Biological Acetabular Component With High Placement Technique In Hip Revision Arthroplasty

Objective: To investigate the feasibility and mid-term clinical efficacy of biological acetabular component with high placement technique in hip revision arthroplasty.Methods: From March 2006 to March 2015, 34 patients (35 hips) underwent hip revision arthroplasty with biological acetabular components with high placement technique.There were 15 males (15 hips) and 19 females (20 hips) with an average of 55 years (range,26-74 years). There were 22 hips caused by aseptic loosening and 13 hips by infection. The acetabular bone defects included Paprosky ?A in 3 cases, ?B in 4, ?C in 2, ?A in 17, and?B in 9. Modular tapered stems with distal fixation were performed in most femoral sides.The height of hip center was greater than 2.5 cm for all the patients, which were divided into two groups according to the degree of placement: 2.5-3.5 cm for the high placement group, greater than 3.5 cm for the high hip center group. Harris hip score, pain visual analogue score (VAS), leg length difference, gait characteristics were compared between two groups postoperatively and at the final follow-up respectively. The height of hip center and the horizontal distance between hip center and teardrop were measured in the hip X-ray. Radiolucent lines and migrations were also recorded.Results: The average operation time and blood loss was 108 min (100-220 min) and 825 ml (300-1 200 ml) in two groups respectively. All the patients were followed up for average 49.2 months (range, 12-116 months). At the final follow-up, the average Harris hip score improved from 36.52±17.17 points preoperatively to 83.46±7.63 (t=18.99,P=0.00). The average VAS score decreased from 8.06±1.24 points preoperatively to 1.91±1.62 postoperatively (t=18.57, P=0.00). The height of hip center was 1.47±0.33 cm preoperatively and 3.85±1.13 cm postoperatively (t=12.15, P=0.00). The horizontal distance was 3.33±0.53 cm pre-operatively and 3.23±0.63 cm post-operatively (t=0.98,P=0.64). At the final follow-up, Trendelenburg sign improved from 25/10 (positive/negative, hips) preoperatively to 7/28 (?2 ?18.65, P=0.00) . There was 1 case of severe limp, moderate in 1, mild in 8 and other cases had no limp. The leg length discrepancy decreased from 1.84±1.92 cm preoperatively to 0.71 ± 1.57 postoperatively (t=4.24, P=0.00).There were 6 cases of Paprosky ?b with the use of ultra small cup and extremely high placement. The average Harris hip score improved from 26.65±13.46 points preoperatively to 79.83±10.55 (t=12.33,P=0.001). The average VAS score decreased from 8.50±1.38 points preoperatively to 2.83±2.64 postoperatively (t=4.61,P=0.006). One case had acetabular loosening at 4 years later postoperatively and re-revision surgery was performed. Other patients had no infection, dislocation, periprosthetic fracture or any other complications at the final follow-up.Conclusion: Highly placement of biological acetabular component with a distal tapered modular stem can get enough contact with the host bone and achieve optimal clinical outcomes, regardless of the degree of high placement. Particularly, using ultra small cup in extremely high placement shows good effectiveness in simplified operation,and it can be used in many complicated or even impossible acetabular reconstruction.