Isolated spring ligament failure as a cause of adult-acquired flatfoot deformity.

BACKGROUND: Adult-acquired flatfoot deformity is usually secondary to failure of the tibialis posterior tendon, with secondary injury to the surrounding osseous-ligamentous complex. Rarely, patients may present with a normal tibialis posterior tendon and an isolated injury of the plantar calcaneonavicular, or spring, ligament. The current study describes the clinical presentation and operative management of 6 patients with isolated spring ligament ruptures who presented with symptomatic flexible flatfoot deformities.
METHODS: Six consecutive patients with unilateral flatfoot deformities secondary to spring ligament failure were operatively treated at one institution between 2003 and 2010. All patients presented with symptomatic flatfoot deformities recalcitrant to conservative management. No patients had previous flatfoot reconstructive surgery, but all had undergone some combination of orthotic use, immobilization, or activity modifications prior to operative treatment. In each case, intraoperative findings demonstrated a tear of the spring ligament complex with a normal tibialis posterior tendon. To address the deformities, spring ligament repairs and adjunctive flatfoot reconstructions were performed. A retrospective chart study was performed to document patient presentation, demographics, and outcomes.
RESULTS: Average patient age was 42 years. All 6 patients were female. All patients presented with medial foot pain for a mean of 27 months prior to presentation. Spring ligament abnormality was demonstrated in all 5 patients who received preoperative magnetic resonance imaging. Intraoperatively, all 6 patients demonstrated spring ligament tears and no significant tibialis posterior tendon abnormality. All 6 patients underwent spring ligament repairs with or without adjunctive flatfoot reconstructions. At mean follow-up of 13 months, all but 1 patient were pain-free without orthotics, and all patients were without residual deformity. There was a single patient with delayed bone graft healing and no other minor or major complications in this series.
CONCLUSIONS: Adult-acquired flatfoot deformity is usually secondary to tibialis posterior tendon failure but in rare cases may be secondary to isolated spring ligament injury without tibialis posterior tendon abnormality. This unique clinical entity should be considered in patients who present with flatfoot deformities. In this study, although preoperative magnetic resonance imaging was not required, it identified a suspected spring ligament tear in all cases in which it was used. Thorough intraoperative exploration can identify an injury to the spring ligament and a normal tibialis posterior tendon. Failure to recognize an isolated spring ligament injury as the primary cause of a flatfoot deformity could lead to inappropriate operative management. LEVEL OF EVIDENCE: Level IV, retrospective study.