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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 46 - 46
7 Aug 2023
INTERFERENCE AND KEEL DESIGN SIGNIFICANTLY INFLUENCE SAGITTAL MICROMOTION IN CEMENTLESS UNICOMPARTMENTAL KNEE ARTHROPLASTY
Rahman A Heath D Mellon S Murray D
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Abstract

Introduction

In cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions.

Method

A high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed.

Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_7 | Pages 85 - 85
1 Jul 2022
THE KEEL PLAYS A ROLE IN PERIPROSTHETIC FRACTURES OF THE TIBIAL COMPONENT IN CEMENTLESS UNICOMPARTMENTAL KNEE ARTHROPLASTY
Rahman A Heath D Mellon S Murray D
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Abstract

Introduction

In cementless UKR, primary fixation of the tibial component is achieved by press-fitting a keel (i.e. with interference) into a vertical slot cut into the proximal tibia. This may adversely affect the structural integrity of surrounding bone. Early post-operative peri-prosthetic tibial fractures are 7x more common in very small knees, but the aetiology of these fractures is unknown - such sizes are rarely used in the UK but more common in Asian populations. This study explores the effect of keel-related features in fracture risk of these very small tibias.

Method

This in vitro study compares the effect of keel and slot depth (standard vs 33% shallower vs nil) and loading position (anterior/posterior gait range limits: mid-tibia vs 8mm posterior) on fracture load and path. 3D-printed titanium components were implanted using surgical instrumentation/technique, in bone-analogue foam machined to a CT-reconstructed very small tibia which subsequently experienced a peri-prosthetic fracture.