Session IV: New Techniques and Concepts in Total Knee Replacement

Knee replacement constantly is evolving, changing, and improving. Despite the fact that it already is one of the two most successful surgical procedures in the history of orthopaedics (the other being THR) orthopaedic surgeons, bioengineers, and materials specialists continue to develop improvements that will make the benefits of knee replacement available for younger and more active patients, and for patients with special needs. This symposium will discuss some of these new cutting edge technologies, their potential benefits, and potential downsides. Minimally-invasive surgery has become the mantra of surgeons in many subspecialties. There is no doubt that the smaller the incision, the less soft tissue that is disrupted, and the faster the potential for healing. For example, I have been using a minimally-invasive approach to knee replacement with a skin incision of 8 to 10 cm and a minimidvastus approach that does not disrupt the major part of the suprapatellar pouch (Fig 1), and which is done without having to evert the patella. Using smaller instruments, it has become possible to safely and to accurately do knee replacement through such small incisions (Fig 2). I have found that in a review of 45 patients operated on using this system, that the amount of analgesics required in the postoperative period is diminished by approximately 40%. The rapidity of regaining flexion, as shown in Figure 3, has increased as compared with the traditional incision, the blood loss has decreased, and all of these have been obtained while maintaining correct radiographically documented orientation of the implants, and without increasing the surgical time. Patients rehabilitate faster resulting in a diminished hospital stay.Fig 1: The photograph shows minimally-invasive TKA surgical approach using a minimidvastus capsular incision.Fig 2: Specialized instrumentation (Smith and Nephew®, Memphis TN) enables TKA though a minimally-invasive approach.Fig 3: Flexion is regained more rapidly using a minimidvastus minimally-invasive approach as compared with standard rectus splitting approach.Thirty years ago, the image intensifier revolutionized the field of fracture fixation. Can computer-assisted instrumentation do the same for TKR? Computerized surgery may require imaging (fluoroscopic or CT) or may be imageless. What is its accuracy, and what are the logistic constraints attendant to its use? Do the constraints outweigh the potential benefits? My experience in image-guided and imageless computer-assisted surgery has indicated that for the obese patient, the patient with tibial or femoral bowing or with severe deformity, and for patients having revision surgery, surgical navigation can increase the accuracy of the operation. Therefore, should it be used in all patients, or only occasionally? If patients with successful knee replacements are asked what one factor they would like to see improved, almost all will say that they would like to have full motion. Full motion is a relative term. The obese patient with a bulky posterior thigh and calf never will obtain the same amount of flexion as will the thin patient. Patients who all their life have been doing activities of daily living with the knee hyperflexed, as do many patients in the Orient, often will have more potential flexion than patients in the West who rarely use the knee in a hyperflexed position. Even though preoperative flexion is a major factor in determining postoperative flexion there are other factors that can affect motion including the surgical technique and the implant design. For instance, in my experience, not only was the rate of regaining flexion but also the ultimate flexion increased when using a smaller incision that did not cause a major disruption of the quadriceps or suprapatellar pouch. Removing posterior osteophytes and reestablishing the posterior recess can increase potential flexion. Implants have been designed which, through their configuration, can facilitate high degrees of flexion. Are such high flex prostheses a step in the right direction or will they cause more problems with posterior PE wear? Finally, the treatment of the patient with true unicompartmental disease of the knee remains controversial. The precise indications for an osteotomy, a unicompartmental replacement, and a TKR for these patients have remained debatable. We now are presented with a surgical technique in which a metallic spacer is inserted without bone resection and without a counterface of PE. This concept is not new. It existed 35 years ago with the McKeever 1,4 and MacIntosh 3 prostheses in the knee, and the Smith-Peterson cup arthroplasty in the hip. 5 Unfortunately, the results using those procedures were neither as good initially or as long lasting as total joint replacement and were abandoned gradually. One author in this symposium, is reporting on his early experience with his design of such a unispacer for patients with medial compartment OA. During the first postoperative year, 22% of the patients required a revision of the arthroplasty for various factors. Another 20% of the patients had arthrofibrosis significant enough to require a manipulation. Such high complication rates indicate that the procedure still is extremely investigational in nature, and should not be offered to patients except on very controlled outcome studies. This brings us to the final consideration of this symposium. With a field that is evolving rapidly there is serious consideration as to when work in progress should be made available for the scientific and lay communities. When I published my first paper on knee replacement more than 25 years ago, 2 a 2-year followup was considered more than sufficient for one to come to meaningful conclusions. Some valid conclusions can be made with short-term followup; however, surgeons have learned that often one has to look at patients and data for a more prolonged period before one can say safely that one procedure or another is effective. Is, however, our attempt at being “sure before we publish” a disservice to our patients? Does the public deserve to know sooner of new advances? Surely, if the new advances have adverse affects, the public should know as soon as possible, but should this also apply to early good results? Should the non peer-reviewed website expounding wonderful but scientifically unproven results be allowed to supercede the peer-review process? I hope not. This symposium will cover the issues of minimally-invasive surgery, high knee flexion, computer-assisted surgery, metallic spacer surgery, and the right to know issue as a series of pro and con debates from surgeons and scientists who have had specific experience in these fields. A final answer to the issue may not be possible; however, the debates will stimulate thought, and that is what science is all about.