High union rates following surgical treatment of proximal fifth metatarsal stress fractures

Purpose: The primary purpose of this study was to determine the union rate and time for surgical- and non-surgical treatment of stress fractures of the proximal fifth metatarsal (MT5). The secondary purpose was to assess the rate of adverse bone healing events (delayed union, non-union, and refractures) as well as the return to sports time and rate. Methods: A literature search of the EMBASE (Ovid), MEDLINE (PubMed), CINAHL, Web of Science and Google Scholar databases until March 2020 was conducted. Methodological quality was assessed by two independent reviewers using the methodological index for non-randomized studies (MINORS) criteria. The primary outcomes were the union time and rate. Secondary outcomes included the delayed union rate, non-union rate, refracture rate, and return to sport time and rate. A simplified pooling technique was used to analyse the different outcomes (i.e. union rate, time to union, adverse bone healing rates, return to sport rate, and return to sport time) per treatment modality. Additionally, 95% confidence intervals were calculated for the union rate, adverse bone healing rates, and the return to sport rate. Results: The literature search resulted in 2753 articles, of which thirteen studies were included. A total of 393 fractures, with a pooled mean follow-up of 52.5 months, were assessed. Overall, the methodological quality of the included articles was low. The pooled bone union rate was 87% (95% CI 83–90%) and 56% (95% CI 41–70%) for surgically and non-surgically treated fractures, respectively. The pooled radiological union time was 13.1 weeks for surgical treatment and 20.9 weeks for non-surgical treatment. Surgical treatment resulted in a delayed union rate of 3% (95% CI 1–5%), non-union rate of 4% (95% CI 2–6%) and refracture rate of 7% (95% CI 4–10%). Non-surgical treatment resulted in a delayed union rate of 0% (95% CI 0–8%), a non-union rate of 33% (95% CI 20–47%) and a refracture rate of 12% (95% CI 5–24%), respectively. The return to sport rate (at any level) was 100% for both treatment modalities. Return to pre-injury level of sport time was 14.5 weeks (117 fractures) for surgical treatment and 9.9 weeks (6 fractures) for non-surgical treatment. Conclusion: Surgical treatment of stress fractures of the proximal fifth metatarsal results in a higher bone union rate and a shorter union time than non-surgical treatment. Additionally, surgical and non-surgical treatment both showed a high return to sport rate (at any level), albeit with limited clinical evidence for non-surgical treatment due to the underreporting of data. Level of evidence: Level IV, systematic review.