Anatomy of radial nerve and wrist drop

ANATOMY OF RADIAL NERVE AND WRIST DROP

1. ANATOMY OF RADIAL NERVE AND WRIST DROP DR . BIPUL BORTHAKUR PROFESSOR, DEPARTMENT OF ORTHOPAEDICS SILCHAR MEDICAL COLLEGE AND HOSPITAL

2. ANATOMY OF RADIAL NERVE The radial nerve is a continuation of posterior cord of brachial plexus. It is the largest nerve of the brachial plexus . It supplies the posterior (extensor) compartment of upper limb. It carries fibres from all the roots (C5, C6, C7, C8, and Tl ) of brachial plexus .

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4. C O U R S E IN AXILLA The radial nerve lies posterior to the third part of the axillary artery and anterior to the muscles forming the posterior wall of the axilla . Here it gives off the following three branches: Posterior cutaneous nerve of arm Nerve to the long head of triceps. Nerve to the medial head of triceps

5. COURSE IN THE ARM Radial nerve enters the arm at the lower border of the teres major. It passes between the long and medial head of triceps to enter the lower triangular space, through which it reaches the spiral groove along with profunda brachii artery.

6. BRANCHES IN SPIRAL GROOVE Five branches:- Lower lateral cutaneous nerve of the arm. Posterior cutaneous nerve of the forearm. Nerve to lateral head of triceps. Nerve to medial head of triceps. Nerve to anconeus (it runs through the substance of medial head of triceps to reach the anconeus ).

7. At the lower 3 rd of the humerus , it pierces the lateral intermuscular septum to enter anterior part of the arm. It lies between the brachialis medially and brachioradialis and extensor carpi radialis longus laterally.

8. COURSE IN FOREARM To enter the forearm, the radial nerve moves anteriorly over the lateral epicondyle of the humerus . In the cubital fossa , it terminate into two branches: Surperficial branch (sensory). Deep branch (motor) also called as posterior interosseous nerve

9. COURSE OF SUPERFICIAL RADIAL NERVE It descends deep to brachioradialis ,emerges proximal to radial styloid process and passes over the roof of anatomical snuff-box. It supplies skin over the lateral part of the dorsum of hand and dorsal surfaces of lateral 3 ⅟₂ digits (excluding the nail beds).

10. RADIAL NERVE PALSY Clinical findings The patient loses the ability to extend the wrist, fingers and thumb movements that are essential for function grasp. In addition patient loses the grip strength because he cannot stabilize the wrist during power grip. A high radial nerve palsy is defined as an injury proximal to the elbow. Wrist, fingers(MCP joint) and thumb extension and abduction are lost and results in WRIST DROP.

11. RADIAL NERVE PALSY Clinical findings Low radial nerve palsy is defined as injury to the PIN, occurs distally to the elbow. Wrist extension is preserved because the more proximally innervated ECRL remains intact. If the PIN is injured proximally ECU function may be lost resulting in radial deviation and wrist extension. If the injury to the PIN is more distal ECU function is preserved and wrist extension remains balanced.

12. ETIOLOGY Humeral fractures – during fracture (Holstein-Lewis) or during surgery Iatrogenic – upper limb surgery Direct trauma Prolonged application of tourniquet Crutch palsy Intramuscular injections Compression neuropathies- Saturday night paralysis

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14. Lesions of the radial nerve Lesions Motor deficits Sensory loss Lesion at the axilla Triceps weakness Lateral dorsum of the hand and injured by the pressure of the upper end of crutch (crutch palsy), by a dislocation at the shoulder joint, Brachioradialis weakness Extensor weakness of the wrist - " wrist drop ” wrist Dorsum of the thumb Proximal dorsum of fingers 2 and 3 By a fracture of the proximal humerus. Lesion at the spiral Triceps is spared! Lateral dorsum of the hand and wrist Dorsum of the thumb Proximal dorsum of fingers 2 and 3 groove of humerus: Brachioradialis weakness Midshaft fracture of humerus. Wrongly placed Extensor weakness of the wrist - " wrist drop ” intramuscular injection. Saturday night paralysis. Lesion at the radial tunnel (humeroradial joint) Extensor weakness of the wrist - " wrist drop " - may be mild Lateral dorsum of the hand and wrist Dorsum of the thumb Proximal dorsum of fingers 2 & 3.

15. TREATMENT OF RADIAL PALSY Non-operative:- Full passive range of motion in all joints of the wrist and hand and prevention of contractures, including that of the thumb-index web. Splints Wrist drop can be treated successfully by splints

16. INTERNAL SPLINT Burkhalter proposed early transfer of PT-ECRB to restore wrist extension as an adjunct to nerve repair. It restores the power grip quickly and effectively since wrist extension is restored Advantages are: It works as a substitute during nerve regrowth and largely eliminates an external splint Subsequently the transfer aids the newly innervated and weak wrist extensor It continues to act as a substitute in case nerve regeneration is poor or absent

17. INDICATIONS FOR SURGERY In a sharp injury exploration is indicated for diagnostic, therapeutic and prognostic purposes In avulsion , blasting injures –to identification of the nerve injury and making the ends of the nerve with sutures for later repair. When a nerve deficit follows blunt or closed trauma, and no clinical or electrical evidence of regeneration has occurred after an appropriate time, exploration of the nerve is indicated.

18. OPERATIVE MANAGEMENT  Nerve repair  Neurolysis  Tendon transfer

19. TENDON TRANSFER FOR RADIAL NERVE PALSY There are three main goals: Restoration of finger(MCP joint) extension Restoration of thumb extension Restoration of wrist extension Three main patterns of tendon transfer Jones transfer Brand’s transfer Boyes transfer

20. TENDON TRANSFER FOR RADIAL NERVE PALSY Restoration of wrist extension Most accepted method is PT to ECRB transfer. If recovery of the radial nerve is not expected, the transfer should be done in end-to-end fashion. If the radial nerve has been repaired and ECRB re-innervation is expected in the future, the transfer should be done in a end-to-side fashion.

21. TENDON TRANSFER FOR RADIAL NERVE PALSY Restoration of thumb extension The Palmaris longus or ring finger FDS are most often used. When the ring FDS is used, it can be split and inserted into the both EPL and the EIP, allowing concomitant thumb and index finger extension. When the PL is used as a motor, the EPL is usually rerouted volarly to meet the PL in a direct line of pull, which results in abduction of the thumb as well as IPJ extension.

22. TENDON TRANSFER FOR RADIAL NERVE PALSY Restoration of finger MCP joint extension Can be done transferring the FCR, FCU or FDS tendon. Jones transfer: In 1900s Jones popularized the use of FCU to restore MCP extension Jones transfer sacrifices the only remaining ulnar-sided wrist motor which results in radial deviation of the wrist along with the loss of ulnar deviation with wrist flexion which is an important wrist motion essential for activities like hammering and throwing.

23. POST-OPERATIVE CARE AND REHABILITATION Regardless of the procedure performed the patient should be placed in an above elbow splint or cast. The elbow should be flexed at 90 degree with forearm pronated and wrist extended at 30 degree. This takes tension off the PT to ECRB transfer. The thumb should be abducted and extended and MCP joints of the fingers extended to take tension off the transfers to the EDC and the EIP. The IP joints of the fingers should be left free.

24. POST-OPERATIVE CARE AND REHABILITATION The post-operative splint can be changed at one to two weeks for wound check and to refit the splint. At 4 weeks post-operatively a thermoplastic splint should be fabricated. During the first 4 weeks of the surgery it is important to maintain the ROM of the shoulder and the IP joints of the fingers. At 4 weeks mobilization begins and exercises will focus on mobilization of single joints at a time while keeping tension off the transfer. Mobilization begins with active ROM and advance to gentle passive ROM.

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