High-yield overview
Radiological Assessment of Osteoporosis, Paget's, Hyperparathyroidism and Renal Osteodystrophy
—Osteopenia Threshold
30%bone loss on X-ray
—Paget's Prevalence
3-4%over 55 years
—HPT Bone Involvement
10-20%with imaging findings
—Looser Zones
—Pathognomonic for osteomalacia
Bone Scan Patterns
Superscan: Diffuse uptake, no kidneys (metastases or metabolic)
Paget's: Intense uptake, enlarged bone, monostotic or polyostotic
HPT: Diffuse uptake + focal brown tumours
Key: Superscan with uniform uptake favours metabolic; heterogeneous favours metastases
Critical Must-Knows
- Osteoporosis: Decreased density, vertebral fractures, cortical thinning
- Paget's: Enlarged bone, coarse trabeculae, mixed lytic/sclerotic
- Hyperparathyroidism: Subperiosteal resorption, brown tumours, chondrocalcinosis
- Osteomalacia: Looser zones (pseudofractures), generalised osteopenia
- Bone scan superscan in diffuse metabolic disease
Clinical Pearls
- “Rugger jersey spine: Renal osteodystrophy
- “Picture frame vertebra: Paget's
- “Cotton wool skull: Paget's (lytic then sclerotic phases)
- “Salt and pepper skull: Hyperparathyroidism
- “Codfish vertebrae: Osteoporosis with biconcave fractures
Clinical Warning
Metabolic bone disease imaging is commonly tested. Know the classic radiographic signs: Looser zones (osteomalacia), subperiosteal resorption (HPT), picture frame vertebra (Paget's). Understand how to differentiate metabolic superscan from metastatic superscan on bone scan.
Mnemonic
DENSITYSearch Pattern for Metabolic Bone Disease
D
D = Density: is it reduced (osteopenia) or increased/mixed (Paget's, sclerosis)?
E
E = Endplates and trabeculae: coarsened/indistinct (osteomalacia) vs sharp loss (osteoporosis); rugger jersey (renal)
N
N = Notches and resorption: subperiosteal radial phalangeal margins, acro-osteolysis (HPT)
S
S = Soft tissue: vascular/periarticular calcification, chondrocalcinosis
I
I = Insufficiency fractures and Looser zones: bilateral, symmetric, perpendicular to cortex
T
T = Tumours: brown tumours (HPT), sarcomatous change in Paget's
Y
Y = Yield to biochemistry: always correlate with calcium, phosphate, ALP, PTH, vitamin D
Hook:Decide first whether the dominant abnormality is QUANTITY (osteoporosis), MINERALISATION (osteomalacia), RESORPTION (HPT) or REMODELLING (Paget's) — then confirm with the targeted signs and biochemistry.
Mnemonic
QMRRThe Four Mechanisms
Q
Q = Quantity reduced — osteoporosis (normal mineralisation, less bone)
M
M = Mineralisation defective — osteomalacia / rickets (Looser zones)
R
R = Resorption excess — hyperparathyroidism (subperiosteal resorption, brown tumours)
R
R = Remodelling disordered — Paget's disease (enlarged bone, coarse trabeculae)
Hook:Renal osteodystrophy combines defective mineralisation + excess resorption + sclerosis, which is why its radiographs show mixed features.
Overview
Metabolic bone disease encompasses systemic disorders that disturb the normal balance of bone formation, resorption and mineralisation. Because the abnormality is metabolic rather than focal, the imaging signs are usually generalised and bilateral, with characteristic regional accentuation that points to a specific diagnosis. The radiologist's task is to recognise the dominant abnormality — reduced quantity of mineralised bone (osteoporosis), defective mineralisation of osteoid (osteomalacia/rickets), excessive resorption driven by parathyroid hormone (hyperparathyroidism), disordered remodelling (Paget's disease), or the mixed picture of chronic kidney disease (renal osteodystrophy).
Osteoporosis vs Osteomalacia — the core distinction
Osteoporosis is reduced QUANTITY of normally mineralised bone (normal calcium, phosphate, ALP). Osteomalacia is defective MINERALISATION of a normal quantity of osteoid (low/normal calcium, low phosphate, high ALP). Both cause low density on radiographs, but only osteomalacia produces Looser zones and coarsened, indistinct trabeculae.
Why radiographs are insensitive for density loss
Approximately 30-40% of bone mineral must be lost before osteopenia is reliably perceptible on plain radiographs, and the impression is heavily influenced by exposure factors. Quantitative density loss is therefore measured with DXA, not estimated from radiographs.
| Disease | Calcium | Phosphate | ALP | PTH |
|---|---|---|---|---|
| Osteoporosis | Normal | Normal | Normal | Normal |
| Osteomalacia (vit D deficiency) | Low / normal | Low | High | High (secondary) |
| Primary hyperparathyroidism | High | Low | High | High |
| Secondary HPT (CKD) | Low / normal | High | High | High |
| Paget's disease | Normal | Normal | Very high (isolated) | Normal |
Clinical Imaging
No single modality answers every question in metabolic bone disease; the modalities are complementary and each has a defined role.
| Modality | Primary Role | Strengths / Limitations |
|---|---|---|
| Plain radiograph | Pattern recognition of qualitative signs | Shows Looser zones, subperiosteal resorption, Paget's architecture; insensitive to early density loss |
| DXA | Quantify bone mineral density (T-score) | Reference standard for osteoporosis diagnosis; cannot show qualitative signs or assess mineralisation |
| Bone scintigraphy (Tc-99m) | Whole-skeleton survey of turnover | Maps Paget's extent, Looser zones, brown tumours; superscan in diffuse disease; non-specific |
| CT | Cortical detail, fracture and deformity | Defines Paget's cortical thickening, vertebral fractures, brown tumours; higher dose |
| MRI | Marrow and occult/insufficiency fractures | Sensitive for sacral and vertebral insufficiency fractures invisible on radiographs |
Modality sequencing in practice
A symptomatic patient with suspected metabolic bone disease is typically assessed with targeted radiographs (hands for HPT, pelvis/femora for Looser zones, spine for fractures and Paget's) plus biochemistry. DXA quantifies osteoporosis. Bone scan maps polyostotic Paget's or unexplained skeletal pain. MRI is reserved for radiographically occult insufficiency fractures and for excluding malignancy in indeterminate lytic lesions.
Systematic Approach to the Metabolic Bone Radiograph
A disciplined search pattern converts a vague impression of low density into a specific diagnosis. Work through the DENSITY checklist (above): density, endplates/trabeculae, notches/resorption, soft tissue, insufficiency fractures/Looser zones, tumours, and then yield to biochemistry.
| Suspected Disease | Highest-Yield Radiograph | Looking For |
|---|---|---|
| Hyperparathyroidism | Hands (PA), distal clavicles | Subperiosteal resorption on radial phalangeal margins, acro-osteolysis |
| Osteomalacia | Pelvis, proximal femora, scapulae, ribs | Looser zones (bilateral, perpendicular lucent bands) |
| Osteoporosis | Lateral thoracolumbar spine + DXA | Vertebral fractures (Genant grade), low BMD |
| Paget's disease | Affected long bone, skull, pelvis | Bone enlargement, coarse trabeculae, blade-of-grass front |
| Renal osteodystrophy | Hands, lateral spine | Subperiosteal resorption, rugger jersey spine, soft-tissue calcification |
Distribution is the key discriminator
Metabolic disease is generalised and bilaterally symmetric — this is what separates it from focal pathology (metastasis, primary tumour, infection). When a 'metabolic' sign is unilateral or focal, reconsider the diagnosis: a solitary lytic lesion is more likely metastasis than a brown tumour unless biochemistry confirms hyperparathyroidism.
Osteoporosis
| Feature | Description | Location |
|---|---|---|
| Generalised osteopenia | Decreased bone density, increased lucency | Diffuse |
| Cortical thinning | Thin cortices, endosteal scalloping | Long bones |
| Trabecular rarefaction | Loss of horizontal trabeculae, vertical streaking | Vertebrae |
| Vertebral fractures | Wedge, biconcave, or crush morphology | Spine |
| Singh index | Loss of trabecular groups in proximal femur | Hip |
Mnemonic
WBC FracturesVertebral Fracture Morphology
W
W = Wedge (anterior height loss greater than posterior)
B
B = Biconcave / Codfish (endplate depression, middle height loss)
C
C = Crush / Compression (diffuse height loss)
Hook:Greater than 20% height loss or greater than 4mm absolute loss indicates vertebral fracture. Compare with adjacent vertebrae.
Insufficiency Fractures
Common sites: Sacrum (H-shaped pattern), pubic rami, proximal femur. X-ray may be normal initially. MRI or bone scan sensitive for detection. Sacral fractures often missed on X-ray.
Singh Index
Grading system for trabecular pattern in proximal femur (1-6). Grade 6: All trabecular groups visible. Grade 1-3: Significant osteoporosis. Largely replaced by DEXA but may appear in vivas.
Paget's Disease
| Phase | Pathophysiology | X-ray Appearance |
|---|---|---|
| Lytic (early) | Osteoclast predominance | V-shaped lytic lesion (blade of grass), osteoporosis circumscripta (skull) |
| Mixed (active) | Osteoclast and osteoblast activity | Coarse trabeculae, bone enlargement, cortical thickening |
| Sclerotic (late) | Osteoblast predominance | Dense sclerotic bone, ivory vertebra, cotton wool skull |
Bone Scan in Paget's
Intense radiotracer uptake in affected bones. Uptake extent matches affected bone (entire bone involved). Useful for polyostotic disease assessment and monitoring treatment response. Bone scan positive before X-ray changes in early disease.
Hyperparathyroidism
| Feature | Description | Location |
|---|---|---|
| Subperiosteal resorption | Lacy, irregular periosteal margin | Radial aspect of middle phalanges (classic) |
| Acroosteolysis | Resorption of terminal tufts | Distal phalanges |
| Brown tumours | Well-defined lytic lesions | Mandible, pelvis, femur, ribs |
| Chondrocalcinosis | Calcification in cartilage | Knee menisci, TFCC, pubic symphysis |
| Salt and pepper skull | Diffuse granular demineralisation | Skull vault |
| Rugger jersey spine | Sclerotic endplates, lucent centre | More common in renal osteodystrophy |
Mnemonic
Subperiosteal Resorption SitesHPT Classic Sites
R
Radial aspect middle phalanges (most specific)
D
Distal clavicle (AC joint)
S
Sacroiliac joint (pseudo-widening)
S
Symphysis pubis
T
Teeth (lamina dura resorption)
Hook:Look at the radial aspect of the 2nd and 3rd middle phalanges - subperiosteal resorption here is virtually pathognomonic of HPT
Brown Tumours
Not true neoplasms but focal osteoclast accumulation with haemorrhage. Lytic, well-defined, may be expansile. Resolve or ossify with treatment of HPT. Multiple brown tumours in severe/prolonged disease.
Primary vs Secondary HPT
Primary: Parathyroid adenoma, usually less severe bone changes. Secondary: Chronic renal failure, more prominent changes, rugger jersey spine. Tertiary: Autonomous PTH secretion after prolonged secondary.
Osteomalacia and Rickets
| Feature | Description | Significance |
|---|---|---|
| Looser zones (pseudofractures) | Lucent bands perpendicular to cortex, bilateral, symmetric | PATHOGNOMONIC |
| Generalised osteopenia | Decreased bone density | Non-specific |
| Coarsened trabeculae | Fuzzy, indistinct trabeculae | Unmineralised osteoid |
| Biconcave vertebrae | Codfish vertebrae | Softened bone |
| Pelvic deformity | Protrusio, triradiate pelvis | Severe disease |
Looser Zones
Pathognomonic for osteomalacia. Bilateral, symmetric, perpendicular lucencies at: medial femoral neck, pubic rami, lateral scapular border, ribs. Represent unmineralised osteoid at sites of stress. Complete the fracture if untreated.
| Feature | Description | Location |
|---|---|---|
| Metaphyseal cupping | Concave metaphyseal margin | Wrist, knee (most obvious) |
| Metaphyseal fraying | Irregular, brush-like margin | Growth plates |
| Widened physis | Increased physeal width | Active growth plates |
| Rachitic rosary | Enlarged costochondral junctions | Anterior ribs |
| Bowing deformity | Genu varum or valgum | Lower limbs |
Renal Osteodystrophy
Renal Osteodystrophy
Complex bone disease in chronic renal failure combining: Secondary hyperparathyroidism (most prominent), Osteomalacia (vitamin D deficiency), Osteosclerosis, Soft tissue calcification. The combination produces characteristic findings including rugger jersey spine.
| Feature | Cause | Appearance |
|---|---|---|
| Rugger jersey spine | Sclerotic endplates, lucent centre | Horizontal banding like rugby jersey |
| Subperiosteal resorption | Secondary HPT | As in primary HPT |
| Soft tissue calcification | High calcium-phosphate product | Vascular, periarticular |
| Brown tumours | Secondary HPT | Lytic lesions |
| Amyloid deposition | Dialysis-related | Bone cysts, erosions |
Bone Scan Patterns
| Condition | Pattern | Key Features |
|---|---|---|
| Metabolic superscan | Diffuse uptake, no kidneys | Uniform, symmetric, all bones |
| Metastatic superscan | Diffuse uptake, no kidneys | Heterogeneous, asymmetric foci |
| Paget's | Intense focal uptake | Enlarged bone, entire bone involved |
| HPT | Diffuse + focal | Brown tumours show focal uptake |
| Osteomalacia | Pseudofractures show uptake | Looser zone sites positive |
Differentiating Superscans
Both metastases and metabolic disease can cause superscan (diffuse uptake, absent kidneys). Metabolic: uniform, symmetric uptake throughout skeleton. Metastatic: heterogeneous, patchy uptake with hot spots. Additional clues: axial predominance (metastases), specific signs on X-ray (metabolic).
Differential Diagnosis
The classic radiographic signs of metabolic bone disease overlap with focal pathology. The decisive discriminators are distribution (generalised/symmetric vs focal), the accompanying biochemistry, and whether the affected bone is enlarged.
| Finding | Metabolic Cause | Mimic to Exclude | Discriminating Feature |
|---|---|---|---|
| Diffuse low density | Osteoporosis / osteomalacia | Diffuse marrow infiltration (myeloma, leukaemia) | Osteomalacia has coarse trabeculae + Looser zones; myeloma shows punched-out lytic lesions and a paraprotein |
| Solitary lytic lesion | Brown tumour (HPT) | Metastasis, plasmacytoma, GCT | Brown tumour only in proven hyperparathyroidism; check calcium and PTH |
| Dense, expanded bone | Paget's disease | Sclerotic (blastic) metastasis | Paget's ENLARGES bone and coarsens trabeculae; metastasis does not enlarge bone |
| Diffuse bone-scan uptake (superscan) | Metabolic / renal osteodystrophy | Diffuse osteoblastic metastases | Metabolic uptake is uniform and symmetric; metastatic is heterogeneous and patchy |
| Lucent band across cortex | Looser zone (osteomalacia) | Stress/fatigue fracture | Looser zones are bilateral, symmetric, on the concave/medial side; stress fractures are unilateral and at typical sport-related sites |
| Vertebral endplate banding | Rugger jersey spine (renal) | Osteopetrosis (sandwich vertebra) | Renal banding is indistinct; osteopetrosis bands are sharply defined and very dense |
Evidence Base
Evidence
Genant Semiquantitative Vertebral Fracture Grading
Genant HK, Wu CY, van Kuijk C, Nevitt MC • Journal of Bone and Mineral Research (1993)
Key Findings:
- Introduced the semiquantitative (SQ) visual method that grades vertebral deformity by approximate height loss: grade 1 (mild, 20-25%), grade 2 (moderate, 25-40%), grade 3 (severe, over 40%).
- Validated in 57 postmenopausal women aged 65-75 read by three independent observers, showing the SQ approach can be applied reliably for prevalent and incident fractures when well-defined criteria are used.
- Distinguished true osteoporotic fracture morphology (wedge, biconcave, crush) from non-fracture deformity, reducing interobserver variability.
Clinical implication: The Genant SQ method is the internationally adopted standard for reporting vertebral fractures on radiographs and DXA vertebral fracture assessment — examiners expect candidates to grade deformity by approximate height loss using this scheme.
Limitation: A semiquantitative visual method retains some interobserver variability and requires comparison with adjacent vertebrae; it does not by itself establish the cause of the deformity.
Source: Genant HK et al. J Bone Miner Res 1993;8(9):1137-48
Evidence
FRAX — Ten-Year Fracture Probability from Clinical Risk Factors
Kanis JA, Johnell O, Oden A, Johansson H, McCloskey E • Osteoporosis International (2008)
Key Findings:
- Developed the WHO FRAX tool integrating clinical risk factors (age, BMI, prior fracture, parental hip fracture, glucocorticoids, rheumatoid arthritis, smoking, alcohol) with or without femoral neck BMD.
- Ten-year hip fracture probability in women varied roughly 100-fold (0.2% at age 50 without risk factors to 22% at age 80 with parental hip fracture history).
- Demonstrated that most patients who fracture do not meet the DXA T-score definition of osteoporosis, so risk-factor integration improves case-finding.
Clinical implication: FRAX reframed osteoporosis management around absolute 10-year fracture probability rather than BMD threshold alone, and underpins intervention thresholds in AAOS, NOGG and many national guidelines.
Limitation: FRAX does not capture fall risk, dose of glucocorticoids, number/recency of prior fractures, or lumbar spine BMD, and is calibrated to country-specific epidemiology.
Source: Kanis JA et al. Osteoporos Int 2008;19(4):385-97
Guidelines, Registries & Global Practice
Metabolic bone disease is diagnosed and managed worldwide; imaging interpretation is universal, but access to DXA, scintigraphy and biochemistry varies markedly by resource setting.
| Condition | Epidemiology | Imaging-Relevant Point |
|---|---|---|
| Osteoporosis | Most common metabolic bone disease; lifetime fragility-fracture risk roughly 1 in 2 women and 1 in 5 men over 50 | DXA-defined; FRAX adds clinical risk factors |
| Paget's disease | Estimated 0.4-1% of adults, rising after age 55; marked geographic and declining temporal variation | Often incidental on CT/radiographs (Husseini 2022) |
| Osteomalacia / rickets | Re-emerging with vitamin D deficiency, malabsorption and limited sun exposure; major burden in some low-resource regions | Looser zones and metaphyseal change are diagnostic clues |
| Renal osteodystrophy | Affects most patients with advanced CKD on dialysis | Hand radiographs highest yield (Lacativa 2009) |
| Body | Scope | Imaging-Relevant Position |
|---|---|---|
| WHO / IOF | Osteoporosis definition | T-score at or below -2.5 by central DXA defines osteoporosis; -1 to -2.5 osteopenia |
| AAOS (US) | Fragility fracture / osteoporosis care | Endorses DXA plus fracture-risk assessment and secondary-fracture prevention after fragility fracture |
| NOGG / NICE / BOA (UK) | Fracture risk assessment | FRAX-based intervention thresholds; DXA where FRAX indicates; vertebral fracture assessment encouraged |
| Endocrine Society / international Paget's consensus | Paget's disease | Plain radiographs for diagnosis, radionuclide bone scan to map extent, ALP to monitor; treat symptomatic disease |
| KDIGO | CKD-mineral and bone disorder | Cautions against relying on plain radiographs alone; biochemistry and selective imaging guide CKD-MBD diagnosis |
High- vs Limited-Resource Practice Variation
In high-resource settings, central DXA, FRAX, bone scintigraphy and biochemistry are routinely combined. In limited-resource settings, DXA and scintigraphy may be scarce, so plain radiographs and basic biochemistry (calcium, phosphate, ALP) carry greater diagnostic weight — making confident recognition of qualitative signs (Looser zones, subperiosteal resorption, Paget's architecture) even more important. Quantitative ultrasound of the calcaneus is sometimes used for screening where DXA is unavailable but cannot be used with the DXA T-score threshold and does not confirm a DXA-based diagnosis.
Areas of Uncertainty / Controversy
Debated points include: the optimal vertebral fracture assessment workflow (DXA-VFA vs spine radiographs); whether opportunistic CT (Hounsfield-unit-based screening) should be used to flag low bone density on scans done for other reasons; the threshold for treating asymptomatic Paget's; and how best to disentangle the overlapping osteomalacia, hyperparathyroid and osteosclerotic components of renal osteodystrophy without bone biopsy. Country-specific FRAX calibration also means absolute risk outputs are not interchangeable between populations.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“A 70-year-old man presents with a painful, bowed tibia. X-ray shows an enlarged bone with coarse trabeculae, cortical thickening, and mixed lytic and sclerotic areas.”
Practical approach
This is Paget's disease of bone, showing the classic features of enlarged bone (pathognomonic), coarse trabeculation, cortical thickening, and mixed lytic-sclerotic appearance consistent with the mixed/active phase. The bowing deformity is typical in weight-bearing bones. Complications to be aware of: (1) Pathological fracture - often transverse ('banana fracture'), (2) Secondary osteoarthritis - if near joints, (3) Sarcomatous transformation (less than 1%) - look for new aggressive lytic destruction or soft tissue mass, (4) High-output cardiac failure - if extensive skeletal involvement, (5) Nerve compression - especially if skull base involved. I would order blood tests (elevated ALP with normal calcium/phosphate in Paget's) and consider bone scan to assess extent of skeletal involvement.
Key clinical points
Bone enlargement is pathognomonic of Paget's
Mixed lytic-sclerotic = active phase
Complications: Fracture, OA, sarcoma, HF
ALP elevated, Ca/PO4 normal
Bone scan shows extent of disease
Common pitfalls
Missing sarcomatous transformation signs
Not recognising bone enlargement as key feature
Confusing with metastases (mets don't enlarge bone)
Further questions
“What would alert you to sarcomatous transformation? How would you monitor and treat this patient?”
Viva scenarioChallenging
Clinical prompt
“A patient with chronic kidney disease has hand X-rays showing irregular erosions along the radial aspect of the middle phalanges and loss of the lamina dura around teeth.”
Practical approach
This is secondary hyperparathyroidism due to chronic renal failure, showing the classic subperiosteal resorption on the radial aspect of the middle phalanges - this location is virtually pathognomonic for hyperparathyroidism. Other expected findings include: (1) Acroosteolysis - resorption of distal phalangeal tufts, (2) Brown tumours - well-defined lytic lesions in mandible, pelvis, long bones, (3) Rugger jersey spine - horizontal sclerotic endplate bands with lucent central vertebral bodies (classic for renal osteodystrophy), (4) Chondrocalcinosis - calcification in cartilage (menisci, TFCC), (5) Vascular and soft tissue calcification - due to high calcium-phosphate product. I would also assess for signs of osteomalacia component (Looser zones).
Key clinical points
Subperiosteal resorption: Radial middle phalanges (pathognomonic)
Secondary HPT due to CKD
Rugger jersey spine in renal osteodystrophy
Brown tumours, chondrocalcinosis also seen
Soft tissue calcification common
Common pitfalls
Missing the radial phalangeal location specificity
Not recognising renal osteodystrophy features
Confusing brown tumours with metastases
Further questions
“How do brown tumours change with treatment? What is the difference between primary, secondary, and tertiary hyperparathyroidism?”
Viva scenarioStandard
Clinical prompt
“A 45-year-old woman with coeliac disease presents with bone pain. X-rays show generalised osteopenia and bilateral symmetric lucent bands perpendicular to the cortex at the medial femoral necks.”
Practical approach
The bilateral symmetric lucent bands perpendicular to the cortex at the medial femoral necks are Looser zones (pseudofractures), which are pathognomonic for osteomalacia. In this patient with coeliac disease, malabsorption of vitamin D is the likely cause. Looser zones represent unmineralised osteoid at sites of mechanical stress. Classic locations include: medial femoral neck (as here), pubic rami, lateral scapular border, and ribs. They are bilateral and symmetric. Without treatment, they can complete into true fractures. I would order vitamin D, calcium, phosphate, PTH, and ALP levels. Treatment involves vitamin D supplementation and addressing the underlying coeliac disease. The generalised osteopenia reflects diffuse undermineralisation.
Key clinical points
Looser zones = pathognomonic for osteomalacia
Bilateral, symmetric, perpendicular to cortex
Classic sites: femoral neck, pubic rami, scapula, ribs
Coeliac disease causes vitamin D malabsorption
Can complete into true fractures if untreated
Common pitfalls
Not recognising Looser zones as diagnostic
Confusing with stress fractures (unilateral, different locations)
Missing the connection to malabsorption
Further questions
“What blood tests would you order? What is the difference between osteomalacia and osteoporosis radiographically?”
Viva scenarioChallenging
Clinical prompt
“A 68-year-old woman is referred after a low-trauma wrist fracture. Her lumbar spine DXA reports a T-score of -1.8 but her femoral neck T-score is -2.7. Lateral spine radiograph shows a grade 2 wedge deformity at T8.”
Practical approach
This patient already has osteoporosis on two grounds. First, the lowest valid central DXA site governs the diagnosis: the femoral neck T-score of -2.7 (at or below -2.5) meets the WHO definition of osteoporosis, even though the lumbar spine T-score of -1.8 is only in the osteopenic range. The discordance is common and is often explained by degenerative change or aortic calcification spuriously elevating the spine value, so I would not be reassured by the spine number. Second, and more importantly, she has sustained a low-trauma (fragility) fracture of the wrist AND has a grade 2 (moderate, 25-40% height loss) vertebral wedge fracture at T8 on the lateral radiograph, graded by the Genant semiquantitative method. A morphometric vertebral fracture is itself diagnostic of osteoporosis irrespective of T-score and is a strong predictor of further fractures. I would formally assess 10-year fracture probability with FRAX (which incorporates her prior fracture), arrange vertebral fracture assessment if not already done, exclude secondary causes biochemically (calcium, phosphate, ALP, vitamin D, PTH, renal function), and initiate antiresorptive therapy with calcium/vitamin D repletion as a secondary-fracture-prevention measure.
Key clinical points
Lowest valid central DXA site defines the diagnosis (femoral neck -2.7 = osteoporosis)
Spine T-score can be falsely elevated by degeneration / aortic calcification
A fragility fracture or morphometric vertebral fracture diagnoses osteoporosis regardless of T-score
Genant grade 2 = 25-40% vertebral height loss
Use FRAX for absolute risk and exclude secondary causes before treating
Common pitfalls
Being reassured by the osteopenic spine value and missing the diagnostic femoral neck score
Overlooking the diagnostic significance of the existing vertebral fracture
Forgetting to screen for secondary osteoporosis before starting treatment
Further questions
“Why might the spine T-score be higher than the hip in an older patient? How does the Genant grade influence fracture-risk stratification?”
Exam day cheat sheet
Metabolic Bone Disease Imaging
Paget's Disease Signs
- Bone enlargement (pathognomonic)
- Blade of grass (lytic phase)
- Cotton wool skull (sclerotic)
- Picture frame vertebra
- Banana fractures
Hyperparathyroidism Signs
- Subperiosteal resorption (radial middle phalanges)
- Salt and pepper skull
- Brown tumours (lytic lesions)
- Chondrocalcinosis
- Rugger jersey spine (renal)
Osteomalacia Signs
- Looser zones (PATHOGNOMONIC)
- Bilateral, symmetric pseudofractures
- Medial femoral neck, pubic rami, scapula
- Generalised osteopenia
- Rickets: Cupping, fraying, widened physis
Bone Scan Patterns
- Metabolic superscan: Uniform, symmetric
- Metastatic superscan: Heterogeneous
- Paget's: Intense, entire bone
- Looser zones show uptake