Technological breakthroughs are not always the driving force behind significant advances in surgical procedures. Sometimes, just by looking at things a little differently, we discover new surgical approaches that make a real difference for our patients. When it comes to total hip arthroplasty (THA), that is precisely what we have done. By respecting the local anatomy and using modified instruments, we can now implant conventional cementless total hip prostheses through two incisions as small as 1.5 inches.

On the average, my minimally invasive THA patients are free of all assisted devices after nine days and are back to work in eight days. This compares with an average four- to five-day length of stay for conventional total hip patients, who typically need assisted devices for six or more weeks post-operatively.

My experience
The minimally invasive approach aims to preserve some or all of the structures damaged during conventional THA. Namely, open THA requires full exposure of the hip via an 8- to 14-inch-long incision; cutting of significant structures like the gluteus maximus, piriformis, quadratus, vastus and/or gluteus minimus and medius muscles (depending on the surgical approach) and forcible dislocation of the femur.

Currently, there are two approaches to minimally invasive THA, the single-incision technique (a more traditional approach that uses a smaller-than-usual incision) and the two-incision techniques (the one I prefer).

With the two-incision technique, I prepare and insert the acetabular component through one 1.5- to 2-inch-long incision and the femoral component through another 1.5- to 2-inch incision, often with the aid of fluoroscopy. This two-incision procedure spares all the muscles and tendons surrounding the hip and obviates the need for forcible hip dislocation. Both minimally invasive procedures require specialized retractors and instrumentation; specifically, I use a self-designed set of curved instruments outfitted with fiber-optic lights that enables access to and visualization of the hip.

To date, I have performed more than 200 minimally invasive THAs. Of my most recent 100 cases, 97 percent went home the same afternoon, and all went home within 23 hours with oral pain medications only. Importantly, however, just 38 percent of my total hip patients currently qualify for the minimally invasive procedure. Typically, these patients have few or well-controlled comorbidities.

Considerations
Here are some of the primary considerations for minimally invasive THA:

• Patient selection. Again, 38 percent of my total hip replacement patients qualify for this minimally invasive procedure. I have not attempted this procedure on patients with a history of significant hip operations (including those with existing orthopedic implants), those with significant deformity, morbidly obese patients, or patients with significant or uncontrolled comorbidities. As with any major outpatient procedure, other considerations also come into play - such as patient motivation and willingness, as well as the availability of family members or other nursing personnel to support the patient post-operatively.
• Complications. As with any surgical procedure, there is a risk of complications. Some theorize that the potential for inappropriate visualization may increase the risk of component malpositioning, intraoperative fracture and/or leg-length discrepancy. Clearly, it will be important to track results as more surgeons start performing the procedure. However, in my experience, I have had no indication that the minimally invasive procedure will result in higher rates of complications than the conventional, open procedure. In fact, of my first 150 cases, I have seen just one complication: an intraoperative femoral fracture, which occurs in approximately 2 to 6 percent of open procedures.

There is also concern that this procedure may extend operative times. After performing more than 200 cases, my average operative time is now one hour and 40 minutes. This compares favorably with the average operative time for the conventional procedure.

In addition, some have expressed concern that surgeons performing this procedure may tend to retract the soft tissues excessively, and thereby increase the potential for skin damage. However, I have not experienced any wound complications to date. When performed well, the minimally invasive procedure is much less traumatic to the soft tissues than the conventional, open approach.

• Learning curve. The minimally invasive procedure is quite different from the conventional, open approach and is technically demanding. Since the soft-tissue approach is the key to the procedure, a two-stage training program that involves cadaver work followed by the tutelage of an experienced surgeon is imperative. It often takes many cases for surgeons to become adept at the procedure. Technical training is also essential for OR nurses.
• Paradigm shift. The nursing and other support staff also undergo a substantial learning curve. It can be very hard to accept THA as an outpatient procedure, and everyone needs to work as a team to adopt this new paradigm. In addition, although the procedure does not require the nursing or support staff to put in more time overall, it does require a more intense and focused effort up front. For example, our therapist now works with patients before they go home, and this requires a relatively intense session that requires more organization, planning and up-front time commitment. In addition, in our hospital environment, our discharge planner now has to call patients beforehand because there is no time to complete these arrangements on the day of surgery.
• Reimbursement. Currently, insurers do not reimburse outpatient facilities for THA. Ultimately, as our experience grows, I am optimistic that insurers will reimburse minimally invasive THA as an outpatient procedure, given that it can reduce hospital costs substantially.

The future is upon us
Our greatest challenge has been the fundamental change in mindset that minimally invasive THA requires. Now that we have performed more than 200 of these procedures, however, our surgical team is convinced that THAs can be done on an outpatient basis. The keys to our success have been surgeon training and expertise, proper patient preparation and selection, and good logistical support. For us here at the Rush-Presbyterian-St. Luke's Medical Center, conventional large-incision THA is already following in the footsteps of open knee surgery and open cholecystectomy.