147 - Alignment of Each Lumbar Vertebra in Relation to the Hip Centre for bo...

Oral Posters: Innovative Technologies

Presented by: K.A. Tan - View Audio/Video Presentation (Members Only)

Author(s):

K.A. Tan(1), H.W.D. Hey(1), C.S.E. Neo(1), E.T.C. Lau(1), D.A.W. Choong(2), L.L. Lau(1), G.K.P. Liu(1), H.K. Wong(1)

(1) National University Health System, Orthopaedic Surgery, Singapore, Singapore
(2) National University Health System, Diagnostic Imaging, Singapore, Singapore

Abstract

Purpose of the Study: Reference values in deformity correction have been challenged by recent studies that propose to consider also the sitting profile on top of the conventional standing profile in an attempt to reduce PJK/PJF. However, these studies lack spatial correlation between each vertebra and the hip centre which is crucial for understanding spinopelvic balance. The objective of this study is to examine this spatial correlation between the lumbar spine and the hip centre in both standing and sitting postures. Describe the methods used: This is a prospective, comparative study of 53 healthy, young adults aged 19-35 years recruited over a 6-month period. All subjects presented to the spine clinic with the first episode of recent onset (within 6 months) isolated lower back pain with no red flag symptoms and no appreciable spinal deformity. All patients had standardized lateral standing and sitting views of their entire spine obtained via slot scanning technology performed in a randomized sequence. Measurement of radiographic parameters was carried out by two independent orthopaedic specialists and comprised of SVA, CL, TK, LL, and standard spinopelvic parameters such as PI, PT and SS. Variables for each lumbar vertebra in relation to the hip are measured based on the concept of PI = PT + SS and are accordingly termed lumbar incidence (LI), lumbar tilt (LT) and lumbar slope (LS). Statistical analyses of all variables in both postures were performed using t-tests. Further statistical comparisons using the equivalent parameters at S1 and L5 levels were also performed. Summarize the

Findings: The mean age of the patient cohort was 25.4 years. The mean SVA for standing and sitting were -1.59cm and +5.05cm respectively. In terms of angular alignment, the means of CL, TK and LL were 3.40°, 34.45° and 52.87° for standing and 4.81°, 24.44° and 29.86° for sitting. The mean PI, PT and SS values were 47.28°, 12.73° and 34.45° for standing and 49.04°, 27.84° and 21.02° for sitting respectively. PI is constant regardless of posture (47.28° in standing vs 49.04° in sitting; p=0.376). LI follows a gradual downward trend moving cranially. In the standing posture, LI turns negative at L3 and plateaus at L1. In the sitting posture, LI remains positive throughout the lumbar spine. LT stays positive throughout the standing lumbar spine with a nadir at L4 (3.08 degrees). However, the sitting spine LT shows gradual downward trend moving cranially. LS follows the downward trend of LI closely. LS turned negative at L3/4 and L1/2 in standing and sitting respectively. All statistical comparisons between both postures with the exception of PI (p=0.376) and L1T (p=0.239) were significant. Similarly significant differences were seen between spinopelvic parameters measured from S1 versus those measured from L5. Include statement of

Conclusions: The alignment of each lumbar vertebra in relation to the hip varies for both postures. Significant differences occur such that deformity correction which immobilizes the spine in the standing profile should be avoided as it would inevitably lead to supraphysiological stress at junctional areas. The findings from this study may provide insight into selective lumbar fusion targets, as well as conditions such as transitional vertebra, spondylolisthesis and retrolisthesis.