Biomechanical Tests and Finite Element Analyses of Pelvic Stability using Bilateral Single Iliac Screw with Different Channels in Lumbo-iliac Fixation

Background: In lumbo-iliac fixation, the iliac screw can be placed in a number of locations and directions, and multiple screws can be placed to enhance the fixation effect. At present, there is no uniform standard for the placement of single iliac screw. Biomechanical tests and finite element analyses were used to compare the effect of bilateral single iliac screw with three channels on pelvic stability in lumbo-iliac fixation, so as to provide a basis for determining the best single iliac screw channel.Methods: Five adult embalmed cadaver pelvic specimens were selected. Unstable Tile C1 pelvic injury model (pubic symphysis separation and left sacral Denis II fracture) was established. The pubic symphysis was fixed with five-hole reconstruction plate. Lumbo-iliac fixation for the treatment of pelvic posterior ring injury: three channels of bilateral single iliac screw (channel A from PSIS to AIIS, channel B from 1 cm medial and 1 cm caudal of PSIS to AIIS, channel C from 2 cm below PSIS to AIIS). At the same time, the finite element model of unstable pelvic posterior ring injury treated with lumbo-iliac fixation was established, which were used to analyze and explore the effect of bilateral single iliac screw with three channels on the biomechanical stability of the pelvis, including the stress distribution and the maximum Von Mises stress of internal fixation, vertebral body and ilium.Results: Biomechanical tests revealed that under vertical compression load, the compressive stiffness of pelvic specimens fixed with three channels of bilateral single iliac screw was lower than that of complete pelvic specimens (P < 0.05). The vertical displacement fixed by channel B was smaller than that fixed by channel A and channel C; however, there was no significant difference between channel B and channel A (P > 0.05). The compressive stiffness fixed by channel B was better than that fixed by channel A and channel C. Under torsional load, the torsional stiffness fixed by channel B was stronger than that fixed by channel A and channel C. Finite element analyses conformed that the maximum Von Mises stress of the internal fixator fixed in channel B under the conditions of vertical, forward bending, backward extension, left bending, left rotating and right bending were significantly lower than that fixed in channel A and channel C. Under various working conditions, the maximum Von Mises stress of the internal fixture of channel B was less than that of channel A. In terms of the maximum Von Mises stress of the vertebral body and iliac, compared with the other two iliac screw channels, the overall stress distribution fixed by channel B was more reasonable.Conclusions: Bilateral single iliac screw with three channels in lumbo-iliac fixation could effectively restore pelvic stability. The construct stiffness of the channel from 1cm medial and 1cm caudal of PSIS to AIIS is better than that of the other two channels. This channel has the advantages of good biomechanical stability, reasonable stress distribution, small maximum Von Mises stress of internal fixation, strong fatigue resistance and not easy to break screws and robs.

Transforaminal Percutaneous Endoscopic Discectomy in the Treatment of Adolescent Lumbar Disc Herniations With Posterior Ring Apophysis Separation

Objective: To assess the efficacy of transforaminal percutaneous endoscopic discectomy in the treatment of adolescent lumbar disc herniations with posterior ring apophysis separation Methods: Overall 23 cases of adolescent lumbar disc herniations with posterior ring apophysis separation were treated with the procedure of transforaminal percutaneous endoscopic discectomy between January 2016 and December 2019. Preoperative and postoperative (6 week, 6 month and 12 month) clinical outcome data (back and leg VAS and Macnab criteria) were collected along with clinical assessments of motor strength (graded 0-5).Results All patients were discharged to home on the same day of surgery. The average leg Visual Analog Scale improved from 8.7 ± 1.5 to 2.0± 0.5 (p < 0.005). Fifteen patients had excellent outcomes, six had good outcomes, two had fair outcomes, and no had poor outcomes, according to the Macnab criteria. Ten of eleven patients had excellent or good outcomes, for an overall success rate of 91.3%. No patients required reoperation. There were no incidental durotomies, infections, vascular or visceral injuries. There was 1 complication, a case of leg numbness caused by ganglion injury. The numbness improved after 3 weeks. After 2 months, it was obvious that the total area of numbness in the legs had become smaller. At last follow-up, the patient had no pain, and only a few areas with numbness remained and did not affect the patient’s activities of daily living. Conclusion:Transforaminal percutaneous endoscopic discectomy achieve satisfactory results for adolescent lumbar disc herniations with posterior ring apophysis separation.

Fracture progression in fragility fractures of the pelvis: A case report

Introduction Fragility fractures of the pelvis (FFP) are becoming increasingly common as our population ages. Usually treated conservatively the concept of fracture progression is little recognized but can have important consequences for the patient if missed. Case report A patient with a FFP presented with increase of pain after initial conservative treatment. Additional imaging revealed extensive fracture progression resulting in an unstable pelvic ring, requiring surgical intervention. Most FFPs are currently treated conservatively. However, initially stable FFPs can progress into more unstable fracture patterns that may require invasive treatment. Conclusion Physicians should be aware of fracture progression and concomitant posterior ring fractures in case of prolonged or recurrent pain or mobilization difficulties. Careful follow-up and awareness might help to prevent or treat debilitation in an early phase and improve outcomes.

Surgical management of pelvic ring injuries: a study of twelve cases

<p>The bony pelvic ring is constituted of the sacrum and bilateral innominate bones and stabilized by the sacroiliac, sacrospinous and sacro tuberous ligaments. Secondary stabilization is provided by the iliolumbar ligaments. Injury to the posterior ring structures brings more severe clinical instabilities. Assessment of mechanisms and mode of injuries is necessary for management of pelvic injury. Twelve patients were involved in this study of different kinds of injuries by classification and methods of treatment four patients were treated by anterior fixation. Three by posterior and three by anterior as well as posterior. One was by conservative means. Anterior includes symphysis plating, posterior includes intrapelvic plates as well as sacroiliac percutaneous screw fixation. Combined includes posterior plating and sacroiliac screw and external fixator anteriorly. All patients showed good results in terms of stability, union of fracture, relief of pain and movements. Two patients had some residual neurological deficit as foot drop. Pelvic ring injuries need a specialized approach for management and outcomes. Application of appropriate classification for management plays a significant role in outcomes.</p>

Microendoscope-Assisted Decompression Surgery With Resection of Bony Fragment for Treating a Separation of Lumbar Posterior Ring Apophysis in Young Athletes

Study Design: Case series. Objectives: To report the clinical outcomes of the decompression procedure using the microendoscopic discectomy system for the treatment of a separation of lumbar posterior ring apophysis in young active athletes. Methods: We retrospectively reviewed 17 cases that underwent the microendoscopic surgery to treat a symptomatic separated lumbar ring apophysis between 2001 and 2014 at our institute or our associated hospital. The cases consisted of 15 males and 2 females, with their ages ranging from 12 to 19 years. The surgeries were performed at total of 18 lumbar levels, including 15 L4/5 and 3 L5/S1 levels. All patients were young athletes. We evaluated the following: (1) the Japanese Orthopaedic Association (JOA) score for low back pain, (2) recovery rates using Hirabayashi’s method, (3) operating time, (4) intraoperative blood loss, (5) perioperative complications, (6) the status of comeback to sports, and (7) the period taken to return to sports. Results: The JOA score was improved after the surgery in all cases. Recovery rate was 92.0% ± 8.1%. The mean operating time per level was 89.2 ± 33.3 minutes. The mean intraoperative blood loss per level was 95.3 ± 93.1 mL. A pinhole size dural tear occurred in one case as a perioperative complication. All cases returned to sports. The mean period taken to return to sports was 10.9 ± 3.5 weeks. Conclusion: Microendoscopic decompression surgery is useful for treating a separation of lumbar posterior ring apophysis.