Experimental study on the effect of mechanical stimulation on the early stage of fracture healing.

In an attempt to ascertain the effects of mechanical stimulation on callus in the early stage of bone fracture healing, a tibial fracture was induced in rats and mechanical stimulation applied to the fractures. The callus was then measured quantitatively, while the fractures were analyzed both radiographically and histologically. Following the induction of a closed transverse fracture in the tibia, external anchors were applied and the rats raised by suspending the fractured leg. The rats were divided into two main groups: a Stimulation Group (S Group) and a Control Group (C Group) without the application of any mechanical stimulation. The S Group was further divided into the following three subgroups: an axial compression group (Sc Group) receiving stimulation in the positive direction; an axial distraction group (Sd Group) receiving stimulation in the negative direction; and an axial dynamization group (Sdy Group) receiving stimulation in both directions alternately. For mechanical stimulation, 1.4-N sine waves were applied continuously for 30 minutes a day, three times a week, starting 2 days after fracture-inducing surgery. At 3, 7, and 14 days after surgery, transverse sections of each fractured bone sample were prepared. At 14 days after surgery, each transverse section was divided into two peripheral and central regions to permit calculation of the area ratio of callus. Radiographically, no marked differences were observed among the groups; histologically, differences were seen 7 days after surgery, suggesting that mechanical stimulation facilitated bone healing soon after surgery. At 14 days after surgery, the amount of callus for the C Group was less than that for all three stimulation groups. In the C Group, the amount of callus in the peripheral region was greater than in the central region, and in the Sc Group, the results were the same: callus in the peripheral region was greater than in the central region. In the Sd Group, callus was greater in the central region than in peripheral regions. In the Sdy Group, favorable callus was observed in both the central and peripheral regions. These findings suggest that axial compression facilitates callus primarily in the peripheral region, while axial distraction facilitates callus primarily in the central region. When axial compression and distraction were alternated (dynamization), callus was significantly facilitated in both the central and peripheral regions. Of the three axial stimulation techniques, dynamization was the most effective in facilitating callus in the early stage of bone fracture healing.

Anterior cruciate ligament injuries among wakeboarders: a case report.

No previous cases of anterior cruciate ligament (ACL) injuries sustained during wake-boarding have been reported. We report on a case involving an ACL injury sustained during wakeboarding. A 27-year-old man sustained an injury while attempting a wakeboarding maneuver(a heel-side back roll, consisting of a jump and simultaneous roll toward the heel side). He failed to complete his roll before landing, striking the water with his right shoulder foremost, then plunging underwater. When his wakeboard struck the water, his left knee was sprained by the rotational force exerted by the board. The patient was diagnosed with an isolated ACL injury and underwent arthroscopic ACL reconstructive surgery. The board used in wakeboarding is wider and subject to greater water resistance than that used in water skiing. The feet of the wakeboarder are firmly attached by binding boots to a board, laterally with respect to the direction of motion, impeding easy separation of the board from the feet in the event of a fall. Thus, wakeboarding conditions would appear to put wakeboarders at particular risk for ACL injuries. These conditions need be assessed from a medical perspective in order to devise ways to minimize the risk of such injuries.