Re: R. Shane Tubbs et al. Relationships between the Posterior Interosseous Nerve and the Supinator Muscle: Applications to Peripheral Nerve Compression Syndromes and Nerve Transfer Procedures

I read with much interest the article by Tubbs et al[1] on the anatomical conditions in and around the supinator tunnel with the N. interosseous posterior (NIP) being the neuroanatomical structure of interest. With the experience of > 1600 operations between 1998 and today on patients diagnosed for supinator tunnel syndrome, I would like to make some comments from the clinical point of view:

1. Compression of the deep branch of the radial nerve in the forearm underneath the upper layer of the supinator muscle, that is, supinator tunnel syndrome (STS), in my view is the most frequently undiagnosed nontraumatic peripheral nerve lesion in the forearm and is far from accounting for only 1% of all nerve entrapments in the human forearm.[2] The reason for that is simple: Neurologists and non-neurologists (mostly orthopedists) are not familiar with the clinical presentation of STS. That is a pity because it were orthopedists who diagnosed by chance this forearm nerve entrapment.[3] [4]

2. Epicondylopathia humeri radialis (EHR) (the term epicondylitis is a misnomer because there is no “-itis” suggesting an inflammatory state), in turn, represents by far the most frequent enthesopathy around the elbow joint that an orthopedist confronts. Every EHR persisting even after operative deinsertion is highly suspicious for algesic STS.

3. Because an electrophysiologic test is negative in approximately a third of all examined patients, some authors[2] suggested considering STS as a special entity of the more general posterior interosseous nerve syndrome. I believe both entities are one thing, one being merely algesic (without electrophysiologic abnormalities) and the other being paretic (weakness of the forearm extensor muscles) demonstrating electrophysiologic abnormalities. The algesic variant is by far the most frequent variant of STS.

4. In clinical practice, this article with its schematic drawings for a beginner in decompressing the NIP is rather frightening and confusing because what is drawn is not congruent with anatomical reality inside the supinator tunnel. I have encountered the variant shown in Fig. 1 in just three forearms of two patients, accounting for approximately 2% in my own series. However, even the examination by Tatars et al and the comparison of fetuses and cadaver arms represents the reality far more realistically,[5] even though extra supinator traveling (5% of all cases examined) contradicts my own findings in patients of both sexes, with a predominance of 60:40 for women. However, in approximately 5% of all cases, the NIP travels on the ulnar side of the radial bone.

5. Also, this article suggests an anatomical skin incision rather than a less traumatic one between 2 and 6 cm long, depending on anatomical conditions, choosing the shortest (i.e., vertical) route. Ludwig Kempe's[6] approach to the supinator tunnel is history and totally unacceptable today, but unfortunately it is still practiced.

6. Being familiar with the clinical picture of STS (i.e., patients' complaints) and with the corresponding result of your own clinical examination), decompression of the NIP takes no longer than 5 to 10 minutes. Patients are grateful thereafter, except you have overseen a concomitant C7 syndrome, which is the case in 30% of all STS patients.

“You only see what you know.”

—Johann Wolfgang von Goethe

“The greatest obstacle to discovery is not ignorance—it is the illusion of knowledge.”

—Daniel J. Boorstin (after Marco Mumenthaler)

• References

• 1 Tubbs RS, Mortazavi MM, Farrington WJ , et al. Relationships between the posterior interosseous nerve and the supinator muscle: applications to peripheral nerve compression syndromes and nerve transfer procedures. J Neurol Surg A 2013; 74: 290-293
• 2 Carfi J, Ma DM. Posterior interosseous syndrome revisited. Muscle Nerve 1985; 8 (6) 499-502
• 3 Coppell HP, Thompson WAL. Peripheral Entrapment Neuropathies. Baltimore, MD: Williams & Wilkins; 1963
• 4 Roles NC, Maudsley RH. Radial tunnel syndrome: resistant tennis elbow as a nerve entrapment. J Bone Joint Surg Br 1972; 54 (3) 499-508
• 5 Tatar I, Kocabiyik N, Gayretli O, Ozan H. The course and branching pattern of the deep branch of the radial nerve in relation to the supinator muscle in fetus elbow. Surg Radiol Anat 2009; 31 (8) 591-596
• 6 Kempe L. Operative Neurosurgery. Vol 2. Berlin, Germany: Springer; 1968