Chronic tibial stress fracture is an unusual condition that is primarily seen in athletes and military personnel. Recurrent or recalcitrant stress fractures can be career-ending because they require lengthy nonoperative treatment. We performed a retrospective review of five patients who underwent intramedullary tibial nailing for recalcitrant stress fractures at Womack Army Medical Center, Ft. Bragg, North Carolina, from 1991 to 1994. Interviews were used to survey the patient's history and outcome. We reviewed each case regarding preoperative symptoms, preoperative treatment, surgery performed, radiographic findings, and functional outcome. In each case there were several similarities in symptoms and, most notably, radiographic findings and failure of nonoperative therapy for more than 1 year. Each patient had an unusually narrow medullary canal, a thickened anterior cortex, and a linear unicortical fracture line on the anterior or tension side. Although functional results varied, all patients reported improvement in their symptoms and could return to limited running. There were two excellent results (defined as unlimited pain-free running and resolved tibial pain) and three good results. We believe intramedullary tibial nailing should be considered for treating chronic stress fractures of the midanterior tibia that are recalcitrant to nonoperative therapy in a selected group of patients.
Many people with Diabetes live with the continuous threat of hypoglycemic attacks and the danger of going into coma. Diabetes Alert Dogs are trained to detect the onset of an attack before the condition of the human handler they are paired with deteriorates, giving them time to take action. We investigated requirements for designing an alarm system allowing dogs to remotely call for help when their human falls unconscious before being able to react to an alert. Through a multispecies ethnographic approach we focus on the requirements for a physical canine user interface, involving dogs, their handlers and specialist dog trainers in the design process. We discuss tensions between the requirements for canine and the human users, argue the need for increased sensitivity towards the needs of individual dogs that goes beyond breed specific physical characteristics, and reflect on how we can move from designing for dogs to designing with dogs.
BackgroundPremature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws.MethodsFatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography.ResultsThe average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of withstanding more than a week of weight bearing. If two small diameter screws are used, our tests showed that the probability of withstanding a week of weight bearing increases from zero to about 20 percent, which is similar to having a single 4.5 mm diameter screw providing fixation.ConclusionOur results show that selecting the system that uses the largest distal locking screws would offer the best fatigue resistance for an unstable fracture pattern subjected to full weight bearing. Furthermore, using multiple screws will substantially reduce the risk of premature hardware failure.
Objectives: Standard titanium nails (TN) or carbon fiber–reinforced PEEK nails (CFN) were compared to evaluate impact of material on fracture union, healing time, knee/ankle, and barometric pain. Design: Longitudinal cohort evaluated retrospectively comparing 2 periods using 2 implant types. Setting: Single surgeon series at one Level II Trauma Center. Patients: Standardized treatment protocol. Fifty-six tibial fracture patients suitable for intramedullary nailing over 5-year period. Intervention: First period—TN; second period—CFN. Main Outcome: Measurements: standard demographic data: OTA/AO fracture classification, fracture location, and nail type. Outcome parameters: cumulative healing at standard time intervals, infection/nonunion, associated injuries, knee/ankle, barometric pain, and implant removal. Statistical analysis comparing incident healing. Results: Patient populations were not statistically different regarding demographics and fracture type/location, although there was a trend toward greater fracture severity/more associated injuries in CFN group. In 56 patients, 26 received CFN and 30 received TN. Healing rates were reported at each time interval. 8 weeks: TN—0%, CFN—19%; 12 weeks: TN—17%, CFN—69%; 16 weeks: TN—57%, CFN—92%; 20 weeks: TN—87%, CFN—96%; and 24 weeks: TN—97%, CFN—96% (P < 0.0001 every interval except 24 weeks). Each group had one infected nonunion in an open fracture that healed with subsequent treatment. There was a trend toward less barometric pain with CFN that did not reach statistical significance (P = 0.065). No statistical differences with knee/ankle pain (P = 0.109)/removal of implant (P = 0.269) potentially due to low power of pilot study. Conclusions: In this pilot study evaluating CFR-PEEK intramedullary nail for tibial shaft fractures, there was a demonstrated accelerated healing times compared to titanium with a potential for less barometric pain. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
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