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Osteoporotic Thoracolumbar Fractures—How Are They Different?—Classification and Treatment Algorithm

Rajasekaran, Shanmuganathan MS, MCh, PhD*; Kanna, Rishi M. MS, MRCS, FNB Spine*; Schnake, Klaus J. MD; Vaccaro, Alexander R. MD, PhD, MBA; Schroeder, Gregory D. MD; Sadiqi, Said MD§; Oner, Cumhur MD, PhD§

Author Information
Journal of Orthopaedic Trauma: September 2017 - Volume 31 - Issue - p S49-S56
doi: 10.1097/BOT.0000000000000949
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Abstract

INTRODUCTION

As the life expectancy of humans increases, the elderly population and the incidence of osteoporosis continue to rise concomitantly.1,2 It has been estimated that in the United States, more than 9.9 million people have osteoporosis and an additional 43.1 million have low bone density with an increased susceptibility to fractures.3 The spine is the most common site for osteoporotic fractures followed by the proximal femur and the distal radius. Osteoporotic vertebral fractures constitute at least 50% of a total 1.5 million osteoporotic fractures that occur annually in the United States.4

Osteoporotic fractures of the spine are increasingly being recognized as an important health care issue because these fractures can result in significant morbidity and potential mortality. Although most fractures are expected to heal, 15%–35% may lead to adverse sequelae, including chronic pain, poor chest function, decreased appetite, kyphotic deformity, fatigue, and neurological deficit with its resultant immobility.5,6 Management of osteoporotic vertebral fractures can be complex because of the altered physiology of old age, poor functional reserves, comorbidities, cognitive dysfunction, multipharmacy, and the like. Although most fractures can be managed conservatively, operative care is indicated in unstable fractures, polytraumatized patients, chronic painful posttraumatic deformities, neurological deficits, and pseudoarthrosis. Percutaneous cement augmentation techniques [vertebroplasty (VP) and kyphoplasty (KP)] are used in patients with failed conservative care.7,8 Patients with unstable fractures, chronic pseudoarthrosis, neurological deficit, and vertebral deformities usually require spinal instrumentation. Instrumentation surgeries can be difficult for reasons including poor bone quality, preexisting spinal deformity, fragile skin, restrictive lung disorders, and coexisting degenerative spinal diseases such as diffuse idiopathic skeletal hyperostosis (DISH), ankylosing spondylitis, and degenerative spondylosis.

Epidemiology of Osteoporotic Fractures

Osteoporosis is characterized by low bone mass, with consequent weakening of bone tissue and architecture and an increase in the risk of fracture.9 According to the World Health Organization classification, osteoporosis is defined by the bone mineral density (BMD) assessment at the hip or lumbar spine, which is less than or equal to 2.5 standard deviations below the mean BMD of a young-adult reference population.10 The estimated lifetime risk of acquiring an osteoporosis-related fracture of the spine, hip, or wrist after the age of 50 years is 40% in women and 13% in men.11

Clinical Features

Majority of osteoporotic fractures occur at the thoracolumbar junction and in the midthoracic region. Although only approximately 30% of vertebral fractures are recognized at the time of injury, most of the remaining “clinically silent” fractures heal without untoward sequelae.12 Gehlbach et al13 observed that 1 or more asymptomatic vertebral fractures were noted in 14% of 934 chest x-ray films obtained in women aged 60 years and older.

Most osteoporotic fractures occur following minor falls or trivial day-to-day activities with no significant trauma. In the acute stage, there is pain in the affected region that is aggravated by activities but the pain usually improves in 2–3 weeks. As the collapsed anterior part of the vertebral body heals, the spine gradually bends forward into kyphosis. Depending on the extent of osteoporosis, further collapse of the vertebral body can occur. Finally, fish–shaped vertebra can result with or without chronic instability. Progressive kyphosis due to multiple fractures and sagittal imbalance can result in muscle fatigue and pain. In a prospective study, it was observed that the overall function declined among patients with vertebral fractures similar to those with hip fractures.14 Apart from chronic pain, sleep disturbance, depression due to decreased mobility and self-esteem, and poor quality of life are all reported sequelae of these fractures. Furthermore, recent studies have observed a relationship between osteoporotic kyphotic deformity in elderly and gastroesophageal reflux disease.15 Vertebral fractures are also associated with increased mortality, presumably due to restrictive pulmonary function, decreased mobility, and cardiovascular disease.16

Evaluation of Osteoporotic Fractures

In all patients with osteoporotic vertebral fractures, the clinician should consider secondary causes of osteoporosis, such as osteomalacia, multiple myeloma, hyperthyroidism, hyperparathyroidism, and renal failure.17 Plain anteroposterior and lateral radiographs are the initial imaging study, which show compression of the anterior aspect of the vertebrae resulting in the classic wedge-shaped vertebral body. Generalized osteoporosis/osteopenia and healed vertebral collapse may be seen in other vertebrae.

Underlying degenerative pathologies, old osteoporotic fractures, and nonspecific clinical symptoms may impede the informational value of plain radiographs. In such situations, magnetic resonance imaging (MRI) Short Tau Inversion Recovery (STIR) sequences help to detect fresh osteoporotic vertebral fractures.18 MRI is a sensitive tool to diagnose osteoporotic fractures because it identifies vertebral body edema, which may be unrecognized in conventional radiographs. MRI is also useful in patients with chronic persistent pain and will show typical fluid signal within the vertebral body diagnostic of pseudoarthrosis (Fig. 1). Tsujio et al5 analyzed whether radiographic and MRI features of acute vertebral fractures can help in predicting future pseudoarthrosis. All the 350 patients were treated conservatively, and at the end of 6-months, 48 patients were classified as having nonunion. Multivariate logistic regression analysis revealed that a vertebral fracture in the thoracolumbar spine, presence of a middlecolumn injury (indicative of a burst fracture), and a confined high-intensity or a diffuse low-intensity area in the fractured vertebrae on T2-weighted magnetic resonance images were significant risk factors for nonunion.

F1
FIGURE 1.:
Imaging a patient with vertebral compression fracture. Anteroposterior and lateral radiographs (A, B) show fractured L1 vertebral body with evidence of nonhealing. The black shadow within the vertebral body indicates nonunion. Sagittal (C) and axial (D) T2 MRI images show a corresponding fluid signal within the body indicative of pseudoarthrosis.

Computed tomographic scan is helpful in identifying the specific morphology of vertebral fractures that are not well visualized on plain films, in demonstrating injury to the posterior vertebral wall, and in the evaluation of the integrity of the posterior bony elements (Fig. 2). BMD studies are useful for evaluating the severity of osteoporosis and in advising patients on the likelihood of subsequent fractures. BMD assessment through dual energy x-ray absorptiometry (DEXA) of the hip and spine is the technology used to establish or confirm a diagnosis of osteoporosis, predict future fracture risk, and monitor patients in the long run.

F2
FIGURE 2.:
Anteroposterior (A) and lateral (B) radiographs of the thoracolumbar spine show an osteoporotic compression fracture of T12 vertebra, resulting in severe collapse and local kyphosis. Sagittal (C) and axial (D) computed tomographic images show posterosuperior corner, retropulsion of the fractured vertebra, and an intravertebral vacuum phenomenon.

Classification of Osteoporotic Vertebral Fractures

Up to now, no classification of osteoporotic vertebral fractures has gained international acceptance.19–23 Currently used classifications like TLICS, AO-Magerl, and AOSpine have been developed based on nonosteoporotic trauma patients and therefore do not address osteoporotic fractures specifically. Sugita et al23 have described a prognostic classification system for osteoporotic vertebral fractures based on their study of 135 fractures in 73 patients. The fractures were classified into 5 types based on the initial lateral radiographs performed after injury: (1) the swelled-front type, in which 50% of the anterior wall of the vertebral body was swollen, (2) the bow type, in which the anterior wall was pinched in and endplate was falling in, resembling the bow of a ship, (3) the projecting type, in which 50% of the anterior wall of the vertebral body was projecting and which appeared as a small bulge without a fracture line, (4) the concave type, in which the endplate was falling in and the anterior wall was intact, and (5) the dented type, in which the center of the anterior wall of the vertebral body was dented and fracture line was shown in the vertebral body. They observed that the swelled-front–type, bow-shaped–type, and projecting-type fractures had a poor prognosis with higher incidence of late collapse and often showing a vacuum cleft.

Schnake et al24 have examined 707 osteoporotic fractures in a prospective multicenter trial and proposed a new morphological osteoporotic fracture classification (OF classification) with 5 subgroups: OF 1: no vertebral deformation (vertebral body edema in MRI-STIR only), OF 2: deformation without or with only minor involvement of the posterior wall (<1/5), OF 3: deformation with distinct involvement of the posterior wall (>1/5); OF 4: loss of vertebral frame structure, vertebral body collapse, or pincer type fracture, and OF 5: injuries with distraction or rotation. Interobserver reliability of the classification was calculated after evaluation of 146 fractures by 6 raters and was found to be substantial with a Kappa of 0.63.25

Management

Conservative Treatment of Osteoporotic Fractures

The care of patients with vertebral fractures includes pain management, early mobilization and rehabilitation, and prevention of further fractures. Acute pain due to osteoporotic fractures usually resolves by 10–12 weeks. Especially, in the early phase, effective analgesia is necessary to allow early mobilization of the usually elderly patients. Bed rest should be short as possible to avoid complications of recumbence. Oral analgesics including acetaminophen, tramadol, codeine, and nonsteroidal anti-inflammatory drugs (diclofenac, aceclofenac, ibuprofen, ketoralac) are standardly prescribed.

Medication used for the treatment of osteoporosis may also provide pain relief in patients with an acute osteoporotic fracture. Calcitonin, administered either by subcutaneous or intranasal routes, can be beneficial in reducing pain from acute vertebral fractures. A recent systematic review and meta-analysis on the use of calcitonin for patients with a painful osteoporotic fracture (n = 246 patients from 5 randomized controlled trials) has supported the use of calcitonin as an effective analgesic for acute pain in recent osteoporotic fractures.26 Bisphosphonates, popularly used in the management of osteoporosis, have also been used in the management of pain. In a randomized, double-blinded, controlled trial on the efficacy of intravenous pamidronate, it was observed that pamidronate provided rapid and sustained pain relief in patients with an acute osteoporotic fracture as compared with a placebo.27 Furthermore, 2 meta-analyses have shown that teriparatide can be used for pain management in patients with acute fractures. Patients randomized to teriparatide had less back pain compared with a placebo or alendronate during a 30-month follow-up period.28,29

Controversy exists regarding the role of bracing in acute painful osteoporotic fractures. Conventionally, a hyperextension orthosis or a thoracolumbar sacral orthosis is usually prescribed for these fractures. Pfeifer et al30 had performed a prospective randomized study on patients with postmenopausal osteoporotic fractures using a new type of spinal orthosis and reported an increased trunk muscle strength and improvement in posture and body height in patients treated with an orthosis. The authors used a rucksack-like orthosis with straps over both shoulders, reminding the patient to extent their back. The orthosis has only minor stabilizing effects on the trunk, but it has a stable part in posterior midline to extend the upper body.

Once the acute pain improves, patients are advised core strengthening exercises for the abdomen and paraspinal muscles. Studies have shown that structured exercise programs for elderly patients after a vertebral fracture have decreased the use of analgesics, improved the quality of life, and increased BMD.31 Regular activity and muscle strengthening exercises have been shown to decrease future vertebral fractures and chronic back pain.32

Once a patient has suffered an osteoporotic fracture, then it is recommended to initiate pharmacologic treatment, irrespective of the BMD scores. Current Food and Drug Administration–approved pharmacologic options for osteoporosis are bisphosphonates (alendronate, ibandronate, risedronate, and zoledronic acid), calcitonin, estrogen agonist/antagonist (raloxifene), estrogens and/or hormone therapy, tissue-selective estrogen complex (conjugated estrogens/bazedoxifene), parathyroid hormone 1–34 (teriparatide), and receptor activator of nuclear factor kappa-B (RANK) ligand inhibitor (denosumab). Combinations of these drugs are not used. In a recent double-blinded, randomized, controlled trial, the use of oral calcitonin was not found to be more beneficial than calcium and vitamin D supplements in the management of osteoporosis.33 There is no uniform recommendation that applies to all patients, and the duration of treatment need to be individualized. Repeat BMD assessment is performed 2–3 years after the initiation of osteoporosis treatment based on which further decision to continue treatment is made. Postmenopausal women and men aged 50 years and older (candidates at risk for osteoporosis) are advised to include adequate amounts of total calcium intake (1000–1200 mg/d), vitamin D intake (800–1000 IU/d), regular weight-bearing and muscle strengthening exercise, and methods to reduce the risk of falls and advise on cessation of tobacco smoking and avoidance of excessive alcohol intake.

Operative Treatment of Osteoporotic Fractures

In approximately 15%–35% of patients, the fracture may not heal completely, resulting in a pseudoarthrosis.5,6 Patients who continue to have severe pain and who do not respond to conservative treatment may be candidates for percutaneous vertebral augmentation procedures. Percutaneous VP involves injecting bone cement into the collapsed vertebra to stabilize and strengthen the fractured vertebral body (Fig. 3). KP involves an initial insertion of an inflatable balloon through the pedicle into the vertebral body to reexpand the collapsed vertebra followed by cementing. KP was developed as an alternative to VP to reduce chances of cement leakage and improve the vertebral height. Meta analytic studies have shown that VP and KP reduce pain comparably, and patient functional outcomes have been similar in most series.34,35 But KP is 10–20 times more expensive than a VP procedure.36 In a systematic review by Akbar et al,37 cement leakage was significantly higher with VP (40%) than with KP (8%), and 3% of VP leaks were symptomatic, whereas no KP leaks were reported to be symptomatic37 (Fig. 4). Eck et al38 performed a meta-analysis of 168 studies to compare both procedures for safety and efficacy and showed that although both techniques were comparable in terms of pain relief, the risk of new fractures was 17.9% with VP versus 14.1% with KP and the risk of cement leak was 19.7% with VP versus 7.0% with KP.

F3
FIGURE 3.:
Management of a painful osteoporotic vertebral fracture with percutaneous VP. Lateral thoraco-lumbar (A) radiograph shows a compression fracture of the L1 vertebra. Sagittal T2 (B) and T1 (C) MRI images show edema and collapse of the L1 vertebra involving the superior endplate. The patient was treated by VP. Note the good fill of the cement within the body in the postoperative AP (D) and lateral (E). radiographs.
F4
FIGURE 4.:
Cement leakage in VP. An osteoporotic fracture at the T12 vertebra is seen in the sagittal MR (A) and lateral (B) radiographs. The patient has been treated by VP at 3 levels (wrongly). Note that the cement has extravasated into the spinal canal and paravertebral regions (C, D). Despite this, the patient had intact neurology.

The role of percutaneous cementing techniques in both acute and chronic fractures has been controversial. To assess the safety and efficacy of VP for osteoporotic fractures, Buchbinder et al39 performed a level-I, multicenter, randomized, double-blinded, placebo-controlled trial in which participants with painful osteoporotic fractures that were of less than 1 year duration were randomly assigned to undergo VP or a sham procedure. Of 78 participants, they observed VP did not result in a significant advantage in any outcome at 1 week, and 1, 3, or 6 months. In another study by Kallmes et al,40 131 patients with painful osteoporotic fractures were assigned to undergo either VP or a simulated procedure (control group). Although both groups had immediate improvement in disability and pain scores at 1 month, there was no significant difference between the 2 groups in either the disability score or the pain rating. Based on these 2 level-I studies, the American Academy of Orthopaedic Surgeons has recommended strongly against the use of VP for patients who present with an osteoporotic spinal compression fracture on imaging with correlating clinical signs and symptoms and who are neurologically intact.41 But the methodology of the trials had been criticized by many authors. Boszczyk42 questioned the procedural details of the 2 studies, specifically with regard to injected Polymethyl Methacrylate (PMMA) volumes, which was an average fill volume of 2.8 ± 1.2 mL per level. He noted that a minimum fill volume of 13%–16% of the vertebral body volume is essential for an appropriate biomechanical effect to restore the strength of a vertebra, which is a minimum of 4 mL PMMA for any thoracic or lumbar vertebra. Similarly, Heini43 pointed out that these studies did not take the technical aspects of the treatment into consideration, and it seems probable that the amount of filler material chosen was too small so that the treatment group also received placebo.

In a recent meta-analysis by Guo et al,44 the safety and efficacy of surgical and nonsurgical interventions for osteoporotic fractures was evaluated. Sixteen reports (11 randomized controlled trials) were considered, and the authors observed that compared with conservative treatment, surgical treatment was more effective in decreasing pain, and no significant mid-term and long-term differences in physical function and quality of life was observed.

VP in the acutely fractured vertebral body is performed in patients who continue to have persistent pain despite adequate analgesia. Although there are theoretical concerns of cement leakage in the acutely fractured vertebral body, Yang et al45 in a prospective, randomized, controlled trial of 107 patients (56 in VP and 51 in conservative treatment) noted that VP resulted in much greater pain relief, more satisfaction, and lower complication rates from postoperative day 1 till 1 year (all P < 0.0001). Recently, Clark et al46 conducted a multicenter, randomized, double-blinded, placebo-controlled trial in patients with osteoporotic vertebral fractures of less than 6-week duration, randomized between VP or placebo injection. Among the total 120 patients enrolled, 24 (44%) patients in the VP group and 12 (21%) in the control group had a pain score of <4/10 at 14 days (P = 0.011). They concluded that VP is superior to placebo intervention for pain reduction in patients with acute osteoporotic spinal fractures of less than 6-week duration.

Geriatric patients who have chronic vertebral pseudoarthrosis with instability or neurological deficit, intractable pain with collapsed vertebra, and kyphotic deformity require spinal instrumentation47 (Fig. 5). Shikata et al48 have demonstrated good results with posterolateral decompression, reconstruction, and stabilization in osteoporotic fractures with neurological deficit. Ataka et al49 postulated that the instability at the fracture site is the main factor causing neurological deficits in patients with osteoporotic thoracolumbar fractures, contrary to the popular belief of neural compression by bone fragments. They studied 14 consecutive patients who had incomplete neurological deficits following osteoporotic fractures and performed long segment posterior instrumented fusion without any canal decompression. They observed that there was no implant failure at a mean follow-up period of 25 months, and in all patients, neurological improvement was obtained by at least 1 modified Frankel grade.

F5
FIGURE 5.:
L3 osteoporotic vertebral collapse in a 73-year-old man, who presented with instability back pain and sudden buckling of the knees while walking. He had early bladder dysfunction. The lateral radiograph of the lumbar spine, and the computed tomography and MRI images (A–D) show osteonecrosis in the L3 body (evident by gas shadow and fluid in the vertebra) and retropulsion into the spinal canal. The patient was treated by posterior stabilization and VP of L3 vertebra as shown in the AP (E) and lateral (F) radiographs.

The presence of degenerative changes such as facet arthropathy, hypertrophied joints, presence of osteophytes, DISH-like changes, etc, poses difficulties during surgical exposure, identification of standard anatomical landmarks, and pedicle screw insertion. Despite being the most rigid form of posterior instrumentation, pedicle screws can have poor fixation in patients with osteoporosis. For additional supplementation, sublaminar wires and pedicle augmentation using materials such as PMMA, calcium phosphate, or calcium hydroxyapatite can be used.50,51 From a surgical point of view, augmentation of pedicle screws with PMMA is the most effective and practical technique to improve the hold of the screws in the bone. However, the surgeon should be wary that the application of PMMA carries risks of cement leakage with possible embolic insults. The combination of KP/VP and instrumentation, so called hybrid stabilization, can effectively shorten the entire construct and therefore help to minimize the surgical trauma. Additionally, percutaneous instrumentation further decreases the invasiveness of the procedure.

CONCLUSIONS

The prevalence of osteoporotic vertebral fractures steadily increases with advancing age. It affects approximately 25% of all postmenopausal women and older men aged >70 years. Most fractures heal well with conservative care, which includes rest, analgesics, antiosteoporotic medications, and bracing. Patients with persistent pain, nonunion, and progressive deformity will benefit from percutaneous intervention procedures like VP and KP. More unstable fractures, chronic nonunions, and those with neurological deficit require spinal instrumentation surgeries. Prevention of future vertebral fractures is a key thing where in appropriate medical management with antiosteoporotic medications, risk stratification, and counseling play a major role. Early detection of osteoporosis through diagnosing and treating predisposing factors, identifying high-risk patients, and educating patients about osteoporosis and measures to prevent falls are important from a socioeconomic perspective.

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Keywords:

osteoporosis; vertebral fractures; vertebroplasty; kyphoplasty

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