Posterior capsule releasing in total knee arthroplasty for patients with rheumatoid arthritis with stiff knees in flexion / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the correct method of bone resection and posterior capsular soft tissue releasing in total knee arthroplasty (TKA) for the patients with rheumatoid arthritis with stiff knee in flexion.</p><p><b>METHODS</b>From November 2009 to January 2012,15 patients with rheumatoid arthritis with stiff knee in flexion underwent primary TKA and releasing of the posterior soft tissues. There were 7 males and 8 females,aged 22 to 75 years old (58.7 years old on average). The preoperative range of movement(ROM) was (3.2 ± 1.7)°. According to Knee Society score (KSS) criterion, the preoperative clinical score was 23.3 ± 12.5 and functional score was 35.2 ± 9.8. Based on the correct osteotomy, effective releasing of posterior structures was used for different degrees of flexion contracture during the TKA procedure.</p><p><b>RESULTS</b>All the patients were followed up, and the average duration was 2.3 years (1.6 to 3 years). At the latest follow-up,the KSS clinical score was 81.7 ± 6.5 and functional score was 82.8 ± 9.3. The flexion and extension ROM of the knee joint was (103.5 ± 13.1). Three knees remained 50 flexion contracture deformity, but the function of the affect knees was good.</p><p><b>CONCLUSION</b>The effective releasing of the soft tissue of posterior capsule is a major management for correction of the flexion contracture in TKA. The correct releasing of posterior structure can not only achieve fundamental gap of TKA but also effectively avoid bone over-resection.</p>

The relationship between microstructure of vertebral cancellous bone and fixation strength of pedicle screws / 医用生物力学

Objective By measuring the microstructure parameters of cancellous bone in vertebral bodies with different bone mineral density (BMD) levels, to study the correlation between such parameters and the corresponding maximum pullout strength (MPS) when fixed by pedicle screws, so as to understand if the microstructure parameters are related with screw stability and further to reveal the cause of screw loosening. Methods Based on the BMD detection results, fresh human cadaver spines were stratified into four levels: normal, osteopenia, osteoporosis and severe osteoporosis, according to diagnosis criteria in clinic. The corresponding vertebral specimens were then instrumented with pedicle screws, and screw pullout tests were conducted to measure the MPS of such screws. All the vertebral specimens were collected subsequently, and the cancellous bone cylinders were drilled from the center of each vertebra for micro CT scanning. Microstructure parameters of the vertebral trabecular bone at different BMD levels were obtained to investigate the interrelationships in between, and the relationships between the microstruture parameters and corresponding MPS of pedicle screws with osteoporosis severity were then compared. Results With the decline of BMD from normal to severe osteoporosis level, the corresponding MPS of pedicle screws was significantly declined. With the severity of osteoporosis increasing, the progressive bone volume loss, mechanical incompetence and microstructure deterioration also appeared evidently. Significant differences were found in microstructure parameters at different BMD levels. Strong correlations were extensively observed among BMD, microstructure parameters and MPS of screws. The MPS of pedicle screws was highly correlated with bone volume over total volume (BV/TV), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) from micro-CT scanning. Conclusions Significant deterioration would occur in bone tissues with the decline of BMD level, and the MPS of pedicle screws was highly correlated with some microstructure parameters.