Transfer of flexor carpi ulnaris branch of the ulnar nerve to the pronator teres nerve: histomorphometric analysis

The muscular branching patterns of the ulnar nerve in fetal forearms

OBJECTIVE

We aimed to present our findings systematically by examining the muscular branching patterns of the ulnar nerve (UN) in the forearms of fetuses.

METHODS

This study was conducted on the 52 forearms of 26 formalin-fixed fetal cadavers with gestational ages varying between 19 and 37 weeks. The anatomical dissection was performed by using stereomicroscope with × 8 magnification. The numbers of muscular branches leaving UN and their order of leaving main nerve were noted down. The findings were classified according to the muscles they reached, and branching typing was done.

RESULTS

It was found that a total of 2-6 muscular branches left UN to reach flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP). UN was classified by separating into five main types according to the number of muscular branches, and these types were classified into 16 different branching patterns according to the order of branches leaving from the main trunk and going to FCU and FDP. The pattern where two branches left UN was classified as Type I (n = 6), three branches left was classified as Type II (n = 18), four branches left was classified as Type III (n = 24), five branches left was classified as Type IV (n = 3), and six branches left was classified as Type V (n = 1). Martin-Gruber connection occurred in 17 (32.7%) fetal forearms.

CONCLUSION

We believe that the information that UN can demonstrate different branching patterns on the forearm can help the surgeons to prevent complications that may develop in potential nerve injury during the selection and transfer of relevant branch.

Comparative study of pronator teres branch transfer and brachialis motor branch transfer to the anterior interosseous nerve to treat lower brachial plexus injury in rats

Distal nerve transfer is used to treat lower brachial plexus palsy, but outcome series on these transfer procedures following lower plexus injuries are sparse. The objective of this study is to compare treatment outcomes after nerve transfer using the brachialis motor branch (BMB) versus that using the pronator teres motor branch (PTMB). One hundred twenty adult rats with C8T1 nerve root avulsion were randomly divided into three groups (40 each): A: BMB transfer to the anterior interosseous nerve (AIN), B: PTMB transfer to the AIN, and C: no repair. Electrophysiological examination result, muscle tension test result, muscle weight and muscle fiber cross-sectional area of the flexor digitorum profundus and flexor pollicis longus, and number of myelinated nerve fibers in the AIN were compared among the groups to evaluate the treatment outcome. Nerve regeneration and muscle recovery in group B was better than those in group A at 4 and 8 weeks postoperatively (P < 0.05). There was no significant difference in the myelinated nerve fibers in groups A and B at 12 and 16 weeks postoperatively. The rats in group B showed greater and more significant improvement in other measured values than those in group A (P < 0.05). In conclusion, the PTMB seems a better donor nerve than the BMB for distal nerve transfer to treat lower brachial plexus injury according to the electrophysiological and histological examination in this rat study.

Upper Extremity Axon Counts and Clinical Implications for Motor Nerve Transfer

BACKGROUND

Nerve transfers are planned based on the following parameters: location, number of branches, and axon count matching of the donor and recipient nerves. The authors have previously defined the former two in upper limb muscles. In the literature, axon counts are obtained from various sources, using different methods of histomorphometry. This study describes the axon counts of the same primary motor nerve branches from the authors' previous study using a uniform method of manual histomorphometry and completes the authors' blueprint of upper limb neuromuscular anatomy for reconstructive surgery.

METHODS

The distal ends of the primary nerve branches of 23 upper limb muscles were harvested from 10 fresh frozen cadaveric upper limbs. Manual quantitative histomorphometry was performed by two independent investigators, and the average was reported.

RESULTS

The primary nerve branches of the arm muscles had higher average axon counts (range, 882 to 1835) compared with those of the forearm muscles (range, 267 to 883). In the forearm, wrist flexor (range, 659 to 746) and extensor (range, 543 to 745) nerve branches had axons counts that were similar to those of potential donors (e.g., supinator, n = 602; pronator teres, n = 625; flexor digitorum superficialis, n = 883; and flexor digitorum profundus, n = 832).

CONCLUSIONS

Apart from describing the axon counts of the upper limb, the authors have found that the forearm axon counts are very comparable. This insight, when combined with information on the location and number of primary nerve branches, will empower surgeons to tailor bespoke nerve transfers for every clinical situation.

Upper Extremity Innervation Patterns and Clinical Implications for Nerve and Tendon Transfer

BACKGROUND

The authors previously studied the intramuscular innervation of 150 upper limb muscles and demonstrated that certain patterns of intramuscular innervation allowed muscles to be split into compartments with independent function. This study aims to determine the location, extramuscular course, and number of motor nerve branches of upper limb peripheral nerves. The authors want to combine this information with their previous work to create a blueprint of upper limb neuromuscular anatomy that would be useful in reconstructive surgery.

METHODS

Ten fresh frozen cadaveric upper limbs were dissected. The origin of branches from the peripheral nerve trunk, their course, and the number of motor nerves per muscle were determined. The authors reviewed all the images of the Sihler-stained muscles from their earlier study.

RESULTS

Motor nerve branches arise at the intersection of nerve trunk and muscle belly and are clustered near the origin of muscle groups. Two patterns of extramuscular innervation were noted, with one group having a single motor nerve and another group with consistently more than one motor nerve. A modified classification of muscles was proposed based on the orientation of muscle fibers to the long axis of the limb, the number of muscle compartments, and the number of heads of origin or the tendons of insertion.

CONCLUSIONS

Motor nerve clusters can be located based on fixed anatomical landmarks. Muscles with multiple motor nerves have morphology that allows them to be split into individual compartments. The authors created a muscle and nerve blueprint that helps in planning nerve and split muscle transfers.

Sensory reanimation of the hand by transfer of the superficial branch of the radial nerve to the median and ulnar nerve

BACKGROUND

It remains a surgical challenge to treat high-grade nerve injuries of the upper extremity. Extra-anatomic reconstructions through the transfer of peripheral nerves have gained clinical importance over the past decades. This contribution outlines the anatomic and histomorphometric basis for the transfer of the superficial branch of the radial nerve (SBRN) to the median nerve (MN) and the superficial branch of the ulnar nerve (SBUN).

METHODS

The SBRN, MN, and SBUN were identified in 15 specimens and the nerve transfer performed. A favorable site for coaptation was chosen and its location described using relevant anatomical landmarks. Histomorphometric characteristics of donor and target were compared to evaluate the chances of a clinical success.

RESULTS

A suitable location for dissecting the SBRN was identified prior to its first bifurcation. Coaptations were possible near the pronator quadratus muscle, approximately 22 cm distal to the lateral epicondyle of the humerus. The MN and SBUN had to be dissected interfasciculary over 82 ± 5.7 mm and 49 ± 5.5 mm, respectively. Histomorphometric analysis revealed sufficient donor-to-recipient axon ratios for both transfers and identified the SBRN as a suitable donor with high axon density.

CONCLUSION

Our anatomic and histomorphometric results indicate that the SBRN is a suitable donor for the MN and SBUN at wrist level. The measurements show feasibility of this procedure and shall help in planning this sensory nerve transfer. High axon density in the SBRN identifies it or its branches an ideal candidate for sensory reanimation of fingers and thumbs.

Restoration of ulnar nerve motor function by pronator quadratus motor branch: an anatomical study

BACKGROUND

The traditional surgical approach to repair of brachial plexus lesions involves use of whole segment ulnar nerve graft for contralateral seventh cervical (cC7) nerve root transfer, which sabotages the possibility of ulnar nerve recovery. We assessed the anatomical feasibility of a new approach that involves preservation of the motor branch of ulnar nerve (MBUN), for a later stage repair using the recovered pronator quadratus motor branch (PQMB), subsequent to the cC7 transfer procedure.

METHODS

Twenty-seven adult cadaver arms and one side of fresh adult cadaver were used in this study. The anterior interosseous nerve and its PQMB, as well as the motor and sensory branches of the ulnar nerve were dissected. The distances from the end of PQMB to the mid-point of a line joining the radial styloid and ulnar styloid, as well as to the point of divergence of the ulnar nerve, were measured. The MBUN was dissected from distal to proximal and the maximum length was measured. The diameter and number of axons of the nerve branches were also recorded.

RESULTS

The distance from the end of the PQMB to the midpoint of the radial styloid and ulnar styloid was 6.04 ± 0.52 cm, and that to the point of divergence of the ulnar nerve was 8.02 ± 0.63 cm. The maximum length of the MBUN after its dissociation was 9.70 ± 1.38 cm. The mean diameters of axons of the MBUN and PQMB were 0.09 ± 0.02 cm and 0.05 ± 0.01 cm, respectively. The corresponding mean numbers of axons were 2913 ± 624 and 757 ± 183, respectively.

CONCLUSIONS

The results indicate that the PQMB is suitable for transferring to the MBUN without nerve graft. This anatomical study paves the way for further testing of this new procedure after cC7 transfer in clinical settings.

A Cadaver Study of Median-to-Radial Nerve Transfer for Radial Nerve Injuries

PURPOSE

To assess the anatomic feasibility of a median-to-radial nerve transfer in cadaver limbs and to quantify the number of axons present in the cut ends of the involved donor and recipient nerves.

METHODS

Ten fresh frozen cadaveric upper limbs were dissected. We investigated whether the flexor carpi radialis (FCR) branch/flexor digitorum superficialis (FDS) branch (donor nerve) reached the posterior interosseous nerve (PIN)/extensor carpi radialis brevis (ECRB) branch (recipient nerve) without tension. We also investigated the length of the transected supinator fascia for FCR-posterior interosseous nerve transfer and the FDS-ECRB positional relationship using the epicondyle line and the midline of the forearm as axes. The findings were used for these 2 types of nerve transfer with evaluation closer to the target muscles. The distance between the point at which the FDS and ECRB branches met and the point at which the ECRB branch entered the muscle was measured. After nerve coaptation, the axon number was determined by histological evaluation.

RESULTS

In all limbs, the FCR and FDS branches reached the PIN and the ECRB branch without tension. The transected supinator fascia was 17 (3-25) mm long. The point at which the FDS branch reached the ECRB branch [corrected] was 48 (23-65) mm distal to the epicondyle line and approximately 23 (18-27) mm radial to the midline of the forearm. The distance between the point at which the FDS and ECRB branches met and the point at which the ECRB branch entered the muscle was 27 (17-40) mm. The mean axon numbers were FCR, 1501 (932-3022); PIN, 5162 (4325-7732); FDS, 885 (558-962); and ECRB, 548 (433-723).

CONCLUSIONS

The FCR branch could be transferred to the PIN [corrected] and the FDS to the ECRB branch in all limbs without tension.

CLINICAL RELEVANCE

We provide anatomical and histological information for median-to-radial nerve transfer.

Transfer of a Terminal Motor Branch Nerve to the Flexor Carpi Ulnaris for Triceps Reinnervation: Anatomical Study and Clinical Cases

PURPOSE

To analyze the anatomical feasibility of transferring a motor branch nerve to the flexor carpi ulnaris (FCU) to the triceps upper medial head motor branch (UMHM) and to report the resultant outcome of the restoration of elbow extension in 5 patients with extensive brachial plexus injury.

METHODS

The ulnar and radial nerves were dissected in 10 cadavers. We measured the length and diameter of the branches to the FCU and the UMHM branch and counted the axons. Then, 5 male patients, mean age 30 years, underwent FCU nerve branch transfer for reconstruction of elbow extension. Elbow flexion was restored via a median nerve branch to biceps transfer.

RESULTS

Mean UMHM nerve length and diameter were 86 and 1.5 mm, respectively. Mean number of branches to the FCU muscle was 2.9. Mean FCU nerve length and diameter were 50 and 1.0 mm, respectively. Mean number of myelinated fibers was 818 and 743 for the UMHM and the longest branch to the FCU, respectively. Coaptation between nerves was possible without tension. All patients recovered functional active elbow extension at a mean follow-up of 19 months with a British Medical Research Council score of M4. After surgery, all patients retained a functional FCU with a British Medical Research Council score of M4.

CONCLUSIONS

Nonselective ulnar nerve fascicles at the root of the limb might not be adequate to restore elbow extension when combined with a median nerve branch transfer for elbow flexion. A selective distal ulnar motor fascicle such as a FCU motor branch could be harvested and connected to a triceps branch to restore elbow extension. Such a nerve transfer would also allow for later transfer of the still functional FCU tendon to the digital extensors.

CLINICAL RELEVANCE

For patients with extensive brachial plexus injury and a preserved medial cord, transferring a motor branch nerve to the FCU is an effective technique for the reconstruction of elbow extension.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Anatomical and histomorphometric observations on the transfer of the anterior interosseous nerve to the deep branch of the ulnar nerve

This study focuses on the anatomical and histomorphometric features of the transfer of the anterior interosseous nerve to the deep motor branch of the ulnar nerve. The transfer was carried out in 15 cadaver specimens and is described using relevant anatomical landmarks. Nerve samples of donor and target nerves were histomorphometrically analysed and compared. The superficial and the deep ulnar branches had to be separated from each other for a length of 67 mm (SD 12; range 50-85) to reach the site of coaptation. We identified a suitable site for coaptation lying proximal to the pronator quadratus muscle, 202 mm (SD 15; range 185-230) distal to the medial epicondyle of the humerus. The features of the anterior interosseous nerve included a smaller nerve diameter, smaller cross-sectional area of fascicles, fewer fascicles and axons, but a similar axon density. The histomorphometric inferiority of the anterior interosseous nerve raises a question about whether it should be transferred only to selected parts of the deep motor branch of the ulnar nerve.Level III.

Principles of nerve repair in complex wounds of the upper extremity

Peripheral nerve injuries are common in the setting of complex upper extremity trauma. Early identification of nerve injuries and intervention is critical for maximizing return of function. In this review, the principles of nerve injury, patient evaluation, and surgical management are discussed. An evidence-based approach to nerve reconstruction is reviewed, including the benefits and limitations of direct repair and nerve gap reconstruction with the use of autografts, processed nerve allografts, and conduits. Further, the principles and indications of commonly used nerve transfers in proximal nerve injuries are also addressed.

Motor and sensory nerve transfers in the forearm and hand

BACKGROUND

Peripheral nerve injury is a significant problem affecting more than 1 million people around the world each year and poses major challenges to the plastic and reconstructive surgeon. For high upper extremity nerve injuries, distal muscle reinnervation and functional outcomes are generally poor. Tendon transfer has been the traditional reconstructive option in these cases to restore hand function. More recently, nerve transfers have been described in the forearm and hand to recover hand and wrist function and critical sensation.

METHODS

This article reviews the surgical principles, donor nerve options, indications, and outcomes of distal nerve transfers for high upper extremity nerve injuries.

RESULTS

The functional results of nerve transfers to date have been comparable to tendon transfers. The primary advantage is the potential for individual finger motion from a donor nerve with singular function. The disadvantage is the longer recovery time required for muscle reinnervation.

CONCLUSIONS

Nerve transfers are a viable option for peripheral nerve injuries distal to the brachial plexus. The choice of management will depend on the patient's individual goals and priorities in terms of the need or desire for individual finger movement and the length of the recovery period.

Advances in nerve transfer surgery

Peripheral nerve injuries are devastating injuries and can result in physical impairments, poor functional outcomes and high levels of disability. Advances in our understanding of peripheral nerve regeneration and nerve topography have lead to the development of nerve transfers to restore function. Over the past two decades, nerve transfers have been performed and modified. With the advancements in surgical management and recognition of importance of cortical plasticity, motor-reeducation and perioperative rehabilitation, nerve transfers are producing improved functional outcomes in patients with nerve injuries. This manuscript explores the recent literature as it relates to current nerve transfer techniques and advances in post-operative rehabilitation protocols, with a focus on indications, techniques and outcomes.

Motor branching patterns of the ulnar nerve in the forearms of fetal cadavers

PURPOSE

The aim of this study was to investigate the branches of the ulnar nerve given to forearm muscles [flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP)] and typing of ulnar nerve according to distribution of these branches to the muscles.

METHODS

From the collection of Anatomy Department Laboratory, Faculty of Medicine, Suleyman Demirel University, 116 upper limbs of fetuses showing no external anomaly and aging between 12th and 40th weeks of pregnancy, were included in this study for anatomical dissection. Parameters about the branching of fetal ulnar nerve were set as follows: branch/branches to FCU muscle and branch/branches to FDP muscle.

RESULTS

Ulnar nerve was typed according to number, sequence, and distribution of motor branches of ulnar nerve. As a result of this typing, eight type branching model of ulnar nerve was confirmed.

CONCLUSIONS

Our study is critically important for implementing successful surgical interventions and minimizing complications especially in ulnar nerve and forearm muscles surgery also in nerve replacement on this area.

A computational model and simulation study of the efferent activity in the brachial nerves during voluntary motor intent

Inherent limitations of the surface myoelectric signal, such as the lack of recording sites in high-level amputations, and the sensitivity to placement and impedance effects, confound its wider application in powered prostheses. Since a functionally topographic distribution (somatotopic organization) of nerve fascicles exists within the peripheral nerves, it is theoretically possible that complete motor control information can be retrieved from peripheral nerve signals. In this study, we present a computational model that simulates the recording from specific nerve fascicles in the upper limb during voluntary contractions while they innervate relevant muscles. A procedure of classifying the nerve data is presented using a set of time domain features and a spike detection algorithm. Recommendations are made to achieve optimal neural signal recognition, with regard to electrode geometry and signal analysis.

Nerve transfers in the forearm and hand

In the forearm, vital and expendable functions have been identified, and tendon transfers use these conventions to maximize function and minimize disability. Using similar concepts, distal nerve transfers offer a reconstruction that often is superior to reconstruction accomplished by traditional grafting. The authors present nerve transfer options for restoring motor and sensory deficits within each nerve distribution on the forearm and hand.

Quantitation of and landmarks for the muscular branches of the ulnar nerve to the forearm for application in peripheral nerve neurotization procedures

Object

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.

Methods

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.

Conclusions

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.

The muscular branching patterns of the ulnar nerve to the flexor carpi ulnaris and flexor digitorum profundus muscles

The branching pattern of the ulnar nerve in the forearm is of great importance in anterior transposition of the ulnar nerve for decompression after neuropathy of cubital tunnel syndrom and malformations resulting from distal end fractures of the humerus. In this study, 37 formalin-fixed forearms were used to demonstrate the muscular branching patterns from the main ulnar nerve to the flexor carpi ulnaris muscle (FCU) and ulnar part of the flexor digitorum profundus muscle (FDP). Eight branching patterns were found and classified into four groups according to the number of the muscular branches leaving the main ulnar nerve. Two (Group I) and three (Group II) branches left the main ulnar nerve in 18 and 17 forearms respectively. The remaining two specimens had four (Group III) and five (Group IV) branches each. Usually one or two branches were associated with the innervation of the FCU. However, in 2 cases, three and in one, four branches to FCU were observed. The FDP received a single branch in all cases, except in four, all of which had two branches. In six forearms, a common trunk was observed arising from the ulnar nerve to supply the FCU and FDP. The distribution of the muscular branches to the revealed muscles was outlined in figures and the distance of the origin of these branches from the interepicondylar line was measured in millimeters. The first muscular branch leaving the main ulnar nerve was the FCU-branch in all specimens. The terminal muscular branch of the ulnar nerve to the forearm muscles arose at the proximal 1/3 of the forearm in all specimens. In 7 forearms, Martin-Gruber anastomosis in form of median to ulnar was observed.

Physiologic and morphologic aspects of nerve regeneration after end-to-end or end-to-side coaptation in a rat model of brachial plexus injury

The results of repairing a transected rat musculocutaneous nerve by suturing the distal stump, end to side or end to end, to the ipsilateral ulnar nerve were assessed at 3 months by retrograde labeling and morphologic and physiologic analysis. Unlike most other models of end-to-side repair in which the injured recipient and donor reinnervating nerves have overlapping neuron pools in the spinal cord, in this model the neurons of the injured musculocutaneous and the reinnervating ulnar nerves are located in mutually exclusive segments of the spinal cord. Using retrograde labeling we show that the reinnervating fibers are derived solely from the ulnar nerve pool. Both end-to-side and end-to-end coaptation resulted in reinnervation of the distal musculocutaneous nerve and significant functional reinnervation of its dependent biceps brachii muscle. Although end-to-end coaptation resulted in better axon morphology and muscle function, it resulted in total loss of donor nerve function. By contrast, end-to-side coaptation resulted in good recovery with only minimal donor nerve deficit. These results show that significant functional reinnervation of biceps brachii muscle can occur solely on the basis of collateral sprouting of intact axons from the adjacent ulnar nerve.

Flexor digitorum superficialis nerve transfer to restore pronation: two case reports and anatomic study

Loss of pronation affects most activities of daily living. We report 2 cases of traumatic loss of pronator teres function and successful reconstruction by transfer of a redundant motor branch to the flexor digitorum superficialis to the pronator teres branch(es). Follow-up period was 2 years and pronation strength was restored to +4/5 and 5/5 in the 2 patients. The anatomy of the median nerve in the proximal forearm was examined by dissecting 31 cadaver specimens. A branching scheme was formulated. The histomorphometric properties of the individual muscular branches were studied in 15 fresh specimens to evaluate their suitability and size match for nerve transfer.