Scheuermann Kyphosis

Although the etiology of Scheuermann kyphosis is not fully understood, the histologic and pathologic findings are well described. Radiographically, the presence of three adjacent wedged vertebral bodies of at least 5° each is pathognomonic for Scheuermann kyphosis. Anatomic findings include a thickened anterior longitudinal ligament (ALL) with narrowed intervertebral disks. The vertebral bodies are wedged, and traumatic disk herniations through the endplates are consistent findings.

The ratio of collagen to proteoglycans in the matrix of the endplate in patients with Scheuermann kyphosis has been described as low in comparison with that in patients without the condition. This relative decrease in collagen has been hypothesized to lead to an alteration in the ossification of the endplate and, thus, to altered vertebral body growth.

Finally, osteoporosis has been postulated to have a role in the pathology and etiology of Scheuermann kyphosis. Bradford reported on 12 patients with Scheuermann kyphosis who were prospectively studied with an extensive osteoporosis workup, including an iliac crest biopsy.[5] Some of the patients with Scheuermann kyphosis were demonstrated to have a mild form of osteoporosis, although the cause and effect of this finding in terms of developing Scheuermann kyphosis was not made.

A follow-up study by Gilsanz reported 20 adolescent patients aged 12-18 years with Scheuermann kyphosis who demonstrated no evidence of osteoporosis as measured by quantitative computed tomography (CT).[6]

Bradford, however, had surmised that the osteoporosis was transient and somehow led to altered vertebral growth and, thus, to the formation of Scheuermann kyphosis.[5] This etiologic hypothesis remains a subject of debate.

The proximate cause of Scheuermann kyphosis remains to be determined. Scheuermann initially hypothesized that avascular necrosis of the ring apophysis led to premature cessation of growth anteriorly and subsequent wedging of the vertebral body. Schmorl later postulated that traumatic herniations of disk material through the vertebral endplates led to subsequent loss of disk height and anterior vertebral wedging. Both of these theories were disproved later.

Halal reported on five families in which Scheuermann kyphosis appeared to transfer in an autosomal-dominant mode of inheritance.[7] To date, the genetic marker has not been determined.

Skogland[8] and Ascani[9] proposed other theories that Scheuermann kyphosis is based on a genetic inheritance.[8] Skogland reported on 62 females aged 9-18 years, whose mean height was an average of 2.5 standard deviations (SDs) above average. Of these 62 females, 18 had thoracic kyphosis of more than 40°, with 11 additional participants having vertebral anomalies consistent with Scheuermann kyphosis.

Ascani also presented work demonstrating a similar correlation between Scheuermann kyphosis and height. He also demonstrated increased levels of growth hormone.[9]

Damborg et al found a heritability of 0.74 in Scheuermann's disease, with a lower threshold in men than women.[10]

A study by Hershkovich et al suggested that height and body mass index (BMI) are associated with the risk and severity of spinal deformities in adolescents.[11] The study, which included 103,249 males and females aged 17 years who had been diagnosed with some degree of kyphosis or scoliosis, found that in underweight males and females, spinal deformities were significantly more common and were more likely to be severe. Greater height was also associated with increased risk and greater severity of spinal deformities in males and females.

Mechanical factors have been postulated as a cause for Scheuermann kyphosis.[12] Scheuermann initially noted a higher incidence of kyphosis in industrial workers and found that hyperextension bracing is helpful in curbing the progression of Scheuermann kyphosis, which would support a mechanical etiology. However, the radiographic and histologic changes of Scheuermann kyphosis have not yet been demonstrated to be in fact secondary or primary in the development of Scheuermann kyphosis.

The prevalence of Scheuermann kyphosis is estimated to be 4-8% of the general population. Sorensen reported a prevalence of 0.4-8.3%.[1] Scoles et al reported on 1384 cadaveric specimens and noted a 7.4% prevalence of Scheuermann kyphosis.[13]

Although the prevalence of Scheuermann kyphosis is generally accepted as being essentially equal in males and females, there has been some debate regarding this finding in the literature. Bradford et al reported a female-to-male ratio of 2:1 for Scheuermann kyphosis.[14, 15] Meanwhile, Murray et al reported the exact opposite finding, with a 2.1:1 male-to-female ratio.[16] In Sorenson's work, 58% of the patients were male, and 42% were female.[1]

Outcome and prognosis depend on the individual patient and treatment rendered. Generally, a patient with moderate-to-mild Scheuermann kyphosis rarely requires surgery or even bracing. These patients can be managed with education, guidance, and overall encouragement to resume and maintain normal activity levels. Aggressive use of exercise and judicious use of anti-inflammatory medications can augment this regimen.

The outcome and prognosis of bracing treatment is more controversial. While the brace is in place, approximately a 50% correction of the deformity should be expected. However, once the brace is removed, a gradual loss of correction is expected over time.

Sachs et al reported on 120 patients reviewed 5 years after discontinuance of bracing[17] ; 69% of these patients had maintained at least 3° of improvement over their presenting radiographs. Other authors have presented similar results. Sachs also reported that the prognosis was less favorable if the presenting curve was 74° or more. One third of these patients failed bracing therapy and progressed to needing surgery.

The current literature largely lacks patient-based outcome studies in patients who have undergone surgical correction of Scheuermann kyphosis, though a number of retrospective reviews have reported high patient satisfaction ratings, as have some studies with insufficient numbers of control subjects. Surgical correction of the deformity affords predictable restoration of normal thoracic kyphosis, thus halting progressive deformities. Reasonable pain relief and resumption of normal activities also are reflected in multiple retrospective reviews.

Graat et al carried out a cohort study that assessed long-term (mean follow-up, 18 years) clinical and radiologic outcomes in 29 patients who underwent surgical treatment of Scheuermann kyphosis via either a posterior approach (n = 13) or a combined anterior-posterior approach (n = 16).[18]  They obtained disappointing radiologic results, but these did not correlate with clinical outcome scores, which were good. Outcomes were better with the combined approach than with the posterior approach.

Scheuermann kyphosis (Scheuermann disease) may be entirely asymptomatic. However, patients with Scheuermann kyphosis who present for medical attention generally have problems that fall under one of the following five categories:

• Pain
• Progressive deformity
• Neurologic compromise
• Cardiopulmonary complaints
• Cosmetic issues

When present, pain should be highly concordant with the location of the spinal deformity in Scheuermann kyphosis. Pain may be present in either adolescence or adulthood, though it is a more typical presenting complaint in adults. Characteristically, the pain is located just distal to the apex of the deformity and then radiates laterally in a paraspinal pattern. The pain also is activity related and often abates with rest.

Address atypical pain, particularly in adolescents, with further diagnostic studies. Adults with pain often have low back pain, secondary to hyperlordosis below the Scheuermann kyphosis and subsequent degenerative disk disease and facet arthropathy, or the pain may be due to associated spondylolisthesis. Note that pain is the presenting complaint in 20-60% of patients with Scheuermann kyphosis.

Progressive deformity in the absence of radiographic conformation is difficult to document, though the history of the deformity should be queried. Patients and, particularly, family members often note a deformity that worsens over time. Clothes fit differently, shoulders appear more rounded, and it may appear that the length of the arms is increasing out of proportion to the rest of the body. Radiographic confirmation of progressive deformities is ideal.

If progression of the curve is documented, particularly in an adolescent, consider more aggressive treatment options.

Neurologic risk related to Scheuermann kyphosis is quite rare, but when it is present, it typically mandates a surgical approach. A short-segment severe deformity generally is considered to be a curve that is at highest risk secondary to the cord being draped over the deformity with anterior compression.

Lonstein et al demonstrated an average kyphosis of 95° in patients who presented with neurologic compromise.[19]  However, Ryan and Taylor presented three patients with Scheuermann kyphosis and neurologic compromise with an average kyphosis of only 54°.[20]

Spinal stenosis of the lumbar spine below the deformity may lead to neurogenic claudication in the adult patient, and although it is not directly attributable to Scheuermann kyphosis, it may complicate the clinical picture.

Congenital thoracic stenosis has been reported in association with Scheuermann kyphosis and may lead to myelopathy or intraoperative complications during correction of the deformity.

Cardiopulmonary compromise as a presenting complaint for patients with Scheuermann kyphosis is quite rare. Restrictive lung disease was documented by Murray et al,[16]  though this was in curves of more than 100°, with the apex of the curve located in the upper thoracic region. Sorensen reported earlier that chest-wall abnormalities in patients with Scheuermann kyphosis had no negative effect on cardiopulmonary function.[1]

Finally, cosmetic issues should not be underestimated in the evaluation of a patient with Scheuermann kyphosis. Address these concerns specifically and aggressively with the individual patient, because they ultimately prove to be the driving force behind the patient's decision process. When cosmesis is the isolated indication for treatment, particularly for surgical care, exercise caution.

After the history has been well documented, a physical examination completes the initial clinical evaluation. Scheuermann kyphosis must be differentiated from postural kyphosis. On physical examination, this difference is made on hyperextension. Patients with Scheuermann kyphosis, even adolescents, demonstrate a structural deformity that only partially corrects on hyperextension. Patients with postural kyphosis, by contrast, have flexible deformities.

Forward flexion delineates the deformity quite well, with shorter angulated curves presenting as an A-frame deformity. Overall, sagittal alignment usually is maintained, secondary to compensatory hyperlordosis of both the cervical and lumbar spine. Perform a lower-extremity neurologic evaluation, paying particular attention to any signs of upper motor neuron compromise. Findings typically are normal.[21]

At present, no genetic markers or laboratory studies exist to assist the physician in confirming the diagnosis of Scheuermann kyphosis (Scheuermann disease). If treatment is rendered, the appropriate laboratory studies should be ordered. For example, if anti-inflammatory medications are started, the appropriate monitoring laboratory studies should be followed. In addition, if surgical care is undertaken, routine preoperative laboratory studies are indicated.

A standard radiographic evaluation of a patient with Scheuermann kyphosis includes anteroposterior (AP) and lateral standing radiographs on long films, which would incorporate the entire thoracolumbar spine on one film. The patient should be standing in a neutral position with hips and knees fully extended to permit an accurate evaluation of sagittal balance.

The diagnosis of Scheuermann kyphosis is confirmed on the lateral radiographs. (See the image below.) The angle between the endplates of each respective vertebral body should be measured with the Cobb technique. Three adjacent vertebral bodies with 5° of anterior wedging confirm the diagnosis of Scheuermann kyphosis.

The Cobb technique should be used to measure the overall degree of kyphosis of the thoracic spine. It is important to pick the appropriate vertebral bodies to measure the thoracic kyphosis. The end vertebral bodies, which are defined as the last vertebral body tilting into the kyphotic deformity, should be selected both proximally and distally. The levels of these particular vertebral bodies should be noted; they are the same vertebral bodies that should be selected on subsequent films to ensure that the examiner is consistent in the evaluation.

Secondary changes of Scheuermann kyphosis should be noted, such as the presence of Schmorl nodes, irregular vertebral endplates, and disk space narrowing.

Scoliosis and spondylolisthesis have been associated with Scheuermann kyphosis. These should be documented on plain radiographs and treated as separate entities.

Other entities that share the differential diagnosis of Scheuermann kyphosis can be excluded radiographically as well. Congenital kyphosis, ankylosing spondylitis, multiple compression fractures, tumor, infection, tuberculosis, and postlaminectomy kyphosis can be distinguished by clinical history and confirmed by radiographic evaluation.

The dynamic quality of the kyphosis should be assessed to distinguish Scheuermann kyphosis from postural kyphosis. A lateral radiograph can be obtained in hyperextension. Should the deformity correct entirely, postural kyphosis is the most likely diagnosis, rather than Scheuermann kyphosis.

It is necessary to account for the rigidity of the curve in treatment decisions; this can affect the ability to achieve correction with bracing and surgical intervention.

Magnetic resonance imaging (MRI), computed tomography (CT), and CT myelography can be helpful adjunctive studies in planning the care of a patient with Scheuermann kyphosis. In particular, MRI helps the surgeon further define the local anatomy; it may also prove useful for flexibility assessment, thereby potentially reducing the patient's exposure to radiation.[25]  Special attention should be paid to the coexistence of thoracic spinal stenosis, syrinx, or any other intrathecal abnormalities that would affect surgical care.

Additionally, an anatomic assessment of the lumbar disks can be made and may impact surgical decision-making in terms of which levels to incorporate in the fusion.

Indications for treatment in patients with Scheuermann kyphosis (Scheuermann disease) typically mirror the presenting complaints—namely, pain, progressive deformity, neurologic compromise, cardiopulmonary issues, or cosmesis. Tailor the recommended treatment to the individual, and base treatment not only on the severity of symptoms but also on the correlation between symptoms and the deformity.

Additionally, in making decisions regarding treatment options, the physician must understand the natural history of Scheuermann kyphosis. Generally, the degree of clinical problems mirrors the magnitude of the deformity. Therefore, expect patients with mild deformities to have mild clinical symptoms.

Murray et al reported the natural history and long-term follow-up of patients with Scheuermann kyphosis,[16]  monitoring 67 patients with a mean kyphotic angle of 71° for an average of 32 years. Patients with Scheuermann kyphosis had more intense back pain (typically localized to the thoracic spine) and overall had less demanding jobs and less mobility in the thoracic spine. However, in both these patients and the age-matched controls, levels of education, absenteeism from work, physical activity, medication use, and social interactions were found to be similar.

Other authors have presented a higher prevalence of problems in patients with Scheuermann kyphosis. Bradford reported a 50% incidence of severe thoracic back pain in his patients with thoracic deformities and a higher incidence of back pain in patients with thoracolumbar deformities.[14]  Lowe et al reported a high correlation between low back pain and severe thoracic deformity.[26]

Despite varying opinions on the natural history of Scheuermann kyphosis, there does appear to be a subset of adult patients who develop refractory pain. Knowing that a subset of adolescents who have progressive curves eventually develop painful deformities in adulthood affects treatment decisions earlier in life. The additional psychosocial effect of the deformity also must be considered. Neurologic and cardiopulmonary risks are exceedingly low; when encountered, they must be addressed on an individual basis.

Contraindications for treatment in patients with Scheuermann kyphosis are relative. With any treatment option, benefits must be weighed against risks for each individual patient. The magnitude of surgical intervention must be considered in the light of the perceived benefit and risk. Surgical care of patients with severe thoracic deformities is a large undertaking, and medical comorbidities must be considered.

Neurologic compromise as a result of surgical intervention is the most catastrophic complication compatible with life that exists in treatment of patients with Scheuermann kyphosis. The incidence of neurologic compromise increases in revision spinal surgery, particularly with revision anterior approaches. Previous history of pulmonary compromise is a relative contraindication for an anterior approach. This should include previous history of empyema, which may complicate the surgical approach.

Although no absolute contraindications exist for surgical treatment of patients with Scheuermann kyphosis, the magnitude of the clinical problem and the pervasiveness of the symptoms in the patient's life must be matched by the radiographic deformity and the surgeon's personal expertise.

Some degree of controversy remains with respect to bracing care and the surgical decision-making process. Proponents of bracing state that bracing postpones indefinitely the need for surgical intervention. Opponents believe that bracing does not affect the ultimate prognosis of the curve and that, if these patients are monitored long enough, the curve continues to settle and resumes its prebracing course of progression.

Surgical care of these patients is also somewhat controversial. Murray et al[16]  reported on 76 patients with a mean kyphosis angle of 71°, treated nonoperatively and monitored for an average of 32 years. In comparison with age-matched controls, no significant differences were noted in level of education, number of days absent from work because of low back pain, extent of pain interfering with activities of daily living, presence of lower-extremity numbness, self-consciousness, self-esteem, social limitations, use of medications for back pain, or level of recreational activities. However, these patients did report more intense back pain.

Patients in this study also tended to have jobs with lower requirements for physical activity.[16]  They had less range of motion (ROM) and reported a different localization of their pain. This study was criticized because of its lack of a surgical patient population as a control. Additionally, the average of 71° generally was deemed low in comparison with surgical groups.

The future of the care for patients with Scheuermann kyphosis will mirror the evolution of the generalized care of patients with spine abnormalities. Dynamic instrumentation systems are being used, and improving surgical techniques with biologic manipulation are almost certain to become mainstream treatment options.

Confirming the diagnosis of Scheuermann kyphosis does not mandate any specific treatment plan.[27] Treatment should be tailored to the individual patient on the basis of symptom severity, patient age, and the nature of the curve. The diagnosis should be confirmed and the history of the problem discussed with the patient. Observation may be the most reasonable treatment plan with no change in activity levels and simple radiographic follow-up. If the curve is progressive or symptomatic, additional treatment options are available.[28, 29]

Anti-inflammatory medications

Anti-inflammatory medications can provide reasonable short-term pain relief in the adolescent and may be considered for long-term use in the adult with symptomatic Scheuermann kyphosis. Obtain serial laboratory tests to monitor renal and liver function.

Physical therapy

Physical therapy should not be used with the thought of altering the natural history of a progressive kyphosis. However, a thoracic extension program and generalized conditioning program can be useful as an aid in reducing symptoms. The program should be catered to the patient's clinical problem. Adults with Scheuermann kyphosis often develop lumbar spondylosis and mechanical low back pain below the deformity. A spinal stabilization program, perhaps even with a flexion component, may prove useful in this patient population.

Bracing

Adolescents with progressive Scheuermann kyphosis early in their growth spurts and whose curves reach a threshold of at least 45° are ideal candidates for bracing. The brace must be high enough to affect forces proximal to the deformity. This typically necessitates a Milwaukee style brace with a neck ring, pelvic girdle, and connecting rods with a pad overlying the posterior apex of the kyphosis.[30, 17]

Employ great vigilance in both brace fitting and subsequent follow-up. Obtain lateral radiographs at the time of initial bracing to confirm the adequacy of bracing correction. Continue follow-up at 3- to 6-month intervals to ensure that the brace is still producing a positive effect. As the patient continues to grow, the braces likely will have to be replaced.

Bracing is continued until skeletal maturity is reached, at which point a weaning process is begun. Lateral radiographs are obtained both during and after the weaning process to monitor the potential loss of correction.

Partial correction in patients who are skeletally mature and who underwent bracing therapy has been documented. Generally, bracing for adults with Scheuermann kyphosis is not recommended. Bracing in this patient population typically is poorly tolerated with poor patient compliance, secondary to brace discomfort, lack of objective improvement, and lack of a specific endpoint.

In patients with severe refractory pain and deformity, bracing may be used to control discomfort in patients who are not surgical candidates and who otherwise are refractory to medical management.

Once a patient with Scheuermann kyphosis, either adult or adolescent, reaches a surgical threshold, the goals for surgery are essentially the same:

• To obtain a solid arthrodesis throughout the length of the kyphosis with appropriate correction of the deformity
• To alleviate pain
• To improve spinal alignment

There are three main surgical options:

• Posterior-alone approach
• Anterior-alone approach
• Combined approach using both anterior and posterior techniques

Single approaches, either solely anterior or solely posterior, typically have been reserved for deformities that exhibit partial ability for correction on a hyperextension film, with the deformity being reduced to less than 50°. Combined approaches typically have been mandated for more substantial deformities,[31] such as curves of 75° or more that do not correct to less than 50° on hyperextension lateral radiographs.

The anterior-alone approach is the least commonly used approach for the correction of Scheuermann kyphosis. It initially was described by Kostuik[32] and uses an interbody fusion technique with a Harrington distraction system. Kostuik reported on 36 patients with a mean preoperative deformity of 75.5° and demonstrated surgical correction maintained at follow-up with a deformity averaging 60°.

The posterior-alone and combined anterior-posterior approaches are described more widely in the literature. The posterior-alone approach has the advantage of offering a single approach, which reduces total blood loss and avoids the risk of a thoracotomy. However, in the absence of an anterior release, the degree of correction obtainable with this technique is less than that obtainable with a combined approach. Additionally, the pseudoarthrosis rate would be predictably higher with a posterior-alone approach than with a combined approach.

A combined approach is necessary for severe deformity correction. This also offers a higher rate of fusion than does a single-side approach. The combined approaches typically are performed under the same anesthetic, depending on surgeon's preference. The anterior release is performed first through a thoracotomy, either open or thoracoscopically assisted, and this is followed by the posterior instrumented approach, which effects the correction of the deformity.

A retrospective review of 1070 patients (32.2% female, 67.8% male) in the KID Inpatient Database found that between 2003 and 2012, there was a trend away from a combined approach and toward an isolated posterior approach, with a concurrent increase in levels treated.[33]  Compared with isolated approaches, a combined approach was associated with higher complication rates, longer hospital stays, and higher total charges.

A systematic review and meta-analysis (13 studies; N = 1147) by Lee et al found that a posterior-only approach with posterior shortening osteotomy (n = 605) corrected Scheuermann kyphosis as successfully as a combined anterior-posterior approach (n = 542).[34]

Preparation for surgery

Preoperative planning for the patient with Scheuermann kyphosis is critically important. A detailed discussion with the patient and family members is conducted to prepare them for the magnitude of the operation and to discuss expectations of the rehabilitative process in the postoperative period. Conveying the specific risks involved with the operative procedures is also important so that a thorough understanding and informed consent is obtained.

The treating physician must first decide on the operative approach (single-side or combined). Concomitant medical conditions must also be considered and incorporated into the operative plan. For example, if concomitant thoracic stenosis is present, a decompressive procedure is indicated. Additionally, if a coexisting coronal deformity is present, this would impact the side of the anterior approach. Generally, approaching the deformity from the convexity is recommended. This facilitates the exposure, as the local vasculature tends to migrate towards the concavity.

Finally, great care must be taken in determining fusion levels. To determine overall sagittal balance, a plumb line is dropped from the C7 vertebral body to the sacral promontory. Sagittal balance is deemed positive when the plumb line falls anterior to the sacral promontory and negative when the plumb line falls posterior to the sacral promontory.

Patients with Scheuermann kyphosis frequently have negative overall sagittal balance. This often is exacerbated by surgical correction, particularly if the surgeon has been overzealous. The risk of overcorrection leads to junctional kyphosis, either proximal or distal, to the fused segments. To avoid this complication, fusion should extend approximately to the end vertebral body and distally beyond the end vertebral body to the first lordotic disk.[35] The surgeon also should avoid overcorrection, with correction not exceeding 50% of the initial deformity and residual kyphosis exceeding 40°.[36]

Posterior approach

The levels to be addressed in the surgical approach to Scheuermann kyphosis must be determined on preoperative radiographic evaluation.[37]

With a patient well padded in the prone position, a midline approach is created to the thoracic spine. An incision is created with a skin knife, and dissection can be taken down through the subcutaneous tissues with an electrocautery.

A marker is placed over the first available thoracic spinous process, and a radiograph is obtained to confirm the appropriate level. It is best to choose the inferior aspect of the incision to mark the spinous process; the radiograph can then incorporate both the pelvis and the marked vertebral body, thereby facilitating the counting of appropriate levels.

A subperiosteal dissection ensues, stripping all of the perispinal muscles from the midline to lateral. Dissection is taken out all the way posterolaterally to the transverse processes of each respective level.

The posterior anatomy and landmarks of the vertebral bodies in individuals with Scheuermann kyphosis are fairly normal. The options for fixation include sublaminar hooks, transverse process hooks, pedicle hooks, and transpedicular screws. Any of these fixation devices then can be attached to a rod device. Take great care in contemplating sublaminar hooks, as staying out of the spinal canal is advisable.

Transpedicular fixation can provide excellent strength, but judicious use in the thoracic spine of transpedicular fixation is advised. Cross-sectional pedicular diameter makes transpedicular screw fixation technically challenging from T9 proximally, in that pedicle diameter narrows considerably. The pedicular starting point for posterior placement of transpedicular screws is relatively proximal on these cephalad thoracic vertebral bodies.[38]

Preoperative computed tomography (CT) may be considered for assessment of pedicular diameter. Laminotomies may be performed to confirm medial or inferior violation of the pedicle during the placement of screws. However, cross-sectional pedicular diameter from T10 to T12 is more favorable for transpedicular fixation. Screws placed at these levels can provide an excellent base for the construct with a combination of pedicular and transverse process hooks proximally.[39]

Hardware prominence also is particularly problematic in the thoracic spine, especially in thinner patients. Take great care in reapposing the paraspinal muscles in the midline covering the hardware.

Anterior approach

The anterior approach to the thoracic spine is often more challenging in patients with Scheuermann kyphosis. A standard posterolateral approach with single-rib resection is a useful approach to the thoracic spine from T4 to T12. If scoliosis coexists with the kyphosis, the incision typically is created to approach the convexity of the deformity. However, if no coronal deformity is present, the approach may be either from the patient's right or left, depending on surgeon preference and on the local vascular anatomy, which must be assessed preoperatively.

Take great care in planning the incision. Patients with Scheuermann kyphosis have more horizontal rib orientation, which must be considered in addressing the appropriate levels to be exposed.

Once the incision is created, the dissection is taken down through the subcutaneous tissues. The first muscle layer encountered is the latissimus dorsi, which crosses the incision anterolaterally; the trapezius is located more posteriorly. Typically, these muscles must be incised in line with the incision to effect a wide exposure to the anterior thoracic spine.

Underlying these muscles is the serratus anterior. In the lower thoracic spine, the serratus anterior can be reflected proximally. In the upper thoracic spine, it must incised in line with the incision.

The level of the selected rib then is palpated. To facilitate an uncomplicated approach, take great care to confirm the appropriate rib to be resected. This may be confirmed by palpation from proximal or distal or confirmed by radiographic evaluation. The rib is subperiosteally exposed, sparing the neurovascular bundle on the inferior aspect of each respective rib. The rib is resected anteriorly and posteriorly as far as the incision will allow, and the chest then is entered by incising the pleura.

The lung then can be retracted. For high thoracic approaches, a double-lumen endotracheal tube is recommended to allow deflation of the lung. For midthoracic and lower-thoracic approaches, a single lumen tube is adequate.

The vertebral column is palpated, and a longitudinal incision is made in the prevertebral pleura to expose the vertebral column. The segmental vessels then are identified. These lie in the waists, or valleys, of the vertebral bodies, in contrast to the disks, which correspond to the peaks of the thoracic spine. If an anterior release with an interbody fusion is planned, the segmental vessels can be left intact. However, if vascular ligation is indicated, either for instrumentation or for wider visualization, they may be resected at the middle aspect of the vertebral body.

Temporarily applying a vascular clip to the segmental vessels without ligating the vessels has been recommended. This is followed by somatosensory evoked potential (SSEP) monitoring to ensure that the patient remains neurologically intact before ligation. However, Winter et al reported that in more than 1200 patients undergoing an anterior spinal approach with vascular ligation, only one neurologic event occurred that was not directly attributable to mechanical causes.

With the vertebral column exposed and the appropriate level confirmed radiographically, diskectomies and anterior release are performed over the apex of the deformity. Patients with Scheuermann kyphosis, by definition, have disk-space height narrowing and wedged vertebral bodies with thickened and tightened anterior longitudinal ligaments (ALLs). This anatomic fact makes an anterior release technically challenging.

A complete release of the ALL is necessary with complete resection of each disk to allow for subsequent maximal correction of the deformity. Occasionally, using an osteotome or burr is necessary to complete the diskectomy, particularly in severe deformities.

A complete annulotomy around the entire vertebral body is necessary to effect a wide release. The anatomy relevant to the anterior spinal column includes the aforementioned segmental vessels. The segmental arteries are direct branches off of the descending thoracic aorta, whereas the segmental veins drain directly into the ascending vena cava.

The thoracic synthetic trunk and intercostal nerves also are readily visualized cascading along the anterior thoracic column and running from the costal grove on the inferior aspect of the rib directly to the vertebral foramen respectively. Additionally, take care to avoid injuring the thoracic duct and lymphatic system.

Combined anterior-posterior approach

The patient should be transferred to the operating room and placed on the operating table in a supine position. General anesthesia should be established. Use of a double-lumen endotracheal tube typically is not necessary, unless the patient is particularly small or the proposed anterior approach is proximal to T6.

After general anesthesia has been established, neurologic monitoring should be established. SSEP or motor-evoked potentials may be used. If neurologic monitoring is not available, a wake-up test is indicated.

The patient is then positioned laterally to perform the thoracotomy. Although one report presented a simultaneous anterior and posterior approach, with the patient positioned prone and the thoracoscopic anterior release being performed while the posterior exposure was being performed simultaneously, this discussion describes an open anterior release in the lateral position.

The incision must be planned with great care. The preoperative lateral x-ray gives the surgeon an idea of the obliqueness of the thoracic ribs. Patients with Scheuermann kyphosis often have more horizontal angles to their ribs, and this must be considered in planning the incision. The goal is to approach the deformity to its most severe levels, obtaining a complete anterior release of the apex of the deformity.

A right-side approach avoids the great vessels. If a left-side approach is contemplated because of a concomitant coronal deformity or for surgical preference, magnetic resonance imaging (MRI) is useful to assess the local vasculature preoperatively. A posteriorly located descending aorta can obstruct the surgeon's approach to the thoracic spine.

A standard thoracotomy is used. The surgeon may elect to use a muscle-sparing approach through a more limited incision if the number of levels indicated in the anterior release is four or fewer. A rib-resecting approach facilitates a wider exposure and also provides for a local bone graft. Once the chest is entered, the lung is displaced proximally and anteriorly, or it is deflated when a double-lumen tube is used.

The pleura overlying the thoracic spine is incised longitudinally, and segmental vessels are identified. Treatment of the segmental vessels is widely debated. Options include sparing the segmental vessels or ligating them. An intermediate approach is to temporarily occlude the segmental vessels with vascular clips and monitor the SSEPs to ensure that they do not change from baseline before proceeding with ligation of the segmentals.

The critical step in the anterior approach is to effect a wide release. The local vasculature must be protected while a complete diskectomy is performed, including resection of the thickened ALL. The goal is a complete 270° release of the annulus to radically mobilize the disk space.

The surgeon then may proceed with the interbody fusion. Options are to perform a structural interbody fusion using the rib graft or to create a trough in the lateral aspect of the vertebral bodies and replace the morselized bone graft into the trough and interbodies. This creates a single column of morselized graft that is maintained during posterior manipulation and correction.

The pleura of the thoracic spine then is closed with a running suture to control blood loss and graft dislodgement. A chest tube is placed prior to closure, and the lung is reinflated under direct visualization. A standard closure then is effected, and the patient is repositioned for the posterior procedure.

The posterior procedure consists of a meticulous subperiosteal exposure of all posterior elements throughout the levels to be incorporated in the fusion. The hardware armamentarium includes hooks and screws with segmentally fixed rods. Hook options include transverse process hooks, sublaminar hooks, and pedicle hooks with the preference toward fixation that remains out of the spinal canal.[40]

The two basic instrumentation techniques that effect posterior correction of the kyphotic deformity are the compression technique and the leverage technique.

The compression technique is a four-rod construct, in which two rods proximally are connected to two rods distally through domino devices located over the apex of the deformity. With the rods in place, compression is applied across the apex of the deformity, reducing the kyphosis. Once the appropriate amount of correction has been effected, the dominoes are tightened and the excess rods are resected.

This technique has the advantage of effecting a smooth correction in one step and shortening the overall posterior length of the spine. It has the disadvantage of a fairly bulky amount of hardware, particularly over the apex of the deformity.

The leverage technique is a two-rod technique, in which the proposed correction is bent into the rod ahead of time. The rod then is secured to the patient's spine, either proximally or distally through a claw technique or through screws (see the image below). The rod then is delivered progressively level-by-level to the spine, effecting segmental correction, as the rod is attached sequentially to the spine.

This technique reduces hardware bulk but does somewhat distract the anterior column. If structural bone graft has been placed anteriorly, the bone graft may become dislodged using this technique.

Meticulous bone grafting technique must be employed, particularly in adult patients, with autogenous bone graft remaining the criterion standard.

Should intraoperative monitoring change from baseline, this must be explained. If no explanation is readily available, a wakeup test is indicated. If the wakeup test yields positive results, all instrumentation should be removed to allow the spine to relax toward baseline. Generally, it is recommended at this juncture to proceed with closure and postoperative evaluation for the cause of the underlying neurologic change. Subsequently, corrective surgery can proceed if indicated.

The patient's hemodynamic and neurologic status must be monitored closely in the early postoperative period. In an uncomplicated recovery, the patient is mobilized and out of bed on postoperative day 1. The surgeon must determine whether a postoperative brace is necessary. Good-quality bone and stable segmental fixation generally makes postoperative bracing unnecessary.

Physical therapy is necessary in the early postoperative period to reestablish ambulation and gait training, to facilitate mobilization out of bed, and to ensure proper hygiene. A standard regimen for chest-tube care is used with serial postoperative chest radiographs, monitoring of chest-tube output, and, ultimately, chest-tube removal on postoperative day 2 or 3 with a radiograph after the tube has been removed.

Discharge from the hospital is indicated once the patient is hemodynamically stable, has reasonable pain control on pain pills, has resumed normal bowel habits and diet, has a clear and dry wound, and is independent with respect to ambulation and transfers in and out of bed. Discharge typically occurs around postoperative day 4-6.

Standard postoperative instructions include wound care and expectations for rehabilitation. Generally, no specific physical therapy program is instituted, but the patient is instructed on daily walking and resumption of normal activities. The patient is cautioned against lifting, bending, twisting, or any athletic endeavors until further notice.

Complications in patients undergoing extensive reconstructive spinal procedures, such as that for Scheuermann kyphosis, are well documented.[41, 42] The complication rate is higher for adult patients than for adolescents. Categorically, however, the complications are similar. The following have been documented:

• Death
• Neurologic compromise
• Hardware failure
• Pseudoarthrosis
• Pulmonary, chest-tube, and thoracotomy complications
• Blood clots
• Pulmonary emboli
• Wound infections
• Dural tears
• Positional and anesthetic complications

Anticipation and vigilance in the identification and treatment of these potential complications are critically important. The number of levels fused appears to be an independent risk factor for major complications.[43]

Follow-up for patients who have undergone surgical correction for Scheuermann kyphosis consists of clinical and radiographic evaluation. Clinical evaluation should include assessment of progress in terms of returning to normal activities and guidance of these activities.

Generally, patients are able to resume fairly normal activities of daily living within the first 4-6 weeks. Resumption of more physical activities occurs at 3-4 months. Radiographic evaluation varies according to individual surgeon preference; however, a reasonable regimen might include radiographs at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperatively.

The patient should be making steady clinical and radiographic progress during this time frame, and any deviation from expectations should be evaluated. The treating physician must maintain a high concern for hardware failure and pseudoarthrosis, which may have fairly indolent clinical presentations.

Radiographic evaluation should assess not only the fusion and correction but also the sagittal and coronal balance and the junctional levels above and below the fusion.