PMC6717068_01
Dynamic change of lateral band under ultrasonography (A: Probe placement over dorsal and radial side of middle phalanx head as transverse section; B: Lateral band in situ over middle phalanx head upon extension of PIPJ; C: Subluxation of lateral band to radial side upon flexion of PIPJ.
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Ultrasonography was then utilized to evaluate the dynamic change of the extensor mechanism with a broadband 7.5-10 MHz linear array scan head with the linear transducer placed transversely and longitudinally on dorsal medial side of the fifth PIPJ. (Acuson X600, Siemens, Germany) In dynamic imaging during flexion of the right fifth PIPJ from extension, subluxation of the lateral band of the extensor tendon to the radial side causing snapping symptoms were detected under the transverse section (Fig. 1) (Video 1).
Surgical finding of subluxation of lateral band (A and B: Subluxation of lateral bands upon flexion of PIPJ before repair of ruptured retinacular ligament; C and D: Lateral band is located stably in situ after repair of ruptured retinacular ligament).
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Exploration of the PIPJ with a curve incision under local anesthesia revealed rupture of the retinacular ligament with partial fibrosis union, laxity and lateral subluxation of the radial side of the lateral band with partial joint capsule rupture over the dorsal PIPJ (Fig. 2).