Reducing the kyphosis effect of anterior short thoracolumbar/lumbar scoliosis correction with an autograft fulcrum effect

Farshad et al. BMC Musculoskeletal Disorders https://doi.org/10.1186/s12891-021-04083-1 (2021) 22:216 RESEARCH ARTICLE Open Access Reducing the kyphosis effect of anterior short thoracolumbar/lumbar scoliosis correction with an autograft fulcrum effect Mazda Farshad1, Andrea Frey1, Thorsten Jentzsch1, Michael Betz1, Jonas Widmer2,3 and José Miguel Spirig1* Abstract Background: Anterior scoliosis correction is a powerful technique with the disadvantage of a kyphotic effect on lumbar and thoracolumbar curves. We aimed to investigate whether a cognizant interposition of a rib graft anteriorly and at the concave side of the scoliotic curve causes significant fulcrum effect to enforce scoliosis correction and to reduce interfusional kyphosis in anterior scoliosis corrections. Methods: Twenty otherwise comparable patients with lumbar and thoracolumbar adolescent idiopathic scoliosis (AIS) curves undergoing anterior short scoliosis correction with (n = 10) or without (n = 10, matched for age, gender and degree of deformity) fulcrum effect were retrospectively compared by means of radiographic measurements (sagittal and coronal profile, Cobb angles and intersegmental deformity correction angles) to evaluate the effect of this modified surgical technique. Results: The overall amount of scoliosis correction was similar with 74 and 60% of initial curves of 57° and 53° in the case and control group respectively with a mean of 3 fused segments (4 screws). Statistically relevant differences were found for intersegmental coronal cobb angles at the apex of 20° to 3° and 17° to 9° with and without fulcrum, respectively (p < 0.05). Creation of kyphosis in the fused segments was reduced with an interfusional kyphotic sagittal cobb angle of 15° pre-operatively vs. 3° post-operatively compared to the control group (13° pre-operatively vs. 18° post-operatively), (p < 0.05). Conclusions: Interfusional hyperkyphosis associated with anterior scoliosis correction for thoracolumbar/lumbar curves can be reduced with cognizant positioning of the bone autograft at the antero-lateral (concave) site in the intervertebral region to create a fulcrum effect. Trial registration: Registered at swissethics: BASEC No.: 2018–00180. Keywords: Scoliosis, Kyphosis correction, Anterior scoliosis correction, Lumbar scoliosis, Thoracolumbar scoliosis, Kyphosis prevention * Correspondence: 1 Spine Division, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008 Zurich, Switzerland Full list of author information is available at the end of the article © The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Farshad et al. BMC Musculoskeletal Disorders (2021) 22:216 Background Since the introduction of the anterior approach to scoliosis correction by Dwyer [1] and its later modification by Zielke [2], the concept has gained popularity following the introduction of rigid rod implants in the early 1990s [3–8]. The anterior approach to scoliosis correction is associated with shorter fusion distance compared to a dorsal technique, thereby sparing spinal motion segments [9, 10]. Additionally, upper thoracic instrumentation can be avoided with the anterior approach to thoracolumbar curves preventing the need to treat compensatory thoracic curves [11]. The disadvantage of this method is a possible reduction of lordosis or a kyphogenic effect caused by a full discectomy and the subsequently applied compression force for bone on bone fusion. Previous studies have demonstrated radiographic and satisfying clinical outcomes of anterior spine fusions over a short-term follow-up (2–5 years) as well as a longer follow-up (12–23 years) [12–14]. However, one main drawback of anterior scoliosis correction remains the occurrence of hyperkyphosis in up to 40% of patients [15]. To our knowledge there are no reports regarding short anterior fusion using cognizant interposition of a rib autograft at the anterior and concave side of the scoliotic curve thereby creating a fulcrum effect to address the problem of kyphosis creation and enhancing coronal scoliosis correction. Therefore, in this study we report the immediate radiographic results, describe the method of choosing fusion levels as well as the specific technique of this surgical procedure. Patients and method The present study was approved by the local ethics committee (Swissethics, BASEC No.: 2018–00180) on research involving humans. Every patient involved in this study gave written informed consent before inclusion. In this cohort study a retrospective review of a very selective patient population with the diagnosis of adolescent idiopathic scoliosis (AIS) with the major curve deformity located in the thoracolumbar or lumbar spine region was performed. All these patients underwent selective short anterior correction fusion with (n = 10, cases) or without (n = 10, controls) interbody interposition of bone autograft specifically at the anterior and concave side of the scoliotic curve. The controls were selected from 118 AIS patients to match the cases according to age, Risser stage, sex, type and degree of scoliotic deformity (Table 1). Radiological measurements were performed by an independent observer on EOS radiographs (antero-posterior and lateral radiographs) immediately prior to surgery and 6 weeks postoperatively to determine the direct effect of corrective deformity changes according to the recommendation of the SRS [16]. Cobb angle vertebral Page 2 of 8 Table 1 Patient demographic data (n = 20) Variable Measurements (median [IQR]) Pvalue* Cases (n = 10) Controls (n = 10) 15 (3) 16 (3) 0.732 Female 9 9 1.000 Males 1 1 4 (0) 4 (1) 0.185 5 4 5 0.653 6 6 5 Age (y) Sex (n) Segments (n) Lenke (n) Risser (n) 0 0 2 1 2 1 2 3 1 3 1 1 4 4 3 5 0 2 0.361 Abbreviations: IQR (interquartile range), y (years) * Wilcoxon rank sum test or Chi-square test levels were determined on the preoperative radiogra (...truncated)