This study reports on the first 150 consecutive Oxford cementless unicompartmental knee arthroplasties (UKA) performed in an independent centre (126 patients). All eligible patients had functional scores (Oxford knee score and high activity arthroplasty score) recorded pre-operatively and at two- and five-years of follow-up. Fluoroscopically aligned radiographs were taken at five years and analysed for any evidence of radiolucent lines (RLLs), subsidence or loosening. The mean age of the cohort was 63.6 years (39 to 86) with 81 (53.1%) males. Excellent functional scores were maintained at five years and there were no progressive RLLs demonstrated on radiographs. Two patients underwent revision to a total knee arthroplasty giving a revision rate of 0.23/100 (95% confidence interval 0.03 to 0.84) component years with overall component survivorship of 98.7% at five years. There were a further four patients who underwent further surgery on the same knee, two underwent bearing exchanges for dislocation and two underwent lateral UKAs for disease progression. This was a marked improvement from other UKAs reported in New Zealand Joint Registry data and supports the designing centre’s early results.

Cite this article: Bone Joint J 2015;97-B:1358–63.

We carried out a prospective investigation into the radiological outcomes of uncemented Oxford medial compartment unicondylar replacement in 220 consecutive patients (231 knees) performed in a single centre with a minimum two-year follow-up. The functional outcomes using the mean Oxford knee score and the mean high-activity arthroplasty score were significantly improved over the pre-operative scores (p < 0.001). There were 196 patients with a two-year radiological examination performed under fluoroscopic guidance, aiming to provide images acceptable for analysis of the bone–implant interface. Of the six tibial zones examined on each knee on the anteroposterior radiograph, only three had a partial radiolucent line. All were in the medial aspect of the tibial base plate (zone 1) and all measured < 1 mm. All of these patients were asymptomatic. There were no radiolucent lines seen around the femoral component or on the lateral view. There was one revision for loosening at one year due to initial inadequate seating of the tibial component. These results confirm that the early uncemented Oxford medial unicompartmental compartmental knee replacements were reliable and the incidence of radiolucent lines was significantly decreased compared with the reported results of cemented versions of this implant. These independent results confirm those of the designing centre.

We compared extrusion of the allograft after medial and lateral meniscal allograft transplantation and examined the correlation between the extent of extrusion and the clinical outcome. A total of 73 lateral and 26 medial meniscus allografts were evaluated by MRI at a mean of 32 months (24 to 59) in 99 patients (67 men, 32 women) with a mean age of 35 years (21 to 52). The absolute values and the proportional widths of extruded menisci as a percentage were measured in coronal images that showed maximum extrusion. Functional assessments were performed using Lysholm scores. The mean extrusion was 4.7 mm (1.8 to 7.7) for lateral menisci and 2.9 mm (1.2 to 6.5) for medial menisci (p < 0.001), and the mean percentage extrusions were 52.0% (23.8% to 81.8%) and 31.2% (11.6% to 63.4%), respectively (p < 0.001). Mean Lysholm scores increased significantly from 49.0 (10 to 83) pre-operatively to 86.6 (33 to 99) at final follow-up for lateral menisci (p = 0.001) and from 50.9 (15 to 88) to 88.3 (32 to 100) for medial menisci (p < 0.001). The final mean Lysholm scores were similar in the two groups (p = 0.312). Furthermore, Lysholm scores were not found to be correlated with degree of extrusion (p = 0.242).

Thus, transplanted lateral menisci extrude more significantly than transplanted medial menisci. However, the clinical outcome after meniscal transplantation was not found to be adversely affected by extrusion of the allograft.