Distal Radius Malunion

Anthony LoGiudice

Hisham M. Awan

INTRODUCTION

Distal radius malunion—an intra-articular or extra-articular distal radius fracture healed in nonanatomic alignment, resulting in wrist pain, degenerative changes, decreased range of motion, altered wrist mechanics, instability, or a combination of these.
The biomechanical effects of malunion were first described by Rouen in 1919; Campbell detailed treatment with biplanar osteotomies in the 1930s.
The distal radius may normally bear loads of up to 4000 N, with 80% normally borne by the radius.
Recent studies showed that increasing ulnar positivity by only 2.5 mm raises the load across the ulna to 42% of the total borne by the wrist.
Deformity does not correlate well with symptom severity.
Key measurements—radial inclination, radial length/height, ulnar variance, and radial/volar tilt (Figure 27.1 and Table 27.1)
Most common deformity is loss of palmar/volar tilt in the sagittal plane and loss of radial length relative to the ulna.
Malunion is the most common complication of distal radius fracture, with an overall rate as high as 17%.
Frequently occurs in distal radius fractures managed nonoperatively and in elderly, osteoporotic bone.
Other causes—inadequate reduction, neglect or delayed presentation, and inadequate fixation or immobilization after operative intervention

EVALUATION

History
- Ulnar-sided wrist pain is the most common complaint and may be a consequence of altered ulnar variance, incongruity, or malalignment of the sigmoid notch.
- Greater severity or duration of deformity may lead to radiocarpal/midcarpal/distal radioulnar instability, wrist deformity, numbness/tingling/weakness in the median nerve distribution, or arthritic/degenerative changes.
- Correlated with a lower DASH (Disabilities of Arm, Shoulder, and Hand) score
Physical examination
- Detailed neurovascular examination
  - Include careful testing of median nerve for carpal tunnel syndrome.
  - Allen test for perfusion, presence of intact deep palmar arch
- Decreased range of motion—shifted flexion/extension arc, decreased pronosupination
- Swelling/edema
- Dinner fork deformity (Figure 27.2)
- Prominence of the ulnar head with pronosupination
- Decreased grip strength (↓50%)
- Prior surgical incisions
- Focused examination—radiocarpal, ulnocarpal, and distal radioulnar joints (DRUJ). Check for pain, crepitus, and instability.
Imaging
- Posteroanterior (PA) and lateral wrist radiographs to measure criteria of malunion (Table 27.1)
- Degenerative changes at the radiocarpal joint, midcarpal joint, and DRUJ should be noted.
- Check carpal alignment for dorsal subluxation of the carpus (Figures 27.3 and 27.4) or dorsal intercalated segment instability.
Advanced imaging is not routinely used in initial evaluation. However, it can be useful to evaluate complex and/or intra-articular deformity.
- Computerized tomography (CT)—shows bony detail of articular incongruity, status of fracture healing, as well as rotational and translational deformities
- MRI—shows gradient of soft tissue injury at the DRUJ, extrinsic or intrinsic carpal ligaments, and articular cartilage
Classification

No widely adopted system.
- Malunions may be described using radiographic parameters (Table 27.1). Alternatively, they may be described using the eponymous fracture pattern from the original injury (Colles fracture, Smith fracture, Barton fracture, etc.).

FIGURE 27.1 A, On a posteroanterior radiograph, the radial inclination (RI) is the angle subtended by a line perpendicular to the long axis of the radius and a line reflecting the articular surface of the radius. B, The radial length/height (RL) is the distance between tangents drawn at the radial styloid and the ulnar head, perpendicular to their shaft axes. C, The ulnar variance (UV) reflects the axial relationship between the ulnar head and ulnarmost aspect of the radius (ulnar edge of lunate fossa). The grayed portion of the ulna represents the prominence (positive UV) at the distal radioulnar joint. D, On a lateral radiograph, the radial/volar tilt (RT) is the angle between the articular surface and a line perpendicular to the radial shaft. Adapted from Graham TJ. Surgical correction of malunited fractures of the distal radius. J Am Acad Orthop Surg. 1997;5:270-281.

TABLE 27.1 Radiographic Assessment of Distal Radius Malunions: Normal Values and Acceptable limits of Deformity^14,17

Parameter	Normal Value^a	Acceptable Limit of Deformity
Radial inclination	22°	15° change (increase or decrease)
Radial length	11 mm	4 mm
Ulnar variance	Neutral	4 mm
Dorsal-volar angulation	11° volar	15° dorsal, 20° volar
Articular congruity	Congruous	≥2 mm gap or step-off
^aAll anatomic parameters are variable among individuals. The true “normal” values in each particular case are determined by comparison radiographs of the contralateral extremity. Adapted from Bushnell BD, Bynum DK. Malunion of the distal radius. J Am Acad Orthop Surg. 2007;15:27-40.

FIGURE 27.2 Dinner fork deformity resulting from loss of radial length, inclination, and palmar tilt.

FIGURE 27.3 Posteroanterior and lateral radiographs of a distal radius malunion demonstrating loss of radial inclination and length, increased ulnar variance, and dorsal angulation.

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