This chapter focuses on the minimally invasive posterior approach for total hip replacement. It presents indications and contraindications as well as the surgical technique. The current literature is discussed, focusing on the impact of minimally invasive techniques on early rehabilitation and the risk of perioperative complications of total hip replacement.
Indications for this procedure include primary hip replacement in patients with a body mass index less than 35 kg/m 2 .
Contraindications include body mass index greater than 35 kg/m 2 , major prior reconstructive hip surgery, revision hip replacement, and hip resurfacing.
Surgical approach is similar to standard posterior approach, and a gradual decrease in incision length is possible.
Special instruments facilitate minimally invasive surgery.
Cemented and uncemented stem fixation is possible.
The minimally invasive posterior approach does not influence the femoral or acetabular implant selection.
Results include a cosmetic scar, decreased blood loss, shortened hospital stay, and improved early rehabilitation.
Increased perioperative complications and less predictable implant positioning occur in inexperienced hands.
Patient selection is key to successful minimally invasive hip replacement.
Templating is essential for adequate level of head resection and restoration of leg length and offset.
Release of the reflected head of the rectus femoris muscle helps mobilize the femur anteriorly.
Offset reamer and acetabular component inserter facilitate correct cup placement.
Release the distal skin and fascia if the cup abduction angle cannot be safely restored.
Mini-incision or minimally invasive total hip replacement has been defined as a total hip replacement performed through an incision of 10 cm or less. Howell et al have suggested dividing the various minimally invasive approaches into two main categories: the mini-incision approaches and the two-incision approach. Although the two-incision approach is a completely new approach, the mini-incision anterior, anterolateral, and posterolateral approaches are modifications of the standard anterior, anterolateral, and posterolateral approaches. In 1998 Woolson et al presented their initial experience with a posterolateral mini-incision approach. Since then the authors have modified the techniques and developed special instruments that facilitate a mini-incision posterolateral total hip arthroplasty (THA). In addition, the authors have performed a number of studies to clarify the risks and benefits of the posterolateral mini-incision approach. The authors believe that implantation of a total hip replacement is feasible through a 7- to 10-cm incision in the majority of patients. Patient selection, special instruments, and a slow transition toward a smaller incision minimize the risk of perioperative complications during the implementation of the procedure.
This chapter describes the technique of a mini-incision THA using a posterolateral approach. It also provides an update on the current literature and discusses the rationale behind mini-incision THA.
INDICATION AND CONTRAINDICATIONS
Patient selection is a key factor for a successful mini-incision total hip replacement. Most patients with a body mass index of 30 kg/m 2 or less qualify for a mini-incision. The length of the incision is determined on an individual basis. Thin female patients with a body mass index of less than 25 kg/m 2 are particularly suitable for an incision length of 7.5 cm or less. A 7.5- to 10-cm incision is necessary to get adequate exposure in patients with a body mass index greater than 25 kg/m 2 . Although an incision of less than 10 cm is appropriate for the majority of patients, the following patients require a longer incision:
Heavy, muscular male patients with a body mass index greater than 35 kg/m 2
Patients with major prior reconstructive surgeries
Patients with Crowe type IV developmental dysplasia
Patients after open reduction and internal fixation of hip fracture requiring hardware removal
Patients undergoing hip resurfacing
Patients undergoing revision total hip replacements
Poor visualization should never be tolerated for the sake of a smaller, more cosmetically appealing incision. The main advantage of the posterior approach is that the incision can always be extended to improve visualization.
The patient is placed in a lateral decubitus position as for a standard posterior approach ( Fig. 21-1 ). An inflatable shoulder float is used in all patients to avoid injury to the cervical plexus. The skin incision is approximately 6 to 10 cm in length with not more than one third of the incision extending proximal to the tip of the greater trochanter ( Fig. 21-2 ). After incising the skin and exposing the fascia lata, the subcutaneous plane between the fat and fascia is developed ( Fig. 21-3 ). This allows the surgeon to use the incision as a mobile window. The fascia lata is incised between the middle and posterior third of the greater trochanter along the axis of the femur. Proximally the incision is angled in line with the fibers of the gluteal fascia. The gluteus maximus is finger split along its fibers proximally. A Charnley retractor is placed deep to the fascial layer, carefully protecting the sciatic nerve. After placing the hip in internal rotation and extension (protects the sciatic nerve), the short external rotators are exposed ( Fig. 21-4 ).
A Hohmann retractor with a right-angle handle is placed underneath the gluteus medius to define the piriformis tendon, and an Aufranc retractor is placed immediately adjacent to the proximal margin of the quadratus femoris around the inferior capsule. Now electrocautery is used to release the piriformis tendon and the conjoined tendon at their bony insertion. Care should be taken to remove the piriformis as far anterior as possible to preserve the length of the tendon and facilitate the repair of the external rotators at the end of the procedure. Both tendons are secured with nonabsorbable tagging sutures. The capsule is then released and tagged with nonabsorbable sutures. The lesser trochanter is exposed by sliding an Aufranc retractor underneath the quadratus femoris muscle. The hip is then dislocated with further flexion, adduction, and internal rotation.
The neck cut is then marked according to the preoperative plan ( Fig. 21-5 ). After cutting the femoral neck with an oscillating saw, the leg is straightened to a neutral position and a C-shaped Hohmann retractor is placed underneath the femur over the anterior wall of the acetabulum to retract the femur anteriorly ( Fig. 21-6 ). A release of the origin of the rectus femoris can be performed to facilitate exposure. After relieving tension by incising the inferior capsule, a wide bent Hohmann retractor is inserted into the posterior wall of the acetabulum between the labrum and the posterior capsule. An Aufranc or Cobra retractor is placed inferiorly around the transverse acetabular ligament in the obturator foramen. The acetabular labrum and overhanging soft tissues are then excised and the acetabulum is prepared in the standard fashion. The use of the “mobile window” to retract the skin incision inferiorly is important to allow the reamers to be horizontal enough to ensure a lateral abduction angle of 35 to 45 degrees ( Fig. 21-7 ).