Description of the condition
Scoliosis is a complex three-dimensional deformity of the spine that comprises a lateral curvature in the frontal plane (this is a vertical plane that divides the body into front and back halves), thoracic lordosis in the sagittal plane (this is a vertical plane that divides the body into right and left halves) and a posterior rib hump, which is produced by rotation of the vertebrae in the transverse plane (horizontal plane); this results in the posterior elevation of the rib cage on the convex side of the curve and a depression on the concave side (Bradford 1987). These underlying skeletal changes are usually reflected by a change in back shape, the unsightly shape of which is generally more of a concern to the patient than is the underlying skeletal deformity (White 1990).The condition if left untreated results in altered spinal mechanics and degenerative changes that lead to pain, loss of spinal mobility and possible loss of function or disability. Cardiac and respiratory dysfunction may also accompany these symptoms, depending on the time of onset of the deformity (White 1990). These physical changes are accompanied by the psychological consequences resulting from the unsightly and deformed shape of the back: a restricted social life, a lower marriage rate, a higher divorce rate, fewer children per marriage and increased psychiatric consultations, including eating disorders and increased suicide rate, have all been reported (Freidel 2002).
Whilst scoliosis may be the expression of a disease, it can also occur secondary to certain diseases and conditions that affect the nervous and muscular systems of the body. The deformity can be caused by defects in spine formation at the embryo stage, or it can be part of certain syndromes. Very rarely, scoliosis can occur secondary to tumours. However, most cases of scoliosis (80% to 90%) are called `Idiopathic’ because the underlying cause cannot be ascertained. Adolescent idiopathic scoliosis (AIS), which is the most common diagnosis, usually develops during adolescence－a period of rapid growth (Kanayama 1996; Stokes 1996).
According to the Scoliosis Research Society and the International Society on Scoliosis Orthopaedic Rehabilitation and Treatment (SOSORT Guidelines 2012), the prevalence of AIS is 2% to 3% in the general population. Almost 10% of patients with AIS will require some form of treatment, and up to 0.1% will eventually require surgery (Lonstein 2006). AIS is more commonly found in females (female/male ratio is around 7:1) and, except for extreme cases, AIS does not typically cause any health problems during growth; however, the resulting surface deformity frequently has a negative impact on adolescents that can give rise to quality of life issues and, in the worst cases, psychological disturbances (Reichel 2003).
The aetiology or causation of idiopathic scoliosis remains unclear (Sevastik 1997; Stokes 1997; Machida 1999; Burwell 2000). Many theories on the causes of scoliosis have been proposed, such as the neuromuscular, growth and genetic theories. White 1990 sums up all hypotheses related to the cause of scoliosis as follows: "The normal spine in a growing person has a precise, precarious, delicate mechanical balance. Asymmetrical changes in primary structures, support structures, growth centres, the position of the spine and related neural or muscular components can all result in the development of scoliosis."
The potential for curve progression has been shown to be related to several factors, including the patient's gender, age, curve magnitude, bone maturity, rate of growth and growth potential at presentation. Dickson 1984 demonstrated that when curves of 10 degrees Cobb and above were considered, the female-to-male ratio was 1.6:1. The Cobb angle is a method of measuring the angle of the spine that was devised by a surgeon named Cobb (Lonstein 2006). This value increased to 12:1 when curves greater than 20 degrees Cobb were considered. Female-to-male ratios for treatment were reported at 7:1 (Rogala 1978). Moreover, when combining curves of all magnitudes, Lonstein 1984 found a negative correlation of age with the percentage incidence of progression. This means that the younger the child at presentation, the greater is the likelihood of progression. The same negative correlation is shown with the Risser sign. This measures how much mature bone has developed (ossification) in the upper rim of the pelvis (iliac crest). The greater the maturity of the child, the greater is the Risser sign. A low Risser sign indicates that greater potential for growth is left, and consequently the potential for curve progression is greater (Bridwell 1999 and Lonstein 2006). Curve magnitude, however, was found to have a positive correlation with the percentage incidence of progression. Thus the greater the magnitude of the curve at presentation, the greater is the potential for progression.
Other factors taken into consideration when growth potential is determined are the changes in secondary sexual characteristics that take place during the growth spurt. Different results have been reported on the progression of various curve patterns. For example, Clarisse 1974 and Fustier 1980 reported that double curves progressed most in their studies, with an incidence of 67% and 75%, respectively. Conversely, Bunnell 1986 and Lonstein 1984 reported that thoracic curves were most progressive. All authors, however, demonstrated that lumbar curves progressed least. Other parameters of prognostic value include apical vertebral rotation (Weinstein 1983; Perdriolle 1985) and the rib vertebral angle (Mehta 1972). When potential for curve progression is assessed, no single factor is taken in isolation, but all factors are taken into account in attempts to predict the likelihood for progression and make a treatment decision.
Depending on the age of the individual at diagnosis, scoliosis evolves and may deteriorate rapidly during periods of fast growth spurt (Goldberg 2002; Asher 2006; Hawes 2006b). Whilst children grow until they have fully matured, growth is more rapid (growth spurt) during certain periods of childhood and adolescence (Weiss 2012).
Early diagnosis is difficult, especially in countries where scoliosis school screening is not implemented, as this condition is most often painless. External change to the body shape is minimal in the early stages and most changes in back shape occur predominantly on the back of the trunk, which makes it difficult for patients to see, and it can be concealed by their clothing (Roaf 1980). Treatment of idiopathic scoliosis is determined by the deformity itself. As most patients with adolescent idiopathic scoliosis progress during growth, the main aims of all interventions are to limit or stop the curvature progression, restore trunk balance (Goldberg 2002; Asher 2006) and prevent the long-term consequences of the deformity.
Description of the intervention
Interventions for the prevention of AIS progression include scoliosis-specific exercises, bracing and surgery (Rowe 1997; Lenssink 2005; Negrini 2005; Weiss 2006a), and other interventions have been reported in the literature. The goals ofALL interventions are to correct the deformity and prevent further deterioration of the curve (i.e. prevent progression) and to restore trunk asymmetry and balance, while minimising morbidity and pain, allowing return to full function (Bridwell 1999; Lonstein 2006 ).
Treatment approaches adopted by various orthopaedic surgeons and physicians specialising in the field of scoliosis around the world are divided, indicating lack of clinical equipoise across different professions and countries. In general, these approaches can be split grossly into two opposing groups. The first group consists of those who regard scoliosis-specific exercises as inefficient; members of the second group use these exercises and advocate their efficacy (Negrini 2005; Weiss 2006b). Similarly, bracing has been abandoned by some (Dolan 2007), but others support its use on the basis of existing weak evidence about efficacy (Negrini 2007); fusion is generally considered to be necessary when AIS exceeds a certain degree (approximately 45 to 50 degrees), when previous treatments have failed or when AIS causes symptoms, but indications vary widely according to the preference of the treating physician/surgeon (Dolan 2007).
These two conflicting approaches to conservative management seem to prevail in different regions of the world. In the United States, the United Kingdom and Australia, the wait-and-see strategy prevails, but in various parts of continental Europe and Eastern and Southern Europe, conservative treatment (scoliosis-specific exercises and bracing) is considered beneficial for the patient and is used routinely by a large majority of scoliosis physicians and surgeons (Lenssink 2005; Negrini 2005; Weiss 2006a). A possible reason for the negative beliefs toward scoliosis-specific exercises within the clinical community in the United Kingdom, in the United States and in some other countries is lack of knowledge within the physical therapy community and among associated clinical specialists. These pathological condition-specific exercises are not taught at an undergraduate or postgraduate level within the physiotherapy curriculum in both countries, and most clinicians (both physiotherapists and surgeons) in the United Kingdom normally do not appreciate the difference between scoliosis-specific exercises and general physiotherapy. Scoliosis-specific exercises consist of individually adapted exercises that are taught to patients in a centre that is totally dedicated to scoliosis treatment. Patients learn an exercise protocol that is personalized according to their own medical and physiotherapeutic evaluation. On the other hand, usual generalised physiotherapy is more generic, consisting of low-impact stretching and strengthening activities like yoga, pilates or tai chi (taiji), but it can include many different exercise protocols. Whilst scoliosis-specific exercises are usually used for treating mild curves of less than 25 to 30 degrees, they are also used frequently with braces to measure curves over this threshold. No side-effects of exercise are known, except for muscle soreness that can be felt if the intensity of exercise is too great (Weiss 2006a).
Bracing is defined as the application of external supports to the trunk; these are usually rigid and are applied with the aim of achieving maximum correction of the pathological curve (Rigo 2006a). Treatment commences when the curve is diagnosed as progressive, or when it exceeds a threshold of 30 degrees Cobb angle (Negrini 2005; Lonstein 2006; Weiss 2006a). Braces generally need to be worn for a considerable period of time per day (at least 20 hours), the treatment extending over several years until the end of bone growth, which usually occurs at 16 years of age for girls and 18 years of age for boys (Katz 2001). This causes a significant negative impact on the lives of children and adolescents (Fallstrom 1986; Noonan 1997; Climent 1999). Other conservative management strategies can be found in the literature: shoe insoles, electrotherapy and chiropractic treatment have all been reported. However, to date, there is a dearth of evidence for the effectiveness of these forms of therapy.
With regard to surgical interventions, a large multitude and variety are described in the literature (Maruyama 2008). These include different surgical approaches (anterior, posterior or combined) and many types of metal implants. The sophistication of spinal implants has grown rapidly in the past 10 to 15 years. Modern surgical techniques follow principles of segmental spinal instrumentation (this means that each vertebra of the spine is attached to a metal rod, wires or screws), and both anterior and posterior implants (surgical rods, wires or screws) are now available. Segmental instrumentation (with hooks or screws) can control sagittal and frontal plane correction in both lumbar and thoracic curves. In contrast to Harrington instrumentation, introduced in the 1960s (Harrington 1962), segmental instrumentation allows early mobilisation of patients, thereby eliminating the need for postoperative casts and braces which were used in the past (Bradford 1987). This type of surgery also reduces the risk of potential neurological complications due to distraction forces (these are forces applied to a body part to separate bony fragments or joint surfaces) that were applied with the Harrington instrumentation (Harrington 1962).
Countless studies have been published in the literature comparing different approaches to the spine (anterior, posterior or combined) and using various types of implants. A single threaded rod inserted through an anterior approach (from the front of the spine) was initially developed by Zielke, but this technique had a reported incidence of rod breakage as high as 31% (Betz 1999). Further development of instrumentation resulted in the use of a double rod technique, such as Kaneda or Cotrel-Dubousset-Hopf, which prevented rod breakage but had the disadvantage of increasing the construct rigidity and favouring screw breakouts (Betz 2000). A further advantage was represented by a lower reoperation rate in double rod fixation (0%) reported by Muschik 2006 as compared with single rod fixation (10%; Betz 1999). The anterior approach is desirable because it can reliably correct curvature yet save the vertebral levels instrumented in lumbar or thoracolumbar curves (Arlet 2000; Kaneda 1996). However, if appropriate consideration is not given to planning and fusing the correct segments (i.e., to neutral and stable vertebrae), this can lead to curve progression and disc degeneration postoperatively (Bridwell 1994). Unfortunately, with the anterior approach to surgery, there is risk of potential trauma to the diaphragm and major abdominal organs. This type of surgery can also affect pulmonary function. If a patient has multiple curves, posterior fusion can achieve good correction and obviate the risks of anterior surgery (Bridwell 1999). The anterior approach also predisposes to a negative effect on pulmonary function for up to five years postoperatively (Kim 2005); therefore, some surgeons prefer a video-assisted thoracoscopy followed by posterior instrumentation, which allows them adequate spinal access but reduces the adverse effects on pulmonary function (Newton 2003).
Luhmann and Lenke (Luhman 2005) suggested that instrumentation through a posterior approach (approaching surgery from the back of the spine) was as efficient as a combined anterior and posterior approach, but the former (posterior approach) eliminated the negative effect on pulmonary function. In other words, approaching the surgical procedure from the back rather than from the front reduces the risks associated with deflating the lungs during the operative procedure (Di Silvestre 2008). A significant variety of implants and approaches to surgical treatment of the spine are available, but double rod posterior instrumentation seems to have become the preferred surgical intervention in cases where progression of scoliosis cannot be stopped by conservative treatment. All types of spinal fusion surgery are associated with significant risk both in the short term and in the long term. The short-term risk for spinal fusion surgery is estimated to be approximately 5%, while long-term risks over a lifetime are estimated to exceed 50% (Weiss 2008a), with reoperation rates ranging from 6% to 20% (Asher 2006). However, reoperation rates may be very high (up to 50%) with the use of more recent instrumentation such as Cotrel-Debusset instrumentation (Mueller 2012).
How the intervention might work
Scoliosis-specific exercises can be used in three main clinical scenarios: (1) the sole use of exercise as the primary treatment of AIS for mild curves, (2) in conjunction with braces for moderate curves and (3) during adulthood if the scoliosis curves exceed certain thresholds (Romano 2012). In the treatment of mild scoliosis, scoliosis-specific exercises can be used on curves greater than 10 to 15 degrees but less than 25 or 30 degrees Cobb. These intense three-dimensional spine- and rib cage－specific exercises are used to try to limit the progression of the curve and thereby avoid the use of a brace. This critical Cobb angle is generally regarded as the threshold for brace prescription (Lonstein 2006; Weiss 2006c). In mild scoliosis cases for which exercise is prescribed, exercise is used predominantly according to the recommendations made by the Study Group on Scoliosis and Orthopaedic and Rehabilitative Treatment (SOSORT Guidelines 2012). The key objectives of physical exercise in mild cases of AIS include stabilisation of the spine combined with three-dimensional auto correction of the pelvis, rib cage and shoulders in combination with isometric muscle contractions (Romano 2012; Weiss 2006c).
Whilst scoliosis-specific exercises use internal corrective forces (i.e. muscles), braces use external corrective forces to correct the trunk; this is usually achieved with the use of rigid supports. However, some braces (called soft braces) are made of material similar to elastic bands and comparable with materials used in physical therapy treatments (Coillard 2003; Rigo 2006a). The mechanical forces of the brace are used to straighten the spine and derotate the pelvis and shoulders to bring the whole body into normal alignment. Negrini 2010 states that the external and proprioceptive inputs due to bracing change the unnatural loading on the spine and rib cage, decrease asymmetrical movements and improve neuromuscular control; this facilitates proper spinal growth, neuromotor reorganization and changes in motor behaviours (Coillard 2002; Lupparelli 2002; Castro 2003; Odermatt 2003; Weiss 2004; Negrini 2006c; Stokes 2006; Grivas 2008; Smania 2008). Unfortunately, most braces have the disadvantage of being not very comfortable to wear, especially for long periods. Further, if bracing is NOT combined with scoliosis-specific exercises, weakening of the back muscles may occur.
With regard to surgical treatment of the scoliotic spine, the two main approaches discussed previously (anterior and posterior) aim to correct the spinal curvature (reduction of the Cobb angle) and fuse the spine with the help of bone grafts that allow the spine to heal to a solid and stable bone fusion mass (spinal fusion), supported by the instrumentation (Haher 2003). Posterior spinal fusion with instrumentation and bone grafting is performed through the patient's back while the patient lies on his or her stomach. During this type of surgery, the surgeon attaches a metal rod to each side of the patient's spine (this can vary depending on the type of instrumentation and procedure used) by using hooks or screws attached to the vertebral bodies (Cailliet 1975). The surgeon then fuses the spine with a bone graft (this is a piece of bone that is usually taken from the patient's hip). The bone grows in between the vertebrae and holds them together, causing the parts of the spine that are fused to become like a rod. The metal rods attached to the spine ensure that the backbone remains straight while spinal fusion takes place (Cailliet 1975). The operation usually takes several hours. With recent advances in technology, patients can be discharged from the hospital within a week and do not require postoperative bracing. Many patients are able to return to school or work within 2 to 4 weeks after the surgery and resume all preoperative activities within 4 to 6 months. With the anterior approach, surgery is conducted through the chest wall instead of through the patient's back. The patient lies on his or her side during surgery. The surgeon places the incision on the patient's side, deflates the lung and removes a rib to reach the spine.There is worldwide general agreement that patients with curves in excess of 45 to 50 degrees are candidates for surgery. The selection of both instrumentation and operative procedure is dependent on curve location, magnitude and flexibility, as well as on sagittal alignment (Akbarnia 1988).
Why it is important to do this review
A scoping literature search identified only two systematic reviews on this topic. However, full methodological appraisals of the quality of included studies within these reviews was very limited (Hawes 2006a; Weiss 2008b). A systematic review conducted with state of the art, high-quality Cochrane methodology is urgently needed.