Treatment of mallet fractures with a transverse two-hole mini plate

Surgical treatment of the bony mallet thumb: a case series and literature review

INTRODUCTION

The aim of this study was to provide a more precise statement on the outcome after surgical treatment of a bony mallet thumb and possibly give a treatment recommendation regarding the surgical fixation method.

PATIENTS AND METHODS

All patients (n = 16) who underwent a surgical treatment for an acute bony mallet thumb fracture between January 2006 and July 2019 were enrolled. The surgical method, complications, the range of motion, tip pinch, lateral key pinch, overall grip strength, visual analog score, Disability of the Arm, Shoulder and Hand Score, Mayo Wrist Score, Patient-Rated Wrist Evaluation Score, Buck-Gramcko Score and radiologic parameters were evaluated. Further, a comprehensive literature search on PubMed was conducted covering a period from 1956 to 2021 to include all possible matching articles on the treatment of the bony mallet thumb (n = 21 articles).

RESULTS

Surgical treatment was very inhomogenous including indirect and direct K-wire fixation, screw fixation, plate fixation and anchor fixation methods. The IP joint range of motion and thumb strength ranged from 66 to 94% in comparison to the contralateral side. An open reduction led to worse functional scores compared to a closed reduction. Treatment methods in the literature were also very inhomogenous with a very low patient count, often even pooling data of bony mallet thumb fractures with bony mallet finger fractures. The risk for infection was higher in K-wire fixation methods than in open reduction and internal fixation methods.

CONCLUSION

The evidence for the best treatment of a bony mallet thumb fracture is low. On one hand the functional outcome can be inferior using an open reduction approach, but on the other hand, K-wire fixation methods with a closed reduction approach showed a higher risk for infection. Future multi-center research must be conducted to find the best treatment procedure for the best outcome of the patient.

Anatomical and clinical study of a new mallet fracture classification method

Background

Mallet fracture is avulsion of the terminal extensor tendon from the base of the distal phalangeal bone with a bony fragment. This study was performed to evaluate the anatomical characteristics of mallet fractures, investigate a new mallet fracture classification system using anatomical and imaging methods, and discuss the treatment schemes for different types of mallet fracture.

Methods

Sixty-four fresh cadaveric fingers were divided into four groups, and models of different types of mallet fracture with distal interphalangeal joint instability were established by dissecting 25%, 50%, 75%, and 100% of the bilateral collateral ligaments. The effect of mallet fractures on the stability of the distal interphalangeal joint was then observed. The lateral radiographs of mallet fractures in 168 patients were analyzed and classified according to the involvement of the joint surface in the fracture, the thickness of fracture, the untreated time after injury, and the complication of distal interphalangeal joint palmar subluxation. Forty-seven patients were surgically treated by reconstruction of extensor tendon insertion, the Ishiguro method, or single Kirschner wire fixation.

Results

The established mallet fracture model showed that the distal interphalangeal joint was stable when the bilateral collateral ligaments were cut off by 25% (t = –0.415, P = 0.684) and significantly unstable when this range was ≥50% (50% transection: t = –6.363, P < 0.001; 75% transection: t = –17.036, P < 0.001; 100% transection: t = –30.977, P < 0.001, respectively). The mallet fractures were divided into Types I, II, and III (fracture involving <20%, 20%–50%, and >50% of the joint surface, respectively). Type II was further divided into Types IIa and IIb according to whether the course of injury was < or ≥2 weeks, respectively. The mean post-operative flexion of the distal interphalangeal joint was 63.4° ± 7.9°, and the mean extension lag was 6.7° ± 4.6°.

Conclusions

The lateral collateral ligament is the main factor that maintains the stability of the distal interphalangeal joint. Classification that combines the involvement of the joint surface in the fracture, the thickness of the fracture, and the untreated time after injury is reasonable and will help to choose an appropriate operational method.