Author Response to Commentary on “Posterior Interosseous Nerve Compression in the Forearm,AKA Radial Tunnel Syndrome: A Clinical Diagnosis”

We would like to thank Dr. Hagart for her thoughtful comments on our study, “Posterior Interosseous Nerve compression in the Forearm, AKA Radial Tunnel Syndrome: A Clinical Diagnosis.” ¹ Her comments primarily address 2 facets of our study, one being our description of posterior interosseous nerve compression in the forearm (PINCF) as presenting with pain and without motor paralysis, and the second concerning our exclusion of patients with a diagnosis of lateral epicondylitis.

Posterior interosseous nerve compression in the forearm is an uncommon diagnosis which is made by a careful and thorough history and physical examination. Patients with PINCF present with pain in the proximal forearm in the interval between the brachioradialis (BR) and extensor carpi radialis/brevis (ECRL/ECRB), 3 to 5 cm distal to the lateral epicondyle. Our patient population did not have objective evidence of weakness. While we agree with Dr. Hagart that there is subtly in the measurement of M4 muscle weakness, the primary presenting complaint and exam finding in this patient population is pain, both with direct palpation and provocative maneuvers. We believe that this is the most useful clinical finding in this challenging patient population. We appreciate the technical aspects of evaluating extensor carpi ulnaris muscle weakness described by Dr. Hagart and highlighted in her commentary and will plan on incorporating this into our evaluation of these patients in the future. ²

We do not believe that the majority of patients with PINCF have concomitant lateral epicondylitis. The incidence of concomitant lateral epicondylitis and PINCF reported in the literature range from 5.7% to 31%. ³ Given the location of pain and the relative lack of awareness of PINCF as a clinical diagnosis, patients with PINCF risk being misdiagnosed as having lateral epicondylitis. While multiple studies have evaluated outcomes of patients treated for PINCF with concomitant lateral epicondylitis,^4,5 our study provides valuable insight into the diagnosis, treatment, and expected outcomes of patients with isolated PINCF. Given the general skepticism regarding the diagnosis of nerve compression with normal electrodiagnostic studies and predominant symptoms being pain, we were careful to exclude patients with associated lateral epicondylitis. Interestingly, many surgeons will decompress the carpal tunnel in patients with symptoms and normal electrical studies and operate on patients with symptoms of ulnar nerve compression and normal electrical studies although they have yet to recognize a Sunderland 0 injury pattern in other compressive neuropathies.