Update on Minimally Invasive Hip and Knee Arthroplasty  CME Disclosures

Don Johnson, MD

Introduction
The momentum behind the advent of minimally invasive arthroplasty has been the concept of faster recovery for the patient, with much less morbidity and pain. Consider the potential economic savings if each one of the estimated 500,000 total hip and knee arthroplasty patients in the United States each year stayed 1 less day in the hospital.

In the arena of sports medicine and arthroscopy, there is no doubt that the advent of minimally invasive surgery (MIS) improved the perioperative morbidity of knee and shoulder reconstruction. However, the main question to ask about minimally invasive joint arthroplasty is, "Is this just marketing hype, or does the short incision really improve patient care?"

The increase in reported complications and the limitation of available instrumentation have made this procedure questionable. The videos that were shown of patients walking several hours after surgery at this year's 72nd Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS) in Washington, DC, by the proponents of the 2-incision hip arthroplasty were certainly impressive.

However, the learning curve necessary to overcome the complication rates associated with MIS techniques may not be attainable by most surgeons. Do minimally invasive techniques really shorten the hospital stay, and reduce pain, without jeopardizing alignment of the components, and without increasing the complication rate? Is the MIS technique market- and patient-driven hype, without scientific evidence that it improves patient outcomes?

Perceived advantages of MIS include:

Shorter incision with better cosmesis;
Less muscle dissection;
Less blood loss;
Less pain;
Shorter hospital stay;
Faster rehabilitation; and
Less time off from work needed and a faster return to recreational activities.
The disadvantages of MIS techniques include:

Less fun, more sweat;
Longer operating room time;
Need for more assistants;
Potential nerve Injury;
Unrecognized fracture;
Recognized fracture;
Malposition of the components;
Skin and muscle damage; and
Yet another learning curve to be surmounted.
A plethora of papers from key opinion leaders in MIS techniques were showcased at a special symposium at AAOS 2005; these studies, which are highlighted below, addressed key positives and negatives of the MIS approach in the setting of both knee and hip arthroplasties.

Paper Number 070: Multi-center Study: Comparison of Standard to Minimally Invasive Total Knee Arthroplasty
A prospective, multicenter, randomized study from Kolisek and colleagues[1] compared the postoperative functional outcome of patients of the mini-invasive technique (less than 2 times the patellar length) with the standard median parapatellar approach (6-cm to 14-cm incision length, with eversion of the patella, and quadriceps splitting) in total knee arthroplasty (TKA).

In this study, 80 patients were studied prospectively. The mean Knee Society score at 3 months was 83 points for the MIS group and 86.0 points for the standard group. The MIS group had higher SF-12 scores, with more MIS patients answering yes to the question of whether they would have the procedure again. Postoperative, radiographic alignment parameters were similar in both groups.

The results of this multicenter study demonstrated that patients who underwent minimally invasive TKA exhibited results that were comparable to patients who underwent traditional surgery, with respect to pain levels, rehabilitation needs, and functional return.

Paper Number 071: Minimally Invasive Lateral Approach to Total Knee Arthroplasty
This study by Mont and colleagues[2] compared the lateral MIS approach (10-cm incision, with no violation of the quadriceps) with and without navigation with standard knee replacement through both traditional and minimal incisions.

Twenty-six knees were done with the minimally invasive lateral approach for TKA. These patients were compared with a matching group of patients who had standard total knee replacements, and with a group of patients undergoing TKA through a minimal incision medial approach. The patients with the lateral approach had better short-term results, including less pain, reduced analgesic use, shorter hospital stay, and better function. Radiologic evaluation showed no difference between the 2 groups.

Paper Number 072: Minimally Invasive Total Knee Replacement: The Impact of Patellar Eversion on Recovery
Conventional wisdom states that patellar eversion during knee replacement contributes to postoperative pain and stiffness. The minimally invasive techniques that do not evert the patella can improve early function. In a study by McAllister and Stepanian[3] of 177 patients who underwent knee arthroplasty, one group of 89 patients underwent standard techniques with patellar eversion and a second group of 88 patients had MIS. The MIS group had smaller incisions (14 cm vs 21 cm); a shorter length of hospital stay (3.6 days vs 4.2 days); and significantly better motion at 2, 6, 12, 26, and 52 weeks. The MIS group required fewer manipulations. There was no difference in alignment, component position, or cement technique. However, the control group had a decreased patellar height compared with the MIS group. The investigators concluded that patella eversion caused stiffness and patella infera.

Conclusion: Minimally Invasive TKA
The consensus from the presenters during this segment of the symposium was that the minimally invasive procedure for TKA did in fact enhance patient outcomes.

Review of Minimally Invasive Total Hip Arthroplasty
Total hip arthroplasty (THA) may be performed through the standard 20-cm length incision, the 10-cm to 12-cm minimal posterior incision, the 2-incision technique, the minimal anterolateral approach, and the anterior approach. Each of these has proponents that can present excellent results. The average arthroplasty surgeon has to look at each approach, practice the technique in a hands-on cadaver learning situation, and then decide what technique works best in each clinical setting. The presentations highlighted below review some of the key data points related to novel approaches to minimally invasive THA.

Paper Number 137: Total Hip Arthroplasty: Does Incision Length Matter?
This randomized, prospective study by Richard Rothman and coworkers[4] evaluated the role of small-incision surgery for THA. This study reported the outcome of THA performed through the conventional and small-incision techniques by a single surgeon. One hundred twenty patients with a mean age of 70.2 years were enrolled in the study. The 2 groups were matched for age, sex, and body mass index. Sixty patients received THA through the conventional technique, and the other 60 patients underwent THA with small-incision exposure. The results showed that there was no detectable difference in outcome between the 2 groups with regard to blood loss, narcotic requirement, functional recovery, and length of stay. One patient in the MIS group required a revision of the femoral component 8 months later. The study authors concluded that there is no reason to do a THA through a small incision, except perhaps because the patient demands this type of approach. They asked the question: "Is the MIS hip arthroplasty patient-driven?"

Paper Number 139: A Prospective Randomized Patient-Blinded Comparison of Mini vs Standard Incision THA
The aim of this study was to assess the effect of incision length (and patient recognition of incision length) on short-term functional outcomes and perioperative analgesic requirements after THA.[5] In this prospective study, 50 patients were randomized to receive either a shortened or a standard-length posterolateral incision. Patients, therapists, and nurses were blinded to the length of the incision for the first 10 postoperative days. A third group of patients refused to be randomized and specifically requested a small incision. There were no statistically significant differences between groups with respect to body mass index, operative time, estimated blood loss, drop in hemoglobin, narcotic utilization, length of stay, distances ambulated during inpatient therapy sessions, or Harris Hip Scores at 10 days, 3 weeks, or 3 months. The group who requested the small incision ambulated greater distances on postoperative days 2 and 3, and used significantly less narcotics than the other 2 groups. Visual Analog Scale pain scores were significantly lower on postoperative day 1 for the small-incision group, but not on days 2 and 3.

The investigators concluded that incision length does not appear to affect early postoperative function or pain when patients are blinded to incision length. Patients who request and are aware that they have received a small incision recover quickly and require less narcotics. This suggests that patient expectations may be a more potent determinant of postoperative recovery than incision length.

Paper Number 141: Minimal Invasive Total Hip Arthroplasty via Direct Anterior Single Incision Approach
The hypothesis of this study by Rachbauer and coworkers,[6] from Innsbruck, Austria, was that minimally invasive THA via a direct anterior single incision is a safe procedure that reduces blood loss, limits postoperative pain, and minimizes hospitalization stay.

In this study, 100 consecutive patients with no exclusion criteria were included. Nineteen patients showed a body mass index > 30.

The median incision length was 6.75 cm. The median angle of cup inclination was 44.1�� and 0�� of the varus/valgus position for the stem. Blood loss was significantly reduced. The rehabilitation was fast (mean Western Ontario and McMaster Universities [WOMAC] score 90.4 at 6 weeks).

Patients noted little postoperative pain. No dislocations or nerve palsies occurred. The complication rate was low with 1 fissure of the proximal femur, 1 perforation of the acetabulum, and 1 deep infection. The study authors concluded that the minimally invasive anterior incision could reduce blood loss, postoperative pain, and the hospitalization time, while maintaining adequate placement of the implants.

Paper Number 142: Muscle Damage After THA Done With the 2-Incision Minimally Invasive and Mini-Posterior Techniques
This study, by Mardones and colleagues,[7] quantified the amount and location of hip muscle damage after a 2-incision technique compared with that after a miniposterior hip arthroplasty. Two-incision hips were done with fluoroscopy, as previously described, with an uncemented socket and a straight fully coated femoral stem. The miniposterior hips were done with the same implants. In this cadaver study, the 2-incision and the miniposterior hip arthroplasty techniques cut or damaged measurable and significant amounts of muscle or tendon in every case.

Paper Number 143: Complications With the 2-Incision Technique in Total Hip Arthroplasty
In this series of 87 patients, the 2-incision surgical technique with intraoperative fluoroscopy was used to implant an uncemented hemispheric socket and an uncemented femoral component.[8]

At 6 months, 10% of the patients required repeat surgery: 2 to treat a femoral fracture that was identified postoperatively, 1 to treat an acute dislocation, 2 to perform superficial debridement for wound drainage, and 4 for early subsidence and loosening of the femoral implant. Twenty-five percent of the patients suffered an injury to the lateral femoral cutaneous nerve. As a comparison, in 96 primary THAs that were performed with the mini-incision direct lateral approach, the overall complication rate was 6% and the reoperation rate was 3%. The investigators concluded that 2-incision hip arthroplasty is a technically demanding procedure even in the hands of an experienced surgeon.

Paper Number 144: Two-Incision THA in 80 Consecutive Unselected Patients: Prevalence of Complications
The proponents of 2-incision THA suggest that this technique is minimally invasive and promotes rapid rehabilitation with a low prevalence of complications. The limited data available involve a selected subgroup of patients who are younger and have fewer medical problems than the typical total hip patient. This study compared 80 consecutive 2-incision hips in unselected patients with the prior 160 unselected, consecutive traditional open total hips.[9] Eighty consecutive patients (45 women, 35 men) with a mean age of 70.5 years had a total hip done with the 2-incision technique. All patients had an uncemented socket and an uncemented proximally coated stem. The mean operative time was 68 minutes. Significant early complications occurred in 14% of patients and included 4 intraoperative proximal femoral fractures treated with a cable; 3 postoperative periprosthetic femoral fractures that required femoral revision, which resulted in 1 deep infection; 1 anterior dislocation that required open reduction; and 1 femoral subsidence that required no treatment. The prevalence of complications in the prior 160 open THAs done with similar implants was 3% (4 intraoperative proximal femoral fractures, no postoperative fractures, and 2 dislocations). The study authors concluded that the early enthusiasm for 2-incision MIS must be tempered because of the complication rate of 14% compared with 3% for traditional surgical techniques.

Paper Number 147: Minimally Invasive Total Hip Arthroplasty: Comparison Between One-Incision and Two-Incision Technique
The aim of this study was to evaluate the early clinical and radiographic results of THA with MIS through 1- or 2-incision techniques.[10] Two hundred eighteen consecutive total hip procedures were analyzed clinically and radiographically (1-incision technique in 100 patients and 2-incision technique in 118 patients). The mean size of the skin incision was 7.5 cm for the 1-incision approach and 12.1 cm for the 2-incision approach. (The anterior incision was 7.45 cm and the posterior incision was 4.65 cm.) The mean operative time was 72 minutes for the 2-incision technique and 52 minutes for the 1-incision technique. The mean length of hospital stay and the period of using crutches in 2-incision THA was reduced when compared with 1-incision THA. The study authors showed videos of patients walking several hours after the operation. The incidence of perioperative complication was higher in the 2-incision group, but the postoperative rehabilitation was faster.

Conclusion: Minimally Invasive THA
The consensus of the attendees at this special symposium was that 2-incision THA increases the risk of complications, causes more muscle damage, and may only slightly reduce hospital stay and rehabilitation time.

Unlike the minimally invasive total knee procedure, most investigators, especially the group from the Mayo Clinic (Rochester, Minnesota), postulated that the 2-incision technique was not indicated for routine THA.

This discourse on the part of the attendees at this session may be deja vu of the discussions of the past related to arthroscopic and laparoscopic procedures. However, once orthopaedic surgeons overcome the learning curve, MIS techniques may emerge as the new standard of care.

References
Kolisek F, Bonutti P, Hozack W, et al. Multi-center study: comparison of standard to minimally invasive total knee arthroplasty. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 070.
Mont M, Bezwada H, Ragland P, Thomas C, Bonutti P. Minimally invasive lateral approach to total knee arthroplasty. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 071.
McAllister C, Stepanian J. Minimally invasive total knee replacement: the impact of patellar eversion on recovery. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 072.
Rothman R, Ciminiello M, Parvizi J. Total hip arthroplasty: does incision length matter? Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 137.
Wright J, Rosse D, Rosse S. A prospective randomized patient-blinded comparison of mini versus standard incision THA. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 139.
Rachbauer F, Nogler M, Krismer M, Kessler O. Minimal invasive total hip arthroplasty via direct anterior single incision approach. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 141.
Mardones R, Nemanich J, Trousdale R, Pagnano M. Muscle damage after THA done with the 2-incision minimally invasive and mini-posterior techniques. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 142.
Bal B, Haltom J Jr. Complications associated with the two-incision technique in primary total hip arthroplasty. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 143.
Pagnano M, Lewallen D, Hanssen A. Two-incision THA in 80 consecutive unselected patients: prevalence of complications. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 144.
Yoon T, Moon E, Rowe S, et al. Minimally invasive total hip arthroplasty: comparison between one-incision and two-incision techniques. Program and abstracts of the American Academy of Orthopaedic Surgeons 72nd Annual Meeting; February 23-27, 2005; Washington, DC. Course Number 147.