Objective To quantify the effect of different hip positions on lumbar lordosis (LL) and spinopelvic parameters in the right lateral decubitus position (RLDP) and identify the configuration that most closely replicates physiologic standing alignment during lateral lumbar interbody fusion in minimally invasive spinal surgery.
Methods Thirty healthy volunteers (15 males, 15 females; mean age, 27.8±8.6 years) underwent lateral lumbar radiographs in standing position and 5 RLDP configurations: neutral hips (NN), 30° flexion of both hips (30FF), 30° flexion of the right hip with left hip neutral (30FN), 60° flexion of both hips (60FF), and 60° flexion of the right hip with left hip neutral (60FN). LL, pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI) were measured. Each position was compared to standing using paired t-tests. Intra- and interobserver reliability were evaluated using intraclass correlation coefficients (ICCs).
Results LL decreased significantly in all RLDP positions compared with standing (51.1°±3.8°). The 30FN position showed the smallest change (ΔLL=-4.9°, p<0.001), whereas 60FF showed the greatest (ΔLL=-15.0°, p<0.001). In 30FN, PT decreased (p=0.013) and SS increased (p=0.003), indicating mild anterior pelvic rotation. PI showed minimal variation across positions. Intra- and interobserver ICCs ranged from 0.92 to 0.99, confirming high measurement reliability.
Conclusion Hip position significantly influences lumbar and pelvic alignment in RLDP. Among tested configurations, the 30FN position (right hip flexed 30°, left neutral) showed the smallest numerical deviation from standing alignment and spinopelvic harmony relative to standing in RLDP.
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Reply Letter: Reconsidering Intraoperative Hip Positioning in Single-Position Lateral Lumbar Interbody Fusion – A Commentary on “Optimal Positioning for
Single-Position Lateral Lumbar Interbody Fusion” Worawat Limthongkul, Natavut Prasertkul, Pakawas Praisarnti, Maruay Tanayavong, Surachat Jaroenwareekul, Wicharn Yingsakmongkol, Weerasak Singhatanadgige, Vit Kotheeranurak Neurospine.2026; 23(3): 756. CrossRef
Reconsidering Intraoperative Hip Positioning in Single-Position Lateral Lumbar Interbody Fusion – A Commentary on “Optimal Positioning for Single-Position Lateral Lumbar Interbody Fusion” Jiayi Chen Neurospine.2026; 23(3): 754. CrossRef
Objective To identify the risk factors for proximal junctional failure (PJF) after adult spinal deformity (ASD) surgery despite ideal sagittal correction according to age-adjusted alignment target.
Methods The study included patients who underwent low thoracic to pelvic fusion for ASD and obtained ideal correction according to age-adjusted pelvic incidence minus lumbar lordosis. PJF was defined either radiographically as a proximal junctional angle (PJA) of >28° plus a difference in PJA of >22° or clinically as revision surgery for proximal junctional complications. Clinical and radiographic variables were assessed to identify the risk factors for PJF.
Results The final study cohort consisted of 196 patients, of whom 170 were women (86.7%), with an average age of 68.3 years. During mean follow-up duration of 45.9 months, PJF occurred in 43 patients (21.9%). Multivariate logistic regression analysis revealed that old age (odds ratio [OR], 1.063; 95% confidence interval [CI], 1.001–1.129; p=0.046), large preoperative sagittal vertical axis (OR, 1.007; 95% CI, 1.001–1.013; p=0.024), nonuse of a transverse process (TP) hook (OR, 5.556; 95% CI, 1.205–19.621; p=0.028), and high lumbar distribution index (LDI) (OR, 1.136; 95% CI, 1.109–1.164; p<0.001) were significant risk factors for PJF development.
Conclusion A sizeable proportion of patients (21.9%) developed PJF despite achieving ideal sagittal correction. Using TP hooks with avoiding excessive LDI can be helpful to further mitigate the risk of PJF development in this patient group.
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Association between lumbar lordosis and proximal junctional failure following adult spinal deformity surgery: a systematic review and meta-analysis Abdullah M. Alharran, AbdulMuhsen AlQallaf, Mohammad Mohammad, Mohammad Salem Alajmi, Mohammad Alkaak, Salem Y. Alenezi, Fahad Mohammad, Ahmad Al Ahmad, Nizar Algarni, Yousef Marwan Spine Deformity.2026; 14(4): 1051. CrossRef
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Objective The lordotic shape of the lumbar spine differs substantially between individuals. Measuring and recording strain during spinal biomechanical tests is an effective method to infer stresses on spinal implants and predict failure mechanisms. The geometry of the spine may have a significant effect on the resultant force distribution, thereby directly affecting rod strain.
Methods Seven fresh-frozen cadaveric specimens (T12-sacrum) underwent standard (7.5 Nm) nondestructive sagittal plane tests: flexion and extension. The conditions tested were intact and pedicle screws and rods (PSR) at L1-sacrum. The posterior right rod was instrumented with strain gauges between L3–4 (index level) and the L5–S1 pedicle screw. All specimens underwent lateral radiographs before testing. Lordotic angles encompassing different levels (L5–S1, L4–S1, L3–S1, L2–S1, and L1–S1) were measured and compared with rod strain. Data were analyzed using Pearson correlation analyses.
Results Strong positive correlations were observed between lordosis and posterior rod strain across different conditions. The L3–S1 lordotic angle in the unloaded intact condition correlated with peak rod strain at L3–4 with PSR during flexion (R = 0.76, p = 0.04). The same angle in the unloaded PSR condition correlated with peak strain in the PSR condition during extension (R = -0.79, p = 0.04). The unloaded intact L2–S1 lordotic angle was significantly correlated with rod strain at L3–4 in the PSR condition during flexion (R = 0.85, p = 0.02) and extension (R = -0.85, p = 0.02) and with rod strain at L5–S1 in the PSR condition during flexion (R = 0.84, p = 0.04).
Conclusion Lordosis measured on intact and instrumented conditions has strong positive correlations with posterior rod strain in cadaveric testing.
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Objective The Dynesys-Transition-Optima (DTO) hybrid system was designed to achieve arthrodesis and stabilization in patients with lumbar degeneration. Satisfactory outcomes were demonstrated previously. However, no study has evaluated the effects of using the DTO system in patients with lumbar spondylolisthesis or stenosis.
Methods This retrospective study included 35 consecutive patients with multilevel lumbar degeneration with or without spondylolisthesis who underwent surgery using the DTO system. Imaging studies included pre- and postoperative radiography, magnetic resonance imaging, and computed tomography. The clinical outcomes were measured by Japanese Orthopedic Association (JOA) scores, Oswestry Disability Index (ODI) scores, and a visual analogue scale (VAS) for back and leg pain.
Results Thirty patients (85.7%) with a mean age of 61.9 years completed the follow-up, with a mean duration of 35.1 months. There were 21 patients in the spondylolisthesis group and 9 in the stenosis group. The spondylolisthesis group had worse functional scores than the stenosis group preoperatively. After DTO surgery, all patients showed significant improvements in clinical outcomes, including VAS for back and leg pain, ODI, and JOA scores (p < 0.05). There were no significant differences in clinical outcomes between the 2 groups. At a 2-year follow-up, lumbar alignment was well maintained in both groups (p = 0.116). There were no significant differences in lumbar alignment between the 2 groups.
Conclusion During a follow-up period of over 2 years, both patients with spondylolisthesis and those with stenosis showed improvements and similar disability and pain scores after surgery using the DTO system. Lumbar alignment was also well maintained.
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