Minimally Invasive, Stereotactic, Wireless, Percutaneous Pedicle Screw Placement in the Lumbar Spine: Accuracy Rates With 182 Consecutive Screws

Development of Augmented Reality Vision for Osteosynthesis Using a 3D Camera

BACKGROUND

We developed a 3D camera system to track motion in a surgical field. This system has the potential to introduce augmented reality (AR) systems non-invasively, eliminating the need for the invasive AR markers conventionally required. The present study was performed to verify the real-time tracking accuracy of this system, assess the feasibility of integrating this system into the surgical workflow, and establish its potential to enhance the accuracy and efficiency of orthopedic procedures.

METHODS

To evaluate the accuracy of AR technology using a 3D camera, a forearm bone model was created. The forearm model was depicted using a 3D camera, and its accuracy was verified in terms of the positional relationship with a 3D bone model created from previously imaged CT data. Images of the surgical field (capturing the actual forearm) were taken and saved in nine poses by rotating the forearm from pronation to supination. The alignment of the reference points was computed at the three points of CT versus the three points of the 3D camera, yielding a 3D rotation matrix representing the positional relationship. In the original system, a stereo vision-based 3D camera, with a depth image resolution of 1280×720 pixels, 30 frames per second, and a lens field of view of 64 specifications, with a baseline of 3 cm, capable of optimally acquiring real-time 3D data at a distance of 40-60 cm from the subject was used. In the modified system, the following modifications were made to improve tracking performance: (1) color filter processing was changed from HSV to RGB, (2) positional detection accuracy was modified with supporting marker sizes of 8 mm in diameter, and (3) the detection of marker positions was stabilized by calculating the marker position for each frame. Tracking accuracy was examined with the original system and modified system for the following parameters: differences in the rotation matrix, maximum and minimum inter-reference point errors between CT-based and camera-based 3D data, and the average error for the three reference points.

RESULTS

In the original system, the average difference in rotation matrices was 5.51±2.68 mm. Average minimum and maximum errors were 1.10±0.61 and 15.53±12.51 mm, respectively. The average error of reference points was 6.26±4.49 mm. In the modified system, the average difference in rotation matrices was 4.22±1.73 mm. Average minimum and maximum errors were 0.79±0.49 and 1.94±0.87 mm, respectively. The average error of reference points was 1.41±0.58 mm. In the original system, once tracking failed, it was difficult to recover tracking accuracy. This resulted in a large maximum error in supination positions. These issues were resolved by the modified system. Significant improvements were achieved in maximum errors and average errors using the modified system (P<0.05).

CONCLUSION

AR technology using a 3D camera was developed. This system allows direct comparisons of 3D data from preoperative CT scans with 3D data acquired from the surgical field using a 3D camera. This method has the advantage of introducing AR into the surgical field without invasive markers.

Advances in Implant Technologies for Spine Surgery

Spine implants are becoming increasingly diversified. Taking inspiration from other industries, three-dimensional modeling of the spinal column has helped meet the custom needs of individual patients as both en bloc replacements and pedicle screw designs. Intraoperative tailoring of devices, a common need in the operating room, has led to expandable versions of cages and interbody spacers.

Biomechanical Assessment of a Novel Sharp-Tipped Screw for 1-Step Minimally Invasive Pedicle Screw Placement Under Navigation

BACKGROUND

The objective of this study was to assess the pullout force of a novel sharp-tipped screw developed for single-step, minimally invasive pedicle screw placement guided by neuronavigation compared with the pullout force for traditional screws.

METHODS

A total of 60 human cadaveric lumbar pedicles were studied. Three different screw insertion techniques were compared: (A) Jamshidi needle and Kirschner wire without tapping; (B) Jamshidi needle and Kirschner wire with tapping; and (C) sharp-tipped screw insertion. Pullout tests were performed at a displacement rate of 10 mm/min recorded at 20 Hz. Mean values of these parameters were compared using paired t tests (left vs right in the same specimen): A vs B, A vs C, and B vs C. Additionally, 3 L1-L5 spine models were used for timing each screw insertion technique for a total of 10 screw insertions for each technique. Insertion times were compared using 1-way analysis of variance.

RESULTS

The mean pullout force for insertion technique A was 1462.3 (597.5) N; for technique B, it was 1693.5 (805.0) N; and for technique C, it was 1319.0 (735.7) N. There was no statistically significant difference in pullout force between techniques (P > 0.08). The average insertion time for condition C was significantly less than that for conditions A and B (P < 0.001).

CONCLUSIONS

The pullout force of the novel sharp-tipped screw placement technique is equivalent to that of traditional techniques. The sharp-tipped screw placement technique appears biomechanically viable and has the advantage of saving time during insertion.

CLINICAL RELEVANCE

Single-step screw placement using high resolution 3-dimensional navigation has the potential to streamline workflow and reduce operative time.

LEVEL OF EVIDENCE: 5

Augmented Reality (AR) in Orthopedics: Current Applications and Future Directions

PURPOSE OF REVIEW

Imaging technologies (X-ray, CT, MRI, and ultrasound) have revolutionized orthopedic surgery, allowing for the more efficient diagnosis, monitoring, and treatment of musculoskeletal aliments. The current review investigates recent literature surrounding the impact of augmented reality (AR) imaging technologies on orthopedic surgery. In particular, it investigates the impact that AR technologies may have on provider cognitive burden, operative times, occupational radiation exposure, and surgical precision and outcomes.

RECENT FINDINGS

Many AR technologies have been shown to lower provider cognitive burden and reduce operative time and radiation exposure while improving surgical precision in pre-clinical cadaveric and sawbones models. So far, only a few platforms focusing on pedicle screw placement have been approved by the FDA. These technologies have been implemented clinically with mixed results when compared to traditional free-hand approaches. It remains to be seen if current AR technologies can deliver upon their multitude of promises, and the ability to do so seems contingent upon continued technological progress. Additionally, the impact of these platforms will likely be highly conditional on clinical indication and provider type. It remains unclear if AR will be broadly accepted and utilized or if it will be reserved for niche indications where it adds significant value. One thing is clear, orthopedics' high utilization of pre- and intra-operative imaging, combined with the relative ease of tracking rigid structures like bone as compared to soft tissues, has made it the clear beachhead market for AR technologies in medicine.

Utility of Power Tool and Intraoperative Neuromonitoring for Percutaneous Pedicle Screw Placement in Single Position Surgery: A Technical Note

OBJECTIVE

This study aimed to demonstrate the utility of power tools and intraoperative neuromonitoring of percutaneous pedicle screw (PPS) insertion (so-called PPS monitoring) by SINGLE-position surgery (SPS) after lateral lumbar interbody fusion.

METHODS

A retrospective analysis of medical records from a single center was performed to identify patients who underwent SPS for lateral lumbar interbody fusion and posterior fixation using PPS during intraoperative computed tomography navigation from 2020 to 2021. We investigated the PPS insertion time and screw positional accuracy of patients who underwent SPS involving power tools and PPS monitoring during this period. In this technical note, we report on this surgical technique.

RESULTS

Twenty-four patients (mean age 72.0 ± 8.5 years, range 53-81 years) were included in this study. There were no intraoperative complications in all cases. Posterior fixation using PPS was added in all cases, and a total of 106 PPSs were inserted. It took an average of 6.2 ± 2.4 seconds to insert the PPS from the PPS insertion point to the end using a power tool and PPS monitoring. Moreover, there were no cases of pedicle breaches.

CONCLUSIONS

Similar to previous reports related to power tools in the prone position, the lateral decubitus SPS technique can also use power tools to save PPS insertion time. Furthermore, we suggest that the use of PPS monitoring may prevent erroneous PPS insertions by using intraoperative computed tomography navigation in advance.

Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Augmented Reality Surgical Navigation for Percutaneous Pedicle Screw Placement

STUDY DESIGN

This was a retrospective observational study.

OBJECTIVE

The aim of this study was to evaluate the accuracy of percutaneous pedicle screw placement using augmented reality surgical navigation during minimally invasive transforaminal lumbar interbody fusion (TLIF).

SUMMARY OF BACKGROUND DATA

Augmented reality-based navigation is a new type of computer-assisted navigation where video cameras are used instead of infrared cameras to track the operated patients and surgical instruments. This technology has not so far been clinically evaluated for percutaneous pedicle screw placement.

MATERIALS AND METHODS

The study assessed percutaneous pedicle screw placement in 20 consecutive patients who underwent single-level minimally invasive TLIF using augmented reality surgical navigation. Facet joint violation and depression by the inserted pedicle screws were evaluated. Secondary outcome such as radiation dose exposure, fluoroscopy time, and operative time were collected for 3 phases of surgery: preparation phase, pedicle screw placement, and decompression with cage placement.

RESULTS

A clinical accuracy for screw placement within the pedicle (Gertzbein 0 or 1) of 94% was achieved. One screw violated the facet joint with a transarticular pathway. The screw head did not depress the facet in 54%. The use of fluoroscopy during navigation correlated with patient body-mass index (r=0.68, P<0.0001). The pedicle screw placement time corresponded to 36±5% of the total operative time of 117±11 minutes. A statistically significant decrease of 10 minutes in operative time was observed between the first and last 10 procedures which corresponded to the pedicle screw placement time decrease (48±9 vs. 38±7 min, P=0.0142). The learning curve model suggests an ultimate operative time decrease to 97 minutes.

CONCLUSION

Augmented reality surgical navigation can be clinically used to place percutaneous screws during minimally invasive TLIF. However, the lack of tracking of the location of the device requires intraoperative fluoroscopy to monitor screw insertion depth especially in obese patients.

LEVEL OF EVIDENCE

Level III.

A cadaveric precision and accuracy analysis of augmented reality-mediated percutaneous pedicle implant insertion

OBJECTIVE

Augmented reality-mediated spine surgery (ARMSS) is a minimally invasive novel technology that has the potential to increase the efficiency, accuracy, and safety of conventional percutaneous pedicle screw insertion methods. Visual 3D spinal anatomical and 2D navigation images are directly projected onto the operator's retina and superimposed over the surgical field, eliminating field of vision and attention shift to a remote display. The objective of this cadaveric study was to assess the accuracy and precision of percutaneous ARMSS pedicle implant insertion.

METHODS

Instrumentation was placed in 5 cadaveric torsos via ARMSS with the xvision augmented reality head-mounted display (AR-HMD) platform at levels ranging from T5 to S1 for a total of 113 total implants (93 pedicle screws and 20 Jamshidi needles). Postprocedural CT scans were graded by two independent neuroradiologists using the Gertzbein-Robbins scale (grades A-E) for clinical accuracy. Technical precision was calculated using superimposition analysis employing the Medical Image Interaction Toolkit to yield angular trajectory (°) and linear screw tip (mm) deviation from the virtual pedicle screw position compared with the actual pedicle screw position on postprocedural CT imaging.

RESULTS

The overall implant insertion clinical accuracy achieved was 99.1%. Lumbosacral and thoracic clinical accuracies were 100% and 98.2%, respectively. Specifically, among all implants inserted, 112 were noted to be Gertzbein-Robbins grade A or B (99.12%), with only 1 medial Gertzbein-Robbins grade C breach (> 2-mm pedicle breach) in a thoracic pedicle at T9. Precision analysis of the inserted pedicle screws yielded a mean screw tip linear deviation of 1.98 mm (99% CI 1.74-2.22 mm) and a mean angular error of 1.29° (99% CI 1.11°-1.46°) from the projected trajectory. These data compare favorably with data from existing navigation platforms and regulatory precision requirements mandating that linear and angular deviation be less than 3 mm (p < 0.01) and 3° (p < 0.01), respectively.

CONCLUSIONS

Percutaneous ARMSS pedicle implant insertion is a technically feasible, accurate, and highly precise method.

Instrumentation Removal following Minimally Invasive Posterior Percutaneous Pedicle Screw-Rod Stabilization (PercStab) of Thoracolumbar Fractures Is Not Always Required

BACKGROUND

Percutaneous stabilization for spinal trauma confers less blood loss, reduces postoperative pain, and is less invasive than open stabilization and fusion. The current standard of care includes instrumentation removal.

OBJECTIVE

1. Reporting patient outcomes following minimally invasive posterior percutaneous pedicle screw-rod stabilization (PercStab). 2. Evaluating the results of instrumentation retention.

METHODS

A prospective observational study of 32 consecutive patients receiving PercStab without direct decompression or fusion. Baseline data demographics were collected. Operative outcomes of interest were operative room (OR) time, blood loss, and length of hospital stay. Follow-up variables of interest included patient satisfaction, Numeric Rating Scales for Back and Leg (NRS-B/L) pain, Oswestry Disability Index (ODI), and return to work. Clinical outcome data (ODI and NRS-B/L) were collected at 3, 12, 24 months and continued at a 24-month interval up to a maximum of 8 years postoperatively.

RESULTS

81.25% of patients (n = 26) retained their instrumentation and reported minimal disability, mild pain, and satisfaction with their surgery and returned to work (mean = 6 months). Six patients required instrumentation removal due to prominence of the instrumentation or screw loosening, causing discomfort/pain. Instrumentation removal patients reported moderate back and leg pain until removal occurred; after removal, they reported minimal disability and mild pain. Neither instrumentation removal nor retention resulted in complications or further surgical intervention.

CONCLUSIONS

PercStab without instrumentation removal provided high patient satisfaction, mild pain, and minimal disability and relieved the patient from the burden of finances and resources allocation of a second surgery.

Posterior Fusion for the Subaxial Cervical Spine: A Review of the Major Techniques

Posterior fusion is a powerful tool to address pathology of the cervical spine, but the decision to fuse at any level should be made with great care. Various methods and constructs for posterior cervical fusion exist, all of which aim to restore the posterior tension band's ability to resist flexion forces. We identified articles regarding posterior fusion of the subaxial cervical spine in MEDLINE, Google Scholar, and PubMed. This article is a narrative review of earlier and current concepts regarding the posterior fusion of the subaxial cervical spine, including wiring, translaminar screws, lateral mass screws, and pedicle screws, weighing the strengths and weakness of the different modalities that the surgeon should bear in mind in creating operative plans individualized to patient pathology.

One-step insertion of navigated pedicle screws in minimally invasive transforaminal lumbar interbody fusion (MITLIF): preliminary results of a novel technique

OBJECTIVE

To describe a novel technique modification and evaluate initial results of pedicle screw insertion in minimally invasive transforaminal lumbar interbody fusion (MITLIF), using self-drilling self-tapping one-step screws.

PATIENTS AND METHODS

All patients who were operated for MITLIF using the one-step technique over the last 6 months period at a single institute, were retrospectively identified. The surgical technique is described and depicted. Outcome evaluation was performed, including screw misplacement, screw insertion time, and post-operative complications.

RESULTS

We describe a novel technique modification in which self-drilling self-tapping navigated screws incorporate an embedded K-wire that enables a one-step insertion which obviates the need for instrument exchange. The first four patients in whom this technique was implemented were included (mean age was 55). All patients had been previously operated at the fused level. The mean surgical duration was 142 minutes and the calculated mean screw insertion time was 8.2 minutes. The mean estimated blood loss was 66 cc. An intraoperative 3D scan demonstrated no screw pedicle breach. There were no neurological complications or wound healing disturbances. The clinical course was uneventful for all patients.

CONCLUSION

To our knowledge, the use of one-step navigation-assisted self-drilling self-tapping pedicle screws with an embedded K-wire has not been previously described. Our initial experience with this novel technique modification was efficient and safe. Navigated surgery allows for newer and safer techniques to be incorporated into the surgeon's toolbox. Further studies should be performed to thoroughly evaluate this technique.

Accuracy of K-Wireless Insertion of Percutaneous Pedicle Screws Using Computer-Assisted Spinal Navigation: A Systematic Review and Single-Center Experience

OBJECTIVE

This study sought to 1) describe the use K-wireless pedicle screw insertion among adults (age ≥18 years) undergoing a minimally invasive fusion and 2) perform a systematic review (SR) of all studies that describe a navigated, K-wireless technique with 3-dimensional fluoroscopy.

METHODS

Patients undergoing a minimally invasive fusion requiring pedicle screw fixation for any indication were prospectively enrolled in the observational component of this study. An assessment of pedicle breach was performed independently and in duplicate based on a modification of the Belmont grading scale. Articles for the SR were identified from a structured search of Medline from inception to May 8, 2019, without restriction of language.

RESULTS

A total of 82 pedicle screws were placed in 20 patients who underwent surgery between January and June 2014. There was no significant difference in mean operative time between the cases included in this study and a matched cohort of 20 patients undergoing surgery with 2-dimensional fluoroscopy and K-wire-assisted pedicle screw placement (95 ± 13 vs. 87 ± 20 minutes, respectively; P > 0.05). There were 2 major pedicle breaches (Belmont grade 3) in a single patient, yielding a major breach rate of 2.44%. A total of 6 papers that described the placement of 700 pedicle screws in 160 patients between May 2011 and March 2017 were included in the SR. The overall breach rate was 7.00% (n = 37).

CONCLUSIONS

Percutaneous pedicle screws can be placed accurately and safely using 3-dimensional navigation without the use of K-wires and may confer benefits to patients and clinicians by reducing K-wire-associated complications and radiation exposure.