By Dr Ng Eng Seng, Consultant Hand & Microsurgeon

Hand and wrist are one of the most complex structures in human body. There are many bones, joints and internal structures (ligaments, tendons, nerves and vessels) in the hand and wrist that allow us to perform a great variety of movement from gross grasping to fine hand work. These structures are tiny as compared to the lower limb counterpart.

Treating hand and wrist problems is a great challenge. The problems that can occur are enormous ranging from congenital, injury, degeneration, inflammatory, metabolic, vascular and tumour. Injury can involve bones, joints, tendons, blood vessels and nerves. Problems of the hand and wrist can be very debilitating and may interfere with our daily activity or work. Due to its complexity, diagnosing a hand problem can be very difficult. Proper history and physical examination may not be able to isolate the cause of the problem. Custom investigation methods like x-ray and CT scan only allow us to view the bony structures and patients are exposed to radiation. Other methods like arthrography (injecting a dye into the joint with x-ray) and ultrasound scan have their own limitations. Investigation of the hand and wrist must be preferably non-invasive and allows us to view clearly and differentiate all the fine structures. MRI scan is the ideal modality of choice and had been increasingly important in evaluating pathology of wrist and hand. It provides images in various planes that are needed for evaluation of small and complex structures. Currently, with the use of 3-Tesla MRI images with the higher strength of magnetic field, detailed structure of muscle, ligament tendon, tendon sheath, vessel, nerve and marrow are shown with great accuracy and excellent resolution. It has high potential to replace conventional methods of investigation. MRI is currently used for evaluation of ligament injury of the wrist, triangular fibro cartilage complex (TFCC) injury, vascularity of scaphoid or lunate bone (Kienbock Disease), fracture and assessment of hand swelling.

Carpal (wrist) ligament injury

Human wrist is strong and it forms a stable link between the forearm and the hand in order to allow our hand to function. It consists of 8 carpal bones joined together by many strong short ligaments. In a normal hand, the bones and ligaments work together to provide a smooth movement of the hand and wrist. These ligaments are prone to injury after a fall. A break in the ligament will change the smooth mechanics of the wrist. The commonest ligament that gets injured is the scapholunate ligament that links the scaphoid and lunate bone. Other ligaments can be injured in lesser frequency. A lot of wrist injuries that are treated as wrist sprain by general practitioners may actually have a ligament tear. Depending on the severity of injury, a torn ligament is best repaired or stabilized as early as 3-6 weeks to ensure a stable wrist. If diagnosis is delayed, the ligament will shrink and make repair difficult. If left untreated, it will invariably lead to osteoarthritic painful wrist in future. MRI scan allows early detection of partial or complete ligament tear. This injury can be treated early with better predictable outcome. It is now the standard investigation in patients with suspected wrist ligament tear. MRI of wrist at 3-tesla is an effective way to detect wrist ligament tear and can avoid unnecessary arthroscopy surgery, according to a study in the American Journal of Roentgography.

Triangular fibrocartilage complex (TFCC) injury

Pain over the ulnar side (the side of the little finger) of the wrist is common and the causes are difficult to elicit. Most of them are treated empirically and wrongly and commonly results in unhappy patients with poor outcome. The commonest cause of ulnar side wrist pain is triangular fibrocartilage complex (TFCC) injury. TFCC is formed by cartilage and ligament that ties the lower end of our forearm (radius and ulnar) bone together. The main role is to stabilize the distal radioulnar joint (DRUJ) (between the lower end of radius ulnar bone) and also provide a cushion to the ulnar side of wrist joint. Tear of the TFCC can be due to injury, degeneration or overuse. It can lead to instability of the DRUJ, persistent ulnar side pain on forearm rotation and finally osteoarthritis of the DRUJ. Plain X-ray is unable to detect early TFCC tear. Diagnosis classically depends on invasive arthrography and there is high false positive due to normal degeneration with aging. Most of the mild TFCC tear can be treated with simple cast to allow the ligament to heal. Early complete tear can be treated with surgical repair. Again a high quality MRI scan allows an accurate early diagnosis of TFCC tear and proper treatment can ensure a congruent and stable DRUJ (see Figure 1).

Scaphoid fracture

Scaphoid fracture is the commonest fracture seen among the wrist bone and usually caused by falling on an outstretched hand. It is the most important wrist bone and acts as the keystone that links all the wrist bones together. Diagnosis of a scaphoid fracture can be made with X-ray but 10-15% of fracture is not shown in early X-ray. Those fractures not seen on x-ray are clearly and easily identified by MRI scan (Figure 2). Scaphoid fracture is an important diagnosis to make because if it is missed, complication such as non union (failure to heal) or avascular necrosis (bone death due to the shutdown of blood supply) can result. This will lead to long term problems such as pain, osteoarthritis of the wrist and impairment of wrist function. CT scan or a radioactive isotope scan is used to confirm an occult fracture. However CT scan has been shown to miss 21% of the occult fracture and radioisotope scan shows less specificity. Many studies had shown MRI had 100% reliability in detecting an occult fracture and picking up other carpal or distal radius fracture. Beside detection of a fracture, assessment of the vascularity or the viability or scaphoid fracture fragment through MRI scan can help us in determining whether a re-vascularised bone grafting surgery is required.

Kienbock disease

Kienbock disease is due to the loss of blood supply to the bone of the wrist (lunate bone). It presents as wrist pain, stiffness and loss of motion. The loss of blood supply can cause bone death called avascular necrosis. It is difficult to diagnose in the early stage as the appearance of the lunate bone is unchanged on X-ray. Early detection is important as it can help to stop the disease from getting worse by putting the arm in a cast or shortening of the radius bone. This gives the bone a chance to regain its blood supply and heal. It can also eliminate pain and keep the normal hand and wrist function. MRI scan allows us to detect early changes in Kienbock disease (Figure 3).

In later stage or if it is not treated, bone death will eventually cause lunate collapse and osteoarthritis of the wrist. X-ray shows dense, collapsed lunate bone that is irreversible. Patient can lose function and risk permanent damage. Hence early detection of Kienbock disease is essential to avoid long term wrist dysfunction.

Hand and wrist tumour

Tumour of the hand wrist is common and most of them are benign ganglion (a gel filled cyst arising from the joint). The commonest aggressive lesion is giant cell tumour of tendon sheath that arises from the tendon sheath of the finger. MRI is essential in helping to make diagnosis, assess the extent and the origin of the tumour before the surgery. As the structures of the hand are small, high resolution images are important in order to view the different structures of the hand clearly.

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