Journal List > J Korean Orthop Assoc > v.45(2) > 1012978

Hahn, Park, Choi, Kang, and Lee: Prognostic Factors of the Extension Block Technique for the Bony Mallet Finger



The purpose of this study was to evaluate the clinical results and prognostic factors of the extension block technique for treating a bony mallet finger.

Materials and Methods

Between July 2002 and January 2009, forty-nine patients who underwent the extension block technique for a bony mallet finger were evaluated. The minimum period of follow up was 6 months. The type of fracture was classified by the Wehbe and Schneider method. The results were evaluated by the Crawford classification. The prognostic factors were analyzed according to age, gender, the timing of the surgery, the mallet fragment angle and the residual displacement.


According the Crawford classification, there were 22 excellent, 20 good, 6 fair and 1 poor results. The poor prognostic factors were an older patient age, subluxation, a smaller mallet fragment angle and smaller postoperative displacement (p<0.05).


The prognostic factors of the extension block technique for bony mallet finger were the patient age, subluxation, the mallet fragment angle (more than 30 degrees) and the postoperative displacement.

Figures and Tables

Figure 1
Mallet fragment angle. *Mallet fragment angle (°)=90°-{An acute angle between an axis of distal phalanx (dotted line) and a line of fracture (solid line)}.
Figure 2
Lateral radiograph of right 3rd finger. (A) Four days ago, a 37-year-old male patient had an injury on his right 3rd finger. Preoperative radiograph showed 70 percents of joint involvement without a joint subluxation. Mallet fragment angle was 55°. (B) Extension block technique was performed. (C) At postoperative 3 months, the fracture was united and the joint was congruent. Excellent result was noted according to the Crawford classification.
Figure 3
Lateral radiograph of right 5th finger. (A) Fourteen days ago, a 24-year-old male patient had an injury on his right 5th finger. Preoperative radiograph showed 50 percents of joint involvement with a joint subluxation. Mallet fragment angle was 20°. (B) Extension block technique was performed. (C) At postoperative 3 months, the fracture was united but the joint was incongruent. Fair result was noted according to the Crawford classification.
Table 1
Wehbe and Schneider's Classification

DIP, Distal interphalangeal.

Table 2
Crawford's Criteria
Table 3
Clinical Results

*Mean value; Mean visual analogue scale (0-10).

Table 4
Correlation with Mallet Fragment Angle

Bivariate correlation analysis (pearson correlation coefficient).

Table 5
Prognostic Factors for Clinical Results (Crawford Classification*)

Bivariate correlation analysis (pearson correlation coefficient); *Excellent= 4, Good=3, Poor=2, Bad=1.

Table 6
Clinical Results according to Mallet Fragment Angle

Independent t-test; *Excellent=4, Good=3, Poor=2, Bad=1.


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