Our Orfit blog shares information and instructions in matching our thermoplastic materials to orthotic designs.
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Today, we focus on the Relative Motion Orthosis also known as the “Yoke” splint. This is a static splint designed to hold the affected digit in relative extension or flexion compared to the adjacent digits.
The relative motion splint is in the news these days, being touted as the “go-to-splint” for a wide variety of conditions affecting the hand and digits. At the recent ASHT meeting in Boston, a panel of experts debated the use of this simply designed splint for acute and chronic boutonniere, acute and chronic sagittal band rupture, digital joint stiffness, tendon injury and repair, nerve repair and other injuries.
The relative motion splint was initially designed for postoperative rehabilitation of extensor tendon injuries with the ICAM or “Immediate Active Controlled Motion” protocol. It was fabricated to be worn with a wrist cock up splint. It was designed to hold one or two digits in relative extension compared to the adjacent digits. It can also be used as an exercise aid to facilitate either flexion or extension of the affected digit depending on the position.
This orthosis is also being used in the management of sagittal band injuries and after repair of extensor tendon ruptures in rheumatoid arthritis. It is proving to be less bulky than other splints, more comfortable for the patient, and easily worn during activities of daily living.
The goals of a relative motion splint are to limit full flexion at the Metacarpal-phalangeal (MCP) joints and to facilitate increased motion at the more distal PIP and DIP joints.
The relative motion splint for extension holds the affected digit in about 15° of MCP joint extension in comparison to the adjacent digits and might be helpful with cases of MCP joint hyper flexion, limited flexor tendon excursion and IP joint stiffness. The relative motion splint for flexion holds the affected digit in about 15° of MCP joint flexion relative to the adjacent digits and is helpful when there is a PIP extension lag.
*A relative motion splint can often be fabricated circumferentially without the need for additional strapping. Patients should be able to put on and take off their splints unaided.
Many of Orfit Industries’ thermoplastic materials (1.6mm (1/16”) 2.0mm (1/12”) and/or 3.2mm (1/8”)) are suitable for the fabrication of the relative motion which requires very little preparation or pattern making. Simply cut a strip of material about 1 ½ times the width of all the digits. It should also be about the width of the proximal phalanx. If using very thin material, the material can be folded in half to give more support.
To fabricate the relative motion splint, rest the patient’s elbow on the table and place the patient’s hand in pronation. Cut a strip of Orficast and activate in hot water. (Fold the Orficast in half lengthwise if the fingers are very short). Dry slightly and stretch the Orficast material. Weave the Orficast under the involved digit and around to the volar surface of the adjacent digits. Secure the material onto itself, creating a double thickness on the volar aspect. Push the affected digit in the dorsal direction from the volar aspect and hold in place until the material hardens. The MCP joint can be positioned in 0-15° degrees of extension relative to the adjacent digits. Smooth all of the Orficast layers together. When sufficiently hardened, remove the splint and trim all sharp edges and corners away. Trim also to allow full PIP flexion. The patient should be able to slide this splint on and off the fingers, and should be able to make a fist with it on, without fully flexing the MCP joint.
Relative Motion splints can also be fabricated for the treatment of:
- Stiff PIP and DIP joints
- Hyper mobile MCP joints
- Limited tendon excursion