Duke Orthopedic Journal

CASE REPORT
Year
: 2020  |  Volume : 10  |  Issue : 1  |  Page : 57--61

Direct visualization of a S1 medial pedicle breach using a novel endoscope: A case report with new endoscopic pedicle breach classification


Michael Gallizzi 
 Anterior Spine Institute for Research and Education, Denver; Skyridge Medical Center, Lone Tree, CO, USA

Correspondence Address:
Dr. Michael Gallizzi
Anterior Spine Institute for Research and Education, 660 Dexter Street, Denver, CO 80220; Skyridge Medical Center, Lone Tree, CO
USA

Abstract

Malpositioned pedicle screws can lead to motor and sensory deficits in the effected level. Traditional intraoperative techniques to avoid a malpositioned pedicle screw include manual palpation of the screw tract, intraoperative imaging (XR, Fluro, and computed tomography), and neuromonitoring. This case report discusses an arthroscopic application of a novel endoscopic camera. This new direct visualization technique answers the intraoperative question of a pedicle screw breach. A 57-year-old male presented to our outpatient clinic for continued left S1 radiculopathy after multiple previous spinal surgeries. His presenting construct was a L4-S1 pedicle screw instrumented posterior spinal fusion with an anterior lumbar interbody fusion interbody at L5-S1 and a TLIF at L4-5 with complete laminectomies of L4-S1. He had failed >12 months of nonoperative treatment for his continued left S1 radiculopathy. He underwent a left S1 hardware removal with arthroscopic intra peculiar evaluation and decompression. Informed consent was obtained from the patient before writing this case report. At 3 months postoperation, the patient demonstrated full resolution of his left S1 radiculopathy, and his strength was rehabilitated back to 5/5. His paresthesia remained in the left S1 dermatome. This case report adds an off-the-shelf intraoperative technique for directly visualizing a pedicle screw breach, evaluating the continuity of the affected nerve, and gives the option to decompress bony fragments which may be a source of continued pain if not removed. The purposed endoscopic breach classification system allows for future studies to give prognostic information about nerve recovery potential based on the amount of breach encountered endoscopically.



How to cite this article:
Gallizzi M. Direct visualization of a S1 medial pedicle breach using a novel endoscope: A case report with new endoscopic pedicle breach classification.Duke Orthop J 2020;10:57-61


How to cite this URL:
Gallizzi M. Direct visualization of a S1 medial pedicle breach using a novel endoscope: A case report with new endoscopic pedicle breach classification. Duke Orthop J [serial online] 2020 [cited 2022 Jan 20 ];10:57-61
Available from: https://www.dukeorthojournal.com/text.asp?2020/10/1/57/316555


Full Text



 Introduction



Malpositioned pedicle screw placement can lead to neurologic impairment, including radicular pain, weakness, sensory loss, or possibly paralysis. A recent literature review by Aoude et al. found no clear method for assessing the position of pedicle screws intraoperatively among surveyed Canadian spine surgeons.[1] Postoperative assessment of pedicle screw placement and management of breaches is typically surgeon dependent and based on the patient's clinical exam.[2] A computed tomography (CT) grading system of 2 mm increments was determined to be the most widely accepted method for accurate pedicle screw placement.[2] Intraoperative neuromonitoring is one modality that can be used, “testing the screws,” to evaluate screw placement intraoperatively, but is not widely used and has significant variability based on the neuromonitoring tech, the neurologist reader and lead placement. Ajiboye et al. found no significant difference in neurologic outcome with or without the use of electromyogram (EMG) for pedicle screw placement in posterior lateral fusions.[3] Other intraoperative assessment modalities is a performance of a laminectomy/laminotomy and palpating the medial border of the pedicle or removing the possible offending screw and palpating the pedicle tract. The feasibility of endoscopically inspecting the integrity of the pedicle wall in a live surgery model has been performed by Radcliff et al. in a porcine model.[4] They concluded that this method was safe and effective.[4] We present the first use of a new endoscopic camera, Arthrex Nanoscope™, and grading system [Figure 1] to visually evaluate a pedicle breach intraoperatively. This direct visualization method may prevent subsequent return visits to the OR formal placed hardware.{Figure 1}

 Case Report



A 57-year-old male, with a history of two previous spinal decompression, L4-5 and L5-S1, and 1 previous L4-S1 fusion, presented to our outpatient clinic complaining of ongoing left leg radiculopathy to his calf and lateral aspect of his foot. After his fusion surgery, L4-S1, on 9/2017 he began to experience worsening left leg radicular pain, paraesthesias, and decreased strength (3/5) with plantar flexion postoperatively. This was confirmed on clinical examination with the addition of complete loss of the Achilles reflex on the left side and well as a positive straight leg raise to 90°. XR of the lumbar spine was performed on 3/2018 which was read as, “Posterior and interbody fusion from L4 through S1. Hardware is radiographically intact.” The above clinical issues continued, and a CT scan of the lumbar spine without contrast was ordered at 1 year postoperative. The CT report states “Fusion is achieved at L4-5 and L5-S1 and there is no loosening of the hardware. Fusion cages and anterior plate and screws are present” Upon my evaluation of his imaging, his left S1 pedicle screw was placed medial to the L5 screw on AP radiograph and his coronal and axial cut on his CT scan demonstrated a 4 mm medial breach on both the coronal and axial cuts into the left S1 neuroforamen [Figure 2]. After failing significant nonoperative treatment for over 2 years and identification of the malposition pedicle screw, the patient elected to undergo Left S1 hardware removal, trans-pedicular endoscopic evaluation, and revision decompression.{Figure 2}

In preparation for this case, informed consent was obtained for the procedure as well as for the case report. The patient was placed on a well-padded open top spine table and underwent typical time out and sterile OR preparation. Pre flip and post flip neuromonitoring (transcranial motor evoked potentials [TcMEPs], somatosensory evoked potentials, and free-run EMG) were performed. No changes from baseline were observed post flip. We used the fluoroscope to identify the Left L5-S1 level and performed a mini-open Wiltse approach. Once the left L5 and S1 screws were identified, we used a metal cutting burr to separate the L5 and S1 rod connection. We then removed the end cap and S1 remaining rod fragment. We then used trigger EMG to stimulate the S1 screw and found it to be at 17 mA of impedance. The left S1 pedicle screw was removed. We then brought in the Arthrex Nanoscope™, which is a 14Gneedle-sized endoscope to perform the endoscopic evaluation of the pedicle [Figure 3]. The set up included gravity fed 0.9% normal saline, the supplied arthroscopic cannula to house the endoscope, and endoscopic probes and kerrisons in preparation for the breach evaluation. Originally, the visualization was difficult due to bleeding. This was mitigated by packing the pedicle tract with gelfoam® soaked thrombin. After 30 s, the pedicle tract was irrigated and the endoscope was introduced. We were able to directly visualize the breach and S1 nerve coursing across 50% of the pedicle screw tract [Figure 4]. We then used microscopic nerve hooks and curettes to remove excess bone surround the S1 nerve and palpate the medial, cranial, and caudal points of the breach [Figure 5], [Figure 6], [Figure 7]. Once, it was felt the nerve was free without impingement, final TCMEPs were run demonstrating increased amplitude of the Left S1 nerve compared to baselines [Figure 8].{Figure 3}{Figure 4}{Figure 5}{Figure 6}{Figure 7}{Figure 8}

The patient made an uneventful recovery and was discharged the same day. The postoperative examination demonstrated resolution of the straight leg on the left with 1 Grade motor improvement in his plantar flexion. At his 3 months postoperative visit, his motor grade remained 5/5 with no radicular symptoms. He continued to have some Left S1 paresthesia.

 Discussion



Well placed spinal instrumentation is necessary for a successful surgical outcome. Intraoperative evaluation of a pedicle screw breach can result in excess radiation, Intraoperative CT scan, further surgery, and/or laminectomy to evaluate the medial wall. In addition, there is the potential for increased morbidity from a return to the OR for revision hardware removal should the breach not be properly identified intraoperatively. Pedicle palpation with a ball-tip probe has low accuracy and may case inadvertent neurological injury.[5],[6],[7] In the thoracic spine, stereotactic image guidance cannot provide perfect pedicle screw placement.[8] Neuromonitoring is not a failsafe for pedicle screw mal placement either.[9],[10] Techniques such as intraosseous ultrasound, robotic guidance, or near-infrared spectroscopy require substantial equipment and are not without false-negative errors.[4],[11],[12],[13],[14],[15],[16],[17],[18],[19]

We present an off the shelf, disposable, intraoperative endoscopic way to evaluate a possible breach. The simple set up, gravity-fed fluid, portable monitor, and a disposable endoscope is a novel application of this 14G endoscope. According to the purposed Gallizzi endoscopic classification of pedicle breach, our case would be a grade 3 (>25% and up to 50% of the screw tract occupied by the neural structure). Clinically, this patient had a resolution of his radiculopathy with a complete return of his motor strength with the persistence of his S1 paresthesia. As more pedicle breach endoscopic evaluations are preformed, the opportunity exists to build both diagnostic and prognostic data to better inform patients on their potential and degree of recovery.

Due to the nature of this case report, the subject of this paper underwent informed consent for the creation of this manuscript per the case report guidelines of the Anterior Spine Institute for Research and Education.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understand that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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