Stacked 1/3 Tubular Plates for Fixation of Pediatric Forearm Fractures: A Biomechanical Study.

Introduction: Among operatively treated pediatric forearm fractures, many different fixation constructs are described. The goal of this study was to define the biomechanical properties of a double stacked 1/3 tubular plate construct used by the senior author for some fractures and to review available literature regarding the use of stacked plates. Methods: Biomechanical testing was performed by 4-point bending of three different plate constructs: 1/3 tubular plate, stacked 1/3 tubular plates, and 2.7 mm LC-DCP plate. Five test specimens were evaluated for each of the three plate constructs. From stress-strain curves, flexural stiffness (N/mm), force to cause plastic deformation (N), and force to cause 10° bend (N) were calculated and compared using standard t-test statistics. Results: Key outcome parameter means (± SD) for the three plate constructs (1/3 tubular plate, stacked 1/3 tubular plates, and 2.7 mm LC-DCP plate) were reported respectively as follows: flexural stiffness (55.4 ± 3.5 N/mm, 131.7 ± 3.5 N/mm, 113.3 ± 12.1 N/mm), force to cause plastic deformation (113.6 ± 11.0 N, 242.1 ± 13.0 N, 192.2 ± 17.9 N), and force to cause a 10° bend (140.0 ± 8.4 N, 299.4 ± 14.1 N, 265.5 ± 21.2 N). Mean values of all three measures were significantly larger for the stacked 1/3 tubular plates than for the other plate constructs. Conclusions: The stacked 1/3 tubular plate construct was biomechanically superior to the other plate constructs tested. Stacked plating significantly improved stiffness of the fracture fixation construct supporting the use of this technique in selected trauma cases.

Cut Cortical Screw Purchase in Diaphyseal Bone: A Biomedical Study.

Introduction: During fracture osteosynthesis, traumatologists may remove screws which are too long, cut the excess length from the screw tip, then reinsert the cut screw (CS) to minimize implant waste. The purpose of this study was to determine if this practice influences screw purchase. Methods: Using an axial-torsion load device, the maximal insertion torque (MIT) required to insert 3.5 mm stainless steel cortical screws into normal and osteoporotic bone models was measured. MIT was determined in three different test conditions: (1) long screw (LS) insertion; (2) LS insertion, removal, and insertion of a normal-length screw (NS); and, (3) LS insertion, removal, cutting excess length from the screw tip, and reinserting the CS. Results: In the normal bone model, mean (± SD) MIT of LS insertion was 546 ± 6 Newton-centimeters (N-cm) compared to 496 ± 61 N-cm for NS reinsertion and 465 ± 69 N-cm for CS reinsertion. In the osteoporotic bone model, MIT of LS insertion was 110 ± 11 N-cm, whereas the values for NS and CS reinsertions were 98 ± 9 N-cm and 101 ± 12 N-cm, respectively. There was no significant difference in MIT between CS and NS reinsertions in the osteoporotic bone analog. Conclusions: Cutting excess length from a 3.5 mm stainless steel cortical screw did not decrease its purchase regardless of bone density. During osteosynthesis, orthopaedists may remove screws which are too long, cut the screw tip, and reinsert the shortened screw as a cost-saving measure without compromising fracture fixation.

Comparative Analysis of Topical Versus Intravenous Administration of Epsilon-Aminocaproic Acid on Blood Management in Total Knee Arthroplasty.

Introduction: Although the use of antifibrinolytics to reduce perioperative blood loss during total knee arthroplasty (TKA) has shown unequivocal benefit in regard to blood conservation, the best route of administration remains in question. This study tested the hypothesis that topical delivery of epsilon-aminocaproic acid (EACA) was superior to intravenous (IV) administration in the setting of primary TKA. Methods: This cross-sectional study included a six-year retrospective chart review of TKA patients done by a single surgeon. Post-operative hemoglobin levels and the incidence of blood transfusions were compared among three patient subgroups: no EACA, topical EACA, or IV EACA. Key outcome measures included post-operative hemoglobin, need for post-operative transfusion, and length of hospital stay. Results: Of the 668 patients included in this study, 351 (52.5%) received IV EACA, 298 (44.6%) received topical EACA, and 19 (2.8%) received no EACA. For the three-way comparisons, significant differences were observed for post-operative mean hemoglobin on day one (p < 0.001), day two (p < 0.001), and day three (p = 0.004), with consistently higher means for participants in the topical group. Eight patients required transfusions in the IV EACA group, but none were needed in the topical EACA group (p = 0.027). Length of stay was shortest for patients in the topical group, with 66% hospitalized for two days, while 84% of the IV group remained hospitalized for three days (p < 0.001). Conclusions: The topical delivery of EACA is superior to IV administration with respect to blood conservation for patients undergoing primary TKA.

Effect of Ultrasound Frequency and Treatment Duration on Antibiotic Elution from Polymethylmethacrylate Bone Cement.

INTRODUCTION: The objective of this study was to evaluate the effect of ultrasound frequency and treatment duration on antibiotic-impregnated polymethylmethacrylate (PMMA) antibiotic elution rates and mechanical strength. METHODS: Two batches of PMMA were prepared: one with five grams of vancomycin powder and one without. Each batch was divided into two frequency groups: kHz and MHz. Each frequency group was divided into two duration groups: two minutes and ten minutes. Elution samples were measured daily using flow injection analysis. After one week of elution, ultrasound treatments were done daily until each group's average concentration fell below those of non-ultrasound control groups. After elution testing, compression testing determined mechanical properties. Paired t-tests were used to compare daily elution amounts to baseline values. Univariate ANOVAs were used to test for effects of both frequency and treatment duration on antibiotic elution amounts and on mechanical properties. RESULTS: All ultrasound treatments resulted in significant increases in antibiotic elution. Frequency and duration had significant effects of increasing antibiotic elution (p < 0.001). The kHz group produced significantly greater antibiotic elution than the MHz group (p < 0.001). The 10-minute duration produced significantly greater antibiotic elution than the two-minute duration (both p < 0.001). Frequency and duration did not have significant effects on yield stress (p = 0.841 and p = 0.179, respectively). Frequency had a significant effect (p = 0.024) on modulus, but duration did not (p = 0.136). CONCLUSIONS: Ultrasound frequency and treatment duration significantly affect antibiotic elution from PMMA which may be helpful for treatment of periprosthetic joint infections during revision arthroplasty.