Hip Arthscopy

Hip arthroscopy

Hip arthroscopy refers to the viewing of the interior of the acetabulofemoral (hip) 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 has gained popularity because of the small incisions used and shorter recovery times when compared with conventional surgical techniques (sometimes referred to as "open surgery"). 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.

Anatomy

The hip is essentially a ball and socket joint. It consists of the head of the femur (the ball) and the acetabulum (the socket). Both the ball and socket are congruous and covered with hyaline (or articular) cartilage, which allows smooth, almost frictionless gliding between the two surfaces. The edge of the acetabulum is surrounded by the acetabular labrum, a fibrous structure that envelops the femoral head. (See fig. 1) The labrum acts as a seal, or gasket, around the femoral head. However, this is not its only function, as it has been shown to contain nerve endings, which may cause pain if damaged.[9] The blood supply of the labrum has also been demonstrated.[19] The joint itself is encompassed by a thick, fibrous joint capsule, which is lined by synovium. The ligaments that keep the hip joint in place are in fact, thickened areas of joint capsule, rather than distinct structures. The synovium generates fluid that lubricates the joint; in that fluid are the nutrients needed to keep the cartilage cells alive. A total of 27 muscles cross the hip joint, making it a very deep part of the body for arthroscopic access. This is one reason why hip arthroscopy can be quite technically demanding. The cartilage lining of the socket is in the shape of an inverted horseshoe. The middle of this is termed the cotyloid fossa. Arising from the cotyloid fossa and connecting to the femoral head lies the ligamentum teres. The function of this in the adult is under debate, but in childhood the ligamentum teres carries a blood vessel from the pelvis to the femoral head. This blood vessel usually becomes redundant with age. Arthroscopic hip surgeons are becoming increasingly convinced that the ligamentum teres acts as an internal stabiliser of the hip joint, and pathological injury to the ligament is now a recognised cause of hip pain and instability

Technique

The procedure is performed with the patient asleep (general anaesthetic) or under spinal anaesthesia. There are two widely used methods, one with the patient on their back (supine) and the other on their side (lateral decubitus). Which is used is down to the surgeon’s preference. To gain access to the central compartment of the hip joint (between the ball and socket), traction is applied to the affected leg after placing the foot into a special boot. (See fig. 2) 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 (or pull) needed is assessed with the help of fluoroscopy (low-dose portable x-ray). (See fig. 3) 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 he 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