Why is there a high incidence of contractures at thoracic level?

Why is there a high incidence of contractures at thoracic level?

• A. Unopposed iliopsoas muscle function because there is no extension movement to counter it
• B. Overactivity of the quadriceps
• C. Excessive trunk extension
• D. Weak abdominal muscles

Answer: (A)

In high thoracic lesions, the hip extensors are weakened or paralyzed, leaving the hip flexor iliopsoas unopposed. The iliopsoas continuously pulls the hip into flexion, and without opposing extension from muscles like the gluteus maximus and hamstrings (and without trunk extension contributing to counterforce), the hip can shorten and develop a fixed flexion contracture. This imbalance between flexors and extensors at that level makes hip flexion contractures especially common. The other options don’t fit as well because they describe muscle actions that wouldn’t directly create a hip flexion contracture in this context: quadriceps overactivity mainly affects knee extension; excessive trunk extension would oppose a flexion contracture; weak abdominal muscles affect trunk control but not the primary hip-specific imbalance driving this pattern.

In high thoracic lesions, the hip extensors are weakened or paralyzed, leaving the hip flexor iliopsoas unopposed. The iliopsoas continuously pulls the hip into flexion, and without opposing extension from muscles like the gluteus maximus and hamstrings (and without trunk extension contributing to counterforce), the hip can shorten and develop a fixed flexion contracture. This imbalance between flexors and extensors at that level makes hip flexion contractures especially common.

The other options don’t fit as well because they describe muscle actions that wouldn’t directly create a hip flexion contracture in this context: quadriceps overactivity mainly affects knee extension; excessive trunk extension would oppose a flexion contracture; weak abdominal muscles affect trunk control but not the primary hip-specific imbalance driving this pattern.