11/11/07

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 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 acheive. Again no one can argue that presering 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 yrs mark. Surgeons who do not  advocate this may be influenced by their early success  with resurfacing but will have to wait 6 yrs 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.