Swedish Trial Sets Up Direct Test of Postoperative Care After Thumb Flexor Repair
Rehabilitation after flexor pollicis longus repair has long been shaped by a tension between protecting the repair and preserving motion. In the thumb, that balance may be even more difficult than in the fingers. The tendon is central to pinch, grasp, and opposition, yet rupture after repair remains a feared complication, and the consequences of failure can be substantial for hand function.
This registry-based multicentre randomised controlled trial is designed to answer a simple but clinically important question: does a period of immobilisation lower rupture risk after primary repair of the FPL in zones 1 and 2, without sacrificing eventual function? Investigators will compare 4 weeks of casted immobilisation with an early active motion strategy that begins 2 to 5 days after surgery, using protection with a dorsal cast and a volar removable splint.
The study is being conducted across five academic hand surgery centres in Sweden and will enroll patients aged 15 years or older with a complete FPL injury in zone 1 or 2. After randomisation in a 1:1 ratio, both groups will eventually follow the same rehabilitation protocol after the initial 4-week period. The design reflects a practical clinical dilemma: early motion may limit adhesions and stiffness, but the thumb’s anatomy and loading pattern may make the repair more vulnerable than standard finger flexor protocols suggest.
A single sentence captures the central risk: rupture after FPL repair is the outcome surgeons most want to avoid.
Why Thumb Flexor Repairs Are Not Just Another Flexor Tendon Problem
The thumb is not a substitute finger. Its range of motion, line of pull, and role in fine motor tasks make rehabilitation decisions more consequential, and protocols developed for digital flexor tendons cannot simply be assumed to translate to the FPL. The trial’s rationale rests on that difference. The thumb must regain enough motion for daily use, but too much early load could jeopardize a repair that is already under mechanical stress.
The protocol also reflects a clinical reality that many hand surgeons already face in practice. Early controlled motion is widely used after FPL repair, yet rupture rates after these injuries are described as higher than those seen with finger flexor tendons. That gap raises the question of whether a more conservative approach could improve safety without producing a trade-off in range of motion, strength, or patient-reported function.
The trial uses the Swedish National Quality Registry for Hand Surgery as the data backbone. That choice should improve completeness and give the study a real-world character, since postoperative rehabilitation and outcome collection will be embedded in routine care rather than built around an isolated efficacy experiment. It also means the results should be easier to interpret for everyday hand surgery practice if the study reaches completion as planned.
What the Trial Will Measure Over 12 Months
The primary endpoint is the frequency of tendon rupture over 12 months. That endpoint is clinically direct and easy to understand at the bedside, where the immediate question after repair is whether the tendon survives the rehabilitation period intact. The investigators will analyse the primary outcome on an intention-to-treat basis, with stratification by centre, and report the absolute risk difference and relative risk with 95% confidence intervals.
Secondary outcomes reach beyond rupture alone. Patient-reported outcome measures and patient satisfaction will be collected, along with active range of motion at the metacarpophalangeal and interphalangeal joints, plus grip and key pinch strength at 3 and 12 months after surgery. Those measures matter because a repair that survives but leaves the thumb stiff or weak still falls short of meaningful recovery.
The contrast between the two arms is straightforward. One group begins active training within days, under protective bracing. The other remains immobilized for 4 weeks before joining the same rehabilitation pathway as the early-motion group. That setup should help isolate the effect of the early postoperative period itself, which is where the biggest mechanical differences are likely to occur.
Registry-Based Design Could Make the Results More Clinically Useful
Embedding the trial in a national quality registry may strengthen the study in ways that matter to clinicians. Registry-based trials can capture routine practice across multiple centres, reduce duplication of data collection, and track outcomes in a more pragmatic setting than a tightly controlled single-centre study. For a question like postoperative rehabilitation, that pragmatic structure is especially relevant because the intervention is delivered in the real world, not in a laboratory.
The unblinded design is unavoidable. Patients and clinicians will know whether early motion or 4-week immobilisation has been assigned, and that opens the door to expectation effects. Yet the primary outcome is rupture, a hard clinical event that is less vulnerable to subjective interpretation than many rehabilitation endpoints. The secondary outcomes, by contrast, will depend partly on patient perception and therapist assessment, so their interpretation will require care.
The sample will include only complete FPL injuries in zone 1 or 2, which keeps the population focused but also narrows how broadly the findings can be applied. Partial injuries, other zones, and other tendon injuries are outside the frame. Still, that specificity may be exactly what the field needs, because the thumb has too often been managed by analogy rather than direct evidence.
Safety, Ethics, and the Question Surgeons Are Actually Asking
Ethical approval has already been secured from the Swedish Ethical Review Authority, and all participants will provide written informed consent. Trial registration under NCT06836349 makes the protocol accessible and sets the stage for transparent reporting once outcomes are available.
The study does not claim that one approach is already superior. It is built to determine whether the more conservative path can lower rupture rates without eroding motion, strength, or patient satisfaction. If immobilisation reduces ruptures, it could alter the way surgeons think about the early postoperative window after thumb flexor repair. If early active motion preserves function without raising rupture risk, it would support the rehabilitation strategies already used in many centres.
Either way, the question is narrow and consequential. Surgeons caring for patients after FPL tendon repair need evidence that speaks directly to the thumb, not just to flexor tendons in general. This trial is designed to provide that evidence, with rupture as the anchor outcome and hand function as the measure of whether protection came at too high a cost.