ahlbäck radiological classification, age, gender and the histologic pattern of the synovial neurovascular bundle around the posterior cruciate ligament.

RESULTS:

In total, 67.5% of the cases presented neural structures in the posterior cruciate ligament. In 65% of the cases, the neurovascular bundle was degenerated. Nervous structures were more commonly detected in varus knees than in valgus knees (77% versus 50%). Additionally, severe histologic degeneration of the posterior cruciate ligament was related to neurovascular bundle degeneration.

CONCLUSIONS:

Severe posterior cruciate ligament degeneration was related to neurovascular bundle compromise. Neural structures were more commonly detected in varus knees. Intrinsic neural structures were detected in the majority of the posterior cruciate ligaments of patients submitted to knee arthroplasty for osteoarthritis.     

Effects of resistance training in older women with knee osteoarthritis and total knee arthroplasty

OBJECTIVES:

This study sought to analyze the effects of resistance training on functional performance, lower-limb loading distribution and balance in older women with total knee arthroplasty (TKA) and osteoarthritis (OA) in the contralateral knee. In addition, this older knee OA and TKA group (OKG) was compared to older (OG) and young women (YG) without musculoskeletal diseases who underwent the same resistance training program.

METHODS:

Twenty-three women divided into OKG (N = 7), OG (N = 8) and YG (N = 8) had their functional performance, lower-limb loading distribution and balance compared before and after 13 weeks of a twice-weekly progressive resistance training program.

RESULTS:

At baseline, the OKG showed lower functional performance and unilateral balance, and impaired lower-limb loading distribution compared to the OG and the YG (p<0.05). After resistance training, the OKG showed improvements in functional performance (∼13% in sit-to-stand and rising from the floor, ∼16% in stair-climbing and ∼23% in 6-minute walking (6 MW)), unilateral balance (∼72% and ∼78% in TKA and OA leg, respectively) and lower-limb loading distribution, which were greater than those observed in the OG and the YG. The OKG showed post-training 6 MW performance similar to that of the OG at baseline. Sit-to-stand performance and unilateral stand balance were further restored to post-training levels of the OG and to baseline levels of the YG.

CONCLUSIONS:

Resistance training partially restored functional, balance and lower-limb loading deficits in older women with TKA and OA in the contralateral knee. These results suggest that resistance training may be an important tool to counteract mobility impairments commonly found in this population.     

The mean anatomical shape of the tibial plateau at the knee arthroplasty resection level: An investigation using MRI

Clinical assessments after Total Knee Arthroplasty (TKA) show persisting pain after implantation in over 20% of patients. Impingement of soft tissue around the knee, due to imprecise geometry of the tibial implant, can be one reason for persisting ailment. Two hundred and thirty seven MRI scans were evaluated using an active contour detection algorithm (snake) to obtain a high-resolution mean anatomical shape of the tibial plateau. Differences between female and male, older and younger (≤ 40/> 40) and left and right averaged shapes were determined. The shapes obtained were asymmetric throughout. Absolute differences between the subgroups fell short of inter-individual variations represented by calculated one-σ confidence intervals. Our results indicate that a differentiation in TKA tibial plateau design by gender, age, or side is of minor relevance.     

Current and Future Burden of Periprosthetic Joint Infection from National Claim Database

BackgroundPeriprosthetic joint infection (PJI) is the most serious complication after total joint arthroplasty. The incidence and burden of PJI in North America have been reported. There might be potential differences according to ethnics and regional practices between western countries and East Asia. Nevertheless, its incidence in East Asia remains unknown. We aimed to evaluate the incidence and economic burden of PJI in Korea and to project the future burden.MethodsWe identified numbers of total hip arthroplasties, total knee arthroplasties and PJIs in Korea from 2010 to 2018 using medical claim data of Korean Health Insurance and Review and Assessment. Annual incidence and medical cost of PJI were calculated. We projected future burden of PJI through 2030 using Quasi-poisson regression model.ResultsThe annual incidence of PJI ranged from 2.3% to 2.8% and the average cost per each PJI patient ranged from $4,361 to $6,016. Total annual cost of PJI increased from $8.0 million in 2010 to $18.0 million in 2018 and was projected to exceed $57.0 million by 2030.ConclusionThe incidence of PJI in Korea is comparable with reported PJI incidence of 2.0%–2.7% in the United States. Our findings would be used for worldwide comparison of PJI epidemiology and establishment of healthcare policies for PJI in East Asia.     

Are pain,functional limitations and quality of life associated with objectively measured physical activity in patients with end-stage osteoarthritis of the hip or knee?

ObjectivesPhysical activity is promoted in patients with hip or knee osteoarthritis (OA), yet little is known about its relationship with symptoms, functional limitations and Quality of Life (QoL). We investigated if OA-associated pain, functional limitations and QoL are associated with objectively measured physical activity in patients with end-stage hip/knee OA.MethodsCross-sectional study including patients scheduled for primary total hip/knee arthroplasty. Patients wore an accelerometer (Activ8) with physical activity assessed over waking hours, and expressed as number of activity daily counts (ADC) per hour, %time spent on physical activity i.e. walking, cycling or running (%PA), and %time spent sedentary (%SB). Pain, functional limitations and joint-specific and general QoL were assessed with the Hip disability/Knee Injury and Osteoarthritis Outcome Score (HOOS/KOOS) and the Short Form (SF)-12. Multivariate linear regression models with the three to Z-scores transformed parameters of physical activity as dependent variables and adjusted for confounding, were conducted.Results49 hip and 48 knee OA patients were included. In hip and knee OA patients the mean number of ADC, %PA and %SB were 18.79 ± 7.25 and 21.19 ± 6.16, 14 ± 6.4 and 15 ± 5.0, and 66 ± 10.5 and 68 ± 8.7, respectively. In hip OA, better joint-specific and general QoL were associated with more ADC, (β 0.028; 95%CI:0.007–0.048, β0.041; 95%CI:0.010–0.071). Also, better general QoL was associated with the %PA (β 0.040, 95%CI:0.007–0.073). No other associations were found.ConclusionWhereas QoL was associated with physical activity in hip OA, pain and functional limitations were not related to objectively measured physical activity in patients with end-stage hip or knee OA.     

Computer- and Robot-Assisted Total Knee Replacement: Analysis of a New Surgical Procedure

This paper describes a nonstandard procedure for total knee replacement (TKR), based on the use of modern tools such as computers, electronic sensors, and robots, to achieve accurate and optimal implant results. The intervention is planned on a standard PC connected to the CT scanner. Dedicated software shows the surgeon limb alignment and knee status and assists in the choice of the best prosthesis. The intervention is then performed with a new device and surgical procedure. At first the femur and the tibia are fixed to the operating table with a special clamp and the knee bones are exposed with the standard technique; then the surgeon digitizes the shape of the joint and the computer transfers the planned surgical strategy to a dedicated surgical robot. Resections are performed by the surgeon on a constrained guide held by the robot. In this paper we summarize the main results on the system performances, and discuss the clinical implications of this new technology in the operating room. Preliminary experiments on cadavers and volunteers show that this methodology can improve the accuracy of the implant to 2.5 mm and 2°, reduce operating time and surgical errors, and may represent a challenging alternative methodology for TKR. © 2000 Biomedical Engineering Society. PAC00: 0707Tw, 8780-y