RECONSTRUCTION 2023, Jan, 08 | 12:00 am

Extended Trochanteric Osteotomy: Posterior Approach

Introduction

  • Total hip arthroplasty can provide predictable pain relief and improve function in patients with degenerative arthritis, and is now recognized as one of the most cost-effective surgical interventions. Despite the overwhelming success and long-term reliability of total hip arthroplasty, several situations necessitate the revision of the femoral component.

  • The use of an extended trochanteric osteotomy allows exposure of the proximal femur through the use of a controlled cortical fracture. This surgical technique is extremely helpful to facilitate the removal of a well-fixed femoral implant, to provide increased surgical exposure, and to provide concentric placement of a new implant. This technique will ultimately minimize undersizing of the femoral components, improve initial implant stability, and minimize the risk of cortical perforation.

  • In order to obtain a successful surgical result during femoral revision, the femoral stem must be removed with minimal bone loss, the remaining host bone must be prepared without inadvertent perforation, and a femoral implant must be inserted concentrically with adequate axial and rotational stability. The extended trochanteric osteotomy can facilitate these goals by allowing

    • Improved access to the implant-bone or implant-cement interface

    • Concentric reaming of the distal femur in patients with proximal femoral deformity

    • Appropriate abductor tensioning

    • Improved acetabular visualization

    • Predictable healing of the osteotomy

  • Familiarity with this surgical technique is crucial for surgeons who frequently perform revision arthroplasty or primary total hip arthroplasty in patients with proximal femoral deformity.

     

    Indications

  • In general, an extended trochanteric osteotomy should be performed if it is contemplated by the surgeon.

  • Common indications:

    • A well-fixed implant may require removal because of sepsis, recurrent dislocation due to femoral component malposition and/or inadequate offset,

       

      231

       

      Extended Trochanteric Osteotomy (Posterior)

       

      a poor track record, or the need to improve acetabular exposure. Removal of a well-fixed femoral implant can be very challenging. Extensive bone loss can occur while attempting to remove a well-fixed implant due to the inability to disrupt the bone-prosthesis interface distally with proximal exposure alone. While a cortical window can be helpful, this technique will weaken the remaining host bone and require a longer stem to bypass the stress riser.

      • The removal of retained distal cement may be necessary, and is equally challenging. Isolated proximal exposure has been shown to result in a higher prevalence of cortical perforation while attempting to remove distal cement. The length of the extended trochanteric osteotomy can be planned to allow easy visual access to the distal cement plug such that standard drills, taps, and curettes can be used to disrupt the bone-cement interface and facilitate the removal of retained cement.

      • Proximal femoral varus remodeling is observed in up to 30% of patients with a loose femoral stem. While component extraction may be relatively easy in these patients, the subsequent surgical reconstruction is challenging due to the deformed proximal bone.

        • The surgical options in patients with proximal femoral deformity include accepting the deformity and cementing a femoral component into the deformity or performing an extended trochanteric osteotomy, which will allow concentric reaming of the femoral canal.

        • Cementing a femoral stem into a varus-remodeled femur is recommended only in a low-demand patient due to the poor results of cement femoral revisions. Attempting to insert an extensively coated stem in a patient with varus remodeling without the use of an extended trochanteric osteotomy will result in a high prevalence of cortical perforation, undersizing of the femoral component, and a varus malposition.

          • Additional relative indications:

      • Need for improved acetabular exposure either due to heterotopic bone formation or in severe acetabular deficiencies requiring extensive visualization of the anterior and posterior column

 

 

 

 

FIGURE 1

  • Use during femoral revision in patients with severe trochanteric osteolysis to minimize inadvertent fracture

    232

     

    Extended Trochanteric Osteotomy (Posterior)

     

  • Rarely, use in the primary setting in patients with prior osteotomies, malunions, or proximal femoral deformity due to congenital dysplasias

    Examination/Imaging

    • Standard anteroposterior (AP) radiographs of the pelvis and AP and lateral radiographs of the femur are required for preoperative planning of and extended trochanteric osteotomy. The AP pelvis radiograph can be used to estimate the leg length discrepancy, while the AP radiograph of the femur can be used to determine the apex of the deformity in a varus-remodeled femur and plan the appropriate length of the osteotomy.

      Surgical Anatomy

    • The length of the osteotomy will be dependent upon the indication.

  • Varus remodeling of the proximal femur will occur in up to 30% of femoral revisions and is most frequently observed at the tip of a loose femoral stem. Due to the remodeling, neutral component alignment cannot be achieved from a proximal starting position. The inability to place a femoral component in neutral position due to varus remodeling has been termed a conflict (Fig. 1). In these situations, the length of the extended trochanteric osteotomy should extend at least to the apex of the deformity. Failure to reach the level of the deformity will necessitate that the femoral preparation remain in a varus alignment.

  • When the extended trochanteric osteotomy is performed for removal of retained distal cement, the length will need to be within a few centimeters of the distal cement plug. A shorter osteotomy can be performed if the indication is to improve surgical exposure or if a loose distal cement mantle is present. However, a sufficient length of cortical bone below the lesser trochanter is required in order to securely reattach the osteotomy fragment at the completion of the procedure. A minimum of two cables is required to securely fix the trochanteric fragment at the completion of the procedure.

     

    233

     

    Extended Trochanteric Osteotomy (Posterior)

     

    • The length of the osteotomy is also dependent upon the implant chosen for the reconstruction.

       

      P EARLS

      • The length of the extended trochanteric osteotomy should be minimized to use the shortest femoral revision stem possible yet should be long enough to bypass the apex of the femoral remodeling, to achieve component/cement removal, and to allow at least two cerclage cables to be placed around the osteotomy.

       

  • Preoperative templates are essential in deciding the length of the osteotomy in order to obtain a stable implant. If an extensively porous coated stem is used, a minimum of 4–5 cm of “scratch fit” will be required in order to obtain sufficient axial and rotational stability. If a tapered stem is chosen, it is important that the osteotomy does not extend past the distal metaphyseal/diaphyseal flare.

  • Once the position of the osteotomy is marked, the location of the transverse limb is measured from a fixed bony landmark such as the tip of the greater trochanter (Fig. 2A and 2B) or the lesser trochanter.

 

 

 

A

 

 

 

FIGURE 2 B

 

234

 

Extended Trochanteric Osteotomy (Posterior)

 

Positioning

Instrumentation

  • An oscillating saw with a narrow blade is required for the longitudinal limb, while a “pencil-tip” burr is required for the transverse limb of the osteotomy.

  • Several wide osteotomes are required to distribute stress along the trochanteric fragment while the osteotomy is being completed.

  • Depending upon the indication for the osteotomy, a metal cutting burr may be required to section a well-fixed extensively porous coated stem before a Gigli saw can be used to remove the proximal portion of the stem and cylindrical trephines be used to remove the distal portion of the stem.

  • Reverse hooks, cement drills, and osteotomes will be required to remove well-fixed distal cement.

  • A minimum of two cerclage wires/cables are required to securely fix the osteotomy fragment upon completion of the procedure.

 

  • When performing the osteotomy, the hip is placed in extension and internal rotation with the knee flexed. This position will minimize the risk of a traction injury to the sciatic nerve yet allow exposure of the posterior aspect of the femur.

    Portals/Exposures

  • The surgical approach in the revision setting may be directed by previous surgical incisions. We prefer to use a posterolateral approach, which allows both proximal and distal extension and provides excellent visualization of both the femur and the acetabulum.

  • The patient is placed in a lateral decubitus position, taking care to stabilize the pelvis with positioners along the sacrum and pubic symphysis.

  • A lateral surgical skin incision is made in line with the femur over the posterior third of the greater trochanter. The tensor fascia lata and the fascia of the gluteus maximus are then split in line with the surgical incision and retracted with a Charnley retractor.

  • The posterior border of the gluteus maximus tendon is identified and retracted anteriorly. The posterior pseudocapsule and the short external rotators are then elevated as a posteriorly based flap. Elevating these structures as a flap will allow a posterior capsular repair at the completion of the surgery.

  • A portion of the gluteus maximus insertion is released to allow mobilization of the femur. The femoral head is now dislocated posteriorly when the hip is placed in flexion and internal rotation. The knee remains flexed to decrease tension on the sciatic nerve.

  • The soft tissue surrounding the proximal portion of the femoral stem is removed and the stability of the femoral component is assessed. If the stem is grossly loose and the greater trochanter is not preventing extrication, the component is removed. However, if the trochanter is preventing component removal or if the stem is well fixed, an in situ extended trochanteric osteotomy should be performed.

  • An in situ osteotomy should also be considered if hip dislocation is difficult due to severe acetabular protrusion or extensive heterotopic bone formation.

     

    235

     

    Extended Trochanteric Osteotomy (Posterior)

     

    Procedure

    Step 1

    • The posterior margin of the vastus lateralis is identified and the muscle belly is mobilized anteriorly off of the lateral femur while attempting to minimize soft tissue stripping.

    • A Chandler or Hohmann retractor is placed around the femoral shaft at the desired length of the osteotomy, exposing the underlying periosteum. The insertion of the gluteus maximus tendon is preserved unless release is required to mobilize the femur for visualization.

      Step 2

    • The position of the proposed osteotomy can now be marked with either electrocautery or a pen. The tip of the greater trochanter can be used as a landmark or, if the femoral stem has been removed, this can be used to determine the length of the osteotomy.

    • A sagittal saw is directed from posterolateral to anterolateral beginning anterior to the linea aspera while the femur remains in full extension and internal rotation. Ideally, the osteotomy fragment should encompass the posterolateral third of the proximal femur and should be oriented perpendicular to the anteversion of the hip (Fig. 3A and 3B).

    • If the femoral component has been previously extracted, the oscillating saw can then be guided toward the far anterolateral cortex, where the cortical bone can be “etched” to facilitate a greenstick-type fracture. If the femoral component is retained, the oscillating saw must be angled anterolaterally in an attempt to maximize the width of the osteotomy yet avoid hitting the retained femoral component.

    • Proximally, the saw is angled posteromedially so that

      the entire greater trochanter is released with the osteotomy.

       

       

       

      236

       

      Extended Trochanteric Osteotomy (Posterior)

       

      A

       

       

       

      B

      FIGURE 3

       

      Step 3

       

      P EARLS

      • When levering the osteotomy anteriorly, multiple wide osteotomes should be used simultaneously to distribute the stress along the greatest distance.

       

  • The distal transverse limb of the osteotomy should be made with the use of a pencil-tip burr (Fig. 4). The corners of the osteotomy should be rounded to eliminate a stress riser and decrease the risk of propagating a distal fracture.

  • An oscillating saw or the pencil-tip burr can be used to initiate the distal anterior limb of the osteotomy.

    Step 4

  • Multiple wide Lambotte osteotomes are used to gently lever the osteotomy site from posterior to anterior (Fig. 5A and 5B).

     

     

     

    FIGURE 4

     

    237

     

    Extended Trochanteric Osteotomy (Posterior)

     

    • The entire osteotomy fragment should be moved as a unit to avoid fracture at the level of the vastus ridge. Once the anterior limb of the osteotomy has been initiated, the trochanteric fragment can be retracted anteriorly with the attached abductors and vastus lateralis.

    • The tight pseudocapsule along the anterior aspect of the greater trochanter must be released while

mobilizing the osteotomy fragment in order to avoid inadvertent fracture of the greater trochanter.

 

 

 

A B

FIGURE 5

 

238

 

Extended Trochanteric Osteotomy (Posterior)

 

  • Since the blood supply and innervation to the vastus enter anteriorly, it is important to minimize dissection along the anterolateral limb of the osteotomy.

    Step 5

  • If the femoral component was extracted prior to the osteotomy, the pseudomembrane within the femur can now be removed.

  • If cement had previously been used, a high-speed burr along with cement splitters can be used to remove the retained cement and the distal plug. Cement remaining on the trochanteric fragment is retained until the end of the procedure in order to strengthen the often compromised trochanteric bone during surgical retraction.

  • If an osteotomy was required to remove a well-fixed proximally coated implant, a pencil-tip burr can now be utilized to expose the implant-bone interface around the majority of the implant. A Gigli saw can then be placed around the proximal femur and be used to disrupt the bone-prosthesis interface before the component removal.

  • If the osteotomy was required to remove a well-fixed extensively coated stem, the stem can now be transected with a metal cutting burr at the junction between the tapered and cylindrical portion of the implant. The proximal portion of the implant can be removed as described above while the remaining distal cylindrical portion of the stem can be removed with the use of a trephine 0.5 mm larger than the implanted stem.

    Step 6: Bone Preparation

  • Once the previous femoral component has been successfully removed, any remaining pseudomembrane or cement should be removed with the use of a reverse hook in order to minimize the risk of inadvertent femoral fracture during femoral preparation.

  • A distal pedestal is often observed in loose cementless implants and should also be removed to allow concentric femoral reaming.

  • The vast majority of femoral revisions are performed using a cementless implant that relies upon distal fixation. Depending upon the pattern of bone loss, the patient’s anatomy, and the length of the osteotomy, either a bowed or a straight extensively coated stem or a distally tapered stem may be chosen.

     

    239

     

    Extended Trochanteric Osteotomy (Posterior)

     

    • Flexible reamers are used to prepare the canal when a curved extensively coated stem is chosen, while a solid straight reamer is used when a straight extensively coated stem is chosen.

    • The femoral canal is sequentially reamed until cortical resistance is encountered.

      • The femoral canal is under-reamed by 0.5 mm to allow axial and rotation stability once the slightly larger implant is inserted. Throughout the reaming, the surgeon should be aware of the depth and the approximate location of the

        new stem.

      • A minimum of 5 cm of diaphyseal bone, scratch fit, is required when utilizing a fully porous coated stem. Alternative methods of reconstruction, such as a tapered stem, should be considered if this amount of scratch fit is not feasible.

    • Once significant endosteal resistance is encountered with the reamers, a femoral trial can be placed. The hip can then be reduced and brought through a range of motion to assess stability.

    • Provided the hip is stable, the amount of required femoral anteversion is marked. If a curved 8-inch or 10-inch stem is utilized, the bow of the femur and the prosthesis will control the ultimate amount of femoral anteversion. If the bowed implant does not allow adequate anteversion and the hip is not stable in this configuration, alternative methods of reconstruction, such as a modular stem, should be considered.

       

      240

       

       

      P EARLS

      • A prophylactic cerclage can be placed distal to the osteotomy before femoral preparation and stem insertion to minimize the risk of fracture.

       

      Extended Trochanteric Osteotomy (Posterior)

       

      Step 7: Prosthesis Implantation

  • The placement of a fully porous coated stem in the revision situation is similar to that used during primary arthroplasty. Figure 6 shows a femoral reconstruction with an extensively coated femoral stem. Note the healing of the osteotomy and the neutral alignment of the femoral stem.

  • A hole gauge should be utilized to verify that the manufacturing process has resulted in the appropriate distal femoral diameter. (For example, an 18-mm component should be able to pass through the 18.25-mm hole and not the 18.00-mm hole.) If the component is slightly oversized, the femoral canal can be reamed an additional 0.5 mm to avoid femoral fracture.

  • A prophylactic cerclage wire can be placed distal to

    the osteotomy site in order to minimize hoop stresses during component insertion and minimize the risk of fracture propagation. Additionally, the introitis at the level of the osteotomy can be reamed line to line for a length of approximately 1 cm to minimize the risk of fracture.

     

     

     

    FIGURE 6

     

    241

     

    Extended Trochanteric Osteotomy (Posterior)

     

    • The femoral component should now be able to be inserted manually within 4–5 cm of the desired depth. If the implant must be seated more than

      5 cm, the canal should be reamed line to line.

       

      P EARLS

      • The osteotomy fragment should be advanced distally and posteriorly before securing it to the remaining shaft of the femur. This will provide appropriate abductor tension and minimize the risk of impingement.

       

    • A series of gentle blows are used to seat the implant while in the appropriate amount of anteversion. Ideally, the stem should advance with each strike of the mallet and require 20–30 impacts until fully seated.

       

      Step 8: Wound Closure

    • Any cement adherent to the trochanteric fragment should be removed once the femoral stem is fully seated.

    • The leg is placed in slight abduction and internal rotation during reattachment of the osteotomy fragment.

    • A minimum of two cables or wires is needed to secure the greater trochanteric fragment to the remaining femoral shaft.

    • A high-speed barrel burr may be required to shape the trochanteric fragment in order to allow the osteotomy to rest against the lateral shoulder of the prosthesis and maximize bony apposition to

      the femoral shaft. The trochanteric fragment will not be able to have bone apposition both anteriorly and posteriorly in situations in which the extended trochanteric osteotomy was performed due to varus femoral remodeling. In these situations, the osteotomy should be advanced slightly distally and posteriorly to improve stability and minimize impingement during internal rotation.

    • The cables around the osteotomy are tightened from

      distally to proximally with a decreasing amount of force. Care must be taken to avoid a trochanteric fracture at the level of the vastus ridge.

    • Bone grafting of the osteotomy site is not routinely performed unless host bone from the reamings of the acetabulum or femur is available.

    • Our preference is to repair the posterior capsule and short external rotators to the posterior aspect of the gluteus medius.

    • The gluteus maximus fascia and the iliotibial band are closed over a drain with a nonabsorbable #1 suture while the subcutaneous tissue is closed with an absorbable 2-0 suture.

       

      242

       

      Extended Trochanteric Osteotomy (Posterior)

       

      Postoperative Care and Expected Outcomes

  • Patients who have undergone a femoral revision may be treated with an abduction orthosis for 6–8 weeks postoperatively to minimize the risk of instability. During this time, they are 30% weight bearing on the operative leg utilizing a walker or crutch for ambulation.

  • At the end of 6–8 weeks, they are converted to a cane and advance their weight bearing as tolerated.

  • Patients are instructed to avoid active abduction for 6–12 weeks until radiographic evidence of healing at the osteotomy site is present.

    Clinical Results

  • The senior author has previously reported his results when using an extended trochanteric osteotomy during revision femoral surgery.

    • From 1992 to 1996, 142 consecutive hip revisions were performed encompassing an extended trochanteric osteotomy; 122 patients were able to be followed at an average of 2.6 years.

    • There were no nonunions of the osteotomized fragments and no cases of proximal migration greater than 2 mm. Radiographically, all cases demonstrated bony union by 3 months.

    • This cohort of patients was re-evaluated with additional patients from 1992 to 1998. At an average 3.9-year follow-up, there were two nonunions (1.2%) and one malunion (0.6%). The remaining osteotomies achieved bony union.

  • Other surgeons have seen similar clinical results with the use of an extended trochanteric osteotomy. Chen et al. reported a 98% union rate in 46 hips when an extended trochanteric osteotomy was used during revision surgery.

    Complications

  • Potential complications with the use of an extended trochanteric osteotomy include proximal migration, nonunion or malunion of the osteotomy fragment, fracture, and recalcitrant trochanteric bursitis.

  • Proximal migration of the osteotomy fragment is rarely a problem since the vastus lateralis prevents significant proximal migration. Similarily, nonunion of the osteotomy is rarely a problem clinically as dense fibrous tissue forms.

     

    243

     

    Extended Trochanteric Osteotomy (Posterior)

     

    • A fracture of the osteotomy fragment at the vastus tubercle can be problematic, leading to trochanteric escape as subsequent abductor weakness.