Contribution of MRI and imaging exams in the diagnosis of lumbar pseudarthrosis.

INTRODUCTION: The diagnosis of pseudoarthrosis is based on imaging and clinical exam findings. The standard for pseudarthrosis diagnosis remains postoperative observation through computer tomography (CT) and patient's symptoms. This can be further augmented by dynamic X-ray imaging or nuclear positron emission tomography (PET) CT to demonstrate an absence of fusion by showing a persistence of mobility. However, there is not a uniform diagnostic approach that is a standard of care amongst spine practioners. The aim of this study is to describe the timeline and diagnostic analysis for pseudoarthrosis between the initial surgery and follow-up procedure. METHODS: This is a single-center retrospective observational study. The aim was to enroll patients reoperated for pseudarthrosis after 1 or 2 level lumbar fusions, between August 1st, 2008 and August 1st, 2018. The exams were reviewed by one surgeon and one radiologist, defining a status either in favor of pseudarthrosis, or against it, or inconclusive, based on the radiological criteria mentioned below. We then investigated different combinations of exams and their specific chronology before a diagnosis was established. RESULTS: Forty-four patients were included, 70.5% male and with a mean age of 47.3 years. The median time between the 2 surgeries was 23.7 months. Plain X-rays supported the diagnosis in 38.7% of cases, dynamic X-rays showed hypermobility in 50% of cases. The CT-scan demonstrated pseudarthrosis in 94,4% of cases. A MODIC 1 signal was observed in 87,2% of cases on MRI. SPECT-CT showed a tracer uptake in 70% of cases. CONCLUSION: Reducing the time to reintervention is a key objective for improving the management and clinical outcomes of these patients. We suggest that MRI is an additional tool in combination with CT in the assessment of suspected mechanical pseudarthrosis, in order to optimize the diagnosis and shorten the time to revision surgery. LEVEL OF EVIDENCE: IV.

Iatrogenic vertebral fracture in ankylosed spine during liver transplantation: a case report and biomechanical study using finite element method.

PURPOSE: The occurrence of an iatrogenic vertebral fracture during non-spinal digestive surgery is an exceptional event that has not been previously documented. Our study aims to explain the occurrence of this fracture from a biomechanical perspective, given its rarity. Using a finite element model of the spine, we will evaluate the strength required to induce a vertebral fracture through a hyperextension mechanism, considering the structure of the patient's spine, whether it is ossified or healthy. METHODS: A 70-year-old patient was diagnosed T12 fracture during a liver transplantation on ankylosed spine. We use a finite element model of the spine. Different mechanical properties were applied to the spine model: first to a healthy spine, the second to a osteoporotic ossified spine. The displacement and force imposed at the Sacrum, the time and location of fractures initiation were recorded and compared between the two spine conditions. RESULTS: A surgical treatment is done associating decompression with posterior fixation. After biomechanical study, we found that the fracture initiation occurred for the ossified spine after a sacrum displacement of 29 mm corresponding to an applied force of 65 N. For the healthy spine it occurred at a sacrum displacement of 52 mm corresponding to an applied force of 350 N. CONCLUSION: The force required to produce a type B fracture in an ankylosed spine is 5 times less than in a healthy spine. These data enable us to propose several points of management to avoid unexpected complications with ankylosed spines during surgical procedures. LEVEL OF EVIDENCE: IV.

Thoracolumbar vertebral fracture in unoperated idiopathic scoliosis.

INTRODUCTION: Traumatic fractures of the thoracolumbar spine are common. Their management considers the fracture type according to the various classifications in existence, as well as the patient's background and age. In some cases, the occurrence of a fracture on a spine with an unoperated scoliotic deformity can be observed. This entity, not described in the literature, can pose a therapeutic challenge and is not present in any existing treatment algorithm. The main objective of this work was to describe the characteristics and management of vertebral fractures in patients with unoperated idiopathic scoliosis. MATERIAL AND METHODS: We carried out a monocentric retrospective study in all patients operated on for a spinal fracture between May 2011 and August 2020, with a history of unoperated adolescent idiopathic scoliosis. We collected epidemiological data including the surgical course of each patient and the final result. The patients were categorized according to the surgical strategy (extensive fusion and correction of the deformity, short osteosynthesis without considering the scoliosis, vertebroplasty and orthopedic treatment) and the final clinical and radiological result evaluated at the last follow-up. RESULTS: Ten patients were included in this study with a total number of 16 fractured vertebrae. The population was 80% female, with an average age of 36.3 years. The majority of fractures were type A, at the thoracolumbar junction. The curves were classified as Lenke 1A in 5 cases, 1B in 2 cases, 1C in 1 case and 5C for 2 patients. Ultimately, 3 patients underwent extended fusion with correction of scoliosis, 6 localized osteosynthesis and 1 percutaneous vertebroplasty. In 50% of cases, a change of surgical strategy had to be made, due to worsening of the deformity or hyperalgesia. The last follow-up was at 19.7 months on average. Five patients had a good final clinical result, 5 patients had persistence of significant pain (lower back pain or cruralgia). CONCLUSION: This is the first study investigating the association of vertebral fractures and the presence of unoperated idiopathic scoliosis. The results of our study highlight the management challenges and difficulties in therapeutic decision-making. The presence of a pre-existing curve is thus an important parameter to consider and should lead to the discussion of performing an extended fusion secondarily in view of the risk of poor results from localized surgery. LEVEL OF EVIDENCE: IV.

Personalised gravitational loading of the cervical spine from biplanar X-rays for asymptomatic and clinical subjects in neutral standing position.

BACKGROUND: As a leading cause of disability with a high societal and economic cost, it is crucial to better understand risk factors of neck pain and surgical complications. Getting subject-specific external loading is essential for quantifying muscle forces and joint loads but it requires exertion trials and load cells which are uncommon in clinical settings. METHODS: This paper presents a method to compute the gravitational loading at four levels of the cervical spine (C3C4, C4C5, C5C6, C6C7) in neutral standing position from biplanar radiographs exclusively. The resulting load was decomposed in local disc frames and its components were used to compare different populations: 118 asymptomatic subjects and 46 patients before and after surgery (anterior cervical discectomy and fusion or total disc replacement). Comparisons were performed at C6C7 and the upper level adjacent to surgery. FINDINGS: Significant changes in gravitational loading were observed with age in healthy subjects as well as in patients after surgery and have been associated with changes in posture. INTERPRETATION: This approach quantifies the influence of postural changes on gravitational loading on the cervical spine. It represents a simple way to obtain necessary input for muscle force quantification models in clinical routine and to use them for patient evaluation. The study of the subsequent subject-specific spinal loading could help further the understanding of cervical spine biomechanics, degeneration mechanisms and complications following surgery.

Halo-gravity traction followed by definitive fusion in severe early onset scoliosis: results of a trunk analysis based on biplanar 3D reconstructions.

PURPOSE: Definitive fusion can be considered in early onset scoliosis (EOS) around triradiate cartilage closure. Halo-gravity traction (HGT) is an old strategy that can help lengthen and balance the spine before fusion. The postoperative changes of the trunk have never been investigated to date with modern imaging. The goal of this study was to analyze the 3D radiological outcomes, and the associated pulmonary function, of a cohort of severe EOS patients treated by definitive posterior fusion prepared by HGT. METHODS: All consecutive EOS patients with severe (> 85°) and stiff (flexibility < 25%) curves, treated by HGT followed by posterior fusion, were followed. 3D radiological measurements and pulmonary function were assessed. RESULTS: Forty-nine EOS patients underwent fusion, with a mean follow-up of 4 years (± 1). Age at surgery averaged 13.5 years old. HGT protocol reached on average 41% of body weight. Mean preoperative 3D Cobb angle was 95° (± 10) and final correction averaged 68.4% after surgery. 3D T4T12 kyphosis was reduced after surgery (11°, p < 0.01), while the apical vertebral rotation was improved by 27.8% (p = 0.06). 3D thoracic volume increased after surgery (p = 0.02), with a 3D T1T12 height gain averaging 3.7 cm (± 2). Both parameters were significantly correlated with total lung capacity improvement. Seven complications (14.2%) were reported, and 5 patients (10.6%) underwent unplanned revision. CONCLUSION: HGT is a safe and efficient strategy to prepare posterior fusion in severe EOS patients. The 3D trunk analysis demonstrated significant postoperative gains in thoracic and spinal lengths, as well as in thoracic volume. LEVEL OF EVIDENCE: IV.

Diagnosis of reoperated cervical non-union: Multicenter retrospective study about 45 patients.

INTRODUCTION: Non-union is one of the main complications of single- or multi-level cervical spine fusion, considerably impairing functional results. The aim of this study was to evaluate the respective contributions of imaging examinations in the diagnostic process, the challenge being to avoid inappropriate surgery and unnecessary complementary examinations. MATERIAL AND METHOD: A retrospective multicenter study included all patients managed for cervical spine non-union between 2008 and 2018. We evaluated the imaging examinations performed on each patient and determined signs of non-union in each image. RESULTS: The study included 45 patients in 4 centers: 55% female; mean age, of 48±8.0 years; 57% smokers. Systematic static radiography showed signs of non-union in 55% of cases. Dynamic X-ray was performed in 34% of patients, and showed hypermobility of the level in 80% of cases. CT supported diagnosis of non-union in 97% of cases, and MRI in 48%. SPECT-CT was positive in all cases of non-union. DISCUSSION: Dynamic X-ray is rarely prescribed, but frequently provided an objective measure of hypermobility of the level in non-union, justifying first-line use. Millimetric-slice CT was reliable for diagnosis. MRI is relevant only once diagnosis has been made, as part of preoperative work-up. Nuclear imaging can be useful in order to solve doubtful cases. CONCLUSION: In suspected cervical spine non-union, we recommend dynamic X-rays (flexion/extension) and CT-scan as first-line diagnosis examinations. LEVEL OF EVIDENCE: IV.