[Effect of Jumbo cups for total hip arthroplasty revision on femoral offset and hip center of rotation].

Objective: To investigate the change of the femoral offset and hip center of rotation (COR) after using Jumbo cups in total hip arthroplasty (THA) revision.

Methods: The clinical data of 23 patients who underwent THA revision using Jumbo cups between January 2010 and May 2015 were retrospectively analyzed. Morselized bone graft was performed on 8 cases, morselized bone graft combined with structural bone graft on 10 cases. There were 10 males and 13 females, aged 65.4 years on average (range, 51-77 years). The disease duration was 1-24 years (mean, 8.57 years). The reasons for revision included aseptic loosening in 21 cases and periprosthetic infection in 2 cases. The Harris hip score and visual analogue scale (VAS) were 43.04±5.05 and 5.70±0.97 before operation respectively. According to the Paprosky acetabular defect classification, there were 5 cases of type I, 5 cases of type II A, 3 cases of type II B, 6 cases of type II C, and 4 cases of type III A. The X-ray films showed that the femoral offset was (40.65±4.09) mm for normal side and was (44.04±5.08) mm for affected side at preoperation, showing significant difference ( t =4.098, P =0.000). Ten patients underwent femoral offset reconstruction (43.48%) but 13 patients did not (56.52%) before operation. The COR was reconstructed in 10 cases (43.48%); COR elevation was observed in 11 cases (47.83%), and COR decline in 2 cases (8.69%) before operation.

Results: Primary healing of incision was obtained in all patients, with no complication of infection, vascular injury, deep vein thrombosis, dislocation of the joint, or fracture around prosthesis. All the patients were followed up 12-76 months (mean, 22.48 months). The Harris hip score and VAS were 82.09±4.53 and 0.74±0.62 at 1 year after operation respectively, showing significant differences when compared with preoperative scores ( t =37.831, P =0.000; t =22.318, P =0.000). The X-ray films showed that the femoral offset was (43.87±3.57) mm for affected side at 1 year after operation, showing no significant difference when compared with preoperative one ( t =0.250, P =0.805), but significant difference was found between affected side and normal side ( t =5.591, P =0.000). The femoral offset was restored in 16 patients (69.57%) and was not restored in 7 patients (30.43%) after operation. The COR was restored in 15 patients (65.22%) and was not restored in 8 patients (34.78%).

Conclusion: Using Jumbo cups or combined with morselized or structural bone graft is effective in restoring hip COR and femoral offset at the maximum limit in THA revision, with good short-term outcome and improved stability of acetabular prosthesis.