Review Question - QID 220000

The patient has evidence of an unstable osteochondritis dissecans (OCD) lesion of the lateral aspect of the medial femoral condyle. Given that he is skeletally mature with an unstable lesion, an attempt at internal fixation is recommended.

Osteochondritis Dissecans (OCD) represents a pathologic lesion affecting juvenile patients' articular cartilage and subchondral bone, most typically of the posterolateral aspect of the medial femoral condyle. Diagnosis may be made radiographically but can be missed, with an MRI usually required to determine the size and stability of the lesion and to document the degree of cartilage injury. Treatment varies based on skeletal maturity and severity of the lesion. Definitive treatment can be non-operative with bracing and restricted weight bearing in children with open physes. But surgical treatment is preferred in older patients with closed physes and for lesions that are unstable. Unstable lesions are those with circumferential fluid signal (Illustration A) that indicates displacement of the cartilage from the subchondral bone; however, arthroscopic findings of a break in the articular cartilage or a mobile flap detected using the arthroscopic probe are the gold standard in diagnosis.

Cruz et al. provide a review of pediatric knee osteochondritis dissecans lesions. The authors note that most pediatric OCD lesions of the knee will heal with non-operative treatment, which includes a period of rest or activity modification with or without immobilization. They conclude, however, that lesions in skeletally mature patients, large lesions, and lesions that show radiographic signs of instability are less likely to heal without surgical intervention, with the goals of surgical treatment including maintenance of articular cartilage congruity and rigid fixation of unstable cartilage flaps.

Heiden et al. provide a technique article for open treatment of unstable osteochondritis dissecans lesions of the knee using autologous bone grafting and bioabsorbable fixation. The authors note that although the pathology can be challenging when treating these lesions operatively, attention to the subchondral bone is critical to success. They conclude that autologous bone graft can easily be obtained locally and used to restore the bony architecture, with the subsequent use of bioabsorbable implants providing a robust means of fixation that allows for single-stage surgery.

Figures A and B are AP and lateral radiographs demonstrating incongruence of the lateral aspect of the medial femoral condyle consistent with an OCD lesion in a skeletally immature individual. Figures C and D represent coronal and sagittal fluid-sensitive MRI sequences showing a ~ 2.5 x 2 cm OCD lesion of the medial femoral condyle with fluid circumferentially surrounding the cartilage fragment indicating an unstable lesion. Illustration A denotes the area of the cartilage flap that allows for the subchondral fluid to accumulate.

Incorrect Answers:
Answer 2: Bracing and non-operative management is indicated in stable lesions in children with open physes and in asymptomatic adults
Answers 3-4: Though MACI and OATS may be indicated if the lesion does not heal with fixation, in a young athlete with an unstable lesion, an attempt at fixation to salvage the patient's native cartilage is a more optimal initial treatment option.
Answer 5: Microfracture has largely fallen out of favor for large lesions and subchondral drilling is only effective in stable lesions without MRI evidence of circumferential fluid enhancement.