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Background It is recommended to have 6 bicortical screws for plate fixation of long bone fractures; however, many metacarpal fractures do not allow 6 screws due to size limitations and proximity of crucial anatomical structures. The purpose of this biomechanical study was to determine whether the mechanical properties of a 4-screw nonlocking construct are noninferior to those of a 6-screw nonlocking construct. Methods Metacarpal sawbones were used to simulate a midshaft, transverse fracture. Nonlocking bicortical screws were placed in the 6-hole plate, and the metacarpals were randomly assigned to 2 equal study groups: (1) 4 screws, 2 on either side of the fracture (4S); and (2) 6 screws, 3 on either side of the fracture (6S). The metacarpals were tested in a cyclic loading mode and load to failure in a cantilever bending mode. Results Maximum deflection was significantly higher for 4S compared with 6S. Cyclic root mean square (RMS) was also significantly greater for 4S at 70 and 100 N. There were no statistically significant differences observed between the 2 constructs for maximum bending load, bending stiffness, and cyclic RMS at 40 N. The maximum bending load in 4S and 6S was 245.6 ± 37.9 N and 230.8 ± 41.9 N, respectively; 4S was noninferior and not superior to 6S. Noninferiority testing was inconclusive for bending stiffness. Conclusions A 4-screw bicortical nonlocking construct is noninferior to a 6-screw bicortical nonlocking construct for fixation of metacarpal fractures, which may be advantageous to minimize disruption of soft tissues while maintaining sufficient construct stability.

Background Prehospital plasma transfusion in trauma reduces mortality. However, the underlying mechanism remains unclear. Reduction in shock severity may play a role. Lactate correlates with physiologic shock severity and mortality after injury. Our objective was to determine if prehospital plasma reduces lactate and if this contributes to the mortality benefit of plasma. Methods Patients in the Prehospital Air Medical Plasma trial in the upper quartile of injury severity (Injury Severity Score, >30) were included to capture severe shock. Trial patients were randomized to prehospital plasma or standard care resuscitation (crystalloid ± packed red blood cells). Regression determined the associations between admission lactate, 30-day mortality, and plasma while adjusting for demographics, prehospital crystalloid, time, mechanism, and injury characteristics. Causal mediation analysis determined what proportion of the effect of plasma on mortality is mediated by lactate reduction. Results A total of 125 patients were included. The plasma group had a lower adjusted admission lactate than standard of care group (coefficient, -1.64; 95% confidence interval [CI], -2.96 to -0.31; p = 0.02). Plasma was associated with lower odds of 30-day mortality (odds ratio [OR], 0.27; 95% CI, 0.08-0.90; p = 0.03). When adding lactate to this model, the effect of plasma on 30-day mortality was no longer significant (OR, 0.36; 95% CI, 0.07-1.88; p = 0.23), while lactate was associated with mortality (OR, 1.74 per 1 mmol/L increase; 95% CI, 1.10-2.73; p = 0.01). Causal mediation demonstrated 35.1% of the total effect of plasma on 30-day mortality was mediated by the reduction in lactate among plasma patients. Conclusion Prehospital plasma is associated with reduced 30-day mortality and lactate in severely injured patients. More than one third of the effect of plasma on mortality is mediated by a reduction in lactate. Thus, reducing the severity of hemorrhagic shock appears to be one mechanism of prehospital plasma benefit. Further study should elucidate other mechanisms and if a dose response exists. Level of evidence Therapeutic, level II.

BACKGROUND Ligamentous ankle injuries are the most common injuries sustained by athletes and by the general population, with an incidence of approximately 2 million per year in the U.S. Injuries to the ankle syndesmosis (i.e., "high ankle sprains") are generally treated operatively. Although cadaveric studies can evaluate syndesmosis fixation strength, they cannot predict how healing, neuromuscular adaptation, or dynamic loading will affect in vivo biomechanics. Using dynamic biplane radiography (DBR), we tested the hypothesis that syndesmosis repair would restore ankle kinematics and ligament elongation during static and dynamic loading. METHODS A convenience sample of 6 male patients who had undergone fixation (2 screw, 3 suspensory, 1 hybrid) of syndesmosis injury were assessed with use of DBR during forward running, backpedaling, a 45° angled single-leg hop, and 1 static standing trial at 2 to 4.5 years postoperatively. Three-dimensional ankle kinematics and elongation of the distal interosseous ligament, anterior inferior tibiofibular ligament, and the posterior inferior tibiofibular ligament were measured bilaterally. Comparisons were made between the operative and uninjured sides. Clinical outcomes were evaluated with use of the Foot and Ankle Ability Measure. RESULTS Static load increased the lengths of the distal interosseous ligament (p = 0.02 to 0.05) and middle segment of the anterior inferior tibiofibular ligament (p = 0.02) in the operative ankle. The distal syndesmosis length was greater on the operative side during the static unloaded and loaded conditions (p = 0.02). Length of the distal syndesmosis on the operative side was greater than the corresponding healthy syndesmosis length during all 3 dynamic activities. On average, the operative ankle was in less dorsiflexion over the support phase of the angled hop (p = 0.05) and running (p < 0.01). The average Foot and Ankle Ability Measure Activities of Daily Living and Sports subscale scores were 95 and 88, respectively. CONCLUSIONS This study provides the first in vivo evidence of post-fixation changes in biomechanics after syndesmosis repair. Syndesmosis repair fails to restore healthy static and dynamic distal tibiofibular anatomy, even in patients who report good to excellent clinical outcomes. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Objective Two major teaching methods available for learning the pivot shift test are active teaching with real-time feedback from an instructor and passive teaching through the use of instructional textbooks or videos. The purpose of this study was to determine the effect of active and passive teaching methods on the execution of the proper technique of the pivot shift test. Methods Six orthopaedic surgery residents each performed 110 pivot shift tests on a fresh-frozen, cadaveric pelvis-to-toe specimen with anterior cruciate ligament insufficiency and lateral meniscectomy. Participants performed 10 repetitions before teaching and a total of 100 repetitions after either active or passive teaching. Six degree-of-freedom kinematics of the knee defined by the Grood/Suntay coordinate system were recorded after every fifth repetition using an electromagnetic tracking system. Anterior/posterior translation of the lateral knee compartment during the reduction event was also quantified. Depending on the normality of the data, a two-tailed t-test or Wilcoxon rank-sum test was used for comparisons of kinematics between the active and passive teaching groups and between successful and unsuccessful trials within each teaching group. Statistical significance was set at p Results The success rate after active teaching was 31.7% compared with 30.0% after passive teaching. However, the starting position of the reduction event in the active teaching group was rotated by more than twice the amount of valgus rotation compared with the passive group (7.4°±3.3° vs 3.0°±2.7°; p Conclusion Successful pivot shift tests can be performed after passive teaching, but the standard technique is not as effectively learnt through passive teaching since traditional external rotation during the reduction event was not used as in the active teaching group. Level of evidence V.

Category: Trauma; Basic Sciences/Biologics Introduction/Purpose: Syndesmotic injuries account for 1-11% of all ankle sprains and are the most predictive factor of chronic ankle dysfunction 6 months after injury. Common surgical techniques include screw fixation (the ‘gold standard’) and dynamic fixation with a suture button device, which may lead to better clinical outcomes than rigid screw. To date, there are no studies comparing the in vivo biomechanics of suture button and rigid screw syndesmotic fixation, and no report of the correlations between biomechanics and patient outcomes. The goal of this study is to characterize the biomechanics of the native ankle syndesmosis, rigid screw fixation, suture button fixation, along with associated patient-reported outcomes. This study will elucidate mechanisms for improved patient-reported outcomes based on the fixation method. Methods: 6 patients (average age:23.6, 4M/1F, 2 suture button, 2 screw fixation and 1 hybrid) consented to participate in this IRB-approved study. After being medically cleared to return to full athletic participation, each participant performed seven movements (two single leg hops (straight and lateral), two alternating single-leg push-offs (front-to-back and side-to-side), vertical jumping, running, and walking within a biplane radiographic system (Figure 1). A validated volumetric model-based tracking system matched patient-specific 3D bone models (obtained from CT) to the synchronized biplane radiographs (Figure 1). Six degree of freedom ankle kinematics were determined for each movement and for the repaired and contralateral ankle of each participant. Patient reported outcomes were also measured using the Foot and Ankle Ability Measure (FAAM) and a Visual Analogue Scale (VAS). Results: The results show that the screw fixation (-0.99 mm) has greater tibiotalar lateral-medial translation of the injured side relative contralateral healthy side compared to the tightrope fixation (-0.73 mm) and hybrid (.05 mm). For the syndesmosis translation, the screw fixation (2.00 mm) also exhibits greater total magnitude of translation compared to the tightrope ((-0.44 mm) and hybrid fixation (1.02 mm). Conclusion: This study shows that the screw fixation exhibits greater translation of the syndemosis and lateral/medial translation of the Talus. This may suggest that this method is inferior to the tight-rope and hybrtid. Future studies will include all the motions and more subjects.