Final answer:
The lateral fin of a shoulder hemiarthroplasty implant should be oriented to achieve 30 degrees of retroversion, which means the anterior surface of the humeral implant is rotated 30 degrees away from the body's midline for correct anatomical alignment.
Step-by-step explanation:
The question pertains to the positioning of the lateral fin of a shoulder hemiarthroplasty implant, which is a type of shoulder replacement surgery. When implanting a prosthesis in shoulder hemiarthroplasty, achieving the appropriate degree of retroversion of the implant is critical for optimal joint function and stability. Retroversion refers to the angle at which the humeral head is rotated backward relative to the transepicondylar axis of the distal humerus.
Retroversion angle is important for the biomechanics of the shoulder because it affects the movement and overall mechanics of the joint. To achieve 30 degrees of retroversion, the lateral fin of a shoulder hemiarthroplasty implant should be oriented in such a way that the anterior surface of the humeral implant is rotated 30 degrees away from the body's midline once in place. This position aligns with the normal anatomical positioning of the humerus relative to the scapula and helps to mimic the natural kinematics of the shoulder joint.