It definitely feels like something of a landmark now having performed over 1000 PAOs. It is interesting to reflect on the progress in surgical technique as well as the understanding of hip dysplasia. The operation itself, originally developed by Professor Reinhold Ganz in Bern Switzerland, represented a major step forwards in terms of a technique to re-orientate the acetabulum and address hip dysplasia and some other abnormalities of acetabular orientation. Every time I perform the operation I find it extraordinary that it was possible to work out how to free the acetabulum from the rest of the pelvic bone to allow it to have such a degree of independent movement to allow major corrections to be possible. The enormous challenge relates to the multitude of important nerves, blood vessels and muscles that surround the acetabulum and that obviously need to be protected throughout such a procedure.
The original surgical approach was quite a major open surgical intervention and in the early days the surgery took a long time and often the focus was on the potential blood loss involved. A number of strategies were developed to deal with blood transfusion requirements, including pre-donating blood before surgery.
Now we can do the same operation through a minimally invasive approach, using an incision that heals very cosmetically and with the surgery typically taking around 90 minutes. Blood loss is now much less of an issue. Routinely we use a cell salvage device which allows us to give back to the patient their own blood at the end of the surgery. The requirement for any form of extra transfusion is exceptionally rare. Recovery is easier because of the less extensive surgical approach and soft tissue damage.
The recovery time overall can remain quite lengthy and this relates to the fact that the bone has been broken and of course has to be allowed to heal. This is where we see quite some difference between surgery in teenagers compared with patients in their 30’s or 40’s . The bone in a younger patient heals so much more quickly and reliably that the recovery is much shorter particularly in terms of getting back to impact exercise. This is simply the way it is, but I suspect that in time we will be able to utilize techniques to make bone healing quicker and so aid recovery.
Having done so many PAOs has allowed us to analyse specifics regarding outcomes and how this relates to the pre-operative shape or condition of the hip. Patients with moderate or severe dysplasia seem to do predictably well with this operation. Some patients with more mild dysplasia who have a lot of pre-operative pain, may not do so well. Similarly some patients with retroversion seem to do exceptionally well but others don’t follow the same path. Why there are these differences in outcome is difficult to determine prior to surgery and remains the focus of ongoing studies.
It is clear that there is still lots to learn about the outcomes of PAOs for hip deformities and continuing to monitor patients to assess the functional recovery of the hip over the longterm remains a very important part of this.
This remains a difficult question to answer and depends on a number of individual circumstances. Increasingly the Orthopaedic community is gathering more and more information from registries from around the world that tell us how certain implants are doing. There can be conflicting information because different countries have a slant towards different implants and it is difficult to rule out the effect of historical bias where certain implants may not have been successful and are no longer used.
Broadly hip replacements can be divided into those which are cemented and those that are uncemented. The cement is a grouting agent which holds the implant in the bone and was the earliest method of fixation of hip implants. Newer technology is able to produce a surface coating on a metal implant that allows the bone to grow into the metal device and anchor it firmly – it effectively become part of the bone. This occurs over about a 6 week period and for that to happen the implant needs to be fixed very tightly in the bone and there should be no significant movement between the implant and the bone during that period.
Both these types of devices are showing good longterm results. Cemented fixation is considered a safer option for older patients where the bone may not be so strong and so may not be able to have a device implanted firmly enough to allow the bone to grow in.
It looks as if in younger patients, data is building to suggest that uncemented hips are starting to look better – certainly on the socket side.
The other major issue is the choice of the ‘bearing surface’. This is the part of the hip replacement that moves – the ball head of the stem against the liner of the new hip socket.
Historically this has been a metal on specialized plastic articulation. Time has shown that the plastic (a special type of polyethylene) is the weak link and the small wear particles can damage the bone over time and subsequently make it much harder to perform a re-do (revision ) hip replacement.
Newer materials have improved these wear properties. The polyethylene has been improved to make this longer lasting. A ceramic articulation continues to show that this has the lowest wear rate and in my view, remains the best material to use for this part of the replacement particularly for younger patients.
The answer to which hip replacement is the best is that there are a number of devices that have been used for many years which show good longterm outcomes. The difficulty is working out which of these is likely to last 30 or 40 years. Registry data is less good at determining which implants are doing well in specific cohorts of patients and for this one has to look at individual studies where this detail is available. The studies relating to ceramic on ceramic articulations continue to look extremely promising, with reports at 20 years showing no signs of wear or damage to the surrounding bone from wear particles. This bodes well for the device continuing to last for many more years.
Decision making with regards to hip dysplasia can at times be very difficult. One of the areas that is often not straightforward is in patients who are perhaps a bit older than the norm for this procedure (over the age of 40) and appear to have a good joint on X-ray. In general terms a hip is not suitable for a PAO if there is too much in the way of wear and tear arthritis in the joint. In these circumstances the best way to improve pain and function is to have a hip replacement. Sometimes one has to accept that it is not possible to preserve the native hip joint even when a patient is young and that a hip replacement will give a better longterm outcome.
The concern is that the younger you are when you have a hip replacement the greater the chance that you will require some form of re-do surgery later in life, possibly more than once. The age of 40 is something of a threshold between joint preservation in the form of a PAO and the option of a hip replacement becoming more of a reasonable option with perhaps less of a chance of more than one re-do procedure.
It does appear that the complication rate is a bit higher in patients over 40 undergoing a PAO and recovery somewhat longer than in younger age groups. On the other hand, if a joint still appears to have good cartilage and little wear and tear, then it seems a shame to lose the option of a joint preservation procedure.
Ultimately the decision making comes down to making an individual assessment of the circumstances of the patient. The quality and strength of the bone is important, overall health and activity level of the patient and the willingness to undergo the rehabilitation. The initial recovery after a hip replacement is certainly easier and overall quicker which may be important in some circumstances, however, where a joint remains in good condition and the circumstances are appropriate a PAO with preservation of the native hip is still potentially a good option for patients over 40.
At the recent meeting of the International Society for Hip Arthroscopy and Hip Preservation, in Melbourne Australia, there was a lot of interest in the idea of a less invasive way of performing a PAO. The original description of the PAO was for it to be performed through a rather large surgical approach and the scar that resulted did not heal in a very cosmetic fashion.
We published our outcomes using a minimally invasive technique last year (Bone and Joint Journal 2017;99-B:22–8 ) and this related to a technique that we developed and have used since 2010. I was asked to give a number of presentations at the meeting relating to the role of a minimally invasive PAO and the technique involved and there is clearly a lot of interest in this.
One of the barriers to some surgeons accepting that open hip surgery such as the PAO, is effective, is because they feel it is relatively invasive when compared to hip arthroscopy . Increasingly, however, it does appear that those persisting with only hip arthroscopy are seeing increasing complications and poor longterm success rates with this approach and so there is now more interest in the PAO particularly in a less invasive form.
There continues to be a lot of debate on what constitutes mild dysplasia and whether hip arthroscopy can continue to be effective in these milder cases. The difficulty is establishing what is really mild and often only one measurement on an X-ray is used to make this assessment – the lateral Centre – Edge angle.
There are a number of other features that can make a hip unstable apart from the centre edge angle , such as the slope of the weight bearing zone of the joint and also the femoral neck anteversion ( the amount the top of the femur points forward). If these other aspects driving potential instability are not recognized then poor results may follow.
It is clear that complication rates from this type of surgery directly relate to the experience and numbers of cases being operated on by the surgeon. With regards to the PAO, we presented out complication rates in over 200 cases using the minimally invasive technique. Fortunately the serious complication rate is extremely low, for instance there were no injuries to major nerves around the hip or pelvis. The infection rate was less than 0.5% and the risk of thrombosis (blood clots) was less than 0.3%.
We did identify some greater risk of complications in patients with higher weight and those with significant hypermobility. These tended to be rather minor issues, but certainly can make recovery more prolonged.
The issue of stress fractures elsewhere in the pelvis remains a concern. These show up as a break in the bone at some distance from the site of the osteotomy and occur at some point during the rehabilitation – often several weeks after the surgery. Mostly they heal by themselves and they may never have caused any symptoms. Very occasionally they may necessitate further intervention in the form of bone grafting and applying a plate to the pelvis to allow the break to go on and heal.
Anything that can be done to accelerate the healing of the bone is likely to be helpful and speed up recovery. One of the sessions at the meeting was on PAO surgery in adolescents and it is apparent that in the younger age group the pelvis heals very quickly and reliably. The recovery and return to sport and higher levels of activity within 5-6 months is very apparent in this age group.
Unfortunately there continue to be significant delays in diagnosis in patients with hip dysplasia and it can still take many years for the condition to be recognised as the reason for hip pain. Awareness in the primary care setting and amongst physiotherapists remains a very important area that can speed up the referral of patients with this condition
The Direct Anterior Approach (DAA) to perform hip replacement surgery is a minimally invasive approach with less in the way of muscle splitting or muscle cutting than other approaches to the hip. At every hip meeting I have been to in the past year there continues to be a lot of debate as to what the advantage is and whether there are longterm gains to be had. There certainly are those who oppose the idea of this being a good approach and this relates to data that is presented in relation to the ‘learning curve’ to safely perform the approach.
The learning curve is the number of procedures a surgeon would have to do to have a complication rate for the particular procedure or success rate, that would be the expected norm. Performing a hip replacement through a different anatomical route is not something that can always easily be achieved. How easy it is to switch from one approach to another depends a lot on the similarities between the anatomical planes and the actual technicalities of inserting the hip implants.
I think it is fair to say that the anatomical planes associated with the DAA are not ones that most surgeons are routinely exposed to and there is no doubt that the specific steps that are needed to insert a hip replacement through this approach are very different from other approaches. Complications that are sometimes presented associated with the learning curve are certainly of concern and indicate that appropriate training needs to be undertaken before the approach is adopted.
The benefits, in my view, of the DAA are quite significant in terms of the ease of recovery after hip replacement surgery. Patients require less in the way of strong pain killers and mobility returns with greater ease. Because the soft tissue envelope around the hip is preserved without cutting muscle, the joint is inherently very stable after surgery so fewer early post-operative restrictions apply.
One of the arguments used against the DAA demonstrating significant advantages is that most studies indicate that by 6 weeks or 3 months there is little difference as to which approach is used. This rather ignores the beneficial effect to the patient of that early recovery period which to many is the most significant element of having to undergo hip replacement surgery.
My experience using this technique for the majority of hip replacements over the past 6 years has been very positive with patients indicating that the recovery appeared much more straightforward than they anticipated. In particular, patients who are having their second side operated on, where they have undergone a different approach for their first side, find the difference very significant.
A further advantage which is important for many young patients, is that the surgery can be performed through a very cosmetic incision (so-called, bikini incision) which heals extremely well and is not very visible.
The Direct Anterior Approach has become increasingly popular for hip replacement surgery in the US, Australia and some European countries. In the UK there are rather few adopting this approach but I am sure that with time and as junior surgeons are increasingly exposed to this approach during training it will become more widespread.
A recent study has concluded that surgical management of FAI gives improved outcomes over a conservative programme with physiotherapy. This is an important study because it was a randomised controlled trial which means that patients who agreed to be part of the study were randomly allocated to treatment with either surgery or physiotherapy. These patients were recruited from a number of different centres. This type of study is the most valid in terms of a scientific investigation. After a follow-up of one year patients were re-evaluated to assess their outcomes and the patients who had undergone arthroscopic surgery had a better outcome than those who had only had physiotherapy.
This study was published in the Lancet earlier this year (Lancet 2018; 391: 2225–3). It reinforced my feelings regarding the management of FAI and it was gratifying to see the results, particularly as we contributed a number of patients to the study from University College London Hospitals.
A further study from Oxford with a similar design has also been completed with similar conclusions.
This does not of course mean that physiotherapy is not important as part of the management of FAI, but it indicates that in the presence of an identified morphological abnormality of the hip, when symptoms persist, patients should be referred for surgery to address the underlying abnormality.
Although there have been a number of studies indicating that arthroscopic surgery is effective in improving pain and function in patients with FAI these recent studies provide the most definitive information we have to date to indicate the effectiveness of arthroscopic intervention. It is also important that we have this information as hip arthroscopy has been under scrutiny as a procedure and with regards to the NHS commissioning this as a treatment these studies provide good evidence that the treatment is effective.
Recently I was at the main international meeting related to hip preservation surgery, the International Society for Hip Arthroscopy and Hip Preservation, in Melbourne Australia. From the presentations and discussions at this meeting it is clear that a lot of the failures associated with hip arthroscopy are related to not making a clear diagnosis and surgery not being performed adequately to address the underlying abnormality. Hip dysplasia remains a significant reason for failure of hip arthroscopy, but it is apparent that a lot of surgeons who only perform hip arthroscopy are now recognising the poor outcomes of surgery when this diagnosis is not recognised.
Arthroscopic surgery for FAI remains a complex procedure, not only in terms of being clear about the diagnosis but the surgery to correct the abnormal shape of the hip is not easy and requires an extensive surgical learning curve with exposure to a large number of cases. In my view this requires a specialised hip practice to see sufficient cases and interpret the imaging findings in conjunction with patient symptoms.
Ultimately, I think it is likely that now we are clear that arthroscopy is effective for FAI, centres will be established where there is a sufficient number of cases for expertise to be built up. This is already very much the case in the NHS but increasingly will have to be similar in the private sector, so as to ensure patients are seeing a surgeon with the appropriate expertise for their condition.
This is a difficult question and we don’t have all the answers to this, however, I believe there are some important things to take into consideration. The type and nature of the FAI condition is important to establish. Some types of FAI, in particular cam impingement tend to cause hip damage in a more aggressive fashion than pincer-type impingement. The concern about this is that the cartilage of the articular surface starts to get injured and this is a material that cannot regenerate itself once damage starts. This means that overtime the joint will be more prone to the development of osteoarthritis. The injury pattern in pincer impingement is different and much less aggressive and does not damage the articular cartilage in the same way.
I often find that patients, in particular athletic individuals, have had symptoms of groin strain type pain for a number of years and frequently a clear diagnosis has never been made. Unfortunately they then present with significant arthritis changes for which a hip preservation procedure is no longer an option.
I have come round to the view that once a patient is symptomatic and the diagnosis is one primarily of a cam impingement then it is better to intervene sooner rather than later. If these individuals continue to be active in sport with these symptoms then further damage will be occurring inside the hip. In many respects, the younger the patient the more sense there is to intervene early before any or when only minimal damage is present. In my experience It is rare for there to be major articular damage in adolescents or those younger than about 23. In addition, at this age the joint seems to recover from surgical intervention exceptionally well and return to sport and activity is quicker than in older individuals.
I was on the faculty of a hip preservation meeting recently in Switzerland, where as part of the teaching programme there were a number of case discussions. This proved to be particularly interesting, as what is clear is that even among ‘experts’ there is quite some difference in interpretation of investigations and therefore of the diagnosis and approach to treatment.
It is often difficult to give an opinion based on pictures alone as talking to and examining the patient is such a critical part of making a diagnosis particularly in relation to the different variations of hip morphology that can lead to symptoms of pain around the hip. There is definitely room for improvement in terms of how investigations are standardised and interpreted and also the definitions that we use to determine whether something is normal or abnormal.
One of the critical issues leading to differences in interpretation is the way individuals tilt their pelvis. A structurally normal hip can behave in a very abnormal way leading to pain if the pelvis is functionally tilted. Determining if the hip is abnormal or not can depend on how the pelvis is tilted at the time of an X-ray, and this will look very different if the X-ray is taken with the patient standing or lying down.
The challenge is to agree on distinct parameters that are abnormal and to develop imaging techniques that can take into account the variations in pelvic tilt during different activities. These are certainly in the process of being developed. Our focus has been on using CT scans with dynamic motion of the hip which provides a lot of additional information and further simulation techniques will undoubtedly shed more light on why some hips become unstable, damaged or painful.
Many patients may have had the experience that they cannot get the necessary referral to the specialist they want with their private medical insurance. This has become an increasingly troublesome phenomenon over the past year. It is particularly frustrating as private health insurance companies seem to be interfering with the referral process in a way that does not happen on the NHS. The basis for this seems to be in changes to their fee structure. That is to say that different insurance companies have unilaterally decided to change the fees they cover in relation to surgical treatments. For example, I myself have not changed my fee structure for hip surgery for the past 5 years and previously insurance companies covered these for their patients. Increasingly, these companies are deciding they do not want to cover these fees and therefore this leaves the patient with the worry of a shortfall.
For the surgeon this becomes very difficult, as individual companies want to agree different contracts. I have never particularly wanted to align myself with any individual insurance company. The problems arise when patients wish to see a particular specialist and the insurance company directs the patient to see someone who may not be appropriate for their particular condition. On the NHS we very rarely have any issues with patients requesting a referral from their GP or via another Orthopaedic Surgeon and we see patients from all over the country. It seems inappropriate that this referral pathway is being distorted in the private sector.
My advice to patients is that if you have done your research or had a recommendation who to see, you should insist on seeing the right person. The individual you speak to on the phone from your insurance company will not necessarily know much about your condition and will most likely be working to a different agenda. The monetary shortfall issues, if there are any, are often rather small and hugely exaggerated by the insurance company. After all, the reason many individuals pay for health insurance is to see and be treated by the person of their choice at a time that is more convenient to them. Insurance companies should be facilitating this, not obstructing it.
This is the key question those of us involved in hip preservation surgery would like to be able to answer. At the present time we only know that timely intervention is effective in getting individuals back to their sport. Timely intervention means before the hip joint has become too damaged. What we do not know is if early intervention, particularly in relation to FAI and arthroscopic hip surgery, will necessarily protect the hip from future damage and the risk of injury and osteoarthritis. There is more evidence that early intervention in dysplastic hips by way of a PAO (periacetabular osteotomy) is effective in delaying in the onset of hip arthritis.
One area that we are gathering more information about is the effect of high level sports training/participation during adolescence. There is increasing evidence that a high level of sports activity during the time that the hips are developing is associated with femoral head changes in particular a cam-type deformity. Initially there was an observation that hips with FAI appearances appeared to be more common in athletic individuals. More focussed studies have now implicated that it is the effect of the training itself that can alter the shape of the hip. This is particularly unfortunate, as with an abnormal hip shape a lot of high level activity is going to be more likely to damage the hip.
At a recent meeting of the International Hip Society in London I had the opportunity to discuss with Prof Ganz, who characterised the nature of the hip injury caused by FAI, why it was that some individuals presented early with pain from their hips and others very late when there was already significant damage with osteoarthritis. The area of the hip that transmits pain is the labrum which is the soft cartilage rim around the hip which provides a suction seal around the femoral head. In certain types of FAI this gets directly traumatised and leads to significant pain early in the development of the condition. The pain therefore provides a warning sign that potentially something bad is going on.
In other cases the labrum is not injured directly and so the damage to the articular cartilage within the joint (which does not have any nerve pain fibres) can continue and become very severe before pain starts to develop; unfortunately by that time it is maybe too late to save the joint. This is the situation in many cases of cam impingement, where the initial injury is caused when the abnormal area of the femoral head slides under the labrum and produces abnormal shear stresses against the articular cartilage of the joint. Eventually the labrum does become increasingly damaged and therefore often starts to cause pain, but the early warning sign was not there.
Ongoing research in this area will allow us to advise patients better as to the optimal time for intervention in these hip conditions.