R. Shane Tubbs, James W. Custis, E. George Salter, Jeffrey P. Blount, W. Jerry Oakes and John C. Wellons III
In neurotization procedures, donor nerves—either whole or in part—with relatively pure motor function can be carefully chosen to provide the optimal nearby motor input with as little donor site morbidity as possible. In this context, the ulnar nerve branches to the forearm muscles are relatively dispensable; however, quantitation of and landmarks for these branches are lacking in the literature.
The ulnar branches to the flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP) muscles in 20 upper extremities obtained in adult cadaveric specimens were dissected and quantified.
In the forearm, a mean of four nerve branches led to the FCU and FDP muscles. A mean of 3.4 branches led to the FCU muscle; of these, one to three were medial branches and zero to two were lateral. Medial branches to the FCU muscle originated a mean of 2.7 cm inferior to the medial epicondyle. Lateral branches to the FCU muscle originated at a mean of 3.3 cm inferior to the medial epicondyle. The mean length of the medial branches was 3.2 cm, whereas the mean length of the lateral branches was 3.3 cm. All nerves had a single trunk for the FDP muscle, and in all specimens this branch was located deep to the main ulnar nerve trunk, originating from the ulnar nerve a mean of 2.7 cm inferior to the medial epicondyle. These branches had a mean length of 5.6 cm. The mean diameter of all medial and lateral branches to the FCU muscle was 1 mm, and the mean diameter of the branch to the FDP muscle was 2.1 mm. All branches to both the FCU and FDP muscles arose from the ulnar nerve, over its first approximately 5 cm from the level of the medial epicondyle. Additionally, all branches could be easily lengthened by gentle proximal dissection from the main ulnar nerve.
Ulnar branches to the forearm can be easily localized and used for neurotization procedures. The branch to the FDP muscle had the greatest diameter and longest length, easily reaching the median nerve and posterior interosseous nerve via a transinterosseous membrane tunneling procedure. Furthermore, this branch could be teased away from the main ulnar nerve trunk and made to reach the distal branches of the musculocutaneous nerve in the arm.
R. Shane Tubbs, James W. Custis, E. George Salter, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes
There are scant data regarding the anterior interosseous nerve (AIN) in the neurosurgical literature. In the current study the authors attempt to provide easily identifiable superficial osseous landmarks for the identification of the AIN.
The AIN in 20 upper extremities obtained in adult cadaveric specimens was dissected and quantified. Measurements were obtained between the nerve and surrounding superficial osseous landmarks.
The AIN originated from the median nerve at mean distances of 5.4 cm distal to the medial epicondyle of the humerus and 21 cm proximal to the ulnar styloid process. The distance from the origin of the AIN to its branch leading to the flexor pollicis longus muscle and to the point it travels deep to the pronator quadratus (PQ) muscle measured a mean 4 and 14.4 cm, respectively. The mean distance from the AIN branch leading to the flexor pollicis longus muscle to the proximal PQ muscle was 12.1 cm, and the mean distance between this branch and the ulnar styloid process was 7.2 cm. The mean diameter of the AIN was 1.6 mm at the midforearm.
Additional landmarks for identification of the AIN can aid the neurosurgeon in more precisely isolating this nerve and avoiding complications. Furthermore, after quantitation of this nerve, the AIN branches can be easily used for neurotization of the median and ulnar nerves, and with the aid of a transinterosseous membrane tunneling technique, passed to the posterior interosseous nerve.
R. Shane Tubbs, E. George Salter, James W. Custis, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes
There is insufficient information in the neurosurgical literature regarding the long thoracic nerve (LTN). Many neurosurgical procedures necessitate a thorough understanding of this nerve's anatomy, for example, brachial plexus exploration/repair, passes for ventriculoperitoneal shunt placement, pleural placement of a ventriculopleural shunt, and scalenotomy. In the present study the authors seek to elucidate further the surgical anatomy of this structure.
Eighteen cadaveric sides were dissected of the LTN, anatomical relationships were observed, and measurements were obtained between it and surrounding osseous landmarks.
The LTN had a mean length of 27 ± 4.5 cm (mean ± standard deviation) and a mean diameter of 3 ± 2.5 mm. The distance from the angle of the mandible to the most proximal portion of the LTN was a mean of 6 ± 1.1 cm. The distance from this proximal portion of the LTN to the carotid tubercle was a mean of 3.3 ± 2 cm. The LTN was located a mean 2.8 cm posterior to the clavicle. In 61% of all sides the C-7 component of the LTN joined the C-5 and C-6 components of the LTN at the level of the second rib posterior to the axillary artery. In one right-sided specimen the C-5 component directly innervated the upper two digitations of the serratus anterior muscle rather than joining the C-6 and C-7 parts of this nerve. The LTN traveled posterior to the axillary vessels and trunks of the brachial plexus in all specimens. It lay between the middle and posterior scalene muscles in 56% of sides. In 11% of sides the C-5 and C-6 components of the LTN traveled through the middle scalene muscle and then combined with the C-7 contribution. In two sides, all contributions to the LTN were situated between the middle scalene muscle and brachial plexus and thus did not travel through any muscle. The C-7 contribution to the LTN was always located anterior to the middle scalene muscle. In all specimens the LTN was found within the axillary sheath superior to the clavicle. Distally, the LTN lay a mean of 15 ± 3.4 cm lateral to the jugular notch and a mean of 22 ± 4.2 cm lateral to the xiphoid process of the sternum.
The neurosurgeon should have knowledge of the topography of the LTN. The results of the present study will allow the surgeon to better localize this structure superior and inferior to the clavicle and decrease morbidity following invasive procedures.