Functional and MRI Outcomes After Arthroscopic Microfracture for Treatment of Osteochondral Lesions of the Distal Tibial Plafond

SLR - March 2015 - Trevor E. Black

Podiatric Residency:  The standard for initial treatment of most osteochondral defects of the talar dome has been established as microfracture. There is an abundance of literature that has evaluated the prognostic indicators of the treatment of talar OCD lesions. However, there is minimal literature that has evaluated arthroscopic microfracture for the treatment of osteochondral defects of the tibial plafond. Further understanding of prognostic factors will help to determine guidelines for surgical treatment of these lesions.  he purpose of the this study was to evaluate functional and MRI outcomes of arthroscopic microfracture for osteochondral lesions of the distal tibial plafond. The authors hypothesized that microfracture of tibial plafond OCD lesions would improve functional outcomes with the infill of fibrocartilage repair tissue. Furthermore, they hypothesize that large lesions and lesions with associated lesions on the side of the talar dome would have worse overall outcomes.

Methods:  The authors retrospectively identified forty-one distal tibial osteochondral lesions in forty-one ankles treated with arthrscopic microfracture between April 2006 and December 2011. Ten ankles were excluded due to limited follow-up. Thirty-one ankles with tibial osteochondral lesions were eligible. Fourteen of the ankles had additional talar osteochondral lesions opposite the tibial osteochondral lesion. Lesions were described using nine-zone anatomic grid scheme. Lesion size was evaluated on pre-operative MRI. Patients underwent arthroscopy via standard anteromedial and anterolateral portals. Debridement of impinged areas, synovectomy, and loose-body removal was performed as indicated. Osteochondral defects were resected with spinal curettes. Microfracture was performed in the osteochondral lesions to a depth of 4mm. Associated talar lesions underwent microfracture at the same time. Two ankles underwent additional treatment via antegrade transmalleolar drilling for the tibial lesions. Four ankles received lateral ankle ligament repair. Patients were placed in short leg splint for two weeks post-op and a CAM boot for the following month during which time they did active range of motion. Full weight bearing was achieved at six weeks at which time they began physical therapy.

Results:  Patients included 17 right ankles and 14 left ankles. Average duration of follow-up was 44 months. Anteromedial or anterolateral impingement was observed in 20 ankles. One ankle underwent subsequent autologous osteochondral transplantation for talar lesion. Average lesion area was 38mm2. Lesions were located in the centromedial and anteromedial regions of the tibial plafond 23 percent and 19 percent respectively.  Average FAOS pain score improved from 50.5 pre-operatively to 74.2 post-operatively. The average SF-12 score improved from 38.7 pre-operatively to 59.5 post-operatively. Age was noted to have a negative correlation with the preoperative to postoperative change in the SF-12 score. No difference was noted in outcome scores between men and women. Lesion location and lesion area was not significantly associated with the preoperative to postoperative change in functional outcome. Lesions with corresponding lesions on the talar dome had no significant difference in functional outcome from isolated tibial plafond lesions. There was no significant difference in functional outcome in the subset of patients that underwent concomitant lateral ligament repair or osteochondral transplantation. MRI was evaluated post-operatively using the Magnetic Resonance Observation of Cartilage Repair Tissue score (MOCART) and the average MOCART score obtained for 23 ankles was 69.4. This was negatively correlated with age.  Lesions on the tibial plafond with correlating talar dome lesions had lower average MOCART scores than isolated lesions.

Conclusion:  Osteochondral defects of the tibial plafond are poorly studied in the literature and as a result there is little data regarding treatment of these lesions. The authors found no significant difference in lesion size, functional outcome, or MOCART score when evaluated based on lesion location. There was no statistically significant difference in functional improvement between patients with isolated tibial plafond OCD lesions and those with concomitant talar dome lesions. However, mean improvement in functional scores was greater in patients with an isolated tibial lesion, but not statistically significant. There was no statistically significant difference between lesion area and improvement in functional outcome score. The authors noted that microfracture of tibial osteochondral lesions provided less functional improvement in patients with advanced age. Furthermore, post-operative MRI findings suggested that fibrocartilage repair tissue that develops following microfracture is compromised compared to normal hyaline cartilage. MOCART scores were negatively correlated with increasing age and increasing lesion area. The strength of the study is that it is the largest case series evaluating osteochondral defects of the tibial plafond that has been published to date. There was relative longevity noted in the follow-up of these patients. The greatest weaknesses of the study are limited sample size, heterogeneity of the surgical procedures on the patients, and variable patient age and lesion size within the cohort.