Background Metacarpal shaft fractures account for 30-50% of hand fractures (Karl et al., 2015; Kollitz et al., 2014; van Onselen et al., 2003), with diaphyseal spiral and oblique fractures of the second to fifth ray posing unique challenges due to the risks of shortening and rotational deformities. Current standard care of displaced fractures involves operative fixation.

However, retrospective studies have indicated that nonoperative treatment, involving early mobilization or buddy taping, can achieve outcomes comparable to operative treatment (Daher et al., 2023). There is only one published, with a small sample size, randomized controlled trial (RCT) investigating this issue (Peyronson et al., 2023). This highlights the need for a robust multicenter RCT to address these gaps in evidence.

Aim The aim of this study is to compare the one-year outcomes of non-operative treatment involving immediate unrestricted mobilization versus operative treatment of displaced oblique or spiral diaphyseal metacarpal fractures in adults.

Materials and Methods This is a multicenter, pragmatic, prospective, noninferiority RCT involving 552 adult patients with displaced oblique and/or spiral diaphyseal metacarpal fractures of the second to fifth ray. Participants will be randomized 1:1 to receive either nonoperative treatment with unrestricted mobilization and rehabilitation) or operative treatment (with screw or plate fixation) followed by rehabilitation.

The primary outcome is grip-strength in the injured hand presented in kilograms at one year.

Secondary outcomes include questionnaires, complications, range of motion, patient reported outcome measures, health related quality of life, patient satisfaction, and radiographic healing.

A power calculation proposes a study size of 552 participants to detect a noninferiority margin of 10% in grip strength.

Inclusion Criteria:

• Age ≥18 years.
• Access to a valid e-mail.
• Injury within 10 days prior to inclusion.
• Normal bilateral hand function prior to injury.
• Ability and willingness to provide written informed consent
• Single, displaced spiral or oblique diaphyseal fracture of the second to fifth metacarpals with definition of diaphysis as described by AO 2018 (AO/OTA as 77.2-5.2A) (Meinberg et al., 2018).
• Fracture line length at least twice the diameter of the bone at the level of the fracture.
• Fractures with at least 2 mm of radiological displacement and/or malrotation of injured finger compared to uninjured side regardless of fracture displacement.

Exclusion Criteria:

• The patient IS NOT expected to have difficulty adhering to the study protocol (e.g., due to insufficient language proficiency, dementia, substance abuse, or other reasons).
• The patient DOES NOT have an open fracture (Gustilo-Anderson grade > I) or a pathological fracture.
• The patient DOES NOT have an ipsilateral fracture of the upper extremity, polytrauma, or generalized joint dysfunction (e.g., rheumatoid arthritis).

Data on group level will be made available upon reasonable request.