Comparing the Effects of Lateral Opening Wedge Distal Femoral Osteotomy and Medial Closing Wedge High Tibial Osteotomy on Tibial Tubercle–Trochlear Groove Distance: A 3D Computed Tomography Simulation Study

Abstract

Background:

Genu valgum is a known risk factor for recurrent patellar instability, and surgical correction of deformity can be utilized as part of the management strategy to improve tracking and optimize outcomes. Tibial tuberosity–trochlear groove (TT-TG) distance is a widely used objective measurement of the lateral quadriceps force vector in patients with patellar instability. The evidence documenting the effect of lateral opening wedge distal femoral osteotomy (LOWDFO) and medial closing wedge high tibial osteotomy (MCWHTO) on TT-TG is limited, with minimal data directly comparing the biomechanical implications of one versus the other.

Purpose/Hypothesis:

The purpose of this study was to directly compare LOWDFO and MCWHTO using a computer model to determine the effect of each osteotomy on TT-TG distance. It was hypothesized that LOWDFO would have a greater effect on TT-TG distance, given the position farther away from the tibial tubercle.

Study Design:

Descriptive laboratory study.

Methods:

A total of 22 knees from 21 patients with patellar instability and valgus malalignment were processed using 3D Slicer (Version 5.4.0) to convert their respective DICOM images into .stl mesh files to be used with Fusion (Autodesk; Version 2601.1.37) computer-aided design software. LOWDFOs and MCWHTOs were then simulated from 0° to 12° in 2° increments. TT-TG distance was then measured after each osteotomy.

Results:

The mean native TT-TG distance for patients included in this cohort was 15.97 mm. TT-TG distance decreased by a mean of 1.83 mm for every 2° in the LOWDFO group and 0.46 mm for every 2° in the MCWHTO group, with all comparisons meeting statistical significance (P < .001). LOWDFO demonstrated the following incremental TT-TG changes for a 2° to 12° coronal plane correction: 1.81 mm, 3.63 mm, 5.46 mm, 7.31 mm, 9.18 mm, and 10.96 mm. In comparison, MCWHTO demonstrated the following TT-TG changes for the same degrees of coronal correction: 0.52 mm, 1.03 mm, 1.53 mm, 2.00 mm, 2.45 mm, and 2.80 mm (P < .001).

Conclusion:

LOWDFO results in a significantly larger magnitude of change in the TT-TG compared with MCWHTO, with distal femoral osteotomy at almost a 1:1 change with TT-TG compared with the correction angle, and high tibial osteotomy about 1:4.

Clinical Relevance:

The LOWDFO may be a more effective procedure in reducing the TT-TG distance, which is important when addressing patellar instability in patients with valgus malalignment.