Abstract

Background: Early postoperative sacral fractures are extremely rare complications of single-level posterior lumbar interbody fusions (PLIFs).

Case Description: A 71-year-old female presented with lower back pain and right S1 radiculopathy attributed to MR-documented L5/S1 isthmic spondylolisthesis. Following a L5 laminectomy and bilateral L5/S1 PLIF, she experienced sacral pain while sitting. When the MR showed a sacral insufficiency fracture with anterolisthesis at L5/S1, a secondary posterior fusion was extended to the pelvis, utilizing bilateral iliac screws. Following this reoperation, the patient did well and went on to achieve arthrodesis.

Conclusion: Early postoperative sacral fractures that occur following single-segment L5/S1 PLIF for isthmic spondylolisthesis warrant fusion to the pelvis with bilateral iliac screws.

Keywords: Iliac screws, Isthmic spondylolisthesis, Sacral fracture, Short-segment posterior lumbar interbody fusion

INTRODUCTION

Early postoperative sacral fractures following L5/S1 posterior lumbar interbody fusion (PLIF) are rare. Here, a 71-year-old female sustained a postoperative sacral fracture after a L5/S1 PLIF performed for isthmic spondylolisthesis. Following a secondary fusion to the pelvis utilizing bilateral iliac screws, the patient’s complaints resolved.

CASE DESCRIPTION

Clinical presentation and first surgery

A 71-year-old female with low back pain and right lower extremity sciatica had initial MR and CT studies that revealed L5/S1 isthmic spondylolisthesis (near Grade 3) and a Cobb’s angle of 19.3° [ Figure 1a - d ]. The L5/S1 PLIF was performed using pedicle screws (7.5 mm × 50 mm and 7.5 × 45 mm) and an interbody cage. One day postoperative lumbar X-rays/CT studies, and the MRI obtained at 1 postoperative week, documented resolution of the L5/S1 isthmic spondylolisthesis [ Figure 2a and b ].

Figure 1:

Anteroposterior (a) and lateral (b) radiographs of the lumbar spine before lumbosacral fusion demonstrated isthmic spondylolisthesis at L5/S1 with mild scoliosis. T1- (c) and T2-weighted images (d) showed isthmic spondylolisthesis of L5 on S1.

Figure 2:

Anteroposterior (a) and lateral (b) radiographs of the lumbar spine after lumbosacral fusion showed improvement of the L5/ S1 spondylolisthesis. T1- (c) and T2-weighted images (d) indicated the sacral fracture (white arrows) 3 weeks after the lumbosacral fusion.

Second surgery

Two weeks later, the right leg numbness recurred. By the ^3rd postoperative week, X-rays and MRI studies showed a sacral insufficiency fracture, with instability above the sacral fracture, and anterolisthesis of S1 [ Figure 2c and d , Figure 3 ]. The posterior fusion was then extended to the pelvis using bilateral iliac screws (8.5 mm × 70 mm and 7.5 mm × 50 mm). One month postoperatively, X-rays, CT, and MRI examinations confirmed fusion, and the patient was now asymptomatic [ Figure 4 , Tables 1, 2 ].

Figure 3:

Lateral radiographs of the lumbar spine in the sitting (a) and supine positions (b) after lumbosacral fusion showing instability at the S1/S2 level.

Figure 4:

Postoperative anteroposterior (a) and lateral (b) radiographs of the lumbar spine following the lumbopelvic fusion.

Table 1:

Summary of the pelvic parameters.

Table 2:

Summary of the VAS score and the ODI score.

DISCUSSION

Sacral insufficiency fractures are typically complications of previous long-segment instrumented lumbosacral fusions, but rarely involve single-level PLIF [ Table 3 ].[ 1 , 3 , 5 - 8 ] According to Klineberg et al. and Odate et al., the incidence of sacral insufficiency fractures is 3.1–4.3% for long-segment versus just 1.3% for short-segment instrumented lumbosacral fusions.[ 2 , 4 ] Before performing short-segmental lumbosacral fusions, bone density studies should be performed to rule out osteoporosis, especially in elderly females with high-grade L5/S1spondylolisthesis. Certainly, patients showing radiographic confirmation of instability/fractures at the postoperative surgical site on X-ray/MR/CT studies and should be considered for placement of bilateral lumbosacral iliac screws.

Table 3:

The risk factors of sacral fractures after lumbosacral fusion.

CONCLUSION

A 71-year-old female developed an early postoperative sacral fracture after a L5/S1 PLIF for isthmic spondylolisthesis. Following extension of the fusion to the pelvis using bilateral iliac screws, the patient became asymptomatic and achieved successful arthrodesis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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