Implant Size Availability Affects Reproduction of Distal Femoral Anatomy

William Z. Morris, Jeremy J. Gebhart, Victor M. Goldberg, Glenn D. Wera

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

A total knee arthroplasty system offers more distal femoral implant anterior-posterior (AP) sizes than its predecessor. The purpose of this study is to investigate the impact of increased size availability on an implant system's ability to reproduce the AP dimension of the native distal femur. We measured 200 cadaveric femora with the AP-sizing guides of Zimmer (Warsaw, IN) NexGen (8 sizes) and Zimmer Persona (12 sizes) total knee arthroplasty systems. We defined size deviation as the difference in the AP dimension between the anatomic size of the native femur and the closest implant size. We defined satisfactory reproduction of distal femoral dimensions as < 1 mm difference between the implant and native femur size. The NexGen system was associated with a mean 0.46 mm greater implant size deviation than Persona (p < 0.001). When using a 1 mm size deviation as a cutoff for satisfactory replication of the native distal femoral anatomy, 85/200 specimens (42.5%) were a poor fit by NexGen, but a satisfactory fit by Persona. Only 1/200 specimens (0.5%) was a poor fit by Persona, but a satisfactory fit by NexGen (p < 0.001). The novel knee system with 12 versus 8 sizes reproduces the AP dimension of the native distal femur more closely than its predecessor. Further study is needed to determine the clinical impact of these differences.

Original languageEnglish (US)
Pages (from-to)409-413
Number of pages5
JournalJournal of Knee Surgery
Volume29
Issue number5
DOIs
StatePublished - Jul 1 2016
Externally publishedYes

Keywords

  • cadaveric study
  • implant personalization
  • implant sizing
  • total knee arthroplasty

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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