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 involving the motor system, or deformities of the lower extremities, we compared the load applied to the plantar aspect of a foot in a cast (as detected with F-Scan computer-monitored pedobarographic sensors) with the total load that an extremity in a cast receives relative to the ground (as detected with force-plates). Six trials were completed three times 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 brace, 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) with only a knee brace, locked in full extension, on the leg. The loads at peak heel-strike for all three trials were averaged and normalized to body weight. The load on the plantar aspect of the foot, as compared with the total load, was reduced a mean of 11 percent when the patellar ligament-bearing cast was worn alone, and it was reduced a mean of 26 percent when the patellar ligament-bearing cast was used with an overlying knee brace locked in full extension. This difference was significant (p = 0.007). With the numbers available, we could not detect a significant difference between the reduction in load when a patellar ligament-bearing cast was worn alone compared with that when a below-the-knee cast 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 ligament-bearing cast was used in a traditional fashion; however, a significant (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.