Failure of Cement-Augmented Pedicle Screws in the Osteoporotic Spine

Abstract

The treatment of patients with osteoporosis and spinal abnormalities that require surgical intervention is difficult because of the challenge of achieving fixation in osteoporotic bone. As the population ages, this challenge is becoming a common problem in the field of spinal surgery. Although numerous publications exist about the biomechanical benefits of various fixation devices and techniques, no standard of care has emerged that offers a clear method for accomplishing spinal stabilization in such patients. This case presents the failure mode of cement-augmented pedicle screws in a patient with severe osteoporosis, a description of the methods used to attain fixation and spinal stability during the revision surgery, and the outcome achieved for the patient 1 year after surgery. An 82-year-old female with a T9 burst fracture and a history of osteoporosis underwent minimally invasive instrumentation from T5 to T12, fusion from T7 to T11, and decompression from T8 to T10. Four weeks after surgery, the patient returned to the hospital because of back pain. Imaging studies showed that the pedicle screws at T11 and T12, which were augmented with polymethylmethacrylate (PMMA), had pulled out of the vertebral bodies. The pedicle screws failed by disengaging from the PMMA and displacing posteriorly and inferiorly. The PMMA did not appear to move during this process. A revision surgery was performed, in which the posterior construct was extended caudally and cephalad, the pedicle screws were augmented with PMMA, and a titanium hook and woven polyester band were used to increase the points of fixation. At 1-year follow-up after revision, our patient showed radiographic evidence of fusion, and the construct continued to maintain stability in the osteoporotic spine.

Novel Polyethylene Terephthalate Screw Sleeve Implant: Salvage Treatment in a Case of Spine Instability after Vertebroplasty Failure

“…In our case, it was paramount to decompress the neurological structures while also stabilizing the spine. Unfortunately, osteoporosis decreases the fixation strength of pedicle screws by 40% to 80% [ 17 ]. Further, augmentation of pedicle screws in an osteoporotic bone is one of the most commonly used methods of osteoporotic spine fixation or revision surgery.…”

Technical Note: Pedicle Cement Augmentation with Proximal Screw Toggle and Loosening

“…Removal of the screws may risk fracturing the vertebrae and neurological injury with screw/cement removal. Mesfin et al reported a revision for a failed cement‐augmented fenestration screws fixation in a osteoporotic patient by extending the posterior construct, cement‐augmentation, and addition of a titanium hook and woven polyester band to increase the points of fixation. If, however, the cement was broken off from the screws during revision as described by Blattert et al, the residual cement can potentially act as a barrier for proper osseointegration between bone and the newly inserted screw.…”

Timing of PMMA cement application for pedicle screw augmentation affects screw anchorage

“…During a reposition maneuver in combination with screw augmentation the screw anchorage can be compromised and cause clinical failure of the instrumentation by disengagement of the screw from the PMMA cement with the cement still attached to the bone [24]. To avoid compromising the screw anchorage, screws can be augmented after the reposition maneuver or in cases with augmentation prior the reposition maneuver sufficient time should be taken to allow the cement to fully cure.…”