Unstable distal radius fractures and the volar locking plate 283 Table III. Average (± SD) ﬁnal wrist and forearm range of motion. Wrist extension (degrees) 55.5 ± 10.3 Wrist ﬂexion (degrees) 59.3 ± 17.5 and the plate is better contoured for application from this aspect rather than on the dorsal cortex of the distal radius (15). The volar cortex of the distal radius was very often not as severely comminuted when compared with the dorsal cortex. Anatomical reduction of the palmar cortex may avoid the shortening of the radius, which is important for its restoration. In our series, ﬁnal ulnar variance was reconstructed to excellent level, and resulted in a wide range of motion. The volar plate system used in our study was a locking plate system, and this must be one of the reasons for retaining good anatomical reduction. Volar plate ﬁxation of unstable distal fractures has been described recently (1–3,5,15,17). Our results are comparable to the ﬁnal follow-up range of motion, radiological evaluation, and functional assessments presented in these recent reports. In regard to com- plications, Orbay and Fernandez (2) reported 1 case among 31 of dorsal tendon irritation from an exces- sively long peg, which was treated with hardware removal. Of nine patients with preoperative median nerve symptoms who had carpal tunnel release, the ﬁnal neurologic examination showed complete reso- lution at the time of late follow-up. Rohit et al. (3) reported an overall 31 patients (27%) with complica- tions. They considered tenosynovitis as a risk factor for progressive damage to the tendons and therefore included tenosynovitis as a complication. There were 17 tendon complications (57% of the total number of complications). Early hardware removal was per- formed in all patients who developed tenosynovitis. Among other complications, three patients suffered carpal tunnel syndrome (3%), screw loosening occurred in two patients (2%), and intra-articular screw displacement occurred in one patient (1%). Kamano et al. (1) used a volar plate in 40 dorsally displaced distal radius fractures. With regard to com- plications, the authors reported that one patient devel- oped a complex regional pain syndrome, and another had a mild skin infection. There was no need for plate removal and no implant failure. In our study, rupture of the ﬂexor pollicis longus tendon was observed in one patient. We could salvage this patient by end-to- end suture, but this rupture often requires tendon transfer (15,17). Early plate removal should be per- formed to avoid this complication. Flexor and exten- sor tendon irritation has also been reported in other studies as the most frequent problems (3,17). Forearm pronation (degrees) Forearm supination (degrees) 86.3 ± 17.2 90.4 ± 5.9 The optimal placement of the distal screws is important: they must be inserted at the radial styloid, beneath the lunate facet, and near the sigmoid notch (18). Therefore, the plate is positioned near the volar radius margin. But ﬁxation implants placed over or distally to the watershed line can exert pressure on the ﬂexor tendons and cause injury (3,19). The watershed line is deﬁned as a transverse ridge that closures the concave surface of the volar radius distally. Distal to this line, the radius slopes in a dorso-distal direction and becomes prominent palmarly (3). The course of the ﬂexor pollicis longus tendon is close to the palmar rim of the distal radius. The plate placed very close to the wrist joint can support the palmar aspect of the articular surface. However, it sometimes causes ﬂexor tendon impairment. In the very distal area, it is not possible for the reattached pronator quadratus muscle to protect the ﬂexor tendons. As a result, the tendons can abrade against the plate and sharp edges of the screw heads. It also must be emphasized that pro- truding screw heads can cause tendon irritation (3). To avoid rupture of the ﬂexor pollicis longus tendons, care has to be taken especially in very distal fractures, type C3 fractures, and osteoporotic bone. Adequate image intensiﬁer control to verify the extra-articular and subchondral position of screws and plate is also quite important. In our study, a patient with rupture of the ﬂexor pollicis longus tendon possessed an implant that was placed distally to the watershed line, and secondary displacement with loosening of the distal screws was observed. If fracture instability demands distal placement of hardware, close follow- up investigations and hardware removal should be considered at the ﬁrst sign of ﬂexor tendon irritation as reported by Drobetz and Kutscha-Lissberg (17). This was also an important point for our study. The Acu-Loc distal radius plate is useful for achiev- ing good anatomical reduction, but care must be taken to avoid the complication of tendon rupture. Placing the plate proximally to the watershed line and removing the plate as soon as the fracture united were necessary to avoid the complication of tendon rup- ture. By these considerations, volar distal radius plates will provide excellent results in treating distal radius fractures. Declaration of interest: The authors report no conﬂicts of interest. The authors alone are responsible for the content and writing of the paper.