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CONDITION/DISORDER SYNONYMS
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Duck-bill deformity
Recurvatum deformity
Volar plate injury
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M20.03 Swan-neck deformity
M20.031 Swan-neck deformity of right finger(s)
M20.032 Swan-neck deformity of left finger(s)
M20.039 Swan-neck deformity of unspecified finger(s)
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PREFERRED PRACTICE PATTERN3
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4D: Impaired Joint Mobility, Motor Function, Muscle Performance, and Range of Motion Associated with Connective Tissue Dysfunction
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PATIENT PRESENTATION
Patient is a 32-year-old woman diagnosed with rheumatoid arthritis 3 years ago. She experienced an exacerbation of symptoms, with increased pain and inflammation in both hands 2 months ago, and was seen by her rheumatologist for medical management. Although pain and inflammation have subsided, she now reports difficulty in her job as a music teacher at the local high school. Her chief complaint is that she is unable to demonstrate playing instruments because her “fingers won’t cooperate.” When trying to straighten the fingers, “the middle joint bends backwards and gets in the way.”
When asked to extend her fingers, the patient moved the index, long, and ring fingers of her right hand into a position involving proximal interphalangeal (PIP) joint hyperextension and distal interphalangeal (DIP) joint flexion; the small finger moved normally into extension. After demonstrating this, the patient then had mild difficulty returning to a flexed position (unintended slight hesitation). The MP joints were slightly swollen, but appeared to be in good alignment and functioning properly. Wrist motion was within normal limits (WNL).
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Injury or loosening of the volar plate (ligament connecting proximal and middle phalanx that prevents hyperextension of the PIP)
Hyperextension of the PIPjoint and flexion of the DIP joint
Duck-bill deformity is the same issue in the thumb less one joint
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Essentials of Diagnosis
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RA most common cause of swan-neck deformity
Chronic inflammation loosens the volar plate and disrupts ligaments and other connective tissues making PIP susceptible to hyperextension
Migration of the lateral bands of the extensor hood dorsally, to become extensor forces at the PIP
As a result, extensor tendon tightens causing DIP to pull into flexed position
Swan-neck classification by Nalebuff4
I: PIP joint flexible in all positions
II: PIP motion limited only by tenodesis effect
III: Fixed PIP joint contracture, x-ray normal
IV: X-ray shows ...