Cervical cages placed bilaterally in the facet joints from a posterior approach significantly increase foraminal area.

PURPOSE: Foraminal stenosis is a common cause of cervical radiculopathy. Posterior cervical cages can indirectly increase foraminal area and decompress the nerve root. The aim of this study was to assess the influence of bilateral posterior cervical cages on the surface area and shape of the neural foramen. METHODS: Radiographic analysis was performed on 43 subjects enrolled in a prospective, multi-center study. CT scans were obtained at baseline and 6- and 12-months after cervical fusion using bilateral posterior cervical cages. The following measurements were performed on CT scan: foraminal area (A), theoretical area (TA), height (H), superior diagonal (DSI), inferior diagonal (DIS), and inferior diagonal without implant (DISI). Comparisons were performed using R-ANOVA with a significance of α < 0.05. RESULTS: Foraminal area, height, TA and DISI were significantly greater following placement of the implant. The mean (SD) A increased from 4.01 (1.09) mm(2) before surgery to 4.24 (1.00) mm(2) at 6 months, and 4.18 (1.05) mm(2) at 12 months after surgery (p < 0.0001). Foraminal height (H) increased from mean (SD) 9.20 (1.08) mm at baseline to 9.65 (1.06) mm and 9.55 (1.14) mm at 6- and 12-months post-operatively, respectively (p < 0.0001). The mean DIS did not change significantly. There was a significant decrease in DSI: 6.18 (1.59) mm pre-operatively, 5.95 (1.47) mm and 5.73 (1.46) mm at 6- and 12-months (p < 0.0001). CONCLUSIONS: Implantation of bilateral posterior cervical cages can increase foraminal area and may indirectly decompress the nerve roots. Correlation between increase in foraminal area and clinical outcomes needs further investigation.

Reliability of cervical lordosis measurement techniques on long-cassette radiographs.

PURPOSE: Lateral radiographs are commonly used to assess cervical sagittal alignment. Three assessment methods have been described and are commonly utilized in clinical practice. These methods are described for perfect lateral cervical radiographs, however in everyday practice radiograph quality varies. The aim of this study was to compare the reliability and reproducibility of 3 cervical lordosis (CL) measurement methods. METHODS: Forty-four standing lateral radiographs were randomly chosen from a lateral long-cassette radiograph database. Measurements of CL were performed with: Cobb method C2-C7 (CM), C2-C7 posterior tangent method (PTM), sum of posterior tangent method for each segment (SPTM). Three independent orthopaedic surgeons measured CL using the three methods on 44 lateral radiographs. One researcher used the three methods to measured CL three times at 4-week time intervals. Agreement between the methods as well as their intra- and interobserver reliability were tested and quantified by intraclass correlation coefficient (ICC) and median error for a single measurement (SEM). ICC of 0.75 or more reflected an excellent agreement/reliability. The results were compared with repeated ANOVA test, with p < 0.05 considered as significant. RESULTS: All methods revealed excellent intra- and interobserver reliability. Agreement (ICC, SEM) between three methods was (0.89°, 3.44°), between CM and SPTM was (0.82°, 4.42°), between CM and PTM was (0.80°, 4.80°) and between PTM and SPTM was (0.99°, 1.10°). Mean values CL for a CM, PTM, SPTM were 10.5° ± 13.9°, 17.5° ± 15.6° and 17.7° ± 15.9° (p < 0.0001), respectively. The significant difference was between CM vs PTM (p < 0.0001) and CM vs SPTM (p < 0.0001), but not between PTM vs SPTM (p > 0.05). CONCLUSIONS: All three methods appeared to be highly reliable. Although, high agreement between all measurement methods was shown, we do not recommend using Cobb measurement method interchangeably with PTM or SPTM within a single study as this could lead to error, whereas, such a comparison between tangent methods can be considered.

Influence of lower limbs discrepancy and pelvic coronal rotation on pelvic incidence, pelvic tilt and sacral slope.

PURPOSE: Pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS) are important parameters in sagittal spine alignment evaluation. The measurements are a projection of the three-dimensional pelvis onto a two-dimensional radiograph and they may be influenced by orientation of the pelvis. The aim of this study was to assess the influence of pelvic rotation in the coronal plane (CPR) on radiographic accuracy of PI, PT, and SS measurements. METHODS: Radiological evaluation of the CPR angel was performed on 1 radiological phantom. The radiographs were taken in 5° CPR increments over a range of 0°-45° (evaluated with a digital protractor). On each of the lateral radiograph, PI, PT, and SS were measured three times by three independent researchers. The lowest CPR that changed PI, PT, or SS by ≥6° (the highest reported error of measurement of these parameters) was considered as unacceptable. Next, CPR was calculated based on the distance between femoral heads (FHD). The agreement of the calculated and measured CPR was quantified by the intraclass correlation coefficient (ICC) and the median error for a single measurement (SEM), with value 0.75 considered as excellent agreement. RESULTS: PI, PT and SS could be measured with an acceptable error of 6° on radiographs with up to 20° pelvic rotation. From 20° CPR onwards the S1 endplate was distorted, that makes the measurements of PI, PT and SS questionable. There was an excellent agreement between CPR measured with a protractor and calculated based on FHD with ICC of 0.99 and SEM of 1.1°. CONCLUSIONS: Rotation of the pelvis in the coronal plane during acquisition of radiographs influences PI, PT and SS measurements. Substantial error of PI, PT and SS measurements occurs with CPR of more than 20° which is equivalent to a lower limb discrepancy of 5.2 cm. CPR may be calculated while acquiring the radiograph. Further evaluation of the influence of CPR on spinopelvic parameters with a larger sample would be valuable.

Pelvic incidence and pelvic tilt measurements using femoral heads or acetabular domes to identify centers of the hips: comparison of two methods.

PURPOSE: The aim of the study was to compare pelvic incidence (PI) and pelvic tilt (PT) measurements using the bicoxofemoral axis obtained from either femoral heads or acetabular domes on lateral digital radiographs of the spine. METHODS: Standing lateral radiographs of the spine of patients without hip pathologies were analyzed. PI and PT were measured on 50 radiographs using the femoral heads first followed by measurements performed with the acetabular domes to define the bicoxofemoral axis. Agreement between the methods was quantified by intraclass correlation coefficient (ICC) and median error for a single measurement (SEM). Intraobserver reproducibility and interobserver reliability of both methods of identification of bicoxofemoral axis and its impact on PI and PT measurements were tested on 31 radiographs and quantified by ICC and SEM. RESULTS: There was an excellent agreement in PI as well as in PT between measurements performed using whether the femoral heads or the acetabular domes (ICC: 0.99; SEM: 0.56° for PI and ICC: 0.99; SEM: 0.2° for PT). Excellent intraobserver reproducibility was revealed for both methods (ICC: 0.99 and SEM: ≤0.17° for PI and ICC: 0.99; SEM: ≤0.18° for PT). Both methods presented excellent interobserver reliability (ICC: 0.99 and SEM: ≤0.54° for PI and ICC: ≥0.98; SEM: ≤0.9° for PT). CONCLUSIONS: We suggest that either the femoral heads or the acetabular domes may be used for reliable PI and PT measurements on the lateral standing long-cassette digital radiographs of the spine.

Influence of cervical spine position on the radiographic parameters of the thoracic inlet alignment.

PURPOSE: Cervical sagittal balance is a complex phenomenon, influenced by many factors, which cannot be described by cervical lordosis alone. Attention has been focused on the relationship between T1 slope, thoracic inlet angle, and cervical sagittal balance. However, the effect of cervical position on these parameters has not been evaluated yet. The aim of this study was to assess the influence of cervical flexion and extension on radiographic thoracic inlet parameters. METHODS: 60 patients with one level radiculopathy symptoms underwent radiological examination. Mean age was 53 (40-72) years; there were 24 males and 34 females. Lateral standing X-rays of cervical spine were taken on the same day in neutral position, full flexion and full extension. Patients with previous cervical operations or congenital malformations were excluded. Thoracic inlet angle (TIA), neck tilt (NT) and thoracic (T1) slope were measured. Agreement between measurements was assessed and quantified by intra-class correlation coefficient (ICC) and median error for a single measurement (SEM). The ICC value greater than 0.75 reflected sufficient agreement. RESULTS: The mean values of the parameters were: (1) for the neutral position: TIA 71.7° ± 9.5°; T1 slope 26.7° ± 6.3°; and NT 44.9° ± 7.2°, (2) In extension: TIA 71.8° ± 9.4°; T1 slope 24.9° ± 7.6°; and NT 46.9° ± 7.2° and (3) In flexion 78.3° ± 10.3°; T1 slope 33.6° ± 7.8°; and NT 44.7° ± 7.4°. An excellent agreement was revealed for all NT measurements (ICC 0.76) and for TIA measured in flexion and neutral position (ICC 0.79). There was insufficient overall and in-pairs agreement for T1 slope measurements. CONCLUSIONS: Neck tilt measurements were not influenced by position of the cervical spine. T1 slope was significantly influenced by flexion and extension of the neck. This puts the concept that TIA is a morphologic parameter into question. This information should be taken into consideration when analyzing lateral radiographs of the cervical spine for clinical decision-making.

Comparison of radiographic sagittal spinopelvic alignment between skeletally immature and skeletally mature individuals with Scheuermann's disease.

PURPOSE: The aim of this study was to compare radiographic sagittal spinopelvic parameters between skeletally immature and skeletally mature patients with Scheuermann's disease (SD). METHODS: Cross-sectional analysis of standing postero-anterior and lateral radiographs of the spine of patients with SD was performed. Sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured on the lateral radiographs. Risser's sign was assessed on the postero-anterior radiographs. All of the parameters measured were compared between skeletally immature (Risser's sign 0-3) versus mature patients (Risser's sign 5). PI, PT, and SS in both groups were compared to PI, PT, and SS reported for normal children, adolescents, and adults. RESULTS: Sixty-six patients with SD (33 immature and 33 mature) were retrospectively reviewed and included in the study. There was no significant difference between the two groups of SD patients in: SVA (-16.6 vs. -22.9 mm, p = 0.74), TK (57.8° vs. 56°, p = 0.66), TLK (7.8° vs. 11.7º, p = 0.14), LL (63.2° vs. 62.2°, p = 0.74), PI (36.7° vs. 39.4°, p = 0.20), PT (3.8° vs. 7.3°, p = 0.10), and SS (32.8° vs. 32.1°, p = 0.75). Both, the immature and mature group of SD patients presented significantly lower PI and SS than normal children, adolescents, and adults, and significantly lower PT than normal adults. CONCLUSIONS: There is no significant difference in sagittal spinopelvic parameters between skeletally immature and mature subjects with SD. Pelvic incidence in both groups of SD patients was significantly lower than PI in normal children, adolescents, and adults. This challenges the role of PI in predicting desired LL in patients with SD.

Calculation of corrected body height in idiopathic scoliosis: comparison of four methods.

PURPOSE: The aim of the study was to analyze four radiographic methods of calculating the loss of body height associated with scoliosis. METHODS: Thirty patients with right thoracic idiopathic scoliosis were examined with standing postero-anterior radiographs. Cobb angles of the upper thoracic, main thoracic and lumbar curves were measured. The loss of body height due to scoliosis was measured directly on the radiographs and then calculated using the methods of Bjure, Kono, Stokes and Ylikoski, respectively. The reproducibility of calculations was tested. Detailed analysis of two patients with similar Cobb angle but different trunk height was performed. RESULTS: The mean Cobb angle of the main thoracic curve was 46° (21°-74°). The mean loss of body height was 23 mm (11-43 mm) calculated by method of Bjure, 7 mm (-24 to 46 mm) by Kono, 20 mm (5-47 mm) by Stokes, 14 mm (3-36 mm) by Ylikoski, versus 18 mm (3-50 mm) measured directly on radiographs. The overall difference between the loss of body heights was significant (p < 0.0001), with significant differences in pairs for: Bjure versus Kono (p < 0.0001), Stokes versus Kono (p = 0.0002), Kono versus measured (p = 0.0061) and Bjure versus Ylikoski (p = 0.0386). Strong linear correlation between the methods was found (r ≥ 0.92; p < 0.0001). High reproducibility of height loss calculations was noticed. The two patients with similar Cobb angle and different trunk height revealed similar height loss calculated, while different loss measured on radiographs. CONCLUSIONS: There existed no overall agreement between the four methods of calculation of the loss of body height associated with scoliosis. Calculations based on the Cobb angle produced inaccuracy and could be supplemented with data considering trunk size.

Comparison of perioperative complications following staged versus one-day anterior and posterior cervical decompression and fusion crossing the cervico-thoracic junction.

INTRODUCTION: Multilevel cervical pathology may be treated via combined anterior cervical decompression and fusion (ACDF) followed by posterior spinal instrumented fusion (PSIF) crossing the cervico-thoracic junction. The purpose of the study was to compare perioperative complication rates following staged versus same day ACDF combined with PSIF crossing the cervico-thoracic junction. MATERIAL AND METHODS: A retrospective review of consecutive patients undergoing ACDF followed by PSIF crossing the cervico-thoracic junction at a single institution was performed. Patients underwent either same day (group A) or staged with one week interval surgeries (group B). The minimum follow-up was 12 months. RESULTS: Thirty-five patients (14 females and 21 males) were analyzed. The average age was 60 years (37-82 years). There were 12 patients in group A and 23 in group B. Twenty-eight complications noted in 14 patients (40%) included: dysphagia in 13 (37%), dysphonia in 6 (17%), post-operative reintubation in 4 (11%), vocal cords paralysis, delirium, superficial incisional infection and cerebrospinal fluid leakage each in one case. Significant differences comparing group A vs. B were found in: the number of levels fused posteriorly (5 vs. 7; p=0.002), total amount of intravenous fluids (3233ml vs. 4683ml; p=0.03), length of hospital stay (10 vs. 18 days; p=0.03) and transfusion of blood products (0 vs. 9 patients). Smoking and cervical myelopathy were the most important risk factors for perioperative complications regardless of the group. CONCLUSIONS: Staging anterior cervical decompression and fusion with posterior cervical instrumented fusion 1 week apart does not decrease the incidence of perioperative complications.

Techniques and materials for enhancement of peripheral nerve regeneration: a literature review.

Peripheral nerve surgery performed under unfavorable conditions results in increased scar formation and suboptimal clinical outcomes. Providing the operated nerve with a protective barrier, reduces fibrosis and adhesion formation and may lead to improved outcomes. The ideal coverage material should prevent scar and adhesion formation, and maintain nerve gliding during motion. Nerve protection using autologous tissues has shown good results, but shortcomings include donor site morbidity and limited availability. Various types of methods and materials have been used to protect nerves. There are both advantages and disadvantages associated with the various materials and techniques. In this report we summarize currently used protective materials applied for nerve coverage under various surgical conditions.

Autonomous lumbar spine pedicle screw planning using machine learning: A validation study.

INTRODUCTION: Several techniques for pedicle screw placement have been described including freehand techniques, fluoroscopy assisted, computed tomography (CT) guidance, and robotics. Image-guided surgery offers the potential to combine the benefits of CT guidance without the added radiation. This study investigated the ability of a neural network to place lumbar pedicle screws with the correct length, diameter, and angulation autonomously within radiographs without the need for human involvement. MATERIALS AND METHODS: The neural network was trained using a machine learning process. The method combines the previously reported autonomous spine segmentation solution with a landmark localization solution. The pedicle screw placement was evaluated using the Zdichavsky, Ravi, and Gertzbein grading systems. RESULTS: In total, the program placed 208 pedicle screws between the L1 and S1 spinal levels. Of the 208 placed pedicle screws, 208 (100%) had a Zdichavsky Score 1A, 206 (99.0%) of all screws were Ravi Grade 1, and Gertzbein Grade A indicating no breech. The final two screws (1.0%) had a Ravi score of 2 (<2 mm breech) and a Gertzbein grade of B (<2 mm breech). CONCLUSION: The results of this experiment can be combined with an image-guided platform to provide an efficient and highly effective method of placing pedicle screws during spinal stabilization surgery.

Augmented reality and artificial intelligence-assisted surgical navigation: Technique and cadaveric feasibility study.

PURPOSE: Augmented reality-based image overlay of virtual bony spine anatomy can be projected onto real spinal anatomy using computer tomography-generated DICOM images acquired intraoperatively. The aim of the study was to develop a technique and assess the accuracy and feasibility of lumbar vertebrae pedicle instrumentation using augmented reality-assisted surgical navigation. SUBJECTS AND METHODS: An augmented reality and artificial intelligence (ARAI)-assisted surgical navigation system was developed. The system consists of a display system which hovers over the surgical field and projects three-dimensional (3D) medical images corresponding with the patient's anatomy. The system was registered to the cadaveric spine using an optical tracker and arrays with reflective markers. The virtual image overlay from the ARAI system was compared to 3D generated images from intraoperative scans and used to percutaneously navigate a probe to the cortex at the corresponding pedicle starting point. Intraoperative scan was used to confirm the probe position. Virtual probe placement was compared to the actual probe position in the bone to determine the accuracy of the navigation system. RESULTS: Four cadaveric thoracolumbar spines were used. The navigated probes were correctly placed in all attempted levels (n = 24 levels), defined as Zdichavsky type 1a, Ravi type I, and Gertzbein type 0. The virtual overlay image corresponded to the 3D generated image in all the tested levels. CONCLUSIONS: The ARAI surgical navigation system correctly and accurately identified the starting points at all the attempted levels. The virtual anatomy image overlay precisely corresponded to the actual anatomy in all the tested scenarios. This technology may lead more uniform outcomes between surgeons and decrease minimally invasive spine surgery learning curves.

The Four Fixation Points of the Axis: Technique and Case Report.

BACKGROUND: Instrumentation of the axis can be accomplished through a variety of techniques including transarticular screw fixation, pars and pedicle screw fixation, translaminar screw fixation, and posterior wiring. We report on the evolution of the axial 4-screw technique. METHODS: Retrospective case review. After exposure of posterior spinal elements, the medial and superior walls of the C2 pedicle were identified from within the spinal canal. A high-speed drill was then advanced under lateral fluoroscopy, which guided craniocaudal angulation. Medial angulation was based on anatomic landmarks and preoperative imaging. This was followed by placement of translaminar screws according to the technique described by Wright. When extending the construct into the subaxial spine or the occiput, lateral connectors are placed in translaminar screws, which are usually more offset. The rod is directly connected to the pedicle screws, which are usually more in alignment with the subaxial/occipital instrumentation. RESULTS: Two male patients ages 56 and 58 underwent posterior instrumentation of the axis employing a combination of pedicle and laminar polyaxial screws. Indications included multilevel spinal cord compression and deformity in a patient with Down syndrome and cervical meningioma, respectively. Follow-up was 1 year and 5 years, respectively. Medical complications (N = 2) occurred in the patient with Down syndrome resulting in prolonged intubation with tracheostomy placement. Reduction was maintained in both patients at last follow-up. There were no neurologic, vascular, or instrumentation related complications. CONCLUSIONS: The axis serves as a versatile anchor point and offers 4 potential points of fixation. Lateral connectors play a crucial role and allow for incorporation of the C2 screws with the rest of the construct. Local anatomy will dictate the necessity and ability to place instrumentation and detailed preoperative planning is of paramount importance.

Length of stay associated with posterior cervical fusion with intervertebral cages: experience from a device registry.

BACKGROUND: Using a multi-center medical device registry, we prospectively collected a set of perioperative and clinical outcomes among patients treated with tissue-sparing, posteriorly-placed intervertebral cage fusion used in the management of symptomatic, degenerative neural compressive disorders of the cervical spine. METHODS: Cervical fusion utilizing posteriorly-placed intervertebral cages offers a tissue-sparing alternative to traditional instrumentation for the treatment of symptomatic cervical radiculopathy. A registry was established to prospectively collect perioperative and clinical data in a real-world clinical practice setting for patients treated via this approach. This study evaluated length of stay as well as estimated blood loss and procedural time in 271 registry patients. RESULTS: The median length of stay was 1.1, 1.1 and 1.2 days for patients having a stand-alone arthrodesis, revision of a pseudoarthrosis, and circumferential fusion (360°), respectively, and was not related to number of levels treated. Historical comparison to published literature demonstrated that average lengths of stay associated with open, posterior lateral mass fixation were consistently ≥4 days. Average blood loss (range, 32-75 mL) and procedural time (range, 51-88 min) were also diminished in patients having tissue-sparing, cervical intervertebral cage fusion compared to open posterior lateral mass fixation. CONCLUSIONS: Adoption of this tissue-sparing procedure may offer substantial cost-constraining benefits by reducing the length of post-operative hospitalization by, at least, 3 days compared to traditional lateral mass fixation.

Complications in Adult Patients with Down Syndrome Undergoing Cervical Spine Surgery Using Current Instrumentation Techniques and rhBMP-2: A Long-Term Follow-Up.

Introduction Cervical spine pathologies are common in Down syndrome (DS) patients. Cervical pathologies may cause cord compression and neurologic deterioration if left untreated. Complication rates of 73-100% have been reported in DS patients after cervical spine surgery in historical studies. This study reports updated perioperative complications rates and long-term outcome in patients with DS undergoing cervical spine surgery. Methods Retrospective review of patients with DS who have undergone cervical spine surgery from 1998 to 2011 (≥ 24 months of follow-up) was undertaken. Series of 17 adults with preoperative diagnoses that included atlantoaxial instability, stenosis, spondylosis, or cervical spondylolisthesis were evaluated. Nine patients received recombinant human bone morphogenetic protein-2 (rhBMP-2). Neurologic and ambulatory status was evaluated at regular intervals included pre- and postoperative imaging, range of motion evaluation, strength/neurologic testing, ambulation observation, and patient and caretaker pain reporting. Results A total of 20 surgical procedures were performed in 17 patients. Average follow-up was 78.7 months (range: 25-156 months). Overall, 37 complications were observed including pneumonia, respiratory distress, reintubation, dysphagia, deep venous thrombosis, sepsis, wound infection, dehiscence, neurologic complications, loss of reduction (LOR), pseudarthrosis, and hardware failure. Postoperative pneumonia was most common (23.5%). Three patients developed pseudarthrosis (all in the rhBMP-2 group); three demonstrated LOR. Neurologic complications (N = 3) included spasticity, loss of ambulation, and postoperative weakness with myelomalacia. Two were transient. Respiratory complications in the rhBMP-2 group were the most common (N = 3). The anterior approach resulted in a higher likelihood of complications than the posterior (p = 0.032). Conclusions Current techniques may improve pseudarthrosis (p = 0.009), LOR (p = 0.043), and first attempt (p = 0.038) and overall fusion rates (p = 0.018) compared with historical studies. Complications continue to challenge most patients (82.4%). A total of 16 of 17 patients (94.1%) demonstrated stabilization or improvement in neurologic status. Apparent successful outcome in the majority appears to warrant the high complication risk associated with cervical spine surgery in DS patients. The anterior approach resulted in a higher risk of complications than posterior (p = 0.032). We report a higher than expected incidence of pseudarthrosis in DS patients receiving rhBMP-2, putting its benefit in DS patients into question.

Cobb angle measurements on digital radiographs using Bunnell scoliometer: Validation of the method.

BACKGROUND: Electronic rulers on computer screen are used to measure the Cobb angle (CA) instead of traditional methods with rulers, protractors and pens. The variety of software used to assess radiographs might make the CA measurements cumbersome in everyday clinical practice. OBJECTIVE: The aim of the study was to verify the method of CA measurements on digital radiographs using Bunnell scoliometer (BS). METHODS: Eighty patients with idiopathic scoliosis were enrolled into the study. CA of each curve was measured by use of Centricity software and BS. CA on 30 randomly chosen patients were measured 3 times by one researcher using only scoliometer. Three researchers measured CA on the same 30 radiographs using BS. RESULTS: The mean CA of 224 curves measured by Centricity and BS were 29° ± 12.2° and 28° ± 11.7°, respectively. The ICC for agreement for 2 methods was 0.96 with SEM of 1.7°. Excellent intra- and interobserver reliability of CA measurements with scoliometer was noted: ICC of 0.96 with SEM of 1.4° and ICC of 0.93 with SEM of 1.9°, respectively. CONCLUSIONS: The study revealed excellent reliability of CA measurements on digital radiographs using the BS. The proposed method of using the Bunnell scoliometer for CA measurements may be clinically useful.

Preliminary Analysis of Adjacent Segment Degeneration in Patients Treated with Posterior Cervical Cages: 2-Year Follow-Up.

OBJECTIVE: Select patients with unremitting symptoms of cervical radiculopathy may be treated with indirect foraminal decompression and fusion via placement of a cervical cage placed bilaterally through a tissue sparing, posterior approach. Segmental fusion is known to affect adjacent segments. The aim of this study was to assess the affect of posterior fusion using bilateral cervical cages on adjacent segment degeneration (ASDegeneration) at 2 years postoperatively. METHODS: Fifty-three patients enrolled in a prospective multicenter study who completed the imaging protocol were available for follow-up at 2 years. Lateral cervical radiographs were acquired preoperatively and at 1- and 2-years postoperatively. Imaging was evaluated for adjacent level degeneration using the following criteria: disk height ratio (DHR) defined as the ratio of the disk height and the lower vertebrae height measured at level above and below; proximal junctional kyphosis (PJK); Kellgren and Lawrence osteoarthritis severity grade (KLOSG); and heterotopic ossification (HO). The results were compared with a repeated analysis of variance test and Bonferroni correction; P < 0.05 was considered significant. RESULTS: At 2 years postoperatively, there were no revision surgeries at the operated level or new surgeries at the adjacent levels. Of the 102 segments evaluated, ASDegeneration was identified at 21 levels cranial to and 21 levels caudal to the index level. At 2 years, new mild ASDegeneration signs developed at 3 levels: 1 in the level above and 2 in the level below the operated segment. In patients with pre-existing disk degeneration, mild progression of ASDegeneration signs developed in 6 upper and 2 lower segments. There were no significant changes in DHR and PJK in all patients; however, when patients with signs of ASDegeneration only were evaluated, a significant decrease of the DHR was found. The mean DHRs before surgery and 1 and 2 years after surgery in all patients were 44.0 ± 8.1, 44.0 ± 8.2, and 43.1 ± 8.4 (P = 0.1006) and in ASD patients were 43.8 ± 7.3, 41.9 ± 6.3, and 39.6 ± 8.3 (P = 0.0062), respectively. Overall, at 2 years postoperatively, ASDegeneration was identified in 9 patients (17.6% when compared with all evaluated patients before surgery). CONCLUSIONS: In the current study, 5.9% of subjects treated with posterior cervical cages placed bilaterally between the facet joints developed adjacent segment degeneration at 2 years. Mild progression of existing degeneration was observed in 11.8% of subjects. Further evaluation to establish long-term incidence is needed.

Pathophysiology of Minimally Invasive Surgical Approaches: Current Concepts.

Spine surgery is a continuously evolving field. Traditional posterior midline approaches to the lumbar spine are associated with muscle injury. Common mechanisms of injury include ischemia, denervation, and mechanical disruption of tendinous attachments of lumbar muscles. Muscle injury may be documented with chemical markers (creatinine kinase, aldolase, proinflammatory cytokines), by imaging studies, or with muscle biopsy. Minimally disruptive surgical approaches to the spine have the potential to minimize the trauma to muscular structures and thus improve the outcomes of surgery. The impact of minimally invasive spinal surgery on long-term clinical outcomes remains unknown. State-of-the-art pathophysiology of minimally invasive spine surgery is presented in this review.

Clinical and Radiographic Results of Indirect Decompression and Posterior Cervical Fusion for Single-Level Cervical Radiculopathy Using an Expandable Implant with 2-Year Follow-Up.

Background Indirect posterior cervical nerve root decompression and fusion performed by placing bilateral posterior cervical cages in the facet joints from a posterior approach has been proposed as an option to treat select patients with cervical radiculopathy. The purpose of this study was to report 2-year clinical and radiologic results of this treatment method. Methods Patients who failed nonsurgical management for single-level cervical radiculopathy were recruited. Surgical treatment involved a posterior approach with decortication of the lateral mass and facet joint at the treated level followed by placement of the DTRAX Expandable Cage (Providence Medical Technology, Lafayette, California, United States) into both facet joints. Iliac crest bone autograft was mixed with demineralized bone matrix and used in all cases. The Neck Disability Index (NDI), visual analog scale (VAS) for neck and arm pain, and SF-12 v.2 questionnaire were evaluated preoperatively and 2 years postoperatively. Segmental (treated level) and overall C2-C7 cervical lordosis, disk height, adjacent segment degeneration, and fusion were assessed on computed tomography scans and radiographs acquired preoperatively and 2 years postoperatively. Results Overall, 53 of 60 enrolled patients were available at 2-year follow-up. There were 35 females and 18 males with a mean age of 53 years (range: 40-75 years). The operated level was C3-C4 (N = 3), C4-C5 (N = 6), C5-C6 (N = 36), and C6-C7 (N = 8). The mean preoperative and 2-year scores were NDI: 32.3 versus 9.1 (p < 0.0001); VAS Neck Pain: 7.4 versus 2.6 (p < 0.0001); VAS Arm Pain: 7.4 versus 2.6 (p < 0.0001); SF-12 Physical Component Summary: 34.6 versus 43.6 (p < 0.0001), and SF-12 Mental Component Summary: 40.8 versus 51.4 (p < 0.0001). No significant changes in overall or segmental lordosis were noted after surgery. Radiographic fusion rate was 98.1%. There was no device failure, implant lucency, or surgical reinterventions. Conclusions Indirect decompression and posterior cervical fusion using an expandable intervertebral cage may be an effective tissue-sparing option in select patients with single-level cervical radiculopathy.