RADIAL NERVE PALSY by liwenting

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									RADIAL NERVE PALSY
Chapman, chapter 55




Introduction
Riordan’s three phases of grasp and release:
       Phase 1: opening the hand
               Requires finger and thumb extensors, abductors of the thumb, intrinsics
       Phase 2: surrounding the object
               Requires long flexors and intrinsics
       Phase 3: gripping
               Requires strong action of long flexors
               Requires wrist extensors
       Release: as in phase 1
High radial nerve palsy affects phases 1 and 3
Low radial nerve palsy (posterior interosseous nerve palsy) affects mostly phase 1,
       because ECRL (and often ECRB) is available for wrist extension


Anatomy
Radial nerve contributions:
       From cervical roots C5 to C8 (mostly C7)
       From posterior cord of the brachial plexus
Posteriorly around proximal humerus with deep brachial artery
Not quite in the spiral groove! Lies on upper part of medial head of triceps, with 3.4mm
       of buscle between nerve and bone
Radial nerve directly against bone only distally, where it passes anteriorly through lateral
       intermuscular septum, 10cm proximal to lateral epicondyle
Innervation of the triceps: up to 10 individual branches arising high in the arm to long
       head, lateral head and medial head
Between brachioradialis and brachialis
Before bifurcation it innervates brachioradialis, ECRL (and brachialis – variable)
Bifurcation (superficial and deep branches) from 4.5cm above to 4cm bellow lateral
       epicondyle (most common at or distal to it)
Innervation to ECRB comes off:
       From superficial branch in 56%
       From deep branch in 36%
       From bifurcation itself in 8%
Superficial branch:
       Purely sensory
       Between brachioradialis and ECRL
       Emerges dorsally from under brachioradialis at junction of middle and distal
               thirds of the forearm
Deep branch:
       Motor, except for sensory branches to carpal capsule
       Enters supinator at arcade of Frohse
       Innervates supinator
       Exits supinator 8cm distal to elbow and immediately divides in multiple branches
               Superficial group to EDC, EDQ, ECU
               Deep group to EPL, EPB, APL, EI


Principles of treatment
Neurapraxia and axonotmesis have high recovery potential; neurolysis beneficial if
      delayed recovery
Neurotmesis has low potential for spontaneous recovery; expect 77% partial recovery
      after primary repair or grafting of the radial nerve; results of primary repair
      combined with delayed tendon transfer are superior to results of tendon transfers
      alone

Radial nerve palsy after humeral fracture
Incidence: 2 to 15%
Prognostic factors:
         Good prognosis: partial injury
         Worst prognosis: comminuted middle third fractures with immediate onset of
                 complete paralysis (Kaiser suggests initial open treatment)
         Bad prognosis: Holstein-Lewis oblique fractures of the distal humerus have high
                 incidence of radial nerve entrapment (suggested open initial treatment)
Pollock: 92% spontaneous recovery rate irrespective of fracture pattern in closed
         fractures with radial nerve palsy
Foster: 64% incidence of radial nerve laceration or interposition in open fractures with
         radial nerve palsy
Initial treatment:
         Category 1:
                 Low energy, closed injury, crush
                 Result in neurapraxia and axonotmesis most often
                 Explore if soft-tissue interposition prevents reduction, especially if
                         Holstein-Lewis type
                 Observe if no sign of interposition
                 Maintain ROM by using static and dynamic splints and physical therapy
                 Investigate with EMG if no beginning of recovery by 3 to 4 weeks
                 Treat with neurolysis at 3 to 4 months if no recovery
         Category 2:
                 Open injuries
                 Explore nerve at initial debridement
Redial nerve palsy after manipulation for reduction:
         Immediate onset: explore early
         Delayed onset: observe
At exploration:
         Remove from fracture site if incarcerated
         Repair directly if lacerated (also fix fracture)
       Inter-fascicular graft if segmental loss


Surgical techniques
Incisions:
        Avoid longitudinal incisions along path of transferred tendons to prevent
               adhesions
        Use multiple separate transverse incisions for tendon sectioning, proximal
               retrieval and anastomosis
Transfer for wrist extension:
        Pronator terres to ECRB
        Avoid transferring same motor on ECRB and ECRL together:
               Lever arm for wrist extension larger for ECRB than for ECRL, therefore
                       action through ECRL causes slack in ECRB which becomes non-
                       functional
               ECRL has important radial deviation effect and lesser wrist extension
                       effect, which is undesirable if pronator terres acts only through
                       ECRL
Place tendon anastomoses so that they will not catch on extensor retinaculum and limit
        excursion

Standard FCU transfer
Useful for older patients, patients that are expected to have difficulty with rehabilitation
       and patients that do not need independent digital control
Includes:
       Pronator terres to ECRB for wrist extension
       ECU to EDC for finger extension
       Palmaris longus (or FDS of ring finger) to re-routed EPL for thumb abduction and
               extension
Disadvantages:
       Short excursion of ECU precludes full finger extension when wrist extended
       Dominance of radial forces
Technique:
       Pronator terres insertion elevated with 3cm periosteal slip off middle third of
               radius through brachioradialis-ECRL interval; transposed superficial to
               brachioradialis over radial border of forearm; attached to ECRB with wrist
               in full extension; this connection is made last, in order to allow testing of
               tenodesis effect and free gliding of other two transfers with wrist flexion-
               extension without endangering ECRB connection
       FCU mobilized from its insertion on pisiform to 5cm distal to its medial
               epicondyle origin; transposed subcutaneously around ulnar side of
               forearm; passed sequentially through all tendons of the EDC at 45o
               proximal-ulnar to distal- radial then sutures with wrist in extension and
               fingers in extension
       EPL transected proximal to extensor retinaculum, retracted distally, then
              transposed in subcutaneous position along radial border of distal forearm
       Palmaris longus displaced subcutaneously along radial border of forearm to attach
              to transposed EPL with thumb in extension and abduction; alternatively
              use FDS to ring finger transected between A1 and A2 pulleys at proximal
              phalanx, then passed proximal to carpal tunnel

Flexor carpi radialis transfer
Indicated for patients that wish to return to heavy labor (FCU important for hammering,
        therefore not expendable)
Includes:
        Pronator terres to ECRB for wrist extension
        FCR to EDC for finger extension
        Palmaris longus (or FDS of ring finger) to re-routed EPL for thumb abduction and
                extension
Advantage: FCR has greater excursion than FCU, therefore allows more finger extension
        even with wrist extended
Detach FCR at level of wrist through same transverse incision as for palmaris longus;
        transpose subcutaneously around radial border of forearm; pass sequentially
        through all EDC tendons at 45o from proximal-radial to distal-ulnar, then suture
        with fingers and wrist in extension

Modified Boyes transfer
Indicated in young patients that are able to cooperate with rehabilitation and that require
        more independent extensor function
Includes:
        Pronator terres to ECRB for wrist extension
        FDS to middle finger to EDC for finger extension
        FDS to ring finger to EIP and EPL for independent thumb/index extension
        Flexor carpi radialis to APL and EPB for thumb abduction
Disadvantage: out-of-phase transfer of a flexor to an extensor position (rehabilitation is
        difficult, but feasible)
Technique:
        Transect FDS to middle and ring fingers between A1 and A2 pulleys at proximal
                phalanx, then retract proximal to carpal tunnel
        Make two 1cmx2cm windows into the interosseous membrane proximal to
                pronator quadratus on each side of the anterior interosseous artery
        Transpose posteriorly through interosseous membrane:
                FDS from middle finger between FDP and FPL; weave through all EDC
                         tendons from proximal-radial to distal-ulnar direction with wrist
                         and fingers in full extension
                FDS from ring finger on the ulnar side of the FDP; weave through EPL
                         and EIP with wrist, thumb and index in full extension
        Transect FCR and weave through APL and EPB with thumb in full abduction
        Pronator terres to ECR
Posterior interosseous nerve palsy
Brachioradialis, ECRL and most of the time ECRB are functional
FCU can not be used for transfer, because this would leave wrist with intact palmar and
       dorsal radial deviators, but no functional ulnar deviator
Possible motors for finger extension:
       FCR (used instead of FCU)
       FDS of middle finger to EPL and EIP combined with FDS to ring finger to EDC
Alternative combinations:
       Standard:
               FCR (used instead of FCU) to EDC for finger extension
               Palmaris longus (of FDS to ring finger) to re-routed EPL for thumb
                       extension and abduction
       More independent extension:
               FDS of middle finger to EPL and EIP for independent thumb and index
                       extension
               FDS to ring finger to EDC
               FCR to APB and EPB for thumb abduction


Early tendon transfers
Some advocate initial transfer of pronator terres to ECRB (functions as an internal splint
        awaiting neurological recovery; obviates need for external bracing)
Reasonable in patients with poor prognosis for early recovery:
        High radial nerve lacerations
        Large segmental defect requiring long graft
        Poor quality of repaired nerve
Remaining transfers performed later if no recovery observed
As for all muscle transfers, this can not be done if full ROM of wrist is not present


Postoperative care
Immobilize elbow at 90o, forearm neutral, wrist in 45o extension, fingers in full
        extension, thumb in abduction and extension for 4 weeks
At 4 weeks maintain wrist in 45o extension, immobilize MPs at 20o flexion and free the
        elbow and interphalangeal joints
Start physical therapy at 4 weeks
Discontinue all splints at 7 weeks


Pitfalls and complications
Flexion or hyper-extension contractures of the PIP following FDS transfer
Avoid out-of-phase transfers in elderly and those that can not cooperate with
       rehabilitation

								
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