The binary complexes of HF, H2O, NH3, N2, O2, F2, CO, and CO2 with HF, H2O, and NH3 have been studied by ab initio molecular orbital theory and natural bond orbital (NBO) analysis. Most of the complexes involving N2, O2, F2, CO, and CO2 are found to have both hydrogen-bonded and non-hydrogen-bonded structures. The NBO analysis provides a consistent picture of the bonding in this entire family of complexes in terms of charge transfer (CT) interactions, showing the close correlation of these interactions with the van der Waals penetration distance and dissociation energy of the complex. Contrary to previous studies based on the Kitaura–Morokuma analysis, we find a clear theoretical distinction between H-bonded and non-H-bonded complexes based on the strength of CT interactions. Charge transfer is generally stronger in H-bonded than in non-H-bonded complexes. It plays an intermediate role in non-H-bonded CO2 complexes which have been studied experimentally. However, the internal rotation barrier (1 kcal mol−1) of the H2O⋅⋅⋅CO2 complex is found to be primarily of electrostatic origin with only a small (π-type) CT contribution. The role of electrostatic interactions, effect of electron correlation, and comparison of theory with experiment are also discussed.

This is a retrospective study of retrograde intramedullary rodding for ankle arthrodesis in 19 ankles in 16 patients. The preoperative diagnosis of 16 patients was diabetic neuropathic arthropathy in seven patients, rheumatoid arthritis in three patients, post traumatic arthrosis in three patients, paraplegia with fixed equinovarus of the foot in two patients, and avascular necrosis of the talus in one patient. Retrograde intramedullary rodding for ankle arthrodesis was done as a salvage procedure in each patient. Fourteen of the 19 ankles had radiographic evidence of solid arthrodesis. In the four patients with five ankles with pseudarthrosis, no case was clinically significant. There was one deep infection and one broken rod. Thirteen of the 16 patients are ambulatory, and nine required either an ankle-foot orthosis or shoe modification. The standard method of ankle fusion using crossed cancellous screws is the procedure of choice because it preserves the subtalar joint. Retrograde intramedullary rodding for ankle arthrodesis should be considered for patients with significant posttraumatic arthrosis and bone loss following distal tibial plafond fractures, concomitant subtalar arthrosis, severe osteopenia, such as in patients with rheumatoid arthritis, or neuropathic arthropathy.

From 1986 to 1990, 42 feet in 30 patients had a combined chevron osteotomy and lateral release to correct their painful bunion deformity. Seventeen patients, 23 feet, were available for follow-up. The purpose of this study was to evaluate the outcome of this procedure and to determine the incidence of avascular necrosis. The patients were examined by an independent examiner, radiographs obtained, and questionnaires filled out. Avascular necrosis was determined using plain films read by a musculoskeletal radiologist who did not know the outcomes. The average age was 45 years at the time of the procedure. Average follow-up was 50 months. The preoperative intermetatarsal angle averaged 13 degrees and the hallux valgus angle averaged 31 degrees. At study follow-up, the intermetatarsal angle averaged 8 degrees and the hallux valgus angle averaged 17.5 degrees. The results were graded by the Mayo Clinic Forefoot Scoring System (75-point scale) and a subjective scoring system. Average postoperative Mayo Clinic score was 67. Fifteen feet were subjectively rated as excellent, six as good, and two as fair. Complications occurred in four feet. Hallux varus occurred in two feet, extension contracture in one foot, and an infection in one foot. None of the feet developed definite radiographic evidence of avascular necrosis. Distal chevron osteotomy combined with a lateral release for corrective bunion surgery has come under scrutiny, because of the risk of avascular necrosis of the first metatarsal head. However, our study showed no evidence of avascular necrosis on radiographs. In addition, 91% of patients had good to excellent results at an average 50-month follow-up.

The structure and energetics of the isomeric H-bonded complexes OC⋅⋅⋅HF and CO⋅⋅⋅HF have been investigated by ab initio molecular orbital theory and by natural bond orbital analysis. Only with the inclusion of electron correlation is a significant preference for the experimentally observed OC⋅⋅⋅HF isomer found. The large effect of correlation upon the relative stability of the two isomers is apparently entirely an electrostatic effect caused by the correlation-induced sign reversal of the dipole moment of CO. Nevertheless, a molecular multipole expansion is found inadequate to account for the principal features of these H-bonded complexes and their relative stability. Contrary to a recent study, we find that ‘‘charge transfer’’ effects are highly significant contributions to the binding in these complexes. The differences in stability of OC⋅⋅⋅HF and CO⋅⋅⋅HF are attributed primarily to differences in the interaction of carbon and oxygen lone pairs of CO donating into the unfilled antibond on HF, i.e., to differences in nC→σHF* and nO→σHF* matrix elements.

Retrograde intramedullary rodding from the calcaneus, through the talus, and into the tibia is currently an evolving procedure being used for salvage of severe foot/ankle deformity, arthritis, tumor, and instability. In this study, retrograde rodding was performed on six cadaver specimens. The specimens were then dissected to determine the subcalcaneal structures at risk and the optimal insertion point for the rod. This study elucidated the structures most at risk and showed the optimal insertion site to be at the junction of the sustentaculum tali and the body of the calcaneus.