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LONG HYDROXYAPATITE COATED STEMS IN REVISION HIP SURGERY

Sunderland Royal Hospital

Introduction: Revision hip surgery is likely to become more frequent with the continued use of cemented primary hip prostheses.

Primitive stem cells from bone marrow become osteocytes in the presence of hydroxyapatite ceramic (HAC). Consequently there is osseointegration of an HAC surface in bleeding cancellous bone/marrow.

However, damaged bone in the revision situation does not provide the necessary stem cells for osseointegration. Revision surgery using standard length (150mm) HA coated stems is not always satisfactory.

Using a 200 mm stem will extend the operating field into fresh, undamaged cancellous bone and marrow.

Method: Since 1988 more than 2600 HAC hips have been implanted for primary and revision hip cases. This includes 148 revisions. The continued use of primary HAC hips has reduced the necessity for revision hip surgery. There is a dwindling population of cemented, loosening hips requiring revision. Patients are assessed radiologically and using the Harris Hip Score (HHS) pre. and post-operatively on an annual basis.

Results: Since 1991 the longer 200mm stems have been used in 73 cases. The results have been rewarding.

The system works with improved HHS. Defects from debris disease fill in and stems are seen to bond to the host bone particularly at the tip. There have been no prosthetic fractures.

Only one case has needed re-revision when a stem remained un-bonded in the presence of a transverse femoral fracture. Two other stems are probably not bonded. This represents 4% failure.

Discussion: HA bonding is a successful system of fixation in primary hip arthroplasty. Using a 200mm stem in revision cases allows virgin bone marrow to provide the necessary stem cells for fixation. These longer HA coated stems should be used in revision surgery.

Correspondence should be addressed to Mr Peter Howard, Editorial Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.