MRI findings change after medial opening-wedge high tibial osteotomy for medial knee osteoarthritis

Abstract

Purpose: Medial opening-wedge high tibial osteotomy (OWHTO) is a surgical procedure that aims to correct the weight-bearing axis of the knee, moving the loads laterally from the medial compartment. In many studies, it was reported that medial OWHTO improved pain in medial knee osteoarthritis (OA). But it isn’t unclear how MRI findings change and why knee pain improves after OWHTO. The purpose was to prospectively evaluate the compartmental changes of OWHTO for medial knee OA with MRI. Methods: 13 medial knee OA patients (mean age 61 ± 9.3 years) with 17 knees undergoing medial OWHTO were assessed pre- and postoperatively with MRI. The implant removal surgery was done 25.4 ± 9.8 months after OWHTO. Pain at rest and walking were assessed using a 0 to 100 Visual Analogue Scale (VAS). Postoperative MRI was done after the implant removal surgery. Subchondral bone marrow lesions (BMLs) area at the medial compartment was calculated through the slice which showed maximum size of BMLs area in the coronal plane using the fat-suppressed T2-weighted FSE images. The articular cartilage and synovitis were scored using Whole-Organ Magnetic Resonance Imaging Scores (WORMS). Femorotibial angle (FTA), the percentage of mechanical axis (%MA), VAS pain at rest, VAS pain at walking, BMLs area, articular cartilage score, synovitis score and relative percentage of medial meniscus extrusion were examined. Results: Preoperative and postoperative assessments of measurements are summarized in Table 1. FTA and %MA were corrected to 180 (IQR 180,183) and 65.8 (IQR 60.4, 69.4) respectively (p < 0.01). VAS pain at rest and walking were reduced after surgery (p<0.05, p<0.01 respectively). BMLs area at both femur and tibia reduced after surgery (p < 0.05). But lateral tibiofemoral joint (LTFJ) and patellofemoral joint (PFJ) articular cartilage score, synovitis score and relative percentage of medial meniscus extrusion weren’t improved after surgery. Conclusions: In this study, OWHTO improved VAS pain and reduced BMLs area. Maybe BMLs area can be associated with pain relief in knee OA after OWHTO. On the other hand, OWHTO couldn’t improve degenerative LTFJ and PFJ articular cartilage score, synovitis score and medial meniscus extrusion. But the further studies will be needed regarding synovitis and medial meniscus extrusion. Because in this study we didn’t use contrast-enhanced MRI, there were possibility that synovitis wasn’t assessed accurately. And also, regarding the meniscus extrusion, we need to assess that not only in a supine position but also in a standing position.Tabled 1Table 1. Details of assessments of measurementspreoperativepostoperativeFTA (°)180 (180, 183)170 (168, 171) **%MA (%)19.0 (13.9, 22.7)65.8 (60.4, 68.4) **VAS pain at rest (0-100)10 (2.5, 15)0 (0, 2.5) *VAS pain at walking (0-100)50 (30, 75)0 (0, 15) **BMLs area at medial femur (cm2)45.6 (0, 96.7)12.3 (6.7, 50.8) *BMLs area at tibia (cm2)52.0 (7.7, 131.6)28.9 (0, 63.6) *MTFJ articular cartilage score (0-30)13 (12, 16)12 (11, 18)LTFJ articular cartilage score (0-30)0 (0, 2)2 (1, 3) *PFJ articular cartilage score (0-24)3 (1, 4)6 (4, 6.5) **Synovitis score (0-3)1 (1, 2)1 (1, 2)Meniscus extrusion (%)52.8 (44.1, 60.7)47.1 (31.2, 62.5) Open table in a new tab