Dr. Mont Interview, Baltimore, MD

Interviewed by Vicky Marlow on September 1, 2008

1.) How did you get started with Hip Resurfacing and tell us about your background and experience as a surgeon. Where did you train for hip resurfacing? Who trained you? Did you continue your training after starting resurfacing?
I began doing hemi-resurfacing for a disease called avascular necrosis or osteonecrosis and sometimes called AVN for short. As some of you may know, this is a disease that involves only the femoral head and is often associated with alcohol abuse or corticosteroid use. Some of you may know that Bo Jackson’s hip problems after getting a dislocation may have led to avascular necrosis which was in the news. So, a traumatic insult such as a fracture or dislocation can also lead to the disease. It’s notable that this affects a lot of young people and eventually leads to arthritis. At one point we were doing hemi-resurfacing which is only the femoral head part of the resurfacing procedure and I originally started doing these because two of my mentors, Dr. David Hungerford and Dr. Kenneth Krackow, had taught me this procedure. Some of the earlier devices we used, for example, did not even have stems. They simply capped the femoral head and I still believe today that the stemmed part of the device is not that important for stability, it is more for teaching and for alignment issues when you first begin performing these procedures.

I began doing the hemi-resurfacings in 1989 and continued doing these and it only became possible to do full resurfacing when there was approval for the Wright Medical trials which began in November of 2000. I did training with Harlan Amstutz for a week and on other occasions with him before I did the full resurfacing. I would also say that I continue my training after starting resurfacing as does every good surgeon to the present day. We all should continue to learn from the results and what we perform and I continuously train surgeons in the most appropriate techniques for performing these procedures.

We keep track of all of our resurfacings in a database which also allows us to analyze successes and failures and appropriate uses of the device.

MontPhoto: Dr. Mont

2.) Do you preserve neck capsule in your surgeries, can you tell us a little about the reason for doing this and explain to us more in detail exactly what it is?
I preserve some of the neck capsule in the procedures that I do that is along the femoral neck and maybe involved in the femoral blood supply. I don’t typically preserve as much as is needed in a posterior approach because I do an anterolateral approach and lately I have been doing an anterior approach which doesn’t go through any muscles. The anterior or anterolateral approaches have much lower dislocation rates and do not need as much capsular preservation to maintain stability.

In addition, I did find when doing both approaches that when the capsule is repaired, it will often hypertrophy or get larger and this can lead to decreased range of motion in some patients. The hypertrophy can be compared to an adhesive capsulitis of the shoulder where there is restricted motion after the repair when the body is trying to further repair the capsule. Since dislocations are not a problem after anterolateral or anterior approaches, this type of capsular repair is not as necessary as in a posterior approach where this can be a problem.

3.) What is the normal hospital stay barring any complications?
Patients typically stay for two to three days. I perform the surgeries on Mondays and Thursdays. If a patient comes in on a Monday, they typically will go home Thursday morning. If they come in on a Thursday for surgery, they’ll go home Sunday morning. Many patients will leave a day early in the afternoon. There are some patients that can do this as an outpatient procedure or leave on post-op day one, but I don’t prefer this approach.

4.) What is your typical recovery time after resurfacing? What is your typical rehab protocol? 90 degree restriction? Walker, Crutches or Cane? Length of time used? Blood thinners? TED stockings? Ice? PT?
Patients are restricted only in the first five weeks to 50% weight bearing and a 90º rule and no crossing their legs. After five weeks, they advance to full weight bearing with absolutely no restrictions on position and they start strengthening. In summary, they use a cane or crutch for the first five weeks with some restrictions of motion and these are lifted at five weeks.

We are presently working on some advanced rehabilitation protocols that should be used for young patients. I believe that many of the rehabilitation protocols that have been used in the past were developed for typical patients that are getting standard total hip replacements who might have an average age of approximately 72 years. In my patient population, the average for resurfacing is 48 years and patients want to return to higher level activities and may need different protocols. We are presently prospectively analyzing these protocols.

Blood thinners, if patients have any history of any problems, are used for 42 days, but typically I will use aspirin for five to six weeks with mechanical compression stockings. We often use ice for post-operative pain.  
5.) What approach do you use, posterior lateral or anterior lateral? and why? What muscles/tendons are cut and do you sew them back up or re-attach them?
The choice of approach to use for resurfacing has received much attention and I believe extra “hype.” In multiple studies now published, there are no reported clinical differences in the short term and up to ten years of follow-up between anterior and posterior approaches.  I believe that any approach can be used and the surgeon should use what they feel most comfortable.

Short-term differences that patients may report with either approach have to do with other factors in my opinion. I use the antero-lateral approach because it affords me easy exposure, lower dislocation risk, less chance to disrupt the blood supply of the femoral head---among other reasons. However, I have no problem with posterior approaches and am currently working on and performing an even more minimally invasive anterior approach in selected patients. Again, I would repeat that a recent prospective randomized study showed no differences in all three approaches.

In summary, the reasons I use the anterolateral approach are as follows:

  1. easier to perform
  2. less chance for dislocation
  3. no difference in posterior approach at six months to one year or in long-term studies
  4. increased range of motion from not having to repair the capsule
  5. multiple studies showing decreased effect on femoral head blood supply

Presently, I’m performing an anterior approach which does not go through any muscles.

6.) What is the recommended time you tell your patients before they can start to run again/do impact sports? Are there any sports you don't want your patients to participate in after surgery? What are some of the sports your hip resurfacing patients have returned to?
Patients have returned to almost every sport one can conceive, including marathon running and bungee jumping. I have professional athletes that want to continue to play baseball, basketball and football at a high level. Whereas, I don’t condone these activities, I like these patients to make sure that their hip muscle strength is appropriate which is the best chance they have.

Typically, patients can run again at approximately three to four and a half months after surgery, but this is a patient to patient variability and it really depends on how strong their hips are and before they can do these activities, I like a certain baseline level of strength approximately ten pounds of 30 reps on each hip of the major muscle groups and that both hips are symmetrical.

We don't yet know the long term effects of these sports (past 7 years) but I encourage patients to regularly exercise their hip muscles to unload the joint if they are going to participate

The best sports in my opinion are less impact---swimming, bicycling, elliptical----these are probably fine---the higher impact sports are more likely to lower the lifespan of any implant

I don't encourage running but the patients do it anyway--in one of our studies we found that 30% of patients returned to high impact sports--tennis, running, etc. after any hip arthroplasty

Many patients resume skiing and hunting after resurfacing. I’m not a fan of skiing because of the problems with a potential fall but I have many patients that ski anyway---for more personal answer would have to contact me

Hockey is always pretty contact so hard to gauge---would have to see x-rays but probably waiting 6 months does not change cysts appreciably but again one needs to know what x-rays look like today--if cysts already well formed this could decrease chance--most cysts are miniscule and this would be an irrelevant factor.

7.) What is your opinion about cementless (femoral) devices for resurfacing?
Cementless femoral devices are being used by a few centers. Some previous generations of designs had high failure rates (over 20%) and at this point, these have to be viewed as experimental. In addition, many patients could not get cementless devices because the bone of their femoral head is already degenerated and has cysts and the bone wouldn’t grown into these devices in my opinion and, therefore, cement is appropriate.

I don’t think there’s a tremendous downside of using the cement in this application as was for cemented devices for previous generations cemented hips and do not believe this is a major issue. At this point, I would question the use of this type of unproven technology that has also had higher failure rates in the past.
8.) Do you have a cut off age for resurfacing patients or do you go on a case by case basis?
We look at patients on a case by case basis. We have recently published a study of patients over 60 years of age compared to patients less than 60 years of age and found no difference in the results. Certainly, there are very active 60 to 70 year old patients that have much better bone stock than some inactive 40 year old patients. They do not to be considered on a case by case basis and we have actually done resurfacing in patients in their 70’s. One still has to view this as cautionary because we do not know the long term results past 6 to 7 years of resurfacing in these patients.
9.) What type of anesthesia do you use, general or epidural?
The type of anesthesia used is on a case by case basis. We typically like to do a spinal or epidural versus a general, since the cases typically take an hour or less, the results of both are not very different in my hands.
10.) Are there any cases that you will not take in particular, AVN, dysplasia, small cysts? Maybe touch on some of the very difficult cases you have been able to resurface?
We have typically taken on very difficult cases which are sometimes considered relative contraindications. For example, patients with avascular necrosis were initially felt not to be appropriate candidates, but we have now done over 150 of them and our first report at close to 7 year follow-up showed success in 41 out of 42 patients. We have done resurfacing in patients with inflammatory arthritis, like rheumatoid arthritis, in a small limited number of patients, although I would not recommend this at the present time.

Again, each patient should be reviewed on a case by case basis and the risks and benefits of doing a resurfacing versus a standard hip replacement should be clearly laid out. Some patients may accept a two- to three-fold increased risk for resurfacing and that might be worth it, whereas it may not be worth it for other patients.

11.) Do you do bilateral surgeries the same day, if not how far apart do you recommend?
I do bilateral surgeries, typically a week apart, if a patient would like that. I don’t believe that the risks of doing unilateral surgery is way under 1% and I personally do not believe that that risk stays under 1% if you do both at the same time. There is time for turning the patient to their other side, putting the dressing on, and doing a procedure. Two one hour procedures are much less risky than one two to three hour procedure. In addition, other surgeons that spend more time doing a single case, in my opinion would even be putting the patient more at risk. Let’s keep the risk to the patient at the most minimal by doing one hip at a time and doing it a week apart is not waiting too long.

12.) If you can't perform a hip resurfacing, what THR device do you prefer and why?
I use different hip replacement devices depending on what the patient wants. Some patients would like an extremely large femoral head and they can get a metal-on-metal head that’s exactly like a resurfacing. Other patients, if they can’t get a resurfacing, would like an interface that doesn’t involve metal-on-metal interfaces and in that situation, I would do ceramic-on-polyethylene because I think it has the lowest wear rate.

13.) What do you consider an adequate number of surgeries for a doctor to be proficient at hip resurfacing?
Some orthopaedic surgeons can do the procedure well after less than twenty cases---others need more. This is a hard question to answer. It may have to do with the type of cases they are performing; are they gaining experience with straightforward hips first and then advancing as they gain experience? This is the correct way which is better than tackling hard cases too early
14.) How long do you feel it takes for the bone to be fully healed, grow into the prosthesis?
Bone starts growing into the prosthetic shell immediately, but starts getting fairly sticky by two weeks and then very strong at six weeks, but is not completely healed probably until three to six months.