Special Poster Session 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Do the Lower Extremities influence the Cone of Economy of Patients with Radiculopathy and Neurogenic Claudication? An Innovative Approach (115384)

Ram Haddas 1 , Gabrielle Santangelo 1 , Haseeb Goheer 1 , Cindy Wang 1 , Paul Rubery 1 , Ashley Lynn Rogerson 1 , Andrew Megas 1 , Robert Molinari 1 , Gabriel Ramirez 1 , Howard Hillstrom 2 , Roger Widmann 2 , Jessica Heyer 2 , Ankush Thakur 2 , Tyler Schmidt 1 , Varun Puvanesarajah 1
  1. University of Rochester Medical Center, Rochester, NY, United States
  2. Hospital for Special Surgery, New York

Introduction: The Cone of Economy (CoE) theory explains maintaining balance with minimal energy expenditure.1-3 Traditionally, CoE was estimated by clinicians; however, objective measures have been established, allowing accurate quantification of both CoE and compensatory maneuvers.4-8  Any pathology of the locomotor system, including low back pain, spinal stenosis, radiculopathy, or claudication could influence the CoE. In degenerative conditions, the compensatory effort to avoid painful positions or to overcome lower extremity weakness may alter the CoE. No previous work has investigated the significance of lower extremity involvement in a patient’s CoE. The purpose of this study was to evaluate the influence of the lower extremities on patients' CoE along with a novel assessment of seated balance using traditional CoE measurements.

Methods: This is a prospective, single-center cohort study examining the CoE in patients who are candidates for lumbar decompressive surgery compared to controls. Functional balance tests were performed and recorded by 3D motion capture in both the standing (Romberg) and seated positions approximately one week before surgery. A custom algorithm was used to determine balance effort utilizing sagittal, and coronal range of sway (RoS) for the CoM (middle CoE ring), the head (upper CoE ring), and overall sway.2-3 Data was analyzed via one-way analysis of variance (ANOVA) to determine differences between both groups’ CoE outcomes for each position.

Results: Eighty-four lumbar degenerative (LD) spine surgery candidates, consisting of 39 patients with unilateral radiculopathy (UR) and 45 patients with neurogenic claudication (NC) with bilateral symptoms, as well as 35 healthy controls were enrolled in the study. The standing CoE was significantly different between the LD group and the control group (p<0.001). The NC group had higher levels of sway in all planes compared to the UR group in the standing and seated positions. The seated head and pelvic sway in the coronal plane were significantly higher in the LD group versus the control group (p=0.005, p<0.0001, respectively). The difference in balance effort measured by total sway of the head, pelvis, and center of mass (CoM) in the seated versus standing position was significant (p<0.001) for all measures between the LD and control groups. 

Discussion: This study demonstrates the influence of the lower extremities on CoE alterations in degenerative lumbar spine conditions.  There was a significant difference in standing balance between the LD groups and the control groups. Our data suggests that the involvement of the lower extremities is critical in compensating for differences in balance efficiency and the CoE dimensions. Patients with UR and NC often have to adopt a forward trunk lean to relieve some of the lower extremity symptoms. Otherwise, the elimination of leg pain by seating may muted the significant amount of sway within the CoE differences between radiculopathy patients versus controls seen while standing. Degenerative spine conditions are associated with increased CoE due to many factors that remain unclear, and future studies will examine these factors. These factors are the subject of future research.

673a69d9f230c-Figure+1.jpg

  1. 1. Hasegawa K, Dubousset JF. Cone of Economy with the Chain of Balance-Historical Perspective and Proof of Concept. Spine Surg Relat Res. 2022;6(4):337-349. doi:10.22603/ssrr.2022-0038
  2. 2. Haddas R, Satin A, Lieberman I. What is actually happening inside the "cone of economy": compensatory mechanisms during a dynamic balance test. Eur Spine J. Sep 2020;29(9):2319-2328. doi:10.1007/s00586-020-06411-w
  3. 3. Haddas R, Lieberman IH. A method to quantify the "cone of economy". Eur Spine J. May 2018;27(5):1178-1187. doi:10.1007/s00586-017-5321-2
  4. 4. Lee JK, Hyun SJ, Kim KJ. Reciprocal Changes in the Whole-Body Following Realignment Surgery in Adult Spinal Deformity. Asian Spine J. Dec 2022;16(6):958-967. doi:10.31616/asj.2021.0451
  5. 5. Diebo BG, Ferrero E, Lafage R, et al. Recruitment of compensatory mechanisms in sagittal spinal malalignment is age and regional deformity dependent: a full-standing axis analysis of key radiographical parameters. Spine (Phila Pa 1976). May 1 2015;40(9):642-9. doi:10.1097/BRS.0000000000000844
  6. 6. Barrey C, Roussouly P, Le Huec JC, D'Acunzi G, Perrin G. Compensatory mechanisms contributing to keep the sagittal balance of the spine. Eur Spine J. Nov 2013;22 Suppl 6(Suppl 6):S834-41. doi:10.1007/s00586-013-3030-z
  7. 7. Day LM, Ramchandran S, Jalai CM, et al. Thoracolumbar Realignment Surgery Results in Simultaneous Reciprocal Changes in Lower Extremities and Cervical Spine. Spine (Phila Pa 1976). Jun 1 2017;42(11):799-807. doi:10.1097/BRS.0000000000001928
  8. 8. Obeid I, Hauger O, Aunoble S, Bourghli A, Pellet N, Vital JM. Global analysis of sagittal spinal alignment in major deformities: correlation between lack of lumbar lordosis and flexion of the knee. Eur Spine J. Sep 2011;20 Suppl 5(Suppl 5):681-5. doi:10.1007/s00586-011-1936-x