Anterolateral Mini-incision Total Hip Arthroplasty

Abstract

At the advent of the total hip arthroplasty (THA), Charnley advocated the transtrochanteric approach (“the lateral exposure with elevation of the greater trochanter”) for THAs.¹ However, surgeons such as Müller and Harris argued that there were many advantages to performing primary THAs without a trochanteric osteotomy, including a shortened operative time, less blood loss, elimination of the need to perform a trochanteric repair, avoidance of common trochanteric complications (e.g., nonunion and painful bursitis due to the irritation caused by the metal fixation wires), and earlier return to unsupported weight bearing.²,³ The most popular alternatives to the transtrochanteric approach are the posterior or posterolateral, the direct lateral, and the anterolateral approaches.

In his 1935 description of femoral neck fracture treatment, Watson-Jones described the anterolateral approach entailing an exposure of the femoral neck through the interval between the gluteus medius and the tensor fasciae femoris. To provide better exposure, he describes dissecting the anterior fibers of the gluteus medius insertion off of the trochanter. In cases where still further exposure is needed, he advocated driving an osteotome into the front of the trochanter and levering out on its intact posterior margin. He warns surgeons not to fully separate the trochanter to avoid bleeding.⁴

Anterolateral Approach

Historical Perspective and Evolution

At the advent of the total hip arthroplasty (THA), Charnley advocated the transtrochanteric approach (“the lateral exposure with elevation of the greater trochanter”) for THAs.1 However, surgeons such as Müller and Harris argued that there were many advantages to performing primary THAs without a trochanteric osteotomy, including a shortened operative time, less blood loss, elimination of the need to perform a trochanteric repair, avoidance of common trochanteric complications (e.g., nonunion and painful bursitis due to the irritation caused by the metal fixation wires), and earlier return to unsupported weight bearing.2,3 The most popular alternatives to the transtrochanteric approach are the posterior or posterolateral, the direct lateral, and the anterolateral approaches.

In his 1935 description of femoral neck fracture treatment, Watson-Jones described the anterolateral approach entailing an exposure of the femoral neck through the interval between the gluteus medius and the tensor fasciae femoris. To provide better exposure, he describes dissecting the anterior fibers of the gluteus medius insertion off of the trochanter. In cases where still further exposure is needed, he advocated driving an osteotome into the front of the trochanter and levering out on its intact posterior margin. He warns surgeons not to fully separate the trochanter to avoid bleeding.4

In 1966, McKee and Watson-Farrar further described the anterolateral approach. Their skin incision started at the anterior superior iliac spine, extended down to the greater trochanter tip, and then continued down the femoral shaft approximately 2–3 in., curving the incision slightly anteriorly. The interval between the tensor fasciae latae (TFL) anteriorly and the gluteus minimus and medius posteriorly was developed. They suggested first developing this plane distally where it is most easily found by the finger after incision of the deep fascia. Proximally, the muscles are more intimately blended and sharp dissection between them is necessary. The reflected head of the rectus femoris and anterior half of the hip joint are then visible and excised, revealing the head of the femur.5

While a classic anterolateral approach involves an intermuscular dissection between the TFL and gluteus medius, most versions of the anterolateral approach involve some degree of intraoperative detachment and subsequent repair of at least a portion of the anterior abductor mechanism. Surgeons either divide the anterior 25–50% of the gluteus medius and minimus, or they anteriorly reflect that portion of the abductors in continuity with a sleeve of vastus lateralis, bridging the two muscles with fascia or a small wafer of greater trochanter bone.6

Several surgeons have modified the anterolateral approach, differing mainly in the degree of abductor disruption. The difference between an anterolateral approach and a direct lateral approach is often blurred both in conversation and in the literature. Although most anterolateral approaches dissect through the abductors, these approaches are generally more anterior to the direct lateral approach described by Hardinge.7

In 1974, Mallory compared the transtrochanteric and anterolateral approaches. He found that pain relief was consistent in both groups. However, at 1-year postoperatively, the trans­trochanteric group did better in terms of loss of limp, improved walking endurance, and active abduction against gravity.8 In 1975, when comparing these two approaches, Thompson and Culver concluded that the anterolateral approach was indicated for most uncomplicated primary THAs in light of the trochanteric complications they encountered (e.g., nonunion and irritation caused by fixation wires). They did note that the trochanteric osteotomies were still “invaluable” for “the difficult, previously operated on hip” and in particular with patients with fixed flexion deformities greater than 30°, fixed external rotation deformities greater than 10°, or “gross distortion of normal pelvi-femoral relations.”9

Advantages of the anterolateral approach include a historically lower dislocation rate than the posterior approaches, ease of surgery with one or no assistants, and avoidance of the sciatic nerve. An early study comparing the anterolateral, transtrochanteric, and posterior surgical approaches in primary THAs revealed that the dislocation rate was four times more common in the posterior approach than in the other two groups and the incidence of trochanteric bursitis was twice as high in the transtrochanteric approach compared with the other two approaches.10

Another study comparing just the posterolateral and anterolateral approaches confirmed a significantly higher rate of dislocation in the posterolateral group (4.21% versus 0%). The authors used Mulliken’s “modified direct lateral approach” as their anterolateral exposure, with a split of the gluteus medius/minimus tendons in continuity with the vastus lateralis at the junction between the anterior one third and posterior two thirds of the gluteus medius. With this approach, the anterolateral group had a higher incidence of limp of any severity (29% versus 17%) and a higher incidence of a moderate or severe limp (7% versus 4%).11 Thus, the classic concept of a trade-off between instability (posterior approach) and limp (anterior approach) was established. This concept has recently been challenged.

With the popularization of a posterior soft tissue repair (i.e., the posterior capsule and short external rotators) in the posterior approaches, the difference in dislocation rates between the anterolateral and posterior approaches has been reported to be reduced. A metaanalysis of studies comparing posterior approaches with and without posterior soft tissue repairs revealed a dislocation rate of 0.49% and 4.46%, respectively. A systemic review of the literature showed a dislocation rate of 0.70% for the anterolateral approach and 1.01% for the posterior approach with a capsular repair.12 However, a posterior capsular repair is not always possible in the posterolateral approach.

Recent modifications to the anterolateral approach have similarly decreased the likelihood of a postoperative limp. Postoperative abductor weakness, resulting in a Trendelenburg gait, is caused by either inadequate repair of the abductors and/or damage to the superior gluteal nerve innervating the gluteus medius and minimus. Jacobs and Buxton identified a “safe area” for the superior gluteal nerve encompassing a band of the gluteus medius approximately 5-cm wide immediately proximal to the greater trochanter.13 Limiting proximal longitudinal dissection of the gluteus medius minimizes risk to the superior gluteal nerve. Recent modifications that limit the portion of anterior gluteus medius detached from the greater trochanter tip minimize postoperative abductor dysfunction.

Mini Anterolateral Approach

The mini anterolateral approach by definition entails a skin incision of 10 cm or less. In 2004, Bertin and Röttinger described a mini anterolateral approach (“a modified Watson-Jones approach”) that dissects between the gluteus medius and the TFL to expose the anterior capsule, preserving the integrity of the abductors. They noted that, using this interval, there is a danger of excessive acetabular anteversion and difficulty with femoral exposure. They proposed releasing sufficient capsule (posteriorly to the area of the piriformis insertion and inferiorly to the medial border of the femoral neck) to facilitate exposure. Overall, after having performed more than 300 of these approaches, they noted that it is “an excellent anterior approach without muscle damage through a small incision,” although they have yet to formally present their results.

Most surgeons performing the mini anterolateral approach dissect the anterior portion of the abductors off the greater trochanter to some degree. In general, however, the mini anterolateral approach involves less abductor disruption than the conventional anterolateral approaches. This less invasive abductor approach theoretically should decrease postoperative abductor weakness and, thus, limp.

Indications and Contraindications

The most important consideration in performing a THA is adequate exposure. Retractors and instruments specifically designed for minimally invasive surgery are strongly preferred as they protect soft tissues and allow reaming and broaching without compromise in position. Surgeons may routinely start with a small incision, but they should not hesitate to extend the incision if the exposure is deemed inadequate or if there is extensive skin traction. Ideal patients for mini anterolateral THAs are female, less muscular, low body mass index (BMI) patients. However, as surgeons gain more experience, their indications for a mini anterolateral approach can vastly expand. Patients with large retained hardware that must be removed (e.g., blade plates or dynamic hip screws), dysplasias requiring femoral osteotomies, severe dysplasia or congenital dislocations requiring a trochanteric osteotomy, and revision THAs involving more than a simple liner exchange are not candidates for this approach.

In developing one’s practice, we agree with Berger’s conservative, progressive approach. Surgeons should begin with the incision with which they are most comfortable and gradually shorten it as they gain more experience. When starting to use mini approaches, the surgeon should choose smaller, less muscular patients with minimal deformity and few osteophytes. Specialized retractors and instrumentation (e.g., fiberoptic lighted retractors and low-profile acetabular reamers with shells that are more than hemispheric) should be sought to facilitate the approach.14 Modification to the deep exposure can accompany smaller skin incisions as well.

Technique and Potential Pitfalls

A beanbag, peg board, or clamp-type positioner holds the patient in a lateral position on a standard operating room table. Stable positioning of the patient is critical for proper component position. The operative table must be flat and the patient must be in a true lateral position to maintain accurate bony landmarks. The anesthesiologist must be warned not to adjust the table without the surgeon’s knowledge. Patient positioning devices cannot impede full flexion or adduction of the hip or else they will compromise exposure during femoral preparation.

One third of the approximately 10-cm incision is posterior and proximal to the palpable tip of the greater trochanter; two thirds of the incision is anterior and distal to this point. The incision progresses distally from posterior to anterior at a 30° angle from horizontal, resulting in the anterior limb of the incision being distal (Figs. 18.1, 18.2, and 18.3). To make this incision even smaller, the incision can be more acutely angled closer to 45° from the horizontal.

Fig. 18.1

Schematic view from above of the patient in the lateral position. There is a dotted line marking the femoral shaft axis. The “X” marks the palpable tip of the greater trochanter. The incision (dotted line with bars at endpoints) is made at a 30° angle to the axis of the femoral shaft. One third of the incision is proximal and posterior to the “X,” two thirds of the incision is distal and anterior to the “X” (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

Fig. 18.2

Illustration of the hip musculature as it relates to the mini anterolateral incision (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

Fig. 18.3

Cross-sectional anatomy of the femoral head and neck as it relates to the mini anterolateral incision (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

The TFL is then exposed and cleared using a Cobb elevator, defining it for later closure. The fascia is then incised in line with the skin exposure. Acetabular exposure can be compromised by a fascial incision that is either too posterior or not long enough. An anterior curve of the incision’s distal extent relaxes the tension on this layer.

The gluteus maximus is now visible proximally and split in line with the fascial incision approximately 3–4 cm using electrocautery. The bursa deep to the gluteus maximus must carefully be excised without compromising the surrounding tissue.

Based on patient factors (i.e., BMI and degree of muscle mass) and surgeon experience, the surgeon must decide what percentage of the anterior gluteus medius to reflect. In the case of a surgeon with relatively less experience or a patient who is obese or very muscular, a larger portion of the gluteus medius may be reflected off the greater trochanter for enhanced exposure. We routinely dissect approximately 10–30% of the anterior abductor muscle mass off of the greater trochanter, translating into approximately a 1-cm transverse distance. The thickest portion of the gluteus medius and minimus tendon, and therefore the most effective area for later repair, is anterior, with the thickest portion in fact slightly anterior to the greater trochanter’s bony border (Figs. 18.4 and 18.5).

Fig. 18.4

The inferior border of the gluteus medius (marked with the hemostat tip) is identified via palpation (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

Fig. 18.5

Up to 30% of the anterior gluteus medius will be split from the posterior 70% of the tendon essentially in line with the femoral neck (planned split marked by electrocautery in the Fig.) (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

Electrocautery is used to split the gluteus medius longitudinally approximately 3 cm from the trochanteric tip, creating an L-shaped gluteus medius incision when viewed in combination with the transverse release of the tendon off the greater trochanter. A dull retractor is then placed to posteriorly retract the gluteus medius, exposing a layer of adipose tissue between the gluteus medius and minimus. A vascular bundle often lies in this interval and should be coagulated before incising the gluteus minimus tendon. The gluteus minimus tendon and anterior hip joint capsule are then incised in line with the femoral neck and head all the way up proximally to the acetabular edge without stopping at the anterior osteophytes. An anterior capsulotomy is then performed using a Cushing forceps and electrocautery. To ease hip dislocation, the anterior–inferior capsule must be thoroughly incised or excised. The hip is then flexed, adducted, and externally rotated to deliver the femoral head anteriorly into the wound.

In order to establish another useful bony landmark, the lesser trochanter can be better exposed by releasing the capsule above it or by more aggressive external rotation of the hip. It is worthwhile to expose the lesser trochanter to ensure that the femoral cut is sufficiently distal to facilitate later acetabular exposure. The femoral neck osteotomy is then performed, the femoral head is freed up with sharp transection of the ligamentum teres, and the femoral head is removed.

A Hibbs retractor placed superiorly and a short cerebellar retractor placed deep and proximal offers excellent ­acetabular exposure. With the leg in a neutral position on the operating room table, the acetabular labrum and any impinging capsule is excised. Standard or, preferably, low-profile reamers are used to prepare the acetabulum. Osteophytes are removed. The cup is then placed in 40–45° of abduction and 10–20° of anteversion.

A cerebellar retractor is placed anteriorly and a curved femoral elevator is placed posteriorly to offer exposure for the femoral preparation. The leg is placed into the anterior leg bag and hyper-externally rotated to both protect the abductors and prevent soft tissue impingement that could cause excessive anteversion (Fig. 18.6). The canal is broached using offset broach handles, the trial femoral stem placed, the trial femoral head is placed, and the hip is carefully relocated, making sure not to impinge on skin, fascia, or musculature as this can result in a femoral fracture. Actual components are then placed if the hip is deemed stable and has acceptable range of motion.

Fig. 18.6

sinto an anterior sterile leg bag for femoral preparati on (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

The capsule has been incised, and therefore the gluteus minimus is first repaired. The anterior portion of the gluteus medius is meticulously repaired with Mersilene sutures in the abductors threaded through two 2.4-mm drill holes in the greater trochanter (Fig. 18.7). The Mersilene sutures are covered and augmented with multiple Vicryl or Ethibond sutures. Covering the heavy Mersilene sutures minimizes the risk of them rubbing against the fascial repair and subsequently causing trochanteric bursitis (Fig. 18.8). The abductor repair sutures are each tightened down with the leg slightly abducted and internally rotated to approximately 10–20°. A drain is only used for patients with a BMI greater than 30. The patient is made weight bearing as tolerated. Daily subcutaneous injections of low-molecular weight heparin are used for thromboembolic prophylaxis.

Fig. 18.7

2.4-mm drill holes are made in the proximal greater trochanter to secure the gluteus medius repair with Mersilene tape (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

Fig. 18.8

Additional Vicryl or Ethibond sutures augment the repair (From Freiberg AA. Anterolateral mini-incision total hip arthroplasty. Oper Tech Orthop. 2006;16:87–92, with permission of Elsevier)

The anesthetic protocol is critical to ease and expedite functional recovery. We utilize preoperative narcotics and intraoperative regional anesthesia supplemented by intraoperative injections of local anesthetic into the musculature, fascia, and subcutaneous tissue at the end of the case. Perioperative oral or intravenous anti-inflammatory drugs in doses high enough to control pain are administered to avoid the potential debilitating side effects of narcotics (e.g., nausea, constipation, and altered mental status).

Results

In presenting results of the mini anterolateral approach, it is important to specify to what degree the abductors are dissected away from the greater trochanter. In a 2003 review of 212 uncemented THAs performed using the anterolateral approach, Higuchi et al. split the gluteus medius just proximally to the tip of the greater trochanter using finger dissection then sharply divided the vastus lateralis longitudinally just distal from the greater trochanter.14 Both muscles were divided for the anterior border of the greater trochanter in continuity. They found that, with a shorter incision length, there was a statistically significant decrease in operative duration and intraoperative blood loss. There were no significant differences in postoperative bleeding and complications between the mini and conventional anterolateral groups. They always initially started with a short skin incision and extended the incision as necessary during the surgery. They found that a longer incision was more commonly needed for those with a high BMI and for male patients.

In 2004, Berger compared two groups of 100 consecutive patients: (1) a standard anterolateral approach (removing 50% of the abductor off the trochanter) and (2) a mini-incision anterolateral (removing only 20–25% of the abductor off the trochanter).15 The blood loss, length of hospital stay, and rate of transfer home (as opposed to a rehabilitation facility) were significantly lower in the mini anterolateral group. There was no difference in operative time or complications between the groups. Neither group had a dislocation.15

In 2006, Jerosch et al. reported on 75 consecutive THAs performed through a mini anterolateral approach. They incised the iliotibial band longitudinally over the greater trochanter and dissected anterior to the gluteus medius, preserving its attachment to the greater trochanter. The average Harris hip score improved from 44 preoperatively to 90 at 1-year follow-up. There were no wound complications, no dislocations, and two patients with a slight Trendelenburg sign.16

Summary

The anterolateral approach entails a spectrum of dissections. At one extreme is an intermuscular dissection between the TFL anteriorly and the anterior border of the gluteus medius posteriorly. However, most surgeons either release between 25 and 50% of the abductors from the greater trochanter or anteriorly retract this portion of the abductors in continuity with a portion of the vastus lateralis inferiorly, bridging the two muscles with either fascia or a wafer of greater trochanter bone. The advantages of the anterolateral approach are classically a lower dislocation rate than the posterolateral approach, although this difference has probably been narrowed by the advent of posterior capsular repairs. Potential disadvantages of the anterolateral approach include abductor dysfunction (either through damaging the superior gluteal nerve or a failed stable repair of the abductors back to the greater trochanter), resulting in a Trendelenburg gait.

The mini anterolateral approach involves a skin incision of 10 cm or less and less dissection of the abductors off the greater trochanter, theoretically decreasing intraoperative blood loss and minimizing abductor dysfunction, thus expediting rehabilitation. We describe a mini anterolateral approach typically involving 10–20% of anterior gluteus medius dissection off of the greater trochanter. There is a paucity of literature reporting on the outcomes of this approach, but the literature available shows that the mini anterolateral approach is a safe approach offering significant advantages over the conventional anterolateral approach in terms of operative time, blood loss, and speed of functional recovery.