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Biomedical subjects

T A DeCoster

Publications and source records attributed to T A DeCoster.

8 recordsLinked to original sources
PubMed1992

Removal of intramedullary rods after femoral shaft fracture.

We are reporting a retrospective review of the removal of 60 intramedullary rods in 58 patients. All fractures had healed at the time of rod extraction. The implant was removed from 34 asymptomatic patients (36 femurs). Twenty-four patients (24 femurs) had preoperative symptoms attributed to the femoral rod. Fourteen patients had symptoms about the greater trochanter preoperatively, five patients had symptoms referable to the knee, and five had infections about the femoral implant. Problems encountered included broken rods in five femurs, one of which was not apparent on preoperative radiographs. There were six patients (six femurs) who required further hospital care for postoperative hematomas. The development of a significant hematoma was not related to the location of the fracture, the presence of interlocking devices requiring removal, the length of time since injury, the performance of this procedure as an inpatient or outpatient, or the presence or absence of a functional drain. Of the 10 patients (10 femurs) who had proximal heterotopic ossification Brooker stage 2 or greater, wound hematomas developed in four patients (40%). There were no refractures. Although there may be an indication for rod removal, we do not recommend the procedure in asymptomatic patients.

Adolescent↗
PubMed1992

Pullout strength of power- and hand-driven staples in synthetic bone: effect of design parameters.

The pullout strength of power-driven and hand-driven staples of different sizes and different leg profiles was investigated in a synthetic bone model. Consistent material properties were reflected in the relatively small standard deviation in pullout strength, which was less than 7% of the mean value for power-driven and less than 10% of the mean value for hand-driven staples. An approximate linear relationship was shown to exist between the mean value of pullout strength and foam density. In paired studies, the mean value of pullout strength was significantly (p less than 0.0005) greater for the power-driven staples than similar size hand-driven staples. It was also shown that a square cross section creates significantly (p less than 0.017) more resistance to pullout force than a circular section of similar or even larger area. Although the pullout strength was not a function of the staple's width, the staple's leg length contributed to its pullout strength in a nonlinear fashion. This study suggests that narrow, long, power-driven staples of rectangular cross section have the best pullout strength for similar cross-sectional area.

Bone Density↗
PubMed1990

Optimizing bone screw pullout force.

Stability of internal fixation by plate and screw depends on the interface of bone and screw threads. Bone-screw thread design was tested in a synthetic bone model to determine maximum bone-screw pullout force. The model was confirmed to provide reproducible results in a clinically relevant range. Consistent material properties were reflected in the relatively small standard deviations in pullout force, which were less than 10% of mean values. As expected, major diameter was an important determinant of pullout force in a roughly linear manner. Pitch was important with a finer thread giving greater purchase. Minor diameter and the ratio of major to minor diameter had a small but significant effect on pullout force. This study was significant for establishing a good bone-screw testing model and suggesting important thread parameters in selecting or manufacturing a bone screw to optimize its holding power.

Biomechanical Phenomena↗
PubMed1989

Hip arthroplasty after biplanar femoral osteotomy.

Hip arthroplasty in patients who have had previous biplanar femoral osteotomy (eg, Southwick) is a technical surgical problem. Distorted proximal femoral anatomy may make routine insertion of a femoral prosthesis impossible. The authors report the short-term results in three patients with hip arthroplasty after biplanar femoral osteotomy. The technique consists of a biplanar closing wedge osteotomy at the level of the lesser trochanter to correct the previous surgical deformity. The remaining proximal femur becomes a vascularized bone graft that is skewered by the femoral prosthesis, which also gains purchase in the medullary canal of the proximal femoral shaft. This technique allows restoration of anatomic femoral alignment and the use of standard prostheses with preservation of bone stock. The initial results have been very good. The appearance of the hip is very similar to that in primary hip arthroplasty.

Adult↗
PubMed1988

Depth of insertion of transpedicular vertebral screws into human vertebrae: effect upon screw-vertebra interface strength.

Improvement in the strength of the transpedicular screw-vertebra interface by increasing the depth of screw insertion may provide improved performance of spinal implants using such screws. Within human cadaveric vertebrae, we measured the failure strength of Vermont Spinal Fixator (VSF) screws under flexion or torsion loads and of Schanz screws under pull-out loads (along the screw axis). Comparisons between opposite pedicles of vertebral specimens were made at 50 vs. 80% and 80 vs. 100% of maximum available insertion depth. Mean failure strength of VSF screws at 50% depth was 75-77% (depending upon load type) of that at 80% depth; strength for screws at 100% ("to-cortex") depth was 124-154% of that at 80%. Reanalysis of the data from Lavaste shows, contrary to his conclusion, a 26% increase in strength from a 5-mm increase in screw depth of insertion. All these differences were significant (p less than 0.05) by the matched-pairs t test. Benefit from the increased strength of deeper screw placement must be balanced against possible increased operative risk. A "near-approach" x-ray view is suggested here to decrease that presumed operative risk.

Bone Screws↗
PubMed1988

Computer corner #19. The computer as an aid to the orthopaedic resident for record-keeping.

This paper delineates a simple method of assisting orthopaedic residents in computer-based record-keeping. A step-by-step example is used to show the ease with which this system can be employed and modified to fit individual needs. Record-keeping is important to verify case load to individual departments and to the Residency Review Committee. It also allows the use of the records for case reviews and research, as well as making the resident more computer-literate.

Computers↗
PubMed1988

Cast brace treatment of proximal tibia fractures. A ten-year follow-up study.

The long-term outcome of tibial plateau fractures treated by cast bracing was observed in 29 patients sustaining 30 tibial plateau fractures more than ten years after injury. Clinical and roentgenographic evaluation was performed and showed 61% good results overall. Range of motion averaged 117 degrees. Iowa knee score averaged 71 of 100 possible points. Thirty-two percent of the patients developed moderate or severe roentgenographic posttraumatic degenerative arthritis. Minimally displaced fractures were observed to do very well clinically without roentgenographic evidence of degenerative joint disease after a ten-year follow-up period. Seventy percent of displaced bicondylar fractures developed degenerative joint disease in clinical and roentgenographic evaluation. Cast bracing of minimally displaced fractures gave satisfactory results, whereas cast bracing of more complex fractures produced variable functional results.

Adult↗