Percutaneous computer-assisted translaminar facet screw: an initial human cadaveric study

Treatment of Lumbar Degenerative Disease with a Novel Interlaminar Screw Elastic Spacer Technique: A Finite Element Analysis

A novel interlaminar elastic screw spacer technique was designed to maintain lumbar mobility in treating lumbar degenerative diseases. A validated finite element model of L4/5 was used to establish an ISES-1/2 model and an ISES-1/3 model based on different insertion points, a unilateral fixation model and a bilateral fixed model based on different fixation methods, and a Coflex-F model based on different implants. The elastic rods were used to fix screws. Under the same mechanical conditions, we compared the biomechanical characteristics to investigate the optimal entry point for ISES technology, demonstrate the effectiveness of unilateral fixation, and validate the feasibility of the ISES technique. Compared to ISES-1/3, the ISES-1/2 model had lower intradiscal pressure, facet cartilage stress, and posterior structural stress. Compared to the ISES-BF model, the ISES-UF model had lower intervertebral pressure, larger mobility, and smaller stress on the posterior structures. The ISES model had a similar intervertebral pressure and limitation of extension as the Coflex-F model. The ISES model retained greater mobility and reduced the stress on the facet cartilage and posterior structure compared with the Coflex-F model. Our study suggests that the ISES technique is a promising treatment of lumbar degenerative diseases, especially those with osteoporosis.

Trajectory of Lumbar Translaminar Facet Screw Under Navigation: A Cadaveric Study

STUDY DESIGN

Anatomic cadaver study.

OBJECTIVE

Translaminar facet screw fixation supplements unilateral pedicle screw-rod fixation in minimally invasive transforaminal lumbar interbody fusion (TLIF). Various screw diameters, lengths, trajectories, and insertion points are used; however, they do not represent true screw trajectory. We aimed to evaluate lumbar laminar anatomy and suggest a safe and effective insertion point and trajectory during lumbar-translaminar facet screw fixation in an anatomic cadaver study.

METHODS

O-arm navigation simulating the true translaminar facet screw trajectory was used to evaluate L1-S1 in cadaveric spines. The inner and outer diameters, length, and trajectory of the screw pathway were measured along the trajectory from the spinous process base through the contralateral lamina, crossing the facet joint to the transverse process base using 2 starting points: cephalad one-third (1/3SL) and one-half (1/2SL) of the spinolaminar junction.

RESULTS

Using the 1/2SL starting point, the outer and inner lamina diameters did not differ significantly from L1-L5 (7.47 ± 1.38 to 6.7 ± 1.84 mm and 4.73 ± 1.04 to 3.86 ± 1.46 mm, respectively). Screw length (36.16 ± 4.02 to 49.29 ± 10.07 mm) and lateral angle increased (50.28° ± 8.78° to 60.77° ± 8.88°), but caudal angle decreased (16.19° ± 9.01° to 1.13° ± 11.31°). Lamina diameter and screw length did not differ with different starting points. L2-L3 caudal angles were lower in the 1/2SL starting point.

CONCLUSION

A 36- to 50-mm translaminar facet screw-with 5.0-mm diameter for L1-L2 and 4.5-mm diameter for L3-L5-can be inserted at the middle of the spinolamina, especially during minimally invasive TLIF, with a 50° to 60° lateral angle relative to the spinous process, and a caudal angle of 16° to 1° relative to the spinolamina from L1-L5.

Anatomic study of the lumbar lamina for safe and effective placement of lumbar translaminar facet screws

Objective

To evaluate the anatomic characteristics of the lumbar lamina and suggest a safe and effective strategy for setting lumbar translaminar facet screws.

Methods

The width and length of the lumbar lamina, screw path, lateral angle of the lamina, and maximum and minimum caudal angles of the lamina from L3 to L5 were measured with Mimics software using 32 patients’ computed tomographic data.

Results

The optimal screw entry point was located at the median of the spinous process base or slightly lower. The ideal screw trajectory was from the entry point to the base of the transverse process and across the center of the facet joint. A length of 35 to 45 mm was suitable for L3 to L4 in most cases, and a length of 45 to 50 mm was safe for L5 in most cases. The screw should be inserted at an angle of 49.4° to 59.29° laterally and 43.68° to 57.58° caudally at L3 to L5. For the ideal caudal angle, error of <3° was considered safe.

Conclusion

The optimal entry point, ideal screw trajectory, ideal screw-setting angles, and safest range of the angle and length of the lumbar lamina were identified in this anatomical study.

Biomechanics and Clinical Application of Translaminar Screws Fixation in Spine: A Review of the Literature

STUDY DESIGN

Broad narrative review.

OBJECTIVES

Translaminar screw (TLS) fixation was first described as a salvage technique for fixation of the axial spine. Better understanding of the spine anatomy allows for advancement in surgical techniques and expansion of TLS indications. The goal of this review is to discuss the anatomic feasibility of the TLS fixation in different region of the spine.

METHODS

A review of the current literatures on the principles, biomechanics, and clinical application of the translaminar screw technique in the axial, subaxial, and thoracolumbar spine.

RESULTS

Anatomic feasibility and biomechanical studies have demonstrated that TLS is a safe and strong fixation methods for fusion beyond just the axial spine. However, not all spine segments have wide enough lamina to accept TLS. Preoperative computed tomography scan can help ensure the feasibility and safety of TLS insertion. Recent clinical reports have validated the application of TLS in subaxial spine, thoracic spine, hangman's fracture, and pediatric population.

CONCLUSIONS

TLS can be used beyond axial spine; however, TLS insertion is only warranted when the lamina is thick enough to avoid further complications such as breakage. Preoperative computed tomography scans can be used to determine feasibility of such fixation construct.

Computer-assisted Orthopaedic Surgery

Nowadays, operating rooms can be inefficient and overcrowded. Patient data and images are at times not well integrated and displayed in a timely fashion. This lack of coordination may cause further reductions in efficiency, jeopardize patient safety, and increase costs. Fortunately, technology has much to offer the surgical disciplines and the ongoing and recent operating room innovations have advanced preoperative planning and surgical procedures by providing visual, navigational, and mechanical computerized assistance. The field of computer-assisted surgery (CAS) broadly refers to surgical interface between surgeons and machines. It is also part of the ongoing initiatives to move away from invasive to less invasive or even noninvasive procedures. CAS can be applied preoperatively, intraoperatively, and/or postoperatively to improve the outcome of orthopaedic surgical procedures as it has the potential for greater precision, control, and flexibility in carrying out surgical tasks, and enables much better visualization of the operating field than conventional methods have afforded. CAS is an active research discipline, which brings together orthopaedic practitioners with traditional technical disciplines such as engineering, computer science, and robotics. However, to achieve the best outcomes, teamwork, open communication, and willingness to adapt and adopt new skills and processes are critical. Because of the relatively short time period over which CAS has developed, long-term follow-up studies have not yet been possible. Consequently, this review aims to outline current CAS applications, limitations, and promising future developments that will continue to impact the operating room (OR) environment and the OR in the future, particularly within orthopedic and spine surgery.

Lumbar Facet Resurfacing: First Experience With the FENIX Implant

STUDY DESIGN

This is a feasibility study to confirm the design, patient population, and the surgical technique for FENIX implants.

OBJECTIVE

This study evaluated the safety and the clinical and radiologic performance of bilaterally implanted FENIX facet resurfacing device.

INTRODUCTION

Facet joint osteoarthritis is responsible for up to 30% of chronic low back pain. Arthroplasty is a surgical treatment option that aims to relieve pain while maintaining or restoring motion.

METHODS

A total of 8 consecutive patients with proven single segmental bilateral lumbar facet joint osteoarthritis as unique pain generator received a bilateral implantation of the FENIX device. Correct device placement and mobility preservation were assessed on x-ray at 6 weeks and at 6, 12, and 24 months after implantation. Magnetic resonance imaging at 12 and 24 months after surgery assessed the bony ingrowth and computed tomography-single photon emision computed tomography was repeated at 6 months to assess evolution of the preoperative inflamed facet joints. The Oswestry disability index, pain visual analogue scale, and the need for analgesic medication were the parameters used for clinical assessment.

RESULTS

At 24 months after surgery, 7 of the 8 patients were found to have all implants in place and all assessed parameters were found to be normal. Patients experienced significant pain relief and functionality improvement. Mobility was maintained and no Modic changes were noted, either at the index or at the adjacent levels. No "hot" lesions at the implanted levels were observed on computed tomography-single photon emision computed tomography. One of the 48 (2%) implants was found to be dislocated at 6 months follow-up.

CONCLUSIONS

The FENIX facet resurfacing technique might be considered in the future as a surgical treatment of well-selected patients suffering from chronic low back pain because of facet joint osteoarthritis. A modification of the superior implant should provide an initial firm fixation preventing implant dislocation.

Emerging Techniques for Posterior Fixation of the Lumbar Spine

Pedicle screw fixation is the preferred method of posterior fusion in lumbar spinal surgery. The technique provides three-column support of the vertebrae, contributing to the biomechanical strength of the construct. However, open pedicle screw fixation often necessitates wide posterior exposure and dissection with soft-tissue disruption of the facet joint. Alternative posterior fixation techniques have been developed to reduce surgical time, soft-tissue dissection, disruption of the adjacent facet joint capsule, neurologic risk, and implant cost. Results of these techniques are comparable to those of standard pedicle screw fixation systems. Certain patients, especially those at a lower risk of nonunion or those who require posterior fixation only as an adjunct to anterior column support, may benefit from the shorter surgical time and limited posterior exposure of the alternative techniques. However, the decreased rigidity of these alternative constructs can result in excessive motion, which can lead to nonunion and early hardware failure.

Percutaneous Transpedicular Fixation: Technical tips and Pitfalls of Sextant and Pathfinder Systems

Study Design

The efficacy of the operative techniques, possible benefits as well as pitfalls and limitations of the techniques are discussed. Potential drawbacks are also detected.

Purpose

This study aims to report indications, techniques, and our experience with the use of the Sextant and PathFinder percutaneous transpedicular screw fixation systems.

Overview of Literature

Percutaneous pedicle screw insertion is a novel technique. Successful percutaneous placement of pedicle screws requires surgical skill and experience because of lack of anatomic surface landmarks. Fluoroscopy-guided percutaneous placement of pedicle screws is effective. Many systems are now available.

Methods

We conducted a prospective operative and postoperative analysis of 40 patients with absolute indication for thoracic or lumbar instability between January 2009 and June 2013. All procedures were performed with the Sextant (group A) and PathFinder (group B) systems under fluoroscopic guidance. Operative techniques are discussed and the results compared.

Results

Percutaneous transpedicular screw fixation minimizes the morbidity associated with open techniques without compromising the quality of fixation. A total of 190 screws were inserted. There was no additional morbidity. Postoperative computed tomography images and plain X-rays were analyzed. Reduction of visual analog scale scores of back pain was evident.

Conclusions

Fluoroscopy-guided percutaneous pedicular screws are feasible and can be safely done. Current systems allow multi-segmental fixation with significantly less difficulties. The described techniques have acceptable intra- and postoperative complication rates, and overall sufficient pain control with early mobilization of patients.

Computer-assisted navigation in orthopedic surgery

Computer-assisted navigation has a role in some orthopedic procedures. It allows the surgeons to obtain real-time feedback and offers the potential to decrease intra-operative errors and optimize the surgical result. Computer-assisted navigation systems can be active or passive. Active navigation systems can either perform surgical tasks or prohibit the surgeon from moving past a predefined zone. Passive navigation systems provide intraoperative information, which is displayed on a monitor, but the surgeon is free to make any decisions he or she deems necessary. This article reviews the available types of computer-assisted navigation, summarizes the clinical applications and reviews the results of related series using navigation, and informs surgeons of the disadvantages and pitfalls of computer-assisted navigation in orthopedic surgery.

Role of facet joints in spine pain and image-guided treatment: a review

Chronic low back and neck pain remain prevalent medical concerns, with much debate regarding the effective evaluation and treatment. Facet disease has been implicated as a source of axial nonradiating low back pain. We discuss patient evaluation, the role of imaging, current and emerging image-guided therapies for facet-related pain, and the increasing importance of outcome-related research in this arena.

[Submuscular approach to the lumbar spine and extraforaminal cage implantation]

The posterior median approach to the lumbar spine may cause significant injury to the erector spinae muscles (ESM) which is minimized using the paralateral approach suggested by Ray. We have adopted this approach and have extended it into the disc space to allow cage implantation from outside the foramen (EPLIF - extraforaminal posterior lumbar interbody fusion). The initial exposure of the posterior vertebral elements between the ESM and the deep lumbar fascia is sufficient to attain the entry points of pedicle screws. The intervertebral foramen and posterior annulus fibrosus are then exposed after which distant lateral disc herniations may be removed, the foramen/lateral recess may be decompressed or an EPLIF performed following clearing and vertical distraction of the disc space. This is followed by ipsilateral transpedicular fixation (TpF), contralateral fixation (second approach) by TpF or translaminar screws. Indications are given for foraminal and extraforaminal disc herniation, stenosis of the foramen and/or of the lateral recess, posterolateral fusion, TpF and EPLIF. The submuscular approach and EPLIF have proven to be valuable alternatives to standard techniques.

Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion

OBJECT

An interspinous anchor (ISA) provides fixation to the lumbar spine to facilitate fusion. The biomechanical stability provided by the Aspen ISA was studied in applications utilizing an anterior lumbar interbody fusion (ALIF) construct.

METHODS

Seven human cadaveric L3-S1 specimens were tested in the following states: 1) intact; 2) after placing an ISA at L4-5; 3) after ALIF with an ISA; 4) after ALIF with an ISA and anterior screw/plate fixation system; 5) after removing the ISA (ALIF with plate only); 6) after removing the plate (ALIF only); and 7) after applying bilateral pedicle screws and rods. Pure moments (7.5 Nm maximum) were applied in flexion and extension, lateral bending, and axial rotation while recording angular motion optoelectronically. Changes in angulation as well as foraminal height were also measured.

RESULTS

All instrumentation variances except ALIF alone reduced angular range of motion (ROM) significantly from normal in all directions of loading. The ISA was most effective in limiting flexion and extension (25% of normal) and less effective in reducing lateral bending (71% of normal) and axial rotation (71% of normal). Overall, ALIF with an ISA provided stability that was statistically equivalent to ALIF with bilateral pedicle screws and rods. An ISA-augmented ALIF allowed less ROM than plate-augmented ALIF during flexion, extension, and lateral bending. Use of the ISA resulted in flexion at the index level, with a resultant increase in foraminal height. Compensatory extension at the adjacent levels prevented any significant change in overall sagittal balance.

CONCLUSIONS

When used with ALIF at L4-5, the ISA provides immediate rigid immobilization of the lumbar spine, allowing equivalent ROM to that of a pedicle screw/rod system, and smaller ROM than an anterior plate. When used with ALIF, the ISA may offer an alternative to anterior plate fixation or bilateral pedicle screw/rod constructs.

Image-guided spine surgery: state of the art and future directions

Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers. The issue of where and when navigation technology should be used is still an issue of debate. It is the aim of this study to give an overview on the current knowledge concerning the technical capabilities of image-guided approaches and to discuss possible future directions of research and implementation of this technique. Based on a Medline search total of 1,462 publications published until October 2008 were retrieved. The abstracts were scanned manually for relevance to the topics of navigated spine surgery in the cervical spine, the thoracic spine, the lumbar spine, as well as ventral spine surgery, radiation exposure, tumor surgery and cost-effectivity in navigated spine surgery. Papers not contributing to these subjects were deleted resulting in 276 papers that were included in the analysis. Image-guided approaches have been investigated and partially implemented into clinical routine in virtually any field of spine surgery. However, the data available is mostly limited to small clinical series, case reports or retrospective studies. Only two RCTs and one metaanalysis have been retrieved. Concerning the most popular application of image-guided approaches, pedicle screw insertion, the evidence of clinical benefit in the most critical areas, e.g. the thoracic spine, is still lacking. In many other areas of spine surgery, e.g. ventral spine surgery or tumor surgery, image-guided approaches are still in an experimental stage. The technical development of image-guided techniques has reached a high level as the accuracies that can be achieved technically meet the anatomical demands. However, there is evidence that the interaction between the surgeon ('human factor') and the navigation system is a source of inaccuracy. It is concluded that more effort needs to be spend to understand this interaction.

Image guided percutaneous trans-pedicular screw fixation of the thoracic spine. A clinical evaluation

OBJECTIVE

We report our preliminary experience with a minimally invasive image guided percutaneous trans-pedicular fixation technique of the thoracic spine in patients with significant co-morbidity. This study aims to demonstrate the feasibility and efficacy of the presented operative technique as well as to detect potential drawbacks.

METHOD

A navigated percutaneous application of trans-pedicular screws was performed in 14 patients with radiological validated instability of the thoracic spine and significant medical co-morbidity. Due to poor bone quality, vertebroplasty of the affected levels had to be performed in nine patients. The levels involved were (T9-12) in ten patients, the middle (T5-8) in two patients and the upper thoracic (T1-4) segments in two others. VAS scores for local back pain were used to assess clinical outcome.

RESULTS

A total of 56 screws were inserted. There was no additional morbidity associated with the procedure. Post-operative CT scans and plain X-rays were obtained in all patients. In 2 (3.5%) medial penetration of the pedicle border occurred without neurological sequelae for the patient. Reduction of VAS scores regarding back pain during the first post-operative week was noted. Follow up ranged between 6 months and 12 months.

CONCLUSION

Navigated percutaneous trans-pedicular fixation of the thoracic spine is feasible and can be performed safely in patients where open surgery is of significant risk. Pre-operative planning is essential in order to avoid intra-operative complications with the instrumentation system.

Minimally invasive spine surgery: a historical perspective

Minimally invasive spine surgery has gained considerable momentum and increased acceptance among spine surgeons throughout the years. An understanding and awareness of the development of minimally invasive spine surgery and its role in the operative treatment of various spine conditions is imperative. This article provides a succinct historical perspective of the development of spine surgery from the more traditional, open procedures to the use of more "minimal access" or minimally invasive spine surgery procedures.