MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION

Irene Yang; Jonathan D. Gammell; David W. Murray; Stephen J. Mellon

doi:10.1302/1358-992X.2021.16.020

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MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION

The British Orthopaedic Research Society (BORS) Annual Meeting 2021, held online, 13–14 September 2021.

Irene Yang
Jonathan D. Gammell
David W. Murray
Stephen J. Mellon

MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION

Yang I, Gammell JD, Murray DW, Mellon SJ. MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION. Orthop Procs. 2021;103-B(SUPP_16):20-20. doi:10.1302/1358-992X.2021.16.020

Yang, Irene, et al. “MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION.” Orthopaedic Proceedings, vol. 103-B, no. SUPP_16, 2021, pp. 20-20., https://doi.org/10.1302/1358-992X.2021.16.020

Yang, I., Gammell, J. D., Murray, D. W., & Mellon, S. J. (2021). MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION. Orthopaedic Proceedings, 103-B(SUPP_16), 20-20. https://doi.org/10.1302/1358-992X.2021.16.020

Yang, I., Gammell, J. D., Murray, D. W. and Mellon, S. J. (2021) “MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION.” Orthopaedic Proceedings, 103-B(SUPP_16), pp. 20-20. Available at: https://doi.org/10.1302/1358-992X.2021.16.020

Yang, Irene, Jonathan D. Gammell, David W. Murray, and Stephen J. Mellon. “MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION.” Orthopaedic Proceedings 103-B, no. SUPP_16 (2021): 20-20. https://doi.org/10.1302/1358-992X.2021.16.020

Yang I, Gammell JD, Murray DW, Mellon SJ. MODIFYING THE DESIGN OF THE OXFORD DOMED LATERAL UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT REDUCES THE RISK OF MEDIAL BEARING DISLOCATION. Orthop Procs. 2021 Dec 1;103-B(SUPP_16):20-20. https://doi.org/10.1302/1358-992X.2021.16.020

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Abstract

Background

The Oxford Domed Lateral (ODL) Unicompartmental Knee Replacement (UKR) has some advantages over other lateral UKRs, but the mobile bearing dislocation rate is high (1–6%). Medial dislocations, with the bearing lodged on the tibial component wall, are most common. Anterior/posterior dislocations are rare. For a dislocation to occur distraction of the joint is required. We have developed and validated a dislocation analysis tool based on a computer model of the ODL with a robotics path-planning algorithm to determine the Vertical Distraction required for a Dislocation (VDD), which is inversely related to the risk of dislocation.

Objectives

To modify the ODL design so the risk of medial dislocation decreases to that of an anterior/posterior dislocation.

Methods

The components were modified using Solidworks. For each modification the dislocation analysis tool was used to determine the VDD for medial dislocation (with bearing 0–6mm from the tibial wall). This was compared with the original implant to identify the modifications that were most effective at reducing the dislocation risk. These modifications were combined into a final design, which was assessed.

Results

Modifying the tibial component plateau, changing the femoral component width and making the bearing wider medially had little effect on VDD. Shifting the femoral sphere centre medially decreased VDD. Shifting the femoral sphere laterally, increasing tibial wall height and increasing bearing width laterally increased VDD. A modified implant with a femoral sphere centre 3mm lateral, wall 2.8mm higher, and bearing 2mm wider laterally, implanted so the bearing is ≤4mm from the tibial wall with a bearing thickness ≥4mm had a minimum VDD for medial dislocation of 5.75mm, which is larger than the minimum VDD for anterior/posterior dislocation of 5.5mm.