Biography:

In the past Marcel Dvorak has collaborated on articles with Anthony Min-Te Choo and Michael Johnson. One of their most recent publications is Arthroscopic anatomy of the hip. Which was published in journal Arthroscopy: The Journal of Arthroscopic & Related Surgery.

More information about Marcel Dvorak research including statistics on their citations can be found on their Copernicus Academic profile page.

Marcel Dvorak's Articles: (3)

Arthroscopic anatomy of the hip

AbstractThe arthroscopic anatomy of the hip has been studied using a number of portals. Both distraction and positioning are necessary to allow insertion of instruments, and to allow exposure of the important anatomical structures. The internal anatomy of the hip joint is described in detail based on the arthroscopic view from the different portals. This study helps orient those interested in arthroscopy of the hip.

Modeling spinal cord contusion, dislocation, and distraction: Characterization of vertebral clamps, injury severities, and node of Ranvier deformations

AbstractSpinal cord contusion and transection models are widely used for studying spinal cord injury (SCI). Clinically, however, other biomechanical injury mechanisms such as vertebral dislocation and distraction frequently occur, but these injuries are difficult to produce in animals. We mechanically characterize a vertebral clamping strategy that enables the modeling of vertebral dislocation and distraction injuries – in addition to the standard contusion paradigm – in the rat cervical spine. These vertebral clamps have a stiffness of 83.6 ± 18.9 N/mm and clamping strength 64.7 ± 10.2 N which allows injuries to be modeled at high-speed (∼100 cm/s). Logistic regression indicated that a moderate-to-severe injury, with an acute mortality rate of 10%, occurs at 2.6 mm of C4/5 dorso-ventral dislocation and 4.1 mm of rostro-caudal distraction between C4 and C5. Injuries produced by dislocation and distraction exhibited features of axonal damage that were absent in contusion injuries. We conducted morphometric analysis at the nodes of Ranvier using immunohistochemistry for potassium channels (Kv1.2) in the juxtaparanodal region. Following distraction injuries, elongated nodes of Ranvier were observed up to 4 mm rostral to the lesion. In contrast, contusion injuries produced distortions in nodal geometry which were restricted to the vicinity of the lesion. The greatest deformations in node of Ranvier geometry occurred at the dislocation epicenter. Given the importance of white matter damage in SCI pathology, the distinctiveness of these injury patterns demonstrate that the dislocation and distraction injury models complement existing contusion models. Together, these three animal models span a broader clinical spectrum for more reliably gauging the potential human efficacy of therapeutic strategies.

Abstract4:48 The radiographic failure of single-segment anterior cervical plate fixation in traumatic cervical flexion/distraction injuries

AbstractPurpose of study: Anterior cervical discectomy fusion (ACDF) and plating is frequently performed for posterior facet fracture subluxations. The objective of this study was to report the rate and predictors of radiographic failure of this technique.Methods used: All single-level unilateral facet fracture subluxations and bilateral facet fracture subluxations treated with a single-level ACDF and plate were included. Retrospectively, 107 cases were identified (87 with complete radiographs) from January 1992 to December 2001. Radiographic failure was defined as a change in translation of greater than 4 mm and/or change in angulation of greater than 11 degrees between the immediate postoperative films and the most recent follow-up. Fusion was assessed radiographically (modified Bridwell).of findings: Radiographic failure was present in 11 of 87 (13%). There was no correlation between radiographic failure and age, gender, surgeon, unilateral or bilateral, plate type, level of injury, degree of translation or alignment at the time of injury. Radiographic failure was associated with preoperative facet fractures and end plate fractures, as well as pseudarthrosis at follow-up.Relationship between findings and existing knowledge: Given the popularity of anterior surgery for posterior cervical injuries, the presence of an end plate fracture, even subtle, or facet fracture should alert the surgeon to a high risk of radiographic failure.Overall significance of findings: Loss of postoperative alignment occurred in 13% of facet fracture subluxations treated with ACDF and plating. Concern regarding mechanical failure of flexion/distraction injuries should be high with associated fractures of either the facets or of the end plate. End plate fracture was associated with both mechanical failure and pseudarthrosis.Disclosures: No disclosures.Conflict of interest: No conflicts.

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