MINIMUM FIVE YEAR FOLLOW-UP OF A CEMENTLESS, MODULAR, TAPERED STEM IN HIP REVISION ARTHROPLASTY

Abstract

Introduction: There has been a proliferation of newer fluted tapered grit-blasted titanium stems in hip revision arthroplasty. However, only a limited number of clinical series have so far been reported in the literature. Moreover, all reports have only a short-term clinical and radiographical follow-up (< 5 years). Medium-term and long-term follow-up studies are lacking. Therefore, the aim of this study was to review a series of a cementless modular tapered revision femoral component (MP Link hip reconstruction prosthesis) with a minimum 5 year follow-up.

Patients and Methods: This study includes 90 consecutive cases (87 patients) with the MP stem. We documented the Harris hip score (HHS) and the Visual analogue scale (VAS) was used to assess pain at rest and movement. Survivorship was calculated using Kaplan-Meier survival analysis. The 95% confidence intervals (CI) for the cumulative 5 year survival were calculated. Radiographs made immediately after the index operation were compared with those at follow-up examination in order to classify the restoration of femoral bone and vertical migration of the implant.

Results: Of the original 90 cases, 24 (27%) died prior to clinical and radiographical review, 2 (2%) had a stem revision and 1 (1%) was lost to follow-up. Patients who died and were lost to follow-up were included in the survival analysis. For those patients, all data concerning complications and revisions were extracted from journal files and the Swedish Hip Register which collects all information on reoperations after hip revision surgery.

The median follow-up time was 6 (5–11) years. The median VAS for pain for the affected hip was 0 (0–5) at rest and 0 (0–9) at movement. The median HHS at follow-up was 78 (16–100) points.

17 (19%) patients dislocated their hips during follow-up. A prosthesis head size of 22 mm was present in 6/17 (35%) patients with dislocation and in 11/73 (15%) patients without dislocation (P = 0.055).

The cumulative 5 year survival rate was 98% (95% CI: 94–100%) with stem removal and 90% (95% CI: 85–96%) with any reoperation as the endpoint.

At follow-up, we noted subjectively that 17% of the cases had evidence of proximal bone restoration, whereas 44% had constant defects. In 39% the quality of the proximal bone appeared to be declining. If present, this was mostly seen around the lesser trochanter. The median vertical stem migration was 2.7 (0–30) mm

Discussion: This is the first report with a clinical and radiographical medium-term follow-up of patients with a cementless modular tapered distally fixated hip revision stem. In our study, we found a discrepancy between a high implant survivorship and good pain relief on one hand and a high dislocation rate on the other hand.