The two-incision minimally invasive total hip arthroplasty is practical and safe for most traditional total hip arthroplasty candidates.
Thin female patients with low muscle mass, small bone structure, and atrophic changes are the best candidates.
This procedure is exceptionally difficult to perform in morbidly obese patients.
Patients with marked abnormal hip joint anatomy, significant prior surgical scarring, or complete hip dislocation may be better candidates for other approaches.
Proper preoperative planning and templating are crucial.
Place the patient supine with a small bolster under the ischium on the affected side.
Make the anterior incision directly over the femoral neck from the base of the femoral head distally approximately 1.5 inches to the intertrochanteric line.
Make a longitudinal incision parallel to the sartorius muscle and tensor fascia lata, avoiding the lateral femoral cutaneous nerve.
Make an in situ neck cut, remove the femoral head, then make the final neck osteotomy based on preoperative templating.
Expose and ream the acetabulum with specially designed low-profile reamers.
View the acetabulum with the fluoroscope and position the cup in 45 degrees of abduction and 20 degrees of anteversion.
Make a 1- to 1.5-inch incision in the posterior lateral buttocks just posterior to a line collinear to the femoral canal.
Use specially designed side-cutting reamers to ream the canal and then broach.
Looking through the anterior wound, align the broach rotationally to the calcar so it matches the native version of the femoral neck.
Place the trial neck and head on the broach from the anterior wound; check stability.
Use the fluoroscope to assess leg length by comparing the level of the lesser trochanters.
Seat the final stem and confirm the position with fluoroscopy.
Initiate occupational and physical therapy a few hours postoperatively.
Avoid making the anterior incision too medial.
Make the first neck cut as high on the head as possible.
A tendency to lever the reamer on the femur exists.
Do not over-antevert the acetabular component.
Do not make the posterior incision too anterior.
A common mistake is to overly antevert the broach and stem, which may result in femoral fracture.
Traditional approaches to total hip replacement have been invasive procedures that involve significant pain and prolonged recovery. But minimally invasive total hip replacements are possible with new techniques that spare the muscles around the hip. Furthermore, if the perioperative pathway is revised and these new techniques adopted, recovery and rehabilitation can be significantly reduced. This chapter describes the two-incision minimally invasive total hip arthroplasty, a new technique that is intended to spare the muscles and tendons around the hip and thereby reduce pain and recovery after total hip replacement.
At Rush Hospital in Chicago, the authors routinely perform the two-incision minimally invasive total hip arthroplasty on an outpatient basis. Our patients benefit from the rapid recovery because the procedure does not damage muscle or tendon, unlike traditional total hip replacement, which involves significant surgical trauma. Although the authors also perform single-incision minimally invasive techniques, the two-incision minimally invasive total hip arthroplasty is preferred because it minimizes surgical trauma, pain, and morbidity and expedites the recovery process. The two-incision minimally invasive total hip arthroplasty works with standard implants to maintain present expectations for implant durability.
This chapter describes the two-incision minimally invasive total hip arthroplasty; one incision is for acetabular preparation and placement, the other for femoral preparation and placement. Because the patient is supine during the procedure, fluoroscopy can be used to ensure proper starting points for the incisions and accurate component placement. Although specialized instruments have been developed to facilitate the procedure, the two-incision minimally invasive total hip arthroplasty still requires meticulous surgical technique. Surgeons interested in performing the two-incision minimally invasive total hip arthroplasty should undergo specialized training.
INDICATIONS AND CONTRAINDICATIONS
As with most surgical procedures, the two-incision minimally invasive total hip arthroplasty (THA) is easiest to perform on thin female patients with low muscle mass, small bone structure, and atrophic changes. These are the best patients to start with; then, after gaining some experience, the surgeon can progress to more challenging patient types. The most difficult patients are heavy, muscular men with big bone structure and hypertrophic changes. And yet the two-incision approach is the easiest minimally invasive technique to perform on these big men because the leg remains in one of two anatomic positions during the entire case, unlike all other minimally invasive THA approaches that require significant movement of the leg throughout the procedure.
Although the two-incision minimally invasive total hip arthroplasty is practical and safe for most traditional THA candidates, certain exceptions remain at this time. Cadaveric work has shown the technique to be exceptionally difficult in morbidly obese patients. In addition, patients with marked abnormal hip joint anatomy, significant prior surgical scarring, or complete hip dislocation may be better candidates for other THA approaches.
Figure 24-1 shows an extreme two-incision case. This patient had five previous surgeries for developmental dysplasia of the hip, including two pelvic osteotomies. Even in this case, however, the two-incision minimally invasive total hip arthroplasty was performed successfully.
Proper preoperative planning and templating are crucial. Because extraarticular landmarks are limited, you must gather the proper anatomic parameters to place the implants correctly. Use preoperative radiographic analysis to calculate optimal femoral and acetabular component fit, the level of the femoral neck cut, the prosthetic neck length, the femoral component offset, and all the appropriate implants needed during surgery. As with other total hip arthroplasties, the anteroposterior (AP) view of the pelvis usually is the most accurate way to determine proper leg length. Only in extreme cases will a scanogram or computed tomographic evaluation help. Once the proper clinical and radiographic information on leg lengths has been obtained, determine the appropriate correction, if any, to be made during surgery.
However, leveling the legs of certain patients may not be possible or even advisable. For example, leveling the legs of patients with unusually large preoperative offset or severe varus deformity can bring unwanted tension to the abductor muscles. And in cases in which hip stability and leg length cannot both be optimized, a stable hip is more important than obtaining leg-length equality. Lastly, when the involved hip is longer than the contralateral hip, there usually is no choice but to further lengthen the hip.
Begin templating with the AP radiograph. Superimpose the acetabular templates sequentially on the pelvic x-ray film with the acetabular component in 45 degrees of abduction. Assess several sizes to estimate which acetabular component will provide the best fit for maximal coverage. Mark the acetabular size, position, and center of the head on the x-ray films. Note the superior coverage of the acetabular component in 45 degrees of abduction to reproduce during surgery to ensure proper component abduction and avoid vertical positioning. Then choose the appropriate femoral template. To estimate the femoral implant size, assess both body and distal stem size on the AP radiograph and then check stem size on the lateral radiograph. The stem of the femoral component should fill, or nearly fill, the medullary canal in the isthmus area on the AP x-ray film. Next, assess the fit of the stem body in the metaphysial area. The medial portion of the body of the component should fill the proximal metaphysis as fully as possible.
Once the appropriate femoral component size has been established, determine how high to place it in the proximal femur. To lengthen the limb, raise the template proximally. To shorten the limb, shift the template distally. Once height is determined, note the distance in millimeters from the collar or most proximal aspect of the porous surface to the top of the lesser trochanter. If the leg length is to remain unchanged, put the center of the prosthesis head at the same level as the center of the femoral head of the patient’s hip, which also should correspond to the center of acetabular rotation.