Wrist Arthritis
Normal Wrist Anatomy and biomechanics
The wrist is a biomechanically complex joint allowing the wrist to move in extension (up), flexion (down), radial deviation (towards the thumb), ulnar deviation (towards the small finger) and minimal degrees of rotation. Functionally the wrist’s primary role, like the shoulder and elbow, is to position the hand in space. This accurate positioning, allows the hand to perform a vast array of activities that range from skillful manipulation of fine objects to handling heavy objects, including supporting the entire body weight.
To understand the wrist we arbitrarily divide it into 3 layers:
- First layer corresponds to the bones
- Second layer corresponds to the capsule and ligaments
- Third layer corresponds to the remaining soft tissues (tendons, muscles, nerves, vessels)
These three layers are covered by the skin which we will discuss below.
The first layer or bonylayer begins at the metacarpal bases distally (finger side), and extends towards the very end of the forearm bones proximally (elbow side). The bones comprising the wrist include the 5 metacarpal bases, 8 carpal bones (wrist bones) which are organized in 2 rows and the distal ends of the radius and ulna (forearm bones). From distal (finger side) to proximal (elbow side), these bones form the following joints:
The five carpo-metacarpal(CMC) joints, midcarpal joint, radiocarpal joint, ulnocarpal jointand thedistal radio-ulnar joint (DRUJ).
The First CMC joint is at the base of the thumb and articulates with the trapezium, a carpal wrist bone, shaped like a horse’s saddle that permits a wide range of motion including thumb rotation of 120 degrees, distinguishing humans from other mammals. The First Metacarpal and Trapezium are supported by a strong set of ligaments that surroundthe joint (second layer) allowing stable, thumb opposition against the rest of the fingers. The ability to oppose the thumb is responsible for 40 % of the function generated by the hand. The CMC joints of the 2nd and 3rd digits have minimal motion secondary to short, taut ligaments that surround the joint at the 2nd (index) and 3rd (middle) metacarpalsbases and the distal end of the carpal bones including the Trapezium,Trapezoid and Hamate bones. This unit serves as the stable foundation around which the thumb, ring and small finger metacarpals move around. The CMC joints of the ring and small fingers are formed by 4th and 5th metacarpals, capitate and hamate wrist bones. These joints are more mobile and together with the 1st metacarpal create a gutter or cup configuration in the palm of the hand that facilitates the gripping of instruments and small objects.
The carpal bones comprise 8 wrist bones that function as a unit by virtue of having limited motion between each other. Only 7 of the 8 carpal (wrist) bones play a significant functional role in wrist stability and mobility.
The 7 important bones are named starting at the distal row (finger side) and from the thumb side:
- Trapezium
- Trapezoid
- Capitate
- Hamate, and in the proximal row starting on the thumb side
- Scaphoid
- Lunate
- Triquetrum.
The Pisiform is the eighth bone but does not play a functional role; however, it can be a source of wrist pain when sustaining a fracture or as a consequence of degenerative arthritis in the pisotriquetral articulation. The carpal bones are almost entirely covered by cartilage and receive their limited blood supply through small vessel branches that enter the bones through little tunnels where the ligaments attach.
Just proximal to the carpal bones (elbow side) are the Radius and Ulna whose articular surfaces form a cup that complements the carpal bones. Together, they form the radiocarpal joint that serves to support the proximal carpal row in a functional ball and socket mechanism. The radius with a much larger articular surface to cradle the carpus, transfers about 80 % of the wrist load. The radius and ulna have a second joint that provides forearm rotation called the Distal Radio Ulnar Joint (DRUJ). The Triangular FibroCartilage Complex is a fibrous structure containing collagenous fibers (ligaments) embedded in a fibrocartilage matrix that complements the distal end of the radius and ulna to complete the cup configuration. The DRUJ provides a cushion between the carpus and the distal ulna and is considered the main stabilizer of the DRUJ. For full normal forearm rotation to occur, the DRUJ is complemented at the elbow by a joint called the proximal radio-ulnar joint (PRUJ).
The Second Layeris composed of the wrist ligaments, a complex intermingling of collagen fibers that join the metacarpals to the carpals and to the radius and ulna, creating stable, balanced wrist motion during our daily activities. These ligaments are taut structures embedded in a thin capsule that function to reinforce key areas of the wrist. Between the carpal bones, a deeper layer of ligaments, called the intra-carpal ligaments, allow a restricted amount of motion and is the reason that the carpal bones function as a unit. The shape and position of the carpal bones is critical for proper function and when injury occurs, it is of vital importance to re-establish the bone anatomic shapes if normal function is to be achieved.
The Third Layer is formed by the tendons, muscles, vessels and nerves.
The tendons about the wrist are divided into flexors (palmar side) and extensors (back hand side). The extensor tendons are in the back of the wrist and travel through 6 independent compartments having 9 of these tendons corresponding to finger motion and 3 tendons corresponding to wrist motion. Compartments 1 and 3 controls the thumb tendons, compartments 2 and 6 the wrist extensors and compartments 4 and 5 the finger extensors.
There are nine flexor tendons that travel through a fibro-osseous tunnel at the wrist called the carpal canal. It is formed by the carpal bones and the transverse carpal ligament. There are three tendons that flex the wrist but only one of these three, the flexor carpi radialis, travels in an independent wrist compartment in the carpal canal.
Radial Artery 
Ulnar Artery
The primary vessels or channels that supply blood to the hand while traveling across the wrist are the Radial and Ulnar Arteries. An arcade of smaller branches that interconnect the radial and ulnar arteriesare safety pathways that allow the continuation of blood flow if the radial and ulnar artery becomes occluded. The blood returns to the heart through the veins which are more prominent in the back of the hand and wrist. The major nerves about the wrist are the Median nerve that travels together with the 9 flexor tendons in the carpal tunnel, the Ulnar nerve that together with the ulnar artery travel through Guyon’s canal and the Radial nerve in the back of the forearm. Terminal smaller branches provide sensation to the superficial and deeper levels within the wrist.
Treatment
In the early phases of a SLAC wrist when the deformity is still reduceable (passively correctable) and the damage to the cartilage is not significant, the treatment may consist on techniques attempting to recreate the ligament stabilizers and re-establish balance. When the collapse is more advanced with arthritis and a static unreducible deformity, an option may be a Proximal Row Carpectomy (PRC) that consists of removal of the bones from the proximal carpal row. A small resection of the radial styloid may be added to avoid the bones impinging on radial side of the wrist. Another option that preserves some wrist motion and provides good strength is a limited carpal fusion (arthrodesis). Patients can expect about 50 % of normal wrist motion as compared to opposite uninvolved wrist and over 70 % of normal grip strength. An example of a limited wrist fusion is a four corner fusion.
Total wrist fusion is a more definitive procedure that is offered when the wrist arthritis is extensive and involves all of the joints of the wrist and is considered a salvage procedure after other strategies have failed to relieve pain. It involves the fusion of both the radiocarpal and midcarpal joints. Other partial fusions and ligament reconstructive procedures have been described that can be discussed by your surgeon as deemed appropriate.
Rheumatoid arthritis is an inflammatory systemic condition of unknown cause that frequently affects the wrist and hand amongst other joints around the body. It is characterized by synovitis (inflammation of the synovial lining) of the wrist joint capsule and tendons around the wrist. Synovitis causes progressive destruction of the joint surfaces, bone stock, ligaments and results in joint instability. Rheumatoid arthritis should be treated according to the patient’s chief complaint and severity of the disease. The most important thing to keep in mind is that rheumatoid arthritis requires a comprehensive approach with a rheumatologist, surgeon and therapist for optimal results.
Nonoperative treatment can be initiated with hand therapy to learn ergonomics, protection from high risk activity and activity modification with the use of adaptive devices. The use of anti-inflammatory medication is at the discretion of the rheumatologist. Local steroid injections can also be used to relieve symptoms with the understanding that the improvement may be partial, temporary and only for symptom relief and not intended as a cure. Therapist participation for splinting and for ergonomic education, occupational therapy is useful. When non operative treatment has failed to relieved symptoms after six months of appropriate rheumatologic control, surgery is indicated.
Surgical treatment for rheumatoid patients may consist of synovectomy (cleaning of the joint from inflammed synovial tissue), tendon repairs or transfer to rebalance developing deformities, arthrodesis (joint fusion), arthroplasties (joint replacements) and other procedures to compensate for the established hand and wrist deformities.
Hand therapy is an integral part of the non-operative and surgical treatment and will be started early in the postoperative period. The focus of the program will center on pain and swelling control, early range of motion with modalitiesthat depend on the presence of tendon repairs or reconstruction. The use of splints to assist function, protect the repairs or for resting positions during daytime and at night will also depend on the particular procedure and stage of the disease. Static progressive splinting may be required in stiff joints