Percutaneous sacroplasty for osteoporotic sacral insufficiency fractures: a prospective, multicenter, observational pilot study

Abstract

Background context

Sacral insufficiency fractures (SIFs) can cause low back pain in osteoporotic patients. Symptomatic improvement may require up to 12 months. Treatment includes limited weightbearing and bed rest, oral analgesics, and sacral corsets. Significant mortality and morbidity are associated with pelvic insufficiency fractures. Percutaneous injection of polymethylmethacrylate (PMMA) into the fractured ala, sacroplasty, is an alternative treatment for SIF patients. Under fluoroscopic control, 13-G bone trochars are inserted into the fractured ala while the patient is maintained under conscious sedation. Initial reports have documented safe and effective performance of sacroplasty. Yet, these uncontrolled findings do not allow any precision in estimating complication rates or expected outcome.

Purpose

Assess rates of complications and observe outcomes after sacroplasty in a medium-sized uncontrolled cohort of SIF patients.

Study design/setting

A prospective observational cohort study of consecutive osteoporotic SIF patients.

Patient sample

Consecutive, osteoporotic patients with symptomatic SIFs electing to enter the study.

Outcome measures

Visual Analogue Scale (VAS) score, analgesic utilization, and patient satisfaction.

Methods

Baseline VAS rating, analgesic usage, and duration of symptoms were recorded. Subsequent VAS ratings were assessed within 30 minutes after the procedure, at 2-, 4-, 12-, 24-, and 52-week postprocedure. Analgesic usage and patient satisfaction were assessed at final follow-up. Each procedure was performed under light intravenous conscious sedation using fluoroscopy. Two bone trochars were inserted between the sacral foramen and sacroiliac joint through which 2 to 3 cc of PMMA were injected.

Results

Fifty-two patients, 40 females, were treated. The mean age was 75.9 years with a mean symptom duration of 34.5 days. All patients were available at each follow-up interval except one patient who died because of unrelated pulmonary disease before the 4-week follow-up. The mean VAS score at baseline was 8.1 and 3.4 within 30 minutes after the procedure, 2.5 at 2, 2.1 at 4, 1.7 at 12, 1.4 at 24, and 0.8 at 52 weeks. Improvement was statistically significant using a repeated measures single-factor analysis of variance. One case of transient S1 radiculitis occurred but resolved completely with one transforaminal epidural steroid injection.

Conclusions

Sacroplasty for SIF appears to be associated with rapid and sustained pain relief in most patients with few complications. More rigorous trials are warranted to provide definitive evidence of the safety and efficacy of sacroplasty for SIFs.

Introduction

Sacral insufficiency fractures (SIFs) are a consequence of the imposition of undue stresses onto weakened bone and are common cause of low back pain in the elderly population. Risk factors for SIFs include osteoporosis, osteopenia, rheumatoid arthritis, corticosteroid use, radiation therapy, renal osteodystrophy, osteomalacia, Paget's disease, hyperparathyroidism, joint arthroplasty, and lumbosacral fusion [1]. Among these, osteoporosis, the most common metabolic bone disorder affecting 25 million people in the United States, is the leading cause and is the most common [2]. Osteoporotic bone is prone to fracture because of decreased bone liberalization and mass. Spontaneous fracture of the osteoporotic sacrum was first described in 1982 by Laurie [3], and manifests clinically as low back or buttock pain with or without referred pain into the lower limb [3], [4], [5]. Although common in the elderly [4], [5], SIFs may escape detection by the treating practitioner because of a low clinical suspicion and poor sensitivity of plain radiography [3], thus delaying appropriate therapeutic interventions.

The traditional therapeutic algorithm for SIFs consists of limited bed rest [4], [5], [6], partial weightbearing and early mobilization [7], analgesic medications, and lumbosacral or pelvic corsets [1]. Deep venous thromboses [8] and pulmonary emboli [9], reduced muscle strength with prolonged recovery [10], postural hypotension and impaired cardiac function [10], atelectasis and pneumonia [10], skin breakdown and pressure ulcers [7], constipation and fecal impaction [7], depression, and intellectual regression [7] are complications of periods of inactivity. The overall 1-year mortality rate associated with pelvic insufficiency fractures is 14.3%, and 50% of affected patients will not return to their prior level of function [11]. Although initial clinical improvement may occur rapidly, complete resolution of symptoms may not occur for up to 9 to 12 months [5], [12]. Despite a favorable natural history, more aggressive treatments may benefit certain patients who are incapacitated by painful SIFs.

Chronic symptoms and disability related to osteoporotic insufficiency fractures are believed to be caused by fracture nonunion, micromotion, or resultant deformity related to the anemic attempts of the weakened bone to heal [13]. The percutaneous injection of polymethylmethacrylate (PMMA) into fractured vertebral bodies (vertebroplasty) has been safely performed to successfully treat painful osteoporotic compression fractures [14], [15], [16], [17]. A natural extension in the application of vertebroplasty is the percutaneous injection of synthetic bone cement into the fractured sacrum (sacroplasty) to treat persistent symptoms and disability. Sacroplasty involves the injection of PMMA under fluoroscopic visualization while the patient is consciously sedated. Sacroplasty was first reported in 2001 as treatment of symptomatic sacral metastatic lesions [18], [19], and subsequent reports have documented its safe and effective performance [20], [21], [22]. However, although provocative, the short follow-up intervals [20], [21], [22], and small study cohorts [22] preclude a more definitive commentary regarding the safety of the procedure and the durability of initial results. We therefore designed this study to better define the incidence of complications, and to evaluate the clinical medium-term outcomes after percutaneous sacroplasty in treating painful osteoporotic SIFs.