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

Abstract

Background Cement augmentation is a technique used to increase the stability and purchase of pedicle screws in poor quality bone. Various methods can be applied for cement delivery, such as cement injection before screw placement and the use of fenestrated screws. However, potential problems can arise with the use of cement augmentation. Case Presentation A 66‐year‐old man with a lower trunk deformity, severe kyphosis, and sagittal imbalance following fusion (L2‐5), with minimal comorbidities, was referred to our unit 9 months after surgery. Pain and progressive kyphosis were investigated clinically and radiographically with computed tomography (CT) scans to assess the status of the hardware and fusion. CT imaging revealed that cement was present only at the distal tip of the fenestrated screws at the L4 vertebral level. A non‐union was present along with loosening and a halo around the body of the pedicle screws, and there was evidence of pullout of inferior screws. Conclusion Single‐level cement augmentation of pedicle screw in a posterior construct and distal tip cement augmentation of the screw results in a fixed pivot point. Micromotion in cranio‐caudal loading during flexion and extension may result in screw toggling with the single‐level cement‐augmented tip as a fulcrum. This may cause screw loosening, which can lead to pullout and loss of construct stability. The halo around the screw suggests bone loss and/or a fibrous tissue interface, which further complicates revision surgery. Stress shielding and polymethylmethacrylate cement present additional difficulties. The findings of this technical note question the risks and benefits of cement‐augmented fenestrated pedicle screw fixation for spinal fusion. Although incidences of such cases are uncommon, surgeons should perform this technique with caution. Accurate restoration of lumbar lordosis during index procedures is important to minimize the risk of construct failure.

Biomechanical Comparison and Three-Dimensional Analysis of Cement Distribution Patterns for Different Pedicle Screw Designs

“…[ 19 ] The use of cement-augmented pedicle screws is easy and feasible, although biomechanical failure can occur if an inadequate amount of bone cement is used or cemented screws are misplaced. [ 24 ] In a series of studies, loosening rate was significantly lower in cement-augmented pedicle screws (4.3%) than noncemented screws (62.8%). [ 25 ] There have been recent reports on the clinical efficacy of cement augmentation using fenestrated screws.…”

Is Kummell’s Disease a Misdiagnosed and/or an Underreported Complication of Osteoporotic Vertebral Compression Fractures? A Pattern of the Condition and Available Treatment Modalities

“…Most studies are made using a cadaver. As such, the clear outcomes clarifying the issues of osseointegration and bone remodeling are not applicable due to the use of cadaveric bones that lack any healing potential [77].…”

Augmentation of Pedicle Screws Using Bone Grafting in Patients with Spinal Osteoporosis

“…In the PMMA technique, the pivot point of the screw is shifted ventrally into the vertebral body [ 17 ]. The limited stability of the augmented screws detected in the fatigue test and the biomechanical changes explain the proximal loosening observed after PMMA augmentation [ 18 ]. The results showed that PMMA augmentation did not completely solve the problem of pedicle screw instability development, since a significant number of proximal loosening cases became apparent.…”