- In this retrospective study, advanced CT modeling was used to quantify the subchondral region of capitellar osteochondritis dissecans (OCD) lesions in 15 patients and compare bone thickness with that of 12 patients with an intact capitellum
- Patients with capitellar OCD had significantly thicker regions of high-density subchondral bone than patients whose elbows had no OCD lesions
- When compared, CT and MRI measurements of subchondral bone thickness were found to be highly correlated by the authors, with low measurement errors; MRI may be a reasonable means of evaluating subchondral bone thickness
- Knowledge of subchondral bone thickness may improve healing potential after arthroscopic debridement and drilling, microfracture, or osteochondral autologous transplantation
Unstable osteochondritis dissecans (OCD) lesions of the capitellum generally demonstrate signs of subchondral sclerosis, but it's unclear whether that reflects reduced healing potential.
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Satoshi Miyamura, MD, PhD, a fellow in the Department of Orthopaedic Surgery at Massachusetts General Hospital, Neal C. Chen, MD, chief of the Hand & Arm Service, and colleagues studied this issue quantitatively and observed increased subchondral bone thickness around capitellar OCD lesions. In The Journal of Hand Surgery, American volume, they explain the implications of their findings for surgical planning.
The retrospective study included 15 patients,12 to 20 years old (average age, 14) who were diagnosed with capitellar OCD between January 2004 and July 2018 and had a CT scan available. 12 of those patients underwent an MRI examination at the time of the CT.
The patient group was compared with 12 control subjects, average age of 19, who had a normal capitellum and underwent CT scanning for treatment of other upper-extremity conditions.
The researchers used the CT data to construct three-dimensional models of the humerus of each subject. This method enabled them to visualize the subchondral bone thickness at the OCD lesion as a colored contour map. Bone thickness was measured relative to the condylar height at the centroid and at the lateral, medial, superior, and inferior edge points of the OCD lesion.
Subchondral Bone Thickness
The tangential thickness of subchondral bone was significantly higher in the OCD group than in the control group (P<0.05 for all comparisons):
- Lateral edge—41% vs. 6%
- Centroid—34% vs. 13%
- Medial edge—31% vs. 14%
The sagittal bone thickness was also significantly higher in the OCD group:
- Superior edge—23% vs. 14% (P<0.05)
- Centroid—32% vs. 13% (P<0.01)
- Inferior edge—26% vs. 4% (P<0.01)
Larger OCDs tended to have higher bone density.
Correlation of CT and MRI
MRI measurements of subchondral bone thickness were highly correlated with CT measurements (r=0.75).
The mean error of the measurements was 4.9% between MRI sagittal and CT sagittal thickness, 6.2% between MRI axial and CT tangential thickness, and 9.1% between MRI coronal and CT tangential thickness.
Applying the Results to the Clinic
In debridement, microfracture, and drilling of OCD lesions, the goal is to debride or puncture the subchondral bone sufficiently to allow marrow elements to egress into the lesion bed. These findings suggest:
- The depth of puncture should be about 7.5 mm to penetrate beyond the sclerotic area
- Osteochondral autologous transplantation plugs should generally be >1 cm thick to bypass subchondral sclerosis and allow for optimal bony ingrowth
- Both CT and MRI may be useful when evaluating sclerosis at the capitellar defect site
Refer a patient to the Hand & Arm Service at Mass General
Learn more about the Hand Surgery Fellowship at Mass General