Patients with a Type II deformity (ie. laterally bowed fifth metatarsal and normal intermetatarsal (IM) angle) require a distal chevron osteotomy. Coughlin's classification scheme for bunionette deformities includes: Type I-lateral prominence of the metatarsal, Type II-lateral bowing of the fifth metatarsal, Type III-widening of the 4-5 IM angle. Examples of the three types are shown in Illustration A with types I,II,III correlating with A,B,C in the figure, respectively.
The review article by Cohen et al review the work-up and surgical indications for bunionette deformities. They state that lateral eminence resection may be considered in type I deformities in patients who will not tolerate weight-bearing restrictions associated with the osteotomies. With regards to type III deformities that have an increased 4-5 IM angle, the authors state that these are best treated with diaphyseal osteotomies. This procedure is also for painful type II and III bunionettes with associated keratotic lesions. Finally, proximal osteotomies are recommended only in patients who remain symptomatic after undergoing a prior distal procedure.
Koti et al provide of review of Bunionette deformities. They state that distal metatarsal osteotomies are indicated if medial translation of the head for one-third of the width of the metatarsal shaft produces a normal fourth-fifth intermetatarsal angle.
Cohen BE, Nicholson CW. Bunionette deformity. J Am Acad Orthop Surg. 2007 May;15(5):300-7. Review.
PMID:17478753 (Link to Abstract)
Koti M, Maffulli N. Bunionette. J Bone Joint Surg Am. 2001 Jul;83-A(7):1076-82. Review.
PMID:11451980 (Link to Abstract)