Upward and inward displacements of the acetabular component increase stress on femoral head in single endoprothesis models

Cementless acetabular component with or without upward placement in dysplasia hip: Early results from a prospective, randomised study

BACKGROUND

Total hip arthroplasty (THA) in developmental dysplasia of hip (DDH) is difficult for the abnormal acetabulum. The purpose of this study was to evaluate the difference of anatomic and upward placement of acetabular component during early stage.

METHODS

From April 2014 through June 2015, forty DDH patients (Crowe I to III, 42 hips) were prospectively randomized to either anatomic or upward group. Patient recorded diaries were collected. Radiographs were reviewed. WOMAC and Harris scores were tabulated from pre-operation to 12 months after surgery.

RESULTS

The patients' characteristics including age and body mass index (BMI) had no significant difference (P > 0.05). There were no statistically differences between two groups for surgery time, intraoperative blood loss, hemoglobin (Hb), blood transfusion, albumin decrease, length of stay-day, but surgery time and blood loss in patients with structural bone graft was much higher in anatomic group. The postoperative limb-length discrepancy (LLD) was also no difference, but limb lengthening was better in anatomic group (P = 0.042). The total hospital costs in the anatomic group were higher, but no significant differences. With regard to Harris and WOMAC score, there were significant improved after surgery in both groups, and the anatomic group was better in the value, but these differences were no statistically significant.

CONCLUSIONS

Acetabular reconstruction for DDH subluxation should be reconstructed as close to the actual acetabular location as possible, but an appropriate (<20 mm) upward placement that can achieve at least 70% native bone coverage of the acetabular implant is a valuable technique for early faster recovery.

The biomechanical differences of rotational acetabular osteotomy, Chiari osteotomy and shelf procedure in developmental dysplasia of hip

BACKGROUND

Rotational acetabular osteotomy (RAO), Chiari osteotomy and shelf procedure are important treatments to delay the progression of osteoarthritis in developmental dysplasia of hip (DDH) patients, but their biomechanical differences are still unknown. This study was to evaluate the different biomechanical changes of hip joint after these three surgeries.

METHODS

Sixteen DDH models of 8 human cadaver specimens were reconstructed, and treated by different surgeries, and then strain around femoral head was evaluated by strain gauges.

RESULTS

Hip strain value of DDH model was decreased after treated by shelf procedure (Pleft = 0.016 and Pright = 0.021) and rotational acetabular osteotomy (P = 0.004), but not in Chiari osteotomy (P = 0.856). Moreover, the improved ratio of RAO treatment was better than shelf procedure (P = 0.015) and Chiari osteotomy (P = 0.0007), and the descendent range of shelf procedure was greater than Chiari osteotomy (P = 0.018).

CONCLUSIONS

From biomechanics points, RAO was more effective in relieving hip joint stress compared with shelf procedure and Chiari osteotomy.

A comparison of biomechanical changes on femoral head following rotational acetabular osteotomy and eccentric rotational acetabular osteotomy in normal cadaveric hip

PURPOSE

Both rotational acetabular osteotomy (RAO) and eccentric rotational acetabular osteotomy (ERAO) are effective procedures for young patients with developmental dysplasia of the hip. However, no comparative study of biomechanical changes has been reported following these two procedures. We therefore explored the stress changes on femoral head after RAO and ERAO under different load conditions.

MATERIALS AND METHODS

Twelve female cadaveric hips without deformity were divided into RAO group and ERAO group. Stress value on femoral head was measured preoperatively and postoperatively after the vertical force was loaded on the cadaveric spine from 0 to 500 N. Stress change value was then calculated base on the measurements.

RESULTS

In the RAO group, preoperative stress increased when loading on spine became larger, but postoperative stress changed its increasing trend into decreasing when the load was greater than 200 N (turning point). Same phenomenon was found in the ERAO group (turning point was 300 N). However, the difference between preoperative and postoperative stress was not statistically significant in both RAO and ERAO groups. Stress change value from each procedure showed similar trends. With the load growth, stress change increased firstly and then decreased, but the difference between RAO and ERAO was not statistically significant.

CONCLUSIONS

Both RAO and ERAO could correct the abnormal biomechanical effect of dysplastic hip; moreover, they may have similar biomechanical effects on femoral head, obtaining the same clinical outcomes. Non-biomechanical factors (surgical trauma, technical complexity, etc.) also play important roles in procedure selection.