SLR - March 2018 - Kurt A. Kibler

Added Value of Preoperative Computed Tomography for Determining Cartilage Degeneration in Patients with Osteochondral Lesions of the Talar Dome

Reference: Nakasa T, Ikuta Y, Yoshikawa M, Sawa M, Tsuyuguchi Y, Adachi N. Added Value of Preoperative Computed Tomography for Determining Cartilage Degeneration in Patients with Osteochondral Lesions of the Talar Dome Am J Sports Med. 2018 Jan;46(1):208–216. doi: 10.1177/0363546517732035. Epub 2017 Oct 10.

Scientific Literature Review

Reviewed By: Kurt A. Kibler, DPM
Residency Program: Grant Medical Center, Columbus, OH

Podiatric Relevance: Osteochondral lesions of the talus (OLTs) often lead to deep ankle pain that is debilitating. Foot and ankle surgeons most often use magnetic resonance imaging (MRI) for preoperative planning. However, increases in signal intensity due to subchondral edema can be patient-dependent and can mislead the surgeon regarding the amount of articular degeneration. The hypothesis of this study is that computed tomography (CT) can successfully evaluate bone metabolism by examining osseous characteristics.

Methods: This was a retrospective study reviewing 58 ankles treated surgically for the treatment of OLTs between January 2008 and January 2017. All underwent preoperative CT with evaluation of the ankle. On the coronal and sagittal views, measurements were taken to assess the area of the lesion. All patients then underwent arthroscopic surgery. The lesions were graded intraoperatively using the Ferkel arthroscopic rating system, which evaluates the articular surface. Then the lesion was evaluated using the International Cartilage Repair Society (ICRS) grading system, which evaluates depth. The lesion was preserved if the ICRS grade was 1 or 2. If unstable, the fragment was fixated with poly-L-lactide pins. The fragment was excised if the ICRS grade was 3 or 4. If the fragment was fixated, a needle biopsy was taken to evaluate the bone. If the fragment was excised, the fragment was sent for analysis, in attempt to correlate CT findings with histologic signs of osseous turnover. Postoperatively, the patients were followed up regularly with AOFAS questionnaires. At one year, an MRI was taken to evaluate articular surface congruity.  

Results: Fragments were preserved in 19 out of the 30 ankles in this study. Thirteen of the 19 were fixated due to instability. The remaining 11 ankles had fragments that were excised. There was a statistically significant difference in age between the two groups (16.0 versus 24.9). There was no significant difference in depth of lesions. On CT, all excision group lesions showed subchondral bed sclerosis, while only 42 percent of the preservation group had this factor. This correlated with the analysis of the fragments isolated. Fine-needle biopsy showed cartilage separation from the subchondral base plate. The deep layers showed ossification nuclei when the base plate was thin or absent. Sclerosis and absorption was present in 78 percent of the cases. Mean follow-up was 18.8 months in the preservation group and 22.5 months in the excision group with a statistically significant improvement in AOFAS scores.

Conclusions: The authors compared CT readings with histologic analysis of OLTs. They attempted to correlate findings, such as sclerosis and absorption, in both samples to evaluate CT as a viable imaging modality. The results suggest that unstable lesions do not maintain cartilage metabolism and lead to sclerosis and absorption. They also propose a method of using CT to determine whether or not to excise or preserve fragments of cartilage from OLTs with no successful way to regenerate articular cartilage to date. This study suggests that CT is a reliable method for surgical planning of OLTs. 

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