Osteotomies for Distal Radius Malunions: Intra- and Extra-articular

RATIONALE AND BASIC SCIENCE

In 1951, Gartland and Werley reported a landmark study on the evaluation of healed Colles’ fractures that emphasized restoration of volar tilt to 11 degrees and radial inclination to 23 degrees to “compensate adequately for the loss of correction which will occur” when fractures are treated with closed means. The authors noted that fractures that settled tended to be associated with a worse functional outcome.

These initial observations have held over time. A recent study of distal radial fractures demonstrated that grip strength, range of motion, and the ability to perform activities of daily living were significantly worse in patients with dorsal angulation of more than 12 degrees than in those with dorsal angulation of 10 degrees or less. Another study has identified carpal malalignment—the displacement of the capitate relative to the longitudinal axis of the radius—as the most important predictor of function.

Researchers have attempted to explain why these parameters have clinical importance using biomechanical studies of simulated distal radial malunions. Studies of cadavers have demonstrated an increase in radiocarpal contact areas and pressures with radial shortening; dorsoulnar migration of contact pressures and midcarpal instability with increased dorsal inclination; and shifts in the instant center of rotation during pronation and supination with changes in radial height, inclination, and dorsal angulation. A number of other in vitro models have demonstrated that radial deformity affects the distal radioulnar joint, leading to increased strain on the triangular fibrocartilage complex and incongruity of the distal radioulnar articulation.

Although studies show that extra-articular malunion leads to abnormal function, other studies have found that intra-articular malunion is associated with radiographic arthritis at mid-term and long-term follow-up. Despite these radiographic changes, current evidence suggests that functional status is comparable for patients with intra-articular malunions and those without. One study found that at 7.1 years of follow-up, there was a strong association between articular stepoff and the development of radiocarpal arthrosis, but no association with physical examination, symptoms, or functional status.

Why address distal radius malunion with osteotomy? Current evidence suggests that correction of intra-/extra-articular malunion is feasible, but most results come from retrospective case series without using validated outcomes. Although this evidence is far from compelling, our rationale in correcting distal radius malunion is as follows: given that our understanding of malunion is incomplete, the potential uncharacterized benefits of restoring anatomic dimensions to the distal radius justify the morbidity and the surgical risk of correction.

INDICATIONS AND CONTRAINDICATIONS

We consider osteotomy in patients with distal radius malunion and functional limitations of the forearm with pain or limitation of supination or pronation, loss of flexion or extension, or loss of grip strength. Extra-articular osteotomy is strongly considered in patients with subluxation of the radiocarpal joint or midcarpal instability ( Fig. 26-1 A and B). Intra-articular osteotomy is strongly considered in patients with subluxation of the radiocarpal joint with coronal incongruity or in patients with an intra-articular stepoff greater than 2 mm.

Distal radius osteotomy should not be performed for all malunions. Contraindications include acceptable function despite malunion ( Fig. 26-2 A–D), advanced degenerative articular changes, fixed carpal malalignment, limited functional capabilities, severe osteoporosis, and complex regional pain syndrome. Age is not a contraindication to surgery.

There is no time limit on the osteotomy; rather, advanced osteoarthrosis is the limiting factor. It is important to note that there is no reason to delay an indicated osteotomy, particularly for intra-articular malunions, since it may lead to advanced arthrosis. In our experience, early reconstruction of nascent extra-articular malunion has results comparable to those with late reconstruction but with a shorter period of disability ( Table 26-1 ).

TABLE 26-1

Indications and Contraindications

Indications	Contraindications
Limitation of function	Advanced arthritic changes
Pain	Advanced osteoporosis
Midcarpal instability	Fixed intercarpal malalignment
Pre-arthritic joint incongruity	Limited functional capacity
	Complex regional pain syndrome

SURGICAL TECHNIQUE

Preoperative Planning

It is important to have a careful preoperative plan before performing a distal radius osteotomy. Radiographs, computed tomography (CT) scans, and three-dimensional reconstructions are useful for determining the fracture configuration, degree of articular incongruity, and amount of angular correction needed. If a structural bone graft is used, preoperative planning is also useful to determine the dimensions of the graft to be interposed. Images of the contralateral wrist provide the best dimensions to which the injured wrist should be restored ( Fig. 26-3 A–F ).

Positioning and Setup

We have used both general and regional anesthesia successfully. The patient is placed supine with a tourniquet around the arm. The operating table is equipped with a radiolucent hand table. The limb is prepped and draped in standard fashion.

Dorsal Approach

For dorsally displaced malunions, a dorsal approach has traditionally been used, but with the introduction of fixed-angle implants, it is also possible to use volar approaches. A dorsal exposure allows direct visualization of the articular surface through a dorsal capsulotomy. It is therefore useful for the treatment of extra-articular or intra-articular malunions associated with dorsal subluxation and simple articular malunions in the sagittal plane ( Figs. 26-4 through 26-7 ).

A longitudinal skin incision is made over Lister’s tubercle. The extensor retinaculum is incised over the extensor pollicis longus in the third dorsal compartment. The extensor pollicis longus is mobilized and transposed dorsoradially into the subcutaneous tissues. The fourth dorsal compartment and the extensor digitorum communis tendons are elevated subperiosteally from the radius, and the radial wrist extensors are retracted radially. The dorsal wrist capsule is incised to visualize the articular surface in intra-articular osteotomy.

Volar Approach

The volar exposure is useful for volar malunions or articular malunions associated with volar subluxation ( Figs. 26-8 through 26-11 ). A volar Henry approach is typically used, but an extended carpal tunnel incision may be used if the need to expose the volar lunate facet is more important than exposing the radial styloid. We attempt to avoid violating the volar wrist capsule, but, if necessary, a limited incision is made.

Realignment and Fixation

Direct visualization and intraoperative image intensification are used for a mature malunion. For mature malunions, the bone is cut at the previous fracture site with a sharp osteotome or an oscillating saw. We often place a laminar spreader in the recreated fracture to help stretch the soft tissues for several minutes. Provisional smooth Kirschner (K) wires can be used to achieve and maintain alignment with or without the assistance of an external fixator. Structural or nonstructural bone graft or bone graft substitute is placed into the fracture site, and then a plate is applied in standard fashion.

Once hardware is placed, the wound is irrigated thoroughly and closed in standard fashion. The wrist is placed in a splint postoperatively, and active range-of-motion exercises of the fingers and wrist are instituted at 2 weeks. A plastic resting splint is used when not performing exercises. When the osteotomy demonstrates radiographic healing, exercises are advanced to include more aggressive range of motion and strengthening. If a large lengthening has been performed (more than 10 mm) or fixation is tenuous, the wrist is immobilized in a below-elbow cast for 6 weeks, and wrist motion is instituted after cast removal.

Intra-articular Malunions

Corrective osteotomy of intra-articular malunions is appealing, since articular incongruity is directly associated with the development of radiocarpal arthrosis. The reluctance to perform a corrective osteotomy is due to concerns regarding surgical exposure, osteonecrosis of the small articular fragments, and the obtaining of adequate fixation. Improvements in both imaging and fixation devices have decreased some of these concerns.

A volar, dorsal, or combined approach can be used, depending on the anatomy of the malunion. With the volar approach, the joint is visualized through the fracture/osteotomy site, leaving the radiocarpal ligaments intact. With a dorsal approach, the joint is visualized through a capsulotomy. The previous fracture site is identified visually and with image intensification. Smooth 0.045-inch K wires are inserted into fracture fragments to be used to “joystick” the fragments for reduction.

A sharp osteotome or a small oscillating blade may be used to open the fracture site. If an oscillating blade is used, an incomplete cut is made and then completed with a sharp osteotome. An osteotome or small Cobb elevator is then used to gently free the original fracture site and to mobilize the articular fragment into proper position. The fragments are manipulated using the previously placed wires and can be provisionally fixed by using either 0.045-inch or 0.062-inch K wires. Another option is to use a mini-external fixator to hold the joysticks. Once gaining provisional fixation, the joysticks may be removed if not holding fixation. A plate-and-screw construct is then applied in standard fashion ( Figs. 26-12 through 26-15 ).