Hip arthroscopy
Hip arthroscopy refers to the viewing of the interior of the acetabulofemoral joint through an arthroscope and the treatment of hip pathology through a minimally invasive approach. This technique is sometimes used to help in the treatment of various joint disorders and has gained popularity because of the small incisions used and shorter recovery times when compared with conventional surgical techniques. Hip arthroscopy was not feasible until recently, new technology in both the tools used and the ability to distract the hip joint has led to a recent surge in the ability to do hip arthroscopy and the popularity of it.
History
The first man to describe the use of an arthroscope to see inside a joint was Severin Nordentoft, from Denmark, in 1912. Since that time, the field of arthroscopy has evolved to encompass diagnostic and therapeutic procedures to many joints. Technical advances in instrument manufacture and optical technologies have, in part, made it possible for the surgeon to gain access to reliable views of increasingly smaller joint spaces. Now, there is an International Society for Hip Arthroscopy, comprising some of the leading hip arthroscopy specialists in the world.Arthroscopic techniques have become an increasingly popular method of treating hip conditions. Although first described in the 1970s, since approximately 2000 the indications and numbers of hip arthroscopic procedures performed worldwide have expanded widely. This is due mainly to the identification of pathological conditions such as femoroacetabular impingement and tears of the acetabular labrum.
The concept of FAI was first described by Smith-Petersen. However, modern diagnosis and treatment of FAI was pioneered by Ganz in 2003, who initially advocated the use of an open surgical dislocation technique for treatment of intra-articular pathology. This involved the use of the 'trochanteric flip' approach to gain access to the hip joint. This is an extensive approach, needing an often large incision over the side of the hip, with the detachment of the greater trochanter of the femur and its attached musculature to gain access to the joint. By using this approach, the ball of the hip joint can be rotated out of the socket, giving 360-degree access to the whole joint. This approach, although considered generally safe, carries with it inherent risks, which is the case with all large incision surgery. The risks of infection and blood clots are always present, and Ganz and his colleagues cite complications such as heterotopic ossification, nerve injuries, failure of the greater trochanter to heal back properly, persistent pain following the formation of scar tissue in the hip joint, and a small risk of damage of the blood supply to the femoral head. The patient usually needs to stay in hospital for a few days, and the post-operative rehabilitation after such extensive surgery can be prolonged. As a result, surgeons have looked to use the arthroscope more extensively in the hip joint in an attempt to avoid the possible pitfalls of large, open surgery. The perceived advantages of this are the avoidance of large scars, decreased blood loss, faster recovery periods and less pain. Hip arthroscopy can be performed as an outpatient procedure.
Indications
Hip arthroscopy was initially used for the diagnosis of unexplained hip pain, but is now widely used in the treatment of conditions both in and outside the hip joint itself. The most common indication is for the treatment of FAI and its associated pathologies such as labral tears and cartilage abnormalities, among others.Table 1. A selection of hip conditions that may be treated arthroscopically.
| Femoroacetabular impingement |
| Labral tears |
| Loose / foreign body removal |
| Hip washout or biopsy |
| Chondral lesions |
| Osteochondritis dissecans |
| Ligamentum teres injuries |
| Iliopsoas tendinopathy |
| Trochanteric pain syndrome |
| Snapping iliotibial band |
| Osteoarthritis |
| Sciatic nerve compression |
| Ischiofemoral impingement |
| Direct assessment of hip replacement |
Technique
The procedure is performed with the patient asleep or under spinal anaesthesia. There are two widely used methods, one with the patient on their back and the other on their side. Which is used is down to the surgeon's preference. To gain access to the central compartment of the hip joint, traction is applied to the affected leg after placing the foot into a special boot. There is specifically designed equipment for this, although some surgeons use a 'traction table', initially designed to help in the operative fixation of broken thigh and lower leg bones. The amount of traction needed is assessed with the help of fluoroscopy. It is usually not possible to distract the ball from the socket with traction alone by more than a few millimetres. Once the surgeon is happy that they will be able to gain access to the hip joint, the patient is then painted with antiseptic and the surgical drapes applied.The next step is to insert a fine needle under x-ray guidance into the hip joint. This breaks the 'suction seal' of the joint and allows further distraction if necessary. The surgeon wishes to see the ball move out the socket by approximately 1 cm, so that access to the hip joint can be achieved with minimal risk of damage to the joint surfaces. Most surgeons will inject fluid into the joint at this stage, again to ensure that there is enough space between the ball and socket for safe instrument access. This needle is then removed.
The next step is placement of the 'portals', or the small holes made to pass instruments into the joint. This is achieved by again passing a fresh hollow needle into the joint under x-ray control, usually in a slightly different position. The reason for this is so the surgeon can ensure that the needle, and subsequent cannulae do not penetrate and damage the acetabular labrum or cartilage joint surfaces. Again, surgeons will have their own preferences as to their preferred placement. Through this hollow needle, a long thin flexible guide wire is passed into the joint, and the needle is removed over it, leaving the guide wire in situ. A small cut in the skin is made around the wire, to allow for larger cannulae to be placed over the wire through the portal. The wire therefore guides the larger cannulae into the joint. The most common external diameters of cannulae used are between 4.5 and 5.5 mm. Once the surgeon is satisfied that the cannula is in the correct position, by a combination of feel and x-ray guidance, the guide wire can be withdrawn. Once the first portal is correctly placed, any further portals may be created once the camera is in position, to ensure that they are placed with minimal risk to the joint surfaces. This process can be repeated to gain as many points of entry to the hip joint as the surgeon requires, normally between two and four. Certain of these entry points will be used for the viewing arthroscope and others for operating instruments.
The operation then begins, a variety of instruments being used. While the surgeon views the interior of the hip joint through the arthroscope, other operating instruments are introduced through the other portals. Once the surgeon has completed the procedure needed between the ball and socket, often referred to as the 'central compartment' of the hip, traction is released, allowing the ball of the hip to sit back snugly into its socket. The arthroscope is then moved to the 'peripheral compartment' an area still inside the hip joint itself but outside its ball and socket portion.
Commonly used arthroscopic tools are the hook probe, used to assess the integrity and consistency of the hip, radiofrequency probes that ablate soft tissue and can also smoothen tissue surfaces, and various shavers or burrs that can take away diseased tissue. If the acetabular labrum requires repair, specially designed anchors may be used. This is by no means a comprehensive list as new instruments are being developed constantly.
Cam-type femoroacetabular impingement
Cam impingement is created by the abnormal development of the femoral head-neck junction causing what has previously been described as a 'pistol-grip deformity'. This type of deformity is characterised by varying amounts of abnormal bone on the anterior and superior femoral neck at the head-neck junction. The head-neck junction is at the base of the ball of the hip, where it joins the short neck, which in turn carries on downwards into the femur, or thighbone, itself. A bony protrusion or bump at the head-neck junction has been likened to a cam, an eccentric part of a rotating device. This leads to joint damage as a result of the non-spherical femoral head being forced into the acetabulum mainly with flexion and/or internal rotation. This may impart compression and shear forces to the articular cartilage, and may lead to labral tears and peeling away of the articular cartilage from the underlying bone, so-called cartilage delamination.Standard arthroscopic treatment of symptomatic cam FAI involves debridement or repair of any labral and chondral injuries in the central compartment of the hip, and subsequent reshaping of the head-neck junction of the upper femur in the peripheral compartment using high-speed motorised burrs that are similar in design to a dentist's drill.
Pincer-type femoroacetabular impingement
In contrast, pincer impingement is a result of an abnormality on the acetabular side of the hip joint. The acetabulum may either have a more posterior orientation than normal, otherwise known as acetabular retroversion, or there may be extra bone around the rim. This results in contact of the femoral neck against the labrum and rim of the acetabulum during hip movement earlier than might otherwise be the case. Repeated contact between the femoral neck and the edge of the acetabulum may lead to damage to the labrum and adjacent articular cartilage. Bone formation, or ossification within the labrum may be commonly seen as a result of this repeated contact. It is thought that this type of impingement may also predispose to the development of osteoarthritis.The goal of the arthroscopic treatment of pincer impingement is to reduce the acetabular over coverage of the hip. Methods to reduce this over coverage of the ball by the socket include labral detachment or peel back, acetabular rim trimming using burrs, often reattaching the labrum with anchors at the end of the procedure. With the exception of cases of severe global over coverage of the hip, or situations in which the existing labrum has turned to bone, excessive acetabular rim resection should be avoided in order to prevent iatrogenic increases in hip joint contact pressures.