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Assessment of Articular Displacement of Distal Radius Fractures

Catalano, Louis, W, III; Barron, O, Alton; Glickel, Steven, Z

Section Editor(s): Olson, Steven A MD, Guest Editor; Marsh, J Lawrence MD, Guest Editor

Clinical Orthopaedics and Related Research: June 2004 - Volume 423 - Issue - p 79-84
doi: 10.1097/01.blo.0000132884.51311.28
SECTION I: SYMPOSIUM: Articular Fractures
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Intraarticular step and gap displacements represent the most common indication for surgical treatment of distal radius fractures. Most often, treatment decision making relies only on good-quality plain radiographs taken before and after reduction with measurement accuracy maximized by using the longitudinal axis method. When plain radiographs alone prove insufficient, CT scans or tomograms will significantly improve interobserver and intraobserver reliability of measurements, especially when evaluated using the arc method. Tomography is an effective method for postoperative evaluation of fractures immobilized in splints or casts. The role of MRI in assessing intraarticular distal radius fractures is limited to confirming injuries to carpal ligaments or the triangular fibrocartilage complex. Intraoperatively, we use fluoroscopy to obtain 30° cephalad posteroanterior views and as 22° lateral views to best observe articular surface reduction. Our current operative indications include fractures with radiocarpal or distal radioulnar joint step or gap deformities greater than 1–2 mm, gross distal radioulnar joint instability, or those with extensive metaphyseal comminution rendering them particularly unstable after closed reduction. In general, we tend to lean toward operative fixation in younger, more active patients.

From the C.V. Starr Hand Surgery Center, Roosevelt Hospital, New York, NY.

No benefits of any kind have been received from a commercial party related directly or indirectly to the subject of this article.

Correspondence to: Louis W. Catalano, III, MD, C.V. Starr Hand Surgery Center, Roosevelt Hospital 1000 Tenth Avenue, New York, N.Y. 10019. Phone: 212-523-7590; Fax: 212-523-7592; E-mail: louiscatalano@aol.com.

The presence of an intraarticular fracture of the distal radius can lead to the development of premature arthritis of the radiocarpal, ulnocarpal, and distal radioulnar joints. Multiple studies have shown that residual articular incongruity of 1–2 mm during fracture healing is associated with radiographic evidence of arthrosis and fair to poor results.4,9,12,21

In contrast, two additional studies5,15 have concluded that symptomatic arthritis is rare after intra-articular distal radius fractures despite radiographic evidence of arthrosis. It is possible that the distal radial articulations are somewhat protected from developing arthritis because the wrist is not a weightbearing joint.

Because each of these studies has shown that persistent residual articular incongruity at the time of fracture union leads to radiographic evidence of premature arthrosis (but not necessarily arthritis), it seems prudent that the treating surgeon obtain as close to an anatomic reduction as possible to minimize the development of early degenerative changes. To accurately assess the distal radius articular surface (prereduction and postreduction), careful radiographic assessment is required.

We will discuss why orthopaedic surgeons should care about articular displacement in the distal radius and how best to use the clinical and radiographic tools available to minimize residual articular incongruity after fracture reduction. Specifically, we will discuss the roles of plain radiography, CT, MRI, and arthroscopy in the evaluation and treatment of intraarticular distal radius fractures. The ultimate question becomes what criteria are used to define treatment regimens, and does using these criteria lead to effective treatment and desired clinical outcomes.

Is there scientific evidence to support the prevailing wisdom that articular incongruity is a critical variable in treating distal radius fractures?

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Cadaveric Studies

Short et al19 showed that 80% of the joint reactive force across the wrist is borne by the radiocarpal joint. Furthermore, radiocarpal joint reactive force is distributed between the scaphoid and lunate facets at 60% and 40%, respectively.22

Wagner et al23 used pressure-sensitive film in 12 cadaveric wrists in which varying amounts of joint depression were created. Although it required 3 mm of lunate fossa depression to statistically increase radioscaphoid joint reactive force, only 1 mm of scaphoid fossa depression resulted in statistically relevant increases in lunate fossa pressure. These findings were similar to those of Baratz et al3 in a simultaneously published study.

Anderson et al2 simulated an intraarticular fracture spanning the lunate and scaphoid facets, and reported statistically significant increases in mean contact stress with a 3-mm step deformity, and not with lesser amounts of incongruity. They implicated other factors in the development of radiocarpal arthritis.

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Clinical Studies

The oft-quoted study by Knirk and Jupiter12 attempted to determine the maximum allowable articular incongruity after fracture union to obviate the development of late arthritis. Of the fractures that healed with greater than 2 mm of residual incongruity of the radiocarpal joint, 100% had radiographic evidence of arthrosis. The distal radioulnar joint also was assessed and residual displacement led to a higher percentage of late degenerative change at this joint as well. However, no effective outcome instrument was used to correlate these radiographic changes with clinical symptomatology.

In an effort to better correlate radiographic and clinical data, Bradway et al4 retrospectively reviewed 16 patients with comminuted intraarticular distal radius fractures at a mean followup of 4.8 years. In addition to the Gartland and Werley scoring system (used by Knirk and Jupiter), the modified Green-O’Brien scoring system was used with greater weighting toward pain and functional status. They reported that articular incongruity of more than 2 mm was associated with only fair results and major degenerative changes.

Fernandez and Geissler9 showed in a retrospective review of 40 patients treated with anatomic reduction of intraarticular distal radius fractures, that only 5% had radiographic evidence of arthritis at a mean followup of 4 years. They reported that 92.5% of the patients achieved healing with less than 1 mm of articular incongruity. In those few patients whose wrists healed with residual articular incongruity, there was a trend toward worse clinical results.

After correcting for severity of the initial distal radius fracture, Trumble et al21 retrospectively reviewed 52 wrists in 49 patients at a mean followup of 38 months to determine which of the various radiographic distal radius parameters had the greatest impact on the patients’ functional outcome. Correction of dorsal and radial tilt did not correlate with improved clinical outcomes, whereas total incongruity (step or gap deformity) did correlate strongly. The authors agreed with Fernandez and Geissler9 that less than 1 mm of total articular incongruity should be the goal of treatment.

The results of these studies prompt the question whether scientific evidence exists to contradict the premise that residual articular congruity (incongruity less than 1–2 mm) must be achieved to ensure consistently good clinical outcomes?

Catalano et al5 studied the issue of clinical outcomes in the face of residual articular incongruity. Twenty-six patients were reviewed radiographically and clinically at a mean followup of 7.1 years. The Musculoskeletal Functional Assessment (MFA) outcomes instrument was used for subjective evaluation, and all patients had radiographic evaluation in the form of plain radiographs and CT scans. Consistent with previous studies, a statistically significant correlation was observed between the development of radiocarpal arthrosis and residual articular incongruity. However, functional outcomes did not correlate with the amount of residual step and gap displacement, with all patients having good or excellent functional outcomes despite radiographic evidence of arthrosis.

In a review of 250 patients with intraarticular and extraarticular distal radius fractures, McKay et al15 determined the incidence of complications. Arthritis was documented as a physician-reported complication in only one of 250 patients, whereas two of 207 patients cited arthritis as a complication of their fracture. The specific location of the arthritis and whether this involved an intraarticular fracture was not reported.

If it is justified to use 1–2 mm of incongruity as the guiding parameter for the treatment of intraarticular distal radius fractures, then how reliable are plain radiographs in measuring this incongruity?

Kreder et al13 assessed intraobserver and interobserver reliability in the measurement of step and gap deformities in healed distal radius fractures. They determined that one observer will differ by more than 2 mm in his measurement at least 10% of the time. Two clinicians measuring the same film will differ by more than 3 mm at least 10% of the time.

Even when using a more standardized and seemingly more reliable technique for step and gap measurement on plain radiographs of distal radius fractures, Cole et al6 reported equally poor interobserver and intraobserver agreement in such measurements. These two studies call into question a clinician’s ability to make a treatment decision based on perceived incongruities of 1–2 mm from plain radiographs as recommended in the literature.

To minimize potential discrepancies regarding exact articular incongruity measurements and fracture classification, Decoster et al8 used a novel method to determine injury severity and quality of fracture reduction in tibial plafond fractures. The rank order method involved three orthopaedic traumatologists ranking the injury and posttreatment radiographs from least to most severe. For both sets of radiographs, the traumatologists ranked the severity of injury to the articular surface and fracture pattern severity. These data then were averaged and compared with clinical ankle outcome scores. DeCoster et al concluded that the rank order method was highly reliable in stratifying injury severity and quality of fracture reduction. Surprisingly, they also found that injury severity and articular reduction quality did not correlate with clinical ankle scores.

Several problems exist, however, with the rank order method that limit its clinical utility. First, the method requires several surgeons to evaluate the radiographs. Second, multiple, adjacent view boxes are necessary to allow for direct comparison of the radiographs. Third, the rank order method provides no treatment recommendations. Finally, although the method had high interobserver reliability, the rank order method had poor clinical predictive value as fractures rated the most severe did not necessarily have the worst clinical outcomes.

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Radiographic Evaluation of Articular Displacement in Distal Radius Fractures

Plain Radiographic Techniques

Decisions regarding the appropriate treatment of distal radius fractures most often are based on a clinician’s interpretation of two or three standard radiographic views of the wrist, the posteroanterior, lateral, and, less consistently, oblique views. This interpretation generally takes place in an emergency department or an office setting. For intraarticular fractures, articular step-off and gap deformities are evaluated to determine whether, according to current recommendations, more than 1–2 mm of step or gap or both are present. If so, surgery usually is recommended.

Although rarely differentiated in the literature, it is intuitive that gap deformities are tolerated better and less likely to result in arthritis than articular step-off. Step deformities alter load distribution but also expose the opposing carpal cartilage to a leading edge of subchondral bone.

As noted previously, a troubling degree of inaccuracy is present when trying to assess step and gap deformities of 1–3 mm. Scientific data and anecdotal clinical experience have led to the widespread use of computed or trispiral tomography when questions regarding the true amount of displacement are raised during the initial clinical evaluation, and the added benefit of these studies will be discussed. Regardless of such inaccuracies, if the same clinicians who differ in their actual measurements still uniformly agree in their treatment recommendations, then does this degree of inaccuracy matter? Probably not, except in those cases where the patient and/or his or her orthopaedic surgeon are unsure of the best treatment option and more accurate measurements may sway them in one direction. Scientific data to support this hypothesis do not exist to date. Regardless, the most important point regarding plain radiographic analysis of any fracture is that the clinician must not accept any radiographs of subpar quality and must have all the views requested, no matter how late it is or how tired the radiology technician may be.

Are there ways to maximize the accuracy of plain radiographs to potentially obviate the need for additional studies?

In comparing the efficacy of plain radiography versus CT, Cole et al6 described the techniques of longitudinal axis measurement and the arc method to standardize the determination of step and gap deformity by five independent observers. These two methods are shown in Figures 1 and 2, the arc method being more accurate for central depression fractures with or without margin fractures, and most accurate in CT scans. The longitudinal axis measurement, although somewhat less accurate overall, cannot be used for CT scans in which images are too truncated to determine the longitudinal axis. The longitudinal axis method seems to improve accuracy in step and gap measurements on plain radiographs.

Fig 1.

Fig 1.

Fig 2.

Fig 2.

Mekhail et al16 determined that a 30° cephalad (distal to proximal) posteroanterior view is helpful in assessing articular incongruities, because the xray beam is directed more parallel to the articular surface. It especially is effective in die-punch fractures of the lunate fossa involving the dorsoulnar fragment.

With similar logic, Lundy et al14 simulated lunate fossa fractures with osteotomies in wrists from cadavers and then assessed the known articular step-off with standard radiographs and the 22° lateral (also a cephalad view), to direct the beam parallel to the articular surface. As expected, step-off measurement accuracy was improved when this view was used in addition to the standard views. Both of these methods may, of course, be used in the operating room while using fluoroscopy. When using fluoroscopy, the best angle generating an unobstructed view of the articular surface should be used rather than rigidly adhering to the 22° or 30° guidelines.

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Computerized Tomography

Because of to the difficulties in determining 1–2 mm of articular incongruity and fair interobserver and intraobserver reliability in assessing articular displacement on plain radiographs, CT commonly is used to additionally evaluate intraarticular distal radius fractures.6,13 Computed tomography may provide significantly more information in the presence of casts or splints, positioning difficulties, metallic hardware, and disuse osteoporosis.17

Pruitt et al18 preoperatively evaluated 18 intraarticular distal radius fractures with plain radiographs and CT scans. They showed that although radiographs and CT scans showed fracture extension into the radiocarpal joint, CT scans better revealed involvement of the distal radioulnar joint (DRUJ), the degree of comminution, and the extent of articular surface depression.

Cole et al6 directly compared the ability of plain radiographs and CT scans to measure step and gap deformity in 19 distal radius fractures. They determined that more reproducible readings were achieved using the arc method (Fig 2) on CT scans versus the longitudinal axis method (Fig 1) on plain radiographs. Thirty percent of the measurements from plain radiographs were significantly lower or higher than corresponding measurements from CT scans.

Concerns have been raised about the high additional costs of CT scans when evaluating distal radius fractures. Pruitt et al18 recommended that only surgical candidates have CT scanning because of the additional cost. However, if one is basing surgical decision-making on the degree of step and gap deformity, and CT scanning has been documented to be more accurate, then CT scanning must be used somewhat more liberally to rule surgery in or out.

Because trispiral tomography is approximately ⅓ of the cost of CT scanning, Freedman et al10 sought to determine whether the relative usefulness of the two techniques was equivalent. They created intraarticular fractures in 12 cadaveric specimens and evaluated these wrists with plain radiographs, tomograms, and CT scans. No statistically significant differences were observed between tomograms and CT scans in measuring articular step-off, and they concluded that tomograms are more cost effective than CT scans for such fractures. Unfortunately, in many medical centers, trispiral tomography no longer is available, having been supplanted by CT scanning and MRI.

In our experience, careful evaluation of high quality plain radiographs taken before and after reduction usually is sufficient to arrive at an appropriate treatment plan. If the longitudinal axis method proves insufficient, as it occasionally does, then we proceed with either tomography or CT scanning as availability dictates. The additional information gained from these studies will determine whether nonoperative or operative treatment is recommended. One additional benefit of tomography is the ability to evaluate the distal radius articular surface postoperatively without removing splints or casts, or cases in which additional fracture displacement of nonoperatively treated fractures is suspected.

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Magnetic Resonance Imaging

Although MRI is not used as a primary imaging modality for distal radius fractures, it can be very useful in assessing associated ligamentous injury. In a study by Spence et al,20 21 consecutive intraarticular distal radius fractures had preoperative MRI evaluation. Ten of 21 wrists had associated soft tissue injuries, including six scapholunate ligament ruptures and two triangular fibrocartilage complex tears (TFCC). Of the five patients with ulnar styloid base avulsions, none had evidence of a TFCC tear. Each fracture associated with a scapholunate ligament tear extended through the junction of the scaphoid and lunate facets.

We carefully assess the scapholunate angle (lateral view) and scapholunate gap (PA view) on the plain radiographs of all distal radius fractures, and order radiographs of the contralateral wrist when borderline abnormalities are seen. Our index of suspicion increases as the oblique fracture line through the radiocarpal joint moves ulnarward. We order adjunctive MRI scans when clinical suspicions are high but definitive radiographic evidence is lacking.

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Arthroscopically Assisted Assessment and Treatment

The use of wrist arthroscopy in the evaluation and treatment of intraarticular distal radius fractures is helpful in selected cases.7,11 It especially is useful for die-punch fractures and fractures with associated ligamentous injuries or suspected carpal chondral fractures.

Contraindications include fractures less than 48 hours old (implying absence of an organized hematoma) to minimize intraoperative fluid extravasation. However, fractures older than 1 week are characterized by excess intraarticular fibrin deposition obscuring observation, and early fracture healing limiting fracture mobilization and accurate reduction. To avoid fluid extravasation, it is imperative to use gravity-only inflow and maintain outflow at all times. If not, acute carpal tunnel syndrome is a potential complication.1

We only occasionally find adjunctive wrist arthroscopy useful in the effective treatment of distal radius fractures. Most commonly, we use arthroscopy for ligamentous evaluation, and less commonly, for observation of pure die-punch fractures reduced through limited open techniques. One other variation on the theme of adjunctive arthroscopy is in the open reduction and internal fixation of volar Barton fractures with adjacent articular depression. In such cases, a dry camera may be placed through a 3-mm window in the volar radiocarpal ligaments to directly visualize the reduction.

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DISCUSSION

Our current operative indications include radiocarpal step or gap deformities greater than 1–2 mm that are evident on plain radiographs. Similarly, distal radioulnar joint articular incongruities of 1–2 mm or greater or gross distal radioulnar joint instability warrant operative treatment. Fractures with extensive metaphyseal comminution are particularly unstable and must be closely followed (at least weekly) after an adequate reduction or treated operatively primarily. If plain radiographs prove insufficient, we use tomography or CT scans to further evaluate the intraarticular fracture. In general, we tend to lean toward operative fixation in younger, more active patients. The potential for cosmetic deformity alone in some patients with considerable loss of radial inclination must be discussed with all patients being treated nonoperatively.

The above review elucidates some of the difficulties facing the clinician who treats distal radius fractures. Although benefits of an anatomic reduction of intraarticular distal radius fractures seem intuitively obvious, the orthopaedic literature does not answer several important questions facing clinicians. It would seem that articular step deformities are less well tolerated than gap deformities. Multiple authors have asserted the need to achieve less than 2 mm of residual articular incongruity but some of these same authors and others also have reported poor intraobserver and interobserver reliability of the various radiographic imaging techniques used to assess these gap and step deformities.4–6,8,10,13,14,22 Even if accurate assessment of the deformities were possible, there are no data proving that nonanatomic articular reductions lead to poorer clinical outcomes or patient satisfaction.5

Despite a lack of definitive answers for these most fundamental questions regarding distal radius fractures, there continue to be presentations and peer-reviewed publications reporting on an ever-burgeoning armamentarium of internal fixation devices. The bulk of these studies are nonrandomized, noncomparative studies financially supported at least in part by the manufactures and distributors of these new devices. Until we have prospective, randomized, comparative outcome studies of various treatment regimens and fixation devices for distal radius fractures, we cannot be too assertive about any treatment, and as always, we must tailor our treatment to each patient’s objective findings and subjective desires.

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References

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