|
Year |
2005 |
|---|---|
|
Question Number |
13. |
|
Category |
Orthopaedic Disease |
Question
Pathologic fractures that occur secondary to metastatic carcinoma most frequently involve what long bone location?
1- Distal femur
2- Proximal humerus
3- Proximal femur
4- Proximal tibia
5- Humeral diaphysis
Figures
Answer (click for answer)
The correct answer is 3.
Cancers that commonly metastasize to bone are prostate, breast, kidney, thyroid and lung. Other types that less commonly metastasize to bone include cancers of the skin, oral cavity, esophagus, cervix, stomach and colon. The most common site of bone metastasis is the spine, however the proximal femur is the most common LONG bone site. The order of frequency are spine > proximal femur > distal femur > humerus > pelvis/acetabulum > other > scapula
The most common destructive lesion of bone in the adult (>40) is metastatic cancer. The most common primary malignancy to spread to bone is breast, followed by prostate, lung, kidney, and thyroid. The first 3 listed are logical since they constitute the 3 most common types of cancer in the US. The fourth most common, Colon Ca, is curiously not on this list. The reason for this is Batson’s venous plexus, a venous system which drains blood from breast, prostate, lung, kidney, and thyroid into the vertebral vein; this vein in turn has intimate association with the spine, pelvis, proximal humerus, and proximal femur.
The proximal femur is an important site of metastastis for 2 reasons: common area of metastasis and normally subject to high loads (making structural change caused by metastasis highly likely to result in pathologic fracture). Mirel’s criteria is used to assess whether metastatic bone lesions warrant prophylactic fixation (to prevent pathologic fracture). It is based on degree of pain/impairment; whether the lesion is lytic, mixed, or blastic; the extent of cortical destruction; and, important to this question, whether the peritrochanteric area of the proximal femur is involved.
Reference: Ward WG. Holsenbeck S. Dorey FJ. Spang J. Howe D. Metastatic disease of the femur: surgical treatment.
Journal Article Clinical Orthopaedics & Related Research. (415 Suppl):S230-44, 2003 Oct.