Extended Trochanteric Osteotomy (ETO)

Definition

Anatomy of the Osteotomy Fragment

• The greater trochanter with attached gluteus medius and minimus (abductors)
• The lateral femoral cortex extending distally (variable length, typically 10-15 cm)
• The origin of vastus lateralis distally (sleeve of tissue maintained)

Fig 1: ETO - musculotendinous sleeve maintained on the fragment (Campbell's Operative Orthopaedics, 15th Ed)

Comparison with Other Trochanteric Osteotomies

Indications

1. Well-fixed cemented or cementless femoral component that cannot be removed by conventional means
2. Cement mantle extending to diaphysis - to allow safe removal under direct vision
3. Broken/fractured femoral stem - distal fragment inaccessible from above
4. Severe femoral deformity - bowing, angular deformity, or previous osteotomy preventing standard reaming
5. Periprosthetic joint infection - when complete cement/implant removal is mandatory
6. Marked femoral osteolysis - with cortical thinning at risk of iatrogenic fracture
7. Significant limb length discrepancy - distal translation of fragment allows abductor tensioning
8. Extensive heterotopic ossification - requiring wide surgical access
9. Failed prior standard trochanteric osteotomy - nonunion with distorted anatomy
10. Severe protrusio acetabuli - extensile acetabular exposure needed

Note: ETO is most appropriately used when a cementless femoral revision is planned, because cement intrusion into the osteotomy site may inhibit union. (Campbell's, p. 338)

Preoperative Planning

• Full-length AP and lateral radiographs of the femur
• Templating to determine osteotomy length: distal extent must be 5-6 cm proximal to the femoral isthmus to allow 5-6 cm of cortical contact for the revision stem
• CT scan to assess bone stock and cement extent
• Plan for revision stem length - stem must bypass the distal osteotomy by at least 2 cortical diameters (~5 cm)
• Cerclage cables and strut allografts prepared

Surgical Technique (Younger et al. - Technique 4.15, Campbell's)

Step-by-Step:

1. Mark osteotomy length so the distal extent of the well-fixed prosthesis is maximally exposed, leaving 5-6 cm of femoral isthmus intact for endosteal contact by the revision stem (Fig. 4.146)
2. Expose the hip via posterolateral approach with circumferential exposure of both implants
3. Protect the sciatic nerve throughout the entire procedure
4. Dislocate the hip - or perform osteotomy before dislocation if complicated by stem subsidence, acetabular protrusion, or hip stiffness
5. Position the thigh in internal rotation
6. Incise the vastus lateralis along its posterior edge to the level of the distal extent of the planned osteotomy
7. Mark the osteotomy longitudinally just lateral to the linea aspera, extending distally to the level determined by preoperative radiographs (Fig. 4.147A)
8. Create posterior cortex osteotomy: Using a thin high-speed burr, make multiple perforations in the posterior femoral cortex and connect them, skirting the lateral edge of the underlying femoral component
9. Transverse distal cut: Divide the lateral cortex transversely at the predetermined distal level
10. Anterior cortex perforations: Perforate the anterior cortex at multiple sites, creating a fragment of approximately one-third the circumference of the femur; leave as much vastus lateralis attached to the fragment as possible
11. Divide the superior anterior cortex with an oscillating saw (the burr may not be long enough in the trochanteric region)
12. Controlled fracture: Insert two or more broad osteotomes into the posterior limb and lever from posterior to anterior, creating a controlled fracture through the perforated anterior cortex while leaving anterior soft-tissue attachments undisturbed (Fig. 4.147B)
13. Reflect fragment anteriorly - lateral surface of femoral component is now visible; remove cement from interfaces under direct vision to allow stem extraction
14. For well-fixed cementless stem: Pass a Gigli saw beneath the collar directed distally, following the medial edge of the component (Fig. 4.147C); divide the interface to the distal extent of porous surface
15. Alternative: Shorten the osteotomy and divide the femoral component with a metal-cutting burr at the junction of triangular and cylindrical portions; remove distal segment with a trephine reamer
16. Prophylactic cerclage: Place a cable/wire around the femoral shaft distal to the osteotomy to prevent fracture propagation
17. Revision stem placement: Ream the diaphysis and impact the revision stem
18. Repair the osteotomy: Multiple cerclage cables; shape the undersurface of the fragment to fit the revision prosthesis; advance distally if needed for abductor tensioning
19. Reinforce if thin: If the fragment is thin and fragile, reinforce with a cortical allograft strut

Fig 2: ETO for difficult stem removal. A: Lines of osteotomy along lateral border of stem. B: Fragment reflected anteriorly. C: Gigli saw passed down medial side of stem disrupting bone ingrowth. (Campbell's Operative Orthopaedics, 15th Ed)

Fragment Fixation Methods

1. Multiple cerclage cables (most common) - 2 to 4 cables around the fragment and shaft; cables provide circumferential compression
2. Cable-plate systems (e.g., Accord trochanteric fixation plate) - proximal hooks capture the trochanteric fragment; plate extension is fixed to femur with cerclage cables; provides better resistance to shear and proximal migration
3. Cortical allograft struts - used when the fragment is thin/osteopenic; placed on the lateral cortex and secured with cables; augments fixation and provides biological advantage

• The hip should not be abducted more than 10-15 degrees during reattachment (excess strain leads to avulsion/nonunion)
• Anatomic reduction or slight distal overlap leads to union within 6 months
• Fragment with superior/medial tilt invariably leads to delayed union or nonunion
• Compression across the osteotomy is required for union

Postoperative Care

• Weight bearing: Toe-touch or partial weight bearing for 8-12 weeks
• Hip precautions: Abduction brace in some patients; avoid extreme flexion and adduction
• Physiotherapy: Graduated abductor strengthening once radiographic callus is evident
• Serial radiographs at 6 weeks, 3 months, 6 months to assess union
• Full weight bearing typically at 3 months if union is progressing

Outcomes

• Union rate: Meta-analysis reports 93% union rate with ETO (Campbell's, p. 338)
• Stem subsidence >5 mm: Reported in 7% with this technique
• Dislocation rate: ~3.7% (systematic review data; higher - up to 5% - in periprosthetic fracture cases)
• Aseptic loosening: ~1% (higher in periprosthetic fracture cases)
• Better outcomes with cementless reconstruction vs. cemented revision

Complications

Intraoperative

1. Uncontrolled fracture propagation distally - prevented by prophylactic cerclage cable below osteotomy
2. Sciatic nerve injury - must be protected throughout; especially at risk with limb lengthening
3. Vascular injury - superficial femoral artery at risk during cable passage
4. Fragment comminution - especially in osteoporotic bone

Early Postoperative

1. Dislocation - higher risk due to abductor disruption; rate ~3.7%
2. Infection - increased operative time and blood loss increase risk
3. Fragment displacement/proximal migration - if fixation fails

Late

1. Trochanteric nonunion - most important complication; reported up to 20% in some series; results in:
   • Trendelenburg gait
   • Abductor weakness and hip instability
   • Pain and reduced function
2. Cerclage wire/cable breakage - common even with solid union; usually not clinically significant
3. Stem subsidence - particularly if cement intrudes into osteotomy; occurs in ~7%
4. Heterotopic ossification - consider prophylaxis in high-risk patients
5. Femoral component loosening - rare (~1%)
6. Trochanteric bursitis - from prominent hardware

Contraindications (Relative)

• Planned cemented femoral reconstruction (cement prevents osteotomy union)
• Severe osteoporosis where fragment too fragile to hold fixation
• Active deep infection without plan for thorough debridement

Modified Techniques

1. Lakstein modification: Posterior capsule and short external rotators left intact to reduce dislocation risk
2. Wagner (anteriorly-based) osteotomy: Anteriorly based rather than laterally based; used when the lateral cortex is thin or compromised
3. Paprosky (laterally-based) osteotomy: Standard ETO as described above; most widely used

Key Points for Examination

Extended Trochanteric Osteotomy (ETO)

Definition

Anatomy of the Fragment

• Greater trochanter with attached gluteus medius and minimus (abductors) proximally
• Lateral femoral cortex extending distally (variable length, typically 10-15 cm)
• Origin of vastus lateralis distally - preserved to prevent proximal migration

Fig 1: ETO - Gluteus medius, gluteus minimus proximally and vastus lateralis distally remain attached to the fragment. (Campbell's Operative Orthopaedics, 15th Ed)

Types of Trochanteric Osteotomy - Comparison

Indications

1. Well-fixed cemented femoral component with cement extending to diaphysis - allows removal under direct vision
2. Well-fixed cementless femoral component that cannot be removed conventionally
3. Broken/fractured femoral stem - distal fragment inaccessible from above
4. Severe femoral deformity - bowing, angular deformity, or previous femoral osteotomy
5. Periprosthetic joint infection - complete implant and cement removal mandatory
6. Extensive femoral osteolysis - cortical thinning with risk of iatrogenic fracture during extraction
7. Significant limb length discrepancy - distal translation of fragment allows precise abductor tensioning
8. Extensive heterotopic ossification requiring wide access
9. Failed prior trochanteric osteotomy with nonunion and distorted anatomy
10. Severe protrusio acetabuli requiring extensile acetabular exposure

Important: ETO is most appropriately used when a cementless femoral revision is planned, because cement intrusion into the osteotomy site may inhibit union. (Campbell's, p. 338)

Preoperative Planning

• Full-length AP and lateral radiographs of entire femur
• Templating: Osteotomy length planned so distal extent exposes the prosthesis fully, leaving 5-6 cm of femoral isthmus intact for revision stem cortical contact
• The revision stem must bypass the distal osteotomy by at least 2 cortical diameters (~5 cm)
• CT to assess bone stock and cement extent
• Prepare cerclage cables, cable plates, and strut allografts

Surgical Technique (Younger et al. - Technique 4.15, Campbell's)

Steps:

Fig 2: ETO steps. A: Lines of osteotomy along lateral border of stem. B: Fragment reflected anteriorly exposing lateral stem surface. C: Gigli saw passed down medial side disrupting bone ingrowth. (Campbell's Operative Orthopaedics, 15th Ed)

Fig 3: A,B: Porous femoral component well-fixed, requiring femoral revision. C,D: ETO simplified removal without bone loss; note callus formation at 3 months with cerclage cable fixation. (Campbell's Operative Orthopaedics, 15th Ed)

Fixation of the Osteotomy Fragment

1. Multiple cerclage cables (most common) - 2-4 cables; provide circumferential compression
2. Cable-plate systems (e.g., Accord plate) - proximal hooks capture the trochanteric fragment; plate extension fixed to femur with cerclage cables; provides better resistance to shear and proximal migration
3. Cortical allograft struts - placed over the lateral cortex and secured with cables; used when the fragment is thin/osteopenic; provides mechanical reinforcement and biological union potential

• Hip must not be abducted >10-15 degrees during reattachment - excess strain causes avulsion and nonunion
• Anatomic reduction or slight distal overlap leads to union within 6 months
• Fragment with superior or medial tilt invariably leads to delayed union or nonunion
• Compression across the osteotomy is essential

Postoperative Protocol

• Weight bearing: Toe-touch or partial weight bearing for 8-12 weeks
• Hip precautions: Avoid extreme flexion, adduction, and internal rotation; abduction brace in selected patients
• Serial radiographs at 6 weeks, 3 months, and 6 months to assess union
• Graduated abductor strengthening once radiographic callus is confirmed
• Full weight bearing typically at 3 months if union progressing well

Outcomes

Complications

Intraoperative

1. Uncontrolled fracture propagation distally - prevented by prophylactic distal cerclage
2. Sciatic nerve injury - must be protected; risk increased with limb lengthening
3. Vascular injury - superficial femoral artery at risk during cable passage
4. Fragment comminution - in osteoporotic bone

Early Postoperative

1. Dislocation - abductor disruption increases risk (~3.7%; higher in periprosthetic fracture cases)
2. Infection - increased by longer operative time and blood loss
3. Fragment displacement or proximal migration - fixation failure

Late

1. Trochanteric nonunion - most significant complication; up to 20% in some series; leads to:
   • Trendelenburg gait and lurch
   • Abductor weakness with hip instability
   • Persistent pain and reduced function
2. Cerclage wire/cable breakage - common even after solid union; usually not clinically significant
3. Stem subsidence (~7%) - especially if cement intrudes into osteotomy site
4. Heterotopic ossification - prophylaxis considered in high-risk patients
5. Femoral component aseptic loosening (~1%)
6. Trochanteric bursitis from prominent hardware

Modified Techniques

1. Lakstein modification: Posterior capsule and short external rotators left intact to reduce dislocation risk
2. Wagner (anteriorly-based) osteotomy: Anteriorly based rather than laterally based; used when lateral cortex is thin
3. Paprosky (laterally-based) osteotomy: Standard ETO as described - most widely used

Summary Table