Kyphosis

The pathophysiology of kyphosis depends on the etiologic factor. The exact cause of Scheuermann disease is still imprecisely defined. Scheuermann postulated that the condition resulted from avascular necrosis of the apophyseal ring. Other theories include histologic abnormalities at the endplate, osteoporosis,[4] and mechanical factors that affect spinal growth.[5] A Danish study demonstrated an important genetic component to the entity.[6]

Postural kyphosis is present when accentuated kyphosis is observed without the characteristic 5° of wedging over three consecutive vertebral segments that defines Scheuermann kyphosis.[7] This is felt to be due to muscular imbalance leading to the round-back appearance of these individuals.

It is noteworthy that hyperkyphosis in persons older than 60 years is usually not due to underlying vertebral fractures, which are only found in a minority (≤ 37%) of patients with hyperkyphosis; it is more often due to disk degeneration, muscle imbalance, and overall change in the shape of the aging spine. This kyphosis is associated with increased fracture risk, poorer pulmonary function, poorer physical function, and increased risk of death, even in those without fracture and osteoporosis.[8]

Familial hyperkyphosis may be related to the inherited pattern of disk degeneration. As disk height is lost, as part of normal aging and degeneration of a disk, the kyphosis increases. As more disks become involved, the effect is potentiated, and the overall kyphosis becomes more significant. 

When focal kyphosis occurs after a fracture, more height is lost in the anterior aspect than in the posterior aspect; this is the typical fracture pattern. The angulation can increase as the fracture heals, placing pressure on the spinal cord and further pressure on the anterior column of the spine. Patients with fractures have historically been treated with laminectomy alone, especially in the thoracic spine, and they often have had progressive kyphosis at the fracture site.[9, 10]

Postinfectious kyphosis occurs in a manner similar to that just described. Mechanical integrity of the anterior column is lost as a consequence of the infectious process. Bending forces then accentuate the normal sagittal contour.

Many potential causes of kyphosis have been described.[11]  Scheuermann disease and postural round back are often identified in adolescents and are the most common causes of hyperkyphosis in that age group.[12, 13, 14]  Congenital abnormalities, such as failure of formation or failure of segmentation of the spinal elements, can cause a pathologic kyphosis. Autoimmune arthropathy, such as ankylosing spondylitis, can cause rigid kyphosis to develop as the spinal elements coalesce. Genetic conditions, such as Ehlers-Danlos syndrome, osteogenesis imperfecta, and Marfan syndrome, can also lead to hyperkyphosis.[15]

Kyphosis can also develop as a result of trauma, a spinal tumor, or an infection. Iatrogenic causes of kyphosis include the effects of laminectomy and irradiation, which lead to incompetence of the anterior or posterior column. Finally, metabolic disorders and dwarfing conditions can lead to kyphosis. This is theorized to be due to ligamentous laxity that develops and lead to accentuation of the kyphosis. 

Results of treatments vary, depending on the etiology of the deformity.

Malcolm et al reviewed 48 patients and achieved a deformity correction rate of 26% and at least partial pain relief in 98% of patients with posttraumatic kyphosis with anterior and/or posterior fusions.[9]

Lehmer et al studied 38 patients who underwent a single-stage closing wedge procedure to treat posttraumatic and postlaminectomy kyphosis.[16] They obtained a mean correction of 35° with three pseudarthroses. Eight of 14 preoperative neurologic deficits improved, and 76% of the patients treated said they would undergo the surgery again if needed.

Kostuick achieved fusion in 36 of 37 patients receiving anterior-only fusion.[17] Pain significantly improved in 78%, and three of eight patients with paraparesis improved.

Outcomes in Scheuermann kyphosis are similar to those just presented, though the amount of correction achieved may not be correlated with pain relief.

In a series of patients who were treated with a posterior Harrington rod, all had pain relief. However, 16 of 22 lost correction.[18]

Lowe and Kasten used posterior instrumentation to achieve a mean correction of 85° down to 43°.[19]

With anterior-posterior and posterior-only surgery, Speck and Chopin gained an average deformity correction of 40%, and 28 of 45 patients were pain-free.[20]  However, four patients had infections, nine lost more than 10° of correction, and one had Brown-Sequard syndrome postoperatively.

Investigators have evaluated advanced techniques, such as osteotomies and new instrumentation. Bridwell et al reported a series of 33 patients treated with pedicle subtraction osteotomy for sagittal imbalance.[21, 22]  The C7 plumb line improved from 16.6 cm positive to 1.7 cm. Pain and Oswestry disability indexes significantly improved. Eight patients had pseudarthrosis, and one had a wound infection. No permanent neurologic injuries occurred.

In a retrospective study, anterior-posterior correction was compared with posterior-only instrumentation with all pedicle screws.[23]  The posterior-only group had significant improvement in terms of blood loss, correction of deformity, and number of complications.

Video-assisted thoracoscopic release followed by posterior arthrodesis has been successful. In one study, deformity correction was 84.8° to 45.3° in patients with thoracic kyphosis associated with Scheuermann disease.[24] Mean loss of correction was 1.6°, and one hook pulled out. No cases of junctional kyphosis were observed.

A 2019 systematic review of treatment of Scheuermann kyphosis demonstrated that most surgeons are moving from anterior and posterior approaches to posterior-only. Nonoperative treatment with bracing and therapy was notable for inferior correction and maintenance of correction, as opposed to surgical treatment.[25]

Evaluation of a patient for spine deformity should include a thorough history. Patients presenting with kyphosis may have as much concern about the cosmesis of the deformity as about the pain. Typically, though, the more significant the deformity is, the greater the pain that will be experienced with ambulation and the performance of activities of daily living (ADLs).[26]  The presence of numbness or tingling sensations in the lower extremities, more frequent falls, and balance issues should prompt evaluation of the spinal cord and neural elements, which can be compressed with significant deformity.

It is important to elucidate the etiology and history of the deformity. The Comprehensive Etiology-Base Adult Spine Deformity Classification described the following eight types of adult spinal deformity (ASD) according to etiology:

• Type 1 - Idiopathic progressive adult deformity
• Type 2 - ASD due to progressive idiopathic adolescent scoliosis (AIS) that was untreated or deformity adjacent to prior surgical fusion
• Type 3 - ASD secondary to iatrogenic sagittal imbalance after flat-back deformity following prior AIS surgery related to Harrington rods instrumentation or due to prior fusion with lack of adequate lordosis
• Type 4 - Junctional spine deformity due to proximal junctional kyphosis (PJK) after prior fusion surgery or distal junctional kyphosis/failure after prior spine fusion
• Type 5 - Posttraumatic, either acute after trauma or showing chronic progression after trauma
• Type 6 - Pathologic deformity after either neoplasm or infection
• Type 7 - Metabolic-related ASD due to osteoporosis or another metabolic bone disorder
• Type 8 - ASD secondary to congenital, neuromuscular, or syndromic etiologies

A 10- to 42-year natural-history study of Scheuermann disease revealed that patients, as compared with control subjects, tended to have increased back pain.[23]  However, they were not more likely to take pain medication, to have sedentary jobs, or to lose motion of the spine. The investigators found no differences between the patient group and the control group with respect to educational level, absenteeism, self-consciousness, or reports of numbness in the legs. Of interest, restrictive lung disease was observed in patients with a curve greater than 100°.

Examination of a patient should begin with inspection of the coronal and sagittal balance while the patient is standing. Specific attention should be directed at the magnitude of trunk shift in the frontal plane, which would indicate a coronal plane deformity, or scoliosis. Inspection of the patient from the side allows evaluation of the head's position in relation to the pelvis.

The patient should also be asked to walk. Significant hip and knee flexion during ambulation indicates that the patient is compensating for the kyphosis by altering the hip and knee position. Whereas such compensation is effective at allowing better forward gait during ambulation, it carries a significantly higher energy cost, negatively correlates with quality-of-life measures, and may increase the risk of falling.[27]

A thorough neurologic examination is also critical in evaluation. A wide-based gait pattern could indicate cervical or thoracic spinal stenosis.  Increased hip and knee flexion during the swing phase of gait could indicate impairment of the ankle dorsiflexion muscles as a consequence of lumbar nerve compression.

Muscle testing should be done systematically and bilaterally so as not to miss any subtle weakness. Hyperactive reflexes or pathologic reflexes, such as clonus or upgoing Babinski, would indicate upper-motor-neuron dysfunction and signify a problem at the level of the cervical or thoracic spine. Alternatively, diminished or absent reflexes could indicate a lower-motor-neuron issue—specifically, at the level of the lumbar spine or more peripherally.

Standard laboratory results should be evaluated whenever surgical intervention is being considered. The laboratory workup should include a complete blood count (CBC), coagulation studies, and routine chemical analyses.

Autodonation of blood can be recommended to the patient in anticipation of the need for intraoperative transfusion.

In patients with a known or suspected infectious etiology, the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) level should be measured to help identify a potential infection or to help track the progress of treatment.

In patients with suspected neoplastic etiology, a full metastatic workup should be performed in concert with a primary care physician or oncology team, particularly in the setting of no preexisting primary cancer diagnosis.

Before a major operation, the patient's nutritional status might also be checked; it considerably influences the patient's ability to heal. This can be evaluated by obtaining a prealbumin level.

Radiographs are crucial both for diagnosing kyphosis and for planning treatment.

The most useful radiographs are upright posteroanterior (PA) and lateral images of the entire spine. These views enable the reviewer to assess the sagittal balance of the entire spine and to determine whether a scoliosis is present. (See the image below.)

Preoperative lateral radiograph of patient with 85° thoracic deformity secondary to Scheuermann kyphosis.

Significant improvement in our understanding of the sagittal radiographic profile has allowed improved quantification and description of deformities and better identification of treatment targets. Measurements are made on radiographs by using the standard Cobb technique for scoliosis, which has been adapted to the measurement of kyphosis. Thoracic kyphosis is measured from T1 to T12, though the upper thoracic vertebral endplates are often difficult to see. All radiographs should be evaluated for pelvic parameters; the critical role the position of the pelvis plays in overall spinal balance and patient satisfaction is well understood. 

Normal measurements for the thoracic spine vary widely, but the generally accepted definition of normal, according to the Scoliosis Research Society (SRS), is 20-40°. A plumb line dropped from C7 should pass through or just anterior to S1 on a lateral full-length image. This technique helps in assessing and quantifying the patient's overall sagittal alignment.

In 2005, Glassman et al published data demonstrating that symptom severity in patients with a significant sagittal imbalance correlated in a linear fashion to the deformity.[26]

Schwab et al identified the following threshold parameters for severe disability,[28] defined as Oswestry Disability Index (ODI) greater than 40:

• Pelvic tilt greater than 22°
• Spinal vertical axis (SVA) greater than 47 mm
• Mismatch between pelvic incidence (PI) and lumbar lordosis (LL), or PI-LL, of 11° or more

These measurements are felt to be solid goals of surgical treatment, as well as useful aids in procedural planning.

Another attempt to measure the sagittal balance is the T1-spinopelvic inclination (T1-SPI), which is another measure of global spinal balance with reference to the position of the pelvis. A study demonstrated that at higher levels of pelvic tilt, patients had much worse function, as measured by poorer scores on the ODI, the Short Form (SF)-12, and the SRS-22 scale.[29] The T1-SPI was found to be better correlated with these health-related quality-of-life (HRQOL) measures than the SVA was.

This measure was refined further by adding the value to the pelvic tilt. The resulting measure, the T1-pelvic angle (TPA), also correlates with HRQOL parameters. Furthermore, bceause it is an angular measurement, it does not change depending on whether the patient is sitting or standing, and it does not require calibration of the film.[30]

Radiographs obtained with the patient in a supine lateral hyperextension position over a bolster can be used to determine the flexibility of the curve. This information is useful in surgical planning. A flexible curve is best corrected with posterior-only fusion, whereas a stiff curve may necessitate an anterior-only or combined anterior-posterior procedure. A curve that corrects to 50° or less on hyperextension can be treated with posterior-only fusion.[18, 31]  Postural kyphosis rarely exceeds 60°, and it should correct to normal with hyperextension.

Another system of global spine evaluation, the GAP (Global Alignment and Proportion) score, was developed and correlated with mechanical complications after surgery. This score uses pelvic version, lumbar lordosis, the relative lordosis in the L4-S1 vs L1-S1 segment, PI, and patient age. When postoperative radiographs were evaluated with this system, mechanical complications were found to be much more common with a higher GAP score.[32]  This again highlights the importance of achieving global balance after operation for sagittal plane deformity.

Evaluation of the L5-kyphosis apex line (L5-KAL) has been described as a potential means of indicating the thoracic curve change in patients with Scheuermann disease or postural kyphosis. In a cross-sectional study by Bezalel et al, significant positive associations were observed between the L5-KAL and thoracic kyphosis, lumbar lordosis, the C7 line, and self-perceived body image.[33]

Magnetic resonance imaging (MRI) can be a useful adjunct in planning treatment for patients with kyphosis. If a neurologic abnormality is present, MRI may aid in localizing impingement on neural structures.

If surgery is being planned for the treatment of postinfectious kyphosis, MRI helps in planning an anterior approach with regard to the amount of resection needed (if any) to remove diseased bone.

Estimation of the overall frailty of the patient may predict complications in spine surgery.[34]  A modified frailty index has been developed that can be used to screen patients for risk. This index comprises the following 11 factors:

• Nonindependent functional status
• History of diabetes mellitus
• History of chronic obstructive pulmonary disease (COPD)
• History of congestive heart failure (CHF)
• History of myocardial infarction (MI)
• History of percutaneous coronary intervention (PCI), cardiac surgery, or angina
• Hypertension requiring the use of medication
• Peripheral vascular disease or rest pain
• Impaired sensorium
• Transient ischemic attack (TIA) or cerebrovascular accident (CVA) without residual deficit
• CVA with deficit 

Modification of risk factors preoperatively may not reduce the overall risk of complications.[35]

Ensuring the adequacy of bone density is imperative when surgical correction of kyphosis is being considered. Correction of the kyphosis relies on instrumentation to reduce the spine, and considerable forces are placed on the instrumentation-bone interface. Osteopenic bone can predispose to loss of correction over time, if the instrumentation cuts through the relatively less dense vertebrae.

If a patient's bone density is in question, bone densitometry can be perform to quantify it. Efforts should be made to maximize bone density before and following surgery. When bone density is poor, the surgeon must usually increase the number of points of fixation to reduce the stress at each point and should consider cement augmentation of the screws and/or augmentation of one or two levels above the fusion's upper instrumented vertebra.[36]

Indications for treatment of kyphosis include the following:

• Unremitting pain
• Neurologic changes
• Progression of deformity ^[37]
• Cosmesis ^[5]

Indications for surgical treatment of Scheuermann kyphosis have changed fairly substantially; however, precise indicators have not been elucidated.

Authors from early clinical series simply cited pain and deformity as reasons to perform fusion. Proposed indications more specific than these are as follows[38] :

• Kyphosis greater than 75°
• Kyphosis greater than 65° with pain
• Unacceptable appearance of the trunk

Other possible indications in severely affected patients are problems with balance while sitting and skin problems due to pressure at the apex of the deformity.

Surgical intervention for posttraumatic kyphosis is recommended in the following circumstances[39] :

• The patient's neurologic status changes
• The condition progresses
• Kyphosis is 30° or more
• Loss of anterior vertebral height exceeds 50%

Contraindications for surgical treatment of kyphosis include a clinically significant cardiopulmonary risk and medical unfitness for surgery.

As surgical implants and techniques have improved, so have the results of surgery. Patient safety should be the foremost goal of the treating physician. Future prospective trials will help in defining the best way to care for patients with clinically significant sagittal imbalances.

Medical therapy for kyphosis consists of exercise, medication, and bracing.[40]  Physical therapy, which usually consists of extension-focused activities, may be of some benefit; however, this has not been proved.[38, 41]

Medications used to treat discomfort associated with kyphosis should be limited to nonsteroidal anti-inflammatory drugs (NSAIDs) and, possibly, muscle relaxants. Narcotics should be avoided for long-term treatment of pain associated with kyphosis.

If a patient has an active infection, such as diskitis or vertebral osteomyelitis, appropriate antibiotics based on culture results should be started as soon as possible.

In some skeletally immature patients with Scheuermann kyphosis, bracing is effective[42] ; however, the correction obtained may diminish as patients approach and pass skeletal maturity.

Sachs et al found that treatment with a Milwaukee brace improved deformity in 76 of 120 (63%) patients who wore the brace regularly; brace treatment seemed to be least effective when the curve was more than 74° at the beginning of treatment.[43]  Bradford et al reported modest success in treating adults with a brace, with some correction of their deformities.[18]

Careful surgical planning is crucial for successful operative treatment of kyphosis. The goals of surgery are to correct the deformity and to remove any neural compression, if present.

The age of the patient choosing surgery should play a role in the planned correction. Aging causes an increase in kyphosis naturally, and some advocate limiting the planned correction in older patients in order to minimize mechanical complications.[44]

Correction of the deformity can be done via an anterior, a posterior, or a combined anterior-posterior approach. Posterior surgery is most commonly described and performed. Posterior arthrodesis for kyphosis can be an extensive operation, with many spinal segments typically included in the fusion mass.[45]  This procedure is most helpful for long, sweeping, flexible curves. In cases of rigid deformity, osteotomies can be performed to improve the correction. Combined anterior-posterior surgery may be required for severe deformities.[46]

Smith-Peterson osteotomy, pedicle-subtraction osteotomy, and vertebral-column resection

Specific osteotomies are aggressive facetectomies at each level, Smith-Peterson osteotomy, pedicle-subtraction osteotomy, and vertebral-column resection. Two-level osteotomies (eg, pedicle-subtraction osteotomy plus Smith-Peterson osteotomy) for correction of severe kyphosis from ankylosing spondylitis have been described.

Smith-Peterson osteotomy involves wedge-shaped resection of posterior elements from the pedicles of the superior vertebra to those of the inferior vertebra. When closed posteriorly, the spine hinges on the disk space; therefore, an open, mobile disk is crucial to the success of this procedure. The osteotomy can be performed at one or multiple levels, if necessary. This permits significant correction, with approximately 1 mm of resection yielding 1° of lordosis.[11]  Some recommend anterior diskectomy and fusion with Smith-Peterson osteotomy to decrease the pseudarthrosis rate.[21, 47, 48]

Pedicle-subtraction osteotomy involves relatively aggressive resection of a wedge of bone, including posterior elements, the pedicles, and the vertebral body.[49, 50]

Vertebral-column resection entails removal of posterior elements, the vertebral body, and adjacent disk material. Because of the destabilizing effect of this resection, both anterior and posterior fixation are often required. Dreimann et al described the use of posterior vertebral-column resection with 360º osteosynthesis to reduce kyphotic deformity.[51, 52]

As kyphosis becomes notably sharp or focal, increasingly aggressive techniques are required for correction. Cho et al demonstrated that the corrections per segment were 10.7° for Smith-Peterson osteotomy and 31.7° for pedicle-subtraction osteotomy.[53]  Procedures involving the anterior column are usually followed by posterior instrumentation and fusion. Vertebral column resection yielded up to 63% improvement in deformity at 5 years in a medium-term study.[54]

Although having a correction “target” is important in preoperative planning, it is often difficult to assess the correction intraoperatively. The lumbar pelvic angle, a portion of the T1-pelvic angle (TPA), may be useful in this regard and also seems to correlate with patient satisfaction.[55]

Zhong et al investigated the use of a two-level pedicle-subtraction osteotomy in comparison with a one-level pedicle-subtraction osteotomy plus a Smith-Peterson osteotomy for severe kyphosis.[56]  The two-level pedicle-subtraction osteotomy was useful, especially in cases of a fixed kyphosis, such as that due to ankylosing spondylitis.

Anterior surgery

Anterior surgery can include single or multiple diskectomies to increase the flexibility of the spine, followed by a posterior arthrodesis. The transthoracic approach allows decompression of the neural elements before the spine is corrected with posterior instrumentation. Anterior-only fusion is most useful for treating relatively short and focal kyphosis, such as posttraumatic or postinfectious kyphosis.[24]

A consecutive series of 48 patients were treated for severe deformity with either anterior diskectomy and posterior fusion or vertebral-column resection and followed for at least 2 years. In this case series, the vertebral-column resection group had better correction but also more blood loss, longer operating times, and longer hospital stays. Patient-reported outcome scores were similar in the two groups.[57]

A novel technique for single-curve scoliosis may also be used to correct kyphosis. The bone-on-bone technique involves an anterior-only approach to perform complete annulectomy and diskectomy at each level in the Cobb angle of the deformity. Then, using sequential compression along two rods, which are affixed with a staple and two screws in each vertebral level, the surgeon brings the bony endplates into immediate contact. Substantial correction can be achieved in this manner.[58]

A technique called anterior-column restoration relies on multiple lateral interbody fusions to release the anterior longitudinal ligament and realign the spine. This is often followed by an open posterior fusion. Possible benefits of this technique over posterior-only bony resection may include less blood loss and dural manipulation and excellent sagittal plane correction; however, further study is needed.[59]

Preparation for surgery

Patients with kyphosis may have subtle neurologic abnormalities that are easily missed during examination. Magnetic resonance imaging (MRI) of the affected area can help in determining whether decompression is necessary before instrumentation and correction of the deformity.

Selection of the fusion level is important. The proximal level is usually the most cranial vertebra rotated into the kyphosis. In the distal aspect, the fusion is commonly extended to the last lordotic segment; however, some have advocated using the sagittal stable vertebra to determine the distal fusion level.[60, 61]  Recommended correction should not exceed 50%, so as to prevent junctional kyphosis at the ends of the fusion.[19]

Operative details

The spinal cord and its roots are at risk during correction of kyphosis, especially when the canal is stenotic or when the cord is tethered at the apex of the kyphosis. In these situations, consideration should be given to performing anterior decompression before the posterior arthrodesis. The cord is also at risk for ischemia if blood flow is altered with the change in spinal alignment.[12]

Manipulation of the spinal cord, especially during osteotomies in the thoracic spine, should be avoided. Evidence suggests that the lower lumbar roots are vulnerable during pedicle-subtraction osteotomy, more so than the upper lumbar roots are.[47]  Careful attention should be paid to the removal of posterior bone and ligament, which may buckle into the canal as the osteotomy is closed.

Thorough central decompression is recommended to help prevent neurologic compromise. Subluxation of the spine can also occur when an osteotomy is being closed; therefore, intraoperative radiography is essential to facilitate rapid identification and correction of subluxation.

Neural monitoring may help identify correctable neurologic injury before the case is concluded. Monitoring of somatosensory and motor evoked potentials can be helpful in detecting reversible neural injury (eg, from stretching during correction of deformity or improper placement of devices). However, neural monitoring may not be useful with isolated root injuries.[21, 22]  A wake-up test can also be performed to assess the patient's gross motor function after the deformity is corrected.

Blood loss can be clinically significant during correction of kyphosis, especially if anterior procedures and large osteotomies are being performed.[62]  Bleeding should be controlled at every step of the operation to keep overall loss to a minimum. Clinically significant blood loss can cause hypotension and potentially injure the spinal cord, myocardium, or retina. Intraoperative blood-loss mitigation techniques include preoperative autodonation, decreasing abdominal pressure, and use of antifibrinolytic drugs.[63, 64, 65]

In terms of intraoperative considerations related to instrumentation, it is important to ensure that the substantial cantilever force applied to the spine with posterior instrumentation is spread over multiple levels. In the thoracic spine, sublaminar wires, hooks, or screws can be used. Pedicle screws in multiple sites will spread the force throughout the construct. Pedicle screws are also useful with aggressive osteotomies, which tend to destabilize the spine. Segmental fixation increases the surgeon's control over the coronal plane, where a deformity can coexist with a sagittal deformity.[11, 66, 67]

In the lumbar spine, pedicle screws are most often used for the reasons just mentioned. Osteoporosis should be addressed with multiple points of posterior fixation, and a low threshold should be maintained for performing concomitant anterior fusion. This approach may help prevent implant pull-out or postoperative collapse and loss of correction.

Intervertebral instrumentation can be useful in increasing the fusion rate and improving deformity correction. Numerous procedures exist for placing an interbody spacer, often filled with osteoconductive matrix, into the spine. These spacers can be placed from the back (transforaminal lumbar interbody fusion, posterior lumbar interbody fusion), from the side (extreme lateral interbody fusion, oblique lumbar interbody fusion), or from the front (anterior lumbar interbody fusion). 

Aggressive correction of the spine can be achieved with vertebral-column resection. In a review of adult and pediatric patients with severe deformities who underwent a vertebral-column resection, the correction at final follow-up was in the range of 53-61%, and improvements were noted on patient-reported outcome measures, despite a 56% complication rate.[54]

Patients usually require clinically significant pain medication after undergoing correction of kyphosis, especially extensive procedures. The amount of narcotics given should be carefully titrated because the drugs may cause ileus, atelectasis, or difficulty in mobilizing the patient after surgery.

Because blood losses can be substantial, patients should be monitored for anemia. Electrolytes should be checked as well, given that notable fluid shifts are common in the perioperative period.

Careful postoperative neurologic examination is important for identifying any changes from the patient's preoperative status.[68]

Possible complications of treatment range from superficial wound infection to complete neurologic injury. The nervous system is at risk with correction because of direct manipulation, traction, or compression resulting from the altered anatomy of the spine. In addition, blood flow to the cord or roots can be impeded. Reported complication rates are quite high, in the range of 40-90%.[32, 69]

Neurologic changes are most often transient. However, if a new deficit is identified postoperatively, transience cannot be assumed. Imaging of the spine should be done to identify any reversible cause of the deficit; if a cause is identified, it should be addressed rapidly. Removing the fixation and allowing the kyphosis to settle may help relieve cord compromise.

Intraoperative blood loss can be clinically significant.[62]  Loss of blood puts the patient at risk for transfusion, hypotension, ischemia to critical tissues, and potentially death. Therefore, careful attention to blood loss is essential.

Mechanical complications are possible as well. Pseudarthrosis can occur, especially with long fusions, inadequate support of the anterior column, and fusions at the thoracolumbar junction.[70]  Other risk factors in long fusions to treat scoliosis include age greater than 55 years,[71]  thoracolumbar kyphosis greater than 20°, and fusion of more than 12 levels.[72]

Implant failure can lead to loss of correction, especially at the proximal portion of the instrumentation. Patients with osteoporosis are at somewhat increased risk of implant failure or even fracture at levels contiguous with the fusion mass.

In some individuals, posterior instrumentation can be prominent and cause discomfort. Overcorrection of the deformity (>50%) and inadequate selection of fusion levels can predispose a patient to junctional kyphosis at the proximal and distal extent of the fusion mass.[19, 73]

Proximal junctional failure is a junctional kyphosis that requires additional surgery. It occurs in 1-5% of all adult spinal deformity procedures.  Failures can be due to disk or ligament issues, failure of the bone, or failure at the bone-implant interface.[74]

Postoperative wound infections can be superficial or deep. As with any surgical procedure, use of prophylactic antibiotics and sterile technique are imperative to lower the incidence of postoperative wound infection. Optimizing the patient's nutritional status before surgery can also help reduce the risk of infection.

In a 2-year postsurgery review of a series of 324 patients, there was a significant improvement in radiographic parameters and a corresponding improvement in pain scores, Oswestry Disability Index (ODI), and Scoliosis Research Society (SRS) scores.[75] Patients with leg pain before surgery continued to have more pain postoperatively than those who did not have preoperative leg pain, despite significant improvement in both groups.

An overall assessment of patient frailty may be an important predictor of risk of complication risk. A validation study of a prior database review identified criteria that assigned people to not-frail, frail, and significantly frail categories and reviewed their postoperative complications and length of stay.[76] As frailty increased, so did the complication rate: 65% for the not-frail group, 78% for the frail group, and 92% for the significantly frail group. Hospital length of stay also increased with frailty.[76]

Standing posteroanterior (PA) and lateral full-length radiographs of the spine should be obtained as soon as possible after surgery and serially for follow-up. Full-length scoliosis films obtained yearly allow evaluation of the patient's curve over time.

Comparison of the postoperative and follow-up images with the preoperative images helps in defining the amount of correction achieved and in determining if correction is being lost over time. Loss of correction should prompt a careful evaluation for implant pull-out or breakage, for subsidence of an anterior implant (if any), or for lack of adequate fusion mass.[77]

A large review of adult spine deformity patients at least 2 years after surgery identified implant-related complications (eg, implant pull-out or rod breakage) in 32%, and over half of those required an additional operation. These complications negatively affected patient function, as reflected on patient-reported outcome measures.[78]

Postoperative measurements of the C7 plumb line should be at or within a few centimeters of S1.