High Yield Overview

PRIMARY TOTAL HIP ARTHROPLASTY

Multiple approaches available - posterior (Moore/Southern), direct anterior (DAA), direct lateral (Hardinge), anterolateral (Watson-Jones) | intermediate

Critical Danger Structures - 5 Key Zones

1. Superior Gluteal Nerve

Location: Exits greater sciatic notch 25-40mm proximal to tip of greater trochanter, runs between gluteus medius and minimus

Protection: Stay within 5cm distal to GT tip (safe zone), never extend muscle split proximally beyond this landmark, use anterior-based approach to avoid

2. Sciatic Nerve

Location: Runs 20-30mm posterior to hip joint capsule, posterior to short external rotators (piriformis is key landmark - nerve 2cm posterior)

Protection: Tag external rotators for identification, gentle retraction only, limit retraction time, avoid leg lengthening greater than 4cm

3. Femoral Nerve & Vessels

Location: Lies 40-60mm anterior/medial to acetabulum, within femoral triangle (NAVEL: nerve, artery, vein, empty space, lymphatics)

Protection: Anterior retractors must stay on bone (ilium/acetabular rim), never slide medially into soft tissue, avoid anteroinferior acetabular screws

4. External Iliac Vessels

Location: Run along pelvic brim anteriorly, 15-25mm anterior to anterior acetabular wall, separated by psoas and iliacus muscles

Protection: No screws in anteroinferior quadrant of acetabulum, screws posterosuperior only, medial wall reaming must be controlled to avoid perforation

5. Medial Femoral Circumflex Artery

Location: Runs deep to quadratus femoris muscle, supplies femoral head via retinacular vessels, critical for femoral head viability

Protection: Preserve quadratus femoris when possible, recognize already disrupted in AVN cases, gentle handling of posterior capsule

Mnemonic

CAPSULECAPSULE - Capsular Repair Benefits

Mnemonic

STABLESTABLE - Testing Hip Stability Intraoperatively

Indications for Primary THA

Primary Indications

End-stage Hip Osteoarthritis

Primary idiopathic OA (most common in elective setting)
Failed conservative management (analgesia, activity modification, physiotherapy)
Radiographic evidence: joint space loss, osteophytes, subchondral sclerosis, cysts
Pain limiting activities of daily living, night pain, functional disability

Secondary Osteoarthritis

Developmental dysplasia of hip (DDH) - complex reconstruction, often requires specialized cups
Avascular necrosis - consider THA vs resurfacing in younger patients
Post-traumatic arthritis - previous acetabular or femoral fracture
Slipped upper femoral epiphysis sequelae
Perthes disease sequelae in adults

Inflammatory Arthritis

Rheumatoid arthritis - often bilateral, bone quality poor, younger age group
Ankylosing spondylitis - fixed spinal deformity affects cup positioning
Psoriatic arthritis

Acute Fracture

Displaced intracapsular NOF in elderly (>75 years, low demand)
THA vs hemiarthroplasty: THA if independent, mobile, good life expectancy

Contraindications

Absolute

Active local or systemic infection
Inadequate soft tissue coverage
Neurogenic arthropathy (Charcot joint) - relative, high failure rate
Severe peripheral vascular disease with ischaemic limb

Relative

Poor bone stock (severe osteoporosis, prior irradiation)
Skeletal immaturity
Medical comorbidities precluding surgery
Non-compliance with postoperative restrictions
Progressive neurological disease affecting lower limb

Preoperative Planning

Templating Requirements

Calibrated digital or analogue templating essential
Template both AP pelvis and lateral femur
Determine cup size, position (restore center of rotation)
Determine stem size, neck length, offset
Plan for leg length restoration (measure from teardrop to lesser trochanter bilaterally)
Identify bone defects requiring augmentation

Australian Context - AOANJRR Data

Uncemented cups used in 90% of primary THA
Cemented stems in 35%, uncemented 60%, hybrid 5%
Ceramic-on-polyethylene most common bearing (40%)
Metal-on-polyethylene 35%, ceramic-on-ceramic 15%
10-year revision rate: 6.5% for primary OA

Exam Pearl

AOANJRR Pearl: "In Australia, uncemented acetabular components account for 90% of primary THA. For femoral stems, younger patients (less than 65) typically receive uncemented stems, while cemented stems are preferred in elderly patients greater than 75 years with osteoporotic bone. Hybrid fixation (uncemented cup, cemented stem) is the gold standard for fracture indications."

Step-by-Step Surgical Technique

Step 1: Patient Positioning & Preparation

Posterior Approach Positioning

Lateral decubitus position, affected hip uppermost
Pelvis perpendicular to floor, secured with anterior/posterior supports
Both supports padded to prevent pressure injury
Dependent leg flexed at hip and knee, pillow between legs
Upper leg free to move for dislocation
Support at sacrum and symphysis pubis

Direct Anterior Approach Positioning

Supine on traction or fracture table
Perineal post for counter-traction
Both legs draped free
C-arm positioned for AP and lateral fluoroscopy

Landmarks to Mark

Greater trochanter
Anterior superior iliac spine
Posterior superior iliac spine
Femoral shaft axis

Exam Pearl

Positioning Pearl: "For the posterior approach, I position the patient in lateral decubitus with the pelvis PERPENDICULAR to the floor - this is critical for accurate cup positioning. I use anterior and posterior pelvic supports at the pubis and sacrum. The dependent leg is flexed to relax the sciatic nerve. I verify position before draping using a pelvic positioner or intraoperative fluoroscopy."

Positioning Dangers

Inadequate pelvic stabilization → cup malposition (most common cause of dislocation)
Brachial plexus injury from arm malposition (check pulse, position arm at less than 90° abduction)
Peroneal nerve injury of dependent leg (check padding over fibular head)
Pressure injuries (sacrum, heel, malleoli)
Pelvic rotation during case → leg length discrepancy, cup malposition

Step 2: Skin Incision & Superficial Dissection (Posterior Approach)

Incision

Curved incision 10-15cm (shorter for minimally invasive, longer for complex cases)
Centered on greater trochanter
Extends proximally toward PSIS
Curves distally along femoral shaft axis
Straight lateral in line with femur for direct lateral approach

Fascial Layer

Incise fascia lata in line with skin incision
Identify gluteus maximus muscle fibers (oblique orientation)
Split gluteus maximus IN LINE with fibers
Use blunt dissection (fingers or Cobb) to develop plane
This is a TRUE internervous plane (dual innervation)

Exam Pearl

Internervous Plane Pearl: "I split gluteus maximus in line with its fibers - this is a true internervous plane because the muscle has dual innervation. The superior third is supplied by the superior gluteal nerve and the inferior two-thirds by the inferior gluteal nerve. Splitting preserves all motor function."

Superficial Dissection Dangers

Sciatic nerve lies deep to gluteus maximus (posterior to short external rotators)
Inferior gluteal neurovascular bundle enters proximal gluteus maximus (stay in distal 2/3)
Cutting across muscle fibers causes denervation and weakness
Superior gluteal nerve at risk if dissection extends greater than 5cm proximal to GT

Step 3: Deep Dissection - Short External Rotators

Identification of Short External Rotators (Superior → Inferior)

Piriformis (most superior, sciatic nerve 2cm posterior)
Superior gemellus
Obturator internus (strong tendon, forms conjoined tendon with gemelli)
Inferior gemellus
Quadratus femoris (most inferior, covers medial circumflex artery)

Technique

Place deep retractors (Hohmann) anterior and posterior to expose rotators
Palpate sciatic nerve posterior to piriformis (protect with retractor)
Tag each tendon with heavy suture BEFORE cutting (essential for repair)
Detach piriformis from posterior femur/GT
Detach conjoined tendon (superior gemellus + OI + inferior gemellus)
May preserve quadratus femoris (protects medial circumflex artery)
Alternatively, perform inside-out technique (detach from capsule instead of femur)

Exam Pearl

External Rotator Pearl: "I tag each short external rotator tendon with a heavy absorbable suture BEFORE cutting - this allows anatomic repair at closure. I identify them superior to inferior: Piriformis, Superior gemellus, Obturator internus, Inferior gemellus, Quadratus femoris. The sciatic nerve is 2cm posterior to the piriformis - I protect it throughout. Some surgeons preserve quadratus femoris to protect the medial femoral circumflex artery."

Deep Dissection Dangers

Sciatic nerve (0.5-2% injury rate): Most common nerve injury in THA, located 2cm posterior to piriformis
Superior gluteal nerve: At risk if dissection extends greater than 5cm proximal to GT
Medial femoral circumflex artery: Deep to quadratus femoris, already disrupted in AVN/fracture
Failure to tag tendons makes repair difficult/impossible

Step 4: Capsulotomy & Hip Dislocation

Capsulotomy Technique

Perform T-shaped or H-shaped capsulotomy
Tag capsular flaps with HEAVY sutures (2-0 or 0 absorbable) for later identification
Superior flap, inferior flap, and posterior flap
Leave adequate tissue for repair (at least 1cm margins)
Excise minimal capsule (most should be preserved for repair)

Hip Dislocation Maneuver

Flex hip to 90°
Adduct across midline
Internally rotate
Apply gentle posterior force
Femoral head should deliver posteriorly
If difficult: increase flexion, check for osteophytes blocking dislocation

Head Removal

Insert corkscrew into femoral head
Extract head with gentle rocking motion
Inspect head: wear pattern (superior pole), osteophytes, loose bodies
Send head for histology and microbiology

Exam Pearl

Capsular Repair Pearl: "I perform a T-shaped capsulotomy and TAG all capsular flaps with heavy sutures - this is critical. At closure, I repair the capsule meticulously, which reduces dislocation rate from 3-5% to less than 1%. Multiple randomized trials support capsular repair. I preserve as much capsule as possible - don't excise, just incise and tag."

Dislocation Step Dangers

Femoral shaft fracture during forced dislocation (especially osteoporotic bone, elderly females)
Acetabular fracture (posterior wall) with vigorous levering
Not tagging capsule makes later identification and repair difficult or impossible
Sciatic nerve traction injury with excessive force

Step 5: Femoral Neck Osteotomy

Level Determination

Based on preoperative templating
Standard: 1cm above lesser trochanter
Horizontal cut at this level (perpendicular to shaft)
Angle of cut affects leg length and offset

Technique

Use oscillating saw with narrow blade
Protect posterior soft tissues with retractor
Cut perpendicular to femoral shaft in coronal plane
Preserve calcar (medial cortical thickening) - provides stability
Remove femoral head with corkscrew extractor
Inspect cut surface for occult fracture lines
Elevate cut surface with retractor if needed for femoral exposure

Exam Pearl

Neck Cut Pearl: "I make the femoral neck cut at the templated level, approximately 1cm above the lesser trochanter. A horizontal cut perpendicular to the shaft preserves the calcar and allows accurate leg length restoration. I inspect the cut surface carefully for occult fracture lines - if present, I may alter my fixation plan to cemented stem or use cerclage prophylactically."

Neck Osteotomy Dangers

Cut too DISTAL → short leg, abductor weakness (moment arm reduced)
Cut too PROXIMAL → long leg, nerve stretch injury, reduced ROM
Calcar fracture propagation into diaphysis
Thermal necrosis from prolonged sawing (cool with irrigation)
Sciatic nerve injury from saw exiting posteriorly

Step 6: Acetabular Exposure & Preparation

Retractor Placement (3-point retraction)

Anterior retractor (Hohmann): Over anterior wall/column, on bone
Posterior retractor: Over posterior wall/ischium, protect sciatic nerve
Inferior retractor: Into obturator foramen (blunt Hohmann)
This provides 360° visualization of acetabulum

Acetabular Preparation

Excise labrum circumferentially
Remove osteophytes (especially inferior)
Identify transverse acetabular ligament (marks inferior extent)
Identify fovea (marks anatomic center)
On fluoroscopy: teardrop marks medial wall

Reaming Technique

Start with smallest reamer (36-38mm typically)
Direct reamer toward ipsilateral shoulder (45° inclination, 15° anteversion)
Ream progressively (2mm increments)
Ream MEDIALLY to subchondral bone (bleeding cancellous bone)
Goal: restore anatomic center of rotation (level of teardrop)
Ream to achieve peripheral rim contact
Final reamer size determines cup size (cup is 1-2mm larger for press-fit)

Exam Pearl

Acetabular Reaming Pearl: "I place three retractors for 360° visualization: anterior, posterior, and inferior in the obturator foramen. The transverse acetabular ligament marks the inferior extent - this is my key anatomical landmark. I ream medially to restore the anatomic center of rotation at the level of the teardrop. Progressive reaming until I achieve bleeding subchondral bone with peripheral rim contact. Final reamer plus 1-2mm determines my cup size for press-fit."

Acetabular Preparation Dangers

Medial wall perforation → intrapelvic migration, vascular injury (especially protrusio acetabuli)
Posterior wall deficiency from over-reaming → instability, need for augmentation
External iliac vessels anterior to acetabulum (15-25mm from anterior wall)
Sciatic nerve posterior, at risk with inferior retractor malposition
Superior gluteal neurovascular bundle exits sciatic notch superiorly

Step 7: Acetabular Component Insertion

Cup Selection

Cup diameter = final reamer + 1-2mm (for press-fit, line-to-line fit)
Larger diameter if bone quality poor or revision setting
Consider augments/cages for significant defects

Lewinnek Safe Zone Positioning

Inclination: 40-45° (radiographic angle)
Anteversion: 15-20°
Use alignment guides, referenced to transverse ligament and patient position
Fluoroscopy can confirm position

Insertion Technique

Impact cup with straight impactor aligned to handle
Aim for peripheral rim contact (avoid central perforation)
Impact until solid seating (change in pitch of impact sound)
Assess stability: no rocking or toggle
Supplemental screws ONLY if stability suboptimal

Screw Placement (if needed)

POSTEROSUPERIOR quadrant only (safe zone)
Avoid anteroinferior quadrant (vascular structures)
Screws directed into ilium/posterior column
Usually 2-3 screws sufficient
Avoid intra-articular penetration

Exam Pearl

Lewinnek Safe Zone Pearl: "I position the cup within the Lewinnek safe zone: 40-45° inclination and 15-20° anteversion. Studies show cups within this zone have 1.5% dislocation rate vs 6.1% outside the zone. However, safe zone is not absolute - I also consider combined anteversion concept: cup anteversion plus stem anteversion should equal 25-45° for optimal stability and impingement-free range of motion."

Cup Insertion Dangers

Cup malposition → dislocation (most common cause of early dislocation)
Excessive anteversion (greater than 25°) → anterior dislocation
Insufficient anteversion (less than 10°) → posterior dislocation
Anteroinferior screws → external iliac vessel injury (potentially fatal)
Central perforation → intrapelvic component migration, need for revision
Vertical cup (greater than 50° inclination) → accelerated polyethylene wear, edge loading

Step 8: Femoral Exposure & Preparation

Femoral Delivery

Place anterolateral retractor (Hohmann) around femoral neck
Elevate/deliver proximal femur into wound
Flex, externally rotate, and extend hip to deliver femur
Remove anterior/superior osteophytes that impede visualization

Canal Preparation

Start with box chisel in piriformis fossa (defines entry point)
Direct handle LATERALLY (prevents varus stem alignment)
Clear soft tissue from canal opening
Use canal finder to confirm canal direction

Broaching Technique

Start with smallest broach (size 1 or 2)
Direct handle laterally (prevents varus)
Progressive broaching (don't skip sizes)
Each broach should advance 2-3mm deeper than previous
Continue until cortical contact achieved (metaphyseal fill for uncemented)
Firm seating without advancement = final broach size
Target 10-15° anteversion (match native femoral version)

Version Assessment

Palpate lesser trochanter (should be posteromedial)
Broach handle should point toward patella with hip extended
Can use trial stem with version guide

Exam Pearl

Broaching Pearl: "I start with a box chisel in the piriformis fossa, directing the handle LATERAL - this is critical to prevent varus stem alignment. Progressive broaching without skipping sizes, each broach advancing 2-3mm deeper. I achieve metaphyseal fill and cortical contact for uncemented fixation. I target 10-15° anteversion matching native femoral version. Combined anteversion (cup + stem) should equal 25-45°."

Femoral Preparation Dangers

Varus stem alignment (broach handle too medial) → reduced offset, instability, early loosening
Calcar fracture (excessive force, tight fit) → may need cerclage wire or cable
Femoral perforation (misdirected broach, bowed femur) → bleeding, cement leak, instability
Greater trochanter fracture (excessive soft tissue tension) → abductor dysfunction
Anterior cortical perforation (excessive anteversion) → need for cement containment or revision

Step 9: Trial Reduction & Stability Assessment

Trial Component Insertion

Insert trial stem matching final broach size
Attach trial head (start with standard neck length, typically +0mm to +4mm)
Trial polyethylene liner in acetabular shell

Hip Reduction

Extend hip
Apply traction
Gentle internal rotation
Head should reduce with minimal force
"Clunk" indicates seating

Systematic Stability Testing - STABLE Mnemonic

Anterior stability test: Full extension + 40° external rotation → should remain reduced
Posterior stability test: 90° flexion + 40° internal rotation + adduction → should remain reduced
Impingement assessment: Take hip through full ROM, check for bony or prosthetic impingement
Stability in all positions: Check stability at various points in arc of motion

Leg Length Assessment

With knees flexed: overlap patellae (crude but effective)
Measure from fixed pelvic point (ASIS or iliac crest) to medial malleolus
Compare to preoperative measurement and contralateral side
Goal: within 5mm of contralateral or preoperative plan
Adjust by changing head size (+/- 4mm) or neck length (+/- 8-12mm)

Offset Assessment

Palpate tension of abductors
Greater offset → more tension → better stability but risk of trochanteric pain
Insufficient offset → laxity → instability

Exam Pearl

Stability Testing Pearl: "I perform systematic stability testing using STABLE: Test anterior stability with full extension and 40° external rotation - this is the position at risk for anterior dislocation with DAA. Test posterior stability with 90° flexion, 40° internal rotation, and adduction - the position at risk for posterior dislocation with posterior approach. I assess leg length by overlapping patellae with knees flexed - goal is within 5mm discrepancy."

Trial Reduction Dangers

Inadequate stability testing → postoperative dislocation (most preventable complication)
Leg length discrepancy greater than 1cm → patient dissatisfaction, nerve stretch, litigation
Excessive offset → trochanteric bursitis, abductor pain, iliotibial band friction
Insufficient offset → instability, impingement, early dislocation
Failure to check impingement → late dislocation from component wear/impingement

Step 10: Final Component Insertion

Trial Removal

Dislocate hip (same maneuver as initial dislocation)
Remove trial head
Extract trial stem with slap hammer
Deliver femur anteriorly for visualization

Uncemented Stem Insertion

Clean canal with dry sponge
Final stem same size as final broach
Insert stem by hand initially
Impact with mallet (straight impactor on trunion)
Avoid varus/valgus malalignment
Seat to planned depth (reference to GT or shoulder of stem)
Confirm version (10-15° anteversion)

Cemented Stem Insertion (Modern Cementing Technique)

Insert cement restrictor at isthmus (2cm beyond stem tip)
Pulsatile lavage with 3L saline (clean canal)
Dry canal thoroughly (ribbon gauze, suction)
Vacuum-mixed cement (reduce porosity)
Retrograde cement gun application (fill from distal to proximal)
Pressurization with cement pressurizer
Insert stem in slight anteversion (10-15°)
Hold in position until cement hardens
Remove excess cement while still soft
Goal: 2-3mm cement mantle circumferentially

Femoral Head Insertion

Modular head (size and length determined from trialing)
Clean trunion with dry sponge (no fluid - affects locking)
Align head with trunion
Impact firmly with head impactor (change in sound indicates seating)
Check for proper seating (no gap between head and neck)

Final Hip Reduction

Extend hip, apply traction, gentle internal rotation
Confirm reduction

Exam Pearl

Modern Cementing Technique Pearl: "For cemented stems, I use modern cementing technique developed by Charnley and refined over decades: cement restrictor at the isthmus, pulsatile lavage with 3L saline, dry canal thoroughly, vacuum-mixed cement to reduce porosity, retrograde gun application from distal to proximal, pressurization, then stem insertion. This achieves optimal cement mantle of 2-3mm circumferentially. AOANJRR data shows excellent results with cemented stems in elderly patients greater than 75 years."

Final Implantation Dangers

Poor cement mantle (less than 2mm) → early loosening, cement fracture
Air in cement → porosity, reduced strength (use vacuum mixing)
Fat embolism during cementing → hypoxia, cardiovascular collapse (vent canal, use restrictor)
Component not fully seated → subsidence, early failure
Femoral head not properly seated → dissociation, pain, metallosis

Step 11: Final Stability Check & Wound Inspection

Final Stability Assessment

Repeat stability tests with permanent components
Anterior: extension + 40° ER
Posterior: 90° flexion + 40° IR + adduction
Full ROM without impingement
Hip should be stable throughout entire arc of motion

Impingement Check

Flexion to 110-120° (no anterior impingement)
Extension to neutral (no posterior impingement)
Internal rotation in flexion (no impingement)
External rotation in extension (no impingement)
Identify any bony prominences causing impingement

Wound Inspection

Pulse lavage with 3L normal saline (or antibiotic solution)
Inspect for: (1) fractures (acetabular, femoral), (2) cement debris, (3) loose bodies
Achieve meticulous hemostasis (electrocautery, bone wax for bleeding cancellous bone)
Check sciatic nerve if any concern (visual inspection, gentle palpation)

Exam Pearl

Final Check Pearl: "I perform comprehensive final stability testing with the permanent components in place. I check full ROM to ensure no impingement - flexion to 110-120°, extension to neutral, full rotation. I pulse lavage with 3L saline for thorough debridement. Meticulous hemostasis is critical - hematoma increases infection risk. I verify no intraoperative fractures before closure."

Final Check Dangers

Unrecognized intraoperative fracture → displacement, subsidence, early failure
Hematoma from inadequate hemostasis → infection risk, delayed rehabilitation
Component instability missed during final check → early dislocation
Sciatic nerve injury not recognized → delayed diagnosis, poor outcome

Step 12: Layered Closure & Hip Precautions

Critical Capsular Repair

Identify tagged capsular flaps
Repair capsule with interrupted heavy absorbable sutures (2-0 or 0)
At least 5-6 sutures for robust repair
Ensure adequate tension (not too tight, not too loose)
Evidence: reduces dislocation from 3-5% to less than 1%

External Rotator Repair

Identify tagged external rotator tendons
Repair piriformis to posterior femur/GT
Repair conjoined tendon (superior gemellus + OI + inferior gemellus)
Use heavy absorbable sutures through bone tunnels or to soft tissue
Restore anatomic tension

Fascial and Muscle Closure

Repair gluteus maximus fascia with absorbable sutures (1 or 0)
Running or interrupted technique
Ensure no dead space

Subcutaneous and Skin Closure

Subcutaneous layer with 2-0 absorbable (reduces seroma)
Skin: staples OR subcuticular absorbable suture
Apply sterile dressing
Consider waterproof dressing for early mobilization

Hip Precautions (Posterior Approach)

NO hip flexion greater than 90° for 6 weeks
NO adduction past midline for 6 weeks
NO internal rotation for 6 weeks
Use elevated toilet seat, avoid low chairs
Sleep with pillow between legs
These precautions protect capsular and rotator repair

Exam Pearl

Capsular Repair Pearl: "I meticulously repair the posterior capsule with heavy absorbable sutures - this is the single most important step for preventing dislocation. Multiple RCTs show capsular repair reduces dislocation from 3-5% to less than 1%. I also repair the short external rotators to restore the posterior soft tissue envelope. Hip precautions for 6 weeks protect this repair: no flexion greater than 90°, no adduction past midline, no internal rotation."

Closure Dangers

No capsular repair → 3-4 times higher dislocation rate (from less than 1% to 3-5%)
Inadequate external rotator repair → posterior instability
Non-compliance with hip precautions → early dislocation (most common in first 6 weeks)
Wound closure under excessive tension → wound dehiscence, necrosis
Dead space → hematoma formation, infection risk

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 68-year-old man presents with severe right hip pain limiting his daily activities. Describe your assessment and management plan for primary total hip arthroplasty."

EXCEPTIONAL ANSWER

I would take a comprehensive approach to this patient. HISTORY: Pain characteristics, functional limitation, failed conservative management, medical comorbidities, medications (anticoagulation), social factors. EXAMINATION: Gait (antalgic, Trendelenburg), ROM (typically restricted internal rotation and flexion), leg length discrepancy, neurovascular status. INVESTIGATIONS: XR AP pelvis and lateral hip (joint space narrowing, osteophytes, sclerosis, cysts confirm OA), consider CT for templating if complex anatomy. PREOPERATIVE PLANNING: Templating to determine component sizes and restore anatomy, medical optimization (anemia correction, diabetic control, smoking cessation), VTE risk assessment. SURGICAL PLAN: Posterior approach (most common in Australia), uncemented cup (90% per AOANJRR) with Lewinnek safe zone positioning, cemented or uncemented stem based on bone quality (cemented in elderly), capsular repair to reduce dislocation. POSTOPERATIVE: Multimodal analgesia, VTE prophylaxis (aspirin or rivaroxaban for 35 days), early mobilization, hip precautions for 6 weeks.

VIVA SCENARIOStandard

EXAMINER

"You are performing a primary THA via posterior approach. Walk me through the key anatomical structures and danger zones you encounter."

EXCEPTIONAL ANSWER

Starting from superficial to deep: SKIN INCISION: Curved 10-15cm centered on greater trochanter. FASCIA LATA: Incised in line with incision. GLUTEUS MAXIMUS: Split in line with fibers - TRUE internervous plane (dual innervation from superior and inferior gluteal nerves). DANGER 1: Inferior gluteal neurovascular bundle enters proximal gluteus maximus. DEEP LAYER: Short external rotators identified superior to inferior - Piriformis, Superior gemellus, Obturator internus, Inferior gemellus, Quadratus femoris. DANGER 2: Sciatic nerve runs 2cm posterior to piriformis - must protect throughout. I tag each rotator with suture before cutting. DANGER 3: Superior gluteal nerve exits sciatic notch 25-40mm proximal to GT tip - stay greater than 5cm distal to GT. CAPSULE: T-shaped capsulotomy, tag all flaps for later repair. ACETABULUM: Place 3 retractors (anterior, posterior, inferior). DANGER 4: External iliac vessels 15-25mm anterior to anterior wall - no anteroinferior screws. DANGER 5: Femoral nerve 40-60mm anteromedial - anterior retractor stays on bone. POSTERIOR WALL: Protect during reaming - sciatic nerve posteriorly.

VIVA SCENARIOStandard

EXAMINER

"What is the Lewinnek safe zone and why is it important? How do you assess and optimize stability intraoperatively?"

EXCEPTIONAL ANSWER

The Lewinnek safe zone describes optimal acetabular component positioning based on Lewinnek's classic study: 40-45° inclination (radiographic angle) and 15-20° anteversion. Cups positioned within this zone have 1.5% dislocation rate compared to 6.1% outside the zone. However, the safe zone is not absolute - it's a guideline. I also consider the COMBINED ANTEVERSION concept: cup anteversion plus stem anteversion should equal 25-45° for optimal stability and impingement-free ROM. INTRAOPERATIVE STABILITY ASSESSMENT: I use the STABLE approach - (1) Trial components before final implants. (2) Test ANTERIOR stability: full extension with 40° external rotation - should remain reduced. (3) Assess POSTERIOR stability: 90° flexion, 40° internal rotation, adduction - should remain reduced. (4) Both directions stable. (5) Leg length assessment: overlap patellae, measure from fixed pelvic point. (6) Examine ROM for impingement. If unstable: I adjust cup position if possible, consider larger head size (36mm preferred over 32mm), adjust neck length to optimize offset and tension, ensure no impingement. Final step is CAPSULAR REPAIR which reduces dislocation 3-4 fold.