Radial Head Arthroplasty (RHA)

Indication. Radial head arthroplasty is performed when the radial head is unreconstructable AND the elbow needs it for stability. The primary indications are: - Mason III fracture — comminuted with greater than three fragments, not amenable to stable ORIF.

• Mason IV fracture — a radial head fracture with an elbow dislocation (the terrible triad pattern).
• Essex-Lopresti injury — radial head fracture with DRUJ disruption; replacement is mandatory to restore longitudinal forearm stability (excision fails here).
• Irreparable fracture with a stability demand — a young, active patient, an MCL-deficient elbow, or a valgus-loading occupation or sport. Secondary indications are a failed ORIF with a painful malunion limiting rotation, post-traumatic radiocapitellar arthritis in a young patient (an alternative to excision), and chronic nonunion or post-excision instability. Relative contraindications are severe capitellar cartilage damage (consider interposition arthroplasty or total elbow arthroplasty in the older patient), active infection, poor bone quality precluding stem fixation, comminution extending into the neck or shaft, and any patient unable to comply with rehabilitation. Excision versus replacement — the one decision. Excision is acceptable for an isolated radial head fracture in a low-demand patient with an elbow that is stable through its range of motion, intact collaterals and no DRUJ instability. Replacement is required whenever stability depends on the head — the terrible triad, Essex-Lopresti, MCL deficiency, and the high-demand valgus-loading patient. Assess the whole injury, not just the head. Before committing, define the associated injuries that change the operation: - Coronoid fracture — Regan-Morrey Type I (less than 50 per cent, observe), II (about 50 per cent, may fix), III (greater than 50 per cent, MUST fix); or O'Driscoll pattern (tip, anteromedial facet, basal).
• LUCL injury — torn by definition in the terrible triad and therefore mandatory to repair.
• Essex-Lopresti — interosseous membrane disruption with DRUJ instability; the head is mandatory.
• MCL injury (valgus instability in 5–10 per cent of terrible triads), capitellar osteochondral damage, medial epicondyle avulsion, and ulnar nerve status. Preoperative planning. AP, lateral and radiocapitellar-oblique elbow films define the Mason type; a CT maps comminution, coronoid and capitellar involvement; forearm and wrist films rule out Essex-Lopresti (DRUJ widening, ulnar variance); and a contralateral elbow film templates head diameter (typically 20–24 mm, range 18–26 mm) and height (8–12 mm). Have a modular implant set with multiple head diameters and neck lengths available. Consent specifically for stiffness (the commonest problem), heterotopic ossification, posterolateral instability, posterior interosseous nerve palsy, capitellar erosion and implant loosening or the need for future revision. Setup. Supine with the arm across the chest on a padded bolster or on a radiolucent arm board (lateral decubitus, arm uppermost, is an alternative), elbow flexed to 90 degrees, upper-arm tourniquet at 250 mmHg. Position C-arm fluoroscopy for AP and lateral views.

The goal: replace an unreconstructable radial head through the Kocher (lateral) approach while protecting the posterior interosseous nerve, restore radiocapitellar contact and radial length, repair the lateral ligament complex, and address any coronoid injury — then mobilise early. The exposure is laid out in full as the first steps below (and in depth on the Kocher approach to the elbow page).

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Structures at risk in the Kocher approach.

Rehabilitation principle. Stiffness is the dominant problem, so the aim is early protected motion that protects the repairs for the first 4–6 weeks while preventing contracture. A simple isolated RHA moves early; a terrible triad moves within a hinged brace. | Phase | Timing | Immobilisation | Therapy | |-------|--------|----------------|---------| | 1 — protection | 0–2 weeks | Simple RHA: posterior splint at 90°. Terrible triad: hinged brace locked 30–100° | Gentle active-assisted motion within brace limits; finger, wrist and shoulder ROM; oedema control | | 2 — progressive motion | 2–4 weeks | Removable brace; advance the arc (20–110°, then 10–120°, then 0–130°) | Active-assisted and active ROM all planes; forearm rotation | | 3 — active motion | 4–6 weeks | Remove brace if stable | Full active ROM (goal 0–130° flexion, 80–80° rotation); gentle isometrics | | 4 — strengthening | 6–12 weeks | Sling for heavy tasks only | Progressive resistance, eccentric and proprioceptive work | | 5 — return to activity | 3–6 months | None | Unrestricted strengthening; sport- and work-specific activity | Range-of-motion goals are flexion-extension of 30–130 degrees (a 100-degree arc is functional for daily living) and pronation-supination of 80–80 degrees. About 80–85 per cent of patients achieve a functional arc after a simple RHA and 70–75 per cent after a terrible triad (where stiffness is the main issue). Most reach maximum improvement by 6 months.

Heterotopic ossification prophylaxis. HO develops in 20–50 per cent of terrible-triad elbows without prophylaxis. - Indomethacin (the most widely used regimen): 25 mg three times daily for 3–6 weeks, starting on postoperative day 1. It reduces clinically significant HO to about 10–15 per cent. Common side effects are GI upset (co-prescribe a PPI in at-risk patients), renal dysfunction (monitor creatinine) and platelet inhibition; contraindicated in active peptic ulcer disease, significant renal impairment, NSAID allergy or concurrent anticoagulation. Counsel the patient that compliance matters. Note the evidence is largely extrapolated from hip and acetabular data — high-quality elbow-specific RCT evidence is limited, so use is selective and risk-stratified.

• Radiation therapy (alternative): a single dose of 7–8 Gy, ideally within 24–72 hours, reserved for NSAID contraindication or very high-risk cases (prior HO, severe trauma, associated head injury). Limitations are radiation exposure, theoretical wound-healing and long-term malignancy concerns in young patients, and the need for radiation oncology coordination.
• High-risk factors: severe trauma, delay to surgery greater than one week, head injury, HO in other joints, and severe soft-tissue injury. Follow-up. At 2 weeks (wound check, sutures, early ROM); 6 weeks (AP and lateral films for implant position, height and early radiolucency or HO, measure ROM, remove the brace if stable); 3 months (clinical and radiographic); 6 months (most plateau here); 1 year (final outcome). Thereafter, yearly films for the first 3 years then every 2–3 years, watching for progressive radiolucency, capitellar erosion, subsidence and HO. Complications

Additional complications. Radial-head dislocation or subsidence (about 5 per cent, from inadequate sizing, stem loosening or fracture propagation — revise); recurrent dislocation or instability (5–10 per cent in terrible triad, from inadequate LCL/coronoid/MCL repair — revision reconstruction with or without a hinged fixator); infection (1–2 per cent, higher in open fractures — debridement, antibiotics, possible implant removal); radioulnar synostosis (rare, under 1 per cent — excision but high recurrence); implant fracture (rare with modern implants — revision); and complex regional pain syndrome (disproportionate pain, swelling, stiffness and skin changes — aggressive hand therapy, desensitisation, sympathetic blocks).

Elbow stability anatomy. The elbow is one of the most congruent and stable joints, with stability roughly half osseous and half ligamentous. The osseous constraints are the ulnohumeral articulation (trochlea–olecranon–coronoid, the primary constraint), the radiocapitellar joint (a secondary valgus buttress) and the coronoid process (anterior buttress preventing posterior subluxation — its height is critical). The ligamentous constraints are the medial collateral ligament (primary valgus restraint, the anterior bundle most important) and the lateral collateral ligament complex — the LUCL (primary restraint to PLRI), the radial collateral ligament (blends with the annular ligament), the annular ligament (encircles the radial head) and a variable accessory band. Radial head biomechanics. The radial head transmits about 60 per cent of axial load across the radiocapitellar joint (40 per cent through the ulnohumeral), is the secondary valgus restraint (becoming primary if the MCL is deficient, as in Essex-Lopresti), is the critical link in longitudinal forearm stability through the interosseous membrane, and articulates with the capitellum for smooth pronation–supination. Terrible triad pathomechanics. A fall on the outstretched hand with the elbow flexed, forearm supinated, and a valgus and axial load produces, in sequence, a posterolateral elbow dislocation, a radial head fracture (impact on the capitellum), a coronoid fracture (shear as the ulna translates posteriorly) and LUCL disruption (tension failure). It is "terrible" because all primary stabilisers — osseous (radial head plus coronoid) and ligamentous (LUCL with or without MCL) — are injured at once, giving severe instability, high complication rates (stiffness, recurrent instability, HO) and technically demanding treatment.

Additional sources. Doornberg JN, Parisien R, van Duijn PJ, Ring D. Radial head arthroplasty with a modular metal spacer to treat acute traumatic elbow instability. J Bone Joint Surg Am. 2007;89(5):1075-1080 (PMID 17473146). Heijink A, Morrey BF, van Riet RP, O'Driscoll SW, Cooney WP. Delayed treatment of elbow pain and dysfunction following Essex-Lopresti injury with metallic radial head replacement. J Shoulder Elbow Surg. 2010;19(6):929-936 (PMID 20713279). AAOS / AO Foundation / national society consensus supports replacement (rather than excision) when the radial head is unreconstructable with associated instability, with anatomic sizing to avoid overstuffing.