Boutonniere deformity - grade 4

Case contributed by Brendan Cullinane
Diagnosis almost certain


Clinically apparent post-traumatic Boutonniere deformity: hyperflexion of the PIP and hyperextension of the DIP of the right 5th finger. The injury occurred during basketball. Further examination showed marked flexion contracture and an inability to passively extend the PIP joint, corresponding to Stage 4.

Patient Data

Age: 30 years
Gender: Male

Hyperflexion of the PIP and hyperextension of the DIP

Hyperflexion of the PIP and hyperextension of the DIP. No avulsion fracture (David Sloane radiographer, John Osborne radiologist).


Rupture of the central extensor tendon slip. A fluid-filled gap is shown between the thickened, retracted central slip of the extensor tendon and its insertion site at the base of the middle phalanx. The tendon was retracted approximately 1cm from its insertion site.

Increased separation of the lateral extensor tendon slips. Distally, the tear of the central slip is shown to extend across its width in the right image. The lateral slips can be seen as echogenic structures at the margins of the proximal phalanx. Hyperflexion of the PIP has forced them further apart.

The RCL is thick and hypoechoic indicating a minor sprain. There is a small hypoechoic defect at the distal part of the UCL indicating a mild to moderate sprain. The palmar plate of the PIP is not seen and there is an effusion from the joint suggesting palmar plate rupture.

Case Discussion

The patient injured his right 5th finger while playing basketball 2 weeks prior. By the time he had presented to our department, he had advanced flexion contracture and no passive extension indicating a grade 4 deformity and the likelihood of a poor outcome.

Ultrasound showed complete rupture of the central extensor tendon slip resulted in a marked Boutonniere deformity with wide separation of the lateral slips. There was tearing of the collateral ligaments and probable rupture of the PIP palmar plate.

There was no evidence of avulsion fracture on ultrasound or X-ray.

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