Subaxial lateral mass prosthesis for posterior reconstruction of cervical spine

Purpose: To obtain the relevant morphometry of the lateral mass of the subaxial cervical spine (C3-C7) and to design a series of lateral mass prostheses for the posterior reconstruction of the stability of cervical spine. Methods: The computed tomography (CT) scans of healthy volunteers were obtained. RadiAnt DICOM Viewer software (Version 2020.1, Medixant, Poland) was used to measure the parameters of lateral mass, such as height, anteroposterior dimension (APD), mediolateral dimension (MLD) and facet joint angle. According to the parameters, a series of cervical lateral mass prostheses were designed. Cadaver experiment was conducted to demonstrate its feasibility. Results: 23 volunteers with an average age of 30.1 ± 7.1 years were enrolled in this study. The height of lateral mass is 14.1 mm averagely. Facet joint angle, APD and MLD of lateral mass averaged 40.1 degrees, 11.2 mm and 12.18 mm, respectively. With these key data, a lateral mass prosthesis consists of a bone grafting column and a posterior fixation plate was designed. The column has a 4.0 mm radius, 41 degrees surface angle and adjustable height of 13, 15, or 17 mm. In the cadaver experiment, the grafting column could function as a supporting structure between adjacent facets, and it would not violate exiting nerve root (NR) or vertebral artery (VA). Conclusion: This study provided detailed morphology of the lateral mass of subaxial cervical spine. A series of subaxial cervical lateral mass prostheses were designed awaiting further clinical application.

Fluoroscopy-Assisted C1–C2 Posterior Fixation for Atlantoaxial Instability: A Single-Center Case Series of 78 Patients

Background and Objectives: Posterior C1–C2 fixation, with trans-articular screws (TAS) or screw-rod-construct (SRC), is the main surgical technique for atlantoaxial instability, and can be performed with a fluoroscopy-assisted free-handed technique or 3D navigation. This study aimed to evaluate complications, radiological and functional outcome in patients treated with a fluoroscopy-assisted technique. Materials and Methods: A single-center consecutive cohort study was conducted of all adult patients who underwent posterior C1–C2 fixation, using TAS or CRS, between 2005–2019. Results: Seventy-eight patients were included, with a median follow-up time of 6.8 years. Trauma was the most common injury mechanism (64%), and cervicalgia the predominant preoperative symptom (88%). TAS was used in 33%, and SRC in 67% of cases. Surgery was associated with a significant reduction in cervicalgia (from 88 to 26%, p < 0.001). The most common complications were vertebral artery injury (n = 2, 2.6%), and screw malposition (n = 5, 6.7%, of which 2 were TAS and 3 were SRC). No patients deteriorated in their functional status following surgery. Conclusions: Fluoroscopy-assisted C1–C2 fixation with TAS or SRC is a safe and effective treatment for atlantoaxial instability, with a low complication rate, few surgical revisions, and pain relief in the majority of the cases.

Indications and Outcomes of the Kocher-Langenbeck Surgical Approach in the Management of Acetabular Fractures in a Resource Limited Setting

The Kocher-Langenbeck (K-L) approach is the ‘workhorse’ of surgery for acetabular fractures needing posterior fixation. It is indicated for most of these fractures for proper surgical technique and optimal outcome. We therefore evaluated the outcome of surgically treated acetabular fractures through the K-L approach in our setting with limited resources. 57 patients were operated by the K-L approach during the 3-year study period. The most common indications of this approach were: posterior wall (38.6%) and transverse + posterior wall fractures (36.8%). Based on Matta’s criteria of fracture reduction, 81 % were judged anatomic, 16% imperfect and 3 % poor. A surgery waiting time of 8 to 14 days after injury, significantly favoured anatomic fracture reduction. The MAP score was excellent in 72 % and unacceptable in 10.6 %. Factors associated with poor outcomes were poor fracture reduction and the development of early post-operative complications. Iatrogenic sciatic nerve palsy (ISNP) was the most significant post-operative complication (19.3%). The levering of Hohmann retractors in the sciatic notches was the major risk factor for developing ISNP, compared to the use of sciatic nerve retractors. Other early and late complications included surgical site infections (12.3%) and heterotopic ossification (8.8 %), respectively. The overall outcome following surgery by the K-L approach is satisfactory. However, there is need to ameliorate the technique, especially at the level of instrumentation, to limit post-operative complications.

Outcomes of half-width vertical rectus transposition augmented with posterior fixation sutures for sixth cranial nerve palsy

AIM: To describe the experience with half-width vertical muscles transposition (VRT) augmented with posterior fixation sutures. METHODS: The clinical charts of all patients, who underwent half-width VRT augmented with posterior fixation sutures for sixth cranial nerve palsy from January 2003 to December 2018, were retrospectively reviewed. For each patient, pre- and post-operatively, the largest measured angle was used for the calculations, usually resulting with the angle for distance, except in young infants, where measurements were made at near fixation using the Krimsky test. RESULTS: Fifteen patients met the inclusion criteria for the study, of them 9 (60.0%) had also medial rectus muscle recession at the time of surgery. Mean follow-up period was 21.4±23.2mo (range 1.5-82mo). Preoperative mean esotropia was 51.3±19.7 prism diopter (PD; range 20-90 PD). Postoperative mean deviation on final follow-up was 7.7±20.2 PD (range -40 to 35 PD; P=0.018). In all patients with preoperative abnormal head position, improvement was noted. Ten (66.7%) patients had improvement in abduction and 10 (66.7%) patients reported improvement in their diplopia, by final follow-up. The addition of medial rectus recession was correlated with a larger change in postoperative horizontal deviation compared to baseline (P=0.026). Two (13.3%) patients developed a vertical deviation in the immediate postoperative period which had resolved in one of them. CONCLUSION: Half-width VRT augmented with posterior fixation suture, with or without medial rectus muscle recession, is an effective and safe procedure for esotropia associated with sixth cranial nerve palsy. A major improvement in the angle of deviation is expected. Most patients will have improvement in their abnormal head position and diplopia.

Treatment of Severe Bone Destruction in L5-S1 Spinal Tuberculosis With Anterior Combined Posterior Approach

Background: There are many studies on the surgical treatment of lumbosacral tuberculosis, but both the anterior and posterior approaches present some shortcomings. This study aimed to evaluate the therapeutic efficacy of anterior debridement and bone graft, posterior fixation and fusion with navigation for L5-S1 tuberculosis with severe bone destruction. Methods: This was a retrospective study of 24 patients with severe tuberculosis in L5-S1 who underwent anterior interbody arthrodesis and posterior pedicle screw internal fixation by open approach under computer navigation between February 2011 and Novenmber 2016. The erythrocyte sedimentation rate(ESR), C-reactive protein level(CRP),visual analogue scale(VAS), and lumbosacral angle were compared between before surgery, after surgery, and at the final follow-up. The fusion status of bone graft was evaluated with computed tomography(CT).Results: The mean operation time was 244.58 minutes. The mean intraoperative blood loss was 413.75ml. The accuracy of screw placement was 96.43%. The mean follow-up period was 26.17 months. The average ESR, CRP, VAS, and lumbosacral angles were 65.96 mm/h, 52.93 mg/L, 4.96 points ,and 107.94°, respectively,at preoperative, 34.17 mm/h, 16.47 mg/L, 1.58 points, and 116.12°, respectively, after surgery, and 14.08 mm/h, 6.20 mg/L, 0.58 points, and 115.97°, respectively, at the final follow-up period. The differences of ESR, CRP, VAS are statistically significant (p < 0.05). The difference of lumbosacral angles before and after surgery is statistically significant (p < 0.05)，but there is no statistically significant difference between after surgery and the final follow-up period (p＞0.05). Nine patients with ASIA Grade D before surgery returned to Grade E by the final follow-up period. All patients achieved bone fusion.There was no recurrence of the disease. Conclusions: Anterior debridement and bone graft fusion combined with navigated posterior pedicle screw fixation is a safe and effective treatment option for patients with severe bone destruction in L5-S1 spinal tuberculosis.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation

OBJECTIVE Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies. METHODS An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4–5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared. RESULTS The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%–82% for LIF, and 69%–86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%–87% for TLIF, 86%–91% for LIF, and 90%–92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios. CONCLUSIONS Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

The effect of posterior compression of the facet joints for initial stability and sagittal profile in the treatment of thoracolumbar fractures: a biomechanical study

Purpose Surgical treatment of thoracolumbar A3-fractures usually comprises posterior fixation—in neutral position or distraction—potentially followed by subsequent anterior support. We hypothesized that additional posterior compression in circumferential stabilization may increase stability by locking the facets, and better restore the sagittal profile. Methods Burst fractures Type A3 were created in six fresh frozen cadaver spine segments (T12–L2). Testing was performed in a custom-made spinal loading simulator. Loads were applied as pure bending moments of ± 3.75 Nm in all six movement axes. We checked range of motion, neutral zone and Cobb’s angle over the injured/treated segment within the following conditions: Intact, fractured, instrumented in neutral alignment, instrumented in distraction, with cage left in posterior distraction, with cage with posterior compression. Results We found that both types of instrumentation with cage stabilized the segment compared to the fractured state in all motion planes. For flexion/extension and lateral bending, flexibility was decreased even compared to the intact state, however, not in axial rotation, being the most critical movement axis. Additional posterior compression in the presence of a cage significantly decreased flexibility in axial rotation, thus achieving stability comparable to the intact state even in this movement axis. In addition, posterior compression with cage significantly increased lordosis compared to the distracted state. Conclusion Among different surgical modifications tested, circumferential fixation with final posterior compression as the last step resulted in superior stability and improved sagittal alignment. Thus, posterior compression as the last step is recommended in these pathologies.

The impact of the lateral decubitus position in the perioperative period on posterior fixation for thoracolumbar fracture with ankylosing spinal disorder

OBJECTIVE Patients with ankylosing spinal disorders (ASDs), such as ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis, often have rigid kyphosis of the spine. The fracture site is sometimes unintentionally displaced when surgery is conducted with the patient prone. To prevent this incident, the authors adopted the lateral decubitus position for patients intraoperatively for this pathology. The aim of this study was to retrospectively assess the impact of the lateral decubitus position in the perioperative period on posterior fixation for thoracolumbar fractures with ASD. METHODS Thirty-seven consecutive patients who underwent posterior instrumentation for thoracolumbar fracture with ASD at the authors’ institute were divided into 15 lateral decubitus positions (group L) and 22 prone positions (group P). Surgical time, estimated blood loss (EBL), number of levels fused, perioperative complications, length of stay (LOS), ratio of fracture voids, and ratio of anterior wall height were investigated. The ratio of fracture void and the ratio of anterior wall height were the radiological assessments showing a degree of reduction in vertebral fracture on CT. RESULTS Age, sex, BMI, fracture level, and LOS were similar between the groups. Levels fused and EBL were significantly shorter and less in group L (p < 0.001 and p = 0.04), but there was no significant difference in surgical time. The complication rate was similar, but 1 death within 90 days after surgery was found in group P. The ratio of fracture voids was 85.4% ± 12.8% for group L and 117.5% ± 37.3% for group P. A significantly larger number of patients with a fracture void ratio of 100% or less was found in group L (86.7% vs 36.4%, p = 0.002). The ratio of anterior wall height was 107.5% ± 12.3% for group L and 116.9% ± 18.8% for group P. A significantly larger number of patients with the anterior wall height ratio of 100% or less was also found in group L (60.0% vs 27.3%, p = 0.046). CONCLUSIONS The results of this study suggest that the lateral decubitus position can be expected to have an effect on closing or maintaining the fracture void or a preventive effect of intraoperative unintentional extension displacement of the fractured site, which is often seen in the prone position during surgery for thoracolumbar fractures involving ASD.

Thoracolumbar spine fractures, short versus long posterior fixation: Guidelines and controversies. A Systematic Review

Background Thoracolumbar spine fractures are common injuries that can result in significant disability, deformity and neurological deficit. Controversies exist regarding the appropriate radiological investigations, the indications for surgical management and the timing, approach and type of surgery. Aim of the Work to discuss: Guidelines and controversies of short versus long posterior fixation in management of thoracolumbar spine fractures. Patients and Methods 20 articles were identified through specified electronic databases. After application of the inclusion and exclusion criteria, 9 comparative studies were finally included in this systematic review. Various other approaches were used in combination with posterior pedicle screw fixation according to the underlying pathology (e.g. Discectomy, Laminectomy, Vertebroplasty, Kyphoplasty, etc.). A total of 194 patients underwent short segment pedicle screw fixation compared to 158 patients who underwent Long segment pedicle screw fixation for various indications. The majority of the included trials were small studies with between 12 and 69 participants. The patients’ characteristics were comparable within each study group. Individual patient data were available from these articles. Results A total of 194 patients underwent short segment pedicle screw fixation compared to 158 patients who underwent Long segment pedicle screw fixation for various indications. The majority of the included trials were small studies with between 12 and 69 participants. The patients’ characteristics were comparable within each study group. Individual patients data were available from these articles; longest follow up post operative record was about 71 months; 162 male and 93 female in these studies; the mean age about 38 years; the level of thoracolumbar fracture was: 60 patients at T12,104 patients at L1 and 41 patients at L2. Conclusion This review suggest work on the guidelines with evaluating of each case according to age, angels, height, weight (BMI), comorbidities, ability to anaesthesia and types of instability in the patient before as osteoporosis and kyphosis. Degree of angels of cobb and kyphotic angel which are major factors determine if posterior long or short.