Clinical Notes on Herbert Screw Fixation for Fracture of Anterior Mandible

Abstract

This article aims to present the outcomes of treating anterior mandibular fractures using Herbert’s screw. A total of 10 patients were treated for fractures of anterior mandible by open reduction and internal fixation using the Herbert screw. The patients were collected starting from June 2016 to November 2017, at the Department of Craniomaxillofacial Surgery, Nasser Institute for Research and Treatment, Cairo, and Faculty of Dentistry, Ain Shams University, Cairo, Egypt. The follow-up plan was done to evaluate the postoperative clinical outcomes for malocclusion, neurosensory status, hardware failure, malunion/ nonunion, pain, and edema. There were no intraoperative or postoperative complications, except for one case where the Herbert screw was insufficient and needed additional 2.0-mm miniplate at the superior border. The postoperative orthopantomograms revealed satisfactory reduction and fixation of the fractures of all cases. The Herbert screw fixation of anterior mandibular fracture is a reliable technique but sensitive and surgeon dependent and needs further clinical investigation.

The purpose of this article is to describe the results of anterior mandibular fracture fixation using the Herbert screw. This study was conducted on 10 patients starting from June 2016 to November 2017, at our trauma centers.

The aim of the current study is to introduce a new technique in fixation of the anterior mandible, avoiding complications associated with conventional lag screw.

Inclusion criteria were as follows: (1) mandibular symphysis fracture (from mental to mental foramina), (2) adult patients, (3) completely or partially dentulous patients, and (4) medically and surgically fit patient. Patients with pathological or comminuted fractures were excluded from the study.

Surgical Technique

The techniques of the Herbert screw insertion are as follows: (1) After complete exposure of the symphysis using transoral vestibular approach, a 2.0-mm drill was used to create the path for future insertion of K-wire that was inserted away from the fracture line by approximately 1.5 to 2 cm crossing and perpendicular to the fracture line at the inferior border to create a path for the cannulated drill to cut into the bone and to assess the length of the Herbert screw to be placed. (2) Preparation of the site for the Herbert screw placement was done using a long cannulated drill with diameter of 2.5 mm from the area of entry at the near stump preparing the traction hole at the far segment. (3) Using a cannulated drill, with a diameter of 3.2 mm, drilling of the outer cortex was done withoutcrossing thefractureline. (4) Bonetapwasglided along the K-wire to create the insertion site for the Herbert screw. (5) Insertion of the Herbert screw was done, after measuring the proper length according to the previously measured K-wire, using screw driver to compress the fractured segments together. (6) After hardware insertion, the IMF was released and the occlusionwas checked for stability, reproducibility, and verification before wound closure in a layered fashion.

Results

When examining the results of postoperative occlusion, the outcome was very satisfactory. Hence, only one case had to undergo spot grinding. No patient was placed into IMF after surgery (Figure 1 and Figure 2).

Regarding postoperative infection following open reduction and internal fixation, no postoperative wound dehiscence was reported. Concerning the nerve sensation, no numbness was detected in all cases.

The postoperative radiographs revealed satisfactory reduction and fixation of the fractures of all cases (Figure 3, Figure 4, Figure 5 and Figure 6).

Discussion

This study was conducted to evaluate the use of the Herbert screw in the treatment of anterior mandibular fracture both clinically and radiographically.

The Herbert screw was introduced in this study mainly to overcome the disadvantages of the head of the lag screw, where the over screwing will cause stress concentration and may induce cracking and loosening of the screw itself. Terheyden et al. revealed that the major disadvantage of conventional lag screw is loosening of hardware after fixation [1].

The technique used for the Herbert screw placement in this study was similar to that described by Herbert and Fisher in the fixation of scaphoid bone fracture except that the anterior mandible is curved and the K-wire was not able to penetrate the outer cortex; so, we used 2.0-mm drill to overcome this problem. The Herbert screw is similar to conventional lag screw in the production of a constant compression during the healing period allowing contact healing rather than gap healing which is found to have faster healing than noncompressive fixation because the principle of axial compression gained by the Herbert screw provides accurate reduction, rigidity, and compressive forces across the fracture line allowing immediate mobilization [2,3].

The Herbert screws differ in having threads at both ends and a blank shaft in between. The threads at the leading end have a larger pitch and smaller diameter, while the threads at the trailing end have a smaller pitch and larger diameter.[3] This differential pitch plays a role in the engagement of the screw into both stumps rather than engaging one stump; which will enhance the reduction of the fracture as the screw turns in.[1,3,4,5] A further advantage is a blank shaft in the center with no threads that allows the approximation of both stumps without hindering the fracture line reduction [4,5].

The Herbert screw was introduced in this study mainly to overcome the disadvantages of the head of the lag screw, where the over-screwing will cause stress concentration and may induce cracking and loosening of the screw itself. Another advantage gained from using the Herbert screw over the conventional lag screw is the headless end that embeds into the drilled path, unlike the lag screw head which is palpable and requires countersinking. This countersinking may jeopardize the stability of the head of the conventional lag screw that became a weak contact with the bone and the resulting subsequent resorption and loosening of the screw itself on functioning [6].

In this study, no patients were put in postoperative maxillomandibular fixation to avoid the airway problems, feeding disturbance, bad oral hygiene, and joint dysfunction due to immobilization.[7,8] This rationale is based on studies done by Kaplan et al. and Valentino and Marentette that advocated immediate mobilization [9,10].

Demographically, the majority of patients were males. The major reason for our traumatic mandibular fracture was road traffic accident which is often observed inyoung adult males [11].

In our study, we did not face complications such as nonunion, broken drills, and infection of the Herbert screw. Also, there was no evidence of hardware exposure. However, Herbert screw fixation, especially in maxillofacial area, is a highly technique-sensitive maneuver.