Introduction: The objective of this study was to evaluate the biomechanical proprieties of a hip resurfacing system in terms of failure of the implant with different positioning of the prosthesis in cadaveric femurs.

Materials and Methods: The study has been divided in 3 phases. First phase: Six-teen cadaveric femurs were tested to failure using a standard MTS device once the Conserve Plus (Wright Medical) system was implanted: 8 femurs after a 4mm notching of the neck and 8 contralateral without notching. Second phase: Six-teen cadaveric femurs were tested using a 210 Kg axial load: 8 with the Conserve Plus system implanted at 140° and 8 contralateral with 10° of varus. Third phase: Eight femurs were tested with the implant having 10 ° of excessive antiversion of the component and 8 with the implant having 10 ° of excessive retroversion. The control group was represented by 16 femurs having the system implanted following the natural version of the femoral neck.

Results: An average of 4865 Newtons(N) was necessary for the failure of the implant after notching, compared to 7043 N without notching. The varus alignment of the implant showed a statistical different increase of the stress on the femoral neck: 15% postero-superiorly and 21% antero-superiorly. The neutral alignment at 140° showed a decrease of the overall stress on the femoral neck. Adding 10 ° of excessive anteversion or retroversion did not show any statistical difference in terms of failure of the implant when compared to the anatomical alignment.

Conclusions: This biomechanical study showed that the correct positioning of the implant represents a fundamental requirement for the success of the hip resurfacing procedure. The notching of the neck decreases significantly the biomechanical proprieties of the implant, while the varus alignment increases the stress on the superior neck cortex.

We describe a new technique of reconstruction of the deficient acetabulum in cementless total hip arthroplasty. The outer iliac table just above the deficient acetabulum is osteotomised and slid downwards. We have termed this an iliac sliding graft. Between October 1997 and November 2001, cementless total hip arthroplasty with an iliac sliding graft was performed on 19 patients (19 hips) with acetabular dysplasia. The mean follow-up was 3.4 years (2 to 6).

The mean pre-operative Harris hip score was 45.1 which improved significantly to 85.3 at the time of the final follow-up. No patient had post-operative abductor dysfunction. Incorporation of the graft was seen after two to three months in all patients. Resorption of the graft and radiolucencies were infrequent. This technique is a useful alternative to femoral head autografting when the patient’s own femoral head cannot be used.

Introduction: In general a loose-balanced total knee arthroplasty (TKA) are believed to gain good postoperative range of motion (ROM), however, too much laxity is thought to be a cause for persistent pain and catastrophic long-term results.

Materials and methods: We measured the antero-posterior and medio-lateral laxity to evaluate the influence of stability after cruciate-retaining TKA on ROM, pain score in Knee Society score and Functional score at 4–7 years after the operation. Twenty-one knees in 15 patients with an average age of 68 years (range, 58–78) who had a PCL retaining TKA for osteoarthrosis were examined (YS-4, 16 knees; AGC-S, 5 knees). There were 12 women and 3 men. Anteroposterior laxity was examined using a KT 2000 arthrometer at 30-degree knee flexion. Mediolateral laxity was examined at full extension with manual stress x-rays.

Results: Average ROM was 112 degrees (range, 90–140 degrees), antero-posterior laxity was 9.7 mm (range, 2–27 mm) and mediolateral laxity was 10.6 degrees (range, 5–22 degrees). Knee Society pain score was 47 (range, 10–50) and Functional score was 82 (range, 40–100). No significant difference in ROM and clinical scores were noted between the lax and the stable knees. Correlations between ROM and anteroposterior or medio-lateral laxity were not significant (P = 0.55, P = 0.05, respectively; Spearman’s correlation efficient).

Discussion and conclusion: A loose-balanced TKA did not gain good post-operative ROM. No parameters suggested that lax knees got better flexion angle, worse pain score and functional score than stable knees.

Although bone loss and ligamentous instability are usually indications for the use of constraining prostheses in revision total knee arthroplasty (TKA), several reports have documented a high rate of failure with these prostheses. We therefore tried using the cruciate retaining augmentable type prosthesis (NexGen CRA) if a good intraoperative ligamentous balance could be obtained with revision TKA.

CRA was used on nine knees of seven patients with an average age of 71.7 years. The follow-up lasted for an average of 1.6 years. Clinical evaluation consisted of instability ratings, knee score, range of motion and %MA (mechanical axis) as an index of the alignment. These patients showed improvement varus instability from a mean of 7.0° preoperatively to a mean of 1.5° postoperatively, and in valgus instability from 5.3° to 1.3°.

The knee score was significantly improved from 41 to 81, but the %MA resulted in an unsatisfactory improvement from −8.8% to 34.0%. The femoral anatomical-mechanical angle (FAMA) was measured as a parameter of bowing deformity of the femur, and the knees were divided into two groups, the bowing group consisting of the knees with an FMA of more than 8° (n=6, average 9.0°), the normal group of knees with an FAMA of less than 7° in FAMA (n=3, average 6.7°). The postoperative %MA showed a mean value of 40.9% for the normal group, and 30.6% in the bowing group. These results demonstrated that the discrepancy between FAMA for the bowing group(=9.0°) and the valgus angle of the stem of the femoral component (6.0°) was the cause of the malalignment in the bowing group. These clinical results suggest that the cruciate retaining augmentable type prosthesis can be used successfully for selected revision cases, but that malalignment in knees with bowed femora may remain a problem.