L4 fixation is not necessary in L5-Iliac spinopelvic fixation after trauma, but coadjutant transilio-transsacral fixation is

INTRODUCTION

Spinopelvic dissociation (SPD) is a severe injury characterized by a discontinuity between the spine and the bony pelvis consisting of a bilateral longitudinal sacral fracture, most of the times through sacral neuroforamen, and a horizontal fracture, usually through the S1 or S2 body. The introduction of the concept of triangular osteosynthesis has shown to be an advance in the stability of spinopelvic fixation (SPF). However, a controversy exists as to whether the spinal fixation should reach up to L4 and, if so, it should be combined with transiliac-transsacral screws (TTS).

OBJECTIVE

The purpose of this study is to compare the biomechanical behavior in the laboratory of four different osteosynthesis constructs for SPD, including spinopelvic fixation of L5 versus L4 and L5; along with or without TTS in both cases.

MATERIAL AND METHODS

By means of a formerly described method by the authors, an unstable standardized H-type sacral fracture in twenty synthetic replicas of a male pelvis articulated to the lumbar spine, L1 to sacrum, (Model: 1300, SawbonesTM; Pacific Research Laboratories, Vashon, WA, USA), instrumented with four different techniques, were mechanically tested. We made 4 different constructs in 5 specimen samples for each construct. Groups: Group 1. Instrumentation of the L5-Iliac bones with TTS. Group 2. Instrumentation of the L4-L5-Iliac bones with TTS. Group 3. Instrumentation of L5-Iliac bones without TTS. Group 4: Instrumentation of L4-L5-Iliac bones without TTS.

RESULTS AND CONCLUSIONS

According to our results, it can be concluded that in SPD, better stability is obtained when proximal fixation is only up to L5, without including L4 (alternative hypothesis), the addition of transiliac-transsacral fixations is essential.

Biomechanical models of in vitro constructs for spinopelvic osteosynthesis

Spinopelvic lesions are the result of high-energy vertical trauma with axial skeletal overload where the spine impacts onto the sacrum, dissociating the lumbar spine from the pelvis. Therefore, lumbopelvic instrumentations are aimed to counteract these vertical forces, although various biomechanical aspects of the combinations of different constructs (with or without iliosacral screws) or the number of lumbar fixation levels (L5 or the combination of L5 with L4) are subject to controversy. The number of patients in each published series is too short, and the nature of the fixation is very different from one article to another, making comparison very difficult. In this paper the methodology for laboratory studies is discussed. The design of the test bench fixture, biomechanical testing protocol and data analysis are very important when inference to the clinical setting is desired.

Operative management of complex lumbosacral dissociations in combat injuries

BACKGROUND CONTEXT

As war injury patterns have changed throughout Operations Iraqi and Enduring Freedom (OIF and OEF), a relative increase in the incidence of complex lumbosacral dissociation (LSD) injuries has been noted. Lumbosacral dissociation injuries are an anatomical separation of the spinal column from the pelvis, and represent a manifestation of severe, high-energy trauma.

PURPOSE

This study aimed to assess the clinical outcomes of combat-related LSD injuries at a mean of 7 years following operative treatment.

STUDY DESIGN

This is a retrospective review.

PATIENT SAMPLE

We identified 20 patients with operatively managed LSDs.

OUTCOME MEASURES

Time from injury to arrival in the United States, operative details, fixation methods, postoperative complications, time to retirement from military service, disability, and ambulatory status at latest follow-up.

METHODS

We performed a retrospective review of outcomes of all patients with operatively managed combat-related LSD from January 1, 2003 to December 31, 2011.

RESULTS

Twenty patients met inclusion criteria and were treated as follows: posterior spinal fusion (12, 60%), sacroiliac screw fixation (7, 35%), and combined anterior-posterior fusion for associated L3 burst fracture (1, 5%). The mean age was 28.2±6.4 years old. The most common mechanism of injury was mounted improvised explosive device (IED, 55%). On average, 2.2 spinal regions were injured per patient. Neurologic dysfunction was present in 15 patients. Three patients underwent operative stabilization of their injuries before evacuation to the United States. Four patients had a postoperative wound infection and two patients underwent reoperation. Mean follow-up was 85.9 months (range: 39.7-140.8 months). At most recent follow-up, seventeen patients were no longer on active duty military service. Eight patients had persistent bowel dysfunction and nine patients had persistent bladder dysfunction. Fifteen patients reported chronic low back pain. Seventeen were ambulating and five had documentation of running following surgery.

CONCLUSIONS

This is the largest series of operatively managed LSD in patients currently reported. Our series suggests that combat-related LSD injuries frequently result in persistent, long-term neurologic dysfunction, disability, and chronic pain. Operative management carries a high postoperative risk of infection. However, a select group of patients are highly functional at latest follow-up.