Total hip arthroplasty (THA) is one of the most successful interventions in modern medicine,1 and within the past two decades, the direct anterior (DA) approach has become increasingly used.2 This trend has been furthered by numerous reports suggesting potentially less pain, decreased narcotic use, improved gait mechanics, lower dislocation rate, shorter recovery times, and decreases in length of hospital stay and discharge to skilled nursing facilities.3–7
One major challenge involving the DA approach is the technical difficulty of overcoming the learning curve for surgeons, particularly regarding the surgical exposure.8,9 Importantly, complications have been reported for surgeons who are early in their learning curve with the DA approach, including nerve injuries, intraoperative femur fractures, wound complications, and ankle fractures.10–15 Thus, any aspect of the DA exposure technique that improves visualization and facilitates the surgeon's ability to perform the procedure safely would be an important way to help shorten the learning curve and improve patient outcomes.
Historically, most authors have described the acetabular exposure using a variation of two or three manual retractors: (1) a sharp Hohmann-type retractor that is placed over the anterior rim of the acetabulum to retract the rectus femoris and soft anterior tissues; (2) a blunt Cobra- or Hohmann-type retractor placed inferior to the acetabulum under the transverse acetabular ligament; and (3) an Aufranc (Cobra) or sharp Hohmann-type retractor placed over the posterior-superior wall.14,16 However, this manual retraction technique may not always provide adequate exposure. Further, it requires considerable retraction effort, especially in obese or muscular patients. Such difficulty with exposure has the potential to make reaming and cup placement more challenging, particularly for surgeons early in the DA learning curve.15,16 Thus, an acetabular retraction technique that (1) provides better exposure and (2) is less labor-intensive to the surgical team would be an attractive option for surgeons learning the DA approach. Such a technique has been previously suggested using all hands-free, self-retaining acetabular retractors, including a modified Charnley retractor.17 However, the authors are not aware of any study that directly compares these two retraction techniques to quantify the acetabular exposure.
Thus, the authors designed the current technique study to investigate the following research questions: (1) Using a DA approach, what is the difference in mean percent exposure of the acetabulum using a traditional three-retractor technique compared with a hands-free, all self-retaining retractor technique? (2) In what percentage of cases does the hands-free, all self-retaining retractor technique provide an improved exposure over the traditional three-retractor technique? (3) Do patient-related factors (ie, body mass index [BMI], age, sex, or diagnosis type) affect the quality of exposure similarly for both retraction techniques? (Video)
Materials and Methods
For the purposes of this technique article, the authors reviewed a prospective series of consecutive patients undergoing DA THA at a high-volume specialty orthopedic hospital. This study received institutional review board approval. The authors included all patients undergoing primary unilateral THA performed by two fellowship-trained arthroplasty surgeons (B.P.G., P.C.P.) via a DA approach between November 2018 and February 2019. A similar surgical technique and the same implant system were used in all cases. The authors excluded patients undergoing revision surgery, or primary surgery using an anterolateral or posterolateral approach. Application of the authors' inclusion and exclusion criteria yielded a total of 65 patients for final enrollment in the study population. Baseline demographics were recorded for the study patients (Table 1).
For each study patient, DA THA was performed using a previously described technique.18 In all cases, a press-fit acetabular component was used with a neutral polyethylene liner (no lateralized or lipped liners were used). After insertion of the acetabular component and polyethylene liner, two “best-view” digital photographs were taken of the surgical exposure by a non-sterile observer looking directly at the acetabular component from an approximate 1-foot distance: (1) a digital photograph using only a hands-free, self-retaining Charnley retractor with flat blades and a blunt cerebellar retractor and (2) a digital photograph using a traditional three-retractor manual exposure. The retractors were held in place by surgical assistants to provide the best possible view of the acetabulum. The digital photographs were then analyzed using imaging processing software (ImageJ; National Institutes of Health). The percent exposure of the polyethylene liner was calculated for each retraction technique in the following manner: First, the visible polyethylene in the digital photograph was outlined by the computer software and the total area of this visible polyethylene was calculated. Second, a “best-fit” ellipse was drawn using the same software to represent what would be total exposure of the full polyethylene liner, and the area of this ellipse was determined by the software. Finally, the total area of visible polyethylene was divided by the area of the best-fit ellipse representing the full polyethylene liner, thereby yielding the percent exposure of the polyethylene liner in that photograph (Figure 1). Each hip served as its own control for comparing the percent exposure of the polyethylene liner using the two retraction techniques.
Clinical photograph of the exposure of the acetabular polyethylene liner. Percent exposure is calculated from the area of the visibly exposed polyethylene (outlined in photograph), divided by the area of the best-fit ellipse that represents the full polyethylene liner. In this example, percent exposure was calculated at 78.0%.
The primary outcome for the current study was the mean percent exposure of the polyethylene liner for each acetabular retraction technique. As a secondary outcome, the authors determined the percentage of patients in whom the Charnley/self-retaining technique provided superior exposure, vs the percentage of patients in whom the traditional three-retractor manual exposure provided superior exposure. As a final secondary outcome, the authors determined whether certain patient demographics, including age, BMI, sex, diagnosis, and side, had any effect on the percent exposure of the acetabulum for either technique.
Description of Exposure Technique
A vertical capsulotomy is made from the superolateral acetabulum from the reflected head of the rectus and extended distally, stopping just medial to the intertrochanteric tubercle on the intertrochanteric line at the superior level of the vastus muscle attachment. This is completed distally in a T-shaped configuration along the intertrochanteric line, inferomedial toward the lesser trochanter and superolateral toward the lateral shoulder of the femoral neck, while protecting the gluteus minimus. Nonabsorbable braided sutures are placed at the two distal corners of the capsulotomy for retraction after performing the T-shaped extension, and to assist mobilizing the capsule during exposure.
For the Charnley/self-retaining exposure, the first step is to place a blunt self-retaining cerebellar retractor distally, in the interval between the tensor fascia lata and rectus femoris muscles (Figure 2). The braided nonabsorbable sutures are then held apart on tension, clearly identifying the medial and lateral limbs of the anterior hip capsule (Figure 3). The blades of the Charnley retractor are now placed under the medial and lateral limbs of the anterior hip capsule at the level of the nonabsorbable sutures, distracting the capsule apart and providing direct, hands-free access to the acetabulum (Figure 4). For the traditional three-retractor manual exposure, a bent sharp Hohmann-type retractor is placed over the anterior wall of the acetabulum, a blunt Aufranc (Cobra) retractor is placed inferior to the acetabulum under the transverse acetabular ligament, and a bent sharp Hohmann-type retractor is placed over the posterior-superior wall of the acetabulum to complete the exposure. Examples of both exposure techniques in the same patient are presented in Figure 5.
The first step of the Charnley/self-retaining exposure is to place a blunt cerebellar retractor distally, in the interval between the tensor fascia lata and rectus femoris muscles. Note the braided nonabsorbable sutures attached to the medial and lateral limbs of the capsule. A right-angled retractor is retracting the tensor fascia lata muscle laterally to better demonstrate the capsule (medial is to the right side of the image; lateral is to the left side of the image).
The braided nonabsorbable sutures are held apart on tension, clearly identifying the medial and lateral limbs of the anterior hip capsule.
To complete the exposure, the blades of the Charnley retractor are placed under the medial and lateral capsule limbs, distracting the capsule apart and providing direct, hands-free access into the acetabulum.
Clinical photograph of the acetabular exposure using a traditional three-retractor manual retraction technique (A), compared with the hands-free, all self-retaining retraction technique (B) in the same patient. Medial, lateral, proximal, and distal directions are labeled in each clinical photograph for orientation purposes. For the hands-free, all self-retaining retraction technique (B), the medial and lateral limbs of the anterior hip capsule are indicated by arrows.
All data were entered, stored, and analyzed using Excel (Microsoft Corporation), StatTools (CUHK), and GraphPad QuickCalcs (Graph-Pad Software). Continuous variables were analyzed using the Student's t test, while categorical variables were analyzed using Fisher's exact test. To determine the effect of patient demographics on percent acetabular exposure, a multivariate linear regression was calculated to predict percent acetabular exposure based on age, BMI, sex, diagnosis, and side; this was calculated for both the Charnley/self-retaining technique and the manual three-retractor technique. In all cases, statistical significance was set at P=.05.
For the 65 patients enrolled in the study, the mean percent acetabular exposure was 80.0% using the Charnley/self-retaining retractor technique, compared with 73.1% using the manual three-retractor technique (P=.0002). Using each patient as their own control to compare the two techniques, 49 patients (49 of 65; 75.4%) had superior acetabular exposure with the Charnley/self-retaining technique, while 16 patients (16 of 65; 24.6%) had superior acetabular exposure with the manual three-retractor technique (P<.0001). No complications occurred in this series.
Multiple linear regression analysis identified a significant negative correlation of BMI (beta=−0.298; P=.015) and diagnosis other than osteoarthritis (OA) (beta=−0.2427; P=.046) with percent exposure of the acetabulum using the Charnley/self-retaining technique (R2=0.1297; P=.0135). The remainder of the variables analyzed did not demonstrate a statistically significant effect in predicting percent acetabular exposure when added into the model (data not shown). Based on the authors' model, the predicted percent acetabular exposure was 97.3752−(BMI [kg/m2]×0.5786)−(OA diagnosis [Yes=0, No=1]×5.4585) when using the Charnley/self-retaining technique.
Using the manual three-retractor technique, multiple linear regression analysis similarly identified a significant negative correlation of BMI (beta=−0.3888; P=.0014) with percent exposure of the acetabulum (R2=0.18; P=.0021). Diagnosis other than OA (beta=−0.225; P=.0568) trended toward but did not reach a statistically significant effect within the model for the manual three-retractor technique. The remainder of the variables analyzed did not demonstrate a statistically significant effect in predicting percent acetabular exposure when added into the model (data not shown). Based on the authors' model, the predicted percent acetabular exposure was 102.736−(BMI [kg/m2]×1.0046)−(OA diagnosis [Yes=0, No=1]×6.7355) when using the manual three-retractor technique.
As in any arthroplasty procedure, adequate exposure during the DA approach is paramount for safely performing the surgery and accurately implanting the components. In this prospective, single-center study, the authors demonstrated that a hands-free, all self-retaining retractor technique provides superior acetabular exposure when compared with the more labor-intensive three-retractor manual exposure technique. The authors additionally found that increasing BMI predicts decreasing percent acetabular exposure with both techniques.
This study was not without limitations. First, the authors relied on a nonsterile observer to photograph the acetabular exposure for each patient. It is possible that a sterile person actually participating in the surgery may have a better visualization than the nonsterile observer taking the photograph; thus, the mean percent exposure reported in this study may not completely represent what the surgeon is actually seeing intraoperatively. However, the authors attempted to mitigate this limitation by having a study protocol in which each hip served as its own control, and they standardized the method in which the digital photographs were taken for all patients to make them as comparable as possible. Another limitation involved the choice of retractors. The authors used retractors that were available at their institution for the acetabular exposure. Therefore, they were unable to rule out that there may exist other retractors available at other institutions that may provide a better or worse exposure than their standard three-retractor set, making this study's results less comparable with those of other institutions. The authors did, however, use standard retractors that are widely available and are in fact the standard retractor set provided by a commonly used device company for DA approach total hip replacement. Thus, the authors believe that their results should apply to a large percentage of surgeons who perform the DA approach. A third limitation is that when using assistants, there exists potential variance in retraction (and thus exposure) from case to case, which may additionally be affected by assistant fatigue, patient body habitus, or other variables. The authors attempted to mitigate this potential variance by comparing digital photographs of the acetabular exposure using both techniques in the same patient, essentially using each hip as its own control to limit confounding variables and the potential variance in retraction that may otherwise be seen between different patients. A fourth limitation was that although this article reports an alternative technique for improving acetabular exposure, the authors did not assess clinical outcome measures. Therefore, they cannot comment as to whether patients will perform better clinically after surgery using either exposure technique.
Multiple authors have previously investigated the learning curve associated with the DA approach. Brun et al8 prospectively reported a significant improvement in safe cup positioning when comparing the second 250 patients with the first 250 patients using a DA approach. Similarly, Masonis et al9 compared a single surgeon's experience with the DA approach between the first 100 patients and the second 100 patients in a consecutive series, finding a statistically significant decrease in surgical time, fluoroscopy time, leg length discrepancy, and intraoperative complications in the second group. Acetabular retractor placement in the DA approach has also been addressed previously in the arthroplasty literature.14,16 A recent study by Sullivan et al19 used a cadaveric model to determine the safe zone for anterior acetabular retractor placement, to decrease the risk of injury to the femoral nerve and external iliac artery.
The current study complements the previous literature, demonstrating that an all self-retaining retraction technique provides improved exposure over the traditional manual three-retractor technique during acetabular preparation. These findings are in agreement with those of Laude,17 who has previously reported the usefulness of the Charnley exposure technique during acetabular exposure with the DA approach. This may have important implications, particularly for surgeons who are still early in their learning curve for the DA approach. First, improved exposure may reduce the risk of component malpositioning, which is more common early in the learning curve. Second, a hands-free, all self-retaining retraction technique permits the surgeon to perform the exposure, resect labrum, ream the acetabulum, and place the acetabular component without the need for an assistant. This avoids assistant fatigue common with obese or muscular patients. Additionally, this technique permits easy access with real-time fluoroscopy during reaming, as there is no need for an assistant on the other side of the table. Furthermore, this technique affords the teaching surgeon excellent visualization of acetabular preparation and reaming from the same side of the table and therefore aids in instruction. Finally, this technique avoids the placement of sharp retractors over the rim of the acetabulum, potentially decreasing the risk of injury to nearby neurovascular structures.19
A hands-free, all self-retaining retraction technique was found to be useful during acetabular preparation in DA THA. This technique is safe and provides improved exposure over the traditional three-retractor method. The authors believe that this technique would be of interest to experienced surgeons as well as those who are early in their learning curve.
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|Age, mean (range), y||63.7 (43–83)|
|Body mass index, mean (range), kg/m2||28.3 (20.6–37.6)|
| Male||32 (49.2%)|
| Female||33 (50.8%)|
| Osteoarthritis||53 (81.5%)|
| Avascular necrosis||7 (10.9%)|
| Fracture||3 (4.6%)|
| Rheumatoid arthritis||1 (1.5%)|
| Perthes disease||1 (1.5%)|
| Left||32 (49.2%)|
| Right||33 (50.8%)|