The purpose of this research was to determine the feasibility of radiostereometric analysis (RSA) as a diagnostic tool for assessing non-union following spinal arthrodesis procedures. Further, to estimate clinical thresholds for precision and accuracy of the proposed method in the cervical and lumbar spine. A three-level lumbo-sacral and a four-level cervical posterior arthrodesis procedures were performed on an artificial spine model (Sawbones, WA). Using a spring loaded inserter (RSA Biomedical, Sweden), eight to ten RSA markers were placed within each of the L4 and L5 segments in the spinous process (L4 only), lamina, transverse processes, posterior and anterior (down the pedicle) wall of the vertebral body. Eight to ten markers were placed within the proximal sacrum (S1) at the medial and lateral crests, tuberosity, and within the sacral canal wall. Four to eight RSA markers were placed into the C3-C6 lateral masses. Titanium screws and rods were applied to the spinal segments. Identical procedures were then performed on a cadaveric spine using similar bead placement and hardware. RSA imaging consisted of 12 double exams (24 exams) of the cervical and lumbar regions for both the Sawbones and cadaveric spine to assess precision of measurement under zero-displacement conditions. The most distal vertebrae were considered the datum against which the movement of all other vertebrae was compared. The artificial spine was then dismantled for accuracy assessment in which the middle vertebrae (L5 and C4-C5) were moved relative to the superior (L4 and C3) and inferior (S1 and C6) vertebrae by known, incremental displacements on an imaging phantom device. Displacements occurred along the superior-inferior, anterior-posterior, and flexion-extension (rotational) axes of motion. RSA images were obtained at each displacement. Image analysis was performed using model-based software (RSACore v3.41, Leiden, Netherlands) to visualize implanted RSA beads in 3-D space. Precision was defined as the 95% confidence interval of error in measuring zero-displacement. Accuracy was defined as the mean difference (with 95% confidence interval) between the known and measured displacement. The rate of RSA bead detection was high with 5–8 implanted beads being visible in both the lumbar and cervical regions of the artificial and cadaveric spines. Translational RSA precision for both spines was better than 0.25 mm and 0.82 mm for the lumbar and cervical regions, respectively. Rotational precision was better than 0.40° and 1.9° for the lumbar and cervical regions, respectively. RSA accuracy for the artificial spine overall demonstrated less than 0.11 mm translational bias (margin < ±0.02 mm) and less than 0.22° rotational bias (margin < ±0.15°). This study demonstrates that RSA achieves sufficient precision and accuracy to detect intervertebral micromotion for the purpose of assessing arthrodesis. Well dispersed RSA bead placement is critical to achieving sufficient accuracy as well as avoiding occlusion by metal hardware. Cervical bead implantation is particularly sensitive to bead clustering due to small vertebrae size and proximity to critical structures. The results of this work will aid in the development of a clinical study to assess arthrodesis in patients.
There is evidence that preoperative physical fitness impacts surgical outcomes, specifically preceding abdominal, cardiovascular and spine surgery. To our knowledge, there are no papers on self-reported exercise frequency as a predictor of cervical spine surgery outcomes. Our objectives were to quantify self-report of exercise frequency in cervical spine surgery patients, and to elucidate if self-reported exercise prior to surgery confers less pain, improved health state and/or less disability post-surgery. We performed a retrospective review of prospectively collected data from the Canadian Spine Outcomes and Research Network (CSORN) Database from the time of its inception. Inclusion criteria specified all elective cervical surgery patients over 18 years old with degenerative pathology who proceeded to surgery and completed the pre- and post-operative outcomes measures up to 24 months post surgery (n=460). Outcome measures were visual analog scales (VAS) for neck and arm pain, Neck Disability Index (NDI), and EuroQOL score at baseline and 3, 12 and 24 months post-op. Exercise frequency was self-reported as “none” (n=212) versus “some” (n=248). These groups were further categorized into “none due to physical limitations”, “none” (not due to physical limitations), those to exercised “once or less per week” and those that exercised “twice or more per week”. Student's t-tests were used to compare the mean scores of the outcome measures, and analysis of variance for subgroup comparisons, with results considered significant at p < 0 .05. At baseline, 56% of total patients reported exercise prior to surgery, of which 73% reported doing so twice or more per week. Of the 44% reporting no exercise, 74% could not exercise due to physical limitations. Those who reported “some” exercise had more favorable VAS neck and arm pain scores pre-operatively (neck: 5.55 vs 6.11, p < 0 .001) (arm: 5.69 vs 6.04, p=0.011), but no difference at 3 and 24 months post-operatively. Significantly lower NDI scores and higher EuroQOL Index scores were seen in the exercise group compared to the no exercise group pre-operatively (NDI: 39 vs 48, p < 0 .001) (EuroQOL: 0.60 vs 0.50 p < 0 .001) as well as at 3, 12, and 24 months post-op (NDI: 24 vs 31, p=0.007) (EuroQOL: 0.75 vs 0.68, p=0.001). Further subgroup analysis demonstrated that compared to the “no exercise due to physical limitation” group, the “twice or more” exercise group showed favorable NDI and EuroQOL scores up to 24 months post-op (NDI: 24.32 vs 32.33, p=0.001) (EuroQOL: 0.76 vs 0.66, p=0.001), whereas the “once or less times per week” group no longer demonstrated any significant difference at 24 months (NDI: 28.79 vs 32.33, p=1) (EuroQOL: 0.73 vs 0.66, p=0.269). Self-reported exercise prior to cervical spine surgery does not predict improved long-term neck and arm pain at 2 years post-op. However, self-reported exercise does demonstrate less disability and improved health state at baseline and up to 2 years post-op and this relationship is dose dependent.
This research determines the feasibility of radiostereometric analysis (RSA) as a diagnostic tool for assessing fusion following spinal arthrodesis. Further, to estimate clinical thresholds for precision and accuracy of the proposed method in the cervical and lumbar spine. Two-level lumbo-sacral and three-level cervical posterior arthrodesis procedures were performed on an artificial spine model and a cadaveric spine (Figure 1). Using a spring-loaded inserter, RSA marker beads were placed within each of the L4-S1 and C3-C6 vertebrae, then analyzed for optimal bead distribution and detection. RSA imaging consisted of 12 double exams (24 exams) of the cervical and lumbar regions for both the Sawbones and cadaveric spine to assess precision of measurement under zero-displacement conditions, defined as the 95% confidence interval of error. Accuracy assessment was performed on the Sawbones model in which the middle vertebrae (L5 and C4-C5) were moved relative to the superior (L4 and C3) and inferior (S1 and C6) vertebrae by known, incremental displacements (Figure 2). RSA images were obtained at each displacement (Figure 3). Accuracy was defined as the mean difference between known and measured displacements.Introduction
Methods
Although patient-reported outcomes (PROs) have become increasingly important in the evaluation of spine surgery patients, interpretability may be limited by a patient's ability to recall pre-intervention impairment. The accuracy of patient recall of preoperative back pain, leg pain, and disability after spine surgery remains unknown. We sought to characterise the accuracy of patient recall of preoperative symptoms in a cohort of lumbar spine surgery patients. We analysed consecutive patients undergoing lumbar decompression or decompression and fusion for lumbar radiculopathy by a single surgeon over a four-year period. Using standardised questionnaires, we recorded back and leg numeric pain scores (NPS) and Oswestry Disability Indices (ODI) preoperatively and asked patients to recall their preoperative status at a minimum of one-year following surgery. We then statistically compared and characterised patient recall of their pre-operative status and their actual pre-operative status. Patients with incomplete follow up or diagnoses other than degenerative lumbar stenosis were excluded. Sixty-seven patients with a mean age of 66.1 years (55% female) were included in the final analysis. All cases were either posterior or combined anterior/ posterior procedures. Mean levels of surgery was 1.7 and 93.8% of all cases were instrumented. Mean duration of preoperative symptoms was 44.5 months (3.7 years). Preoperative vs postoperative PROs improved with regards to NPS back (5.2 vs 2.2, p= to 2 point difference), exceeding the minimal clinical important difference (MCID) for NPS. This pattern was maintained across age, gender, and duration of preoperative symptoms. We also observed cases of symptom minimisation recall bias, and cases in which back and leg pain predominance were switched in severity during recall bias. Significant recall bias of preoperative symptoms exists in patients undergoing spine surgery, potentially limiting accurate assessment and interpretation of PROs. An understanding of PROs and their limitations is essential to assess treatment efficacy of spinal procedures.
