Percutaneous Pediculoplasty for Traumatic Pedicle Fracture

Summary

The objective of this case is to illustrate a technique for performing fluoroscopically guided percutaneous pediculoplasty in the setting of traumatic or non-neoplastic pedicle fractures.

Pediculoplasty has been described in the literature as a complimentary technique performed during vertebroplasty. In this case, isolated pediculoplasty is demonstrated using existing vertebroplasty equipment, which may be utilized as a primary intervention for pedicle fractures in patients who are poor surgical candidates.

Introduction

Pediculoplasty is a bone augmentation procedure based upon vertebroplasty in which polymethylmethacrylate (PMMA) bone cement is injected percutaneously under fluoroscopic guidance into a diseased vertebral pedicle. The purpose of this report is to describe a technique for performing pediculoplasty as a primary intervention for pedicle fracture in patients who are poor candidates for surgical fusion.

Case Report/Technique

An 85-year-old gentleman with a medical history of congestive cardiac failure, atrial fibrillation, hyperlipidemia, diabetes mellitus, hypertension, and hypothyroidism presented with three weeks of severe back pain following a fall. The patient reported subjective pain that was the worst of his life, particularly with breathing. Cross-sectional imaging revealed coronally oriented acute fractures involving both pedicles of the T10 vertebral body (Figure 1A,B). There was also an obliquely oriented T11 vertebral body fracture, with a cleft separating the anterior fracture fragment (Figure 1C-F). Surgical fixation was initially planned for fracture stabilization, but cancelled due to the patient's many comorbidities. He was referred to the Interventional Neuroradiology service at Wake Forest School of Medicine for evaluation. Our treatment plan was discussed with the referring spine surgeon, including conventional vertebroplasty for the T11 compression fracture and percutaneous pediculoplasty for the T10 pedicle fractures to further stabilize the spine. A unilateral pediculoplasty approach was planned to accommodate for possible treatment failure and subsequent surgical fixation requiring future placement of hardware through the pedicle.

Figure 1.

Bipedicular and vertebral body fractures. Axial CT bone algorithm (A) and soft tissue algorithm (B) show bipedicular fractures (white arrows) of the T10 vertebra. Parasagittal CT bone algorithm reconstructed images (C,D) demonstrate T10 pedicle fractures (black arrow) and oblique fracture cleft through the T11 vertebral body, as well as extensive ankylosis at multiple levels (white arrows). Para Sagittal T2-weighted fat-saturated images (E,F) demonstrate T10 pedicle fractures (black arrows) and oblique fracture cleft through the T11 vertebral body (white arrows).

Informed consent was obtained from the patient after detailed discussion of procedure-related risks and benefits. The patient was placed on the angiography table in the prone position and conscious sedation was achieved with a combination of midazolam and fentanyl. A single dose of prophylactic antibiotic (1 mg intravenous cefazolin) was administered at the beginning of the intervention. Local anesthesia of the skin and soft tissues reaching the depth of the periosteum of the targeted pedicle was achieved with 1% lidocaine. A 10.5 gauge (G) externally threaded vertebroplasty needle (Parallax Clear View, ArthroCare, Sunny Vale, CA, USA) was then slowly advanced into the left pedicle of the T10 vertebral body, and further into the mid-body of the vertebra under biplane fluoroscopic guidance (Neurostar Plus, Siemens, Forcheim, Germany). Care was taken to keep the needle away from the medial margin of the pedicle to avoid breaching the central canal. A straighter anteroposterior approach was also taken compared to our usual vertebroplasty approach to ensure better visualization of the cement deposition lateral to the medial boarder of the pedicle (Figure 2 A,B). Next, 13 G and 11 G vertebroplasty needles (Parallax Clear View, ArthroCare, Sunny Vale, CA, USA) were placed into the T11 vertebral body for conventional vertebroplasty. Standard PMMA cement (Parallax Bone Cement, ArthroCare Sunnyvale, CA, USA) was mixed and injected through a Parallax EZ Flow Cement Delivery system (ArthroCare, Sunnyvale, CA, USA) to perform T11 vertebroplasty. This was followed by cement injection into the left T10 pedicle, as follows: The 10.5 G externally threaded needle was gradually withdrawn from the vertebral body into the pedicle via controlled counter clockwise rotational movements under biplane fluoroscopic guidance. A small volume of cement was injected after every few mm of rotational needle withdrawal, filling the void left by the extracted needle. The initial cement delivered into the mid and posterior third of the pedicle was accomplished by using the injector. Cement was delivered into the posterior third of the pedicle and outer cortex by replacing the metallic stylet into the needle, pushing the remaining approximately 0.4 cc of cement through the dead space of needle in a controlled manner (Figure 2 C,D), and thus decreasing the risk of dragging cement into the soft tissues during needle extraction. The patient reported a decrease in severity of pain and increase in mobility within 24 hours of the procedure, with further pain reduction and improved ambulation at a two-week follow-up clinical visit.

Figure 2.

Fluoroscopy-guided percutaneous pediculoplasty and vertebroplasty. Anterior-posterior (AP) fluoroscopic spot image (A) demonstrating threaded needle placement in the left T10 pedicle (black arrow). The medial margin of the pedicle cortex is well seen. Threaded needle in the right T11 vertebral body is also demonstrated (white arrow). Lateral fluoroscopic spot image (B) demonstrates threaded needle placement in the left T10 pedicle (black arrow). Post vertebroplasty, the threaded needle (without stylet) has been withdrawn into the right T11 pedicle (white arrow). AP Fluoroscopic spot image (C) demonstrating cement deposition within the left T10 pedicle (black arrow). Note the medial margin of the pedicular cortex (white arrow) is seen separate from the radiopaque cement. Post-procedural changes of T11 vertebroplasty is also demonstrated, with cement outlining the fracture cleft. Lateral Fluoroscopy spot image (D) demonstrates post-pediculoplasty left T10 pedicle cement deposition (black arrow).

Discussion

To date, pediculoplasty has been described as an adjuvant to vertebroplasty rather than a dedicated primary treatment ^1-4. Pediculoplasty was first performed by Gailloud et al. ¹ to treat a lytic L5 vertebral body/pedicle lesion and more recently by Fuwa et al. ⁴ to treat a T10 vertebral body/pedicle hemangioma. Larger case series have also been conducted ^2-3. Martin et al. ² treated 52 vertebral bodies and associated pedicles in the setting of neoplastic infiltration and Eyheremendy et al. ³ treated five osteoporotic vertebral bodies and associated pedicle fractures. In many of these cases, PMMA was delivered into the vertebral body for initial treatment followed by cement delivery into the pedicle during needle withdrawal. Rather than actively injecting the pedicle, Eyheremendy et al. ³ withdrew the needle gently over a fixed/firmly held stylet to deliver intrapedicular PMMA, similar to our approach for delivering PMMA into the posterior third of the pedicle and outer cortex. Most reports of pediculoplasty describe the use of beveled needles. Indeed, Martin et al. ² specifically recommended the use of beveled needles to allow applied forces to be directed during needle placement. However, the direction of cement delivery is also influenced by the bevel orientation. In contrast to the present case, Fuwa et al. ⁴ noted subtle extravasation of cement into the extradural space, which was thought to be due to venous efflux. This complication may have resulted from the suboptimal visualization of PMMA deposition, which was obscured by the previously injected vertebral body cement.

Pediculoplasty is technically difficult for several reasons, including the immediate proximity of neural structures, i.e., the spinal cord medially and the exiting nerve roots inferomedially combined with the small volume of the pedicle itself, and the difficulty in fluoroscopic visualization of relatively small-volume cement deposition. We believe that our pediculoplasty technique addresses many of these difficulties and, therefore, increases safety. Despite the bilateral pedicle fractures in our case, we chose a uni-pedicular approach for two reasons; one, to preserve pedicle access for possible future neurosurgical spine stabilization in the event of pediculoplasty failure, and two, because of the difficulty in actively visualizing PMMA deposition in the lateral plane after cement delivery to the contralateral pedicle. Unlike other pediculoplasty cases reporting the use of beveled needles ^1-4, we used a 10.5 G non-beveled externally threaded needle. Rotational torque used to advance and withdrawal threaded needles produces a perpendicular vector force that is easily controlled via the degree of rotation. Such controlled needle manipulation prevents potential abrupt movements that could result in loss of access or iatrogenic injury of surrounding neural structures. The 10.5 G externally threaded needle would be expected to provide a lower pressure injection compared to a standard 11 G or 13 G beveled vertebroplasty needle used in other studies, improving the ability to deliver a very small controlled volume (0.4 cc) of PMMA into this small volume osseous structure. Similar to Eyheremendy et al. ³, we used a relatively thick consistency PMMA for pediculoplasty to further ensure slow controlled cement delivery.

The primary goals of pedicle fracture stabilization in this case were to use a small volume of PMMA to improve osseous compressive strength and other post-fracture mechanical properties, as have been shown with PMMA treatment of vertebral body fractures. Previous studies, for example, have demonstrated that treatment of vertebral body fractures with PMMA improves post-fracture compressive strength ^5-6 and increases mechanical failure load ⁷. Indeed, as little as 2 mL of PMMA was required to demonstrate improved compressive strength in the fracture models used by Belkoff et al. ⁶. Another recent study demonstrated that as little as 3.5 mL of PMMA was necessary to normalize stress distributions of fractured vertebral bodies ⁸. In contrast to these apparent benefits of PMMA treatment, however, other studies have demonstrated decreases in vertebral body stiffness post-PMMA treatment compared to pre-fracture levels ^5,7,9-10. It is also known that PMMA has greater strength to resist compressive forces than shear force vectors ^11-12. The precise forces exerted upon PMMA deposited within a pedicle fracture are unknown, and no studies to date have investigated relevant mechanical outcomes in a post-PMMA treatment model of pedicel fracture. As such, more research is necessary to evaluate the true primary mechanical outcomes of PMMA treatment of pedicle fractures.

Our patient reported pain relief and increased mobility post-treatment. Certainly, there is controversy regarding the ability of cementoplasty procedures to decrease pain beyond the effects of placebo. Vertebroplasty and other similar cementoplasty procedures, however, continue to be performed, particularly in cases where no acceptable alternatives are available to suffering and bed-bound patients. Continued technique-related innovations and improvements, therefore, remain critical to make these procedures as safe as possible.

Conclusions

The present report describes unilateral pediculoplasty for pedicle fracture with the aim of spine stabilization, not accompanied by percutaneous vertebroplasty at the same level. We found that precise controlled withdrawal of an externally threaded needle with interrupted small-volume PMMA injection while visualizing the medial cortical pedicular margin allowed successful treatment of a traumatic pedicle fracture, avoiding potential complications, such as migration of cement outside of pedicle, as has been reported ⁴. This technique for performing pediculoplasty may improve operator control and procedure safety.