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X-ray images indicate scapholunate ligament instability when the scapholunate distance is more than 3 mm, which is called scapholunate dissociation. [7] A static scapholunate instability is generally readily visible, but a dynamic scapholunate instability can only be seen radiographically in certain wrist positions or under certain loading conditions, such as when clenching the wrist, or ...
In radiology, the Terry-Thomas sign is a scapholunate ligament dissociation on an anteroposterior view of the wrist. [1] [2] Most commonly a result of a fall on the outstretched hand , the scapholunate ligament ruptures resulting in separation of the lunate and scaphoid bones. This burst causes the scaphoid bone to dorsally rotate. [3]
The reaction of an acid in water solvent is often described as a dissociation + + where HA is a proton acid such as acetic acid, CH 3 COOH. The double arrow means that this is an equilibrium process, with dissociation and recombination occurring at the same time.
The examiner will feel a significant 'clunk' and the patient will experience pain if the test is positive. For completeness, the test must be performed on both wrists for comparison. If the scapholunate ligament is disrupted, the scaphoid will subluxate over the dorsal lip of the distal radius. Original Description by Watson:
The bond-dissociation energy of a bond is the amount of energy required to cleave the bond homolytically. This enthalpy change is one measure of bond strength . The triplet excitation energy of a sigma bond is the energy required for homolytic dissociation, but the actual excitation energy may be higher than the bond-dissociation energy due to ...
Dissociative pathways are characterized by a rate determining step that involves release of a ligand from the coordination sphere of the metal undergoing substitution. The concentration of the substituting nucleophile has no influence on this rate, and an intermediate of reduced coordination number can be detected.
The binding constant, or affinity constant/association constant, is a special case of the equilibrium constant K, [1] and is the inverse of the dissociation constant. [2] It is associated with the binding and unbinding reaction of receptor (R) and ligand (L) molecules, which is formalized as: R + L ⇌ RL
In inorganic chemistry, the S N 1 reaction is often known as the dissociative substitution. This dissociation pathway is well-described by the cis effect. A reaction mechanism was first introduced by Christopher Ingold et al. in 1940. [3] This reaction does not depend much on the strength of the nucleophile, unlike the S N 2 mechanism. This ...