Adult Scoliosis: treatment and challenges

Jeremy L. Fogelson

Adult Scoliosis is an increasingly prevalent disease, with a signifi cant burden to society. In the United States,the next 25 years will witness a doubling in the population aged 65 and older, and similar doubling in the population 85 years and older[1]. Robin et al[2]reported some degree of scoliosis in 70% of patients aged 50-84 years old. This trend of an aging population seems to be amplified in China as well as other countries around the world[3]. The increase in the elderly population is leading to higher prevalence of adult degenerative scoliosis. As life expectancies have increased, so have the patient expectations for optimal quality of life, increasingly requesting treatment for aging conditions, especially spinal disease and scoliosis. Older patients seem to have even more room to improve than younger patients with spinal deformity as they have greater disability[4]. Total spend in healthcare dollars and resource utilization is snowballing, both in non-operative as well as operative arenas.

Typical adult degenerative scoliosis or deformity may present with mild coronal curves less than 20 degrees, or more substantial curves in the range of 40-50 degrees. Many patients have lost signifi cant lumbar lordosis causing sagittal malalignment which has been shown to signifi cantly affect quality of life[5]. Patients typically present with symptoms of low back pain, radiculopathy, inability to stand with a normal posture, as well as cosmetic concerns[6].The overall impact of adult spinal deformity seems to be more severe than the four other diseases ( arthritis, chronic lung disease, congestive heart failure, and diabetes ) according to the SF-36 health survey system[7].

Initial management of Adult Spinal Deformity begins with non-operative measures. Limited evidence supports many of these treatments for durability and effi cacy, yet the non-operative treatments also entail minimal risk and are usually attempted prior to surgical intervention. The mainstay of non-operative interventions is physiotherapy directed at spinal stabilization and strengthening. Medications are frequently utilized, directed at the specifi c pain generator,such as gabapentin for radiculopathy, or antiinfl ammatory medications for mechanical pain. Opioid analgesics may provide signifi cant functional improvements when used sparingly.

Interventional procedures are directed at specific pain generators. In the setting of radiculopathy, especially when it is acute, epidural injections frequently provide relief although it may not be long lasting. Facet injections and rhizotomies also may provide symptom relief. Bracing can be used when patients are initiating therapy and exercise programs, but otherwise should be only used short term except in palliative situations. Overall, the benefi t and costeffectiveness of non-surgical management of adult spinal deformity is unclear and further studies are needed[8-9].

Surgical interventions

There are numerous articles demonstrating that adult spinal deformity surgery improves pain and function[4,10-11].

When considering operative intervention, the first step is to determine if the patient will tolerate surgery with a reasonably low risk of complications. Many patients simply have too much comorbidity and will have prohibitively high complication rates. Further, it is important to understand whether the improvement in symptoms will lead to increased quality of life and decreased functional restrictions. If a patient has debilitating low back pain when ambulatory, but also has substantial COPD preventing signifi cant physical exertion, successful surgery is unlikely to change the patient’s overall function.

Detailed history and physical examination is required to quantify the various possible pain generators and complaints the patient has. Radiographic studies are performed to determine if the patient’s symptoms correlate to the imaging findings. The SRS-Schwab Adult Scoliosis Classifi cation system[12]may be used to define the deformity and is a tool that can assist the provider on deciding to pursue surgical management[13].

After determining that operative invention will be considered, it is paramount to enhance the outcome by optimizing the patient preoperatively. Nicotine use has been shown to inhibit spinal fusion in multiple studies and abstinence from smoking or nicotine supplements is warranted prior to surgery[14]. In addition, obesity correlates with worse outcome in adult deformity patients treated with surgery, and weight loss is advised in the situation of obese BMI. Patients are evaluated for osteoporosis and may be pretreated with teriparatide if the bone mineral density is poor. Other musculoskeletal issues, such as hip osteoarthritis, should be dealt with prior to scoliosis surgery in most circumstances.

If the patient is deemed a candidate for surgery, classifi cation systems may be used assist in determining what intervention to perform. The Lenke-Silva system[15]divides the surgical interventions into 6 Levels of intensity,with Level I being decompression alone, progressing to Level VI intervention which includes signifi cant deformity correction utilizing osteotomies. In situations of signifi cant radiculopathy but also signifi cant scoliosis, it is unlikely that spinal decompression without fusion should be offered, and instead, the levels requiring decompression should be stabilized, and consideration to treat the remaining scoliosis is given[16].

The exact procedure and approach performed will depend on all of the patient factors and well as the surgeon skills and experience. In general, the goals of intervention revolve around achieving the optimal balance of symptom relief while minimizing risk and loss of function.

Future challenges

Although adult spinal deformity surgery has proven to be effi cacious, there is signifi cant room for improvement regarding complications, outcome, and the high cost of intervention. Proximal junctional kyphosis ( PJK ) continues to be the largest challenge that spinal deformity surgeons face. There is nothing more frustrating that performing a major surgical intervention which is successful, only for the patient to return with a failure at the superior end of their construct leading to revision surgery. Major risk factors for this include osteopenia, obesity, age greater than 65,andchanging the lumbar lordosis more than 30 degrees[17-18].

The prevalence rate of PJK approximates 27%-40% of patients who demonstrate at least radiographic changes.Nearly to 4%-15% of patients who develop severe enough PJK are deemed “proximal junctional failures” ( PJF ),with kyphosis or subluxation that it leads to substantial pain, disability, or neurologic dysfunction requiring revision surgery[17-19]. The solution to prevention of this diffi cult problem continues to elude deformity surgeons, but there are strategies that may decrease the overall rate. Any substantial regional kyphosis should be covered with the fusion. For example, when the thoracolumbar junction is kyphotic instead of neutral, typically it is best to fuse to the proximal thoracic spine, especially if the kyphosis is long and sweeping. Prophylactic vertebroplasty can be considered, but little evidence supports this[20]. Some surgeons will utilize a postoperative thoracolo-lumbar-sacral orthosis ( TLSO )for several months, yet at times it seems as if a TLSO causes more harm than good just from the diffi culty getting it on and off, as well as the disuse muscle atrophy that can occur. Conversely, a cervical-thoracic orthosis ( CTO ) is easier to apply and tolerate wearing, so can be considered for 6-12 weeks postoperatively in the patients who are fused to the proximal thoracic spine. A recent article demonstrated higher pain scores in patients with PJK, even if they did not require revision surgery[21]. A great majority of clinical research is submitted each year focused on PJK, and lowering the risk of this complication is one of the most important challenges and goals to improve outcomes of spinal deformity surgery.

When fusing to the sacrum, protecting the sacral screws is of paramount importance. This has a substantial benefi t by lowering the pseudarthrosis rate which may be decreased from 33% to 7.5% in cases of adult spinal deformity. Iliac fixation can prevent the development of severe fixed sagittal imbalance and sacral insuffi ciency fractures. Although iliac screws can lead to pain themselves, it is usually relieved with screw removal[22]. Screw removal is a much easier intervention than repairing a pseudarthrosis at the lumbosacral junction, especially if the patient has developed fixed sagittal malalignment.

The more recent use of S2-Alar-Iliac screws may lead to decreased pain from prominent implants, which could translate to lower incidence of screw remov al. Preliminary studies are promising regarding this technique, but further multi-center validation will be helpful to con firm the safety and effi cacy[23]. Anecdotally, I know of two patients who developed sacral insuffi ciency fractures after proximal thoracic fusions to the sacrum which included transforaminal interbody support and S2-Alar-Iliac Screws which were adequately sized ( minimum 8.5 mm × 80 mm ). This complication seems to be extremely rare with regular iliac screws, so it remains unclear if S2-Alar-Iliac screws are truly superior to standard iliac screws. In fact, it is possible that placing a screw through the sacral ala at the S2 level may be weakening the sacrum leading to post-op sacral fractures. A recent abstract at the Scoliosis Research Society( SRS ) annual meeting presented by Enercan and colleagues demonstrated a high rate of S2-Alar-iliac screw loosening in patients with osteoporosis although there was still a high fusion rate. Further studies are needed regarding this technique.

Neurologic complications continue to be a signifi cant problem, and are especially prevalent in cases requiring three column osteotomy ( 3CO ). Rates range from less than 1% to 17%[24-25]. The most accurate rate of neurologic injury likely comes from the recent prospective Scoli-Risk-1 study showing a 17.2% rate of new motor weakness at 6 week followup after highly complex deformity cases including 3CO, 80 degree curves, congenital deformities, or revision cases with posterior column osteotomies. Continued work is needed to prevent neuro deficits after major spinal reconstructions, and hopefully ongoing studies such as Scoli-Risk will lead to improvements.

The pseudarthrosis rate continues to be the largest reason for revision surgery in adult spinal deformity[26-28].The use of recombinant bone morphogenetic protein ( rhBMP-2 ) may reduce the likelihood of pseudarthrosis[29].However, the potential risks of rhBMP-2, such as increase rate of cancer, heterotopic ossification, osteolysis,radiculitis, seroma formation, retrograde ejaculation are concerning, and the evidence is confl icted and unclear[30-31]. In situations of 3 column osteotomy, adding supplemental rods seems to substantially decrease the rate of symptomatic pseudarthrosis[32].

In summary, adult spinal deformity surgery is an effective treatment option for patients suffering from progressive and severe disease. Major challenges still exist in the goal to provide the most cost-effective care to improve quality of life. Future research focusing on decreasing the rate of revision surgery will likely have the most benefi t to bending the cost-quality curve.

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[32] Hyun SJ, Lenke LG, Kim YC, et al. Comparison of standard 2-rod constructs to multiple-rod constructs for fixation across 3-column spinal osteotomies. Spine, 2014, 39(22):1899-1904.