Which bone forms the lateral boundary of the triangular interval?

Which bone forms the lateral boundary of the triangular interval?

• A. Scapula
• B. Clavicle
• C. Humerus shaft
• D. Radius

Answer: (C)

The triangular interval is a posterior-arm space through which the profunda brachii artery and radial nerve pass to reach the posterior compartment. It is formed medially by the long head of the triceps, laterally by the lateral head of the triceps, and superiorly by the teres major. The structures that travel through this interval run along the posterior aspect of the humeral shaft, making the humeral shaft the boundary on the lateral side. The other bones listed do not form this particular boundary. So the lateral boundary is the humeral shaft.

The triangular interval is a posterior-arm space through which the profunda brachii artery and radial nerve pass to reach the posterior compartment. It is formed medially by the long head of the triceps, laterally by the lateral head of the triceps, and superiorly by the teres major. The structures that travel through this interval run along the posterior aspect of the humeral shaft, making the humeral shaft the boundary on the lateral side. The other bones listed do not form this particular boundary. So the lateral boundary is the humeral shaft.