Date Published: May 2, 2019
Publisher: Springer International Publishing
Author(s): Keaton J. Young, James E. Pierce, Jorge M. Zuniga.
Traditional prosthetic fabrication relies heavily on plaster casting and 3D models for the accurate production of prosthetics to allow patients to begin rehabilitation and participate in daily activities. Recent technological advancements allow for the use of 2D photographs to fabricate individualized prosthetics based on patient anthropometrics. Additive manufacturing (i.e. 3D printing) enhances the capability of prosthesis manufacturing by significantly increasing production speed and decreasing production cost. Existing literature has extensively described the validity of using computer-aided design and 3D printing for fabrication of upper limb prostheses. The present investigation provides a detailed description of the development of a patient specific body-powered 3D printed partial finger prosthesis and compares its qualitative and functional characteristics to a commercially available finger prosthesis.
A 72-year old white male with a partial finger amputation at the proximal interphalangeal joint of the left hand performed a simple gross motor task with two partial finger prostheses and completed two self-reported surveys (QUEST & OPUS). Remote fitting of the 3D printed partial finger began after receipt of 2D photographs of the patient’s affected and non-affected limbs. Prosthetic fitting when using 3D printable materials permitted the use of thermoforming around the patient’s residual limb, allowing for a comfortable but tight-fitting socket. Results of the investigation show improved performance in the Box and Block Test when using both prostheses (22 blocks per minute) as compared to when not using a prosthesis (18 blocks per minute). Both body-powered prostheses demonstrated slightly lower task-efficiency when compared to the non-affected limb (30 blocks per minute) for the gross motor task. Results of the QUEST and OPUS describe specific aspects of both prostheses that are highly relevant to quality of life and functional performance when using partial finger prostheses.
The use of 3D printing exhibits great potential for the fabrication of functional partial finger prostheses that improve function in amputees. In addition, 3D printing provides an alternative means for patients located in underdeveloped or low-income areas to procure a functional finger prosthesis.
Limb loss due to amputation is expected to reach nearly 3.6 million by the year 2050, which will have dramatically increased from the current 1.6 million in 2005 . The majority of these amputations are considered minor amputations, as these individuals are losing only small appendages such as fingers or toes . Amputation of the fingers in the upper limbs is a common occurrence and has significant implications on individuals overall function, coordination and quality of life. Loss of these appendages can reduce functional ability, resulting in difficulties performing activities of daily living (ADL) . The use of prostheses has been shown to improve completion of ADLs, in addition to improving psychosocial self-esteem, body image, interlimb coordination with the contralateral limb and body symmetry [4, 5]. Despite this, prior literature found that nearly 70% of upper limb prosthetic users were unsatisfied with their prosthesis when completing ADLs . In addition, it has been indicated that nearly 52% of upper limb amputees abandon their prosthetic devices due to the functional, aesthetic or other limitations . In contrast to the reported figures of device abandonment, realistic rejection rates and non-usage have been estimated to be even greater due to the lack of communication between clinics and prosthetic non-users . To reduce the large degree of device abandonment, it is recommended that prosthetic device fitting occur immediately or as quickly as possible following a surgical amputation, which may increase the acceptance rate of these devices . Traditional prosthesis fabrication is a lengthy process that requires a certified prosthetist to make multiple castings of the affected limb using plaster, which can be both labor and material intensive. As traditional fabrication methods may not meet the rate at which prostheses must be manufactured, the need for an accelerated method of production presents itself. Modern advances in additive manufacturing (i.e., 3D Printing) have made it possible for the batch-production of low cost, customized upper-limb 3D prostheses using Fused Deposition Modeling (FDM), where the production capacity is limited to the size, type, and the total number of 3D printers available .
In the performance of the gross manual dexterity task, the subject moved 18 blocks per minute (BPM) when no prosthesis was utilized. When a prosthesis was used, performance improved to 22 BPM during the one-minute trial with both the LFP and the MFP. Comparatively, the non-affected limb moved 30 BPM, which demonstrates the relative functional difference of the affected limb.
The primary findings of the current investigation provided evidence that the LFP produced very similar functional results to that of the MFP (Table 3). The results from the current investigation provides evidence demonstrating that both a tension- and linkage- driven body-powered prostheses can produce similar performance outcomes in the BBT. The subject demonstrated a lower functional outcome in the BBT when not using a prosthesis on the affected hand, with 60% task-specific efficiency when compared to the non-affected hand. The use of prostheses improved the task-specific efficiency to 73% of the non-affected hand, suggesting that the use of either the LFP or MFP will improve gross dexterity.Table 3Box and Block TestConditionBlocks per MinuteLocal Prosthetic22Commercial Prosthetic22No Prosthesis18Non-Affected Hand30
The current investigation described two different types of body-powered finger prostheses and observed the functional and satisfaction outcomes of a single subject. An improvement in function is evident when either prostheses was used, with principal differences between the prostheses being the method of fabrication, design, and overall mechanisms of action. As the accessibility to 3D printing continues to enlarge, there is great potential for 3D printing to pave the way for multiple new medical applications and devices, which may transform the fabrication process of future medical devices.