Volar Locking Plating for the Intra- and Extra-articular Distal Radius Fractures With Dorsal Metaphyseal Comminution


 Background: Volar locking plating remains a popular method for the surgical management of distal radius fractures. Dorsal metaphyseal comminution (DMC) is a common fracture pattern which weakens the stability during fracture fixation. In this study, we aimed to compare the radiographic and functional outcome of the intra- and extra-articular distal radius fractures with DMC following volar locking plate fixation.Materials and methods: Patients suffered from a distal radius fracture with DMC were reviewed in the clinical database of the authors’ institution between Jan 2016 and Jan 2020. The included patients were classified into the extra-articular (A3) group or the intra-articular (C2 and C3) group according to the AO/OTA system. The radiological parameters, wrist range of motion, and functional outcomes were evaluated following open reduction and volar locking plate fixation.Results: A total of 130 patients were included in this study with a mean follow-up length of 17.2 months. Compared with the A3 fracture group, no significant fracture re-displacement or reduced wrist ROMs was observed in the C2 fractures after 12-month’s follow-up. However, significantly decreased volar tilt (P = 0.003) as well as the extension/flexion ROMs were observed in the C3 fractures comparing to the A3 fractures. Most of the patients achieved an excellent (n = 75) or good (n = 51) Gartland and Werley wrist score. Four patients with C3 fractures resulted in a fair functional outcome due to a significant loss of volar tilt during follow-up.Conclusions: The volar locking plate fixation provided sufficient stability for distal radius fractures with DMC, and resulted in similar radiological and functional outcomes in the intra-articular distal radius fractures with a simple articular component (C2 fractures) as those in the extra-articular fractures. Considering the intra-articular fractures with multifragmentary articular component (C3 fracture), despite of the subsequent loss of volar tilt, the majority of the patients achieved good to excellent wrist function following volar locking plating.Trial registration: Not applicable because the design of the study is retrospective.


Introduction
Distal radial fractures are common orthopedic injuries comprising 15% of all extremity fractures [1]. For the signi cantly displaced unstable distal radius fractures, volar locking plating remains one of the most popular xation techniques because of a safe and straightforward approach, a low rate of complication, and a rapid return to function recovery [2].
Dorsal metaphyseal comminution (DMC) is the most common fracture pattern observed in 60% of the distal radius fractures [3], which weakens the fracture stability and leads to higher rates of secondary displacement following conservative treatment or percutaneous pinning [3][4][5][6]. Despite the improved strength characteristics compared with the traditional nonlocking plates, the stability provided by volar xed-angled locking plating has also been questioned in this fracture pattern. In vitro, biomechanical studies have testi ed the stability of volar locking plate in extra-articular distal radius fracture models with DMC, and an equivalent [7] or slightly less stability [8,9] can be provide compared with dorsal plating.
However, the e cacy of volar locking plating in the intra-articular distal radius fracture with DMC has not yet been adequately analyzed in biomechanical or clinical studies.
In this study, we analyzed the radiographic and functional outcome of the intra-and extra-articular distal radius fractures with DMC following volar locking plate xation, and hence to investigate the stability of volar locking plating in these fracture patterns.

Materials And Methods
In this retrospective study, patients with distal radius fractures who received open reduction and internal xation in the authors' institution between Jan 2016 and Jan 2020 were reviewed in the trauma database. Inclusion criteria were based on the following protocol: 1) All fractures received surgical treatment according to the indications recommended on the American Association of Orthopaedic Surgeons (AAOS) standard [10]; 2) The fracture was xed with a single volar locking plate; 3) DMC were identi ed in the preoperative radiographs and computed tomographic (CT) images by the authors according to the de nition in literature [11]. Patients with open fractures, delayed fractures, neurovascular injuries, additional ipsilateral upper extremity fractures, or a follow-up period of less than 12 months were excluded from the study. Besides, the patients with complex fragmentation of articular surface, volar or dorsal rim fractures, radiocarpal fracture dislocations, and those are not suitable for a single volar locking plate xation were also excluded. The included patients were classi ed into the extra-articular (A3) group or the intra-articular (C2 and C3) group according to the AO/OTA system [12].
All patients were operated on by two senior attending surgeons (JX and HFS). During operation, the fracture was accessed through the modi ed volar Henry approach. Brie y, the skin was incised along the course of the exor carpi radialis (FCR) tendon. The sheath of the FCR was opened and the FCR tendon and the exor pollicis longus tendon were retracted ulnarly. The radial artery was carefully protected. The pronator quadratus was incised longitudinally and elevated to expose the distal radius. For extra-articular fractures, we applied longitudinal traction and reduced the fracture under direct visualization. For intraarticular fractures, either the radial column or the palmoulnar fragment could be reduced rstly to provide reference for the radial height and radial inclination. Dorsal ulnar fragments were then reduced to restore joint congruency and volar tilt. The joy-stick technique with percutaneous pinning from the dorsal side was used to facilitate reduction of the dorsal fragment if necessary. After temporary K-wire xation, a satisfactory reduction of the extra-and intra-articular fracture was checked using intraoperative C-arm according to the radiographic guidelines described in literature [13]. The fracture was then xed with the 2.4 mm volar locking plate system (Depuy-Synthes, Oberdorf, Switzerland). The distal edge of the plate was carefully positioned proximal to the watershed line to avoid prominence in this area [14]. Multiple uoroscopic views were checked to avoid intraarticular screw penetration and dorsal screw prominence [15]. The stability of the distal radioulnar joint (DRUJ) was routinely checked and compared with the contralateral side. Cast immobilization, radioulnar pinning, or ulnar styloid ORIF was performed based on the instability of DRUJ according to the established protocol [16,17]. Gentle wrist active range of motion and midrange forearm rotation were allowed postoperatively. The patients were followed at 6 weeks, 3 months, 6 months, and 12 months according to our routine follow-up regime [17].
Radiological parameters, including radial inclination, volar tilt, radial height, and ulnar variance, were measured in the follow-up radiographs according to the protocols described in literature [18]. In each group, the radiological parameters measured at the 12-month follow-up were compared with those measured postoperatively using paired-sample t test. The fracture re-displacement (FRD), de ned as the absolute value of the difference between the postoperative parameters and those taken at the 12-month follow-up, was then calculated and compared between the intra-articular and the extra-articular group using Independent t test. Clinical assessment and complications of included patients were recorded  Table 1. According to the AO/OTA system, the patients were classi ed into A3 (41 cases), C2 (56 cases), or C3 (33 cases) fractures. The measured radiological parameters were shown in Table 2. No statistically signi cant change in volar tilt, radial inclination, radial height, or ulnar variance was observed between the immediate postoperative and 12-month follow-up measurements in either of the A3 or the C2 fracture group. However, a signi cant change of the volar tilt was observed in the C3 fracture group comparing the immediate postoperative measurements with the 12-month follow-up data (P = 0.037). Comparing the FRD calculated in the intraarticular fractures to the extra-articular ones, a signi cant decrease of the volar tilt was observed in C3 fractures than in A3 (P = 0.003) fractures ( Table 3). The difference between the C2 and A3 fractures, however, did not achieve statistical signi cance (P = 0.540). Considering the radial height, the ulnar variance, and the radial inclination, no signi cant difference of FRD was observed between the intraarticular and the extra-articular fractures (Table 3).  At 12 months postoperatively, the mean ROMs of the wrist were shown in Table 4. All of the patients achieved more than 75% recovery of extension/ exion and more than 95% recovery of pronation/supination in the injured wrist compared to the contralateral normal wrist. All of the patients achieved adequate functional ROMs according to Ryu's standard [19]. Considering the pronation/supination ROM, no signi cant difference was observed between the intra-articular (either C2 or C3) fractures and the extra-articular (A3) fractures. However, the C3 fracture group presented signi cantly decreased extension/ exion ROMs compared with the A3 fracture group. The mean DASH score was 9.8 (0-40) at 12 months follow-up. Most patients in our study achieved an excellent (n = 75) or good (n = 51) Gartland and Werley wrist score. Four patients with C3 fractures resulted in a fair functional outcome due to a signi cant loss of volar tilt during follow-up ( Fig. 1 to Fig. 4). Previously, biomechanical studies using extra-articular fracture models have con rmed that the volar locking plating could provide an equivalent or slightly less stability compared with dorsal plating in distal radius fractures with DMC [7][8][9]. In clinical studies, Guillou reported 22 patients with a dorsally comminuted extra-articular distal radius fracture xed with volar locking plate. Most (95.4%) of the patients maintained the stability without secondary displacement at 6 months postoperatively [20]. We observed similar radiological results in our study, wherein no signi cant radiographic change in volar tilt, radial inclination, radial height, or ulnar variance was found in the A3 fracture group during the 12 months' follow-up. Our ndings provided extra clinical evidence for the application of volar locking xation in the extra-articular distal radius fractures with DMC.
Considering the intra-articular fractures with DMC, no straightforward biomechanical studies could be found in literature. In clinical studies, Khamaisy compared the outcome of volar locking plating in the dorsally comminuted (DC) and the dorsally intact (DI) distal radius fractures [21]. The vast majority of the cases included in Khamaisy's study were AO/OTA type C fractures, and a satis ed fracture reduction was preserved in the DC fractures compared to the DI ones with no signi cant difference observed in radial inclination, volar tilt, and radial length. These results implied that volar locking plating could provide su cient stability for the intra-articular fractures despite of the occurrence of DMC. However, the authors didn't compare the outcome among different sub-types of intra-articular fractures due to limited sample size. In our study, volar locking plating was testi ed to preserve fracture reduction in the C2 fractures, but not in the C3 fractures.
Our results were in contrast to Chou's study, wherein 41 patients with AO/OTA C3 dorsally comminuted distal radial fractures were treated using either dorsal (n = 22) or volar (n = 19) locking plate [15]. In both groups, no signi cant re-displacement was observed in terms of radial inclination, volar tilt, and ulnar variance. Compared with Chou's study, a larger number of cases were included in our study, and the signi cant loss of volar tilt in the C3 fractures in our study was possibly caused by a compromised subchondral support of the thin and displaced dorsal fragment provided by the distal row of screws with inadequate length (Fig. 3 ) [22][23][24]. The subsequent loss of fracture reduction was also observed by Gogna's study, wherein 33 dorsally comminuted distal radius fractures were xed with volar locking plate and followed for over a year [15,20,25]. Totally three cases of C3 fractures (18.7%) were reported to present a dorsal subluxation of the carpus or a loss of dorsal tilt after one-year follow-up. These results were comparable with our study, and called for attention to the usage of volar locking plate in the C3 fractures with DMC, especially for the fractures with the occurrence of radiocarpal fracture dislocation or dorsal rim fractures [26].
To prevent the loss of reduction in C3 fractures, different solutions were reported in literature. An appropriate length of the distal row of locking screws was proven crucial for the single volar plating construct [24]. However, the risk of extensor tendon irritation would increase with longer distal radius screws [27]. Multi-row of volar locking screws was considered more stable than the single row screw construct. However, little evidence was provided to support the use of two rows of distal screws over one row in the xation of distal radius fractures [27]. Besides, the combined usage of volar and dorsal plating was recommended to provide extra buttress for the dorsal fragment [9,28,29].
With regard to the recovery of wrist function, Chou reported a progressive improvement of wrist range of motion following volar plating of C3 dorsally comminuted distal radius fractures [15]. After one-year follow-up, the patients showed an 89% recovery of exion-extension and a 97% recovery of supinationpronation compared with that of the contralateral healthy wrists. Compared with Chou's study, the patients with C3 fractures achieved comparable recovery of supination-pronation range of motion in our study. The relatively lower percentage of exion-extension recovery in our study was possibly associated with the loss of volar tilt in radiological ndings. Even so, the majority (87.9%) of the patients with C3 fractures achieved an excellent or good Gartland and Werley wrist score. Four patients (3.1%) with a signi cant loss of volar tilt resulted in decreased exion-extension range of motion and a fair functional outcome (Fig. 4). This was consistent with Gupta and Perugia's ndings that volar tilt was one of the most important radiographic parameters affecting the functional outcome of distal radius fractures [30,31].
There are several limitations to our study. First, the study was based on retrospective data, which could harbor confounding sources of bias. Second, the length of the follow-up in our study was reported to be su cient for the conclusion of radiological and functional outcome, but relatively short for the record of long-term complications [32].
In conclusion, the volar locking plate xation provided su cient stability for distal radius fractures with DMC, and resulted in similar radiological and functional outcomes in all of the C2 fractures as those in the extra-articular fractures. Considering the C3 fractures, despite of the subsequent loss of volar tilt, the majority of the patients achieved good to excellent wrist function following volar locking plating.
Attention should be paid to the subchondral support of the thin and displaced dorsal fragment using locking screws with appropriate length.