The prosthetic receiving cavity is the interface component of human body mechanical system, which can comfortably store the residual limb in it and effectively transmit the relevant force to the distal part of the prosthetic limb. There are many ways to contain the stump in the socket of the load-bearing prosthesis. Therefore, the receiving cavity can be divided into several types.

Suction prosthetic receiving chamber

If the bottom of the receiving cavity does not contact with the residual end, there is a suction space between them, and the suction valve is used for sealing. This kind of receiving cavity is called suction receiving cavity. The negative pressure produced by the suction space is one of the mechanisms of the suspension of the receiving cavity. In addition, the compression and volume extrusion of soft tissue, the elastic longitudinal tension, the passive expansion of soft tissue, the active extension of muscles, the friction between the cavity wall and the residual limb play an active role in the suspension of the cavity. Under the action of suction negative pressure, the blood is trapped in the stump, which is easy to cause congestion and edema in the stump and cause injury to the patient. Because the stump does not contact with the receiving cavity, the contact area between the stump and the receiving cavity decreases. The forces on the surface of the stump are correspondingly reduced. More force is transmitted through the ischium. This way of force transmission will have an adverse effect on the gait of patients wearing artificial limbs. For some patients, it can also cause discomfort in the Ischia. Suction type receiving cavity is not conducive to the blood return of the stump, only suitable for the patients with poor soft tissue coverage of the stump, or the stump is too sensitive to contact.　

Elastic contact prosthetic receiving cavity

Filling the suction space at the bottom of the suction receiving cavity with silicone rubber or other soft elastic materials will form the elastic inclusion and contact of the residual end. This kind of elastic mat also has the effect of promoting venous return. Such a receiving cavity is called an elastic contact receiving cavity. It can be used as an over form of full contact receiving cavity. It is suitable for amputees with poor soft tissue condition.

Full contact prosthetic receiving cavity

The full contact receiving cavity contains all the stumps, and the stump is in direct contact with the receiving cavity. The volume of the receiving cavity is equal to that of the residual limb. Wearing the full contact thigh prosthesis, the whole surface of the stump is in contact with the receiving cavity, increasing the contact area. The average pressure per unit area decreased (P = f / a), which made some overloaded skin partially free of charge. Only for the stump, the load it can bear in the vertical direction is limited. However, when the stump is enclosed, its load capacity is greatly improved. And the larger the containment area, the greater the load-bearing capacity.

Full contact can prevent swelling of the stump. There was less sliding between the stump and the receiving cavity, and less skin irritation and injury. In the residual limb, the micro twitch of the femur in the soft tissue is always inevitable. When swinging the leg, the femur twitches upward and blood is drawn into the distal end of the stump. In the middle of standing, the internal pressure of the stump contained in the receiving cavity increases, and the blood sucked into the stump is pumped out. In each gait cycle, blood is alternately inhaled and pumped out, which promotes the blood circulation of the stump.

Compared with other types of receiving cavity, the full contact receiving cavity has the following advantages: the patient has the feeling of touching the ground; promotes the blood circulation of the stump; avoids swelling of the stump; avoids discoloration and hyperkeratosis of the skin; alleviates and improves phantom limb pain; distributes the strength to the whole stump surface to avoid excessive local pressure.

The full contact receiving cavity is suitable for all patients with good residual limb condition. The patients who can't touch the stump are not suitable for full contact receiving cavity. If the stump is completely untouchable, suction type receiving cavity can be selected; if the stump is allergic to hard contact, elastic contact type receiving cavity can be selected. For different situation of the stump, different technology of the inclusion of the stump should be used.