2017 ISAKOS Biennial Congress ePoster #1709

 

Major Factors that Affect Tibial Tuberosity-Trochlear Groove (TT-TG) Distance: A CT Study

Keitaro Tahara, MD, Tokyo JAPAN
Shuji Taketomi, MD, PhD, Tokyo JAPAN
Hiroshi Inui, PhD, Tokyo JAPAN
Kosuke Uehara, MD, Tokyo JAPAN
Nobuyuki Shirakawa, MD, Tokyo JAPAN
Sakae Tanaka, MD, PhD, Tokyo JAPAN

The University of Tokyo, Tokyo, JAPAN

FDA Status Cleared

Summary

We investigated the correlation of tibial tubercle-posterior cruciate ligament (TT-PCL) and femorotibial rotation with TT-TG distance which is an important parameter for the etiology and treatment of recurrent patellar dislocation. The results of this study using CT data revealed that both tubercle lateralization and femorotibial rotation were strongly associated with increased TT-TG distance.

Abstract

Background

Tibial tuberosity-trochlear groove (TT-TG) distance is an important parameter for the etiology and treatment of recurrent patellar dislocation (RDP). In patients with TT-TG distance of 20mm or more, tibial tubercle transfer or other distal realignment procedure is often needed in addition to medial patellofemoral ligament (MPFL) reconstruction. TT-TG distance is measured across the knee joint; therefore, various factors, such as femoral or tibial bony morphology or femorotibial rotation, can affect increased TT-TG distance. Some reports have recently suggested that tibial tubercle-posterior cruciate ligament (TT-PCL) distance, which is one of the parameters of proximal tibial morphology, or femorotibial rotation can elucidate the etiology of RDP. We hypothesized that most patients with increased TT-TG distance would show either tibial tubercle lateralization or femorotibial rotation.

Purpose

The purpose of this study was to clarify the correlation of TT-PCL and femorotibial rotation with TT-TG distance.

Methods

A consecutive series of 37 knees in 20 patients with RDP examined from 2010 to 2016 were included in this study. Patients who had undergone previous surgery for RDP were excluded from this study. There were three males and 17 females, with a mean age of 34.1 years (range, 14–65 years). TT-TG distance, TT-PCL distance, and femorotibial rotation were retrospectively measured using computed tomography (CT) in accordance with previous studies. The relationship between TT-TG distance and the other two parameters was statistically assessed using cluster analysis and multiple regression analysis.

Results

Thirty knees showed TT-TG distance of 20 mm or more on CT. Knees with increased TT-TG distance of 20 mm or more were divided into two groups: a group with TT-PCL distance of 24mm or more and femoral internal rotation of less than 9° and a group with TT-PCL distance of less than 24mm and femoral internal rotation of 9° or more. Knees with TT-TG distance of less than 20 mm were categorized as patients with TT-PCL distance of less than 24mm and femoral internal rotation of less than 9°. Both the TT-PCL distance and femorotibial rotation were strongly correlated with TT-TG distance (adjusted R²=0.71).

Discussion

The results of this study showed that there were two major factors related to increased TT-TG distance: tubercle lateralization and femorotibial rotation. Although the distal realignment procedure has usually been performed for RDP with increased TT-TG distance, a different type of surgery may be required for different pathological conditions.