Background: Although the incidence of os supranaviculare (OSSN) is generally low, symptomatic OSSN affects athletes. The aim of this study was to assess the variations of OSSN and the results of osteosynthesis between the OSSN and the navicular bone.
Methods: Eleven feet of 10 elite athletes with symptomatic OSSN were treated. There were 3 male and 7 female patients with an average age of 19 years. Eight feet exhibited navicular stress fracture (NSF). Operative treatment was performed in 9 feet of 8 patients and 2 conservatively. Seven OSSNs were fixed with 1 or 2 screw(s) according to their size, using an autologous bone graft. The accompanying NSF was also treated surgically in 4 feet. Foot condition was evaluated using the Japanese Society for Surgery of the Foot (JSSF) midfoot rating scale and sports activity score of the Self-Administered Foot Evaluation Questionnaire (SAFE-Q).
Results: The median OSSN was 12.7 mm in width, 5.6 mm in length, and 6.6 mm in height. The dorsal surface of the OSSN required at least 70 mm2 to be fixed using 2 screws. Seven OSSNs of 6 patients treated surgically successfully fused with the navicular. Two small OSSNs that were not stabilized with screws also fused after surgical treatment for NSF. However, one of the 2 OSSNs with NSF treated nonoperatively did not achieve fusion. The patients were followed up for 24-161 months. The median JSSF score improved from 87 to 97.7 postoperatively (P = .00312). The median postoperative SAFE-Q sports score was 84.8. All patients returned to their original activities.
Conclusion: Our results suggest that osteosynthesis with autologous bone graft was effective for symptomatic OSSNs. Even when the OSSN was small and not suitable for internal fixation, treatment of NSF was effective for union of OSSNs. The OSSN possibly belongs to a part or subtype of NSF.
Level of evidence: Level IV, retrospective case series.
Keywords: Os supranaviculare; athlete; navicular stress fracture; tarsal navicular; treatment.