Flexor tendon injuries in the thumb occur across all ages and genders. Each year, approximately 400 patients undergo surgery for a flexor tendon injury in Sweden. These injuries are exclusively treated at one of the seven specialized hand surgery clinics, as the surgery is technically demanding, and postoperative rehabilitation is critical, specialized, and requires expertise from hand therapists. To prevent tendon adhesions and stiffness in the thumb or fingers, controlled active motion therapy is usually initiated within a few days after surgery. Studies on finger flexor tendon injuries have shown that early active movement therapy leads to better mobility compared to immobilization. Consequently, early active training is now the standard treatment following flexor tendon repair. However, during postoperative rehabilitation, the repaired flexor tendon may rupture, often necessitating revision surgery.

The rupture rate after flexor tendon repair in the thumb is approximately three times higher than in other fingers (10% vs. 3%). While most studies on flexor tendon injuries focus on finger tendons, research on the outcomes of thumb flexor tendon injuries is limited. The biomechanics and anatomy of the thumb's flexor tendon differ significantly from those of finger tendons.

The objective of this study is to determine whether the rupture rate following thumb flexor tendon surgery can be reduced by immobilizing the thumb in a cast for four weeks postoperatively, compared to standard early active motion therapy, without negatively affecting joint mobility and thumb strength. Additionally, the study will evaluate patient-reported outcomes one year post-surgery for both rehabilitation regimens (immobilization vs. mobilization).

This study is a registry-randomized clinical trial (RRCT) involving five hand surgery clinics in Sweden. Data following randomization between the two rehabilitation protocols will be collected through follow-up in the Swedish National Hand Surgery Quality Registry (HAKIR).

Inclusion Criteria:

Complete laceration of the thumb flexor tendon (Flexor Pollicis Longus; FPL) within zone 1 and 2.

Age over 15 years. Minors (<18 years) are considered to have sufficient maturity to understand the implications of the research.

Swedish-speaking / able to understand spoken and written Swedish. Surgery performed within 14 days from the time of injury.

Exclusion Criteria:

Tendon injury with a defect requiring tendon grafting. Another complete tendon injury in the same hand. Extensive associated injuries, such as fracture, vascular injury with circulatory impairment, large skin defect, or preoperative signs of infection. Patient deemed unsuitable for early active motion therapy due to factors such as lack of cooperation, cognitive impairment, or substance abuse issues.

Patient declines follow-up in the HAKIR quality registry. Wound infection making early active motion therapy inappropriate.

Deidentified data might be shared upon request for metaanalyses.

After the results are analyzed and publish and 10 years ahead

Researchers with an ethical permitt, as descibed above, by request to maria.wilcke@ki.se