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Information

Differential Diagnosis of Musculoskeletal Disorders

Thoracic Deformity!!navigator!!

Pectus Carinatum = Pigeon Breast

  • = anterior displacement of sternum
  • Frequency: 1÷1500 live births; in 25% familial
  • In >30% associated with: scoliosis
  • Types:
    1. chondrogladiolar deformity = protrusion of middle + lower sternum [gladiolus, Latin, diminutive for gladius = sword]
    2. chondromanubrial deformity (Currrarino-Silverman syndrome) = protrusion of manubrium + upper sternum [manubrium, Latin = a handle]
  • shortness of breath, exercise intolerance
  • increase in AP diameter
  • pectus index (TRV diameter ÷ AP diameter of chest): <1.42–1.98

Pectus Excavatum = Funnel Chest

= posterior depression of sternum with reduction of prevertebral space compressing heart against spine

Frequency: 1÷400 to 1÷1000 live births; M÷F = 4÷1

Cause: rapid misdirected growth of lower costal cartilages

  • Most common congenital deformity of the sternum
  • Most frequently an isolated anomaly (45% familial)!

May be associated with:

  • prematurity, homocystinuria, Marfan syndrome, Poland syndrome, Noonan syndrome, fetal alcohol syndrome, congenital heart disease

In >20% associated with: scoliosis

  • decreased total lung capacity
  • decreased cardiac stroke volume
  • depressed position of sternum (LATERAL)
  • indistinct right heart border mimicking right middle lobe process (FRONTAL) = leftward displacement + axial rotation of heart
  • decreased heart density (FRONTAL)
  • leftward displacement of heart mimicking cardiomegaly (FRONTAL)
  • horizontal course of posterior portion of ribs
  • accentuated downward course of anterior portions of ribs (FRONTAL)

CT:

  • pectus index (TRV diameter ÷ AP diameter of chest): >2.56 ± 0.35

Rx: surgical correction with pectus index >3.25

Barrel Chest

= large sagittal diameter of thorax

Cause: COPD, emphysema

  • lateral segments of ribs elongated + straight pointing vertical (FRONTAL)
  • square shape on cross section (CT)

Congenital Rib Anomalies!!navigator!!

Prevalence: 1.4%

  1. Cervical rib (0.2–1–8%)
    M<F
    • usually asymptomatic
    • thoracic outlet syndrome (due to elevation of floor of scalene triangle with decrease of costoclavicular space):
      • 10–20% of symptomatic patients have a responsible cervical rib
      • 5–10% of complete cervical ribs cause symptoms

    May be associated with: Klippel-Feil anomaly
    • uni- / bilateral
    • may fuse with first ribs anteriorly
    • adjacent transverse process angulated inferiorly

    Cx: aneurysmal dilatation of subclavian a.
    DDx: elongated transverse process of 7th cervical vertebra; hypoplastic 1st thoracic rib
  2. Forked / bifid rib (0.6%) = duplication of anterior portion
    Location: 4th rib (most often)
    May be associated with: Gorlin basal cell nevus syndrome
    • A single bifid rib is most commonly a normal incidental finding!
  3. Rib fusion (0.3%)
    May be associated with: vertebral segmentation anomalies
    Location: 1st + 2nd rib / several adjacent ribs
    Site: posterior / anterior portion
  4. Bone bridging = focal joining by bone outgrowth
    Cause: congenital / posttraumatic
    Location: anywhere along one pair of ribs / several adjacent ribs
    • complete bridging / pseudarthrosis
  5. Rudimentary / hypoplastic rib (0.2%)
    Location: 1st rib (usually)
    • transverse process angulated superiorly

    DDx: cervical rib
  6. Pseudarthrosis of 1st rib (0.1%)
    • radiolucent line through mid portion with dense sclerotic borders
  7. Intrathoracic / pelvic rib (rare)
  8. Abnormal number of ribs
    1. supernumerary: trisomy 21, VATER syndrome
    2. 11 pairs: normal individuals (5–8%); trisomy 21 (33%); cleidocranial dysplasia; camptomelic dysplasia

Short Ribs

  1. Thanatophoric dysplasia
  2. Jeune asphyxiating thoracic dysplasia
  3. Ellis-van Creveld chondroectodermal dysplasia
  4. Short rib-polydactyly syndromes (Saldino-Noonan, Majewski, Verma-Naumoff)
  5. Achondroplasia
  6. Achondrogenesis
  7. Mesomelic dwarfism
  8. Spondyloepiphyseal dysplasia
  9. Enchondromatosis

Rib Lesions!!navigator!!

  1. BENIGN RIB TUMOR
    1. Fibrous dysplasia (most common benign lesion)
      • predominantly posterior / lateral location
      • expansile remodeling of protracted length of bone
      • typical ground-glass appearance
    2. Enchondroma (2nd most common)
      • at costochondral junction
      • high SI on T2WI + lobulated contour
    3. Osteochondroma / exostosis (8%):
      • at costochondral / costovertebral junction

      Associated with: spontaneous hemothorax
    4. Langerhans cell histiocytosis (eosinophilic granuloma)
      • age <30 years
      • “black hole” on CT of lower density
      • aggressive features like periostitis + cortical breakthrough + soft-tissue mass
    5. Benign cortical defect
    6. Hemangioma of bone
    7. Giant cell tumor
      • low to intermediate SI on T1WI + T2WI
    8. Aneurysmal bone cyst
      • lobulated septated mass with thin well-defined rim of low SI + fluid levels
    9. Osteoblastoma
    10. Osteoid osteoma
    11. Chondroblastoma
      • at costovertebral / costochondral junction
    12. Enostosis = bone island (0.4%)
    13. Paget disease
    14. Brown tumor of HPT
    15. Xanthogranuloma
    16. Nonossifying fibroma = fibroxanthoma
      • eccentric intracortical location, smaller in size
      • spontaneous regression with age
  2. PRIMARY MALIGNANT RIB TUMOR
    1. Chondrosarcoma (33%)
    2. Plasmacytoma
    3. Lymphoma
    4. Osteosarcoma (1.3%)
    5. Fibrosarcoma
    6. Primitive neuroectodermal tumor / Askin tumor
  3. SECONDARY MALIGNANT RIB TUMOR
    › in adult:
    1. Metastasis (most common malignant lesion)
    2. Multiple myeloma
    3. Desmoid tumor

    › in child:
    1. Ewing sarcoma (most common malignant rib tumor of children and adolescents)
    2. Metastatic neuroblastoma
  4. TRAUMATIC RIB DISORDER
    1. Healing fracture
    2. Radiation osteitis

    DDx: pulmonary nodule
  5. AGGRESSIVE GRANULOMATOUS INFECTIONS
    = osteomyelitis

Expansile Rib Lesion

mnemonic: O FEEL THE CLAMP

  • Osteochondroma (25% of all benign rib tumors)
  • Fibrous dysplasia
  • Eosinophilic granuloma
  • Enchondroma (7% of all benign rib tumors)
  • Lymphoma / Leukemia
  • Tuberculosis
  • Hematopoiesis
  • Ewing sarcoma
  • Chondromyxoid fibroma
  • Lymphangiomatosis
  • Aneurysmal bone cyst
  • Metastases
  • Plasmacytoma

Abnormal Rib Shape!!navigator!!

Rib Notching on Inferior Margin

= minimal concave scalloping / deep ridges along the neurovascular groove with reactive sclerosis

  • Minor undulations in the inferior ribs are normal!
  • The medial third of posterior ribs near transverse process of vertebrae may be notched normally!
  1. ARTERIAL
    Cause: intercostal aa. function as collaterals to descending aorta / lung
    1. Aorta: coarctation (usually affects ribs 4–8; rare before age 8 years), thrombosis
    2. Subclavian artery: Blalock-Taussig shunt
    3. Pulmonary artery: pulmonary stenosis, tetralogy of Fallot, absent pulmonary artery
  2. VENOUS
    Cause: enlargement of intercostal veins
    1. AV malformation of chest wall
    2. Superior vena cava obstruction
  3. NEUROGENIC
    1. Intercostal neuroma
    2. Neurofibromatosis type 1
    3. Poliomyelitis / quadriplegia / paraplegia
  4. OSSEOUS
    1. Hyperparathyroidism
    2. Thalassemia
    3. Melnick-Needles syndrome

Unilateral Rib Notching on Inferior Margin

  1. Postoperative Blalock-Taussig shunt (subclavian to pulmonary artery)
  2. Coarctation between origin of innominate a. + L subclavian a.
  3. Coarctation proximal to aberrant subclavian a.

Rib Notching on Superior Margin

  1. Rheumatoid arthritis
  2. Scleroderma
  3. Systemic lupus erythematosus
  4. Hyperparathyroidism
  5. Restrictive lung disease
  6. Marfan syndrome

Dysplastic Twisted Ribbon Ribs

  1. Osteogenesis imperfecta
  2. Neurofibromatosis

Bulbous Enlargement of Costochondral Junction

  1. Rachitic rosary
  2. Scurvy
  3. Achondroplasia
  4. Hypophosphatasia
  5. Metaphyseal chondrodysplasia
  6. Acromegaly

Wide Ribs

  1. Marrow hyperplasia (anemias)
  2. Fibrous dysplasia
  3. Paget disease
  4. Achondroplasia
  5. Mucopolysaccharidoses

Slender Ribs

  1. Trisomy 18 syndrome
  2. Neurofibromatosis

Dense Ribs!!navigator!!

  1. Tuberous sclerosis
  2. Osteopetrosis
  3. Mastocytosis
  4. Fluorosis
  5. Fibrous dysplasia
  6. Chronic infection
  7. Trauma
  8. Subperiosteal rib resection

Hyperlucent Ribs!!navigator!!

Congenitally Lucent Ribs

  1. Osteogenesis imperfecta
  2. Achondrogenesis
  3. Hypophosphatasia
  4. Camptomelic dysplasia

Acquired Lucent Ribs

  1. Cushing disease
  2. Acromegaly
  3. Scurvy

Outline