Eric W. Nottmeier

Placement of thoracolumbar pedicle screws using three-dimensional image guidance: experience in a large patient cohort

OBJECTnThe goal of this study was to analyze the placement accuracy and complications of thoracolumbar pedicle screws (PSs) inserted using 3D image guidance in a large patient cohort.nnnMETHODSnThe authors reviewed the charts of 220 consecutive patients undergoing posterior spinal fusion using 3D image guidance for instrumentation placement. A total of 1084 thoracolumbar PSs were placed using either the BrainLAB Vector Vision (BrainLAB, Inc.) or Medtronic StealthStation Treon (Medtronic, Inc.) image guidance systems. Postoperative CT scanning was performed in 184 patients, allowing for 951 screws to be graded by an independent radiologist for bone breach. All complications resulting from instrumentation placement were noted. Using the intraoperative planning function of the image-guided system, the largest diameter screw possible in each particular case was placed. The screw diameter of instrumentation placed into the L3-S1 levels was noted.nnnRESULTSnNo vascular or visceral complications occurred as a result of screw placement. Two nerve root injuries occurred in 1084 screws placed, resulting in a 0.2% per screw incidence and a 0.9% patient incidence of nerve root injury. Neither nerve root injury was associated with a motor deficit. The breach rate was 7.5%. Grade 1 and minor anterolateral tip out breaches accounted for 90% of the total breaches. Patients undergoing revision surgery accounted for 46% of the patients in this study. Accordingly, 154 screws placed through previous fusion mass could be evaluated using postoperative CT scanning. The breach rate in this specific cohort was 7.8%. A total of 765 PSs were placed into the L3-S1 levels in this study; 546 (71%) of these screws were > or = 7.5 mm in diameter. No statistical difference in breach rate was noted in PSs placed through revision spinal levels versus nonrevision spinal levels (p = 0.499). Additionally, no increase in breach rate was noted with placement of 7.5-mm-diameter screws.nnnCONCLUSIONSnThree-dimensional image guidance is a useful adjunct to placement of spinal instrumentation. The complication rate in this study was low, and accurate placement of instrumentation was achieved despite the high percentage of revision surgery cases in our patient population. Additionally, because active fluoroscopy was not used for instrumentation placement, there was minimal to no radiation exposure to the surgeon or operating room staff.

Stabilization of the atlantoaxial complex via C-1 lateral mass and C-2 pedicle screw fixation in a multicenter clinical experience in 102 patients: modification of the Harms and Goel techniques

OBJECTnStabilization of the atlantoaxial complex has proven to be very challenging. Because of the high mobility of the C1-2 motion segment, fusion rates at this level have been substantially lower than those at the subaxial spine. The set of potential surgical interventions is limited by the anatomy of this region. In 2001 Jürgen Harms described a novel technique for individual fixation of the C-1 lateral mass and the C-2 pedicle by using polyaxial screws and rods. This method has been shown to confer excellent stability in biomechanical studies. Cadaveric and radiographic analyses have indicated that it is safe with respect to osseous and vascular anatomy. Clinical outcome studies and fusion rates have been limited to small case series thus far. The authors reviewed the multicenter experience with 102 patients undergoing C1-2 fusion via the polyaxial screw/rod technique. They also describe a modification to the Harms technique.nnnMETHODSnOne hundred two patients (60 female and 42 male) with an average age of 62 years were included in this analysis. The average follow-up was 16.4 months. Indications for surgery were instability at the C1-2 level, and a chronic Type II odontoid fracture was the most frequent underlying cause. All patients had evidence of instability on flexion and extension studies. All underwent posterior C-1 lateral mass to C-2 pedicle or pars screw fixation, according to the method of Harms. Thirty-nine patients also underwent distraction and placement of an allograft spacer into the C1-2 joint, the authors modification of the Harms technique. None of the patients had supplemental sublaminar wiring.nnnRESULTSnAll but 2 patients with at least a 12-month follow-up had radiographic evidence of fusion or lack of motion on flexion and extension films. All patients with an allograft spacer demonstrated bridging bone across the joint space on plain x-ray films and computed tomography. The C-2 root was sacrificed bilaterally in all patients. A postoperative wound infection developed in 4 patients and was treated conservatively with antibiotics and local wound care. One patient required surgical debridement of the wound. No patient suffered a neurological injury. Unfavorable anatomy precluded the use of C-2 pedicle screws in 23 patients, and thus, they underwent placement of pars screws instead.nnnCONCLUSIONSnFusion of C1-2 according to the Harms technique is a safe and effective treatment modality. It is suitable for a wide variety of fracture patterns, congenital abnormalities, or other causes of atlantoaxial instability. Modification of the Harms technique with distraction and placement of an allograft spacer in the joint space may restore C1-2 height and enhance radiographic detection of fusion by demonstrating a graft-bone interface on plain x-ray films, which is easier to visualize than the C1-2 joint.

Accuracy of upper thoracic pedicle screw placement using three-dimensional image guidance

BACKGROUND CONTEXTnPedicle screw malposition rates using conventional techniques have been reported to occur with a frequency of 6% to 41%. The upper thoracic spine (T1-T3) is a challenging area for pedicle screw placement secondary to the small size of the pedicles, the inability to visualize this area with lateral fluoroscopy, and significant consequences for malpositioned screws. We describe our experience placing 150 pedicle screws in the T1-T3 levels using three-dimensional (3D) image guidance.nnnPURPOSEnThe aim of this study was to assess the accuracy of 3D image guidance for placing pedicle screws in the first three thoracic vertebrae.nnnSTUDY DESIGNnThe accuracy of pedicle screw placement in the first three thoracic vertebrae was evaluated using postoperative thin-section computed tomography (CT) scans of the cervicothoracic region.nnnPATIENT SAMPLEnThirty-four patients who underwent cervicothoracic fusion were included.nnnOUTCOME MEASURESnRadiological investigation with CT scans was performed during the postoperative period.nnnMETHODSnThirty-four consecutive patients underwent cervicothoracic instrumentation and fusion for a total of 150 pedicle screws placed in the first three thoracic vertebrae. All screws were placed using 3D image guidance. Medical records and postoperative imaging of the cervicothoracic junction for each patient were retrospectively reviewed. An independent radiologist reviewed the placement of the pedicle screws and assessed for pedicle breach. All cortical violations were reported as Grade 1, 0 to 2 mm; Grade 2, 2 to 4 mm; and Grade 3, greater than 4 mm.nnnRESULTSnOverall, 140 (93.3%) out of 150 screws were contained solely in the desired pedicle. All 10 pedicle violations were Grade 1. The direction of pedicle violation included three medial, four inferior, two superior, and one minor anterolateral vertebral body. No complication occurred as a result of screw placement or the use of image guidance.nnnCONCLUSIONSnUpper thoracic pedicle screw placement is technically demanding as a result of variable pedicle anatomy and difficulty with two-dimensional visualization. This study demonstrates the accuracy and reliability of 3D image guidance when placing pedicle screws in this region. Advantages of this technology in our practice include safe and accurate placement of spinal instrumentation with little to no radiation exposure to the surgeon and operating room staff.

Biomechanical Analysis of Rigid Stabilization Techniques for Three-Column Injury in the Lower Cervical Spine

Study Design. Comparison of nondestructive multidirectional flexibility in groups of specimens receiving two different posterior instrumentation constructs with or without anterior plating. Objective. To compare stability after a three-column injury stabilized posteriorly by lateral mass screws-rods at C5–C6 and pedicle screws-rods at C7 (“LLP”) or by pedicle screws-rods at C5–C6–C7 (“PPP”), and to compare posterior, anterior, and combined anterior-posterior fixation. Summary of Background Data. Pedicle screws resist pullout better than lateral mass screws, but little research has compared the stability of pedicle screws to that of lateral mass screws used within constructs. Methods. Fourteen human cadaveric C4–T1 specimens were tested intact, posteriorly instrumented (7 LLP and 7 PPP), anteriorly instrumented, or with combined (anterior-posterior) instrumentation. Nonconstraining, nondestructive torques induced flexion, extension, lateral bending, and axial rotation while angular motion was recorded optically. Results. Posterior, anterior, and combined instrumentation each significantly improved stability (P < 0.05). Combined fixation provided significantly better stability than either anterior or posterior instrumentation alone. In no loading mode and in no testing condition was any parameter significantly different between LLP and PPP.Posterior instrumentation provided significantly better stability than anterior instrumentation. Conclusions. Anterior plate and posterior screw-rod fixation alone improve stability in a two-level, three-column cervical injury model. Combined fixation further improves stability. There is little discernible difference in immediate postoperative stability between posterior rod constructs combining lateral mass and pedicle screws and those using only pedicle screws.

Rheumatoid arthritis of the craniovertebral junction.

BACKGROUNDRheumatoid arthritis (RA) is the most common inflammatory disease involving the spine. It has a predilection for involving the craniocervical spine. Despite widespread involvement of the cervical spine with RA, few patients need surgery. The 3 major spinal manifestations of RA in the cervical spine are basilar invagination, atlantoaxial instability, and subaxial subluxations. Surgical management of RA involving the craniovertebral junction remains a challenge despite a decline in severe cases and an improvement in surgical techniques. METHODSWe conducted an exhaustive review of English-language publications discussing RA involving the craniovertebral junction. We paid special attention to publications detailing modern surgical management of these conditions. In addition, we outline our own surgical experience with such patients. RESULTSWe discuss alternative surgical methods for treating basilar invagination, atlantoaxial instability, and concurrent subaxial subluxations. We detail our surgical technique for transoral odontoidectomy, occipital cervical fusion, and atlantoaxial fusion. We detail the use of spinal surgical navigation in both of these procedures. CONCLUSIONSurgical management of RA remains a challenging field. There clearly has been a decrease in cases of mutilating RA involving the craniovertebral junction. Surgical techniques for managing these conditions have steadily improved.BACKGROUNDnRheumatoid arthritis (RA) is the most common inflammatory disease involving the spine. It has a predilection for involving the craniocervical spine. Despite widespread involvement of the cervical spine with RA, few patients need surgery. The 3 major spinal manifestations of RA in the cervical spine are basilar invagination, atlantoaxial instability, and subaxial subluxations. Surgical management of RA involving the craniovertebral junction remains a challenge despite a decline in severe cases and an improvement in surgical techniques.nnnMETHODSnWe conducted an exhaustive review of English-language publications discussing RA involving the craniovertebral junction. We paid special attention to publications detailing modern surgical management of these conditions. In addition, we outline our own surgical experience with such patients.nnnRESULTSnWe discuss alternative surgical methods for treating basilar invagination, atlantoaxial instability, and concurrent subaxial subluxations. We detail our surgical technique for transoral odontoidectomy, occipital cervical fusion, and atlantoaxial fusion. We detail the use of spinal surgical navigation in both of these procedures.nnnCONCLUSIONnSurgical management of RA remains a challenging field. There clearly has been a decrease in cases of mutilating RA involving the craniovertebral junction. Surgical techniques for managing these conditions have steadily improved.

Intraoperative image-guided spinal navigation: technical pitfalls and their avoidance.

Spinal instrumentation has made significant advances in the last two decades, with transpedicular constructs now widely used in spinal fixation. Pedicle screw constructs are routinely used in thoracolumbar-instrumented fusions, and in recent years, the cervical spine as well. Three-column fixations with pedicle screws provide the most rigid form of posterior stabilization. Surgical landmarks and fluoroscopy have been used routinely for pedicle screw insertion, but a number of studies reveal inaccuracies in placement using these conventional techniques (ranging from 10% to 50%). The ability to combine 3D imaging with intraoperative navigation systems has improved the accuracy and safety of pedicle screw placement, especially in more complex spinal deformities. However, in the authors experience with image guidance in more than 1500 cases, several potential pitfalls have been identified while using intraoperative spinal navigation that could lead to suboptimal results. This article summarizes the authors experience with these various pitfalls using spinal navigation, and gives practical tips on their avoidance and management.

Timing of paired points and surface matching registration in three-dimensional (3D) image-guided spinal surgery.

Image-guidance can increase the safety and accuracy of spinal instrumentation placement. However, many spine surgeons are reluctant to incorporate spinal image-guidance into their surgical practice due to the perception that it is time-consuming and tedious, especially the task of vertebral registration. The authors evaluated the time required for paired points and surface matching registration when using the BrainLAB (BrainLAB, Westchester, IL) image-guided spine application for spinal surgery cases. The time required to register vertebral segments using paired points and surface matching techniques was assessed in 13 consecutive patients undergoing spinal fusions by the senior author. Overall, 23 vertebral segments were registered spanning from T1 to S1. Note was made of the vertebral segments that required reregistration due to poor accuracy. The average time required to register a single vertebral segment using the paired points and surface matching technique was 117 seconds (1u2009min 57u2009s). Average accuracy obtained was 0.9u2009mm. Inaccurate registration occurred in 3/23 (13%) of the segments requiring a second attempt at registration. In 3/23 (13%) of segments, adequate navigation accuracy was maintained on an adjacent vertebral segment thereby allowing for instrumentation to be placed in that adjacent segment without having to register that segment. Though associated with a learning curve, image-guidance can be used effectively and efficiently in spinal surgery. Average time required for registration of a vertebral segment using the BrainLAB spine application in this study was less than 2 minutes. The average accuracy obtained was 0.9u2009mm.

Image-Guided Placement of Occipitocervical Instrumentation Using a Reference Arc Attached to the Headholder

OBJECTIVE To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder. METHODS The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach. RESULTS No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred. CONCLUSIONS This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

Cervical kyphotic deformity correction using 360-degree reconstruction

Objective The authors report on their experience with cervical sagittal deformity correction using 360-degree reconstruction. Summary of Background Data A paucity of literature exists concerning 360-degree approaches for the correction of cervical kyphotic sagittal deformity in which the amount of deformity correction achieved, as well as the maintenance of deformity correction, is detailed. Methods The charts of all patients undergoing 360-degree cervical reconstruction for kyphotic sagittal plane deformity between 2000 and 2006 at Mayo Clinic Jacksonville and Mayo Clinic Scottsdale were retrospectively reviewed. Only patients with a minimum of 1-year follow-up were included in this study; 41 patients fit this criterion. The clinical data were further analyzed in this cohort to determine preoperative and postoperative sagittal angle, loss of correction, fusion rate, complications, and clinical status at last follow-up. Results Average follow-up was 19 months (range: 12 to 48u2009mo). The mean preoperative sagittal angle was 18 degrees of kyphosis (range: 3 to 58 degrees). The mean correction of sagittal angle was 22 degrees (range: 4 to 56 degrees), resulting in a postoperative mean sagittal angle of 4-degree lordosis. There was no loss of correction across the instrumented segments in any patient. Neurologic complications included 1 case of quadriparesis and 1 case of transient C8 radiculopathy. Conclusions The correction of cervical kyphotic sagittal plane deformity can be accomplished safely and effectively using a 360-degree approach. The incidence of major complications in this study was low. All patients could be corrected to a neutral or lordotic alignment. No loss of deformity correction was seen in any patient, and a 97.5% fusion rate was obtained.

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

OBJECTIVEnThe technique of rod-screw fixation of the cervical spine is well described. However, there is very little data on the complications incurred by the application of these devices. The purpose of this study was to quantify the risks associated with rod fixation of the cervical spine.nnnMETHODSnA prospective study was performed on 100 consecutive patients treated with this technique. Clinical and radiographic assessment was performed immediately after surgery 3, 6, and 12 months postoperatively, and annually thereafter. The mean follow-up interval was 16.7 months.nnnRESULTSnA total of 888 screws were implanted in 100 patients. Perioperative complications included radiculopathy (n = 4, 0.45% per screw placed), infection and other wound-healing problems (n = 4), screw malposition (n = 2), loss of alignment (n = 1), and cerebrospinal fluid leak (n = 1). There were no examples of spinal cord or vertebral artery injury. Early complications (within 6 mo of surgery) included pseudarthrosis (n = 2) and screw breakage (n = 2, 0.22% per screw placed). There were no late complications. Reoperation was required in eight cases, all within 6 months of the index procedure. Indications for reoperation included wound-healing problems (n = 4), malpositioned screw (n = 2), and pseudarthrosis (n = 2). No patient required another operation for any indication beyond the 6-month postoperative interval.nnnCONCLUSIONnRod-screw fixation was an effective method of posterior cervical stabilization that could be safely applied in a wide range of spinal disorders. In a complex group of patients, the complication rates were modest, and compared favorably with other methods of fixation.