Abstract: BACKGROUND: Revision total hip arthroplasty with serious bone defect of acetabulum is complicated problem with technical challenges to joint surgeons, because of prosthetic installation difficulties, poor initial stability, postoperative prosthesis loosening.  
OBJECTIVE: To evaluate the effectiveness of structural bone grafting in revision total hip arthroplasty with Paprosky IIIA acetabular defect.
METHODS:  Between January 2010 and January 2018, 15 patients (15 hips) with Paprosky IIIA acetabular defect underwent revision total hip arthroplasty by structural bone grafting. All patients underwent revision total hip arthroplasty, with intramedullary reconstruction of the acetabulum with allogeneic femoral head during operation and weight-bearing walking in strict accordance with the rehabilitation program after operation. Standardized hip radiographs were assessed postoperatively 7 days, and at 6 months, 1 year and annually thereafter. The following outcomes were assessed: acetabulum cup coverage, bone graft coverage, the height and horizontal distance of center of hip rotation, bone graft healing and absorption, bone ingrowth, cup loosening, periprosthetic osteolysis, and Harris hip score.  
RESULTS AND CONCLUSION: (1) All patients were followed up for 2.5-10.0 years. The Harris score of the hip joint at the last follow-up was (83.2±5.8) points; compared with the preoperative data (25.3±5.3) points, the difference was significant (t=28.739, P=0.000). (2) The coverage rate of the acetabular cup was 91.7%-100% at postoperative 7 days, with an average of (95.6±2.2)%. The coverage rate of the bone graft at postoperative 7 days was 21.5%-53.2%, with an average of (37.4±10.0)%. (3) The horizontal displacement of the hip joint rotation center at postoperative 7 days was (5.8±1.7) mm; compared with the preoperative data (8.2±3.9) mm, the difference was significant (t=-2.128, P=0.042). At postoperative 7 days, vertical displacement of the center of rotation was (4.8±2.1) mm; compared with (22.2±4.2) mm before operation, the difference was significant (t=-14.321, P=0.000). (4) From 6 months to 1 year after surgery, 4 cases (4 hips) had mild absorption of allogeneic femoral heads, and the absorption was all located in the lateral non-stress distribution area, and did not affect the stability of the acetabular cup. In 15 cases (15 hips), trabecular bone connection could be found in allogeneic femoral head and acetabular bone junction. At the last follow-up, allogeneic femoral head and acetabular bone presented bone union, no nonunion. (5) Fifteen patients (15 hips) showed bone ingrowth into acetabula cup, and no acetabular loosening occurred at latest follow-up. No osteolysis was observed in acetabular zone. There were no complications in all patients, without deep vein thrombosis, infection, neurological damage, or dislocation. (6) It is concluded that structural bone grafting in revision total hip arthroplasty with Paprosky IIIA acetabular defect can effectively restore acetabular bone defects and reconstruct acetabulum. The eccentricity and rotation center of the hip joint recovered well; the hip joint function was good after operation; and good prosthesis stability was obtained; the early and mid-term clinical efficacy was satisfactory, but the long-term efficacy needs further clinical follow-up observation.

Key words: allogeneic femoral head, structural bone grafting, Paprosky IIIA, acetabular defect, hip revision