Download avoiding surgical mistakes in the treatment of gait

Avoiding Pitfalls in the Management of Gait
Dysfunction in Children with Cerebral Palsy
Handout for IC 6:
Michael Healy, MD [[email protected]]
Tom Novacheck, MD [TNovacheck@ gillettechildrens.com]
Michael Partingon, MD, [[email protected]]
Libby Weber, MD [[email protected]]
What causes Gait abnormalities in Cerebral Palsy?
Spastic Cerebral Palsy is a static encephalopathy caused at the cellular level by
hypoxia or anoxia in-utero or during the first two years of brain
development.
Premature infants are particularly susceptible to anoxic brain insult for a
variety of reasons:
1. In the developing vascular system of the brain – arterioles grow into
the white matter and towards the ventricles. Pre-term, this system is
immature, frail and insufficient – particularly in the peri-ventricular
area.
2. The auto-regulatory mechanism which typically controls cerebral
blood flow in relation to arterial blood flow is immature and unable
to provide appropriate cerebral pressure control in response to
fluctuations or low pressures of the pre-term infant.
The resultant injury causes a permanent but non-progressive interruption in the
typical relationship between excitatory and inhibitory impulses from brain to
limbs.
Co-excitation of the agonist AND the antagonist muscles causes a velocity
dependant resistance to passive stretch.
Abnormalities of Gait
Gait atypia in Spastic Cerebral Palsy can be characterized in three categories:
1. Primary
a. Loss of selective motor control
b. Impaired balance
c. Abnormal tone
2. Secondary (develops over time)
a. Muscle contractures
i. Normal stretch absent so muscle growth is inhibited
ii. Bi-articular muscles more affected
b. Abnormal bone growth: examples
i. Persistent femoral anteversion
ii. Compensatory external tibial torsion
3. Tertiary (compensations): examples
a. Hemi-pelvic retraction on the weaker side
i. To compensate for inability to turn the femoral
anteversion forward
b. Abductor lurch
i. To compensate for functionally short/weak abductors
c. Circumduction or vaulting
i. To compensate for a long or functionally long limb
d. Knee hyperextension
i. To compensate for tight heel cords with inadequate
dorsiflexion
Lever Arm Dysfunction:
Moment: force over (perpendicular) distance to create angular acceleration
(torque) around a fulcrum
In the human body:
Force: Muscle contraction
Perpendicular Distance: Lever Arm (typically a long bone)
Fulcrum: Joint
Internal force is the muscle acting on the lever arm
External force is the weight of limb or body or ground reaction
There are three types of lever arms depending on where the fulcrum is relative
to the internal force and the external force – all have applications in the
human body.
Types of dysfunction
1. Torsional deformities of long bones
a. Femoral anteversion
b. Tibial torsion
2. Hip subluxation or dislocation
3. Foot deformities
4. Positional anomalies (ex. Crouch)
How do we accurately assess gait?
Computerized Gait Analysis
-Full objective physical exam
-torsions quantitated
-spasticity quantitated
-limb length discrepancies quantitated
-Video – gait by observation
-3 dimensional measurement of motion (kinematics)
-Reported as gait plots in the Coronal, Sagittal and Axial planes
-Reported relative to a data base of typical gait (which highlights
deviations)
-Measurement of moments and power generation/absorption (kinetics)
-Estimations of functional tendon lengths (Psoas and Hamstrings)
-Dynamic electromyography
-Oxygen consumption
-Dynamic foot pressure
-Appropriate radiographic imaging
What can Neurosurgeons do to treat Gait Abnormalities in CP?
1. SDR (selective dorsal rhizotomy)
2. ITB (intrathecal baclofen pump)
What could go wrong?
-Wrong diagnosis: FSP (familial spastic paraparesis) can present like and be
diagnosed as CP.
-1/3 of the FSP alleles code for a progressive encephalopathy unlike the
lesions in CP, which are static.
-Mistaking tone for strength:
-GMFCS III or IV patient who is “walking” with assistive device, may
be carrying themselves on their tone. When this tone is removed
they become wheelchair dependant. Consider:
-parent’s expectations
-aggressive postoperative rehab
-Poor ability to rehabilitate after SDR
What surgeries can Orthopaedic Surgeons perform to treat Gait Abnormalities in CP?
1. Muscle/Tendon lengthening for contractures
2. Osteotomies for torsed or deformed bones
What could go wrong?
Wrong operation:
-Choosing to lengthen (i.e. weaken) muscles that are not too short
-heel cord instead of gastroc
-hamstrings when functionally normal
-Complete tendon transfers in CP
-Psoas off the lesser troch
-Obturator neurectomy or aggressive adductor release for scissoring
Too little surgery:
-correcting only one of many deformities will not optimize gait
Unrealistic goals of family:
-Surgery can’t address problems with:
-balance
-selective motor control
-insufficient strength
Orthopaedic surgery without tone management.
Tone management without correction of bony deformities.
Any surgery without adequate rehabilitation.