[Pinch deficit of the thumb-index finger due to a lesion of the anterior interosseous nerve. Apropos of 17 cases].

We report 17 cases of abnormal pinch due to anterior interosseous nerve (AIN) palsy. The AIN lesion was complete with palsy of flexor pollicis longus (FPL) and Flexor digitorum profondus of the second digit (FDP2) in nine cases. A partial lesion with FPL palsy was observed in four cases, and FDP2 in four other cases. Three of this eight cases were initially considered to be tendon ruptures. Electrodiagnosis assessed AIN lesion and respect of the main median trunk in all cases. Pronator quadratus examination provided the diagnosis in 14/17 cases and FPL or FPD2 examination established the diagnosis in the other 3 cases. Associated nerve lesions were found in four cases. Pinch grip was spontaneously recovered in 9/10 cases. The AIN lesion was due to compression in 3 cases and to mononeuritis such as Parsonage Turner neuralgic amyotrophy in 14 cases. As 2/3 cases of compression resolved spontaneously, surgery indications are rare and should not be considered before 12 to 16 months when the lesion is not traumatic.