PubMed · 8335672
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W H Harris. 1993. One step back; two steps forward.. https://doi.org/10.2106/00004623-199307000-00001
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From 1930 to 1994, 54 patients with primary malignant tumors of the sternum were seen. Fifty patients were first seen with a mass, and one half of them also had pain in the sternal region. Two patients had no symptoms at presentation. Among 39 solid tumors were 26 chondrosarcomas, 10 osteosarcomas, 1 fibrosarcoma, 1 angiosarcoma, and 1 malignant fibrous histiocytoma. Of these, 25 were low-grade and 14 were high-grade tumors. Among 15 small cell tumors were 8 plasmacytomas, 6 malignant lymphomas, and 1 Ewing's sarcoma. Partial or subtotal sternectomy was done in 37 patients and total sternectomy in 3. Of the remaining 14 patients, 3 had local excision; 10 had external radiation or chemotherapy without operation, or both; and 1 had no treatment. All but one patient treated by wide resection (N = 40) had some form of skeletal reconstruction of the chest wall defect. Thirty-one (78%) underwent repair with Marlex mesh, and in 25 this was combined with methyl methacrylate. The skin edges were closed per primum in 32 patients; 8 required muscle, omentum, or skin flaps. Resection in chondrosarcomas yielded a 5-year survival (Kaplan-Meier) of 80% (median follow-up, 17 years). The 5-year survival in osteosarcomas was 14%. Resection was curative in 64% of low-grade sarcomas but in only 7% of high-grade sarcomas. In small cell tumors, resection and radiation were helpful for local control; all failures were a result of distant metastases. We conclude that primary sarcomas of the sternum though uncommon are potentially curable by wide surgical excision. With rigid prostheses to repair the skeletal defects, the surgical complication rates are low. Overall survival after complete surgical resection is related to tumor histologic type and grade.
Resistance to compressive strength after setting of the calcium phosphate cement consisting of tetracalcium phosphate (TECP), dicalcium phosphate dihydrate (DCPD), and 40 wt/wt% of a synthetic hydroxyapatite (HAP) was tested. An equimolar mixture of the calcium phosphate powder containing DCPD (particle diameter [D] 0.52-3.33 microns) and TECP (D, 1.1-13.1 microns) transformed into HAP at 37 degrees C, 100% RH after being mixed with 25 mM phosphoric acid. X-ray diffraction suggested that the cement containing fine particles of DCPD and TECP completely transformed to HAP, but that mixtures containing larger particles did not. Because particle size of both DCPD and TECP affected the compressive strength of the cement, the crystal growth of HAP during cement formation depended on the specific surface area (Sw) of the raw materials. The crystallite size of transformed HAP was estimated based on X-ray diffraction peaks at 25.8 and 32.8 degrees attributable to the 002 and 300 planes. The crystalline size attributable to the 300 plane decreased with increasing Sw, but that attributable to the 002 plane showed no significant relationship. The compressive strength of the cement after hardening increased with an increase of its Sw. This suggested that the harder calcium phosphate cement was (derived) from the smaller particle size of the raw materials.
Compressive creep testing of cylindrical specimens machined from two commercial self-polymerizing acrylic bone cements demonstrated measurable creep strains with higher creep strains for the hand-mixed cement specimens compared to vacuum-mixed cement ones. The average creep strains of hand-mixed cement, after 6 h of constant load, ranged from 0.11% at 10.5 MPa to 14.0% at 50 MPa of applied stress. Vacuum mixing reduced the average creep strain to 6.7% after 6 h of applied stress at 50 MPa. There were no significant differences in the creep response between the two types of acrylic cements. The difference in creep resistance of the two cements was reduced after vacuum mixing (P = .013), which also significantly reduced the cement's internal porosity.