Lower motor neuron conditions

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Paediatric Orthopaedics Presentation
2nd July 2014
Introduction
 Motor neuron disorders are neurologic disorders that
selectively affect motor neurons
 Generally progressive causing increasing disability
 Of orthopaedic interest due to contractures, subluxations
and spine deformities that may occur as a consequence
 Can be:
 Acquired
 Hereditary
 Upper motor
 Lower motor
Lower motor neuron
 This originates from the
brainstem cranial nerve
nuclei or
 Anterior horn cells of the
spinal cord
 They directly innervate
skeletal muscles
Clinical presentation
 Muscle paresis/paralysis
 Hypotonia/atonia
 Fibrillation/Fasciculation
 Hyporeflexia/areflexia
 Muscle atrophy
Classification
 Acquired:
 Poliomyelitis
 Trauma
 Iatrogenic
 Hereditary:
 Spinal Muscular Atrophy
 HMSNs
Poliomyelitis
 Acute infectious disease caused by a neurotrophic virus;
type I,II and II poliovirus
 Spread via faecal – oral route
 Virus causes necrosis of anterior horn cells
 Results in loss of innervation of motor units
 Virtually eradicated by extensive vaccination campaigns
Pathology
 Most commonly affect lumbar and cervical
enlargement
 Involvement from minimal injury with recovery to
complete irreversible injury
 Percentage of damaged motor units varies
corresponding with resulting muscle weakness
Clinical course
 Acute: 5 – 10 days. Pre paralytic and paralytic phases.
Complete when fever absent for 48 hrs. Asymmetric
paralysis
 Convalescent: 16 – 18 months. Varying degree of
recovery. Sensitive and insensitive phase
 Chronic: after recovery of muscle power has occurred
Prognosis
 Recovery most marked in the first 3 – 6 months,
potential for recovery upto 18 months
 Total paralysis beyond 2 months, chance of recovery
poor
 Muscle spasm, antagonist muscle contracture,
deformity and inadequate care influence recovery
Treatment: acute phase
 Supportive by paediatric team
 Patient positioning in correct anatomic alignment
 Frequent turning
 Passive range of motion exercises
 Moist heat application for muscle pain
Convalescent phase
 Attainment of maximal recovery in individual muscles
 Restoration and maintenance of normal joint ROM
 Prevention and correction of deformities
 Serial muscle testing: monthly 1st four months,
bimonthly next 8 months then quarterly upto 2 years
Attaining maximal recovery
 Replacement of action of weaker muscle by stronger
synergistic muscles avoided by physical therapy
centred on strengthening this muscle
 Avoiding fatigue of weak muscle which may retard it’s
recovery
Restoration of normal joint ROM
 Vigorous passive stretching exercises
 Night splints to keep joint in anatomical position
Prevention and correction of
deformities
 Active exercises preventing fatigue to address muscle
imbalance
 Passive stretch and nigh splints to prevent
contractures
 Pain relief to reduce muscle pain and sensitivity
 Readjustment to cater for growth
Chronic phase: physical therapy
 Active hypertrophy exercises. To increase strength of
synergistic muscles to obtain function
 Passive stretch exercises: to prevent deformity.
Augmented by night splints to maintain joint in
anatomical position
 Functional training: teaching to use all available
muscles to perform tasks
Chronic phase: orthoses
 Support:
 Enable walking and functional capabilities
 Prevent deformity and malposition
 Protect weak muscle form overstretching
 Substitution:
 Augment weak muscle
 Replace paralysed muscles
 Correction:
 Stretch muscle that have contracted
Lower limb orthosis
 Plantar flexion assist -
dosriflexion stop ankle
orthosis–
weak/paralysed plantar
flexors and vice versa
Surgical management
 Performed for correction of paralytic deformities
 Examples:
 Tendon transfers
 Fasciotomy
 Capsulotomy
 Osteotomy
 Arthrodesis
Tendon transfer
 Moving insertion of muscle to new site with aim of
replacing paralysed muscle or to restore dynamic
muscle balance
Principles (Green – 1957)
 Muscle to be transferred must have adequate motor
strength to carry out new function
 Range of motion of muscle transferred must equal that
of muscle being replaced
 Gain from transferred muscle > loss from donor site
 Joints on which transferred muscle is to act must have
functional ROM
 Smooth gliding channel must be created – use native
tendon sheath, sub muscular, wide opening in septa
 Preserve neurovascular supply of muscle
 Ensure straight line of contraction without angles or
pulleys
 Reattachment with sufficient tension to allow maximal
range of contraction
Post operative rehabilitation
 Support joint in overcorrected position until full
function achieved
 Preoperative training to localise contraction of muscle
to be transferred
 Training of patient to use previously localised muscle
to perform new movement
 Incorporation of transfer into new functional pattern
Examples
 Ilipsoas or external oblique transfer to GT in hip abductor
paralysis
 Erector spinae or iliotibial band transfer to GT for G max
paralysis
 Anterior transfer of peroneus longus in dorsiflexor
paralysis
 Semitendinosus and biceps femoris transfer to patella in
quadriceps paralysis
Fasciotomy
 Iliotibial band contracture
contributes to multiple
lower limb deformities
 Flexion, abduction,
external rotation
contracture of the hip
 Flexion and valgus
deformity of the knee joint
with external torsion of
tibia upto posterolateral
subluxation
 Pelvic obliquity
 Lumbar scoliosis
 Subluxation of
contralateral hip
 Exaggerated lumbar
lordosis – bilateral
flexion contractures
Fasciotomy
 Initial conservative management
 Ober’s fasciotomy – proximal lateral incision with release of
fascia over the sartorius, rectus femoris, tensor fasciae lata, and
gluteus medius and minimus
 Section of lateral intermuscular septum and iliotibial band upto
greater trochanter
 Yount procedure – excision of segment of iliotibial band and
lateral intermuscular septum in distal thigh
 May be combined with fractional hamstring lengthening to
correct the tibial version
Post operative care
 Bilateral long leg cast
 Suspension traction
 Passive extension, adduction and internal rotation
exercises
 For 3 weeks
Paralytic hip dislocation
 Muscle imbalance – weak abductors, normal flexors
and adductors
 Progressive coxa valgus deformity upto neck shaft
angle of 180 degrees
 Excessive anteversion
 Capsular laxity
 Subluxation then dislocation
 Acetabular dysplasia late
Surgical management
 Tendon transfers to address muscle imbalance
 Indicated at 4 – 5 years of age with coxa valga < 150o
 Coxa valga > 1500, then a varization osteotomy
performed with tendon transfer later
 Varization osteotomy – intertrochanteric oblique
osteotomy to correct coxa valga and excessive
anteversion
Osteotomy and arthrodesis
 Supracondylar osteotomy for fixed flexion deformity of
knee
 Dome osteotomies of proximal tibia for genu
recarvatum
 Knee arthrodesis for flail knee
 Hip athrodesis
Shoulder
 Deltoid paralysis managed with transfer of trapezius to
proximal humerus
 Supraspinatus – levator scapulae transfer
 Infraspinatus – latissmus dorsi
 Subscapularis – upper 2 digitations of serratus anterior
Trapezius transfer for deltoid paralysis
Serratus anterior transfer for
subscapularis paralysis
Levator scapulae transfer for supraspinatus paralysis
Shoulder arthrodesis
 Indicated in paralytic subluxation/dislocation and
extensive paralysis of the scapulohumeral muscles
 Optimum position – 50o abduction, 20o flexion, 25o
internal rotation
 Scapulo-thoracic motion compensates to position
hand in space for function
Elbow flexor paralysis
 Morbidity high due to inability to lift hand to face,
trunk
 Steindler flexorplasty
 Pectoralis major transfer
 Anterior transfer of triceps brachii
Steindler’s flexorplasty
Clark
Brooks and Seddon
Anterior transfer of triceps brachii
Supination contracture of forearm
 Paralysed forearm flexors with normal biceps
 Progressive supination contracture due to interosseous
membrane contraction and radial bowing
 Radial corrective osteotomy performed to correct
 Transfer of insertion of biceps to radial aspect of radius
(pronator)
Spinal muscular atrophy
 Hereditary disease characterised by degeneration of
anterior horn cells of the spinal cord
 Progressive hypotonia
 Lower limb > upper limbs
 Proximal > distal muscles
 1:15,000 – 20,000 live births
Pathogenesis
 Autosomal recessive in chromosome 5q
 Neuronal Apoptosis Inhibitory protein (NAIP) abnormal in
67% of patients
 Survival Motor Neuron (SMA) abnormal in 98% of patients
 Leads to unregulated apoptosis of α motor neurons
 1st trimester molecular genetic technology diagnosis
possible
*Type I – acute infantile/WerdnigHoffmann SMA
 Onset between 0 – 6 months
 Floppy and inactive, frog leg posture, unable to lift
head, fingers and toes active
 Tongue fasciculation characteristic
 Progressive course, usually death by 2 years due to
respiratory failure
*Byers and Banker classification
Type II – chronic infantile
 Onset 6 – 12 months
 Achieve head control, 75% sitting. Wheelchair ambulators
 Tongue fasciculation and upper limb tremors
 Patella areflexia, biceps and triceps reflex may be present
 Survival upto 5th decade
Type II - Kugelberg-Welander
 Onset 2 – 15 years
 Proximal muscle weakness – difficulty climbing stairs,
trendelenburg gait, lumbar hyperlordosis
 Ambulant upto adolescence, wheelchair bound as
adults
 Normal lifespan
Orthopaedic complications
 Contractures
 Hip subluxation/dislocation
 Scoliosis
Contractures
 Hip and knee flexion contractures in non ambulant
patients
 Gentle passive stretch exercises to prevent and treat
 Surgical releases of dubious value in non ambulant
child and frequently recur
 Orthoses to prevent equinus and cavovarus foot
deformities
Hip subluxation/dislocation
 Proximal muscle weakness – coxa valga – subluxation –
dislocation
 Bilateral dislocation – lumbar hyperlordosis
 Unilateral dislocation – pelvic obliquity – pressure sores –
aggravate scoliosis
 Passive stretch exercises to prevent, derotation osteotomies
to reduce the hip
 Poor results of surgical procedures reported
Scoliosis
 Universal in non ambulatory patients, prevalent in type III
 Predominance of thoracolumbar curves
 Typically more flexible but progress rapidly
 Orthoses assist sitting posture but do not retard
progression
 Surgical management – posterior fusion and segmental
instrumentation
Herditary Motor and Sensory
Neuropathies
 Group of hereditary neuropathies
 Characteristics:
 Predominant motor involvement
 Autosomal dominant
 Slowly progressive
 Symmetric
 Charcot –Marie – Tooth (CMT) disease most common
 Has six other types
CMT
 Most common heritable neuropathy. 1:2500 – 5000
 Multiple subtypes
 Defects in genes that regulate myelin sheath formation
 Lead to demyelination and axonal degeneration
 Onset variable but most common in 2nd decade
Clinical features
 Symmetric distal muscle atrophy
 Areflexia proceeding proximally
 Palpable enlargement of peripheral nerves
 More involvement of peroneal muscles as opposed to tibial
muscles
 Leads to toe, midfoot and ankle deformities
 Sensory loss variable
Orthopaedic manifestations
 Pes cavovarus:
 Increased longitudinal
arch due to intrinsic
muscle atrophy and
fibrosis
 Imbalance between
tibialis posterior and
anterior puts hind foot
in varus
 Meary’s angle between
longitudinal axis of talus
and 1st metatarsal
 On standing lateral
radiograph
 Normal 0 – 5o
 Average 18o in CMT
Management
 Soft tissue releases – capsulotomies and plantar fascia
release
 Muscle transfers – posterior tibial to dorsum
 Proximal metatarsal osteotomies to correct forefoot
plantar flexion
 Triple arthrodesis when deformity fixed
Orthopaedic manifestations
 Hip subluxation/dislocation
 Scoliosis
 Managed as for the previous muscle paralysis
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