import { HighYieldBox, ExamCheatSheet, Tabs, Tab, ComparisonTable, VivaScenario, ContentSection, SpecialTestCard , MedicalImage} from '@/components/content' # Elbow Instability Examination Elbow instability examination requires understanding the different instability patterns and their associated structures. Examiners expect you to differentiate posterolateral rotatory instability (PLRI - lateral collateral ligament complex injury) from valgus instability (MCL injury), and understand the "terrible triad" injury pattern. ## Quick Reference One-Pager ## Anatomy and Stabilizers **Primary Stabilizers:** - **Ulnohumeral articulation** (bony stability) - **Anterior MCL bundle** (valgus stability) - **Lateral ulnar collateral ligament (LUCL)** (rotatory stability) **Secondary Stabilizers:** - Radial head - Common extensor origin - Common flexor origin - Capsule **MCL Complex:** - Anterior bundle: Primary valgus restraint (taut in extension) - Posterior bundle: Secondary restraint (taut in flexion) - Transverse ligament: No significant role **LCL Complex:** - LUCL: Most important for PLRI prevention - Radial collateral ligament (RCL) - Annular ligament - Accessory LCL **Posterolateral Rotatory Instability (PLRI):** - Most common chronic elbow instability pattern - Caused by LUCL injury (usually from dislocation) - Radius and ulna rotate externally and subluxate posterolaterally - Patient reports elbow "giving way" with arm extended ## Clinical Presentation **Posterolateral Rotatory Instability:** **History:** - Previous elbow dislocation (often "reduced spontaneously") - Elbow "gives way" or "clicks" with arm extended - Difficulty pushing up from chair with arms - May have recurrent subluxations **Mechanism:** - Fall on outstretched hand - Elbow dislocation with LUCL avulsion - Iatrogenic (lateral epicondyle surgery) **Key Feature:** - Instability occurs with forearm supination, elbow extension, and axial/valgus load **Medial Collateral Ligament Injury:** **History:** - Overhead athlete (baseball pitcher, tennis) - Acute pop with throwing - Medial elbow pain with valgus stress - Decreased throwing velocity and accuracy **Mechanism:** - Chronic valgus overload (repetitive) - Acute dislocation - Fall with valgus force **Key Feature:** - Pain and instability with valgus stress at 30° flexion ## Provocative Tests - PLRI **Lateral Pivot Shift Interpretation:** - Often difficult to elicit in awake patients (guarding) - May need to perform under anesthesia for definitive diagnosis - Reduction "clunk" occurs at approximately 40° flexion - Supination is critical - pronation stabilizes the joint ## Provocative Tests - MCL (Valgus Instability) **Why Test at 30° Flexion:** - At 30°, posterior capsule is relaxed - Isolated MCL stress (not confounded by posterior capsule) - Anterior bundle of MCL is primary restraint - Compare with contralateral side for laxity ## Additional Assessment **PLRI Assessment:** - Radial head tenderness (associated fracture) - Lateral epicondyle tenderness (extensor origin) - Ulnar nerve symptoms (subluxation over medial epicondyle) **MCL Assessment:** - Ulnar nerve symptoms (runs behind medial epicondyle) - Flexor mass tenderness - Cubital tunnel assessment **Posterior Stability:** - Olecranon fracture (posterior instability) - Triceps integrity - Posterior drawer (rare isolated finding) **Three Components:** 1. Elbow dislocation 2. Radial head fracture 3. Coronoid fracture **Examination Findings:** - Significant swelling - Limited ROM - Potential instability in all directions - May have crepitus (fracture) **Important:** - Usually assessed post-reduction - May require examination under anesthesia - High risk of recurrent instability without surgical repair ## Instability Patterns ## Differential Diagnosis ## Summary Presentation ## Examiner Tips