VOL. 88-B, No. 3, MARCH 2006 315 Five-year prospective clinical and radiological results of a new cannulated cemented polished Tri-Taper femoral stem R. E. Field, P. J. Singh, A. M. H. Latif, M. D. Cronin, D. J. Matthews From Epsom and St Helier University Hospital NHS Trust, Carshalton, England " R. E. Field, PhD, FRCS(Orth), Consultant Orthopaedic Surgeon and Director of Orthopaedic Research South West London Elective Orthopaedic Centre Epsom General Hospital, Dorking Road, Epsom, Surrey KT18 7EG, UK. " P. J. Singh, MRCS, Specialist Orthopaedic Registrar Oxford Rotation, Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX3 7LD, UK. " A. M. H. Latif, MBBChir, Research Fellow " M. D. Cronin, MRCS, Research Fellow " D. J. Matthews, MRCS, Research Fellow Orthopaedic Research Unit St Helier Hospital, Epsom and St Helier University Hospitals NHS Trust, Wrythe Lane, Carshalton, Surrey SM5 1AA, UK. Correspondence should be sent to Mr R. E. Field; e-mail: richardefield@aol.com ©2006 British Editorial Society of Bone and Joint Surgery doi:10.1302/0301-620X.88B3. 17314 $2.00 J Bone Joint Surg [Br] 2006;88-B:315-20. Received 17 October 2005; Accepted 9 November 2005 We describe the results at five years of a prospective study of a new tri-tapered polished, cannulated, cemented femoral stem implanted in 51 patients (54 hips) with osteoarthritis. The mean age and body mass index of the patients was 74 years and 27.9, respectively. Using the anterolateral approach, half of the stems were implanted by a consultant orthopaedic surgeon and half by six different registrars. There were three withdrawals from the study because of psychiatric illness, a deep infection and a recurrent dislocation. Five deaths occurred prior to five-year follow-up and one patient withdrew from clinical review. In the remaining 51 hips the mean pre-operative Oxford hip score was 47 points which decreased to 19 points at five years (45 hips). Of the stems 49 (98%) were implanted within 1˚ of neutral in the femoral canal. The mean migration of the stem at five years was 1.9 mm and the survivorship for aseptic loosening was 100%. There was no significant difference in outcome between the consultant and registrar groups. At five years, the results were comparable with those of other polished, tapered, cemented stems. Long-term surveillance continues. We describe the results at a maximum of five years of a pilot study of a new cannulated, tri- tapered, polished, femoral stem for use in cemented or hybrid hip replacement. The study had three aims: 1) to identify whether a combination of the design features reported in the literature as advantageous could produce a successful new implant; 2) to determine if the new design would deliver a consistently good clinical outcome when im- planted by surgeons of differing experience; and 3) to evaluate the clinical performance of the new design before its commercial release. The successful long-term fixation of the Charnley (Depuy Orthopaedics Inc., Warsaw, Indiana), Exeter (Stryker, Herouville, France) and Müller (Zimmer Inc., Warsaw, Indiana) stems has demonstrated the suitability of stain- less steel for the manufacture of cemented fem- oral stems. 1-5 Mediolateral and anteroposterior longitudi- nal tapers provide a wedge-shaped stem which transfers compressive load to the cement-bone interface. A third lateral to medial taper is reported to enhance load transfer from the stem to the medial cortex of the proximal femur. 6 A polished stem allows subsidence within the cement mantle. 7 Longitudinal can- nulation of a stem enables implantation to be done over a guide wire which has been screwed into the centre of the distal femoral cement restrictor. This ensures that the tip of the implanted stem is situated close to the centre of the femoral canal. 8 The guide wire can be removed once the cement has polymerised. Longitudinal recesses with smooth edges on the anterior, posterior and lateral aspects of the proximal portion enhance rotational stability within the cement mantle and help to resist the torsional stresses which are known to cause posterior rotation of the stem. 7,9 Reproduction of the normal femoral geometry gives a com- ponent with a neck-shaft angle and stem-head offset within the physiological range. 10,11 Patients and Methods The Tri-Taper stems were produced from wrought, high-nitrogen stainless steel in four sizes ranging in length from 130 mm to 140 mm with the offset increasing incrementally from 37.2 mm to 47.3 mm. Pre-clinical fatigue testing was performed in accordance with the ISO7206-4 12 and ISO7206-8 13 standards. All the components had a neck-shaft angle of 135˚ and a polished finish with a surface roughness of 0.2 mRa. The trunnion was a 12/14 Euro- cone Morse taper suitable for attachment of cobalt chrome, stainless steel or ceramic mod- ular heads. The proximal end of the stem can- nulation was recessed and threaded for attach-