7 Neuromuscular Deformities
The term neuromuscular disease in childhood refers to those conditions generally hereditary that affect the spinal cord, peripheral nerves, neuromuscular junctions, and muscles. 1 This classification can be seen in ▶ Table 7.1.
Spinal muscular atrophy
The muscular dystrophies
It is crucially important for the spinal surgeon to understand the fundamentals of these conditions, their prognosis, and their treatment so that the spine is not isolated from the underlying condition. Although cerebral palsy (CP) and poliomyelitis are not strictly “true” neuromuscular deformities in the child, notwithstanding, these conditions can produce significant spinal deformities and thus it is appropriate to describe them in a section on neuromuscular deformities.
7.2 Cerebral Palsy
This refers to all those conditions in which interference with the control of the motor system arises as a result of lesions within the brain. Despite the significant advances made in obstetric and pediatric practice since Little first described perinatal cerebral palsy (CP), 2 along with a significant reduction in neonatal death rate, the incidence of CP has remained much the same with about 2 per 1,000 affected children. 3 Cerebral palsy is caused by a broad group of developmental, genetic, metabolic, ischemic, infectious disorders and others that result in a common group of neurological phenotypes (▶ Table 7.2). CP can be associated with other abnormalities 4 of speech (25–80%), vision (34–80%), and intellect as well as epilepsy (33%) but many individuals with CP perform intellectually well with no evidence of cognitive dysfunction and 60% achieve gainful employment. 5 CP subtypes have historically been considered as being prenatal, perinatal, and postnatal. 6 There is a mortality rate of 10% in the first year while prenatal and perinatal types are clinically manifest by the age of 3 years; 10% of cerebral palsy cases are postnatal.
Periventricular leukomalacia (PVL)
Endocrine/metabolic (e.g., thyroid)
Endocrine/metabolic, general developmental
Stroke in utero or neonatal
Periventricular hemorrhagic infarction
Extrapyramidal (athetoid, dyskinetic)
Pathology: putamen, globus pallidus, thalamus, basal ganglia
Asphyxia Kernicterus Mitochondrial
Source: With permission from Johnston MV. Encephalopathies. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia: Saunders Elsevier; 2008:2494.
The Collaborative Perinatal Project in which just over 50,000 children were regularly monitored from in utero to the age of 7 years showed that most children with CP were born at term following uncomplicated pregnancies and deliveries. 7 Antenatal factors causing abnormal brain development were found in more than three-quarters. Asphyxia during delivery was found in fewer than 10% but exposure to maternal infection in utero was a significant risk factor confirmed by raised levels of inflammatory cytokines. Low birth weight was also a significant factor particularly if less than 1 kg.
Physiologically 50% are spastic, 25% athetoid, 7% rigid, 5% ataxic, and the remainder mixed. 4 There are four principal clinical groups: spastic hemiplegia, spastic quadriplegia, extrapyramidal cerebral palsy, and minimal brain dysfunction (maybe just a clumsy child). All hemiplegics are able to walk independently although contractures can produce a poor base for balance and all have one normal hand allowing them to participate in some type of occupation. While the extrapyramidal group demonstrates the involuntary movements of tension athetosis which hinders effective walking, sitting, and head control throughout life compounded by contractures, these are the most intelligent children in the whole range of cerebral palsies. It is behavioral abnormalities, mental retardation, and epilepsy that are the principal obstacles to competitive performance in adult life. In quadriplegia, however, mental impairment is commonly considerable 5 and it is not often to find normal intelligence. There is a close correlation between intelligence and physical handicap and this is particularly important as regards treatment because patient enthusiasm and drive are essential to a successful rehabilitation program 8 and psychological help is therefore necessary to optimize the program. The role of the educational psychologist is extremely important to assess and advise child, family, and surgeon. As a result of the Warnock report in the United Kingdom (a government report on the Education of Handicapped Children and Young People in 1978) appreciably more children have gone to their local school albeit with appropriate support, 9 demonstrating the essential requirement for good team work. Consequently, a multidisciplinary approach including social as well as physical and academic development is necessary to address treatment for these patients in a holistic fashion. At the same time, it is important to appreciate that 25% of patients can attend ordinary schools while a further 25% are so retarded that permanent sheltered residential conditions are required. Minimal brain dysfunction may be the lesion in a substantial number of mentally retarded children. It is very important for the orthopaedic surgeon to appreciate that at least 50% of all children with CP have a significant sensory impairment and so surgeons should not be under the illusion that the problem is essentially a motor one. 10
Computed tomography (CT) or magnetic resonance imaging (MRI) may show an atrophic cerebral hemisphere with a dilated lateral ventricle contralateral to the side of the affected extremities in diplegia although MRI is far more sensitive than CT for most lesions in CP. 11
7.2.1 General Orthopaedic Principles
The basic underlying principles governing the orthopaedic management of neuromuscular conditions are probably known to all orthopaedic surgeons but a more comprehensive knowledge (although not detailed) is required to set the scene for spinal deformities. Getting this additional knowledge (and understanding it) is not easy and, for example, James Robb’s chapter in Children’s Orthopaedics and Fractures 12 is a must-read providing us with so much important information in such a short and readable text. (There will be many more chapters in pediatric orthopaedic textbooks that you can look at but this one is particularly good.) Deformities may be mobile or fixed due to disorganized posture, balance, and movement. Delay in acquiring motor skills means that these appear late and maybe fewer than normal. If equilibrium is poor, then movement may not be able to be initiated even though voluntary motion is possible. Postural control of the trunk and head are crucial matters for the orthopaedic spine surgeon because, for surgery with a collapsing CP spine in the sitter, it must be the spine that is causing loss of sitting stability and balance and not retarded postural mechanisms. Normal postures develop as muscles shorten or by a compensatory mechanism to maintain equilibrium. To stand erect may require spasticity as a compensation. It is not isolated muscle groups that are spastic but an imbalance between agonists and antagonists with the effect that the weaker antagonist produces deformity that can be well seen at the hip.
Gait is particularly important to understand in the ambulatory CP patient which is very difficult with multiple lower limb joint deformities. Robb recommends physiotherapy records with the use of gait scores, such as the Edinburgh Gait Score. 13 In addition to gait analysis, it is particularly important to examine gait in detail and a comprehensive evaluation would include kinematics, kinetics, energy consumption, and dynamic electromyography. Interestingly gait analysis was first used clinically to optimize management in CP children. 14 This is the area that is really important for the orthopaedic spine surgeon. Assessment of sitting stability prior to surgery is relatively straightforward but which walkers merit correction and fusion of their scoliosis is much more difficult to define particularly in those with already difficult walking ability.
Surgery in such cases can render the ambulatory patient unable to walk which was pointed out in the very responsible article by Lonstein from Minneapolis. 15 Understanding more about the complexities of gait by way of this comprehensive gait evaluation would be very important here before surgery as for the walker it would be easy to do more harm than good. A preoperative trial in a brace or cast to see the effect on ambulation would seem a rather simplistic notion but may be very useful in doubtful cases.
“The aim of clinical examination and gait analysis is to define a list of biomechanical problems apart from the neurological disorder” 12 and therefore an important aim in the management of patients with CP involves control of posture and daily activities during which the available range of joint movement and muscle length should be used. “Compromises may have to be made between in the balance of benefit from intervention and the disadvantages, for example, standing with the knees bent places a load on the quadriceps which is tiring while straightening the knees can solve this stance phase problem for the patient but may cause difficulties in the swing phase of gait.” 12 Orthopaedic procedures for the lower limbs may involve muscle or tendon lengthening, tendon transfers, tenotomy, and bony operations to improve rotational problems, to relocate joints, and neurectomy. Treatment for hip dislocation is indicated for instability, reduced motion, and pain although whether the cerebral palsy hip is really painful is uncertain. 16 Passive physiotherapy stretching and intramuscular Botulinum toxin A, in conjunction with functional and positional orthoses, are part of the therapeutic armamentarium for the appendicular skeleton. As regards the lower limb, adductor tenotomy and obturator neurectomy are important to try and keep the adducted internally rotated and flexed hip in joint with or without additional femoral or acetabular osteotomy and this is certainly going to be very important in trying to maintain walking ability.
The windswept deformity, where there is significant adduction at one hip and abduction at the other (▶ Fig. 7.1), is a typical finding in the nonwalker and necessarily contributes to pelvic obliquity. It is extremely difficult to treat. Graham, one of the real experts in cerebral palsy orthopaedic treatment, found that abduction, bracing, and Botulinum toxin injections were not effective in a comparative trial. 17 However “one hip in and one hip out” is not a satisfactory endpoint. Treatment for this situation is very difficult but left untreated does lead to pelvic obliquity which is a very undesirable platform for the spinal deformity above and can cause great difficulty with perineal hygiene. In this regard the complex lumbopelvic movements required for ambulation can be markedly disrupted by making the thoracolumbar spine straight but absolutely stiff with surgery. 15
Fig. 7.1 Windswept deformity in cerebral palsy. (a) One hip adducted the other abducted, a common cause of pelvic obliquity. (b) The treatment aim would be to surgically get the hip on the high side abducted and contained to try and square the pelvis.
(Reproduced with the permission from Springer Publishing, Children’s Orthopaedics and Fractures, 3rd Ed, Eds Benson M, Fixsen J, Macnicol M, Parsch K, Chapter 3, Fig 3.6.)
Of course while the orthopaedic spine surgeon may well be consulted when the child is at an early age if the degree of cerebral palsy is severe, most often it is the adverse effect of growth that leads to presentation to the scoliosis surgeon and by this time the patient will have been seen and treated perhaps on many occasions by his pediatric orthopaedic surgical colleague in which case it will be imperative to review the overall aims and objectives for that particular patient so that the scoliosis surgery fits into a sensible and comprehensive treatment schedule. Of course those with minimal brain dysfunction and a spinal deformity that will not trouble function should not be ignored as such individuals surely deserve the same sort of attention to the psychosocial aspects of deformity and their effect on personal dignity as the patient with idiopathic scoliosis.
7.2.2 The Spine in Cerebral Palsy
Robson looked at the prevalence rate of scoliosis in adolescents and young adults with CP and examined 152 diplegics and athetoids. 18 There were 73 deformities of which half were structural and the remainder related to pelvic obliquity.
Males and females were equally represented. Balmer and McKeown looked at 100 children with CP and found 21 with a scoliosis measuring 10 degrees or more, only 2 of which were larger than 60 degrees. 19 The biggest group of children with CP was studied by Samilson and Bechard and of 906 children 232 had a spinal deformity, of which 193 were spastic quadriplegics. 20 The most severe curves were in the thoracolumbar region, compounded in the majority of cases by either a fixed pelvic obliquity or a hip contracture or dislocation (▶ Fig. 7.2). One New York group found the prevalence rate of scoliosis with CP to be of the order of 40%, with only one case greater than 40 degrees. 21
Fig. 7.2 (a,b) Two severe thoracolumbar collapsing C-shaped curves down to fixed pelvic obliquity. These two teenagers had always been bed-ridden. They were pain free. Surgery was neither indicated nor prescribed.
Early experience of surgery for CP scoliosis focused on posterior fusion with Harrington instrumentation. 22 However, whereas the polio thoracolumbar C-shaped collapsing scoliosis does remain flexible for a longish period of time, the same cannot be said for the much more rigid cerebral palsy curve. Accordingly, there is a trend for the more severe curves to be dealt with by a preliminary anterior instrumentation stage. Dwyer invented the anterior instrumentation that bears his name 23 and indeed it was first designed for the treatment of thoracolumbar and lumbar idiopathic curves but many scoliosis surgeons were concerned about going anteriorly for idiopathic cases and so it gained popularity as an initial anterior instrumentation and fusion worldwide for neuromuscular curves, including CP. The principle behind this was that with secure fixation and fusion down to L5 then this favorably corrected pelvic obliquity because of the attachment of L5 to S1 by the immensely strong iliolumbar and lumbosacral ligaments. Then in the second stage segmental spinal instrumentation posteriorly allowed the back of the spine to be stacked up above this solid base (▶ Fig. 6.50 and ▶ Fig. 7.3).
Fig. 7.3 (a) Maximum traction PA X-ray of a C-shaped thoracolumbar curve with pelvic obliquity showing better than expected flexibility. (b,c) PA and lateral X-rays after anterior Zielke instrumentation and fusion and posterior unit rod fixation to the sacrum. Anterior and posterior instrumentation and fusion ensured this excellent correction was maintained.
In the early 1980s Lonstein and Akbarnia reported the Minneapolis experience of 109 scolioses in CP and mental retardation. 15 They noted the important difference between balanced and unbalanced curve configurations which comprised 44 and 63, respectively, of the 107 CP patients with a scoliosis. Traction was of no benefit, not surprisingly. For balanced curves not involving the sacrum a posterior approach alone sufficed and of course these were ambulatory patients toward the mild end of the CP spectrum. For unbalanced curves involving the pelvis, both anterior and posterior approaches were necessary but complications occurred in more than 80% of patients making scoliosis surgery for CP scoliosis a very important risks and rewards equation. Some who were walkers were rendered wheelchair bound by stiffening the lumbar spine in an area where the somewhat bizarre lumbopelvic spinal movements are required for ambulation. They emphasized that the best indication for surgery in CP was the patient with the unbalanced curve down to the pelvis who was a permanent sitter and was losing sitting stability and, of course, to aid perineal hygiene. With the advent of segmental wiring to posterior L rods 24 it was thought that perhaps this more rigid posterior procedure would suffice but of the 27 patients so treated 10 required an additional anterior procedure. 15
Then in the early 1980s Zielke in Germany brought out an updated anterior metalwork system 25 which gradually replaced the Dwyer. So it came to be that surgery for balanced curves not involving the pelvis treatment was by single-stage posterior segmental instrumentation while for the unbalanced collapsing C-shaped thoracolumbar curves anterior and posterior instrumentation and fusion became the norm in all but the most moderate and flexible cases (▶ Fig. 6.50 and ▶ Fig. 7.3). It is however the very devil to obtain a lumbosacral fusion in paralytic scoliosis and, indeed, the excellent John Hall in Boston told us that that he didn’t think he had ever managed to achieve an L5/S1 fusion in such cases.
Debate continued however about fixation to the sacrum as it became quite clear that sacral bone did not appear to be strong enough and the L5/S1 joint was very difficult to fuse in neuromuscular cases. Alan and Ferguson addressed this by developing transiliac metalwork extension into the pelvis, referred to as the Galveston technique, and focused particularly on CP and poliomyelitis cases 26 (▶ Fig. 7.4). They demonstrated improved results in having a more securely instrumented base for the construct and fusion above.
Fig. 7.4 (a) Typical severe collapsing C-shaped lordoscoliosis with considerable pelvic obliquity in a 10-year-old wheelchair-bound boy. (b) Lateral radiograph showing the characteristic pseudokyphotic appearance when lateral X-rays of the patient and not the deformity are taken. (c) PA radiograph at follow-up more than 3 years after long transpedicular fixation down to the pelvis where Galveston-type fixation has been used. There is a superb correction of the scoliosis underpinned by almost complete correction of the pelvic obliquity. (d) Lateral radiograph postoperatively showing a very nice re-creation of a natural sagittal profile. Once the scoliosis is corrected the spine is brought toward the midline and so the lateral X-ray of the patient more closely resembles a true lateral X-ray of the deformity.
(We are most grateful to our colleague and friend Professor Thanos Tsrikos for the case shown in Fig. 7.4.)
In 1991 the Minneapolis experience was published of 68 cases of neuromuscular scoliosis and pelvic obliquity corrected by the Luque-Galveston procedure. 27 Thirty-four had CP and the other 34 had other neuromuscular diseases. The average age at surgery was 14 years and 20 patients had an anterior fusion without instrumentation. The scoliosis averaged 73 degrees before surgery and 33 degrees at a minimum 4-year follow-up. Those having their preliminary anterior diskectomy had a more severe scoliosis and greater pelvic obliquity but the percentage correction was similar. There were instrumentation problems in just over 20% but only four had broken rods and there were no broken wires. Seven had pseudarthroses. Three patients had minor transient neurological problems. They concluded by saying that the Luque-Galveston procedure was the most effective available method of treatment for neuromuscular spine deformities requiring fusion to the sacrum. In addition, anterior fusion from T10 to the sacrum reduces the pseudarthrosis rate and improves the correction of scoliosis and pelvic obliquity. So that was the state of play in the 1990s—but, in scoliosis surgery, the status quo never lasts for long.
When the Luque construct was introduced there were two L rods with the shorter L angulated down into the ilium. Separate, unlinked rods could however swivel or translate with respect to one another. leading to a loss of curve correction and pelvic obliquity and so a one piece “unit rod” construct was developed. 28 This one piece unit rod comprised two L rods with a U connection at the top to provide greater stability and maintenance of correction of both the spinal curvature and the pelvic obliquity (▶ Fig. 7.3). Then came a report of a comparative study of 15 patients treated with a unit rod construct versus 15 treated with two L rods. 29 The correction of both Cobb angle and pelvic obliquity was much greater in those treated with the unit rod construct. This second generation segmental instrumentation technique, whether two rods or one-unit rod, continued to dominate the scene. Meanwhile in France a third generation instrumentation system was being developed by Cotrel and Dubousset whereby with the use of two rods and hooks distraction and compression could be applied on the same rod at different sites. 30 This is the prototype for all subsequent third generation systems albeit now with much greater use of transpedicular fixation particularly in the lower spine. In 2006 the Milan Group published the results of 60 patients with CP treated with CD instrumentation with a mean follow-up of 6.5 years. 31 There were 34 posterior only and 26 anterior and posterior procedures. Scoliosis correction and pelvic obliquity correction were 60% and 40%, respectively. They claimed to have a lower pseudarthrosis rate than with second generation systems. As usual, complications in CP patients were considerable.
The Seoul Group, in a retrospective study of 55 cases, showed that the amount of pelvic obliquity preoperatively mattered as regards the need for and success of pelvic fixation. If pelvic obliquity was greater than 15 degrees, then pelvic fixation was necessary but not if preoperative pelvic obliquity was less than 15 degrees. 32 The results were poor, however, if pelvic obliquity exceeded 15 degrees and there was no pelvic fixation.
In a recent review of 52 scoliosis patients with CP who underwent posterior only pedicle screw fixation the Cobb angle was improved from 77 degrees to 32 degrees and the overall pelvic obliquity from 9 degrees to 4 degrees. Interestingly, the mean age of these patients was all of 22 years, very much older than the usual age of 14 years or thereabouts at the time of surgery, and there were two perioperative deaths and one temporary neurological problem! The amount of pelvic obliquity going in being less than 10 degrees certainly wasn’t substantial. 33 Others reported good results with transpedicular instrumentation. 34
Posterior multilevel vertebral osteotomy (average number of osteotomies four) in seven CP patients achieved improvement in Cobb angles and pelvic obliquity from 118 degrees and 17 degrees to 49 degrees and 8 degrees, respectively, without any neurological or vascular injuries and with no postoperative ventilatory support required. 35 The mean age was all of 21 years and follow-up only 2 years.
In a retrospective study of 61 patients with CP, 19 had a unit rod correction with anterior release compared with 42 without an anterior release. Not surprisingly those who underwent an anterior release had larger curves averaging 91 degrees versus 72 degrees for the posterior only construct. Similarly, pelvic obliquity was 26 degrees in the anterior release and 19 in the posterior only group. Percentage corrections were similar but of course these groups were not really comparable. 36 In a recent study of how beneficial surgery is in spastic CP, 84 patients/families of spastic CP patients responded to a questionnaire and although the overall satisfaction rate was more than 90% functional improvements were much less. 37
In one study 26 patients underwent posterior only surgery compared with 26 who underwent anterior and posterior surgery; no benefit was claimed for a preliminary anterior release. All patients underwent halo-femoral traction preoperatively. 38 No anterior instrumentation was however used and so unless the anterior tension side is closed down after diskectomies, and therefore shortened with instrumentation, it may be that the maximum benefit of an anterior procedure wasn’t achieved.
In 2011 Lonstein published the results of 93 patients instrumented with the Luque-Galveston technique who had CP or encephalopathy with a preoperative scoliosis Cobb angle of 72 degrees corrected down to 33 degrees but there were complications in more than half the patients. 39 However, there were no deaths or neurological complications and only one wound infection. There was a pseudarthrosis rate of 7.5% but most of the complications were relatively minor.
The Edinburgh Group recently published their results of 45 consecutive patients with quadriplegia who underwent pedicle screw instrumentation. 40 All were wheelchair bound with a collapsing thoracolumbar scoliosis and pelvic obliquity. The mean age was 13 years and the scoliosis was corrected from 83 degrees to 21 degrees and the pelvic obliquity from 24 degrees to 4 degrees. These are excellent results (▶ Fig. 7.4). There was no neurological deficit but one deep infection and one reoperation for prominent implants. Very good parent satisfaction was reported. The Swiss Group who looked at health-related quality of life after spinal fusion for patients with CP noted high levels of satisfaction but these did not correlate with objective radiographic improvements. 41
The Dallas Group reported 53 patients with significant infection after instrumentation for scoliosis—10 had CP while 21 had idiopathic scoliosis. 42 In this group of patients there was a 50% chance that the infection would remain if all the instrumentation was not removed. Coagulase-negative Staphylococcus was the organism in nearly 50% of cases and they recommended that prophylactic antibiotic coverage for this organism must be used at the time of the initial spinal fusion. 41
There is no doubt that when properly indicated and prescribed spinal deformity surgery can be hugely beneficial in terms of quality of life in these unfortunate CP patients.
Poliomyelitis is an acute infectious disease caused by a neurotropic group of viruses spread as direct person to person contact with infected mucus, phlegm, or feces. Entry is through the mouth and nose and into the intestinal and respiratory tracts and then to the blood and lymph channels to the central nervous system. Both the anterior horn cells of the spinal cord and centers in the brain stem nuclei are involved in the infectious process and it was shown 60 years ago that infected nerve cells undergo chromatolysis and that the pathogenesis was not simply due to inflammatory edema. Bodian also pointed out that as a result the nerve cells are either destroyed or not and only in the latter event was recovery possible. 43 Outbreaks occurred in both the UK and United States in the early 19th century. Major epidemics occurred 100 years later in the 1940s. Routine vaccination has seen very few cases in the Western hemisphere but outbreaks still occur in underdeveloped or developing countries but a huge worldwide vaccination program has left polio cases in only a few places in Africa and South Asia, with a 95% reduction in cases over the past 30 years. 44
The condition can be subclinical (95%), nonparalytic, or paralytic and there are three traditional phases: the acute phase, the convalescent phase, and the residual phase. During the stage of paralysis that extends from the end of the acute phase through the convalescent phase, musculoskeletal management lies principally in the prevention of deformity. The convalescent phase—when recovery can occur—lasts up to 2 years although most of this recovery occurs in the first 3 to 6 months. It is in the residual phase of paralytic poliomyelitis where orthopaedic deformities may require reconstructive surgery. 45
Deformities can be fixed or mobile and for mobile deformities physiotherapy and splintage, dynamic or static, are the basis of treatment. Splintage is required to keep the joint in the over-corrected position to prevent recurrence. Although previous generations of consultant orthopaedic surgeons were very often “brought up,” so to speak, on the array of conservative and surgical treatment required for poliomyelitis, younger generations have missed this unique experience and would do well with familiarizing themselves about the principles of surgical treatment in poliomyelitis as a background to learning and understanding surgical treatment for the polio spine. A good summary can be found in Chow. 45 Clearly as regards scoliosis the status of the lower extremities is particularly important and again the spine should not be isolated from the other affected joints. These may contribute to or cause pelvic obliquity.
Yount described the abduction deformity due to iliotibial band tightness and indeed recommended division of this band in such circumstances. 46 However, Kaplan did not believe it was a significant deforming force. 47 The hip joint itself dislocating as a result of paralysis with progressive coxa valga is a major factor in producing pelvic obliquity and may require soft tissue or bony surgery according to the stage of the dislocation process. 48 Where pelvic obliquity is really important is in its true causation 49– 51 (▶ Table 7.3). There are three types of pelvic obliquity—infrapelvic, transpelvic, and suprapelvic—and more often than not while the hip may contribute to an unstable pelvis the chief deforming force lies with the collapsing spinal deformity above (suprapelvic pelvic obliquity). Suprapelvic pelvic obliquity is the unstable paralytic C-shaped thoracolumbar scoliosis that goes down to the pelvis and causes the pelvic obliquity (down on the convex side) (▶ Fig. 7.4). All too often trying to treat transpelvic pelvic obliquity, such as, the Sharrard transfer of iliopsoas posterior and lateral to the hip joint through a large hole in the ilium, 52 necessarily fails when the real cause of the pelvic obliquity is the collapsing paralytic scoliosis above.
Leg length inequality
Unequal contraction/contracture of iliopsoas
Collapsing thoracolumbar paralytic scoliosis
7.3.1 The Spine in Poliomyelitis
It is difficult to determine the prevalence rate of spinal deformity in poliomyelitis but in the 1920s a third of cases of scoliosis were due to poliomyelitis. 53 Fifty years ago in Oxford only 19 of the 321 cases of scoliosis were due to poliomyelitis. 54 There have been several attempts to relate muscle paralysis to curve characteristics. 55– 60 The most detailed study was performed by James in 193 patients with polio scoliosis and he compared their muscle function with 280 patients with polio but with no spinal deformity. 57 A total of 118 of his cases were thoracic curves and those with a high thoracic apex had the worst prognosis—the majority going on to develop curves measuring 100 degrees or more by maturity. He noted the high prevalence rate of intercostal muscle paralysis on the convex side. This combined with the characteristic convex rib drooping and crowding clearly differentiated the thoracic polio scoliosis from the idiopathic one and put James very much against the concept that there was a subclinical neuromuscular problem at the heart of idiopathic scoliosis, another nail in the coffin of the neuromuscular advocates. A total of 47 of his curves were thoracolumbar and he incriminated weakness of the lateral abdominal flexor muscles while quadratus lumborum weakness specifically was responsible for his 17 lumbar cases. Only 13 were double structural thoracic and lumbar curves. He noted that the function of the midline muscles (erector spinae and the anterior abdominals) only influenced spinal shape in the sagittal plane. Then in the same journal Roaf reported his experience and considered four types of deformity: the thoracolumbar C-shaped curve, the collapsing combined thoracic and lumbar curve, the primary lumbar curve, and the primary thoracic curve. 58 He observed that the thoracolumbar C curve was mild, not usually rotated, and was due to gravity shifting the trunk toward the weak side. He noted this curve to be a very flexible one and responded well to surgical correction. He also noted that some mild C-shaped curves did go on to the collapsing combined type for which treatment was much more difficult and had to involve an extensive fusion. Interestingly for the primary thoracic curve he felt that closing wedge osteotomy provided a better correction than posterior fusion. Garrett reduced these different types to two groups: those as a result of asymmetric paralysis that produced higher curves and those due to symmetric collapsing paralysis that involved the sacrum with pelvic obliquity and required a fusion to the pelvis. 59 Garrett’s two subgroups are probably the best and simplest way of looking at the polio scoliosis spine. Pavon and Manning noted a leg length inequality to be present in at least half of all patients which contributed an infrapelvic mechanism to the suprapelvic pelvic obliquity. 61
For polio curves not extending down to the pelvis, Milwaukee brace treatment was popular years ago in the hope that the necessary surgical stabilization could be delayed but there is no evidence that this form of treatment was effective and indeed the brace was specifically designed to support the polio spine after surgery and not as a conservative treatment option. 62 Before the era of Harrington instrumentation surgical treatment was a difficult matter, correction being obtained by cast techniques. Then through a window in the back of the cast a posterior fusion was performed with whatever bone could be found, pelvic or tibial. 63 This was then followed by a period of prolonged recumbency followed by mobilization with a spinal support. Not surprisingly the pseudarthrosis rate was high and curve correction disappointing. 64 When Harrington instrumentation began to be used 65 this heralded the era of poliomyelitis distraction instrumentation for the spine and then the Milwaukee brace to support the paralytic spine postoperatively. While the period of recumbency was only of the order of 3 weeks for the instrumented cases, the pseudarthrosis rate was unfortunately unchanged. 66 Meanwhile Dwyer in Australia produced his anterior instrumentation (albeit for idiopathic scoliosis) which appeared to be eminently suitable for the paralytic deformity in polio. 23 Then the Hong Kong Group revolutionized the treatment of the collapsing paralytic polio curve by establishing that both anterior and posterior instrumentation and fusion were necessary with first stage anterior Dwyer instrumentation down to the fifth lumbar vertebra and second stage Harrington instrumentation. 67 Fixation down to the fifth lumbar vertebra influenced the obliquity of the first sacral segment because of the attachment of the immensely strong iliolumbar and lumbosacral ligaments. Thus arose the concept that it was the obliquity of the pelvis which was the primary target for surgical treatment although of course the scoliosis was corrected pari passu. In the second stage there was a long posterior fusion to the sacrum using Harrington instrumentation. 68 In due course the Zielke system was introduced providing more anterior rigidity. 69 Then the segmental instrumentation system devised by Luque in Mexico was developed whereby the generally early flexible polio curve could be managed by one posterior operation. 70 Not surprisingly there was a higher correction rate with a lower complication rate including pseudarthrosis and loss of correction. For cases with particularly severe pelvic obliquity Alan and Ferguson introduced the concept of passing the short arm of the L rod into the pelvis (the Galveston technique). 26
Two important series of patients with poliomyelitis and scoliosis were published one involving the Hong Kong patients 71 and the other the patients in Taiwan. 72 Leong and colleagues reviewed 110 patients with paralytic scoliosis who were operated upon, 58 had lumbar curves, 26 thoracic curves, 14 long C-shaped curves, 8 had thoracolumbar curves, and 4 had double major curves. These patients had developed polio before the age of 3 years. The average age of surgery was in the early teens. The earliest surgical experience involved Harrington instrumentation only but much better results were achieved with preliminary anterior Dwyer instrumentation followed by posterior fusion at a second stage (▶ Fig. 7.5). Percentage correction of Cobb angle varied from 50% to almost 100% and this related strongly to initial curve angle (53 degrees to 105 degrees). They used traction for bigger rigid curves which of course makes biomechanical sense (the bigger a curve is the more it requires a pull from top and bottom while milder curves require a push from the side) (▶ Fig. 7.6). Posterior fusions alone had a 25% pseudarthrosis rate while with combined anterior and posterior fusions the pseudarthrosis rate was reduced to 7% with none in thoracic curves and 12% in the long C-shaped curves. 71
Fig. 7.5 (a) PA radiograph of a low thoracic polio curve in a girl of 14. (b) Clinical view of this significant deformity. (c) After anterior apical Dwyer instrumentation and a long Harrington rod showing an excellent correction and a solid spinal fusion. (d) Clinical appearance 2 years after surgery showing an excellent correction and a well-balanced spine.
(We are most grateful to our colleagues Professors John Leong and Ken Cheung for the cases shown in Fig. 7.5 and Fig. 7.6.)