AAOS Comprehensive Orthopaedic Review

Section 7 - Spine

Chapter 71. Osteoporosis of the Spine and Vertebral Compression Fractures

I. Introduction

A. Bone mass and bone density

 

1. With age, both total bone mass and bone mineral density (BMD) decrease.

 

2. BMD peaks between 25 and 30 years of age.

 

3. BMD declines at a rate of 0.3% to 0.5% per year, but the rate can be 2% to 3% per year in women during the first postmenopausal decade. (10% of cortical and 30% of trabecular bone mass may be lost.)

 

4. BMD correlates strongly with bone strength and is a predictor of fracture risk.

 

5. The World Health Organization defines osteoporosis as BMD with a T-score at or below -2.5 (2.5 SDs below the young adult mean BMD).

 

B. Pathogenesis of osteoporosis

 

1. Osteoporosis is a condition in which the bone is normal but of reduced quantity. (In osteomalacia, on the other hand, the bone is abnormal bone but of normal quantity.)

 

2. The cortices are thinned, and the cancellous bone has decreased trabecular continuity.

 

3. Bone metabolism is uncoupled, with bone resorption outpacing bone formation.

 

4. Reduced BMD and prior compression fractures are the biggest risk factors for future fractures.

 

C. Epidemiology and problems of osteoporosis

 

1. The biggest problem associated with osteoporosis is fragility fractures.

 

2. Although hip fractures get more attention, the most common site for osteoporotic fractures is the spine.

 

3. Approximately 700,000 vertebral compression fractures (VCFs) occur annually in the United States.

 

a. The lack of attention to VCFs has been partly due to the fact that no effective orthopaedic treatment was available; this has changed with the advent of percutaneous vertebral cement augmentation procedures.

 

b. 25% of patients with osteoporotic VCFs become sufficiently or intractably symptomatic to the extent that they will seek medical attention.

 

c. These account for approximately 66,000 physician visits and 70,000 hospitalizations annually in the United States.

 

d. Some form of transitional care facility admission is needed in half of these hospitalizations.

 

D. Fracture consequences and societal impact

 

1. In VCF patients, the 2-year mortality is increased 1.5 times, which is equal to that for patients with hip fractures.

 

2. Because these patients are elderly, multiple medical comorbidities often exist.

 

3. The socioeconomic cost of VCFs is immense. The economic cost of VCF treatment in the United States may be more than $15 billion annually.

 

4. The loss of productivity, transition to functional dependency, and aggravation of medical comorbidities add to the social and economic burden.

 

5. The loss of vertebral height and ensuing local kyphosis contribute to reduction of standing height, compression of the abdominal cavity (which can lead to early satiety and weight loss), and reduced pulmonary function.

 

6. Each thoracic VCF can be expected to cause a 9% reduction in predicted forced vital capacity of the lung.



II. Clinical Evaluation

A. History and physical examination

 

1. Because of medical risk factors in this patient population, a comprehensive history and physical examination is always necessary.

 

2. The possibility of a tumor causing the pathologic VCF should always be entertained. An oncologic origin may be indicated by the following:

 

a. Fractures above the T5 level

 

b. Atypical radiographic findings

 

c. The presence of constitutional symptoms

 

d. Failure to thrive

 

3. Less than half of the time, the patient can recall a specific incident related to the timing of the fracture.

 

4. The pain is usually well localized to the fracture level.

 

a. The pain is usually posterior, and can often be reproduced by deep palpation of the spinous process of the fractured vertebra.

 

b. The pain may wrap around the trunk, especially if the fracture irritates the exiting nerve root.

 

c. The pain is usually mechanical in nature, and worse with load-bearing positions such as standing and flexing.

 

5. Neurologic signs and symptoms are rare but need to be ruled out because such findings may require open surgical procedures (decompression and/or stabilization).

 

6. A 9% reduction in predicted forced vital capacity of the lung can be expected for each thoracic VCF.

 

B. Further medical workup

 

1. Involving one or more medical specialists in the care, whatever the reason for the fracture, is always recommended.

 

2. A complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate, and urine and serum protein electrophoresis may assist in the detection of an underlying infectious, metabolic, or malignant cause.

 

3. Some authors recommend a tissue (core) biopsy for every VCF patient who fails nonsurgical management and requires surgical treatment (at least during the first surgical treatment).



III. Diagnostic Imaging

A. Plain radiographs

 

1. Plain radiography is the initial modality of choice for VCFs.

 

[

Figure 1. Compression fractures in the thoracic and lumbar spine. A, Typical wedge compression fracture seen in the thoracic spine. B, Typical biconcave compression fracture in the lumbar spine after injection of cement.]

2. These patients often have diffuse spinal demineralization, manifesting as decreased bony opacity.

 

3. A VCF is radiographically defined as loss of anterior, middle, or posterior vertebral height by 20% or at least 4 mm.

 

4. There is a bimodal anatomic distribution of VCFs, with most occurring at the midthoracic or thoracolumbar spine.

 

5. VCFs are described as wedge, crush, or biconcave but frequently do not conform to these descriptions.

 

a. Biconcave VCFs are more common in the lumbar spine.

 

b. Wedge VCFs are more common in the thoracic spine (Figure 1).

 

6. VCF severity can be graded as:

 

a. Mild (20% to 25% loss of anterior, middle, or posterior vertebral height)

 

b. Moderate (25% to 40% height reduction)

 

c. Severe (>40% height reduction)

 

B. Magnetic resonance imaging

 

1. MRI is useful when a VCF is suspected clinically but the radiographs are not definitive (

Figure 2); even without any fracture deformity, vertebral bony edema may be obvious on MRI.

 

2. MRI is also a useful confirmatory tool, as it can differentiate unhealed (and presumably painful) VCFs (bony edema is present) from healed chronic (and presumably nonpainful) VCFs.

 

3. Although edema can usually be seen on T1 and T2 sequences, it is most obvious on fat-suppressed short T1 inversion recovery (STIR) sequences.

 

[Figure 2. Images of the spine of a patient with symptoms consistent with a compression fracture of the spine. A, Radiograph does not show a deformity. On T1- (B) and T2-weighted (C) MRI, the same spine is seen to have bony edema indicative of a pathologic process or fracture.]

C. Bone scan

 

1. Like MRI, nuclear bone scans are useful to differentiate healed versus nonhealed fractures.

 

2. Bone scans are less specific than MRI, however, because scintigraphic uptake may be elevated for up to 1 year after fracture, even with treatment.

 

D. Computed tomography scans

 

1. CT scans can determine acute versus chronic fractures to a certain extent by the sharpness of fracture lines.

 

2. CT scans are not useful for diagnosing stress fractures without fracture lines or cleavage.

 

3. CT scans may be useful, however, to better study the fracture anatomy before cement augmentation procedures to minimize the risk of extravasation. They are also useful to analyze cement containment after such procedures.



IV. Differential Diagnoses of Tumors

A. Incidence

 

1. The spine is a frequent site of tumor metastases, probably because of the numerous valveless epidural veins in the spine referred to as Batson's venous plexus.

 

2. Metastatic tumors of the spine occur mostly in the thoracic spine (60%), versus 20% each in the cervical and lumbar spine.

 

B. Primary benign spine tumors

 

1. Enostosis (bone island)

 

2. Osteoid osteoma

 

3. Osteoblastoma

 

4. Aneurysmal bone cyst

 

5. Osteochondroma

 

6. Giant cell tumor

 

C. Primary malignant spine tumors

 

1. Chondrosarcoma

 

2. Ewing sarcoma

 

3. Osteosarcoma

 

4. Chordoma

 

5. Multiple myeloma

 

6. Solitary plasmacytoma

 

D. Metastatic tumors

 

1. Prostate cancer

 

2. Breast cancer

 

3. Lung cancer

 

4. Renal cell carcinoma

 

5. Gastric carcinoma

 

E. Diagnostic characteristics of tumor versus fracture

 

1. Blastic or lytic appearance is more common with tumor than with fracture.

 

2. Cortical involvement is more discrete in fracture lines than with tumor destruction.

 

3. Pedicular destruction (winking owl sign on AP radiograph) usually indicates tumor.

 

4. Presence of soft-tissue masses around the pathologic lesion implies tumor.

 

5. Existence of overlying skin changes implies tumor.

 

6. Multiple or noncontiguous vertebral involvement should raise suspicion for tumor.

 

7. Multiple myeloma/plasmacytoma may be cold (will not light up) on bone scan.

 

8. Any history of cancer should heighten suspicion of metastasis.



V. Nonsurgical Management

A. General management

 

1. Any patient with a fragility fracture should be treated aggressively for overall bone health. It is advisable to recruit the help of other health care professionals, including the primary care physician as well as other medical specialists, social workers, dieticians, and therapists as necessary.

 

2. Pharmacotherapy for osteoporosis can reduce osteoporotic fracture incidence by 50%, and is even more effective in reducing the risk of multiple fractures. Two main categories of drugs are used:

 

a. Anticatabolic therapies (hormone replacement, calcitonin, raloxifene, and the bisphospohonates [alendronate, ibandronate, risedronate])

 

b. Anabolic therapy (teriparatide)

 

B. Vertebral compression fractures

 

1. Fortunately, symptoms from most VCFs are self-limited. They respond to simple measures such as rest, activity modification, analgesics, and bracing.

 

2. The fracture pain usually resolves within a few months.

 

3. The disadvantages of extended activity modification and bracing, however, include muscular deconditioning and further bone loss due to lack of loading.

 

4. Physical therapy should begin as needed after the fracture and symptoms stabilize.



VI. Surgical Management

A. Indications

 

1. In two thirds of patients, symptoms from VCFs will subside in a few months without surgical intervention. There are several reasons not to wait this long, however, especially with the minimally invasive options now available.

 

a. Even if the pain becomes tolerable, some insidious effects of the vertebral fracture may persist indefinitely, as explained above in the section on fracture consequences.

 

b. If the pain is debilitating and restricts the patient from getting out of bed, it may be advisable to perform surgery to relieve the pain.

 

2. As with any fracture, pain from an unhealed VCF is believed to result from motion of the fragmented bone.

 

3. Progressive loss of vertebral height and kyphosis may be indications for percutaneous cement augmentation as well.

 

4. Neurologic issues that mandate open surgical treatment are rare in osteoporotic VCFs. However, decompression and stabilization may be needed in cases of neurologic compromise.

 

a. The particular surgical approach depends on the fracture location and characteristics.

 

b. Options are an anterior (corpectomy and fusion) or posterior (laminectomy and fusion) approach.

 

B. Surgical management

 

1. Goals

 

a. To address both the pain as well as possible adverse sequelae related to loss of height and sagittal alignment, the surgery should improve or arrest the deformity, as well as stabilize the fracture fragments.

 

b. The surgery should be as minimal as possible, with the least amount of potential complications, because patients in this age group are less than ideal surgical candidates.

 

c. Complications related to surgery in this population have been reported to be as high as 80%, so both the surgeon and patient should solicit the involvement of necessary medical specialists as early and often as possible.

 

2. Instrumentation in osteoporotic bone requires more points of fixation for stability than in normal bone, possibly larger screws, possible cement augmentation of screws, and addition of hooks or wires for additional fixation.

 

3. In the absence of neurologic involvement requiring surgical decompression, percutaneous methods of fracture reduction and stabilization are now available, as discussed below.



VII. Novel Technology

A. Percutaneous vertebral augmentation

 

1. Vertebroplasty and kyphoplasty are minimally invasive procedures that have revolutionized the treatment of intractably painful VCFs (

Figure 3).

 

2. The procedures consist of the percutaneous cannulation of the fractured vertebral body, followed by injection of bone cement for fracture stabilization, all under fluoroscopic guidance.

 

3. Vertebroplasty involves immobilizing the fracture in its unreduced fracture state (although some reduction may be obtained during prone positioning on the table).

 

4. Kyphoplasty, in contrast, involves trying to reduce the fracture via balloon inflation, increasing vertebral height and decreasing kyphotic angle.

 

5. Kyphoplasty is claimed to be safer due to the creation of an intervertebral cavity, which reduces the pressure of cement injection; however, this concept has been challenged.

 

6. Restoration of vertebral height restoration has not been proved to lead to decreased morbidity, improved global alignment, and better clinical outcomes.

 

7. A well-designed prospective head-to-head study comparing the two techniques has not yet been performed, but published studies show similar clinical results and complication rates.

 

8. Many studies have demonstrated the effectiveness of pain control with these techniques in subacute to chronic fractures, but a prospective, randomized, and controlled study for early cement augmentation of these fractures has not yet been conducted.

 

B. Results

 

1. Vertebroplasty and kyphoplasty result in almost immediate pain relief.

 

2. The exact mechanism of the effectiveness of these techniques is unknown, although the accepted understanding is that the elimination of micromotion of fracture fragments confers pain relief.

 

3. It is also postulated that the chemical and/or thermal neurolytic effect of the curing of the polymethylmethacrylate (PMMA) cement may help with pain relief.

 

[Figure 3. Drawings showing vertebroplasty and kyphoplasty. A, Vertebroplasty consists of simply injecting cement into the fractured vertebra. B, With kyphoplasty, reduction of the fracture with a balloon tamp is attempted before cement injection.]

4. Other reasons for back pain often coexist in this patient population, however, and therefore surgical treatment of the VCF may not result in complete pain relief.

 

C. Complications

 

1. Clinically significant complications associated with vertebroplasty and kyphoplasty are infrequent and are often due to technical error (such as inaccurate needle placement or inattention to cement injection).

 

2. When treating osteoporotic VCFs, this clinical complication rate can be expected to be less than 1%, but may be higher in other pathologic fractures because of greater compromise of bony integrity.

 

3. Actual cement extravasation rates have been reported to range from 7% to 70%, with most contemporary studies reporting approximately 10%. Obviously, the amount and location of the extravasation determines clinical sequelae.

 

4. Assessing whether fractures subsequent to vertebral augmentation are excessive requires an understanding of the natural history of fractures in the osteoporotic spine after one (or more) has already occurred.

 

5. Published rates of subsequent VCFs after percutaneous cement augmentation have ranged from 0 to 52%, over periods of 6 weeks to 5 years.

 

6. The risk of subsequent VCF is greater with increasing age, multiple medical comorbidities, multiple number of prevalent fractures, degree of spinal kyphosis, the rate of falling, and glucocorticoid intake.

 

7. The risk of adjacent-segment fracture may also be highest in the first month or two after augmentation, but then becomes closer to natural history later. This may be attributable to biomechanical adaptation of the adjacent vertebrae, as well as the effectiveness of medical treatment.



Top Testing Facts

1. VCFs are the most common fragility fractures in the elderly.

 

2. One fourth to one third of these VCFs become symptomatic enough to require medical care.

 

3. A 9% reduction in predicted forced vital capacity of the lung can be expected for each thoracic VCF.

 

4. Medical specialists and therapists need to be involved early on in the management of these patients.

 

5. Although the pain of a VCF is usually localized, radicular pain can occur with nerve root irritation.

 

6. Thoracic VCFs are usually wedge-shaped, whereas lumbar VCFs tend to be biconcave.

 

7. An MRI or bone scan is used to diagnose a radiographically ambiguous but clinically suspected VCF.

 

8. There are two main categories of antiosteoporotic drugs: anticatabolic and anabolic.

 

9. Vertebroplasty and kyphoplasty are highly effective minimally invasive surgical treatments of VCFs.

 

10. The rate of clinically significant complications with vertebroplasty or kyphoplasty is minimal.



Bibliography

Bouza C, Lopez T, Magro A, Navalpotro L, Amate JM: Efficacy and safety of balloon kyphoplasty in the treatment of vertebral compression fractures: A systematic review. Eur Spine J 2006;15:1050-1067.

Fribourg D, Tang C, Sra P, Delamarter R, Bae H: Incidence of subsequent vertebral fracture after kyphoplasty. Spine 2004; 29:2270-2276.

Kallmes DF: Randomized vertebroplasty trials: Current status and challenges. Acad Radiol 2006;13:546-549.

Lieberman IH, Dudeney S, Reinhardt MK, Bell G: Initial outcome and efficacy of "kyphoplasty" in the treatment of painful osteoporotic vertebral compression fractures. Spine 2001; 26:1631-1638.

Lindsay R, Silverman SL, Cooper C, et al: Risk of new vertebral fracture in the year following a fracture. JAMA 2001; 285:320-323.

Machinis TG, Fountas KN, Feltes CH, Johnston KW, Robinson JS: Pain outcome and vertebral body height restoration in patients undergoing kyphoplasty. South Med J 2006;99:457-460.

Mathis J, Deramond H, Belkoff S: Percutaneous Vertebroplasty. New York, NY, Springer, 2002.

McKiernan F, Faciszewski T, Jensen R: Quality of life following vertebroplasty. J Bone Joint Surg Am 2004;86:2600-2606.

Pradhan BB, Bae HW, Kropf MA, Patel VV, Delamarter RB: Kyphoplasty reduction of osteoporotic vertebral compression fractures: Correction of local kyphosis versus overall sagittal alignment. Spine2006;31:435-441.

Rao RD, Singrakhia MD: Painful osteoporotic vertebral fracture: Pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management. J Bone Joint Surg Am 2003;85:2010-2022.

Wu SS, Lachmann E, Nagler W: Current medical, rehabilitation, and surgical management of vertebral compression fractures. J Womens Health (Larchmt) 2003;12:17-26.