Cementless fixation in Oxford unicompartmental knee replacement

Abstract

The Cementless Oxford Unicompartmental Knee Replacement (OUKR) was developed to address problems related to cementation, and has been demonstrated in a randomised study to have similar clinical outcomes with fewer radiolucencies than observed with the cemented device. However, before its widespread use it is necessary to clarify contraindications and assess the complications. This requires a larger study than any previously published. We present a prospective multicentre series of 1000 cementless OUKRs in 881 patients at a minimum follow-up of one year. All patients had radiological assessment aligned to the bone-implant interfaces and clinical scores. Analysis was performed at a mean of 38.2 months (19 to 88) following surgery. A total of 17 patients died (comprising 19 knees (1.9%)), none as a result of surgery; there were no tibial or femoral loosenings. A total of 19 knees (1.9%) had significant implant-related complications or required revision. Implant survival at six years was 97.2%, and there was a partial radiolucency at the bone-implant interface in 72 knees (8.9%), with no complete radiolucencies. There was no significant increase in complication rate compared with cemented fixation (p = 0.87), and no specific contraindications to cementless fixation were identified. Cementless OUKR appears to be safe and reproducible in patients with end-stage anteromedial osteoarthritis of the knee, with radiological evidence of improved fixation compared with previous reports using cemented fixation.

Advantages of a Cementless Unicompartmental Knee Arthroplasty Approach

“…This happened at 901 flexion at higher loads as determined by a test method designed by the author. 38 The load and flexion angles for failure are consistent with a stair-ascent-type activity of daily living.…”

“…Using this novel technique for micromotion measurements to compare the design of UKA cementless tibial trays, the Porous Structure Technology design demonstrated reduced liftoff as compared with commercially available designs. 38 In addition, medial and lateral mechanical testing and finite-element modeling demonstrated no evidence of subsidence in the sawbones block or increased pressure at the lateral aspect of the tibial implant, which is thought to cause the valgus subsidence in the Oxford design (Fig. 3).…”

“…This is believed to be because of the stress shielding caused by improper cement application. 37,38 Cementless UKA…”

“…In a large multicenter study of more than 1000 knees undergoing cementless Oxford UKA, implant survival was 97.2% at 6 years with no increased complication rate compared with cemented UKA. 38 No specific patient contraindications were identified. Finally, the bone-implant radiolucencies were found in only 9% of cementless UKA (with no complete radiolucencies), which is dramatically less than traditionally seen in cemented UKA.…”

“…Finally, the bone-implant radiolucencies were found in only 9% of cementless UKA (with no complete radiolucencies), which is dramatically less than traditionally seen in cemented UKA. 38 Cumulatively, the Oxford data suggest that cementless fixation strategies may improve fixation in Oxford unicompartmental knee replacement with diminished stress shielding.…”