Pelvic incidence change on the operating table

Morphological features of lower lumbar degenerative kyphosis

PURPOSE

Kyphosis in the lower lumbar spine (L4-S1) significantly affects sagittal alignment. However, the characteristics of the spinopelvic parameters and compensatory mechanisms in patients with lower lumbar degenerative kyphosis (LLDK) have not been described in detail. The objective of this retrospective study was to analyze the morphological characteristics in patients with sagittal imbalance due to LLDK.

METHODS

In this retrospective study, we reviewed the clinical records of consecutive patients who underwent corrective surgery for adult spinal deformity (ASD) at a single institution. We defined LLDK as (i) kyphotic deformity in lower lumbar spine (L4-S1) or (ii) inappropriate distribution of lordosis (lordosis distribution index < 40%) in the lower lumbar spine. Global spine parameters of ASD patients and MRI findings were compared between those with LLDK (LLDK group) and without LLDK (control group).

RESULTS

A total of 95 patients were enrolled in this study, of which the LLDK group included 14 patients (14.7%). Compared to the control, LLDK presented significantly higher pelvic incidence (62.1° vs 52.6°) and pelvic tilt (40.0° vs 33.4°), larger lordosis at the thoracolumbar junction (12.0° vs -19.6°), and smaller thoracic kyphosis (9.3° vs 26.0°). In LLDK, there was significantly less disc degeneration at L2/3 and L3/4.

CONCLUSION

LLDK patients had high pelvic incidence, large pelvic tilt, and a long compensatory curve at the thoracolumbar junction and thoracic spine region.

Randomized Trial of Augmented Pelvic Fixation in Patients Undergoing Thoracolumbar Fusion for Adult Spine Deformity: Initial Results from a Multicenter Randomized Trial

BACKGROUND

The optimal configuration for spinopelvic fixation during multilevel spine fusion surgery for adult spine deformity remains unclear. Postoperative sacroiliac (SI) joint pain, S2AI screw loosening and implant breakage could be related to continued motion of the SI joint with use of only a single point of fixation across the SI joint.

METHODS

Prospective, international, multicenter randomized controlled trial of 222 patients with adult spine deformity scheduled for multilevel (4 or more levels) spine fusion surgery with pelvic fixation. Subjects were randomized to sacroalar (S2) iliac (S2AI) screws alone for pelvic fixation or S2AI + triangular titanium implants placed cephalad to S2AI screws. Quad rod techniques were not allowed or used. Baseline spinal deformity measures were read by an independent radiologist. Site-reported perioperative adverse events were reviewed by a clinical events committee. Quality of life questionnaires and other clinical outcomes are in process with planned 2-year follow-up.

RESULTS

One hundred thirteen participants were assigned to S2AI and 109 to S2AI + titanium triangular implants (TTI). 35/222 (16%) of all subjects had a history of SI joint pain or were diagnosed with SI joint pain during preoperative workup. Three-month follow-up was available in all but 4 subjects. TTI placement was successful in 106 of 109 (98%) subjects assigned to TTI. In 2 cases, TTI could not be placed due to anatomical considerations. Three TTI ventral iliac breaches were observed, all of which were managed non-surgically. One TTI subject had a transverse sacral fracture and 1 TTI subject had malposition of the implant requiring removal.

CONCLUSIONS

SI joint pain is common in patients with adult spinal deformity who are candidates for multilevel spine fusion surgery. Concurrent placement of TTI parallel to S2AI screws during multilevel spine fusion surgery is feasible and safe. Further follow-up will help to determine the clinical value of this approach to augment pelvic fixation.

Decrease in pelvic incidence after adult spinal deformity surgery is a predictive factor for progression of hip joint osteoarthritis

BACKGROUND

This study aimed to evaluate the association between spinopelvic alignment parameters and hip osteoarthritis progression after spinal alignment correction surgery for adult spinal deformity, focusing on the preoperative to postoperative change in spinopelvic alignment.

METHODS

This retrospective study enrolled 100 adult spinal deformity patients (196 hip joints) who underwent spinal fusion surgery, after excluding four joints with previous total hip arthroplasty. Acetabular roof obliquity (ARO), center edge angle (CE) and Kellgren and Lawrence (KL) grade were measured in the hip joint. Spinopelvic alignment parameters were measured preoperatively and 1-month postoperatively and the changes (Δ) during this period were calculated. Patients were followed-up for ≥ 5 years and factors associated with KL grade progression at 5-years postoperatively were determined by logistic regression analysis.

RESULTS

In the analysis with all cases, KL grade progressed in 23 joints. Logistic regression analysis revealed age (OR: 1.098, 95% CI: 1.007-1.198, p = 0.019), ARO (OR: 1.176, 95% CI: 1.01-1.37, p = 0.026), and Δ PI (OR: 0.791, 95% CI: 0.688-0.997, p < 0.001) as parameters significantly associated with KL grade progression. On the other hand, in the analysis limited to 185 cases with 1-month postoperative KL grade of 0, KL grade progressed in 13 joints. Logistic regression analysis revealed PI-LL (OR: 1.058, 95% CI: 1.001-1.117, p = 0.04), ΔPI (OR: 0.785, 95% CI: 0.649-0.951, p < 0.001), and ΔCobb (OR: 1.127, 95% CI: 1.012-1.253, p = 0.009) as parameters significantly associated with progression.

CONCLUSIONS

Both the overall and limited analyzes of this study identified preoperative to postoperative change in PI as parameters affecting the hip osteoarthritis progression after spinal fusion surgery. Decrease in PI might represent preexisting sacroiliac joint laxity. Patients with this risk factor should be carefully followed for possible hip osteoarthritis progression.

Hip-Spine Syndrome: A Focus on the Pelvic Incidence in Hip Disorders

Since Offierski and MacNab reported a close association between the hip and spine as hip-spine syndrome in 1983, many studies on spinal alignment in hip disorders have been conducted. Notably, the pelvic incidence angle (PI) is the most important parameter and is determined by the anatomical variations in the sacroiliac joint and hip. Studies on the association of the PI with hip disorders can help in understanding the pathophysiology of hip-spine syndrome. A PI increase has been observed during the evolution of bipedal locomotion in humans and in the acquisition of gait during child development. Although the PI is a fixed parameter that is stable and unaffected by posture from adulthood onwards, it has become clear that it increases in the standing position in older people. While it may be associated with a greater risk of developing or progressing to spinal disorders, the association between the PI and hip disorders remains controversial because of the multifactorial nature of hip osteoarthritis (HOA) and the wide range of PIs in HOA (18-96°), making the interpretation of results difficult. However, several hip disorders (i.e., femoroacetabular impingement and rapid destructive coxarthrosis) have been shown to be associated with the PI. Further investigation on this topic is, therefore, warranted.

Pelvic thickness, sex, ethnicity, and age affect pelvic incidence in healthy volunteers of Multi-Ethnic Alignment Normative Study (MEANS) database

BACKGROUND

The purpose of this study was to investigate the affecting factors on pelvic incidence (PI) and to test the hypothesis that PI changes even after skeletal maturity probably due to hypermobility of the sacroiliac joint using a large international multi-center database.

METHODS

A prospective and cross-sectional healthy adult volunteers, ages 18-80 years, across 5 countries were used. Radiographic measurements included standard whole body alignment parameters. Bivariate regression analyses between PI versus demographics and spino-pelvic anatomical parameters were performed. An effect of sex on pelvic anatomical parameters was also investigated. Multivariate logistic regression with a forward stepwise procedure was performed to identify the contributing factors to PI, and an appropriate model was obtained.

RESULTS

PI showed a significant positive correlation with age in pooled data. Divided by sex, however, there was no correlation in men, but women showed a significant higher correlation coefficient. Pelvic thickness (PTh) had a significant negative correlation with age in pooled data. Divided by sex, no correlation was found in men, but there was a significant correlation in women with higher correlation coefficient. The stepwise multivariate analysis for the factors on PI identified four significant factors: age, sex, ethnicity, and PTh.

CONCLUSIONS

PTh, sex, ethnicity, and age affected PI. There was a positive correlation between PI and age. The tendency was more significant in woman than in man. The results support the hypothesis that PI increases with aging, but the change seems to be small and needs to be verified in a longitudinal evaluation.