Advertisement for orthosearch.org.uk
Orthopaedic Proceedings Logo

Receive monthly Table of Contents alerts from Orthopaedic Proceedings

Comprehensive article alerts can be set up and managed through your account settings

View my account settings

Visit Orthopaedic Proceedings at:

Loading...

Loading...

Full Access

General Orthopaedics

The Accuracy of Leg Length and Offset Measurements Made by an Imageless Navigation System in Total Hip Arthroplasty

International Society for Technology in Arthroplasty (ISTA) 2012 Annual Congress



Abstract

Introduction

Leg length and offset are important considerations in total hip arthroplasty (THA). Navigation systems are capable of providing intra-operative measurements of leg length and offset, and high accuracy has been shown in experimental studies.

Objective

This in-vivo study assesses the accuracy of an imageless navigation system, with a pin-less femoral array, in measuring offset and leg length changes.

Method

A prospective, consecutive series of 24 patients undergoing navigated total hip arthroplasty were included in the study. Intra-operative measurements of leg length and offset were recorded using the navigation system. For each patient pre- and post-operative digital radiographs were scaled and analysed to provide radiographic measurements of change in leg length and offset.

Results

Measurements of leg length change made by the navigation system showed a statistically significant correlation with the size of change measured radiographically (R=.77, P < 0.0001). The mean difference between the radiographic and navigational measurement was 0.4 ± 2.8 mm. The navigation system was accurate to within 1 mm of the radiographic measurement in 50% of cases, within 2 mm in 67% of cases, and within 5 mm in 96% of cases.

Measurements of offset change by the navigation system also showed a statistically significant correlation with radiographic measurements, however the correlation was less pronounced (R=.47, P=0.02). The mean difference between navigational and radiographic measurements was 1.4 ± 6.4 mm. The navigation system was accurate to within 1 mm of the radiographic measurement in 8% of cases, within 2 mm in 25% of cases, and within 5 mm in 75% of cases.

Conclusion

This study demonstrates in-vivo that an imageless, non-invasive navigation system is a reliable tool for intra-operative leg length and offset measurement.