21 Extra-articular Malunion
Abstract
Extra-articular malunion is still a common complication of the distal radius fractures (DRF). Also, not all nonanatomically aligned DRFs lead to a poor clinical outcome, many patients with a malunion of the distal radius have disabilities of arm and wrist. If ever indicated, corrective osteotomy is the best option to treat an extra-articular radial malunion. While in former times dorsal malunions were mostly approached dorsally, now with use of locking plates, designed to fix acute dorsally tilted fractures from the palmar side, palmar and dorsal malunions are routinely treated through a palmar approach. There is a discussion whether a structural or nonstructural bone graft should be used, and actually whether there is a need for a bone graft at all. Independent of whether a structural or nonstructural bone graft is used, in most cases the distal radius will heal quickly. The more anatomical relation between the distal radius and the distal ulna and the carpus improves wrist and forearm motion and grip strength and diminishes pain. The changes from pre- to postoperative are statistically significant. Furthermore, there is a correlation between functional and radiological outcome. If the radius is restored more anatomically, the clinical outcome will be better.
21.1 Introduction
Despite the advances in the treatment of distal radius fractures (DRFs), malunion remains one of the most common complications. Distal radius malunion (DRM) mostly occurs following conservative treatment. Now, that surgical fixation of DRF has become more commonplace, there is an increasing number of malunion following operative treatment. 1
DRM may be extra-articular, intra-articular, or com bined intra-extra-articular. 2 In most extra-articular malunion, a combination by an angulation in the sagittal and frontal plane with a loss of length relative to the ulna is found, while a pure sagittal rotational malunion is rare. 3 In addition, a rotational deformity of the distal fragment with respect to the diaphysis can be seen. 4 Moreover, there may be a translation of the distal fragment in either the sagittal and/or the frontal plane. 5 Isolated shortening of the radius is a rare condition. In our own experience, the amount loss of length is greater in dorsally titled than in palmarly tilted malunion.
It may be true that not all nonanatomically aligned DRF result in a poor functioning outcome. However, many patients with a malunited DRF complain about a decreased range of wrist motion and forearm rotation, weakness, and pain. In palmar malunion, supination of the forearm is more affected than pronation. Due to a posttraumatic ulnar impaction, often the pain is located on the ulnar side of the wrist. Many patients, both women and men, are unhappy with the unpleasant appearance of the wrist with a prominent ulna head typically for malunited Colles type fractures and a bayonet deformity typically for a Smith type fracture. DRM can lead to a subclinical irritation of the median nerve, while a manifest carpal tunnel syndrome is less often seen. 6
21.1.1 Biomechanics of Distal Radial Malunion
Normal wrist biomechanics depend upon maintenance of the anatomical position of the distal end of the radius with respect to the carpus and the distal end of the ulna. Normal wrist motion consists of greater than 120 degrees of wrist flexion and extension, 50 degrees of wrist radial and ulnar deviation, and 150 degrees of forearm rotation at the distal radioulnar joint (DRUJ). The distal radius carries 80% of the axial load through the wrist and the distal ulna carries 20%. 7
The osseous deformity in DRM affects the normal mechanics of the radiocarpal joint producing a limitation of the extension–flexion arc of motion. In addition, the malalignment affects the normal load transmission not only through the radiocarpal joint, but also across the whole wrist joint. Dorsal tilting of radial surface decreases the joint contact area by shifting axial loading through the wrist dorsally and ulnarly. Therefore, the pressure distribution on the radial articular surfaces becomes more concentrated 7 , 8 , 9 and may represent a prearthritic condition of the wrist joint. 10 The force borne by the ulna increases with shortening of the radius and dorsal tilting of the articular surface. As the angulation of the distal radius fragment increases from 10 degree of palmar tilt to 45 degree of dorsal tilt, the load through the ulna increases from 21 to 67% of the total load. 11 Lengthening of the ulna by 2.5 mm relative to the radius increases the force borne by the ulna from 18.4 to 41.9% of the total axial load. 7
Malalignment of the surface of the distal radius in both the sagittal and coronal planes may result in a decreased mechanical advantage of the flexor tendons as they pass through the carpal tunnel, diminishing the grip strength. 12 In addition, median nerve compression neuropathy can also be encountered as a result of the deformity of the distal radius. 6
At the midcarpal level, dorsal tilt of the distal radius, as an adaptive response to the dorsally rotated proximal carpal row, may lead to a compensatory flexion deformity, 13 an extrinsic midcarpal dynamic instability, 14 and a fixed carpal malalignment in dorsiflexion. 15
Tilting and shortening of the distal radius may cause incongruity of the DRUJ and reduction of radioulnar contact area. 16 Radial shortening in relation to the distal part of the ulna can increase the strain in the triangular fibrocartilage complex 17 and result in a disruption of the deep portion of the dorsal radioulnar ligament. 18 These factors may limit the arc of forearm rotation. 19
Fellmann et al 20 showed that an anatomical reduction of acute DRF correlates with a significantly better range of motion, while McQueen and Caspers 21 found that motion was significantly worse in wrists with dorsal tilting of more than 12 degrees. Jenkins and Mintowt-Czyz, 22 and Cooney et al 23 reported a close relationship between decreased grip strength and the severity of residual fracture deformity. Aro and Koivunen 24 found that only 4% of patients with an acceptable anatomic result had an unsatisfactory functional end result, compared with 25% of the patients with minor shortening and 31% of patients with gross shortening of the radius.
21.1.2 Treatment Options
Treatment options for symptomatic DRM must take into account the functional demands of the patient, patient’s motivation, and the anatomy of the deformity. Fixed-angle devices allowing a stable fixation even of osteoporotic bone have made the bone quality less important.
Intervention to correct symptomatic malunion may be categorized into four broad areas: procedures aimed at restoring anatomic relationships, procedures aimed solely at gaining a functional improvement, procedures aimed at eliminating pain, and procedures that combined two or more of the above approaches.
Procedures aimed at eliminating pain are wrist denervation 25 and arthrodesis. For extra-articular DRM, arthrodesis is rarely indicated. In the setting of an extra-articular malunion combined with a carpal collapse due to scapholunate dissociation, radioscapholunate fusion reduces pain and preserves a certain degree of wrist motion as long as the midcarpal joint is intact. 26 Otherwise a total wrist joint might be indicated.
From the different procedures aimed solely at gaining a functional improvement on forearm rotation, satisfactory results can be achieved with Bowers hemiresection interposition arthroplasty and ulnar head replacement. 27 , 28
Procedures aimed at restoring anatomic relationships between the distal end of the radius and the carpus and the distal end of the ulna are primarily osteotomies of the distal radius and the ulna.
21.2 Indications and Contraindications
The indication for corrective osteotomy of an extraarticular radial malunion is symptomatic, rather than radiological. It depends on the limitation of function, the severity of pain, the presence of midcarpal instability, the associated problems of the DRUJ, and the displeasing appearance of the wrist.
From a radiological standpoint, there are no fixed parameters to indicate a radial corrective osteotomy (RCO). However, because any angular deformity in the sagittal plane affects the DRUJ, shortening of the ulna is only indicated for dorsal malunion with dorsal tilting less than 10 degree and palmar malunion with less than 20 degree palmar angulation. 29 In more severe multidirectional deformities, an open wedge osteotomy of the distal radius or a combined closed wedge osteotomy of the distal radius with an ulna shortening is needed to restore the anatomic relationships between the distal end of the radius and the carpus and the distal end of the ulna as base of an almost normal wrist and forearm function. Radial shortening up to 12 mm can often be managed by RCO alone. If there is a greater radial shorting, a combined closed wedge osteotomy of the radius and ulna shortening should be considered. 30
Poor general health and marked degenerative changes of the radiocarpal joint are contraindications for RCO. Moreover, fixed carpal malalignment is a contraindication, because in this setting the carpus does not correct with the radius and the patient will have ongoing pain midcarpal, where the head of the capitate is sitting on the dorsal pole of the lunate. There is always a discussion, whether evidence of an acute sympathetic reflex dystrophy is a contraindication for RCO. If the reflex dystrophy is caused by an irritation of the median nerve by the malaligned distal fragment, RCO can address the problem. Patients with reduced finger function should undergo physiotherapy prior to the operative intervention. As locking plates allow a more rigid fixation of the distal radius, only a really severe osteoporosis is a contraindication for RCO.
A slight instability of the DRUJ is not a contraindication for radial osteotomy, because the restored anatomical relation between the distal radius and the distal ulna restabilize the DRUJ. In several patients, we observed a healing of a nonunited ulnar styloid following RCO without any procedure on the ulnar side of the wrist. Also, a marked instability of the DRUJ is no contraindication for RCO, but requires a simultaneous or a secondary procedure on the ulnar side of the wrist, such as an Adams procedure. 31
The combination of a DRM with degenerative changes of the DRUJ, located either at the sigmoid notch or the ulnar head, can be addressed with RCO combined with Bowers procedure. 27 Due to persisting postoperative problems in some patients following Bowers hemiresection arthroplasty, ulnar head replacement in combination with RCO is preferred nowadays. 28
Based on the overall good results after RCO, there is no longer an upper age limit for RCO, provided that there is good general health. Elderly people can benefit significantly from RCO, even though they do not recover as much as younger patients. 32 Due to the enormous remodeling capacity of the distal radius, there is rarely a need for osteotomy in children. 33 It is indicated if there is a growth arrest or if the time left for remodeling is too short for a complete spontaneous correction (▶Fig. 21.1a–f).
21.3 Surgical Technique
21.3.1 Timing for Radial Correction Osteotomy in an Extra-articular Malunion
In patients who are still in work or retired but still very active, RCO should be performed after the fracture as soon as it is decided that the patient meets the criteria and the swelling is subsided. Jupiter and Ring retrospectively compared the results of 10 patients in whom DRM had been corrected within 6–14 weeks after the injury with the results of 10 patients with late RCO, i.e., 30–48 weeks after the injury. 34 They found that the results were comparable, early reconstruction is technically easier and reduces the overall period out of work.
For patients who are retired and less active, there is no need for early intervention. With respect to their individual demands many of these patients will achieve satisfied or even good clinical results. Those who suffer from persisting disabilities of the wrist can undergo a late RCO leading to the same good clinical outcome as with an early correction.
21.3.2 Preoperative Work-up
Patients with extra-articular DRM often present with associated concerns that can degrade the outcome. Therefore, a meticulous preoperative physical and radiographic evaluation is imperative. Physicians should identify the location of the discomfort, check the stability of the DRUJ, and measure both the range of motion of the wrist and forearm motion, and grip strength compared to that of the contralateral side. The disabilities of the arm, shoulder and hand (DASH) questionnaire can be used preoperatively to assess the subjective disabilities of the patients and quantify self-rated treatment effectiveness after surgery.
Standard biplanar radiographs of the injured and uninjured wrist are mostly adequate for planning the operative treatment of patients with an extra-articular DRM (▶Fig. 21.2a). Comparison with the uninjured side is crucial to determine carpal alignment, ulnar variance, and inclination of the articular surface of the distal radius in the sagittal and frontal plane (▶Fig. 21.2b). Computed tomography (CT) scanning may be helpful to detect degenerative changes and malalignment of the DRUJ and assess malrotation of the distal fragment with respect to the diaphysis. An arthroscopy of the wrist may be indicated to assess the ligaments and the articular cartilage, if a ligament tear is suspected. The lunate follows the articular surface of the radius in the malposition. There might be a scapholunate dissociation, if the tilting of the lunate is greater as 10 degree as the tilting of the distal radius in the sagittal plane.
Preoperative drawing of the planned surgical intervention showing the level of osteotomy, the angle of correction, the ulnar plus, and the size of the osteotomy gap is essential. Nowadays, the preoperative planning of the surgical intervention is often done on a computer. 35
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