Modularity in total hip replacement(THR) enables precise recreation of native hip biomechanics. However, there have been concerns about raised metal ion levels with increased number of interfaces. We present the 3 year results of ML taper with Kinectiv technology(MLKT), a modular neck uncemented stem. This system has modular neck options, but has only one [0] head in various diameters. 97 hips in 97 patients with a MLKT stem and Continuum socket were included in this prospective study. Harris hip score, Oxford hip scores (HHS and OHS) and yearly blood Cobalt(Co), Chromium(Cr) and Titanium(Ti) were recorded. The primary end point was revision for any reason. Paired t- test was used to assess improvement in functional scores.Background
Methods
High failure rates have been associated with large diameter metal-on-metal total hip replacements (MoM THR). However there is limited literature describing the outcomes following the revision of MoM THR for adverse local tissue reaction (ALTR). A total of 98 large diameter MoM THRs underwent revision for ALTR at our institution. The data was obtained from the clinical records and included the demographics, intra-operative findings of ALTR and post-operative complications. Any subsequent procedures and re-revision for any reason was analysed in detail. The clinical outcome was measured using functional outcome scores using the Oxford hip score (OHS), Western Ontario and McMaster Universities osteo-arthritis index (WOMAC) score and Short Form (SF12). The mean age of the patients at the time of revision was 58.2 yrs. At a mean follow-up of 3.9 years (1.0 to 8.6) from revision for ALTR, there were 15 hips (15.3 %) with post-operative complications and 8 hips (8 %) requiring re-revision. The Kaplan–Meier five-year survival rate for ALTR revision was 91 % (95% confidence interval 78.9 to 98.0). There were no statistically significant predictors of re-revision. The rate of postoperative dislocation following revision was 9.2% (9 hips). The post-operative functional outcome depends on the intra-operative findings of tissue destruction secondary to ALTR. The short term results following revision of large diameter MoM THR for ALTR are comparable with other reports in the literature. The use of constrained liners reduces the incidence of post-operative dislocation. There is an increased risk of postoperative instability following revision THR for ALTR. Early identification and intervention seems to be the logical approach in the management of patients with ALTR.
