Summary

This project presents a case series centered around the evaluation of clinical and MRI-based healing of osteochondritis dissecans lesions treated with open reduction internal fixation and assessed with short echo time gradient-recalled T2* MRI mapping sequence.

Abstract

Introduction

Osteochondritis dissecans (OCD) of the knee can be a challenging pathology to achieve healing dependably. We have utilized an advanced MRI protocol that provides a CT-like bone window to evaluate healing of unstable OCD lesions following open bone grafting and fixation [1,2]. This is a case series evaluating the clinical healing and MRI-based healing following this approach.

Methods

Patients were identified with an OCD lesion utilizing short echo time (TE = 2.6 ms) gradient-recalled echo (GRE) T2* mapping sequence (repetition time = 1150 ms, resolution = 0.43×0.43×2 mm3), which is a routine clinical MRI sequence. The MRI findings were evaluated on the short TE GRE images with inverted CT-like bone window and were correlated with clinical symptoms. All patients treated surgically with open reduction internal fixation (ORIF) with proximal tibial bone grafting of the OCD who also underwent a post-operative MRI with bone windows were included. All patients were treated with metal screws and subsequent hardware removal followed by post-operative MRI. The MRI was interpreted by a musculoskeletal radiologist as healing/healed or non-healing. Clinical healing was also assessed based on pre-operative symptoms prior to hardware removal and an assessment of the stability of the OCD fragment at the time of hardware removal.

Results

This study included 16 knees from 14 patients (10 male, 4 female, mean age at time of surgery 16.6 years, range 10-23 years). This was a revision surgery in 3 knees and primary surgery in 13 knees. Post-operative complete or ongoing healing was observed in 15/16 knees, with the mean time from surgery to post-operative MRI being 12.2 months. All knees had no swelling, pain, or other symptoms prior to hardware removal. All OCD lesions were found to be healed at the time of hardware removal, except for one which demonstrated healing of 60-70% of lesion while the remainder of the lesion was loose and removed at the time of surgery. No patients have required revision surgery utilizing this technique.

Discussion

From the patients in this study, 93.75% demonstrated complete or ongoing healing upon evaluation of post-operative MRI. From a clinical perspective, all patients demonstrated satisfactory clinical healing prior to progressing to the hardware removal stage. Despite the fact that one patient was categorized to have a non-healing lesion on MR imaging and had a portion of the lesion removed, none of the patients in this study have required revision surgery. This patient cohort demonstrates that surgical intervention with proximal tibial bone grafting and ORIF for unstable OCD lesions provides predictable clinical and radiographic healing.

References
1. Ellermann J, Johnson CP, Wang L, et al. 2017. Insights into the Epiphyseal Cartilage Origin and Subsequent Osseous Manifestation of Juvenile Osteochondritis Dissecans with a Modified Clinical MR Imaging Protocol: A Pilot Study. Radiology 282:798-806.
2. Zbyn S, Santiago C, Johnson CP, et al. 2021. Compositional evaluation of lesion and parent bone in patients with juvenile osteochondritis dissecans of the knee using T2 * mapping. J Orthop Res.