| Since a surgeon at a small country hospital in England introduced total hip arthroplasty (THA) in 1962, it has become an exhaustively documented orthopedic mainstay. Hundreds of broad studies have demonstrated the efficacy and predictable outcomes of the procedure, which achieves a success rate is above 90 percent with more than 10 years of follow-up after the operation. 1Despite such unmitigated good results, as with so many other forms of surgery both in orthopedics and other specialties, the objectives of minimal surgical trauma, reduced intraoperative blood loss, lessened pain, hastened recovery, smaller scar and shortened procedure time have prompted the development of minimally invasive alternatives to the long-established standard.
Even while still regarded as investigational among many surgeons, minimally invasive total hip arthroplasty (MITHA) is quickly gaining ground in the public mind. In a review of advancements in minimally invasive technique, Waldman2 cited a network news stories that described minimally invasive THA as a “new hip replacement procedure that may have patients up and walking hours after surgery and can result in less pain and a faster recovery.” Such accolades inevitably lead patients to seek out sources for the newer technique once they decide that hip replacement in some form is preferable to their chronic discomfort and limited functionality.
Aggressive marketing of the new technique also encompasses many hospital and physician Internet sites, device manufacturers’ advertising campaigns and further positive news articles in the popular media. This widespread publicity has tended to predispose potential patients to minimally invasive procedures before any long term and extensive peer review can be completed.3 Thus, market pressures “can present problems to practicing orthopedic surgeons. With a paucity of data, making recommendations to patients becomes difficult.”4 This brief review, then, will aim to provide an overview of the rapidly developing options for MITHRA, while recognizing its developmental status.
The investigational nature of MITHA is underscored by the fact that, no precise definition for the surgery has thus far emerged. “Minimal invasiveness” can range from modified standard posterior THA with a smaller incision (perhaps 3-5 inches rather than 6 or 8 inches), a much shorter incision (an approach calling for a 3 inch incision is popular in some places), or even two 1.5-inch incisions using an x-ray machine to find the bones and put the components in the right place. Although techniques are clearly still evolving, several procedures are in use.
MITHA Techniques
The most prevalent procedure at this time is the posterior approach, employing a shorter incision and tighter surgical field than with standard posterior THA, but remaining centered on the greater trochanter. Although the limited field requires the use of specialized instruments, the procedure seems more a modification of the standard THA than an altogether novel surgery and thus entails the shortest learning curve of any of the various MITHA formats. In the posterior approach the surgeon detaches short rotator tendons to access the hip joint, reattaching them following prosthetic installation and adjustment. Despite the relative familiarity of the posterior approach, the involvement of tendons appears to prolong patient convalescence somewhat beyond that of the other procedures. As in any MITHA technique, the smaller incision of the posterior approach causes less intraoperative blood loss and reduced trauma to the muscles and ligaments around the hip than standard THA.
The anterolateral approach accesses the hip joint either through the interval between the anterior one-third and posterior two-thirds of the abductors, or between the medius and the tensor fasciata. Waldman notes that while the technique affords good acetabular exposure, elevating the femoral component can be difficult and care should be taken not to damage the abductors. A partial release of the gluteus minimus tendon posteriorly is used to afford some mobility of the femur. A total anterior capsulectomy is also performed, which is approximately 30 to 40 percent of the capsule. Some surgeons retract the capsule and repair it later.
A recent approach of increasing interest is the two-incision technique described by Berger5 in which a 1 ½ - 2-inch anterolateral incision creates access for osteotomy of the femoral head and placement of the acetabular prosthesis. A second short, posterior incision accommodates introduction of the prosthetic femoral head. C-arm visualization guides placement of the prostheses. Since no muscles are cut in this technique, it is reported that normal ambulation returns sooner with this approach than with any other.
An anterior approach alone can be used by extending the anterior incision used in the two-incision technique to approximately 4 inches. The procedure also uses C-arm guidance. This approach presents a considerable challenge for visualizing and aligning the femur and for the placement and sizing of the femoral component.
The Outlook for MITHA
The recent introduction of minimally invasive techniques necessarily limits the extent of short-term and long-term postoperative studies and peer-reviewed literature. Nevertheless, reporting of positive findings and few untoward intraoperative events and post-operative complications associated with minimally invasive procedures is appearing with growing frequency.678 With most current MITHA procedures, the majority of patients are discharged on the second postoperative day, most commonly with full weight bearing on crutches or a walker. Not only are minimally invasive approaches shortening recovery time, the seemingly inevitable use of these techniques on an outpatient basis is now available in several sites. While prudence dictates caution and there is some possibility of unanticipated negative sequelae becoming apparent at some future time, it appears that minimally invasive approaches will inevitably represent a steadily increasing percentage of THAs.
As new procedures with highly circumscribed surgical fields, all of the MITHA techniques are technically demanding and surgeons performing them must anticipate thorough training and a relatively steep learning curve to achieve exquisite technique. Acquisition of specialized instruments is also necessary. Device manufacturers such as Biomet and Zimmer are developing instrument systems specifically designed for MITHA procedures, and providing associated training and information. New implants have been designed to reproduce the normal motion and function of the replaced joint. These new designs incorporate new materials (metals, plastics, and ceramics) and new biologically active coatings for the implants. These materials include highly crosslinked polyethylene for the hip and knee. This new plastic has been approved by the F.D.A. for regular use in the United States. Laboratory tests have shown implants made of this material to last two or three times as long as previous types.9
Unquestionably, as surgeons gain experience with MITHA and longer-term studies identify issues to be addressed these techniques will further evolve. Future developments may include computer-guided navigation to enhance landmark identification and assure accurate implant positioning. Leopold suggests that arthroscopic-type instruments, such as retractors with fiberoptic lights and small cameras that allow better visualization, may also be useful. Modified components might also help to obtain fixation with less damage to the soft tissues on introduction.10
Device manufacturers are working to develop instrument sets, modified implants and training programs to support the transition to MITHA.
Biomet, Inc., Warsaw Ind., has developed a Microplasty™ Minimally Invasive Hip Program that includes instrumentation designed to protect anatomy while affording adequate exposure for acetabular and femoral preparation. The program also offers extensive training opportunities to help surgeons adapt to the technical requirements of MITHA procedures. There is also a turn-key practice enhancement program to communicate the surgeon’s minimally invasive surgery expertise within the community. Community.
Zimmer, Austin, Texas, also offers a suite of instruments designed to facilitate MITHA techniques, and has launched the Zimmer Institute to provide a range of training programs to help practitioners learn new approaches.
DePuy Orthopaedics, like Biomet, headquartered in Warsaw, Ind., a Johnson & Johnson company, has introduced refined soft-tissue retractors for minimally invasive hip replacement surgery.
Using these retractors, the company says that surgeons can make a three-to-four inch incision and still have a good view of the operative area. The surgery uses a technique the company has been developing since 1994. “An important advantage of the mini-incision technique is that it is not as disruptive to the strong muscles of the leg as conventional surgery,” said Wayne Goldstein, M.D., president of the Illinois Bone and Joint Institute who practices at Rush North Shore Hospital outside Chicago. “We believe that mini-incision total hip replacements result in less pain and quicker recovery for our patients,” Dr. Goldstein said.
1Seth S. Leopold, M.D., editor, Surgical options: “traditional” or “minimally-invasive” hip replacement? http://www.orthop.washington.edu/faculty/Leopold/hipreplacement/04
2Barry J. Waldman, MD Advancements in Minimally Invasive Total Hip Arthroplasty http://www.orthobluejournal.com/supp/0803/waldman.asp
3One surgeon’s Internet site: http://www.utahhipandknee.com includes an edited videotape of a minimally invasive procedure.
4Ibid
5Berger R. Two-incision technique. Paper presented at: 70th Annual Meeting of the American Academy of Orthopaedic Surgeons; February 5-9, 2003; New Orleans, La.
6Chimento GF, Pavone V, Sharrock NE, et al. Minimally invasive total hip arthroplasty: a prospective randomized study. Paper presented at: 70th Annual Meeting of the American Academy of Orthopaedic Surgeons; February 5-9, 2003; New Orleans, La.
7Kennon R, Keggi JM, Westmore RS, Zatorski L, Keggi KJ. Anterior approach total hip arthroplasty via mini-incision technique: experience with more than 6000 cases. Paper presented at: American Academy of Orthopaedic Surgeons. 70th Annual Meeting; February 5-9, 2003; New Orleans, La.
8 Wenz JF, Gurkan I, Jibodh SR. Mini-incision total hip arthroplasty: a comparative assessment of perioperative outcomes. Orthopedics. 2002; 25:1031-1043.
9Leopold, op. cit.
10Ibid
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