Boutonnière deformation: why and mechanism of symptom formation
Deformation of boutonnière can develop secondary to trauma or progress secondary to arthritis. This term is used to describe the patient's finger exhibiting a pathological flexion in the joint.
The boutonnière deformity can develop in the acute (secondary to traumatic) or progressive (secondary after arthritis) phase. This term is used to describe a clinical scenario in which a patient's finger exhibits a pathological flexion in the joint.
Used to describe the deformation of the finger in which the proximal joint (PIP) is permanently folded towards the palm of the hand, while the distal joint (DIP) is bent away from the palm of the hand.
Figure. Mechanism of finger stretching
A Proximal joint is extended by the central tendon (an extension of the muscle that stretches the back tendon of the hand).
BX is a functional representation of the tendon connections between the two systems.
The focus of this mechanism is the disruption or uptake of the central tendon slip. In fact, this sign derives its name from the appearance of the central tendon slip, which is said to resemble a stud (boutonniere in French) when torn.
The medial tendon attaches to the bases of the knuckle between the fingers and its main job is to operate the joint near the PIP with the assistance of several other tendon bands.
If the central tendon is broken or lifted (pulled away from the base of the inter-finger knuckle), the action of the folded tendon ligaments (pulling the median joint toward the palm of the hand) will be less difficult.
The distal joints are excessively stretched as the elastic central tendon contracts and pulls back on the transverse.
Maximum folding of the proximal joint fold increase can cause central tendon slip separation.
Also, a crushing injury or any other trauma that damages the central tendon can cause a boutonniere deformation.
A direct tear of the central tendon causes deformation through the above mechanisms.
Joint and/or skin infections can lead to internal inflammation and disruption of the central tendon.
Synovial burs in the PIP joint (as seen in rheumatoid arthritis)
can insert into the central tendon and break it, thus, leading to characteristic changes.
In addition, chronic inflammation and inflammation of the synovial membrane of the joint can push it over, stretching the central tendon and eventually rupturing.