Biopsy of the anterior interosseous motor branch for the pronator quadratus muscle: a safe and minimally invasive diagnostic tool for peripheral neuropathies. Anatomical surgery and surgical technique

Background and objectives: Choosing the correct site for a nerve biopsy remains a challenge due to nerve sacrifice and major donor site complications, such as neuroma, as seen in sural nerve biopsy. Selecting a deeper donor nerve can help in burying nerve stumps in deep soft tissues, preventing neuroma. Moreover, using an expendable, deeply situated motor nerve can aid indiagnosis when a motor neuropathy is suspected. The authors propose using the pronator quadratus (PQ) branch for this purpose, as it is located deep between the bellies of the flexor muscles and the interosseous membrane in the forearm. This branch is expendable since the denervation of the PQ has a negligible effect on forearm pronation, which is primarily sustained by the pronator teres. Methods: The surgical approach is the same as the approach for anterior interosseous nerve transfer to the motor component of the ulnar nerve in the distal forearm: access is in the midline in the middle third of the forearm under local anesthesia Blunt dissection is performed, separating and retracting the flexor musculotendinous junction to reach the interosseous membrane where the PQ branch is identified. A careful dissection of the nerve branch is performed, allowing a 2 cm long segment to be cut and removed. The proximal stump is then buried into an adjacent muscle belly and the surgical site is closed. Results: The technique is safe and reproducible in experienced hands. Conclusion: This technique may be especially applicable in cases where neurologists need to study motor neuropathies. Contraindications of the technique include wrist instability and high median nerve palsies.