The clamshell fracture and adjunctive acetabuloplasty in the arthroscopic osteosynthesis of femoral head fractures with femoroacetabular impingement.

The clamshell fracture of the femoral head and its arthroscopic osteosynthesis are described. This suprafoveal osteochondral fracture may have folded onto itself during closed reduction of the associated anterior hip dislocation. The resultant fracture fragment had almost circumferential chondral coverage that required arthroscopic manipulation to "pry apart the clamshell," permitting arthroscopic reduction. This patient also had pre-existing silent femoroacetabular impingement, and the novel use of arthroscopic acetabuloplasty permitted internal fixation by improving the path for headless screw fixation. The arthroscopic techniques and clinical outcome at greater than 2 years are presented. Albeit rare, the clamshell fracture configuration should be recognized and may be amenable to successful arthroscopic osteosynthesis. Of broader clinical impact and application, adjunctive acetabuloplasty may permit the successful osteosynthesis of select femoral head fractures in patients with concurrent acetabular overcoverage by completely arthroscopic techniques that engage both the fracture fragment and the attractive benefits of less invasive surgery.