Factors associated with recurrent fifth metatarsal stress fracture.

Abstract

BACKGROUND: Many surgeons agree that fifth metatarsal stress fractures have a tendency toward delayed union, nonunion, and possibly refracture. Difficulty healing seems to be correlated with fracture classification. However, refracture sometimes occurs after low-grade fracture, even long after apparent resolution.

METHODS: The records of 168 consecutive cases of fifth metatarsal stress fracture (163 patients) treated by modified tension band wiring from March 2002 to June 2011 were evaluated retrospectively. Mean length of follow-up was 23.6 months (range, 10-112 months). Forty-nine cases classified as Torg III were bone grafted initially also. All enrolled patients were elite athletes. Eleven patients experienced nonunion and 18 refracture. The 11 nonunion cases were bone grafted. The 157 patients (excluding nonunion cases) were allocated to either a refracture group or a union group. Clinical features, such as age, weight, fracture classification, time to union, and reinjury history, were compared. Radiological parameters representing cavus deformity and fifth metatarsal head protrusion were compared to evaluate the influence of structural abnormalities.

RESULTS: Mean group weights were significantly different (P = .041), but mean ages (P = .879), fracture grades (P = .216, P = .962), and time from surgery to rehabilitation (P = .539) were similar. No significant intergroup differences were found for talocalcaneal (TC) angle (P = .470), calcaneal pitch (CP) angle (P = .847), or talo-first metatarsal (T-MT1) angle (P = .407) on lateral radiographs; for fifth metatarsal lateral deviation (MT5-LD) angle (P = .623) on anteroposterior (AP) radiographs; or for MT5-LD angle (P = .065) on the 30-degree medial oblique radiographs. However, the mean fourth-fifth intermetatarsal (IMA4-5) angle on AP radiographs was significantly greater in the refracture group, and for Torg II cases, mean weight (P = .042), IMA4-5 angle on AP radiographs (P = .014), and MT5-LD angle (P = .043) on 30-degree medial oblique radiographs were significantly greater in the refracture group. For B2 cases (incomplete fracture and a plantar gap of 1 mm or larger), mean weight (P = .046), IMA4-5 angle on AP radiographs (P = .019), and MT5-LD angle (P = .045) on 30-degree medial oblique radiographs were significantly greater in the refracture group. All cases of refracture had a traumatic history after bone union. Refracture developed within 6 months of starting rehabilitation in 13 cases and within 3 months in 8 cases.

CONCLUSION: The development of refracture after the surgical treatment of fifth metatarsal stress fractures was found to be associated with higher body mass index (BMI) and with radiological parameters (IMA4-5 on AP radiographs, MT5-LD on oblique radiographs) associated with protrusion of the fifth metatarsal head. The study indicates that patients with a protruding fifth metatarsal head and a high BMI should approach rehabilitation with care before considering a return to previous sporting activity levels.

LEVEL OF EVIDENCE: Level III, retrospective comparative series.