Hand and digit injuries

Intrinsic hand muscles

• Thenar muscles (superficial to deep)
  • Abductor pollicis brevis, opponens pollicis, flexor pollicis brevis
  • Motor branch of median nerve supplies all except deep head of flexor pollicis brevis (ulnar nerve)
    • Remember median nerve supplies LOAF (lateral two lumbricals + above)
  • Adductor pollicis brevis supplied by ulnar nerve
• Hypothenar muscles (superficial to deep)
  • Abductor digiti minimi, flexor digiti minimi and opponens digiti minimi
  • All innervated by ulnar nerve

• Interosseous muscles
  • Three palmar and four dorsal
  • All innervated by ulnar nerve
  • DAB and PAD (dorsal abduct and palmar adduct)
• Lumbricals
  • FDP tendons to tendons on radial side of digits
  • Flex MCP and extend IP joints
  • Lateral two innervated by median nerve and medial two by ulnar nerve

Extensor tendons

• Extensor digitorum tendons connected by juncturae at distal dorsal aspect of hand – thus finger extension may still be possible with complete tendon laceration proximal to this
• Central slips attach to middle phalanx and two lateral bands join with tendons of lumbricals and interossei to attach to dorsal base of distal phalanx as the terminal tendon

Flexor tendons

• Flexor carpi radialis, flexor carpi ulnaris and palmaris longus do not run through carpal tunnel and primarily flex the wrist
• 4 FDP, 4 FDS and flexor pollicis longus run through carpal tunnel
• FPL inserts onto base of distal phalanx of thumb
• FDS inserts into the volar, proximal half of middle phalanx and flexes the PIP and MCP joints
• FDP runs deep to FDS until level of MCP at which point it bifurcates and inserts at volar base of distal phalanx and primarily flexes DIP + PIP/MCP
• Enclosed in synovial sheaths and thus prone to deep space infections

Flexor tenosynovitis

• Kanavel signs
  • 1. Finger held in slight flexion
  • 2. Fusiform swelling of phalanx
  • 3. Tenderness along flexor sheath
  • 4. Worsening pain on passive extension
• Thumb and little finger sheaths extend to carpal tunnel – spread of infection to wrist and forearm
• Index, middle and ring finger sheaths extend to midpalmar space
• If presents within 24 hours – Attempt IV antibiotics
• If >48 hours or fails IV antibiotics – Surgical debridement
• Complications – Flexor tendon necrosis and digital contracture

Vascular supply

• Radial artery forms deep palmar arch
• Ulnar artery forms superficial palmar arch (distal to deep arch)
• Common digital arteries (in 2^nd/3^rd/4^th web spaces) arise from the superficial palmar arch and supply the fingers
  • Divide into proper digital arteries at web spaces
  • Give dorsal branches distal to PIP joints
  • Dominant arteries run on ulnar aspect of digits
• Blood supply to thumb arises from princeps pollicis, which is the radial artery as it turns into the palm
• Radialis indicis artery, on radial side of index finger arises from the radial artery

Nerve supply

• Radial nerve – Dorsal aspect of hand up to PIP joint (and not including ulnar aspect of hand)
• Ulnar nerve – Entire ulnar aspect including tips of fingers and ulnar half of 4^th finger
• Median nerve – Palm of hand (not including ulnar aspect) and dorsal aspect of tips of 2/3/radial half of 4^th digits
• Always assess two-point discrimination as digital nerves easily injured
  • Normal is 5mm
• Digital nerves
  • Single common palmar digital nerves divide into proper digital nerves at distal palm
  • Main digital nerves run on ventrolateral aspect of finger immediately lateral to the flexor tendon sheath
  • Small dorsal digital nerves run on dorsolateral aspect of the finger and supply innervation to back of fingers as far as PIP joint

Ulnar claw hand

• Results from below elbow ulnar nerve injury
• Ulnar nerve innervation to FDP intact
• Ask patient to extend 4th/5^th fingers
  • Results in hyperextension at MCP and flexion of IP joints as unopposed FDP action due to absent interossei/lumbrical function
• Also known as the intrinsic minus hand (as intrinsics are paralysed)

Ulnar nerve paradox

• The closer the injury is to the elbow, the more likely FDP innervation is lost, resulting in a less pronounced ulnar claw hand (4^th/5^th fingers are simply paralysed in extended position)

Hand of benediction

• Median nerve injury means when ask patient to flex fingers, 2^nd/3^rd fingers remain in extension

Intrinsic plus hand

• Due to intrinsic muscle spasm and/or extrinsic muscle weakness
• Characterised by MCP flexion and PIP/DIP extension (POSI appearance)

Nerve testing

• Median nerve – Flex thumb IP joint (FPL) or FDP function of 2^nd/3^rd digits
  • OK sign tests both of these
  • Can also test palmar abduction of thumb and palpate abductor pollicis brevis at same time
  • If injury is at wrist level, innervation of FDP and FPL occurs proximal to this and will be intact. Thus, can only determine median nerve injury at wrist level by testing sensation and thenar eminence muscle function (APB)

• Ulnar nerve
  • Have patient abduct fingers and then test resistance against adduction force on ulnar aspect
  • Can test thumb adduction also (hold piece of paper with volar pulp of thumb against radial side of PIP joint of index finger)
    • If cannot hold paper and uses FPL to flex thumb IP joint = positive Froment’s sign

• Radial nerve
  • Hyperextend finger MCP joint against resistance (extensor digitorum communis tendons)
  • Easiest if palm down on flat surface and have to hyperextend each finger in turn
  • Important to keep MCP joint in extension as if MCP flexed, interossei can extend the IP joints
  • Extend thumb against resistance (EPL)
  • If posterior interosseous nerve injury (branch of radial nerve to extensor muscles) will not be able to hyperextend digits but may be able to extend wrist due to intact supply to ECR and extensor radialis brevis

Nerve testing

• 2-point discrimination is best
• <5mm normal (<6mm in elderly)
• Hand surgeons recommend testing 2-4 times on each aspect of each digit as can guess
• >80% accuracy is sufficient
• <80% accuracy suggests digital nerve injury
• Sensory deficit implies possible digital artery laceration due to close proximity of two structures

Testing of tendons

• Important to assess against resistance as can have 90% laceration with preservation of ROM without resistance
• Extensor tendon lacerations may be compensated for by extensor juncturae tendinum with intact extension ROM but will not have the same power resistance
• Pain along course of tendon even with normal strength suggests a partial laceration
• Test FDP by DIP joint flexion with PIP held in extension
• Test FDS by PIP joint flexion while other fingers held in extension
  • As FDP cannot fire thus isolating FDS

Testing of tendons

• Elson’s test
  • To determine if central slip is intact of extensor digitorum
  • Hold PIP in flexion and have patient try to extend the PIP joint against resistance
  • If DIP remains loose, central slip is intact and extension force is being transmitted to the central slip
  • If DIP becomes rigid and PIP does not extend, Elson’s test positive, meaning central slip is not intact and extension force is being transmitted through the lateral bands to the terminal tendon to the DIP joint

Flexor tendon injuries

• <25% usually do not need repair but assessment must be made by hand surgeon
• Zone I – Distal to insertion of FDS
  • Involves only FDP
  • Lose flexion at DIP joint
• Zone II – Between distal palmar crease and FDS insertion
  • No man’s land
  • Poor outcomes historically due to narrow fibro-osseous tunnel
  • Typically partial lacerations vs. complete

Flexor tendon injuries

• Zone III – Distal edge of carpal tunnel to proximal edge of flexor tendon pulley system
  • Lumbricals originate from FDP tendons in this region. Generally good outcomes
• Zone IV – Level of carpal tunnel
  • Requires careful exploration as isolated injuries are the exception
• Zone V – Proximal to carpal tunnel
  • Injuries tend to be severe and often involve multiple tendons +- median/ulnar nerves
  • Spaghetti wrist

Extensor tendon injuries

• <25% tend not to need repair
• Previously repaired in ED, however, consensus seems to be that operative repair provides better outcomes
• Zone I – Distal phalanx and DIP joint
  • Mallet finger typically results
  • Type I – Tendon-only rupture
    • DIP immobilisation (never remove splint) in extension for 6-10 weeks
  • Type II – Small avulsion fracture
    • Can be treated the same if DIP joint congruent
  • Type III – >25% articular surface involved
    • Requires surgery
  • Chronic untreated mallet finger results in Swan-neck deformity as lateral bands are displaced dorsally with extension forces on PIP

• Zone II – Middle phalanx. Treated as for Zone I
• Zone III – Area over PIP joint
  • Central tendon most commonly injured
  • Complete disruption of central tendon can cause lateral bands to move volarly, causing them to act as flexors
  • Extensor hood then retracts, causing extension of DIP joint causing boutonniere deformity
  • Closed injuries initially treated with PIP immobilisation in continuous extension for 5-6 weeks with hand surgeon follow-up
• Zone IV – Area over proximal phalanx
  • Similar clinical findings to Zone III but better outcomes

• Zone V – Area over MCP joint
  • Open injuries to this area are considered human bites until proven otherwise
  • Wounds from human bites should receive IV antibiotics and delayed repair at 24 hours
• Zone VI – Dorsum of hand
  • If proximal to juncturae tendinae, patient may still be able to extend the MCP joint (but will not be as strong as expected)
  • Required advanced operative closure
• Zone VII – Over wrist
  • Repair difficult due to extensor retinaculum so operative repair required
• Zone VIII – Distal forearm
  • Require thorough exploration to identify all injured structures
  • Tendons frequently retract
  • Requires operative exploration and repair followed by splinting in 15 degree wrist extension, MCP joint 15 degrees flexion and IP joint 15 degree flexion (POSI)

Ligamentous injuries and dislocations

• DIP joint
  • Rarely dislocated due to firm attachments
  • Typically dorsal dislocation if it does occur
  • May be irreducible due to entrapment of avulsion fracture, profundus tendon or volar plate

Ligamentous injuries and dislocations

• PIP joint
  • Far more commonly dislocated
  • Dorsal dislocation occurs when volar plate ruptured
  • Lateral dislocations when collateral ligaments injured with at least partial avulsion of the volar plate from the middle phalanx
  • Usually ulnar deviation as radial collateral 6x more likely to rupture than ulnar collateral
  • If joint irreducible or evidence of complete collateral rupture, operative repair is required

• MCP joint
  • Typically hyperextension with rupture of volar plate causing dorsal dislocation
  • Reduction does not involve hyperextension and traction (as in others)
  • Reduction requires flexing wrist to relax flexor tendons and then pressure over proximal phalanx dorsal surface
  • Splint in flexion with f/u
  • Volar dislocations are rare and usually require operative repair

• Carpometacarpal joint
  • Uncommon as strong ligamentous and broad flexor/extensor tendons
  • Usually dorsally oriented and associated with fracture if does occur
  • Traction, flexion and pressure over dorsal surface of metacarpal will reduce most under regional anaesthesia
  • Consult hand surgeon after reduction
• Thumb IP joint
  • Rare but if do occur, are typically open
  • Typically hyperextension with rupture of volar plate
  • Reduce with hyperextension and traction then splint in 15 degrees flexion for 3 weeks with f/u
• Thumb MCP joint
  • Usually dorsal from hyperextension
  • Can reduce with radial nerve block using dorsal surface pressure
  • Immobilise in thumb spica and f/u

• Thumb MCP ulnar collateral ligament rupture (Gamekeeper’s/Skier’s thumb)
  • Radial deviation (abduction) of MCP joint
  • Tear at distal insertion most commonly with significant injury to dorsal capsule and volar plate
  • Hand surgery referral for all patients with suspected complete tears
  • Test in full extension and 30 degrees MCP flexion
    • If lax >30 degrees in full extension = both actual and accessory ligament rupture
    • If lax >30 degrees in 30 degrees flexion only = actual ligament rupture only
  • >30 degrees radial angulation or 10-15 degrees more than other side suggests complete rupture and warrants immediate consult
  • Thumb spica with repair within 1 week if discharged home
  • Stener lesion
    • Specifically refers to interposition of the adductor pollicis aponeurosis between the ulnar collateral ligament (torn) and the MCP joint
    • Occurs in 50% of ulnar collateral ligament tears
    • Can be diagnosed on USS or MRI

• Radial collateral ligament rupture
  • Far less common and requires same treatment

• Thumb CMC joint
  • Rare compared with more common Bennet’s fracture
  • Easy to reduce but unstable
  • Thumb spica and hand surgeon consult

Fractures

• Distal phalanx
  • Tuft, shaft or intra-articular
  • May involve flexor or extensor tendon insertions if proximal
  • Tuft fracture often involve nail bed lacerations
  • Treat as soft tissue injuries, remove nail bed to assess injury if required, washout approximate nail bed lacerations with 6-0 or 7-0 absorbable sutures or dermabond and place old nail or petroleum-impregnated gauze under cuticle for 3 weeks with f/u
  • Splint with aluminium gelufoam until f/u

• Middle phalanx
  • FDS tendon inserts at proximal volar half
  • Extensor tendon inserts at proximal base
  • Fractures as base demonstrate apex dorsal angulation
  • Fractures at neck result in apex volar angulation
• Proximal phalanx
  • No tendinous attachments so end up in apex volar angulation due to forces of extensor and interosseous muscles

• General
  • Direct blow leads to transverse or comminuted fracture
  • Twisting mechanism leads to spiral fractures
  • Usually non-displaced and stable treatable with buddy strapping only
  • If unstable but amenable to reduction, can be splinted from MCP to DIP with MCP flexed 70 degrees and IP in extension
  • Midshaft transverse fractures, intra-articular fractures and spiral fractures often require internal fixation

• Metacarpal 2^nd-5^th fractures
  • 2^nd and 3^rd metacarpals relatively immobile and need anatomic reduction
  • 4^th/5^th metacarpals have 20 degrees AP motion and can compensate for some malunion
  • CMC joint dislocation often accompanies these fractures and is often missed
  • Metacarpal head fractures
    • Distal to insertion of collateral ligaments and often comminuted
    • If laceration evident, consider human bite
    • Ice, elevation, immobilisation and hand surgeon consult

• Metacarpal neck fractures
  • Fracture of 5^th metacarpal neck = Boxer’s fracture
  • Usually unstable with volar angulation
  • Always check for rotational deformity as cannot be compensated for
  • >15 degrees angulation of 2^nd or 3^rd metacarpals requires reduction and surgical fixation
  • >20 degrees angulation in 4^th and >40 degrees angulation in 5^th will require reduction +- fixation
  • Reduction is required if greater than this
    • Flex wrist and MCP joint
    • Slight force to volar aspect of affected metacarpal and phalangeal traction
    • Splint with wrist 15 degrees extension, MCP 70 degree flexion

• Metacarpal shaft fractures
  • Usually direct blow
  • Rotational deformity and shortening are more likely with shaft vs. neck fractures
  • If manipulative reduction is required, operative fixation is usually necessary
• Metacarpal base fractures
  • Usually direct blow or axial force
  • Often associated with carpal bone fractures
  • Suspect CMC joint dislocation
  • CT may be required due to difficult plain film interpretation
  • Fractures of base of 4^th/5^th metacarpals can result in paralysis of motor branch of ulnar nerve

• Thumb metacarpal fractures
  • Usually involve the base
  • Extra-articular
    • Mobility of CMC joint can allow for 30 degrees of angular deformity
    • >30 degrees angulation requires reduction and thumb spica for 4 weeks
    • Spiral fractures often require fixation
  • Intra-articular
    • Bennet’s fracture
      • Intra-articular base of metacarpal fracture with CMC subluxation/dislocation
      • The ulnar portion of the metacarpal usually remains in place (constant fragment) while distal portion subluxes radially and dorsally from pull of abductor pollicis longus and adductor pollicis
      • Need thumb spica and ortho referral
    • Rolando’s fracture
      • Intra-articular comminuted fracture at metacarpal base
      • Thumb spica and ortho referral

High-pressure injection injury

• Often appears benign initially but is a true ortho emergency
• Initial kinetic injury and subsequent inflammatory response leads to tissue oedema and ischaemia
• Paint, especially oil-based, leads to intense inflammatory response
• Over time hand becomes oedematous, pale and severely tender to palpation
• Plain X-rays show opaque substances or subcutaneous emphysema
• Definitive treatment is early surgical decompression and debridement of ischaemic areas
• Immediate hand surgery consult, immobilise, elevate, ADT, IV cefazolin + metronidazole and analgesia
• Amputations rates are as high as 30%

• Amputation rate up to 70% for oil-based substances
• Mason and Queen phases
  • Early: Swelling, numbness, vascular insufficiency
  • Intermediate: Foreign body granuloma, widespread vessel thrombosis, coagulative necrosis of skin, tendon sheath fibrosis
  • Late phase: Persistent ulceration and sinuses over granuloma with secondary infection

• Prognostic factors
  • Material injected: Paint thinner, oil-based substances worst
  • Viscosity: Less viscous = more damage
  • Site: IP joint line has weaker tendon sheaths allowing spread. 
  • Little finger or thumb: More likely to spread to wrist
  • Distal digit: Worse prognosis due to lack of distensibility
  • Volume: Poorer functional results if greater volume
  • Time to definitive surgery

Digit amputation

• If finger amputated proximal to insertion of FDS, not usually suitable for replantation as get stiff PIP
• Single digit amputations are usually not worth replanting
• Handle amputated tip carefully, do not debride, clean, wrap in saline-soaked gauze, bag and then keep on ice (without freezing)
• Clean and cover wound, given Cefazolin + Metronidazole and consider replantation
• Always remember ADT +- TIG

• Care of stump
  • Remove any tourniquet
  • Direct pressure with sterile combine
  • If uncontrolled haemorrhage – Temporary digit tourniquet on way to theatre
• Time to reimplantation
  • <6 hours warm
  • >12 hours cool (up to 24 hours)

• Prognostic factors
  • Clean cut vs. shearing
  • Time to presentation
  • Contamination
  • Shrinkage at edges
  • Wrist better than forearm (tendons repair better than muscle)
  • Fingers do well if amputated distal to FDP insertion
  • Better prognosis if proximal to PIP joint
  • Patient factors (diabetic, smoker, PVD, on steroids)

• Relative CI to replantation
  • Long ischaemia time
  • Crush with extensive soft tissue injury
  • PVD
  • Grossly contaminated
  • Devitalised
• AVOID digital or nerve blocks before hand surgeon review
• Through DIP
  • Usually just needs formalisation

Finger tip amputation

• <1cm2
  • Use IV-3000 technique
  • As good cosmetic and functional outcome as skin grafts
• >1cm2
  • Requires bone nibble, grafting

Last Updated on November 10, 2023 by Andrew Crofton