THE LOAD APPLIED TO THE FOOT IN A PATELLAR LIGAMENT-BEARING CAST

The purpose of this study was to determine whether a patellar ligament -bearing cast reduces the load applied to a foot in a cast. In a study of ten people who had no history of gait abnormalities, disease invol ving the motor system, or deformities of the lower extremities, we com pared the load applied to the plantar aspect of a foot in a cast (as d etected with F-Scan computer-monitored pedobarographic sensors) with t he total load that an extremity in a cast receives relative to the gro und (as detected,vith force-plates), Six trials were completed three t imes by each person, The trials consisted of walking (1) while wearing regular shoes; (2) with a patellar ligament-bearing cast on one leg; (3) with a patellar ligament-bearing cast and an overlying soft knee b race, locked in full extension, on the leg; (4) with only a below-the- knee cast on the leg; (5) with a below-the-knee cast and an overlying knee brace, locked in full extension, on the leg; and (6),vith only a knee brace, locked in full extension, on the leg, The loads at peak he el-strike for all three trials were averaged and normalized to body we ight. The load on the plantar aspect of the foot, as compared,vith the total load, was reduced a mean of 11 percent when the patellar ligame nt-bearing cast was worn alone, and it was reduced a mean of 26 percen t when the patellar ligament-bearing cast was used with an overlying k nee brace locked in full extension. This difference was significant (p = 0.007). With the numbers available, we could not detect a significa nt difference between the reduction in load when a patellar ligament-b earing cast was worn alone compared with that when a below-the-knee ca st was worn alone or between the reduction when a below-the-knee cast was worn alone compared with that when a below-the-knee cast was used with a knee brace (p = 0.3), In conclusion, we could not demonstrate a significant reduction in the load on the foot when a patellar ligamen t-bearing cast was used in a traditional fashion; however, a significa nt (p = 0.007) reduction in load was found when a knee brace locked in full extension was worn in addition to the patellar ligament-bearing cast.