Digit-Specific Positioning for Extensor Tendon Repair: The Role of the Relative Motion Orthosis

Zone V extensor tendon repairs require careful postoperative management to balance protection and early motion while minimizing complications such as adhesions and stiffness. The relative motion concept has demonstrated excellent functional outcomes when applied through a digit-specific orthosis.^1,2,3

As hand therapists, we know that extensor tendons lack a true synovial sheath, making them highly susceptible to adhesion formation—a major factor that can limit functional recovery if not properly managed. I’ve seen cases where, despite a successful surgical repair, excessive scarring led to significant motion restrictions, prolonging rehabilitation. This is why early controlled motion is crucial in preventing stiffness and optimizing outcomes.

The position of the repaired digit within the orthosis is critical—each digit requires a specific placement to ensure tendon protection, controlled loading, and functional hand balance. In this article, we’ll explore the rationale behind the relative motion orthosis, provide a step-by-step fabrication guide, and discuss key clinical considerations for success.

Postoperative management of extensor tendon repairs in zones V and VI

Several protocols exist for managing Zone V and VI extensor tendon injuries, each with varying levels of motion restriction and early mobilization:

• Static immobilization protocols: The digits are placed in extension for several weeks, preventing early motion to protect the repaired extensor tendon.

• Dynamic protocols: Utilize a dynamic extension splint to allow controlled movement while preventing excessive tension on the extensor tendon repair site.

• Relative motion: A key component of the relative motion protocol, the relative motion orthosis facilitates early controlled motion while maintaining extensor tendon protection, leading to better functional outcomes and reduced risk of stiffness.^1-6

While many hand therapists are familiar with the relative motion orthosis, understanding its digit-specific application and role in tendon protection is crucial for maximizing patient outcomes.

Why use a relative motion orthosis for extensor tendon repair?

The relative motion orthosis helps redistribute force across the extensor mechanism by placing the repaired tendon in a controlled 15 to 20 degrees more extension than adjacent tendons.^1-3 The juncturae tendinum also plays a key role in stabilizing motion, unloading the repair site.⁴ 

This controlled positioning protects the healing tendon while still allowing functional movement, minimizing strain, and supporting early rehabilitation:

• After extensor tendon repair, the healing tendon in the relative motion orthosis experiences less force than the adjacent tendons with controlled, safe motion.^5,6 

• If the injured digit is held in more extension than the others, this may “harness the extension force of the juncturae tendinum and the adjacent fingers,” preventing excessive tension at the repair site.⁴

• Earlier protocols included a wrist orthosis alongside the relative motion yoke orthosis during the first 21 postoperative days, positioning the wrist in 20 to 25 degrees of extension to limit tendon excursion before transitioning to the yoke alone.^1,3,6 Current research demonstrates that wrist orthosis is no longer needed with relative motion orthosis.^1,2,3,6

Digit-specific positioning for the orthosis

When fabricating a relative motion orthosis, proper positioning is key to protecting the repaired tendon while maintaining functional balance across the hand. Since the juncturae tendinum interconnects extensor tendons, incorrect placement can disrupt force distribution, leading to excessive strain on the repair or compensatory movement patterns. The repaired tendon must experience less relative motion than adjacent tendons, but the orthosis should also support balanced motion across the MCP joints to avoid excessive tension.

The finger position in the orthosis is based on which extensor tendon is repaired:

• Index or small finger repair: The affected digit is placed in 15 to 20 degrees more extension than the others.¹ If the index or small finger is repaired, both should be positioned in more extension to maintain balance in the orthosis.

• Long (middle) finger repair: If the long finger extensor tendon is repaired, it alone is held in more extension than the other digits in the orthosis.

• Ring finger repair: If the ring finger extensor tendon is repaired, earlier literature placed the long (also called middle) finger in more extension for balance. More recently, therapists have held the ring finger alone in more extension than the other digits. 

Clinical insight: Positioning the wrong combination of fingers can overload the repaired tendon or alter movement patterns that slow recovery. Always consider balance across the MCP joints when fabricating the orthosis to optimize function and healing.

Fabricating a relative motion orthosis for extensor tendon repair

A well-constructed orthosis ensures optimal tendon protection and early functional movement following extensor tendon repair. This step-by-step guide will walk you through creating a digit-specific relative motion orthosis, ensuring proper fit, stability, and patient compliance. Here are the steps to follow:

1. Gather materials

2. Heat and mold the thermoplastic with a pen or pencil to help with digit placement

3. Secure the digit in the proper position 

4. Educate the patient 

Let’s take a closer look at how you can create an effective orthosis for your patient.

1. Gather materials

• Thermoplastic material (approximately 1/16-inch thickness) provides structure while remaining flexible for adjustments.

• Soft strapping (Velcro or elastic bands) helps secure the orthosis in place while allowing mobility.

• Scissors and a heat source are necessary for cutting and shaping the thermoplastic material.

• A pen or pencil to help with digit placement

2. Heat and mold the thermoplastic

• Cut a narrow strip (approximately 1 to 1.5 centimeters wide).

• Heat the material until moldable, ensuring it remains pliable but not too soft to maintain structure.

• Place a pen or pencil to hold the involved digit in more extension during the fabrication process at the middle phalanges.

• Mold the orthosis around the proximal phalanges, ensuring a snug but comfortable fit distal to the MCP joints.

3. Secure the orthosis in position

• Adjust the orthosis based on the specific digit involved to maintain proper alignment.

• Attach soft strapping to stabilize the orthosis while allowing full movement at the PIP and DIP joints.

4. Educate the patient

• Wear full-time for 6 weeks and then for “at-risk activities.”^1-3

• Perform controlled active motion while avoiding forceful gripping or excessive flexion.

• Monitor for discomfort, skin irritation, or necessary adjustments, and report concerns to the therapist.

Thorough patient education ensures proper use of the orthosis and reduces the risk of complications during recovery. Taking the time to explain the importance of movement restrictions and wearing the orthosis full-time will set your patient up for successful rehabilitation.

Clinical considerations and patient selection

Is a wrist orthosis necessary?

Merritt's original study included a wrist orthosis alongside the relative motion orthosis in extensor tendon rehabilitation. However, more recent research demonstrated no ruptures when using the relative motion orthosis alone from day one and that a wrist orthosis is no longer necessary in Zones IV-VI.^1,2,3

Patient compliance matters

Successful rehabilitation with a relative motion orthosis depends on patient adherence to movement restrictions and proper orthosis use full-time. This protocol is most effective when patients are motivated and able to follow instructions, as active-controlled motion is essential for optimal tendon healing. For children or individuals with cognitive impairments, a delayed motion approach using static immobilization may be a safer alternative to prevent unintended strain on the repaired tendon. Therapists should assess each patient’s ability to comply with movement precautions before selecting an early motion protocol.

Scar management and strengthening

Between 8 to 12 weeks post-repair, rehabilitation should shift focus toward progressive strengthening while continuing to protect tendon integrity. Gradual strengthening exercises should be introduced to restore grip and dexterity, while passive and active-assisted motion help achieve a full range of motion in the affected fingers. Many patients develop compensatory, one-handed movement patterns during early healing; therefore, therapists should guide them in relearning bilateral hand use to improve overall function. Careful monitoring of scar tissue mobility is also essential, as adhesions can restrict movement and delay functional recovery.

Optimizing extensor tendon repair outcomes

The relative motion orthosis is more than just an orthosis—it’s a strategic approach to extensor tendon repair and rehabilitation, balancing protection and mobility to optimize recovery. When fabricated and applied correctly, it reduces strain on the repaired tendon while allowing functional movement, helping patients regain hand function more efficiently. However, successful outcomes depend on more than just the orthosis itself—therapist expertise, proper patient selection, and adherence to movement precautions all play a critical role.

While this approach has been shown to produce excellent results, not every patient is an ideal candidate. Children and individuals with cognitive impairments may require a more structured or delayed motion protocol to prevent unintentional strain. Knowing when to implement relative motion splinting—and when to modify treatment—ensures optimal healing, improved function, and better long-term outcomes in extensor tendon repairs.

Want to refine your expertise in extensor tendon repair and rehabilitation? My Medbridge courses provide evidence-based insights and hands-on demonstrations to help you confidently manage extensor tendon injuries across all zones:

• Extensor Tendon Rehabilitation Update: Zones I–II

  • Anatomy review of terminal extensor insertions

  • Conservative and postoperative treatment interventions

  • Step-by-step orthosis demonstrations for optimal tendon protection

• Extensor Tendon Rehabilitation Update: Zones III–IV

  • Current evidence-based management strategies

  • Conservative vs. postoperative treatment approaches

  • Orthotic fabrication techniques for central slip and sagittal band injuries

• Extensor Tendon Rehabilitation Update: Zones V–VI

  • Anatomy and function of the extensor tendons at the MCP joints

  • Guided treatment interventions for postoperative and conservative care

  • Detailed orthosis fabrication demonstrations for the relative motion yoke orthosis

  
  

References

1. Merritt, W. H., Robinson, S., Hardy, M. (2023). A commentary from the pioneers on the innovation of the relative motion concept: History, biologic considerations, and anatomic rational. Journal of Hand Therapy, 36,251-257.

2. Collocott, S. J., Kelly, E., & Ellis, R. F. (2018). Optimal early active mobilization protocol after extensor tendon repairs in zones V and VI: A systematic review of literature. Hand Therapy, 23(1), 3–18. https://doi.org/10.1177/1758998317729713

3. Merritt, W. H., Wong, A. L., & Lalonde, D. H. (2020). Recent Developments Are Changing Extensor Tendon Management. Plastic and reconstructive surgery, 145(3), 617e–628e. https://doi.org/10.1097/PRS.0000000000006556

4. Howell, J. W., Merritt, W. H., & Robinson, S. J. (2005). Immediate controlled active motion following zone 4-7 extensor tendon repair. Journal of hand therapy : official journal of the American Society of Hand Therapists, 18(2), 182–190. https://doi.org/10.1197/j.jht.2005.02.011

5. Hardy, M., Feehan, L., Savvides, G., & Wong, J. (2023). How controlled motion alters the biophysical properties of musculoskeletal tissue architecture. Journal of hand therapy : official journal of the American Society of Hand Therapists, 36(2), 269–279. https://doi.org/10.1016/j.jht.2022.12.003

6. Merritt W. H. (2014). Relative motion splint: Active motion after extensor tendon injury and repair. The Journal of Hand Surgery, 39(6), 1187–1194. https://doi.org/10.1016/j.jhsa.2014.03.015