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International Journal of Bioprinting 3D printing of custom mallet splints

Keywords: Mallet finger; Mallet Injury; 3D printing; Additive Manufacturing

1. Introduction hospitals found that ED teams are restricted in their choice
of splint due to stock availability. Being readily available
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An epidemiologic study of soft tissue musculoskeletal in the ED, generic Stack splints appear to be the most used
injuries found that mallet fingers were the fifth most in that department.
common bodily injury. Thus, mallet finger injuries are
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common in Emergency Departments (ED) and Injury Units Generic Stack splints are not without limitations. Due
(IUs) of hospitals. Mallet finger injuries result from forced to variability in finger size and shape between patients, and
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flexion or hyperextension of the distal interphalangeal joint swelling of the injured finger, a correct or optimal fit may
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(DIPj). The overextension of the DIPj tears the extensor not be achieved. This can then affect patient compliance.
tendon where it inserts into the distal phalanx. This injury Stack splints typically come in eight sizes, but perfect fit
may occur with or without an associated fracture, resulting may not be realized for every patient. In addition, generic
in the loss of extensor mechanism. If not managed Stack splints do not consider the finger length of the
appropriately, a permanent extension lag and a possible individual patient, so the PIPj may not be free to move if
swan neck deformity may occur. These injuries commonly the splint is too long. There is no proven benefit to recovery
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occur across all demographic groups as a result of work when both the PIPj and DIPj are immobilized. Therefore,
or sports activities. Another less common presentation is patients need to be able to continue to move their PIPj
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spontaneous mallet injury, whereby no external trauma has while the DIPj is immobilized. The generic Stack splint
occurred to cause the injury. This form of injury, though also needs to be secured in place. This typically involves
less common, is associated with other underlying illnesses, taping around the injured finger. However, this can be
such as rheumatoid arthritis or osteoarthritis. challenging for patients who are trying to manage the injury
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by themselves. In addition, generic Stack splints have been
Mallet finger injuries should be treated with
immobilization or “static” splinting in extension or found to increase the risk of skin complications compared
to custom-made orthoses. Skin complications such as
slight hyperextension for up to 8 weeks, which includes mechanical dermatitis from tape placement and adhesive
2 weeks of night splinting at the end of treatment. This sensitivity have been documented for many years. 15
mode of treatment, when supported by effective discharge
advice and strong patient compliance, allows healing by The numerous challenges faced by hospital staffing
maintaining an upward force on the injured finger until the systems make provision of personalized healthcare difficult.
tendon injury or fracture heals. The splint must be worn Custom-made splints require a specialized hand therapist
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continuously, and the proximal interphalangeal joint (PIPj) to provide individualized care. Hand therapists apply the
must have enough clearance to bend to ensure the patient required splint to the patients, based on their anatomy.
does not lose range of movement. If the splint is removed They also factor in their daily activities to help optimize
and the injured finger is allowed to bend, the extensor recovery. These custom splints take approximately 30 min
tendon may re-rupture, requiring the splinting process to to create. Unfortunately, the low availability of specialist
be repeated. This can delay healing by several weeks and hand therapists in Irish hospitals indicates that custom
can lead to a swan neck deformity. An unhealed mallet splinting for mallet injuries is generally not available.
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finger injury may not function properly, resulting in pain Three-dimensional (3D) printing offers tremendous
and, in time, arthritis. 8 opportunities in the development of patient-centered
There are several splinting options that follow bespoke care. The use of 3D printing to create bespoke
similar modes of treatment. Some splints are provided devices to directly treat patients has been increasing in
by companies directly to hospitals, an example being recent years. Advances in materials, printing technology,
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prefabricated generic Stack splints. Other splints are and experience have led to increased clinical use, moving
custom-made for patients, with the most notable example away from the one-size-fits-all model. 3D printing is
being the thermoplastic splint, which is molded, typically now beginning to harness medical imaging data to
by a skilled hand therapist, to fit the patient’s finger. Of optimize patient-specific devices such as splints and casts.
these splinting methods, custom splinting is the preferred Initially, 3D printing was used primarily for anatomical
treatment option. However, prefabricated generic Stack modeling, to aid in education and planning. However, its
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splints remain the most common treatment provided application has been expanded to the creation of patient-
by healthcare facilities. A study that investigated the specific devices in the realm of point of care (POC). 3D
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conservative management of mallet splinting in Irish printing can enable the production of anatomically
Volume 10 Issue 2 (2024) 519 doi: 10.36922/ijb.1963