Abstract
Introduction The accuracy of UCA implantation is an important prognostic factor in survivorship. Previously, conventional instrumentation was adapted for UCA, possibly contributing to a lower long-term survivorship. This study aims to assess UCA position on x-rays, performed through a minimally invasive approach, in comparison to UCAs utilising an open approach.
Methods Patients were selected for UCA according to strict criteria. In particular, a varus knee < 15 and correct-able,< 15 fixed flexion deformity, intact cruciate ligaments and weight bearing knee x-rays indicating osteoarthritis in the antero-medial region and relative lateral compartment sparing. Patello-femoral joint disease was not an exclusion criterion. Ultimately, the decision to proceed with UCA was made at the time of surgery where the cruciates and lateral compartment could be inspected directly. Data was retrieved retrospectively for a continuous cohort of patients. Radiographs of component alignment were measured by an independent observer not involved in the surgery. Radiographs were measured for 56 UCAs, performed by one of the authors. Twelve patients had bilateral UCAs at the same surgery and one patient had a combined UCA/TKR. Short knee x-rays (anterior-posterior and lateral views) were used to estimate the axes of the femur and tibia as the reference points for component measurements.
Results The femoral component varus/valgus angle was 5.6° (range: 2 to 10) and flexion/extension angle was 4.9° (range: 0 to 11). The tibial component varus/valgus angle was 86.4° (range: 80 to 89°) and the postero-inferior tilt angle was 83° (range: 80 to 85). There was no radiolucency at the tibial plateau interface greater than one millimetre. One patient was treated for deep vain thrombosis and two patients underwent manipulations due to reduced range of motion. There were no deep or superficial infections and no UCA revisions.
Conclusions Radiological analysis of Oxford UCAs using a minimally invasive technique demonstrates similar implant positioning compared to the open approach. Patients gain the advantage of earlier recovery due to less synovial and quadriceps disturbance and no patella dislocation. Ongoing follow-up is required to determine whether these benefits extend to improved prosthesis survivorship.
The abstracts were prepared by Mr Jerzy Sikorski. Correspondence should be addressed to him at the Australian Orthopaedic Association, Ground Floor, William Bland Centre, 229 Macquarie Street, Sydney NSW 2000, Australia.
None of the authors have received any payment or consideration from any source for the conduct of this study.
