Bone density changes after radiation for extremity sarcomas: exploring the etiology of pathologic fractures.

PURPOSE: The incidental irradiation (RT) of adjacent bone that takes place during treatment of soft tissue extremity sarcomas is generally presumed to "weaken" the bone by decreasing its density, which subsequently increases the risk for pathologic fracture. This investigation intended to assess the relative effects on bone density of both RT and diminished mechanical loading secondary to tumor-induced and therapy-induced functional extremity impairment. METHODS AND MATERIALS: 19 patients treated with surgical excision and RT for soft tissue extremity sarcomas had bone density measured using dual energy X-ray absorptiometry at four sites: the irradiated (A) and contralateral (B) bone, and an uninvolved bone (C) in the treated extremity and its contralateral counterpart (D). Analysis included (1) [A-B], (2) [C-D], (3) [(A-B), - (C-D)], and (4) [(A-B)/B - (C-D)/D]. RESULTS: The mean bone density for all irradiated sites was increased 0.08 ± 0.22 g/cm(2) (variance) compared to the contralateral unirradiated side when corrected for weight-bearing effects (3). An average increase in bone density of 9 ± 22% (p = 0.08) was also seen when the differences were divided by individual control densities to normalize variation in density of different anatomic sites (4). CONCLUSIONS: RT does not routinely decrease bone density when corrected for weight bearing or mechanical effects. The pathogenesis for the known increased risk of pathologic fracture in irradiated bones is likely multifactorial, including possible alterations in bone remodeling that can result in stable, or even increased, bone density. Further clinical and basic studies are needed to confirm our unexpected findings.

Bovine thrombin induces an acquired coagulopathy in sensitized patients undergoing revision spinal surgery: a report of two cases.

STUDY DESIGN: A report of two cases is presented. OBJECTIVE: To raise awareness of bovine thrombin-induced factor V deficiency. SUMMARY OF BACKGROUND DATA: Bovine thrombin is a frequently used hemostatic agent in spinal surgery. Current preparations contain clotting factors in addition to thrombin, particularly factor V, which are immunogenic. Re-exposure of sensitized patients to bovine thrombin products during subsequent surgery may lead to the formation of antibodies that cross-react with human clotting factors, most commonly against factor V. Hemorrhagic complications have been reported in nonspinal patients due to a bovine thrombin-induced factor V deficiency. METHODS: Two spinal cases are reported, and the literature is reviewed. RESULTS: In the cases outlined, both patients underwent revision spinal surgery, with re-exposure to bovine thrombin. Both patients developed abnormal coagulation profiles, with an acquired factor V deficiency. No hemorrhagic complications occurred; however, second-stage surgery was delayed in one patient and not undertaken in the other. In both patients, the coagulopathy resolved spontaneously. CONCLUSIONS: Bovine thrombin-induced coagulopathy is well recognized in cardiac surgery but has not been reported in spinal surgical patients. Data available from cardiac surgical patients suggests that those who are sensitized to two or more bovine clotting factors are at greatest risk of hemorrhagic complications. The cases we present demonstrate that this phenomenon occurs in spinal surgical patients and serve to raise awareness of the potential danger of bovine thrombin in sensitized patients.