A cadaveric model that incorporated quadriceps and hamstrings muscle loads was developed to simulate the squat exercise. The addition of hamstrings load affected knee kinematics in two ways. First, anterior tibial translation during flexion ("femoral roll-back") was significantly reduced (P = 0.003) and second, internal tibial rotation during flexion was reduced (P = 0.008). However, quadriceps force was unaffected by the addition of hamstrings load. Thus, it seems likely that hamstrings muscle activity that has been observed in vivo during a squat probably functions synergistically with the anterior cruciate ligament to provide anterior knee stability. After the ACL was sectioned, anterior tibial translation was significantly increased during the squat (P = 0.04). The anterior cruciate ligament was then reconstructed using a graft instrumented with a load cell. During passive motion, maximal graft tension was at full extension. During simulated squat exercise, the addition of hamstrings caused a significant decrease in graft load (P = 0.006). During the squat, maximal graft tension was at full extension, and was equal to the graft tension at full passive extension. Thus, the squat exercise may be useful in the early stages of anterior cruciate ligament rehabilitation.

Individual variations in patellar tendon anatomy should be considered when choosing the proper entry site for tibial nailing. Based on the assumption that the ideal entry point for tibial nailing is just medial to the tibial spine at the anterior margin of the articular surface, a preoperative fluoroscopic measurement before incision can guide the surgeon as to whether a medial parapatellar, transpatellar, or lateral parapatellar approach provides the most direct access to this entry site. The routine use of a single approach for all tibial nails may no longer be justified.

We treated two children with the unusual complication of ulnar nerve palsy after closed both-bone forearm fractures. Both patients developed an ulnar claw-hand deformity within 7 weeks of injury that resolved spontaneously by 20 weeks postinjury with nonoperative treatment. No patient showed any signs or symptoms of an ischemic compartment syndrome. Both nerve injuries were identified immediately at the time of fracture by a careful neurologic examination. This avoids confusion with a postreduction nerve entrapment injury or ischemic injury after a localized compartment syndrome, which may have considerably different treatments and outcomes. We recommend that a careful neurologic examination be recorded before any manipulative reduction of forearm fractures in children. If an ulnar nerve palsy is detected, it is probably a result of nerve contusion and should resolve without the need for surgical exploration.

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