Overview
Malunion is one of the common adverse outcomes of distal radius fractures, together with nerve and tendon injury. There is no consensus on a single definition. This guide summarizes how Rockwood defines distal radius malunion, when corrective osteotomy is indicated, how radiographic deformity relates to function, and the principles that guide correction. The source chapter does not give a step-by-step surgical technique, so none is described here. (Rockwood)
Definition and Classification
A recent review of the literature and expert opinion defines distal radius malunion by any of: (Rockwood)
Radial inclination under 10 degrees.
Volar tilt over 20 degrees, or dorsal tilt over 20 degrees.
Radial height under 10 mm.
Ulnar variance over +2 mm.
Intra-articular incongruity or step/gap over 2 mm.
For simplicity, malunions are classified by morphology as dorsally displaced, volarly displaced or intra-articular. Some fractures show features of more than one type. (Rockwood)
Relationship Between Deformity and Function
Cadaver studies show that increased dorsal tilt changes pressure distribution, reduces congruity of the distal joint surfaces including the DRUJ, and can lead to midcarpal instability. Dorsally angulated fractures can produce a non-dissociative (type IV) form of carpal instability. (Rockwood)
There is debate about how much tilt matters, but there is consensus that dorsal tilt over 10 degrees is associated with functional limitations and worse DASH scores a year after fracture. (Rockwood)
Radial shortening of more than 4 mm has been linked with wrist pain a year after injury. Loss of radial height alters DRUJ kinematics and increases ulnar variance, which has been linked to reduced grip strength, ulnar-sided wrist pain and worse DASH scores. Radial inclination is closely related to radial height. (Rockwood)
Carpal malalignment is mostly a compensatory carpal flexion or extension in response to residual tilt of the distal radius, and can be improved with corrective osteotomy. (Rockwood)
Radiographic outcomes do not always correlate with function or subjective results, particularly in older patients. The influence of residual joint incongruity on later degeneration is unclear. A series with a mean follow-up of 38 years found posttraumatic arthritis in 68% of those with prior intra-articular fractures, with DASH scores no different from population norms. (Rockwood)
Lower-demand patients can tolerate some malunion while maintaining function. The treatment goal is restoration of normal anatomy, but not every patient needs it to function at baseline. (Rockwood)
Indications for Corrective Osteotomy
Indications are based on the patient's symptoms, particularly in the elderly, because radiographic results do not reliably track function. Malunion can cause reduced grip strength, restricted motion, pain and unacceptable cosmetic deformity. In that setting corrective osteotomy is indicated to restore normal radiocarpal and distal radioulnar relationships. (Rockwood)
Timing is debated. There is not enough evidence to firmly compare "early" correction before the fracture has fully consolidated and "late" osteotomy after healing. More recent data suggest that intervention as early as 6 weeks is technically less demanding for the surgeon and shortens the patient's overall disability. (Rockwood)
Planning Principles
The most frequent symptomatic malunion is the dorsally displaced distal radius malunion. It typically shows marked dorsal angulation and shortening relative to the radial shaft. As a result, the DRUJ is often incongruent. (Rockwood)
No technique has been shown superior for dorsally or volarly displaced malunions or for intra-articular incongruity. In all distal radius corrective osteotomies the main aim is to restore both radiocarpal and distal radioulnar joint congruity. (Rockwood)
Intraoperative arthroscopy has been described to improve accuracy of correction in intra-articular malunions. (Rockwood)
Compare with the opposite wrist when judging inclination, radial height, tilt and ulnar variance. (Planning against the normal side is general practice for malunion; see the malunion assessment guide.)
Both surgeon and patient must understand that surgery for distal radius malunion rarely produces a normal wrist. Radiographic parameters and outcome scores (Michigan Hand Outcomes Questionnaire, DASH) improve, but deficits in motion and grip strength compared with the opposite side often persist, and grip strength rarely exceeds 70% of the contralateral side. (Rockwood)
Related Adverse Outcomes (Rockwood)
Nerve injury. Carpal tunnel syndrome is among the most common complications of distal radius fracture and can appear acutely, subacutely or as late as 25 years afterward. Acute carpal tunnel syndrome shows progressive pain and median-nerve symptoms and needs urgent decompression. Median nerve contusion is nonprogressive and improves with time. Ulnar nerve injury is rare and is usually a self-limited neurapraxia.
Tendon injury. Most often EPL rupture (after operative and nonoperative treatment). The authors prefer EIP tendon transfer for reconstruction. Flexor tendon rupture, particularly FPL, can result from volar plate irritation, especially when distal locking is done without checking that the radius is properly reduced to the plate. Treat with implant removal and primary repair, graft or transfer. Prevent by placing the plate proximal to the radial watershed line and avoiding prominent dorsal screws.
Complications
Residual stiffness, grip weakness and ulnar-sided wrist pain after malunion correction. (Rockwood)
Carpal instability and DRUJ incongruity if tilt and shortening are left uncorrected. (Rockwood)
Tendon irritation or rupture related to implants. (Rockwood)
References
Chapter 43, distal radius and ulna fractures. In: Tornetta P III, Ricci WM, Ostrum RF, McKee MD, Ollivere BJ, de Ridder VA, eds. Rockwood and Green's Fractures in Adults. 10th ed. Wolters Kluwer; 2024 (Turkish edition: Erişkin Kırıkları).