Dynamic Hip Screw (DHS) for Intertrochanteric Fracture

Absolute Indications:

• Stable intertrochanteric fractures (AO/OTA 31-A1) - the ideal DHS fracture pattern
• Simple pertrochanteric fractures (AO/OTA 31-A2.1) with intact medial cortex and lateral wall
• Lateral wall thickness >20mm on pre-reduction imaging (Palm criteria)
• Basicervical femoral neck fractures in elderly with osteoporotic bone (selected cases)

Relative Indications:

• Selected A2.2 patterns with reconstructable medial cortex
• Patients where intramedullary device contraindicated (severe femoral bowing, narrow canal)
• Surgeon expertise with DHS for borderline patterns

Australian Context:

• ANZHFR 2023: 48% of intertrochanteric fractures receive DHS, 52% receive cephalomedullary nail
• Medicare MBS item 47528: Internal fixation of intertrochanteric fracture - $1,247.55
• LMWH or DOAC for VTE prophylaxis (enoxaparin 40mg daily or rivaroxaban 10mg daily for 35 days)

Absolute Contraindications:

• Reverse obliquity patterns (AO 31-A3) - fracture line runs superomedial to inferolateral, DHS cannot resist varus collapse
• Lateral wall thickness <20mm or comminuted - lateral wall required for barrel plate stability
• Subtrochanteric extension - DHS cannot control long lever arm of distal fragment
• Pathological fractures with metastatic bone disease - inadequate bone for screw purchase

Relative Contraindications:

• Severe osteoporosis with eggshell cortex - high cut-out risk
• Combined neck-shaft fractures - complex pattern better suited to reconstruction nail
• Fracture in young patient (<50 years) - consider anatomic reduction ORIF if fit for longer surgery
• Morbid obesity (BMI >40) - increased mechanical demands

Bony Landmarks:

• Greater trochanter (GT) - most prominent lateral hip landmark, entry point for guide wire
• Lesser trochanter - level of neck cut reference, attachment of iliopsoas
• Intertrochanteric crest - joins GT to LT posteriorly, defines fracture region
• Calcar femorale - dense medial cortex, critical for load-bearing in DHS

Femoral Neck Anatomy:

• Normal neck-shaft angle: 125-135° (average 130°)
• Femoral neck anteversion: 10-15° (affects guide wire rotation)
• Trabecular architecture: Compressive trabeculae (medial), tensile trabeculae (lateral), Ward's triangle (central deficiency)
• Cortical thickness: Medial cortex thickest (calcar), lateral thinnest

Vascular Anatomy:

• Profunda femoris artery: Runs posterior to femur in adductor canal, gives off perforating branches
• Perforating arteries: 3-4 branches traverse vastus lateralis from posterior to anterior
• Medial femoral circumflex artery (MFCA): Main blood supply to femoral head - runs along posterior neck, protected by leaving quadratus femoris intact
• Lateral femoral circumflex artery: Supplies anterolateral thigh, branches encountered during approach

Neural Anatomy:

• Sciatic nerve: Exits pelvis below piriformis, runs posterior to hip 5cm posterior to GT, at risk with posterior retractor placement
• Superior gluteal nerve: Exits above piriformis, 3-5cm proximal to GT tip - safe zone below GT
• Femoral nerve: Lies anteromedial in femoral triangle, protected by strictly lateral approach
• Lateral femoral cutaneous nerve: Exits lateral to ASIS, can be injured with anterior extension

Surface Landmarks:

• Palpate greater trochanter - most prominent lateral bony point
• Femoral shaft axis - line from GT to lateral femoral condyle
• Vastus ridge - palpable ridge on lateral femur distal to GT

Incision:

• Start just distal to GT tip, extend distally along lateral femoral shaft
• Length: 8-12cm (adjust for body habitus and plate length)
• Orientation: Straight, parallel to femoral shaft axis

Superficial Dissection:

1. Incise skin and subcutaneous fat to fascia lata
2. Identify and incise fascia lata (iliotibial band) in line with skin incision
3. Fascia lata is thick, strong layer - incise carefully to avoid muscle
4. Retract edges to expose vastus lateralis muscle belly

Deep Dissection: Two options for vastus lateralis:

1. SPLIT technique (preferred): Split muscle in line with fibers running obliquely from superolateral to inferomedial. Less bleeding, preserves muscle function.
2. ELEVATE technique: Elevate muscle anteriorly off lateral intermuscular septum. More bleeding, but may give better exposure.

Control perforating vessels from profunda femoris with electrocautery as encountered.

Internervous Plane:

• This approach is NOT a true internervous plane
• Vastus lateralis is supplied by femoral nerve throughout its belly
• The approach works by SPLITTING vastus lateralis in line with muscle fibers
• This is an INTRAmuscular plane, not INTERnervous
• Safe because splitting in fiber direction minimizes denervation

Comparison to Other Hip Approaches:

• Posterior approach: Gluteus maximus (inf. gluteal) vs gluteus medius (sup. gluteal) - true internervous superficially
• Anterior approach: Sartorius (femoral) vs TFL (sup. gluteal) - true internervous
• Anterolateral (Watson-Jones): TFL vs gluteus medius - NOT internervous (both sup. gluteal)
• Lateral (Hardinge): Splits gluteus medius - NOT internervous
• Direct lateral (DHS): Splits vastus lateralis - NOT internervous (all femoral)

Standard Imaging:

• AP pelvis - shows both hips for comparison, measures neck-shaft angle
• Lateral hip (cross-table or shoot-through) - essential for assessing posterior comminution
• Traction view if fracture severely displaced (reduces fracture, better pattern assessment)

Advanced Imaging (When Indicated):

• CT scan if:
  • Complex pattern or concern for lateral wall integrity
  • Occult femoral neck fracture suspected (5% have concomitant intracapsular fracture)
  • Pathological fracture requiring assessment of bone stock
• MRI rarely indicated in elderly trauma

AO/OTA 31-A Classification:

• 31-A1: Simple pertrochanteric (2 fragments)

  • A1.1: Along intertrochanteric line - IDEAL for DHS
  • A1.2: Through greater trochanter
  • A1.3: Below lesser trochanter

• 31-A2: Multifragmentary pertrochanteric (>2 fragments)

  • A2.1: One intermediate fragment - DHS suitable if lateral wall intact
  • A2.2: Several intermediate fragments - NAIL preferred
  • A2.3: Extending more than 1cm below lesser trochanter - NAIL preferred

• 31-A3: Intertrochanteric/reverse obliquity

  • A3.1: Simple oblique - NAIL MANDATORY
  • A3.2: Simple transverse - NAIL MANDATORY
  • A3.3: Wedge or comminuted - NAIL MANDATORY

Palm Criteria (Palm et al. JBJS 2007):

• Measure lateral wall thickness on AP radiograph
• Distance from lateral cortex to level where lag screw will sit
• >20mm = Intact lateral wall → DHS appropriate
• <20mm = Deficient lateral wall → High failure risk, NAIL preferred

Why Lateral Wall Matters:

• DHS barrel plate sits on lateral cortex
• If lateral wall fractures during surgery → implant loses buttress
• Lateral wall fracture converts stable to unstable pattern
• Failure rate increases from 5% to 40% with lateral wall fracture

Plate Angle Selection:

• 135° angle (standard): Most common, suits most patients
• 150° angle: For high neck-shaft angle (>135°), or coxa valga
• Match angle guide to plate angle selected

Plate Length:

• 4-hole barrel plate: Standard for most fractures
• 6-hole or longer: Consider for osteoporosis, subtrochanteric extension, comminution

Lag Screw Length:

• Typically 85-105mm in adults
• Measure intraoperatively to confirm (should end 5-10mm from subchondral bone)
• Select based on guide wire measurement minus 5-10mm

Procedure-Specific Risks:

• Cut-out (5-15%): Lag screw migration through femoral head - most common mechanical complication
• Non-union (<5%): Higher with varus malalignment, poor medial cortex contact
• Malunion: Varus, shortening, rotational deformity
• AVN (<2% in extracapsular fractures - rare because blood supply preserved)
• Infection (1-3%): Superficial or deep
• DVT/PE (10-20% without prophylaxis, <5% with prophylaxis)
• Need for revision surgery (5-10%)

General Risks:

• Bleeding requiring transfusion (20-30%) - elderly patients often anemic at baseline
• Medical complications (cardiac 5%, respiratory 5%, renal 3%, delirium 10-30%)
• Mortality: 30-day 5-10%, 1-year 20-30% in elderly with hip fracture

Functional Outcome:

• Most patients mobilise weight-bearing as tolerated (WBAT)
• 50% return to pre-injury function at 1 year
• 30% remain below baseline function at 1 year
• Many require ongoing mobility aids (frame, stick)

Step 1: Anaesthesia and Patient Positioning

Patient under general or spinal anaesthesia on fracture table. Affected leg in traction boot with longitudinal traction applied. Internal rotation 10-15 degrees to correct typical external rotation deformity of distal fragment. Perineal post well-padded and positioned lateral to genitals. Contralateral leg abducted in hemilithotomy or extended. Confirm C-arm can obtain clear AP and lateral views BEFORE draping.

Step 2: Closed Reduction

Apply gentle longitudinal traction and internal rotation. Check reduction on AP and lateral C-arm views. ACCEPTABLE REDUCTION CRITERIA:

• Anatomic or slight valgus alignment (5-10°) - valgus preferred over varus
• Restoration of medial cortical continuity (CRITICAL for DHS biomechanics)
• No posterior sag on lateral view (common pitfall)
• Normal or slightly increased neck-shaft angle (125-135°)
• Rotation corrected (patella facing ceiling)

If closed reduction inadequate, use Schanz pin joystick in greater trochanter to manipulate proximal fragment. DO NOT proceed until reduction acceptable.

Step 3: Skin Incision and Superficial Dissection

Palpate greater trochanter. Make longitudinal incision 8-12cm, starting just distal to GT, extending distally along lateral femoral shaft. Incise skin and subcutaneous tissue to fascia lata. Identify and incise fascia lata (iliotibial band) in line with skin incision. Retract edges with self-retaining retractor to expose vastus lateralis muscle.

Step 4: Deep Dissection and Femoral Exposure

Two options for vastus lateralis management:

1. SPLIT along muscle fibres (preferred - less bleeding)
2. ELEVATE anteriorly off lateral intermuscular septum

Expose lateral femoral cortex for plate length required (minimum 8-10cm). Identify and coagulate perforating vessels from profunda femoris as encountered. Clear periosteum ONLY where plate will sit - minimize periosteal stripping.

Step 5: Guide Wire Insertion and Positioning

Attach angle guide (135° standard) to lateral femoral cortex at level of lesser trochanter. Entry point: junction of proximal and middle thirds of femur, at or just above lesser trochanter level. Advance guide wire under fluoroscopy toward femoral head centre.

TARGET POSITION (CRITICAL):

• Centre-centre position in femoral head on AP view
• Centre-centre OR inferior-centre on lateral view
• NEVER superior position - increases cut-out 3-4 fold

Advance wire to within 5-10mm of subchondral bone. Calculate Tip-Apex Distance (TAD) at this point.

Step 6: Tip-Apex Distance Calculation

Calculate TAD to confirm acceptable wire position:

1. Measure tip-to-apex distance on AP view (in mm)
2. Measure tip-to-apex distance on lateral view (in mm)
3. Correct for magnification using known wire/screw diameter
4. Sum both measurements: TAD = AP distance + Lateral distance

TARGET: TAD <25mm

• TAD <25mm: Cut-out risk 2-5%
• TAD 25-30mm: Cut-out risk increases
• TAD >30mm: Cut-out risk 6-fold higher (30%+)

If TAD >25mm, REPOSITION guide wire before proceeding.

Step 7: Triple Reaming

Perform triple reaming over guide wire to measured depth (5-10mm short of subchondral bone). Triple reaming creates a smooth, three-part channel:

• Outer diameter for barrel plate seating
• Middle diameter for lag screw threads
• Inner diameter for lag screw core

This allows:

• Easy lag screw insertion without resistance
• Lag screw SLIDING for dynamic compression as fracture settles

Irrigate during reaming to prevent thermal necrosis. Confirm depth with gauge.

Step 8: Lag Screw Insertion

Select lag screw length based on measurement (typically 85-100mm). Insert over guide wire through reamed channel. Advance to within 5-10mm of subchondral bone - check with fluoroscopy.

CONFIRM FINAL POSITION:

• Centre-centre or inferior-centre on AP view
• Centre-centre or inferior-centre on lateral view
• Calculate and DOCUMENT final TAD - MUST be <25mm
• Screw threads fully within femoral head

Step 9: Barrel Plate Application

Slide barrel plate over lag screw. CRITICAL: Seat plate FLUSH against lateral femoral cortex - plate must NOT be proud. Ensure plate aligned with femoral shaft axis without flexion/extension or rotation. Apply provisional fixation with one distal cortical screw.

PLATE SEATING CHECK:

• No gap between plate and cortex
• Plate parallel to femoral shaft
• No rotation of plate
• Barrel fully engaged on lag screw

Step 10: Cortical Screw Fixation

Insert cortical screws through remaining plate holes achieving BICORTICAL purchase. Minimum 4 cortices of fixation distally (2 screws × 2 cortices). Consider anti-rotation screw in proximal hole above barrel for added rotational stability of femoral head. Confirm ALL screws bicortical on fluoroscopy.

SCREW PLACEMENT GOALS:

• Bicortical purchase (30-44mm screws typical)
• Perpendicular to plate and cortex
• All screw tips visible on lateral view
• No screws in fracture zone

Step 11: Compression and Final Fluoroscopic Check

Remove guide wire from lag screw. Apply compression through barrel plate compression screw mechanism to engage dynamic lag effect. Release traction gradually and observe for stability.

COMPREHENSIVE FINAL CHECK:

1. Reduction maintained (valgus acceptable, medial cortex intact)
2. Lag screw centre-centre or inferior-centre on BOTH views
3. TAD <25mm DOCUMENTED in operative note
4. Screw 5-10mm from subchondral bone, NO joint penetration
5. Plate FLUSH on lateral cortex
6. ALL screws bicortical
7. Rotation and length correct (compare to contralateral leg)
8. Compression applied - fracture impacted

Step 12: Wound Closure and Post-operative Management

Copious irrigation with saline. Meticulous haemostasis with electrocautery. Consider drain for high-risk patients (anticoagulation, large haematoma anticipated). Repair vastus lateralis muscle if elevated. Close fascia lata with strong absorbable suture (0 or 1 Vicryl) - provides soft tissue coverage of implant. Subcutaneous closure with 2-0 absorbable. Skin with staples or subcuticular suture. Sterile dressing.

Avascular Necrosis (<2% for extracapsular fractures):

• Rare in intertrochanteric fractures because blood supply preserved
• Medial femoral circumflex artery runs along posterior neck - protected by leaving quadratus femoris intact
• May occur if lag screw damages MFCA or with posterior perforation
• Management: If symptomatic, consider arthroplasty

Nerve Injury (<1%):

• Sciatic nerve: Posterior retractor placement, excessive traction
• Superior gluteal nerve: Proximal dissection above GT
• Pudendal nerve: Perineal post malposition
• Prevention: Careful retractor placement, padded post lateral to genitals, limit traction
• Management: Document, EMG at 3 weeks, observation (most neuropraxia recover)

Heterotopic Ossification (5-10% radiographic, 1-2% symptomatic):

• Less common than in THA
• Risk factors: Head injury, burns, prolonged immobilisation
• Prevention: Not routine - consider indomethacin if high risk
• Management: Observation if asymptomatic, excision if severe restriction

Hip Fracture Epidemiology:

• 26,000+ hip fractures annually in Australia
• 50% intertrochanteric, 45% intracapsular, 5% subtrochanteric
• Mean age: 84 years for women, 80 years for men
• Female:Male ratio 3:1

Implant Selection Trends:

• Intertrochanteric fractures: 48% DHS, 52% cephalomedullary nail
• Trend toward increasing nail use for all patterns
• DHS use declining but remains appropriate for stable patterns

Timing of Surgery:

• ANZHFR target: Surgery within 48 hours for 80% of patients
• Current performance: 72% achieve this target
• Delay beyond 48 hours associated with 10% increased mortality per day

30-Day Outcomes:

• Mortality: 7-10%
• Medical complications: Cardiac 5%, Pneumonia 6%, UTI 10%, Delirium 25%
• Return to theatre: 2-3%

1-Year Outcomes:

• Mortality: 20-30% (highest in first 3 months)
• Residential care admission: 25% (previously community-dwelling)
• Return to pre-injury function: 50%
• Mobility aids required: 70%

Tip-Apex Distance (Baumgaertner et al. JBJS 1995):

• Landmark paper defining TAD
• Cut-out rate: 2% if TAD <25mm vs 16% if TAD >25mm
• Superior screw position increased cut-out 3-4 fold
• MUST KNOW for exam - cite this paper

Lateral Wall Importance (Palm et al. JBJS 2007):

• Lateral wall thickness <20mm → failure rate 40%
• Lateral wall thickness >20mm → failure rate 5%
• Pre-operative CT can assess wall integrity
• Lateral wall fracture converts stable to unstable pattern

DHS vs Nail for Stable Fractures (Cochrane Review 2010, updated 2017):

• No significant difference in outcomes for stable A1/A2.1 fractures
• Similar mortality, function, reoperation rates
• DHS slightly shorter operative time and less blood loss
• Nail has theoretical advantage of load-sharing but not borne out in stable fractures

DHS vs Nail for Unstable Fractures (Multiple RCTs):

• Nail superior for A2.3 and A3 patterns
• Lower failure rate with nail for unstable fractures
• Parker 2012, Reindl 2015, Zhang 2017 meta-analyses support nail for unstable patterns

Early Surgery (Moran et al. JBJS 2005):

• Delay beyond 48 hours increases mortality 10% per day
• Complications increase with delay
• Surgery within 36 hours optimal if medically cleared
• Supports current ANZHFR 48-hour target

Orthogeriatric Co-management (Grigoryan et al. BMC Geriatr 2014):

• Orthogeriatric care reduces mortality 20-30%
• Reduces length of stay
• Reduces complications (delirium, pressure injuries, infections)
• Cost-effective intervention - standard of care in Australia

VTE Prophylaxis (NHMRC Guidelines):

• LMWH (enoxaparin 40mg daily) or DOAC (rivaroxaban 10mg daily) for 35 days
• Start 6-12 hours postoperatively (balance bleeding vs VTE risk)
• Mechanical prophylaxis: TED stockings, foot pumps, early mobilisation
• High-risk (previous VTE): Extended prophylaxis, consider IVC filter

Antibiotic Prophylaxis (eTG - Therapeutic Guidelines):

• Cefazolin 2g IV within 60 minutes of incision
• 4g if >120kg body weight
• Penicillin allergy: Vancomycin 15-20mg/kg IV (max 2g)
• Single dose sufficient - no benefit to extended prophylaxis

Medicare MBS Item Numbers:

• 47528: Internal fixation of intertrochanteric fracture - $1,247.55
• Includes DHS, cephalomedullary nail, or other fixation devices

ANZHFR Quality Standards:

• Surgery within 48 hours (target 80%)
• Orthogeriatric care (target 100%)
• Pressure injury prevention
• Delirium screening and prevention
• Falls prevention and bone health assessment