2017 ISAKOS Biennial Congress ePoster #1701

 

MRI Validation of Tibial Tubercle Transfer Distance: A Clinical and Cadaveric Study

Joseph N. Liu, MD, Loma Linda, CA UNITED STATES
Sabrina M. Strickland, MD, New York, NY UNITED STATES
Douglas Mintz, MD, New York, NY UNITED STATES
Joseph T. Nguyen, MPH, New York, NY UNITED STATES
Jacqueline M. Brady, MD, Portland, OR UNITED STATES
Beth Ellen Shubin Stein, MD, New York, NY UNITED STATES

Hospital for Special Surgery, New York, New York, UNITED STATES

FDA Status Not Applicable

Summary

Surgeons often overestimate the anteriorization and medialization distance and the osteotomy angle in the Fulkerson Osteotomy; the steepest osteotomy angle possible is often less than 60 degrees.

Abstract

Introduction

The Fulkerson Osteotomy is a reliable method for treating moderate patellofemoral arthritis or overload and correcting extensor mechanism malalignment seen with patellar instability. However, studies that validate the tibial tubercle transfer distance or osteotomy angle have not been performed. The study’s purpose was to verify the amount of medialization and anteriorization estimated by surgeons intraoperatively with advanced postoperative axial imaging.

Methods

All patients that underwent tibial tubercle osteotomies with pre- and postoperative magnetic resonance imaging (MRI) studies were included. Using multiplanar reformats, the distances from the lateral edge of the fibula to the center of the tibial tubercle and from the posterior aspect of the tibia to the most anterior aspect of the tubercle were measured; the differences between pre- and postoperative MRI measurements were the distance medialized and anteriorized. The osteotomy angle was measured on the postoperative MRI with respect to the posterior tibia at the joint line. In order to help validate this method, osteotomies performed on 3 cadaver knee specimens were scanned with pre- and post-procedure MRIs to correlate intraoperative measurements with MRI findings.

Results

40 patients (41 knees) were included. Compared to intraoperative assessment, MRI measured medialization values average 94.7% (SD 37.7) of dictated values (p = 0.1). MRI measured anteriorization averaged less than half of dictated values (48.9%, SD 18.2%, p < 0.0001). MRI measured osteotomy angles averaged 67.2% of dictated values (SD 50.3%, p < 0.0001). In the cadaver specimens, the steepest osteotomy angle that could be performed (with or without using a commercially available jig) without endangering the posterior neurovascular structures measured 46 degrees on MRI.

Discussion

and Conclusions: Surgeons often overestimate the anteriorization and medialization distance and the osteotomy angle in the Fulkerson Osteotomy. The steepest osteotomy angle possible is often less than 60 degrees.