Friday, February 02, 2007
M.A.S. Socket: A Transfemoral Revolution
By Miki Fairley
The M.A.S.® socket design is an evolution--and perhaps even a "revolution"--in the development of ischial containment (IC) socket concepts. Since 1999, when Marlo Ortiz Vazquez del Mercado, Ortiz Internacional, Jalisco, Mexico, first unveiled his new design, it has continued to arouse interest throughout the O&P worldwide community. Recently the design was featured in the Thranhardt lecture series during the American Academy of Orthotists & Prosthetists 2004 Annual Meeting and Scientific Symposium.
The new design provides several clinical benefits: patients can sit more comfortably; there is no plastic beneath the gluteus; the prosthesis is easier to don; patients enjoy full range of motion, better functional gait--and important to patients and family members too--much better cosmesis. Seeing a video of patients walking, sitting, and demonstrating the range of motion possible is truly amazing.
Ortiz, who is a prosthetist and engineer, has fit hundreds of patients with the design to date. These patients reportedly have had no difficulty in wearing the socket for long periods of time. In fact, one amputee, due to his work schedule, actually wore the socket for 28 straight hours with no discomfort.
Agnes Curran, CP, OPGA prosthetist, pointed out that the design seems to be surprisingly skin-friendly despite the intimately fitting contours. Generally there is no skin irritation, and some amputees who had worn previous prostheses found that existing skin problems cleared up.
OPGA, Waterloo, Iowa, along with O&P1, Waterloo, hosted an initial seminar in January 2004 in which Ortiz taught how to cast, modify, and fit the design. An office worker who came with prosthetists from Nebraska attending the first seminar served as one of the patient models. She wore her check socket all the way home to Nebraska and asked the prosthetists to come in over the weekend to laminate it so she could begin wearing it immediately. Another patient waited all day for his new socket rather than go home with the old one. This patient enthusiasm is testimonial to their acceptance of this new design.
Bob Tillges, CPO, FAAOP, Tillges Certified Orthotic Prosthetic Inc., Maplewood, Minnesota, is enormously enthusiastic about the new design. At the time of this writing, Tillges, who attended the initial OPGA seminar, has fit nine amputees with the socket and is in the process of fitting two more.
"All my patients have been very satisfied," he said. "They have no discomfort; there's better ischial containment and range of motion. In fact, one of my patients' wives called me and said, "This is the most awesome prosthesis my husband has ever worn! I can't even see it under his slacks." She added that it had always bothered her before when her husband's prosthesis outline was visible.
"I'm taking time to learn and understand the mechanics of Marlo's system, and I'm getting very good results," Tillges added. Although most of Ortiz's patients are younger, Tillges has a large percentage of geriatric amputees. He has fit amputees aged from 44 to 81, including several in their 70s. Four of the 11 use some auxiliary suspension, but the others use true suction suspension only. "These sockets stay in total contact with flexion, extension, adduction, and abduction," Tillges said. "Something that has always bothered me as a professional is when you can see gapping, spaces, or outline of the socket under clothing." Although many were skeptical at first and thought the design would cause proximal tissue roll development, Tillges said, "We have not experienced that problem." He added, "With better ischial containment, you reduce the amount of tension values needed for suction, get more comfort, and achieve better suspension."
Tillges started his O&P career carving and fitting wood sockets in the 1970s; he has seen socket technology develop through 30 years up to the present. Some iterations of the ischial containment concept through the years have included the quadrilateral "quad" socket shape taught by the O&P schools at New York University (NYU), Northwestern, and the University of California-Los Angeles (UCLA). Ivan Long, CP, developed his Long's Line, and John Sabolich, CPO, came up with the Contoured Anterior Trochanteric Controlled Alignment (CAT/CAM) method. Tillges feels that Ortiz has gone beyond these in IC design excellence. He noted how much his patients who have worn other socket designs appreciate the new sockets: "No way do they want to go back to what they had before." Tillges is also educating his company's residents and young practitioners in the technique.
The Design: What Is It?
So, what is the M.A.S. socket? Ortiz describes his design: "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." Generally, the medial wall is lowered anteriorly to avoid pressure on the ascending ramus; effectively ischioramal weight-bearing eliminates the need for gluteal support, so those tissues can be excluded from the socket, he explained.
In the conventional design, posterior trim lines include part of the gluteus maximus. In the M.A.S. design, the height of the posterior wall has been lowered to the gluteal fold, so the entire muscle belly can be free of the socket. "This will not only improve cosmesis but with this configuration, we have found that ischial tuberosity and part of the ischial ramus are encapsulated more effectively with no restriction in hip movement," Ortiz said.
"With the gluteal cutout, no weight bearing occurs in this area, and weight-bearing forces are vectored from the captured medial aspect of the ramus with a resultant force projecting to the anterior/lateral area of the socket," explained Al Pike, CP, in "A New Concept in Above-Knee Socket Design" (The O&P EDGE, November 2002).
What About CAD/CAM?
Can the design be adapted to CAD/CAM? Perhaps "down the road," is the answer. "The difficulty is not in measuring; it's in being able to modify the complex individual anatomical shapes correctly," said Dennis Clark, CPO. However, he foresees a time when the necessary tools can be incorporated into the CAD software to accomplish the socket design.
"Once people under-stand all the concepts of the design, they can identify what they are not getting from current CAD tools--and then it will be easier to develop what's needed," said John Michael, CPO, FAAOP, who also participated in the January seminar. Michael is a consultant to OPGA and is assisting in the development of the course series.