A 15-year-old, postmenarchal high school freshman, volleyball player, injured her right nondominant fifth finger while trying to set a volleyball in a varsity competition. She had intense pain at the metacarpal- phalangeal joint. The digit was abducted away from the remaining fingers and straightened at courtside by her coach. She was sent to the emergency room, where radiographs (see Figure 1) revealed a right fifth finger proximal phalangeal basilar fracture that involved a 20% of the articular surface. Radiographs demonstrated significant displacement of the fracture fragments; the articular surface was rotated at least 180[masculine ordinal indicator] counterclockwise (see the arrow in Figure 1) from its normal plane of orientation.
|Figure 1. (A & B) An anterior-posterior view of the right fifth finger demonstrating a displaced avulsion fracture of the radial base of the proximal phalanx. The smooth subchondral portion of the bone is markedly rotated and is facing distally (arrow). In this situation, internal fixation is mandated to reestablish joint surface and prevent instability.|
Five days after injury, she was taken to the operating room for an open reduction of the displaced fracture. Upon entering the joint, the small basilar proximal phalangeal fragment was attached to the radial collateral ligament of the metacarpal-phalangeal joint. The articular cartilage was attached to the avulsion fragment and extended beyond the bony segment. It involved one third of the joint surface and much of it had peeled off of the bony base of the larger fracture fragment. The articular surface indeed had rotated 180[masculine ordinal indicator] and faced distally.
The fragment was mobilized, realigned, and held with a 1.5-mm-diameter lag screw (see Figure 2). Intraoperative radiographs demonstrated restoration of bony and joint surface alignment. The patient was splinted in full extension for 8 days when sutures were removed. The fifth finger was then buddy taped with 1/2-in. adhesive tape to the fourth finger at the proximal and middle phalangeal levels to allow for early protected motion. At 4 weeks, she had no tenderness at the fracture site and had excellent range of motion. Competitive volleyball was then permitted with the finger buddy taped.
|Figure 2. After internal fixation with a 1.5-mm-diameter screw, the anterior-posterior view shows restoration of articular surface congruity.|
Displaced intra-articular fractures usually require internal fixation to avoid joint surface incongruity, which causes posttraumatic arthritis (Calandruccio et al., 2008; Lee & Jupiter, 2000). It has been shown that 2 mm or more of articular surface depression results in arthritis (O'Rourke, Gaur, & Barton, 1989). If an interarticular fracture fragment comprises 20% or more of the articular surface of the joint, it is recommended that the fragment be internally fixed to avoid joint instability (Hastings, 1987). However, a fracture fragment must be at least three times the diameter of the screw intended to fix it. Otherwise, the screw will split the fragment into smaller unfixable pieces. In this case, the finger was abducted away from the hand when it struck the ball, placing the radial corner of the little finger proximal phalanx under a tensile force. The collateral ligament of the metacarpal-phalangeal joint still attached to the proximal phalangeal fragment caused an avulsion fracture of the articular surface, radial corner. In younger patients, there is frequently a greater amount of articular cartilage attached to the fracture fragment than is initially seen on radiographs. A close analysis of the radiographs shows that the smooth articular bony subchondral surface is markedly displaced (see the arrow in Figure 1). Had this fragment not been fixed, the finger would have had adduction instability with loss of grip strength and the ability to use the hand to scoop (Hastings, 1987).
In children who still have growth plates at the base of the proximal phalanx, this type of fracture is called an "extra-octave" fracture, as the small finger is forced into position away the remainder of the hand as if the little finger was attempting to stretch to play another octave of notes on a piano. In children with open growth plates, the fracture propagates along the weaker growth plate cartilage. In this 15-year-old with a closed growth plate, the failure was via tensile, distractive ligament avulsion.