We conducted a randomised controlled trial to assess the accuracy
of positioning and alignment of the components in total knee arthroplasty
(TKA), comparing those undertaken using standard intramedullary
cutting jigs and those with patient-specific instruments (PSI). There were 64 TKAs in the standard group and 69 in the PSI group. The post-operative hip-knee-ankle (HKA) angle and positioning
was investigated using CT scans. Deviation of >
3° from the planned
position was regarded as an outlier. The operating time, Oxford
Knee Scores (OKS) and Short Form-12 (SF-12) scores were recorded.Aims
Patients and Methods
We report long-term results of the first non-designer study of the HA coated Unix UKR. 85 consecutive UKR's were carried out between 1998 and 2002 using the Unix cementless HA coated UKR. 7 were lost to follow up, 6 were deceased and 6 had undergone revision. The remainder had a mean follow-up of 10 years (range 8–13). Oxford Knee Scores, WOMAC questionnaire and radiological assessment were carried out. Average age at surgery was 65 years. The mean Oxford Knee Score was 38.56 (13–48) with 67% scoring over 40, the mean WOMAC Score was 20.16 (0–72) with 58% scoring under 15. Survivorship analysis showed a survival rate of 95% with aseptic loosening as the end-point. Radiographic assessment was carried out by the senior author and an independent radiologist and showed lysis around the tibial base plate in 6% of patients with no lysis evident around the central fin region. The Unix UKR has the unique design of a central horizontal fin inserting under the tibial spine. The survivorship results from this study confirm those of Epinette's showing 100% survivorship at 13 years. Australian Joint Registry data shows high revision rates for UKR's mainly due to tibial loosening. Approximately 70% of the force is transmitted through the medial compartment and recreating this in a UKR results in large forces in the antero-medial proximal tibia. Simpson et al found that with either a central fin or HA coating on the lateral wall, the strain levels in the proximal tibia fell by approximately 66%. We feel that the central fin design is key to dissipating large forces throughout the proximal tibia, resulting in low levels of tibial loosening reported in both the Unix UKR series to date.
