The classic skin incision of the Hueter approach is longitudinal in line with the fibers of the tensor fascia lata (TFL). It starts slightly distal and lateral to the anterior superior iliac spine (ASIS) and aims in the direction toward the fibular head. A length of about 8 to 10 cm is usually sufficient for primary THA. Because this incision is perpendicular to Langer skin tension lines and the shear forces in the groin are in line with the incision, the cosmesis of the scar is often not optimal. In 2013, a variation of the incision for the DAA was published,¹ and it was named the “skin crease bikini incision for anterior approach total hip arthroplasty.” The modification aimed to improve scar results without affecting functional or pain scores and without causing more complications than with the traditional DAA. Since then, many groups performing the DAA have adopted the skin crease incision, and to date the data available in different studies corroborate that first description by Leunig et al¹ as a safe procedure not only associated with better wound healing but also related to many other advantages. This chapter aims to review the rationale behind this incision, to describe the technique, and to review the published articles and outcomes associated with this particular approach.

Wound complications in THA are relatively uncommon regardless of the surgical approach. In 2019, the Australian National Joint Replacement Registry demonstrated an overall risk of prosthetic revision for infection of 0.7%, with lower rates being associated with the use of the anterior approach in comparison with posterior approach interventions. Multiple factors potentially influence patient satisfaction with the scar associated with their hip replacement, including (but not limited to) incision location, length, and overall appearance. Mow et al² evaluated the scar cosmesis of posterior approach THA procedures at 2 years after surgery using a patient-reported outcome questionnaire and blinded independent medical observers using a standardized rating scale. Although patients rated their scars as being acceptable regardless of the incision length, surgeries conducted with mini-incisions were more likely to have wound complications and were rated as inferior using a standardized rating scale. Despite the wound appearance, patients consistently rated quality of pain relief and longevity of the implant to be of a higher priority. Therefore, it is important to note that smaller incisions do not necessarily equate to a better cosmetic result because smaller incisions may be associated with greater degrees of soft tissue trauma, even in patients with a lower body mass index.

Surgeons may also adopt multiple other adjunctive strategies to improve the wound appearance after hip replacement surgery, including the method of skin closure and the dressing selection. It is also relevant to consider the factors that can influence the reliability of wound healing, particularly with respect to facilitating rapid discharge and lowering the risk of readmission after surgical intervention. Siddiqui et al³ evaluated the use of 2-octyl cyanoacrylate (Dermabond, Ethicon) glue and dressing selection in relation to the frequency of wound leakage and the requirement for dressing changes. They determined that wound cosmesis outcome was not significantly influenced by the dressing selection or the use of glue. In addition, nonabsorbent dressings and Dermabond were associated with the lowest rate of postsurgical dressing interventions and drainage, an outcome that should be considered to simplify the logistics of managing patients in the community setting after hip replacement surgery. Similarly, the method of skin closure may also impact the functional wound outcome, with reduced rates of postsurgical drainage and associated delays in hospital discharge associated with the use of subcuticular closure in comparison with staples.⁴

The surgical approach and the direction of the incision are also factors directly under the influence of the operating surgeon that influence the cosmetic result and patient satisfaction of the procedure; in this regard, we introduce the explanation of the tension lines of the skin.

In order to provide the best cosmesis, one should consider the tension (cleavage) lines of the skin. The first description is commonly attributed to Karl Langer, who lived from
1819 to 1887 and was a professor of anatomy at Joseph’s Academy in Vienna.⁵ However, in 1861, Langer, in his first publication dealing with this subject, credited Guillaume Dupuytren with the discovery in 1834. Dupuytren observed that the wounds in the chest in a man who attempted suicide responded differently despite the fact that the instrument was the same; the direction of the skin cut counted. After that observation by Dupuytren, Langer performed a large series of these wounds on cadavers and performed a thorough mapping of tension lines that is known till today. These lines have received multiple names including tension (or cleavage) lines of the skin, crease lines, lines of elasticity of the skin, flexure lines, junction lines, or natural lines; all these terms are among the many variations of nomination that this concept has received.

Despite apparently being paramount for good cosmesis, present-day surgical practice has a variable use of Langer lines, and Lange lines are even discouraged in some anatomic locations. Better than the lines described by Langer, some authors recommend the “relaxed skin tension lines” (RSTLs) as described by Borges and Alexander.⁶ These RSTLs can be located by joint mobilization, muscle contraction, or pinching, with the last being the most reliable according to Waldorf et al.⁷ By performing the pinch test with the thumb and the index finger, the lines created in the skin are uniform and linear when the pinch is at the right angles to the RSTLs (Figure 12.1). For facial surgery, for instance, wrinkle lines and RSTLs show subtle and reconcilable variations, but Langer lines differ considerably and are not recommended. Regarding this chapter about the anterior hip, Langer lines do not vary significantly from RSTLs as described by Waldorf et al,⁷ and those are the same as the ones that occur when flexing the hip.

Throughout the surgical literature, there is a debate about the use of the cleavage lines of the skin. For instance, in general surgery, in a systematic review evaluating approaches for hemicolectomy, laparotomic right hemicolectomy with a transverse skin crease incision was preferable to laparotomic hemicolectomy with a midline incision.⁸ The review showed that a transverse incision offered less postoperative pain after physical activity, less need to administer analgesic therapy after surgery, better esthetic results, and better postoperative pulmonary function. Open surgery with a transverse or midline incision ensured a shorter operative time, lower costs, and a greater length of the incision compared with the laparoscopic incision. On the other hand, no differences were observed in oncologic outcomes.

Discussion about the possible use of skin crease incisions is not common in orthopaedic surgery, but some authors defend its use depending on the anatomic location. Incisions for hand surgery are complex and deserve many considerations, but in general terms the incision patterns include the Bruner zigzag incision and midlateral incision, both avoiding a longitudinal incision over the midvolar aspect of an interphalangeal joint. For the elbow, in a recent series evaluating an anterior approach for capitellum fractures, the authors performed an anterior approach incision to the elbow using a skin crease orientation with excellent results.⁹ In the knee, Haldeman and Hanna¹⁰ described the incision to treat neurofibromas of the peroneal nerve, and they reported that incisions across
a skin crease can be either oblique or zigzag but never perpendicular to it. Skin crease incisions have also shown advantages in foot and ankle surgery. In a series by Kim et al¹¹ published in 2014, the authors described the skin crease approach as a novelty. They presented a series of 95 ankles (57 patients) operated on for Achilles tendon tightness; the surgery was performed using an incision on a skin crease of the heel and Z-lengthening of the tendon. The authors reported a low rate of complications such as scarring, adhesion, total transection, excessive lengthening, and recurrence of shortening. Kim et al¹¹ advocated in favor of the skin crease incision due to excellent cosmesis and the short operative time.

In hip arthroscopy, the orientation of the incision for the portals could also have implications in the subsequent scar characteristics. Babazadeh et al¹² evaluated the scars of 75 patients who underwent bilateral arthroscopy; a longitudinal incision was made on one side and a transverse incision on the opposite side. The study showed that transverse portal positions for hip arthroscopy have an advantage over longitudinal portal positions in terms of the total scar area and thickness up to 6 months postoperatively.¹²

For the pelvis, one of the most commonly used incisions is the Pfannenstiel incision, also known as the Kerr incision.¹³ This skin crease incision is the most common method for performing cesarean sections for obstetric delivery. It is also used for hernia repair and is used in orthopaedic surgery to approach both pubic rami in the setting of pelvic fracture. Additionally, the Stoppa approach, which can be performed to treat acetabular fractures¹⁴ and has even been suggested for retrieving intrapelvic cup migration in a total hip replacement,¹⁵ uses this classic skin crease approach. The Pfannenstiel incision is superior in terms of esthetic results compared with other approaches; several studies have shown fewer wound infections and less postoperative pain. In analogy to the incision described in this chapter, the Pfannenstiel incision is usually called the bikini incision or the bikini cut because of its esthetic advantage and the proximity to the limit of the bikini outfit.

Anecdotical but interesting for this chapter with the term bikini, the swimsuit “bikini” was invented by the French engineer Louis Réard in 1946. He got the name from the atomic bomb tests taking place during that era in the Bikini Atoll, just before he was about to launch this new swimsuit design. It is important to outline at this point that the bikini incision is not necessarily a “groin” incision and that it can be performed distally to the groin, maintaining the same objectives (Figure 12.2); the technique is described in the following section.