Bilateral CS-rod fixation provided about the same stability in cadaveric specimens as PS-rod fixation regardless of the presence of interbody, TLIF, or DLIF support.

The MPT craniotomy provides comparable surgical exposure to that offered by the PT. The advantages of the MPT include reduction of tissue trauma and bony removal, a decrease in surgical time, and improved cosmetic outcomes.

OBJECTIVE: To compare anatomically the surgical exposure provided by pterional (PT), orbitozygomatic (OZ), and minisupraorbital (SO) craniotomies. @@METHODS:@@ Seven sides of six fixed cadaver heads injected with silicone were used. The mini-SO craniotomy followed by the PT and OZ approaches were performed sequentially. The bony flaps were attached with miniplates and screws, allowing easy conversion between the approaches. A frameless stereotactic device was used to calculate an area of surgical exposure and the angles of approach for six different anatomic targets. An image guidance system was used to demonstrate the limits of the surgical exposure for each technique. RESULTS: No significant differences were observed in the total area of surgical exposure when comparing the mini-SO (A = 1831.2 ± 415.3 mm2), PT (A = 1860.0 ± 617.2 mm2), and OZ approaches (A = 1843.3 ± 358.1 mm2; P > 0.05). Angular exposure was greater for the OZ and PT approaches than for the mini-SO approach, either in the vertical and horizontal axes, considering all of the six targets studied (P< 0.05). Except for the distal segment of the ipsilateral sylvian fissure, no practical differences in the limits of the exposure were detected. CONCLUSION: The mini-SO approach may offer a similar surgical working area compared with that provided by standard craniotomies and constitutes an excellent alternative to the OZ and PT craniotomies in selected patients. Selection should not be based primarily on the area to be exposed, but rather on the working angles that are anticipated to be required. The key point is to use the most adequate technique for a particular patient, rather than using a one-size-fits-all approach for all patients.

It is mechanically advantageous to include as many fixation points as possible when atlantoaxial instability is treated surgically.

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Study Design-Correlation of locations of sacral insufficiency fractures are made to regions of stress depicted by finite element analysis derived from biomechanical models of patient activities.Objective-Sacral insufficiency fractures occur at consistent locations. It was postulated that sacral anatomy and sites of stress within the sacrum with routine activities in the setting of osteoporosis are foundations for determining patterns for the majority of sacral insufficiency fractures. Summary of Background Data-The predominant vertical components of sacral insufficiency fractures most frequently occur bilaterally through the alar regions of the sacrum which are the thickest and most robust appearing portions of the sacrum instead of subjacent to the central sacrum which bears the downward force of the spine.Methods-First, the exact locations of 108 cases of sacral insufficiency fractures were catalogued and compared to sacral anatomy. Second, different routine activities were simulated by pelvic models from CT scans of the pelvis and finite element analysis. Analyses were done to correlate sites of stress with activities within the sacrum and pelvis compared to patterns of sacral insufficiency fractures from 108 cases.Results-The sites of stress depicted by the finite element analysis walking model strongly correlated with identical locations for most sacral and pelvic insufficiency fractures. Consistent patterns of sacral insufficiency fractures emerged from the 108 cases and a biomechanical classification system is introduced. Additionally, alteration of walking mechanics and asymmetric sacral stress may alter the pattern of sacral insufficiency fractures noted with hip pathology (p=.002).Conclusions-Locations of sacral insufficiency fractures are nearly congruous with stress depicted by walking biomechanical models. Knowledge of stress locations with activities, cortical bone transmission of stress, usual fracture patterns, intensity of sacral stress with different activities, and modifiers of walking mechanics may aid medical management, interventional, or surgical efforts. NIH Public AccessAuthor Manuscript Spine (Phila Pa 1976). Author manuscript; available in PMC 2009 July 13. Published in final edited form as:Spine (Phila Pa 1976 Key Points• Identify the exact locations of sacral insufficiency fractures from large a consecutive series of cases by MRI and/or CT anatomical imaging methods.• Biomechanical model simulations to determine locations of stress within the sacrum with patient activities determined by finite element analysis.• Match clinical locations of sacral insufficiency fractures and sacral stress with activities as identified by the biomechanical models.• Sacral insufficiency fracture biomechanical classification system is introduced.• Knowledge of sacral stress locations with activities, cortical bone transmission of stress, usual sacral insufficiency fracture patterns, intensity of sacral stress with different activities, and modifiers of walking mechanics may aid medical, interve...

Object. The purpose of this study was to compare cable techniques used in occipitocervical fixation with two types of screw fixation. The authors hypothesized that screw fixation would provide superior immobilization compared with cable methods. Methods. Ten cadaveric specimens were prepared for biomechanical analyses by using standard techniques. Angular and linear displacement data were recorded from the occiput to C-6 with infrared optical sensors after conditioning runs. Specimens underwent retesting after fatiguing. Six methods of fixation were analyzed: Steinmann pin with and without C-1 incorporation; Cotrel-Dubousett horseshoe with and without C-1 incorporation; Mayfield loop with C1–2 transarticular screw fixation; and a custom-designed occipitocervical transarticular screw-plate system. Sublaminar techniques were extended to include C-3 in the fusion construct, whereas transarticular techniques incorporated the occiput, C-1, and C-2 only. All methods of fixation provided significant immobilization in all specimens compared with the nonconstrained destabilized state. Despite incorporation of an additional vertebral segment, sublaminar techniques performed worse as a function of applied load than screw fixation techniques. Following fatiguing, these differences were more pronounced. The sublaminar techniques failed most prominently in flexion—extension and in axial rotation. On gross inspection, increased angular displacement associated with loosening of the sublaminar cables was observed. Conclusion. Occipitocervical fixation can be performed using a variety of techniques; all bestow significant immobilization compared with the destabilized spine. All methods tested in this study were susceptible to fatigue and loss of reduction and were weakest in resisting vertical settling. Screw fixation of the occiput—C2 reduces the number of vertebral segments that are necessary to incorporate into the fusion construct while providing superior immobilization and resistance to fatigue and vertical settling compared with sublaminar methods.

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