Cervical facet force analysis after disc replacement versus fusion.

BACKGROUND: Cervical total disc replacement was developed to preserve motion and reduce adjacent-level degeneration relative to fusion, yet concerns remain that total disc replacement will lead to altered facet joint loading and long-term facet joint arthrosis. This study is intended to evaluate changes in facet contact force, pressure and surface area at the treated and superior adjacent levels before and after discectomy, disc replacement, and fusion. METHODS: Ten fresh-frozen human cadaveric cervical spines were potted from C2 to C7 with pressure sensors placed into the facet joints of C3-C4 and C4-C5 via slits in the facet capsules. Moments were applied to the specimens to produce axial rotation, lateral bending and extension. Facet contact force and pressure were measured at both levels for intact, discectomy at C4-C5, disc replacement with ProDisc-C (Synthes Spine, West Chester, Pennsylvania, USA) at C4-C5, and anterior discectomy and fusion with Cervical Spine Locking Plate (Synthes Spine, West Chester, Pennsylvania, USA) at C4-C5. Facet contact area was calculated from the force and pressure measurements. An analysis of variance was used to determine significant differences with P-values <0.05 indicating significance. FINDINGS: Facet contact force was elevated at the treated level under extension following both discectomy and disc replacement, while facet contact pressure and area were relatively unchanged. Facet contact force and area were decreased at the treated level following fusion for all three loading conditions. INTERPRETATION: Total disc replacement preserved facet contact force for all scenarios except extension at the treated level, highlighting the importance of the anterior disco-ligamentous complex. This could promote treated-level facet joint disease.

A new 3-dimensional method for measuring precision in surgical navigation and methods to optimize navigation accuracy.

PURPOSE: Description of a novel method for evaluation of pedicle screws in 3 dimensions utilizing O-arm(®) and StealthStation(®) navigation; identifying sources of error, and pearls for more precise screw placement. METHODS: O-arm and StealthStation navigation were utilized to place pedicle screws. Initial and final O-arm scans were performed, and the projected pedicle probe track, projected pedicle screw track, and final screw position were saved for evaluation. They were compared to evaluate the precision of the system as well as overall accuracy of final screw placement. RESULTS: Thoracolumbar deformity patients were analyzed, with 153 of 158 screws in adequate position. Only 5 screws were malpositioned, requiring replacement or removal. All 5 were breached laterally and no neurologic or other complications were noted in any of these patients. This resulted in 97 % accuracy using the navigation system, and no neurological injuries or deficits. The average distance of the screw tip and angle of separation for the predicted path versus the final pedicle screw position were analyzed for precision. The mean screw tip distance from the projected tip was 6.43 mm, with a standard deviation of 3.49 mm when utilizing a navigated probe alone and 5.92 mm with a standard deviation of 3.50 mm using a navigated probe and navigated screwdriver (p = 0.23). Mean angle differences were 4.02° and 3.09° respectively (p < 0.01), with standard deviations of 2.63° and 2.12°. CONCLUSIONS: This new technique evaluating precision of screw placement in 3 dimensions improves the ability to define screw placement. Pedicle screw position at final imaging showed the use of StealthStation navigation to be accurate and safe. As this is a preliminary evaluation, we have identified several factors affecting the precision of pedicle screw final position relative to that predicted with navigation.

Prospective analysis of Hemodialysis Reliable Outflow (HeRO) vascular access graft vs. cuffed catheter access in hemodialysis.

The Hemodialysis Reliable Outflow (HeRO) graft was compared to the cuffed catheter in end-stage renal disease patients. All consented patients were evaluated for HeRO graft placement. Eligible patients that did not receive a graft were enrolled in the control group. Participants who had not exhausted peripheral venous access sites suitable for fistulas and grafts were excluded. Differences in quality of life and incidence of bacteremia, vascular interventions, hospitalizations, and death were evaluated over one year. In thirty-three patients included in the analysis--16 HeRO, 17 control--significantly fewer bacteremia events (93.8% vs. 64.7%) and a significantly increased number of vascular interventions (64.7% vs. 25%) were reported for the HeRO versus Control group. The increased interventions in the HeRO group may be due to the two-step placement process.

Balamuthia mandrillaris meningoencephalitis associated with solid organ transplantation--review of cases.

We report the first identified transmission of Balamuthia mandrillaris through solid organ transplantation. Kidneys were transplanted from a donor with presumptive diagnosis of autoimmune encephalitis. Shortly after, the recipients developed neurologic symptoms. Magnetic Resonance Imaging of the brain from the donor and both kidney recipients demonstrated multiple ring enhancing lesions with surrounding edema and adjacent leptomeningeal extension. In addition most of the lesions demonstrated signal changes suggesting central hemorrhagic foci. Specimens were tested locally and at the Centers for Disease Control and Prevention. Histopathology revealed B. mandrillaris in either brain tissue and/or cerebral spinal fluid in the donor and recipients.