Development of a method to characterise tibial shape: Implications for the success of the Oxford Unicompartmental Knee arthroplasty

Antonia Trent, Alexander D Liddle, Stephen J Mellon, David Murray, Hemant Pandit, Elise Pegg

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Abstract

Introduction
The Oxford Unicompartmental knee arthroplasty (UKA) is indicated in patients with anteromedial osteoarthritis. Although the Oxford UKA preserves knee kinematics and function more than total knee replacement designs, outcome is variable with comparatively high revision rates reported. Proximal tibial (PT) shape shows considerable natural variation; however, it is unknown whether PT morphology has any impact on the functional outcome of the Oxford UKA.

Method
AP radiographs from 78 patients with 81 medial Oxford UKA were analysed to characterise PT shape according to 7 parameters, 4 dimensional and 3 angular. These were: Total Tibial Area (TTA); Tibial Area Beneath Tibial Tray (TABT); Tibial Width (TW); Tibial Canal Flare Index (TCFI); Lateral Tibial Angle (LTA); Medial Shaft Angle (MSA); Lateral Shaft Angle (LSA). The aims of the study were threefold: (1) to assess the feasibility of using a semi-automated measurement process by comparing Active Shape Modelling (ASM) results to manual measurements, (2) to assess the validity of the characterisation by comparing the resulting distributions to known variation in PT shape, (3) to assess the impact of established variation in PT morphology on functional outcome using the Oxford Knee Score (OKS).

Results
Results showed a high degree of correlation between ASM and manual measurements, particularly for the area measurements (TTA: 0.908, TABT: 0.922). Angular measurements were more reliably achieved using ASM (Inter-observer ICC LTA: 0.050). Bland-Altman plots demonstrated a consistent deviation in ASM dimensional results suggesting modification of the process is required (TTA MD: 330.37, TABT MD: 99.28). The validity of the characterisation was supported by trends in parameter variation according to gender, height, weight and age.

Conclusions
No association was found between PT shape and functional Oxford UKA outcome. However, this preliminary work was limited by cohort size and should be extended to allow for more high-powered analysis.
Original languageEnglish
Publication statusPublished - Aug 2013
Event4th Joint Meeting of the Bone Research Society & the British Orthopaedic Research Society - Oxford, UK United Kingdom
Duration: 4 Sep 20135 Sep 2013

Conference

Conference4th Joint Meeting of the Bone Research Society & the British Orthopaedic Research Society
CountryUK United Kingdom
CityOxford
Period4/09/135/09/13

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    Trent, A., Liddle, A. D., Mellon, S. J., Murray, D., Pandit, H., & Pegg, E. (2013). Development of a method to characterise tibial shape: Implications for the success of the Oxford Unicompartmental Knee arthroplasty. Poster session presented at 4th Joint Meeting of the Bone Research Society & the British Orthopaedic Research Society, Oxford, UK United Kingdom.