The management of unstable sacral fractures, especially those with associated multisystem injuries and overlapping fracture patterns, is a challenge even to the most experienced surgeon. Any sacral fracture with associated posterior pelvic ring disruption is deemed unstable, and vertical instability, being the worst, warrants surgical stabilization. Spinopelvic dissociation is a relatively newer terminology that represents a spectrum of highly complex atypical sacral fractures resulting in multiplanar instability of the lumbopelvic. Optimal management guidelines are still lacking probably due to the rarity of these injuries and varying fixation trends.

Among the surgical techniques described for sacral fractures like sacroiliac (SI) screws, posterior tension band plating, and transiliac rods among others, lumbopelvic fixation (LPF) with or without percutaneous SI screws has surpassed all other techniques, and their combination, otherwise known as “triangular osteosynthesis”, is reported to have the greatest mechanical stability [1]. The description of closed reduction and minimally invasive strategies has popularized LPF and is the preferred option for spinopelvic dissociation.

Although the advantages of LPF have been proven clinically and biomechanically in rotationally and vertically unstable injuries not amenable to SI screw fixation, a rising trend exists toward its routine use in every unstable sacral fracture [2]. LPF is considered an overtreatment adding to surgical morbidity especially in patients with multisystem afflictions unless indicated [3]. Moreover, a steep learning curve, loss of motion segments, and implant-related complications further deter its routine use. This study sought to evaluate the outcome of SI screw and LPF strategies in unstable sacral fractures and thereby delineate the indications for each.

Included in this study are 67 patients (40 and 27 patients in the SI and LPF groups, respectively). The road traffic accident was the most common mode of injury (67.16%) while the remaining cases were due to falling (32.84%). The most common sacral fracture morphology was vertical (79.1%), and APC-type II (47.7%) was the most common injury followed by vertical shear (20.9%) injury among the associated pelvic ring injuries. Different morphological patterns are detailed in Table 1. The average follow-up period was 28.4 months (range, 26–49 months). Thirteen patients (19.4%) required supplemental anterior stabilization (symphyseal plating, n=7; pubic ramus screw, n=1; and infix, n=5) (Fig. 3). Infix removal was routinely performed as an outpatient procedure at 6-month follow-up after confirming radiological healing. The initial ex-fix application was required in nine patients, and distal femoral traction was applied in 14 patients which were removed at the time of definitive surgery.

Nine patients had associated spine trauma at other locations requiring surgical stabilization (lumbar, n=4; thoracic, n=4; and cervical, n=1) and 15 had other orthopedic injuries. None of the associated spine trauma patients had neurodeficit. Nine patients had other system injuries (head, n=3; chest, n=4; and abdomen, n=2), and the mean ISS score was 23.5±11.6. Three patients had neurodeficit at presentation, all associated with Denis zone III injury, and had undergone decompression (S1–4 laminectomy using high-speed burr). No open injuries were noticeable although four had associated Morel-Lavelle lesions, which necessitated open debridement.

Fractures of the sacrum, although rare, with a reported incidence of approximately 45% of all pelvic fractures, can have a significant impact on the patient’s quality of life as a consequence of chronic pelvic instability, deformity, prolonged recumbency, and neurological impairment [5]. The role of surgical management in promoting early mobilization and improved outcomes have been demonstrated [11,12]. However, no single management algorithm is applicable for all traumatic sacral fractures, and proper treatment has yet to be standardized. Despite the numerous salvage techniques described over the last 3 decades, recent advances in intraoperative imaging have led to the emergence of the SI screw and LPF as two major pillars for surgeons to lean on [1].

This study deliberately excluded isolated sacral fractures without pelvic ring disruption as it seldom creates any management dilemma in the minds of the treating surgeon. Even then, the sample size (n=67) of this study was large enough compared with the majority of the literature on unstable sacral fractures [13–16]. Associated vertebral fracture was seen in 13.4% of patients as opposed to 44.26% by Park et al. [17] in his retrospective study on 71 patients. Although this appears low, a less likelihood for missed injuries exists in the institute of this study due to the polytrauma protocol being followed in which all patients had a whole-body CT scan and whole spine screening. Operative stabilization was performed for the vertebral fractures on the same day of definitive pelvic surgery. Moreover, it did not have any significant impact on treatment outcomes because none of them had any neurological deficit. Jazini et al. [2] reported an average ISS score of 27±13.6 in his retrospective study of LPF on 32 patients, which is comparable to the score (23.5±11.6) of the current study.

The incidence of spinopelvic dissociation in this study was 49.25%, which is significantly higher than the previously reported rates of 3%–10% [17,18]. This is probably due to the inclusion of only those patients having a combination of unstable sacral fractures and pelvic ring disruption, which invariably signifies a high-velocity trauma. Initial reports on LPF and triangular osteosynthesis have considered the presence of vertical instability with fracture comminution and/or spinopelvic dissociation as the only indication for these procedures [19,20]. However, a review of recent literature on the management of unstable fractures showed a major drift toward the routine use of LPF irrespective of the presence of fracture comminution or spinopelvic dissociation. The introduction of minimally invasive techniques expanded this further [2,16]. This study did not consider LPF imperative for all vertically unstable injuries unlike the aforementioned publications provided the fracture was noncomminuted, neurologically normal, and acceptable closed reduction could be preoperatively obtained (Fig. 3). Eleven patients in the SI group had vertical instability and all of them had a satisfactory outcome in the long term both clinically and radiologically compared with that achieved using LPF (Table 2). Moreover, surgical duration, intraoperative blood loss, and complications were also found to be lower in the SI group though a statistical analysis is not possible due to an unmatched cohort of patients in the two groups (Tables 5, 6). A high mean ISS score (23.5±11.6) also denotes the magnitude of injury, which would justify intervention with the least possible surgical trauma. In a retrospective analysis of 38 vertically unstable pelvic injuries treated by SI screw, Keating et al. [21] observed favorable outcomes with fewer complication rates. Similarly in 2015, the review by Iorio et al. [22] pointed out the advantages and effectiveness of the SI screw even in patients with vertical instability or spinopelvic dissociation. Complex fracture patterns like the U- and H-shaped sacral fractures have also been managed successfully by an SI screw fixation with the satisfactory restoration of the pelvic parameters using a novel closed reduction technique described by Ruatti et al. [23] in 2013.

The outcome scores in the series of this study corresponded closely with previously reported similar studies. In a retrospective analysis of 22 patients with AO/type C posterior pelvic ring injuries treated by contemporary spinal instrumentation, Korovessis et al. [16] reported good and excellent Majeed and Matta scores in 81.81% and 95.45% of the patients, respectively. With a sample size almost three times higher than a study of Korovessis et al. [16], the functional and radiological scores of this study were comparable (86.57% and 92.54%, respectively).

The complication rates of this study were very low (8.9%) as opposed to the existing publications on the SI screw as well as LPF [13,24]. All the surgeries being performed by the senior author as well as appropriate patient selection and precautionary measures taken in screw head recession may have helped the cause. Moreover, the subject of this study is comprised of patients in the younger age group (mean, 35.61±14.01 years), which may have reduced the complications related to implant purchase and wound healing. The complication rate was higher in the LPF group although the number is too small for statistical analysis. This could partly be attributed to injury factors as well because all patients had sustained a high-velocity trauma. Patients with neurodeficit all belonged to zone III injury, which was consistent with the findings of Denis et al. [5] in his retrospective analysis of 236 patients. Regardless of the role of decompression surgery in neurodeficit, direct decompression was performed in all patients (n=3) wherein one had a complete recovery [25–27].

Although this study was limited by its retrospective design, it would be rather justified by the rarity of these injuries as evidenced by smaller sample sizes in the existing literature [2,11,14,16]. It is also agreeable that the sample size of the current study is inadequate for power analysis and has a high risk for type-II error to occur. The series of this study is difficult if not impossible to compare and draw a conclusion because the subject included varying patterns of complex sacral fractures forming an unmatched cohort of patients managed by two separate techniques. A relatively younger age group of the patient population may restrict the applicability of inference in older, osteoporotic patients with similar injuries. A prospective study design with matched study groups and randomization is ideally needed for better interpretation of conclusions. Through this study, it is believed that LPF is not always the rule in unstable sacral fracture management. Although it offers early weight-bearing compared with SI screw fixation, this is often precluded by associated injuries in the form of intra-articular fractures of the lower limb or other systemic injuries.

Unstable sacral fractures can be effectively managed with percutaneous SI screw including vertically unstable injuries by paying strict attention to preoperative patient selection in terms of fracture pattern and comminution, neurodeficit, and closed reduction techniques thereby reducing the complications associated with LPF. Furthermore, LPF can be reserved for comminuted fractures with vertical instability, unacceptable closed reduction, associated neurodeficit, lumbosacral dysmorphism, and high transverse fractures.