Relationship between Tibial conformation, cage size and advancement achieved in TTA procedure

R L Meeson,I Calvo,M C Conroy,L Corah

doi:10.1186/s12917-018-1433-0

Abstract

BackgroundPrevious studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted. The purpose of this study was to test and quantify this in clinical cases. The hypothesis was that the advancement of the tibial tuberosity as measured by the widening of the proximal tibia at the tibial tuberosity level after a standard TTA, will be less than the cage sized used, with no particular cage size providing a relative smaller or higher under-advancement, and that the conformation of the proximal tibia will have an influence on the amount of advancement achieved.ResultsOne hundred sixty-four dogs met the inclusion criteria. The mean percentage under-advancement was 15.5%. All dogs had an advancement less than the stated cage size inserted. An association between the proximal tibial tuberosity angle (increased in cases with low patellar tendon insertion), and percentage under-advancement was found, with an increase of 0.45% under-advancement for every 1 degree increase in angle a (p = 0.003). There was also evidence of a difference between the mean percentage under-advancement in breeds (p = 0.001) with the Labrador having the biggest under-advancement. Cage size (p = 0.83) and preoperative tibial plateau angle (p = 0.27) did not affect under-advancement.ConclusionsThe conformation of the tibial tuberosity and therefore the relative cage positioning have an impact on mean percentage under-advancement of the tibial tuberosity after standard TTA. In all evaluated cases, the advancement of the tibial tuberosity was less than intended by the cage size selected.

Highlights

Previous studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted
The translation distance required of the tibial tuberosity to advance the patellar tendon angle to a 90 degree tangent to the tibial plateau is measured pre-operatively by one of several methods, at the level of the patellar tendon insertion point [11]
A cage size matching the required translation distance is inserted into the osteotomy with the intention of advancing the patellar tendon insertion the intended distance and subsequently altering the patella-tendon angle (PTA) to the desired advancement

Summary

Introduction

Previous studies have suggested that there is a theoretical discrepancy between the cage size and the resultant tibial tuberosity advancement, with the cage size consistently providing less tibial tuberosity advancement than predicted. One of the newer surgical techniques, the tibial tuberosity advancement (TTA), has been shown to reduce tibial translation in the CCL-deficient stifle and to provide good clinical outcomes [9]. The translation distance required of the tibial tuberosity to advance the patellar tendon angle to a 90 degree tangent to the tibial plateau is measured pre-operatively by one of several methods, at the level of the patellar tendon insertion point [11]. A cage size matching the required translation distance is inserted into the osteotomy with the intention of advancing the patellar tendon insertion the intended distance (cage size) and subsequently altering the patella-tendon angle (PTA) to the desired advancement

Objectives

Methods

Results

Conclusion