Lower motor neuron conditions
Download
Report
Transcript Lower motor neuron conditions
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