Dalteparin in Preventing DVT in Participants With Cancer

Inclusion Criteria:

* GROUP A
* Metastatic disease, myeloma, lymphoma.
* Pathologic fracture or impending pathologic fracture of the femur.
* Intramedullary rod, plating, cementation, hip arthroplasty, or knee arthroplasty.
* GROUP B
* Primary sarcoma of bone or soft tissue of the lower extremity.
* T2 tumor (\> 5 cm by \< 20 cm).
* Radical resection of tumor, which may necessitate major bone or soft tissue reconstruction.

Exclusion Criteria:

* Presence of DVT on pre-operative screening ultrasound study.
* Massive tumor (\> 20 cm in greatest dimension).
* Amputation of the affected leg as treatment of tumor.
* Estimated blood loss \> 2 liters during surgery.
* Surgical drain output \> 500 cc of bloody fluid during first 8 hours.
* International normalized ratio (I.N.R.) \> 1.3 pre-operatively or \> 1.5 post-operatively.
* Platelet count \< 100,000 either pre-operatively or post-operatively.
* Indwelling post-operative epidural catheter for pain control.
* History of underlying bleeding disorder, such as hemophilia.
* History of adverse reaction to heparin such as heparin-induced thrombocytopenia.
* Severe liver or renal insufficiency.
* History of hypertensive or diabetic retinopathy.
* History of gastro-intestinal bleeding within 12 months.
* Treatment with warfarin, clopidogrel, aspirin, nonsteroidal antiinflammatory drugs (NSAIDs), low molecular weight heparin (LMWH) or other anti-coagulants for conditions.
* History of stroke.
* Women of child bearing potential having a positive urine or serum pregnancy test (human chorionic gonadotropin \[hCG\]) at the time of pre-operative evaluation (within 7 days of surgery).
* Women who are breastfeeding.
* Hemoglobin \< 8.0 g/dL.
* Platelet count \< 100,000/L.
* Alanine aminotransferase \> 100 IU/L.
* Aspartate aminotransferase \> 100 IU/L.
* Direct bilirubin \> 0.5mg/dL.
* Serum creatinine \> 2.0 mg/dL.
* Patients taking COX-2 inhibitors.
* Patients who have fragmented mechanical heart valves.