Spontaneous Midsubstance Flexor Tendon Ruptures of the Hand.

Spontaneous midsubstance ruptures of the flexor digitorum profundus (FDP) tendon are rare and often overlooked because of their subtle presentation and lack of preceding trauma. These injuries most often involve the little finger. We report two cases of spontaneous midsubstance FDP rupture in otherwise healthy males who presented with loss of active distal interphalangeal and proximal interphalangeal joint flexion and benign examination findings. Magnetic resonance imaging in both cases demonstrated complete midsubstance rupture of the FDP tendon in the palm with an atrophic flexor digitorum superficialis. Each patient underwent primary four-strand core repair with an epitendinous running suture. One required carpal tunnel and Guyon canal release after a five-week delay to surgery. Both patients achieved excellent functional recovery with no pain and near-full range of motion at 5 months after surgery. As demonstrated by these cases, finger flexion deficits without edema or pain should prompt consideration of midsubstance FDP rupture, for which timely direct repair can yield excellent outcomes.