[Effect of a single proximal interphalangeal Joint Fusion of the Index, Middle or Ring Finger on the Grip and Finger Force and Load Distribution in the Hand].

BACKGROUND

Due to the functional coupling of adjacent finger joints and the quadriga effect, arthrodesis of the proximal interphalangeal joint (PIPJ) can be assumed to lead to a different grip pattern resulting in altered force distribution of the hand.

PATIENTS AND METHOD

Ten patients with isolated arthrodesis of the PIPJ due to posttraumatic osteoarthritis (4×PIPJ II, 4×PIPJ III, 2×PIPJ IV) were assessed 59 (17-121) months postoperatively on average. The angle of arthrodesis was assessed by radiographs. Grip force and load distribution of both hands were measured by manugraphy using 3 differently sized cylinders. Grip force was separately assessed and compared for the whole hand as well as for each of the fingers and each phalanx.

RESULTS

Average total grip force of the affected hand compared to the uninjured opposite side was 74% (38-136%) for the small cylinder, 104% (68-180%) for the mid-sized cylinder and 110% (69%-240%) for the large cylinder. Arthrodesis of the PIPJ of the index finger led to a reduction of the grip force (91%) for the small cylinder, but increased grip force for the mid-sized (120%) and large cylinder (139%). Grip force was reduced for all cylinder sizes by arthrodesis of the PIPJ of the middle finger (56%, 88% and 91%). Arthrodesis of the PIPJ of the ring finger resulted in a grip force of 76%, 105% and 91%, respectively, for the different cylinder sizes.The finger force of the affected finger was reduced after arthrodesis of the PIPJ, with the exception of the index finger, which was stronger than the unaffected opposite finger when using the large cylinder. The force of the healthy fingers on the affected side was greater when compared with the same finger on the opposite side, which led to increased grip force for the mid-sized and the large cylinder of the affected hand. A reduction in load distribution was measured mostly for the middle phalanx but also for the distal phalanx of the operated-on finger.

CONCLUSION

Arthrodesis of the PIPJ almost always led to force reduction in the middle and distal phalanx of the affected finger. However, the total grip force of the hand was compensated by a higher force of the adjacent healthy fingers. In many cases, total grip force was even higher on the affected side. However, arthrodesis of the PIPJ resulted in a noticeable force reduction when smaller objects were gripped.