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Nerve injuries in Total Hip Arthroplasty

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Anatomy of peripheral nerves about the hip (cont.) Obturator nerve supplies adductors and a medial patch of skin on thigh persistent pain in groin or thigh, ... – PowerPoint PPT presentation

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Title: Nerve injuries in Total Hip Arthroplasty


1
Nerve injuries in Total Hip Arthroplasty
  • Presented by Drs. Marc DeHart and Lee Riley
  • Reviewed by Nimr Ikram, D.O.
  • April 20, 1999

2
Introduction
  • About 1-2 of those undergoing THA obtain some
    nerve injury
  • most common in those undergoing revision THA or
    pts with DDH
  • inj to peroneal branch of sciatic is most common,
    but obturator, sup. gluteal, and femoral nerves
    may also be injured
  • worst prognosis is complete motor and sensory
    deficits.

3
Peripheral nerve anatomy and physiology
  • Each nerve cell is composed of 4 regions
    dendrite, cell body, axon, and terminal branches
  • dendrite collect signals from other cells
  • cell body contains nucleus and cell body dealing
    with metabolism
  • axon transports proteins and transmits actions
    pot.
  • terminal branches relay messages to other nerve
    cells

4
Peripheral nerve anatomy and physiology (cont.)
  • sensory nerves are afferent fibers that transmit
    a.p. toward dorsal root ganglia of CNS
  • Motor nerves are efferent and carry a.p. to motor
    end-plates on muscle spindles
  • oligodendrocytes and Schwann cells produce the
    myelin sheath
  • oligodendrocytes only in CNS
  • Schwann cells found in peripheral nerv. ystem
  • demyelinating diseases include multiple sclerosis
    and Guillain-Barre.

5
Nerve Injury
  • Seddon classified nerve inj. into 3 types
  • neurapraxia - conduction block of anatomically
    intact nerves caused by minor inj. Have a period
    of loss of sensation but recovery is complete
  • axonotmesis - axons are disrupted but the
    connective tissue survives. Wallerian degen.
    occurs with disintegration of axon and myelin
    sheath distal to site of inj. Intact endoneurium
    allows slow regen. (1 mm/day)
  • neurotmesis - complete disruption of nerve may
    lead to painful neuromas

6
Nerve injury (cont.)
  • Damage occurs by compression, stretch, ischemia,
    and transection.
  • Lundborgs exp. with tourniquets showed normal
    circ. when inflation lt 2 hrs.
  • If 4-6 hrs., took 2-3 min. for circ. to return
  • at 8-10 hrs., took 5-20 minutes to return evid.
    of microvasc. stasis.
  • The amount of stretch a nerve tolerates depends
    on whether it is freely mobile or bound.

7
Nerve injury (cont.)
  • Histologic changes notices after lengthening
    4-11
  • nerve microcirc. impaired after 8 stretch and
    stopped after 15 stretch.
  • 4 factors that increase prob. of mech. disruption
  • 1. Increased load due to compression or stretch
  • 2. Increased rate of loading
  • 3. Increased duration of loading
  • 4. Uneven application of load to tissues

8
Anatomy of peripheral nerves about the hip
  • Sup. gluteal nerve arises from L4 - S1 and exits
    sciatic notch to supply gluteus medius, minimus,
    and tensor fascia lata.
  • Travels with sup. gluteal art. deep to medius and
    max. but superficial to minimus
  • ant branches supplying tensor may be sacrificed
    during ant.lat. approach.
  • Also at risk when 3-5 cm safe zone prox. to
    greater troch. is violated with direct lat.
    approach
  • Trendelenburg sign or gait indicates damage

9
Anatomy of peripheral nerves about the hip (cont.)
  • Obturator nerve arises from L2 - L4 within post.
    psoas and emerges medially at sacral ala to
    travel along iliopectineal line.
  • Rarely injured
  • at risk when cement, screws, or reamers penetrate
    the ant. quadrants of the acetabulum.

10
Anatomy of peripheral nerves about the hip (cont.)
  • Obturator nerve supplies adductors and a medial
    patch of skin on thigh
  • persistent pain in groin or thigh, adductor
    weakness after intrapelvic screws, or cement
    visible on x-rays suggest nerve inj.

11
Anatomy of peripheral nerves about the hip (cont.)
  • Femoral nerve arises from L2 - L4
  • passes thru psoas major muscle and travels b/n
    psoas and iliacus and finally enter femoral
    triangle
  • supplies motor to quadriceps and sensation to
    medial thigh and calf.
  • Prolonged hyperext can cause nerve traction inj.
  • Iliacus hematomas are well-known causes of fem.
    nerve palsy
  • most at risk during placement of ant. retractors
    when ant. or ant.lat. approaches used.

12
Sciatic nerve injury
  • Arises from L4 - S3 and is composed of preaxial
    ant. tibial and postaxial post. peroneal
    divisions
  • located deep to the piriformis inside the pelvis
    and travels distally deep to gluteal muscles and
    superficial to ext. rotators at level of hip.
  • at risk during placement of post. acet.
    retractors or from ant. or lat. traction on the
    femur

13
Sciatic nerve injury (cont.)
  • Distal to lesser troch. and ischial tuberosity,
    nerve passes b/n adductor magnus and long head of
    biceps, medial to gluteal sling
  • all medial branches arise from tibial division
    and supply hamstrings
  • short head of biceps is only thigh muscle supply
    by peroneal division of sciatic.
  • At sup. aspect of popliteal fossa, 2 divisions
    split into tibial nerve and common peroneal.

14
Sciatic nerve injury (cont.)
  • Most commonly injured nerve during THA
  • Schmalzried et al had a sutdy of 3000 pts with 53
    nerve injuries
  • 90 involved the sciatic nerve
  • incidence in primary THA is b/n 0.6 - 3.7
  • Weber et al noted that only severe injuries
    present as clinical problem so may occur more
    often then documented.
  • With pre and post op EMGs, 70 had subclinical
    sciatic nerve inj.

15
Sciatic nerve injury (cont.)
  • Etiology
  • Direct trauma - scalpel, cautery, retractors,
    wires, reamers, bone fragments, or cement
    protrusion
  • Constriction - suture, wire, or cable
  • Heat - from polymerization of cement
  • Compression - from dislocation
  • Excessive lengthening
  • Subfascial hematoma
  • cause of gt 50 of nerve palsies unknown.

16
Sciatic nerve injury (cont.)
  • Peroneal division more susceptible
  • Schmalzried found that 94 of sciatic nerve inj
    involved peroneal division
  • superficial position at fibular head makes it
    vulnerable to compression
  • relatively more fixed at sciatic notch and at the
    fibular head so susceptible to stretch.

17
Sciatic nerve injury (cont.)
  • Risk factors include revision THA, DDH, and
    lengthening
  • Johanson et al noted increased blood loss and
    time of surgery in pts with nerve inj.
  • nerves will tolerate only a finite amount of
    acute stretch
  • Mayo Clinic review of DDH pts who underwent THA
  • 13 had sciatic nerve palsies
  • no nerve inj. occurred in those with lengthening
    lt 4 cm.
  • Nercessian reported on 66 pts length 2-5.8 cm s
    deficit
  • calculated amount of lengthening as a of length
    of the femur and concluded up to 10 was safe.

18
Diagnosis
  • Clinical assessment alone underestimates the true
    incidence of nerve injury
  • proper preop documentation of neurovasc status
  • if weakness of ankle dorsiflexion, damage to
    peroneal division of sciatic
  • EMG recording of short head of biceps tells if
    peroneal division affected at hip or fibular
    head.

19
Prognosis
  • Related to factors specific to the injury and
    clinical factors related to patient
  • causalgic pain most highly predicts major
    disability
  • Schmalzried found that pts who recovered neuro
    fxn did so by 7 months.
  • Pts with some motor fxn during hosp stay had a
    good recovery.

20
Treatment
  • If no specific cause is identified, no immediate
    tx is indicated.
  • EMGs and NCS may provide an objective measure of
    the level of injury, the degree of injury, and
    evidence of recovery of motor fxn.
  • If intraop transection of nerve occurs, an
    attempt at repair is warranted
  • delayed onset of prog neuro symptoms after a
    normal postop check, should consider evacuation
    of subfascial hematoma

21
Treatment (cont.)
  • Motor deficits can be managed with P.T.
  • AFOs can be used to treat foot drop
  • Dysesthesias and causalgic pain are best treated
    with antidepressants and early and repeated
    sympathetic nerve blocks.

22
Prevention
  • The best treatment of any complication is
    prevention
  • most important to identify the pt who is most at
    risk
  • revision THA, DDH, and excessive leg lenghtening
  • there is no strong evidence favoring any one
    approach for prevention of nerve injury

23
Prevention (cont.)
  • Technical factors include
  • wide exposure and meticulous hemostasis to
    ensure visualization
  • constant attention to nerve position
  • careful placement and replacement of retractors
  • careful placement of fixation screws and
    attention to drill-bit depth are essential
  • avoid anterior quadrant screws
  • proper placement of components minimize
    dislocations and need for revision surgery

24
Electrodiagnostic studies
  • Several studies have used evoked potentials and
    EMG to warn surgeons of impending damage to
    peripheral nerves during surgery.
  • Evoked potentials are voltage changes in sensory
    fibers after stimulation of peripheral nerves
  • damage alters electrical signals by dec size
    (amplitude) or increasing transmission time
    (latency)
  • dec of gt50 in amplitude or an inc of gt10 in
    latency suggests neurologic compromise
  • amplitude change can be influenced by pt. temp.,
    blood pressure, PCO2, level of anesthesia, and OR
    noise.

25
Electrodiagnostic studies (cont)
  • Stone et al used SSEP monitoring of peroneal
    nerve and found 20 incidence of intraop signal
    changes
  • noted with retractor placement, leg positioning
    for femoral reaming and cement removal, ant. or
    lat. retraction of femur, and hip reduction
  • valuable method for use in revisions and
    reoperations
  • Black et al found no reduction in sciatic nerve
    palsy in monitored vs unmonitored pts

26
Electrodiagnostic studies (cont)
  • Rasmussen et al compared revision cases, found no
    statistical significance b/n groups
  • also reported 2 pts who had postop palsies had no
    SSEP changes during the procedure.
  • Another method to monitor nerve fxn is intraop
    EMG responses
  • no studies have been done on this.

27
Summary
  • Nerve injury in THA is uncommon, occurring in
    1-2 of all pts who undergo primary THA.
  • Peroneal division of sciatic nerve is most
    frequently injured
  • risk factors include revision THA, DDH, and limb
    lengthening
  • lengthening of gt 4cm or gt 10 of femur length
    predispose to nerve injury

28
Summary (cont.)
  • Complete loss of neuro fxn or severe causalgic
    pain carries the worst prognosis
  • importance of prevention is best summarized by
    Schmalzried
  • No amount of preoperative discussion or
    postoperative consultation decreased the high
    degree of dissatisfaction that was expressed by
    these patients

29
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