Musculoskeletal · Metabolic Bone Disease
The facts most likely to be tested
Press 1–5 to rate · ↑↓ to navigate
The gold standard for diagnosis is Dual-energy X-ray absorptiometry (DXA) scan showing a T-score of ≤ -2.5 at the lumbar spine, femoral neck, or total hip.
Universal screening for osteoporosis is recommended for all women aged ≥ 65 years and younger postmenopausal women with equivalent fracture risk factors.
Bisphosphonates (e.g., alendronate) are the first-line pharmacologic therapy for patients at high risk of fracture to inhibit osteoclast-mediated bone resorption.
FRAX score calculation is utilized to estimate the 10-year probability of a major osteoporotic fracture to guide treatment decisions in patients with osteopenia.
Glucocorticoid-induced osteoporosis is the most common form of secondary osteoporosis; any patient on prednisone ≥ 2.5 mg/day for ≥ 3 months needs a fracture risk assessment (glucocorticoid-adjusted FRAX ± BMD), with treatment (typically oral bisphosphonates) for moderate or high risk and an anabolic agent preferred at very high risk.
Denosumab, a monoclonal antibody against RANK ligand, is an effective alternative for patients who cannot tolerate oral bisphosphonates or have impaired renal function; however, in advanced CKD (especially dialysis) it carries an FDA boxed warning for severe hypocalcemia, so calcium and vitamin D must be corrected and monitored closely.
Vertebral compression fractures are the most common clinical manifestation, often presenting as acute back pain following minimal trauma or sudden movement.
Vignette unlocked
A 72-year-old postmenopausal woman presents to the clinic for a routine wellness exam. She has a history of hypertension and a remote smoking history. She reports no recent falls or trauma but notes a loss of 2 inches in height over the last 5 years and occasional mid-thoracic back pain. Physical examination reveals kyphosis of the thoracic spine. Her laboratory workup, including calcium, phosphorus, and vitamin D levels, is within normal limits.
What is the most appropriate next step in the management of this patient?
Dual-energy X-ray absorptiometry (DXA) scan
The patient's clinical presentation of height loss and kyphosis is highly suggestive of vertebral compression fractures secondary to osteoporosis, necessitating a DXA scan to confirm the diagnosis and quantify bone mineral density.
Full handout
High yield triage
Etiology / Epidemiology
Postmenopausal women and elderly patients with low bone mass and microarchitectural deterioration.
Clinical Manifestations
Asymptomatic until fracture; dowager's hump and loss of height are classic.
Diagnosis
DXA scan with a T-score ≤ -2.5 is the diagnostic threshold.
Treatment
Bisphosphonates are first-line; esophagitis and osteonecrosis of the jaw are key risks. Denosumab must never be stopped abruptly — discontinuation causes rebound vertebral fractures unless followed by a bisphosphonate.
Prognosis
Hip fractures carry the highest morbidity; 20% mortality within one year.
Full handout
Epidemiology & Etiology
Primary osteoporosis is driven by estrogen deficiency in postmenopausal women and age-related decline in osteoblast activity. Secondary causes include chronic glucocorticoid use, hyperthyroidism, and malabsorption syndromes. Caucasian/Asian ethnicity and low body mass index are major non-modifiable risk factors.
Pertinent Anatomy
Trabecular bone (cancellous) is affected earlier than cortical bone due to higher metabolic turnover. The vertebral bodies, proximal femur, and distal radius are the most common sites of fragility fractures.
Pathophysiology
An imbalance between bone resorption (osteoclasts) and bone formation (osteoblasts) leads to net bone loss. Estrogen normally inhibits osteoclast activity; its withdrawal accelerates bone turnover. The resulting porous bone structure lacks the structural integrity to withstand normal mechanical stress.
Clinical Manifestations
Patients are typically asymptomatic until a fragility fracture occurs. Physical exam may reveal dowager's hump (kyphosis) and a measurable loss of height (>2 cm). Acute back pain following minor trauma suggests a vertebral compression fracture.
Diagnosis
The DXA scan (Dual-energy X-ray absorptiometry) is the gold standard for diagnosis. A T-score ≤ -2.5 confirms osteoporosis, while -1.0 to -2.5 indicates osteopenia. Osteoporosis is also diagnosed clinically by a hip or vertebral fragility fracture, regardless of T-score. The FRAX score is used to estimate the 10-year probability of major osteoporotic fracture.
Treatment
Alendronate is the first-line therapy for most patients; those at very high fracture risk (e.g., recent or multiple fragility fractures, T-score < -3.0) are started on an anabolic agent (teriparatide, abaloparatide, or romosozumab) followed by an antiresorptive. Patients must remain upright for 30 minutes post-dose to avoid esophagitis. Fracture risk is reassessed after 3-5 years of therapy: low-to-moderate-risk patients are offered a 'drug holiday' because of atypical femoral fractures and osteonecrosis of the jaw, while patients who remain high risk continue treatment rather than stopping. Calcium and Vitamin D supplementation are mandatory adjuncts.
Prognosis
Fractures lead to chronic pain, loss of independence, and increased mortality. Hip fractures are the most severe complication, often requiring surgical intervention and intensive rehabilitation. Serial DXA scans are performed every 1-2 years to monitor treatment efficacy.
Differential Diagnosis
Osteomalacia: characterized by defective mineralization, often due to Vitamin D deficiency
Multiple Myeloma: presents with lytic lesions and elevated serum protein gap
Hyperparathyroidism: associated with elevated calcium and brown tumors
Paget Disease: shows elevated alkaline phosphatase and thickened, disorganized bone
Metastatic Bone Disease: usually presents with a known primary malignancy