Abstract
The Os subfibulare, or round ossicles at the tip of the lateral malleolus, are often regarded as accessory bone. Some patients with such fragments, however, complain of ankle pain and repeated sprain. This study addresses whether these fragments are unnecessary and ignorable?
Materials and method: From 1986 to 1998, we treated 54 ankles in 52 patients surgically. The average age at surgery was 18 years; the mean follow up period was 4.7 years. The whole the fragment was fixed to the lateral malleolus using a tension band.
Results: Each fragment was attached to at least one ligament. We classified these attachments as follows:
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Type I a: only ATFL was attached to one fragment
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Type I b: ATFL and CF were attached to one fragment
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Type I c: ATFL, CF, and PTFL were attached to one fragment
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Type II : ATFL and CF were attached to two individual fragments
There were 7 Type I a, 37 Type I b, 6 Type I c, and 4 Type II. Fifty-one ankles (94%) developed bony union and three united fibrously. The talar tilt was restored from 9.8 to 4.7 degrees after surgery. The American Orthopaedic Foot and Ankle Societyñs clinical rating system for the ankle-hindfoot improved from 77 to 98 and ankle pain decreased dramatically.
Conclusion: The fragment at the tip of the lateral malleolus is the origin site of the lateral ligaments. This fragment can be united with the lateral malleolus. We believe that the fragments are keystones of the lateral ankle ligament complex.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
