Humeral shaft fractures represent 1-3% of all fractures and 20% of the humeral fractures. These fractures have historically been treated mainly conservatively with good results. Recent development in fracture treatment and findings that certain fracture types are more prone to non-union and bracing-related functional problems of adjacent joints are somewhat common have caused increasing interest in treating these fractures surgically. Return to activities is also considered to be quicker among surgically treated patients.

The purpose of this study is to evaluate effectiveness and cost-effectiveness of surgical treatment of humeral shaft fractures. Patients with an unilateral humeral shaft fracture who are willing to participate in the study after informed consent are randomly assigned to two different treatment methods:

1. Surgical treatment with an open reduction and internal fixation with a 4,5mm locking plate.
2. Conservative treatment with functional bracing

The randomization is done using blocked randomization (block sizes are not known by the enrolling or assigning physician) and stratification is done according to fracture type (AO-OTA type A vs. type B/C) and radial nerve status (total/subtotal motor palsy vs. no palsy).

Standard follow-up visits at 6 weeks, 3, 6 and 12 months are arranged. Later follow-up visits are arranged at 2, 5 and 10 years for the study purpose. Patients fill evaluation forms and clinical and radiological assessments are made. The physiotherapist doing objective functional measurements is blinded to treatment method. Both study groups receive physiotherapy after the initial treatment.

Inclusion Criteria:

• Over 18 years old patient who agrees to the consent to participation in this study
• Unilateral dislocated humeral shaft fracture (dislocation over thickness of the bone cortex, fracture below the level of insertion of pectoralis major muscle and 5 cm above the olecranon fossa)
• Randomization can be done within 10 days and operation within 14 days after the initial trauma
• Patient is willing to participate all follow-up visits

Exclusion Criteria:

• Bilateral humeral shaft fracture
• A significant concomitant trauma of the same upper extremity that warrants operative treatment (fracture, tendon injury, soft tissue trauma)
• Other fracture or abdominal/thoracal trauma that warrants operative treatment
• Open fracture
• Pathological fracture
• Multi-trauma patient
• Vascular injury
• Plexus injury
• Previous trauma in the same upper extremity that causes functional deficit
• Trauma or condition that warrants use of walking aid (crutches, wheelchair etc)
• Disease that affects significantly general condition of the patient
• Significantly impaired ability to co-operate for any reason (substance abuse, mental disorder, dementia)
• Unwilling to accept both treatment methods