Proximal Humerus Intramedullary Nailing

Surgical Indications

Absolute Indications

• Displaced 2-part surgical neck fracture with greater than 50% translation or greater than 30 degrees angulation in a physiologically young or active patient
• Segmental proximal humerus fractures extending into the diaphysis where a load-sharing implant is biomechanically advantageous
• Pathological fractures through metastatic lesions in the proximal humerus where immediate stability is required for palliation
• Failed non-operative treatment of a surgical neck fracture with ongoing pain and loss of function at 6-8 weeks

Relative Indications

• Osteoporotic 2-part or 3-part fractures in elderly patients where locking-plate fixation carries high risk of screw cut-out
• Bilateral proximal humerus fractures where a single implant allows earlier mobilisation
• Patients with poor soft-tissue envelope or comorbidities precluding extensive open reduction and plate fixation

Contraindications

Absolute:

• Active infection at the surgical site or systemic sepsis
• Severe pre-existing rotator cuff arthropathy or irreparable cuff tear that would render nailing ineffective
• Open proximal humerus fracture with extensive soft-tissue loss requiring flap coverage

Relative:

• Greater tuberosity displacement greater than 1 cm that cannot be adequately reduced and fixed through the nail (consider plate or combined approach)
• Severe varus deformity with medial comminution where anatomic reduction cannot be achieved closed (consider open reduction or plate)
• Patient non-compliance with protected weight-bearing in the early post-operative period

Evidence for Intramedullary Nailing versus Locking Plate

Biomechanical and Clinical Rationale

• Modern straight intramedullary nails provide a load-sharing construct that is particularly advantageous in osteoporotic bone and segmental fracture patterns
• The medial entry point completely spares the rotator cuff footprint, eliminating the iatrogenic cuff injury inherent in older bent-nail designs
• A systematic review of randomised trials comparing nailing versus locking-plate fixation found no significant difference in functional scores or complication rates at 1 year, but nailing was associated with shorter operative time and lower blood loss
• Nonunion rates are low (less than 5%) with both techniques when reduction is anatomic; varus malunion remains the most common technical error with nailing and strongly predicts poorer outcome

Comparison of Outcomes

Key Evidence

Relevant Surgical Anatomy for Antegrade Nailing

Humeral Head and Neck Geometry

• The humeral head articular surface is retroverted approximately 20-30 degrees relative to the transepicondylar axis and inclined 130-140 degrees to the shaft
• The anatomic neck is the oblique groove separating the articular surface from the tuberosities; the surgical neck lies distal to the tuberosities at the metaphyseal-diaphyseal junction
• The bicipital groove lies between the greater and lesser tuberosities and serves as a key landmark for rotational reduction

Rotator Cuff Footprint and Entry Point Implications

• The supraspinatus inserts on the superior facet of the greater tuberosity; the infraspinatus on the middle and inferior facets; the teres minor on the inferior facet
• Older bent-nail designs required a lateral entry through the supraspinatus tendon footprint, producing iatrogenic cuff injury in up to 25% of cases
• Modern straight nails allow a true medial entry at the apex of the articular cartilage, completely sparing the cuff footprint and eliminating this complication

Axillary Nerve Course

• The axillary nerve exits the quadrilateral space posteriorly and courses transversely across the deep surface of the deltoid approximately 5-7 cm distal to the acromion
• It lies within the subdeltoid bursa and can be palpated as a cord-like structure before visual identification
• The nerve divides into anterior and posterior branches; the anterior branch supplies the anterior and middle deltoid and is at greatest risk during the split

Radial Nerve at Risk During Distal Interlocking

• The radial nerve descends in the spiral groove on the posterior humerus, approximately 10-12 cm proximal to the lateral epicondyle
• It pierces the lateral intermuscular septum and becomes superficial in the distal third of the arm
• During distal interlocking the arm must be positioned in slight abduction and external rotation to move the nerve away from the lateral cortex trajectory

Vascular Supply and Avascular Necrosis Risk

• The ascending branch of the anterior circumflex humeral artery (arcuate artery) enters the humeral head at the superomedial aspect of the bicipital groove and supplies the majority of the head
• Anatomic reduction and preservation of the medial periosteal hinge are critical to maintaining head perfusion
• Avascular necrosis occurs in 3-10% of 3-part and 4-part fractures and is higher with varus malreduction or excessive soft-tissue stripping

Positioning and Preparation

Patient position: Beach-chair position with the head secured in a Mayfield headrest. The arm is draped free and placed on a radiolucent hand table or supported by an assistant. The C-arm is positioned to allow true AP, scapular-Y, and axillary views without moving the patient.

Anaesthesia: General anaesthesia with an interscalene block for post-operative analgesia. Muscle relaxation is essential for closed reduction manoeuvres.

Consent: Counsel regarding axillary nerve injury (2-3%), rotator cuff injury (less than 5% with straight nails), varus malunion (10-20%), screw back-out (5-10%), nonunion (less than 5%), avascular necrosis (3-8%), and the need for protected weight-bearing for 6 weeks.

Anterosuperior Deltoid-Split Approach — Step-by-Step

Step 1: Skin Incision and Superficial Dissection

Make a 4-6 cm longitudinal incision from the anterolateral corner of the acromion distally along the deltoid raphe. The raphe is identified by the orientation of deltoid fibres and the relative paucity of vessels.

Deepen through subcutaneous fat to the deltoid fascia. Split the deltoid fibres in line with the raphe using blunt dissection with scissors or finger.

Step 2: Axillary Nerve Identification and Protection

Insert a finger or blunt instrument along the deep surface of the deltoid and palpate the axillary nerve as a transverse cord 5-7 cm distal to the acromion. Place a vessel loop around the nerve and gently retract it distally.

The safe zone for the deltoid split is proximal to the nerve; any distal extension must be performed under direct vision with the nerve protected.

Step 3: Subdeltoid Bursa Exposure and Rotator Cuff Visualisation

Incise the subdeltoid bursa and retract the deltoid laterally. Identify the long head of biceps tendon in the bicipital groove as the key rotational landmark. Visualise the greater and lesser tuberosities and the humeral head articular surface.

Step 4: Fracture Reduction and Entry Point Preparation

Perform closed reduction manoeuvres: longitudinal traction, abduction, and external rotation to correct varus and restore the head-shaft angle. Use the image intensifier to confirm reduction on AP and scapular-Y views.

The entry point is located at the apex of the humeral head articular surface, just medial to the rotator cuff footprint and in line with the medullary canal. This point is confirmed on the AP view (medial to the greater tuberosity) and the axillary view (centred on the head).

Step 5: Nail Insertion and Proximal Locking

Select the appropriate nail length and diameter (typically 9-11 mm diameter for most adults). Insert the nail over the guide wire with the arm in slight abduction to avoid varus.

The proximal nail end must sit 2-3 mm below the articular surface to prevent subacromial impingement. Confirm on the AP view.

Proximal locking is performed using the targeting guide. Achieve multiplanar fixation: typically two or three proximal screws in different planes (one anterior, one posterior, one superior). When the greater tuberosity is displaced, use the nail's tuberosity-specific locking options or pass heavy non-absorbable sutures through the cuff and secure to the nail or a separate screw.

Step 6: Distal Interlocking

Position the arm in slight abduction and external rotation to move the radial nerve away from the lateral cortex. Use the free-hand technique or distal targeting guide to place two distal interlocking screws. Confirm screw position and length on the AP and lateral views.

Step 7: Final Reduction Check and Closure

Obtain final AP, scapular-Y, and axillary views to confirm anatomic reduction, correct nail position, and secure tuberosity fixation. Irrigate the wound. Close the deltoid fascia with absorbable sutures and the skin with non-absorbable interrupted sutures. Apply a sling.

Post-operative Protocol

Early Phase (Week 0-2)

• Sling immobilisation: For comfort; remove for gentle pendulum exercises from day 1
• Pendulum and passive range: Begin immediately under physiotherapist supervision
• Active-assisted abduction: Limited to 60 degrees for first 2 weeks to protect proximal fixation
• Weight-bearing: None through the operative arm; non-weight-bearing for 6 weeks
• Wound review: At 10-14 days for suture removal

Intermediate Phase (Week 3-6)

• Progressive active range: Advance to full active forward elevation and external rotation as pain allows
• Isometric strengthening: Begin deltoid and rotator cuff isometrics at 4 weeks
• Continue sling for comfort when not exercising

Late Phase (Week 7-12)

• Active strengthening: Theraband and light dumbbell exercises for rotator cuff and deltoid
• Functional training: Return to light activities of daily living; driving when safe to control steering wheel
• Progressive weight-bearing: Begin at 6 weeks with gradual increase to full weight by 12 weeks

Return to Function

• Light work: 6-8 weeks
• Manual labour: 3-4 months
• Contact sports or heavy lifting: 4-6 months after radiographic union

Rehabilitation Pearls

• Early passive motion prevents stiffness but must not compromise reduction
• In osteoporotic bone, extend protected weight-bearing to 8-10 weeks
• Formal physiotherapy input is essential; patient-directed home exercises alone are insufficient

Special Considerations

Osteoporotic Bone

• Consider PMMA augmentation of proximal locking screws
• Use the largest diameter proximal screws available in the implant system
• Extend protected weight-bearing and delay active abduction
• Serial radiographs every 2 weeks for the first 6 weeks to detect early collapse

Tuberosity Fixation

• When the greater tuberosity is displaced greater than 5 mm, pass heavy non-absorbable sutures through the cuff and secure to the nail or a separate screw
• Confirm tuberosity position on the axillary view before final locking
• Post-operative abduction limited to 60 degrees for 4 weeks to protect the repair