import { ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, InfoCard, InfoCardGrid, MedicalImage, MnemonicCard, OnePagerSummary, SafetyAlert, Tab, Tabs, VivaScenario, VivaScenarioSection } from '@/components/mdx' Between **Anconeus** (radial nerve proper) and **ECU** (posterior interosseous nerve). True internervous plane. **PIN** winds around radial neck ~4cm distal to head. **Supinate** forearm to move PIN away. Avoid excessive pronation or distal dissection. **Lateral ulnar collateral ligament** originates from lateral epicondyle. May need to be incised for exposure. Must be **repaired** to prevent posterolateral rotatory instability. **Radial head**, **capitellum**, **lateral column**. Good for radial head ORIF/replacement, capitellar fractures, lateral ligament reconstruction. The Kocher approach is a lateral approach to the elbow using the true internervous plane between **anconeus** (radial nerve proper) and **ECU** (posterior interosseous nerve). The primary indication is access to the radial head, capitellum, and lateral column for fracture fixation or radial head replacement. The **posterior interosseous nerve (PIN)** is at risk as it winds around the radial neck approximately 4cm distal to the radial head - keeping the **forearm supinated** moves the PIN away from the surgical field and provides protection. The lateral ulnar collateral ligament (LUCL) may need to be incised for exposure and must be repaired to prevent posterolateral rotatory instability. **Indications**: - Radial head fracture (ORIF or replacement) - Capitellum fracture - Lateral column fractures - LUCL repair/reconstruction - Lateral epicondylitis (rare) - Elbow arthroplasty (lateral approach) **Patient Position**: - Supine with arm across chest or on arm board - Lateral decubitus with arm over bolster - **Forearm supinated** to protect PIN **Incision**: Curved incision over lateral epicondyle, may curve proximally or distally depending on pathology. Approximately 6-8cm. **Fascia**: Incise fascia. Identify interval between **anconeus** (posteriorly) and **ECU** (anteriorly). **Interval Development**: Develop interval between anconeus and ECU. This is the internervous plane: anconeus (radial nerve proper) and ECU (posterior interosseous nerve). **Capsule**: Incise the lateral joint capsule. This may involve the **LUCL** origin at the lateral epicondyle - mark and repair if incised. **Annular Ligament**: May need to be incised for radial head access. Repair at closure. **Exposure**: Visualize radial head, capitellum, radiocapitellar joint. **Supination**: Keep forearm **supinated** throughout to protect PIN. **Annular Ligament**: Repair if incised. **LUCL**: Essential to repair to prevent posterolateral rotatory instability. **Capsule**: May close or leave open (controversy). **Muscle Interval**: May not need formal repair as muscle fibers separate. **Fascia and Skin**: Standard closure. **Posterior Interosseous Nerve (PIN)**: Winds around radial neck ~4cm distal to radial head. At greatest risk with forearm pronation (PIN moves anterior) and distal dissection. **SUPINATE** forearm to protect. **Lateral Ulnar Collateral Ligament (LUCL)**: Originates from lateral epicondyle. Must be preserved or repaired to prevent posterolateral rotatory instability (PLRI). **Annular Ligament**: Stabilizes radial head. Repair if divided. **PIN Protection**: - **Supinate** forearm (PIN moves posteriorly) - Avoid dissection greater than 4cm distal to radial head - Avoid excessive pronation during surgery - Be aware PIN position varies with rotation **Q: What is the internervous plane utilized in the Kocher approach to the elbow?** A: **Anconeus** (radial nerve proper) and **ECU** (posterior interosseous nerve). This is a true internervous plane. The anconeus is supplied by the radial nerve before it divides, while ECU is supplied by the PIN after the division at the arcade of Frohse. **Q: How far distal to the radial head is it safe to dissect in the Kocher approach?** A: **4 cm (approximately 3 fingerbreadths)** distal to the radial head. Beyond this, the **PIN** is at risk as it winds around the radial neck. The nerve lies directly on the radius during pronation, so always keep the forearm **supinated** during dissection to move the PIN away from the operative field. **Q: What structures can be accessed through the Kocher approach?** A: **Radial head**, **capitellum**, **lateral column of distal humerus**, **LUCL** (lateral ulnar collateral ligament), and **lateral epicondyle**. This approach is ideal for radial head fractures, capitellum fractures, and lateral column procedures. Cannot adequately visualize coronoid or medial structures. **Q: Why must the LUCL be protected during the Kocher approach?** A: The **LUCL** is the primary restraint to **posterolateral rotatory instability (PLRI)**. It originates from the lateral epicondyle and inserts on the supinator crest of the ulna. Division or failure to repair leads to **pivot shift phenomenon** with the forearm supinating and the radial head subluxing posteriorly under valgus load. **Q: What position should the forearm be maintained during the Kocher approach and why?** A: The forearm should be **supinated**. This moves the **PIN** medially away from the surgical field as the nerve wraps around the radial neck within the supinator muscle. In pronation, the PIN lies directly on bone and is vulnerable. Additionally, supination relaxes the extensor musculature facilitating exposure. ### Australian Epidemiology and Practice **Australian Elbow Trauma Epidemiology:** - Radial head fractures are one of the most common elbow fractures in adults in Australia - Approximately 30% of elbow fractures involve the radial head - Peak incidence in young adults (falls from height, sports injuries) and elderly (osteoporotic fragility fractures) - The Kocher approach remains the standard lateral approach for radial head pathology across Australian orthopaedic units **RACS Orthopaedic Training Relevance:** - The Kocher approach is a core FRACS Orthopaedic examination topic, particularly for the Surgical Approaches viva - Examiners commonly test knowledge of the internervous plane (anconeus-ECU interval), PIN protection techniques, and LUCL anatomy - Candidates must be able to describe the approach step-by-step, including indications, patient positioning, dissection planes, and structures at risk - Understanding of PIN anatomy and protection (forearm supination, limit distal dissection to 4cm) is essential - LUCL repair and prevention of posterolateral rotatory instability (PLRI) is a frequent examination topic **Australian Elbow Surgery Practice:** - Major trauma centres (Royal Melbourne Hospital, Royal Adelaide Hospital, Royal Brisbane and Women's Hospital) manage complex elbow trauma requiring the Kocher approach - Elbow subspecialty fellowships available at several Australian centres for advanced training - Australian Orthopaedic Association (AOA) Scientific Meetings regularly feature elbow trauma and reconstruction sessions - Increasing use of radial head arthroplasty for comminuted fractures (Mason III-IV) using the Kocher approach **Antibiotic Prophylaxis (eTG Recommendations):** - For elbow fracture fixation via the Kocher approach: Cefazolin 2g IV at induction (or 3g if greater than 120kg body weight) - Single dose prophylaxis is sufficient for uncomplicated procedures - For patients with penicillin allergy: Vancomycin 25mg/kg IV as alternative **Post-operative Rehabilitation:** - Australian physiotherapy protocols emphasise early controlled range of motion after radial head fixation or replacement - Hinged elbow orthoses may be used for LUCL reconstruction cases - Outpatient orthopaedic rehabilitation services coordinate post-operative care

Kocher Approach to the Elbow

Kocher Approach to the Elbow