SLR - March 2019 - Meagan R. Coleman

Surgical Treatment of Subfibular Ossicle in Children: A Retrospective Study of 36 Patients with Functional Instability

Reference: Moukoko D, Henric N, Gouron R, Peyronnet A, Bin K. Surgical Treatment of Subfibular Ossicle in Children: A Retrospective Study of 36 Patients with Functional Instability. J Pediatr Orthop. 2018 Oct;38(9):e524–e529.

Scientific Literature Review

Reviewed By: Meagan R. Coleman, DPM 
Residency Program: Detroit Medical Center, Detroit, MI

Podiatric Relevance:
In the pediatric population, accessory ossicles of the foot and ankle are often coincidental findings. However, when symptomatic, they can be the cause of chronic pain, instability and overall decrease in function. Initial symptoms can arise from trauma, such as an ankle sprain. In severe inversion ankle sprains, radiographs performed may reveal a subfibular ossicle at the area of maximum tenderness. Initial immobilization is considered as the first line of treatment. However, if conservative management fails, surgical intervention should be considered. This study focuses on the surgical treatment for symptomatic subfibular ossicles that resulted in significant improvements in pain, instability and overall function as compared to a nonoperatively managed pediatric patient population.

Methods: This Level IV retrospective study looked at 36 patients, with an average age of eight years and five months of persistent pain one year after an acute inversion ankle sprain. On initial presentation, radiographs were obtained showing a bilateral accessory ossicle at the distal fibula. These patients were immobilized for three to four weeks, then splinted until week 6. Following this, the patients underwent several weeks of rehabilitative therapy, including ROM exercises and balance and proprioceptive training. All 36 patients with pain > one year post initial injury were offered surgical intervention. Seventeen patients and families consented for resection of the subfibular ossicle, while 19 refused. These 19 patients served as the nonoperative, control group. The surgical technique consisted of resection of the ossicle without ligament repair or reconstruction. These two groups were assessed on pain, minor episodes of instability as well as the American Orthopedic Foot and Ankle Society (AOFAS) score and Visual Analogue Scale (VAS).

Results: The surgical resection group showed statistically significant improvements to AOFAS score with a mean gain of 31 points versus 7 points in the nonoperative, control group (P < 0.001). The mean final follow-up was four years and one month for the control group and four years and six months for the resection group. Of the 17 patients who had the subfibular ossicle resection, 15 patients noted improvements, eight patients were asymptomatic and six others described mechanical pain occurring “rarely” with a VAS averaging 3.4/10. In the control group, mechanical pain had a VAS score averaging 4.8/10. Recurrent severe ankle sprains needing emergency medical attention were observed in 10 patients, and mild instability episodes were reported in 16 of the 19 patients.

Conclusion: The AOFAS score of the resection group compared to the nonoperative control group was statistically significant. VAS on pain was also noted to decrease with resection. Limitations to this study included the lack of objective findings, such as quantifiable ankle ligamentous testing and an average size of the offending subfibular ossicle. The study focused solely on clinician-based assessment and patient-reported findings, which may result in report bias. However, these subjective results should not be overlooked. Patients who underwent resection reported a decrease in pain, decrease in episodes of instability and increase in overall function at follow-up. Resection of a subfibular ossicle in children and even adults can be an effective surgical option when conservative management has failed.

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