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General Orthopaedics

REVISIONS OF THE OXFORD PHASE 3 CEMENTED MEDIAL UNICOMPARTMENTAL KNEE JOINT ARTHROPLASTY: AN AUDIT OF THE NEW ZEALAND JOINT REGISTRY OVER TEN YEARS

12th Combined Meeting of the Orthopaedic Associations (AAOS, AOA, AOA, BOA, COA, NZOA, SAOA)



Abstract

Purpose

To identify the incidence and reasons for revision of the Oxford prosthesis (OXF) in New Zealand.

Methods

Review and compare UKA and TKA data including patient-generated Oxford scores after operation.

Results

105 surgeons performed 3,624 OXF (66.5% of all UKA). UKA made up 12.8% of all knee arthroplasties. There were 216 OXF revisions and revision rate (RR) of 1.39 per 100 component-years (p100cy); for UKA this was 1.42 p100cy, and for TKA 0.54 p100cy (OXF vs TKA p< 0.0001). The indications for OXF revisions were unexplained pain (38.0%); aseptic loosening (38.0%); bearing dislocation (9.3%) and deep sepsis (4.2%). For TKA, unexplained pain (28%) was significantly lower than from OXF (p=0.005). Revision for deep sepsis was significantly lower for OXF compared with TKA (4.2% vs 13.1%, p < 0.001). The Oxford scores 6 months post-op were excellent or good in 79% of OXF vs 72% TKA patients (p< 0.0001); at 5 years after operation these were 88% for OXF and 81% for TKA (p=0.001). Twenty high-use OXF surgeons (10 or more operations/year) performed 44% of the operations (RR of 1.3 p100cy), 62 medium-use surgeons (2-9/year) performed 54% (RR of 1.3 p100cy). 23 low-use surgeons (2 or less/year) performed 2% (RR of 3.9p100cy). The differences in RR high vs low users (p< 0.001) and medium vs low groups (p< 0.001) were significant. RR for OXF high or medium users was significantly higher than the overall rate for TKA (p< 0.001).

Conclusion

RR for the OXF was 2.5 times greater than that for TKA. Deep infection rate was lower, and 6-month and 5-year function scores were significantly higher OXF vs TKA.


R Tregonning, Wellington School of Medicine & Health Sciences, 5 Anne St, Wellington 6012, New Zealand