Side specific differences of Hounsfield-Units in the osteoporotic lumbar spine.

Background: Gold standard for determining bone density as a surrogate parameter of bone quality is measurement of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA), most commonly performed on the lumbar spine (L1-L4). Computed tomography (CT) data are often available for surgical planning prior to spine procedures, but currently this information is not standardized for bone quality assessment. Besides, measuring the Hounsfield-Units (HU) is also of great importance in the context of biomechanical studies. This in vitro study aims in comparing BMD from DXA and HU based on diagnostic CT scans. In addition, methods are presented to quantify local density variations within bones. Methods: One hundred and seventy-six vertebrae (L1-L4) from 44 body donors (age 84.0±8.7 years) were studied. DXA measurements were obtained on the complete vertebrae to determine BMD, as well as axial CT scans with a slice thickness of 1 mm. Using Mimics Innovation Suite image processing software (Materialise NV, Leuven, Belgium), two volumes (whole vertebra vs. spongious bone) were formed for each vertebra, which in turn were divided in their left and right sides. From these total of six volumes, the respective mean HU was determined. HU of the whole vertebra and just spongious HU were compared with the BMD of the corresponding vertebrae. Side specific differences were calculated as relative values. Results: Whole bone and spongious HU correlated significantly (P>0.001; α=0.01) with BMD. A positive linear correlation was found, which was more pronounced for whole bone HU (R=0.72) than for spongious HU (R=0.62). When comparing the left and right sides within each vertebra, the HU was found to be 10% larger on average on one side compared to the opposite side. In some cases, the difference of left and right spongious bone can be up to 170%. There is a tendency for the side comparison to be larger for the spongious HU than for the whole vertebra. Conclusions: Determination of HU from clinical CT scans is an important tool for assessing bone quality, primarily by including the cortical portion in the calculation of HU. Unlike BMD, HU can be used to distinguish precisely between individual regions. Some of the very large side-specific gradients of the HU indicate an enormous application potential for preoperative patient-specific planning.

Cervical spine fractures in ankylosing spondylitis patients: an analysis of the presentation and clinical results of 110 surgically managed patients in two spine centers.

PURPOSE: In this work, a two-center study was performed to study the clinical presentation of cervical spine fractures in ankylosing spondylitis (AS) patients and assess the surgical management of these fractures. METHODS: A retrospective analysis of prospectively collected data in two level-1 spine surgery centers was performed. Both spine centers have a standard database for all admitted patients. Inclusion criteria were surgically treated AS with cervical spine fracture diagnosis (from C1 to Th3) and postoperative follow-up minimum of 12 months. RESULTS: One hundred ten patients (105 male/5 female) were included. The mean age was 62 ± 10 years. The mean time between trauma and surgery was 49 ± 42 days. There was a history of mild trauma in 72 patients (65.4%). The clinical presentation was a pain in all patients. Twenty-seven (24.6%) had a neurological deficit at admission. The most common fracture level was C6/7 in 63 patients (57.23%). The VAS was 7 ± 1, and NDI was 34 ± 8 in the preoperative assessment. The mean preoperative kyphosis angle was 48 ± 26° between C2 and C7. Positioning and preparing of the patients on the operation table took a mean of 57 ± 28 min. The surgical approach was dorsal in 59 patients (53.6%), combined in 45 patients (40.9%), and ventral in 6 patients (6,5%). The mean number of the fixed levels was 6 ± 2 levels. Intraoperative complications occurred in 9 patients (8.2%). Postoperative Cobb angle improved to a mean of 17 ± 9 degrees. Neurological improvement occurred in 20/27 patients. In 12 patients, the recovery was complete. The mean postoperative follow-up was 46 ± 18 months. VAS improved to 3 ± 1, and NDI improved to 14 ± 6 at the last postoperative visit. The improvement was clinically significant (p = 0.01 and 0.00, respectively). CONCLUSION: High suspicion of cervical spine fractures is necessary for patients with AS. CT and MRI images are necessary to rule out cervical spine fractures in AS patients, especially to detect occult fractures. Surgical treatment is safe, and the posterior approach with long-segment fusion is the approach of choice in this group of patients.

[Etiology, epidemiology, prognosis and biomechanical principles of neuromuscular scoliosis]. / Ätiologie, Epidemiologie, Prognose und biomechanische Besonderheiten neuromuskulärer Skoliosen.

Deformity due to neuromuscular disease is often progressive and associated with reduced vital capacity. In general, all treatment should be performed in specialized centers, since invasive measures are associated with an increased morbidity compared to adolescent scoliosis. Derived from the etiology and the resulting biomechanical basis (characteristics), important aspects and considerations arise for all healthcare institutions from the examination interval to the duration of conservative therapy and initiation of surgical therapy. Proper monitoring and assessment are key components to identify curve progression and to achieve preservation or improvement of basic functions.

Spondylodiscitis due to transmitted mycotic aortic aneurysm or infected grafts after endovascular aortic aneurysm repair (EVAR): A retrospective single-centre experience with short-term outcomes.

PURPOSE: To report the challenging therapeutic approach and the clinical outcome of patients with pyogenic spondylodiscitis transmitted due to infected retroperitoneal regions of primary infected mycotic aortic aneurysms (MAAs) or secondary infected aortic stent grafts after endovascular aneurysm repair (EVAR). METHODS: Between 2012 and 2019, all patients suffering from spondylodiscitis based on a transmitted infection after the EVAR procedure were retrospectively identified. Patient data were analysed regarding the time between primary and secondary EVAR infection and spondylodiscitis detection, potential source of infection, pathogens, antibiotic treatment, complications, recovery from infection, mortality, numeric rating scale (NRS), COBB angle and cage subsidence. RESULTS: Fifteen patients with spondylodiscitis transmitted from primary or secondary infected aortic aneurysms after EVAR were included. The median follow-up time was 8 months (range 1-47). Surgery for spondylodiscitis was performed in 12 patients. In 9 patients, the infected graft was treated conservatively. MAAs were treated in 4 patients first with percutaneous aortic stent graft implantation followed by posterior surgery of the infected spinal region in a two-step procedure. Infection recovery was recorded in 11 patients during follow-up. The overall mortality rate was 27% (n = 4). The mean pain intensity improved from an NRS score of 8.4 (3.2-8.3) to 3.1 (1.3-6.7) at the last follow-up. CONCLUSION: EVAR was used predominantly to treat primary infected MAAs. Secondary infected grafts were treated conservatively. Independent of vascular therapy, surgery of the spine led to recovery in most cases. Thus, surgery should be considered for the treatment of EVAR- and MAA-related spondylodiscitis.

Paget's disease of the lumbar spine: decompressive surgery following 17 years of bisphosphonate treatment.

BACKGROUND: We present a rare case of Paget's disease (PD) with involvement of the lumbar spine over a period of 19 years. We discuss the diagnostic process to rule out alternative diagnoses and medical and surgical treatment strategies. CASE DESCRIPTION: A 58-year-old man first diagnosed with PD in 1998 with solid involvement of the 4th lumbar vertebra has been undergoing periodic examinations over a period of 18 years. Since then, the patient has been treated conservatively with bisphosphonates. When conservative treatment options have been exhausted, surgery was indicated due to a progressively reduced ability to walk. Surgery with undercutting decompression via laminotomy was performed. PD was confirmed by biopsy. Bisphosphonate treatment was continued pre- and postoperatively. Follow-up examinations showed an improvement in clinical outcome measures. CONCLUSIONS: Conservative treatment remains the gold standard for PD with spinal involvement. This patient had been asymptomatic on bisphosphonate therapy for almost 17 years, but presented with new onset back pain. In such cases, fracture and rare conversion into sarcoma must be ruled out, and biopsy should be performed even in the absence of signs of malignancy. Currently, there are no clear treatment recommendations available in the literature regarding cases of PD with expansive growth and involvement of the spinal canal causing neurologic deficits. Furthermore, laminectomy has been shown to cause complications in up to 27% of cases with the risk of early postoperative death. In contrast, extended laminotomy and undercutting decompression should be considered.