Superficial Deltoid Ligament and Deep Deltoid Ligament Play Equally Important Roles in the Stability of Isolated Lateral Malleolus (OTA/AO 44-B1) Fractures: A Biomechanical Study.

OBJECTIVE: To evaluate the individual contributions to stability of the superficial and deep deltoid ligaments in the setting of SER IV ankle fractures. METHODS: Nineteen total cadaveric specimens were used. SER IV injuries were created with the rupture of either the superficial (SER IV-S) (n = 9) or deep deltoid (SER IV-D) (n = 10). These were tested by applying an external rotation force (1 Nm, 2 Nm, 3 Nm, and 4 Nm). Changes in the position of the talus were recorded with a 3D motion tracker. Injury conditions were compared with a 4-step general linear model with repeated measures. Injury condition was also compared with the intact state and to each other using 2-tailed t tests. RESULTS: The general linear model showed that increased loading had a significant effect with axial rotation (P = 0.02) and sagittal translation (P = 0.003). SER IV-S and SER IV-D showed significantly greater instability compared with the intact state in axial rotation (1 Nm, 2 Nm, and 3 Nm). SER IV-S and SER IV-D did not significantly differ from each other. CONCLUSIONS: SER IV fracture patterns can be unstable with isolated injury to either the superficial or deep deltoid. This challenges the notion that deep deltoid rupture is necessary. Further clinical studies would help quantify the consequences of this instability.

A biomechanical comparison of superior ramus plating versus intramedullary screw fixation for unstable lateral compression pelvic ring injuries,,.

INTRODUCTION: Management of the anterior component of unstable lateral compression (LC) pelvic ring injuries remains controversial. Common internal fixation options include plating and superior pubic ramus screws. These constructs have been evaluated in anterior-posterior compression (APC) fracture patterns, but no study has compared the two for unstable LC patterns, which is the purpose of this study. METHODS: A rotationally unstable LC pelvic ring injury was modeled in 10 fresh frozen cadaver specimens by creating a complete sacral fracture, disruption of posterior ligaments, and ipsilateral superior and inferior rami osteotomies. All specimens were repaired posteriorly with two fully threaded 7 mm cannulated transiliac-transsacral screws through the S1 and S2 corridors. The superior ramus was repaired with either a 3.5 mm pelvic reconstruction plate (n = 5) or a bicortical 5.5 mm cannulated retrograde superior ramus screw (n = 5). Specimens were loaded axially in single leg support for 1000 cycles at 400 N followed by an additional 3 cycles at 800 N. Displacement and angulation of the superior and inferior rami osteotomies were measured with a three-dimensional (3D) motion tracker. The two fixation methods were then compared with Mann-Whitney U-Tests. RESULTS: Retrograde superior ramus screw fixation had lower average displacement and angulation than plate fixation in all categories, with the motion at the inferior ramus at 800 N of loading showing a statistically significant difference in angulation. CONCLUSION: Although management of the anterior ring in unstable LC injuries remains controversial, indications for fixation are becoming more defined over time. In this study, the 5.5 mm cannulated retrograde superior ramus screw significantly outperformed the 3.5 mm reconstruction plate in angulation of the inferior ramus fracture at 800 N. No other significance was found, however the ramus screw demonstrated lower average displacements and angulations in all categories for both the inferior and superior ramus fractures.

Can preoperative radiographs predict hardware complication or fracture displacement after operative treatment of pelvic ring injuries?

INTRODUCTION: Operative fixation of pelvic ring injuries is associated with a high risk of hardware failure and loss of reduction. The purpose of this study was to determine whether preoperative radiographs can predict failure after operative treatment of pelvic ring injuries and if the method of fixation effects their risk. PATIENTS AND METHODS: We conducted a retrospective cohort study of 143 patients with pelvic ring injuries treated with operative fixation at a level 1 trauma center. Preoperative radiographs were examined for the presence of the following characteristics: bilateral rami fractures, segmental or comminuted rami fractures, contralateral anterior and posterior injuries, complete sacral fracture, and displaced inferior ramus fractures. The method of fixation was classified based on the presence of anterior, posterior, or combined anterior and posterior fixation as well as whether or not posterior fixation was performed at a single or multiple sacral levels. Post-operative radiographs were examined for hardware failure or loss of reduction. RESULTS: Twenty-one patients (14.7%) demonstrated either hardware complication or fracture displacement within 6 months of surgery. Male sex was associated with a decreased risk of hardware complication (OR 0.11 [0.014, 0.86]; p=0.03). Posterior pelvic ring fixation at multiple sacral levels was associated with a decreased risk of fracture displacement (OR 0.21 [0.056, 0.83]; p=0.02). We were unable to demonstrate a significant association between preoperative radiographic characteristics and risk of hardware failure or fracture displacement. CONCLUSION: Our study demonstrates that both gender and the method of posterior fixation are associated with hardware failure or displacement.

Does Provisional Minifragment Fixation Prevent Compression With Dynamic Compression Plating? A Biomechanical Analysis.

OBJECTIVES: To compare the compressive force generated by a 3.5-mm compression plate with and without provisional fixation using a 2.0-mm minifragment plate. METHODS: Fourth generation composite large humeral sawbones underwent transection and were divided into 2 groups. The first group underwent fixation with a 3.5-mm compression plate; the second group underwent provisional fixation with a 2.0-mm plate followed by definitive fixation using a 3.5-mm plate. Using a load cell, the compressive force generated was measured after insertion of each of 2 eccentrical placed screws and the total compression recorded. RESULTS: There was no difference in the force generated after each successive compression screw (P = 0.59 and 0.58, respectively). Likewise, there was no significant difference in the total compression generated when the preload was accounted for (P = 0.93). CONCLUSION: Provisional minifragment fixation does not have any adverse effect on the forces generated during compression plating. These findings suggest that provisional minifragment plates do not need to be removed before definitive fixation.

Deltoid ligament repair reduces and stabilizes the talus in unstable ankle fractures.

INTRODUCTION: Treatment of supination external rotation type IV (SER-IV) ankle injuries has focused on reduction and fixation of the fibula and syndesmosis (ORIF), not repair of the deltoid ligament. METHODS: Twenty-one ankles were analyzed with a motion capture system. Uninjured ankles were stressed and compared to ankles with SER-IV injuries, then with ORIF, and finally ORIF and deltoid repair. RESULTS: After deltoid ligament repair, talar coronal and axial rotation normalized to the uninjured state and were significantly reduced compared to ORIF alone. DISCUSSION: Deltoid ligament repair after an SER-IV ankle injury can help directly reduce and stabilize the tibiotalar joint.