Review Question - QID 499

Certain anatomic structures are at risk with percutaneous pinning of proximal humerus fractures. The red arrow in Figure A marks a proximal lateral pin that would place the anterior branch of the axillary nerve at risk.

Rowles and McGrory performed an anatomic study of the structures at risk with closed reduction and percuatneous pinning of the proximal humerus and found that proximal lateral pins were a mean of 3mm from the anterior branch of the axillary nerve. Pins placed through the anterior cortex and directed into the humeral head fragment were a mean of 2mm from the long head of the biceps tendon and greater tuberosity pins were found to be 8mm from the posterior humeral circumflex and 10mm from the main trunk of the axillary nerve as they penetrated the medial cortex of the humerus.

Jaberg et al retrospectively reviewed the clinical and radiographic results of 48 patients at an average of 3 years after undergoing closed reduction and percutaneous pinning of a proximal humerus fracture. 70% good to excellent results with their described technique, and the authors caution that radiographic malunion did not correlate with patient function.

Incorrect Answers
Answer 2: The posterior humeral circumflex artery (PHCA) is at risk from a greater tuberosity pin as it penetrates the medial cortex. In the anatomic study by Rowles and McGrory, the distance between the pin and the PHCA/axillary nerve was decreased with internal rotation and increased with external rotation.
Answer 3: The long head of the biceps tendon would be at risk from a pin placed through the anterior cortex and directed into the humeral head and was perforated by three pins in the study by Rowles and McGrory.
Answer 4: The cephalic vein is at risk with anterior pins (mean of 11mm in the referenced study)
Answer 5: The musculocutaneous nerve is at risk with anterior pins (mean of 17mm in the referenced study)