Role of Pre-reduction Coronal Radial Translation & DRUJ Gap as Predictors of Foveal TFCC Detachment in Extra-articular Distal Radius Fractures*

Introduction: Residual distal radioulnar joint (DRUJ) instability after treatment of extra-articular distal radius fractures (DRFs) in patients with maximum functional needs is an incapacitating complication that may require secondary surgery.

Reliable radiographic clues suggesting triangular fibrocartilage complex (TFCC) foveal detachment would lead the surgeon to consider surgical TFCC foveal reattachment in addition to DRF fixation to optimize TFCC healing.

Our hypothesis was that prereduction coronal radial translation (CRT) and DRUJ diastasis are predictors of foveal TFCC detachment associated with extra-articular DRF. Our secondary hypothesis was that DRUJ diastasis was a better predictor than CRT.

Methods: From January 2012 to June 2015 a total of 630 consecutive unilateral DRFs were prospectively included into the patient assessment file (PAF) database of a single academic center. A total of 68 wrists (Group A) were selected according to the following inclusion criteria: (1) extra-articular fractures, (2) posterior displacement, (3) patient with maximum functional needs, (4) patient aged less than 60 years, (5) DRF fixation with volar plating.

Within group A, a total of 18 wrists (18 patients) displayed CRT and/or DRUJ diastasis on their prereduction posteroanterior (PA) X-rays. The average age of these 18 patients was 45 years (minimum 23, maximum 57). The female/male ratio was 12/6. Measurement of CRT was done according to Nakamura, Ross, and Herzberg techniques. Measurement of DRUJ diastasis was expressed in mm. A DRUJ diastasis was defined as a DRUJ space width of more than 2.5 mm.

CRT and DRUJ diastasis measurements were correlated with the result of manual DRUJ stress test after fixation of the DRF. When there was a high index of suspicion of associated foveal TFCC detachment, arthroscopy was performed (5 cases) at the acute stage in conjunction with DRF fixation to confirm (loss of trampoline effect and positive hook sign) and treat (transosseous Nakamura technique) the TFCC avulsion.

Results:

	N	Positive DRUJ manual stress	Foveal TFCC avulsion found at arthroscopy
CRT +, no DRUJ diastasis	11	1 (9%)	1 (9%)
CRT +, DRUJ diastasis +	6	4 (66%)	3 (50%)
No CRT, DRUJ diastasis +	1	1 (100%)	1 (100%)

Discussion: Little attention has been paid in the literature to TFCC foveal detachment occurring in combination with extra-articular DRF. Manual DRUJ stress test after DRF reduction and fixation has been generally reported as very reliable to diagnose associated TFCC injury. However, to the best of our knowledge, no series specifically addresses preoperative radiological diagnostic clues to TFCC injury in a group of extra-articular fractures occurring in active, nonelderly patients.

On the other hand, there is considerable interest about factors that could predict TFCC foveal avulsion in combination with acute DRF. Both CRT and DRUJ diastasis accompanying fresh DRF have been reported as predictors of TFCC foveal avulsion combined with DRF.

Fujitani addressed CRT and DRUJ diastasis simultaneously in a combined index. They found that a positive index was an important predictor of DRUJ instability accompanying unstable DRF. They considered extra- and intra-articular fractures together.

Moritomo, Dy, Wolfe, and Tate Hepper extensively studied in cadavers the significance of CRT. They found in several recent reports that CRT unloads the distal band of the interosseous membrane (IOM) of the forearm. They found that proper reduction of CRT is critical to retensioning the distal band of the IOM to optimize DRUJ stabilization following DRF fixation.

Ross recently provided a normal standard against which residual postreduction radial translation of the distal radius in DRF can be measured to assess reduction.

Our study is the first series specifically addressing the value of prereduction CRT and DRUJ diastasis in extra-articular fresh DRF. In this series, prereduction CRT alone was not a good predictor of TFCC foveal avulsion. Only one wrist out of 11 showing CRT alone displayed a positive DRUJ manual stress test and a foveal TFCC avulsion confirmed at arthroscopy. By contrast, when the prereduction radiographs showed a combination of CRT and DRUJ diastasis, a positive DRUJ manual stress test was found in 66%. A foveal TFCC avulsion was confirmed at arthroscopy in 50%. When there was a combination of CRT, DRUJ diastasis, and positive DRUJ manual stress, we found a 100% incidence of TFCC foveal avulsion when arthroscopy was performed.

Although limited by a small number of cases, our study suggests that prereduction DRUJ diastasis is a more reliable predictor of TFCC foveal avulsion than CRT alone and that these two radiological criteria should be carefully and separately addressed when dealing with a fresh extra-articular DRF.

It should also be reminded that the superior clinical outcome of immediate arthroscopic fixation of TFCC foveal avulsion associated with extra-articular DRF, compared with spontaneous healing in long-arm cast, for 3 weeks remains to be proven.