Pushing the Clinical Envelope with CAD/CAM

Jennifer Dowell, CPO, LPO

Until recently, the clinical abilities afforded by CAD/CAM were restricted primarily to relatively straightforward lower-limb prosthetic cases and still required casting the patient. Patients with more complicated shapes, such as focal deficiencies or severe contours and 90-degree bends, were not candidates for CAD/CAM applications. The inability to address these complex cases limited the utilization and value of CAD/CAM systems in the P&O industry, and demonstrated a pronounced need for further CAD/CAM development.

Fortunately, efforts to create more sophisticated shape-capture technology and modification software have paid off. Today's CAD/CAM technology provides the ability to capture or create a variety of complex shapes for both prosthetic and orthotic clinical applications, as evidenced by the following patient examples.

Hemipelvectomy Patient Profile

This patient, treated by Mike Nunnery, CPO, LPO, of Nunnery Orthotic and Prosthetic Technologies, North Kingstown, Rhode Island, is a 34-year-old male who become a left hemipelvectomy from a traumatic amputation secondary to an industrial accident in December of 2007. Extensive surgical reconstruction was necessary at the amputation site, resulting in significant scar and graft tissue at the weight bearing sites of the lower left torso due to the absence of the gluteal musculature. Surgical reconstruction to the digestive tract and colorectal system were necessary, resulting in the installation of a permanent colostomy.


Patient, view of left side.	Patient, posterior view.

CAD shape file, left anterior angle.	Cad shape file, left posterior angle.


Patient wearing "silicone pants."	Initial fitting of pelvic stabilizer.

Fortunately, the patient possessed good balance and strong upper-body strength as well as sound-side lower-limb strength. After the amputation and ancillary surgeries, the patient found sitting to be difficult, and there were concerns regarding the development of spine and trunk deformities over time. Determining that CAD technology would be a viable option, Nunnery devised a scanning "platform" to provide an efficient method of conducting a full-torso scan. The image was captured with an OMEGA Scanner directly over the patient's skin in order to achieve a detailed image that exhibited no bridging over any invaginated scar tissue.

Patient, anterior view.

A foam model was created and used as the basis for fabricating custom "silicone pants." Under Armour® underwear was customized by a seamstress to fit the foam model so the patient would be able to use the underwear as a wicking interface between the skin and liner. After the patient was fit with the silicone liner, a pelvic stabilizing socket was fabricated and assembled to a set of lightweight components. This patient, who was previously unable to maintain balance for sitting, is now able to sit. He is also able to ambulate with crutches during the early stages of gait training. The definitive prosthesis will consist of a final carbon fiber epoxy lamination over the NorthPlex protosocket and hard foam bridge to build out for the hip-joint attachment.

Congenital Prosthetic Patient Profile

This patient, 14, has a right PFFD resulting in an atypical limb contour. Extremely active, she shows horses and plays basketball and volleyball. When she first visited Jeff Denune, CP, of Ohio Willow Wood, Mt. Sterling, Ohio, she was wearing a lotion-fit suction socket consisting of a rigid frame with windows and flexible interface for ease of donning.

After scanning the patient directly over her skin with an OMEGA Scanner, Denune used the OMEGA Tracer software to create an Alpha DESIGN® Liner with a highly customized gel pattern and a socket with aggressive contours.

To create the socket, the patient was scanned in a partially weight bearing position to flex and load the metatarsal area of the foot. This scan was then merged to a predesigned transfemoral brim shape to create a complete socket shape. Suspension was achieved using a combination of a Green Dot upper-limb air-expulsion valve for cosmetic reasons, the gel distribution within the DESIGN Liner, and socket contouring. The DESIGN liner, which was created with Velcro®-compatible Spirit fabric, was reflected over the proximal brim of the socket and secured with Velcro tabs to provide additional suspension and rotation control. Additional suspension was achieved by placing Velcro on the inner surface of the socket in the metatarsal area. When the patient participates in higher-level activities, an AK suspension and Tess belt are also employed.


Design liner CAD file.	Socket shape.	Final prosthesis.

Upper-Limb Prosthetic Patient Profile

Nunnery also used the OMEGA System to update the prosthesis of a 64-year-old man who had become an interscapulothoracic amputee at the age of 13 due to osteosarcoma. The patient wore a body-powered prosthesis in his teenage years and used a passive arm for four years in his job as a vocational rehabilitation counselor and for 28 years as a rehabilitation office director/manager.


UA patient, anterior view.	Modified CAD shape file.

By scanning the patient with the OMEGA Scanner and using the OMEGA Tracer software for modifications, Nunnery was able to create an accurate patient model for the design and fabrication of an interscapulothoracic socket interface. The carved model allowed him and his staff to build and "fit" the prosthesis directly to the model, allowing them to "take the hassle out of harnessing." The carved model also provided the ability to properly locate the prosthesis on the model. Additionally, the light weight of the carved model was an ergonomic plus for the staff.

Pectus Carinatum Orthotic Patient Profile

Another patient of Nunnery, this 14-year old male had been diagnosed with pectus carinatum at age 11. His condition progressed significantly over the next two years, at which point corrective surgery was performed at the University of Minnesota. After being managed post-surgically with a "hybrid" Jewett orthosis, the patient subsequently received a prescription for a lightweight protective chest plate for use in sporting activities such as umpiring baseball.

A non-contact/non-invasive scan obtained with the OMEGA Scanner provided a highly detailed and accurate post-operative shape capture of the patient. The use of the OMEGA Tracer System provided an exceptional model for modification and fabrication, and enabled the patient to benefit from a more positive experience.

A variety of both general and spinal-specific tools in the software allowed the model to be easily modified. The initial chest protector was fabricated directly to the mold using �-inch copoly and was fit as a "check socket" for evaluation by the surgical team. The final device was made of a carbon/epoxy lamination.


Before fitting.	CAD shape file-modified.	Overlay of two different scans.

Nunnery believes that the easily obtained pre- and post-surgical scans that are possible with this technology could provide the ability for "pectus surgery outcome studies due to the ease of shape capture and accurate documentation for the medical and team and third-party payers."

Transfemoral Prosthetic Patient Profile

This patient is a 56-year-old active male who received a left above-knee amputation secondary to a shark attack in 2003. He has heavy scarring, a considerable amount of redundant tissue, and irregular limb contours. The limb also changes shape during ambulation.

Patient, lateral view.

His prosthetist, John Reynolds, CPO, FAAOP, of Reynolds Prosthetics & Orthotics, Maryville, Tennessee, needed to find a way to contain this tissue to control rotation and to maximize muscular control and efficiency.

His initial approach in 2005 was to create an Alpha DESIGN Liner using a shape obtained with the OMEGA Tracer Pen. The liner contained the loose tissue, but considerable motion was still present during contraction. A new liner was fabricated in 2006 with thicker gel coverage to better secure the soft tissue.

In 2007, a new scan taken with the OMEGA Scanner (pictured here) provided greater accuracy and detail, resulting in more accurate placement of gel in the liner, improved stabilization of the loose tissue, and enhanced control of the muscle movement. According to Reynolds, "use of OMEGA Tracer shape-capture devices facilitates an initial accuracy that allows the prosthetist to create a more normalized and traditional socket shape over an otherwise more challenging limb shape."

These patients all have vastly different clinical needs, but each was treated with a protocol that involved the use of CAD/CAM technology. The ability to scan negative and positive models instead of the patients themselves is also beneficial and is sometimes necessary. The inner surface of a negative impression can be imaged by splitting the cast in half, scanning each section, and allowing the software to reassemble the model. This option is an advantageous when significant correction is needed but cannot be achieved during the direct scanning of the patient. For example, a corrected cast of an AFO or spinal patient can be imaged with the OMEGA Scanner, then reassembled and modified in the software in preparation for milling and fabrication. In this scenario, the clinician may continue to use a specific casting technique while still benefiting from the ability to electronically modify, fabricate, and store the patient's shape file.


Unmodified shape file, lateral.	Design liner, lateral.

While CAD/CAM development in the O&P industry has certainly made significant strides, there are undoubtedly still patients whose clinical needs exceed CAD/CAM's grasp. Further development must continue in order to accommodate an even larger patient population to improve patient care and increase the versatility of CAD/CAM for prosthetics and orthotics.

Jennifer Dowell, CPO, LPO, earned a bachelor of science degree in prosthetics and orthotics from the University of Washington, Seattle, in 1990. After several years of traditional clinical practice, she began specializing in the development, testing, and instruction of CAD/CAM technology for the O&P industry. A proponent of incorporating CAD/CAM into clinical practice, Dowell has been involved in the development and advancement of CAD/CAM technologies and specifically with the OMEGA Tracer System since 1999.