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Comparison of Primary Total Hip Replacements Performed with a Standard Incision or a Mini-Incision
Steven T. Woolson, MD1; Christopher S. Mow, MD2; Jose Fernando Syquia, MD2; John V. Lannin, MD3; David J. Schurman, MD4
1 1101 Welch Road, Suite C8, Palo Alto, CA 94304. E-mail address: stevewoolson@yahoo.com
2 500 Arguelo Street, Suite 100, Redwood City, CA 94063
3 795 El Camino Real, Palo Alto, CA 94301
4 Stanford Medical Center, 300 Pasteur Drive, R-144, Stanford, CA 94305
View Disclosures and Other Information
The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at Stanford University Hospital, Stanford, California

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2004 Jul 01;86(7):1353-1358
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Background: Primary total hip replacement performed through an incision that is =10 cm in length has been advocated as a minimally invasive technique. Proponents have claimed that mini-incision techniques reduce blood loss, transfusion requirements, postoperative pain, and the length of the hospital stay compared with standard techniques through a longer incision. However, we are aware of no well-designed comparison study that supports these claims. The purpose of the present study was to compare the short-term results of a mini-incision with a standard incision technique for total hip replacement.

Methods: A consecutive series of patients who underwent 135 primary unilateral total hip replacements (fifty with use of a mini-incision [=10 cm] and eighty-five with use of a standard incision) by three surgeons at one hospital were studied. Each surgeon selected patients to have a mini-incision procedure and performed a standard approach in the remaining patients. A posterior approach was used for all procedures. In-hospital data were collected retrospectively, and the initial postoperative radiographs were analyzed. Because of the selection process, the patients who had a mini-incision had both a significantly lower average body-mass index (p = 0.008) and a lower average score on the American Society of Anesthesiologists rating (p = 0.006), indicating that they were thinner and healthier than the patients who had a standard incision.

Results: With the numbers of patients available, no significant differences were found between the groups with respect to the average surgical time, intraoperative blood loss, in-hospital transfusion rate, length of hospital stay, or the patients' disposition after discharge. The mini-incision group was found to have a significantly higher risk of a wound complication (p = 0.02), a higher percentage of acetabular component malposition (p = 0.04), and poor fit and fill of femoral components inserted without cement (p = 0.0036).

Conclusions: There was no evidence that the mini-incision technique resulted in less bleeding or less trauma to the soft tissues of the hip, factors that would have produced a quicker recovery and a shorter hospital stay, than did the standard technique. The present study, which was based on the authors' initial experience with the mini-incision technique, failed to confirm the positive clinical outcomes reported by previous uncontrolled cohort studies, and the findings suggest that further analysis of this new technique is needed before it can be recommended for general use.

Level of Evidence: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Steven T. Woolson md
    Posted on November 19, 2004
    Dr. Woolson responds to Dr. Boniface

    To the editor:

    We are grateful for the comments by Dr. Boniface regarding our response to Dr. Dorr's criticism of our paper. We agree with his conclusion that fads and unproven techniques are frequently promoted by surgeons and implant manufacturers as marketing ploys in our orthopaedic specialty. An example of this would be the THARIES hip implant that later proved to be a failed experiment. Objective evidence from well-designed research should always precede widespread dissemination of a new technique: otherwise, the cart preceeds the horse.

    Steven T. Woolson, MD

    Raymond J. Boniface MD
    Posted on October 29, 2004
    On Dr. Woolson's response to Dr. Dorr
    Boniface Orthopaedics, Inc

    To the editor,

    My congratulations to Dr. Woolson, not only for his important study, but also for his trenchant response to Dr. Dorr's criticism.

    Having trained during the 1980's boom in implant innovation, I was impressed with the frequency with which unproven techniques and implants were widely and rapidly adopted. Many patients were ill-served by this. The excessive entrepreneurial zeal of some implant surgeon "innovators" contributed to this trend.

    We and our patients are well served by researchers who cast a critical eye on the latest surgical fads.

    Raymond J. Boniface MD FACS

    Steven T. Woolson, M.D.
    Posted on August 17, 2004
    Dr. Woolson responds to Dr. Dorr:
    Stanford University Hospital

    To the Editor:

    We would like to address some of the assumptions made by Dr. Dorr regarding our recent article. We emphasized that these results represented our learning curve with the procedure. All of the surgeons gradually reduced the size of their standard incisions prior to beginning this series of mini-incision cases, as suggested by Dr. Dorr. These mini-incision procedures were begun in 2001, the same year that Dr. Dorr began his experience (1) with the procedure using a 10-12-cm incision with standard hip instruments and retractors. The surgeon who performed procedures using incisions shorter than 10 cm did use specialized retractors. Two of the three surgeons had training in the technique prior to using it including one surgeon who has attended Dr. Dorr’s annual course and has watched him perform live mini-incision hip replacement surgery for the last three years.

    We did obtain IRB approval for this retrospective study. We are surprised that Dr. Dorr feels that IRB approval must be obtained in order to ethically perform a mini-incision hip replacement, since he and the other proponents of mini-incision technique have not mentioned this proviso in their publications. The AAOS has supported courses, technique DVD’s and other educational resources regarding the mini-incision procedure and has published patient information about it on their website, but to our knowledge has not regarded it as an experimental operation requiring IRB approval. All of our patients were given explicit informed consent regarding the risks and complications of total hip replacement and were told of the size and location of their incision.

    Dr. Dorr wisely stated in his AOA symposium talk (1) that his claims of good pain relief and rapid functional recovery for mini-incision technique could possibly be explained by anesthesia and pain management techniques rather than the procedure itself and also admitted that he had no data comparing mini-incision with standard technique. We feel that it should be the responsibility of the innovators of the technique to provide randomized, prospective studies of similar groups of patients with respect to BMI, age and gender using standard and mini-incision technique with the same implants and postoperative rehabilitation protocols. Until peer- reviewed scientific evidence demonstrates significant short-term benefits from the procedure with equal safety and acceptable component orientation, we do not believe that the procedure should be recommended for general use. This is also the stance that the AAHKS has suggested. It must be kept in mind that the use of a small incision for total hip replacement is not claimed to have any long-term benefit. If other studies concur with our results that it has few short-term benefits, is not as safe, and is more difficult to perform, we are not sure what the indications for the procedure are. We are ready to embrace any new technique that is an improvement over an old one, but not based on results of single cohort studies alone.


    1. Dorr, L.D., Single-Incision Minimally Invasive Total Hip Arthroplasty. J. Bone Joint Surg. 85A:2236-2238, 2003

    Steven T. Woolson, MD
    Posted on August 09, 2004
    Dr. Woolson responds to Dr. Sherry:
    Stanford University

    To the Editor:

    Thank you for your comments on our manuscript. We agree wholeheartedly with your last observation and hope that further prospective studies will vindicate MIS hip replacement. We too look forward to a way to do hip replacement better.

    Peter F Holmes MS MD
    Posted on August 09, 2004
    Reply to "Mini-Incision" vs Standard Incision Hip Replacement
    Private Practice

    To the Editor:

    The article by Woolson, et.al brings to the forefront three important issues. First, this is one of the best-controlled studies comparing systems showing no superiority of one or the other. Contrast this to implant messages on the web or in the Physician’s Weekly, surgery edition stating “Advancement in minimally invasive techniques are helping surgeons reduce post-surgical pain, recovery time, and hospital stay for hip replacement patients.” This contrast is important because procedures are being recommended by the implant people without scientific evidence supporting their data. Unfortunately this allows these implant services to underwrite the orthopedic activities, which seems condoned by the Academy which ought to stand up to these web pages that promote unproven benefits until such benefits are proven and then it should be orthopaedic surgeons instead of implant web pages making the recommendation. It is a gross conflict of interest for the academy and other meetings to ask these implant companies to underwrite their costs.

    Second, it seems the point of the minimally invasive hip is to get someone out of the hospital in 2 days. I can essentially get any patient out of the hospital within 2 days. However, there is a social structure attached to this patient. They are Medicare and have paid into the system for 45 years and deserve better. In my opinion many should go to a rehab facility and they deserve to have their home set up during that rehab time to accommodate their recent surgeries, be it minimally invasive or regular surgical techniques.

    Lastly, think about the battle about reimbursements. You get the message out that we can get these patients out in 2 days, however improper that is, then Medicare is going to say “Okay, and here are your new reimbursement rates.” I think you are cutting our throats based on unproven information from a web page from drug and implant people that has recently been shown to be unproven by this article.

    Eugene Sherry
    Posted on August 01, 2004
    MIS=Much Improved Surgery
    Sydney Private Hospital

    Dear Sir,

    Woolson et al (J Bone Joint Surg Am 2004; 86: 1353-1358) have provided a useful paper in the development of MIS Hip Surgery. The challenge of this new technique will be met in the same way most surgeons passed from standard incision to arthroscopic ACL knee surgery. MIS should stand for "Much Improved Surgery"; it is an opportunity to do a better THR.

    Our philosophy is that surgeons require the right patients(ideally <80kg and in whom the greater trochanter is easily palpable); the right instruments( to guide the surgeon,orientate the components and balance the soft tissues); and the desire to learn a new technique (it is not only on the beaches of Rio that scar size matters).

    Lawrence D Dorr
    Posted on July 30, 2004
    An Inappropriate Study
    The Arthritis Institute

    To the Editor:

    The “study”' “Comparison of Primary Total Hip Replacements Performed with a Standard Incision or a Mini- incision”, by Woolson, et.al,is probably the quintessential example of comparing apples to oranges because the authors retrospectively compared their standard operation, with which it is assumed they were skilled, to a new operation with which they were not skilled, without any scientific model, training, instrumentation or guidance. It was also bad science because they performed a study operation on patients without Institutional Review Board approval. This is the second study published from Stanford in the last year in which the IRB was not involved in surgery that was “experimental”(1).

    This manuscript is simply an arrogant statement by the authors who assumed that with fellowship training and experience of 10+ years they could perform a new operation as well as they perform the operations they have done for all those previous years.

    There is not a single innovator of the small incision operations that has suggested that these operations were as easy, were not more stressful, or did not require a learning curve with special instrumentation, as compared to THA using standard incisions. At every meeting at which I have participated regarding this subject, it has always been emphasized that a surgeon should not go directly to a 10 cm or less incision. The incision should gradually be decreased so that the surgeon becomes comfortable with the field of vision. These surgeons were less responsible to their patients than a low volume surgeon who obtains training, has the proper instrumentation, and initially learns the operation with supervision.

    The authors were also not well informed of the knowledge that the use of a mini-incision is more than just the incision and is a change in the process of total hip replacement. In combination with a shorter incision there must be preoperative education, staff training, and coordination of the anesthesia and pain management for earlier discharge to be possible.

    If the authors want to contribute to the orthopedic community they should design an appropriate scientific study model, such as the randomized study of Chimento and Sculco (2), and they should not subject patients to a new operation without obtaining the skill, understanding the principles of the new operation, and informing patients of their study. Otherwise, they simply contribute more “junk science”. If the authors and the editors of the Journal of Bone and Joint Surgery wanted to publish information that mini-incision operations are not easy, are stressful, and require knowledge, skill and training, they could have better done this with an editorial rather than publishing bad science that is apples vs. oranges.

    1 Woolsen ST, Northrup GD: Mobile-vs. fixed-bearing total knee arthroplasty: A clinical and radiologic study. J Arthroplasty 2004, Vol 19: 135-140.

    2 Chimento G, Sculco TP: Minimally invasive total hip arthroplasty. Operative Techniques in Orthopedics 2001, 11:270-273.

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