Radiographic Accuracy of Identifying Anterolateral Tibial Plafond Involvement in Pronation Abduction Ankle Fractures.

OBJECTIVES: To evaluate the incidence of anterolateral tibial plafond involvement in pronation-abduction (PAB) ankle fractures and analyze the accuracy of radiographs in detecting anterolateral tibial plafond involvement, impaction, and predicting the need for direct visualization and an articular reduction. METHODS: Design: A multi-institutional retrospective chart review. SETTING: Five level 1 trauma centers in the United States. PATIENT SELECTION CRITERIA: Adult patients with PAB ankle fractures (OTA/AO 44B2.3, 44C2.2, 44C2.3) from 2020-2022 were reviewed by 7 fellowship-trained orthopedic trauma surgeons. They were queried about the presence of anterolateral tibial plafond involvement and impaction, and whether they would need direct visualization and an articular reduction using both radiographs and CT. OUTCOME MEASUREMENTS AND COMPARISONS: The presence of anterolateral tibial plafond impaction was tabulated separately using radiographs and CT scans. The accuracy of radiographs and changes in surgical plan after CT review were calculated using CT as the gold standard. RESULTS: 61 fractures in 61 patients were evaluated with CT and/or plain radiographs. Using plain radiographs, anterolateral tibial plafond involvement and impaction were identified in 61% and 36% of cases, respectively. In the 38 fractures with both plain radiographs and CT scans, anterolateral tibial plafond involvement was identified in 66% of radiographs and 74% of CT scans (p = 0.4). Plafond impaction was identified in 42% of plain radiographs and 37% of CT scans (p = 0.62). There was no difference in the rate of involvement between radiographs and CT scan. The diagnosis of anterolateral tibial plafond impaction using plain radiographs was correct in 74% of fractures when compared to CT imaging, resulting in a sensitivity of 71%, a specificity of 75%, a positive predictive value (PPV) of 62%, and a negative predictive value (NPV) of 82%. Plain radiographs correctly predicted the need for direct visualization and an articular reduction in 74% of cases and had a PPV of 59% and a NPV of 86%. CONCLUSIONS: Anterolateral tibial plafond involvement and impaction was present on CT in 74% and 37% of pronation-abduction (PAB) ankle fractures, respectively. Plain radiographs had higher NPV for identifying impaction and the need for articular reduction than they did sensitivity, specificity or PPV. CT is an important tool for preoperative planning that should be considered when planning for operative fixation of PAB ankle fractures. LEVEL OF EVIDENCE: Prognostic level III. See Instructions for Authors for a complete description of levels of evidence.

Is Immediate Weight-Bearing Safe After Single Implant Fixation of Elderly Distal Femur Fractures?

OBJECTIVES: To compare early complications in elderly patients with extra-articular distal femur fractures (DFFs) allowed to weight-bear as tolerated (WBAT) immediately versus patients prescribed initial touchdown weight-bearing (TDWB). DESIGN: Retrospective cohort study. SETTING: Level 1 academic trauma center. PATIENTS: One hundred thirty-five patients 60 years or older who underwent surgical fixation of an extra-articular DFF, including the OTA/AO fracture classification of 33-A1-3, and periprosthetic fractures with a stable knee prosthesis (Lewis and Rorabeck type I or II) with at least 6 months follow-up. INTERVENTION: Immediate WBAT or TDWB after surgical fixation of an extra-articular DFF with either an intramedullary nail or locked plate. MAIN OUTCOME MEASUREMENTS: The primary outcome was a major adverse event within the first 6 months, defined as (1) early fixation failure or change in alignment leading to reoperation, (2) nonunion, or (3) deep infection. Secondary outcomes included postoperative inpatient length of stay, discharge disposition (secondary facility vs. home), malunion, mortality, and patient-reported outcomes. RESULTS: The rate of early adverse events requiring reoperation was similar between the WBAT group (6, 10.7%) and the TDWB group (15, 19.0%; P = 0.23). There was no difference between groups with respect to length of stay, discharge disposition, malunion, and patient-reported outcomes. CONCLUSIONS: This study supports allowing carefully selected elderly patients, based on surgeon preference, to immediately weight-bear after operative fixation of an extra-articular DFF regardless of implant choice. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Ascorbate enhancement of H1 histamine receptor sensitivity coincides with ascorbate oxidation inhibition by histamine receptors.

Ascorbate has previously been shown to enhance both alpha(1)- and beta(2)-adrenergic activity. This activity is mediated by ascorbate binding to the extracellular domain of the adrenergic receptor, which also decreases the oxidation rate of ascorbate. H1 histamine receptors have extracellular agonist or ascorbate binding sites with strong similarities to alpha(1-) and beta(2)-adrenergic receptors. Physiological concentrations of ascorbate (50 microM) significantly enhanced histamine contractions of rabbit aorta on the lower half of the histamine dose-response curve, increasing contractions of 0.1, 0.2, and 0.3 microM histamine by two- to threefold. Increases in ascorbate concentration significantly enhanced 0.2 microM histamine (5-500 microM ascorbate) and 0.3 microM histamine (15-500 microM ascorbate) in a dose-dependent manner. Histamine does not measurably oxidize over 20 h in oxygenated PSS at 37 degrees C. Thus the ascorbate enhancement is independent of ascorbate's antioxidant effects. Ascorbate in solution oxidizes rapidly. Transfected histamine receptor membrane suspension with protein concentration at >3.1 microg/ml (56 nM maximum histamine receptor) decreases the oxidation rate of 392 microM ascorbate, and virtually no ascorbate oxidation occurs at >0.0004 mol histamine receptor/mol ascorbate. Histamine receptor membrane had an initial ascorbate oxidation inhibition rate of 0.094 min.microg protein(-1).ml(-1), compared with rates for transfected ANG II membrane (0.055 min.microg protein(-1).ml(-1)), untransfected membrane (0.052 min.microg protein(-1).ml(-1)), creatine kinase (0.0082 min.microg protein(-1).ml(-1)), keyhole limpet hemocyanin (0.00092 min.microg protein(-1).ml(-1)), and osmotically lysed aortic rings (0.00057 min.microg wet weight(-1).ml(-1)). Ascorbate enhancement of seven-transmembrane-spanning membrane receptor activity occurs in both adrenergic and histaminergic receptors. These receptors may play a significant role in maintaining extracellular ascorbate in a reduced state.

Molecular shielding of electric field complex dissociation.

We have previously demonstrated the ability of electric fields to dissociate ascorbate and catecholamines and shown that the electric field generated by cell membranes is sufficient to produce dissociation of these complexes up to 8 nm from the cell membrane. We show here that this process is applicable to a wide range of biological complexes including small molecules (norepinephrine-morphine sulfate), protein-protein complexes (insulin-glucagon), and small molecule-protein complexes (epinephrine-bovine serum albumin). The extrapolation of the slope of the electric field dependence to zero electric field can be used to estimate the log of the dissociation constant (K(D)) of a complex and, by multiplying the log(K(D)) by -2.303RT, the association energy (E) of the complex. The slope of the electric field dependence is inversely related to the molecular radii, with the best fit of the slope related to E*(1/r1 + 1/r2), where r is the estimated radius of each molecule in the complementary pair. This indicates that the binding site of the pair is shielded by the remaining parts of the molecules, and the larger the molecule the greater the shielding. When the slope of the electric field dependence goes to 0 as r goes to infinity and 1/r goes to 0, the molecular shielding constant is 7.04 x 10(-8) cm2/V. Very large complexes will be minimally affected by the electric field due to molecular shielding and reduced electric field as their radius restricts approach to the membrane. Large protein receptors will deflect the membrane electric field and allow agonist binding.