Types of Primary Osteoporosis

Primary osteoporosis can be divided into type I (postmenopausal) osteoporosis and type II (senile) osteoporosis.

Type I osteoporosis results from loss of estrogen and predominantly affects trabecular/cancellous bone. Type I osteoporosis is most frequently associated with vertebral and wrist fractures in postmenopausal women.

Type II osteoporosis, on the other hand, results from diminished absorption of calcium and reduced serum levels of vitamin D, leading predominantly to resorption of cortical bone. Type II osteoporosis is associated with hip fractures in men and women older than 70 or so.

References

Duque G, Troen BR. Understanding the mechanisms of senile osteoporosis: new facts for a major geriatric syndrome. J Am Geriatr Soc. 2008 May;56(5):935-41.

Solitary Skull Lesions

A mnemonic for solitary skull lesions is "I help me"

• Infection: Permeative margin
• Hemangioma: Well-circumscribed diploic space lesion with a "Spoke wheel" or "reticulated" pattern
• Epidermoid/dermoid: Epidermoid has sclerotic margins
• Leptomeningeal cyst: Smoothly marginated skull defect. "Growing fracture" refers to dural herniation and expansion of defect.
• Plasmacytoma: Scalloped, poorly marginated, non-sclerotic skull base margin.
• Paget: AKA osteoporosis circumscripta. Lytic phase shows a well-defined defect with involvement of the inner > outer tables. More common in the frontal bone. Look for cortical thickening and coarse trabeculation.
• Post surgical: Well-marginated
• Metastases: Permeative margin
• Eosinophilic granuloma: Beveled edge (inner table involved to a greater extent than the outer table). Properly called Langerhans cell histiocytosis under the new classification of histiocytic disordere.
• Encephalocele: Conegnital form is usually parietal or occipital.

In addition to being needlessly long, this mnemonic has the added benefit of being impossible to remember.

Oncogenic (Tumoral) Osteomalacia

Oncogenic osteomalacia occurs with bone or soft-tissue tumors and is characterized by renal phosphate wasting and hypophosphatemia and decreased serum 1,25-dihydroxycholecalciferol levels. Patients with rickets or osteomalacia unexplained by nutrition should be investigated for occult tumor.

Oncogenic osteomalacia is most frequently associated with the phosphaturic mesenchymal tumor, mixed connective tissue variant, but a search for more common tumors such as prostate, breast, small-cell carcinoma of the lung, fibrous dysplasia, and neurofibromatosis is also indicated.

Many cases of hemangiopericytoma leading to oncogenic osteomalacia are now thought to actually represent cases of phosphaturic mesenchymal tumor. In addition, the concept of hemangiopericytoma as a distinct entity has been called into question.

References

• Avila NA, Skarulis M, Rubino DM, Doppman JL. Oncogenic osteomalacia: lesion detection by MR skeletal survey. AJR Am J Roentgenol. 1996 Aug;167(2):343-5.
• Folpe AL, Fanburg-Smith JC, Billings SD, Bisceglia M, Bertoni F, Cho JY, Econs MJ, Inwards CY, Jan de Beur SM, Mentzel T, Montgomery E, Michal M, Miettinen M, Mills SE, Reith JD, O'Connell JX, Rosenberg AE, Rubin BP, Sweet DE, Vinh TN, Wold LE, Wehrli BM, White KE, Zaino RJ, Weiss SW. Most osteomalacia-associated mesenchymal tumors are a single histopathologic entity: an analysis of 32 cases and a comprehensive review of the literature. Am J Surg Pathol. 2004 Jan;28(1):1-30.
• Renton P, Shaw DG. Hypophosphatemic-osteomalacia secondary to vascular tumors of bone and soft tissue. Skeletal Radiol 1976; 5:21-24.

Salter I Fractures of the Toes: Not So Simple

Salter I fractures of the great toe, as seen with stubbed toe injuries, should be considered occult compound fractures due to the intimate relationship of skin, nail, and bone in the toes. As a result, fractures through the growth plate of a distal phalanx carry a high risk of infection and should be treated accordingly.

References

Pinckney LE; Currarino G; Kennedy LA. The stubbed great toe: a cause of occult compound fracture and infection. Radiology. 1981; 138(2):375-7

Pelvic Avulsion Fractures

Avulsion fractures can occur at many points in the pelvis. Going clockwise from the iliac crest to the pubic symphysis on the left we have:

• Iliac crest: Abdominal muscles
• Anterior superior iliac crest: Sartorius
• Anterior inferior iliac crest: Rectus femoris
• Greater trochanter: Gluteal muscles
• Lesser trochanter: Iliopsoas. Isolated nontraumatic avulsion fractures of the lesser trochanter in adults is a pathognomonic sign of metastatic disease.
• Ischial tuberosity: Hamstrings
• Pubic symphysis: Adductor group

A stupid mnemonic is: Alabama's stoned rappers got ill hunting armadillos.

References

Bui-Mansfield LT, Chew FS, Lenchik L, Kline MJ, Boles CA. Nontraumatic avulsions of the pelvis. AJR Am J Roentgenol. 2002 Feb;178(2):423-7.

Tennis Leg

Tennis leg classically presents in a middle-aged person with sport-related acute pain in the middle portion of the calf, associated with a snapping sensation. Initially attributed to rupture of the plantaris tendon, more recent work has implicated rupture of the medial head of the gastrocnemius muscle at the musculotendinous junction as a more common etiology.

References

Delgado GJ, Chung CB, Lektrakul N, Azocar P, Botte MJ, Coria D, Bosch E, Resnick D. Tennis leg: clinical US study of 141 patients and anatomic investigation of four cadavers with MR imaging and US. Radiology. 2002 Jul;224(1):112-9.

Unilateral Rib Notching

Rib notching can be caused by collateral flow through intercostal vessels from the following conditions:

• Coarctation of the aorta proximal to the left subclavian artery: Right-sided
• Coarctation of the aorta with an aberrant right subclavian artery: Left-sided. Occurs when the aberrant right subclavian artery arises after the coarctation.
• Subclavian artery stenosis: Ipsilateral to the side of stenosis
• Blalock-Thomas-Taussig shunt: Ipsilateral to the side of shunt. Due to division of all the branches of the first part of the subclavian artery performed during shunt creation.
• Neurofibromatosis of the intercostal nerves:
• Vascular malformations of the thoracic wall: Enlarged intercostal veins cause the rib notching.
• Superior vena cava obstruction: Due to development of collateral channels to the inferior vena cava via the intercostal veins
• Taboparesis:

References

• Shapiro S, Schrire V. Unilateral notching of the ribs in cyanotic heart disease. Br Heart J. 1964 Sep; 26:620-4.