Surgical Approach by Mr. McMinn

I started back in 1991 with the antero-lateral approach to the hip for resurfacing. At that time we were worried about blood supply to the femoral head and on theoretical grounds the antero-lateral approach preserved the blood supply well. For many patients the approach was satisfactory but there were some problems. The exposure obtained in large patients was not good. This meant that heavy retraction had to be used, and heavy retraction caused trauma to muscle and other soft tissues which in turn led to heterotopic ossification. The other problem was that some patients had a permanent limp after my surgery as a result of the surgical approach. Please understand that the instruments were crude back then compared to today where newer designs of instruments would cause less tissue trauma and make the antero-lateral approach a better option. The sight of limping patients persuaded me to change my approach to the posterior approach. The theoretical objection to this approach was that it may cause more damage to the femoral head blood supply. It turns out that the problems with femoral head blood supply using the posterior approach are very rare, as you heard at the conference. The big advantage is that an excellent exposure can be obtained, giving the surgeon the best opportunity for perfect component positioning. As you heard, inaccuracy with respect to acetabular component positioning is badly tolerated and a high acetabular component inclination angle is the single biggest reason for early bearing failure following a metal on metal resurfacing. The other great advantage is that very little trauma to the soft tissues need occur with a posterior approach resurfacing. The other thing is that a mini-incision posterior approach can be done by those surgeons experienced in the resurfacing operation with good exposure and minimal tissue trauma. My unit published our mini-incision resurfacing results a few years ago, the average incision length was under 12 cm and measured component position was good. There are two other surgical approaches to be considered by surgeons, but for different reasons these are not reasonable at this time. The other issue is how well an inexperienced surgeon can be taught to reliably perform an uncomplicated resurfacing operation. It’s no use talking about Ronan Treacy’s or my own abilities in this regard as we have each performed well over 3,000 resurfacing procedures, and no matter how hard we work, we cannot make any impact on the world demand for this procedure. New surgeons therefore must be trained. As you heard, we tested how good newcomers to the BHR using the posterior approach really were and over 100 new surgeons, as well as Ronan and myself, entered our patients on the Oswestry Outcome Centre database. All those patients have been independently followed up. At 9 years post-op Ronan’s and my results are still statistically significantly better, both with regard to failure requiring revision and also with regard to hip function. Never mind statistics, the fact is that the newcomer surgeons achieved very creditable outcomes, which means that the whole package with respect to training, patient selection, surgical technique and implant durability really does work. If anything in that mixture changes then the outcomes achieved may significantly change. To give you one example, during 1996, one year before I started the BHR, I carried out the Corin, double heat treated resurfacing which I designed. All the other ingredients of the package were the same. Now that time has passed we can see the effect of one factor, implant design, on the outcomes. At 5 years there is no difference between the Corin and the BHR design on my outcomes. At 10 years, however, the Corin series has an 86 % implant survival whereas the BHR series has a 96 % implant survival. In addition, in the patients who have had the Corin resurfacing and have not been revised at 10 years, 20 % have osteolysis or early loosening. These features bode badly for the future. Heat treatment of the metal of the implant is not something that the surgeon can see, and I wasn’t aware that the manufacturer had started to use this even though I was the implant designer! The implant looks the same as the historically proven, as-cast alloy and the early results give no cause for concern. The longer term sadly is a different matter. I understand your interest in the surgical approach, but it’s the complete package that counts. For a patient, therefore, the key questions for their surgeon are: How long have you done metal on metal resurfacing? Am I a good candidate for hip resurfacing? Is my bone good enough? Do I have avascular necrosis which may increase the failure rate with hip resurfacing? Do I have dysplasia or any other condition which may seriously complicate the procedure and are you confident you can handle any difficulties? What surgical approach do you use and why? How were you trained and what was the resurfacing experience of your trainer? What are your results— how many have you done and how many failures have you had? What are the hip scores in your resurfacing patients? What complications have you had with hip resurfacing? What type of hip resurfacing do you propose using on me? What are the results of that design used in a) the inventor’s hands and b) what are the results of that design of implant in the hands of independent surgeons e.g. what are that implants results on the Australian national register? If your surgeon is using a device with either no independent results or poor results on the Australian register the question to be answered is: Why are you using it e.g. are you paid to use it or is your hospital paid to use it by the manufacturer of the device?