AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY

Chau R, Gulati A, Pandit HG, et al. AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY. Orthop Procs. 2009;91-B(SUPP_III):411-412. doi:10.1302/0301-620X.91BSUPP_III.0910411e

Chau, R, et al. “AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY.” Orthopaedic Proceedings, vol. 91-B, no. SUPP_III, 2009, pp. 411-412., https://doi.org/10.1302/0301-620X.91BSUPP_III.0910411e

Chau, R., Gulati, A., Pandit, H. G., Beard, D. J., Gill, H. S., Dodd, C. A. F., Simpson, D. J., & Murray, D. W. (2009). AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY. Orthopaedic Proceedings, 91-B(SUPP_III), 411-412. https://doi.org/10.1302/0301-620X.91BSUPP_III.0910411e

Chau, R., Gulati, A., Pandit, H. G., Beard, D. J., Gill, H. S., Dodd, C. A. F. et al. (2009) “AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY.” Orthopaedic Proceedings, 91-B(SUPP_III), pp. 411-412. Available at: https://doi.org/10.1302/0301-620X.91BSUPP_III.0910411e

Chau, R, A Gulati, H G Pandit, D J Beard, H S Gill, C A F Dodd, D J Simpson, and D W Murray. “AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY.” Orthopaedic Proceedings 91-B, no. SUPP_III (2009): 411-412. https://doi.org/10.1302/0301-620X.91BSUPP_III.0910411e

Chau R, Gulati A, Pandit HG, Beard DJ, Gill HS, Dodd CAF, et al. AN ACCEPTABLE LIMIT OF TIBIAL COMPONENT OVERHANG IN THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY. Orthop Procs. 2009 Sep 1;91-B(SUPP_III):411-412. https://doi.org/10.1302/0301-620X.91BSUPP_III.0910411e

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Abstract

Purpose: To evaluate the effects of underhanging/overhanging tibial components on clinical outcome following the Oxford unicompartmental knee arthroplasty (UKA), and to identify an acceptable sizing limit.

Method: One hundred and sixty-three knees which had undergone the Phase 3 medial Oxford UKA (Biomet, Swindon) were measured. Based on five-year post-operative radiographs, they were divided into groups with tibial component underhang (n=38), none or minimal overhang of less than three millimetres (n=121), and a group with overhang equal to or in excess of three millimetres (n=13). Clinical outcome was assessed by changes in the twelve-question Oxford Knee Score (ΔOKS) and pain score (ΔPS) component (questions 1,4,5,8,9) from pre-operative assessment to five years following surgery.

Results: At five years after surgery, ΔOKS was significantly worse in the overhang group compared to both the neutral and underhang groups (p=0.015, and p=0.028 respectively). ΔPS was also shown to be significantly worse between the overhang and the neutral group (p=0.026 respectively).

Conclusion: Appropriate sizing of the tibial component is essential to optimise load bearing in total knee arthroplasty. In UKA such sizing is critical due to halving of the bony support for the tibial component and the lack of room for a large stem. Excessive undersizing of the prosthesis may lead to subsidence and loosening, whilst excessive overhanging may cause local soft tissue irritation and pain.

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.

Correspondence should be addressed to Mr T Wilton, c/o BOA, BASK at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.