Medial Approach Derotational Humeral Osteotomy in Patients with Brachial Plexus Birth Palsy.

Background: Medial-approach derotational humeral osteotomy is indicated in patients with brachial plexus birth palsy (BPBP) who have internal rotation contracture, a condition that substantially limits upper-extremity function and creates cosmetic concerns as a result of excessive internal rotation. This procedure enhances the range of motion of the arm by surgically externally rotating the humerus, thereby facilitating essential activities such as bringing the hand to the mouth and neck without the need for compensatory movements. In addition, the medial approach offers cosmetic benefits; the incision along the inner arm is less conspicuous than those of traditional lateral approaches. The anteromedial humeral surface provides an ideal site for secure plate fixation, which promotes stability and optimal healing.

Description: Preoperative evaluation is critical to determine the precise degree of humeral rotation required. Both active and passive ranges of motion are measured-with special emphasis on shoulder adduction-to quantify available glenohumeral rotation. The active arc of internal rotation is recorded from the end range of passive external rotation, and the additional external rotation necessary for functional tasks (e.g., touching the back of the head), including scapulothoracic contributions, is determined passively. The operative plan involves calculating the degree of correction by subtracting the patient's active external rotation from the total required rotation, ensuring that adequate internal rotation is preserved for midline functions such as reaching the beltline. The goal is to achieve neutral glenohumeral alignment with restored external rotation, typically with a correction of approximately 60° to 70°.The procedure begins with the application of an arm tourniquet to minimize bleeding. A medial incision is made over the intermuscular septum and midshaft of the humerus while carefully protecting the ulnar and median nerves and brachial vessels. The intermuscular septum is identified and excised. The ulnar nerve is retracted posteriorly, whereas the median nerve and brachial artery are retracted anteriorly, thereby reducing the risk of nerve compression. The humeral diaphysis is then exposed, and the periosteum is elevated at the planned osteotomy site. A 6 to 8-hole plate (typically 2.7 or 3.5 mm) is temporarily applied, and proximal bicortical screws are inserted. A Kirschner wire is placed in the distal fragment to mark the desired correction angle, with its position verified via goniometry and visual assessment. Following removal of the plate, an oscillating saw is utilized to perform the osteotomy. The humerus is rotated to align the screw holes with the Kirschner wire, the plate is reapplied, and final fixation is achieved with use of standard compression screw techniques.

Alternatives: Alternatives include glenohumeral joint reconstruction and external rotation osteotomy. The latter is performed above the deltoid tuberosity to improve external rotation.

Rationale: The medial approach offers several distinct advantages over alternative treatments. It provides improved cosmesis as a result of a less visible medial incision, enhanced functional positioning for daily activities, and a technically straightforward method for osteotomy reduction and fixation. The anteromedial surface of the humerus facilitates secure plate application, ensuring stable fixation and predictable healing. These benefits make this procedure particularly suitable for older children and adolescents with BPBP who require both functional and cosmetic improvements.

Expected Outcomes: Patients who undergo this procedure typically experience a marked improvement in external rotation, leading to easier hand-to-mouth and hand-to-neck movements, which are essential for daily activities. For instance, Abzug et al. documented an average increase of 44° in external rotation following the osteotomy, while other studies have similarly reported enhanced elbow flexion and overall limb alignment. Despite occasional complications such as hypertrophic scarring requiring revision, incomplete correction necessitating repeat osteotomy, or a humeral diaphyseal fracture distal to the plate, the procedure is regarded as relatively safe, with high rates of functional and aesthetic satisfaction. It is crucial, however, to avoid overcorrection, which can result in a fixed external rotation posture that is functionally disabling.

Important Tips: Conduct thorough evaluations, including imaging, to determine the extent of the deformity and plan the necessary degree of derotation.Discuss the operative plan, expected outcomes, and potential risks with patients and families.Precisely perform the medial incision in order to minimize nerve injury and optimize cosmetic results. Ensure meticulous dissection to protect the ulnar nerve, median nerve, and brachial artery.Incise the periosteum at the osteotomy site in order to preserve healing potential.Utilize a Kirschner wire and goniometer to accurately mark and verify the correction angle.Select an appropriate plate and secure it with proximal bicortical screws prior to osteotomy.Reapply the plate following derotation, ensuring alignment before final fixation.

Acronyms And Abbreviations: BPBP = brachial plexus birth palsyK-wire = Kirschner wire.