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Long-Term Survival of Cemented Distal Femoral Endoprostheses with a Hydroxyapatite-Coated Collar: A Histological Study and a Radiographic Follow-up

Coathup, Melanie Jean BSc(Hon), PhD; Batta, Vineet MBBS, MS, MRCS, DipSEM; Pollock, Robin C. MBBS, BSc, FRCS(Orth); Aston, William J. BSc, MBBS, MRCSEd, FRCSEd(Tr & Orth); Cannon, Stephen R. MA, MChOrth, FRCS(Eng), FRCS(Ed), MRCOG; Skinner, John A. MBBS, FRCS(Eng), FRCS(Orth); Briggs, Timothy W.R. MBBS, MChOrth, FRCS(Ed), FRCS(Eng); Unwin, Paul S. BSc, MSc, PhD; Blunn, Gordon William BSc(Hon), PhD

Journal of Bone & Joint Surgery - American Volume: 4 September 2013 - Volume 95 - Issue 17 - p 1569–1575
doi: 10.2106/JBJS.L.00362
Scientific Articles
Supplementary Content

Background: The objective of this study was to examine the degree of osteointegration into a hydroxyapatite-coated collar and relate this finding to aseptic loosening in patients with a distal femoral replacement used to treat primary bone cancer. Our hypothesis was that the implant collar would increase osteointegration and reduce the rate of aseptic implant loosening.

Methods: Sixty-one patients treated with a primary cemented distal femoral prosthesis between 1992 and 2001 were included in this study. The mean duration of follow-up was 8.5 years (range, two to eighteen years). Extracortical bone growth into the grooved hydroxyapatite-coated collar was quantified radiographically. Histological sections through four hydroxyapatite-coated collars and four implants with no collar, retrieved following amputation due to local recurrence or at autopsy at a mean of 3.5 years (range, 1.4 to 6.1 years) after implantation, were evaluated as well.

Results: Five (8%) of the implants were revised because of aseptic loosening, 3% of the implants fractured, and 3% were revised because of infection. Six limbs (10%) required amputation because of local tumor recurrence. On radiographs, osteointegration into the collar was seen to have occurred in 70% of the patients and did not correlate with sex, age, diagnosis, or length of time postoperatively. Histological analysis showed mature lamellar bone within the grooves of the hydroxyapatite-coated collar, and bone was observed in direct contact with the hydroxyapatite coating. Extracortical bone failed to make direct contact with the surface of the implants manufactured without a collar.

Conclusions: The use of cemented distal femoral massive bone tumor prostheses with a hydroxyapatite-coated collar located at the shoulder of the implant was followed by a low (8%) rate of revision due to aseptic loosening. The use of hydroxyapatite grooved collars may lead to osteointegration of the implant shoulder (collar) and may reduce the rate of aseptic loosening.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

1John Scales Centre for Biomedical Engineering, Institute of Orthopaedics and Musculoskeletal Science, Division of Surgery and Interventional Science, University College London, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex HA7 4LP, United Kingdom. E-mail address for M.J. Coathup: m.coathup@ucl.ac.uk

2Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex HA7 4LP, United Kingdom

3Stanmore Implants, Centennial Park, Elstree, Hertfordshire WD6 3SJ, United Kingdom

Copyright 2013 by The Journal of Bone and Joint Surgery, Incorporated
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