Abstract
We report a three year Medical Devices Agency and Local Ethical Committee approved prospective study for a new tri-tapered polished cannulated cemented femoral component. Our stem was implanted in 53 primary total hip replacements. Eleven male patients (11 hips) and 39 female patients (39 hips). The mean age at surgery was 73 (range 65 to 84). The mean weight was 71.76 kg (range 49.3 kg to 94.6 kg) with a mean BMI of 28 (range 20.20 to 40.26). All patients had a pre operative diagnosis of osteoarthritis. All the hips were implanted via the anterolateral approach. Twenty-six (51%) hips were implanted by a single consultant and 24 (49%) were implanted by six different registrars. Pre-operative and sequential post-operative clinical and radiological evaluations were undertaken.
The mean pre-operative Oxford hip score was 47 points.which declined 19 points at three years. Radiological analysis, using the Johnston criteria, did not reveal any untoward features. Prosthetic stem migration was measured using a technique developed in our unit and validated as accurate to 0.61 mm; as previously reported. Stem migration measured averaged 1.38 mm (n=52; sd ±1.38) 6 months post implantation. This progressed to 1.71 mm (n=50; SD=1.18) at one year; 1.61mm (n=48; sd ±1.17) at 2 years. and 1.55 mm (n=28; SD 1.13). At 3 years average stem migration for hips implanted by the registrar group and the consultant group was not sig-nificantly different (p=0.2048) and the migration curve, against time was similar for both groups.
Our study has demonstrated initial component migration, comparable to that of other polished tapered cemented stem designs. The improvement in Oxford hip score parallels other reported series and no adverse radiological signs have been observed. Long-term surveillance of our cohort will provide further data to compare the new design with substantial equivalents. More sophisticated studies, such as RSA analysis would provide further data on early femoral component migration.
The abstracts were prepared by Nico Verdoschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, Universitair Medisch Centrum, Orthopaedie / CSS1, Huispost 800, Postbus 9101, 6500 HB Nijmegen, Th. Craanenlaan 7, 6525 GH Nijmegen, The Netherlands.
