gms | German Medical Science

Objectives/Interrogation: This study investigates in vivo if an isolated fusion of a single PIP joint influences the grip force and the load distribution of the hand when gripping a cylindrical object

Methods: Ten patients, who had one single PIP joint fused due to posttraumatic joint destruction (4 x index, 4 x middle, 2 x ring finger), but without other structural lesions of the hands were included in this study. On average 59 (17-121) months p.o., patients returned for a manugraphy analysis. Patients performed grip force tests, using three cylinders (100mm, 150mm and 200mm circumference) covered with a pressure sensor matrix to measure the total grip force and load distribution pattern of both hands. Grip force and the load applied by each of the four fingers were compared for the affected and the healthy hand.The fusion-angle was determined by x-ray, which also confirmed the bony healing of the fusion. Due to the small number of patients, only descriptive statistics were provided.

Results and Conclusions: The total grip force of the affected compared to the healthy hand was reduced after PIP-joint fusion of middle- and ring finger for all cylinder sizes (PIP III 56%/88%/91%, PIP IV 76%/105%/91%). After PIP-joint fusion of the index finger grip force was only reduced at the smallest cylinder (91%), while it was increased to 120% at the middle and 139% at the large cylinder. Compared to the opposite side, the load applied exclusively by each affected finger was always reduced, except for the large cylinder, where even the fused index-fingers exerted more strength then the healthy side. The loss of strength by the fused finger was partially compensated through a gain of strength of the other fingers of the affected hand. So, 5/10 patients showed a higher grip strength than the opposite side using the middle cylinder, 6/10 using the large cylinder.

After PIP-joint-fusion grip force is severely impaired when gripping small cylindrical objects, but less affected when gripping larger objects. The load applied by the fused finger is always reduced, but for the total grip force this can often be compensated by the other fingers of the affected hand, especially while gripping large objects.