Posterior dislocation of the Oxford knee meniscal bearing: a treatment option

Unicompartmental knee replacement (UKR) is now established as a treatment for medial compartment arthritis. The Oxford UKR (Biomet Orthopedics, Inc, Warsaw, IN, USA) has a mobile-bearing system, which minimizes wear. This has been shown to provide excellent long-term results. Dislocation of the mobile-bearing device is rare with an incidence of 1 in 200 (0.5 %). The treatment usually involves exploration of the knee through the original anteromedial incision, removal of the dislocated bearing and rectification of the underlying cause for the dislocation. We describe two cases of a posterior dislocation in which the mobile bearing could not be retrieved and was left in situ. In both cases a good outcome was achieved. We conclude that in extremely rare cases where a dislocated bearing has migrated posteromedially and cannot be retrieved, it can be left in place rather than exploring the joint acutely through a separate posterior incision.     

Acute meniscal injury following successful unicompartmental knee arthroplasty

The case of an active 53-year-old man with a well-functioning unicompartmental knee arthroplasty who suffered an acute athletic injury to the knee is described. A mechanical problem was diagnosed and he was successfully treated by arthroscopic partial lateral meniscectomy for a displaced meniscal tear. This case points to an important difference noted by history and physical examination between an acute injury to the unreplaced compartment of a knee with a unicompartmental knee arthroplasty and progression of the arthritic process.     

Ten-year in vivo wear measurement of a fully congruent mobile bearing unicompartmental knee arthroplasty

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique. In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year. The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term.     

Incarceration of a dislocated mobile bearing to the popliteal fossa after unicompartmental knee arthroplasty

The mobile meniscal bearing of unicompartmental knee arthroplasty is completely free moving, and dislocation of this bearing is a major concern for all mobile-bearing designs. Most dislocations are located in the intracapsular area; however, posterior dislocation of the polyethylene bearing to an extra-articular area of the knee after unicompartmental arthroplasty has not been previously reported. During a revision surgery, separate incision was necessary to remove a dislocated meniscal bearing in the popliteal fossa. The authors present a case of incarceration of a dislocated mobile bearing to the popliteal fossa after unicompartmental knee arthroplasty that was missed during initial diagnosis.     

Dissecting a popliteal cyst after failed unicompartmental knee arthroplasty

This report documents the first case of a popliteal cyst in a knee with failed unicompartmental knee arthroplasty (UKA). The cyst was treated successfully with the creation of a small communication hole between the posteromedial compartment and the popliteal cyst under direct arthroscopic visualization. This was followed by the replacement of a worn polyethylene insert via a small arthrotomy. Three months later, the popliteal mass had disappeared. This case suggests that a dissecting popliteal cyst may occur after UKA as one of the signs of a malfunction. It also suggests that treatment should be directed toward the joint and not the cyst itself.     

Knee stability in meniscal bearing total knee arthroplasty

The effect of a meniscal bearing on knee laxity in anterior cruciate ligament-sacrificing total knee arthroplasty was evaluated in 7 cadaver knees using a knee testing device that measured knee flexion angle as well as laxity to medial-lateral, anterior-posterior [AP], and rotational loads. A standard fixed tibial component and mobile tibial components (AP sliding, rotationally sliding, and AP and rotationally sliding) were used to evaluate AP, rotational, and varus-valgus stability and maximal flexion and extension with the neutrally positioned and malrotated tibial tray. The AP movable components increased AP laxity, and the fixed component decreased rotational laxity significantly when compared with the normal knees. The rotationally movable components did not change knee laxities significantly even when the tibial tray was malrotated. No significant difference among the components was detected when the maximal flexion and extension angles were compared in the neutrally positioned tibial tray. Malrotation of the tibial tray decreased the maximal extension angle in the fixed component. This study showed that the rotationally movable component can achieve near-normal laxity regardless of tibial tray rotation, but AP mobility of the bearing produces AP laxity that could lead to implant failure.     

Oxford meniscal bearing knee versus the Marmor knee in unicompartmental arthroplasty for arthrosis: A Swedish multicenter survival study

In the Swedish Knee Arthroplasty Study, all 699 Oxford meniscal bearing cemented unicompartmental prostheses (Biomet, Bridgend, UK) were identified and analyzed regarding failure pattern and compared with all Marmor prostheses (Smith & Nephew Richards, Orthez, France) and with a time-, age-, and sex-matched subset of Marmor prostheses using survival statistics expressed as cumulative revision rates. After 1 year there was already a higher rate, and after 6 years the rate of the Oxford group was more than twice that of the Marmor group. There were 50 revisions in the Oxford group: dislocating meniscus in 16, loosening of the femoral component in 6, tibial component in 4, both components in 4, contralateral arthrosis in 10, infection in 4, and technical failure with instability, pain, and/or impingement of the meniscal bearing anterior in the femoral condyle in 6. It is still unclear if the design with the sliding menisci will, in the long turn, reduce wear and loosening, thereby compensating for the initially inferior results. It is recommended that until this question is clarified, the Oxford knee should be used on a limited scale for long-term comparative studies only.     

Posterior dislocation of total knee arthroplasty.

Posterior dislocation of the prosthesis after total knee arthroplasty is an infrequent but serious complication. Seven patients with this complication were treated from January 1985 until October 1989. Five of the seven dislocations occurred in primary total knee arthroplasties and two occurred after revision arthroplasty. Limb alignment before arthroplasty, when it could be determined, was valgus in all patients, averaging 25 degrees. In each case there was an identifiable problem with the knee extensor mechanism: five had patellar dislocations, one a patellar tendon rupture, and one a patellar fracture. In three of the posterior dislocations, there was also an imbalance of the flexion and extension gaps with excessive laxity of the ligaments in flexion. Treatment was individualized. In two patients, the knee was reduced closed and the patella subsequently tracked so that no reoperation was necessary. One ruptured patellar tendon could not be repaired in a 94-year-old patient with cardiac disease. A cylinder cast was applied with poor results. Operative intervention was required in four patients, one of whom required only a patellar realignment procedure. The three other patients required component revision procedures, however, in addition to patellar realignment procedures. In these three patients, laxity of the knee in flexion was so severe that posterior instability could not be corrected merely by patellar relocation. At a follow-up examination (average, 21 months postoperatively), all six patients who were treated as recommended had good results with no further dislocations, with the exception of the one patient with a patellar tendon rupture.     

Contact stress analysis in meniscal bearing total knee arthroplasty

The effect of a mobile meniscal bearing on tibiofemoral contact stress was tested with a standard fixed tibial component and with movable tibial components (anteroposterior sliding, rotationally sliding, and anteroposterior and rotationally sliding). A digital electronic sensor was used to detect tibiofemoral contact location in five cadaver knees, then the location was reproduced while peak and mean stresses were measured under compressive load at 0°, 30°, 60°, and 90° of flexion. Stresses were measured when the tibial component was normally aligned and at 15° internal and 15° external rotation. To evaluate the effect of excessive overhang of the polyethylene articular surface, undersurface stress of the rotationally sliding component was also measured with a 30° and a 45° malrotated tibial tray. Uppersurface stresses of the fixed-bearing components were significantly higher at full extension than those recorded in components with rotational mobility. Undersurface stresses were always lower than uppersurface stresses, but correlated with uppersurface stresses. Undersurface stresses of the rotationally sliding component gradually increased as the malrotation angle of the tray increased. A mobile meniscal bearing surface appears to offer an advantage over a standard fixed component when rotational malalignment of the tibial component occurs. However, with severe rotational malalignment, edge contact markedly increases undersurface stresses, which could cause deformity and subluxation.     

Effect of tibial component position on short-term clinical outcome in Oxford mobile bearing unicompartmental knee arthroplasty

Background

Malposition of the tibial components is a well-known complication of unicompartmental knee arthroplasty. In this study, we aimed to ascertain the relationship between the tibial component position and clinical outcomes of unicompartmental knee arthroplasty. We focused on the tibial component height and obliquity in the coronal plane.

Delayed failure of meniscal bearing elements in total knee arthroplasty

Dislocation and early fracture of meniscal bearing elements have been reported after New Jersey low-contact-stress (DePuy, Warsaw, IN) total knee arthroplasty. Delayed wear and subsequent failure of meniscal bearing elements in two cases, 8 and 9 years after surgery, are reported.     

An unusual case of meniscal hematoma mimicking a medial meniscal cyst

This is a case report of a so-called meniscal hematoma that mimicked a meniscal cyst. A literature search found no previous report of it before. Treatment with arthroscopic intra-articular decompression alone is enough. We discuss the possibility of its pathogenesis and treatment.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 5 (May-June), 2002: E22     

固定平台单髁置换治疗外侧单间室膝骨关节炎的早期疗效

目的探讨外侧固定平台单髁关节置换术治疗外侧单间隙骨关节炎手术策略及早期疗效。 方法选取2016年8月至2017年1月在济南军区总医院骨病科行膝关节外侧单髁关节置换术病人11人,纳入标准：外侧单间隙骨关节炎;无关节外畸形,不伴或伴轻度膝外翻畸形;前后交叉韧带及内外侧副韧带完整;共11膝,男性5人,女性6人。平均年龄(57±6)岁,身体质量指数为(29.5±2.7),术前行膝关节负重正侧位、双下肢全长正位及髌骨轴位X线片检查。行外侧单髁关节置换术,手术入路选择膝关节正中切口,沿髌骨外缘切开关节囊,清理外侧间室,胫骨行髓外定位进行垂直及水平截骨,股骨切除软骨至软骨下骨,调和骨水泥,安放假体。应用牛津大学膝关节评分系统(OKS)及美国膝关节协会评分系统(KSS)评价术后功能改善情况。采用Mann-Whitney U检验进行统计学分析。 结果11名病人均获得随访,随访时间平均(5.0±1.1)月,术后OKS及KSS评分均得到明显改善,OKS评分(Z ＝－11.345,P <0.05)和KSS评分(Z ＝－15.542,P<0.05)差异具有统计学意义,膝关节功能良好,术后病人满意度改善。随访终点均未发现并发症。 结论外侧单髁关节置换术治疗外侧单间隙骨关节炎是1种有效的保膝治疗方式,可以有效保存膝关节韧带,减少截骨量,患者术后膝关节功能良好。     

全膝关节置换中固定平台假体和活动平台假体相比较的Meta分析

[目的]应用Meta分析的方法,评价全膝关节置换术(total knee arthroplasty,TKA)中应用固定平台型假体(fixed bearing total knee arthroplasty,FB)和活动平台型假体(mobile bearing total knee arthroplasty,MB)的疗效差异,为临床选择适当类型假体进行TKA术提供依据。[方法]计算机检索Pubmed、EMBASE、Ovid和Cochrane图书馆关于TKA术中应用FB和MB的随机或半随机对照试验,按照文中所述纳入标准收集后进行比较,利用RevMan5.0软件进行异质性分析及Meta分析,绘制森林图。[结果]本文检索了1979～2009年间发表的1 718篇关于TKA术中应用FB和MB的文献,经过筛选和评价,最后收集到已发表的14篇(共1 305例患者)随机或半随机的对照试验,符合本次Meta分析所纳入的试验标准。结果发现两组在KSS评分、关节活动度、患者满意率、放射学指标和假体相关并发症上差异无统计学意义(95%显著区间有重叠)。[结论]相对MB的先进设计理念,现有临床研究结果尚不支持在TKA术中应用MB疗效显著优于FB。     

膝关节单髁置换术研究进展

目的总结膝关节单髁置换术(unicompartmental knee arthroplasty,UKA)的临床应用及研究进展。方法广泛查阅近年国内外UKA相关文献,从UKA新出现的手术指征、假体类型选择、与其他术式对比以及最新进展等方面进行总结分析。结果临床研究表明UKA具有创伤小、恢复快、术后并发症少等诸多优点。目前该手术适应证有所扩展,体质量指数>25 kg/m^2、年龄<60岁、髌股关节炎及前交叉韧带功能不良不再属于手术禁忌证。UKA术中假体类型的选择需要充分考虑患者情况。近年,临床逐渐开展的机器人辅助UKA可有效改善手术疗效,提高患者术后满意度,降低术后并发症。结论随着手术技术、假体材料及机器人技术的发展,UKA临床应用会更广泛,但目前大多为短、中期随访研究,需要进一步观察长期随访结果以指导临床实践。     

Posterior stabilization in total knee arthroplasty with use of an ultracongruent polyethylene insert

Fifty-three primary and 47 revision posterior cruciate ligament (PCL)-substituting total knee arthroplasties (TKAs) using a highly conforming (ultracongruent) polyethylene insert were retrospectively reviewed over a 48- to 106-month (mean, 60+/-11 months) follow-up period. These 100 knees were age and sex matched with another 100 TKAs performed using a PCL-sparing design. The ultracongruent design has an anterior buildup of 12.5 mm and a more conforming articular surface to match better the radius of the femoral component. In primary and revision TKAs, the average Hospital for Special Surgery knee score (P = .3) and range of motion (P = .43) were similar between the PCL-sparing and ultracongruent groups. In primary and revision TKAs, there were no revisions resulting from instability for patients receiving an ultracongruent insert versus 5 knees in the PCL-sparing control group secondary to subsequent postoperative anteroposterior instability and PCL insufficiency.     

旋转平台假体在全膝关节置换术中的应用及早期疗效观察

[目的]观察旋转平台人工膝关节置换术的临床疗效.[方法]对79例患者93膝行TKA,采用正中切口髌旁内侧入路,安装假体,膝关节均未进行髌骨置换.术后复查X线片观察假体固定情况,采用美国膝关节学会评分(KSS评分)评定膝评分及膝功能评分,观察并发症发生情况.[结果]本组平均随访时间(33.61±7.34)个月(24～48个月).末次随访时,关节总活动度明显增加,由术前68.76°增加至术后107.53°(P相似文献