Shoulder Disarticulation Interface Design Challenges Prosthetists

Designing the best interface for shoulder disarticulation amputees can mean the
difference between proper fitting, functional use or complete rejection. A
major obstacle in attaining optimized fit and function is that there are a
limited number of these patients and, therefore, a limited opportunity to
develop standard clinical methods.

  Gerald Stark
  Gerald Stark

According to a study by Timothy R. Dillingham, MD, there were only about
1,300 shoulder disarticulation patients from 1988 to 1996, Gerald Stark, MSEM,
CPO/L, FAAOP, vice president of product development and education at The
Fillauer Companies, said.

“On average a prosthetist would only see a shoulder disarticulation
patient maybe once or once every other year or so,” Stark said.
“Specialists can develop a standard clinical method because they are
exposed to more cases.”

Prosthetists approach their initial decisions about interface designs
much differently, depending on their previous experience with these patients.
In addition, practitioners face the basic challenges of creating optimal
suspension without anatomic structure, minimizing prosthetic weight and skin
coverage, and — because of these issues — preventing a high rate of
rejection, he told O&P Business News.

“When you create the interface you have to make sure you create
relief for the clavicle, spine of the scapula, acromium and the distal costal
area,” Stark said. “You also should minimize the size of the
interface to allow for heat dissipation because you’re covering up roughly
a quarter of the body. While making sure that you’re getting a snug fit
with good indexing and stability, it must be easy to breathe and function
within the interface.”

Stark conducted a survey of 34 prosthetists he identified as upper
extremity specialists and found that, of the 12 respondents, they see an
average of five of these patients for fittings each year.

To determine which of the available shoulder disarticulation interface
design features were most popular among this population, Stark asked his
respondents to rank 10 different design features of the following:
anterior-posterior compression, liner and frame construction,
X-Frame/Micro-Frame construction, shoulder mounting on the axilla, inferior
trimline, open proximal design, supraspinatus suspension, corrugation,
viscoelastic panels for the electrodes, and spandex donning garments.

  A-P Compression, X-Frame Construction, flexible liner and rigid frame, and supraspinatus loading ranked highest among the various shoulder disarticulation design attributes.
  A-P Compression, X-Frame
Construction, flexible liner and rigid frame, and supraspinatus loading ranked
highest among the various shoulder disarticulation design attributes.
  Source: Gerald Stark

Using the raw data, the top four attributes were weighted. From this, he
created a weighted Pareto histogram, a product engineering technique showing
how 20% of attributes can satisfy 80% of the needs or compatibility. He found
A-P compression, X-Frame construction, flexible liner/rigid frame and
supraspinatus loading to rank first, second, third and fourth, respectively, as
the preferred characteristics among specialists.

“If you use those four characteristics, you will be within 84.35%
compliance of responses,” Stark said. “If you incorporate just those
four things, you will be following more than what 80% of what all upper
extremity specialists would do, or at least the ones I tested.

“If you include open proximal window and a construction
corrugation, now you’re adhering to 93.04% of the responses, or

Stark posed the same question to his respondents to determine their
favorite casting and impression techniques, which were ordered from most to
least popular: multiple splints, CAD/CAM, compression wrap, and thoracic wrap.
Of the 14 responses; two people answered that they used more than one of the

Working with children presents its own set of challenges unique to their
circumstances, Stark said, although shoulder disarticulation among children is
fairly uncommon, unless it is a result of trauma, infection or cancer.

“It’s important to remember that you’re dealing with the
parent and the child as a system. Pediatric fitting in general needs to be
approached by addressing the parents’ needs directly,” he said.
“The child may be ambivalent about the prosthesis, where it is the parents
who have a majority of the anxiety.”

Practitioners must be sensitive to these requests, as well as to the
child’s growth potential, which could prevent the appearance of functional

“It’s important to remember that there’s no one part that
works independently of the other. The type of socket you work with has to take
into consideration control method, components and the patient’s functional
goals … it all works together,” he said. “It’s important to
look at the patient as a whole and remember that the patient should participate
in the decisions to share responsibility and accept the device.”
by Stephanie Z. Pavlou


Since most practitioners do not gain much experience with fitting
shoulder disarticulation-level amputations, it is imperative that, when a
fitting opportunity does emerge, the practitioner obtains as much education and
knowledge as possible on the various fitting procedures prior to the clinical
intervention to make sure they provide their patient with the best possible

The shoulder disarticulation-level prosthesis not only has its
challenges in fitting, but, more importantly, has its challenges in wearing by
the user. As new technologies and techniques emerge, which help to reduce or
minimize these various challenges, they are important to understand and
integrate into clinical practices.

The goal as a practitioner is to enable our patients to gain the
greatest level of comfort, mobility and function with their prosthesis. Because
the shoulder disarticulation level conventionally has so many challenges
surrounding its fitting and clinical use, eliminating or reducing these
challenges through education and understanding of the various options for a
given patient is critical. The outcome — enabling those with this
challenging level of amputation to gain life back through proper clinical care.

— Jay Martin, CP, LP, FAAOP

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