Structure, metallurgy, and mechanical properties of a porous tantalum foam.

This study evaluated a porous tantalum biomaterial (Hedrocel) designed to function as a scaffold for osseous ingrowth. Samples were characterized for structure, Vickers microhardness, compressive cantilever bending, and tensile properties, as well as compressive and cantilever bending fatigue. The structure consisted of regularly arranged cells having struts with a vitreous carbon core with layers of CVI deposited crystalline tantalum. Microhardness values ranged from 240-393, compressive strength was 60 +/- 18 MPa, tensile strength was 63 +/- 6 MPa, and bending strength was 110 +/- 14 MPa. The compressive fatigue endurance limit was 23 MPa at 5 x 10(6) cycles with samples exhibiting significant plastic deformation. SEM examination showed cracking at strut junctions 45 degrees to the axis of the applied load. The cantilever bending fatigue endurance limit was 35 MPa at 5 x 10(6) cycles, and SEM examination showed failure due to cracking of the struts on the tension side of the sample. While properties were variable due to morphology, results indicate that the material provides structural support while bone ingrowth is occurring. These findings, coupled with the superior biocompatibility of tantalum, makes the material a candidate for a number of clinical applications and warrants further and continued laboratory and clinical investigation.

Torsional properties of healed canine diaphyseal defects grafted with a fibrillar collagen and hydroxyapatite/tricalcium phosphate composite.

The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFTTM), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFTTM material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFTTM had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFTTM. The final conclusion is that in this model, grafting with COLLAGRAFTTM provided torsional properties at one year postoperatively at least equivalent to autogenous bone.

Factors influencing the risk of early and late serious infection in adults after splenectomy for trauma.

We reviewed the clinical course of 245 adults who underwent splenectomy for trauma to assess the risk of both early and late serious infection. Twenty-one patients (9%) had an early serious infection (sepsis) during hospitalization for splenectomy. The mortality rate was 62% in patients with early sepsis, and encapsulated bacteria were isolated from the blood of 43% of patients with sepsis. Only one of 58 patients with isolated splenic injury had sepsis (2%), and the risk of early sepsis increased when three or more concomitant injuries were present (p less than 0.05). Stepwise multiple regression analysis revealed that patients with injuries to the pancreas, colon, or central nervous system or with extremity fractures had an increased risk of sepsis (p less than 0.05). The risk of sepsis was not influenced by age, the type of injury, delay in operation, use of drains, or other individual injuries. Sufficient information was available to assess the risk of late serious infection for 140 surviving patients (63%). Follow-up ranged from 2 to 277 months. Three late infections occurred at 2, 8, and 15 years after splenectomy; two were due to Streptococcus pneumoniae. None of these patients died. There were no identifiable factors influencing the risk of late infection. These results suggest that the risk of early serious infection in adults after splenectomy for trauma is low when isolated splenic injury is present but that this risk is increased by both the degree of injury and the presence of certain associated injuries. Encapsulated bacteria are frequent pathogens in both early and late infections. The mortality rate related to an early septic episode is high, but the risk of late serious infection is low and is not related to identifiable factors that decrease host defenses.

Developing trends in acute cholecystitis and choledocholithiasis.

Among 2,347 operations performed for acute cholecystitis during a 46 year period, 1932 to 1978, choledochotomy was combined with either cholecystectomy or cholecystostomy in 364 instances. A report published for the first period, 1932 to 1955, is compared with a comparable period, 1955 to 1978. A greater number of patients were operated upon during the second period, 83 for the first 23 years and 276 for the second 23 year period. The average age increased from 49.6 to 65.3 years. The incidence of choledocholithiasis increased from 59 to 62 per cent. The ratio of females to males shifted from 4.2:1.0 for 1932 to 1955 to 1.6:1.0 for 1955 to 1978. Associated conditions recognized preoperatively increased from 2.5 per patient to 4.9 per patient. Postoperative complications increased from 27 in 83 patients, 1932 to 1955, to 250 complications in the 276 patients, 281 operations, in the second series, 1955 to 1978. The mortality increased from 2.5 to 10.9 per cent. In the past 46 years, 97 per cent of the deaths occurred in patients 50 years of age or older, with only one death, 3 per cent, occurring in a patient less than 50 years old, and this patient was operated upon in the second series, 1955 to 1978. It is suggested that the increased age and associated conditions at the time of operation for a sequelae of calculous biliary tract disease account fort the increased mortality. Undelayed cholecystectomy for cholelithiasis following the establishment of the diagnosis should prevent the sequelae of acute cholecystitis with presumed choledocholithiasis.