Final answer:
In tarsometatarsal amputation, to prevent supination deformity, preserving the interosseous membrane is essential to maintain muscle balance and proper limb alignment.
Step-by-step explanation:
To prevent supination deformity in a tarsometatarsal amputation, it is crucial to preserve the interosseous membrane, particularly in the forearm. The interosseous membrane provides stability and areas for muscle attachment. In cases where the interosseous membrane is damaged, such as with a fracture and tear of the membrane, it can result in pain, instability, and potential damage to muscles that attach to it. Supination deformity can arise if the muscles attached to the interosseous membrane become unbalanced due to injury or inadequate immobilization, leading to improper alignment of the bones.
If the interosseous membrane is not preserved during amputation, the muscles attaching to it can become uncoordinated, which would further risk supination deformity as they could pull the limb into an abnormal position. Proper immobilization of the site with a cast or splint is necessary to ensure the alignment of the bones and prevent the muscles from causing misalignment during the healing process. A gomphosis is a type of joint that is not directly related to the question but is included for reference purposes.