Introduction

Osteoporosis is a large-scale issue among the general population, affecting more than 10 million Americans. Osteoporosis-related fractures occur at a rate of 1.5 million/year in the US, and are a significant economic burden related to surgery, hospital stay, rehab, disability, and long-term care. Patients with rheumatic diseases are at increased risk of osteoporosis due to glucocorticoid and other medications, decreased activity, and decreased vitamin D.

Diagnosis

• Patients who have suffered a fragility or insufficiency fracture have osteoporosis by definition, regardless of DEXA (dual energy x-ray absorptiometry) results
  
• DEXA is used to diagnose patients with osteoporosis before a fragility fracture is sustained
  
  
  
  • Plain films are not appropriate for early screening of osteoporosis as 30% of bone mineral density is lost before this is apparent on x-ray!
  
  
• WHO criteria for osteoporosis based on DEXA (Table 10.1)
  
  
  
  • Osteoporosis if T score is ≤ −2.5
    
  • Severe osteoporosis if T score is ≤ −2.5 and presence of fragility fracture
    
  • Osteopenia if T score is between −1 and −2.5
  
  
• Limitations of DEXA scanning
  
  
  
  • WHO criteria for osteoporosis are based on a postmenopausal, white female study population; applicability to other ethnic groups or males is unknown
    
  • Peripheral sites of DEXA scanning (i.e. wrist) are less sensitive than central sites (hip, spine); if suspicion is high, a normal study at the wrist should prompt testing of central sites for osteoporosis
    
  • Low bone mineral density (BMD) is not always primary osteoporosis and may indicate another medical condition, see Causes of secondary osteoporosis
    
  • Spine measurements may be falsely elevated or normal in patients with significant osteophytes or aortic calcification at the site of measurement
  
  
• Fracture Risk Assessment Tool (FRAX)
  
  
  
  • Developed because DEXA scanning in clinical practice has proven specific, but not sensitive, for identification of patients at high risk of fracture – retrospective studies showed that up to 50% of women with postmenopausal fragility fractures did not have osteoporosis by DEXA scan
    
  • FRAX incorporates clinical risk factors (Table 10.2) to predict the 10-year risk of hip or other major osteoporotic fracture in an individual patient
    
  • The National Osteoporosis Foundation (NOF) FRAX tool is available for clinician use at www.shef.ac.uk/FRAX
    
  • Limitations of FRAX assessment:
    
    
    
    • Does not include bone turnover markers due to lack of data, although the authors propose this may be included in the future
      
    • Does not include DEXA measured at peripheral sites (but peripheral site measurements lack sensitivity anyway)
      
    • Study population is still mostly women, limiting generaliza­bility
  
  
• Who should be screened for osteoporosis?
  
  
  
  • All females aged >65 years, males >70 years
    
  • Postmenopausal women and men aged >50 years based on risk factor profile
    
  • Anyone with an insufficiency fracture, to determine severity of disease
    
  • Females on hormone replacement therapy
    
  • Patients on glucocorticoid therapy of >7.5 mg/day for longer than 3 months
  
  
• Who should be treated for osteoporosis? National Osteoporosis Foundation (NOF) guidelines
  
  
  
  • Any patient who has suffered an insufficiency fracture
    
  • Osteoporosis defined by BMD T score ≤ −2.5
    
  • Postmenopausal women and men aged >50 with T score between −1 and −2.5 with a FRAX score showing 10-year hip fracture risk >3% or 10-year major osteoporotic fracture risk >20%
    
  
  
• Markers of bone resorption: a biomarker for osteoporosis?
  
  
  
  • NTx, CTx are collagen X-linked telopeptides of type I collagen that are released during osteoclast activity and subsequent collagen breakdown
    
  • Elevated levels >50 ng/mL may suggest faster bone turnover and increased fracture risk
    
  • Lower levels after initiation of osteoporosis treatment may suggest treatment response or be used to judge treatment adherence
    
  • Limitations:
    
    
    
    • Marked physiologic variability and diurnal variability makes a single value difficult to interpret
      
    • Clinical relevance not well established