Severe metallosis following total knee arthroplasty: a case report and review of radiographic signs

Metallosis is an uncommon complication following total knee arthroplasty that leads to osteolysis and implant loosening due to chronic inflammatory reaction. Abrasion between the metallic surfaces of the implant releases metallic debris that interacts with the periprosthetic soft tissues and causes chronic synovitis. Here we present a case of a 65-year-old man who had undergone total knee arthroplasty 10 years ago and developed implant loosening associated with severe metallosis and varus instability. Radiographs show the three typical signs of metallosis: metal-line sign, bubble sign, and cloud sign. This patient was subjected to revision surgery consisting of debridement and primary implant replacement by a hinged endoprosthesis. Knowledge of the typical radiographic and clinical findings of metallosis is important to rapidly diagnose this complication and avoid progressive joint destruction.     

The imaging appearances of metallosis

Metallosis is an uncommon condition in which there is infiltration of periprosthetic soft tissues and bone by metallic debris resulting from wear of joint arthroplasties. It is often associated with significant osteolysis; therefore the identification of metallosis is an indication for revision arthroplasty. The radiographic, CT and MRI features of metallosis in a 63-year-old man who presented 16 years post-arthroplasty are described in this case report.     

Extensive osteolytic cystlike area associated with polyethylene wear debris adjacent to an aseptic, stable, uncemented unicompartmental knee prosthesis: case report

We present the case of a patient who after uncemented unicompartmental knee arthroplasty developed a large osteolytic cystlike area in the lateral aspect of the tibial metaphysis, contralateral to a well-fixed tibial component at revision surgery. The lesion contained fibrotic soft tissue, evidence of a foreign-body giant cell reaction and polyethylene particles, but no metal wear debris, infection, or malignancy. This case demonstrates that there is a direct communication between the joint cavity and the cyst.     

胫骨高位截骨术失败后行全膝关节假体置换术的长期疗效观察

目的 针对胫骨高位截骨术(high tibial osteotomy,HTO)失败后行全膝人工关节置换术(total knee arthmplasty,TKA)进行长期疗效观察,分析其远期临床疗效及术中注意事项.方法 选择法国Medico-Chirurgical du Cedre中心1990年3月-1992年6月18例(19膝)HTO术后失败的患者并行TKA治疗.所有关节均有内外侧间室退变,4例伴有外侧胫骨平台中度骨缺损.采用X线测量和膝关节协会评分系统(Knee Society Scoring System,KSS)评估手术疗效,X线测量包括髋膝踝角(hip knee ankle,HKA)、α角、β角、髌骨指数、胫骨平台后倾角等.结果 TKA中11膝因HTO术后严重外翻和髌骨外侧半脱位而在TKA中行胫骨结节截骨及内移术;5膝因侧方软组织条件差或平衡不良而置入半限制型假体.随访时18例患者中2例死亡,获访16例(17膝).无失访和翻修病例.7膝在随访时出现严重聚乙烯衬垫磨损,但临床症状较轻.随访时KSS平均147.2分,优良率82%. 结论 HTO术后行TKA临床疗效优良.但由于外翻畸形和髌股关节并发症多见,可能需采用胫骨结节截骨术并内移术;HTO术后外翻畸形为TKA软组织平衡和胫骨截骨造成一定困难,术前应准备置入限制性更高的假体.     

Fully automated software to monitor wear in prosthetic knees using fluoroscopic images

Total knee arthroplasty is now a widely accepted treatment for late-stage arthritis. Wear of the polyethylene layer in prosthetic knees is a known cause of implant failure. Early detection of wear may allow prediction of device failure. In this paper we describe a fully automated image processing algorithm to measure the minimum tibiofemoral joint space width (mJSW) for monitoring prosthesis wear radiographically. The femoral portion and tibial plate were automatically delineated and mJSW was calculated in each compartment. The software also delineated the tip of the prosthesis pin in order to make a magnification correction. The algorithm was tested with a set of triplicate acquisitions of 18 fluoroscopic knee images. The RMS standard deviation (RMSSD) for the triplicate measurements was calculated as a figure of merit. The RMSSD was 0.077 and 0.087 mm for the lateral and medial compartments. The computer successfully found the minimum JSW for both compartments in all 54 images. A single case (2% of total) required user interaction to correct for an obvious failure to delineate the prosthesis pin. We document a robust and precise tool for quantifying mJSW to monitor prosthesis wear.     

屈膝过程中的胫股运动特性分析

本文采用三维位移测量方法，测试１０例离体人膝标本的胫股关节三维运动特性。发现屈膝过程中，胫股运动也具有典型的三维运动特点。其中在屈膝初期的３０°内，胫骨内旋最明显并伴有胫骨内翻现象，平均内旋８°，内翻６－７ｍｍ，膝关节完全伸直时胫股扣锁使膝关节稳定，屈曲时胫股“解锁”使膝关节松弛，具重要的临床意义，同时提示，在解释传统的胫股扣锁现象时不应遗漏伴随发生的胫骨内／外翻现象。     

Patellofemoral kinematics during deep knee flexion after total knee replacement: a computational simulation

Purpose

Actions requiring deep knee flexion, such as kneeling and squatting, are challenging to perform after total knee replacement (TKR), though many manufactures emphasize that their knee prostheses could safely achieve high flexion. Little is known about the patellofemoral kinematics during deep flexion. This study aimed to track the movement of the patella during kneeling and squatting through dynamic computational simulation.

Methods

A validated knee model was used to analyse the patellar kinematics after TKR, including shifting, tilting and rotation. The data were captured from full extension to 135° of knee flexion. For kneeling, an anterior force of 500 N was applied perpendicularly on the tibial tubercle as the knee flexed from 90° to 135°. For squatting, a ground reaction force was applied through the tibia from full extension to 135° of flexion.

Results

This study found that patellar shifting and rotation in kneeling were similar to those while squatting. However, during kneeling, the patella had a greater medial tilt and showed signs of abrupt patellar tilt owning to an external force being concentrated on the tibial tubercle.

Conclusions

In terms of squatting and kneeling movements, the latter is a more strenuous action for the patellofemoral joint after TKR due to the high forces acting on the tibial tubercle. It is suggested that overweight patients or those requiring high flexion should try to avoid kneeling to reduce the risk of the polyethylene wear. Further modification of trochlear geometry may be required to accommodate abrupt changes in patellar tilting.

Level of evidence

II.     

Clinical results of posterior cruciate ligament retaining TKA with alumina ceramic condylar prosthesis: comparison to Co–Cr alloy prosthesis

In a prospective study, 194 knees undergoing total knee arthroplasty (110 knees with alumina ceramic prostheses; 84 knees with Co–Cr alloy prostheses) were clinically and radiologically evaluated. Average follow-up period was 66 months (36–124 months). Average age at the time of surgery was 66 years. In the ceramic prostheses, two revision surgeries were performed because of breakage of the tibial tray and late infection, whereas two revisions of the Co–Cr alloy prostheses were carried out due to loosening and late infection. In the other patients, there were no significant differences in clinical parameters (HSS knee score and range of motion) between the two prostheses. In radiological evaluation, we could not find any radiolucent lines around the femoral ceramic component while radiolucency was present in three knees (3.6%) around the Co–Cr femoral component. Beneath the tibial tray, three knees (2.7%) showed a radiolucent line around the former prosthesis while eight knees (9.5%) demonstrated a radiolucent line around the latter prosthesis. Chi-square tests showed a significant difference in the occurrence of radiolucent line around both of the femoral and tibial prosthesis. This study demonstrated that clinical results of the alumina ceramic PCL retaining total knee prosthesis are comparable to the standard Co–Cr alloy PCL retaining total knee prosthesis. Although we could not draw any conclusions regarding the superiority of the ceramic prosthesis with respect to UHMWPE wear and long-term survivorship, this report encouraged a long-term follow-up study on ceramic prostheses. Presented in part at the meeting of the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine, New Zealand, 2003.     

A biomechanical comparison of tibial inlay and tibial tunnel posterior cruciate ligament reconstruction techniques: graft pretension and knee laxity

BACKGROUND: Most posterior cruciate ligament reconstruction techniques use a tibial bone tunnel, which results in an acute bend in the graft as it passes over the posterior portion of the tibial plateau. HYPOTHESIS: The tibial inlay technique will result in lower graft pretensions, less laxity, and less stretch-out after cyclic loading. STUDY DESIGN: Controlled laboratory study. METHODS: Graft pretensions necessary to restore normal laxity at 90 degrees of knee flexion (laxity match pretension) and anteroposterior laxities at five knee flexion angles were recorded in 12 fresh-frozen knee specimens with bone-patellar tendon-bone posterior cruciate ligament graft reconstructions using both techniques and two femoral tunnel positions. RESULTS: When the graft was placed in a central femoral tunnel, the tibial tunnel reconstruction required an average 15.6 N greater laxity match pretension than the tibial inlay reconstruction. There were no significant differences in mean knee laxities between the tibial tunnel and tibial inlay techniques at any knee flexion angle; both reconstruction techniques restored mean knee laxity to within 1.6 mm of intact knee values over the entire flexion range. CONCLUSIONS: There was no important advantage of one technique over the other with respect to the biomechanical parameters measured.     

Focal osteolysis in total hip replacement: CT findings

Objective To describe the CT findings of focal osteolysis following total hip replacement (THR).Design and patients CT imaging features of 30 THRs with focal osteolysis visualized on follow-up radiographs and undertaken revision surgery were reviewed. On CT scans, the shape and anatomic location of osteolytic lesions was recorded, as well as their size and number. The presence of cortical disruption or expansion, liner wear, metallosis, and heterotopic ossification was also noted. In each case, surgical and histologic findings were correlated with imaging features.Results Focal osteolysis was common in the superior part of acetabular and femoral components. CT features of focal osteolysis were multiple, expansile, oval, or round radiolucencies, which were conglomerated into multilobular shape. The cortex adjacent to the osteolytic lesions revealed irregular thinning and discontinuity (29/30, 97%) accompanied by a few tiny fragments. Liner wear was common (27/30, 90%), and metallosis was frequent (8/30, 26.7%). Pathologic results were foreign body reaction in 20 patients, chronic inflammation in eight, and fibrosis in two.Conclusion CT appearances of focal osteolysis following THR are multilobulated lucent areas with expansile periosteal reaction and cortical abnormalities, mimicking infection or tumor. We consider that CT is useful for the prediction and assessment of the nature and extent of focal osteolysis.     

The position of the tibia during graft fixation affects knee kinematics and graft forces for anterior cruciate ligament reconstruction.

Ten cadaveric knees (donor ages, 36 to 66 years) were tested at full extension, 15 degrees, 30 degrees, and 90 degrees of flexion under a 134-N anterior tibial load. In each knee, the kinematics as well as in situ force in the graft were compared when the graft was fixed with the tibia in four different positions: full knee extension while the surgeon applied a posterior tibial load (Position 1), 30 degrees of flexion with the tibia at the neutral position of the intact knee (Position 2), 30 degrees of flexion with a 67-N posterior tibial load (Position 3), and 30 degrees of flexion with a 134-N posterior tibial load (Position 4). For Positions 1 and 2, the anterior tibial translation and the in situ forces were up to 60% greater and 36% smaller, respectively, than that of the intact knee. For Position 3, knee kinematics and in situ forces were closest to those observed in the intact knee. For Position 4, anterior tibial translation was significantly decreased by up to 2 mm and the in situ force increased up to 31 N. These results suggest that the position of the tibia during graft fixation is an important consideration for the biomechanical performance of an anterior cruciate ligament-reconstructed knee.     

An analysis of the sidestep cutting manoeuvre

The sidestep cutting manoeuvre is a common mechanism of noncontact or isolated ACL ruptures in athletes. We analyzed the amount and direction of tibial rotation that occurred at the knee joint with a triaxial electrogoniometer on 11 male subjects who performed the sidestep cutting manoeuvre. The mean total tibial rotation was 19.84 +/- 5.63 degrees and the mean maximum point of internal tibial rotation occurred at 34.77 +/- 5.30% of the stance phase. However, greater values for internal tibial rotation occurred in the swing phase in association with a greater angle of knee flexion. Therefore, in our subjects, during the sidestep cutting manoeuvre, internal tibial rotation did occur at the knee but was not maximal. Under normal circumstances when performing the sidestep cutting manoeuvre, maximum internal tibial rotation does not occur and so the ACL is not placed under excessive strain in such a manoeuvre. If the ACL ruptures during a sidestep cutting manoeuvre then a possible cause may be the athlete's loss of the ability to control internal tibial rotation of the knee.     

Biomechanical analysis of tibial torque and knee flexion angle: implications for understanding knee injury

Knee injuries are common in sports activities. Understanding the mechanisms of injury allows for better treatment of these injuries and for the development of effective prevention programmes. Tibial torque and knee flexion angle have been associated with several mechanisms of injury in the knee. This article focuses on the injury to the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL) and the meniscus of the knee as they relate to knee flexion angle and tibial torque. Hyperflexion and hyperextension with the application of tibial torque have both been implicated in the mechanism of ACL injury. A combination of anterior tibial force and internal tibial torque near full extension puts the ACL at high risk for injury. Hyperflexion also increases ACL force; however, in this position, internal and external tibial torque only minimally increase ACL force. Several successful prevention programmes have been based on these biomechanical factors. Injury to the PCL typically occurs in a flexed or hyperflexed knee position. The effects of application of a tibial torque, both internally and externally, remains controversial. Biomechanical studies have shown an increase in PCL force with knee flexion and the application of internal tibial torque, while others have shown that PCL-deficient knees have greater external tibial rotation. The meniscus must endure greater compressive loads at higher flexion angles of the knee and, as a result, are more prone to injury in these positions. In addition, ACL deficiency puts the meniscus at greater risk for injury. Reducing the forces on the ACL, PCL and meniscus during athletic activity through training, the use of appropriate equipment and safe surfaces will help to reduce injury to these structures.     

The role of the anteromedial and posterolateral bundles of the anterior cruciate ligament in anterior tibial translation and internal rotation

BACKGROUND: A rupture of the entire fibers of the anterior cruciate ligament leads to knee instability due to increased anterior tibial translation and increased internal tibial rotation. The influence of isolated deficiency of the anteromedial or posterolateral bundle of the anterior cruciate ligament on the resulting knee kinematics have not yet been reported. HYPOTHESIS: Transection of the anteromedial bundle will lead to increased anterior tibial translation at 90 degrees. Transection of the posterolateral bundle will show an increased anterior tibial translation as well as a combined rotatory instability at 30 degrees. STUDY DESIGN: Controlled laboratory study. METHODS: Kinematics of the intact knee were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 N.m valgus and 4 N.m internal tibial rotation using a robotic/universal force moment sensor testing system. Subsequently, the fibers of the anteromedial and posterolateral bundle were resected in an alternating order and the new translation in response to the same external loading conditions measured. Statistical analysis was performed using a 2-way ANOVA test. RESULTS: Transection of the anteromedial bundle increased anterior tibial translation at 60 degrees and 90 degrees of knee flexion significantly. Isolated transsection of the posterolateral bundle increased anterior tibial translation in response to 134-N anterior load at 30 degrees of knee flexion significantly and resulted in a significant increase in combined rotation at 0 degrees and 30 degrees in response to a combined rotatory load compared with the intact knee and isolated resection of the anteromedial bundle. CONCLUSION: The anteromedial and posterolateral bundles stabilize the knee joint in response to anterior tibial loads and combined rotatory loads in a synergistic way. CLINICAL RELEVANCE: The results of the current study suggest that, from a biomechanical point of view, it may be beneficial to reconstruct both bundles of the anterior cruciate ligament to better restore normal anterior tibial translation and combined rotation.     

胫骨平台骨折及膝关节附属结构损伤的MRI诊断

目的评价胫骨平台骨折合并膝关节附属结构损伤的MRI表现.资料与方法 27例胫骨平台骨折病例经X线平片检查后作MRI扫描,分析不同类型胫骨平台骨折所合并的膝关节附属结构损伤的MRI形态学表现.结果 MRI能准确显示骨折所合并的膝关节附属结构的损伤性病变,包括关节软骨断裂、半月板撕裂和移位、侧副韧带和肌腱的撕裂、关节腔脂肪血性积液等,其中双髁骨折引起的损伤最为严重,撕脱骨折引起的损伤较轻.结论 MRI能准确诊断胫骨平台骨折合并的膝关节附属结构损伤,应作为膝关节外伤的常规检查手段.     

Similar survival between screw cementless and cemented tibial components in young patients with osteoarthritis

Purpose

The aim of this study was to compare the outcomes of tibial fixation with either a cemented or cementless with screw augmentation component in young patients with non-inflammatory arthritis.

Methods

Ninety-three patients aged 55 or younger with non-inflammatory arthritis were randomized to compare outcomes between cemented tibial fixation (48 patients) and cementless fixation with screw augmentation (45 patients). The femoral component was cementless in both groups. Post-operative evaluation was assessed by the clinical and radiological criteria of The Knee Society and WOMAC questionnaire.

Results

The median follow-up was 6.7 (5–12) years. Significant differences were found for knee score (p = 0.02), range of motion (p = 0.04), and WOMAC score (p = 0.03). In the cemented group, there was one deep wound infection, four tibial aseptic loosening, and one polyethylene wear, all of which were revised. In the cementless group there was one tibial aseptic loosening and one polyethylene wear, both being revised. There was no difference in revision rate, and the cumulative survival at 9-year for aseptic reason was 93.7 % (95 % CI, 82–100 %) in the cementless group and 90.0 % (95 % CI, 80–100 %) in the cemented group (n.s.).

Conclusions

Cementless total knee arthroplasty was found to be a reliable option in younger patients with osteoarthritis. Although the revision rate and survival were similar in both groups, better clinical outcomes were obtained with cementless tibial components.

Level of evidence

I.     

Biomechanics of the PCL and related structures: posterolateral,posteromedial and meniscofemoral ligaments

This paper reviews and updates our knowledge of the anatomy and biomechanics of the posterior cruciate ligament, and of the posterolateral, posteromedial and meniscofemoral ligaments of the knee. The posterior cruciate ligament is shown to have two functional fibre bundles that are tight at different angles of knee flexion. It is the primary restraint to tibial posterior draw at all angles of knee flexion apart from near full extension. In contrast, the posterolateral and posteromedial structures are shown to tighten as the knee extends, and to be well-aligned to resist tibial posterior draw. These structures also act as primary restraints against other tibial displacements. Tibial internal rotation is restrained by the medial and posteromedial structures, while tibial external rotation is restrained by the lateral and posterolateral structures. They are also the primary restraints against tibial abduction-adduction rotations. The meniscofemoral ligaments are shown, for the first time, to contribute significantly to resisting tibial posterior draw, and to have a strength of approximately 300 N. Taken together, this evidence shows how the posterolateral and posteromedial structures are responsible for posterior knee stability near extension, and this, along with the action of the meniscofemoral ligaments, may explain why an isolated rupture of the posterior cruciate ligament does not often lead to knee instability     

Articular cartilage contact pressure after tibial tuberosity transfer. A cadaveric study

Medial transfer of the tibial tuberosity has been commonly used for treatment of recurrent dislocation of the patella and patellofemoral malalignment. In this study, six fresh human cadaveric knees were used. Static intrajoint loads were recorded using Fuji Prescale pressure-sensitive film for contact pressure and contact area determination in a closed kinetic chain knee testing protocol. Peak pressures, average contact pressures, and contact areas of the patellofemoral and tibiofemoral joints were calculated on native intact knee specimens and after tibial tuberosity transfer. All native intact knee specimens had a normal Q angle. Medialization of the tibial tuberosity significantly increased the patellofemoral contact pressure. Medial displacement of the tibial tuberosity also significantly increased the average contact pressure of the medial tibiofemoral compartment and changed the balance of tibiofemoral joint loading. The results of our study suggest that caution should be used when transferring a patellar tendon in the face of a preexisting normal Q angle as this will result in abnormally high peak pressure within the tibiofemoral joint. Overmedialization of the tibial tuberosity should be avoided in the varus knee, the knee after medial meniscectomy, and the knee with preexisting degenerative arthritis of the medial compartment.     

Measurement of posterior tibial translation in the posterior cruciate ligament-reconstructed knee: significance of the shift in the reference position

BACKGROUND: The measurement of anterior or posterior tibial translation depends on the existence of a repeatable and accurate reference position of the knee from which the corresponding translation is measured. HYPOTHESIS: Clinical measurements of posterior tibial translation alone do not accurately reflect the laxity of posterior cruciate ligament-reconstructed knees. STUDY DESIGN: Controlled laboratory study. METHODS: Ten human cadaveric knees were tested by using a robotic/universal force-moment sensor testing system. The reference positions and the resulting kinematics in response to a 134-N anterior-posterior tibial load were determined for the intact and reconstructed knees. Posterior cruciate ligament reconstruction was performed with the graft tensioned and fixed at two different positions: 1) 90 degrees of knee flexion with a 134-N anterior tibial load and 2) full extension with no load. RESULTS: Posterior cruciate ligament reconstruction with graft fixation at full extension with no load resulted in anterior shift of the reference position by 1.5 to 3.2 mm. The reconstruction resulted in an overconstrained knee with significantly decreased total anterior-posterior translation of 2.6 to 3.2 mm. However, the posterior tibial translation measured was not significantly different from that of the intact knee. Posterior cruciate ligament reconstruction with graft fixation performed at 90 degrees of flexion with a 134-N anterior tibial load resulted in kinematics similar to those of the intact knee. CONCLUSION: Posterior tibial translations that are measured clinically can be misleading because the reference position of the knee can be shifted significantly after posterior cruciate ligament reconstruction. Clinical Relevance: The measurement of total anterior-posterior translation may be a more accurate way to assess kinematics of the reconstructed knee.     

Tibial slope changes following dome-type high tibial osteotomy

The tibial slope is essential in knee biomechanics, both for ligament function and knee kinematics. High tibial osteotomy (HTO) designed primarily to correct frontal plane malalignment in osteoarthritis of the knee joint can cause unintentional tibial slope changes. We evaluated tibial slope changes in 40 knees in patients with medial compartment osteoarthritis treated by dome-type HTO and external fixation on one side, and followed up for 55 months on average. Four different tibial slope measurement methods (anterior tibial cortex, proximal tibial anatomic axis, posterior tibial cortex, and proximal fibular anatomic axis) were used preoperatively and postoperatively on both sides. Patients were allocated into three groups according to their final frontal plane alignment of the knee joint (hypercorrection, normocorrection, and undercorrection groups) based on tibiofemoral anatomic axis angle. As a whole, preoperative slope values (11.2°, 7.5°, 5.6°, and 8.2° for the four methods, respectively) displayed a significant decrease postoperatively (on average 7.9°, 4.8°, 2.2°, and 3.7°, respectively). Patients with undercorrection (or recurrence of deformity) had a more remarkable decrease in slope than those with normocorrection or hypercorrection. The higher the degree of postoperative mechanical axis valgus, the higher the degree of posterior tibial slope that resulted. Sagittal plane changes after dome-type HTO basically decreasing the tibial slope should be taken into account for subsequent reconstructive procedures such as total knee arthroplasty.