SYM18: You Want To Do Your First Nerve Transfer Moderator(s): Amy M. Moore, MD Faculty: Stacy Baker, MOT, OTR/L, CHT, Jayme A. Bertelli, MD, PhD, and Christopher J. Dy, MD, MPH, FACS Session Handouts Saturday, October 03, 2020 75TH VIRTUAL ANNUAL MEETING OF THE ASSH OCTOBER 1-3, 2020 822 West Washington Blvd Chicago, IL 60607 Phone: (312) 880-1900 Web: www.assh.org Email: [email protected] All property rights in the material presented, including common-law copyright, are expressly reserved to the speaker or the ASSH. No statement or presentation made is to be regarded as dedicated to the public domain. Nerve Transfers Amy M. Moore, MD, Plastic and Reconstructive Surgery The Ohio State University I. Introduction Following high nerve injuries, motor and sensory recovery can be less than optimal. Nerve transfers can provide a distal source of motor and/or sensory innervation closer to the target end organ which allows faster recovery and improved outcome. This course will focus on the use of nerve transfers to restore function. It will include discussion on patient selection, surgical options and techniques (including demonstrative videos/case presentations). Nerve transfer (def) – transfer of an expendable donor nerve or fascicle to a denervated recipient nerve to restore function to the recipient end-organ (skin for sensation or muscle for motor). Benefits: 1. Performed closer to recipient target allowing for earlier reinnervation. 2. Can be performed outside of the zone of injury and scarred field. 3. Can be performed on patients with delayed presentations. 4. Avoids interposition nerve grafting which fosters increased regenerating nerve fibers making it to the target end-organ. (1, 2) Goal: Reinnervation of the target muscle within 12-18 months to avoid irreversible atrophy (3, 4). Classification of Nerve Injuries TINEL'S DEGREE OF RATE OF SURGICAL SIGN RECOVERY INJURY RECOVERY PROCEDURE PRESENT Up to 12 I Neurapraxia No Complete None Weeks II Axonotmesis Yes Complete 1" per month None None or III Yes Varies* 1" per month Neurolysis Neuroma In- Yes, but no Nerve repair, IV None None Continuity advancement graft, or transfer Yes, but no Nerve repair, V Neurotmesis advancement None None graft, or transfer Some Some Depends on Neurolysis, Mixed Injury VI fascicles fascicles degree of nerve repair, (I to V) (II,III) (II,III) injury (I-V) graft, or transfer * Recovery can vary from excellent to poor depending on the amount of scarring and the sensory versus motor axon misdirection to target receptors Principles of nerve transfers: 1. History and Physical Exam: a. Timing from injury b. Extent of involvement (level and degree of nerve injury) c. Current functional limitations d. Presence of potential donor nerves 2. Donor Selection: a. expendable motor nerve b. close to the motor end plates of the target muscle c. large number of motor nerve axons and MRC grade 4 strength d. synergistic muscle function - motor reeducation more straightforward 3. Preoperative Studies: a. EMG/NCS – at 10-12 weeks post injury i. identify extent of injury and recovery ii. identify donors intact Pearls and Pitfalls: • Remind anesthesiologist—no long acting paralytics • Short or no tourniquet use to avoid neurapraxia and inability to stimulate nerves • Evaluate recipient with nerve stimulator before transection • Evaluate donor with nerve stimulator to confirm function and strength • “Donor DISTAL, Recipient PROXIMAL” • Perform coaptations without tension. II. A list of common injury patterns and treatment options (both nerve transfer and traditional treatment options): Upper plexus injury—loss of elbow flexion: • Double fascicular nerve transfer (from median and ulnar nerves to biceps and brachialis nerve branches) • Transfer of triceps, latissimus or pectoralis nerve branches to the elbow flexors; Steindler flexorplasty, long nerve grafts Upper plexus injury—loss of shoulder function: • Spinal accessory nerve to suprascapular nerve and triceps to deltoid nerve branch transfers • Shoulder fusion, Saha procedure, long nerve grafts Lower plexus injury—loss of pronation • Brachialis or extensor carpi radialis brevis (if C7 is spared) to pronator nerve branch transfer • Biceps, brachioradialis or brachialis muscle rerouting Lower plexus injury—loss of thumb and index finger flexion • Supinator branch to anterior interosseous nerve transfer • Brachialis branch to anterior interosseous nerve transfer • Tendon transfers (brachioradialis to flexor pollicis longus and extensor carpi radialis longus to index flexor digitorum profundus) Axillary nerve injury • Triceps, medial pectoral or thoracodorsal nerve to axillary nerve transfer • Shoulder fusion, long nerve grafts Radial nerve injury • Median (flexor carpi radialis, flexor digitorum superficialis branches) to radial (extensor carpi radialis brevis and posterior interosseous nerve branches) nerve transfers • Tendon transfers (pronator teres to extensor carpi radialis brevis, palmaris longus to extensor pollicis longus, and flexor carpi ulnaris, flexor carpi radialis or flexor digitorum superficialis to extensor digitorum communis) Loss of median innervated pronation • extensor carpi radialis brevis to pronator teres branch • Biceps, brachialis or brachialis muscle rerouting Loss of median innervated thumb and finger flexion • Supinator or brachialis to anterior interosseous nerve branch (combine w/ tenodesis of long to ring/small flexors) • Tendon transfers (brachioradialis or extensor carpi radialis longus to flexor pollicis longus and side to side tenodesis with ulnar flexor digitorum profundus or extensor carpi radialis longus to index/long flexor digitorum profundus) Isolated AIN injury • flexor digitorum superficialis to anterior interosseous nerve branch • brachioradialis to flexor pollicis longus tendon transfer and flexor digitorum profundus tenodesis, fusion of interphalangeal joint of thumb Distal median nerve injury • AIN to median motor branch • Opponensplasty Distal ulnar nerve injury • anterior interosseous nerve to ulnar nerve deep motor branch • Static and dynamic claw hand correction procedures III. Nerve Transfers to Restore of Elbow Flexion (Musculocutaneous Nerve) Double Fascicular Transfer – our preferred operation when hand function is preserved. a. FCU fascicle to biceps branch of musculocutaneous b. FCR/FDS fascicle to brachialis branch of musculocutaneous Figure 1. Double fascicular transfer demonstrating FCU fascicle to biceps branch and FCR fascicle to brachialis branch of musculocutaneous nerve Pearls and Pitfalls: • Use handheld stimulator to identify donor fascicles as well as to ensure adequate function is remaining in the donor nerve • Avoid downgrading function of donor – ensure MRC grade 4 strength • Understand the topography of the median and ulnar nerves in the upper arm. Hint: the donor fascicles on ulnar and median nerve face each other. • Neurolyse the LABC branch away from coaptation to avoid axon loss down the sensory pathway. • “Donor DISTAL, Recipient PROXIMAL” • Perform coaptations without tension. IV. Nerve Transfers to Restore Radial Nerve Function Key Points • Patient Selection is key: Needs to be willing to wait for reinnervation window of 6-9 months (in contrast to 4-8 weeks with tendon transfers) • As with tendon transfers – synergistic transfers should be performed: FCR/PL to PIN and FDS to ECRB • Tensionless repair V. High Median Nerve Injury Nerve Transfers to restore hand function 1. Brachialis branch to anterior interosseous nerve transfer.(8) a. For patients with intact, strong elbow flexion b. Restores FPL and FDP to the index (and sometimes long finger) c. While coaptation is performed at level of arm, more extensile dissection of median nerve and branches is often required to avoid inadvertent innervation of non-critical median fascicles (sensory, FDS/FCR or other branches) Figure 5. Transfer of the brachialis branch to the anterior interosseous nerve. VI. Sensory Nerve Transfers Sensory donor nerve a. non-critical sensory distribution b. pure sensory nerve c. good size match between donor and target nerve d. common sensory nerve transfers e. Nerve to the 4th webspace to 1st web space transfer to restore sensation to the radial side of the index and ulnar side of the thumb f. End-to-side repair of 2nd and 3rd web space to ulnar digital nerve to the small to restore sensation to the 2nd and 3rd web spaces g. End-to-side repair of ulnar sensory and dorsal ulnar sensory nerves to median nerve to restore sensation to the small and ring fingers and ulnar dorsal skin VII. Tips and Pearls of Nerve Transfers “Donor distal, recipient proximal”: • this concept is crucial to ensuring adequate length is obtained • the donor nerve is cut at it’s distal-most useful portion • the recipient nerve is divided proximally enough so that it can be mobilized • this avoids interpositional grafts, which could substantially downgrade results Tension-free repair: • nerve repair must be tension-free and allow full passive range of motion at the time of surgery • tension will dramatically downgrade the functional outcome Align fascicles of the same modality (motor or sensory): • crucial for successful recovery of function Natural cleavage planes: • between critical fascicle groups • often identified by prominent longitudinal microvessels • can also be identified by tapping micro-forceps gently across the transverse diameter of the nerve • the forceps will “fall” into the natural cleavage plane End-to-Side Repairs: • A: motor donor nerves must be subjected to axotomy or