Arthritis of the hips is a very debilitating disease, because it is a weight-bearing joint with a wide arc of range of motion. Arthritis of the hips affect walking, stair climbing, sitting and is also characterised by night pain. That is why a total hip replacement has been judged to be one of the major medical advances of the 20th century. There have been many developments in prosthesis design as well as surgical technique techniques in the past 50 years, since Sir John Charnley managed to achieve good results with accurate surgical technique, prevention of infection, with cemented prosthesis and low friction metal- on- plastic articulation. Many 1st world countries have helped to advance the technology by recording every single replacement surgery in their countries on registers.
Pain is the indication for THR in 90% of cases. The only other indication is to repair functional stability in cases where the joint or surrounding bone has been destroyed.
Only severe hip pain, that affects all activities of daily living, (especially sleeping and walking) warrants a THR. The decision to do a THR is only considered once analgesics, anti-inflammatory medications and adjustment of activities of daily living have been tried. Only the patient themselves are in a position to make the decision when the pain is severe enough for them to be ready for a THR. When the patient is in doubt, delaying the decision will not lead to complications.
Life expectancy is increasing rapidly, through advances in management of chronic diseases in the 21st century. Participation in sports, even competitively, at a much older age, has become the norm. Patients expect more from their THRs and have the operations at a younger age.
Not only are patients expecting greater longevity from THR, but also demanding more stability whilst putting more strain on the prosthesis.
Uncemented prosthesis designs have come a long way since the earlier designs. The newer designs have resulted in increased longevity and with less host bone resorption compared to the earlier cemented and first generation high density polyethylene designs.
The challenge of modern day hip replacements is a safe, robust prosthesis that will allow younger patients more functional abilities and last longer so that the patient can carry on with their sport and hobbies at the same level.
Because the aim is more than 20 year survival and excellent function for that period, it is important that attention is given to alignment and soft tissue tension. With improved survival of newer ceramic on ceramic prosthesis, it seems that hard articulations could deliver extended survival of hip replacements, possibly outlive soft articulations (metal on plastic). This means that the interfaces between the different bearing surfaces and titanium stems or acetabular prosthetic components, is the next challenge for discerning surgeons. The best interface is achieved with bone dry components.
THR are the oldest of the different joint replacements and the results are better than with the other joints, due to it being a ball and socket joint. In THR there are 3 major surgical approaches to the joint. (All the other joint replacements the surgical approach, to give access to the joint, is limited to primarily 1).
All 3 of these surgical approaches have their pros and cons.
The posterior approach is one of the traditional surgical approaches to the hip and is done in the decubitus position. It provides excellent acetabulum exposure and is an excellent approach for revision surgery. With posterior approach surgery there is a higher incidence of dislocations when performed by inexperienced surgeons.
With anterior lateral approach, one of the traditional approaches, excellent exposure of acetabulum and the femur is achieved with patient on positioned on his or her side (decubitus position). It is also an excellent approach for revision surgery. Traditionally there used to be a residual abductor weakness associated with this approach which was characterised with a waddling gait (Trendelenburg gait). With modifications to the approach this very seldom occur and is temporary.
The direct anterior approaches are popular in France and it is gaining popularity in the rest of the world. Although this exposure is good in experienced surgeons hands, in most cases, special traction device are needed. It has a longer learning curve for surgeons and large patients present with a special challenge. It is a difficult exposure for revision surgery.
It has become fashionable to do hip replacements through smaller incisions and less than 10cm is regarded as minimally invasive per definition. There have been advances in instrument designs to enable smaller surgical incisions and it is often part of marketing. The prosthesis sizes are determined by the size of the patient’s anatomy. Instruments are extensions of the anatomy and one of the references that surgeons use to determine alignment, which has ultimately a big bearing on the longevity of the prosthesis.
Most important is that the surgeon is experienced in the approach that he prefers to get the best outcome through correct alignment and tension of the prosthesis. Less important are the size of the scar and few hours of potential earlier mobilisation.
Soft tissue healing after THR dependents on the different approaches and is important for longevity of the prosthesis, but early mobilisation also plays and important role in prevention of complications. The advantage of early mobilisation is less pain and lower risk of deep vein thrombosis. The enhanced recovery protocol is multidisciplinary approach to early safe mobilisation and decreased hospital stay. It involves the anaesthetist, physiotherapists and all the nursing staff. By adjusting pain medication, patients’ mobilization is started the same day as the operation.
The general incidence of dislocations following total hip replacements is: There seems to be a higher incidence of dislocations with THR performed through the posterior approach, but experienced surgeons can achieve the same figures with all the different approaches. Attention to detail in alignment of the prosthesis, tension of soft tissue and post-operative rehabilitation play an important role in prevention of dislocations. Early, safe, post- operative mobilisation, play an important role in prevention of dislocations. The larger the femoral articulations the more stable the replaced hip will be.
There is a risk for DVT in primary total hip replacements and pulmonary embolism as complication. Prevention of DVT is important and depends on good hydration, early mobilisation, foot pumps, and chemical trombo-prophylaxis ( low molecular heparin, Warfarin and newer anticoagulants).
There is always a risk of infections with major procedures and despite advances in prevention and antibiotics, it remains a concern. Prevention is still the best way of cure. For that reason the patient is investigated for any possible source of infection. Intra-operatively the principles that we adhere to prevent infections is laminar flow operating theatres, prophylactic antibiotics, accurate and precise surgical techniques, prevention of haematomas ( collection of blood in operating sites) and special care with barrier nursing. Superficial infections can be treated effectively with antibiotics, but deep chronic infection might need revision of the prosthesis.
Complex regional pain syndrome (CRPS) is a chronic pain condition most often affecting one of the limbs (arms, legs, hands, or feet), usually after an injury, trauma or trauma to that limb. CRPS is believed to be caused by malfunction of the peripheral and central nervous systems. It can occur after THR, although rare. It is important that it is diagnosed early and pain modulation treatment is started early for resolution of this potentially debilitating condition.
There are so many different makes of THR prosthesis which can be classified in cemented and uncemeted prosthesis with hard on soft and hard on hard articulations. There is also bone conserving metal on metal (resurfacing) prosthesis. Generally younger patients have better bone quality and will demand longer survival from their prosthesis. There are very specific indications for different prosthesis in different patients. These days the Swedish, Norwegian, British, American, Australian and New Zealand national joint registers provide us with data on any prosthesis.
Each of the different articulations has their pros and cons. Modern cross linking techniques of high density polyethylene HDPE (plastic) and Vit E treatment promises extended survival of plastic acetabular liners/prosthesis. Ceramic femoral head prosthesis seems to promise better longevity in labarotory studies than metal (cobalt chrome). There will always be particles released in plastic ceramic or cobalt chrome articulations, but these stay contained in the hip.
20 years ago when resurfacing prosthesis were designed in the UK it seemed to promise a stable large head articulation and bone preservation that promised to be the solution surgeons and patients were looking for.
In many cases these resurfacing hip procedures did very well, but when the acetabular prosthesis alignment was not accurate, it led to foreign body reactions and early revision procedures for the patients. The different designs from other companies in resurfacing prosthesis that followed the original designs, could also not deliver the same result. Excellent medium term results have been achieved by experienced surgeons with the original prosthesis. If a male patient considers a resurfacing prosthesis it is essential to find an experienced surgeon in the procedure and to have the original design implanted. Females and patients with sensitivity to metal must not consider it as an option. Metal on metal articulations carry a risk of elevated cobalt and chrome ions in the blood and possible long term issues for patients. There are also a very small percentage of patients with allergies to chrome and nickel that develop allergic reactions to these ions in the body.
It depends on your age, demands and bone morphology. The best is to choose a surgeon that you trust, who does a reasonable amount of total hip replacements and is available if there are any post- surgery hick-ups. Let the surgeon choose the prosthesis after all the pros and cons have been discussed.
Each of the different approaches has their pro and cons. The alignment and soft tissue tension determines the long term survival of the prosthesis and is much more important than the promise of returning to sport a few days quicker. It is best that the surgeon is comfortable with the approach that gives him, or her. the best ability to align the prosthesis and achieve the necessary exposure to implant prosthesis with the necessary care to detail for the best long term outcome.
The length of the surgical scar is less important than the alignment and tissue tension in determining long term outcomes. Hip replacements, although a very successful procedure, still carries a risk and often specialised observation in the immediate post-operative period can prevent complications. Cosmetics are important, but should not be more important than the patient’s health or long term outcomes.
Depending on each surgeon’s approach and experience and soft tissue must be allowed, but a general rule is that 4-6 weeks after a THR should be a safe period to return to driving motor vehicles.
Soft tissue healing in the immediate few weeks post-surgery is important to ensure longevity. The physiotherapist will instruct patients how to safely navigate and mobilize sufficiently for enhanced recovery. Keeping to 4 basic principles: not to cross legs, not bend legs up beyond 90 degrees, not sit on sofas or in low chairs and not to sleep on the side should aid the results.
THR implants are large prosthesis and there can be an increased risk with systemic bacterial infections. Small surgical procedures and localised infections are most probably not an extreme high risk, but taking amoxicillin as prophylactic antibiotic also should not lead to complications. General principles of early detection of systemic infections and balanced lifestyle supporting a vibrant immune system should be enough to ensure longevity of prosthesis.
All low impact sports that the patient participated in before the THR, should be safe. Contact sports and high impact sports will not be possible. Low impact sports include; tennis, golf, cycling, lawn bowls, alpine skiing, hockey, social squash, hiking and body boarding. High impact sports include long distance running, rugby and extreme sports like kite boarding, wake boarding, surfing and bungy jumping. If someone is skilled at certain sports like alpine skiing or water skiing for instance it will be a safe sport to return to, but not to start as a new sport after THR.