RESUMEN
[This corrects the article DOI: 10.3389/fbioe.2021.646079.].
RESUMEN
While spinal fusion using rigid rods remains the gold standard treatment modality for various lumbar degenerative conditions, its adverse effects, including accelerated adjacent segment disease (ASD), are well known. In order to better understand the performance of semirigid constructs using polyetheretherketone (PEEK) in fixation surgeries, the objective of this study was to analyze the biomechanical performance of PEEK versus Ti rods using a geometrically patient-specific poroelastic finite element (FE) analyses. Ten subject-specific preoperative models were developed, and the validity of the models was evaluated with previous studies. Furthermore, FE models of those lumbar spines were regenerated based on postoperation images for posterolateral fixation at the L4-L5 level. Biomechanical responses for instrumented and adjacent intervertebral discs (IVDs) were analyzed and compared subjected to static and cyclic loading. The preoperative model results were well comparable with previous FE studies. The PEEK construct demonstrated a slightly increased range of motion (ROM) at the instrumented level, but decreased ROM at adjacent levels, as compared with the Ti. However, no significant changes were detected during axial rotation. During cyclic loading, disc height loss, fluid loss, axial stress, and collagen fiber strain in the adjacent IVDs were higher for the Ti construct when compared with the intact and PEEK models. Increased ROM, experienced stress in AF, and fiber strain at adjacent levels were observed for the Ti rod group compared with the intact and PEEK rod group, which can indicate the risk of ASD for rigid fixation. Similar to the aforementioned pattern, disc height loss and fluid loss were significantly higher at adjacent levels in the Ti rod group after cycling loading which alter the fluid-solid interaction of the adjacent IVDs. This phenomenon debilitates the damping quality, which results in disc disability in absorbing stress. Such finding may suggest the advantage of using a semirigid fixation system to decrease the chance of ASD.
RESUMEN
BACKGROUND: The goal of this study was to report the results of selective open reduction and internal fixation of fractures of the posterior malleolus with a posterolateral approach and to compare the results of the 2 techniques. METHODS: We prospectively evaluated 40 patients who underwent posterior malleolar fracture fixation between 2008 and 2012. The patients were treated with a posterolateral approach. We assigned alternating patients to receive plate fixation and the next screw fixation, consecutively, based on the order in which they presented to our institution. Fixation of the posterior malleolus was made with lag screws in 20 patients and a buttress plate in 20 patients. We used American Orthopaedic Foot and Ankle Society (AOFAS) scores, range of motion (ROM) of the ankle, and radiographic evaluations as the main outcome measurements. The mean follow-up was 38.2 (range, 24-51) months. RESULTS: Full union without any loss of reduction was obtained in 38 of the 40 patients. We detected a union with a step-off of 3 mm in 1 patient in the screw group and a step-off of 2 mm in 1 patient in the plate group. At the final follow-up, the mean AOFAS score of the patients regardless of fixation type was 94.1 (range, 85-100). The statistical results showed no significant difference between the patients regardless of the fixation type of the posterior malleolus in terms of AOFAS scores and ROM of the ankle (P > .05). CONCLUSIONS: Good (AOFAS score of 94/100) and equivalent (within 3 points) results were obtained using the 2 techniques (screws or plate) for fixation after open reduction of posterior malleolar fragments. LEVEL OF EVIDENCE: Level II, prospective case series.