What ligaments exist in the wrist?
This question is best explained by first outlining the number of bones in the wrist and how complex the wrist actually is. The wrist starts at the end of the two major bones coming down from the forearm which are the radius (which forms the main cup (articular surface) to the wrist) and the ulnar (the smaller bone of the forearm). The end of the ulna bone has the attachment of the triangular fibrocartilage, the soft tissue that allows the larger bone (radius) to swivel around the smaller bone (ulna) to allow rotation of the forearm, so as to allow the ability to place the hand into the upward facing position and downward facing position if required.
These bones connect to two rows of smaller bones called carpal bones. There are two rows of four bones each. The first row (proximal row) consists of the scaphoid, lunate, triquetrum and pisiform. The second row consists of the trapezium, trapezoid, capitate and hamate. These bones then join to the metacarpals which are the beginning of the rays of the fingers and thumb.
The scaphoid bone crosses from the first row to the second row and thus is the main drive shaft of the wrist, it itself being stabilised by the connection to the lunate with the scaphoid and lunate forming the main joint surface to the wrist.
Between all of these bones are ligaments: extrinsic ligaments that go from the radius and ulna into the carpal bones, and intrinsic ligaments that connect between the carpal bones.
One of the more important intrinsic ligaments is the scapholunate ligaments, which holds the scaphoid and lunate together.
What are the common ligaments that are injured?
The most common one involves the extrinsic ligament on the back of the wrist, which is a form of an avulsion (pulling a chip of bone off) of the triquetrum. Often the patient will present after a fall and be diagnosed as having a fractured wrist involving the triquetral bone. In this case, the extrinsic ligament running from the radius to the triquetrum pulls a chip of bone off the triquetrum.
This is treated as a wrist sprain and warrants rest and immobilisation in a splint for up to 6 weeks. On occasions, the chip of bone can be quite large and usually is quite comminuted (in multiple pieces).
Surgery for this is not required and by resting the wrist in the neutral position, the ligaments will heal back to the bone. It would be extremely rare to undertake any further intervention other than a wrist splint for 6 weeks, and the wrist usually improves with little issues. The main problem will be some discomfort, which may take some time to settle.
Scapholunate ligament injuries can occur after a fall on an outstretched wrist and may present with wrist pain without a fracture being identified. In this case, an MRI scan may help diagnose the condition. It is thought partial ligament injuries do not require treatment, but a significant ligament injury may warrant attempt of stabilising or repairing the ligament.
A rarer and more significant injury is that of the scapholunate ligament. The scapholunate is the main ligament between the scaphoid and the lunate bone which when disrupted can lead to mal-position of the scaphoid, joining the radius, and development of arthritis at the joint between the radius and the scaphoid (and then progressing to arthritis between the scaphoid and the capitate). This inter-carpal arthritis can progress to cause pain and require surgery in the form of a four corner fusion.
What is a significant scapholunate ligament injury?
It is thought that a disruption of the complete ligament in the form of volar, membranous, and dorsal aspects (ie. full length of the ligament) is important as if left, can lead to arthritis.
There are several points to note:
- Time since injury is important, as a repair is really only appropriate in the first 6 weeks after injury. Left longer, it goes into the chronic stage in which case it cannot be repaired and a reconstruction type procedure needs to be undertaken, such as an attempted reconstruction of the ligament using other tendons in the wrist or a partial wrist fusion to stabilise the bones.
- In the acute setting, the diagnosis is often confirmed with an arthroscopy and then proceeding to a bigger incision over the back of the wrist to repair the ligament itself and stabilising the bones with wires. These remain in position for 8 to 10 weeks. The aim is that the wrist will heal if held in the correct position when the ligament is held down to the bone. The idea of an acute repair is to prevent arthritis long term.
- In an older patient or one that has already developed some arthritis, one needs to be aware that the diagnosis of ligament tear (whilst only being made recently) may actually be an old injury which could have caused the arthritis.
Treatment of scapholunate ligament injuries can be quite complex and each patient needs to be taken on an individualised approach.
What other ligament injuries occur around the wrist?
There is a possibility for other intercarpal ligaments to be sprained, and with the diagnosis MRI scan these are more often diagnosed. However, these in general are treated as a severe wrist sprain.
The triangular fibrocartilage complex is also prone to injury and is covered in the section on ulnar sided wrist pain.
Scapholunate ligament injuries and other wrist ligament injuries are rare but are important to diagnosis and at Glenelg Orthopaedics we will provide individualised and holistic approach in assessment of your wrist injuries.
Call us on 08 8376 9988 to get a thorough examination of your wrist, so you can decide what the most appropriate action is.
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