Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 66 potx

Figure 7. Technique of posterior scoliosis correction The technique of posterior scoliosis correction is exemplified using the Universal Spine System. a, b Pedicle screws are inserted in the target vertebra and a rod is first inserted on the concave side of the curve and connected to the screws, c, d Insertion of the convex rod and levering it to the lower screws allows the concave apex screw to be narrowed to the rod achieving a good correction. A posterior fusion is added. shorter fusion lengths and better vertebral derotation compared to posterior procedures. The fusion usually incorporates all segments between upper and lower end vertebrae [10, 112, 128, 209, 218]. The spine is exposed by a thoracotomy, lumbo- tomy or a thoraco-lumbotomy depending on the anatomical location of the curve. The intervertebral discs are completely removed at the levels selected for fusion. Correction in the coronal, sagittal and axial planes is achieved by proper placement of the screws into the vertebral bodies and connection to a pre-bent The rod needs to be pre-bent, creating a lordosis single or double rod (Fig. 8, Case Introduction).Thediscspacecanbefilledwith bone (e.g., resected rib) to enhance interbody fusion. These approaches are obvi- ously technically more demanding than a posterior approach and are restricted to the mid thoracic to upper lumbar levels. The morbidity caused by a thoracot- omy is not negligible but can be kept very low in experienced hands. Recently, thoracoscopic procedures have been introduced which are even more demand- ing [134, 152, 177, 178, 181, 206, 232]. Newton et al. [152, 153] reported on compa- rable results after thoracoscopic correction of thoracic curves compared with open techniques. Similar findings were reported by Grewal et al. [75] even though they reported a higher intraoperative blood loss in the thoracoscopic group. During the first year, the thoracoscopic approach was found to cause fewer declines in the vital capacity compared to the open anterior approach. Idiopathic Scoliosis Chapter 23 643 82 Figure 8. Technique of anterior scoliosis correction The instrumentation is exemplified using the Universal Spine System. Prior to instrumentation the intervertebral discs are completely excised. a The insertion of the vertebral screws is anterior to the base of the pedicles. b, c Pedicle screws are inserted in the vertebral body and a pre-bent rod is connected to the screws in the upper and lower vertebrae. d A complex reduction forceps is used to narrow the remaining screws to the rod derotating the spine. e, f Disc spaces are compressed on the convex side after filling the disc spaces with bone. Full correction of the deformity is achieved. Combined Anterior and Posterior Approach Anterior fusion avoids the crankshaft phenomenon in immature patients Furthergrowthoftheanteriorspinalcolumnafterposteriorfusionbeforethe pubertal growth spurt may lead to a loss of correction. The so-called crankshaft phenomenon leads to an increasing angulation and rotation of the spine [55], i.e., the spine is crankshafting around the posterior fusion mass. Dubousset, who first described this phenomenon, concluded that young patients with a high remaining growth potential should be fused anteriorly and posteriorly to prevent 644 Section Spinal Deformities and Malformations crankshafting. Shufflebarger et al. [196] and Dohin et al. [51] provided evidence that this procedure was successful. Open tri-radiate cartilage and surgery before or during the peak growth velocity are strong positive predictors for the crank- shaft phenomenon whereas later surgery is a strong negative predictor [190]. Curve rigidity may require a combined surgery Another indication for using a combined anterior and posterior approach may be given by the rigidity of a curve. If the deformity is too rigid to prevent a satis- factory correction, an anterior release can be done prior to posterior fusion ( Case Study 1 ). By performing a thoracotomy or thoracoscopy, the intervertebral discs in the apex region are removed. In a second step the correction and fusion of the spine is done from posteriorly. While a few studies doubt the need for anterior release even in severe adolescent idiopathic scoliosis [4, 26, 88, 130, 207], Cheung et al. found it to effectively improve spinal flexibility [33]. Severe deformities of adult idiopathic scoliosis may also require anterior release and posterior fusion [1]. Fusion Levels Pedicle screw fixation allows forbettercurvecorrection and shorter fusion One of the most challenging issues in scoliosis surgery is to define the correct fusion levels. First, all structural curves must be determined [103, 113]. In a sec- ond step, the neutral (no rotation) vertebrae at the upper and lower end of the curve are determined for each curve. Thirdly, the central sacral vertical line is drawn. The stable lower end vertebra is then defined as the one being closest to the curve’s lower neutral end-vertebra and most nearly bisected by the central sacral vertical line. Usually a fusion to the stable end vertebra defined by the cen- tral sacral vertical line results in a good correction with a balanced spine. How- ever, the decision whether the fusion may exclude one segment or include one additional segment is also dependent on the individual curve and the surgeon’s experience. Bernstein and Hall reported on the selection of fusion levels for ante- rior fusion of lumbar and thoracolumbar curves [12]. They showed that by Lumbar levels should be preserved whenever possible including one vertebra above and below the apex vertebra, good results can be achieved if a slight overcorrection is performed. Only in severe curves (>60°) and if the apex was an intervertebral disc did they include two vertebrae above and below. Recently, it has been shown that the posterior segmental instrumenta- tion with pedicle screws allows for a shorter fusion than with Harrington rods [114] or hooks alone [101]. Halm et al. [82] showed that anterior instrumentation of lumbar curves allows one caudad segment to be spared compared to a segmental posterior pedicle instrumentation. However, Hee et al. [87] found comparable fusion lengths. Bitan et al. [13] and Min et al. [142] reported shorter fusion lengths by using the anterior approach compared with a posterior approach. Spinal Profile and Spinal Balance A slight hypokyphosis is common in right thoracic curves A thoracic kyphosis of 20°–40° and a lumbar lordosis of 40°–60° can be consid- ered normal [70, 146, 202]. In AIS a slight thoracic hypokyphosis is common. However, especially left convex idiopathic curves may be associated with thoracic hyperkyphosis as well. By using a modern instrumentation system through an isolated posterior approach, thoracic hypokyphosis can be corrected about 5°– 10° [20]. Even though anterior correction was reported to allow for a better cor- rection of hypokyphosis [89, 98], severe thoracic hypokyphosis or even thoracic lordosis may necessitate a combined anterior and posterior approach [18]. In thoracolumbar and lumbar curves usually a hypolordosis or even a slight kypho- sis is present in AIS patients. It has been reported that an anterior instrumenta- tion allows for a good segmental restoration of the lordosis [89, 99]. Despite the Idiopathic Scoliosis Chapter 23 645 ab c d ef g Case Study 1 A 16-year-old patient presented with a severe thoracic idiopathic scoliosis (a). Although a back asymmetry had been noted for 2 years, the patient did not consult a physician because she was pain free. At the time of presentation, standard radiographs ( b, c) showed a thoracic curve (T5–T12) of 75 degrees which corrected to 45 degrees on supine bending (d). Although the anteroposterior radiograph demonstrated Risser Type IV indicating only a minimal remaining growth potential, surgery was suggested because of the curve magnitude. In a first step, an anterior release was done to allow for a better curve correction, followed by a posterior instrumentation with pedicle screws and curve correction during the same intervention. Ten years after the operation, the patient was pain free and working full time as a mechanic ( e). The follow-up radiographs demonstrate a curve correction to 20 degrees and a balanced spine ( f, g). 646 Section Spinal Deformities and Malformations kyphogenic character of the anterior instrumentation, a good correction can be achieved even without structural intervertebral support [127]. Severe hypolor- dosis or kyphosis in middle-aged adults with degenerative changes often requires combined anterior and posterior surgery and longer fusion length to restore sagittal profile and spinal balance [1, 18]. A complication of the early scoliosis correction with Harrington distraction rods was a proneness to result in a so-called iatrogenic flat back syndrome, i.e., a loss of the normal sagittal profile (decreased lumbar lordosis and thoracic kyphosis). In cases in which the whole lumbosacral spine is flattened, patients have problems standing upright and need to bend their knees to rebalance the spine because the trunk is inclined anteriorly. This problem is infrequent today because the modern instrumentation systems also allow sagittal balance and profile to be addressed [226]. A special issue of concern after scoliosis surgery is the development of iatro- genic coronal imbalance. This problem occurs when correcting the major curve beyond the compensatory potential of the minor curves. The rigidity of the minor curves has to be taken into account prior to fully correcting the major curve. Thoracoplasty The rib hump in thoracic scoliosis results from vertebral rotation and concomi- tantdeformationoftheribcage.Therefore,theribhumpcanonlypartiallybe corrected by vertebral derotation. In cases in which this deformity should be addressed for cosmetic reasons, a thoracoplasty can be done by a removal of parts of the most prominent ribs [69, 203]. It is generally accepted that thoraco- plasty in addition to scoliosis correction should be considered when the rib hump measures more than 15° [143]. Disadvantages to be considered are a possi- ble temporary decrease of pulmonary function and the potential risk for compli- cations such as pneumothorax and intercostal pain [115]. Impaired vascular sup- ply to the spinal cord by coagulation of the segmental vessels can occur when per- forming an internal (transthoracic) thoracoplasty [197]. Surgical Decision-Making A detailed description of treatment guidelines and surgical procedures is far beyond the scope of this chapter. However, we want to provide here a short over- view of surgical decision-making ( Table 3). Infantile and Juvenile Idiopathic Scoliosis In cases of severe scoliosis in young children, the application of serial orthotic castsorbracesmaynotbesufficienttostopcurveprogression.Ontheother hand, fusion in a young child should be avoided to prevent growth arrest or crankshafting resulting in a short trunk with consecutive disproportionate body habitus or impaired lung function. Therefore, fusion should be postponed as long as possible and spinal instrumentation without fusion is performed if con- Expandable spinal instru- mentation is indicated when spinal growth should be preserved servative therapy fails to control the curve. The main objective of using expand- able spinal instrumentation is to stop progression of the curve, maintain spinal balance and allow spinal growth. Definitive fusion surgery is delayed as long as possible. In 1984, Moe et al. [145] described a technique using a Harrington dis- traction rod which was continuously lengthened with growth or, if necessary, replaced by a longer one. Even though progression may be stopped in most patients by this procedure, there is the drawback of repeated interventions and Idiopathic Scoliosis Chapter 23 647 Table 3. Surgical indications and techniques Age of onset Infant (0 –2 yrs) Juvenile (3– 9 yrs) Adolescent (10– 17 yrs) Adult (>17 yrs) General considerations large age span affords variable indications arrest of curve progression, defor- mity correction and solid spinal fusion is the main objective indication guided by the predominant symptoms loss of spinal height, chest wall growth and lung growth in case of fusion are a major concern Age >6 yrs if possible (maturation of the lungs) [208] crankshaft phenomenon must be avoided higher risk of surgery related morbidity >40 yrs [17, 46, 210] Cobb angle progressive curves >45–60° despite former orthotic treatment [50, 116] progressive curves > 40° in skele- tally immature patients progressive and/or symptomatic curves curves >45–50° even in skeletally mature patients [5, 179, 222] Techniques Growing rod young children – – Anterior and posterior fusion older children (8– 10 yrs) at risk of crankshaft phenomenon [51, 190, 196] skeletally immature patients at risk of crankshaft phenomenon [51, 190, 196] severe cases with spi- nal imbalance or flat back syndrome [1, 46] Anterior release and posterior fusion –– indicated in patients with severe rigid deformity [4, 26, 33, 88, 130, 207] – Anterior or posterior fusion –– depending on the curve type usually only posterior or combined fusion complications such as rod fracture or hook displacement [144]. More recent methods with single or dual growing rod techniques are used [14, 144]. Dual rods were reported to be stronger than single rods and provide a better correction and maintenance of correction as well as fewer complications [3, 214]. Despite the improvements obtained by these newer methods, complications and reintervent- ions remain unavoidable. A special instrumentation system, the so-called vertical expandable pros- thetic titanium rib (VEPTR), allows for an indirect correction of the scoliosis by lengthening of the deformed thorax on the concave side of the curve [28, 29]. Pre- liminary data indicate that this technique is particularly effective in the treat- ment of congenital scoliosis with rib cage deformities [213]. It remains unclear whether this technique is also effective for juvenile scoliosis. Adolescent Idiopathic Scoliosis The main objectives are arrest of curve progression and fusion The main objective of surgical treatment is correction of the deformity and maintaining the correction by spinal fusion. When surgically addressing AIS, one would therefore want to improve the coronal deformity (Cobb angle), try to reduce the most visible deformity, i.e., rib hump, restore a normal sagittal profile andachieveorpreservesagittalandcoronalspinalbalance. Thoracic Curves A single thoracic curve may be treated by anterior or posterior fusion, the latter being the classic approach. The posterior approach usually includes fusion of the entire curve. Using pedicle screws instead of hooks offers a better curve correc- 648 Section Spinal Deformities and Malformations abcd Figure 9. Anterior thoracic scoliosis correction a, b Preoperative radiographs showing a decompensated King type III curve (same patient as Fig. 2c). c, d Postoperative radiographs showing excellent curve correction and restoration of the coronal balance. Pedicle screws allow for a better scoliosis correction tion and enables a slightly shorter fusion length than with the use of hooks [101]. The use of pedicle screws allows for a better rotational and coronal correction [109]. In the hands of an experienced surgeon, neurological problems were not found to be higher with the use of pedicle screws [101]. The advantage of an ante- rior correction is the shorter fusion length and better derotation ( Fig. 9). The anterior approach has a cosmetic advantage if the operation is performed by means of a mini-thoracotomy or thoracoscopy leaving only small scars. Although spontaneous lumbar curve correction occurs after both selective pos- terior and anterior thoracic fusion, the correction was found to be better in the In double thoracic curves attention must be paid to shoulder balance, curve size and rigidity latter approach [111]. When planning surgery for double-thoracic curves,preop- erative shoulder balance (T1-tilt) and size (Cobb angle) and rigidity of the proxi- mal thoracic curve must be considered to achieve a good outcome [108]. If the shoulder is elevated on the convex side of the major thoracic curve (i.e., on the right side) and the proximal thoracic curve corrects to less than 25° in the side bending view, spontaneous correction of the proximal thoracic curve with level shoulders can be expected after isolated selective anterior fusion of the major curve [108]. If both thoracic curves need fusion, the operation must be done from posteriorly. Thoracolumbar and Lumbar Curves Thoracolumbar curves are best treated from anteriorly An isolated fusion of these curve types without addressing the thoracic curve (if present) is possible if the thoracic curve reduces to less than 25° in the bending radiograph [142]. These curves benefit most from a short anterior scoliosis cor- rection ( Case Introduction), preserving more mobile motion segments com- Idiopathic Scoliosis Chapter 23 649 pared to posterior fusion [60, 142]. If the thoracic curve remains larger than 25° in the bending radiograph, it should probably be addressed surgically in order to avoid decompensation of spine and shoulder balance. Double Major Curves These curve patterns with a thoracic and a thoracolumbar or lumbar structural curve are usually operated on from posteriorly indicating that a big part of the spine has to be fused. Attempts to fuse the lumbar curve anteriorly and only the thoracic curve posteriorly have recently been suggested. It was reported that an anterior release with instrumented fusion of the lumbar curve was superior to an anterior release followed by posterior instrumented fusion [236]. Only prelimi- nary data is available on the short selective anterior fusion of both the thoracic Motion segment preser- vation is an important goal and the lumbar curve with the potential advantage of preserving motion seg- ments in double major curves [141]. Adult Idiopathic Scoliosis The general state of health, age and bone quality play important roles in the sur- gical decision-making. Morbidity for surgery is lower in younger patients (<40 years) and the chance of a better outcome will also be higher than in older Surgical treatment is strongly influenced by the pain sources patients (>40 years) [17, 46, 210]. Surgical decision-making in adult idiopathic scoliosis strongly depends on the underlying causes of pain, which have to be explored thoroughly. With predominant irradiating pain or claudication without relevant back pain, selective spinal decompression may be performed as a stand- alone procedure [1]. In younger patients a partial correction of the deformity may already lead to a sufficient decompression without a formal decompression being performed ( Case Study 2). If additional segmental instability, extensive degenerative changes and progressive deformity lead to back pain, posterior and/or anterior fusion and stabilization with/without decompression and cor- rection may be required [194]. To achieve a ba lanced spine and prevent a postop- erative collapse of the adjacent segment, the fusion usually has to extend beyond the major curve. Stopping the fusion of a lumbar curve below the thoracolumbar junction usually bears a high risk of sagittal decompensation of the spine crani- ally [83]. It is still controversial whether or not the lumbosacral junction should be included in the fusion [17, 19, 45, 90]. If unfused, the L5/S1 segment has to take all the movements and loads of the fused lumbar spine [107, 194]. Furthermore, a fusion to the sacrum leads to higher stress for the sacroiliac and hip joints. On the other hand, it is difficult to achieve a solid fusion at this level. Non- union rates of up to 30% are reported if the fusion is not done circumferentially [19, 59]. The goal is to achieve a balanced spine without pain and normal neurology It has to be borne in mind that the spine may be in a fragile balance before sur- gery and that a decompression and/or a partial fusion may lead to a deterioration of this balance leading to progressive deformity and disability. If spinal balance is preserved, fusion in situ will often be the method of choice as an adjunct to decompression [1]. If there is a derangement either in the coronal and/or sagittal plane (e.g., flat back syndrome), additional correction of the deformity is neces- sary [1]. An imbalanced spine with secondary degenerative changes requires extensive release of the posterior structures and in some cases multiple spinal osteotomies (see Chapter 26 ). Frequently, a combined anterior and posterior approach may be necessary [46]. 650 Section Spinal Deformities and Malformations ab cd ef Case Study 2 A 25-year-old female with a known but untreated scoliosis for many years presented because of incapacitating lum- bar back and leg pain with inability to continue with full time work. Standard radiographs demonstrated a major thoracolumbar curve of 56 degrees and a minor thoracic curve of 42 degrees ( a, b). Both curves corrected to 45 degrees on supine bending. Indication for surgery was prompted by the painful adult scoliosis ( c, d). A combined anterior/posterior approach was done during the same surgery consisting of an anterior release at T11–L3 and posterior pedicle screw instrumentation at T4–L4 with scoliosis correction. At 5 years follow-up the patient was very satisfied with the result. The radiographs revealed a bal- anced spine with excellent curve correction ( e, f). Complications The most deleterious complication of scoliosis surgery is a neurological compro- mise particularly in AIS ( Table 4). Complications of scoliosis surgery are dis- cussed in more detail in Chapter 39 . Neurological injury can result from either direct contusion or an ischemic insult. Generally, resolution of the deficits is more likely to occur after contusion. In experienced hands, spinal cord injury is rare Table 4. Complications in scoliosis surgery Complication Incidence References spinal cord injury 0.5– 3% [54, 126] nerve root injury 0.5% [126] early wound infection 0.1– 5 % [72, 140, 212, 217] delayed wound infection 0.6– 1.7% [7, 35, 229] non-union 0– 2.2% [7, 200, 223] Idiopathic Scoliosis Chapter 23 651 Ischemia of the spinal cord can result from stretching of the blood vessels feeding the spinal cord or by prolonged hypotension. Therefore, a reduction of the cor- rection and restoration of a sufficient perfusion should be achieved if neurologi- cal injury is noticed intraoperatively. Ligation of anterior segmental arteries has also been suggested to increase the likelihood of ischemia of the cord [21]. Early wound infections occur within 12 weeks of the initial intervention. Mal- nourished and immunocompromised patients are at substantially higher risk for infections [104]. To minimize intraoperative infection, antibiotic prophylaxes are routinely used. If an early wound infection is diagnosed, wound revision and antibiotic treatment after isolation of the germ is indicated. The wound is thor- oughly debrided and loose bone graft is removed. Titanium implants can be left in place to avoid loss of correction and non-union [212]. Delayed wound infections are caused by low-virulent germs Delayed wound infections occur 20 weeks or longer after the initial interven- tion. Usually patients become symptomatic only after 2–3 years [35]. If the diag- nosis is confirmed, surgical intervention is indicated removing all implants. If the fusion is solid, usually no further measures are necessary besides implant removal. Non-union may be associated with hardware loosening, dislodgement or breakage requiring revision surgery. Recapitulation Epidemiology. Idiopathic scoliosis is the most com- mon structural spinal deformity in the child and ad- olescent. The overall prevalence of adolescent idio- pathic scoliosis is about 2–3% in the adolescent population. The prevalence decreases to about 0.1–0.3% for curves larger than 30°. Adolescent idi- opathic scoliosis is the most frequent type (80%). Only about 1% of idiopathic scoliosis affects chil- dren younger than 3 years. Considering AIS requir- ing therapy, girls are three times more often affect- ed than boys. Pathogenesis. Thereissomeevidencethatan asymmetrical vertebral growth of the anterior col- umn with tethering of the posterior structures leads to the deformity. Genetic aspects, platelet de- fects, cell membrane defects, abnormalities of cal- modulin and melatonin levels have been suspected to play a role in scoliosis development. Classification. According to the age of onset,the disease is divided into infantile (0–3 years), juvenile (3–10 years), adolescent (10–18 years) and adult (>18 years) idiopathic scoliosis. King has proposed a classification of the thoracic curve into five types. The Lenke classification includes not only thoracic but also thoracolumbar and lumbar curve types as well as the sagittal profile. The curve types are help- ful when selecting fusion levels. Clinical presentation. Most often scoliosis is discov- ered accidentally. Pain or functional disability is rare in adolescent scoliosis. If present, pain should raise suspicion about a secondary etiology (i.e., non-idio- pathic), prompting further diagnostic investigations into the etiology. Family and developmental medi- cal history must be assessed with emphasis on growth spurt and menarche. Small asymmetries such as an S-shaped line of the spinal processes, a slightly more prominent scapula or asymmetric lumbar triangles may indicate the presence of scoli- osis and the location on physical examination. The most reliable clinical sign for scoliosis is the pres- ence of a rib hump on the convex side of the curve best seen in forward bending. Convexity and flexi- bility of all curves must be assessed. Diagnostic work-up. Standard radiography of the entire spine with the patient in standing position is still the hallmark of the imaging studies. The radio- logical assessment considers curve size and location, spinal balance in the coronal and sagittal plane, pel- vic and shoulder level, as well as the sagittal profile (i.e., hypo-/hyper-kyphosis/lordosis). Supine bend- ing radiographs are necessary to determine curve ri- gidity and are necessary for surgical planning. Atypi- cal curve pattern (left thoracic curve) and neurologi- cal deficits such as absent abdominal wall reflexes may indicate intramedullary pathologies and re- quire further investigation with MRI. 652 Section Spinal Deformities and Malformations . degenerative changes often requires combined anterior and posterior surgery and longer fusion length to restore sagittal profile and spinal balance [1, 18]. A complication of the early scoliosis. control the curve. The main objective of using expand- able spinal instrumentation is to stop progression of the curve, maintain spinal balance and allow spinal growth. Definitive fusion surgery. main objectives are arrest of curve progression and fusion The main objective of surgical treatment is correction of the deformity and maintaining the correction by spinal fusion. When surgically