Differences in the Exposure of the Lumbar Nerve Root Between Experts and Novices: Results From a Realistic Simulation Pilot Study With Force Sensors.

STUDY DESIGN: Nonrandomized prospective trial. OBJECTIVE: Several studies could demonstrate "learning curves" in almost every single surgical procedure for unexperienced surgeons. This is in sharp contrast to the rising quality requirements in public health care to provide surgical training at patients "expense." The aim of this study was to visualize, measure, and set a baseline of the pressure load on the spinal nerve root during a simulated microdiscectomy on a standardized and validated model (RealSpine) under the influence of the level of surgical experience and individual skills. METHODS: Five highly experienced spine surgeons and 5 trainees without considerable surgical experience were selected to perform a standardized microsurgical discectomy on a validated RealSpine simulator. Force-torque sensors were integrated in this simulator to measure the load on the nerve root. The forces were recorded every 125 ms. RESULTS: We could identify cumulative for the total intervention as well as for defined single surgical steps of this procedure and as well in between the single subjects a significant higher tension and contusion forces on the nerve for the trainee group (Δp contusion 83-765 Ncs and Δp tension 159-1131 Ncs for the trainees. Δp contusion 16-171 Ncs and Δp tension 27-146 Ncs for the experts). CONCLUSION: We could measure a difference between unexperienced and experienced surgeons regarding the manipulations of the nerve root during a standardized simulated microdiscectomy. This possibility could be the starting point for a new and innovative surgical education to improve outcome without negative side effects of "learning curves."

Mid- to long-term results of total lumbar disc replacement: a prospective analysis with 5- to 10-year follow-up.

BACKGROUND CONTEXT: The role of fusion of lumbar motion segments for the treatment of intractable low back pain (LBP) from degenerative disc disease (DDD) without deformities or instabilities remains controversially debated. Total lumbar disc replacement (TDR) has been used as an alternative in a highly selected patient cohort. However, the amount of long-term follow-up (FU) data on TDR is limited. In the United States, insurers have refused to reimburse surgeons for TDRs for fear of delayed complications, revisions, and unknown secondary costs, leading to a drastic decline in TDR numbers. PURPOSE: To assess the mid- and long-term clinical efficacy as well as patient safety of TDR in terms of perioperative complication and reoperation rates. STUDY DESIGN/SETTING: Prospective, single-center clinical investigation of TDR with ProDisc II (Synthes, Paoli, PA, USA) for the treatment of LBP from lumbar DDD that has proven unresponsive to conservative therapy. PATIENT SAMPLE: Patients with a minimum of 5-year FU after TDR, performed for the treatment of intractable and predominant (≥80%) axial LBP resulting from DDD without any deformities or instabilities. OUTCOME MEASURES: Visual analog scale (VAS), Oswestry Disability Index (ODI), and patient satisfaction rates (three-scale outcome rating); complication and reoperation rates as well as elapsed time until revision surgery; patient's professional activity/employment status. METHODS: Clinical outcome scores were acquired within the framework of an ongoing prospective clinical trial. Patients were examined preoperatively, 3, 6, and 12 months postoperatively, annually from then onward. The data acquisition was performed by members of the clinic's spine unit including medical staff, research assistants, and research nurses who were not involved in the process of pre- or postoperative decision-making. RESULTS: The initial cohort consisted of 201 patients; 181 patients were available for final FU, resembling a 90.0% FU rate after a mean FU of 7.4 years (range 5.0-10.8 years). The overall results revealed a highly significant improvement from baseline VAS and ODI levels at all postoperative FU stages (p<.0001). VAS scores demonstrated a slight (from VAS 2.6 to 3.3) but statistically significant deterioration from 48 months onward (p<.05). Patient satisfaction rates remained stable throughout the entire postoperative course, with 63.6% of patients reporting a highly satisfactory or a satisfactory (22.7%) outcome, whereas 13.7% of patients were not satisfied. The overall complication rate was 14.4% (N=26/181). The incidence of revision surgeries for general and/or device-related complications was 7.2% (N=13/181). Two-level TDRs demonstrated a significant improvement of VAS and ODI scores in comparison to baseline levels (p<.05). Nevertheless, the results were significantly inferior in comparison to one-level cases and were associated with higher complication (11.9% vs. 27.6%; p=.03) and inferior satisfaction rates (p<.003). CONCLUSIONS: Despite the fact that the current data comprises the early experiences and learning curve associated with a new surgical technique, the results demonstrate satisfactory and maintained mid- to long-term clinical results after a mean FU of 7.4 years. Patient safety was proven with acceptable complication and reoperation rates. Fear of excessive late complications or reoperations following the primary TDR procedure cannot be substantiated with the present data. In carefully selected cases, TDR can be considered a viable treatment alternative to lumbar fusion for which spine communities around the world seem to have accepted mediocre clinical results as well as obvious and significant drawbacks.

Influence of lumbar intervertebral disc degeneration on the outcome of total lumbar disc replacement: a prospective clinical, histological, X-ray and MRI investigation.

INTRODUCTION: The role of fusion of lumbar motion segments for the treatment of axial low back pain (LBP) from lumbar degenerative disc disease (DDD) without any true deformities or instabilities remains controversially debated. In an attempt to avoid previously published and fusion-related negative side effects, motion preserving technologies such as total lumbar disc replacement (TDR) have been introduced. The adequate extent of preoperative DDD for TDR remains unknown, the number of previously published studies is scarce and the limited data available reveal contradictory results. The goal of this current analysis was to perform a prospective histological, X-ray and MRI investigation of the index-segment's degree of DDD and to correlate these data with each patient's pre- and postoperative clinical outcome parameters from an ongoing prospective clinical trial with ProDisc II (Synthes, Paoli, U.S.A.). MATERIALS AND METHODS: Nucleus pulposus (NP) and annulus fibrosus (AF) changes were evaluated according to a previously validated quantitative histological degeneration score (HDS). X-ray evaluation included assessment of the mean, anterior and posterior disc space height (DSH). MRI investigation of DDD was performed on a 5-scale grading system. The prospective clinical outcome assessment included visual analogue scale (VAS), Oswestry Disability Index (ODI) scores as well as the patient's subjective satisfaction rates. RESULTS: Data from 51 patients with an average follow-up of 50.5 months (range 6.1-91.9 months) were included in the study. Postoperative VAS and ODI scores improved significantly in comparison to preoperative levels (p < 0.002). A significant correlation and interdependence was established between various parameters of DDD preoperatively (p < 0.05). Degenerative changes of NP tissue samples were significantly more pronounced in comparison to those of AF material (p < 0.001) with no significant correlation between each other (p > 0.05). Preoperatively, the extent of DDD was not significantly correlated with the patient's symptomatology (p > 0.05). No negative influence was associated with increasing stages of DDD on the postoperative clinical outcome parameters following TDR (p > 0.05). Increasing stages of DDD in terms of lower DSH scores were not associated with inferior clinical results as outlined by postoperative VAS or ODI scores or the patient's subjective outcome evaluation at the last FU examination (p > 0.05). Conversely, some potential positive effects on the postoperative outcome were observed in patients with advanced stages of preoperative DDD. Patients with more severe preoperative HDS scores of NP samples demonstrated significantly lower VAS scores during the early postoperative course (p = 0.02). CONCLUSION: Increasing stages of DDD did not negatively impact on the outcome following TDR in a highly selected patient population. In particular, no preoperative DDD threshold value was identified from which an inferior postoperative outcome could have been deduced. Conversely, some positive effects on the postoperative outcome were detected in patients with advanced stages of DDD. Combined advantageous effects of progressive morphological structural rigidity of the index segment and restabilizing effects from larger distraction in degenerated segments may compensate for increasing axial rotational instability, one of TDR's perceived disadvantages. Our data reveal a "therapeutic window" for TDR in a cohort of patients with various stages of DDD as long as preoperative facet joint complaints or degenerative facet arthropathies can be excluded and stringent preoperative decision making criteria are adhered to. Previously published absolute DSH values as contraindication against TDR should be reconsidered.

The fate of facet joint and adjacent level disc degeneration following total lumbar disc replacement: a prospective clinical, X-ray, and magnetic resonance imaging investigation.

STUDY DESIGN: Prospective clinical, x-ray, and magnetic resonance imaging investigation following total lumbar disc replacement (TDR) with ProDisc II (Synthes, Paoli, PA). OBJECTIVE: To examine the progression of adjacent level degeneration (ALD), facet joint degeneration (FJD) as well as associated risk factors following TDR. SUMMARY OF BACKGROUND DATA: Fusion procedures have been associated with adjacent level morbidities and facet joint pathologies in a considerable number of patients. Whether the incidence of these negative side effects can be reduced with TDR remains unestablished. METHODS: Clinical outcome scores Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) and patient satisfaction rates were acquired within the framework of an ongoing prospective study with ProDisc II. The mean index-level ROM was established for every patient over the entire postoperative period from multiple flexion/extension x-ray images. The progression of ALD and FJD was evaluated from pre- and postoperative magnetic resonance images by 2 independent radiologists. RESULTS: Results from 93 patients with an average follow-up of 53.4 months (range, 24.1-98.7 months) were included in this study. The overall results revealed a significant improvement from preoperative VAS and ODI levels (P < 0.0001).The incidence of ALD was 10.2% (n = 11/108 levels). The degenerative changes were mild and occurred late after surgery (mean, 65.2 months; range, 37.9-85.6 months). There was no significant correlation between index-level ROM and the occurrence of ALD (P > 0.05).Progression of FJD was observed in 20.0% of all facet joints (n = 44/220). FJD occurred significantly more often following TDR at the lumbosacral junction in comparison to the level above the lumbosacral junction (P < 0.02) and was observed more frequently at index-levels than at nonindex levels (P < 0.001).The degenerative changes were associated with a negative influence on postoperative outcome parameters VAS and ODI (P < 0.03) that were already detected early after surgery. The mean postoperative ROM was significantly lower in patients with progression of FJD in comparison to the remaining cohort (P < 0.0001). CONCLUSION: TDR proved to have a beneficial effect with respect to adjacent level disc preservation. The degenerative changes were mild, occurred late after surgery and did not reveal a negative effect on postoperative clinical outcome. There was no significant correlation between index-level ROM and the occurrence of ALD (P > 0.05).TDR was, however, associated with a progression of index-level FJD in a considerable number of patients, particularly at the lumbosacral junction. Lower segmental mobility and less favorable clinical results point to the fact that a particular cohort of patients may predominantly be affected in which TDR shows inferior compatibility with the index-segment's biomechanics.

Interdependence between disc space height, range of motion and clinical outcome in total lumbar disc replacement.

STUDY DESIGN: Clinical and radiologic assessment obtained from an ongoing prospective trial following total lumbar disc replacement (TDR) with ProDisc II. OBJECTIVE: To analyze the interaction between the parameters of disc space height (DSH), range of motion (ROM) and clinical outcome scores following TDR. SUMMARY OF BACKGROUND DATA: The interdependence between DSH, ROM and the clinical symptomatology has been well documented for patients with degenerative disc disease, fusion candidates and healthy control subjects. In the case of TDR, previously published data show conflicting results. METHODS: All TDRs were performed monosegmentally at L4/5 or L5-S1. The clinical outcome assessment included the patient's subjective outcome evaluation, Visual Analogue Scale, and Oswestry Disability Index scores (ODI). The radiologic evaluation included measurement of the mean, anterior and posterior DSH, as well as the ROM. The parameters were correlated pre- and postoperatively with each other. RESULTS: Data from 62 patients with an average follow-up of 42.4 months (range: 24.2-77.6 months) were included in this study. Visual Analogue Scale and ODI scores showed a significant and maintained improvement in comparison to preoperative levels (P < 0.0001). The DSH increased from 5.7 mm (range: 2-11.3 mm) to 11.2 mm (range: 8-13.4 mm), whereas ROM decreased from 8.1 degrees (range: 0 degrees-23.1 degrees) to 5.1 degrees (range: 0 degrees-12.8 degrees). This loss in ROM was significant following TDR at L5-S1 (P < 0.01). Preoperative DSH and ROM were positively correlated with postoperative segmental ROM (r = 0.45, P < 0.002 and r = 0.35, P < 0.01). The highest satisfaction rates were observed in the group of patients with the smallest preoperative DSH of < 4.5 mm (P < 0.024). CONCLUSION: A significant interdependence was observed between the parameters DSH, ROM and the clinical outcome following TDR. Whilst the DSH is restored, TDR leads to a significant decrease in postoperative ROM, particularly at the lumbosacral junction. Higher preoperative DSH and ROM revealed a beneficial effect on the postoperative segmental mobility. The subjective outcome evaluation indicates that TDR is a viable treatment option even in advanced stages of degenerative disc disease in the absence of other contraindications, in particular facet joint arthropathies.