The condition of cerebral palsy refers to a varied group of permanent disorders of movement and posture caused by injury to the immature brain in utero, at birth or in the first years of life. These lesions are static not progressive and can be caused by a wide variety of factors such as intrauterine infections, trauma, neonatal stroke and genes, often in combination. Reflecting the varied aetiology and sites of injury cerebral palsy is often accompanied by neurological disturbances in cognition, behaviour, sensation and epilepsy. Most significantly from the orthopaedic perspective is that it leads to a progressive musculoskeletal pathology and abnormalities of muscle strength, tone and joint movement. These tend to be hidden at birth and are only revealed during the rapid growth of childhood as spasticity leads to abnormal posturing and thus secondary contractures and impaired torsional bone remodelling. Eventually this process leads to problems such as scoliosis, hip dislocation and the development of fixed contractures.1
It is here that orthopaedic surgery can intervene by correcting fixed deformities leading to improved function and appearance. Cerebral palsy is the most common cause of referral to elective paediatric orthopaedic units.2 This essay will discuss the various surgical techniques that can be employed to tackle the musculoskeletal problems caused by cerebral palsy.
Cerebral palsy is classified based on the type of movement disorder present. The spastic form is the predominant type and can be divided into the subcategories of hemiplegic, diplegic or quadriplegic depending on topography. Appropriate management varies between these forms based on the level of functional outcome that can be expected; the most significant factor being whether the child is ambulant or not.
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It was the advent of gait analysis in the 1990s that revolutionised treatment of ambulatory cerebral palsy. Prior to this surgical intervention to improve gait was a matter of opinion, and often led to unexpected new problems which were even more intractable. The systematic empirical approach of gait analysis, however, enabled both more targeted and precise interventions and also critical evaluation of the outcomes of surgery.3
[Image 1: Distribution of symptoms in subtypes of cerebral palsy. Source: Cerebral Palsy League4]
Modern gait analysis takes place in a specialised laboratory and includes a standardised physical exam, video recording, kinematic and kinetic measurements, electromyography, pedobarography and estimation of the energy consumption of walking.5
Generally speaking surgery for ambulant CP is not attempted until after the age of 7 by which time a mature gait pattern has developed. Between this age and the onset of the growth spurt in adolescence bone surgery is sometimes required in order to stabilise the bony levers of progression in the leg. These include femoral or tibial derotation osteotomies, intertrochanteric derotation of the femur and stabilisation of the subtalar complex.6
It is between the ages of 8 and the main adolescent growth spurt (12-13 in girls, 13-14 in boys) that soft tissue surgery is undertaken, the ideal timing remaining contentious.7 Increasing maturity and awareness allow for more complex surgeries that require strict compliance with rehabilitation programmes to succeed. Yet this must be balanced against the effects of the rapid growth of bone and muscle that may exacerbate and complicate deformity.
Surgery for spastic diplegia
Despite advances in the usage of botulinum toxin A, intrathecal baclofen and selective dorsal rhizotomy to reduce spasticity most children with cerebral palsy still develop progressive musculoskeletal deformities as they grow. These include fixed joint contractures and bony deformities collectively referred to as ‘lever arm disease’ and which can only be treated effectively surgically.8 In the past a child with spastic CP typically presented with ‘toe-walking’ and was managed by lengthening of the tendo Achillis. Although this procedure successfully levelled the foot it often led to a crouch gait as contractures of the knee and hip developed progressively in late childhood. Nowadays there is a strong consensus that the best approach is to gait correction is to address all deformities simultaneously in what is known as single-event multi-level surgery.9
Correcting fixed contractures is achieved by either fractional lengthening or muscle-tendon recession. Established procedures include tenotomy (lengthening) of the psoas muscle at the pelvic brim, rectus femoris transfer to semitendinosus or sartorius and fractional lengthening of the medial hamstrings.
To correct bony torsional abnormalities necessitates rotational osteotomies. For femoral anteversion and concomitant hip internal rotation, femoral derotation osteotomy has proven to produce very effective and durable results.10 In order to correct a valgus foot deformity there are two options; a lengthening osteotomy of the os calcis or more commonly an extra-articular subtalar joint fusion utilizing an autogenous graft of bone from the iliac crest combined with a screw fixation .11
The most common joint deformities in the upper limb include internal rotation of the shoulder, elbow flexion, forearm pronation, wrist flexion and ulnar deviation, and swan-neck and thumb-in-palm deformities in the digits .12 Muscular injection with BTX-A can be useful in managing stiffness and increasing range of movement but is not effective at improving function.13
As with gait correction deformities in the upper limb are treated in a one-stage multilevel operation combining muscle releases and tendon transfers. The most common procedures are biceps aponeurosis and pronator teres release for pronation of the forearm, tendon transfers to extensor carpi radialis longus or brevis for ulnar deviation/wrist flexion (with first web z-plasty) and first dorsal interosseous and adductor muscle release with tendon transfer for thumb-in-palm.12
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Patterns of gait in spastic hemiplegia have been classified comprehensively by Winters et al. and can be used to plan surgical management. In groups I and II the primary abnormality is drop foot due to equinus contracture which can be treated by lengthening of the gastrocsoleus muscle and appropriate orthosis. The situation is more complex, however in groups III and IV which require multilevel surgical intervention and gait analysis due to the involvement of proximal muscles leading to jump knee gait and in the case of group IV fixed hip flexion on top of equinovarus. These can be managed in the same way as soft tissue deformities in spastic diplegia by fractional lengthening or muscle-tendon recession.14
[Image 2: Saggital gait patterns in hemiplegia: classification and management. For each group: contractures shown in orange text, orthoses in green, surgical correction in red. Adapted from Winter et al.14]
Tendon transfers to correct muscle imbalances are also employed in hemiplegia. This is most useful for equinovarus deformity, which is treated with split tendon transfer of the tibialis posterior (useful in the younger patient with more flexible deformity) or anterior combined with lengthening of the gastrocsoleus and tibialis posterior (better for older children with stiffer deformity).15, 16
Another possible problem in hemiplegia is limb shortening, presenting most commonly in the tibia and ranging from 1-3 cm. If necessary operative correction can be achieved by epiphysiodesis at the end of growth plates proximal to the knee at the appropriate age.7
Surgical management of a child with spastic quadriplegia is particularly challenging owing to the presence of multiple co-morbidities such as epilepsy, osteopenia, respiratory disease and nutritional deficiencies. As such it requires the close co-operation of a multi-disciplinary team to manage possible complications as well as follow-up in terms of pain and intensive care. A variety of tests are important to help assess suitability for surgery. Lung function tests are used to evaluate the likely necessity of protracted assisted ventilation after the operation. Testing serum total protein and albumin levels is used to spot malnutrition associated with poor wound healing and infection. Detection of osteomalcia due to anti-epileptic medication is important and must be treated, and improving general nutritional state through supplementation is often desirable. Finally, identification of the degree of osteoporosis due to disuse is relevant in assessing the stability of any surgical fixation desired.7
Hip displacement is rarest in spastic hemiplegia at 1%, uncommon in spastic hemiplegia at 5%, but much more common in spastic quadriplegia with an estimated incidence of 35-55%.17 If left untreated it may lead kyphotic sitting posture and pelvic obliquity increasing the risk of spinal deformity as well as chronic hip pain and increased difficulties in activities of daily living. In hemiplegia and diplegia the gait is so severely impacted that subluxation is identified early due to rapid orthopaedic referral. In quadriplegia, however, due to the higher visibility of issues such as seizures and feeding difficulties and the fact hip displacement is hidden in the early stages, it often can go undetected. Thus systematic radiographic screening is vital to detect it early with one study recommending commencing at 30 months and following up every 6 months thereafter.18
When abnormality is detected it is best to intervene early to try to prevent dislocation. The favoured soft tissue surgical approach is adductor and psoas tenotomies.19 If dislocation has already been established more drastic intervention is required with a single-stage open reduction of the hip, combined with a varus shortening derotation osteotomy of the proximal femur, which relieves pressure from the rim of the acetabulum stimulating growth and balancing the soft tissues by re-tensioning the hip abductors and relaxing the adductors, and a pelvic osteotomy to improve the shape and coverage of the acetabulum.20 Although this procedure offers the best long-term prognosis in terms of stability, further dislocations are not infrequent.21
Scoliosis in cerebral palsy can be non-structural secondary to femoral and pelvic muscular spasticity or structural secondary to contractures of the intrinsic spinal muscles. In non-ambulant patients it often extends to the sacrum and is associated with poor sitting posture, pelvic obliquity and hip dislocation. Prevention of these is thus vital to reducing the risk of distortion of the spine. Surgically the established management of severe scoliosis is instrumented posterior fusion along the length of the spine to the pelvis.6
As surgical techniques for correcting deformities have proliferated and been refined in recent decades so the orthopaedic management of cerebral palsy has progressed from art to science. We are now in the pleasing position of having a tried and tested toolbox of procedures to deploy in the common musculoskeletal pathologies induced by diplegia, hemiplegia or quadriplegia.
Yet a tool is only useful if it is used in the right place and so it is arguably the standardised assessment provided by ‘gait analysis’ as well as improved understanding of the development of gait that has made the most difference by allowing clinicians to target interventions precisely temporally and anatomically to ensure the best outcomes. Although validated evaluations exist for the upper arm they have yet to reach the same level of reliability and universality as gait analysis, a desirable goal for future research.
It is also important to remember that orthopaedic interventions can only ever ameliorate rather than solve the lifelong disabilities caused by cerebral palsy. For this reason it is vital that management first and foremost takes into account the desired outcomes of patients and carers including concerns such as cosmesis and independence. Likewise it is important to emphasise functional outcomes rather than abstract measures of deformity as these are in the end more important to patients.
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