Functional disability , sagittal alignment and pelvic balance in lumbar spondylolisthesis

Objetivos: Demostrar la recuperacion de la alineacion sagital lumbar y del balance pelvico sagital tras la reduccion quirurgica de la espondilolistesis lumbar y establecer los beneficios del procedimiento quirurgico de reduccion y fijacion de la espondilolistesis lumbar con artrodesis circunferencial de 360° por dos vias de abordaje mediante la evaluacion clinico-funcional. Metodos: Se revisaron 8 pacientes con espondilolistesis lumbar tratados con reduccion y fijacion quirurgica de la listesis y artrodesis circunferencial segmentaria por dos vias de abordaje. Se evaluaron antes y despues del tratamiento con las escalas Oswestry, Visual Analogica del dolor y Odom, efectuando la medicion radiografica de la alineacion sagital lumbar y del balance pelvico sagital con la tecnica del radio pelviano. Resultados: Las escalas de Oswestry y EVA reportaron mejoria de la sintomatologia despues del tratamiento en los 8 casos; la escala Odom reporto 6 casos excelentes. La alineacion sagital lumbar reporto los angulos de lordosis lumbosacra y de lordosis lumbopelvica disminuidos en 4 casos y aumentados en 4 restantes; el balance pelvico sagital aumento el angulo pelvico en 4 casos y disminuyo en 3 casos; la traslacion sacra del eje de las caderas al promontorio aumento en 6 casos. Conclusion: El procedimiento quirurgico evaluado demuestra su utilidad al modificar la alineacion lumbar y el balance pelvico sagital y reducir la sintomatologia, lo que permite la movilidad y el desplazamiento del paciente y la consecuente satisfaccion con la cirugia.


INTRODUCTION
The human spine maintains proper balance in the sagittal and coronal planes in order to minimize the muscular effort required to maintain an erect posture when standing.The minimum energy expenditure is achieved by maintaining the center of gravity of the torso right at the midpoint between the hips in the coronal plane, and immediately above the imaginary line that connects the center of the hips in the sagittal plane. 1,2arious points of reference have been described in the literature for the radiological evaluation of sagittal balance, but the reciprocal relationships between these so-called points of reference vary greatly among healthy individuals.The degree of lumbar lordosis and the sagittal rotation of the pelvis around the hip axis is one of the compensatory mechanisms that maintains balance in the sagittal plane.][4][5][6][7][8] One of the consequences of the variations in sagittal deformities (spondylolisthesis) is the reduced capacity to use this compensatory balance mechanism. 3,9,10,11he surgical treatment, performed with arthrodesis in situ and the use of autologous bone grafts in the transverse apophysis in patients with varying degrees of slippage, together with decompression of the spinal canal, has an arthrodesis consolidation failure rate of 20%.Patients with an angle of displacement due to slippage of more than 50% develop kyphotic deformity following posterior approach fusion attempts, so there have been innovations in alternative surgical procedures to resolve this problem. 3,12oday, the roles played by different fixation techniques and reduction of vertebral listhesis are not clearly specified in the literature, but reports of the esthetic benefits following surgery describe significant improvement after segmental fusions with reduction of the angle of slippage and improved alignment in the sagittal plane.At the same time, the increase in radicular lesions characteristic of instrumented reduction from the posterior approach is avoided. 3,11,13,14owever, reconstruction of the anterior spine for surgical treatment of spondylolisthesis is recommended, with varying outcomes, but with lower incidence of nerve lesions.Recovery of disk height via posterior and anterior intervertebral lumbar fusion provides rigidity to the mobile segment being surgically treated.][13][14] The natural history of listhesic disease of the lumbar spine includes changes in mechanical stability that promote mechanisms of corporal compensation.][13][14] The objective of this study is to demonstrate the recovery of sagittal lumbar alignment and sagittal pelvic balance following surgical reduction of lumbar spondylolisthesis and to define the benefits of the surgical procedures of reduction and fixation of lumbar spondylolisthesis and of 360° circumferential arthrodesis from two approaches.

MATERIAL AND METhODS
This is a prospective, longitudinal, descriptive, and observational study of a case series approved by the Institutional Review Board.
We studied eight adult patients with lumbar spondylolisthesis in the Spine Surgery Service of the U.M.A.E.Hospital de Traumatología y Ortopedia "Lomas Verdes".All the patients signed an informed consent form.All patients underwent surgical treatment in two stages with an interval of from 1 to 5 weeks, the first consisting of the widening of the lumbar spinal canal in the segment narrowed by the listhesis, reduction of the listhesis, and surgical segmental fixation with the Universal Spine System (USS) transpedicle system, and bilateral posterolateral arthrodesis with an autologous bone and tricalcium phosphate graft.The second surgery consisted of anterior interbody arthrodesis with a Syncage-L titanium cage and tricalcium phosphate bone substitute graft.Patients were evaluated pre and post treatment using the Oswestry Disability Index for lumbar function, 15 the Visual Analog Scale for pain (VAS), 15 and Odom's Criteria 15 for surgical satisfaction, performing the radiographic evaluation with the pelvic radius to determine the sagittal lumbar alignment by measuring the pelvic morphology angle (PMA), the lumbosacral lordosis angle (LSLA), and the lumbopelvic lordosis angle (LPLA) and the sagittal pelvic balance by measuring the sacral translation (ST) and the pelvic angle (PA).

RESULTS
The results of the evaluation of the sagittal lumbar alignment was measured by the PMA, the LSLA, and the LPLA, before and after surgery are shown in Table 1.e observed that the pelvic morphology angle showed no difference between the pre-and postoperative measurements and that the lumbosacral and lumbopelvic lordosis decreased in four cases and increased in 4 cases following the procedure.
Pelvic sagittal balance was measured by the PA, the VP, and the VAPSS1.The results are shown in Table 2 in degrees or millimeters.We observed an increase in the pelvic angle in four cases, a decrease in three cases, and one case that remained consistent from pre-to postoperative measurements.The sacral translation of the axis from the hips to the promontory increased in six cases and decreased in two, while the sacral translation from the axis of the hips to the posterosuperior angle of S1 increased in seven cases and decreased in one.
The results of the Oswestry Disability Index for lumbar function and the VAS were obtained both pre-and postoperatively and Odom's Criteria for postoperative satisfaction with the surgery are described in Table 3. Table 3 shows a considerable decrease in the Oswestry and VAS scores following the procedure in eight cases, and Odom's Criteria reports six excellent and two good ratings.

DISCUSSION
The pelvic morphology angle remained consistent in the preand postoperative measurements, as reported by Jackson and colleagues [4][5][6][7] and Legate and colleagues. 9,10he parameters of lumbosacral and lumbopelvic lordosis changed in 100% of the cases following the procedure, 50% increasing and the other 50% decreasing their values, but it was not possible the establish any relationship with the change in the pelvic balance parameter described by Legaye, 10 Tebet, 11 Lazennec, 13 Videbaek. 14e observed modifications in the sagittal lumbar alignment and the sagittal pelvic balance following the surgical procedure of reduction and posterior fixation of the listhesis and the reconstruction of the anterior spine with a titanium cage, although we observed no correlation between them, as reported by Videbaek and colleagues. 14ile we cannot say that there is recovery of the alignment and balance, we can say that the technique of reduction and fixation with circumferential arthrodesis alters the balance of the lumbar and pelvic segment.
Changes in the sacrolumbar and sacropelvic indices and their variability are described as the consequences of the modification to pelvic balance, also referenced by Roussouly and colleagues. 8he Oswestry Disability Index for lumbar function showed an evident improvement in the disabling painful lumbar symptoms ranging from 50 to 88%, which is closely related to that obtained in the VAS, with improvement in pain ranging from 80 to 100%.It is possible that this reflects the influence of not only the reconstruction of the anterior column as stated by Roussouly and colleagues, 8 but also of the decompression of the lumbar stenosis.
Odom's Criteria validated the use of the surgical procedure with 80% of the outcomes rated excellent and 20% rated good.

CONCLUSION
Circumferential arthrodesis in patients with lumbar spondylolisthesis is a resource that demonstrates its usefulness by modifying lumbar alignment and decreasing the lumbosacral lordosis angle.It also changes sagittal pelvic balance, which consequently reduces painful symptoms, since modifying the pathological balance of the lumbar spine reduces pain by reducing the distension of ligamentous structures and the overload on articular structures, resulting in improvements in the quality of life of the patients objectively, both in work and personal activities, and with a high level of patient satisfaction since it restores the lumbar spine to a state that allows patient mobility and displacement, showing an improvement in the quality of life of the patient.
This study demonstrates that circumferential arthrodesis in patients with lumbar pain secondary to spondylolisthesis alters the balance of the lumbar and pelvic segment, a consequence of the modification of the degrees of sacrolumbar and sacropelvic lordosis and improves the disabling lumbar pain, with good and excellent outcomes in most patients.
All authors declare no potential conflict of interest concerning this article.