Coronoid Process Fracture Fixation

Indication. Fixation is indicated when the coronoid fragment threatens elbow stability rather than bone union on its own. The decision turns on the fracture pattern (the O'Driscoll subtype), the degree of displacement, and whether the elbow remains unstable after the lateral column has been rebuilt. Absolute indications - Displaced anteromedial facet fracture greater than 2 mm with varus posteromedial rotatory instability on stress fluoroscopy

• Basal coronoid fracture (Regan-Morrey Type III or O'Driscoll basal subtype) with elbow instability after radial head fixation
• Terrible triad injury (elbow dislocation with radial head and coronoid fractures) with persistent posterior or posteromedial subluxation after radial head and lateral collateral ligament reconstruction
• Isolated coronoid fracture with greater than 50 percent involvement and a mechanical block to motion Relative indications - Tip fragment greater than 5 mm in a young active patient after elbow dislocation
• Anteromedial facet fracture with 1 to 2 mm displacement and borderline varus stress stability
• Patient preference for definitive fixation over non-operative management in borderline cases Contraindications. Absolute: active elbow infection, or an open fracture with gross contamination; severe osteoporosis precluding stable fixation; a patient medically unfit for surgery. Relative: a minimally displaced tip fragment less than 5 mm in a low-demand elderly patient; a chronic malunited coronoid fracture with established arthrosis (consider arthroscopic debridement or arthroplasty instead).

Consent. Discuss the risk of ulnar nerve injury or irritation (5 to 10 percent), recurrent instability (5 to 10 percent), stiffness requiring reoperation (10 to 15 percent), heterotopic ossification, arthrosis, and the possible need for staged ulnar nerve transposition. Setup. Supine on a radiolucent table with the arm abducted 90 degrees on a hand table; upper-arm tourniquet to 250 mmHg. General anaesthesia with a supraclavicular or axillary block for postoperative analgesia. Position a mini C-arm or image intensifier for true lateral and anteroposterior views and confirm you can achieve a concentric reduction before incision. Prepare the ipsilateral iliac crest if bone graft is anticipated. Special situations. - Terrible triad injuries are the classic indication for combined medial and lateral reconstruction. The accepted sequence is: (1) coronoid fixation, (2) radial head ORIF or replacement, (3) lateral collateral ligament repair, (4) medial collateral ligament assessment and repair if needed, and (5) ulnar nerve transposition if indicated. Confirm concentric reduction after each step; the stable arc is usually narrower than for an isolated coronoid fracture.

• Isolated anteromedial facet fractures often present with varus posteromedial rotatory instability without a frank dislocation. The Hotchkiss medial approach alone is sufficient, and a buttress plate is mandatory — a suture lasso alone is inadequate for facet fractures displaced greater than 2 mm.
• Paediatric coronoid fractures are rare and usually occur with elbow dislocation. Favour non-operative management for minimally displaced tip fractures with a stable elbow; if fixation is required, use a suture lasso or small cannulated screws and avoid plates because of physeal proximity.

The goal is to restore the anterior coronoid buttress so the ulnohumeral joint tracks concentrically through a stable arc. The exposure that does this directly is the Hotchkiss medial over-the-top approach, which reaches the anteromedial facet while keeping the ulnar nerve under vision and the medial collateral ligament intact. In a terrible triad the coronoid is usually fixed first through this medial exposure; the radial head and lateral collateral ligament are then rebuilt through a lateral Kocher approach and the elbow is stress-tested at the end. The sequence below details the medial coronoid reconstruction.

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Rehabilitation - Immediate (day 0 to 14): posterior splint at 90 degrees flexion for 5 to 7 days, then transition to a hinged brace; begin active-assisted flexion and extension within the intraoperative stable arc from day 3 to 5; monitor for ulnar neuritis (night extension splint if transposed); remove sutures at 10 to 14 days.

• Protected motion (week 2 to 6): hinged brace locked at the extremes of the stable arc; active motion within the arc; delay aggressive terminal extension until 4 to 6 weeks if the arc was marginal (less than 20 degrees extension); isometric strengthening only, no resistance until 6 weeks; indomethacin 25 mg three times daily for 3 weeks for heterotopic ossification prophylaxis in high-risk patients.
• Functional recovery (week 6 to 12): wean the brace at 6 to 8 weeks if stable; progress to full active range as tolerated; progressive resistance for elbow flexors, extensors and forearm rotators; light activities at 8 to 10 weeks, manual work or sport at 4 to 6 months.
• Long-term surveillance: radiographs at 6 weeks, 3, 6 and 12 months, then annually for 5 years to monitor reduction, hardware and early arthrosis; assess stability with varus and posteromedial rotatory stress testing at each visit. Complications

Surgical anatomy. The coronoid process is the anterior projection of the proximal ulna and the anterior buttress of the ulnohumeral joint. It has a tip, an anteromedial facet and a basal body. The sublime tubercle lies just distal and slightly posterior to the anteromedial facet and is the insertion of the anterior band of the medial collateral ligament. The coronoid tip measures about 6 to 8 mm in height and carries the anterior capsule insertion, which attaches 5 to 6 mm distal to the tip and is the primary restraint against posterior translation when the bony buttress is deficient. Why the anteromedial facet matters. Once the lateral collateral ligament is intact, the anteromedial facet is the primary bony restraint to varus and posteromedial rotation. A fracture here produces varus posteromedial rotatory instability (VPMRI); even a fragment displaced greater than 2 mm allows chronic posteromedial subluxation, capitellar erosion and early arthrosis if it is not buttressed. Buttress plating restores the facet and prevents that sequence. Classification. Two systems are used together — Regan-Morrey by height, and O'Driscoll by anatomical subtype (the more surgically relevant of the two):

Why small fragments matter. The coronoid tip carries the anterior capsule insertion, so losing it allows posterior translation even after a radial head replacement and lateral collateral repair. Cadaveric sectioning studies show that removing the coronoid tip alone produces measurable posterior subluxation at 30 to 40 degrees flexion, and clinical series associate unreduced tip fragments greater than 5 mm with higher rates of recurrent instability and early arthrosis after terrible triad reconstruction. Fixation outcomes. A suture lasso for tip fragments gives stable fixation with a low complication rate when combined with lateral collateral ligament repair. Buttress plating of the anteromedial facet provides rigid fixation that allows early motion, with good to excellent outcomes across multiple series. In terrible triad injuries, combined medial and lateral approaches yield a stable concentric elbow in greater than 85 percent of cases when the coronoid buttress is restored.