Abstract
Introduction: The conversion of the fused hip to a total hip replacement poses a challenging reconstructive problem. The technical pitfalls depend on the aetiology of the arthrodesis, the surgical technique used and the available bone stock. Indications include painful pseudo arthrosis, disabling back or ipsilateral knee pain and malposition of the arthrodesed hip. There are often difficulties restoring appropriate biomechanics and providing a functionally useful outcome. We present a short series where a custom CAD/CAM femoral prosthesis was used to accommodate the anatomical problems caused by previous spontaneous and operative arthrodesis.
Patients and Method: 5 patients (4 female, 1 male) with primary diagnoses of septic arthritis, TB, trauma and DDH were reviewed. The average age at the time of conversion was 43.6 years (Range 20–62 years). The patients were reviewed with a mean follow up of 82 months (Range 24–110 months). All the patients were evaluated by an independent observer radiologically and clinically using Harris, WOMAC and Oxford hip scores.
Results: The patients improved from preoperative HHS 55 (Range 39–73), Oxford 40 (Range 37–46) and WOMAC 80 (Range 65–92) to postoperative HHS 73 (Range 44–94), Oxford 26 (Range 17–42) and WOMAC 45 (Range 24–79). These results compare poorly to a large series of age and sex matched cases undergoing primary and revision hip arthroplasty. Nevertheless, 4 patients were extremely satisfied with the results of their operation. 1 patient showed no improvement in his scores although he reports that his spinal symptoms are better. His operation was complicated by non-union of the greater trochanter.
Conclusion: Most series report poor results after the conversion of arthrodeses to total hip replacements. The commonest problems include instability, sepsis, fractures, limited mobility of the hip replacement and poor function. Careful planning is required to accommodate the atypical anatomy. The use of CAD/CAM femoral stems in the conversion of the arthrodesed hip has allowed preservation of valuable bone stock in anatomically abnormal femora whilst optimising biomechanics and improving function.
Theses abstracts were prepared by Mr Peter Kay. Correspondence should be address to him at The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
