The direct anterior approach: initial experience of a minimally invasive technique for total hip arthroplasty
© Hallert et al.; licensee BioMed Central Ltd. 2012
Received: 29 June 2011
Accepted: 25 April 2012
Published: 25 April 2012
Less invasive approaches for hip arthroplasty have been developed in order to decrease traumatisation of soft tissue and shorten hospital stay. However, the benefits with a new technique can be at the expense of a new panorama of problems. This manuscript describes, with emphasis on postoperative complications, our experience from the first 200 cases of unilateral hip replacement using the direct anterior minimally invasive (MIS) approach.
A straight incision in front of the greater trochanter was used and the tensor muscle was approached subfascially and retracted laterally. The joint was opened and the femoral head was removed. Usually excellent acetabular exposure was obtained. In order to get access to the proximal femur, the hip capsule was released posterolaterally so that the femur could be lifted using a special retractor behind the tip of the trochanter. After insertion of the prostheses, the wound was closed using running sutures in the fascia overlying the tensor, sub- and intracutaneously.
There was a small influence of BMI on the duration of surgery, and obese patients tended to have the cup positioned at a higher degree of deviation. There were in total 17 complications of which 5 necessitated revision surgery; 3 peroperative femoral fractures and 2 dislocations. Another 4 dislocations were treated with closed reduction and did not recur. 3 cases of nerve injury were noted, all resolved within 12 months. Three cases of DVT were diagnosed as well as 2 cases of postoperative infection; none of these led to chronic disability.
The technique is perhaps more technically demanding than the lateral approaches used today due to the somewhat limited surgical exposure. Morbidly obese or very muscular patients as well as patients with a short femoral neck or acetabular protrusion can represent particular problems. Our results indicate that there are certain risks when adopting this procedure but the complications noted are avoidable.
There is a strong tendency for surgical techniques to be improved over time and as new instruments are developed less invasive approaches are possible . Currently the most often used surgical exposures for hip replacement such as the anterolateral and the posterolateral approaches involve splitting muscles with risk of partial denervation and detachment of tendons with a risk for incomplete healing. In many cases this results in weakness of hip abductor muscles and notable limp. Using the direct anterior approach for total hip arthroplasty these problems are largely avoided and several reports in the literature have documented advantages with the technique [2–6]. A short rehabilitation time due to minimal soft tissue trauma is often emphasized. Complications have also been encountered, such as injury to the lateral femoral cutaneous nerve, component malposition, damage to the femoral shaft and delayed wound healing [2–5, 7]. Obviously, the benefits with the new technique are at the expense of a new panorama of complications and intraoperative difficulties. Exceptionally skilled surgeons might be the first to describe the results and when the technique is more widely adopted more problems can become apparent. This report describes the initial experience by a team of four surgeons, a senior surgeon, a recently board certified orthopaedic surgeon and two orthopaedic residents. The aim of the study was to describe early complications so that surgeons who adopt the technique will be informed not only about potential benefits but also of potential risks with the technique.
Surgical technique and clinical follow-up
The deviation of the acetabular cup was measured on pelvic AP-radiographs being the angle between a line joining the ischial tuberosities and the line through the ellipse described by the acetabular cup. The anteversion was calculated, using the method described by Ackland, Bourne and Uhthoff . The findings could be compared to the mandatory postoperative X-rays.
Statistical methods and data management
Multiple comparisons of continuous data were performed by analysis of variance, ANOVA. In the case of a statistically significant result in the ANOVA, statistical comparisons were made by use of the post-hoc test proposed by Fisher to control for multiplicity. The Pearson correlation coefficient was used in order to test independence between variables. In addition to that, descriptive statistics was used to characterize the data. In the case of a statistically significant result the probability value (p-value) has been given.
Patients (n = 200)
29–88 (mean 67,4)
17–43 (mean 26,7)
Blood loss, operating time and cup position
Time of surgery (min)
Blood loss (ml)
Influence of the BMI
y = 1,1179x + 85,113
R2 = 0,0317
P < 0,05
y = 0,2816x + 38,473
R2 = 0,0238
P < 0,05
Complication (% of all)
Periprostethic femoral fractures (1,5%)
ORIF with wiring
No further dislocation
Deep infection (S.Aureus) (0,5%)
Irrigation and antibiotic therapy
Resolved, prosthesis retained
Closed treatment/observation only
Complication (% of all)
Injury to lat. fem. cut. n. (0,5%)
Peroneal n. palsy (0,5%)
Injury to femoral n. (0,5%)
118; 169; 189; 192
There was no significant correlation between complication and gender, age or BMI.
The introduction of new approaches and instruments can be expected to temporarily be associated with complications, such as neurovascular injury and component malposition. It is important to have information about the risk for various complications and predisposing factors. This study is based on non-selected, consecutive, primary unilateral total hip replacements. The very reason to use this approach is the possibility to minimize surgical soft tissue injury and to maintain normal muscle function and stability of the hip [1, 7, 9–13]. The approach is internervous and does not include the release of muscles or tendons. In the literature there is little evidence for a higher complication rate with the direct anterior approach compared to lateral approaches. It is however of interest to demonstrate and discuss the hardships involved when the technique is adopted by a team of surgeons with mixed experience.
Overall the distribution of complications was fairly even among the 200 cases included in the study. Aside from the first 10 cases, this study does not well delineate a learning curve. An almost linear reduction in intraoperative blood loss was noted among the first 10 cases; in two of them cracks occurred in the proximal femur – this was not seen in cases done later.
The direct anterior approach subjects the lateral femoral cutaneous nerve and the femoral nerve to higher risk than lateral approaches. Even though the posterior branch of the lateral femoral cutaneous nerve can be injured [2, 12, 16] the technique described here seems to be effective in avoiding clinically relevant damage to the nerve. This is important since dysesthesia due to injury of this nerve may lead to considerable discomfort in the thigh for several months. Injury to the femoral nerve with the anterior approach has been mentioned by others [3, 17, 18]. We believe that it can be caused by the retractor placed anteriorly so that the iliopsoas muscle and the femoral nerve are compressed against fascial structures. This retraction should be directed cranially, towards the opposite shoulder and not transversely. In addition we have also constructed a retractor which sits around the ilium at the level of the anterior inferior iliac spine. This instrument is useful in difficult cases such as patients with pronounced abdominal obesity. Fortunately, femoral nerve injury seems to have a good prognosis and should resolve completely within a few months.
We decided to use the direct anterior approach even in cases with morbid obesity and in cases with grade 1 and 2 acetabular dysplasia. In obese patients we found that there was a specific problem in positioning the acetabular component. A high BMI was also associated with a longer operative time but not with a significantly higher intraoperative blood loss.
In summary our intention with this report is to discuss the risks involved with the adoption of a MIS technique for total hip replacement. It has the theoretical advantage of minimal soft tissue injury and it has been shown that the expectations of facilitated early rehabilitation can be fulfilled [9, 10]. In our opinion the present results do not obviate the technique as a routine for total hip arthroplasty but it is necessary to have a thorough understanding of the risks beforehand. Although technical difficulties necessitating revision surgery were more obvious among the early cases other complications such as dislocations may appear later. The technique is perhaps more technically demanding than the lateral approaches used today due to the somewhat limited surgical exposure. It should be reserved for specially trained surgeons who have the possibility to treat many patients in order to maintain good skills. It has been our overall impression that morbidly obese or very muscular patients as well as patients with a short femoral neck or acetabular protrusion can represent particular problems.
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