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🦴 ORTHO DAY 1 - FEMUR + HIP JOINT + FEMORAL NECK FRACTURE X-RAY + CLINICAL CASE

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PART 1 - THE FEMUR (Bone)

General Facts (High-Yield)

• The femur is the longest, strongest, and heaviest bone in the human body
• It is subjected to forces during powerful muscle contraction and weight transmission
• Structurally, the femoral neck acts as an oblique strut between the pelvis (horizontal beam) and the femoral shaft (vertical beam) - this geometry allows wide range of motion but creates significant shearing forces at the neck

Regional Anatomy

Parts of the Femur

• Femoral head - 2/3 sphere; covered with articular cartilage except at the fovea capitis (where ligamentum teres attaches)
• Femoral neck - projects superolaterally from shaft; normal neck-shaft angle = 125-135° (coxa vara < 120°, coxa valga > 140°)
• Anteversion angle - femoral neck is anteverted ~10-15° relative to the femoral condyles
• Greater trochanter - attachment of gluteus medius and minimus (key abductors)
• Lesser trochanter - attachment of iliopsoas (main hip flexor)
• Intertrochanteric line (anterior) / Intertrochanteric crest (posterior) - mark the capsular attachment
• Femoral shaft - cylindrical; linea aspera on posterior surface provides attachment for adductors, hamstrings, and vastus muscles
• Distal femur - medial and lateral condyles; adductor tubercle on medial condyle (landmark)

Angulation Angles to Know

Muscle Compartments of the Thigh

Blood Supply of the Femur

1. Medial femoral circumflex artery (MFCA) - most important; branch of profunda femoris (deep femoral artery). Runs posteriorly and ascends around the femoral neck → forms the extracapsular arterial ring → gives ascending cervical arteries → form subsynovial intracapsular ring → give lateral epiphyseal arterial group (retinacular vessels) which supply the bulk of the femoral head
2. Lateral femoral circumflex artery (LFCA) - contributes less; supplies mostly the anterior head
3. Artery of ligamentum teres (from obturator artery) - supplies only a small area near the fovea; clinically relevant mainly in children

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PART 2 - THE HIP JOINT (Joint)

Joint Type

• Synovial ball-and-socket joint (enarthrosis)
• Most stable joint in the body due to: deep acetabulum + labrum + strong capsule + powerful muscles

Articular Surfaces

• Femoral head (ball) - fits into the acetabulum
• Acetabulum (socket) - formed by ilium (above), ischium (behind-below), pubis (front-below); covered by lunate surface (horseshoe-shaped articular cartilage); central acetabular fossa is non-articular (contains fat pad and ligamentum teres)
• Acetabular labrum - fibrocartilaginous rim that deepens the acetabulum by ~20%; seals the joint space

Capsule and Ligaments

Movements and Muscles

Trendelenburg Sign (High-Yield)

• Tests gluteus medius (superior gluteal nerve L4-S1)
• Positive sign: when standing on the affected leg, the contralateral pelvis drops (instead of rising)
• Caused by: Superior gluteal nerve palsy, hip pathology, coxa vara, weak abductors
• Walking version = Trendelenburg gait (lurching toward affected side to reduce abductor moment arm)

Neurovascular Relations at the Hip

• Nerve (femoral nerve) - lateral
• Artery (femoral artery) - middle; midpoint between ASIS and pubic symphysis
• Vein (femoral vein) - medial
• Empty space (femoral canal - potential hernia site)
• Lymphatics

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PART 3 - X-RAY: FEMORAL NECK FRACTURE

How to Read a Hip X-Ray - Systematic Approach

1. Shenton's line - smooth arc from inferior femoral neck to inferior pubic ramus. BROKEN in hip dislocation, fractures, developmental dysplasia
2. Neck-shaft angle - should be 125-135°
3. Trabecular pattern - medial compressive trabeculae / lateral tensile trabeculae of the femoral neck
4. Acetabular reference lines - iliopectineal line (anterior column), ilioischial line (posterior column), Köhler's teardrop, acetabular roof

X-Ray Anatomy of the Proximal Femur

Classification of Femoral Neck Fractures

A. By Anatomical Location (most fundamental)

B. Garden Classification (most widely used clinically)

• Garden III: neck and head still have contact; trabecular lines between head and acetabulum are NOT aligned (head has tilted)
• Garden IV: neck and head have NO contact; BUT trabecular lines between head and acetabulum RE-align (head has rotated back with acetabulum, completely free from neck)

• Garden I + II = Undisplaced → treat with internal fixation
• Garden III + IV = Displaced → treat with arthroplasty (hemi or THA) in elderly

C. Pauwels Classification (based on biomechanics)

What to Look for on the X-Ray (Checklist)

• Is the fracture intracapsular or extracapsular?
• Is there displacement? (Is Shenton's line broken?)
• What is the neck-shaft angle? (Varus = displaced)
• Are trabecular lines aligned in the femoral head vs acetabulum? (Garden grading)
• What is the Pauwels angle?
• Is there associated fracture (acetabulum, shaft, pelvis)?
• Any signs of pre-existing pathology (Paget disease, metastasis, osteoporosis)?

• ~15% of femoral neck fractures are radiographically occult on plain film
• MRI is the gold standard for occult fractures (detects marrow edema)
• CT useful if MRI unavailable or for assessing comminution

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PART 4 - CLINICAL CASE

Case Presentation

• Right lower limb is shortened and externally rotated (pathognomonic position)
• Groin pain that worsens with active movement
• Pain on axial loading (heel strike test / telescoping)
• No distal neurovascular deficit

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Step-by-Step Approach

• Femoral neck fracture (most likely)
• Intertrochanteric fracture (also causes shortening + ER)
• Subtrochanteric fracture
• Acetabular fracture
• Pubic ramus fracture (less shortening/ER)
• Hip dislocation (posterior = flexed + IR; anterior = extended + ER - but usually requires high energy in elderly)

Femoral Neck Fracture
        │
        ├─── YOUNG patient (<60 yrs) + any garden grade
        │         → URGENT internal fixation (within 6-12 hrs)
        │         → Goal: save the femoral head
        │         → Cannulated screws or sliding hip screw
        │
        └─── ELDERLY patient (>60-65 yrs)
                  │
                  ├─── Undisplaced (Garden I/II)
                  │         → Internal fixation (cannulated screws)
                  │         → (some centres use hemiarthroplasty for very elderly)
                  │
                  └─── Displaced (Garden III/IV)
                            │
                            ├─── NOT independently mobile / dementia / limited prognosis
                            │         → HEMIARTHROPLASTY (cemented preferred in elderly)
                            │
                            └─── INDEPENDENTLY MOBILE (walking outdoors before injury)
                                      → TOTAL HIP ARTHROPLASTY (THA)
                                      → Better functional outcomes in active elderly

• 1-year mortality after hip fracture in the elderly is 20-30%
• Surgery within 48 hours significantly reduces mortality
• Hip fracture is managed as a medical emergency, not an elective procedure

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Exam Mnemonics

"1 = Incomplete valgus; 2 = Complete no displacement; 3 = Complete varus; 4 = Completely gone (displaced)"

"Vertical = Vicious" (Type III with steep vertical fracture is worst)

• Fracture = Shortened + Externally Rotated (capsule torn, limb collapses into ER)
• Posterior dislocation = Flexed + Internally Rotated + Adducted (FIAD)
• Anterior dislocation = Extended + Externally Rotated + Abducted

"Medial Femoral Circumflex = Major Flow to Cartilage" - it's the primary supply. Destroy it = AVN.

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QUICK-RECALL SUMMARY TABLE

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WHAT'S NEXT (Day 2 suggestion)

• Bone: Tibia/Fibula anatomy
• Joint: Knee joint (most complex joint - menisci, cruciate ligaments, collateral ligaments)
• X-ray: Tibial plateau fracture (Schatzker classification)
• Clinical case: 35-year-old motorcyclist, valgus knee injury - tibial plateau fracture

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