Radial Neck Dilatory Remodeling After Radial Head Arthroplasty With an Uncemented, Press Fit, Fully Chemically Etched Stem Design.

OBJECTIVES: To compare the radiographic outcomes of 2 widely used side loading, press fit, RHA implants used to reconstruct complex elbow trauma. DESIGN: Retrospective cohort study. SETTING: Level-1 Academic trauma center. PARTICIPANTS: Patients undergoing RHA. INTERVENTION: Cohort 1 received Synthes Radial Head Prosthesis. Cohort 2 received Biomet ExploR Radial Head Replacement. MAIN OUTCOME MEASUREMENTS: Radial neck dilatory remodeling. RESULTS: Eighty-two subjects were included in final analysis, 63 from the Biomet Cohort, and 19 from Synthes cohort. Demographic and injury characteristics were similar among cohorts. Radial neck dilatory remodeling as well as periprosthetic radiographic lucency were seen significantly more frequently and to a significantly greater degree in the Synthes cohort. The average percentage of dilatory remodeling of the Synthes cohort was 34.9% and that of the Biomet cohort was 2.7%. There were no differences in rates of revision surgery. CONCLUSIONS: Our study demonstrates significant radiographic differences between 2 frequently used RHA implants. Radial neck dilatory remodeling is a common, rapidly progressive, and dramatic finding frequently seen with the Synthes Radial Head Prosthesis. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Binding Patterns in Single-Ligand Complexes of NH(3), H(2)O, OH(-), and F(-) with First Series Transition Metals.

Single-ligand complexes of first series transition metals with ammonia, water, hydroxide, and fluoride, many known in the gas phase, have been studied in calculations covering the 20 mono- and divalent cations and some very unusual binding patterns have been found. Binding energies and binding geometries were calculated at MP2 level, using a basis with a (6d/4d) contraction in the metal d space and 6-311+G sets for the ligands. The results were used to distinguish the effect of steadily increasing nuclear charge across the series from the varying effects of d shell occupation. Even with only one ligand, the M(2+) adducts displayed the familiar ligand field effects, d shell repulsion in the expected d(delta) < d(pi) < d(sigma) order being superimposed on a regular progression to stronger binding and shorter bonds; that progression was disturbed only at the d(5) and d(10) positions, when the d(sigma) orbital was occupied. Monovalent metal adducts behaved in strikingly different fashion, with irregular changes across early and late series metals in both bond length and bond strength. The irregularities are only partly attributable to the presence of both d(n)()(-)(1)s and d(n)() ground states in the series. The other part of the explanation is the binding of anionic ligands inside the radial maximum of the 4s orbital. At these distances the normal binding preference shown by H(2)O and NH(3) for d(n)() over sd(n)()(-)(1) cations is reversed. In contrast to steeply rising binding energies across the divalent metal ion adducts, the trend lines for the monovalent series are flat, the increments in nuclear charge being insufficent to offset the extra repulsion of electrons added to the d shell.