Patella Tendon Bearing (PTB) Prostesis arliamedica
Subject 2, however, exhibited high-pressure concentration at both proximal and distal regions of the anterior wall in the PTB socket. Rectifications were done to the lateral aspect of the tibia (i.e., along anterior tibial muscle) as well as the medial aspect of the tibia (i.e., along tibia facet), and relief was given to the distal end of the tibia. The subject had concurred that the socket was comfortable before the test was done. Therefore, we could not explain the high pressure measured at the anterior-distal region, which decreased from weight acceptance to push-off. Furthermore, the test socket was not expected to be similar to his regular prosthesis. We are not certain that after a long period of time, he might feel some discomfort in the anterior-distal region. Subject 3 consistently exhibited high pressure distally in the PCast socket.
Pearson JR, Holmgren G, March L, Oberg K
Four subjects volunteered for this study. One subject consistently exhibited a "ring" of high pressure at the proximal brim in the PTB socket, while another subject consistently exhibited high pressure distally in the PCast socket.
The ML weight-bearing characteristics of the PCast socket are possibly similar to those of the PTB socket during standing. However, it would be interesting to study whether it occurs during gait as well.
The Orthopaedic Speciality Clinic
Subject 1's GRF line of action was acting posterior to the knee, thus creating a tendency to flex the knee in the PTB socket during weight acceptance. However, the GRF line of action was observed to be acting anterior to the knee in the PCast socket during weight acceptance, thus creating a tendency to extend the knee. Theoretically, this knee extension moment would cause high-pressure concentration at the anterior-proximal and posterior-distal regions. This finding is verified by the higher pressure concentration measured at the anterior-proximal region in the PCast socket.
Total Knee Replacement | Pinnacle Orthopaedics
Subject 4 consistently exhibited higher pressure at the proximal region in the PTB socket. This finding is similar to the study done by Convery and Buis . While subjects 1, 2, and 3's PTB and PCast sockets exhibited similar ML pressure profiles during static tests, only subject 2's continued to do so during gait. Subject 3's medial pressure profile was more uniform in the PTB socket. Although subject 1 exhibited similar pressure profiles at the medial wall, higher pressure at the lateral proximal region was recorded in the PCast socket. These could also be due to differences in socket alignment, which was not measured in the study.
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Subject 4 consistently exhibited high pressure at the proximal brim in the PTB socket throughout stance. This could be because the proximal brim was too small, although he found the PTB socket comfortable. We are not certain whether the subject would have preferred one with a wider proximal brim, but this further demonstrates the current PTB practice of fabricating a comfortable fitting socket by trial and error, which highly depends on the skills and experience of a prosthetist.
Total Knee Replacement Rehabilitation
This paper compared the pressure distribution of the PCast socket with the traditional PTB socket. To fabricate a PCast socket, we required the subject to place his residual limb in a tank filled with water. Pressure was then applied to the residual limb. Pressure cast has the potential to "let nature dictate the most realistic and achievable pressure distribution" [8,12]. During the casting process, manual dexterity and interprosthetist variances were eliminated without any need for rectifications. Such a method would minimize the skills needed and reduce time and costs in fabricating prosthetic sockets.