The Influence of the Fusion Degree of the Vertebrae on the Process of Destabilization of the Pedicle Fixation System after TLIF and PLIF
Authors: Basankin Igor , Porhanov Vladimir , Tahmazyan Karapet , Shapovalov Vladimir , Malahov Sergei , Volynsky Alexey 
Published: April 2016

Introduction The stability of the PSF system in the postoperative period of time is an important component of well-being of the patients. In case of destabilization of PSF systems revision surgery is often required and brings high costs and has increased number of complications. The main reasons for the destabilization of the rigid stabilization systems are: osteoporosis, non fusion, pseudarthrosis, a violation of the prescribed protective regime Material and Methods 409 patients after decompressive-stabilizing operations on the lumbar spine type TLIF or PLIF. All patients were operated because of spinal stenosis in the period since 25.12.2012 till12.27.2013 by five surgeons working in the same department. There were 235 male (57.5%) and 174 female (42.5%) aged 18–75 (50,3 ± 1,2). There were one-level process - 296 (72.4%), two-level process - 98 (23.9%), a three-level process - 11 (2.6%), more than 3 levels - 4 (1.1%). Totaly 539 segments were operated. We used following cages as interbody implants: Leopard – 65 (12%), Concorde – 92 (17%), Capstone – 156 (29%), Surgical Titanium Mesh – 226 (42%). Cages were filled with autologous bone graft. Crushed bone stacked densely around the cage. After installation cage we performed compression on the elements of PSF system. Follow-up period was of 2 years. Formation of the bone block was evaluated by Bridwell classification Results Complete regression of the initial neurological symptoms as a result of the decompression achieved in 325 (79,5%) patients, partial – 58 (14%), no change – 20 (5%), the deterioration – 6 (1.5%). Post-operative examination and X-ray and CT control were delivered within 3–6-12 and 24 months. 335 (82%) patients were control examined after 1 year, 258 (63%) after 2 years. After 1 year the 1st Bridwell fusion grade was marked at 325 (79.6%) patients, grade 2 – 60 (14.7%), grade 3 – 13 (3.2%), grade 4 – 10 (2.5%). The material of the implant had no effect on the fusion. Among patients (23 patients total) with 3 and 4 Bridwell grade of fusion we used as interbody implant: Peek 7 (30,6%), Carbon 8 (34,7%), Surgical titanium mesh 8 (34,7%). It is obvious that the reason of non fusion is not the material of the implant, and other factors (quality of treatment interbody gap, cage height and the degree of contact with the endplate vertebral body, especially vertebral vascularization, surgical technique, and others). Instability and fractures of nodes of PSF system for two years after surgery were found in 13 (3,17%) patients. This revealed that the destabilization or fracture structure were determined just in cases of pseudarthrosis (3 and 4 Bridwell grade) Conclusion The main goal of TLIF and PLIF is fusion in operated segment. Non fusion with pseudarthrosis cause instability and fracture of PSF in most cases. The interbody implant material does not matter. Quality of treatment interbody gap and degree of contact with the vertebral endplates, сage and bonegraft are most important.