In some cases where patients either have suspected or proven pathology inside the hip joint, intra-articular injection of the hip may well prove beneficial.

To book an appointment with one of our specialist surgeons – CLICK HERE

What conditions can it be performed for?

Hip injection may provide some degree of symptom relief in cases of:

• labral tears
• femoroacetabular impingement
• early osteoarthritis of the hip
• inflammatory arthritis of the hip

What is injected?

Normally, a mixture of local anaesthetic plus steroid is injected into the joint. The local anaesthetic gives rapid pain relief, although this wears off quite quickly. The steroid (also sometime called cortisone) acts as a very powerful anti-inflammatory – like taking a massive dose of Nurofen, although it acts just locally, within the joint. Patients do not get all the same side effects from a steroid injection as they do from having high dose i.v. steroids or prolonged courses of steroid tablets – this is because the steroid acts just locally, within the joint, to reduce inflammation.

How is it done?

Because the hip joint is quite deep and tight, a long thin needle is used and this is guided into the hip joint under X-ray control. One the needle appears to be in the correct position, a dye is then injected to make sure that the tip of the needle is actually inside the hip joint. The local anaesthetic and steroid can then be injected into the hip joint.

Intra-articular injections into the hip joint are normally done in the operating theatre with a small amount of local anaesthetic, with the patient awake. This ensures the cleanest possible environment, to minimise the potential risks of introducing infection.

Hip injections are normally done as a quick day-case procedure. Patients are normally able to fully weight bear pretty much straight away afterwards, although they may potentially need a crutch for assistance afterwards for a short period.

Does it work?

Intra-articular injection into the hip is not  going to cure things such as arthritis within the joint. However, it can normally offer good pain relief for a reasonable length of time, although this can range from anywhere between a few weeks up to several months, depending on what pathology is present and how severe that pathology might actually be.

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To book an appointment with one of our specialist surgeons – CLICK HERE

One particular type of hip replacement that has attracted a lot of publicity over the past few years is Hip Resurfacing Arthroplasty (HRA). In HRA, instead of the bone of the ball of the hip joint (the femoral head) being cut away completely and replaced with a new ball, the surface of the femoral head is shaved off, and a new dome-shaped surface is attached onto the top instead. This metal dome is fixed into a large metal socket in the pelvis.

Hip resurfacing arthroplasty prostheses – a metal ‘mushroom’ is placed onto the top of the shaved femoral head, and this fits into a metal shell that is inserted into the acetabulum (socket) of the pelvis.

A post-operative X-ray showing a hip resurfacing prosthesis in place.

The potential advantages of hip resurfacing over traditional hip replacement are that a) the joint is actually more stable, and less liable to potential dislocations, and b) less bone is removed, meaning that future potential revision surgery may be technically easier.

However, there are potential disadvantages with hip resurfacing. First, it relies on a metal-on-metal bearing, which may be a problem in people with metal sensitivity (as detailed above). Second, there is a risk of the femoral neck (the bone beneath the ball part of the joint) fracturing either during or after the operation. If this does occur, then the procedure has to be converted to a traditional hip replacement.

It is important to discuss the various options available for joint replacement directly with your own surgeon.

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What is a hip replacement?

The procedure of total hip replacement (THR) has been practiced for many years now, with excellent results reported. Modern hip replacements last many many years, and in excess of 95% of the hips that we put in last more than 10 years.

THR involves removing the arthritic bone around a hip and replacing the joint with a new artificial bearing. The hip is a ball and socket joint, with the ball being at the top of the thigh bone (femur) and the socket (acetabulum) being in the side of the pelvis.

The various steps in performing a total hip replacement: A) The femoral head is removed. B) the acetabulum is reamed. C) the femur is reamed. D) a plastic cup is cemented into the socket of the hip, a metal stem is inserted down the centre of the femur and a metal ball is placed onto the top of the metal stem. E) the hip is ‘reduced’ – the new head is relocated into the new socket.

With a traditional hip replacement, the ball of bone (the femoral head) is cut away, and a metal stem is fixed inside the bone of the top of the femur. The metal is fixed into the bone with a special bone ‘cement’, made of an artificial substance called polymethylmethacrylate, which sets solid. A metal ball is then placed onto the top of the metal stem. The bone of the socket in the pelvis is then scraped out (reamed), and a polyethylene cup is cemented into the pelvis. The metal ball is then located into the new plastic cup, giving a good strong artificial ball and socket joint.

The Stryker Exeter total hip replacement. A polished double-taper femoral stem with a metal head that sits in a plastic cup. Both the stem and the cup are cemented onto the bone.

A post-op X-ray showing an Exeter total hip replacement cemented into the femur and the pelvis, with a metal ball in a plastic socket.

Although hip replacement surgery has excellent outcomes, the operation itself should not be underestimated. It requires either a general or a spinal anaesthetic, and the surgery itself can last 1 hours. Patients can, not infrequently, require blood transfusions after the surgery, due to the blood loss that inevitably occurs during the procedure. Patients are generally kept in hospital for something in the region of 3 to 5 days post-operatively, depending on their general fitness.

Different Types of Hip Replacement

Most traditional THRs use a special type of bone cement to fix the prostheses into the bone of the femur and the pelvis. However, there are many THRs available now that do not rely on cement, and which instead are press-fit into the bone. They are normally textured and/or coated with chemicals (hydroxyapetite) that encourage the bone to grow onto the surface of the prosthesis.

The Stryker ABG uncemented hip replacement. A ceramic socket sits inside the metal acetabular shell, and a ceramic head sits at the top of the uncemented stem. The acetabular shell and the femoral stem are coated in a layer of hydroxyapetite, so that the bone grows onto the surface of the metal.

Metal-on-metal hip replacement – a metal head sits in a metal actetabular shell.

Some companies have developed hip replacements with harder bearing surfaces, such as ceramics or metal-on-metal. These each have their potential merits and potential problems. In the past there have been some concerns with the use of ceramic balls and sockets, where there were cases where the ceramics were too brittle and therefore cracked and broke. Modern ceramics, however, are more reliable and the wear rate with a ceramic-on-ceramic hip can be as much as 1000 times less than is seen in a traditional metal-on-plastic hip.

Here at London Sports Orthopaedics, we are able to offer custom-made total hip replacements, which may provide better patient outcomes compared to standard ‘off-the-shelf’ implants: CLICK HERE to read more about ‘Custom Made Hips’.

Other companies have focused on the development of hip replacements using metal balls in metal sockets. In these hips, the opposing metal surfaces actually polish each other smooth, and after an initial ‘bedding in’ period, the wear rate can be very low.

However, one of the potential disadvantages of a metal-on-metal THR is that they produce very high numbers of very tiny metal particles. These metal particles are too small to activate the local bone cells to resorb bone, which is a very positive thing. However, studies have shown that the metal particles to accumulate in the local soft tissues and in lymph nodes throughout the body, and there are some concerns regarding what the potential long-term consequences of this might be, such as the formation of tumours. However, to-date, no studies have demonstrated any such association.
One particular concern that does exist with metal-on-metal THRs is that the metal always contains small traces of impurities, such as Nickel. As much as 10% of the population may have some degree of Nickel sensitivity. There have been cases reported where metal-on-metal THRs have loosened prematurely due to what appears to have been an ‘allergic’ reaction to the metal particles. Therefore, especially in any individual with a history of reacting to metals (such as cheap jewellery, which has a high nickel content) it is probably advisable to perform patch-testing on the skin prior to surgery, or to even avoid metal-on-metal bearings altogether.

Risks & Complications

As with any major surgery, there are risks and complications. With Total Hip Replacement, the main risks are infection, deep vein thrombosis, and dislocation of the joint. Also, with time, the replacement joint may wear out and require another replacement (a revision total hip replacement).

Infection

Hip replacements are major surgery, and as is the case with any major procedure, there are various potential complications that can occur. Probably the biggest worry that is at the forefront of most people’s minds is the risk of infection. Bacteria exist all around us; in our skin, in the air and even sometimes in our blood. Bacteria can sometimes stick to the metal surface of a hip replacement, where they can multiply. They can then form a sticky membrane around themselves that makes it difficult for antibiotics to get to them. Superficial infections near the surface of a wound are more common and can normally be treated effectively with a simple course of antibiotics. However, deep infections affecting the joint itself are far harder to treat, and sometimes it becomes necessary to remove the entire artificial hip joint, leaving a shortened leg with a stiff hip.

For the above reasons, the risk of infection is taken very seriously in THR, especially with the prevalence of new antibiotic resistant strains of bacteria, such as MRSA. Patients are therefore given 1 dose of prophylactic antibiotics before the surgery, followed by 2 doses postoperatively. Furthermore, the procedure is carried out under full aseptic conditions, in a theatre with ultra-filtered air that is carefully controlled using a laminar airflow environment.

The risk of infection is considerably lower in the private sector than it is in the NHS. However, it should be stressed that this does not necessarily reflect better surgical or nursing care, or cleaner hospitals, and it may potentially simply be a reflection of the more complex cases and sicker patients that generally tend to be treated within NHS hospitals, with the inherent greater risk of infection that this carries.

Deep vein thrombosis

One of the other main potential complications that is associated with joint replacement is the formation of deep vein thromboses (DVTs). DVTs can develop in the veins of any limb that remains static for too long. The risk of thrombosis also increases due to the stress hormones that are released after any kind of major surgery. Small DVTs, below the level of the knee, are frequent and can often cause no actual symptoms. However, larger DVTs, especially those that develop above the level of the knee can actually cause painful swelling in the leg, and they can break off and pass into the circulation and potentially lodge in the lungs (a pulmonary embolus) – which can on rare occasions be fatal.

Again, this potential complication is also taken very seriously and to try and reduce the risk patients are given low-molecular-weight heparin injections once a day after the surgery, which slightly thins the blood, reducing the potential for clots to form. In addition, patients are mobilised as early as possible postoperatively, and are encouraged to repeatedly exercise and contract the calf muscles in order to pump blood and keep it moving through the veins of the leg.

Dislocation and Leg Length Discrepancy

Artificial joints are never as stable as the natural hip joint. Dislocation can occur with a THR post-operatively, with the literature suggesting that this may occur in as much as 2% of patients. Most dislocated hip replacements can be put back into socket fairly easily, either under sedation or under a brief general anaesthetic. A majority of these dislocations then stabilize after a period of rest. However, on rare occasions where THRs become recurrently unstable and dislocate repeatedly, further surgery may become necessary in order to, for example, change the socket to a more stable prosthesis.

When arthritis is severe, the bone around a hip joint can wear aware significantly, resulting in a slightly shortened leg. When surgeons replace a hip joint, the aim is always to restore leg length where possible, and to match the length of both legs equally. However, the main priority in THR surgery is to obtain a stable joint, and therefore balancing of the joint length and the soft tissue (muscle/tendon) tension is paramount. It is not uncommon for there to be minor discrepancies, therefore, in leg length post-operatively. However, this is rarely any greater than about 1cm in magnitude, and it can normally be corrected for easily with a heel raise shoe insert on the appropriate side.

Wearing out and loosening of the THR

Natural hip joints are made of living tissue that is constantly in a cycle of repairing and rebuilding itself. Hip replacements, however, use metals, plastics and ceramics – all of which can wear out with time.

In a standard hip replacement, there is a metal ball sitting in a plastic (polyethylene) socket. The ball can wear into the plastic, creating a debris of tiny plastic particles. These particles can affect the local bone cells, causing them to resorb bone tissue, thus making the hip replacement become loose. A loose hip replacement often causes significant pain, and if the loosening is sufficiently severe, then the THR may need to be removed, and a new hip inserted (a revision hip replacement).

Revision Hip Replacements

Revision THRs are technically more difficult procedures, with a greater risk of blood loss, and with perhaps twice the potential complications of a standard primary THR. Furthermore, the longevity of a revision THR is less than it is for a primary THR, meaning that the revision THR may not actually last as long as the first one did.

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The hip joint is the largest ball and socket joint in the body and goes through seven million movement cycles per year in the average person. The hip joint can be prone to wear and tear and arthritis in older individuals. However, younger people can also develop a variety of hip joint problems that can affect walking, running, sport and daily activities.

Advances in technology and an increased awareness of pathology have allowed us to investigate and image problems of the hip joint with a new degree of accuracy. Scans such as MRI-arthrograms can show tears of the cartilage within the hip joint clearly.

The word ‘arthroscopy’ means literally ‘looking into the joint’. Knee arthroscopy was first introduced into the UK in the 1970s and is now one of the most commonly performed orthopaedic operations. Arthroscopy of the hip joint is a much newer procedure due to the added technical complexities, and is currently only being performed by relatively few orthopaedic surgeons.

Problems in the hip joint that can potentially be treated by arthroscopic surgery of the hip include:

• Loose bodies (loose bits of cartilage floating around inside the joint)
• Labral tears (tears of the rim of cartilage surrounding the socket)
• Chondral damage (wear and tear of the layer of cartilage covering the bone)
• Femoro-acetabular impingement (extra lumps of bone catching and rubbing in the joint)

There is a wide variety of different symptoms that these pathologies in the hip joint may cause, including:

• Pain in the hip (often felt in the groin)
• Clicking within the joint
• Giving way (where the leg just ‘gives out’)
• Discomfort when moving the hip into certain positions (especially lifting the knee up and rotating the leg inwards)
• Stiffness of the joint
• Difficulty walking or running

Traditional open surgery of the hip joint is a major procedure and involves large cuts through the skin and the muscles to get to the joint. Arthroscopy of the hip, however, allows the joint to be visualized with tiny telescopes and cameras and for pathology within the joint to be treated with specialized probes, through tiny skin incisions with minimal damage to the tissues.

Hip arthroscopy is performed under a general anaesthetic. The patient’s leg is strapped into a traction table that gives distraction of the hip joint, pulling the joint open in order to allow the passage of the arthroscope (a small rigid telescope with a digital camera on the end) into the space between the ball (femoral head) and socket (acetabulum) of the joint. Small probes and other specialised instruments that can be introduced into the hip joint to allow a wide variety of different surgical procedures to be performed.

Intra-operative picture showing a hip arthroscope inserted into a hip joint.

Intra-operative arthroscopy picture showing two loose pieces of cartilage within a hip joint just before they are surgically removed.

Patients are kept in hospital overnight, after hip arthroscopy surgery, but are normally able to go home the following day. Post-op, patients are normally allowed to partially weight bear, with the help of a crutch. However, after hip arthroscopy you are normally advised not to run or do sport for at least 6 weeks, to allow the joint to recover from the operation first. If more major pathology is found within the hip joint and more major procedures are performed, then sometime it is necessary to protect the joint by resting it and avoiding running for up to 3 months.

If you have a hip arthroscopy then your surgeon will advise you of exactly what they found inside your hip, what was done, and therefore what rehab will be necessary for you individually.

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The ‘normal’ hip?

“Custom-made hip replacements – the latest orthopaedic technology is a leap forward for hip replacement patients.”

Are you average? Do you think you look the same as the person sitting next to you? Do you have an arthritic hip? Is your hip the same size and the same shape as the person sitting next to you? Will your hip be ‘OK’ with a standard off-the-shelf replacement, or could you, possibly, need something different from ‘the norm’?

These are all questions that you should ask yourself, but which no doubt most patients needing a hip replacement probably haven’t.

It is true that most patients can be served perfectly well by the standard hip replacement prostheses currently in use in the UK. However, there is data available from large banks of CT scans of hips [Husmann et al. J of Arthroplasty. Vol 12 No 4 1997], which show clearly that there is actually great variation between individuals with respect to:

• the width and internal dimensions of the bones,
• the valgus / varus angle of the hip,
• the anteversion / retroversion angle of the hip, and
• the offset distance of the femoral head.

Valgus hip (more vertical neck)

Normal angled femoral neck

Varus hip (more horizontal neck)

Retroverted (backward angled) femoral neck

Normally anteverted (forward angled) femoral neck

Excessively anteverted (forwardly angled) femoral neck.

Hip Offset = the perpendicular distance from the middle of the femoral head to a line running down the middle of the shaft of the femur (shown on the diagram as the horizontal dotted line).

Femoral Offset

The offset is the distance from the centre of the femoral head to a line running down the anatomical long axis of the femur

Most importantly, recent research [Krishnan et al. J of Arthroplasty. Vol 21 No 3 2006] has shown that each of these variables can alter independently of each other. This means that surgically implanting a bigger prosthesis to correct for one large variable may actually overcompensate for one of the others, or vice versa.

Does any of this matter?

Decrease in the offset in the hip joint significantly weakens the abductor muscles of the hip. Research [Asayama et al. J of Arthroplasty. Vol 20 No 4 2006] has shown that a decrease hip abductor muscle strength by anything more than just 12% causes functional problems such as early fatigue and limping.

Further research [Jolles et al. J of Arthroplasty. Vol 17 Issue 3 282-288 2002] has also shown that implanting a hip where the femoral stem angle plus the cup angle cumulatively fall outside of the “safe range” of 40 – 60 degrees leads to a 7- times greater risk of post-operative dislocation of the hip replacement.

Attempts to appropriately correct all of the different variables in hip geometry with standard hip replacements can potentially lead to surgeons inserting the hip prosthesis in a position that is good for the hip joint itself, but which unfortunately leads to either shortening or lengthening of the overall leg length. Leg length discrepancies in the region of just 1cm are noticeable to patients, and leg length inequality can cause a variety of problems, including limping and low back pain. Small leg length discrepancies can be corrected for by patients using heel raise inserts inside their shoes. However, leg length differences of more than 1cm normally require a built-up shoe on the short side, which can be very restrictive in terms of footwear.

“Proper pre-operative planning prevents particularly poor performance!”

State-of-the-art 3D planning software now allows precise pre-operative planning, allowing the correction prosthetic opitons to be chosen to ensure anatomical reconstruction.

One the main difficulties lies with the fact that simple X-rays are notoriously bad at measuring true hip dimensions and geometry, and they can often be misleading.

Fortunately, the latest technology that has been specially developed in Switzerland allows for extremely accurate 3-dimensional mapping and measurement of the hip joint using rapid CT-scanning, with a radiation dose not significantly different from a simple plain X-ray. The data from the scan is interpreted by software that allows 3-dimensional reconstruction of a patient’s bones and hip joints on a computer. This then allows measurements of relevant distances, dimensions and angles to determine exactly what offset, neck angles and neck lengths are required to anatomically reconstruct the patient’s hip joint.

The software then allows the surgeon to see whether or not a standard off-the-shelf prosthesis would be appropriate or adequate for surgical use.

Data has shown that for somewhere in the region of 50% of patients, their joint geometry falls outside the anatomical reconstructive capabilities of a standard off-the-shelf hip replacement [Personal communication – Jean Pl, Symbios].

Recent research has shown that 3-D imaging software from Symbios allows unprecedented degrees of accuracy in hip replacement surgery:-

“Accuracy of reconstruction of the hip using computerised three-dimensional pre-operative planning and a cementless modular neck.”
Journal of Bone and Joint Surgery – British Volume, Vol 91-B, Issue 3, 333-340

The solution

The Symbios range of modular neck implants provide a wide range of variation for valgus/varus, ante/retroversion and neck length.

Symbios [www.symbios.ch], an Orthopaedic company based in Switzerland, has developed a range of uncemented femoral stems for hip replacements with what are described as ‘modular’ femoral necks. This allows for great variation in neck length, neck valgus/varus angle and neck anteversion/retroversion – all independently. Thus, true anatomic reconstruction of all the different joint variables can be achieved in the large majority of patients, without having to compromise on loss of offset and without creating leg length discrepancies.

The Symbios Modular Neck with Ceramic Head

The ‘state-of-the-art’ Symbios Modular SPS ceramic-on-ceramic uncemented hip prosthesis

The Symbios Custom-made hip prosthesis – 3D computerised planning model shown fitting a severely deformed hip.

There is, however, a small number of patients in who even the new generation of modular implants does not have the sufficient range of shapes and sizes to adequately restore appropriate anatomy. Clinical experience has demonstrated that somewhere in the region of 5% of patients may fall into this category [Personal communication – Jean Pl, Symbios]. For such patients as this, a new generation of custom-made hip prostheses are now available, which are designed specifically for the size and shape of an individual’s anatomy, allowing for relatively easy reconstruction even in patients with significant deformity of the hip and the proximal femur.

Patient experience

CLICK HERE to read a patient’s direct account of her experiences of having a Symbios Custom Made Hip Replacement for her severely deformed hip joint, by Robin Allmark, July 2012.

This video show’s Robin Allmark, a 37-year-old lady, just 6 weeks after having her complex left hip replaced with a custom-made Symbios uncemented ceramic-on-ceramic hip replacement.

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