Variation of Global Sagittal Alignment Parameters According to Gender, Pelvic Incidence, and Age.

STUDY DESIGN: Retrospective cross-sectional study. OBJECTIVE: The aim was to describe existing global sagittal alignment parameters across ages and to analyze differences according to gender and pelvic incidence (PI). SUMMARY OF BACKGROUND DATA: Variability with age has been reported. It remains unclear how gender and spinopelvic morphology could additionally influence global alignment parameters. MATERIALS AND METHODS: Radiographs of 2599 individuals (5-93 y) were analyzed. Translation parameters were: Sagittal Vertical Axis (SVA)-C7, SVA-C2, SVA-Center Acoustic Meatus (CAM), C7/Sacrofemoral Distance (SFD) ratio. Inclination parameters were: C7-Vertical Tilt (VT), T1-VT and T9-VT, Odontoid-Hip Axis (OD-HA), OD-CAM. Pelvic compensation parameters were: T1-Pelvic Angle (TPA), Global Tilt (GT), Spino-Sacral Angle (SSA). Global sagittal alignment (GSA) was considered among formulae. The distribution of parameters was analyzed using a Bayesian inference. Correlations with spinopelvic parameters were investigated. RESULTS: SVA-C7, SVA-C2, SVA-CAM were larger in males and high PI, and increased significantly after 50 years (Pr>0.9999). C7/SFD decreased during growth and was larger in low PI (Pr=0.951). There was no correlation with spinopelvic parameters. Age-related variations of inclination parameters were nonsignificant. T1-VT and T9-VT increased with PI and were significantly larger in high PI (Pr>0.95). C7-VT was significantly larger in low PI (Pr>0.9999). OD-HA and OD-CAM were constant and increased after 80 years. TPA and GT increased with PI (Pr>0.9999) and age after 35 years (Pr>0.9999). SSA decreased nonsignificantly after 50 years. TPA correlated with PI (ρ=0.6130) and pelvic tilt (PT) (ρ=0.8375). GT correlated with PI (ρ=0.5961) and PT (ρ=0.8996). SSA correlated with sacral slope (ρ=0.9026). GSA was larger in high PI (Pr>0.9999) and increased after 35 years (Pr>0.9999). GSA correlated with PT (ρ=0.7732). CONCLUSION: Translation parameters increase with age, more prominently in males and high PI. Variations of inclination parameters are smaller. Pelvic compensation parameters and GSA increase with age and are closely related to PT and spinopelvic morphology. LEVEL OF EVIDENCE: Level III.

Revision Surgery of Total Lumbar Disk Replacement: Review of 48 Cases.

STUDY DESIGN: This was a retrospective clinical review. OBJECTIVE: The objective of this study was to analyze failure mechanisms after total lumbar disk replacement (TDR) and surgical revision strategies in patients with recurrent low back pain (LBP). SUMMARY AND BACKGROUND DATA: Several reports indicate that TDR revision surgery carries a major risk and that it should not be recommended. The clinical results of posterior instrumented fusion using the prosthesis like an interbody cage have not been well analyzed. MATERIALS AND METHODS: From 2003 to 2018, 48 patients with recurrent LBP after TDR underwent revision surgery. The average age was 39 years (24-61 y). The mean follow-up was 100.4 months (24.6-207.7 mo). Clinical data, self-assessment of patient satisfaction, and Oswestry Disability Index collected at each clinical control or by phone call for the older files and radiologic assessments were reviewed. The surgical revision strategy included posterior fusion in 41 patients (group A) and TDR removal and anterior fusion in 7 patients (group B), of which 6 patients had an additional posterior fixation. RESULTS: Facet joint osteoarthritis was associated with TDR failure in 85%. In 68% the position of the prosthesis was suboptimal. Range of motion was preserved in 25%, limited in extension in 65%, and limited in flexion in 40%. Limited range of motion and facet joint osteoarthritis were significantly related (P=0.0008). The complication rate in group B was 43% including iliac vein laceration. Preoperative and 2-year follow-up Oswestry Disability Index were 25.5 and 22.0, respectively, in group A versus 27.9 and 21.3 in group B. CONCLUSIONS: Posterior osteoarthritis was the principal cause of recurrent LBP in failed TDR. The anterior approach for revision carried a major vascular risk, whereas a simple posterior instrumented fusion leads to the same clinical results. LEVEL OF EVIDENCE: Level IV.

Thoracic Kyphosis and Lumbar Lordosis Distribution After Idiopathic Scoliosis Correction Using Posterior Hybrid Versus Screw Instrumentation.

STUDY DESIGN: This was a retrospective observational study. OBJECTIVE: The aim of this study was to evaluate kyphosis and lordosis distribution, inflexion points, and the relationship with proximal junctional kyphosis (PJK) comparing hybrid instrumentation (in situ contouring, derotation) versus screw instrumentation (thoracic cantilever reduction, lumbar in situ contouring, and derotation). SUMMARY OF BACKGROUND DATA: The combination of reduction techniques aims at restoring the levels of lumbar apex and thoracolumbar inflexion point according to Roussouly alignment types. This approach could minimize the PJK risk after adolescent idiopathic scoliosis (AIS) surgery. MATERIALS AND METHODS: The study assessed coronal curve correction, thoracolumbar and spinopelvic sagittal parameters in 86 skeletally mature adolescents and young adults 2.2 years after AIS correction, comparing a hybrid group (HG, n=34) to a screw group (SG, n=52). Segmental kyphosis and lordosis distribution, number of vertebrae included in curves, thoracic and lumbar apex, thoracolumbar inflexion point and Roussouly types were modeled using KEOPS software. RESULTS: Global coronal and sagittal correction were similar in both groups. In the SG, lumbar lordosis (LL) decreased from 61.1 to 53.9 degrees (P<0.0001) and matched with pelvic incidence (r=0.69), whereas LL did not change in the HG. Postoperatively, the thoracolumbar inflexion point migrated cranially, resulting in a longer LL in both groups. Postoperative thoracolumbar inflexion point (P<0.0001) and the lumbar apex (P=0.0274) were more caudal in the SG compared with the HG. The PJK rate was 14.7% in the HG and 7.7% in the SG. In patients with PJK, lumbar apex and thoracolumbar inflexion point shifted cranially and were too high according to the Roussouly type. CONCLUSIONS: Hybrid and screw instrumentation led to similar global AIS correction, but the use of cantilever reduction in the SG allowed setting the thoracolumbar inflexion point and the lumbar apex lower than in the HG. Cranial migration of these points was identified as PJK risk factor. LEVEL OF EVIDENCE: Level III.

Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Augmented Reality Surgical Navigation for Percutaneous Pedicle Screw Placement.

STUDY DESIGN: This was a retrospective observational study. OBJECTIVE: The aim of this study was to evaluate the accuracy of percutaneous pedicle screw placement using augmented reality surgical navigation during minimally invasive transforaminal lumbar interbody fusion (TLIF). SUMMARY OF BACKGROUND DATA: Augmented reality-based navigation is a new type of computer-assisted navigation where video cameras are used instead of infrared cameras to track the operated patients and surgical instruments. This technology has not so far been clinically evaluated for percutaneous pedicle screw placement. MATERIALS AND METHODS: The study assessed percutaneous pedicle screw placement in 20 consecutive patients who underwent single-level minimally invasive TLIF using augmented reality surgical navigation. Facet joint violation and depression by the inserted pedicle screws were evaluated. Secondary outcome such as radiation dose exposure, fluoroscopy time, and operative time were collected for 3 phases of surgery: preparation phase, pedicle screw placement, and decompression with cage placement. RESULTS: A clinical accuracy for screw placement within the pedicle (Gertzbein 0 or 1) of 94% was achieved. One screw violated the facet joint with a transarticular pathway. The screw head did not depress the facet in 54%. The use of fluoroscopy during navigation correlated with patient body-mass index (r=0.68, P<0.0001). The pedicle screw placement time corresponded to 36±5% of the total operative time of 117±11 minutes. A statistically significant decrease of 10 minutes in operative time was observed between the first and last 10 procedures which corresponded to the pedicle screw placement time decrease (48±9 vs. 38±7 min, P=0.0142). The learning curve model suggests an ultimate operative time decrease to 97 minutes. CONCLUSION: Augmented reality surgical navigation can be clinically used to place percutaneous screws during minimally invasive TLIF. However, the lack of tracking of the location of the device requires intraoperative fluoroscopy to monitor screw insertion depth especially in obese patients. LEVEL OF EVIDENCE: Level III.