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Biomedical subjects

M Vrahas

Publications and source records attributed to M Vrahas.

5 recordsLinked to original sources
PubMed1995

Ligamentous contributions to pelvic stability.

The purpose of this study was to examine the ligamentous contributions to pelvic stability. Thirteen fresh frozen cadaver pelves were loaded in an MTS materials testing machine, and the supporting ligaments were sequentially cut. After each ligament was cut, measurements of pelvic stability were made. Pelvic stability was maintained most effectively when the pelvic ring remained intact. The sacrotuberous and sacrospinous ligaments contributed little to overall pelvic stability. The posterior sacroiliac ligament and the pubic symphyseal ligaments contributed most to pelvic stability, but overall it was clear that a ligament's contributions to pelvic stability depended not only on the ligament's size, but also on the other ligament remaining intact and the mode in which the pelvis was loaded.

Biomechanical Phenomena↗
PubMed1994

Intraarticular contact stresses with simulated ankle malunions.

Peak contact stresses were evaluated in a human cadaver ankle model of ankle fracture malunion. In one set of experiments, changes in peak contact stresses were evaluated for ankles loaded with lateral displacements of the talus and fibula of 1, 2, 3, and 4 mm. In a second set of experiments, peak contact stresses were evaluated after removal of posterior malleolar fragments. Peak contact stresses were concentrated over the anterior medial talar dome in normal specimens, and in specimens with stimulated malunions. There were relatively low stresses beneath the medial malleolus. Peak stresses for ankles without talar displacements ranged from 1.9 MPa to 12.4 MPa (eliminating one disparate specimen). There was no increase in peak stresses with lateral displacements of the talus or with removal of posterior malleolar fragments. The fact that peak stresses with simulated ankle malunions were not elevated suggests that factors other than the magnitude of normal contact stresses are of greater importance in the pathogenesis of posttraumatic arthritis.

Ankle Injuries↗
PubMed1994

Simple intraoperative traction system for acetabular fracture surgery.

The open reduction and internal fixation of complex acetabular fractures generally require some amount of sustained intraoperative traction. This traction can be provided by either specialized traction tables or scrubbed assistants. Both methods have their advantages and disadvantages. Specialized traction tables provide excellent controlled traction but are costly. Interested assistants are less costly, but at many institutions an adequate number of them are unavailable. We describe the design, construction, and use of a simple intraoperative traction device to aid in the open reduction and internal fixation of acetabular fractures.

Acetabulum↗
PubMed1992

Intraoperative somatosensory evoked potential monitoring of pelvic and acetabular fractures.

The efficacy of intraoperative somatosensory evoked potential (SSEP) monitoring was evaluated in the surgical management of 82 patients with pelvic and acetabular fractures. The injuries consisted of 45 acetabular fractures, 30 pelvic ring disruptions, and seven combined injuries. Preoperative neurological deficits were recorded in 34% of the study group (29% of those with an acetabular fracture and 47% of those with a pelvic ring injury). Three patients sustained an iatrogenic sciatic nerve injury during the study period (all of which were documented in the first 40 cases). Two patients sustained an exacerbation of an existing sciatic nerve injury. In the group of pelvic fractures, hazardous parts of the exposure, reduction, and fixation were identified by the SSEP monitoring. Removal of the provocative stimulus by the surgeon led to reversal of the SSEP abnormalities, and none of this group of patients sustained an iatrogenic injury. When the intraoperative SSEP changes were noted during an acetabular fracture fixation, immediate attempts were made to relieve the excessive tension on the sciatic nerve by replacing or removing a retractor, flexing the knee, extending the hip, or dividing the femoral insertion of the gluteus maximus. None of the SSEP changes were associated with the lacerative injury to the sciatic nerve. For the method to be clinically effective in reducing the incidence of neurological deficit, even subtle changes in the SSEP tracing must be recognized immediately by the neurophysiologist so that a corresponding corrective measure can be rapidly undertaken by the surgeon to remove the offending stimulus.

Acetabulum↗