Meniscal and Cartilage Changes on Serial MRI After Medial Opening-Wedge High Tibial Osteotomy

Abstract

Background: Assessments of the effects of realignment using opening-wedge high tibial osteotomy (OWHTO) on the medial, lateral, and patellofemoral compartments have been limited to cartilage evaluations.

Purpose/hypothesis: The purpose was to evaluate the effects of OWHTO on the meniscus and cartilage of each compartment as a cooperative unit (meniscochondral unit) using serial magnetic resonance imaging (MRI). It was hypothesized that (1) favorable changes in the meniscochondral unit would occur in the medial compartment and (2) that changes in the patellofemoral and lateral compartments would be negligible.

Study design: Case series; Level of evidence, 4.

Methods: Included were 36 knees that underwent OWHTO from March 2014 to February 2016 and had postoperative serial MRI. The MRI was performed at 19.9 ± 7.4 and 52.3 ± 8.3 months postoperatively, and the cartilage and meniscal changes were evaluated by highlighting the regions of interest. We evaluated the T2 relaxation times of each cartilage and meniscal area, the cross-sectional area of the menisci, and the extrusion of the medial meniscus (MM). The meniscochondral unit was assessed using subgroup analyses according to the status of the MM.

Results: Significant decreases were seen in T2 relaxation times in the medial femoral condyle (MFC) (P < .001) and medial tibial plateau (MTP) (P = .050), and significant increases were seen in the lateral femoral condyle (LFC) (P = .036). The change was more prominent in the MFC compared with the MTP and LFC (P = .003). No significant changes were observed in the lateral tibial plateau, patella, or trochlear groove. The area of the lateral meniscus (body and posterior horn) was decreased compared with preoperative MRI (P < .001 for both). The extent of MM extrusion decreased between the preoperative, first follow-up, and second follow-up MRIs (P < .001).

Conclusion: OWHTO affected the medial compartment positively, the lateral compartment negatively, and the patellofemoral compartment negligibly. The effects were more prominent and consistent in the medial than in the lateral compartment.

Keywords: T2 relaxation time; cartilage; magnetic resonance imaging; meniscus; opening wedge high tibial osteotomy.

Figure 1.

Flowchart for study selection. ACLR, anterior cruciate ligament reconstruction; HTO, high tibial osteotomy; MRI, magnetic resonance imaging; OWHTO, opening-wedge high tibial osteotomy.

Figure 2.

Regions of interest were drawn manually to delineate cartilage areas of the T2 mapping images. The T2 maps were color-coded on the drawn regions of interest (ROIs) from 1 to 81 milliseconds on a pixel-by-pixel basis. (A, C, E) Scout images for selecting the cut that draws the ROIs. (B, D, F) Sagittal cuts of red dashed line points on A, C, and E images. The ROIs for the (B) medial and (D) lateral compartment were drawn at the most prominent point of each femoral condyle using the coronal scout images to match the slices (dashed lines in A and C). (F) The ROIs for the patellofemoral compartment were drawn on the ridge of the patella (dashed line in E) and the deepest point of the trochlear groove.

Figure 3.

Evaluation of T2 relaxation time in the medial and lateral menisci. The regions of interest (ROIs) were drawn separately on the anterior and posterior horn of the (A) medial meniscus and (B) lateral meniscus. The T2 maps were color- coded on the drawn ROIs from 1 to 81 milliseconds on a pixel-by-pixel basis.

Figure 4.

Measuring the cross-sectional area of the meniscus. The (A) meniscal body, (B) anterior and posterior horn were segmented separately for the lateral (B) and medial (C) meniscus, and the cross-sectional area of each segment was measured using regions of interest drawn by hand.

Figure 5.

The extent of the medial meniscal extrusion on magnetic resonance imaging. The extent of medial meniscal extrusion was measured from the medial margin of the tibial plateau (right yellow arrow) to the medial margin of the medial meniscus (left yellow arrow) on the image at the midpoint of the medial femoral condyle.