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Background Internal fixation of OTA type 31-A2 proximal femoral fractures can be performed with either a sliding hip screw and side plate (SHS-P) or a sliding hip screw and intramedullary nail (SHS-IMN). Controversy exists as to which is the best implant for these types of fractures. The primary aim of this study was to investigate the stability of 31-A2 fractures as a function of loss of medial cortical buttress. The secondary aim was to assess the influence of fracture stability on the different internal fixation constructs. Methods Simulated simple intertrochanteric fractures were made in 12 cadaver proximal femurs. Six fractures were fixed with an SHS-P and 6 with an SHS-IMN. Both implants were instrumented with a strain gauge at the lag screw-nail/plate interface to allow assessment of implant load bearing (ILB). A primary fracture line, in accordance with the 31-A2 OTA classification, was created after which 3 subsequent horizontal osteotomies in 1-cm increments were made across the medial cortex. Compressive loading up to 1050 N was performed after each osteotomy. Results ILB was presented as percentage of maximal ILB. SHS-P constructs increased their load bearing gradually. For SHS-P constructs, ILB was 8.1% ± 1.8% in the intact state, increasing to 49.6% ± 14.0% after the initial intertrochanteric osteotomy (P = 0.0002), 68.7% ± 15.9% after the first medial osteotomy (P = 0.028), and 80.0% ± 15.9% after the second medial osteotomy (P = 0.15). After the first-level medial osteotomy, SHS-IMN constructs reached a plateau in which the implant carried the entire load. Conclusions Type 31-A2 fractures become increasingly unstable with increased medial comminution (or fragment size). SHS-P constructs were more load sharing than SHS-IMN constructs. These findings may help guide the surgeon in choice of implant for a 31-A2 intertrochanteric fracture, leaning toward SHS-IMN for the more unstable fracture patterns.

OBJECTIVES The goal of this study is to compare the fatigue strength of a locking intramedullary nail (LN) construct with a double locking plate (DLP) construct in comminuted proximal extra-articular tibia fractures. METHODS Eight pairs of fresh frozen cadaveric tibias with low bone mineral density [age: 80 ± 7 (SD) years, T-score: -2.3 ± 1.2] were used. One tibia from each pair was fixed with LN, whereas the contralateral side was fixed with DLP for complex extra-articular multifragmentary metaphyseal fractures (simulating OTA 41-A3.3). Specimens were cyclically loaded under compression simulating single-leg stance by staircase method out to 260,000 cycles. Every 2500 cycles, localized gap displacements were measured with a 3D motion tracking system, and x-ray images of the proximal tibia were acquired. To allow for mechanical settling, initial metrics were calculated at 2500 cycles. The 2 groups were compared regarding initial construct stiffness, initial medial and lateral gap displacements, stiffness at 30,000 cycles, medial and lateral gap displacements at 30,000 cycles, failure load, number of cycles to failure, and failure mode. Failure metrics were reported for initial and catastrophic failures. RESULTS DLP constructs exhibited higher initial stiffness and stiffness at 30,000 cycles compared with LN constructs (P < 0.03). There were no significant differences between groups for loads at failure or cycles to failure. CONCLUSIONS For the fixation of extra-articular proximal tibia fractures, a LN provides a similar fatigue performance to double locked plates. The locked nail could be safely used for fixation of proximal tibia fractures with the advantage of limited extramedullary soft tissue damage.

OBJECTIVES Inlet and outlet views are essential in the evaluation of patients with pelvic injuries. The optimal angles that should be used to obtain these views are still debated. METHODS Computed tomography scans of 70 patients without pelvic ring injuries were analyzed. Using the raw data from the computed tomography images, virtual pelvic x-rays were generated. The images were rotated 1 degree at a time and a total of 360 images were generated. The same procedure was repeated to create solid 3-dimensional (3D) reconstructions. Two trauma-trained orthopaedic surgeons then reviewed all 360 images to select inlet and outlet views as described in previous literature. Intraclass correlation coefficients were calculated for each inlet and outlet value. RESULTS The average inlet angle (caudal tilt) that was required to achieve a view where the promontory overlaps the S1 body was found to be 26.7 degrees (95% confidence interval, 25-29) with virtual x-rays and 24.3 degrees (95% confidence interval, 22-26) with 3D reconstructions. The average outlet angle (cephalad tilt) that was required to achieve a view where the superior border of the pubic symphysis overlaps the S2 body was 43.7 degrees (95% confidence interval, 42-45) with virtual x-rays and 43.8 degrees (95% confidence interval, 42-45) with 3D reconstructions. There was no difference in these angles based on gender, whereas sacral dysmorphism increased the angle needed to obtain the outlet view by an average of 5 degrees. CONCLUSIONS This study demonstrated that the ideal angle to obtain inlet views should be approximately 25 degrees and to obtain outlet views should be approximately 45 degrees during screening x-rays to evaluate patients who were diagnosed with pelvic injuries. Application of these new values in the clinical practice would provide higher rates of adequate studies and further prospective clinical studies should be performed to validate these parameters.

Objectives Iliosacral fixation of unstable pelvic fractures does not produce enough stability to allow for immediate postoperative weight bearing. Triangular osteosynthesis creates additional resistance to vertical displacement and rotation. A disadvantage is the loss of the L5/S1 motion segment. We propose a modification of the standard triangular osteosynthesis construct in which the contralateral S1 pedicle is used. As the ipsilateral L5 pedicle is unavailable for fixation in a saw-bones composite pelvic model, we compared ipsilateral and contralateral S1 pedicle screw constructs. We hypothesized that ipsilateral and contralateral S1 pedicle screw constructs would demonstrate no difference in displacement or rotation. Methods Seven saw bones pelvic models were tested. A 5-mm vertical fracture gap was created through the left sacrum while the pubic symphysis was completely dissociated. Each pelvis was tested sequentially in 4 triangular osteosynthesis configurations: ipsilateral S1 screw with anterior plate, contralateral S1 screw with anterior plate, contralateral S1 screw without anterior plate, and ipsilateral S1 screw without anterior plate. Specimens were cyclically loaded from 100-200 N at 0.25 Hz for 25 cycles and then loaded up to 300 N at 10 mm/min while displacement and rotation at the sacral and pubic fracture sites were measured. Results There was no difference in any of the displacement measures between ipsilateral and contralateral constructs. When comparing rotation, the contralateral configuration experienced significantly less rotation than the ipsilateral configuration with and without the anterior plate applied. Conclusions Within the limitations of the current model, contralateral S1 constructs for modified triangular osteosynthesis were biomechanically equal to ipsilateral constructs in preventing displacement and superior in preventing rotation.