Increase in early polyethylene wear after sterilization with ethylene oxideRadiostereometric analyses of 201 total hips

We evaluated polyethylene wear by measuring femoral head penetration in 201 THA (median age 62 (31-81) years, 117 women) extracted from 5 randomized studies aimed to assess various fixation principles. There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment, 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas. Moreover, 37 cemented cups were sterilized with ethylene oxide (Reflection all-poly) and 69 porous-coated cups had liners sterilized in ethylene oxide (Reflection). 28 mm femoral heads were used in all cups. The patients were followed with repeated radiostereometric measurements (RSA) up to 2 years. The activity level of the patients was evaluated by a questionnaire. After 2 years, cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates, as compared with gamma-sterilized polyethylene. The penetration did not differ between the gamma-irradiated designs. Using stepwise linear regression analysis, we found that the type of sterilization, age and weight were the most important predictors and that they determined the direction of the proximal penetration rate. Activity score, male gender and proximal migration of the cup had little effect. The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients.     

Increase in early polyethylene wear after sterilization with ethylene oxide

We evaluated polyethylene wear by measuring femoral head penetration in 201 THA (median age 62 (31-81) years, 117 women) extracted from 5 randomized studies aimed to assess various fixation principles. There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment, 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas. Moreover, 37 cemented cups were sterilized with ethylene oxide (Reflection all-poly) and 69 porous-coated cups had liners sterilized in ethylene oxide (Reflection). 28 mm femoral heads were used in all cups. The patients were followed with repeated radiostereometric measurements (RSA) up to 2 years. The activity level of the patients was evaluated by a questionnaire. After 2 years, cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates, as compared with gamma-sterilized polyethylene. The penetration did not differ between the gamma-irradiated designs. Using stepwise linear regression analysis, we found that the type of sterilization, age and weight were the most important predictors and that they determined the direction of the proximal penetration rate. Activity score, male gender and proximal migration of the cup had little effect. The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients.     

Tribological and material analyses of retrieved alumina and zirconia ceramic heads correlated with polyethylene wear after total hip replacement

It has been suggested that the wear of ultra-high molecular weight polyethylene (UHMWPE) in total hip replacement is substantially reduced when the femoral head is ceramic rather than metal. However, studies of alumina and zirconia ceramic femoral heads on the penetration of an UHMWPE liner in vivo have given conflicting results. The purpose of this study was to examine the surface characteristics of 30 alumina and 24 zirconia ceramic femoral heads and to identify any phase transformation in the zirconia heads. We also studied the penetration rate of alumina and zirconia heads into contemporary UHMWPE liners. The alumina heads had been implanted for a mean of 11.3 years (8.1 to 16.2) and zirconia heads for a mean of 9.8 years (7.5 to 15). The mean surface roughness values of the explanted alumina heads (Ra 40.12 nm and Rpm 578.34 nm) were similar to those for the explanted zirconia heads (Ra 36.21 nm and Rpm 607.34 nm). The mean value of the monoclinic phase of two control zirconia heads was 1% (0.8% to 1.5%) and 1.2% (0.9% to 1.3%), respectively. The mean value of the monoclinic phase of 24 explanted zirconia heads was 7.3% (1% to 26%). In the alumina group, the mean linear penetration rate of the UMWPE liner was 0.10 mm/yr (0.09 to 0.12) in hips with low Ra and Rpm values (13.22 nm and 85.91 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.13 mm/yr (0.07 to 0.23) in hips with high Ra and Rpm values (198.72 nm and 1329 nm, respectively). This difference was significant (p = 0.041). In the zirconia head group, the mean linear penetration rate of the UHMWPE liner was 0.09 mm/yr (0.07 to 0.14) in hips with low Ra and Rpm values (12.78 nm and 92.99 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.12 mm/yr (0.08 to 0.22) in hips with high Ra and Rpm values (199.21 nm and 1381 nm, respectively). This difference was significant (p = 0.039). The explanted zirconia heads which had a minimal phase transformation had similar surface roughness and a similar penetration rate of UHMWPE liner as the explanted alumina head.     

Arthroscopy for evaluation of polyethylene wear after total knee arthroplasty

BACKGROUND: The purpose of this report is to demonstrate the severity of polyethylene wear by arthroscopy after total knee arthroplasty (TKA). METHODS: Polyethylene wear of TKA prostheses was evaluated endoscopically in eight knees (six patients). Arthroscopy was indicated when the patients had persistent but slight hydroarthrosis and instability confirmed by stress radiography, but these findings were insufficient for a consensus on polyethylene revision. The average interval between primary TKA and arthroscopy was 9 years 3 months. RESULTS: All knees had unexpectedly widespread, severe polyethylene wear characterized by delamination. Based on arthroscopic visualization of the damage to the polyethylene, all patients consented to undergo isolated polyethylene surface revision surgery. The severity of polyethylene wear was worse than anticipated at the evaluation arthroscopy. After a mean follow-up of 5 years 6 months, all knees were stable and symptom-free. CONCLUSIONS: The usefulness of arthroscopy is validated in certain groups of patients with polyethylene wear when diagnosed with careful clinical examination and stress radiography.     

Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up

BACKGROUND: The development of osteolysis, a commonly reported complication after total hip arthroplasty without cement, is perceived to be related to the amount of polyethylene particles generated from the bearing surfaces. Although the literature has suggested that the prevalence of osteolysis increases with increasing rates of polyethylene wear, this relationship has never been quantified. The goals of this study were to quantify the relationship between the prevalence of osteolysis and both linear and volumetric wear and to evaluate the risk of osteolysis as a function of wear in a currently used, porous-coated cup design. METHODS: Polyethylene wear and osteolysis were examined in fifty-six hips with a Duraloc-100 acetabular cup articulating with a 28-mm femoral head. Penetration of the prosthetic head into the polyethylene liner was measured, with use of a validated computer-assisted technique, from anteroposterior pelvic radiographs of each patient. From these measurements, linear and volumetric wear rates were calculated. Each patient's series of radiographs was examined independently for the presence of osteolysis. A logistic regression analysis was performed to determine the risk of osteolysis associated with a given change in linear or volumetric wear rate. RESULTS: Osteolysis was found in twenty-three of the fifty-six hips. The hips with osteolysis had significantly higher linear (p < 0.001) and volumetric (p = 0.003) wear rates than the hips without osteolysis. Logistic regression revealed that every 0.1-mm/yr increase in the linear wear rate increased the likelihood of the development of osteolysis by a factor of four. Each 40-mm (3) /yr increase in volumetric wear raised the risk of osteolysis by about three times. CONCLUSIONS: To our knowledge, this study represents the first time that the relationship between polyethylene wear, as determined by both linear wear and volumetric wear, and the prevalence of osteolysis has been quantified. The use of the linear wear rate as a predictor of osteolysis can be a valuable tool in assessing the longevity of a particular implant. The results of our analysis provide quantitative support to the observation that a wear rate of 0.2 mm/yr seems to represent a "critical threshold" for the development of osteolysis. Close radiographic monitoring with the determination of linear wear rates to assess the risk of osteolysis is recommended for all patients after total hip arthroplasty.     

Tibial baseplate fracture associated with polyethylene wear and osteolysis after total knee arthroplasty

INTRODUCTION

Fracture of the tibial baseplate following total knee arthroplasty is very rare given the developments in modern prosthesis design. Tibial baseplate fracture secondary to polyethylene wear, osteolysis and component malalignment in an elderly obese patient is reported in the present article.

PRESENTATION OF CASE

A 69-year-old woman had undergone total knee arthroplasty eleven years prior to presentation and reported nine months of chronic pain, which was caused by a neglected fracture of the baseplate.

DISCUSSION

We discuss the prevention of implant fracture after total knee arthroplasty and address the risk factors associated with this complication.

CONCLUSION

The present case emphasizes the importance of properly informing patients and encouraging them to report such complaints immediately to allow for early revision and prevention of component fracture, especially in patients with risk factors such as obesity and component, malalignment.     

Experimental assessment of precision and accuracy of radiostereometric analysis for the determination of polyethylene wear in a total hip replacement model.

The purpose of this study was to develop and test a phantom model based on actual total hip replacement (THR) components to simulate the true penetration of the femoral head resulting from polyethylene wear. This model was used to study both the accuracy and the precision of radiostereometric analysis, RSA, in measuring wear. We also used this model to evaluate optimum tantalum bead configuration for this particular cup design when used in a clinical setting. A physical model of a total hip replacement (a phantom) was constructed which could simulate progressive, three-dimensional (3-D) penetration of the femoral head into the polyethylene component of a THR. Using a coordinate measuring machine (CMM) the positioning of the femoral head using the phantom was measured to be accurate to within 7 microm. The accuracy and precision of an RSA analysis system was determined from five repeat examinations of the phantom using various experimental set-ups of the phantom. The accuracy of the radiostereometric analysis, in this optimal experimental set-up studied was 33 microm for the medial direction, 22 microm for the superior direction, 86 microm for the posterior direction and 55 microm for the resultant 3-D vector length. The corresponding precision at the 95% confidence interval of the test results for repositioning the phantom five times, measured 8.4 microm for the medial direction, 5.5 microm for the superior direction, 16.0 microm for the posterior direction, and 13.5 microm for the resultant 3-D vector length. This in vitro model is proposed as a useful tool for developing a standard for the evaluation of radiostereometric and other radiographic methods used to measure in vivo wear.     

Assessment of polyethylene wear in total hip replacement

The three-dimensional technique is a method for the measurement of polyethylene wear in patients with total hip joint replacement. Application of image processing technology allows automation of point selection from digital images of radiographs scanned into the computer. Validation of image processing modifications reveals a three-fold increase in accuracy and a 40-fold increase in reproducibility compared with manual input of points from a digitizer during bench testing. A review of three-dimensional technique application to clinical patients gives information on the factors that influence polyethylene wear. Increasing age, activity level, femoral head size, decreasing polyethylene thickness, and insertion of total hip prostheses without cement all increase polyethylene wear. Restoration of femoral offset during total hip replacement seems to decreases polyethylene wear. No apparent difference in polyethylene wear rate could be found between two groups of patients, one group had a stainless steel-polyethylene articulation and the other had a ceramic-polyethylene articulation. Measurement of the serial polyethylene wear of individual patients reveals a high rate of femoral head penetration during the first 2 years after total hip replacement using metal-backed acetabular components inserted without cement. Interpretation of this femoral head penetration as true polyethylene wear may be erroneous, however, because creep of the polyethylene and acetabular liner movement within its metal shell cannot be measured.     

Radiographic methods for the assessment of polyethylene wear after total hip arthroplasty

All wear-measurement techniques assess femoral head penetration and therefore cannot distinguish between true polyethylene wear and bedding-in. Multiple wear measurements that are made at different time-intervals after bedding-in has occurred are required to determine the true wear rate. Computer-assisted edge-detection techniques offer improved accuracy and precision compared with manual techniques and appear to be ideally suited for the retrospective and prospective examination of large groups of patients with intermediate to long-term radiographic follow-up (more than five years). While radiostereometric analysis offers improved accuracy and precision compared with computer-assisted edge-detection techniques, widescale clinical application is limited because of its relative expense, the required expertise, and the fact that it can only be used in a prospective fashion.     

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty (TKA) has not been well reported before. A 63-year-old man with osteoarthritis of the right knee underwent TKA with a New Jersey LCS Knee, with cementing on the tibia and patella but not on the femoral component. After 42 months, in addition to wearing of polyethylene of the tibia and patella, severe osteonecrosis of the medial femoral condyle was noted. Osteonecrosis caused loss of osseous support of the medial flange of the femoral component, and the bone ingrowth of the central and lateral flange to the distal femur was so good that it overcame the yield stress of the metal of the femoral component and caused fracture of the femoral component. The osteolytic area was filled with autogenous iliac bone, and a new femoral component was inserted and cemented. The patient's condition became satisfactory with relief of pain. Although uncommon, fracture of the femoral component does occur associated with polyethylene wear and osteolysis.     

金属对聚乙烯假体全髋关节置换术后磨损的中期随访研究

【摘要】〓目的〓对金属-聚乙烯(MOP)全髋关节置换术(THA)后患者的界面磨损进行回顾性研究,探讨不同年龄段患者金属-聚乙烯全髋关节置换术的临床疗效。 方法〓收集2003年5月到2008年11月期间于常熟市第一人民医院行THA患者资料研究,共获得完整病例资料84例(88髋),按年龄及活动量分为两组:年龄<50岁和活动量大病例组(A组)和年龄≥50岁和活动量小病例组(B组)。全髋假体为钻铬钼合金-高分子聚乙烯全髋假体,临床疗效应用Harris评分标准进行临床随访和对比研究,影像学进行内衬磨损率及骨溶解测量分析。 结果〓所有病例均取的至少5年的完整随访资料,其中A组有3例3髋(7.7%)因假体松动而最终行翻修手术,而B组资料中无任何翻修病例。所有病例均未发生骨折、感染、深静脉血栓(DVT)等常见并发症。A组Harris评分由术前34.13±6.28改善至手术后91.35±2.68,B组35.51±5.32改善至90.05±2.47;影像学观察,A组内衬磨损率为每年0.19±0.24 mm,B组为每年0.09±0.13 mm,两组中MOP内衬磨损差异具有统计学意义(P<0.05);A组MOP全部发生不同程度的骨溶解,B组MOP骨溶解的发生率为63.16%,两组比较,P<0.05)。结论〓对于小于50岁和活动量大的患者,MOP假体的内衬磨损、骨溶解及影像学松动率均明显高于年龄≥50岁和活动量小的病例组,因此,对于年轻患者使用MOP假体应慎重,而对于老年病人和低活动需求的病人行THA时中期疗效较好。     

Polyethylene wear and synovitis in total hip arthroplasty: a sonographic study of 48 hips

Forty-six patients (48 hips), operated on with cemented total hip arthroplasty (THA) because of arthrosis, were examined radiographically and sonographically at 10-year follow-up. Polyethylene wear of acetabular cups was measured on conventional non-weight-bearing pelvic radiographs, and the volume of polyethylene debris was calculated. Radiographic signs of loosening were identified. The capsular distance (ie, thickness of the synovium or synovial contents) was measured sonographically. We found a significant correlation between increased volumetric wear and increased capsular distance. Hips with radiographically loose acetabular components had significantly greater volumetric wear and capsular distance than those without signs of acetabular loosening. This relationship was not observed in hips with radiographically loose femoral components. In cemented THA, the volume of polyethylene wear debris and the thickness of the synovium and the synovial contents are related. In the event of radiographic loosening of the acetabular component, they are both increased.     

Comparison of two and three-dimensional computerized polyethylene wear analysis after total hip arthroplasty

BACKGROUND: The accurate determination of acetabular polyethylene wear in vivo is necessary to assess the clinical performance of the bearing surfaces of total hip replacements. Our objective in this study was to determine the clinical performance of two and three-dimensional computerized wear analysis and to assess the implications of this performance on requirements for patient enrollment in studies designed to detect wear of total hip prostheses. METHODS: Two and three-dimensional digital computerized analyses of acetabular polyethylene wear were performed on 153 hips in 140 patients. The acetabular components consisted of a polyethylene insert in a titanium shell, articulating with a 28-mm cobalt-chromium femoral component. The average duration of radiographic follow-up was 8.4 years. The correlation coefficient for two-dimensional versus three-dimensional analysis was calculated, as was the difference between the wear detected by the two techniques. The same observer analyzed each image twice, allowing an assessment of the repeatability of the two-dimensional and three-dimensional analyses. The impact of the clinical performance of each technique on the sample size needed for adequate power in prospective studies was evaluated. RESULTS: There was a high correlation between two-dimensional and three-dimensional wear analysis (r (2) = 0.933). In thirty-one (5.2%) of 595 observations, the wear values derived with the two-dimensional and three-dimensional techniques were not consistent. Logistic regression demonstrated that acetabular anteversion had a significant effect on the likelihood of such inconsistency occurring. The two-dimensional technique detected 90.1% of the total linear wear subsequently detected by the three-dimensional analysis. The average wear value was 1.09 mm as detected by two-dimensional analysis and 1.21 mm as detected by three-dimensional analysis. The two-dimensional technique was four times more repeatable than the three-dimensional technique. Power analysis indicated that up to 1.4 times more patients need to be enrolled if the three-dimensional technique is used for wear analysis. CONCLUSIONS: While three-dimensional analysis detected 10% more wear, its repeatability was four times worse than that of the two-dimensional technique and, as a consequence, patient enrollment requirements for wear detection were higher. The poor quality of the lateral radiographs contributed to the decrease in the repeatability of the three-dimensional analysis. Three-dimensional analysis may be useful for highly anteverted cups, but the limited improvement in wear detection achieved with that technique, coupled with its inferior repeatability, limits its clinical value.     

全髋关节置换术后股骨偏距减小与聚乙烯内衬磨损的关系

 目的 探讨全髋关节置换术后股骨偏距减小与聚乙烯内衬磨损的关系。方法　选择90例单侧全髋关节置换术后即刻拍摄双髋正位X线片的病例。利用Coreldraw 12.0等比例重建术后即刻双髋正位X线片,依据股骨偏距减小值(F)分为五组：F＜2 mm组、2≤F≤4 mm组、4＜F≤6 mm组、6＜F≤8 mm组、8＜F≤10 mm组,每组18例;等比例重建终末随访(4～7年,平均5.6年)双髋正位X线片,测量聚乙烯内衬线性磨损量、速度和角度。结果　(1)五组聚乙烯内衬线性磨损量分别为(0.72±0.13) mm、(0.78±0.11) mm、(0.87±0.09) mm、(0.99±0.09) mm、(1.17±0.15) mm,除第1组与第2组外其余组间差异有统计学意义。(2)聚乙烯内衬线性磨损速度分别为(0.132±0.025) mm/年、(0.139±0.019) mm/年、(0.159±0.029) mm/年、(0.183±0.032) mm/年、(0.213±0.023) mm/年,除第1组与第2组外其余组间差异有统计学意义。(3)聚乙烯内衬线性磨损角度分别为5.0°±3.5°、3.2°±3.8°、-4.3°±4.9°、-8.7°±4.1°、-13.0°±4.7°,除第1组与第2组外其余组间差异有统计学意义。结论 全髋关节置换术中股骨偏距的重建应尽量达到正常解剖水平,股骨头中心向外上方迁移可能会造成应力分布不均和假体磨损增加。     

Prediction of long-term polyethylene wear in total hip arthroplasty,based on early wear measurements made using digital image analysis

The capability to reliably predict long-term in vivo wear of polyethylene would be of great value for the early identification of problematic total hip designs. Formal quantitative estimates of long-term polyethylene wear were made from a series of 197 patients who had a total hip arthroplasty and who were followed for a minimum of 10 years; the estimates were based on the wear that was apparent radiographically at nominally 2 years after the operation. A newly developed digital image-analysis edge-detection procedure was applied to 1,237 archived follow-up radiographs. The edge-detection measurements were analyzed with a robust regression random-coefficients statistical formulation developed especially to address the distributions of wear rate observed across this population over time. Formal regression equations were reported, which can be used to estimate late-wear depth for a patient radiographed at a 2-year follow-up visit. Series wide, the correlation between predicted and observed wear depths was 0.73 at 4 years, with a correlation decline of approximately 0.03 per additional year.