To explore the clinical efficacy of total hip arthroplasty for the treatment of severe acetabular protrusion secondary to rheumatoid arthritis.

From January 2011 to November 2014, 18 patients(20 hips) with were treated with total hip arthroplasty (THA), including six males (six hips) and 12 females(14 hips). The age ranged from 37 to 68 years, (46±8)years on average.Inclusion criteria: protrusio acetabuli secondary to hip rheumatoid arthritis, according to the classification of Sotello-Garza and Charnley, no hip was type Ⅰ (protrusio acetabuli 1~5 mm), 15 cases (17 hips) were type Ⅱ (6~15 mm), and three cases (three hips) were type Ⅲ (>15 mm). Exclusion criteria: protrusio acetabuli secondary to congenital, traumatic or osteoarthritis. THA was accomplished through posterolateral approach. The femoral heads were moved out with retrograde method after the osteotomy of femoral neck. Autolgous-bone grafting was used to repair acetabular defects and cementless tantalum trabecular metal cups were planted with press-fit skills. At the follow-up, radiographic measurement was performed with hip X-ray films to assess the cup loosening, re-protrusion and the union of graft hone. The range of motion and the Harris scores were used to evaluate the clinical efficacy. The preoperative and postoperative data of Harris hip score and the distance between the center of femoral head to Kohler’ line were analyzed by paired t test.

The average operation time and blood loss was(89±8)min (55 to 131 min) and(295±11)ml (165 to 480 ml) respectively. The meantime of follow-up was (4.5±1.7)years (range, 2.5 to six years). According to X-ray films, bone grafting fusion was observed within 4.5 months after operation. At the last follow-up, the average Harris hip score improved from (55±4) points preoperatively to (92±4) points post-operatively (t=12.81, P <0.01). The distance between the center of femoral head to Kohler’ line improved from (20±4) mm preoperatively to (21±3) mm post-operatively, showing significant difference(t=2.312, P <0.01). No loosening of acetabular components was found in this group.

The acetabular protrusion secondary to rheumatoid arthritis has the characteristic of hip osteoporosis and abnormal shape of acetabulum. Restoration hip rotation center and satisfied clinical outcome benefit from impacted allograft bone transplant combined with tantalum trabecular metal cup.