Survival analysis of hip resurfacing arthroplasty / 医学研究生学报

Objective At present, there is little report of clinical results of metal-on-metal HRA in China.This study was aimed at retrospectively analyzing the factors of survival rate of HRA in China. Methods A retrospective study was conducted in 113 patients who accepted HRA in our hospital from September 2005 to May 2010.All patients were followed up by telephone or outpatient visit,and the average follow-up time was 10.2 years.The clinical function was evaluated by Harris score,and the prosthesis was evalu-ated by pelvic film.Inductively coupled plasma mass spectrometry(ICP-MS)was used to detect the concentration of blood metal ions, ultrasound and MRI were used to screen and diagnose inflammatory pseudotumor.Cox proportional hazards models were used to analyze the factors affecting the survival rate of the prosthesis. Results A total of 91 patients(120 hips)were followed up while 22 patients (26 hips)were lost,the follow-up rate was 80.5%.17 patients underwent revision surgeries,including 8 cases of femoral neck fracture and 8 cases of aseptic loosening,the other one was infection.Revision in 13 cases was within 3 years, the proportion was as high as 76.5%.The 10-year survival rate of prosthesis was 87.1%,the abduction angle of acetabular prosthesis is the only risk factor affecting the survival. Conclusion Postoperative survival rate of HRA is relatively high, and the survival rate of prosthesis is relevant to socket position.We should notice that the risk increased when the acetabular abduction angle of the prosthesis was over 55 degree.O-verall,HRA is still a successful surgical method.

Biomechanical comparison between resurfacing hip arthroplasty and normal proximal femur / 医用生物力学

Objective To investigate the variation of stress distributions on proximal femur after hip resurfacing arthroplasty (HRA) by using three-dimensional (3D) finite element method. Methods The 3D finite element model of proximal femur was reconstructed based on 64-slice spiral CT scan image data. Both the stress distributions on proximal femur after metal-on-metal HRA and normal proximal femur were studied, so as to analyze the biomechanical environment changes after HRA. Results After HRA, the superior, anterior, rear and inferior area of the proximal femoral head showed significant stress shielding, with peak stress of 0.60, 0.57, 0.66, 0.79 MPa, respectively, and stress shielding rate of 99.80%, 99.16%, 98.92%, 96.66%, respectively. Increased stress occurred in most regions of the distal femoral head, while stress shielding appeared only in rear area of the distal femoral head, with stress shielding rate of 4.92%. Increased stress occurred in anterior region of the proximal femoral neck, while stress shielding appeared in the superior, inferior and rear area of the proximal femoral neck, with shielding rate of 16.48%, 22.75% and 7.83%, respectively. Increased stress also occurred in inferior area of the distal femoral neck, while the remaining area showed stress shielding. The stress in greater trochanter increased by 9.22%, and the stress shielding rate for lesser trochanter area and basal area of femoral neck were 2.49% and 14.44%, respectively. Conclusions Stress distributions on most regions of proximal femur after HRA were similar to that on normal femur, and the stress transfer was close to physiological status, which could effectively avoid obvious stress shielding in proximal femur and preserve bone mass, which could contribute to normal physiological activity of patients.

Hip Resurfacing Arthroplasty in Patients with Rheumatoid Arthritis

OBJECTIVE: This study analyzed the midterm results of hip resurfacing arthroplasty in patients with rheumatoid arthritis. METHODS: Between October of 2003 and September of 2008, 13 consecutive hips that were treated with hip resurfacing arthroplasty due to rheumatoid arthritis were analyzed. The average follow up period was 48.6 months and the mean age at the time of operation was 35.9 years old. The mean BMI at the operation was 23.2 kg/m2. The implanted prostheses were the Conserve Plus system in five hips, the Birmingham hip resurfacing system in four hips and the Durom system in four hips. The results were clinically evaluated with the Harris hip score, the UCLA activity score, hip or thigh pain, the limb length discrepancy and the range of motion. As radiological evaluation, we observed the patterns of bone remodeling and complications such as femoral neck fracture, loosening and osteolysis. RESULTS: The average Harris hip score improved from 62.2 to 98.9 at the final visit. The range of motion improved to 0degrees in flexion contracture, 118.1degrees in further flexion, 22.7degrees in internal rotation, 40.4degrees in external rotation, 28.8degrees in adduction and 38.1degrees in abduction, respectively. No patient complained of a limb length discrepancy and hip or thigh pain. Radiographically, impingement between the acetabular component and the femoral neck was observed in one case. However, radiographic findings such as osteolysis, radiolucency, wear and loosening were not observed. CONCLUSION: The midterm results of hip resurfacing arthroplasty in patients with rheumatoid arthritis were excellent. But long-term studies are needed to determine the survivorship and to evaluate the osteoporotic change, the metal ion level and their influence after hip resurfacing arthroplasty.

Minimum 4 Year Follow-up Results of Metalon Metal Hip Resurfacing Arthroplasty / 대한정형외과학회잡지

PURPOSE: To report the minimum 4 year follow up results of metal on metal hip resurfacing arthroplasty. MATERIALS AND METHODS: 39 hips from 36 patients, who received hip resurfacing from November 1998 to September 2001 and were followed up for at least 4 years, were enrolled in this study. The average age was 45 years (28-69 years) and the average follow up period was 51.9 months (48-82 months). A clinical evaluation was performed with the Harris Hip Score and gait analysis postoperatively. A radiologic evaluation was performed regularly after surgery using anteroposterior and lateral simple radiographs. The post-operative cobalt-chrome serum concentration was measured and compared using 21 cases of ceramic-on-ceramic total hip arthroplasty as a control group. RESULTS: The Harris Hip Score improved from 61 points (31-74) preoperatively to 96 points (85-99) postoperatively. There were no cases of acetabular loosening, and the average angle of femoral insert to the shaft was 136 degrees with 22 hips (61.1%) being within 130-140 degrees. The 4 year follow-up survival rate was 97.4%. The serum cobalt and chrome levels were higher than the control group (p<0.05). CONCLUSION: Hip resurfacing showed excellent survival rate after a short-term follow-up, but still requires a long-term evaluation with more cases and further metal ion release studies.

Changes in BMD in the Proximal Femur after Cementless Total Hip Arthroplasty and Resurfacing Arthroplasty: Prospective, Longitudinal, ComparativeStudy / 대한정형외과학회잡지

PURPOSE: This study analyzed the differences in bone remodeling and stress shielding between cementless total hip arthroplasty and resurfacing arthroplasty by examining the serial bone mineral density around the prosthesis. MATERIALS AND METHODS: Fifty total hip arthroplasty procedures and 50 resurfacing arthroplasty procedures, which were performed between July 2002 and June 2003, were examined to this comparative study. The mean age at surgery was 44 years in the THA group and 36 years in the resurfacing arthroplasty group. The bone mineral density was measured by the DEXA at preoperation and 3 months, 6 months, 12 months after surgery in zone I-III of the acetabulum (classified by DeLee & Charnley) and zone I-VII of the femur (classified by Gruen), and the medial and lateral side of the femoral neck in the resurfacing arthroplasty group. RESULTS: In the acetabulum, zones I and II of both groups showed a significant decrease in the BMD 12 months after surgery but the level of bone loss in the resurfacing arthroplasty group was relatively small compared with those in the THA group. In the proximal femur, the overall amount of bone loss at 3, 6 and 12 months postoperatively were 0.7%, 5%, and 2.6% respectively, and those in zones I and VII at 12 months postoperatively in the THA group were 7.8% and 7.7%, respectively. In the BHR group, the overall bone loss in the proximal femur at 3, 6 and 12 months postoperatively were 5.8%, 4.4%, and 2.9%, respectively. However, those Gruen zones I and VII at 12 months postoperatively were 2.6% and 0.6%, respectively. CONCLUSION: The level of bone loss in Gruen zones I and VII of the resurfacing arthroplaty group was much lower, which suggests that resurfacing arthroplasty can prevent stress shielding and preserve the proximal bone stock around the femoral stem.

Metal Ion Release after a Metal-on-Metal Hip Arthroplasty: Comparison between Resurfacing Arthroplasty and Total Hip Arthroplasty / 대한정형외과학회잡지

PURPOSE: To verify that the metal-on-metal (MOM) surfaces produce metal ions and to ascertain the differences between large and small femoral head diameters with regard to the release of metal ions. MATERIALS AND METHODS: Forty two cases of MOM hip resurfacing arthroplasty (mean head diameter: 47.1 mm) and 39 cases of conventional total hip replacement arthroplasty (head diameter: 28 mm) were performed at our hospital from June 1998 to April 2003. All the cases were followed-up using the serum cobalt and chromium ion levels. The serum cobalt and chromium ion levels were compared in the 21 cases in each group, which were matched by age, weight and follow-up period. The control group involved 21 patients who had undergone an alumina-alumina total hip arthroplasty. The patient's serum metal ion concentration was measured from the serum, which had been separated from the whole blood and diluted using inductively-coupled plasma mass spectrometry (Agilent 4500, Rhode Island, USA). RESULTS: All MOM bearing implants produced higher serum levels of cobalt and chromium ions than the control. The serum concentration of cobalt with MOM resurfacing was higher than that observed with a 28 mm MOM total hip arthroplasty (p=0.025), but the chromium levels were not significantly different (p=0.501). CONCLUSION: The MOM bearing implants in this study produced elevated serum levels of cobalt and chromium ions. In addition, large diameter heads resulted in greater systemic exposure of cobalt ions than the small diameter heads. However, a long-term follow-up will be needed to determine the clinical significance.