What is the primary purpose of the Thompson Test?

The primary purpose of the Thompson Test is to diagnose an Achilles tendon sprain or rupture. This clinical test is performed by having the patient lie prone with their feet hanging off the edge of the examination table. The examiner squeezes the calf muscles to assess whether the foot moves into plantar flexion, which indicates the integrity of the Achilles tendon. If the foot does not move when the calf is squeezed, it suggests a rupture of the tendon. This test is specifically designed to evaluate the condition of the Achilles tendon, making it a critical assessment tool in sports medicine and orthopedic practice.

Other options pertain to different anatomical structures or conditions unrelated to the Achilles tendon. For example, assessing biceps tendon involvement would require different tests, such as the Speeds or Yergason's tests. Evaluating shoulder instability involves examinations focused on the shoulder joint, like the apprehension or relocation tests. Lastly, determining the integrity of the tibial nerve would be assessed through sensory and motor function tests rather than the Thompson Test. Thus, the correct option aligns with the specific clinical scenario being evaluated.