A Review of Strategies to Improve Biomechanical Fixation in the Cervical Spine

Study Design Systematic review. Objectives Review the surgical techniques and construct options aimed at improving the biomechanical strength of cervical constructs. Methods A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of the MEDLINE, Embase, and Cochrane Library databases was performed to identify all studies examining biomechanical strategies utilized in the osteoporotic cervical spine. Screening was performed in duplicate for all stages of the review process. Results An initial search returned 3887 articles. After deletion of duplications and review of abstracts and full text, 39 articles met inclusion criteria. Overall, the surgical techniques reviewed aimed at obtaining rigid fixation in the setting of poor bone quality, or dispersing the forces at the bone-implant interface. We identified 6 key techniques to improve biomechanical fixation. These include bicortical fixation, appropriate screw selection (size and trajectory), PMMA augmentation, load sharing techniques, consideration of ancillary fixation around the occipitocervical junction, and supplementing the construct with post-operative collar or halo. Conclusion The summation of the literature highlights a framework of modalities available to surgeons to improve biomechanical fixation in the cervical spine. While these may improve construct strength in the setting of osteoporosis, there is a paucity of evidence available to make recommendations in this patient population.

Poor bone quality in patients with rheumatoid arthritis receiving long-term bisphosphonate therapy for glucocorticoid-induced osteoporosis: an iliac bone biopsy study

Background Bisphosphonates (BPs) have been shown to reduce the incidence of vertebral fractures during the first year or two of glucocorticoid (GC) treatments and are therefore recommended as a first-line treatment for the prevention and treatment of GC-induced osteoporosis (GIO). However, there are theoretical concerns about the long-term use of BPs in low-turnover osteoporosis caused by chronic GC therapy. Methods We analyzed the trabecular microarchitecture, bone metabolism, and material strength of bone biopsy samples from the iliac crest of female patients with rheumatoid arthritis (RA) receiving an average of 6.7 years of BP therapy for GIO (GIOBP group, n = 10), compared with those of age- and bone mineral density (BMD)-matched non-RA postmenopausal women with no history of anti-osteoporosis medication use (reference group, n=10). Results Patients in the GIOBP group had a significantly greater fracture severity index, as calculated by the sum of the Genant visual semiquantitative grading scores of vertebral fractures (T4-L5) compared with the reference patients. Micro-computed tomography analysis showed that the degree of mineralization and trabecular microarchitecture were significantly lower in the GIOBP group than in the BMD-matched reference patients. Patients in the GIOBP group exhibited lower bone contact stiffness, determined by micro-indentation testing, than in the reference group. The contact stiffness of the bone was negatively correlated with the fracture severity index and the daily prednisolone dosage. Immunohistochemistry and serum bone turnover markers showed decreased osteoclastic activity, impaired mineralization, and an increased fraction of empty lacunae in the GIOBP group. Conclusions Our findings indicate that patients with RA receiving long-term BP for GIO are still at high risk for fragility fractures because of poor bone quality.

Spontaneous Spine Fracture in Patient with Ankylosing Spondylitis under Spinal Anesthesia: A Case Report and Review of the Literature

Factures in ankylosing spondylitis (AS) patients tend to occur due to the absence of motion between vertebrae, poor bone quality, and a long lever arm that generates extension force. However, most patients have a history of at least minor trauma. The aim of this report was that a vertebral fracture in a patient with AS can be caused not only by minor trauma, but also by position changes or maintenance of position for examination due to structural weakness. A 75-year-old woman with AS visited her local hospital on foot for back pain. She usually had back pain. However, she had increased back pain after falling over three weeks prior. In plain radiographs, no fracture was apparent. The doctor tried to perform magnetic resonance imaging (MRI) for further evaluation. However, several attempts of MRI failed due to continuous movement arising from pain. As a result, MRI was performed under spinal anesthesia for pain control. However, complete paraplegia developed during the MRI examination. MRI showed extension-type vertebral fracture with displacement and the patient was transferred to our hospital. We performed emergency posterior fusion, but neurological symptoms did not improve. This case suggests the need for careful positioning, sedation, or anesthesia when performing an examination or surgery in AS patients. We recommend that all patients with AS should be carefully positioned at all times during testing or surgery.

Prevalence of Poor Bone Quality in Patients Undergoing Spine Surgery: A Comprehensive Approach

Study Design: A cross-sectional study. Objectives: To investigate the prevalence of poor bone quality in patients requiring spine surgery through comprehensive evaluation with bone mass density (BMD), trabecular bone score (TBS), FRAX, and vitamin D status. Methods: we prospectively recruited patients of > 50 years old candidates for lumbar or cervical spine fusion surgery at our institution. Recorded data were: demographic, body mass index (BMI), risk factors for osteoporosis, daily calcium intake, FRAX score, disability index for lumbar and cervical spine, and VAS for pain. Serum 25 OH vitamin D, BMD using DXA, and TBS was also evaluated. Results: A total of 104 patients were recruited, osteoporosis by BMD was detected in 9.6%, and osteopenia in 34.6% of patients. 69.4% of patients with osteopenia had a degraded or partially degraded bone microarchitecture by TBS. Low levels of vitamin D were detected in 79.8% of patients. Increased pain was associated with low BMD levels. Adding TBS to BMD for the determination of bone strength resulted in 33.7% of patients with poor bone quality. Lastly, the combination of BMD, TBS, and FRAX revealed 37,5% of patients with poor bone quality. Conclusions: Poor bone quality and low vitamin D levels are quite common among patients aged ≥ 50 years undergoing spine surgery. DXA alone seems not enough for preoperative identification of impaired bone quality cases. FRAX is useful for identifying high-risk patients and TBS is a valuable complement to DXA by adding the dimension of bone quality.