MIPO Anterior Humeral Corridor

What it exposes. The anterior MIPO corridor delivers a long submuscular bridge plate to the humeral shaft through two small windows — a proximal deltopectoral window and a distal anterolateral window — joined by an extrasynovial, epiperiosteal tunnel on the anterior cortex, with no direct exposure of the fracture. Primary indications: - Comminuted or segmental humeral shaft fractures where biological preservation favours bridge plating over rigid compression

• Unstable shaft fractures unsuitable for non-operative management (shortening, angulation, displacement, or failure of functional bracing)
• Pathological or impending pathological fractures of the humeral diaphysis
• Polytrauma where early definitive or damage-control stabilisation is desirable
• Selected open fractures with soft-tissue compromise where long extensile incisions are best avoided
• Paediatric and adolescent humeral shaft fractures in selected cases where fixation is indicated Why this approach is chosen. MIPO respects the biological environment at the fracture by avoiding direct exposure of the fracture haematoma and the soft-tissue attachments. A long plate is slid through two small windows along the anterior humeral surface, which is broad, relatively flat and largely submuscular. This delivers a long, elastic bridge construct that distributes strain and supports indirect healing, in contrast to open plating (which strips biology) or intramedullary nailing (which carries distinct shoulder entry-point and radial-nerve considerations). Contraindications: - Intra-articular extension requiring direct open reduction (use a formal articular approach instead)
• Active wound infection or gross contamination over the planned windows (until controlled)
• Fracture patterns where the radial nerve is interposed between fragments and must be directly visualised (some surgeons prefer a posterior approach with nerve identification)
• Vascular injury requiring open exploration and repair
• Inability to obtain adequate fluoroscopic imaging of the whole humerus intra-operatively

Position & landmarks. The supine position is central to the anterior MIPO corridor. Place the patient supine on a radiolucent table with a small bolster under the ipsilateral scapula to bring the arm forward, and rest the arm on a radiolucent armboard or across the chest on a sterile bolster. The aim is unobstructed fluoroscopic visualisation of the entire humerus in AP and lateral — confirm both views before draping. A well-padded tourniquet is used only if it will not obstruct plate length or imaging; many surgeons operate without one. Proximal window landmarks: the coracoid process (palpable guide to the deltopectoral interval), the anterolateral corner of the acromion (proximal extent for a deltoid-splitting variant), the deltopectoral groove containing the cephalic vein, and the long head of biceps tendon in the intertubercular groove. Distal window landmarks: the biceps brachii muscle belly and tendon (the medial boundary, retracted medially), the lateral supracondylar ridge and lateral epicondyle, the mobile wad (brachioradialis and extensor carpi radialis longus and brevis) marking where the radial nerve lies, and the brachialis filling the interval between biceps and the lateral musculature.

Work from two windows remote from the fracture, develop an internervous plane at each, and join them with a submuscular tunnel on the anterior cortex. The broad, flat anterior humeral surface is the plate-bearing surface, and the brachialis is the muscular buffer that shields the radial nerve throughout.

Two internervous planes, one tunnel. The proximal window uses the deltopectoral interval — deltoid (axillary nerve) versus pectoralis major (pectoral nerves). The distal window runs between biceps (musculocutaneous nerve), retracted medially, and the underlying brachialis; the brachialis is then split longitudinally to bone. This split is safe because the brachialis has dual innervation — the medial half from the musculocutaneous nerve and the lateral half from the radial nerve — so neither half is denervated. Leaving the lateral half of brachialis attached interposes muscle between the plate and the radial nerve, which lies further lateral, between brachialis and brachioradialis.

Structures at risk, by layer

Radial nerve injury management: - Document pre-operative radial nerve function (wrist and finger extension, first web sensation) on every patient.

• If the nerve is identified as injured intra-operatively, visualise it and repair or graft as appropriate.
• A new post-operative palsy: remove constrictive dressings, exclude a compressive cause, document and observe; obtain electromyography at three to four weeks and consider exploration if there is no recovery by the expected timeframe.
• Most traction neurapraxias recover; a persistent complete palsy may require tendon transfers. Extensile modifications. Extend the deltopectoral window proximally for proximal humeral involvement, or use a deltoid-splitting anterolateral acromial approach to reach the proximal humeral head and greater tuberosity (beware the axillary nerve wrapping the surgical neck — stay proximal and on bone). Extend the anterolateral window distally along the Henry approach toward the elbow for distal-third fractures, where the radial nerve can be formally identified and protected as it emerges between brachialis and brachioradialis. Segmental fractures suit MIPO well, as one long plate spans multiple zones without exposure; intra-articular extension requires a separate formal open approach rather than continuing the corridor. Complications

Post-operative care and outcomes. Perform a neurovascular check documenting wrist and finger extension against the pre-operative baseline; a sling or splint is used for comfort, with early gentle pendulum and elbow movement as the construct is usually stable. Progress to active-assisted shoulder and elbow range of movement, then strengthening once callus appears, with typical union at three to four months. Follow up at two weeks (wound check and suture removal), six weeks (radiographs, assess callus, advance movement), twelve weeks (radiographs, confirm progression to union, progress loading) and six months (clinical and radiographic review of union). MIPO aims to preserve biology so the construct fails by callus rather than hardware; compared with open plating it reports lower infection and comparable union, and compared with intramedullary nailing it avoids shoulder entry-point problems but demands greater reliance on fluoroscopy and indirect reduction.

At a glance. The anterior MIPO corridor delivers a long, biology-preserving bridge plate through two small windows — a proximal deltopectoral window (deltoid, axillary nerve, versus pectoralis major, pectoral nerves) and a distal anterolateral window between biceps (musculocutaneous nerve) and brachialis — joined by a submuscular, extrasynovial, epiperiosteal tunnel on the anterior cortex. The patient is positioned supine on a radiolucent table with the whole humerus visible to fluoroscopy. The brachialis is the key protective structure: splitting it in its mid-substance and leaving the lateral half intact interposes muscle between the plate and the radial nerve, which pierces the lateral intermuscular septum roughly 10 cm proximal to the lateral epicondyle. Reduction is indirect — length, alignment and rotation are restored under image intensification with traction, percutaneous clamps, blocking screws and the plate itself as a template, while the fracture haematoma is left undisturbed.

Guidelines, registries and global practice. Humeral shaft fractures are managed worldwide, and operative decision-making converges across examination systems. The majority of closed shaft fractures can be managed non-operatively with functional bracing; operative fixation is reserved for unacceptable alignment, open fractures, polytrauma, bilateral injuries, vascular compromise and pathology. MIPO bridge plating is a recognised biological option alongside intramedullary nailing and open plating. Side-by-side principles (where guidance converges):

Registry and population evidence: - Humeral shaft fractures represent a small fraction of long-bone fractures, with an incidence of roughly 13 to 15 per 100,000 per year and a bimodal distribution (high-energy in young adults, low-energy falls in older patients).

• Functional bracing remains the benchmark non-operative comparator, with high union rates reported in large cohorts; operative series for MIPO and nailing report broadly comparable union with technique-specific complications. Global practice variation. In high-resource settings, pre-contoured locking anterior humeral plates and full intra-operative fluoroscopy are standard. In resource-limited settings, the same biological principles are achieved with standard large-fragment plates contoured intra-operatively, and functional bracing retains a larger role. Consent (globally applicable): discuss iatrogenic radial nerve palsy (the principal neurological risk), infection (low with small incisions), nonunion and malunion, hardware irritation, and the possibility of revision surgery.