There are of course many views and opinions amongst surgeons regarding the best approach and what to preserve during the surgical approach. Failures in resurfacing which occurs due to faulty approaches and vascularity issue, do so at the 3-6 yrs mark ( slow varus collapse with loosening of femoral component ie AVN of the entire head). Hence, it is difficult to prove or disprove any concept regarding this issue with statistical proof. One needs a large number of cases followed up carefully for a long time and have an opposite approach as a control group. This would be very difficult in a clinical setting.
Therefore, the best option would be to adopt a common sense path based on some consensus that has already emerged in the resurfacing fraternity.
It is now more or less accepted that the anterior, anterolat or post approach really has no influence as regards to the blood supply to the femoral head. (However other factors like muscle damage, etc, may differentiate the Clinical result from these approaches.)
There are two components of blood supply to the femoral head intra osseus ( within bone ) and extra osseus ( from outside bone). The relative importance of these two blood supply is again a source of great controversy amongst surgeons. There is agreement however that in primary osteophytic OA, there is more of the intraosseus component and in non -OA cases there is less of the intraosseus component.
The intraosseus blood supply can be preserved by using a vent during femoral preparation. This prevents fat and cement debris blocking the small veins in the head of femur and neck. Though some surgeons would not subscribe to this theory no one will argue that venting the femur causes any harm. Hence it an excellent idea in my opinion and this was developed by Derek Mcminn.
The extraosseus blood supply is maintained by preserving the retinacular vessels on the femoral neck. This has been
experimentally again proved by Prof. Sugano and there is a consensus on this. The best insurance one has in preserving the retinacular vessels would be to preserve the capsule. In theory one can take the capsule off and preserve only the synovium to retain the retinacular vessels. This may be alright but more risky and technically difficult to achieve. Again no one can argue that preserving the capsule does any harm. Hence I advocate this strongly.
Therefore not venting the femur and not preserving the capsule could potentially cause great harm with femoral component failure at the 3-6 year mark. Surgeons who do not advocate this may be influenced by their early success with resurfacing but will have to wait 6 years before they can say with conviction that these technical issues are not important.
The added advantage of preserving the neck capsule is the ability to repair capsule to capsule at the end of surgery which accelerates the immediate rehab . It may restore proprioception to an extent.
The NCP approach (Neck Capsule Preserving approach )was developed at the ARCH centre in Chennai, India and is being
increasingly adopted by surgeons the world over for hip resurfacing surgery.
Saving the capsule is good with a THR because it may decrease the rate of dislocation. In regular THR it can go either way saving or not. Due to the technical needs of the resurf procedure the capsule must be fully opened and partially removed. There is no way to do a resurf and fully preserve the capsule. This is not a problem though because the resurfs are more stable then a THR and dislocations are very unlikely. I certainly wouldn’t let the
need to sacrifice the capsule turn you off to resurfacing. The anatomy of the resurf makes the capsule less necessary then in a THR.
The capsule is the membrane connecting the rim of the acetabulum and the base of the femoral neck. It helps stabilize the hip and provides some of the blood supply to the femoral head. I may not have been clear regarding how it is handled in a resurf. It is cut all the way around to allow the head to be dislocated enough to expose the head to resurface it. A small portion around the neck is left to preserve the blood supply. The part near the
side of approach (posterior for most surgeons) is sometimes removed. At the end the part that is assessable is usually repaired and the rest scars back in. As for motion it is likely that a good therapy program and activity does more to keep the hip mobile then how much capsule is removed. That said I try to retain as much as possible
and still be able to do the job.
Scott Rubinstein M.D.
The NCP approach, at least the way that we mean it, is a different way to incise the capsule in order to gain access to the hip joint. Usually with THR, the capsule is detached from the femoral neck and flipped back. It is usually preserved and repaired in order to avoid dislocation.
With the NCP approach in hip resurfacing, we cut the capsule along the femoral head, so the capsule along the neck is not disturbed. This preservation of the neck capsule should help preserve important blood vessels along the
femoral neck, which may in turn preserve blood supply for the femoral head. This will hopefully improve longevity of the resurfacing. This is all in theory at present, but the results of Dr. Bose speaks in favor of it. At the end of the operation, the capsule is sewn together. This should help prevent dislocation and may help other things such as lubrication of the joint.
So the NCP is more about preserving blood supply during the approach. I don’t think that it would have a difference on range of motion, but the fact that I can get a nice capsular closure gives me confidence to allow patients immediate range of motion of the hip without restrictions.