Average and peak contact stress distribution evaluation of total knee arthroplasties

Seven total knee arthroplasty systems were tested to determine contact stress patterns and contact areas using a calibrated Fuji film stress analysis technique. Knees were loaded to 2,000 N (204 kg) at 15°, 60°, 90°, and 135° flexion at 24 and 37°C. Evaluation of stresses at 37°C at 15° and 60° using an average contact stress assessment technique indicated that the LCS meniscal bearing knee system, (DePuy, Warsaw, IN), the AMK knee with a constrained insert (DePuy), and the PFC knee with a posterior-lipped insert (Johnson and Johnson, Raynham, MA) had the lowest average contact stresses (near or below 10 MPa). The PFC with a regular insert (Johnson and Johnson), the Ortholoc II (Dow Corning Wright, Arlington, TN), and the AMK with a regular insert (DePuy) had intermediate contact stresses. The AMK with a Hylamer-M insert (DePuy) and the MG II (Zimmer, Warsaw, IN) had the highest average contact stresses (near or above 20 MPa). A stress-calibrated Fuji film measurement technique has shown that an assessment of ranges of contact stress provides much more information about regions of expected wear than an assessment of average contact stresses. Testing of the tibiofemoral articulation of artificial knees revealed that all knees had some areas of contact with maximum stresses in excess of 15 MPa. As the yield strength of ultrahigh-molecular-weight polyethylene is approximately 15 MPa, all tibial inserts could wear to some extent. Peak contact stresses at four test angles of the AMK, Series 7000 (Osteonics, Allendale, NJ:) Genesis (Smith & Nephew Orthopaedics, Memphis, TN), and MG II patellofemoral articulations were high (above 30 MPa). Contact areas varied from line-shaped to bilateral circular or elliptical shapes. The LCS knee system experienced substantially lower patellofemoral contact stresses and larger contact areas. Changes in conformity of knee designs are warranted to overcome wear problems. Peak contact stresses measured from the LCS meniscal bearing tibiofemoral and patellofemoral joint were in excess of 30 MPa in some areas at low flexion angles. This design does create large areas of contact at very low contact pressures, however, and for this reason is expected to wear less than other designs.     

Clinical and radiological profile of symptomatic knee osteoarthritis in Malaysia

Aims: To create a clinical and radiological profile of patients with symptomatic osteoarthritis of the knee in Malaysia. Methods: One hundred consecutive patients presenting with symptomatic knee osteoarthritis at a private rheumatology clinic were profiled for demographic and clinical features. Anteroposterior weight‐bearing, skyline and lateral knee X‐rays were taken. Statistical Package for Social Sciences was used for data analysis. Results: Women predominated (93%). Fifty‐eight percent of the patients reported bilateral knee pain. Difficulty in walking, climbing and squatting was high (85%, 97% and 93% respectively). Patients with knee pain had a higher BMI than controls. Radiological abnormality, related to osteoarthritis was present in 97%. Osteophytes were generally tricompartmental while joint space narrowing was less evident in the lateral tibiofemoral joint than in the medial tibiofemoral joint and the patellofemoral joint. Almost half (49%) the patients manifested radiological varus deformity The severity of radiological abnormality increased with age. Although patients with unilateral pain had milder radiological abnormality, it tended to be bilateral. Clinically detectable hip abnormality and nodal osteoarthritis were uncommon, as was radiological chondrocalcinosis. Conclusions: Patients presenting with symptomatic knee osteoarthritis to a rheumatology service had a high degree of disability, radiological abnormality and varus deformity. Radiological abnormalities were essentially bilateral and tricompartmental.     

应用力学因素检测膝关节功能的实验研究

目的研究应用力学因素检测膝关节功能方法的有效性.方法利用测力平台测量得到人体下肢在运动过程中的力学曲线,用数学方法确定力学曲线的最大值F和曲线特征值R.结果给出51例骨关节炎患者的分析数据,并给出30例正常人的结果作为对照.结论应用力学因素可以有效地检测膝关节功能状态.     

髋臼转位截骨(TAO)治疗DDH继发早期OA

目的　介绍一种治疗髋臼发育不良并早期骨性关节炎的髋臼转位截骨术并评价其结果。方法　 4 3例髋关节发育不良 (DDH)并发骨关节病 (OA) ,全部病人实施了髋臼转位截骨术。结果　术后平均 12个月 (10～ 17个月 )随访 ,术后 Harris评分 93分 (85～ 10 0分 ) ,平均增加 2 5分 ,两者比较有显著性差异 ;术后 CE角 2 0°～ 2 8°,平均 2 4°,两者比较有显著性差异 ;术后髋臼指数 37°～ 4 8°,平均 4 5°,两者比较有显著性差异 ;术后 AHI81% (75 %～ 98% ) ,两者比较有显著性差异。结论　髋臼转位截骨术是治疗髋关节发育不良 ( 型 )并发骨关节病 ( 期 )有效的方法     

Bone Mineral Density in the Proximal Femur and Contralateral Knee After Total Knee Arthroplasty

Osteoarthrosis (OA) is often associated with pain and disability, which are relieved after total knee arthroplasty (TKA), but the nature of bone changes associated with OA is controversial. We examined preoperative hip and contralateral knee bone mineral density (BMD) in patients requiring TKA and monitored the BMD changes postoperatively. Sixty-nine patients, scheduled to have TKA for osteoarthrotic knees, had both hips and contralateral knee BMD measured by dual-energy X-ray absorptiometry (DXA) at the time of operation (baseline) and at 1 yr after operation. X-rays of the knee joints were also taken to evaluate the severity of OA. Preoperatively, 27% and 38% of the patients had total hip BMD Z-score more than 1 SD in the operated side and contralateral hips, respectively. In all regions of interest (ROI), the mean baseline BMD of the affected side proximal femur was significantly lower than that of the contralateral side (p < 0.0005-0.019). The severity of OA was not associated with BMD. During 1-yr follow-up, the postoperative knee status and the physical activity of the patients (AKS score) improved. However, neither the hip nor the nonoperated knee BMDs increased. Knee OA is associated with significantly lower BMD values in the affected side compared with the contralateral hip, and these levels remained similar or decreased during a 1-yr follow-up. We conclude that improved mobility after TKA does not improve the effects of preoperative disuse-associated bone loss in the short term.     

Bone mineral density of the proximal tibia following uncemented arthroplasty

Bone mineral density (BMD, g/cm2) was measured using dual-photon absorptiometry (DPA) in selected areas of the proximal tibia following uncemented PCA knee prosthesis. In nine patients with 14 alloplastic operations, measurements were taken at 3-6-month intervals for the first 3 1/2 years after operation. There was a significant increase in BMD of about 15% during the first 6 months after operation. The following year it remained increased, although not significantly, compared with the initial values, then gradually diminished. Increased bone density after arthroplasty may be explained mainly by stimulation of bone formation from weight bearing due to improved walking ability. Stress shielding of the proximal part of the supporting tibial bone did not seem to occur.     

膝关节镜手术并发症临床分析

1997年1月～2005年12月，我院对324例膝关节疾病患者行关节镜手术治疗，其中23例出现各种并发症。笔者总结分析其产生原因并提出防治措施。     

有限切开固定治疗复杂胫骨平台骨折

目的探讨采用有限切开固定治疗复杂胫骨平台骨折的临床效果。方法采用间接复位有限切开固定治疗复杂胫骨平台骨折37例,SchatzkerⅣ型骨折采用前内侧小切口,T型钢板固定,SchatzkerⅤ、Ⅵ型骨折采用前外侧小切口联合后内侧切口,后内侧用1/3管型钢板固定支撑,外侧以高尔夫棒型钢板固定。结果随访6-30个月,37例均于12周内骨折愈合。所有患者均恢复了患肢的正常力线及患膝的骨性稳定。采用Sanders膝关节评分法评估疗效：优13例,良20例,可4例。结论有限切开固定治疗复杂胫骨平台骨折是一种安全有效的生物学固定方法,创伤小,骨折愈合快,可早期功能锻炼,膝关节功能恢复满意。     

胫骨高位截骨对胫骨近端解剖形态的影响

[目的]测量胫骨高位截骨术后胫骨近端解剖形态,并与术前比较,探讨其变化的临床意义.[方法]2001～2005年,35例(59膝)因膝关节内侧室骨性关节炎接受胫骨高位截骨术患者的完整影像学资料,在术前、术后标准正侧位X线片中测量胫骨角;胫骨后倾角度;胫骨近端关节面外移;关节线高度.所得资料采用配对t检验进行统计学分析,以P＜0.01为差异有显著性意义.[结果]胫骨角术前平均为99.1°±4.3°,术后平均为91.1°±3.8°;胫骨后倾角度术前平均为8.9°±2.6°,术后平均为5.0°±2.3°;胫骨近端关节面外移术前平均为(46.2±3.6)%,术后平均为(53.1±3.9)%;关节线高度术前平均(41.2±3.6)mm,术后平均(38.0±3.2)mm.手术前后差异均有显著性意义(P＜0.01).[结论]胫骨近端解剖形态在胫骨高位截骨术后会发生明显变化,如胫骨角变小,后倾角度变小,胫骨近端关节面外移,关节线高度相对下降等,将对转行全膝关节置换术产生不良影响.