Osteoporosis in Spinal

Surgery

Clifford Lin, MD

Assistant Professor

Department of Orthopaedics and Rehabilitation

Oregon Health & Science University

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Outline

Definitions

Bone metabolism

Epidemiology

Classification

Presentation

Diagnosis

Management

Techniques in Spinal Fixation

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Osteoporosis

Age-related decrease in bone mass secondary to unbalanced bone metabolism characterized by:

Microarchitectural deterioration of bone tissue

Skeletal fragility

Increased risk of fractureOHSU

Bone Metabolism

Osteoblasts

Mononucleated cells

Osteoblasts

Mononucleated cells

Synthesize unmineralized bone matrix Type 1 Collagen

Proteoglycans

Osteoblasts

Mononucleated cells

Synthesize unmineralized bone matrix Type 1 Collagen

Proteoglycans

Synthesize bone mineral Hydroxyapatite

Deposited into Type 1 collagen

Osteoblasts

Mononucleated cells

Synthesize unmineralized bone matrix Type 1 Collagen

Proteoglycans

Synthesize bone mineral Hydroxyapatite

Deposited into Type 1 collagen

Osteoblasts embedded in the matrix become osteocytes

Maintain the bone matrix

Osteoblasts

Mononucleated cells

Synthesize unmineralized bone matrix Type 1 Collagen

Proteoglycans

Synthesize bone mineral Hydroxyapatite

Deposited into Type 1 collagen

Osteoblasts embedded in the matrix become osteocytes

Maintain the bone matrix

Blastic phase takes 80 days

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Bone Metabolism

Osteoclasts

Multinucleated cells

Bind to bone integrins to form resorption cavity (Howship lacuna)

Creates acidic microenvironment that dissolves hydroxyapatite mineral

Clastic phase takes 20 days

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Regulation of Bone Metabolism

PTH

Secreted in response to

↓ ionized calcium

Increases reabsorption of calcium in kidneys

Activates Vitamin D

Stimulates bone resorption by osteoclasts

Vitamin D

Increases absorption of calcium from GI

Calcitonin

Inhibits osteoclast activity and favors storage of calcium in bone

Gonadal hormones

Stimulate osteoblast proliferation and synthesis of bone

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Epidemiology

The Recent Prevalence of Osteoporosis and Low Bone Mass in the United States Based on Bone

Mineral Density at the Femoral Neck or Lumbar Spine

Journal of Bone and Mineral Research

Volume 29, Issue 11, pages 2520-2526, 20 OCT 2014 DOI: 10.1002/jbmr.2269

http://onlinelibrary.wiley.com/doi/10.1002/jbmr.2269/full#jbmr2269-fig-0001

Per

cen

tage

of

adult

s ove

r ag

e 50

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Epidemiology

The Prevalence of Osteoporosis and Low Bone Mass in the United States Based on Bone Mineral

Density among Men and Women

Bone Health and Osteoporosis: A Report of the Surgeon General.

Office of the Surgeon General (US).

Rockville (MD): Office of the Surgeon General (US); 2004.

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EpidemiologyMean Bone Mineral Density among Men and Women by Age and Ethnicity

Bone Health and Osteoporosis: A Report of the Surgeon General.

Office of the Surgeon General (US).

Rockville (MD): Office of the Surgeon General (US); 2004.

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Economic Impact

Bone Health and Osteoporosis: A Report of the Surgeon General.

Office of the Surgeon General (US).

Rockville (MD): Office of the Surgeon General (US); 2004.

2002 Annual Direct Care Expenditures (Hospital and Nursing Home Care) $17 billion dollars

$47 million dollars daily

7% of all healthcare costs among women 45 and older

2030 Estimates $60 billion dollars

$154 million dollars daily

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Classification

Primary Osteoporosis Occurs as a result of aging

Slow phase

Occurs in both men and women

Due to impaired Vitamin D metabolism by kidneys

Bone mass decreases at rate of 0.3% -0.5% per year

Accelerated phase

Occurs only in post-menopausal women

Due to loss of estrogen and increased bone resorption

Bone mass decreases at rate of 2% -3% per year

Lasts ~5 years

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Primary Osteoporosis

Protective Factors Higher peak bone mass – attained in mid 30s

Balanced diet

Regular exercise

Gonadal hormones

Risk Factors Late menarche or premature menopause

Poor calcium intake

Sedentary lifestyle

Tobacco and alcohol use

Gender

Ethnicity

Family History

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Secondary Osteoporosis

Secondary Osteoporosis Results from any medical condition or medication that

contributes to accelerated loss of bone density

Higher prevalence in men

Medical conditions

Endocrinopathies

Hypogonadism

Hyperthyroidism

Gastrointestinal

Inflammatory bowel disease

Celiac sprue

Hematological

Bone marrow dysplasia

Chronic nutritional deficiencies

Medications

Corticosteroids

Anticonvulsants

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Risk Factors

Orthobullets, - https://www.orthobullets.com/basic-science/9032/osteopenia-and-osteoporosis

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Presentation

Asymptomatic Incidental compression fractures

Generalized osteopenia without fracture

Symptomatic Painful fractures

Spine – 700,000

Comprise half of all osteoporotic fractures

Back pain

Rarely associated with neurological compromise

Pain resolves once fracture heals

Multiple fractures can lead to progressive kyphosis and sagittal imbalance

Other locations

Hip – 300,000

Wrist – 250,000

Other Locations – 250,000

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Diagnosis

DEXA

Assesses bone mineral density at areas

prone to osteoporotic fractures

(ie, spine and hip)

Procedure

Measures values in lumbar spine from

L1-L4, total hip, and femoral neck

Computes T score and Z score

Analysis

T score

BMD for normal healthy young controls at peak bone mas

Estimates the number of SDs the patient’s BMD is below this value

Z score

BMD for healthy gender and age-matched controls

Estimates number of SDs the patient’s BMD is below expected value for age

Cannot be used to diagnosis osteoporosis

Useful for screening for secondary causes

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Medical Management

Prevention

Good nutrition

Vitamin D and calcium supplementation

1500 mg/day calcium

2000 IU/day Vitamin D3

Weight-bearing, impact exercises

Smoking cessation

Medications

Bisphosphonates

Estrogen hormonal replacement

Calcitonin

PTH

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Medical Management

Bisphosphonates

First-line drug

Inhibit osteoclastic activity in resorption cavity

Efficacy

Increase bone mass by 5% at 2 years

Reduce risk of spinal and hip fractures by 50%

Side effects

Dyspepsia, osteonecrosis of jaw

Estrogens

Estrogen HRT

Increases bone mass in post-menopausal women

Also significantly increases risk of breast cancer, endometrial cancer, stroke, and DVT.

Not recommended for treatment of osteoporosis

SERMs

Activate estrogen receptors in bone and inhibit osteoclastic activity

Have anti-estrogenic effects in breast and endometrium

Reduces risk of vertebral body fractures

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Medical Management

Calcitonin

Intranasal formulation

Inhibits osteoclast activity

Efficacy

Not as efficacious as other agents in increasing BMD

Reduces risk of vertebral body fractures

Analgesic property makes it useful in treating painful vertebral compression fractures

PTH (Teriparatide)

Anabolic agent

Intermittent doses stimulate osteoblastic activity

Efficacy

Increases bone mass by 10% over 2 years

Reduces risk of all osteoporotic fractures by over 50%

Contraindications

Paget disease, previous skeletal radiation, osteosarcoma

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Surgical Management

Osteoporotic vertebral compression fractures

Bedrest

Pain Management

Bracing

Vertebroplasty and Kyphoplasty

Decrease pain

Improve mobility and function

Indications

Chronically painful VCFs in patients who have failed 4-6 weeks conservative therapy

Contraindications

Fractures with disruption of posterior vertebral wall

Neurological deficit

Complete collapse of vertebral body

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Vertebroplasty

Technique

Described in 1987

Percutaneous transpedicular needle insertion into VB

PMMA injected to fill VB

Injection terminated if extra-VB extravasation occurs

Outcomes

70-90% experience pain improvement in non-randomized studies

Complications

Extravertebral extravasation occurs in 30-65%

Clinically significant complications occur in 10%

Increased pain, radiculopathy, spinal cord injury, pulmonary embolism, rib fracture, infection

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Kyphoplasty

Technique

Percutaneous insertion of inflatable

bone tamp into VB

Tamp elevates the depressed VB and

creates cavity

Cavity is filled with PMMA

Advantage

Improves VB height and sagittal

alignment

Outcomes

90% experience pain improvement in

non-randomized studies

Complications

Extravertebral extravasation occurs in

less than 10%

Clinically significant complications

occur in less than 2%

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Study Design

Multi-center double-blinded randomized clinical trial assigning 131 patients with

1-3 osteoporotic compression fractures to undergo either vertebroplasty or

placebo procedure between 2004 and 2008

Assessed outcomes at 1 month

Outcomes

Both groups experienced improvement in pain and disability

No difference in pain or pain-related disability between the two groups

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Study Design

Multi-center double-blinded randomized clinical trial assigning 78 patients with 1-

2 osteoporotic fractures to undergo either vertebroplasty or placebo procedure

between 2004 and 2008

Assessed outcomes at 1 week, 1 month, 3 months, and 6 months

Outcomes

Both groups experienced improvement in pain, physical function, quality of life

No benefit of vertebroplasty over placebo

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Osteoporosis and Spinal Fusion

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Methods

Identified 2293 patients with adult spinal deformity undergoing thoracolumbar fusion > 8 levels

Multivariate analysis of risk factors for revision surgery at 1 and 5 years

Results

44% of patients had osteoporosis

10.5% revision rate at 1 year and 18.5% revision rate at 5 years

Osteoporosis significantly associated with revision surgery in univariate analysis at 1, 2, 3, 4, and 5 years

Osteoporosis was significantly associated with revision surgery in multivariate analysis at 5 years

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Osteoporosis and Spinal Fixation

Strategies Screw Placement

Screw Augmentation with Hooks

Screw Augmentation with Cement

Multiple Points of Fixation

Expandable ScrewsOHSU

Screw Placement

Increase Screw Length Greater pullout strength

Increase Screw Diameter Greater pullout strength

Bicortical screws 30% greater pullout strength

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Cement

PMMA bone cement Can be injected into the pedicle around the screw

Increases screw pullout strength by three-fold

Risks

Extraosseous extravasationOHSU

Multiple Fixation Points

Fixation Include additional levels in construct

Decreases stress on each individual screw

Reduces risk of pullout failure at each segment

Expandable Screws Distal half split lengthwise

Fins can be opened as screw

advances

Increases diameter of tip by 2 mm

Superior in pullout strength to

standard pedicle screws

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Conclusions

Osteoporosis matters

Ensure patient is appropriately treated medically

Vertebroplasty is controversial

Many techniques available to reduce risk of construct failure

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Thank YouOHSU