It is a commonly used statement that a BHR is as ‘stable’ as a normal hip. However this is a highly qualified statement. This statement is true only if the following criteria are met:1. Native angles, inclination , offsets and all anatomical parameters have to be replicated.. If this is not done fully and only accuracy of say 80% is obtained – then the stability is likely to be approx in the region of 80% only. Having said this ,even in this situation, the stability is likely to be many times that of a conventional THR. Therefore I would not call it a surgical error. As surgeons, we get better and better at this replication as we gain experience.
2. The capsule should be repaired to capsule preferably as it restores the joint ‘proprioception'( or position sense). This would kick in the event of a potential dislocation as it would in a normal hip. If the capsule is repaired to bone , it is many times better than doing nothing but does not achieve the proximity to the stability of a normal hip. Again it is not a surgical error if capsule to capsule repair is not done but one cannot expect natural stability.
3. Other factors that can potentially cause dislocation like impingement must be carefully addressed . The most common offender is the non -restoration of the head neck offsetOne must keep in mind that the BHR is the Ferrari of hips and the conventional THR is an old fiat.Even if the Gear knob of a ferrari is not the right size for the driver it shows up because it is pushed to the limit and built for performance. However even if the chassis is broken in an old fiat , it would probably go unnoticed by the owner as it is never ‘pushed’ for performance. There are many patients after THR s with trochanteric non-unions going on for many years without even being aware of it!