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OBJECTIVE To compare immediate quality of open reduction of femoral neck fractures by alternative surgical approaches. DESIGN Retrospective cohort study. SETTING Twelve Level 1 North American trauma centers. PATIENTS Eighty adults 18-65 years of age with isolated, displaced, OTA/AO type 31-B2 or -B3 femoral neck fractures treated with internal fixation. INTERVENTION Thirty-two modified Smith-Petersen anterior approaches versus 48 Watson-Jones anterolateral approaches for open reduction performed by fellowship-trained orthopaedic trauma surgeons. MAIN OUTCOME Reduction quality as assessed by 3 senior orthopaedic traumatologists as "acceptable" or "unacceptable" on AP and lateral postoperative radiographs. RESULTS No difference was observed in the rate of acceptable reduction by modified Smith-Petersen (81%) versus Watson-Jones (81%) approach (risk difference null, 95% confidence interval -17.4% to 17.4%, P = 1.00) with 90.4% panel agreement (Fleiss' weighted κ = 0.63, P < 0.01). Stratified analyses did not identify a significant difference in the rate of acceptable reduction between approaches when stratified by Pauwels angle, basicervical or transcervical fracture location, or posterior comminution. The Smith-Petersen approach afforded a better reduction when preoperative skeletal traction was not applied (RR = 1.67 [95% CI 1.10-2.52] vs. RR = 0.87 [95% CI 0.70-1.08], P = 0.006). CONCLUSIONS No difference was observed in the quality of open reduction of displaced femoral neck fractures in young adults when a Watson-Jones anterolateral approach versus a modified Smith-Petersen anterior approach was performed by orthopaedic trauma surgeons. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Objectives To determine (1) which factors are associated with the choice to perform an open reduction and (2) by adjusting for these factors, if the choice of reduction method is associated with reoperation. Design Retrospective cohort study with radiograph and chart review. Setting Twelve Level 1 North American trauma centers. Patients Two hundred thirty-four adults 18-65 years of age with an isolated, displaced, OTA/AO type 31-B2 or type 31-B3 femoral neck fracture treated with internal fixation with minimum of 6-month follow-up or reoperation. Exclusion criteria were pathologic fractures, associated femoral head or shaft fractures, and primary arthroplasty. Intervention Open or closed reduction technique during internal fixation. Main outcome Cox proportional hazard of reoperation adjusting for propensity score for open reduction based on injury, demographic, and medical factors. Reduction quality was assessed by 3 senior orthopaedic traumatologists as "acceptable" or "unacceptable" on AP and lateral postoperative radiographs. Results Median follow-up was 1.5 years. One hundred six (45%) patients underwent open reduction. Reduction quality was not significantly affected by open versus closed approach (71% vs. 69% acceptable, P = 0.378). The propensity to receive an open reduction was associated with study center; younger age; male sex; no history of injection drug use, osteoporosis, or cerebrovascular disease; transcervical fracture location; posterior fracture comminution; and surgery within 12 hours. A total of 35 (33%) versus 28 (22%) reoperations occurred after open versus closed reduction (P = 0.056). Open reduction was associated with a 2.4-fold greater propensity-adjusted hazard of reoperation (95% confidence interval 1.3-4.4, P = 0.004). A total of 35 (15%) patients underwent subsequent total hip arthroplasty or hemiarthroplasty. Conclusions Open reduction of displaced femoral neck fractures in nonelderly adults is associated with a greater hazard of reoperation without significantly improving reduction. Prospective randomized trials are indicated to confirm a causative effect of open versus closed reduction on outcomes after femoral neck fracture. Level of evidence Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Traditionally, the orthopaedic trauma literature has been dominated by small studies that were largely single-center initiatives. More recently, there has been a paradigm shift toward larger, multicenter studies because the orthopaedic community embraced the concepts of evidence-based medicine and the need for high-quality research to guide clinical practice. The International Orthopaedic Multicenter Study in Fracture Care is a large multicenter international cohort study in musculoskeletal trauma in Africa, Asia, and Latin America. This is the first study of this magnitude within the global orthopaedic trauma community. The International Orthopaedic Multicenter Study in Fracture Care study has provided an opportunity to form new international collaborative relationships and to develop new research capacity and global collaborative relationships that will provide the foundation for future studies in injury prevention and management. Levels of evidence IV.

In March 2016, North American academic leaders with an interest in and commitment to the field of global orthopaedics met in Orlando, Florida, to gauge each institution's clinical, research, and educational programs in developing countries, establish the main limitations to participating in global health efforts, and assess areas of need for both the participating institutions and their international partners. After this inaugural meeting, a needs assessment survey was distributed to the group to better understand how to organize and unify the individual institutional global efforts. The results revealed that surgeons believed there was a vital need for improved communication, mentorship, and infrastructural support between North American universities. To this end, the Consortium of Orthopaedic Academic Traumatologists (COACT) was founded. The COACT seeks to promote a novel framework geared toward improving trauma care capacity by building collaborative partnerships among leading academic centers across the United States and Canada. The consortium represents a comprehensive partnership that promotes communication, collaboration, and advocacy through a central network to facilitate investigative, educational, and clinical services. Academic partners share best practices, resources, and opportunities in their international outreach projects in low- and middle-income countries in the field of orthopaedic trauma. Over the course of the past 2 years, the COACT has grown to more than 80 faculty, fellow, resident, and student members, representing over 20 orthopaedic institutions across North America.

Trauma continues to be a leading cause of mortality and morbidity in lower to middle-income countries. To meet the ever-growing need of musculoskeletal care in trauma patients, orthopaedic surgeons play an instrumental role in providing care, guided by relevant clinical research studies. Promoting research and publishing results are both crucial to influencing trauma-related skeletal injury treatment in lower to middle-income countries. Currently, few opportunities exist for trauma surgeons in Latin America to participate in clinical research or to contribute to academic publications, thereby limiting their ability to address potentially critical treatment questions faced by their specific patient populations. In response to these obstacles, in 2017, a group of 60 surgeon leaders representing 18 countries throughout Latin America developed the Asociación de Cirujanos Traumatólogos de las Américas (ACTUAR; www.actuarla.org). The ACTUAR supports investigative opportunities for Latin American orthopaedic trauma surgeons who want to contribute through collaborative research work. This pioneering initiative aims to improve trauma-related research, clinical care, and health care policies through the development of an international network across the Americas.

BACKGROUND Although orthopaedic trauma occurs at higher rates in low- and middle-income countries (LMICs), most research on this topic is conducted in high-resource settings. Few initiatives exist to promote local research in LMICs. Investigators created the Institute for Global Orthopaedics and Traumatology (IGOT) International Research Symposium to promote local research initiatives by surgeons practicing in low-resource environments. The purpose of this study is to determine the efficacy of this symposium in teaching orthopaedic surgeons practicing in LMICs how to conduct clinical research. METHODS In this prospective observational study, orthopaedic surgeons from LMICs with no formal research training were recruited to attend the 1-day IGOT International Research Symposium in San Francisco. A survey was administered immediately before and after the symposium to inquire about the participants' confidence in different aspects related to research using a 1-5 Likert scale. A second survey, conducted 2 years later, recorded the attendees' research productivity after the workshop. RESULTS Forty-three participants representing 10 different LMICs from Africa and Asia attended the 2013 course. At 2 year postcourse, participants reported starting 25 research projects, authored 7 "accepted or published manuscripts" (vs. 1 before the course; P < 0.01), and were selected for 12 podium or poster presentations (vs. 3 before the course; P < 0.01). Two research symposium attendees received "Top International Forum Paper" at the 2015 Orthopaedic Trauma Association Annual Meeting. DISCUSSION A 1-day research course resulted in increased participant confidence in conducting research. This was associated with greater research productivity by participants 2 years later. These results suggest that the IGOT International Research Symposium can improve the number of initiated research projects by surgeons in LMICs.

Purpose: There are an estimated 1.2 million deaths from road traffic injuries annually, disproportionately affecting patients in low- resource settings. The purpose of this scoping review is to identify knowledge gaps in global orthopaedic trauma in an effort to help prioritize future research. Methods: Using the 6-stage Arksey and O’Malley framework for conducting a scoping review, orthopaedic trauma literature was reviewed over a ten-year period from 2004 to 2014. Studies from low-resource settings were included and categorized by geographic location, anatomic region, study type, and level of evidence. Results: Of 548 included studies, 51.4% were from low- and middle-income countries in South Asia and 33.7% were from sub- Saharan Africa. Therapeutic (53.3%), epidemiologic (26.4%), and qualitative (8.9%) studies were most common. Only 10.2% of the studies were considered high level of evidence, whereas the vast majority (89.8%) was level 3 or below. Overall, lower extremity injuries were much more frequently represented in the literature compared with upper extremity injuries (233 vs. 78). Pelvic and acetabular fractures were the least studied anatomic region of the lower extremity (3.4%). Conclusions: Our study identified a lack of cost-effectiveness analyses pertaining to injury and intervention, paucity of high- quality research, and under-representation of pelvic, acetabular, and upper extremity injuries. Improved and prioritized research in low- and middle-income countries may help optimize care and inform policy makers of how to reduce the global burden of musculoskeletal trauma.

Objectives: Advanced age is a factor associated with altered fracture healing. Delays in healing may increase the incidence of complications in the elderly, who are less able to tolerate long periods of immobilization and activity restrictions. This study sought to determine whether fracture repair could be enhanced in elderly animals by: (1) inhibiting macrophage activation, (2) blocking the M-CSF receptor c-fms, and (3) inhibiting monocyte trafficking using CC chemokine receptor-2 (CCR2) knockout mice. Methods: Closed unstable tibial shaft fractures were produced in mice aged 4, 12, and 78 weeks. Mice were then fed a diet containing PLX3397 or a control diet from days 1–10 after injury. Fractures were similarly made in CCR2−/− mice aged 78 weeks. The fracture callus was collected during fracture healing and was assessed for its size and the presence of macrophages, both of which were evaluated using the Mann–Whitney U test. Results: PLX3397 treatment resulted in a decrease in the number of macrophages in the fracture callus at day 5. Calluses in juvenile mice trended toward being smaller compared with those in elderly mice (P = 0.08). There was also a trend toward larger callus size and increased bone formation in PLX3397-treated elderly animals when compared with those of the control animals (P = 0.12). Similar increases in bone formation (P = 0.013) and decreases in cartilage within the callus (P = 0.03) were seen at day 10 in CCR2−/− mice. Conclusions: The inhibition of macrophages in elderly mice may lead to an acceleration of fracture healing. Altering macrophage activation after fracture may represent a therapeutic strategy for preventing delayed healing and nonunion in the elderly.

Lessons learned from battle have been fundamental to advancing the care of injuries that occur in civilian life. Equally important is the need to further refine these advances in civilian practice, so they are available during future conflicts. The Major Extremity Trauma Research Consortium (METRC) was established to address these needs.METRC is a network of 22 core level I civilian trauma centers and 4 core military treatment centers-with the ability to expand patient recruitment to more than 30 additional satellite trauma centers for the purpose of conducting multicenter research studies relevant to the treatment and outcomes of orthopaedic trauma sustained in the military. Early measures of success of the Consortium pertain to building of an infrastructure to support the network, managing the regulatory process, and enrolling and following patients in multiple studies.METRC has been successful in maintaining the engagement of several leading, high volume, level I trauma centers that form the core of METRC; together they operatively manage 15,432 major fractures annually. METRC is currently funded to conduct 18 prospective studies that address 6 priority areas. The design and implementation of these studies are managed through a single coordinating center. As of December 1, 2015, a total of 4560 participants have been enrolled.Success of METRC to date confirms the potential for civilian and military trauma centers to collaborate on critical research issues and leverage the strength that comes from engaging patients and providers from across multiple centers.

Tremendous advances in quality, reliability, performance, and versatility of surgical instrumentation and devices have been achieved over the past 50 years using biomaterials. The global orthopaedic implant industry is expected to grow to $41.8 billion by 2016, driven primarily by advancements in implant designs, including materials that provide improved biocompatibility, durability, and expanded clinical applications. Biomaterials have evolved through 3 clinical "generations": (1) "bio-inert materials," (2) materials with intrinsic bioactivity and degradability, and (3) biomaterials that stimulate specific biological host responses. In all cases, surface modifications, including coatings, represent a key strategy for improvements in tissue-contacting properties. Surfaces continue to be a focus for many device improvements and for tissue interfacing, especially for many orthopaedic structural implants comprising metal and metal alloys. Progress in implant materials processing, coating technologies, and coating combinations with therapeutic agents provide new properties and functionalities to improve device-tissue integration and reduce foreign body reactions and infections. Performance criteria for these surface modifications success in clinical practice are daunting, and translation of several technologies from in vitro proof-of-concept to in vivo applications has proven challenging.

Heterotopic ossification (HO) can be defined as the pathological formation of bone in extra-skeletal tissues. There has been a substantial amount of recent research on the pathophysiology, prophylaxis and treatment of HO and traumatic conditions associated with the development of HO. This research has advanced our understanding of this disease and helped to clarify evidence-based approaches to both the prophylaxis and treatment of HO. This article reviews the literature on these topics with a focus on their application in orthopaedic trauma.

This review summarizes symposium presentations from the OTA's Basic Science Focus Forum on care for osteoporotic fractures. The limitations of diaphyseal osteoporotic animal bone models are discussed, together with the potential benefits of using metaphyseal models to study osteoporotic fracture fixation constructs. Metaphyseal bone repair models provide better simulation of the most common osteoporotic fractures. Selection of an osteoporotic model for mechanical testing is also challenging. One should always thoroughly define the clinical problem to be addressed. The selected model should then be validated for behavior matched to known clinical behavior with known fixation configurations. The medical management of osteoporosis is directed at enhancing bone mass, improving bone quality, and lowering fracture risk. Medical strategies to achieve these goals are discussed. The medical strategy should include provision of an adequate calcium and vitamin D environment to facilitate well-mineralized bone and improve bone quality, prevent excessive bone resorption, and provide an anabolic stimulus to enhance bone formation. Atypical femur fractures continue to be a serious issue for the orthopaedic community. Risk factors, treatment modalities, and prevention strategies are discussed. A comprehensive strategy for the improved treatment of osteoporotic fractures must address both biological and mechanical issues and includes 4 specific approaches: (1) removal of inhibitors to bone healing; (2) introduction of bone healing stimulants; (3) modification of fracture fixation constructs; and (4) application of bone augmentation or substitutes. There is currently no optimal bone substitute. Substitutes should be chosen based on the most critical need when treating a particular fracture.

Objectives/Hypothesis: Proximal and distal femur fractures have traditionally been treated with open reduction and internal fixation through a standard lateral approach. New, "minimally invasive" internal fixation techniques, however, have been developed in an effort to devascularize the bone less than the traditional method. The purpose of this study was to determine whether a minimally invasive percutaneous plating technique better preserves bone vascularity relative to the traditional method by comparing the effect of the two approaches on the blood supply of the distal femur using silicone arterial dye injection in a cadaveric model. Study Design/Methods: Ten fresh human cadavers underwent lateral conventional plate osteosynthesis (CPO) through a standard lateral approach on one side and minimally invasive plate osteosynthesis (MIPO) through two three-centimeter incisions on the contralateral side. After injection of silicone dye, a dissection was performed bilaterally to identify the femoral perforating and nutrient arteries. Results: All MIPO specimens showed intact perforating and nutrient arteries, whereas the CPO specimens had a variable incidence of vessel disruption. The MIPO group demonstrated better periosteal perfusion in each of the cadavers and improved medullary perfusion in 70 percent of the MIPO specimens compared with the CPO specimens. Conclusion: A percutaneous minimally invasive plating technique disrupts the femoral blood supply less than the traditional open method. Such minimally invasive methods may be more advantageous biologically than the traditional method.

Although the clinical experience with reamed intramedullary nailing has been successful for the treatment of femur and tibia fractures, similar success has not been duplicated when this technique has been applied in the humerus. Although the cortical vascular response to nailing of the humerus is presently assumed to be similar to that of the femur, the response of the humerus to reaming has not been documented in vivo. The following case depicts avascularity of the humeral diaphyseal cortex as a complication of reamed intramedullary nailing and illustrates the sensitivity of the humerus to this treatment.

Cortical bone porosis associated with the dynamic compression plate (DCP) prompted the development of the limited-contact dynamic compression plate (LC-DCP) and the point-contact fixator (PC-Fix) to increase bone vascularity. However, the comparative fixation characteristics of the three designs are unknown. Transverse fractures were physiologically created in paired cadaveric sheep tibiae, which were plated before torsion testing and four-point bending to failure. The tibiae were grouped randomly and compared as follows: DCP versus LC-DCP, DCP versus PC-Fix, and LC-DCP versus PC-Fix. Mean torque to failure demonstrated no significant difference between the three plates (p < 0.33). Mean bending stiffness, gap opening, and moment to failure also demonstrated no significant difference between the three designs with p < 0.29, < 0.13, and < 0.16, respectively. The LC-DCP and PC-Fix have torsion and bending properties comparable with the DCP in the fixation of simple transverse diaphyseal fractures.

The goal of this study was to determine to what extent mechanical stability affects vascular repair during fracture healing.Stabilized and nonstabilized tibia fractures were created in adult mice. Fracture tissues were collected at multiple time points during early fracture healing. Vasculature in fractured limbs was visualized by immunohistochemistry with an anti-PECAM-1 antibody on tissue sections and then quantified with stereology. Oxygen tension, vascular endothelial growth factor expression, and lactate accumulation at the fracture site were measured. Gene expression was compared between stabilized and nonstabilized fractures by microarray analysis.We found that new blood vessel formation was robust by 3 days after fracture. Quantitative analysis showed that nonstabilized fractures had higher length density and surface density than stabilized fractures at 3 days after injury, suggesting that nonstabilized fractures were more vascularized. Oximetry analysis did not detect a significant difference in oxygen tension at the fracture site between stabilized and nonstabilized fractures during the first 3 days after injury. Further microarray analysis was performed to determine the effects of mechanical stability on the expression of angiogenic factors. No significant difference in the expression of vascular endothelial growth factors and other angiogenic factors was detected between stabilized and nonstabilized fractures.Mechanical instability promotes angiogenesis during early fracture healing and further research is required to determine the underlying mechanisms.

Osteoporotic fractures present a number of significant challenges for surgical management, including high degrees of fracture comminution, poor implant fixation secondary to inferior bone quality, and compromised capacity for fracture healing. Osteobiologics are materials/agents that can promote fracture healing and enhance fracture stability. Given the challenges presented by osteoporotic fractures, they seem ideally suited to potentially benefit from the application of osteobiologics. Despite this, limited clinical investigation into the use of osteobiologics in the management of osteoporotic fractures has been performed. This article reviews a select number of osteobiologic products and the evidence for their use in osteoporotic fractures.

Fractures of the distal radius are one of the most common injuries presented to orthopaedic surgeons. A variety of treatment options are available for the vast array of fracture patterns. Research that explores bone fragility and fracture healing has led to new treatment modalities. As new products and methods are derived to aid in fracture healing it is essential to develop noninvasive and/or nondestructive techniques to assess structural information about bone. Quantitative assessment of macro-structural characteristics such as geometry, and microstructural features such as relative trabecular volume, trabecular spacing, and connectivity may improve our ability to estimate bone strength. Methods for quantitatively assessing macrostructure include (besides conventional radiographs) dual x-ray absorptiometry (DXA) and computed tomography (CT), particularly volumetric quantitative computed tomography (vQCT). Methods for assessing microstructure of trabecular bone include high resolution computed tomography (hrCT), micro computed tomography (microCT), high resolution magnetic resonance (hrMR), and micro magnetic resonance microMR. Volumetric QCT, hrCT and hrMR are generally applicable in vivo; microCT and microMR are principally applicable in vitro. Clinically, the challenges for bone imaging include balancing the advantages of simple bone densitometry versus the more complex architectural features of bone, or the deeper research requirements versus the broader clinical needs.

Objective To determine the effectiveness of high-pressure pulsatile lavage (HPL) versus bulb syringe (BS) irrigation in removing particulate matter from metaphyseal cancellous bone. Design Four grams of particulate graphite were placed in twenty distal femoral intraarticular osteotomies performed on New Zealand rabbit hind limbs. Two groups of ten specimens were then irrigated using either HPL or BS irrigation. A representative coronal section from each specimen was then prepared for histologic evaluation using 400x light microscopy. The number and distribution of graphite particles-present as small (less than 20 micrometers), medium (20 to 50 micrometers), and large (greater than 50 micrometers) aggregates-were then recorded. Results The mean maximum perpendicular distance of graphite aggregates of all sizes from the osteotomy site was 12.4 millimeters (+/-SD 2.5) in the HPL group and 12.5 millimeters (+/-SD 2.0) in the BS group (p > 0.5). The mean number of aggregates within four 400x fields (1.08 millimeters) of the osteotomy site was 21.9 (+/-SD 22.0) in the HPL group and 21.8 (+/-SD 27.5) in the BS group (p > 0.5). The mean total number of aggregates in the area surveyed was 129.4 (+/-SD 79.6) in the HPL group and 137.5 (+/-SD 113.6) in the BS group (p > 0.5). Separate analyses controlling for aggregate size of the specimens also revealed no significant differences between HPL and BS irrigation. Conclusion HPL and BS irrigation appear equally effective in removing particulate matter from metaphyseal cancellous bone in an intraarticular fracture model. Furthermore, HPL does not appear to drive particulate matter farther into metaphyseal cancellous bone than BS irrigation.

To evaluate the effects of pulsatile lavage and bulb syringe irrigation on fracture healing in vivo.Randomized prospective trial in an animal model.Medical school orthopaedic department.Thirty New Zealand white rabbits.The control group (C) underwent osteotomy of the medial femoral condyle, stabilization, and closure. The bulb syringe and pulsatile lavage groups underwent the same procedure as group C, with the addition of irrigation with one liter of normal saline via a bulb syringe (B) or a pulsatile lavage system (P). Animals were administered two fluorescent bone stains: xylenol orange at the time of operation, and calcein green one week postoperatively. Animals were euthanized two weeks postoperatively and femurs were retrieved for histological analysis.Union was determined by examination of microradiographs under light microscopy. The viability of bone along the fracture site was determined by evaluation of xylenol orange and calcein green staining under fluorescent microscopy. The density of new bone formed in the osteotomy site was assessed by computerized digitization of standardized regions of the proximal and distal osteotomy.Xylenol orange bands were present a mean of 66 +/- 8 percent (mean +/- standard error of the mean), 65 +/- 6 percent, and 44 +/- 5 percent of the distance along the osteotomy in groups C, B, and P, respectively (p0.001). Calcein green bands were present throughout the osteotomy site in all specimens. Calcified new bone was present in 62 +/- 4 percent, 58 +/- 7 percent, and 41 +/- 9 percent of the area measured in groups C, B, and P, respectively (p = 0.07). Twenty percent of the osteotomies in groups C and B did not unite, compared with 30 percent in group P (p0.5).Pulsatile lavage irrigation of fresh intraarticular fractures in rabbits has a detrimental effect on early new bone formation; this effect, however, is no longer apparent two weeks following irrigation. While this study evaluated the effects of pulsatile lavage irrigation in noncontaminated fractures without extensive soft tissue injury, the detrimental effects observed on early new bone formation may translate to an increased risk of nonunion in the setting of a contaminated open fracture with extensive soft tissue injury. Based on the results of this investigation, the selective use of pulsatile lavage irrigation appears warranted. In the absence of gross wound contamination, irrigation with a bulb syringe appears less likely to impair fracture healing than does pulsatile lavage irrigation. Expansion of the model used in this study to include bacterial contamination and soft tissue crushing may further elucidate the effects of pulsatile lavage irrigation on fracture healing.

OBJECTIVES Recently, radiation-independent aiming devices for the tibia that compensate for insertion-related implant deformation have been developed, but the benefits of such systems have not been determined. This study prospectively evaluated the duration of the nailing procedure, the length of radiation time, and the accuracy of interlocking screw placement when using a radiation-independent distal aiming device (DAD) versus the freehand technique (FHT). MATERIALS AND METHODS In an oblique cadaveric tibial fracture, a surgeon inexperienced in both techniques (DAD and FHT) performed statically locked intramedullary nailing. RESULTS For the DAD and the FHT, respectively, the total operation time was 25.4 +/- 11.3 (mean +/- standard deviation) versus 30.9 +/- 14.3 minutes (p = 0.029), the distal locking time was 16.7 +/- 8.6 versus 21.9 +/- 10.5 minutes (p = 0.004), the total fluoroscopy time was 9 +/- 5 versus 93 +/- 34 seconds (p < 0.0001), the distal locking fluoroscopy time was zero versus 88 +/- 33 seconds (p < 0.0001), and the screw wear was -0.7 +/- 5.2 versus 26.8 +/- 31.6 micrometers (p = 0.001). The failure rate was 1.6 percent (one of sixty screws) in both groups. CONCLUSION These results suggest that the DAD can eliminate the need for radiation during placement of distal interlocking screws.

While gap defect models provide greater graft stability and are more representative of many clinical situations than segmental defect models, the healing in these models has not been well documented. To study the histologic course of cancellous bone graft healing in a long bone gap defect, 12 adult mongrel dogs were killed in groups of two at 1, 2, 3, 4, 6, and 12 weeks. Graft incorporation in these dogs was studied using macro- and microradiography, histologic sections, and computer-assisted digital surface analysis ; results are described. Unlike that seen in segmental defect models, the pattern of repair in a cancellous bone grafted gap defect provides consistent healing at 12 weeks and follows the same healing process seen with stable defects.

The effect of tobramycin on osteoblasts was studied. Osteoblast-like cells from the MG-63 human osteosarcoma cell line were grown in antibiotic-free media and exposed to concentrations of tobramycin: first at order of magnitude intervals between 0 and 10,000 micrograms/ml, and then at closer intervals between 100 and 1,000 micrograms/ml to more accurately define toxic levels. Cell number and 3H-thymidine incorporation at 0, 24 and 72 h were determined. Similarly, primary cultures of rat osteoblasts were exposed to the same concentrations of tobramycin to confirm the validity of the MG-63 cell line as a model for nontransformed cells. The results of this study demonstrate that local levels of tobramycin of < or = 200 micrograms/ml have little or no effect on osteoblast replication. Concentrations of 400 micrograms/ml significantly decreased cell replication, and concentrations of 10,000 micrograms/ml caused cell death. Results obtained with primary rat osteoblast cultures were similar to those obtained from the MG-63 cultures at the tested tobramycin concentrations.

The use of unicortical screws instead of bicortical screws in the extreme outer holes of dynamic compression plates (DCPs) has been recommended to minimize the stress riser effect at the end of the plates. The authors examined in vitro two groups of paired canine femurs after compression plates had been applied to the anterolateral diaphyseal surface bilaterally. Group I: intact paired femurs with bicortical peripheral screws in one DCP and unicortical peripheral screws in the other; Group II: osteotomized paired femurs again comparing unicortical and bicortical peripheral DCP screws. All specimens were torsion tested to failure and the torque, stiffness, energy, rotation, and failure fracture length were calculated. Unicortical screws did not enhance the torsional strength in either group, and significantly compromised stiffness, energy, and rotation in the osteotomized group. The only apparent benefit of unicortical peripheral screws in a DCP was a shorter, less comminuted fracture upon failure.