Introduction

Previous studies have shown that the instantaneous centre of rotation (ICR) of the stifle moves following cranial cruciate ligament transection. Restoration of ICR position might be indicative of successful stifle stabilisation surgery.

Objectives

The aim of this study was to identify ICR positional changes following cranial cruciate ligament transection (CCU), medial meniscal release (MMR) and triple tibial osteotomy (TTO) compared to intact canine stifles.

Methods

Fluoroscopic video recordings were obtained from 9 stifles under intact, CCU, MMR and TTO conditions. Using cubic splines and a least squares approach, bony landmarks were used to calculate ICR positions, and resulting curves aligned and scaled using Blumensaat’s line to enable visual comparison (Figure 1).

Figure 1 ICR coordinate system x-axis aligned with Blumensaat ‘s line on femur.

Results

The shape, range and general location of ICR curves were broadly similar within each condition, particularly for intact and TTO. Visually, there were curve similarities between intact and TTO conditions and between MMR and CCU conditions. Curve variability increased markedly in MMR and CCU stifles and was reduced (but not to intact levels) following TTO (Figure 2). ICR curves in CCU and MMR stifles were displaced proximally relative to Blumensaat ‘s line compared to intact stifles. TTO surgery reduced but did not eliminate this displacement, possibly reflecting residual instability or changes in effective joint angle.

Figure 2. Mean ICR coordinates

Conclusions

Analysis of ICR curves may assist in identifying which stifle stabilisation techniques are biomechanically superior for management of cranial cruciate ligament deficiency, despite assessment being limited to the sagittal plane.