Mixed manufacturer dual mobility bearing and the Exeter V40 Stem: is it safe? Short-term results in primary and revision hip replacement.

The aim is to review clinical and radiological outcomes for all cases of primary and revision THA, combining a cemented stem (Exeter V40) with a dual mobility component from a different manufacturer (SERF Novae), to evaluate whether concerns regarding mixing components from different manufacturers are justified. We identified 72 hip replacements performed between May 2010 and December 2015 using the SERF Novae dual mobility cup with an Exeter V40 stem, the majority of which were cemented (90%) and revisions (58%). Patients were evaluated clinically and radiologically at a minimum of two years. There were five (6.9%) dislocations; three (4.2%) requiring revision - one of which was an intra-prosthetic disarticulation and two infections. No cases were lost to follow-up and 49 surviving cases were reviewed at a mean of 4.0 (range 1.8-8.1) years following surgery. Pain and functional outcome scores all improved. There were no radiological failures and no revisions for aseptic loosening of stem or cup. The combination of Exeter cemented stem with a dual mobility bearing from a different manufacturer results in acceptable short-term outcomes in terms of hip stability, revision rates and patient-reported measures.

Dual-mobility bearings in complex revision hip arthroplasty.

BACKGROUND: Revision total hip arthroplasty (rTHA) is associated with an increased dislocation risk. Dual-mobility (DM) bearings have been used to address this issue. Such constructs offer increased range of motion and enhanced stability whilst avoiding some issues associated with fully-constrained devices. DM bearings have been used in our unit since 2013. METHODS: All rTHA cases since 2013 were reviewed using the following criteria: (1) use of a DM bearing; (2) extensive soft tissue or bone loss resulting from ARMD, infection or multiple revisions, or requiring custom or megaprosthetic reconstruction; (3) minimum 2-month follow-up. RESULTS: 52 cases were identified with a median of 2 previous operations (range 1-6) and mean follow-up of 14 (2-41) months. The Novae-Stick component was used in 50 cases, the Avantage in 2 and the Trident MDM in 1 case. 19 required acetabular reconstruction using trabecular metal and four required custom acetabular components. 19 required femoral reconstruction with a proximal or total femoral replacement.Postoperatively, 8 patients (15.4%) sustained a dislocation at a mean of 1.6 (range 1-3) months. 3 (5.8%) requiring re-revision. 1 required excision arthroplasty and 2 a constrained liner, 1 of which went on to have further instability. There were no intraprosthetic dislocations. CONCLUSIONS: Dual-mobility components are a viable option in the complex rTHA setting. Early dislocations can occur but the rate of instability is acceptable in this high-risk group.

Hip resurfacing arthroplasty in patients with varus deformity of the femoral neck-shaft angle.

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) is associated with poorer outcomes. Our experience has not reflected this. We examined the Oxford Hip Scores (OHS), Harris Hip Scores (HHS) and outcomes of patients with varus hips against a normal cohort to ascertain any significant difference. We identified 179 patients. Measurement of the femoral neck-shaft angle was undertaken from antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients with a NSA of less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with published anatomical studies. The 'varus' cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74). Mean OHS and HHS were 16 and 93.5 respectively. Complications included 2 cases of trochanteric non-union, but there were no femoral neck fractures, early failures or revisions. The 'normal' cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76). The OHS and HSS were 18.8 and 88.9 respectively. Complications included 5 trochanteric non-unions and 1 revision due to an acetabular fracture following a fall. Statistical analysis demonstrated no statistical difference between the cohorts' OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. We have not yet experienced any femoral neck fractures, which we believe is in part due to the use of an uncemented femoral component and preservation of blood supply.