Comparison of interface pressures with pin and suction suspension systems.

A common mode of limb suspension for transtibial amputees is the pin liner/shuttle lock system. Despite its popularity, some clinicians question its use because of observed daily and chronic changes to the residual limb. For this study, we measured limb interface pressures during ambulation with pin and suction suspension systems. No pressure differences were seen between the modes of suspension during stance phase. However, during swing phase, pin suspension maintained an average occlusive compressive pressure of 6.7 kPa on the proximal tissues, as compared to the subocclusive pressure of 1.1 kPa with suction suspension. Simultaneously, pin suspension elevated the peak magnitude of suction to -39.5 kPa at the distal residual limb, compared to -26.1 kPa with suction suspension. During swing phase, the pin liner squeezes proximally while creating a large suction distally on the residual limb and is the likely cause of daily and chronic skin changes observed in pin users.