Early complications of posterior rod-screw fixation of the cervical and upper thoracic spine

Risk factors of instrumentation failure after laminectomy and posterior cervical fusions (PCF)

BACKGROUND

For patients with multilevel degenerative cervical myelopathy, laminectomy and posterior cervical fusions (PCF) with instrumentation are widely accepted techniques for symptom relief. However, hardware failure is not rare and results in neck pain or even permanent neurological lesions. There are no in-depth studies of hardware-related complications following laminectomy and PCF with instrumentation.

METHODS

The present study was a retrospective, single centre, observational study. Patients who underwent laminectomy and PCF with instrumentation in a single institution between January 2019 and January 2021 were included. Patients were divided into hardware failure and no hardware failure group according to whether there was a hardware failure. Data, including sex, age, screw density, end vertebra (C7 or T1), cervical sagittal alignment parameters (C2-C7 cervical lordosis, C2-C7 sagittal vertical axis, T1 slope, Cervical lordosis correction), regional Hounsfield units (HU) of the screw trajectory and osteoporosis status, were collected and compared between the two groups.

RESULTS

We analysed the clinical data of 56 patients in total. The mean overall follow-up duration was 20.6 months (range, 12-30 months). Patients were divided into the hardware failure group (n = 14) and no hardware failure group (n = 42). There were no significant differences in the general information (age, sex, follow-up period) of patients between the two groups. The differences in fusion rate, fixation levels, and screw density between the two groups were not statistically significant (p > 0.05). The failure rate of fixation ending at T1 was lower than that at C7 (9% vs. 36.3%) (p = 0.019). The regional HU values of the pedicle screw (PS) and lateral mass screw (LMS) in the failure group were lower than those in the no failure group (PS: 267 ± 45 vs. 368 ± 43, p = 0.001; LMS: 308 ± 53 vs. 412 ± 41, p = 0.001). The sagittal alignment parameters did not show significant differences between the two groups before surgery or at the final follow-up (p > 0.05). The hardware failure rate in patients without osteoporosis was lower than that in patients with osteoporosis (14.3% vs. 57.1%) (p = 0.001).

CONCLUSIONS

Osteoporosis, fixation ending at C7, and low regional HU value of the screw trajectory were the independent risk factors of hardware failure after laminectomy and PCF. Future studies should illuminate if preventive measures targeting these factors can help reduce hardware failure and identified more risk factors, and perform long-term follow-up.

EARLY COMPLICATIONS OF SURGICAL TREATMENT OF CERVICAL SPONDYLOTIC MYELOPATHY

Objective

To evaluate the early postoperative complications associated with the surgical approach of the cervical spine of patients with cervical spondylotic myelopathy (CSM), comparing the anterior surgical, the posterior surgical, and the combined approaches.

Methods

This is a retrospective study based on a database with 169 patients. Demographic data, such as gender and age, and surgical data, such as surgical approach, number of segments with arthrodesis, surgical time, and complications, were evaluated. Complications were divided into major (deep surgical wound infection, intercurrence with the implant, early new compression, and heart failure) and minor (dysphagia, superficial infection, pain, urinary intercurrence, neuropraxia of the C5 root, acute confusional state, and surgical wound hematoma).

Results

This included 169 patients, 57 women (33.7%) and 112 men (66.2%). Age ranged from 21 to 87 years, with a mean of 56.48 (± 11) years. Of these, 52 (30.8%) underwent the anterior approach; 111 (65.7%), the posterior approach; and 6 (3.5%), the combined approach.

Conclusion

As in the literature, we evinced dysphagia, pain, and superficial infection of the surgical wound as the most frequent postoperative complications. However, it was impossible to establish a statistical relationship between the incidence of complications and surgical time, access route, and number of fixed segments. Level of Evidence III, Retrospective Comparative Study.

Complex Revision Surgery for Cervical Deformity or Implant Failure

Postoperative cervical deformity sometimes occurs in the short or long term after primary surgery for cervical disorders related to the degenerative aging spine, neoplastic etiologies, hemodialysis, infection, inflammation, trauma, etc. Cervical kyphosis after posterior decompression surgery, such as laminectomy or laminoplasty, is a common problem for spine surgeons. However, revision surgery for cervical deformity is definitely one of the most challenging areas for spine surgeons. There is no doubt that surgery for cervical deformity carries a high risk of surgery-related complications that might result in aggravation of health-related quality of life. Revision surgery is even more challenging. Hence, spine surgeons need to assess carefully the overall severity of the underlying condition before revision surgery, and try to refine the surgical strategy to secure safe surgery. Needless to say, spine surgeons are now facing great challenges in making spine surgery a much more reliable and convincing entity.

Cervical Laminectomy With or Without Lateral Mass Instrumentation: A Comparison of Outcomes

STUDY DESIGN

Narrative review.

BACKGROUND

Cervical decompressive laminectomy is a common posterior approach for addressing multilevel cervical spondylotic myelopathy. However, there is a concern that cervical laminectomy can lead to kyphotic deformity with subsequent neurological decline. In this context, cervical laminectomy with fusion using lateral mass instrumentation has become increasingly utilized with the aim of reducing the risk of developing postoperative kyphotic deformity, which is thought to predispose to poorer neurological outcomes in the long term.

OBJECTIVE

To compare the evidence for stand-alone cervical laminectomy with laminectomy with posterior fusion in terms of clinical outcomes and the incidence of adverse events, particularly the development of postoperative cervical kyphosis.

MATERIAL AND METHODS

Initial Medline search using MeSH terms yielded 226 articles, 23 of which were selected. An additional PubMed search and the reference list of individual papers were utilized to identify the remaining papers of relevance.

RESULTS

Cervical laminectomy both with and without fusion offers effective decompression for symptomatic multilevel cervical spondylotic myelopathy. The incidence of postlaminectomy kyphosis is lower following posterior fusion; however, there seems to be no clinical-radiologic correlation given that patients who develop postoperative kyphosis often do not progress to clinical myelopathy. Furthermore, there are specific additional risks of posterior instrumentation that need to be considered.

CONCLUSION

In carefully selected patients with normal preoperative cervical sagittal alignment, stand-alone cervical laminectomy may offer acceptably low rates of postoperative kyphosis. In patients with preoperative loss of cervical lordosis and/or kyphosis, posterior fusion is recommended to reduce the risk of progression to postoperative kyphotic deformity, bearing in mind that radiologic evidence of kyphosis may not necessarily correlate with poorer clinical outcomes. Furthermore, the specific risks associated with posterior fusion (instrumentation failure, pseudarthrosis, infection, C5 nerve root palsy, and vertebral artery injury) need to be considered and weighed up against potential benefits.

Posterior cervical spine crisscross fixation: Biomechanical evaluation

BACKGROUND

Biomechanical/anatomic limitations may limit the successful implantation, maintenance, and risk acceptance of posterior cervical plate/rod fixation for one stage decompression-fusion. A method of posterior fixation (crisscross) that resolves biomechanical deficiencies of previous facet wiring techniques and not reliant upon screw implantation has been devised. The biomechanical performance of the new method of facet fixation was compared to the traditional lateral mass plate/screw fixation method.

METHODS

Thirteen human cadaver spine segments (C2-T1) were tested under flexion-compression loading and four were evaluated additionally under pure-moment load. Preparations were evaluated in a sequence of surgical alterations with intact, laminectomy, lateral mass plate/screw fixation, and crisscross facet fixation using forces, displacements and kinematics.

FINDINGS

Combined loading demonstrated significantly lower bending stiffness (p < 0.05) between laminectomy compared to crisscross and lateral mass plate/screw preparations. Crisscross fixation showed a comparative tendency for increased stiffness. The increased overall motion induced by laminectomy was resolved by both fixation techniques, with crisscross fixation demonstrating a comparatively more uniform change in segmental motions.

INTERPRETATION

The crisscross technique of facet fixation offers immediate mechanical stability with resolution of increased flexural rotations induced by multi-level laminectomy. Many of the anatomic limitations and potentially deleterious variables that may be associated with multi-level screw fixation are not associated with facet wire passage, and the subsequent fixation using a pattern of wire connection crossing each facet joint exhibits a comparatively more uniform load distribution. Crisscross wire fixation is a valuable addition to the surgical armamentarium for extensive posterior cervical single-stage decompression-fixation.

Quantitative Gross and CT measurements of Cadaveric Cervical Vertebrae (C3 - C6) as Guidelines for the Lateral mass screw fixation

BACKGROUND

Lateral mass screw fixation is the treatment of choice for posterior cervical stabilization. Long or misdirected screws carry a risk of injury to spinal nerve roots or vertebral artery. This study was aimed to assess the gross anatomic and CT measurements of typical cervical vertebrae for the selection of lateral mass screws.

METHODS

Dimensions of the articular pillars were measured on 1) Dry cervical vertebrae with Vernier calipers and 2) Multiplanar reformations of CT scans of the same vertebrae with Viewer software package. The data was statistically evaluated.

RESULTS

The transverse diameter of the articular pillars with Vernier calipers varied from 6.0 to 15.4 mm (mean=10.5 mm ± 1.5) and on CT scans ranged from 8.2 - 16.1 mm (mean=11.6 mm ± 1.4). The antero-posterior diameter, an estimate of the screw length by Roy-Camille technique varied from 3.9 to 12.7 mm (mean=8.6 mm ± 1.6) by Vernier calipers and from 6.4 to 13.3 mm (mean=9.1 ± 1.2) on CT scans. The oblique AP diameter, an estimate of screw length by Magerl method varied from 10.8 to 20.3 mm (mean=14.9 mm ± 1.8) by Vernier calipers and from 11.4 to 19.3 mm (mean=14.5 mm ± 1.7) on CT. The CT measurements for height, transverse and AP diameter of the articular pillars were 0.5 - 1.0 mm larger than dimensions by Vernier calipers. No statistically significant difference was observed between the caliper and CT measurements for the oblique AP diameter.

CONCLUSION

CT measurements of the articular pillars may slightly overestimate the desired screw length selected by spine surgeons when compared to actual anatomy. Although means of the articular pillars correspond to the screw lengths used, substantial number of observations below 10 mm for Roy-Camille trajectory and below 14 mm for Magerl trajectory requires careful preoperative planning and intra-operative confirmation to avoid long/misdirected lateral mass screws.

Rod Migration to the Thoracic Subarachnoid Space after C1-2 Instrumentation: A Case Report and Literature Review

Posterior instrumented fusion of the cervical spine is a common surgical procedure in the treatment of cervical subluxation, fractures, and stenosis. Although malpositions are commonly seen, it is rare to observe the malposition of the rod or interconnection because of hardware failure. A 62-year-old woman with spastic tetraparesis as a sequel to pediatric meningitis with C₁ -C₂ cervical subluxation and myelomalacia had undergone laminectomy of C₁ and C₁ lateral mass and C₂ bilateral pedicular screw fixation. Three years after the stabilization, she presented with complaints of headache, neck pain, and difficulty walking. There was no history of trauma during that period. A previously unrecorded and unusual migration of a rod through the thoracic subarachnoid space was detected. In this study, we report a case of atlantoaxial stabilization using the screw-rod technique that was followed by rod migration to the thoracic subarachnoid space, and outline the subsequent management of the case. Failure of bony fusion can result in micromotion and subsequent migration of fixation device components. Routine radiographic follow-up could be used to identify migration events.

Utility of Routine Outpatient Cervical Spine Imaging Following Anterior Cervical Corpectomy and Fusion

Background: Construct failure is an uncommon but well-recognized complication following anterior cervical corpectomy and fusion (ACCF). In order to screen for these complications, many centers routinely image patients at outpatient visits following surgery. There remains, however, little data on the utility of such imaging.

Methods: The electronic medical record of all patients undergoing anterior cervical corpectomy and fusion at Dartmouth-Hitchcock Medical Center between 2004 and 2009 were reviewed. All patients had routine cervical spine radiographs performed perioperatively. Follow-up visits up to two years postoperatively were analyzed. 

Results: Sixty-five patients (mean age 52.2) underwent surgery during the time period. Eighteen patients were female. Forty patients had surgery performed for spondylosis, 20 for trauma, three for tumor, and two for infection. Forty-three patients underwent one-level corpectomy, 20 underwent two-level corpectomy, and two underwent three-level corpectomy, using an allograft, autograft, or both. Sixty-two of the fusions were instrumented using a plate and 13 had posterior augmentation. Fifty-seven patients had follow-up with imaging at four to 12 weeks following surgery, 54 with plain radiographs, two with CT scans, and one with an MRI scan. Unexpected findings were noted in six cases. One of those patients, found to have asymptomatic recurrent kyphosis following a two-level corpectomy, had repeat surgery because of those findings. Only one further patient was found to have abnormal imaging up to two years, and this patient required no further intervention.

Conclusions: Routine imaging after ACCF can demonstrate asymptomatic occurrences of clinically significant instrument failure. In 43 consecutive single-level ACCF however, routine imaging did not change management, even when an abnormality was discovered. This may suggest a limited role for routine imaging after ACCF in longer constructs involving multiple levels.

Predicting sagittal deformity after surgery for intramedullary tumors

OBJECT

Spinal deformity after surgery for intramedullary tumors is a potentially serious complication that may require subsequent fusion. The aim of this study was to determine whether there were risk factors that could be used to predict postoperative sagittal deformity.

METHODS

The authors conducted a retrospective study of patients harboring an intramedullary tumor who had undergone surgery at a single center between 1985 and 2011. The main outcome of interest was the difference, at the last follow-up, between post- and preoperative measures of the Cobb angle formed by the superior and inferior limits of the laminectomy (ΔCobb).

RESULTS

Sixty-three patients were eligible for inclusion in the study. The mean sagittal deformity, measured as described above, was 15.9° (range 0°-77°) at a mean follow-up of 85.4 months (range 4-240 months). Univariate analysis showed increased sagittal deformity in patients 30 years old or younger (21.9° vs 13.7°, p = 0.04), undergoing a laminectomy involving 4 or more levels (19.3° vs 12.1°, p = 0.04), and undergoing a laminectomy that included a spinal junction (20.8° vs 12.4°, p = 0.02). Multivariate analysis showed that only age (p = 0.01) and the number of spinal levels involved in the laminectomy (p = 0.014) were significant and independent predictors of postoperative sagittal deformity. The linear regression equation drawn from this model allows one to quantitatively predict sagittal deformity for any follow-up time point after surgery.

CONCLUSIONS

Authors of this study developed a statistical tool that could be used to plan surgery and follow-up as regards the risk of sagittal spinal deformity in patients undergoing surgery for intramedullary tumors.

An extension-distraction injury of the thoracic spine with traumatic partial correction of thoracic kyphosis

Study Design The study is a case report. Objective The authors aim to report an unusual injury pattern in a patient previously treated for thoracic kyphoscoliosis. Methods A postoperative (computed tomography) CT of a healthy 24-year-old man who underwent posterior instrumentation and fusion for a kyphoscoliosis deformity was compared with a CT performed after a motor vehicle accident (MVA) 1 year later, which resulted in an extension-distraction injury of T8 with no neurologic deficit. Cobb angles of the thoracic sagittal images of both CTs were measured using a digital measuring device and the values were recorded. Results Initial postoperative sagittal CT images demonstrate a 67-degree residual thoracic kyphosis compared with the post-MVA sagittal CT images, which reveal a 54-degree thoracic kyphosis, a 13-degree improvement in sagittal alignment. Conclusion It is unusual for a patient with long posterior instrumentation of the spine to sustain a spinal fracture without breakage of the rods, which were 6-mm nickel-titanium alloy with two crosslinks. Although sustaining plastic deformation, the rods maintained their integrity to the degree that the patient required no subsequent treatment to his spine at 12 months follow-up. It is rare to sustain a vertebral fracture without implant failure, which occurred in this case.

Anatomy of subaxial cervical foramens: the safety zone for lateral mass screwing

INTRODUCTION

The purpose of this study was to measure the structures of the ventral of lateral masses using cadaver specimens and to quantitatively compare the safety zone for the two major techniques used on each vertebral level from C3 to C6.

METHODS

This study is based on 52 cervical vertebrae of 13 cadavers. The anatomical measurements focused on the anterior surface of the lateral mass. We investigated the safety width, heights, and the height of nerve roots.

RESULTS

The mean values of the safety width of the Magerl technique from C3 to C6 were 6.1, 7.3, 6.4 and 4.3 mm, respectively. The mean values of the safety width of the Roy-Camille technique were 6.7, 6.6, 5.8 and 5.4 mm, respectively. The mean values of the safety height of the Magerl technique were 5.0, 5.4, 5.8 and 5.2 mm, respectively. The mean values of the safety height of the Roy-Camille technique were 4.9, 4.0, 1.0 and -1.2 mm, respectively. The mean values of the nerve root height were 3.9, 4.9, 5.9 and 6.9 mm, respectively.

CONCLUSION

The safety width of the Magerl technique was shorter at C6 because the vertebral artery runs more laterally at C6. The height for the Magerl technique was not significantly different from C3 to C6, however, the safety height for the Roy-Camille technique was significantly shorter at C5 and C6. Our findings suggest that it is important to ensure that the screw(s) penetrate through the cranial side of the ventral aspect of a lateral mass when performing the Magerl technique at all vertebral levels, and to carefully select the screw length when using the Roy-Camille technique, especially at C5 and C6, in order to avoid nerve root injury.

Mechanical implant failure in posterior cervical spine fusion

PURPOSE

The aim of this study was to determine whether the recent refinement and downsizing of the implants for posterior cervical fusion increase the occurrence of implant failure.

METHODS

One hundred forty-two consecutive cases of cervical fusion, using either cannulated Magerl screws or a multiaxial pedicle screw-rod system, were reviewed retrospectively after an average follow-up period of more than 3 years, and the rate and characteristics of the failure of these implants were evaluated.

RESULTS

Implant failure occurred in six (4.2%) patients: five with rheumatoid arthritis and one with athetoid cerebral palsy. Occipital plate fracture occurred in two patients, Magerl screw breakage in one patient, cervical pedicle screw fracture in two patients, and disassembly of the pedicle screw and rod in two patients (one with an occipital plate fracture). There was no rod fracture. The implant failures were asymptomatic, except in one patient. Disassembly of the pedicle screw and rod was observed immediately after another surgical procedure under general anesthesia in two patients.

CONCLUSIONS

The failure rate of 4.2% was similar to the rates reported in the literature for posterior lumbar spinal fusion, confirming the reliability of the recent cervical screw-rod system.

Increased in-hospital complications after primary posterior versus primary anterior cervical fusion

BACKGROUND

Although anterior (ACDF) and posterior cervical fusion (PCDF) are relatively common procedures and both are associated with certain complications, the relative frequency and severity of these complications is unclear. Since for some patients either approach might be reasonable it is important to know the relative perioperative risks for decision-making.

QUESTIONS/PURPOSES

The purposes of this study were to: (1) characterize the patient population undergoing ACDF and PCDF; (2) compare perioperative complication rates; (3) determine independent risk factors for adverse perioperative events; and (4) aid in surgical decision-making in cases in which clinical equipoise exists between anterior and posterior cervical fusion procedures.

METHODS

The National Inpatient Sample was used and entries for ACDF and PCDF between 1998 and 2006 were analyzed. Demographics and complication rates were determined and regression analysis was performed to identify independent risk factors for mortality after ACDF and PCDF.

RESULTS

ACDF had a shorter length of stay and their procedures were more frequently performed at nonteaching institutions. The incidence of complications and mortality was 4.14% and 0.26% among patients undergoing ACDF and 15.35% and 1.44% for patients undergoing PCDF, respectively. When controlling for overall comorbidity burden and other demographic variables, PCDF was associated with a twofold increased risk of a fatal outcome compared with ACDF. Pulmonary, circulatory, and renal disease were associated with the highest odds for in-hospital mortality.

CONCLUSIONS

PCDF procedures were associated with higher perioperative rates of complications and mortality compared with ACDF surgeries. Despite limitations, these data should be considered in cases in which clinical equipoise exists between both approaches.

LEVEL OF EVIDENCE

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Surgical treatment of cervical kyphosis

Cervical kyphosis is an uncommon but potentially debilitating and challenging condition. We reviewed the etiology, presentation, clinical and radiological evaluation, and treatment of cervical kyphosis. Based on the current controversy as to the ideal mode of surgical management, we paid particular attention to the available surgical strategies. There are three approaches for cervical kyphosis: the anterior, posterior or combined procedures. The principal indication for the posterior strategy is a flexible kyphosis or kyphosis caused by ankylosing spondylitis. The main point of debate is between the choice of the anterior or the combined strategy. The two strategies were compared with regard to clinical outcome, correction of deformity, rate of fusion, complications, revision surgery, and mortality. The combined strategy appears to result in a greater degree of correction than the anterior-alone strategy, and it is more likely to improve the cervical alignment to achieve a lordosis. However, the procedure carries a higher rate of postoperative neurological deterioration, complications, revision surgery, and mortality. Although the anterior-alone strategy achieves a smaller reduction of cervical kyphosis, it has a lower rate of postoperative neurological deterioration, complications, revision surgery, and mortality. We recommend that the surgical treatment of cervical kyphosis should be planned on an individual basis. A multicenter, prospective, randomized controlled study would be necessary to determine the ideal mode of treatment for complex cervical kyphosis.

Utility of modified transarticular screw in the middle and lower cervical spine as intermediate fixation in posterior long fusion surgery

OBJECT

The use of a pedicle screw (PS) in the cervical spine ensures strong fixation. However, 6.7-29% of such screws appear to be malpositioned using manual insertion techniques, especially at C-3 to C-6 where the pedicle diameter is smaller, potentially causing catastrophic complications such as vertebral artery (VA) and spinal cord or nerve root injuries. To optimize safety, the authors use a new technique: cephalad and/or caudad ends at C-2 and C-7/T-1, respectively, are fixed with PSs, and intermediate points around C3-6 are fixed using a modified transarticular screw technique that captures 3 dorsal cortices and preserves the ventral cortex of the facet in posterior long fusion surgery involving occipitospinal fixation. The purpose of the present study was to demonstrate this technique and evaluate the clinical and radiological outcomes.

METHODS

Thirty-nine patients, 8 men and 31 women, with a mean age of 61.7 +/- 11.0 years at surgery, were included in the study. Twenty-eight occipitospinal fusions and 11 posterior long fusions were performed. Patients were divided into 2 groups: a rheumatoid arthritis (RA) group consisting of 26 patients and a non-RA group of 13 patients including 7 with athetoid cerebral palsy. Clinical outcomes were evaluated according to the Japanese Orthopaedic Association (JOA) score. For radiological evaluation, the Cobb angle on lateral radiographs was measured preoperatively, postoperatively, and at the final follow-up, and the degree of realignment from pre- to postoperation and the loss of correction from postoperation to the follow-up were compared between the 2 patient groups.

RESULTS

The recovery rate of the JOA score was 50.6 +/- 20.7% in the RA group and 37.3 +/- 24.3% in the non-RA group. Neither VA injury nor spinal cord or nerve root injury occurred among this series. The degree of realignment was greater in the non-RA group (9.2 +/- 13.9 degrees ) than the RA group (1.4 +/- 12.7 degrees ) as the Cobb angle was more kyphotic preoperatively in the non-RA group (2.9 +/- 18.6 degrees ) than in the RA group (17.4 +/- 15.7 degrees ). However, 38.5% of patients in the non-RA group had a correction loss > 10% compared with 7.7% in the RA group; this difference was statistically significant.

CONCLUSIONS

The featured transarticular screw technique, which preserves the ventral cortex of the facet, as intermediate fixation in long fusion is a safe and easy procedure with few complications. It ensures acceptable clinical and radiological outcomes, especially in patients with RA.

In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)

Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.

Percutaneous multilevel decompressive laminectomy, foraminotomy, and instrumented fusion for cervical spondylotic radiculopathy and myelopathy: assessment of feasibility and surgical technique

OBJECT

Extensive muscle dissection associated with conventional dorsal approaches to the cervical spine frequently results in local pain, muscle wasting, and temporarily painful and restricted neck movement. The utility of a percutaneous muscle-sparing access technique and specifically modified instrumentation for multilevel posterior cervical decompression and fusion were evaluated.

METHODS

Eleven patients (six men, five woman; mean age 72.8 +/- 6.3 years) presenting with refractory neck pain and progressive multilevel cervical radiculopathy and/or myelopathy due to cervical spondylosis with spinal canal and neural foraminal stenosis underwent multilevel laminectomy, foraminotomy, and subsequent instrumented posterior fusion via bilateral or unilateral percutaneous muscle dilation approaches. A novel cannulated polyaxial instrumentation system was used for unilateral transpedicular/translaminar fixation.

RESULTS

Significant reduction of Neck Disability Index and Nurick Scale scores and partial or complete recovery of upper extremity radicular deficits was observed during follow-up (mean 14.6 months). Mean procedural blood loss was 45.5 ml, and mean length of stay in hospital was 5.7 days. Fusion was demonstrated in 10 patients between 12 and 14 months postoperatively. Operative exposure and instrumentation were significantly facilitated by specific modifications of retractor/access port systems, surgical instruments, and implants.

CONCLUSIONS

Muscle sparing posterior decompression and instrumented fusion constitutes a safe and effective surgical option in a selected subgroup of patients with multilevel cervical spondylotic radiculomyelopathy. Specific modifications in surgical technique, instrumentation, and implants are mandatory for effective achievement of the surgical goals. The use of refined image guidance technology and intraoperative imaging can further improve surgical safety and efficacy.