This study demonstrates that medial overhang of less than three millimetres for the tibial component is acceptable in the Oxford UKA. Excessive overhang equal to this or more results in significantly worse ΔOKS and ΔPS. However, no difference in the five year ΔOKS and ΔPS was demonstrated between underhang and the other two groups in this study.
patients’ pre-operative demographics for age, weight, height, BMI, intra-operative variables such as the operating surgeon (n=2), insert and component sizes, post-operative varus/valgus deformity, and clinical outcome, assessed by the change in Oxford knee (OKS) and Tegner (TS) scores, from before surgery to five-year post-operatively.
We found no significant relationship between physiological RL, pre-operative demographics, intra-operative variables and clinical outcome scores in this study. Tibial RL remains a common finding following the Oxford UKA yet we do not know why it occurs but in the medium term, clinical outcome is not influenced by RL. In particular, it is not a sign of loosening. Physiological RL can therefore be ignored even if associated with adverse symptoms following the Oxford UKA.
Narrow, well-defined radiolucent lines commonly observed at the bone-implant interface of unicompartmental knee replacement tibial components have been referred to as physiological radiolucencies. These should be distinguished from pathological radiolucencies, which are poorly defined, wide and progressive, and associated with loosening and infection. We studied the incidence and clinical significance of tibial radiolucent lines in 161 Oxford unicondylar knee replacements five years after surgery. All the radiographs were aligned with fluoroscopic control to obtain views parallel to the tibial tray to reveal the tibial bone-implant interface. We found that 49 knees (30%) had complete, 52 (32%) had partial and 60 (37%) had no radiolucent lines. There was no relationship between the incidence of radiolucent lines and patient factors such as gender, body mass index and activity, or operative factors including the status of the anterior cruciate ligament and residual varus deformity. Nor was any statistical relationship established between the presence of radiolucent lines and clinical outcome, particularly pain, assessed by the Oxford Knee score and the American Knee Society score. We conclude that radiolucent lines are common after Oxford unicompartmental knee replacement but that their aetiology remains unclear. Radiolucent lines were not a source of adverse symptoms or pain. Therefore, when attempting to identify a source of postoperative pain after Oxford unicompartmental knee replacement the presence of a physiological radiolucency should be ignored.
It is not known whether the effect of Foot Pumps is enhanced by simultaneous use of graduated compression stockings (GCS) (by controlling calf compliance) or hindered (by restricting preload). The peak velocity in the popliteal vein was measured in twenty volunteers with duplex ultrasound at rest with the legs flat, foot-up and foot-down; it was then measured when the AV Impulse was activated. These measurements were each performed with and without graduated compression stockings. Data were analysed using Wilcoxon Rank Sum test. In each position of the leg (flat, foot-up and foot-down), the Peak venous velocity was greater if GCS were not used in comparison with the peak velocity if stockings were used. There was no significant difference in resting velocity with the foot flat, foot down or foot up without stockings or with stockings. Various studies have shown the efficacy of foot pumps in reducing the incidence of DVT in patients with joint replacements and hip fractures. They do not cause soft tissue side effects and are well tolerated. The value of GCS in orthopaedic surgery is uncertain, although in other surgical specialities they seem to be effective. Stockings, by reducing the capacitance of vessels in the foot reduce the amount of blood available for expulsion by the foot pumps. Nevertheless, our study presents physiological evidence for the hypothesis that, for optimum benefit, stockings should not be used simultaneously with Foot Pumps.