Effect of acetabular defect on hip stress in adults: three-dimensional finite element analysis / 中国组织工程研究

BACKGROUND: Acetabular defect is one of the typical characteristics of adult developmental dysplasia of the hip. The acetabular defect caused an insufficient coverage to the femoral head, which means the contact area between them decreased and the pressure increased. Stress concentration could quicken hip wear and lead to arthritis or dislocation of the hip. Till now, there is no accepted objective criterion about what degree defect could lead to biomechanics changes in the hip. OBJECTIVE: To analyze the influence of different degrees of acetabular defect on the stress distribution of hip joint by using three-dimensional finite element method, and provide theoretical guidance for clinical treatment of hip dysplasia. METHODS: CT thin layer scanning data of normal adult hip were selected. Hip dysplasia models with varying degrees of bone defect were built by using Mimics15.0 and Hypermesh software. Von Mises stress distribution on the subchondral bone of the hip was analyzed by using Ansys10.0 software in the case of single foot touchdown. RESULTS AND CONCLUSION: Each model result was consistent with the actual situation. The maximum Von Mises stress value appeared at the top of the acetabulum dome and medial posterior femoral neck. When simulating one leg standing, the smaller the CE angle, the greater the maximum Von Mises stress on femoral head was; and acetabulum increased from 2.768 MPa and 3.029 MPa with 30° CE angle to 11.075 MPa and 15.322 MPa with 5° CE angle. This change was more obvious when CE angle was less than 15°. These findings confirmed that acetabular defect increases the peak stress of the hip joint, and the greater the defect, the greater the stress was. It is suggested that clinical intervention should be done as early as possible in patients with acetabular defect.

Three-D gait patterns before and after total hip arthroplasty / 中华外科杂志

<p><b>OBJECTIVE</b>To determine how selected gait parameters may change as a result of total hip arthroplasty (THA).</p><p><b>METHODS</b>From February 2006 to February 2007 the study was performed on 53 osteonecrosis of femoral head subjects prior to and 6 weeks, 3, 6 and 12 months after total hip arthroplasty surgery. Gait analysis was performed using the three-dimensional Infrared-based system (Dalian Dong Fang Xin Rui Company, China). Kinematic data were recorded for the lower limb. The results obtained from the osteonecrosis of femoral head subjects were compared with those of 40 individuals without osteonecrosis. Using a three-dimensional motion analyzer, the following were measured: (1) gait speed, stride length, cadence; (2) step length, stride width; (3) standing phase time, walking phase time; (4) gait cycle time, Joint movement angular.</p><p><b>RESULTS</b>Compared with persons before total hip arthroplasty, THA patients showed significantly increased gait speed, gait frequency, step length and affected limb stand phase (P < 0.01). Angle timetable: preoperative hip-maximum flexion was 15 degrees, post-extension was 8 degrees, knee-maximum flexion was 70 degrees, ankle-maximum flexion was 15 degrees. Postop hip-maximum flexion was 27, post-extension was 17 degrees, knee-maximum flexion was 50 degrees, ankle-maximum flexion was 14 degrees; parameters of hip, knee between preoperative and postoperative was significance (P < 0.01).</p><p><b>CONCLUSION</b>These results suggest that 3-D gait analysis before and after total hip arthroplasty can evaluate precisely hip vitodynamics variation.</p>

Free iliac crest grafts with periosteum for treatment of old acetabular defects / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To inquire into the therapeutic effectiveness of free iliac crest grafts with periosteum on old acetabular defects.</p><p><b>METHODS</b>From February 1996 to June 2005, 9 patients were treated with free iliac crest grafts with periosteum to reconstruct old acetabular defects. There were 7 males and 2 females and the average age was 41.3 years. The acetabular defects were caused by traffic accidents in 6 cases and fall injury in 3 cases. The time from injury to treatment was 4-13 months and averaged 8 months. Intraoperatively we firstly removed the acetabular fracture fragments of the posterior wall. The femoral head was then reduced. Bone graft was harvested from the iliac crest with periosteum, which was sculpted with a rongeur to conform to the defect. The concave (iliac fossa) side of the graft was placed toward the femoral head. The graft was securely fixed by two to three leg screws.</p><p><b>RESULTS</b>Postoperative syndrome was not found in any of the cases. Harris' score system showed that the score raised from 32.3 points preoperatively to 81 points postoperatively. The hip function was evaluated as excellent in 3 cases, good in 4 cases and fair in 2 cases.</p><p><b>CONCLUSIONS</b>Although this procedure could not exactly reproduce the anatomy of the hip joint, it enables to restore the posterior stability, provide bone-stock for the hip joints and prevent dislocation of the femoral head.</p>