Subtalar fusion for pes valgus in cerebral palsy: results of a modified technique in the setting of single event multilevel surgery.

BACKGROUND

We studied the use of cortico-cancellous circular allograft combined with cannulated screw fixation for the correction of dorsolateral peritalar subluxation in a series of children with bilateral spastic cerebral palsy undergoing single event multilevel surgery.

METHODS

Forty-six children who underwent bilateral subtalar fusion between January 1999 and December 2004 were retrospectively reviewed. Gait laboratory records, Gross Motor Function Classification System (GMFCS) levels, Functional Mobility Scale (FMS) scores, and radiographs were reviewed. The surgical technique used an Ollier type incision with a precut cortico-cancellous allograft press-fit into the prepared sinus tarsi. One or two 7.3 mm fully threaded cancellous screws were used to fix the subtalar joint. Radiographic analysis included preoperative and postoperative standing lateral radiographs measuring the lateral talocalcaneal angle, lateral talo-first metatarsal angle, and navicular cuboid overlap. Fusion rate was assessed with radiographs >12 months after surgery.

RESULTS

The mean patient age was 12.9 years (range, 7.8 to 18.4 y) with an average follow-up of 55 months. Statistically significant improvement postoperatively was found for all 3 radiographic indices: lateral talocalcaneal angle, mean improvement 20 degrees (95% CI, 17.5-22.1; P<0.001); lateral talo-first metatarsal angle, mean improvement 21 degrees (95% CI, 19.2-23.4; P<0.001); and navicular cuboid overlap, mean improvement 29% (95% CI, 25.7%-32.6%; P<0.001). FMS improved across all patients, with Gross Motor Function Classification System III children experiencing a 70% improvement across all 3 FMS distances (5, 50, and 500 m). All 3 radiographic measures improved significantly (P<0.001). Fusion was achieved in 45 patients and there were no wound complications.

CONCLUSIONS

With this study, we demonstrate significant improvement in radiographic segmental alignment and overall function outcome with this modified subtalar fusion technique. We conclude that this technique is an effective complement for children with dorsolateral peritalar subluxation undergoing single event multilevel surgery.

LEVEL OF EVIDENCE: Level IV.