Correction of Radial Neck Malunion: The Modified Inhofe and Moneim Technique

INTRODUCTION TO RADIAL NECK MALUNION

Radial neck fractures, while relatively common in both pediatric and adult populations, can lead to profound functional impairment if managed inadequately. Malunion of the radial neck alters the complex biomechanics of the radiocapitellar and proximal radioulnar joints (PRUJ). The resulting angular or translational deformity creates a "cam effect" during forearm rotation, leading to mechanical impingement, severe restriction of pronation and supination, and progressive radiocapitellar arthrosis.

The surgical correction of a radial neck malunion is a technically demanding procedure reserved for symptomatic patients with preserved articular cartilage. The modified Inhofe and Moneim technique provides a reliable, reproducible method for restoring the anatomical axis of the proximal radius. By executing a precise metaphyseal osteotomy, realigning the articular surface, and securing the construct with rigid internal fixation, the orthopedic surgeon can restore joint congruity, alleviate pain, and significantly improve the patient's functional arc of motion.

This comprehensive guide details the indications, preoperative planning, surgical anatomy, and step-by-step execution of the modified Inhofe and Moneim technique for the correction of radial neck malunion.

INDICATIONS AND CONTRAINDICATIONS

Patient selection is the most critical determinant of success in radial neck osteotomies. The procedure is designed to restore mechanics in a joint that has not yet succumbed to end-stage degenerative changes.

Indications

• Symptomatic Loss of Motion: Clinically significant restriction of forearm pronation and supination directly attributable to the mechanical block of the malunion.
• Radiocapitellar Pain: Pain localized to the lateral compartment of the elbow during forearm rotation or axial loading.
• Preserved Articular Cartilage: Radiographic and intraoperative evidence of viable cartilage on both the radial head and the capitellum.
• Impending Arthrosis: Correction of the deformity to normalize joint contact pressures and delay or prevent post-traumatic osteoarthritis.

Contraindications

• Absolute:
  • Advanced radiocapitellar or proximal radioulnar osteoarthritis (Outerbridge Grade III/IV).
  • Active joint infection or osteomyelitis.
  • Asymptomatic malunion with functional, pain-free range of motion.
• Relative:
  • Severe osteopenia or osteoporosis that would compromise hardware purchase.
  • Chronic, fixed soft-tissue contractures that will not resolve with bony realignment alone.
  • Non-compliant patients unable to adhere to strict postoperative rehabilitation protocols.

💡 Clinical Pearl: The Salvage Threshold

Always consent the patient for a radial head excision or radial head arthroplasty prior to surgery. If intraoperative inspection reveals extensive, full-thickness cartilage loss on the capitellum or radial head, an osteotomy will likely fail to relieve pain, and the surgeon must immediately pivot to a salvage arthroplasty or excision.

PREOPERATIVE PLANNING AND IMAGING

Meticulous preoperative planning is essential for determining the apex of the deformity, the plane of the osteotomy, and the required hardware.

Radiographic Evaluation

• Standard Radiographs: True anteroposterior (AP) and lateral views of the elbow, along with a dedicated radiocapitellar view, are mandatory. Assess the degree of angulation, translation, and any signs of early arthrosis (subchondral sclerosis, osteophytes, joint space narrowing).
• Computed Tomography (CT): A thin-slice CT scan with 3D reconstructions is the gold standard for evaluating radial neck malunions. It allows for precise mapping of the deformity in the axial, coronal, and sagittal planes, facilitating accurate templating of the osteotomy site.
• Contralateral Imaging: Radiographs of the uninjured, contralateral elbow serve as a template for restoring the patient's native radial neck angle and radial head height.

Templating and Hardware Selection

• Determine the exact distance from the articular surface to the apex of the deformity (typically around 1.5 cm).
• Select appropriate fixation devices. Headless compression screws (e.g., Herbert screws) are preferred if the trajectory traverses the articular surface. Alternatively, 2.0 mm or 2.7 mm minifragment lag screws or Kirschner wires (K-wires) can be utilized depending on the fracture geometry and bone quality.

SURGICAL ANATOMY AND BIOMECHANICS

A profound understanding of the lateral elbow anatomy is required to safely expose the proximal radius and prevent iatrogenic injury.

The Posterolateral (Kocher) Interval

The Kocher approach utilizes the internervous plane between the anconeus (innervated by the radial nerve) and the extensor carpi ulnaris (ECU) (innervated by the posterior interosseous nerve). This approach provides excellent visualization of the radiocapitellar joint and the lateral collateral ligament (LCL) complex.

The Posterior Interosseous Nerve (PIN)

The PIN is the most critical structure at risk during proximal radius surgery. It branches from the radial nerve anterior to the radiocapitellar joint, travels distally, and enters the arcade of Frohse at the proximal edge of the supinator muscle.
* The nerve crosses the radial neck approximately 3 to 5 cm distal to the radiocapitellar joint.
* Pronation of the forearm moves the PIN anteriorly and medially, distancing it from the surgical field. Supination brings the nerve closer to the lateral surgical approach.

⚠️ Surgical Warning: PIN Protection

Never place retractors blindly around the anterior or posterior neck of the radius. Always maintain the forearm in pronation during deep dissection and osteotomy to maximize the distance between the PIN and the surgical field. Use blunt, malleable retractors placed subperiosteally.

The Radial Head "Safe Zone"

If hardware must be placed through the non-articulating portion of the radial head, it must be confined to the "safe zone." This is a 90-degree to 110-degree arc of the radial head that does not articulate with the lesser sigmoid notch of the ulna during forearm rotation. It is reliably identified intraoperatively by bisecting the radial head with the forearm in neutral rotation; the lateral half represents the safe zone.

SURGICAL TECHNIQUE: STEP-BY-STEP

The modified Inhofe and Moneim technique requires meticulous soft-tissue handling, precise bone cuts, and rigid fixation.

1. Patient Positioning and Anesthesia

• Anesthesia: General anesthesia is typically preferred, often supplemented with a regional supraclavicular or axillary nerve block for postoperative pain control.
• Positioning: The patient is placed in the supine position with the operative arm draped free on a radiolucent hand table. Alternatively, the lateral decubitus position with the arm over a post can be used.
• Tourniquet: A sterile pneumatic tourniquet is applied high on the brachium and inflated to 250 mm Hg after exsanguination.

2. The Posterolateral (Kocher) Approach

• Incision: Make a 5 to 7 cm oblique incision starting at the lateral epicondyle and extending distally toward the posterior border of the ulna.
• Superficial Dissection: Incise the deep fascia in line with the skin incision. Identify the interval between the anconeus (posterior) and the ECU (anterior).
• Deep Dissection: Elevate the anconeus posteriorly and the ECU anteriorly. Identify the lateral ulnar collateral ligament (LUCL) and the annular ligament.
• Arthrotomy: Perform an arthrotomy through the annular ligament, taking care to preserve the LUCL. If the LUCL must be elevated or split for adequate exposure, tag it with non-absorbable sutures for meticulous repair during closure.

3. Joint Inspection and Debridement

• Synovectomy: Thoroughly débride the joint of any hypertrophic, inflamed synovium to improve visualization.
• Cartilage Assessment: Inspect the articular cartilage of the capitellum and the proximal radius.
• Decision Point: If the cartilage exhibits severe, full-thickness loss (Outerbridge Grade IV) that precludes a good functional result, abandon the osteotomy and proceed with radial head arthroplasty. If the cartilage is viable, proceed with the correction.

4. The Corrective Osteotomy

• Exposure: Expose the proximal radius subperiosteally. Place blunt Hohmann or malleable retractors carefully around the radial neck, keeping the forearm in pronation to protect the PIN.
• Marking the Cut: Identify the apex of the malunion. The osteotomy is typically planned approximately 1.5 cm distal to the articular surface of the radial head. This preserves enough metaphyseal bone proximally for hardware purchase while allowing correction of the deformity.
• Execution: Use a small motorized oscillating saw with a fine blade to perform the osteotomy. Irrigate copiously with cold saline to prevent thermal necrosis of the bone.
• Alternative: A sharp, thin osteotome can be used to divide the bone, which may preserve bone stock and allow for a more controlled, incomplete cut if a closing wedge technique is desired.

🔪 Surgical Pitfall: Thermal Necrosis

When using an oscillating saw on the dense cortical bone of the radial neck, thermal necrosis is a significant risk. This can lead to nonunion or hardware failure. Always use a sharp blade, apply minimal pressure, and use continuous cold saline irrigation.

5. Realignment and Internal Fixation

• Reduction: Realign the proximal radius to restore the anatomical neck-shaft angle and the congruity of the radiocapitellar joint. Temporarily provision the reduction with 1.25 mm K-wires.
• Fluoroscopic Verification: Check the reduction under multi-planar fluoroscopy. Ensure that the radiocapitellar line is restored in all views and that the radial head tracks smoothly during a trial of pronation and supination.
• Definitive Fixation: Fix the osteotomy with two Herbert screws (headless compression screws).
  • Trajectory: Direct the screws from proximal to distal, starting within the "safe zone" of the radial head.
  • Recessing: It is imperative to recess the screw heads completely below the surface of the articular cartilage to prevent catastrophic iatrogenic damage to the capitellum.
• Alternative Fixation: If the fracture geometry dictates, minifragment lag screws (2.0 mm or 2.7 mm) or crossed K-wires can be utilized. If using standard screws, ensure the heads do not impinge on the PRUJ during rotation.

6. Bone Grafting

• Corrective osteotomies often create a structural void, particularly if an opening wedge technique is utilized to restore radial length.
• Harvest: Obtain cancellous autograft from the lateral epicondyle of the humerus through the same surgical incision. Use a small curette or gouge to harvest the graft.
• Placement: Pack the bone graft tightly into the osteotomy site to provide osteoconductive and osteoinductive support, accelerating union and providing structural stability.

7. Ligamentous Repair and Closure

• LCL and Annular Ligament Repair: This is a critical step to prevent postoperative posterolateral rotatory instability (PLRI). Repair the annular ligament and the lateral collateral ligament complex using heavy non-absorbable sutures (e.g., #2 FiberWire) or suture anchors placed into the isometric point on the lateral epicondyle.
• Wound Closure: Deflate the tourniquet and achieve meticulous hemostasis. Close the deep fascia, subcutaneous tissue, and skin in a layered fashion.
• Splinting: Apply a sterile dressing and a well-padded posterior long-arm splint.

POSTOPERATIVE CARE AND REHABILITATION

The postoperative protocol must balance the need for osteotomy healing with the prevention of elbow stiffness.

Phase I: Protection and Healing (Weeks 0-2)

• Immobilization: The elbow is immobilized in a posterior splint in mid-flexion (90 degrees) and mid-supination (neutral rotation) for 2 weeks. This position minimizes tension on the LCL repair and the osteotomy site.
• Edema Control: Strict elevation and cryotherapy are employed to manage swelling.
• Adjacent Joints: Active range of motion of the shoulder, wrist, and digits is encouraged immediately to prevent secondary stiffness.

Phase II: Early Motion (Weeks 2-6)

• Orthosis: At 2 weeks, the rigid splint is removed, and sutures are extracted. The patient is transitioned to a removable hinged elbow brace or functional orthosis.
• Active ROM: Progressive active and active-assisted range-of-motion exercises for elbow flexion/extension and forearm pronation/supination are initiated.
• Restrictions: Passive stretching and forceful manipulation are strictly prohibited to protect the osteotomy and ligamentous repair. Lifting is restricted to less than 1 pound.

Phase III: Strengthening and Weaning (Weeks 6-12)

• Radiographic Check: Clinical and radiographic evaluation is performed at 6 weeks to assess osteotomy healing.
• Discontinuing Support: External support (the hinged brace) can be discontinued once radiographic evidence of secure bony healing is observed (bridging callus across the osteotomy).
• Strengthening: Progressive isometric and isotonic strengthening exercises are introduced. Passive stretching may be gently initiated if stiffness persists, provided the osteotomy is fully united.
• Return to Activity: Return to heavy manual labor or contact sports is typically delayed until 4 to 6 months postoperatively, contingent upon full radiographic union and restoration of functional strength.

COMPLICATIONS AND MANAGEMENT

While highly effective, the correction of radial neck malunions carries specific risks that the surgeon must be prepared to manage.

• Posterior Interosseous Nerve (PIN) Palsy: The most feared complication. Usually transient due to traction or retractor pressure. Managed with observation and a wrist splint. If the nerve was known to be transected, early exploration and repair/grafting are indicated.
• Nonunion or Delayed Union: Risk is minimized by using meticulous surgical technique, avoiding thermal necrosis, utilizing rigid fixation, and applying autologous bone graft. Established nonunions require revision internal fixation and repeat bone grafting.
• Avascular Necrosis (AVN) of the Radial Head: Extensive soft-tissue stripping of the radial neck can disrupt the tenuous blood supply to the radial head. Limit subperiosteal dissection to the minimum required for the osteotomy. Symptomatic AVN may eventually require radial head excision or arthroplasty.
• Hardware Prominence/Impingement: Failure to recess Herbert screws below the cartilage or placing screws outside the "safe zone" will cause severe pain, mechanical block, and rapid destruction of the capitellum or lesser sigmoid notch. Immediate hardware removal or revision is required.
• Posterolateral Rotatory Instability (PLRI): Caused by failure to adequately repair the LUCL at the conclusion of the procedure. Presents with lateral elbow pain and a sense of instability during extension and supination. Requires surgical ligamentous reconstruction if symptomatic.
• Postoperative Stiffness: The elbow is notoriously prone to stiffness following trauma and surgery. Adherence to the early active motion protocol is essential. Refractory stiffness may require late arthroscopic or open capsular release after the osteotomy has fully healed.