Combined Petrosal Intertentorial Approach: A Cadaveric Study of Comparison With the Standard Combined Petrosectomy.

BACKGROUND AND OBJECTIVES: The combined petrosal intertentorial approach (CPIA) has been proposed as an alternative to standard combined petrosal approach (SCPA). CPIA has been designed to maintain integrity of the temporal dura with a view to reduce temporal lobe morbidity and venous complications. This study has been designed to perform a quantitative comparison between these approaches. METHODS: Five human specimens were used for this study. CPIA was performed on one side and SCPA on the opposite side. The area of exposure (petroclival and brainstem), surgical freedom, and angles of attack to a predefined target were measured and compared. RESULTS: SCPA provided a significantly larger petroclival area of exposure (6.81 ± 0.60 cm2) over the CPIA (5.59 ± 0.59 cm2), P = .012. The area of brainstem exposed with SCPA was greater than with CPIA (7.17 ± 0.84 vs 5.63 ± 0.72, P = .014). The area of surgical freedom was greater in SCPA rather than in CPIA (8.59 ± 0.55 and 7.13 ± 0.96 cm2, respectively, P = .019). There was no significative difference between CPIA and SCPA in the vertical angles of attack for the Meckel cave, Dorello canal, and root entry zone of cranial nerve VII. Conversely, the horizontal angles of attack permitted by the CPIA were significantly smaller for the Meckel cave (52.36° ± 5.01° vs 64.4° ± 5.3°, P = .006) and root entry zone of cranial nerve VII (30.7° ± 4.4° vs 40.1° ± 6.2°, P = .025). CONCLUSION: CPIA is associated with a reduction in terms of the area of surgical freedom (22%), skull base (18%), brainstem exposure (17%), and horizontal angles of attack (18%-23%) when compared with SCPA. This loss in terms of exposure is counterbalanced by the advantage of keeping the temporal lobe covered by an extra layer of meningeal tissue, thus possibly reducing the risk of temporal lobe injury and venous infarction. These results need to be validated with adequate clinical experience.

Simultaneous Evaluation of Bone Cut and Implant Placement Accuracy in Robotic-Assisted Total Knee Arthroplasty.

Background: This study aimed to evaluate the accuracy of bone cuts and implant placements, simultaneously, for total knee arthroplasty (TKA) performed using a system with an active robotic arm. Methods: Two experienced orthopaedic surgeons performed TKA on ten cadaveric legs. Computed tomography scans were performed to compare the bone cuts and implant placements with the preoperative planning. The differences between the planned and actual bone cuts and implant placements were assessed using positional and angular errors in the three anatomical planes. Additionally, the cut-implant deviations were calculated. Statistical analysis was performed to detect systematic errors in the bone cuts and implant placements and to quantify the correlations between these errors. Results: The root-mean-square (RMS) errors of the bone cuts (with respect to the planning) were between 0.7-1.5 mm and 0.6-1.7°. The RMS implant placement errors (with respect to the planning) varied between 0.6-1.6 mm and 0.4-1.5°, except for the femur and tibia in the sagittal plane (2.9°). Systematic errors in the bone cuts and implant placements were observed, respectively, in three and two degrees of freedom. For cut-implant deviations, the RMS values ranged between 0.3-2.0 mm and 0.6-1.9°. The bone cut and implant placement errors were significantly correlated in eight degrees-of-freedom (ρ ≥ 0.67, p < 0.05). Conclusions: With most of the errors below 2 mm or 2°, this study supported the value of active robotic TKA in achieving accurate bone cuts and implant placements. The findings also highlighted the need for both accurate bone cuts and proper implantation technique to achieve accurate implant placements.

Anterior Petrosectomy With Intertentorial Approach.

BACKGROUND AND OBJECTIVES: The extradural anterior petrosal approach (EAPA) can present a challenge because it deals with critical structures in a narrow, confined corridor. It is associated with several potential approach-related risks including temporal lobe and venous injuries. Tentorial peeling has the potential to largely eliminate these risks during the approach and may offer more options for tailoring the dural opening to the anatomic region that one wants to expose. METHODS: Anatomic dissections of five adult injected non-formalin-fixed cadaveric heads were performed. Anterior petrosectomy with intertentorial approach (APIA) through a tentorial peeling was completed. Step-by-step documentation of the cadaveric dissections and diagrammatic representations are presented along with an illustrative case. RESULTS: Tentorial peeling separates the tentorium into a temporal tentorial leaf and posterior fossa tentorial leaf, adding a fourth dural layer to the three classic ones described during a standard EAPA. This opens out the intertentorial space and offers more options for tailoring the dural incisions specific to the pathology being treated. This represents a unique possibility to address brainstem or skull base pathology along the mid- and upper clivus with the ability to keep the entire temporal lobe and basal temporal veins covered by the temporal tentorial leaf. The APIA was successfully used for the resection of a large clival chordoma in the illustrative case. CONCLUSION: APIA is an interesting modification to the classic EAPA to reduce the approach-related morbidity. The risk reduction achieved is by eliminating the exposure of the temporal lobe while maintaining the excellent access to the petroclival region. It also provides several options to tailor the durotomies based on the localization of the lesion.

An Expert-Supervised Registration Method for Multiparameter Description of the Knee Joint Using Serial Imaging.

As knee osteoarthritis is a disease of the entire joint, our pathophysiological understanding could be improved by the characterization of the relationships among the knee components. Diverse quantitative parameters can be characterized using magnetic resonance imaging (MRI) and computed tomography (CT). However, a lack of methods for the coordinated measurement of multiple parameters hinders global analyses. This study aimed to design an expert-supervised registration method to facilitate multiparameter description using complementary image sets obtained by serial imaging. The method is based on three-dimensional tissue models positioned in the image sets of interest using manually placed attraction points. Two datasets, with 10 knees CT-scanned twice and 10 knees imaged by CT and MRI were used to assess the method when registering the distal femur and proximal tibia. The median interoperator registration errors, quantified using the mean absolute distance and Dice index, were ≤0.45 mm and ≥0.96 unit, respectively. These values differed by less than 0.1 mm and 0.005 units compared to the errors obtained with gold standard methods. In conclusion, an expert-supervised registration method was introduced. Its capacity to register the distal femur and proximal tibia supports further developments for multiparameter description of healthy and osteoarthritic knee joints, among other applications.

Three-Dimensional Quantification of Bone Mineral Density in the Distal Femur and Proximal Tibia Based on Computed Tomography: In Vitro Evaluation of an Extended Standardization Method.

While alterations in bone mineral density (BMD) are of interest in a number of musculoskeletal conditions affecting the knee, their analysis is limited by a lack of tools able to take full advantage of modern imaging modalities. This study introduced a new method, combining computed tomography (CT) and computational anatomy algorithms, to produce standardized three-dimensional BMD quantification in the distal femur and proximal tibia. The method was evaluated on ten cadaveric knees CT-scanned twice and processed following three different experimental settings to assess the influence of different scans and operators. The median reliability (intraclass correlation coefficient (ICC)) ranged from 0.96 to 0.99 and the median reproducibility (precision error (RMSSD)) ranged from 3.97 to 10.75 mg/cc for the different experimental settings. In conclusion, this paper presented a method to standardize three-dimensional knee BMD with excellent reliability and adequate reproducibility to be used in research and clinical applications. The perspectives offered by this novel method are further reinforced by the fact it relies on conventional CT scan of the knee. The standardization method introduced in this work is not limited to BMD and could be adapted to quantify other bone parameters in three dimension based on CT images or images acquired using different modalities.

Posterior to anterior malleolar extended lateral approach to the ankle (PAMELA): a cadaveric anatomic study.

INTRODUCTION: The posterolateral approach is used in most cases of surgical treatment of ankle fractures involving the posterior and lateral malleoli. However, this approach does not allow access to the anterolateral structures of the ankle, which represent important landmarks to allow an anatomical reduction in case of complex ankle fracture. Our objective is to propose a novel surgical approach for optimal management of injuries including both a fracture of the posterior malleolus and a complex lesion of the lateral and/or anterolateral portions of the ankle. METHODS: Cadaveric dissection, including a vascular study, was performed on eight specimens. Assessment included density of the vascular supply around the lateral malleolus, identification of the structures at risk, quality of exposure of the bony structures, and convenience of hardware fixation. RESULTS: The cutaneous flap benefits from a rich interconnected arterial supply. Structures at risk, including the superficial peroneal and sural nerves, the lesser saphenous vein, and the peroneal artery are easily identified and protected. The interval between the peroneal tendons and the flexor hallucis longus muscle provides optimal access to the posterior malleolus. The lateral malleolus is exposed by retracting the peroneal tendons medially. An anterolateral arthrotomy, respecting the anterior talofibular and tibiofibular ligaments, offers a sharp view on the talo-tibio-fibular junction. Hardware placement can be done with optimal access to any exposed surfaces. CONCLUSIONS: The PAMELA opens a new perspective in the optimal management of complex fractures of the ankle. The approach allows optimal exposure to address fractures of the posterior malleolus, of the lateral malleolus, and of the anterolateral portion of the ankle through a single incision. Application in clinical practice is the subject of a future study in our institution.

Toward safer thanatopraxy cares: formaldehyde-releasers use.

Human cadavers constitute very useful educational tools to teach anatomy in medical scholarship and related disciplines such as physiology, for example. However, as biological material, human body is subjected to decay. Thanatopraxy cares such as embalming have been developed to slow down and inhibit this decay, but the formula used for the preservation fluids are mainly formaldehyde (FA)-based. Very recently, other formulas were developed in order to replace FA, and to avoid its toxicity leading to important environmental and professional exposure concerns. However, these alternative FA-free fluids are still not validated or commercialized, and their efficiency is still under discussion. In this context, the use of FA-releasing substances, already used in the cosmetics industry, may offer interesting alternatives in order to reduce professional exposures to FA. Simultaneously, the preservation of the body is still guaranteed by FA generated over time from FA-releasers. The aim of this review is to revaluate the use of FA in thanatopraxy cares, to present its benefits and disadvantages, and finally to propose an alternative to reduce FA professional exposure during thanatopraxy cares thanks to FA-releasers use.

Practical teaching of preclinical anatomy

We illustrate here why today practical teaching in preclinical anatomy is important and why the use of human cadavers is still essential for learning human anatomy by taking two examples. We explain why it is important for a student to be able to dissect and learn anatomy by exploratory anatomy. Several alternatives are discussed and modern teaching tools are illustrated with on-line and computer-based resources, anatomical models, reconstructions and radiographic images that could supplement the traditional dissection courses. Newer techniques such as anatomical body painting, projections, ultrasound or living anatomy may help in the understanding of topographical anatomy. We underline the authenticity that comes from using human tissue and consider the strengths and limitations of different teaching tools. Here we discuss also how far one should go in teaching anatomical variations in preclinical teaching. In Europe there is no consensus regarding anatomical teaching, and each institution has its own curriculum. It would be helpful to set up an anatomical data bank with images and PowerPoint slides that could be used in teaching programs. Here the Trans-European Pedagogic Anatomical Research Group (TEPARG) for Europe and the International Federation of Associations of Anatomists (IFAA) at an international level could play an essential role

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Role of the microtubule destabilizing proteins SCG10 and stathmin in neuronal growth.

The related proteins SCG10 and stathmin are highly expressed in the developing nervous system. Recently it was discovered that they are potent microtubule destabilizing factors. While stathmin is expressed in a variety of cell types and shows a cytosolic distribution, SCG10 is neuron-specific and membrane-associated. It contains an N-terminal targeting sequence that mediates its transport to the growing tips of axons and dendrites. SCG10 accumulates in the central domain of the growth cone, a region that also contains highly dynamic microtubules. These dynamic microtubules are known to be important for growth cone advance and responses to guidance cues. Because overexpression of SCG10 strongly enhances neurite outgrowth, SCG10 appears to be an important factor for the dynamic assembly and disassembly of growth cone microtubules during axonal elongation. Phosphorylation negatively regulates the microtubule destabilizing activity of SCG10 and stathmin, suggesting that these proteins may link extracellular signals to the rearrangement of the neuronal cytoskeleton. A role for these proteins in axonal elongation is also supported by their growth-associated expression pattern in nervous system development as well as during neuronal regeneration.