Isolated Lesser Trochanter Fractures in Adults: A Systematic Review of Malignant, Infectious, and Benign Etiologies.

Isolated lesser trochanter (LT) fractures are uncommon in adults and may be the first clue to an underlying pathologic process. In contrast to adolescent apophyseal avulsions, the same finding in a skeletally mature patient has been linked to metastatic disease, primary bone tumors, hematologic malignancy, infection, and, less often, benign traumatic, stress-related, osteoporotic, or metabolic causes. This review examined the malignant, infectious, and benign etiologies, diagnostic pathways, treatments, and outcomes that have been reported in adults aged 18 years or older presenting with a radiographically isolated LT fracture or avulsion fracture. PubMed, Embase, and Scopus were searched for English-language case reports and case series with extractable patient-level data, and one additional eligible report was identified during peer review. Twenty-eight studies involving 46 published patient cases were included. Metastatic solid malignancy was the most commonly reported etiology (27/46, 58.7%), followed by primary malignant bone or plasma-cell tumors (7/46, 15.2%) and benign/nonpathologic causes, including metabolic bone disease (8/46, 17.4%). Hematologic malignancy (2/46, 4.3%), infectious disease (1/46, 2.2%), and other tumor-like disease (1/46, 2.2%) were less common. Among the 36 malignant cases, malignancy was first recognized after the LT fracture in 25 cases (25/36, 69.4%; equivalent to 25/46, 54.3% of all included cases), was known before the fracture in eight, and was unclear or not reported in three cases. These values describe selected published cases and should not be interpreted as population prevalence. Atraumatic, low-energy, or radiographically suspicious adult isolated LT fractures warrant evaluation for underlying malignancy or infection, while metabolic bone disease should remain in the differential diagnosis​​​​​​.