Keywords
wrist fracture - radius fracture - translation deformity - distal radioulnar joint
Distal radial fractures are one of the most common fractures of the upper extremity.[1]
[2] Instability of the distal radioulnar joint (DRUJ) can occur following such fractures.[3] Stability of the DRUJ is influenced by the osseous anatomy, DRUJ capsule, palmar
and dorsal radioulnar ligaments, triangular fibrocartilage complex, ulnocarpal ligaments,
interosseous membrane (IOM), carpi ulnaris, and pronator quadratus.[4]
[5] The biomechanics of this joint are complex, and the relative importance of each
structure in the maintenance of stability remains controversial.[4] With advances in the treatment of these fractures that promote stable anatomic fixation
(including fragment-specific fixation of the distal radius to gain anatomical reduction
and early movement), we have observed a decreased need for ulnar-sided stabilization
procedures at the time of distal radial fracture fixation.[6] When we first began pursuing internal fixation with anatomic reduction of these
fractures around 1999, we utilized fragment-specific fixation, which includes a radial
buttress implant that is anatomically contoured; when applied to the radial aspect
of the distal radius, it automatically corrects radial translation of the distal fragments.
Simultaneously, we observed a decrease in instability of the DRUJ intraoperatively,
with a decrease in the number of procedures to fix the ulnar styloid or repair the
triangular fibrocartilage complex (TFCC). We believed that this observation related
to the improved anatomic reduction of the distal radius, but we did not define the
specific parameters in fracture reduction that may be related. Later, during our initial
experience with fixation of distal radius fractures using volar locked plating systems,
we observed an increase in intraoperative instability of the DRUJ that required intraoperative
or subsequent procedures on the ulnar side of the wrist.[6] We examined these cases in detail and postulated that residual radial translation
may be the cause.[6] We believe that the almost obligate correction of this coronal-plane radial translation
deformity with the radial buttress plate in the Trimed system (Trimed Inc., Santa
Clarita, CA, USA) is the explanation for this marked observed change in the DRUJ stability
post reduction. As a corollary, although the anatomic contouring of angle-stable volar
plates facilitates reduction of sagittal plane deformity, it does not facilitate correction
of coronal plane deformity unless the surgeon is aware of this potential malreduction.
The treatment of DRUJ instability is complex, and several procedures have been described
in an attempt to manage this difficult problem.[7]
[8]
[9] Persistent DRUJ instability following distal radius fracture is often attributed
to a disruption of the foveal insertion of the TFCC, which may occur as a purely soft
tissue injury but is often identified by the presence of a basiulnar styloid fragment[8]
[9] However, DRUJ stability may not be restored even when the ulnar styloid fragment
is reduced and the foveal insertion of the TFCC is reattached ([Fig. 1]). We have observed cases where Type 3 ulnar styloid fractures have been internally
fixed with complete reattachment of the foveal attachment, yet DRUJ instability has
persisted in association with residual radial translation ([Fig. 2]). Conversely, particularly when restoration of anatomy is achieved, the DRUJ may
remain stable even when a large ulnar styloid fragment is not fixed ([Fig. 3]).
Fig. 1 Radial translation malunion with persistent DRUJ instability in spite of ORIF ulnar
styloid and transosseous foveal repair of TFCC.
Fig. 2 (a) Radial translation deformity with type 3 ulnar styloid and noted DRUJ instability.
No abnormal finding according to Fujitani's classification on pre-operation X-ray.
(b) Correction of radial translation deformity and no procedure required on ulnar side.
Instability was corrected intraoperatively, and no instability was noted postoperatively.
Fig. 3 Radial translation osteotomy for DRUJ instability with successful stability achieved
with no ulnar-sided procedure.
Radiographic parameters previously described, including radial inclination, ulnar
variance, and volar tilt, do not accurately describe or measure the malreduction in
terms of radial translation. It is hypothesized that radial translation deformity
detensions the IOM and pronator quadratus, which may lead to DRUJ instability[6]. To define this potentially problematic malreduction better, we studied the radiographic
parameters of normal distal radial radiographs in an attempt to provide a simple and
reproducible technique that can be used to identify and evaluate the presence of residual
radial translation during or after distal radius fracture treatment. In more recent
work, Wolfe and colleagues[10] have performed cadaveric testing of DRUJ stability and demonstrated that when there
was a distinct dorsal oblique band of the IOM, there was a significant decrease in
stability if there was radial translation of the distal fragment in simulated distal
radius fracture fixation.
We describe this parameter as “radial translation” since all the other parameters
for defining reduction of distal radius fractures also reference the relationship
between the distal fragments and the radial shaft. Although some of the biomechanical
implications of this malreduction relate to ulnar displacement of the radial shaft
relative to the ulnar shaft, we believe the description of radial translation of the
distal radius is more consistent with existing conventions in describing parameters
of distal radial fracture reduction.
In addition, using the radiographic technique we describe, it is easier to measure
the malreduction consistently and reproducibly and reference it to radiographs of
the uninjured side when there is uncertainty regarding reduction. We have observed
that intraoperative radiographs (using fluoroscopy) to assess reduction will show
a decrease in the gap between radial and ulnar shafts if there is residual radial
translation present, but it is difficult to quantify. It is rare to see widening of
the DRUJ intraoperatively following internal fixation. However, trying to measure
the space between the radial and ulnar shafts is unpredictable and difficult to standardize
with respect to patient size and image planes.
The purpose of this article is to establish a reproducible technique for measuring
radial translation that can be readily and easily used to identify the presence of
this deformity.
Patients and Methods
Posteroanterior (PA) radiographs, using a standardized technique, of skeletally mature
individuals with anatomically unaltered DRUJs, no history of DRUJ instability, and
no associated history of wrist fracture or dislocation were identified from a large
radiographic database. Ethics approval was obtained from the appropriate Human Research
Ethics Committee Board. The radiographs were examined using a standard Webpacs viewer
(Inteleviewer Version 3.7). Radiographs were excluded if any of the following was
true:
-
The distal 10 cm of the radius was not visible.
-
There was evidence of radiocarpal pathology.
-
There was more than 5 degrees of radial or ulnar deviation of the wrist, assessed
by deviation of the long axis of the middle metacarpal from that of the radius.
Radial translation was measured by drawing a line along the ulnar aspect of the radial
shaft proximal to the metaphyseal flare and extended distally through the proximal
row of the carpus on the PA radiograph. This line intersects the lunate. The point
of intersection was evaluated by drawing a second line along the transverse width
of the lunate on the AP radiograph, parallel to the distal radial articulation. The
point of intersection of these two lines was measured from the radial side of the
lunate to determine the percentage of lunate radial to this point ([Fig. 4]).
Fig. 4 A line is drawn parallel to the ulnar aspect of the radius proximal to the metaphyseal
flare and extrapolated distally into the proximal row of the carpus. The point of
intersection within the lunate is evaluated by drawing a second line along the transverse
width of the lunate on the AP radiograph that is parallel with the distal radial articulation.
The percentage of lunate radial to this line is calculated.
A single observer repeated these measurements for all 100 radiographs studied at two
separate sittings 1 month apart to evaluate for intraobserver agreement. Interobserver
agreement was calculated on 25 radiographs by three fellowship-trained orthopedic
surgeons with an interest in wrist surgery. Each of these surgeons reviewed 25 radiographs
to calculate the inter-rater reliability of this parameter. Single-measure intraobserver
and interobserver reliability were assessed using the intraclass correlation coefficient
(ICC) calculations using a two-way random effects model for absolute agreement (i.e.,
systematic differences between raters are considered relevant). We used 95% confidence
intervals (CI). ICC values were interpreted as: >0.75 was excellent or high level
of agreement, 0.40–0.75 was fair to good level of agreement, and <0.40 was considered
poor.[11] Statistical analysis, including ICC calculations, computed with SPSS Version 21.
Results
One hundred radiographs fulfilling the study inclusion and exclusion criteria were
identified. There were 42 females and 58 males, with a mean age of 43 years (range
18–66).
For all individuals studied, the point of intersection had a mean of 45.48% (SD = 9.6%;
range 25–73.68%) of the lunate remaining on the radial side and a mode of 50% ([Fig. 5]).
Fig. 5 Percentage of lunate radial to point of intersection of lunate with extrapolated
line on ulnar aspect of radial shaft.
Three percent of wrists measured had a shaft intersection point < 30 percent. Seventy-five
percent of wrists measured had a shaft intersection point between 30–50 percent of
the lunate, meaning that between 50–70 percent of the lunate was ulnar to the reference
line from the radial shaft. Fourteen percent measured a shaft intersection between
51–60 percent of the lunate. Eight percent of wrists measured had a shaft intersection
point > 60 percent. No shaft intersection points were measured below 25 percent or
above 73.68 percent of the lunate width.
Intraobserver Reliability
The intraclass correlation (ICC) is used to assess the consistency, or conformity,
of measurements made by multiple observers measuring the same quantity. Interobserver
variability refers to systematic differences among the observer. Intraobserver variability
refers to deviations of a particular observer's score. The intraobserver reliability
calculation of the shaft intersection point revealed a high level of agreement using
ICC and 95% confidence intervals (95% CI) using an absolute agreement definition (p < 0.001).
ICC = 0.967, (95% CI, 0.945 to 0.979)
Cronbach's α for the two items is 0.985, suggesting that the items have relatively
high internal consistency. This measures how closely related a set of items are as
a group. A “high” value of α is used as a measure that the items reflect the underlying
construct that they are attempting to measure.
Interobserver Reliability
The interobserver (between observer) reliability calculation also revealed a high
level of agreement using ICC and 95% CIs and an absolute agreement definition (p < 0.001).
Interobserver reliability was calculated using ICCs as follows:
ICC (Rater 1 and 2): 0.78 (95% CI, 0.621 to 0.889)
ICC (Rater 1 and 3): 0.79 (95%CI, 0.518 to 0.909)
ICC (Rater 2 and 3): 0.80 (95% CI, 0.539 to 0.914)
The Cronbach's α coefficient for the three raters was 0.905.
Discussion
With the increasing popularity of volar locked plating systems (used for the treatment
of distal radius fractures), the potential for the creation of a stable construct
with a radial translation malreduction is ever-present. Angle-stable volar plates
are very effective at facilitating correction of radial length and volar tilt. However,
they do not automatically correct radial translation, because they are applied to
an essentially flat surface without any inherent guide to their positioning in the
coronal plane. Radial column buttress plates such as the radial pin plate from Trimed™
(Trimed Inc, Santa Clarita, CA, USA) do force correction of this deformity. However,
the existing classic parameters of distal radial anatomy (radial shortening, palmar
inclination, and radial tilt)[12] do not describe the presence of a postreduction radial translation deformity of
the distal fragments. This type of deformity has been noted in the literature previously,
albeit variably between pre- and postreduction radiographs.[6]
[12]
[13]
[14] The relationship between the distal attachment of the brachioradialis and the “radial
beak” pattern of distal radius fractures was seen in 51% of patients in Koh's series.[13] However, the relationship is difficult to assess reliably on intraoperative or postoperative
radiographs due to comminution of the radial aspect of the fracture line, variability
of the radial flare, and obscurity caused by the overlying fixation plate. Due to
the deforming force of the brachioradialis on the distal fracture fragment, release
of its tendinous insertion has been advocated to aid open reduction, as closed reduction
is usually not possible ([Fig. 6]). Other techniques for correcting this translational deformity have been described.[6]
[14]
Fig. 6 (a) PA radiographs of a distal radius fracture displaying radial translation deformity.
(b) The percentage of the lunate ulnar to the reference limit has been corrected after
anatomical open reduction and internal fixation.
There is a paucity of literature investigating the importance of this type of deformity
and the presence of DRUJ instability.
The technique previously described by Fujitani and co-authors[12] discussed radial translation as a prognostic indicator for DRUJ instability based
on prereduction injury radiographs and made no reference whatsoever to reduction parameters
of the fracture. The radial translation was expressed as a ratio of increased DRUJ
clear-space to radial shaft dimension proximal to the fracture line.[12] This technique is complicated and difficult to reproduce. The technique relies on
the accurate identification of the cortical margin of the ulna aspect of the sigmoid
notch of the radius at the DRUJ and does not comment on whether the dorsal or volar
margin should be used in a rotated distal radial fragment. No intra- or interobserver
reliability testing was calculated. Furthermore, these landmarks as a ratio to radial
width are difficult to calculate, particularly intraoperatively using image intensification.
Variations in proximal extent of the fracture line influence the width of the radial
shaft relative to the ratio in regard to different fracture patterns. The intraoperative
utility is questionable, since the DRUJ clear space (numerator) is very small compared
with the radial width (denominator), potentially lowering its sensitivity in an intraoperative
environment.
Additionally, in Fujitani's technique[12] the actual gap radiographically in the DRUJ on films taken at the time of injury
may also be influenced by a large number of external factors, particularly with regard
to arm positioning. We have observed this phenomenon in our observation of distal
radial fracture films and found extreme variation of the DRUJ gap with the same patient,
on different images and techniques. In particular, if one attempts to standardize
these pictures by taking X-ray images in a 90/90 position, the weight of the arm on
the radius will close the gap between the sigmoid notch and the distal ulna, thereby
artificially eliminating an abnormal finding.
The fact that the DRUJ interval may be normal in spite of significant persistent radial
translation of the distal fragment is very adequately demonstrated by the radiographs
in [Fig. 6]. In this radiograph, the DRUJ interval is normal even though 87% of the lunate is
lying radial to our defined axis line; when the fracture is reduced and the radial
translation is corrected, the radioulnar joint interval remains the same. Fujitani's
parameter promotes awareness of the possibility of DRUJ instability based on prereduction
radiographs[12] but offers no specific guidance to the assessment of radial fracture reduction.
Bronstein et al[15] touched on consideration of a variety of aspects of distal radius fracture reduction,
including coronal plane translation. They did not, however, present any method for
radiographic measurement of parameters of distal radial fracture reduction. They measured
forearm rotation range with differing configurations of distal radial malreduction
in a cadaveric model. In regard to translation of the distal radius in the radial
direction, they stated that there was no significant difference in rotation with translation
of the distal radius up to 10 mm in the radial direction.
Following distal radius fracture, attention is often turned to the presence of an
associated ulnar styloid fracture if persistent DRUJ instability exists after fixation.
However, in our experience the radial translation of the distal fragment, with ulnar
translation of the proximal radial shaft relative to the ulna, may lead to detensioning
of pronator quadratus and the distal oblique bundle (DOB) of the IOM where present.[10]
[16] It can be difficult to assess this radial translation deformity in these fractures,
due to the lack of bony landmarks and anatomical variation in the sigmoid notch on
plain radiographs.[17]
Awareness of this potential malreduction in distal radial fracture fixation, combined
with a simple radiographic tool to assess this parameter, allows radial translation
to be assessed and addressed. We recommend that surgeons pay careful attention to
this aspect of reduction when internally fixing distal radius fractures. Volar plate
fixation has allowed excellent control of all the classically described parameters
for assessment of distal radial fracture reduction, particularly in the sagittal plane,
yet it has no inherent control over radial translation in the coronal plane. When
DRUJ instability is noted intraoperatively after fixation, consideration should be
given to correcting any residual radial translation first rather than immediately
performing bony or soft tissue repair in the region of the distal ulna or styloid.
We have found in our experience that with correction of the bony anatomy anatomically
in light of the assessment of the presence of radial translation deformity, any instability
of the DRUJ often resolves. This can usually be achieved by fixing the plate initially
to the distal fragments and then to the shaft with a single proximal shaft screw and
assessing DRUJ instability. Translation can be adjusted using the proximal shaft screw
as a fulcrum, and once DRUJ stability is confirmed by translating the distal fragment
in an ulnar direction, the remaining shaft screws can be inserted.
In addition, following radius fracture union (after either operative or nonoperative
treatment), if DRUJ instability is present, this parameter should be assessed and
corrected by radial osteotomy rather than ulnar-sided stabilization surgery. If concerns
regarding DRUJ stability exist during fixation of acute fractures, this parameter
can also be used to make a quantifiable comparison of reduction with radiographs of
the uninjured side. Similar comparisons with the other side can be made when planning
corrective osteotomy for DRUJ instability associated with this deformity.
In our clinical experience, we have virtually eliminated the need for ulnar-sided
repair in acute fractures by attending to this aspect of reduction. Furthermore, when
DRUJ instability is associated with this malunion in healed fractures, we have found
corrective osteotomy to be simpler and more predictable than complex ulnar-sided soft
tissue reconstructions. We have successfully treated DRUJ instability after radius
fracture union with a corrective osteotomy targeting only radial translation of the
radius, even when all other classic parameters of reduction are normal. Stability
has been achieved without the need for fixation of an associated ulnar styloid fracture
or TFCC repair.
Limitations of this study include the fact that although the radiographs in the database
were PA radiographs taken according to a consistent standardized protocol for our
department, they were not standardized according to the specific published criteria
by Metz and colleagues.[18]
Although intraobserver agreement was very high, there was only 78–80% agreement between
observers. Although this is considered to be an excellent outcome in the context of
such assessments,[11] it cannot be ignored that a level of disagreement did exist. However, the clinical
purpose of this parameter is to determine whether radial translation exists and requires
intraoperative correction, and observers were able to determine that radial translation
did (or did not) exist in 100% of cases. The ICC statistics were performed on the
exact measurement calculations of the intersection, and a level of disagreement (using
an absolute agreement method) would be expected. This study attempts to establish
the normal value for the radiographic parameter, and although there is a small level
of disagreement between raters, the degree of percentage difference that resulted
in classification of a statistical disagreement between observers is small (<6%) relative
to the range of results. We do not believe that this influences its clinical utility,
particularly when the parameter is used to make a comparison with radiographs of the
uninjured side. That is, in the patient with a distal radius fracture, does a significant
radial translation deformity exist and does it impact on DRUJ instability?
Current research conducted by the authors aims to define the clinical relevance of
this radiological parameter in adults with distal radius fractures.
Conclusions
The results of this study can be used to define a normal standard against which residual
radial translation can be measured in the unstable DRUJ associated with distal radius
fractures. We have termed this parameter “radial translation.” This new parameter
aids in the development of surgical techniques to correct residual radial translation
deformity. In addition, awareness and correction of this potential malreduction at
the time of surgery may decrease the need for other procedures on the ulnar side of
the wrist to improve DRUJ stability, such as ulnar styloid fixation, TFCC repair,
or ligamentous grafting.
Although preoperative radial translation deformity may be more likely to occur when
there is greater disruption of the ulnar-sided stabilizing structures, this makes
it even more important for the surgeon to be aware of this deformity and to ensure
that from a technical perspective, the radial deformity is corrected at the time of
surgery. It may well be that cases without significant ulnar-sided soft tissue disruption
are less likely to have this deformity preoperatively, and it may also be of less
relevance in patients without significant ulnar-sided disruption. Further, there is
evidence that in the 50–60% of patients who do not have a discrete DOB of the IOM,[10]
[16] DRUJ instability may not result from this malreduction. Given that it is difficult
at the time of surgery to quantify the degree of ulnar-sided soft tissue disruption
or the presence of a discrete DOB of the IOM, it is even more important for surgeons
to ensure that they correct the bony anatomy of the radius appropriately in every
distal radius fracture fixation case.
This article has been changed according to the Erratum published on February 26, 2014
(DOI: 10.1055/s-0034-1371547). The “Background” section of the abstract has been revised.
