Displacement of an anterior pelvic ring fracture after L5, S1, and iliac screw fixation: a case report
Article information
Abstract
Multiple fractures and fractures associated with underlying diseases commonly occur in older adults. The lower lumbar spine, sacrum, and pelvis are anatomically interconnected, and multiple simultaneous fractures frequently result from trauma. In this case, a patient with isthmic lumbosacral spondylolisthesis and severe osteoporosis sustained post-traumatic vertebral fractures involving the first and second sacral bodies, fractures of the left sacral ala, and fractures of the right anterior pelvic ring. During the initial conservative treatment period, the pelvic ring fracture remained stable. However, following lumbar, sacral, and iliac posterior fixation and fusion, the right anterior pelvic ring fracture worsened. Subsequently, conservative treatment without anterior pelvic fixation led to improvement. The purpose of this study is to review the evaluation and management of combined fractures involving the anterior pelvic ring through both a literature review and an analysis of this case.
Introduction
As society progresses toward an aging population, the number of patients with osteoporosis is steadily increasing. Consequently, the incidence of fractures resulting from trauma is also rising. Among osteoporotic patients, fractures frequently occur due to falls, with the pelvis, spine, and forearm being particularly common sites [1].
In cases involving fractures and concomitant degenerative diseases, surgical intervention is often required. However, in patients with multiple fractures where only partial fixation is performed, other fracture sites may deteriorate. In particular, when posterior fixation is used to treat combined anterior and posterior pelvic fractures, the anterior pelvic ring fracture may be aggravated due to the anatomical continuity of the pelvic ring.
We report a case in which an anterior pelvic ring fracture became displaced and worsened following lumbar, sacral, and iliac screw fixation.
Case Report
A 77-year-old female patient presented with right inguinal pain. She had sustained multiple falls prior to her hospital visit and reported subjective weakness in both legs, particularly on the right side. Radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and dual-energy X-ray absorptiometry for bone marrow density (BMD) were performed. The findings included severe osteoporosis (BMD, –4.7), isthmic spondylolisthesis at L5-S1 with central canal and foraminal stenosis, a linear fracture of the right superior pubic ramus, and a hematoma in the right obturator externus muscle (Fig. 1).
Initial lumbar magnetic resonance imaging (MRI) and hip MRI. (A) Isthmic spondylolisthesis L5-S1. (B) Foraminal stenosis L5-S1. (C) Right parasymphysis fracture and mild hematoma on obturator externus (arrow).
After receiving 3 spinal block procedures and undergoing physical therapy, the patient’s pain improved significantly, and she was discharged.
Two weeks later, she returned to the hospital with severe buttock pain, reporting 2 additional falls since discharge that had exacerbated her symptoms. Follow-up MRI and CT scans revealed new fractures involving the S1 and S2 vertebral bodies and the left sacral ala (Fig. 2).
Preoperative lumbar magnetic resonance imaging and lumbosacral computed tomography. (A) Acute vertebral body of S1, 2 (arrow). (B) Vertical S1, 2 vertbral body fracture and left sacral ala fracture (arrow).
The patient underwent transforaminal lumbar interbody fusion at L5-S1, pedicle screw fixation at L5-S1, and iliac screw fixation. Immediately after surgery, the right pelvic pain and radiating pain in the right lower extremity improved. However, 10 days postoperatively, both the right pelvic pain and radiating symptoms recurred and worsened. Follow-up pelvic radiographs and MRI demonstrated aggravation of the anterior pelvic ring fracture (Fig. 3).
Follow-up hip radiograph and magnetic resonance imaging. (A) Preoperative pelvic X-ray: no displacement of pelvic ring. (B) Post-operative pelvic X-ray: aggravation of right anterior pelvic ring displacement (arrow). (C) Right superoinferior rami parasymphysis fracture with persistent fracture gap (white arrow). Fluid accumulation at fracture gap suggesting instability.
After several days of conservative treatment, including physical therapy and bed rest, the patient’s symptoms partially improved. Over 2 months of conservative management postoperatively, her pain continued to improve, and she regained the ability to ambulate independently. During outpatient follow-up, she was able to walk with a walker and reported reduced right pelvic pain. Teriparatide was administered for 6 months, after which the anterior pelvic ring fracture was found to be stable.
Discussion
Patients with osteoporosis often sustain multiple fractures, even after minor trauma. In elderly individuals, it is common for degenerative disease and traumatic injury to coexist. In this case, the patient had sacral vertebral body and ala fractures, an anterior pelvic ring insufficiency fracture, and isthmic spondylolisthesis.
The pelvic ring consists of the sacrum and 2 hip bones (ilium, ischium, and pubis), which are connected by 3 joints: the 2 sacroiliac (SI) joints and the pubic symphysis. The pubic symphysis is composed of hyaline and fibrous cartilage [2], whereas the SI joints primarily consist of fibrous cartilage reinforced by a strong joint capsule and robust ligaments [3–5].
Although pelvic ring fractures in the elderly are relatively rare, their incidence increases with age. The primary goal of treatment is early mobilization, as prolonged immobilization can lead to severe complications such as disuse sarcopenia, pneumonia, and thromboembolic events (e.g., deep vein thrombosis, pulmonary embolism) [6].
Pelvic ring fractures are classified using various systems, with the AO classification being the most widely used. This system categorizes fractures based on the affected part of the pelvic ring and provides insight into the ring’s stability [7]: (1) type A: injury to the anterior ring, iliac crest, or sacral bone below the SI joints; (2) type B: injury to the anterior ring with partial involvement of the posterior ring; (3) type C: complete disruption of the posterior ring, often with concomitant anterior ring injury (Fig. 4).
Pelvic ring fracture subtypes by AO classification. Type A: injury to the anterior ring, iliac crest, or sacral bone below the sacroiliac joints. Type B: injury to the anterior ring with partial involvement of the posterior ring. Type C: complete disruption of the posterior ring, often with concomitant anterior ring injury.
Fractures of the anterior pelvic ring (type A) are often considered minor injuries, especially when non-displaced. As surgical intervention is typically not required, conservative treatment—including analgesics, physical therapy to promote early mobilization, and osteoporosis management—is recommended [8,9].
In the present case, conservative treatment was initially chosen for the isolated, non-displaced anterior pelvic ring fracture. However, due to isthmic spondylolisthesis and foraminal stenosis, spinal fusion and screw fixation were necessary to enable early mobilization. Despite the implementation of conservative treatment prior to spinal fusion, the anterior pelvic ring fracture failed to heal, potentially due to osteoporosis, which may have compromised the bone tissue’s regenerative capacity [10].
Preoperative assessment of anterior pelvic ring stability should be conducted prior to surgery [11]. Even if the preoperative evaluation suggests stability, anterior instability may still occur. Ellis et al. recommend performing an examination under anesthesia (EUA) to detect occult instability [12]. In this case, conducting EUA prior to posterior fixation might have revealed instability and altered the surgical plan.
If anterior pelvic instability is identified, various surgical fixation techniques are available, including external fixation, symphyseal plating, ramus screws, subcutaneous internal fixation, and others [13,14]. The choice of technique depends on factors such as fracture pattern, deforming forces, posterior ring injury, bone quality, patient body habitus, and overall health status [15]. Regardless of the technique chosen, achieving stability of the anterior pelvic ring is essential.
During iliac screw insertion, the application of clockwise torque may produce upward pressure on the insufficiency fracture site, potentially aggravating the fracture. Additionally, vertical loading from the spine during standing may be transmitted axially through the rods and screws, exacerbating stress at the anterior pelvic ring.
In conclusion, Preoperative evaluation of anterior pelvic ring stability is essential before performing posterior fixation. Intraoperative evaluation under anesthesia should be considered both before and after posterior fixation to detect occult instability. If anterior pelvic instability is identified, appropriate anterior fixation should be implemented. During iliac screw insertion, torque control is crucial to prevent anterior ring displacement. In cases where anterior fixation is not performed, patients must be closely monitored postoperatively for signs of fracture progression. The patient provided written informed consent for publication of the clinical details and images.
Notes
Conflict of Interest
No potential conflict of interest relevant to this article was reported.