Risk of adjacent segment disease after 'topping-off' multi-level lumbar fusions with posterior dynamic stabilisers: an observational cohort study.

PURPOSE: To determine whether 'topping-off' lumbar fusions, using posterior dynamic stabilising devices (PDSs) with specific biomechanical parameters, reduces the risk of adjacent segment disease (ASD). METHODS: Survival analysis of two non-randomised cohorts, with or without 'topping-off' (T/O or NoT/O), compared the risk of further surgery for ASD following multi-level posterior lumbar interbody fusion (PLIF). The study sample comprised consecutive patients, aged 55 + years, with degenerative pathology at 2, 3 or 4 levels. The NoT/O cohort underwent surgery between August 1993 and September 2019 (n = 425) and the T/O cohort between September 2011 and September 2019 (n = 146). Comparison of ASD risk between cohorts used Cox proportional hazards (CPH) modelling and Kaplan-Meier survivorship analysis. RESULTS: Analysis was completed on 571 operations across 507 patients. Median follow-up was 63 months (range 0.3-196) and 37 months (range 1.7-98) for the NoT/O and T/O cohorts, respectively. Of 423 patients, 125 (29.6%) patients in the NoT/O cohort underwent further surgery for ASD and 16/145 (11.03%) in the T/O cohort. The hazard ratio (T/O: NoT/O) from the CPH model was 0.42 (95% CL: 0.24-0.74, P = 0.003). Mean annual incidence across the first 5 years was 5.0% in the NoT/O cohort compared with 2.8% in the T/O cohort (P = 0.029). No patient required surgery or developed ASD at a 'topped-off' level. Two patients developed asymptomatic pedicle screw loosening at the level of the PDS device. PROMs were similar between cohorts. CONCLUSION: This large, non-randomised, observational study found an approximately 60% reduction in further surgery for ASD with the use of the PDS to 'top-off' PLIF fusions. PDS device-related complications were very low.

Monitoring image guidance system accuracy during spinal surgery with mini-screw fiducials: technical note.

STUDY DESIGN: A technical note. OBJECTIVE: To describe a technique for measuring accuracy of intraoperative image guidance systems in spine surgery. SUMMARY OF BACKGROUND DATA: Image guidance may be of use when performing complex procedures on the spine. However, as the operation progresses and, in particular, once any deformity has been corrected, the image guidance system may become unreliable. In practice, this often results in repeated image acquisitions thus increasing the radiation exposure to the patient. METHODS: Small titanium, cranio-facial screws were placed on the dorsal aspect of the spine intraoperatively, before the acquisition of images and used as fiducials. RESULTS: The authors were able to accurately discern the true precision of the image guidance system used with an intraoperative computed tomography scanner, throughout the procedure. CONCLUSIONS: By using intraoperatively placed mini-screw fiducials, the surgeon may check and quantify the underlying system accuracy both initially and throughout the surgery. In the future, "auto-adjust" functions may be integrated into the computer software to automatically recalibrate the system when a probe is placed into the fiducials without the need for rescanning.

Lumbo-pelvic lordosis and the pelvic radius technique in the assessment of spinal sagittal balance: strengths and caveats.

INTRODUCTION: The two main methodologies described for the assessment of spinal sagittal alignment are the pelvic radius (PR) technique and that based on measures of the Pelvic Incidence (PI) and Spino-Sacral Angle (SSA). Both methods stress the fundamental relationship between the anatomical position and orientation of the sacrum within the pelvis and the spinal curves above. The aim of the current study was to assess the strengths and potential weaknesses of the PR technique. The PR technique uses measures based on a line (the PR), drawn between the hip axis and the posterior corner of the S1 endplate. The angle formed between the PR line and the sacral endplate, PRS1, is a developmental measure of sacropelvic morphology. Geometrically, PI and PRS1 are approximately complementary angles and both reflect reciprocal alterations in pelvic tilt (for PI) or angulation (for PRS1) and the slope of the S1 endplate. The angle formed between PR and T12, the PR-T12, reflects a combined measure of pelvic morphology and lumbar lordosis. It appears to be a useful measure, which provides a simple and rapid assessment of lumbopelvic sagittal balance, but only in the presence of a congruent thoracic curvature. MATERIALS AND METHODS: After reviewing the literature, published measures made using the PR technique were compared to measures taken from a substantial patient population (479 adult patients). CONCLUSIONS: Errors can occur using the PR technique if the PRT12 is viewed in isolation from the thoracic kyphosis. We found the ratio of the thoracic kyphosis to lumbar lordosis (T4-T12/T12-S1) to be a useful predictor of congruent sagittal alignment, which may alert the clinician to situations where use of the PR-T12 in isolation may be misleading.

Incidence and prevalence of surgery at segments adjacent to a previous posterior lumbar arthrodesis.

BACKGROUND CONTEXT: Adjacent segment disease (ASD) after lumbar spinal fusion has been an important reason behind the development of nonfusion stabilization technology. However, the incidence, prevalence, and factors contributing to adjacent segment degeneration in the lumbar spine remain unclear. A range of prevalence rates for ASD have been reported in the lumbar spinal literature, but the annual incidence has not been widely studied in this region. Conflicting reports exist regarding risk factors, especially fusion length. PURPOSE: To determine the annual incidence and prevalence of further surgery for adjacent segment disease (SxASD) after posterior lumbar arthrodesis and examine possible risk factors. STUDY DESIGN: Retrospective cohort study. PATIENT SAMPLE: Nine hundred twelve patients who underwent 1,000 consecutive posterior lumbar interbody fusion procedures, with mean follow-up duration of 63 months (range, 5 months-16 years). OUTCOME MEASURES: Further surgery for ASD or surgery-free survival. METHODS: A postal and telephone survey. Follow-up rate: 91% of patients. The annual incidence and prevalence of ASD requiring further surgery were determined using Kaplan-Meier survivorship analysis. Cox proportional-hazards (Cox) regression was used for multivariate analysis of possible risk factors. Significance was set at p<.05. RESULTS: Further surgery for ASD occurred following 130 of 1,000 or 13% of procedures at a mean time of 43 months (range, 2.3-162 months). The mean annual incidence of SxASD over the first 10 years, in all patients, was 2.5% (95% confidence interval [95% CI], 1.9-3.1) with prevalences of 13.6% and 22.2% at 5 and 10 years, respectively. Cox regression modeling found that the number of levels fused (p≤.0003), age of the patient, fusing to L5, and performing an additional laminectomy adjacent to a fusion all independently affect the risk of SxASD. The mean annual incidence figures in the first 10 years after a lumbar fusion were 1.7% (95% CI, 1.3-2.2) after fusion at single levels, 3.6% (2.1-5.2) after two levels, and 5.0% (3.3-6.7) after three and four levels. The 5- and 10-year prevalences were 9% and 16%, 17% and 31%, and 29% and 40% after single-, two-, and three-/four-level fusions, respectively. The risk of SxASD in patients younger than 45 years was one-quarter (95% CI, 10-64) the risk of patients older than 60 years (p=.003). A laminectomy adjacent to a fusion increases the relative risk by 2.4 times (95% CI, 1.1-5.2; p=.03). Stopping a fusion at L5 is associated with a 1.7-fold increased risk (95% CI, 1.2-2.4; p=.007) of SxASD compared with a fusion to S1, for fusions of the same length. CONCLUSION: The overall annual incidence and predicted 10-year prevalence of further surgery for ASD after lumbar arthrodesis were 2.5% and 22.2%, respectively. These rates varied widely depending on the identified risk factors. Although young patients who underwent single-level fusions were at low risk, patients who underwent fusion of three or four levels had a threefold increased risk of further surgery, compared with single-level fusions (p<.0001), and a predicted 10-year prevalence of 40%.

Health-related quality of life: a comparison of outcomes after lumbar fusion for degenerative spondylolisthesis with large joint replacement surgery and population norms.

BACKGROUND CONTEXT: Degenerative spine disease will become an increasing health problem, and a significant number of patients will be considered for surgery. Spinal surgeries have evolved since the last decades, and there is a positive impact on the clinical outcomes. Few works in the literature have reviewed the outcome compared with large joint replacement surgery, which is considered a benchmark for operative restoration of patients' quality of life. PURPOSE: The purpose of this study was to investigate if spinal fusion can return patients' health-related quality of life to that of age-matched population norms and yield outcomes comparable with those of total hip and knee joint replacement. STUDY DESIGN: This is a prospective cohort study. PATIENT SAMPLE: The sample consists of 100 consecutive patients who were enrolled between December 1997 and January 2007. OUTCOME MEASURES: The 12-item Short Form Health Survey (SF-12) was chosen for outcome measurement. METHODS: All patients underwent wide decompressive laminectomy and single-level posterior lumbar interbody fusion for spinal stenosis associated with degenerative spondylolisthesis. RESULTS: The preoperative and postoperative physical component summary (PCS)-12 scores of the spinal fusion patients were comparable with those of both the total knee and hip replacement patients. The mean improvement in PCS-12 scores after spine surgery was 11 (95% confidence interval [CI]: 9-14, p<.0001). It was equal to that after total hip replacement surgery, which was 11 (95% CI: 9-13), and higher than that of total knee replacement patients, which had an improvement of 8 (95% CI: 7-9). The postoperative mean and 95% CI of the PCS-12 scores for the three surgical procedures approached the population norm value of 44 (95% CI: 43-46).There was no statistical difference between the postoperative mental component summary-12 score among all the three surgical groups, which approached similar to the population norm value of 54 (95% CI: 53-54). CONCLUSIONS: The current study demonstrated that spinal surgery can return patients' HRQL to that of age-matched population norms and yield outcomes comparable with those of total hip and knee joint replacement patients.

Atlantoaxial stabilization using multiaxial C-1 posterior arch screws.

The authors present a novel technique of atlantoaxial fixation using multiaxial C-1 posterior arch screws. The technique involves the insertion of bilateral multiaxial C-1 posterior arch screws, which are connected by crosslinked rods to bilateral multiaxial C-2 pars screws. The clinical results are presented in 3 patients in whom anomalies of the vertebral arteries, C-1 lateral masses, and/or posterior arch of C-1 presented difficulty using existing fixation techniques with transarticular screws, C-1 lateral mass screws, or posterior wiring. The C-1 posterior arch screws achieved solid fixation and their insertion appeared to be technically less demanding than that of transarticular or C-1 lateral mass screws. This technique may reduce the risk of complications compared with existing techniques, especially in patients with anatomical variants of the vertebral artery, C-1 lateral masses, or C-1 posterior arch. This technique may prove to be an attractive fixation option in patients with normal anatomy.

Segmental malalignment with the Bryan cervical disc prosthesis--contributing factors.

Part 1 of the current study found that use of the Bryan Cervical Disc prosthesis resulted in a median loss of 2 degrees in functional spinal unit (FSU) lordosis when compared with preoperative imaging (P<0.0001, range: 8-degree loss to 5-degree gain). The observed changes were generally small but varied among both the patients and the surgeons, suggesting that variables may exist which affect postoperative sagittal alignment. The aim of the current study was to identify which, if any, of a range of patient and surgical variables may contribute significantly to postoperative FSU malalignment. The change in FSU angulation between the preoperative and postoperative neutral, erect x-rays of 67 consecutive patients (88 disc levels) were correlated with 35 demographic and radiographic variables. Postoperative change in disc space height, angle of prosthesis insertion, and the amount of bone removed from the anterior aspect of the cephalad vertebra varied significantly among the 3 surgeons and correlated with change in FSU alignment. Intraoperative disc space distraction correlated with subsequent loss of disc space height. Multiple linear regression analysis confirmed that loss of disc space height and angle of prosthesis insertion contributed independently to a model with a coefficient of determination of 0.39 (P<0.0001). Attempts to identify factors contributing to change in alignment have not shown any single factor to be wholly responsible. Although the prescribed surgical technique is relatively standardized, it seems likely that a number of surgical variables, particularly those leading to loss of disc space height and affecting annular tension are important.

Segmental malalignment with the Bryan Cervical Disc prosthesis--does it occur?

The early clinical results with the Bryan Cervical Disc prosthesis are encouraging but 2 recent small published series have noted postoperative radiologic kyphosis of the functional spinal unit (FSU) of 4 and 6 degrees. The current study was undertaken to accurately assess the extent of any sagittal deformity after the use of this prosthesis in a substantial, multisurgeon case series. The neutral, erect x-rays of 67 consecutive patients (88 disc levels) operated by one of 3 surgeons, were examined using manual and digital image analysis techniques for FSU sagittal angulation (lordosis), prosthesis shell angulation, segmental olisthesis, and overall cervical alignment. Measurement accuracy was confirmed using interobserver and intraobserver studies. There was a median loss of 2 degrees in FSU lordosis when compared with preoperative imaging (P<0.0001, range: 8-degree loss to 5-degree gain). A median 2 degrees of prosthesis shell kyphosis also occurred (range: 15-degree kyphosis to 12-degree lordosis) but shell angulation correlated weakly with the change in FSU lordosis (rs=0.37, P=0.001). There was a significant difference in the median loss of FSU lordosis between surgeon 1 and surgeons 2 and 3 (3.5 degrees vs. 2 degrees, P=0.005). Median olisthesis of the prosthesis shells was -0.1 mm (range: +1.5 to -2.5 mm). Median postoperative overall cervical lordosis reduced by 4 degrees (P<0.004). A small loss in median FSU lordosis was observed after insertion of the Bryan disc. The observed changes were generally small but varied among both the patients and the surgeons, suggesting that variables may exist which contribute to postoperative sagittal alignment. These are the subject of an accompanying study.

Complications with cervical arthroplasty.

OBJECT: Spinal arthroplasty is becoming more widely performed in the treatment of degenerative cervical disc disease. Although this new technology may offer benefits over arthrodesis, it also requires that the surgeon acquire new operative techniques, and new potential complications are introduced. To determine the incidence and distribution of perioperative complications, the authors analyzed their early data obtained in a series of patients treated with the Bryan Cervical Disc prosthesis. METHODS: The authors prospectively recorded operative data, complications, and clinical and radiographic outcome data in all patients treated with Bryan prosthesis-based arthroplasty at two tertiary care centers since 2001. Patients underwent standard anterior cervical discectomy followed by one- to three-level arthroplasty. Ninety-six discs were implanted in 74 patients. The perioperative complication rate was 6.2% per treated level. In one patient a retropharyngeal hematoma developed, requiring evacuation. Neurological worsening occurred in three patients. Intraoperative migration of the prosthesis was observed in one two-level case, whereas delayed migration occurred in one patient with postoperative segmental kyphosis. In another patient with severe postoperative segmental kyphosis, revision was required with a customized lordotic prosthesis. Heterotopic ossification and spontaneous fusion occurred in two cases; motion was preserved in the remaining 94 prostheses. Partial dislocation of the prosthesis in extension occurred in one patient with preoperative segmental hypermobility, the first reported failure of a Bryan prosthesis. Twenty-five percent of patients reported neck and shoulder pain during the late follow-up period. There was a trend toward increased kyphosis of the C2-7 curvature postoperatively. CONCLUSIONS: The Bryan prosthesis was effective in maintaining spinal motion. Major perioperative and device-related complications were infrequent.

Similarities and differences in the treatment of spine trauma between surgical specialties and location of practice.

STUDY DESIGN: Questionnaires administered to practicing orthopedic and neurosurgical spine surgeons from various regions of the United States and abroad. OBJECTIVES: To determine similarities and differences in the treatment of spinal trauma. SUMMARY OF BACKGROUND DATA: Spinal trauma is generally referred to subspecialists of orthopedic or neurosurgical training. Prior studies have suggested that there is significant variability in the management of such injuries. METHODS: Questionnaires based on eight clinical scenarios of commonly encountered cervical, thoracic, and lumbar injuries were administered to 35 experienced spinal surgeons. Surgeons completed profile information and answered approximately one dozen questions for each case. Data were analyzed with SPSS software to determine the levels of agreement and characteristics of respondents that might account for a lack of agreement on particular aspects of management. RESULTS: Of the 35 surgeons completing the questionnaire, 63% were orthopedists, 37% were neurosurgeons, and 80% had been in practice for more than 5 years. Considerable agreement was found in the majority of clinical decisions, including whether or not to operate and the timing of surgery. Of the differences noted, neurosurgeons were more likely to obtain a MRI, and orthopedists were more likely to use autograft as a sole graft material. Physicians from abroad were, in general, more likely to operate and to use an anterior approach during surgery than physicians from the northeastern United States. CONCLUSIONS: More commonalities were identified in the management of spinal trauma than previously reported. When found, variability in opinion was related to professional and regional differences.

Use of the ophthalmic phacoemulsification instrument for tumors of the spinal cord: report of seven cases.

In this retrospective cohort study, we examined the safety, efficacy, and benefits of utilizing the readily available ophthalmic phacoemulsification instrument for the surgery of seven intramedullary spinal cord tumors. Historically, the conventional neurosurgical ultrasonic aspirator was an adaptation of the original Cavitron Phaco-Emulsifier aspirator used in cataract surgery. The ophthalmic instrument has a 1.0-mm internal diameter operating tip. This is much smaller and provides improved visualization and surgical control when compared with the conventional neurosurgical instrument, which has a tip diameter of 3-4 mm. A satisfactory surgical and clinical outcome was achieved in all seven patients with safe and substantial subtotal excision of their tumors. We found the ophthalmic instrument provided excellent visualization and precision in operating on cases of intramedullary spinal cord tumor.

Effects of a cervical disc prosthesis on segmental and cervical spine alignment.

OBJECT: Cervical arthroplasty offers the promise of maintaining motion of the functional spinal unit (FSU) after anterior cervical discectomy. The impact of cervical arthroplasty on sagittal alignment of the FSU needs to be addressed, together with its effect on overall sagittal balance of the cervical spine. METHODS: The authors prospectively reviewed radiographic and clinical outcomes in 14 patients who received the Bryan Cervical Disc prosthesis (Medtronic Sofamor Danek, Memphis, TN), for whom early (< 6 months) and late (6-24 months) follow-up data were available. Static and dynamic radiographs were measured by hand and computer to determine the angles formed by the endplates of the natural disc preoperatively, those formed by the shells of the implanted prosthesis, the angle of the FSU, and the C2-7 Cobb angle. The range of motion (ROM) was also determined radiographically, whereas clinical outcomes were assessed using the Neck Disability Index (NDI), and Short Form-36 (SF-36) questionnaires. The ROM was preserved following surgery, with a mean preoperative sagittal rotation angle of 8.96 degrees , which was not significantly different from the late postoperative value of 8.25 degrees . When compared with the preoperative disc space angle, the shell endplate angle in the neutral position became kyphotic in the early and late postoperative periods (mean change -3.8 degrees in the late follow-up period; p = 0.0035). The FSU angles also became significantly more kyphotic postoperatively, with a mean change of -6 degrees (p = 0.0006). The Cobb angles varied widely preoperatively and did not change significantly after surgery. There was no statistical correlation between the NDI and SF-36 outcomes and cervical kyphosis. CONCLUSIONS: Cervical arthroplasty preserves motion of the FSU. Both the endplate angle of the treated disc space and the angle of the FSU became kyphotic after insertion of the Bryan prosthesis. The overall sagittal balance of the cervical spine, however, was preserved.