A New Navigational Tool for Pedicle Screw Placement in Patients With Severe Scoliosis: A Pilot Study to Prove Feasibility, Accuracy, and Identify Operative Challenges.

STUDY DESIGN: Pilot study. OBJECTIVE: To develop and validate the feasibility and accuracy of a newly designed navigational spinal instrument guiding tool for patient-matched thoracic and lumbar pedicle screw placement in patients with severe scoliosis, and to identify intraoperative challenges that may be relevant. SUMMARY OF BACKGROUND DATA: Pedicle screw placement is challenging in severely rotated scoliotic spine with small diameters and asymmetrical shape of the pedicles and vertebrae. Patient-specific drill/positioning guides with preplanned trajectory have been developed as a promising solution in spinal surgery for precise screw insertion. METHODS: In 4 patients with severe scoliosis, navigational templates and models of all vertebrae to be instrumented were manufactured using a computed tomography (CT)-based 3-dimensional model of the thoracic and lumbar spine. The guides were designed differently for thoracic and lumbar segments according to the individual anatomy to achieve an optimal coupling to the surface of the patient's spine, to maximize the stability of the device itself, and to increase user friendliness for the complete screw positioning process. Intraoperative challenges and opportunities for device and process improvements regarding the handling of the guides during the surgery were recorded. Postoperatively, the intrapedicular screw positions were evaluated versus the preoperative plan and evaluated for cortical violation based on CT scans. RESULTS: A total of 76 pedicle screws were implanted (56 thoracic, 20 lumbar). Two screws (2.6%) were assessed to be misplaced intraoperatively and repositioned. Eighty-four percent of the pedicle screws were completely intrapedicular, 96.1% within <2 mm cortical breech. CT scans did not demonstrate medial pedicle violation, or misplaced screw contact to neurovascular structures. No screw-related clinical complaints were reported postoperatively. CONCLUSIONS: The new custom-made positioning guide is a feasible navigational tool that permits a safe and accurate implantation of pedicle screws in patients with severe scoliosis.

ALIF and total disc replacement versus 2-level circumferential fusion with TLIF: a prospective, randomized, clinical and radiological trial.

STUDY DESIGN: Prospective, randomized trial. PURPOSE: The treatment of degenerative disc disease (DDD) with two-level fusion has been associated with a reasonable rate of complications. The aim of the present study was to compare (Hybrid) stand-alone anterior lumbar interbody fusion (ALIF) at L5/S1 with total disc replacement at L4/5 (TDR) as an alternative surgical strategy to (Fusion) 2-level circumferential fusion employing transforaminal lumbar interbody fusion (TLIF) with transpedicular stabilization at L4-S1. METHODS: A total of 62 patients with symptomatic DDD of segments L5/S1 (Modic ≥2°) and L4/5 (Modic ≤2°; positive discography) were enrolled; 31 were treated with Hybrid and 31 with Fusion. Preoperatively, at 0, 12, and a mean follow-up of 37 months, clinical (ODI, VAS) and radiological evaluations (plain/extension-flexion radiographs evaluated for implant failure, fusion, global and segmental lordosis, and ROM) were performed. RESULTS: In 26 of 31 Hybrid and 24 of 31 Fusion patients available at the final follow-up, we found a significant clinical improvement compared to preoperatively. Hybrid patients had significantly lower VAS scores immediately postoperatively and at follow-up compared to Fusion patients. The complication rates were low and similar between the groups. Lumbar lordosis increased in both groups. The increase was mainly located at L4-S1 in the Hybrid group and at L1-L4 in the Fusion group. Hybrid patients presented with increased ROM at L4/5 and L3/4, and Fusion patients presented with increased ROM at L3/4, with significantly greater ROM at L3/4 compared to Hybrid patients at follow-up. CONCLUSIONS: Hybrid surgery is a viable surgical alternative for the presented indication. Approach-related inferior trauma and the balanced restoration of lumbar lordosis resulted in superior clinical outcomes compared to two-level circumferential fusion with TLIF.

Postoperative posterior lumbar muscle changes and their relationship to segmental motion preservation or restriction: a randomized prospective study.

OBJECTIVE: To date, it remains unclear whether the preservation of segmental motion by total disc replacement (TDR) or motion restriction by stand-alone anterior lumbar interbody fusion (ALIF) have an influence on postoperative degeneration of the posterior paraspinal muscles or the associated clinical results. Therefore, the purpose of the present prospective randomized study was to evaluate the clinical parameters and 3D quantitative radiological changes in the paraspinal muscles of the lumbar spine in surgically treated segments and superior adjacent segments after ALIF and TDR. METHODS: A total of 50 patients with chronic low-back pain caused by single-level intervertebral disc degeneration (Pfirrmann Grade ≥ III) and/or osteochondrosis (Modic Type ≤ 2) without symptomatic facet joint degeneration (Fujiwara Grade ≤ 2, infiltration test) of the segments L4-5 or L5-S1 were randomly assigned to 2 treatment groups. Twenty-five patients were treated with a stand-alone ALIF and the remaining 25 patients underwent TDR. For ALIF and TDR, a retroperitoneal approach was used. At 1 week and at 12 months after surgery, CT was used to analyze paraspinal lumbar muscle tissue volume and relative fat content. Residual muscle tissue volume at 12 months and change in the relative fat content were compared between the groups. In addition, clinical parameters (visual analog scale [VAS] for low-back pain and Oswestry Disability Index [ODI] Questionnaire Version 2 for function) were compared. RESULTS: Compared with 1 week after surgery, the radiological analysis at 12 months revealed a small decrease in the posterior muscle volume (the mean decrease was < 2.5%), along with a small increase in the relative fat content (the mean increase was < 1.9%), in both groups at the index and superior adjacent segments. At the adjacent segment, the ALIF group presented significantly less muscle tissue volume atrophy and a smaller increase in fat content compared with the TDR group. At final follow-up, the clinical parameters related to pain and function were significantly improved in both groups compared with 1 week postsurgery, but there were no differences between the groups. CONCLUSIONS: Motion restriction via stand-alone ALIF and motion preservation via TDR both present small changes in the posterior lumbar paraspinal muscles with regard to volume atrophy or fatty degeneration at the index and superior adjacent segments. Therefore, although the clinical outcome was not affected by the observed muscular changes, the authors concluded that the expected negative influence of motion restriction on the posterior muscles compared with motion preservation does not occur on a clinically relevant level.

Influence of the Type of Sagittal Profile on Clinical Results of Lumbar Total Disk Replacement After a Mean Follow-Up of 39 Months.

STUDY DESIGN: Retrospective analysis of clinical and radiologic data of a prospective cohort study. OBJECTIVE: To research the clinical differences after lumbar total disk replacement (TDR) with respect to the preoperative global and the adaptation at the local sagittal profile (SP) of the spine. SUMMARY OF BACKGROUND DATA: It was suggested that facet loads and degeneration are dependent on epidemiologically defined types of SP. Moreover, the success of TDR was related to segmental facet joint loads. The influences of the preoperative SP or of the changes of the local SP after TDR on the clinical outcome after TDR remain unclear. METHODS: Fifty-two patients included in a prospective cohort study regarding lumbar single-level TDR L4/5 (n=22) or L5/S1 (n=30) because of degenerative disk disease (Modic ≤2 degrees) were clinically (visual analog scale for back, leg, and overall pain; Oswestry Disability Index) and radiologically (extension-flexion radiographs, plain-spine, and whole-spine lateral radiographs in upright standing position) reevaluated after a minimum follow-up of 24 (24-69) months. On the basis of preoperative plain radiographs in upright standing position, patients were retrospectively assigned to 4 groups according to the individual sagittal profile type (SPT). In patients with persistent back pain, a facet infiltration at the index level was performed. RESULTS: For all patients, an SPT could be defined. Global SP did not change compared with the preoperative state. All groups improved clinically over follow-up. At the last follow-up, types 1 and 4 demonstrated significantly inferior scores for pain and function. TDR-induced changes at the superior adjacent segment and the posterior disk height at the index level were also correlated to inferior clinical results. Infiltration test was positive in type 1-4: 67%, 40%, 33%, and 75%, respectively, of the symptomatic patients. CONCLUSIONS: We suggest SPTs 1 and 4 to represent a contraindication for lumbar TDR of levels L4/5 or L5/S1. Local adaptation in the adjacent segment to TDR may influence the clinical outcome as well.

Parameters influencing the outcome after total disc replacement at the lumbosacral junction. Part 2: distraction and posterior translation lead to clinical failure after a mean follow-up of 5 years.

PURPOSE: The aim of the second part of the study was to investigate the influence of parameters that lead to increased facet joint contact or capsule tensile forces (disc height, lordosis, and sagittal misalignment) on the clinical outcome after total disc replacement (TDR) at the lumbosacral junction. METHODS: A total of 40 patients of a prospective cohort study who received TDR because of degenerative disc disease or osteochondrosis L5/S1 were invited to an additional follow-up for clinical (ODI and VAS for overall, back, and leg pain) and radiographic analysis (a change in disc height, lordosis, or sagittal vertebral misalignment compared with the preoperative state). Based on the final ODI, patients were retrospectively distributed into groups N (normal: <25 %) or F (failure ≥ 25 %) for radiographic parameter comparison. A correlation analysis was performed between the clinical and radiological results. RESULTS: A total of 34 patients were available at a mean follow-up of 59.5 months. Both groups (N = 24; F = 10 patients) presented a significant improvement in overall pain, back pain, and ODI over time. At the final follow-up, higher clinical scores correlated with a larger disc height, increased lordosis, and posterior translation of the superior vertebra, which was also reflected by significant differences in these parameters in the group comparison. CONCLUSIONS: Parameters associated with increased facet joint capsule tensile forces lead to an inferior clinical outcome at mid-term follow-up. When performing TDR, we therefore suggest avoiding iatrogenic posterior translation and overdistraction (and consecutive lordosis).

Can discoblock replace discography for identifying painful degenerated discs?

OBJECTIVES: The aim of the present study was to intra-individually compare provocative discography and discoblock (disc analgesia) of idiopathic degenerated discs (IDD) results to each other, to clinical parameters, and to MRI findings. By this the value of both diagnostic features should be critically reevaluated. METHODS: 31 intervertebral IDD (Pfirrmann III°-IV°) of 26 patients were analyzed for surgery decision making by combined discoblock/discography procedure in an open MRI at 1T. A correlation analysis was performed between the Dallas Discogram Scale, pain discrimination score (PDS: concordant/discordant/no pain), positive discoblock (Numerical Rating Scale [NRS] reduction by ≥ 3, 60 min after intervention), presence of Modic changes or high intensity zones (HIZ), patient sex and age, intervention level, injection pressure and discography endpoint analysis (pain/pressure/anatomic/volume). RESULTS: Concordant pain could be evoked in 35% of the IDDs whereas discoblock was positive in 64%. Patients' age, sex, Dallas I, Dallas II, and Pfirrmann scores, as well as the presence of HIZ did not correlate to PDS or discoblock results. Discoblock correlated positively to concordant pain. Further positive correlation was found between PDS and intervention level/pressure, between discoblock and Modic changes/discography endpoint as well as between HIZ and discography endpoint. CONCLUSIONS: We suggest discoblock to be an additional tool for surgery decision making in patients with IDD because it correlates to concordant pain evoked by provocative discography as well as to presence of Modic changes. Additionally, assessment of a release instead of provocation of pain can be of advantage.