Surgical Approaches-Posterolateral

Introduction

Total hip arthroplasty (THA) is one of the most common and successful orthopaedic procedures currently being performed. Charnley1 initially used a transtrochanteric approach for his low friction arthroplasty. Since then, various other approaches have been introduced, such as the anterior (Smith Peterson2), lateral (Hardinge3), anterolateral (Watson Jones4) and posterior (Gibson5), which have been used for total hip replacement with good results. The current trend is to use minimally invasive approaches for performing total hip replacement. Visualization of the surrounding anatomic landmarks is necessary for proper orientation and correct positioning of the components. Attempts to perform surgery through an inadequately small skin incision may lead to component malposition, significant soft tissue damage, and higher complication rates which can affect the clinical longevity of the procedure.6 Here, we describe our surgical technique for total hip replacement using a posterolateral approach which enables complete exposure of the proximal femur and acetabulum with reduced tissue trauma,6 enhanced posterior soft tissue repair and multimodal pain management.

Surgical Technique

A thorough history and physical examination are performed for all patients. Meticulous preoperative planning and templating (Fig. 6.1) are done on the anteroposterior radiographic views of the pelvis and the lateral view of the hip. We prefer regional spinal or epidural hypotensive anesthesia to minimize intraoperative bleeding, which facilitates visualization. Prophylactic preoperative antibiotics and warfarin 5 mg are given to every patient before surgery.

PATIENT POSITIONING AND DRAPING

The patient is placed in the lateral decubitus position with the affected hip facing up on a custom designed fracture table (Fig. 6.2). The pelvis is supported by separate padded posts placed anteriorly in front of the pubic ramus and posteriorly behind the sacrum. The back is also supported firmly to secure the patient and prevent any forward or backward rolling of the body. Proper and secure positioning of the patient is important for accurate intraoperative assessment of pelvic orientation during acetabular component implantation. The table also allows for intraoperative tilting of the patient to facilitate acetabular reaming. All of the bony prominences are padded, and the back is supported posteriorly by a post placed below the scapula. The patient's surgical preparation is done as per standard protocols. Shaving of the

Total Hip Arthroplasty

Figure 6.1: Preop templating data with templated hip X-ray

Figure 6.2: Patient positioning on the custom hip table

operative site is done just before surgery with a safety razor followed by a prescrub with betadine soap. The skin is finally prepped with betadine solution. The operative site is covered with an iodine-impregnated plastic drape to make the operative field impervious to skin flora.

APPROACH AND TECHNICAL DESCRIPTION

First, the anatomic bony landmarks are palpated and marked with a surgical pen. The anterior superior and posterior superior iliac spine of the pelvis and the high point of the iliac crest are marked. The posterolateral border of the greater trochanter is also palpated and marked. In an obese patient, rotation of the limb can help in palpating this bony landmark. The anterior superior border and prominence of the greater trochanter are also marked (Fig. 6.3). The skin incision is curved gently and centered over the trochanteric prominence

Surgical Approaches-Posterolateral

Figure 6.3: Skin incision with other bony landmarks marked

and is then extended distally for 5 to 10 cm along the posterior part of the femoral shaft. It is also extended proximally the same distance and angled about 40 degrees toward the posterior superior iliac spine. When the hip is flexed to 60 degrees, the incision is generally seen as a straight line along the posterior border of the femur.

The incision is modified according to the patient's skeletal anatomy and body habitus. The superior portion of the incision is curved more posteriorly in patients with an increased varus neck angle and less posteriorly in those with an increased valgus neck angle. The length of the incision can be modified depending on patient soft tissue laxity and adipose tissue. The fascia is incised within the line of the skin incision, and the fibers of the gluteus maximus muscle are split to expose the proximal part of the greater trochanter. Two cotton lap pads soaked in antibiotic solution (polymyxin and bacitracin) are applied to the skin margins, and a self-retaining Charnley retractor is used to retract the fascial and muscle edge. The hip joint is then gently rotated internally with slight flexion and adduction, and the foot is placed on a padded mayo stand to make the external rotators more easily palpated. The trochanteric bursa is incised and the fatty tissue is removed to clearly expose the external rotators. The piriformis tendon is palpated and blunt dissection is used to develop the interval between the posterior border of gluteus medius tendon and the piriformis. A bent Hohmann retractor is placed within this anatomic interval to gently retract the abductor muscles . The proximal portion of the gluteus maximus tendon insertion from the femur is then released preserving a stump of 2 to 3 mm at its insertion to minimize any sciatic nerve injury7 and also allow better exposure of the femoral neck . Using diathermy, the external rotators from the piriformis to the quadratus along with the posterior capsule are subsequently detached together as a single layer from the posterior border of the femoral neck. Care is taken to maintain the dissection close to the bone to avoid the branches of the circumflex vessels and obtain maximum length of these soft tissues to facilitate their later repair during wound closure.

Depending on which hip is to be replaced, the inferior capsulotomy is done near the 5 o'clock position for a left hip and 7 o'clock position for a right hip. An Aufranc retractor is placed in the acetabular notch through a small incision made in the inferior capsule. Prior to dislocation, a Steinman pin is inserted in the infracotyloid groove.8 This pin is aligned vertically with the leg in a neutral position and the corresponding relation on the greater trochanter is noted to assess leg length during the procedure (Fig. 6.4). The hip is then dislocated posteriorly by a maneuver of flexion, adduction and internal rotation. The center of the femoral head is

Total Hip Arthroplasty

Figure 6.4: Steinman pin in the infracotyloid groove and marking of trochanter for measuring the leg length

Figure 6.5: Marking of the center of the femoral head

marked with the help of a matching acetabular trial (Fig. 6.5). The lesser trochanter is identified and the preoperatively templated neck cut is measured from its proximal border. The distance from the lesser trochanter to the center of the head is measured and recorded for future reference (Fig. 6.6). The distance from the trochanter to center of the femoral head is also measured to assess the femoral offset (Fig. 6.7). The neck is osteotomized with a sagittal saw directed parallel to the head with care taken to avoid damaging the abductors or trochanter. If the patient has significant anterior soft tissue tightness or preoperative flexion contracture, the limb is internally rotated and the anterior capsule is released near the anterior surface of the femoral neck from the intertrochanteric crest.

Surgical Approaches-Posterolateral

Figure 6.6: Measuring of the lesser trochanter to center distance

Figure 6.7: Measuring the offset from trochanter to center of femoral head

ACETABULAR EXPOSURE

The acetabulum should be completely visualized before any acetabular preparation is started. The femur is retracted anteriorly with a curved C-shaped retractor placed along the anterior acetabular rim toward the anterior inferior iliac spine. The anterolateral capsule and reflected head of the rectus femoris is released from the anterosuperior border of the acetabulum as needed to help anterior mobilization of the femur. A bent Hohmann is then placed posteriorly behind the ischium within the capsule but outside the labrum. An Aufranc retractor is placed below the acetabular notch to retract the inferior soft tissues and facilitate hemostasis. A Steinman pin is placed in the supra-acetabular region to retract the gluteus medius and minimus. The femur is positioned into slight abduction, flexion and neutral rotation behind the C-retractor to facilitate global exposure of the acetabulum (Fig. 6.8). The labrum and

Total Hip Arthroplasty

Figure 6.8: Circumferential view of the acetabulum with the 4 retractors-C retractor, Aufranc inferior, Pin superior and bent Hohmann posteriorly

Figure 6.9: Excision of the labrum and pulvinar

pulvinar are cleared (Fig. 6.9) to gain a complete view of the bony anatomy of the acetabular socket. The acetabulum is reamed in a progressive and concentric manner to expose cancellous bleeding of the bone. The initial reamer is directed medially to "medialize" the socket until true acetabular floor is reached. The socket is then reamed in a concentric manner in 2 mm increments until bleeding cancellous pubic and ischial bone is seen (Fig. 6.10). An acetabular trial of the same outer diameter is used to check its stability and to assess proper concentric reaming of the socket. Bony anatomical landmarks of the acetabular socket are used to evaluate the desired anteversion and inclination angles of the acetabular cup trial. The final prosthesis is positioned between 15 to 25 degrees of anteversion and 40 to 45 degrees of abduction (Fig. 6.11). If present, any osteophytes are removed using an osteotome and ronguer to prevent component impingement.

Surgical Approaches-Posterolateral

Figure 6.10: Acetabulum reamed with bleeding cancellous bone

Figure 6.11: Final acetabular component in place in 15 to 25 degrees of anteversion and 40 to 45 degrees of abduction

FEMORAL EXPOSURE

After the acetabular cup implantation is completed, attention is directed toward preparation of the femur. The femur is flexed, adducted and internally rotated, and a broad femoral neck retractor is used to elevate the proximal femur into full view. An Aufranc retractor is placed inferiorly beneath the lesser trochanter and behind the femoral retractor. A narrow right-angled Hohmann retractor is placed anterior to the greater trochanter between the gluteus medius and minimus muscles to protect the abductors and completely expose the femoral neck. The trochanteric fossa is cleared of all soft tissue and debris. This step allows complete visualization of the proximal femoral neck so that it may be safely and correctly broached (Figs 6.12 and 6.13). A high-speed burr is used to make an entry point in the posterolateral portion of the neck. A canal finder is inserted in line with the femoral shaft and pointed

Total Hip Arthroplasty

Figure 6.12: Broaching of the femur

Figure 6.13: Femoral exposure using jaws and Aufranc retractor after final broaching

toward the medial femoral condyle to identify the center of the femoral canal. The femoral canal is progressively broached to the proper size in the desired anteversion within the femoral neck. Lateralization of the implant helps to align the femoral prosthesis along the neutral axis of the femur. The appropriately sized broach is kept within the canal and used for trial after modular head and neck components based on preoperative templating are placed on top of it.

TRIAL REDUCTION

During trial reduction, the hip is taken through a range of motion and checked for stability. A Steinmann pin is placed in the infracotyloid groove, aligned vertically with the leg placed in neutral position as earlier to mark the trochanter. This marking is compared with the

Surgical Approaches-Posterolateral

Figure 6.14: Steinman pin in the infracotyloid groove and marking of trochanter for measuring the leg length after surgery

Figure 6.15: Coplanar test for measuring the combined anteversion

marking preoperatively to objectively assess the leg length difference made after surgery (Fig. 6.14). The combined anteversion of the femoral and acetabular components is checked by the coplanar test (Fig. 6.15) by bringing the femur into 30 to 45 degrees of internal rotation.9 The component stability is checked by bringing the leg into flexion, adduction and internal rotation. The anterior capsular tension is checked by passive external rotation which should bring the proximal femur to within one finger breadth from the ischial tuberosity. The Ober test is used to check the length and tightness of the tensor fascia lata and iliotibial band. The distance from the lesser trochanter to the center of the head and the femoral neck offset are measured and compared with the same measurements obtained earlier in the operation. At this stage, leg length, offset and soft tissue adjustments can be made by changing seating of the implant, head neck length and offset modularity in order to preserve

Total Hip Arthroplasty

Figures 6.16A and B: Final modular femoral components to be implanted

preoperative length and stability. All anterior osteophytes are removed to prevent any bony impingement. The anterior soft tissue and iliotibial band may be released as required to adjust the soft tissue tension. The hip is dislocated, the trial femoral components are removed and the final implant is assembled for implantation (Figs 6.16A and B). The implants are then seated to the desired level in proper anteversion. The hip is reduced, and via pulsed lavage, the wound is irrigated thoroughly with antibiotic solution to remove all bony and soft tissue debris.

SOFT TISSUE CLOSURE

A steroid-containing local anesthetic mixture (Fig. 6.17) is injected periarticularly around the hip joint. We believe that the steroid helps to decrease local soft tissue inflammation, and the morphine within the mixture helps to decrease perioperative pain and postoperative parenteral narcotic analgesia requirement.10 Two non-absorbable braided sutures are used for the repair. One is placed in the piriformis and superior part of the posterior capsular flap

Figure 6.17: Ranawat Orthopaedic Center (ROC) cocktail for pain management for periarticular injection

Surgical Approaches-Posterolateral

Figure 6.18: Passing of the external rotator tendons through drill holes for post soft tissue closure

Figure 6.19: Post soft tissue closure over drill holes made in the trochanter

and the other is passed into the conjoint tendon and inferior part of the capsular flap. Two holes are drilled into the greater trochanter 1 cm apart to serve as anchors for the suture repair of the external rotators and posterior capsule. The sutures are passed through the drill holes with the help of a suture passer (Fig. 6.18). They are tightly knotted (Fig. 6.19) with the leg in slight external rotation to allow the posterior tissues to come in close proximity to the femur. The gluteus maximus tendon is sutured to its remaining insertion and the quadratus femoris muscle is re-approximated to the posterior aspect of the femur. A suture is placed superiorly between the piriformis and abductor tendons to complete the posterior soft tissue sleeve (Fig. 6.20). The fascia is securely closed with interrupted, continuous vicryl sutures to attain a watertight closure. The wound is closed in layers, sterile dressing is applied and the limb is wrapped in a hip spica fashion using an Ace bandage. An abduction pillow is applied and the patient is shifted securely to bed.

Total Hip Arthroplasty

Figure 6.20: Final posterior soft tissue closure

Summary

A well-executed THA gives excellent function and pain relief for the patient. Attention to detail during every step of the procedure and surgical expertise must be utilized to ensure the ultimate longevity of the procedure. The extensile posterior approach described here provides wide exposure of both the acetabulum and proximal femur giving superb three-dimensional visualization of the bony anatomy. We have found our surgical technique to be reproducible and tissue-sparing. It provides outstanding clinical results for our patients.

References

1. Charnley J. Total hip replacement by low-friction arthroplasty. Clin Orthop Relat Res 1970;72: 7-21.

2. Smith-Petersen MN. Approach to and exposure of the hip joint for mold arthroplasty. J Bone Joint Surg Am 1949;31A(1):40-6.

3. Hardinge K. The direct lateral approach to the hip. J Bone Joint Surg Br 1982;64(1):17-9.

4. Watson-Jones. Fractures of the neck of the femur. Br J Surg 1930;23:787-808.

5. Gibson A. Vitallium-cup arthroplasty of the hip joint; review of approximately 100 cases. J Bone Joint Surg Am 1949;31A(4):861-8.

6. Ranawat CS, Ranawat AS. A common sense approach to minimally invasive total hip replacement. Orthopedics 2005;28(9):937-8.

7. Hurd JL, Potter HG, Dua V, Ranawat CS. Sciatic nerve palsy after primary total hip arthroplasty: a new perspective. J Arthroplasty 2006;21(6):796-802.

8. Ranawat CS, Rao RR, Rodriguez JA, Bhende HS. Correction of limb-length inequality during total hip arthroplasty. Journal of Arthroplasty 2001;16(6):715-20.