How long do you feel it takes for the bone to be fully healed, actually grow into the prosthesis?
For the socket, I believe it takes 3 to 6 months before the bone is fully grown onto the implant. I believe the femoral bone is something that continually remodels, since it is alive. I believe that it is weaker initially after surgery, but strengthens with gradual activity, to the point that it is probably strong enough for impact activity at 6 months.
The evidence from a DEXA study on BHR patients published from Japan is that the bone density in the proximal femur returns to normal 1 year after operation. The at-risk period for femoral neck fracture following the BHR is in the 6 months after surgery. I advise patients not to return to impact sport for 1 year after surgery. For those patients who want to road run, I get them running on a treadmill at 10 months post-op and they resume road running at 12 months post-op. My unit published on activity level after resurfacing some years ago in a group of patients who followed those rules. In young men with a single osteoarthritic hip resurfaced, 92 % played sport and 62 % played impact sport. The ladies were not quite as active, but you can see from the publication that they still had an impressive activity level. In the total group their 10 year implant survival is 99.8 % showing that high activity introduced at a sensible time does not deteriorate the results.
Dog studies show that the process has already started by 6 weeks postop. I suspect 90% of ultimate strength has developed by 6 months and 100% by 1 year.
The bone is well healed at 6-12 weeks. I allow running at 6 months. I do not use cementless resurfacing. I use Smith and Nephew Birmingham hip.
It is a gradual process, starting within about a month and maturing for the ensuing 6 months.
I think it takes 6-8 weeks for the bone to effectively grow into the acetabular component but I restrict high impact activities longer than that to avoid stress fracture in the femoral neck in patients that have not been able to be active for some time. if the patient has forced themselves to be impacting right up to the time of surgery like Gary then I would let them get back sooner. In general, I hold off the patient from high impact heel strike for 4-6 months post-op. They can run in a pool and jump rope sooner. Each case is individualized based on the patient's bone quality at the time of surgery.
There are a number of retrieval studies that demonstrate bone ingrowth can continue to accrue for up to 2 years in humans. Animal studies indicate that sufficient bone ingrowth to insure stability under physiologic loading occurs by 6 weeks in an implant that is initially well-fiwe
Dr. De Smet
6 to 9 weeks for the cup. For the bone to be fully healed at the femoral side it is 1 year.
I feel that bone integrates into the acatabular component in 6 weeks but takes about 4-6 months to fully mature. In the cemented femoral component I use there is no bone growing into the prosthesis but the femoral bone needs to remodel to the new stress patterns applied to it by the implant. That takes 4-6 months.
From clinical and laboratory research, it would seem that the acetabulum is generally adequately fixed from an ingrowth perspective at about 3 months for most patients, but this process evolves significantly more for 1 year and then more slowly (like all living bone) for the rest of the life of the patient.
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.