Flexor Tendon Irritations after Locked Plate Fixation of the Distal Radius with the 3.5 mm T-Plate: Identification of Risk Factors

Aim: Volar locked plate fixation of distal radius fractures has become an established procedure in the past decade, although reports of flexor tendon injuries due to volar plating have been increasing. The aim of the present study is to identify the risk factors which produce irritations of flexor tendons using the locking palmar 3.5 mm T-plate, with special emphasis placed on the watershed line and the pronator quadratus muscle. Method: In this retrospective study, all patients with distal radius fractures who had been treated with a locking volar 3.5 mm T-plate between 2001 and 2005 were evaluated. The X-ray controls were analysed with regard to secondary losses of reduction, bony healing disturbances and the topographic relation to the watershed line. Follow-up included a clinical and subjective assessment using the DASH score. All patients underwent sonography to identify irritations of the tendons under functional conditions (neural and dorsal wrist flexion). Results: A total of 151 patients were treated with the locked volar 3.5 mm T-plate. Of these, 68 patients could be included for follow-up. The mean age was 47.8 years with a mean follow-up period of 3.5 years. Fracture classification according to the AO indicated 13 A, 14 B and 41 C fractures with 37 Colles and 31 Smith fractures. Fracture union was achieved in all patients. A mean palmar tilt of 2.8 degrees (range: 1 to 9 degrees) was observed, with a loss of reduction in three cases of about 5 degrees. There were no implant failures. The mean DASH score was 12. The watershed line was reached by the distal edge of the plate in 48 patients and was exceeded in 20 cases. In 30 patients the pronator quadratus muscle could not be identified. In the remaining 38 cases the mean diameter was reduced to 1.4 mm, while the unaffected contralateral muscle had a mean diameter of 3.8 mm (range: 2.8 to 7 mm). Irritations of flexor tendons occurred only in 4 cases, in those patients where the pronator quadratus muscle could not be identified (2 tendon erosions and 2 tenosynovitises; 5.9%). Relevant functional distal plate prominence was detected in dorsal flexion (power grip) in 3 cases (4.4%), producing tendon deflection. The topographic relation of the plate to the watershed line played a minor role in causing tendon irritations, in contrast to the muscular coverage of the distal plate. Plate coverage by a vital reconstructed pronator quadratus muscle produces a greater distance of the tendon compartment to the plate, whereas a complete muscular coverage of the distal plate edge is difficult to realise, although it is not necessary regarding functional conditions. Conclusion: Stabilisation of distal radius fractures with dorsal and volar displacement by the locked palmar 3.5 mm T-plate produces positive results. A careful reconstruction of the pronator quadratus is more important than respecting the watershed line in that it achieves muscular coverage, and thus provides a greater distance of the plate to the tendon compartment. We recommend sonography after bony healing to identify functional plate prominence or tendon irritations under functional conditions (dorsal wrist flexion) and, if necessary, plate removal. Further systematic sonographic examinations should be undertaken including other locked plate systems.