Mapping the evidence: Effects of malnutrition and sarcopenia on fracture healing

To determine how sarcopenia and malnutrition affect fracture-healing outcomes and to identify clinical implications for screening and peri-fracture care.

A PRISMA-guided search (PubMed/MEDLINE, Cochrane Central, Cochrane Library; last search June 25, 2024; English language) identified in vivo human and animal studies evaluating fracture healing in the presence of sarcopenia or malnutrition. Two reviewers independently screened records, extracted data, and assessed the risk of bias using the MINORS tool.

nonunion (as defined in each study).

time-to-union, surgical complications, mortality, and biomechanical properties. Owing to heterogeneity, a structured narrative synthesis was performed.

Twelve studies met criteria: seven human (four malnutrition; three sarcopenia) and five animal (malnutrition). Large database studies linked malnutrition to higher nonunion risk (e.g., OR ≈2.0) and to post-operative complications and mortality. Definitions of malnutrition and sarcopenia varied widely across studies and included biochemical markers, anthropometric measures, imaging-based muscle assessments, and clinical screening tools. Due to this heterogeneity, associations with fracture healing outcomes were evaluated using study-level definitions rather than standardized diagnostic thresholds. Small clinical cohorts have associated sarcopenia with higher nonunion rates, and in one randomized pilot study, dietary protein/energy, combined with exercise, improved function and reduced pain while modestly shortening the time-to-union. Animal models consistently demonstrated lower BMD/BMC, altered callus composition, and reduced early mechanical strength under protein restriction, with partial reversal after re-feeding. Study heterogeneity and moderate-to-poor quality limited generalizability.

Across human and animal data, malnutrition and sarcopenia adversely affect fracture healing, increasing the risk of nonunion and complications, and impairing early callus quality. These findings highlight the importance of early identification of sarcopenia and nutritional risk in fracture patients. While emerging data suggest potential benefit from targeted interventions, the current evidence remains limited, underscoring the need for adequately powered randomized trials before routine clinical implementation.

Systematic Review, I.