· symptoms and signs due to compression of median nerve in carpal tunnel
· middle-aged women
· M:F = 2:1
· peak age 40-50 yrs
· often bilateral
· decreased size of carpal tunnel
· bony abnormalities
· thickened transverse carpal ligament
· increased contents of canal
· neuroma
· lipoma
· myeloma
· abnormal muscle bellies
· persistent median artery
· hypertrophic synovium
· distal radius fracture callus
· post-traumatic osteophytes
· haematoma
· neuropathic conditions
· diabetes
· alcoholism
· proximal lesion of median nerve (double crush syndrome)
· inflammatory conditions
· tenosynovitis
· rheumatoid arthritis
· infection
· gout
· alterations of fluid balance
· pregnancy
· eclampsia
· myxoedema
· haemodialysis
· sleep (horizontal position and muscle relaxation)
· Raynaud's disease
· obesity
· other diseases
· acromegaly
· amyloidosis
· repetitive flexion and extension or squeezing and release
· manual labour
· finger motion with wrist extended
· typing
· playing musical instruments
· weight-bearing with wrist extended
· paraplegia
· long-distance cycling
· exposure of hand to vibration
· presentation may be diverse
· classical history is
· pain and parasthesiae in radial three and one half digits
· worse at night
· relief from hanging arm over side or bed or shaking hand
· other features
· radiation of pain up forearm, arm and shoulder
· clumsiness
· worse with pinching (eg. reading newspaper)
· worse with grasping (eg. driving)
· common associated conditions
· diabetes
· RA
· hypothyroidism
· gout
· may be no abnormalities
· skin changes in distribution of median nerve
· dry, red, shiny
· loss of fingerprints
· trophic changes
· decreased sensation in median n distribution
· wasting of thenar muscles
· weakness of AbPB
Phalen's test
· patient places elbows on the table, forearms vertically and wrists flexed
· positive result indicated by numbness or tingling on radial side digits within 60 seconds
· positive result is suggestive of CTS
· sensitivity 0.75 *
· specificity 0.47
Tinel's test
· examiner lightly taps along median nerve at wrist, distal to proximal
· positive result is tingling response in fingers at site of compression
· positive result at wrist is suggestive of CTS
· sensitivity 0.6
· specificity 0.94 *
Hand diagram
· patient marks sites of pain or altered sensation on outline diagram of hand
· positive result is signs on radial digits without signs on palm
· positive result is suggestive of CTS
· sensitivity 0.96
· specificity 0.73
· negative predictive value of negative test 0.91
Two pont discrimination test
· examiner determines minimum separation of two points perceived as distinct when lightly touched to palmar surface of digit
· positive result is inability to discriminate points > 6 mm apart
· positive result suggests advanced nerve dysfunction
· operator dependent
· usually use for comparison
· published tables
· ipsilateral ulnar nerve
· contralateral median nerve
· problems with this
· population variance
· systemic general peripheral neuropathies
· bilateral carpal tunnel syndrome
Distal sensory latency and conduction velocity
· involves orthodromic stimulus and recording across wrist
· positive result is latency > 3.5 mm/s or asymmetry of conduction velocity (cf other side) > 0.5 mm/s
Distal motor latency and conduction
· involves orthodromic stimulus and recording across wrist
· positive result is latency > 4.5 mm/s or asymmetry of conduction velocity (cf other side) > 1 mm/s
EMG
· needle electrodes palced in the thenar muscles
· positive result is fibrillation potentials, sharp waves, increased insertional activity
· indicates denervation of thenar muscles
· cervical
· disc disease
· spondylosis
· thoracic outlet syndrome
· median nerve compression elsewhere
· find and treat underlying conditions
· trial of abstinence from activities
· splinting wrist in neutral position
· oral anti-inflammatory medications
· direct injection of steroids into carpal tunnel
· relief in 80%
· permanent in 20%
· carpal tunnel release
Open
Technique
· tourniquet
· regional or general anaesthesia
· loupes preferable
· incision either curved 1-2 mm ulnar to thenar crease OR straight in line with ring finger beginning at Kaplan's line
· superficial palmar fascia and transverse carpal ligament divided
· distal forearm fascia divided under direct vision
· contents of carpal tunnel inspected
· skin closed
· soft dressing applied
Length of incision
· short incision
· adequate exposure
· less morbidity
· better cosmesis
· long incision that crosses wrist crease
· better exposure
· better access
· better appreciation of anatomical anomalies
· increases scar sensitivity
· probably indicated for re-exploration
Synovectomy
· flexor tendon synovitis common
· may be
· reaction of flexor tendons to tight tunnel (usual)
· primary cause of CTS
· routine synovectomy not indicated
· causes bleeding and scar formation
· may result in adherence of nerve to tendons
· may restrict tendon movement
· appropriate only where flexor synovium primarily involved (eg. rheumatoid arthritis)
Neurolysis
· goal is to relieve inelastic constructions and restore normal fluid flow within nerve
· studies have shown no advantage
· may cause damage to nerve
· thus not indicated
Retinacular reconstruction
· disruption of pulley may lead to palmar displacement of flexor tendons with altered biomechanics and loss of grip strength
· routine reconstruction with lengthening of transverse carpal ligament proposed
· ligament heals without reconstruction
· weakness mostly due to widening of carpal arch
· no obvious advantage to ligament reconstruction
Postoperative splinting
· conventional treatment is splinting in neutral for a week or more
· study showed mobilisation in soft dressing after 24 hrs resulted in more rapid return to work with no increase in complications
Effect
· volume of carpal tunnel increases 25%
· changes shape from oval to circular
· Guyon’s canal increases in size and shape
· explains relief from ulnar symptoms
· should not perform routine Guyon’s canal release
Problems with open decompression
· persistent weakness
· tenderness of scar
· pain in thenar and hypothenar eminences (pillar pain)
· delay in return to ADL and work
Endoscopic
· alternative to open method to avoid problems of open decompression
Technique
· tourniquet
· regional (preferable) or general anaesthesia
· 2 cm transverse incision between palmaris longus and flexor carpi ulnaris tendons just proximal to wrist crease
· rectangular distally based flap cut in transverse carpal ligament
· second 1.5 cm transverse incision along Kaplan's line in line with ring finger
· superficial palmar arch, digital branches of median nerve and distal edge of transverse carpal ligament identified
· wrist placed in 30o extension
· trocar and sheath passed through proximal incision into carpal canal and out through distal incision
· endoscope inserted proximally
· undersurface of ligament examined
· upward-cutting triangular knife inserted and withdrawn with upward pressure to divide ligament
· wound closed
· dressing applied
Comparison with open method
· similar efficacy
· subjective parasthesiae
· clinical tests of nerve function
Advantages
· decreased incidence of scar tenderness and pillar pain
· earlier return to ADL and work (14-16 cf 28-46 days)
Disadvantages
· operative complications
· division of median nerve, ulnar nerve, digital nerves, flexor tendons, superficial palmar arch
· incomplete decompression requiring subsequent open procedure
· expense (costs $700)
· time (takes 10 min longer)
· learning curve
· requires formal training and practice on cadavers
Acute
· seen with fracture of distal radius
· increased with
· circular cast
· wrist in flexion
· if median nerve symptoms occur, remove cast
· if no better after 2-4 hrs, measure carpal canal pressure
· if > 45 mm Hg, perform open release with extension into forearm
Incorrect diagnosis
· most often overdiagnosed nerve compression
· can be minimised by
· careful assessment
· determination of cause
· NCS if diagnosis equivocal
Injection into median nerve
· can occur with HCLA injection
· can be avoided by
· practicing during open procedures
· withdrawing needle with parasthesias
Incomplete decompression
· one of most common complications
· often due to deep fascia of forearm proximally
· can be avoided by
· effective tourniquet
· adequate skin incision
· proximal retraction and decompression
Division of palmar branch
· common
· confirmed by
· dysaesthesia in palm
· positive Tinel’s sign
· relief with injection of local anaesthetic
· can be avoided by
· incision in line with ulnar aspect of ring finger
· no transverse incision at wrist crease
· difficult to treat
· often too small to identify or repair
· neuroma may be identifiable and removable
· proximal division of nerve may cause another neuroma
Hypersensitive scar
· increased with incision that crosses wrist crease
· incision that crosses wrist crease probably only indicated in re-exploration
· difficult to treat
· excision and z-plasty may be indicated
Reflex sympathetic dystrophy
· decreased by
· minimising trauma to nerve
· avoiding internal neurolysis
· thorough haemostasis (release tourniquet)
· use of soft bulky dressing
Division of recurrent branch
· prevented by
· knowledge of anatomy and variants
· adequate visualisation and careful section
· should be repaired once recognised
Motor branch of median nerve
· most important structure at risk
· location can vary
· variations include
1. extraligamentous recurrent
· most common (50%)
· branches distal to TCL
· recurrent course to thenar muscles
2. subligamentous
· next most common (30%)
· branches beneath TCL
· lies close to median n
· recurrent course to thenar muscles distal to TCL
3. transligamentous
· less common (20%)
· branches beneath TCL
· pierces TCL
· enters thenar muscles
4. other
· high division
· branching from ulnar border of median nerve
· nerve superficial to TCL
Palmar cutaneous branch of median nerve
· arises in distal 1/3 of forearm
· from palmar-radial side of median nerve
· usually 5 cm proximal to wrist
· passes distally
· parallel and superficial to median nerve
· ulnar and superficial to FCR
· pierces deep fascia
· symptoms and signs from compression of median nerve in forearm
Ligament of Struthers
· remnant of 3rd head of coracobrachialis
· runs
· from supracondylar spur on anteromedial humerus
· to medial epicondyle
· median n and brachial a may run beneath it
Bicipital aponeurosis
· syn. lacertus fibrosis
· runs
· from medial border of biceps tendon at level of elbow
· to subcutaneous border of ulna via deep fascia
· runs over median n
Pronator teres
· may
· be hypertrophied
· have fascia on surface
· median n runs between heads
Arch of FDS
· runs from humeroulnar head
· common origin (medial epicondyle)
· sublime tubercle on medial coronoid
· passes to radius
· anterior oblique line on radial head
· median n passes under it
· pain in volar aspect of distal arm and in forearm
· sensory symptoms in distribution of median n
· weakness of intrinsic and extrinsic muscles
· wasting of intrinsic and extrinsic muscles
· provoked by
· resisted flexion of elbow at 135o (ligament of Struthers)
· resisted flexion of pronated elbow (bicipital aponeurosis)
· resisted pronation of elbow (pronator teres)
· resisted flexion of FDS of middle finger (arch of FDS)
· confirm location
· exploration of median nerve about elbow
· symptoms and signs from compression of anterior interosseous nerve
· compression in proximal forearm
· numerous structures implicated
· vague pain in proximal forearm
· worsened by exercise and relieved by rest
· no sensory disturbance
· weakness or paralysis of
· index FDP
· FPL
· pronator quadratus
· unusual pinch
· hyperextension of DIP jt of index and IP jt of thumb
· no sensory signs
· confirm location
· exploration of median and anterior interosseous nerves in forearm