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

Direct Vertebral Rotation (DVR)

Introduction

• Coronal plane - lateral curve (Cobb angle)
• Sagittal plane - loss of normal kyphosis/lordosis
• Transverse (axial) plane - vertebral rotation (responsible for rib hump and cosmetic deformity)

Definition

Background: Pathomechanics of Scoliosis Deformity

Limitations of Simple Rod Derotation (SRD)

1. A posteromedial vector force that corrects the coronal curve
2. The rod rotates on its own axis, which may paradoxically aggravate vertebral rotation in severe/rigid curves (because the direction of rod rotation axis coincides with the direction of vertebral rotation)
3. In mild/flexible curves, the screw may glide on the rod, providing some but incomplete rotational correction
4. Axial/transverse plane correction is minimal and unreliable with rod derotation alone

Principle of DVR

• The derotation is applied directly to the vertebral body via pedicle screws (which traverse the pedicle and enter the vertebral body)
• Force is applied simultaneously from both concave and convex sides
• Direction: opposite to the pathological vertebral rotation
  • For right thoracic scoliosis: vertebrae are rotated counter-clockwise (correcting the clockwise pathological rotation)
• The procedure is performed en bloc (multiple levels simultaneously) using a Vertebral Column Manipulator (VCM), or sequentially at individual levels

"The direct vertebral rotation is opposite to that of the vertebral rotation in the thoracic curve; apical and juxta-apical vertebrae are rotated clockwise for right thoracic curves in the transverse plane." (Campbell's Operative Orthopaedics, 15th Ed, Technique 40.14, p. 2027)

Prerequisite: Segmental Pedicle Screw Fixation

• Hooks and sublaminar wires do not provide a strong enough purchase to transmit rotational forces to the vertebral body
• Pedicle screws are the only implant that directly engages the vertebral body via the pedicle
• Bilateral screws at each level are needed to apply a couple force (not just a unidirectional force) allowing true rotation rather than translation

Instrumentation - Vertebral Column Manipulator (VCM)

• Implant holders (derotator tubes) are attached to pedicle screws on both concave and convex sides
• Connected to each other by preloaded bridge nuts/cross-connectors at their cephalad ends - creating a triangulated or quadrilateral rigid construct
• For flexible curves: single triangulated segment at apex
• For large/rigid curves: quadrilateral frame connecting apical and juxta-apical vertebrae
• Handles allow application of rotational forces:
  • Superior handle (vertical): controls rotation
  • Convex horizontal handle: aids in directionality
• The entire construct rotates the scoliosis apex en bloc in the transverse plane

Surgical Technique (Technique 40.14, Campbell's Operative Orthopaedics, 15th Ed)

Step-by-Step:

• This is mandatory - unilateral screws are insufficient for DVR
• Screws must be accurately placed (free-hand technique, fluoroscopy, or navigation)
• The direct vertebral rotation direction is opposite to the vertebral rotation in the thoracic curve; for right thoracic curves, apical and juxta-apical vertebrae are rotated clockwise in the transverse plane (i.e., the correction is counter-clockwise/anti-clockwise for the body rotation)
• Identify the neutral (least rotated) vertebra distally and begin derotation proximal to this level

• A mean arterial pressure (MAP) of at least 70 mmHg must be maintained throughout, because corrective forces placed on the spine can compromise spinal cord perfusion

• Derotate the vertebrae as much as possible
• This can be done en bloc (multiple levels simultaneously) or at each individual level

Fig 1: Direct Vertebral Rotation. Screw derotators applied to bilateral pedicle screws at apical vertebrae. Downward force on convex side, upward force on concave side achieves vertebral derotation. (Campbell's Operative Orthopaedics, 15th Ed, Fig 40.67)

• Push down on the convex screws and pull up on the concave screws simultaneously
• An assistant applies downward pressure on the convex apical ribs to aid in derotation
• This combined maneuver corrects deformity in all three planes simultaneously

• This process can be repeated multiple times until the desired correction is obtained

• With modern rigid segmental instrumentation, patients ambulate immediately after surgery
• Bracing is rarely required
• Multimodal pain management and accelerated discharge protocols are used
• One study showed 31% decrease in hospital stay with such protocols

DVR in Different Curve Patterns (Suk Classification)

Advantages of DVR over Simple Rod Derotation

Indications

1. Adolescent idiopathic scoliosis (AIS) - primary indication; all Lenke curve types
2. Significant apical vertebral rotation - particularly where rib hump is the primary cosmetic concern
3. Rigid/severe curves (Cobb angle >45-50°) - where rod derotation alone is insufficient
4. Thoracic curves - best results; also applicable in thoracolumbar and lumbar curves
5. When bilateral pedicle screw construct is being used
6. As a supplementary maneuver to rod derotation in all three-dimensional corrections

Contraindications / Limitations

• Unilateral or hook/wire constructs - DVR cannot be performed without bilateral pedicle screws
• Severe osteoporosis - risk of screw pullout during derotation forces
• Very rigid curves - may require supplementary osteotomies (Ponte, Smith-Petersen)
• Neurological deficits requiring cautious force application

Outcomes and Evidence

Complications

1. Neurological deficit - most serious; risk from forceful derotation; prevented by continuous intraoperative neuromonitoring (IONM) with MEP and SSEP
2. Spinal cord ischemia - from reduced spinal perfusion during derotation; prevented by maintaining MAP ≥70 mmHg
3. Pedicle screw pullout - during derotation forces; risk with osteoporosis or misplaced screws
4. Pedicle fracture - from excessive rotational force
5. Incomplete derotation - in rigid curves; may need supplementary osteotomies
6. Proximal junctional kyphosis (PJK) - if instrumentation ends at a sagittal apex; use stable sagittal vertebra (SSV) concept
7. Distal junctional kyphosis (DJK) - ends in middle of structural curve; use Lenke criteria for level selection
8. Coronal decompensation - with selective thoracic fusion; lower instrumented vertebra should touch center sacral line
9. Infection, pseudarthrosis, implant failure - general spinal fusion complications

Comparison with Other Derotation Methods

Summary / Key Points