Subtalar fusion for pes valgus in children with cerebral palsy: surgical technique and results

Subtalar fusion for pes valgus in children with cerebral palsy: surgical technique and results
BJ SHORE MD FRCSC, A RIAZI MBBS, N WHITE MBBS,P SELBER MD FRACS, K GRAHAM MD FRCS ED FRACS
Orthopaedics, Royal Children’s Hospital, Parkville, VIC, Australia

Background/Objectives: Surgical correction of pes valgus is an important component of single event multilevel surgery (SEMLS) for children with cerebral palsy (CP). Since the original description of extra-articular subtalar fusion by Grice (1952), many modifications have been made including variations in the graft material and the introduction of internal fixation. We report the use of cortico-cancellous circular allograft combined with cannulated screw fixation for the correction of pes valgus in a series of children with spastic CP in the context of SEMLS.
Design: Retrospective case series.
Participants and Setting: Forty-six children with spastic diplegic CP (gross motor function classification system levels [GMFCS] II [n=10], III [n=21], and IV [n=15], age: 7-18 years). Patients underwent bilateral subtalar fusion in the setting of SEMLS surgery between Januarys 1999and December 2004.
Materials/Methods: Gait laboratory, hospital records and radiographs were reviewed. The surgical technique utilized a Collier’s type incision, using a hemi-spherical reamer for the fusion surface. A precut cortico-cancellous allograft was then press-fit into the prepared sinus tarsi. One or two 8 mm partially threaded cancellous screws were used to fixate the talus and os calcis. Pre- and post-operative standing lateral radiographs were utilized to assess the degree of surgical correction. Lateral talocalcaneal angle (LTCA), lateral talo first metatarsal angle (LTMtA) and navicular cuboid overlap (NCO) were the three main radiographic indices. Normal comparison radiographic values were used from previous literature (Davids, JPO, 2005). Fusion rate was assessed with radiographs greater than 12 months after index surgery.
Results: The mean patient age was 12.5 years and there was an average 55-month follow-up period. Statistically significant improvement post-operatively was found in all three radiographic indices. The LTCA improved an average of 20 degrees (95% CI 17.5-22.1, P<0.001) to a mean angle of 38. The LTMtA improved and average of 21 degrees (95% CI 19.2-23.4, P<0.001) to a mean angle of 11 degrees. Similar improvements were seen with the NCO with a 29% decrease (95% CI 25.7-32.6%, <0.001) in absolute percent overlap to a mean percentage of 33. Fusion was achieved in 45 patients; one patient had bilateral stable fibrous unions, after receiving donor allograft from a different source. There were no wound complications.
Conclusions/Significance: In subtalar fusion, the use of allograft can be advantageous, avoiding the need for additional incisions and harvesting of iliac crest bone graft, which is often of poor quality and associated with increased patient morbidity. The immediate stability of screw fixation to allow early, unrestricted weight bearing is a further advantage of this technique. Using standardized radiographic parameters, we demonstrate significant improvement in segmental alignment with the described fusion technique. We conclude that this is an ideal technique, as part of SEMLS, in children and adolescents with CP.

 
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