Background

Cup anteversion and inclination are important to avoid implant impingement and dislocation in total hip arthroplasty (THA). However, it is well known that functional cup anteversion and cup inclination also change as the pelvic sagittal inclination (PSI) changes, and many reports have been made to investigate the PSI in supine and standing positions. However, the maximum numbers of subjects studied are around 150 due to the requirement of considerable manual input in measuring the PSIs. Therefore, PSI in supine and standing positions were measured fully automatically with a computational method in a large cohort, and the factors which relate to the PSI change from supine to standing were analyzed in this study.

Aims: The concept of balancing ßexion and extension gap during total knee arthroplasty (TKA) is reported to be crucial. However, difþculties in 1)deþning the ideal distraction force to create a gap, and 2)equalizing ßexion and extension gap are often encountered during TKA for rheumatoid arthritis (RA). This study was performed to analyze these difþculties biomechanically in vivo. Methods: 35 knee at randomly selected TKA for RA were studied as follows. After soft tissue balancing, distraction force for both gaps was applied by ligament balancer. Force was gradually increased with recording the length of the gap created by consecutive force, in order to obtain load-elongation curve for each case. Results: Load-elongation curve showed various patterns, indicating soft tissues including ligamentous structure has been altered its biomechanical property due to the variety of rheumatoid pathology. If ideal force for extension gap was determined at the point when low stiffness changes to high stiffness in the curve, it would be about 120–200N. This force differed reasonably in each case. However, measured ßexion gap curve hardly reached this force in more than 60% of the35 knee, presumably due to functional loss of posterior structures. Interestingly, this phenomenon was often unpredictable at examination before the operation. Conclusions: Ideal tension for þlling the gap with implant seems to be different in each case from load-elongation curve analysis. From this study, we raise question to the concept of equal ßexion and extension gap. This concept, although sounds attractive, is often difþcult to obtain in rheumatoid knee. This observation may suggest which type of TKA (þxed or mobile) is safer for replacing the rheumatoid knee.

Using a lateral approach during which the greater trochanter is excised, we performed domical pelvic osteotomy (modified chiari’s prpcedure) different from the original Chiarifs procedure. In a series of 176 modified Chiari pelvic osteotomies in 175 patients over 40 years old of the advanced coxarthrosis with acetabular dysplasia , in whom the postoperative courses were followed for more than 5 years (average, 6.9 years). JOA hip scores were improved in pain from 15.6 to 34.2 points and a total JOA score was improved from 55.7 to 76.5 points ,almost satisfactory results were obtained in 72.8% . In particular, markedly satisfactory results were obtained with respect to the improvement of pain in 84%. Radiographically, the coverage of the femoral head was markedly improved .The joint space was more dilated in 55% compared to that before surgery., however, the stage of coxarthrosis was more advanced in 18patients . In addition, the pathologic conditions of coxarthrosis had clinically deteriorated in 11 patients, resulting in treatment by total hip arthroplasty. As a result, there were more satisfactory results obtained, even in patients with advanced coxarthrosis, than expected.

Based on the results of this study, we considered that the Modified Chiari’s procedure is most effectively indicated for mature patients with the flat headed hip joints complicated by acetabular sclerosis. Therefore, we perform this procedure in combination with femoral valgus osteotomy. In contrast, satisfactory results cannot be expected from this combination therapy particularly in patients with the atrophic type roundheaded hip joints exhibiting poor acetabular sclerosis.

It is considered that the Modified Chiari’s procedure will be a useful treatment modality substituting for total hip arthroplasty even in mature patients, if applicable cases are carefully selected.

Subsequently, we radiographically evaluated the prognosis of the acetabulum based on its preoperative status. Levels of acetabular sclerosis were classified into the following 3 grades : : atrophic, nornopholic and hypertrophic type.After surgery, the joint space was dilated or maintained in all patients with the hypertrophic type hip joints. However, most patients with the atrophic type hip joints showed the poor prognoses because the stage of coxarthrosis was further advanced in 18% of them. Concerning the capital morphology before surgery, when the prognoses were evaluated based on the preoperative capital morphology, 96% of the proliferative headed hip joints were successfully treated, while only 83% of the round headed hip joints were successfully treated.

Even when the stage of coxarthrosis advanced during the prolonged period of follow-up and total hip arthroplasty is performed, it is the merit of this procedure that a larger size cup be applied without bone grafting.Because the matrix is formed satisfactorily in the newly generated acetabulum where osteotomy was performed.

The present study evaluated the results of the Modified Chiari’s procedure performed mature patients with advanced coxarthrosis caused by acetabular dysplasia .