“Minimally invasive” hip replacement was widely introduced to the orthopaedic community and public several years ago and has been greeted variably with enthusiasm, concern, and skepticism1. Enthusiasm has centered around the potential for quicker recovery, a better cosmetic result, and less perceived invasion of the body. Concern has focused on the potential for more complications, related to poorer operative visualization and the learning curve for new methods. Remarkably, despite widespread marketing of minimally invasive methods by companies and orthopaedic surgeons and much dissemination of information of varying accuracy by the lay press, little objective data quantifying the risks and benefits of these methods compared with traditional methods have been available. Early short-term follow-up studies suggested possible benefits of the techniques, but those investigations mostly involved selected patient populations and often were performed with modified pain management and rehabilitation protocols1.
In this issue of The Journal, Ogonda et al. report on the first large, prospective, randomized blinded trial of a minimally invasive total hip arthroplasty technique, and the results call into question many assumptions that have been made about minimally invasive total hip arthroplasty. In an extremely carefully performed and comprehensive trial, the authors demonstrated that the procedure, as performed through a posterior approach, provided no objective short-term benefit with respect to postoperative pain level, postoperative use of pain medication, perioperative blood loss, time until hospital discharge, or speed of early functional recovery. Thus, when the results of this form of minimally invasive hip replacement were viewed objectively, without observer or selection bias, the authors could not verify that any of the main putative advantages of minimally invasive total hip arthroplasty actually were gained.
This important study has value when viewed narrowly as new information about the benefits of minimally invasive total hip arthroplasty, but it is also of broader importance to the orthopaedic community because it provides insight about responsible assessment and adoption of new technologies and operative techniques. The study demonstrated that there is no substitute for rigorous scientific comparison of new and traditional methods in trials that remove selection and observer bias. The results of the study by Ogonda et al. are notably different from those of early studies performed with less rigorous scientific methodologies. These different results highlight the value of considering the level of evidence when evaluating published material, a practice being increasingly adopted in orthopaedic publications2.
Most will agree that a study of this caliber on minimally invasive total hip replacement is overdue, and it is easy to be critical about widespread dissemination of new methods without rigorous testing of purported advantages. However, critics also should recognize the impediments to performing prospective, randomized trials of operative techniques, particularly in the United States, where patients especially value exercising their own choice regarding invasive procedures. Rapid recruitment of large patient cohorts for such studies is challenging.
In their prospective trial, Ogonda et al. found the complication rates of conventional and minimally invasive methods to be similar, which is encouraging, but that observation should be interpreted with caution. The trial was performed only after the one surgeon in the study had learned the technique well, having performed over 300 minimally invasive total hip arthroplasties before the trial began; thus, the surgeon's learning curve was not included in this trial. Also, a trial with just over 100 patients in each study group does not have the power to detect modest differences in the rates of complications that occur infrequently, such as infection, nerve injury, and dislocation.
In a second article in this issue, Fehring and Mason report on the serious complications that occurred in three patients treated with minimally invasive total hip arthroplasty. Each of these cases was from an unknown patient-pool denominator and represents complications that also can occur with conventional total hip arthroplasty. Nevertheless, when viewed in combination with recent articles by Woolson et al.3 and Archibeck and White4 that demonstrated a high rate of complications of minimally invasive total hip arthroplasty during surgeons' early experience with these methods, these case reports should remind surgeons and patients to focus not only on potential benefits but also on risks of new techniques. Most surgeons have a learning curve with any new operation, and, in general, the more radical the departure from established methods the greater the risk of unanticipated complications.
These valuable articles should not be interpreted as the last word on minimally invasive total hip arthroplasty. Champions of minimally invasive total hip arthroplasty methods have already reinvigorated the field of primary hip arthroplasty by challenging the established paradigms of hip-replacement technique and perioperative patient care1. The emphasis on quicker functional recovery and reduced pain spawned by minimally invasive operative methods has already had a dramatic effect on many hip-replacement practices, providing much improved perioperative pain management, much more rapid weight-bearing, and quicker functional recovery, regardless of the operative method used. The prospective trial by Ogonda et al. involved just one surgeon's experience with one minimally invasive technique, and minimally invasive total hip arthroplasty includes a whole family of different operations. More studies are needed to determine whether the findings of this study are generalizable to other surgeons or other methods of minimally invasive total hip arthroplasty.
It remains difficult to escape the common sense logic—already demonstrated in other fields such as arthroscopy and laparoscopy—that less invasive operative methods can provide benefits to patients, who find such methods appealing. As emphasized by the important information published in this issue, the benefits of minimally invasive total hip arthroplasty remain unproven, and one should remember that minimally invasive methods in some fields (such as arthroscopic carpal tunnel release) have failed to gain widespread acceptance. New technology frequently is greeted with unbridled enthusiasm, then there is a critical reappraisal, and then the procedure is either refined and adopted or discarded1. Hip surgeons will note that this cycle of popularity occurred with cementless implant fixation. Minimally invasive total hip arthroplasty will continue to evolve as instrumentation and techniques are refined and computer-assisted methods are integrated with these techniques, and it may ultimately surpass the results of conventional total hip arthroplasty5. As these methods develop, one hopes that they are subjected to careful scientific study and evaluation before widespread adoption. Total hip arthroplasty is already one of the most successful operations invented, and before radical changes in its practice are instituted, it is incumbent on developers of new methods to rigorously compare these new methods with traditional techniques, in the scientific manner highlighted in this issue of The Journal.
1. Berry DJ, Berger RA, Callaghan JJ, Dorr LD, Duwelius PJ, Hartzband MA, Lieberman JR, Mears DC. Symposium: minimally invasive total hip arthroplasty. Development, early results, and a critical analysis. J Bone Joint Surg Am. 2003;85: 2235-46.
2. Wright JG, Swiontkowski MF, Heckman JD. Introducing levels of evidence to the journal. J Bone Joint Surg Am. 2003;85: 1-3.
3. Woolson ST, Mow CS, Syquia JF, Lannin JV, Schurman DJ. Comparison of primary total hip replacements performed with a standard incision or a miniincision. J Bone Joint Surg Am. 2004;86: 1353-8.
4. Archibeck MJ, White RE Jr. Learning curve for the two-incision total hip replacement. Clin Orthop. 2004;429: 232-8.
5. DiGioia AM 3rd, Plakseychuk AY, Levison TJ, Jaramaz B. Mini-incision technique for total hip arthroplasty with navigation. J Arthroplasty. 2003;18: 123-8.