From the Research
The Trendelenburg sign is directly related to coxa vara, as coxa vara is a common cause of a positive Trendelenburg sign, characterized by a decreased femoral neck-shaft angle, which reduces the mechanical advantage of the hip abductor muscles. Coxa vara is a hip deformity that can lead to a positive Trendelenburg sign, which is a clinical indication of hip abductor insufficiency. When a person with coxa vara stands on the affected leg, the weakened abductors cannot adequately stabilize the pelvis, causing it to tilt downward on the opposite side instead of remaining level or tilting upward. This downward pelvic tilt on the unaffected side during single-leg stance constitutes a positive Trendelenburg sign.
The biomechanical explanation involves lever arm mechanics: the decreased neck-shaft angle in coxa vara shortens the lever arm of the abductor muscles, reducing their mechanical efficiency and making it difficult to generate sufficient force to maintain pelvic stability. According to a study published in the Journal of Pediatric Orthopedics in 2024 1, surgical correction of coxa vara can improve hip function and eliminate the Trendelenburg sign. The study found that correcting the Hilgenreiner-epiphyseal angle to ≤ 35 degrees or the neck-shaft angle to >110 degrees can prevent deformity recurrence and improve hip function.
Key points to consider:
- Coxa vara is a common cause of a positive Trendelenburg sign
- The decreased neck-shaft angle in coxa vara reduces the mechanical advantage of the hip abductor muscles
- Surgical correction of coxa vara can improve hip function and eliminate the Trendelenburg sign
- Correcting the Hilgenreiner-epiphyseal angle to ≤ 35 degrees or the neck-shaft angle to >110 degrees can prevent deformity recurrence and improve hip function, as supported by the study published in 2024 1.
It is essential to investigate underlying hip pathologies, including coxa vara, in patients with a positive Trendelenburg sign, as it may require orthopedic intervention depending on severity, functional limitations, and progression of the deformity. The relationship between the Trendelenburg sign and coxa vara is crucial in clinical practice, as it can guide diagnosis and treatment decisions, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.