Surgical approach and AVN: This is an article linked on surfacehippy on May 2, 2007 which describes a study making a good case that the posterior approach which sacrifices the medial femoral circumflex artery causes a significant (50% or more) reduction in blood supply to the femoral head and increased risk of AVN. I just ran across this today - July 9, 2007. It looks to be quite important.
Most hip surgeons, including Dr. Gross, use the posterior surgical appoach. This saves more muscle and soft tissue from trauma. However, the blood supply to the femoral head mostly arrives from the medial femoral circumflex artery, according to the sources I have read. This artery is apparently damaged or cut as part of this surgical approach. Or, instead, is the MFCA cut where it inserts into the femoral head due to the drilling and shaping of the femoral head and neck (in which case, though, it would seem that surgical approach is irrelevant)? What does this mean for the future danger of AVN to the femoral head? There are apparently other blood avenues (the Gautier paper below says that there is an anastomosis between the MFCA and the inferior gluteal artery), but are they sufficient to prevent AVN even under demanding conditions such as a return to high activity (running, backpacking, occasional falls, hard cycling, basketball...)? Do other blood sources sense the loss of the medial femoral circumflex artery and expand their capacity through revascularization to bring the blood supply back to near normal? If so, what is the time scale for this revascularization? Should this not impact the recommendations for post-surgical physical therapy and how rapidly one returns to activity? Post-surgical AVN happens in only 1-2% of resurfacing surgeries. But how are these correlated with activity levels? These are the kind of questions that I am now trying to answer.
"Anatomy of the medial femoral circumflex artery and its surgical implications" Gautier E. etal.
"Notching of the femoral neck during resurfacing arthroplasty of the hip - A vascular study"; Beaule' P. etal. Jan '06
"The effect of surgical approach on blood flow to the femoral head during resurfacing"; Khan, A. etal. Jan '07
As of July 12, here's what Lee and Dr. Gross had to say to another cementless Biomet patient of his on this subject...
(surfacehippy msg #112990): "Dr. Gross mentioned that it is not a good idea to jog or have repetitive pounding until at least 6 months out. He explained it thus: (if I can remember it correctly) When the operation is performed many blood capillaries are compromised in the head and neck of the femur. It generally takes 3 months for these capillaries to regenerate. After that 3 month period new bone growth starts in earnest. So the weakest point for the neck of the femur and the ball is around 3 months out. At 6 months the new bone growth is substantial, but will not be complete until at least 1 year. After 6 weeks, the hip capsule has regenerated sufficiently for dislocation not to be a problem."
July 13, '07: Niel Berger sent me this link: A classic paper on the Blood Supply to the Femoral Head from 1949 (!)