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Marlo Anatomical socket, an overview
-Mark Ledger MBAPO Sr. Pros
Introduction
The 4 of the Limbless Association remain Capability, Comfort, Caring, and Cosmesis. Recent work by the Mexican Prosthetist Marlo Ortiz has led to the development of the M.A.S (Marlo Anatomical Socket) socket for Transfemoral amputees. This socket design whilst not widely used in the U.K. seeks to address two of these principles, Comfort and Cosmesis.
In March 2002 Marlo Ortiz came to the U.K. and ran a short seminar at Dorset Orthopaedic on the new technique. As a result of the work achieved during this week several patients were fitted with the new socket design.
Marlo presented at BAPO in March 2003 to a keen audience having completed a further week seminar in the U.K. at Dorset Orthopaedic. The M.A.S. technique is becoming one of the most rapidly adopted techniques for the Transfemoral amputee in the States, but remains relatively unknown in the U.K.
Socket design
The M.A.S socket design is based on the ischeal containment type socket with several important variations. The ischeal containment is more Medial, therefore the counter forces are controlled by the lateral wall. This means that the anterior section of the socket can be kept completely free. As a result the patient can achieve maximum hip flexion without socket interference. So for activities such as driving, where such hip flexion is required the socket becomes more comfortable. An additional benefit of this design is that the containment of the Ischeam locks the limb fairly well to the residuum, and thus stabilising the limb. In our experience this has allowed a relatively inexperienced amputee to run quite soon after delivery of the limb.
Marlo has pointed out that there is an additional cosmetic advantage to this socket design. Due to the shape of the socket there is no projecting helf ?at the posterior edge. This means that the socket simply disappears under the clothing.
EVOLUTION OF ISCHIAL CONTAINMENT SOCKET
Marlo Ortiz Vazquez del Mercado P.O.
Ortiz Internacional S.A. de C.V.
Guadalajara, Jalisco México
Through the years there has been a transition in socket design for transfemoral amputees from the plug fitting, pre quad, quadrilateral and the latest ischial containment.
When considering an ischial containment socket there are many socket shape variations such as: SABOLICH, UCLA, LONG, DOMINGUEZ HILLS and prefabricated brims such as IPOS, BREAKEY and other devices.
The use of anatomical shapes are not new, in the past Thomas Canty and the U.S. Navy made some attempts to create an anatomical A/K socket. Some techniques do not use the traditional Scarpas triangle shape and others create an acute angle at the anterior medial corner; in our technique the Scarpas triangle shape is applied.
Our first acknowledgement of ischial containment sockets was in UCLA in 1986 and since then we have made some modifications through the years. Some of those modifications are at the anterior aspect, we have changed it to a quadrilateral shape; at the posterior aspect we get it closer to the posterior portion of the ischial tuberosity and we should take into consideration the anatomical A-P and M-L dimensions
It is very important to consider the angle of the ischial ramus. The ischial tuberosity and part of the ramus as well as the medial aspect of the ramus are encapsulated within the medial aspect of the socket brim. In the medial aspect of the socket below the ischium the contraction of hamstring tendons over the inferior containment wall provide control to stabilize the socket.
Although the trim lines of a conventional ischial containment socket are usually above the ischial level, the height of the brim will depend on each individual, generally with the MAS socket the medial wall is lowered to avoid pressure on the ramus, pressure below the ischium on the posterior wall provides good gluteal support.
In the new M A S (Marlo Anatomical Socket) design there are some differences in the trim lines. In the conventional design posterior trim lines include part of the gluteus maximus. In the new design we have lowered the height of the posterior wall to the gluteal fold to permit the gluteus maximus to be out of the socket. This will improve cosmesis and there is no gluteal support. With this configuration we found that the ischial tuberosity and part of the ischial ramus are encapsulated easily with no restriction in movement
Not only the posterior wall trim lines but the anterior and medial walls have been lowered below the ischial level this allows a greater range of motion and comfort. Hamstring tendons fit over the inferior containment wall to enhance a closer fitting of the lateral wall.
The height of these trim lines will be established according to the anatomy of each patient. From a posterior view you can see how the cosmesis is improved and there is no gluteal support.
If we take a look at the inside shape of the new socket design let’s check the forces applied. As you are all aware there are two main anatomical dimensions: A-P and M-L, but the resultant force is not usually considered; this force gives us a better control of some situations such as stabilization of the lateral wall, rotational control and ischial containment itself. (Fig 3)
The antero-lateral proximal corner of the socket is critical in order to maintain the socket control and should follow the anatomical shape of this area for cosmesis as well.
In the anterior quad shape we have to take into consideration the measurement between the Anterior Superior Iliac Spine and the adductor longus tendon, this give us a better idea for the anterior proximal wall dimension.
The MAS socket is not a conventional ischial containment socket design, what we have done is to move the containment wall more anterior in order to get a medial ramus containment socket. There is no a ischial weight bearing support and even the medial ramus is not a weight bearing area, in fact, patients should not feel any excessive pressure over the ramus.
A maximum of ¼” (5mm) play is allowed for comfort in this area
As there is no proximal weight bearing area the design provides a quasi-hydrostatic weight bearing system over the rest of the stump and the resultant force will provide socket control. Gluteal containment is common to other designs but not used with the Marlo Anatomical Socket.
Dynamic Alignment
There have been many suggestions for the position of the femur. This new socket design with its very low trim lines improves ischial containment and allows the femur to move in to an over adducted position in order to get as equal as possible to the angle of the sound side. This will give a better functional gait.
Benefits of the M A S design
There are several benefits of this new socket design: patients can sit more comfortably, there is no plastic beneath the gluteus, easy to put on, full range of motion, better functional gait and something very important to some patients, cosmesis.
When donned the Prosthesis looks cosmetically very normal and its hard to find any discrepancy of the gluteus maximus as well as any protrusion of socket trim lines.
Range of motion is improved. A full range of hip flexion is obtained (Fig. 4) and depending on the length of the stump and flexibility of the hip, patients can have a full range of external rotation where they can cross legs up to 90 degrees
Functional gait is also improved, the base gait is narrow, there is no rotation of the foot and lateral trunk bending or lateral displacement of the center of gravity is minimized
The appearance of the hip and buttocks when patients walk is very normal and it is hard to see any discrepancy.
This socket design has been fitted with silicone liners for suspension. Some15 % of our patients have been fitted with silicone liners and the rest with suction valve. None of them have been fitted without any suction system or auxiliary suspension belts
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