Biomedical subjects

William A Jiranek

Publications and source records attributed to William A Jiranek.

7 recordsLinked to original sources

PubMed2006

Effect of pigmentation on the mechanical and polymerization characteristics of bone cement.

The impact on performance of additives to bone cement must be assessed before clinical use of the modified product. This study performed several standard acrylic bone cement tests on 3 commercially available products: Endurance, Surgical Simplex P, and Pigmented Endurance. The polymerization characteristics, consisting of doughing time, setting time, and maximum exothermic temperature, were found to be acceptable by the standards of the American Society for Testing and Materials/International Organization for Standards. For the mechanical characterization, analysis revealed statistical equivalence among all cement types, with the exception of compressive strength where Pigmented Endurance was stronger than Surgical Simplex P (P < .02). In mechanical fatigue, there were no significant differences in the log cycles to failure among the cements; however, Weibull analysis predicted Surgical Simplex P to have a higher characteristic life than the other cements. In conclusion, differences do exist among cement types, but the addition of pigment to Endurance did not alter its performance.

Biomechanical Phenomena↗

PubMed2006

Antibiotic-loaded bone cement for infection prophylaxis in total joint replacement.

Use of antibiotic-loaded bone cement for prophylaxis against infection is not indicated for patients not at high risk for infection who are undergoing routine primary or revision joint replacement with cement. The mechanical and elution properties of commercially available premixed antibiotic-loaded bone-cement products are superior to those of hand-mixed preparations. Use of commercially available antibiotic-loaded bone-cement products has been cleared by the United States Food and Drug Administration only for use in the second stage of a two-stage total joint revision following removal of the original prosthesis and elimination of active periprosthetic infection. Use of antibiotic-loaded bone cement for prophylaxis against infection in the second stage of a two-stage total joint revision involves low doses of antibiotics. Active infection cannot be treated with commercially available antibiotic-loaded bone cement as such treatment requires higher doses of antibiotics.

Anti-Bacterial Agents↗

PubMed2005

Mechanical effects of the extended trochanteric osteotomy.

BACKGROUND: The extended trochanteric osteotomy was introduced as a safe and effective exposure technique for revision hip surgery; however, intraoperative iatrogenic femoral fractures have been reported. This study examined the effects of the extended trochanteric osteotomy on the torsional strength of the femur with use of cadaver bones. We hypothesized that repair of the osteotomy fragment would restore the torsional strength to that of an intact femur and that an osteotomized femur containing a well-fixed stem would have the same torsional strength as an intact femur with a stem. METHODS: Fifty-eight cadaveric human femora were divided into five groups, according to the repair technique, to examine the effects of the extended trochanteric osteotomy: intact, osteotomy, repaired osteotomy, implant, and implant-repaired osteotomy. Osteotomy fragments were reattached with use of three double-looped 18-gauge wires. A femoral stem was cemented into the last two groups. Specimens were tested mechanically in rotation until failure. Rotational properties were compared with one-way analysis of variance followed by post hoc pairwise comparisons. Linear regression analysis was performed for bone mineral density and torsional strength. RESULTS: Torque to failure was reduced by 73% for the specimens in the osteotomy group compared with the intact group (p < 0.0001). Repair of the osteotomy did not improve torque to failure (p > 0.99). Femora in the implant-repaired osteotomy group displayed significantly improved torque-to-failure values compared with the specimens in the osteotomy and repaired osteotomy groups (p < 0.0001). However, the strength of the femora in the implant-repaired osteotomy group remained significantly less than that of the specimens in the implant group (p < 0.007). A significant linear relationship was observed between bone mineral density and torque to failure for femora in the intact (p < 0.006), osteotomy (p < 0.002), and repaired osteotomy (p < 0.001) groups. CONCLUSIONS: The extended trochanteric osteotomy reduces torsional strength by 73% even when the osteotomy fragment is repaired. Bone mineral density directly affects absolute femoral strength in this model.

Adult↗

PubMed2004

The results of tibial tubercle osteotomy for revision total knee arthroplasty.

Tibial tubercle osteotomy was used in the surgical exposure of 67 knees in 64 patients undergoing revision total knee arthroplasty. The clinical and radiographic results were reviewed retrospectively. The mean follow-up time was 30 months (range, 5-60 months). Knee Society scores (KSS) confirmed good or excellent results in 87% of the knees, and the mean KSS was 86. The procedure was particularly effective in 2-stage exchanges for infected total knee arthroplasty, in which infection was eradicated in 9 of 10 cases, with a mean KSS of 82. In this series, no patellofemoral complications, no component malalignments, and no avulsions of the patellar tendon occurred. Serious complications directly related to the tibial tubercle osteotomy occurred in 5 patients (7%).

Adult↗

PubMed2004

The incidence of heterotopic ossification after total knee arthroplasty.

Five hundred consecutive patients undergoing primary cemented knee arthroplasties were prospectively followed up and evaluated for the presence of heterotopic ossification. Of the patients studied, 95% had osteoarthritis and 5% had inflammation. A radiographic grading system was devised based on the size and location of the heterotopic bone. The overall incidence of heterotopic ossification in this group was 15%. The patients who developed HO tended to be heavier than the average and were more likely to be men. This is the most comprehensive prospective study of the incidence of HO in primary cemented knee arthroplasty. Other than a small subset of the patients (4 of 500), HO does not appear to have a major influence on the outcome of knee arthroplasty.

Aged↗

PubMed2004

Dynamic confirmation of fixation techniques of the tibial tubercle osteotomy.

The tibial tubercle osteotomy is gaining popularity for revision total knee arthroplasty; however, the potential for tubercle displacement has been a concern. This study compared the mechanical behavior of the tibial tubercle osteotomy after screw and cerclage wire fixation. Tibial tubercle osteotomy was done on 40 tibias from cadavers with equal numbers fixed by either screws or wires. Specimens were loaded cyclically to simulate straight leg raises and then loaded to failure with the patellar tendon oriented 0 degrees or 25 degrees from the tibial axis. Tibial tubercle osteotomy cyclic displacement was greater for wire constructs at 25 degrees than all other constructs. Failure loads were greater for screw constructs at 25 degrees than both wire constructs. Screw constructs failed at 1429 +/- 348 N (0 degrees) and at 1925 +/- 982 N (25 degrees). Wire constructs failed at 1072 +/- 260 N (0 degrees) and at 893 +/- 293 N (25 degrees). Bone mineral density correlated positively with failure loads. Straight leg raise (400 N) and knee extension (250 N) against gravity during rehabilitation should be feasible with either screw or wire fixation after tibial tubercle osteotomy. Special care should be taken for the large patient and patients with decreased bone density.

Biomechanical Phenomena↗

PubMed2003

Acetabular liner fixation by cement.

Many situations in revision THA require the exchange of a PE liner in the setting of a well-fixed cementless acetabular shell. Unfortunately, a replacement liner is not always available, the locking mechanism of the metal shell may be damaged or incompatible with the desired liner, or the shell is malpositioned. Revision of a well-fixed cementless acetabular shell has been associated with considerable morbidity. This raises several questions: can a new PE liner be fixed in the existing shell using bone cement, and if so, which techniques can improve the end result, and in which patients should they be used? Biomechanical testing of cemented PE liners has shown initial fixation strengths that exceed conventional locking mechanisms. It is not known during what period this initial fixation will fail, but clinical reports with followup of as many as 6 years have shown survival in approximately 90% of cases. These studies have shown the importance of proper patient selection, accurate sizing of the PE liner, careful preparation of the substrate of the liner and the shell, and good cement technique. The potential advantages of this technique are less surgical morbidity, more rapid surgery and patient recovery, the ability to incorporate antibiotics in the cement, and more liner options.

Acetabulum↗