Malunion of Hand Fracture 

Malunion may be defined as healing of a fracture in an abnormal (nonanatomic) position. In the hand, it presents a combined functional and aesthetic problem. The management of malunion of hand fractures is more complex than the management of malunion of fractures elsewhere in the skeleton.^{[1, 2, 3, 4]} See the images below.

Good hand function depends on joint mobility, sensibility, good skin coverage, adequate vascularity, and the gliding of a complex flexor and extensor tendon mechanism. Preexisting problems related to any of these factors may limit the usefulness of the digit, and surgical intervention can cause additional scarring and dysfunction. As a consequence, the management of malunion in the hand is predicated on a careful analysis of the risks and benefits of surgical intervention and on the functional goals and the likelihood that the operation can achieve them.^[1]

Fractures of the hand are among the most common fractures of the skeletal system. Most of these fractures are acquired in the workplace or as a result of crush injuries, falls, or sports injuries.

Most of these injuries can be managed nonoperatively, but certain fractures, such as intra-articular fractures, open fractures, unstable fractures, and displaced or angulated fractures, may require surgical correction with Kirschner wires (K-wires), plates, or screws. If these fractures are not treated properly, malunited fractures may result, leading to considerable loss of function and cosmetic disfigurement. Malunited fractures involving the joint surfaces can ultimately lead to posttraumatic osteoarthritis.

Most fractures of the hand bones occur in young, active adults who are involved in many various occupational and sporting activities. If these fractures are not managed carefully, they may result in malunion. This may lead to loss of function due to malalignment, malrotation, or shortening, which may result in decreased and disordered motion of fingers and poor outcomes.

Frequency

Malunion strictly implies union with abnormal anatomic alignment. However, in the hand, this does not necessarily mean a dysfunctional hand or finger, because this is not often the case. The frequency of malunited fractures may be high in the hands, but few require treatment. This is especially true with malunion of metacarpal neck fractures of the little fingers, which typically do not require treatment because they seldom produce deformity or interfere with function.^[2] Tubiana showed that, of 10,000 hand injuries, only 30 malunions required treatment.^[5]

Malunion of hand fractures may result from inadequate treatment or failure of treatment. Accurate anatomic restoration may not be the goal of nonoperative treatment or even certain operative treatments for hand fractures. Hence, inaccurate anatomic restoration after treatment may not be considered evidence of inadequate treatment.

Patterns of malunion

Malunion is the most common bony complication of phalangeal fractures. Four patterns of deformity are recognized: malrotation, volar angulation, lateral angulation, and shortening.

Malrotation usually is seen after oblique or spiral fractures of the proximal and middle phalanges. The best method to assess malrotation is to ask the patient to make a fist and look for digital overlap.

In adults with proximal phalangeal fractures, volar angulation >25-30° may result in pseudoclawing. This deformity makes using the hand awkward and can result in a fixed flexion contracture of the proximal interphalangeal joint. The appearance may be aesthetically unacceptable.

Lateral angulation and malrotation often occur concomitantly. If correction is considered, carefully identify the components of the deformity.

Shortening may occur after a comminuted fracture is allowed to heal in a collapsed fashion or after a long spiral fracture.

In malunion of metacarpal neck fractures, sunken knuckle may be the clinical presentation. It is more of a cosmetic problem than a functional problem. In metacarpal shaft malunion, tendon imbalance and intrinsic contracture of the proximal interphalangeal joint may occur; however, function may still be preserved.

Other aspects of malunion

Intra-articular malunion occurs when intra-articular anatomy is not restored. Unreduced condylar fractures that extend into the proximal interphalangeal joint may produce pain, angulatory deformity, limited mobility, and, ultimately, degenerative arthritis.

Regarding metacarpal fractures, malunion can follow a transverse fracture, which results in dorsal angulation in the sagittal plane. Compensatory hyperextension (pseudoclawing) at the metacarpal phalangeal joint can result. Malunion after a spiral or oblique fracture results in malrotation.

In patients with second and third metacarpal fractures, dorsal angulation is bothersome both cosmetically (pseudoclawing) and functionally. The prominent metacarpal head in the palm can be painful when the individual grips.

Rotational malunion of metacarpal fractures results in overlapping of the affected finger over an adjacent finger. The cosmetic deformity is often marked, and the grip is often impaired.

After crushing injuries or open fractures, shortening and associated problems of the soft tissue (eg, tendon adhesions, poor skin coverage, neurologic deficit) may occur.

Malunion most commonly affects the scaphoid among the carpal bones. Malalignment after union is evident as carpal collapse initially, and is reflected later in direct measurements of intrascaphoid alignment. The lateral appearance on radiographs shows the typical humpback scaphoid, which describes a deformity resulting from flexion angulation between the proximal and distal poles. Scaphoid malunion can alter carpal mechanics, leading to pain, weakness, limited motion, and degenerative arthritis.

Relationship between shortening of metacarpal and joint function

Some authors have performed cadaveric studies to find the relationship between metacarpal shortening and extension of the metacarpophalangeal joint (MCPJ) or the proximal interphalangeal joint (PIPJ). Strauch et al observed that for every 2 mm shortening of metacarpal there was a 7° lag in extension of the MCPJ.^[6] However, this is not seen clinically because of the ability of the MCPJ to hyperextend. Vahey et al found that for every 1 mm of shortening of proximal phalanx there was a 12° lag in the PIPJ extension.^[7] They also found that there is a linear relationship between proximal phalanx shortening and PIPJ extensor lag and that increased angulation of the phalangeal fracture led to increased lag in extension of the PIPJ.

History

Malunited hand fractures are not usually difficult to diagnose. Most patients provide a history of injury associated with the deformity. The form of treatment the patient received should be noted. Such treatment may include both nonoperative measures such as splinting, immobilization, and physiotherapy and operative measures such as internal or external fixation or both. The history must include the patient's age, occupation, hand dominance, function and restriction of hand function after the fracture, and the effect of the malunion on his or her activities.

Physical examination

Physical examination is of vital importance in evaluating the malunited hand. Commence the hand examination by comparing the affected hand with the uninjured hand. Note any obvious swelling or deformity. Look for the anatomic bony landmarks and their interrelationships, and compare them with those of the healthy hand. Abnormal positioning may indicate a malunited fracture or tendon rupture or adherence. The deformity should be categorized in each plane, to include the ulnar-radial and the volar-dorsal plane. Also important is the rotational alignment. See the image below.

The most important aspect of the examination is the functional assessment of the hand. Because the fingers converge with flexion and diverge with extension, certain deformities can be appreciated with the fingers in flexion. The ability to make a complete fist must be assessed. Because the flexor digitorum profundus tendons of the fingers work in unison, any restriction in movement of 1 finger or any decrease in length of 1 finger may seriously affect the power of the patient's hand grip. Hence, it may notably interfere with normal function of the hand.

Grip strength should be measured by using a dynamometer, and the results can be compared with those of the healthy hand. Normal maximum grip strength is 52 kPa in men and 31 kPa in women. The pinch-grip strength can be measured by using a manual pinch meter. However, a pinch-grip analyzer can be used to measure both pinch and grip strengths, and it may be a useful tool for objectively assessing hand function.

The examination must include neurologic and vascular assessments. Any previous scar due to surgery or injury should be assessed to plan incisions if surgery is contemplated.

Indications for surgery include pain, loss of function, cosmetic deformity, loss of motion in the neighboring joint, and bony exostosis causing skin irritation and posing a threat of tendon attrition. When treating hand malunions, one must remember that the potential risks of surgery (eg, tendon adhesions, joint stiffness) may outweigh any anticipated advantage.

The hand is a highly complex structure that requires integrated function of extrinsic and intrinsic motor units across a complex and limited bony and articular framework. The hand also functions as a sensory organ and an organ of communication. All these factors should be considered before reconstruction is undertaken.

The absolute contraindication for surgery is local infection. Relative contraindications include functionless limb, poor bone quality, and poor general medical condition.