(P 255) CAN LARGE, LIPOMATOUS LESIONS ADJACENT TO THE SUPINATOR MUSCLE BE REMOVED WITHOUT INJURING THE POSTERIOR INTEROSSEOUS NERVE? A RETROSPECTIVE REVIEW

Objective: Patients with a large, deep lipomatous mass in the proximal forearm can present with pain and sensorimotor defects due to compression and entrapment of the radial nerve and its branches. Indications for surgery include malignancy or continued growth that may lead to nerve palsy. A mass arising adjacent to the supinator muscle and posterior interosseous nerve (PIN), can present difficulties when separating the tumor from the surrounding structures.

Methods: A retrospective review was conducted for patients that underwent removal of a lipomatous tumor of the proximal forearm from November 2018 to May 2024. Patient data collected included gender, age, BMI, tumor size, follow-up time, and postoperative range of motion and motor strength.

Results: Thirteen patients (F=69.2%,n=9) were included with an average age of 63.6+/-9.4years(range=49-79) and BMI of 26.4+/-4.4 kg/m2 (range=20.1-30.1). The tumors had an average size of 8.3+/-2cm (range=6-10). All patients had suggestions of radial nerve involvement on preoperative MRI and more than half (53.8%,n=7) of patients presented with sensorimotor defects on a clinical exam. Intraoperatively, the PIN was compressed and adhered to the surface of the tumor in all but one patient where it was encased. Pathology results of masses demonstrated 11 lipomas, an angiolipoma, a spindle cell lipoma, and no atypical lipomas or low-grade liposarcomas. Average follow-up time was 53days (range=11-200,median=37), and all patients but one presented with full range of motion and normal grip strength. The patient with the encased nerve developed radial nerve palsy postoperatively, but demonstrated improved range of motion on final follow-up with an expected full recovery.

Conclusion: If left untreated, lipomatous lesions around the supinator may continue to grow and irreversibly damage the radial nerve and transform into a malignancy. Our study demonstrates that removing these lesions can be safe and result in quick recuperation and full recovery.