Oral Posters: Thoraco-lumbar Degenerative
Presented by: A. Patwardhan - View Audio/Video Presentation (Members Only)
A. Patwardhan(1,2), S. Khayatzadeh(2), A. Faundez(3), R. Havey(1,2), G. Carandang(2), L. Voronov(1,2), J.C. Le Huec(4)
(1) Loyola University Chicago, Orthopaedic Surgery and Rehabilitation, Maywood, IL, United States
(2) Edward Hines Jr. VA Hospital, Hines, IL, United States
(3) Hopital La Tour, Meyrin, Switzerland
(4) Bordeaux University Hospital, Bordeaux, France
Introduction: The relationship between pelvic incidence (PI=Pelvic tilt + sacral slope) and lumbar lordosis has been extensively studied in the asymptomatic adult populations. Approximately two-thirds (67%) of the total lumbar (L1-S1) lordosis is localized in the lower two (L4-S1) segments. A loss of lordosis resulting from age-related degeneration or as a consequence of inadequate fusion surgery may cause forward inclination of the trunk leading to impaired standing balance. It is generally suggested that a patient's ability to compensate for loss of lordosis in the lower lumbar levels improves with increasing magnitude of pelvic incidence. In this study we tested the hypothesis that with increasing pelvic incidence the upper lumbar segments play a greater role in contributing to the lordotic alignment of the lumbar spine.
Methods: We analyzed full-length standing lateral radiographs of 30 asymptomatic subjects [age: 35.2 years (SD: 13.5), 21M/9F], who were imaged in a standing posture in an EOS machine. Bony landmarks were digitized using custom software to calculate the lumbo-pelvic alignment parameters including: pelvic tilt, sacral slope, pelvic incidence, L1-S1 lordosis, L4-S1 lordosis, and L1-L3 lordosis.
Results: The total lumbar lordosis across L1-S1 averaged 52 degrees (SD: 9.8 degrees), of which 59.4% (11.2%) was localized across L4-S1 and 18.1% (11.5%) across L1-L3. The pelvic incidence, pelvic tilt, and sacral slope values averaged 49.3 degrees (10.3), 12.5 degrees (6.2), and 36.8 degrees (7.3), respectively.The total lumbar (L1-S1) lordosis increased significantly with increasing magnitude of Pelvic Incidence (R2=0.4, p< 0.05), while the lordosis across L4-S1 remained relatively constant (R2=0.10, p=0.103). As a result, the contribution of L4-S1 towards the total lumbar lordosis [(L4-S1)/(L1-S1)] decreased significantly with increasing Pelvic Incidence (R2=0.22, p=0.013). Conversely, the L1-L3 lordosis magnitude and its contribution to the total lumbar lordosis [(L1-L3)/(L1-S1)] increased significantly with increasing magnitude of Pelvic Incidence (R2=0.52 and 0.48, respectively; p< 0.001) (Fig. 1).
Conclusions: Increasing magnitude of pelvic incidence alters the morphology of the lumbar curve by bringing the upper lumbar (L1-L3) segments into the lordotic curve. This is consistent with the qualitative illustrations of the four types of lumbar curves described by Pierre Roussouly.The incorporation of the whole lumbar spine in the lordotic profile as evidenced in the above results may be one mechanism by which patients with a large pelvic incidence are better “equipped” and able to compensate for a loss of lordosis across the lower lumbar spine (Example: Fig. 2).