Median nerve injuries

orthopaedics and nerve injuries

1. MEDIAN NERVE INJURIES Dr. mahak jain Dnb resident

2. Median nerve introduction The median nerve is derived from both the lateral and medial cords of the brachial plexus, with the lateral cord providing mostly sensory axons from C6 and C7, and the medial cord providing motor axons from C8 and T1 . Also called labourer’s nerve.

3. Motor Functions The median nerve innervates the majority of the muscles in the  anterior forearm , and some intrinsic hand  muscles. The Anterior Forearm In the forearm, the median nerve directly innervates muscles in the superficial and intermediate layers: Superficial layer:  Pronator teres , flexor carpi radialis and palmaris longus . Intermediate layer : Flexor digitorm superficialis . The median nerve also gives rise to the anterior interosseous nerve, which supplies the deep flexors: Deep layer:  Flexor pollicis longus , pronator quadratus , and the lateral half of the flexor digitorum profundus (the medial half of the muscle is innervated by the ulnar nerve). In general these muscles perform pronation of the forearm, flexion of the wrist and flexion of the digits of the hand .

4. Cont : HAND: The median nerve innervates some of the muscles in the hand via two branches. The recurrent branch  of the median nerve innervates the  thenar muscles  – muscles associated with movements of the thumb. The   palmar digital branch  innervates the lateral two lumbricals  – these muscles perform flexion at the metacarpophalangeal joints of the index and middle fingers

5. Innervation Motor superficial volar forearm group  Pronator teres  Flexor carpi radialis  Palmaris longus intermediate group  Flexor digitorum superficialis deep group  Flexor digitorum profundus (lateral)  Flexor pollicis longus  Pronator quadratus hand  1st and 2nd lumbricals   Opponens pollicis  Abductor pollicis brevis  Flexor pollicis brevis

6. Sensory innervation: The median nerve is responsible for the cutaneous innervation of part of the hand. This is achieved via two branches: Palmar cutaneous branch  – Arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome. Palmar digital cutaneous branch  – Arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.

7. Course of median nerve Anterior compartment of arm anterior compartment ( anteromedial to humerus ) runs with brachial artery (lateral in upper arm / medial at elbow) no branches in the arm Forearm enters the forearm between the pronator teres and biceps tendon travels between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) then emerges between the FDS and flexor pollicis longus (FPL)

8. Hand the nerve then enters the hand via the carpal tunnel, along with the tendons of the FDS, FDP and FPL Terminal branches anterior interosseous branch (AIN) innervates the deep volar compartment of forearm except the ulnar half of the FDP palmar cutaneous branch  supplies sensory innervation to lateral palm recurrent branch (to thenar compartment) digital cutaneous branches supply the radial 3 1/2 digits (palmar) can also supply the index, long, and ring fingers dorsally

9. Clinical findings: 1. Injury at the Elbow:  Supracondylar fracture of the humerus . Motor functions:   The flexors and pronators in the forearm are paralysed , with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus . The forearm constantly supinated, and flexion is weak (often accompanied by adduction, because of the pull of the flexor carpi ulnaris ). Flexion at the thumb is also prevented, as both the longus and brevis muscles are paralysed . The lateral two lumbrical muscles are paralysed , and the patient will not be able to flex at the MCP joints or extend at IP joints of the index and middle fingers. Sensory functions : Lack of sensation over the areas that the median nerve innervates. Characteristic signs:  The thenar eminence is wasted, due to atrophy of the thenar muscles. If patient tries to make a fist, only the little and ring fingers can flex completely. This results in a characteristic shape of the hand, known as  hand of benediction .

10. 2. Injury at the Wrist: How it commonly occurs:  Lacerations just proximal to the flexor reticaculum . Motor functions:   Thenar muscles paralysed , as are the lateral two lumbricals . This affects opposition of the thumb and flexion of the index and middle fingers. Sensory functions:  Same as an injury at the elbow.

11. Median nerve clinical assessment: 1. Pronator teres (C6, C7) assessment: The patient’s forearm is extended and fully pronated . The patient is then instructed to resist supination of the forearm by the examiner.

12. 2. Flexor carpi radialis (C6, C7) assessment: The patient flexes the wrist along the trajectory of the forearm . Wrist deviates ulnarly .

13. 3. Flexor digitorum superficialis (C8, T1) assessment: To test proximal interphalangeal joint flexion, the supinated forearm and hand are placed straight. This maneuver places the finger to be tested in mild flexion at the metacarpal–phalangeal (knuckle) joint, and stabilizes the remaining fingers in extension, a position that allows isolation of the flexor digitorum superficialis . Ask the patient to flex PIP jt against resistance.

14. 4. Flexor digitorum profundus (C8, T1) assessment: To assess the median innervation of the flexor digitorum profundus one should concentrate on the index finger. To do so, hold the metacarpal-phalangeal and proximal interphalangeal joints immobile, and have the patient flex the distal phalanx against your resistance.

15. Ochsner’s clasping test: flexor digitorum superficialis and profundus ( lateral half)

16. The Thenar Group 5. Flexor pollicis longus (C8, T1) assessment: Immobilize the thumb, except the interphalangeal joint, and then ask the patient to flex the distal phalanx against resistance.

17. 6. Okay ” or “circle” sign with anterior interosseous nerve weakness. A quick way to assess the flexor digitorum profundus and flexor pollicis longus innervation from the anterior interosseous nerve is to ask the patient to make an okay sign by touching the tips of the thumb and index finger together . With weakness in these muscles , the distal phalanges cannot flex, and instead of the fingertips touching, the volar surfaces of each distal phalanx make contact.

18. 7.Pronator quadratus (C7 , C8) assessment : Have the patient resist supination of a fully flexed and pronated forearm. With full forearm flexion, pronation by the usually dominant pronator teres is minimized.

19. 8. Abductor pollicis brevis (C8, T1) assessment: Resist movement of the thumb away from the plane of the palm (palmar abduction), while stabilizing the metacarpals of the remaining fingers.

20. 9. Flexor pollicis brevis (C8, T1) assessment The patient flexes the thumb at the metacarpal-phalangeal joint against resistance placed over both the proximal and distal phalanges. Make certain the distal interphalangeal joint does not flex because in allowing this, substitution by the flexor pollicis longus occurs. Use your other hand to immobilize the first metacarpal to reduce substitution by the opponens pollicis . Because of its dual innervation, even with complete thenar motor branch palsies some thumb flexion still occurs.

21. 10: Opponens pollicis (C8, T1) assessment: Have the patient forcibly maintain contact between the volar pads of the distal thumb and fifth digit, while you try to pull the distal first metacarpal away from the fifth digit. Although thumb opposition is only innervated by the median nerve, a combination of thumb adduction (adductor pollicis , ulnar nerve ) and thumb flexion (flexor pollicis brevis , deep head, ulnar nerve) may mimic thumb opposition even when there is complete median nerve palsy present.

22. 11. Lumbrical of second digit (C8, T1) assessment: Stabilize the patient’s index finger in a hyper-extended position at the metacarpal-phalangeal joint and then provide resistance as the patient extends the finger at the MCP joint.

23. Sensory system examination Modality test – pain,touch,temperature ,pressure and vibration Functional tests –two point discrimination , seddons coin test ,ridge sensitometer Objective test – (a) sweat test (iodine starch test)- dusting extremities with quinizarine powder In denervated area powder remain dry and light gray In normal sweating area it become deep purple colour

24. (b)Skin resistance test Richter dermometer is used Absence of sweating demonstrate increased resistance to passage of electric current (c)wrinkle test denervated skin do not wrinkle on exposure to water for prolonged period ( 4*C for 30 min.)

25. (d) T inel’s sign- tested by gentle percussion along course of nerve from distal to proximal direction. Tingling sensation felt by patient in distribution of nerve. Tingling should persist for several seconds Importance of T inel’s sign Whether Nerve interrupted Whether in Process of regeneration Rate of regeneration Success of nerve repair

26. Electrophysiological study Electromyography Around 3 wks after denervation, the muscle fibres will twitch rhythmically and involuntarily These fibrillations cannot be seen clinically but can be measured by EMG Fibrillations are called denervation fibrillation

27. Nerve conduction test First calculate threshold by stimulating on sound side If twice the threshold fails to produce muscle contraction nerve conduction is absent Slow rate of conduction suggest damage to nerve Compound muscle action potential can be recorded from both proximal and distal Forearm extensor muscles

28. CLASSIFICATION OF NERVE INJURIES SEDDON’S CLASSIFICATION Neuropraxia – temporary paralysis of a nerve caused by lack of blood flow or by pressure on the affected nerve with no loss of structural continuity. Axonotmesis – neural tube is intact but axons are disrupted. Nerves are likely to recover. Neurotmesis – neural tube is severed. Injuries are likely to be permanent without repair.

29. SUNDERLAND’S CLASSIFICATION

30. Median nerve Compression Syndromes Carpal Tunnel Pronator Teres Anterior Interosseous

31. Carpal Tunnel Syndrome Compressive neuropathy as the nerve passes through the Carpal Tunnel Causes: - Idiopathic : Most common - Inflammatory : Rheumatoid Arthritis : Wrist osteoarthritis - Post traumatic : Bone thickening - Endocrine : Myxoedema : Acromegaly - Pregnancy - Gout - Repetitive wrist movts : Typists & Computer users

32. Carpal Tunnel

33. Symptoms Hand and wrist Pain Paraesthesia Hypoaesthsia Sparing of Palmar cutaneous branch supply Patient wakes at night with burning or aching pain and shakes the hand to obtain relief and restore sensation Aggravated by elevation of hand Thenar atrophy and weakness of thumb opposition and abduction may develop late

34. Diagnosis History Clinical examination: - Thenar wasting - Phalen’s sign - Tinel’s sign - Carpal compression test Electro Diagnostic Studies: - Very reliable for evaluation - Atypical cases may be present

35. Thenar atrophy

36. Tinel’s Sign

37. Carpal Compression test/ Durkan’s test

38. Management Splinting – prevents wrist flexion Corticosteroid/anesthetic injection Surgical decompression:Division of the transverse carpal ligament - Open - Endoscopic

39. Complications Injury to palmar cutaneous /recurrent motor branch of the median nerve Hypertrophic scarring Hematoma/Arterial injury

40. Pronator teres syndrome High Compression neuropathy It is rare compared to CTS and AIS Misnomer  Proximal forearm median nerve compression

41. Symptoms & signs Symptoms are similar to those of carpal tunnel syndrome Sensory disturbances - Thumb & Index > Middle finger Night pain is unusual and forearm pain is more common Hand numbness on gripping Phalen’s test negative Symptoms provoked by resisted elbow flexion with forearm supinated ( tightening of bicipital aponeurosis ) By resisted forearm pronation with the elbow extended ( pronator tension )

42. Management No relief with steroids Surgical decompression

43. Anterior Interosseous Syndrome Damage to the Anterior Interosseous Nerve Pain in the forearm Weakness of the gripping movement of the thumb and index finger( unable to make ok sign ) Causes: - Injury to elbow - Injury during open/closed reduction

44. Management Corticosteroids Surgery: - Resection/detachment of deep head of PT

45. Tendon transfer in median nerve injuries Median nerve palsy is perhaps the most devastating single nerve injury of the upper extremity. Not only is there a loss of fine motor control and opposition, but sensibility is lost over the area of the hand used for precision movements and prehensile functioning . Tendon transfer procedures to restore movement may be ineffective if sensibility cannot be restored . High median nerve palsy is defined as an injury proximal to the innervation of the forearm muscles. Although PT and FCR functions are lost, forearm pronation and wrist flexion are compensated for by other muscles, and do not need to be restored.

46. Although the FDS to all four fingers is lost, flexion is maintained in the ring and small fingers by the functioning ulnar-innervated FDP muscle bellies. However, even though ring and small finger flexion is preserved, grip strength is diminished. More importantly, there is a loss of thumb IPJ flexion and index and middle finger DIPJ flexion due to loss of the AIN innervated muscles. This results in a lack of fine motor control of the hand, which is normally provided by precise movements of the IPJ of the thumb and the IPJ’s of the index and middle fingers. In addition to these deficits, crucial thumb opposition is lost. Low median nerve palsy, on the other hand, results in loss of thumb opposition and sensory loss only. The fact that some degree of sensory reinnervation is likely when a low median nerve injury has been repaired makes this a potentially less devastating injury than high median nerve palsy.

47. General indications of surgery In sharp injury exploration for diagnostic as well as theurapeutic purpose . Nerorrhaphy can be done at time of exploration or delayed In avulsion or blast injury –to identify and suture of nerve ends for delayed repair No improvement since last 12 weeks following close injury

48. Time of surgery Primary repair within 6-8 hours gives best results Delayed primary repair – between 7- 18 days Secondary repair - 3 to 6 weeks later .preferable in crushed , avulsed,contaminated wounds where patients life is seriously endangerd

49. Surgical techniques Coaptation Approximating the cut ends of nerve in such a way that motor fasiculi meets another motor fasiculi and sensory to sensory Conventionally done by 8-0 to 10-0 nylon suture Sutureless methods includes fibrin clots, adhesive tapes ,collagen tubulization

50. Neurolysis Neurolysis is dissection to free nerve fibers Exo Neurolysis - removal of neuroma or binding cicatrix Endo Neurolysis - seperation of of each of fasciculi from surrounding non fascicular tissue

51. Neurorrhaphy Neurorrhaphy is end to end suturing of nerve Types Partial Neurorrhaphy Epineural Neurorrhaphy Perineural (fascicular) Neurorrhaphy Epiperineural Neurorrhaphy Interfascicular nerve grafting

52. Epineural neurorrhaphy

53. Perineural neurorrhaphy

54. Epiperineural neurorrhaphy

55. Inter fascicular nerve grafting

56. Nerve grafting A gap between cut ends more than 2.5-4 cm is indication of nerve graft Types of grafts Trunk graft Cable graft Pedicle nerve graft Inter fascicular nerve graft Pre vascularised nerve graft

57. Critical Limit of Delay of Suture Return of motor function should not be expected when suture has been delayed for more than 15 months .

58. Reconstructive procedure 1 Tendon transfer 2 Arthrodesis When neighboring tendons are intact and if all criteria for tendon transfer met ,then tendon transfer is treatment of choice Tendon transfer should be delayed for 6 months

59. Criteria for tendon transfer Muscle power grade 5 (preferably),if not atleast grade 4 Should have its own nerve and blood supply Synergistic group are chosen because of easier rehabilitation Age should be more than 5 years Disease should not progress and infection to be controlled Prior to transfer joint stiffness,contracture and malunion are corrected Tendon transferred should not be at an acute angle

60. 1. Restoring thumb opposition: The most devastating loss of movement following high or low median nerve injury is the loss of thumb opposition. This can be restored with an opponensplasty , or opposition transfer. Thumb opposition is a complex movement that involves palmar abduction, pronation, and flexion of the thumb metacarpal and proximal phalanx. The ideal insertion for an opposition transfer is the APB insertion. Insertion at this point most reliably causes the combination of movements that result in thumb opposition . The angle of pull should be from the location of the pisiform, because this approximates the normal direction of pull of the APB. A pulley is often necessary to create the proper line of pull. The transverse carpal ligament, the palmar fascia edge, a loop of the FCU tendon, and the FCU tendon itself have all been used as pulleys

61. The superficialis opponensplasty described by Royle in 1938, involves dividing the ring inger FDS distally in the finger, retrieving the FDS proximal to the carpal tunnel, re-directing the tendon distally through the FPL sheath, and inserting it into the thumb . The main disadvantage of the superficialis opponensplasty is that it can only be used in cases of low median nerve palsy, because the FDS is paralyzed in high median nerve palsy

62. Superficialis opponensplasty using ring finger FDS for restoration of opposition in low median nerve palsy.

63. The EIP(extensor indicis propius ) opponensplasty : in cases of both low and high median nerve injury , and is the most commonly employed opposition transfer in high median nerve palsy Although the EIP is a weak motor, it is sufficiently strong to move the thumb into opposition. The EIP is tunneled around the ulnar aspect of the wrist, routed across the palm from the level of the pisiform, and inserted on the APB. It is important to close the extensor hood of the index MCPJ after EIP harvest to prevent postoperative extension lag at the index MCPJ . Functional loss with the EIP transfer is minimal, and retraining the EIP to perform thumb opposition is not difficult.

64. EIP opponensplasty for restoration of opposition in high median nerve palsy.

65. The Huber transfer: employs the ulnar nerve-innervated abductor digiti minimi (ADM) to restore opposition. This transfer is usually used in cases of congenital absence of the thenar muscles , and in cases where the FDS and EIP are not available. The ADM is released from its insertion , turned over 180 degrees, and inserted on the APB insertion. Strength and excursion are well matched to the deficit, and the transfer is synergistic

66. HUBER PROCEDURE:

67. Restoring Thumb IPJ flexion and index finger DIPJ flexion In cases of high median nerve injury, thumb IPJ flexion and index finger DIPJ flexion can be restored with transfer of the BR, the ECRL, or ECU. The most common transfers are BR to FPL and ECRL to index FDP. However, it should be remembered that reinnervation of the FPL and FDP is common after a high median nerve injury has been repaired. If a return of function is anticipated, an end-to-side transfer should be performed. If recovery is not expected, an end-to-end transfer results in a more direct line of pull.

68. Rehabilitation: First 4 weeks: splint that should take tension off the tendon transfer(s) performed. For example, if a transfer was performed to improve clawing, the splint should keep the MCPJ’s flexed and the IPJ’s extended . maintain mobility in the non-immobilized joints of the upper extremity. After 4 weeks: Mobilization should start with gentle active and assisted range of motion exercises. It is important to mobilize one joint at a time to prevent placing too much tension on the transfer. For example, if an ECRB transfer to treat clawing was performed, the therapist should mobilize the MCPJ’s while keeping the wrist and IPJ’s immobile. 6 weeks: exercises that activate the muscles used in the tendon transfer, and should begin muscle retraining. Electrical stimulation and biofeedback may be used to assist with retraining . 8 weeks: At eight weeks postoperatively, strengthening exercises should be initiated, and the splint can be weaned off over the next four weeks. Full activity is resumed at twelve weeks.

69. COMPLICATIONS: Tendon adhesions, transfer rupture, T ransfer weakness Infection Neuro vascular injuries

70. Thank you