Exposure for Revision Total Hip Arthroplasty





CASE STUDY


Case 1: Extended Trochanteric Osteotomy


A 67-year-old woman presented with a 4-month history of right thigh pain with weight bearing 10 years after a right hybrid total hip arthroplasty (THA) (see Fig. 53.1 ). She previously had no pain or limitation with weight bearing. After considering the results of laboratory tests and radiographic studies, femoral component revision was recommended.




FIGURE 53.1


A 67-year-old woman presented with thigh pain 10 years after a hybrid right total hip arthroplasty. A, The anteroposterior radiograph of the hip shows a well-fixed acetabular component, cement debonding, and a radiolucent line at the cement–implant interface along femoral component. B, Lateral, frog-leg radiograph shows the long, distal cement plug and stem.




Extended Trochanteric Osteotomy


Introduction


Because of multiple muscle attachments and planes arising from the pelvis and proximal femur, total hip arthroplasty (THA) may use a variety of approaches, including anterior, anterolateral, transtrochanteric, and posterolateral. For simple revision THAs, use of the surgeon’s standard primary approach may be sufficient for adequate exposure. More extensile exposure is often necessary for management of pelvic bone loss, acetabular protrusio, retained cement or well-fixed femoral components, and femoral deformity.


If an anterolateral approach is routinely used, it can easily be extended to create a vastus slide exposure, in which the released anterior one third of the gluteus medius is left in continuity with the proximal vastus lateralis muscle while the vastus is reflected anteriorly off the femur to allow more extensive anterior retraction of the muscle flap to facilitate exposure. A classic trochanteric osteotomy as described by Charnley, in which the trochanter is osteotomized and detached from the proximal vastus lateralis and reflected superiorly, provides excellent exposure and access to the proximal femur and acetabulum, but it is associated with higher rates of trochanteric nonunion and trochanteric escape compared with other exposures.


An alternative to the classic trochanteric osteotomy is the trochanteric slide osteotomy. The vastus lateralis muscle is left in continuity with the osteotomy fragment, and the entire sleeve of abductors, trochanter, and vastus lateralis can be retracted to allow acetabular exposure. When access to the femoral canal is required for cement removal, resection of well-fixed femoral components, or correction of a proximal femoral deformity, an extended trochanteric osteotomy (ETO) is preferred. Femoral canal access is unparalleled with this approach, and retraction of the osteotomy fragment can aid in acetabular exposure when more complex acetabular revision procedures are necessary. In Case 1, an ETO was used to facilitate cement removal and reconstruction for aseptic loosening of a cemented femoral component.


Indications and Contraindications


An ETO is preferred over other approaches in several clinical situations. It is most frequently indicated for expeditious removal and revision of a femoral component. The ease with which cement can be extracted from the proximal femur after an ETO is unparalleled. For removal of proximally porous-coated, cementless implants, an ETO is preferred when access to the proximal femur for passage of flexible osteotomes is difficult or when proximal femoral bone quality is poor and the surgeon risks damaging or fracturing the trochanter in the absence of an extended osteotomy.


An ETO is often necessary for removal of well-fixed, fully porous-coated stems when access to the bone–implant interface cannot be achieved from above. For cases in which there is significant femoral varus remodeling or other deformity, an ETO can be incorporated into the approach to help realign the proximal femur with the revision stem. In patients with trochanteric osteolysis, an ETO is recommended over a trochanteric slide osteotomy or classic trochanteric osteotomy to avoid fragmentation and excessive damage to the trochanter.


Equipment


The standard equipment for patient positioning and initial exposure should be used according to the surgeon’s preference. Additional equipment necessary for an ETO includes an oscillating saw; a pencil-tip, high-speed bur, and broad, flat and curved osteotomes for completion of the osteotomy. Multiple Gigli saws should be available for removal of a well-fixed, cementless stem. If a fully porous-coated or long, bowed stem needs to be removed, metal-cutting bur tips are necessary for transection of the stem, along with multiple trephines for removal of the distal cylindrical stem. Specialized cement osteotomes are useful for cement removal (discussed later). Osteotomy fragment fixation is routinely performed with braided cerclage cables, although heavy-gauge wire can also be used.


Surgical Techniques


Anatomy and Approaches


If an anterolateral approach is planned, the abductor muscles are identified and divided at the junction of the anterior third and posterior two thirds of their tendinous insertion on the trochanter. If possible, they should be kept in continuity with the distal vastus fascia in case a vastus slide osteotomy is necessary for a more extensile exposure.


If a posterolateral approach is planned, the posterior border of the gluteus medius muscle is identified and protected, and a posterior arthrotomy may be performed for access to the prosthetic joint. For revision of a cemented stem, the hip is dislocated, the stem is extracted, and the surgeon proceeds with the ETO. Removal of the stem before the osteotomy is desired, because the osteotomy is much easier to perform in the absence of the femoral stem. If the ETO is being performed for removal of a well-fixed, cementless stem, an initial posterior arthrotomy may not be necessary.


Examination and Imaging


For the patient in Case 1, plain radiographs revealed cement debonding and a radiolucency at the cement–implant interface, suggesting femoral component loosening ( Fig. 53.1 ). Results of the workup for infection were negative, including normal erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values. Based on the examination results and these findings, femoral component revision was recommended.


Procedure


Step 1. Initial Approach


If possible, previous skin incisions should be used for revision exposure, provided that the planned approach will not be compromised by the existing incision. Even if the primary scar is positioned slightly more anteriorly or posteriorly than desired, with extension of the incision length, a subcutaneous flap can be undermined 2 to 3 cm anteriorly or posteriorly at the level of the deep fascia so that it can be incised at the desired location. The fascia and iliotibial band are incised in line with the proximal femur up to the level of the greater trochanter, and the incision typically is extended posteriorly toward the posterior superior iliac spine at an approximately 30-degree angle. Care should be taken to avoid damage to the gluteus medius, because it is frequently scarred to the tensor in the revision situation. Abduction and slight external rotation of the leg can facilitate development of this tissue plane.


Step 2. Deep Approach and Arthrotomy


After the iliotibial band and gluteus maximus are divided, the scarred bursal tissue along the posterior aspect of the femur is divided with electrocautery carefully to avoid damage to or retraction of the sciatic nerve. The sciatic nerve should be palpated and protected throughout the case. We do not advocate dissection and extensive exposure unless large posterior column reconstruction is necessary to avoid iatrogenic damage.


Step 3. Release of the Gluteus Maximus Tendon Insertion


The tendinous insertion of the gluteus maximus on the posterior femur is partially divided in most cases to help with mobilization of the proximal femur. A 1-cm cuff of tendon should be preserved on the femur for eventual repair. Care should be taken to avoid inadvertent damage to the sciatic nerve, which lies just medial to this tendon insertion.


Step 4. Posterior Arthrotomy


In the case of a previous posterolateral approach, the tissue planes defining a repaired posterior hip capsule are often indistinct. The posterior border of the gluteus medius muscle and tendon insertion on the greater trochanter should be used as landmarks, and the initial limb of the arthrotomy can be performed at this site, avoiding any damage to the gluteus medius muscle. The scarred posterior hip capsule and external rotators are released off the proximal femur to the level of the lesser trochanter, which allows visualization of the scarred pseudocapsule in the joint. This pseudocapsule should be excised from the femoral neck up to the level of the gluteus minimus muscle superiorly and inferiorly to the level of the lesser trochanter, which improves the surgeon’s ability to rotate and mobilize the proximal femur.


The anterior pseudocapsule should be excised. If acetabular revision is planned, the origin of the rectus femoris may need to be elevated so that the femur can be retracted anteriorly for adequate acetabular exposure and reconstruction.


Step 5. Stem Removal


For the patient in Case 1 with a loose, cemented stem, the hip was dislocated, and the stem was tapped out ( ). Adequate excision of the superolateral pseudocapsule and fibrous tissue is necessary to avoid iatrogenic damage to the trochanter during stem removal. In some cases, it may be necessary to use a bur and remove some of the medial trochanteric bone to safely extract the stem.


Step 6. Lateral Femoral Exposure


The lateral aspect of the femur is exposed so that the location and distal extent of the osteotomy can be marked appropriately. The vastus lateralis is carefully elevated off the posterior intramuscular septum and retracted anteriorly, minimizing subperiosteal stripping of this muscle off the lateral femur so that the blood supply to the osteotomized fragment can be maintained. Subperiosteal exposure at the distal aspect of the osteotomy is necessary. The length of the osteotomy and distal exposure is dictated by the type of stem to be removed or the length of the cement column. It should be long enough to allow fixation with two or three cerclage wires or cables.


Step 7. Osteotomy of the Posterior Femoral Cortex


An oscillating saw is used to divide the posterior cortical femur. When it is complete, approximately one third of the lateral femur is included in the osteotomy fragment. The osteotomy should be perpendicular to the trochanter, or in the case of a well-fixed stem, it should be perpendicular to the stem version to help facilitate stem removal. For Case 1, the oscillating saw was used to divide the posterior femoral cortex, the posterior cement mantle, the anterior cement mantel, and score but not completely divide the anterior cortex. The proximal extent of the osteotomy should include the entire trochanter, and the orientation of the osteotomy must ensure that the anterior portion of the trochanter is included in the osteotomy fragment.


Step 8. Osteotomy of the Distal Lateral Femoral Cortex


A pencil-tip, high-speed bur is routinely used to divide the lateral distal femoral cortex in a curved manner to minimize the chance of a stress riser associated with the sharp edge of bone. The bur tip is extended anteriorly to begin the anterior limb of the osteotomy to help avoid fracture at the site when the osteotomy is completed.


Step 9. Completion of the Osteotomy


Broad osteotomes are used to gradually divide the anterior cortex in a posterior to anterior direction to complete the osteotomy. They should be sequentially advanced into the anterior femoral bone and elevated as a unit to avoid fracturing the osteotomy fragment.


Step 10. Mobilization of the Osteotomy Fragment


After the osteotomy is complete, the fragment can be mobilized and reflected anteriorly to gain access to the femoral canal for cement removal or stem extraction. Often, the anterosuperior pseudocapsule tethers the proximal extent of the osteotomy fragment, and care should be taken to divide and release this scar tissue so that fracture of the trochanter does not occur inadvertently.


Step 11. Femoral Component Revision


Femoral component revision is the next step. In Case 1, cement osteotomes were used to extract the cement from the proximal femur and femoral canal. It is necessary to place a prophylactic cerclage cable around the upper aspect of the femoral diaphysis just distal to the end of the osteotomy to help protect the bone from fracture during stem insertion. The femoral canal was reamed with flexible reamers, and a fully porous-coated revision stem was inserted before closure of the osteotomy.


Step 12. Reduction of the Osteotomy


After femoral revision is complete, the osteotomy fragment is reduced to the femoral stem and medial femoral bone. A bur is usually needed to create an adequate recess within the osteotomy fragment and allow good bony contact of the osteotomy fragment edges with the medial femoral cortex to ensure healing. For cases in which trochanteric advancement is necessary, small amounts of the distal osteotomy fragment can be resected, and the trochanter can be advanced distally. For severely osteopenic bone or in cases with significant trochanteric osteolysis, an allograft strut can be incorporated into the reduction and osteotomy repair.


Step 13. Fixation of the Osteotomy


Fixation of the osteotomy is usually achieved by passing a sufficient number of cerclage cables around the fragment to secure it in its reduced position ( Fig. 53.2 ). The use of an allograft strut or a trochanteric claw plate is not routine, but it may be necessary in cases of trochanteric fragment fracture or poor-quality trochanteric bone, in which the cables themselves can damage or cut into the trochanteric fragment.


May 29, 2019 | Posted by in ORTHOPEDIC | Comments Off on Exposure for Revision Total Hip Arthroplasty
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