Impact of Tendon Gap on Decision-Making in Acute Achilles Tendon Rupture: A Systematic Review.

Acute Achilles tendon rupture (AATR) is a prevalent injury that significantly impacts clinical decision-making, particularly concerning the initial gap size following the rupture. This review aims to evaluate the influence of initial gap size on treatment decisions in managing acute Achilles tendon complete ruptures. A comprehensive search was conducted across four electronic databases - PubMed, Scopus, Web of Science (WoS), and the Cochrane Library - as well as Google Scholar. Two independent reviewers assessed the methodological quality of each included study using the Newcastle-Ottawa Scale (NOS), with studies classified as poor (0-3 stars), fair (4-6 stars), or good (7-9 stars). Discrepancies between reviewers were resolved by the senior author. Initially, 531 articles were identified; after removing 183 duplicates, 348 articles remained for title and abstract screening. From these, 305 were excluded, resulting in 43 studies selected for full-text assessment. Ultimately, eight studies, encompassing a total of 679 patients, met the specified inclusion and exclusion criteria and were included in the final synthesis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram illustrates the study selection process. Eight studies, encompassing 679 patients, were included. Gap-based treatment protocols were commonly employed, with a threshold of 5-10 mm influencing surgical decision-making. Re-rupture rates were consistently low across both operative and nonoperative groups, with no statistically significant differences reported in most studies. While several studies found no correlation between gap size and the Achilles tendon Total Rupture Score (ATRS), others demonstrated that gaps >5 mm or >10 mm were associated with significantly worse functional outcomes or plantarflexion strength deficits. One study highlighted that the location of the rupture relative to the calcaneal enthesis may better predict long-term strength and fatigue scores than gap size alone. The quality of the included studies varied, with six rated as fair quality and two as good quality; none were classified as poor quality. Larger initial gaps in AATR (especially >5-10 mm) tend to be associated with marginally poorer functional outcomes and a higher risk of re-rupture, though evidence is mixed. Many clinicians, therefore, use a conservative cut-off (<10 mm) when selecting nonoperative treatment. However, patients with large gaps may still do well with modern functional protocols. In decision-making, the tendon gap should be considered alongside patient activity level and preferences. The literature is limited by small cohorts and variable methods; future trials are needed to define optimal gap-based guidelines.