Ratio of dislocation types of the proximal interphalangeal joint of the fingers: A new classification system for initial therapy

We proposed a new system named the sagittal, coronal, axial, rotational and fracture (SCARF) classification, which can simply explain any condition of proximal interphalangeal (PIP) joint dislocations of the fingers. The purpose of this study was to verify that this classification would contribute to management of PIP joint dislocations at the initial therapy. We determined ratios of five factors in PIP dislocations with SCARF by interpreting radiographs and assessed the interobserver and intraobserver variability.

In total, 68 fingers in 67 consecutive patients were studied. The SCARF classification is composed of five factors: (1) sagittal plane displacement is rated by dorsal (D), volar (V), or neutral (N); (2) coronal plane displacement, by ulnar (U), radial (R), or neutral (N); (3) axial force, by compression (C), traction (T), or no (N); (4) rotational displacement, by supine (S), prone (P), or neutral (N); and (5) fracture concomitance, by minus (-) or plus (+). The row of the five characters explains each condition of PIP joint dislocations. Interobserver and intraobserver variability was determined after six orthopedic surgeons independently classified the same radiographs twice.

All 68 dislocations were classified into 14 types, unless fracture concomitance was considered. The most common type was DUNN (35%). In coronal plane displacements, the two ulnar fingers showed a higher tendency to the ulnar position. Ring finger fracture concomitance was higher than in middle fingers or little fingers. In interobserver analysis, mean kappa coefficient for each factor was 0.63, 0.75, 0.68, 0.33, and 0.84, respectively. In intraobserver analysis, that was 0.73, 0.79, 0.71, 0.41, and 0.81, respectively.

Even other than hand specialists can specify the type of every PIP dislocation by using the SCARF classification and will have better understanding of the disorder. It would contribute to management of PIP dislocations at the initial therapy.

Diagnostic II.