Reconstructive Orthopedic Center

Fractures of the Wrist

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:

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) metacarpals bases 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:

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.

Pathology

Wrist Fracturesor breaks in the wrist are the most frequent fractures seen in the emergency room. Distal Radius Fractures with and without a distal ulnar fracture is one of the most common fractures of the upper extremity, second only to hip fractures in frequency. Wrist fractures have a bimodal distribution, with peak ages between 6-10years of age and between 60-69 years of age often occurring after a fall at ground level. Higher energy injuries occur more frequently with a fall from a height, a sports injury, or a motor vehicle accident. Over 50 % of distal radius fractures extend into the joint surface (intra-articular), involving theradio-carpal joint or the radio-ulnarjoint. This type of fracture requiresthe anatomic restoration of the joint surface post-traumatic arthritis. Fractures not involving the joint surfaces (Extra-articular) are frequentlyunstable despitean acceptable initial reduction and casting because of the poor bone quality or high level of fragmentation that occurs in elderly individuals.

Treatment

Many distal radius fractures, particularly in the elderly, have been undertreated because of the poor results that were initially achieved with an open reduction and internal fixation (ORIF). However, with more rigorous scrutiny of the Personality of the fracture indicating which type will collapse and lose the alignment initially obtained with a reduction, if not operated upon and with improvement in the plates and screws used for fixation, the trend is now leaning towards fixing many of the fractures previously treated in a cast.

Fractures that are not separated (displaced), significantly shortened or angulated or can be reduced to an acceptable position and has a high likelihood of maintaining the position, can often be treated with a splint initially that includes the elbow called a sugartong splint, followed by ashort arm cast 3 weeks later, and early controlled motion exercises when the cast is removed around 6 weeks after injury, if the x-rays demonstrate sufficient fracture healing has occurred. The consultation of a therapist will assist in preventing the wrist and hand from becoming stiff and will guide the therapy protocol until the best level of activity is achieved.

When the fracture fragments are separated, significantly shortened, angulated, extend into the joint or if there are multiple small fragments (comminution), these findings alone or in combination can result in an unstable fracture which means that if the fracture is reduced and casted, the likelihood it will hold its position until healing occurs, is unlikely. In this instance, surgery is indicated. Different methods of fracture fixation to stabilize the fracture have been described which are used include: Pins, Headless screws, External fixation and plates and screws. Recently, distal radius fracture fixation has had improved results due to newer plates and screws that lock to each other, consequently providing an improved hold on the fragments until the fracture heals. This newer plate and screw systems are placedon the palmar side of the wrist where there is improved padding due to the muscles on this side of the forearm, causing less plate prominence often eliminating the need for their removal in the future after the fracture has healed. The Locking plates increase the rigidity of the fixation which allows earlier motion of the wrist and digits even in poor bone quality exists, which in turn minimizes the stiffness often associated with these injuries and delivers improved and earlier return of normal function.

Severe fractures often have associated conditions like acute carpal tunnel syndrome (compression of the median nerve due to severe swelling about the wrist) demanding release of the nerve on same surgical setting. Ligament injures associated with distal radius fractures must also be considered as well as, injury to the distal radial ulnar joint as occurs when a ulnar styloid fracture is present.

After fracture fixation, the patient can start immediate active motion of the fingers and wrist to prevent stiffness. A removable wrist splint is used during the perioperative period to provide psychological confidence for elderly patients concerned about losing their balance. The patients are evaluated 1 week after surgery for an initial wound check and for the initiation of formal therapy and are given a protective brace that is allowed removal for hygiene and wrist and hand exercises. It takes up to 3- 4 months to obtain about 75% of function and it may take a full year to obtain maximal improvement. The timeframe depends on the severity of the fracture, associated injuries and the age of the patient.

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