Pelvic discontinuity is a separation through the acetabulum with the ilium displacing superiorly and the ischium/pubis displacing inferiorly. This is a biomechanically challenging environment with a high rate of failure for standard acetabular components. The cup-cage reconstruction involves the use of a highly porous metal cup to achieve biological bone ingrowth on both sides of the pelvic discontinuity and an ilioischial cage to provide secure fixation across the discontinuity and bring the articulating hip center to the correct level. The purpose of this study was to report long term follow up of the use of the cup-cage to treat pelvic discontinuity. All hip revision procedures between January 2003 and January 2022 where a cup-cage was used for a hip with a pelvic discontinuity were included in this retrospective review. All patients received a Trabecular Metal Revision Shell with either a ZCA cage or TMARS cage (Zimmer-Biomet Inc.). Pelvic discontinuity was diagnosed on pre-operative radiographs and/or intraoperatively. Kaplan-Meier survival analysis was performed with failure defined as revision of the cup-cage reconstruction. Fifty-seven cup-cages in 56 patients were included with an average follow-up of 6.25 years (0.10 to 19.98 years). The average age of patients was 72.09 years (43 to 92 years) and 70.2% of patients were female. The five year Kaplan-Meier survival was 92.0% (95% CI 84.55 to 99.45) and the ten year survival was 80.5% (95% CI 58.35 to 102.65). There were 5 major complications that required revision of the cup-cage reconstruction (3 infections and 2 mechanical failures). There were 9 complications that required re-operation without revision of the cup-cage reconstruction (5 dislocations, 3 washouts for infection and one femoral revision for aseptic loosening). In our hands the cup-cage reconstruction has provided a reliable tool to address pelvic discontinuity with an acceptable complication rate.
Patients with longstanding hip fusion are predisposed to symptomatic degenerative changes of the lumbar spine, ipsilateral knee and contralateral hip The aim of this study was to determine the functional results and complications in patients undergoing hip fusion conversion to total hip replacement, performed or supervised by a single surgeon. Twenty-eight hip fusions were converted between 1996 and 2016. Mean follow up was 7 years (3 to 18 years). The reasons for arthrodesis were trauma 11, septic arthritis 10, and dysplasia 7. The mean age at conversion was 52.4 years (26 to 77). A trochanteric osteotomy was performed in all hips. Uncemented components were used. A constrained liner was used in 7 hips. Heterotopic ossification prophylaxis was not used in this series. HHS improved a mean of 27 points (37.4 pre-op to 64.3 post-op). A cane was used in 30% of patients before conversion and 80% after. Heterotopic ossification occurred in 12 (42.9%) hips. There was 2 peroneal nerve injuries, 1 dislocation, 1 GT non-union and 1 infection. There have been 5 revisions; 2 for aseptic loosening, 1 for infection, 1 for recurrent dislocation and 1 for leg length discrepancy. Conversion of hip fusion to hip replacement carries an increased risk of heterotopic ossification and neurological injury. We advise prophylaxis against heterotropic ossification. When there is concern about hip stability we suggest that the use of a constrained acetabular liner is considered. Despite the potential for complications, this procedure had a high success rate and was effective in restoring hip function.
