The Critical Size of Ulnar Styloid Fragment for the DRUJ Stability

Abstract

Background Ulnar styloid fractures can be associated with clinically significant instability of the distal radioulnar joint (DRUJ). However, the exact fragment size that results in DRUJ instability is unknown. Purpose The objective of this study was to determine the critical size of an ulnar styloid fracture that would result in a significant increase in DRUJ translation and forearm rotation. Methods Eight cadaveric specimens were used to investigate the effects of three different ulnar styloid fracture sizes on DRUJ instability: tip fracture, base fracture, and a fracture including the fovea. Forearm rotation and dorsopalmar DRUJ translation were measured after each sequential increase in fracture size. Results Relative to the uninjured state, a significant increase in forearm rotation and dorsopalmar translation was found for all three fractures. However, the fovea fracture showed a statistically significant increase in forearm rotation compared with all other fracture types and a statistically significant increase in total dorsopalmar translation compared with the tip fracture. Conclusion In this study, ulnar styloid fractures involving the fovea resulted in significantly greater DRUJ instability comparted to tip and base fractures alone. This study provides important biomechanical data regarding the critical size of ulnar styloid fractures that result in DRUJ instability and may aid in the surgical decision-making algorithm in these patients.

Residual stability of the distal radioulnar joint following ulnar styloid fracture: influence of the remnant distal radioulnar ligaments

“…Specimens were tested in a custom system used also in prior studies (Maniglio et al, 2021a(Maniglio et al, , 2021b(Maniglio et al, , 2021c (Figures 1 and S1). The forearm was mounted using the PVC potting to position the humerus in a static, horizontal position.…”

“…Several recent studies have suggested that USFs have little influence on the patient-reported outcomes (Buijze and Ring, 2010; Kim et al., 2010; Souer et al., 2009), while other authors have reported an association with poorer outcome of wrist function with remaining DRUJ instability (Baradaran et al., 2017; May et al., 2002; Wysocki and Ruch, 2012). The importance of the fracture height has been discussed by many authors (Maniglio et al., 2021b; May et al., 2002; Pidgeon et al., 2018; Stoffelen et al., 1998) stating that only basal USFs may affect the outcome. Biomechanical studies have proved this concept and showed an increase in forearm rotation and dorsopalmar (DP) translation of the DRUJ (Maniglio et al., 2021b; Mirarchi et al., 2008; Pidgeon et al., 2018).…”

“…The importance of the fracture height has been discussed by many authors (Maniglio et al., 2021b; May et al., 2002; Pidgeon et al., 2018; Stoffelen et al., 1998) stating that only basal USFs may affect the outcome. Biomechanical studies have proved this concept and showed an increase in forearm rotation and dorsopalmar (DP) translation of the DRUJ (Maniglio et al., 2021b; Mirarchi et al., 2008; Pidgeon et al., 2018). So why does this increased instability not affect the patient outcomes?…”

“…Because of the insertion of the distal radioulnar ligaments (DRUL) at the ulnar styloid (af Ekenstam and Hagert, 1985;Stoffelen et al, 1998) and into the fovea (Ishii et al, 1998;Maniglio et al, 2020;Nakamura et al, 1996;Pidgeon et al, 2018), an ulnar styloid fracture (USF) including the fovea, is conceptionally a bony avulsion of these ligaments, which are considered to be the major stabilizers of the distal radioulnar joint (DRUJ) (Buijze and Ring, 2010;Kazemian, et al 2011;Kleinman, 2007;Maniglio et al, 2021b). Therefore, fracture may directly alter the mechanics of the DRUJ (Kihara et al, 1995;May et al, 2002;Pidgeon et al, 2015).…”

Should We Repair the Pronator Quadratus in a Distal Radius Fracture with an Ulnar Styloid Base Fracture? A Biomechanical Study

“…In our model, we assumed that a perfect, fully repaired PQ achieved the same function as an intact PQ so that we used the same loading than in other biomechanical studies. 21 A poorer repair or partially repaired was simulated with half of this loading. After testing, all specimens were checked to ensure fractures were placed accurately.…”