Everyone’s hip anatomy is different in terms of the size and shape of all of the individual parts that make up the hip joint. The hip joint is a ball and socket where each is covered in articular cartilage. Arthritis is essentially damage or loss of the articular cartilage The ball ( femoral head ) sits on the femoral neck which is at the top of the thigh bone (femur) and the socket (acetabulum ) forms part of the pelvis.

Anatomical studies have shown the variability between these anatomical structures i.e. a big canal does not mean a big neck and a big head and therefore a big socket, however this is how standard implants are designed. 3D planning takes all of these parameters into account so we have a customised fit for everyone.

The 3D plan also provides a roadmap during surgery so we can be sure to place implants accurately during the procedure as we
are able to look out for certain consistent landmarks. Standard implants come in approximately 8 sizes and are not anatomically shaped nor is there a 3D plan. Therefore a reproducible anatomical reconstruction is not possible which results in limb length discrepancy ( long or short leg) or in higher risk of fracture or incorrect cup placement.

Even though we have a range of ready made anatomically shaped implants a proportion of patients will not have a match to their 3D plan. We therefore have to make a fully customised implant for them. This takes six weeks to make at the factory in Switzerland. Symbios started out as a custom implant company over 30years ago based just outside Lausanne utilising the local population, knowledge and skillset of precision watchmaking.
A patient’s individual hip anatomy is of vital importance, and a 3D CT scan performed according to the hip plan process helps us understand each individual’s patient anatomy. Most implant companies will only have approximately eight sizes to make everyone’s anatomy (please see hip anatomy section above). Therefore, as each implant gets bigger, so does every parameter. We know from anatomical studies that every parameter is independent of the other. Consequently, it is vitally important to have 3D planning to reconstruct that patient’s exact anatomy.

Unfortunately, several insurance companies do not understand this concept, and this can be understandable because custom implants are more expensive, but usually, there is an alarm bell that rings when the word custom is used even in custom planning scenarios which does in 95% of the time result in an off the shelf implant being required which costs the same as any other implant that is off the shelf but not matched to the patient exactly.

A CT scan is required to 3D Hip plan which is low dose radiation with specific sequences that are taken to hip knee and ankle. This data is uploaded in Symbios’s proprietary software program which produces a custom match for the patient . 90% of the time we have a ready made anatomically shaped implant that will match the patient to within 2mm. The 10% where we have no match due to abnormal anatomy we recommend making an implant.

Common reasons for a hip implant include:

• Osteoarthritis is the most common
• Inflammatory arthritis, including rheumatoid disease
• Osteonecrosis (avascular necrosis)
• Hip fracture
• Tumours to the hip joint
• Significant articular cartilage damage was found as a consequence of femoroacetabular impingement (osteoarthritis)
• Slipped capital femoral apophysis dysplasia

Common symptoms for patients requiring hip implant:

• Pain present around the hip joint; this can be in the groin but also could be laterally or posteriorly
• Stiffness of the hip joint
• Significant reduction in range of motion of the hip joint, especially in specific movements, including rotation
• Pain that might not be occurring in the knee and the back due to altered walking patterns and mobility to undertake the activities that they would like to undertake and inability to take part in activities of daily living

All patients go through a pre-assessment process; this involves filling out a medical questionnaire, which may highlight specific issues related to medical health, especially cardiac disease, respiratory disease, and other systemic diseases. In addition, certain drugs can affect the assessments involved with surgery, especially when considering anticoagulation therapy and other rare medicines that might interact with the anaesthetic agents. All of this will be assessed through the pre-assessment programme. Ideally, we would like to do these 1 – 2 weeks before surgery unless we have more warning and ideally, the more notice we have of medical conditions, the better.

We like patients to have had a recent up to date review from their medical specialists if they have other significant medical morbidities, i.e. cardiac disease, respiratory disease, diabetes and significant medical conditions and surgical treatments.

I will see the patient as part of a thorough consultation. This involves taking history, performing a thorough examination and then arranging investigations which will consist of an x-ray in the first instance.

Depending on how the patient is, they may have had either an MRI scan or a CT scan, as these imaging modalities give different information. X-rays which are abnormal with significant bone on bone contact present in the joint, make the diagnosis very easy for osteoarthritis. However, I will see patients who have what appeared to be regular looking x-rays because there is a joint space at the top of the joint but the problem with this 2D imagery is that it does not show the wear pattern at the front or the back of the joint or even in the inner aspect of the joint which is where CT imaging comes into play as this will then show whether there is true arthritis or bone on bone contact in the joint.

A CT scan can be used for implant planning as well. I would expect patients to have utilised all the usual conservative measures, which would include weight loss, walking aids, analgesics, physiotherapy and any other complementary treatment pathway, and it is only when there is a significant quality of life change or failure of the above treatment processes would we then consider total joint replacement.

I also have a significant hip arthroscopic practice. Hip arthroscopy (keyhole surgery) is only suitable for patients we pick up early on in the process and do not have substantial full-thickness articular cartilage loss areas. However, it is still possible to perform cartilage repair techniques on patients who may have been deemed to have hip arthritis. Cartilage repair techniques tend to only work in patients who are sub 55/60 years of age.

When we have decided to proceed down the route of hip replacement, it is suitable for a patient to have undertaken a certain degree of prehabilitation. It can, of course, be quite challenging to do, given the hip is painful, but hydrotherapy and access to an antigravity treadmill can be of benefit in helping build strength and control. It is also essential for the patient to understand that their hip would have degenerated over several years. They would have been compensating during that time and hence, will not be using the correct muscles in the right way. Therefore, the more dysfunctioned they are, the longer the process of rehabilitation and physiotherapy or alternative therapies the patient will require to get back to full strength and control. This is vitally important to understand.

Patients usually attend on the day of surgery in the morning. They must be starved of food for 6 hours before surgery at the minimum. In addition, they will be starved of clear drinks for 2 hours before the beginning of surgery.

Surgery is undertaken ideally under low dose spinal anaesthesia and either sedation or general anaesthetic. We have found this gives the best results. The surgery takes approximately 1 hour and 15 minutes but can vary, and I believe it takes as long as I need to do an excellent job; these times can be longer or shorter.

All patients will have a 3D plan; I would have discussed and gone through the 3D plan in great detail with the representative from the company prior to surgery. We have the ability to make corrections at a millimetric level during surgery if we make slight changes to the plan. I utilise a mini posterior approach. We go between the muscles, detach the rotators and reattach them at the end of surgery. This is a very minimally invasive approach. There are other approaches to the hip joint.

I do not advocate an anterolateral approach, given this involves detaching of the gluteal muscles, which, whilst they are reattached, will never quite function in the same way. There is a known association with patients having a limp after this type of approach. The anterior approach is gaining popularity. Currently, it has been the approach of choice in France, given they were the earliest adp. It is also a very good approach, given it is muscle sparing, but usually requires the addition of a special table and an extra assistant, which is an extra logistical issue of the surgery. However, what is far more important is the exact placement of implants as opposed to the surgical approach. We achieve this with our 3D planning.

COVID also plays a role, and currently, we would like patients to have been free from COVID infection for several weeks prior to surgery (these dates and times are changing according to various government and health guidelines).

This is not an issue of spreading COVID; it is more the issue of the medical health status of the patient should they catch COVID during the time of a surgical procedure, given they will be slightly immunocompromised. The immunocompromised state would lessen their ability to fight off a significant COVID infection. Therefore, dates are set for surgery well in advance.

Driving can be undertaken when an emergency stop can be performed, taking emergency evasive action, and having an acceptable brake reaction time. I would expect this to be 4 – 6 weeks after surgery. It is important that the therapist undertakes an assessment to make sure that a patient is able to achieve this.

We advise patients not to fly for six weeks after hip replacement surgery. This is because they have had a lower limb surgery, and there is an increased Deep Vein Thrombosis risk. They will be provided with anticoagulation for the first four weeks after surgery and are expected to take this, even though they may well feel fully mobile.

We expect patients to be in physiotherapy within the first week of surgery. They should be attending 1-2 times per week for the first 6-8 weeks and then once per week for the next 6-8 weeks and then once per fortnight for the following 6-8 weeks and then once a month thereafter.

The physiotherapy programme will lead to a strength and conditioning programme. It is important that the joint is not just exercised, but it also involves a certain degree of manual work. The muscles that are being worked are becoming tight and, therefore, need to be loosened. Early on, we advise an increase in walking distances, ideally 10% increments at a time.

One can get onto a static bike and start doing work on a bike again to increase the range of motion with low resistance and a higher saddle height.

Swimming is also possible after hip replacement surgery. One must consider accessing a pool and how that is undertaken; we advise starting with a front crawl, but then there is no reason why patients cannot move on to breaststroke, but this should be after at least six weeks.