2017 ISAKOS Biennial Congress ePoster #1038

 

Strength Testing Following Anterior Cruciate Ligament Reconstruction. A Prospective Cohort Study Investigating Overlap of Tests

Kristoffer W. Barfod, MD, PhD, Virum DENMARK
Julian A. Feller, FRACS, FAOrthA, Melbourne, VIC AUSTRALIA
Ross Clark, PhD, Melbourne, Victoria AUSTRALIA
Taylor Hartwig, MSc, Melbourne AUSTRALIA
Brian M. Devitt, MD, PhD, FRCS, FRACS, Dublin, Leinster IRELAND
Kate E. Webster, PhD, Bundoora, Victoria AUSTRALIA

OrthoSport Victoria Research Unit, Deakin University and Epworth HealthCare, Melbourne, Victoria, AUSTRALIA

FDA Status Not Applicable

Summary

This is a prospective cohort study aimed to determine whether overlap exists between individual tests in a strength testing protocol used after ACL reconstruction. On the basis of overlap between tests, there is little room for omission of strength testing protocol components.

Abstract

Introduction

Restoration of muscle strength after anterior cruciate ligament (ACL) reconstruction is considered important in order to safely return to sport, but comprehensive strength testing protocols can be very time-consuming. The purpose of the present study was to determine whether overlap exists between individual tests in one such protocol. If overlap were present, one or more components could potentially be omitted to make the testing protocol more efficient, but without compromising the usefulness of the testing.

Methods

The study was performed as a prospective cohort study of 69 patients (46 male, 23 female) who completed 6 and 12 months testing after ACL reconstruction. The following knee flexor and extensor strength tests were performed using a HUMAC NORM Dynamometer: isokinetic concentric strength at 60°/s and 180°/s, isokinetic eccentric strength at 60°/s, and isometric knee flexor strength at 60° flexion. Peak and average torque values were extracted and the ratio between the operated and non-operated limb calculated as a limb symmetry index. Overlap of strength tests was investigated by fitting a linear regression model to the data with an R2 threshold of 0.7 used as an indication of overlap.

Results

Overlap between peak and mean torque was present for extensor and flexor concentric and eccentric measurements at 12 months and for concentric measurements at 6 months. Peak torque measurements were therefore used for subsequent analysis. Concentric extensor peak torque at 60deg/s and 180deg/s showed overlap at 6 months (R2 = 0.73) but not at 12 months (R2 = 0.37). No other overlap was identified.

Conclusions

On the basis of overlap between tests, there is little room for omission of strength testing protocol components. However, either peak or mean torque values can be used. Only concentric knee extensor peak torque at 60deg/s and 180deg/s showed overlap at 6 months, but as there was no overlap for knee flexor peak torque, there is little to be gained by testing at only one speed.