Bikini Incision: Sexy and yet Functional
Although there is a “near” universal way of making an incision for knee replacement (some people make a curvilinear incision or even lateral based incision), there are different skin incisions for hip replacement depending on surgeons’ training and preference for surgical approach. I often tell my patients that “there is more than one way to skin a cat.” As seen in the Figure 1, incisions can be made on the side of hip or slightly on the back of the buttock or slightly towards the groin, corresponding to lateral, posterior, and anterior approaches, respectively.
These represent the most typical approaches used in the world. Lateral hip approach is most common in Europe and Canada. Posterior and anterior hip approaches are more common here in the United States.
Direct anterior approach, or simply “anterior,” has become more prevalent and popular recently. Considered as a muscle-sparing approach, the direct anterior approach in hip replacement can lead to a quicker recovery. Patients can get rid of their walkers or canes sooner and return to work at earlier time. In our capitalistic society where returning to work early is essential for many reasons, this is godsend.
I also enjoy doing direct anterior approaches for other reasons as well. Not only do I see my patients recover quickly and walk faster and better, there are also technical advantages that come with the direct anterior approach. For instance, I can compare leg lengths more accurately, test stability of the hip, and incorporate x-ray easily to make sure that implants are positioned well when the patient is lying down on his or her back. These cannot be done well when the patient is lying on his or her side with either posterior or lateral approach.
Even with the direct anterior approach, there are different ways to make incisions. A traditional and more common way of making an incision is a vertical or longitudinal incision as seen in Figure 2. This is located high up on the upper outer thigh, along where the pockets of pants are located.
Another incision that can be made using anterior hip approach is more horizontal along the groin crease. This is also known as the Bikini incision (see Figure 3). Bikini incision is trendy and popular for obvious reason: you can wear a Bikini or underwear and not show any of scar that you had from hip replacement. Yes, this horizontal incision is more cosmetically pleasing in that sense. However, there’s more to this cosmesis than meets the eye. Let me explain.
There is a reason why a certain incision at a certain angle heals better than another incision of same-length but of different angle. Incision heals better under compression than under tension. Collagen fibers under the skin are oriented in certain directions depending on where they are located. You can see how they are oriented on your own skin. Take a look at your own armpit skin folds and groin creases. Also make wrinkles on your forehead. These skin folds, creases, and wrinkles form in certain directions according to the orientation of collagen fibers. You can even test where the natural skin folds by pinching your skin or pressing the skin with your index finger. You can do this much easier if you go along or parallel to the direction of collagen fibers. If you pinch or press the skin against (or perpendicular to) the direction of collagen fibers, you would feel more resistance.
The whole map of collagen fiber orientation in a human body has been drawn and represented as “Langerss Lines” seen in Figure 4. Plastic surgeons pay attention to these lines as any incision along these lines heals better than the incision against them. Any incision against Langer’s Lines can lead to more prominent scarring as there is force pulling skin edges apart over time (tension!). Vertical incision used in standard anterior hip approach, unfortunately, goes “against” Langer’s Lines. I personally have seen some young patients developing prominent scars with this approach (especially for those who had great results after their surgeries and had been quiet active, likely providing constant tension over their incisions and spreading the skin edges apart, thereby creating these prominent scars). The top corner of vertical incision especially has difficulty healing (especially for those who are obese, smoke, or have poor healing potential for various reasons), which can lead to more infection.
Bikini’s incision, on the hand, is made parallel to the Langer’s Lines, leading to better wound approximation and healing. When patients sit and stand, there is more compressive force along skin edges, bringing them together for better wound healing. The better the wound healing is, the less infection you are going to have. The less prominent the scar is, the more satisfied the patient is going to be. In other words, this Bikini incision has both cosmetic and functional benefits.
There you go, folks. Now, you know why I am utilizing Bikini incision for the majority of anterior approach in total hip replacement.
Figure 1. Surgical approaches used in total hip replacement
Figure 2. Standard Anterior Incision
Figure 3. Bikini Incision
Figure 4. Langer’s Lines
