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Lag-screw fixation of mandibular parasymphyseal and angle fractures
Lag-screw fixation of mandibular parasymphyseal and angle fractures Ilkka Kallela, MD, DDS, a Tateyuki llzuka, MD, DDS, PhD, b Pekka Laine, DDS, PhD, c and Christian Lindqvist, MD, DDS, PhD, d Helsinki, Finland HELSINKI UNIVERSITY CENTRAL HOSPITAL
Objective. This study was carried out to evaluate clinical and radiologic results after lag-screw fixation (LSF) of mandibular parasymphyseal and angular fractures was performed. Study design. Seven angle and 17 parasymphyseal fractures in 23 adult patients with mandibular fractures were treated by transoral reduction and LSF. Clinical and radiologic examinations were undertaken during a 3-month follow-up period Results. All parasymphyseal fractures and four angular fractures went to good bone union after surgery. Infectious complications occurred in two patients with parasymphyseal fractures. These resolved with simple procedures. Three angular fractures needed refixing because of instability. Slight occlusal adjustment was needed in five patients. Postoperative neurosensory deficits were transient in every case in which they were seen. Conclusions. LSF of mandibular parasymphyseal fractures is a practical and effective way of fixing such fractures internally, it leads to good bone healing without permanent neurosensory deficit or increased risk of malocclusion. In mandibular angle fractures LSF is likely to be too technique-sensitive to allow its extensive use. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;81:510-6)
Open reduction and fixation of mandibular fractures is now a well-established means of treatment of displaced mandibular fractures. 1 For fixation of fragments metallic bone plates and screws are usually used.2, 3 Single screws for fixation of fragments have, however, not been widely used in cases of mandibular trauma, although there have been some reports of use of lag-screws in the treatment of mandibular-angle, 4-6 condyle, 7-1~ and anterior 11 fractures. Use of single screws instead of plates and screws would seem likely to be associated with several advantages. Less implant material should be needed, costs should be lower, technique should be simple (no need to bend plates), and surgical exposure should be limited. Compressing fractured bone fragments against each other when performing osteosynthesis has been shown to result in greater stability of fracture repair: 12 Although some investigators 3 do not agree that there is a need for compression osteosynthesis in cases of mandibular trauma, data indicating the importance of rigidity of fixation exist. It has been aMaxillofacial Surgeon, Department of Maxillofacial Surgery. bSenior Maxillofacial Surgeon, Department of Maxillofacial Surgery. cSenior Maxillofacial Surgeon, Department of Maxillofacial Surgery. aHead, Department of Maxillofacial Surgery, Helsinki University Central Hospital. Received for publication Jan. 12, 1996; returned for revision Feb. 14, 1996; accpted for publication Apr. 17, 1996. Copyright 9 1996 by Mosby Year Book, Inc. 1079-2104/96/$5.00 + 0 7112/75441
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suggested that rigidity is important to resist infection in mandibular fractures. 2, 13 In this article we report our experience with lag-screw fixation (LSF)in the treatment of mandibular parasymphyseal and angle fractures. PATIENTS
Between September 1993 and December 1994, 23 adult patients with a displaced parasymphyseal fracture, a displaced angular mandibular fracture, or both were randomized and subjected to operation with LSF. Ninety-five patients underwent operation for all kinds of mandibular fractures in the Department of Maxillofacial Surgery, Helsinki University Central Hospital, Helsinki, Finland, during the period. In 48 patients the fractures were fixed transorally with miniplates. In 18 patients they were fixed extraorally with rigid plates (AO/ASIF 2.7 or 2.4 plates). In six cases a combination of rigid plates and miniplates was used. The patients undergoing LSF therefore represented 24% of all surgically treated patients with mandibular fractures in our department during the period concerned. The mean age of the patients undergoing LSF was 29 years (range 15 to 48 years). Four female and 19 male patients were in the study. All patients were dentulous, having at least the second bicuspids as the most distal tooth on both sides and in both jaws. Injury had been caused by assault in 13 cases. Other causes were road traffic accidents (five cases), a fall (two cases), sports injuries (two cases), and one epileptic seizure. Signs of chronic alcohol or drug abuse in were seen in nine patients.
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Angular and parasymphyseal fractures were fixed in one patient with lag-screws during the same procedure. In all of the others an angular fracture (6 patients) or a parasymphyseal fracture (16 patients) was fixed. All parasymphyseal fractures in these patients were treated with LSF, but the decision to fix an angular fracture with lag-screws or by other means was made randomly. Twenty-four fractures were treated with LSF. Ten of the patients with parasymphyseal fractures had other mandibular fractures. Two also had fractures of the middle third of the facial skeleton. Three of the patients with angular fractures had other mandibular fractures. METHOD All operations were performed with the patients under general anesthesia with nasotracheal intubation. Erich-type arch bars were applied to both jaws. The angular fractures were exposed through a standard sagittal split osteotomy incision. Reduction was accomplished with special reduction forceps (Fig. 1) placed transbuccally and secured to drilled holes on both sides of the fracture line according to the method described by Nishioka and Van Sickels 14 (Fig. 2). Maxillomandibular fixation (MMF) was then accomplished with wires. The reduction forceps were opened slightly to allow the proximal fragment to rotate to its original position in the temporomandibular fossa, and the forceps were then tightened. Lag-screw osteosynthesis with one cortical 2.7 m m screw was accomplished with standard lag-screw equipment from the AO/ASIF mandibular 2.7 set (Fig. 3). A transbuccal soft-tissue tunnel below the mental nerve was created for instrumentation. 4,15 Extra-long screws (between 30 and 40 m m long) were used (Fig.4). Finally, M M F was released, and the stability of the osteosynthesis was checked by forceful manipulation. In five of seven angular fractures an impacted third molar was in the fracture line. Such teeth were left in place. Mandibular parasymphyseal fractures were exposed through vestibular incisions between the mental foramina. Reduction was accomplished with the reduction forceps at the apical level. Occlusion was then secured in the same way as in the angular region. Two lag-screws were placed across the fracture line from one buccal cortex to the other, except that in one patient only one screw was used, and in another the screw was placed from the buccal to the lingual cortex. In six cases the screws were placed in a crisscross manner from opposing sides. Again, extra-long screws were used (Fig.4). Small suction drains were inserted before closure was performed. Drainage was maintained for 24
Fig. 1. Tips of reduction forceps. We shortened peaks of standard small A t towel clip like reduction forceps and made small grooves in ends to allow better grip on burr holes. Advantage of small reduction forceps is that unlike similar commercial forceps, they fit snugly in burr holes without need for manual support. Precompression achieved is nevertheless enough for perfect reduction to be achieved. It is possible to move bone fragments in all three planes. hours. Prophylactic antibiotic treatment, started in the emergency department, was continued for 1 week. Other concomitant mandibular fractures (unless condylar) were treated with surgery. Seven patients with parasymphyseal LSF fractures received MMF for 3 weeks to treat condylar fractures. In the other patients no immobilization was used. Soft diet was recommended for 2 weeks, and then the patient was encouraged to resume a normal diet, if otherwise possible. During the hospital stay postoperative radiographs (panoramic and Towne views of the mandible) were taken. Accuracy of reduction (displacement/no displacement) and positioning of the screws in relation to teeth and neurovascular structures were assessed.
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Fig. 2. Photograph showing use of special reduction forceps. Drill holes in buccal cortical bone were made through two small transbuccal tunnels, and trocar was used. Drill holes should be roughly central between superior border of alveolar process and inferior border of mandible. Reduction forceps were introduced through same transbuccal tunnels. Drill holes should penetrate only cortical bone to avoid nerve damage.
The follow-up schedule involved clinical examination 2 weeks after operation and clinical and radiologic examination (panoramic and Towne views of the mandible) 6 weeks and 3 months after surgery. During follow-up visits clinical signs relating to stability/instability of osteosynthesis, infection, occlusion, and mental-nerve function were recorded. Mental nerve function was evaluated in the same way as before operation by stroking the skin in the region of the mental nerve and chin with cotton wool and by pricking the same area with a dental probe. The subjective sensations of the patient were recorded. On radiologic evaluation positioning of repositioned fragments (displacement/no displacement) and bone healing (visibility of fracture gap and external callus) were assessed by one surgeon in the study group. Additional visits were arranged when needed.
RESULTS Postoperative radiographs revealed anatomic reduction without detectable displacement in LSF fractures in 21 (88%) cases. In two (8%) cases displacement was slight (1 to 2 mm). In one (4%) case osteosynthesis had broken down. There were no signs that the screws had engaged the mandibular canal or roots of the teeth in any patient.
Follow-up was complete within 3 months in 19 (86%) of 22 patients with LSF in place on leaving hospital. During follow-up clinical signs relating to instability of fixation and infection were noted in one (5%) patient and to infection in an additional two (9%) (see Complications). After surgery slight occlusal adjustment was needed in five (23%) patients (6, 7, 11, 16, and 23). In patients with only parasymphyseal fracture (13) no neurosensory disturbances (anesthesia, hypesthesia, or paresthesia) were noted before surgery. After surgery there were disturbances in eight (68%) patients in the region of the mental nerve, chin, or both. All of these recovered within 5.4 weeks on average (range 38 weeks). In three patients who underwent parasymphyseal LSF one-sided angular fractures were fixed with means other than lag-screws. Before surgery all had neurosensory disturbance on the same side as the angle fracture. After surgery two also had disturbances in the contralateral mental region. Disturbances evident before surgery resolved in 4 and 6 months except in one case, in which total anesthesia was still evident after 10 months. Disturbances caused by the operation resolved within 6 to 12 weeks.
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Fig. 3. Steps in performing lag screw fixation with AO/ASIF standard equipment. 1. Above, left. Drilling of near cortex with 2.7 mm drill bit. 2. Above, right. Countersinking. 3. Center, right. Drilling through entire bone with 2 mm drill bit with centering drill guide. 4. Center, left. Measuring screw length with depth gauge. 5. Below, right. Tapping. 6. Below, left. Screw in place.
In patients with angular fracture fixed with lagscrews there were neurosensory disturbance in two (29%) cases before surgery. They recovered after surgery in between 4 and 16 weeks. One (14%) patient with an angular fracture who had no preoperative disturbances had development of anesthesia in the ipsilateral mental-nerve region. It resolved in 19 weeks. In another four (57%) patients with angular fixation no postoperative disturbances occurred. No displacement of repositioned fragments or screws from previous positions was noted on radiologic evaluation during follow-up except in patient 12 (5%). At 6 weeks the fracture line was more visible in seven (37%) patients than it had been in the immediate postoperative radiograph. In six (32%) patients the appearance was exactly the same as in the postoperative view. In two (10%) patients the fracture gap was considered to have narrowed. In four (21%) it was invisible. At 3 months all fracture gaps were less visible than at 6 weeks, In 10 (53%) cases the fracture line could no longer be detected. No external callus formation was seen in any radiograph.
COMPLICATIONS Two (9%) complications occurred during surgery and in the immediate postoperative period. In one patient (11) the parasymphyseal and right-sided angular fractures were to be fixed with lag-screws. In both locations on drilling the outer cortex with a 2 m m drill bit, the bit fractured and remained inside the mandible. Preparation in relation to the parasymphyseal fracture was accomplished with a new drill bit, and LSF was performed in the normal way. In the angle the lag-screw did not provide adequate stability in relation to the fracture line. The screw was removed and the fracture line stabilized with a miniplate along the external oblique ridge. In another patient (14) postoperative radiographs revealed that the right angular L S F had broken after 3 days, although it had been considered to be stable during operation. The patient was taken to the operating department, the screw was removed, and the fracture was reduced and fixed with a miniplate along the external oblique ridge. Bone healing was subsequently uneventful. Slight mental nerve neurosensory
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Fig. 4. Postoperative radiograph shows perfect reductions and lag-screw fixations. deficit apparent before surgery disappeared in 4 weeks. During follow-up complications were noted in three (14%) cases. Three weeks after surgery patient 17 presented with swelling and discharge of pus around the left lower canine tooth in the fracture line. During primary operation the apex of this tooth had been found to be extensively exposed in the fracture gap. Local incision, peroral antibiotics, and root canal therapy resolved the situation. Subsequent healing was uneventful. Patient 12 presented 4 weeks after surgery with fever, pain, and massive swelling in the left cheek area. The left angular fracture with LSF was found to be unstable. The abscess was incised through a left submandibular incision, the screw was removed, and the fracture was restabilized with an 11hole AO/ASIF 2.7 m m reconstruction plate. An impacted left third molar was also removed. The postoperative course was uneventful, and the fracture went to union. Patient 11 had left angular pain 4 months after surgery. On clinical evaluation slight swelling and pain on palpation were noted in the left angular region, buccally. On radiologic evaluation resorption was detected in this region around the fractured drill bit. The drill bit was removed. The postoperative course was uneventful, with cessation of all symptoms and no permanent neurosensory deficit.
DISCUSSION Our first experience with LSF in treating mandibular-angle fractures was mixed. Although in five patients rigid osteosynthesis leading to good bone union was achieved, there were three failures that could be accounted for by instability. It would seem important
to manipulate fixation forcefully to check for instability after releasing M M F as recommended by Ellis and Ghali. 5 If stability is doubtful, it is better to remove the screw and stabilize the fracture with, for example, a miniplate instead of subjecting the patient to MMF. The most crucial factor in achieving sound compression is screw angulation in the anteroposteriot direction, which should be almost sagittal. 5 There is a tendency to drill the screw canal in a lingual direction, which results in the screw bit failing to hold in the thin lingual cortical bone. When drilling is then directed in an almost sagittal plane, it is difficult to find enough bone in the buccal cortex to hold the screw head after countersinking. The biomechanical validity of this fixation method has been shown in vitro. 16 There have been reports of success with LSF in angular fractures. In 50 patients Niederdellman and Shetty 4 reported that only 4% of patients needed major intervention because of complications resulting from infection. Ellis and Ghali 5 reported that 13% of their 30 patients needed similar interventions. In contrast to these findings, our early results were disappointing. It could be that this method is not practical for extensive use. Surgeons using this procedure should have a strong interest in and significant experience of LSF in fracture treatment. Our results with LSF used to treat mandibular parasymphyseal fractures were, however, promising. We saw two complications necessitating further procedures but not affecting fracture healing. One was a local infection related to a devitalized tooth in the fracture line and could not be related to the type of osteosynthesis. Nonvitality of teeth in dislocated fracture lines with exposure of the apex is high. 17 The
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other c o m p l i c a t i o n was related to faulty technique w h e n drilling, initially with a 2 m m bit. W e f o u n d that it is m a n d a t o r y to use sharp drill bits and to w i t h d r a w and a d v a n c e the bit at times to resist the t e n d e n c y o f the bit to c l o g in the far cortex. It is obvious that in creating e x t e n s i v e burr canals in bone that cooling and rinsing actions o f the c o o l a n t liquid are r e d u c e d at the far side o f the canal. It is also i m p o r t a n t in perf o r m i n g L S F in anterior fractures to a d v a n c e the 2 m m drill bit v e r y s l o w l y f r o m the m e d u l l a r y c a v i t y into the outer cortex; o t h e r w i s e the drill bit will slip along the inner surface o f the outer cortex and be f o r c e d into the angular region. In their study o f 41 patients subjected to L S F , Ellis and G h a l i 11 r e c o r d e d two p o s t o p e r a t i v e infections. O n e led to sequestrectomy, the other to r e m o v a l o f the fracture-line tooth and screw. External pin fixation was u n d e r t a k e n after surgery. In 1993, Assael118 r e p o r t e d a high i n c i d e n c e o f t e c h n i q u e - r e l a t e d failures w h e n surgeons w e r e perf o r m i n g L S F in a teaching l a b o r a t o r y setting during A O / A S I F courses. In our study w e saw no failures l e a d i n g to m a l p o s i t i o n i n g o f fragments or s e v e r a n c e o f n e u r o v a s c u l a r structures or teeth. This result is in a c c o r d a n c e with the clinical results o f Ellis and G h a li. l i In our patients p o s t o p e r a t i v e n e u r o s e n s o r y deficit was p r o b a b l y c a u s e d b y stretching o f the mental nerve and soft tissues during operation. Such disturbances w e r e transient in e v e r y case. It is usually practical to a p p l y one screw first along the b u l k y inferior b o r d e r o f the anterior m a n d i b l e and the s e c o n d at the level b e t w e e n the f o r m e r and the apexes o f the teeth. L i k e Ellis and G h a l i 11 w e b e l i e v e that the orthopedic principl e d e m a n d i n g p l a c e m e n t o f lagscrews a l o n g a course that bisects the angle b e t w e e n the outer cortex and the line o f fracture with the tip o f the screw penetrating the inner cortex 19 can be neg l e c t e d in p e r f o r m i n g L S F in m a n d i b u l a r p a r a s y m p h y s e a l fractures. W e p l a c e d screws from the b u c c a l outer c o r t e x across the fracture line in e v e r y case exc e p t one to repenetrate the b u c c a l outer cortex on the o p p o s i t e side o f the fracture. The centers o f the screws were situated r o u g h l y on the fracture line. The obliqueness o f the fracture line was not taken into account in directing drill bits. T h e r e always s e e m e d to b e so m a n y interdigitations in the fracture surfaces in this area that w e saw no t e n d e n c y o f fragments to override. P l a c i n g screws in a crisscross m a n n e r can be valuable, i f there is a d a n g e r o f there being insufficient b o n e left after c o u n t e r s i n k i n g two points o f entry b e s i d e each other. H o w e v e r , screws inserted in a crisscross m a n n e r take l o n g e r to r e m o v e than screws not inserted in this way. The c o n s i d e r a b l e d e g r e e o f c o m p r e s s i o n a c h i e v e d
with l a g - s c r e w s b e c o m e s e v i d e n t on tightening the screws during operation. In a p e r f e c t l y r e p o s i t i o n e d fracture the fracture line a l m o s t c o m p l e t e l y vanishes. It is important to understand that the stability o f this k i n d o f osteosynthesis relies solely on c o m p r e s s i o n b e t w e e n the fragments. I f there is fragmentation, this single stabilizing factor is lost, and the fracture m u s t be treated with b o n e plates and screws in a neutral position. It m i g h t be s u p p o s e d that c o m p r e s s i o n caused b y the screws w o u l d b e too extensive, resulting in b o n e necrosis and m a l i g n m e n t and l e a d i n g to m a l o c c l u sion. H o w e v e r , w e f o u n d no a b n o r m a l i t i e s o f b o n e healing on clinical or r a d i o l o g i c evaluation. Occlusal a d j u s t m e n t in the f o r m o f o c c l u s a l grinding was n e e d e d in five patients. A l l h a d c o n c o m i t a n t m a n d i b ular or m i d - f a c e fractures. It was not p o s s i b l e to determine reasons for m a l o c c l u s i o n in these patients. Ellis and Ghali 11 f o u n d no p o s t o p e r a t i v e realocclusion in 41 patients, 29 o f w h o m had associated m a n d i b u l a r fractures. F e a r o f i m p a i r e d b o n e healing and p o s t o p e r a t i v e m a l o c c l u s i o n w o u l d s e e m to be unjustified. CONCLUSIONS L a g - s c r e w fixation o f m a n d i b u l a r p a r a s y m p h y s e a l fractures is a practical and effective w a y o f fixing such fractures internally. It leads to g o o d b o n e healing without p e r m a n e n t n e u r o s e n s o r y deficit or inc r e a s e d risk o f m a l o c c l u s i o n . In m a n d i b u l a r angle fractures L S F is l i k e l y to b e too technique-sensitive to a l l o w its e x t e n s i v e use. REFERENCES
1. Bruce R, Fonseca RJ. Mandibular fractures. In: Fonseca RJ, Walker RV, editors. Oral and maxillofacial trauma. Philadelphia: WB Saunders Company, 1991:359-417. 2. Spiessl B. Rigid internal fixation of the mandible. A manual of AO/ASIF principles. Berlin, Germany: Springer Verlag, 1989. 3. Champy M, Lodde JP, Schmit R, et al. Mandibular osteosynthesis by miniature screwed plates via buccal approach. J Maxillofacial Surg 1978;6:14-21. 4. Niederdellmann H, Shetty V. Solitary lag screw osteosynthesis in the treatment of fractures of the angle of mandible: a retrospective study. Plast Reconstr Surg 1987;80:688-74. 5. Ellis E, Ghali G. Lag screw fixation of mandibular angle fractures. J Oral Maxillofac Surg 1991;49:234-43. 6. Farris P, Dierks E. Single oblique lag screw fixation of mandibular angle fractures. Laryngoscope 1992;102:1070-2. 7. Kitayama S. A new method of intra oral open reduction using a screw applied through the mandibular crest of condylar fractures. J Craniomaxillofac Surg 1989; 17:16-23. 8. Eckelt U. Zugscraubenosteosynthese bei Unterkiefergelenkfortsatzfracturen. Dtsch Z Mund Kiefer GesichtsChir 1991; 15:5!-7. 9. Krenkel C. Axial "anchor screw" (lag screw with biconcave washer) or "slanted screw" plate for osteosynthesis of fractures of the mandibular condylar process. J Craniomaxillofac Surg 1992;20:348-53.
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10. Kallela I, Soderholm A-L, Paukku P, Lindqvist C. Lag-screw osteosynthesis of mandibular condyle fractures: a clinical and radiological study. J Oral Maxillofac Surg 1995 ;53:1397-404. 11. Ellis E, Ghali G. Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 1991 ;49:13-21. 12. 12. Muller ME, Allg6ver M, Schneider R, Willenegger H. Manual of internal fixation. 3rd ed. Berlin: Springer-Verlag, 1995. 13. Iizuka T, Lindqvist C, Hallikainen D, Paukku P. Infection after rigid internal fixation of mandibular fractures. A clinical and radiological study. J Oral Maxillofac Surg 1991;49:58593. 14. Nishioka G, Van Sickels J. Transoral plating of mandibular angle fractures: a technique. Oral Surg 1988;66:531-5. 15. Niederdellmann H, Akuam oa-boateng E, Uhlig G. Lag-screw osteosynthesis: a new procedure for treating fractures of the mandibular angle. J Oral Surg 1981;9:938-40. 16. Shetty V, Caputo A. Biomechanical validation of the solitary lag screw technique for reducing mandibular angle fractures. J Oral Maxillofac Surg 1992;50:603-7. 17. Kamboozia A, Punnia-Moorthy A. The fate of teeth in mandibular fracture lines. A clinical and radiological follow-up study. Int J Oral Maxillofac Surg 1993;22:97-101. 18. Assael L. Evalution of rigid internal fixation of mandible fractures performed in the teaching laboratory. J Oral Maxillofac Surg 1993;51:1315-9.
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 1996 19. Leonard M. The use of lag screws in mandibular fractures. Otolaryngol Clin North Am 1987;20:479-93.
Reprint requests: Ilkka Kallela, MD, DDS Departmem of Maxillofacial Surgery Helsinki University Central Hospital Kasarmikatu 11-13, SF-00130 Helsinki, Finland
CORRECTION
In the article "Gingival mass as the primary manifestation of multiple myeloma: Report of two cases," which appeared in the July 1996 issue (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:75-9), the authors were Shiou-Hwei Lee, DDS, Jane-Jane Huang, DDS, Whei-Lin Pan, DDS, and Chin-Po Chan, DDS from Chang-Gang Memorial Hospital in Taipei, Taiwan.
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Objective. This study was carried out to evaluate clinical and radiologic results after lag-screw fixation (LSF) of mandibular parasymphyseal and angular fractures was performed. Study design. Seven angle and 17 parasymphyseal fractures in 23 adult patients with mandibular fractures were treated by transoral reduction and LSF. Clinical and radiologic examinations were undertaken during a 3-month follow-up period Results. All parasymphyseal fractures and four angular fractures went to good bone union after surgery. Infectious complications occurred in two patients with parasymphyseal fractures. These resolved with simple procedures. Three angular fractures needed refixing because of instability. Slight occlusal adjustment was needed in five patients. Postoperative neurosensory deficits were transient in every case in which they were seen. Conclusions. LSF of mandibular parasymphyseal fractures is a practical and effective way of fixing such fractures internally, it leads to good bone healing without permanent neurosensory deficit or increased risk of malocclusion. In mandibular angle fractures LSF is likely to be too technique-sensitive to allow its extensive use. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;81:510-6)
Open reduction and fixation of mandibular fractures is now a well-established means of treatment of displaced mandibular fractures. 1 For fixation of fragments metallic bone plates and screws are usually used.2, 3 Single screws for fixation of fragments have, however, not been widely used in cases of mandibular trauma, although there have been some reports of use of lag-screws in the treatment of mandibular-angle, 4-6 condyle, 7-1~ and anterior 11 fractures. Use of single screws instead of plates and screws would seem likely to be associated with several advantages. Less implant material should be needed, costs should be lower, technique should be simple (no need to bend plates), and surgical exposure should be limited. Compressing fractured bone fragments against each other when performing osteosynthesis has been shown to result in greater stability of fracture repair: 12 Although some investigators 3 do not agree that there is a need for compression osteosynthesis in cases of mandibular trauma, data indicating the importance of rigidity of fixation exist. It has been aMaxillofacial Surgeon, Department of Maxillofacial Surgery. bSenior Maxillofacial Surgeon, Department of Maxillofacial Surgery. cSenior Maxillofacial Surgeon, Department of Maxillofacial Surgery. aHead, Department of Maxillofacial Surgery, Helsinki University Central Hospital. Received for publication Jan. 12, 1996; returned for revision Feb. 14, 1996; accpted for publication Apr. 17, 1996. Copyright 9 1996 by Mosby Year Book, Inc. 1079-2104/96/$5.00 + 0 7112/75441
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suggested that rigidity is important to resist infection in mandibular fractures. 2, 13 In this article we report our experience with lag-screw fixation (LSF)in the treatment of mandibular parasymphyseal and angle fractures. PATIENTS
Between September 1993 and December 1994, 23 adult patients with a displaced parasymphyseal fracture, a displaced angular mandibular fracture, or both were randomized and subjected to operation with LSF. Ninety-five patients underwent operation for all kinds of mandibular fractures in the Department of Maxillofacial Surgery, Helsinki University Central Hospital, Helsinki, Finland, during the period. In 48 patients the fractures were fixed transorally with miniplates. In 18 patients they were fixed extraorally with rigid plates (AO/ASIF 2.7 or 2.4 plates). In six cases a combination of rigid plates and miniplates was used. The patients undergoing LSF therefore represented 24% of all surgically treated patients with mandibular fractures in our department during the period concerned. The mean age of the patients undergoing LSF was 29 years (range 15 to 48 years). Four female and 19 male patients were in the study. All patients were dentulous, having at least the second bicuspids as the most distal tooth on both sides and in both jaws. Injury had been caused by assault in 13 cases. Other causes were road traffic accidents (five cases), a fall (two cases), sports injuries (two cases), and one epileptic seizure. Signs of chronic alcohol or drug abuse in were seen in nine patients.
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Angular and parasymphyseal fractures were fixed in one patient with lag-screws during the same procedure. In all of the others an angular fracture (6 patients) or a parasymphyseal fracture (16 patients) was fixed. All parasymphyseal fractures in these patients were treated with LSF, but the decision to fix an angular fracture with lag-screws or by other means was made randomly. Twenty-four fractures were treated with LSF. Ten of the patients with parasymphyseal fractures had other mandibular fractures. Two also had fractures of the middle third of the facial skeleton. Three of the patients with angular fractures had other mandibular fractures. METHOD All operations were performed with the patients under general anesthesia with nasotracheal intubation. Erich-type arch bars were applied to both jaws. The angular fractures were exposed through a standard sagittal split osteotomy incision. Reduction was accomplished with special reduction forceps (Fig. 1) placed transbuccally and secured to drilled holes on both sides of the fracture line according to the method described by Nishioka and Van Sickels 14 (Fig. 2). Maxillomandibular fixation (MMF) was then accomplished with wires. The reduction forceps were opened slightly to allow the proximal fragment to rotate to its original position in the temporomandibular fossa, and the forceps were then tightened. Lag-screw osteosynthesis with one cortical 2.7 m m screw was accomplished with standard lag-screw equipment from the AO/ASIF mandibular 2.7 set (Fig. 3). A transbuccal soft-tissue tunnel below the mental nerve was created for instrumentation. 4,15 Extra-long screws (between 30 and 40 m m long) were used (Fig.4). Finally, M M F was released, and the stability of the osteosynthesis was checked by forceful manipulation. In five of seven angular fractures an impacted third molar was in the fracture line. Such teeth were left in place. Mandibular parasymphyseal fractures were exposed through vestibular incisions between the mental foramina. Reduction was accomplished with the reduction forceps at the apical level. Occlusion was then secured in the same way as in the angular region. Two lag-screws were placed across the fracture line from one buccal cortex to the other, except that in one patient only one screw was used, and in another the screw was placed from the buccal to the lingual cortex. In six cases the screws were placed in a crisscross manner from opposing sides. Again, extra-long screws were used (Fig.4). Small suction drains were inserted before closure was performed. Drainage was maintained for 24
Fig. 1. Tips of reduction forceps. We shortened peaks of standard small A t towel clip like reduction forceps and made small grooves in ends to allow better grip on burr holes. Advantage of small reduction forceps is that unlike similar commercial forceps, they fit snugly in burr holes without need for manual support. Precompression achieved is nevertheless enough for perfect reduction to be achieved. It is possible to move bone fragments in all three planes. hours. Prophylactic antibiotic treatment, started in the emergency department, was continued for 1 week. Other concomitant mandibular fractures (unless condylar) were treated with surgery. Seven patients with parasymphyseal LSF fractures received MMF for 3 weeks to treat condylar fractures. In the other patients no immobilization was used. Soft diet was recommended for 2 weeks, and then the patient was encouraged to resume a normal diet, if otherwise possible. During the hospital stay postoperative radiographs (panoramic and Towne views of the mandible) were taken. Accuracy of reduction (displacement/no displacement) and positioning of the screws in relation to teeth and neurovascular structures were assessed.
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Fig. 2. Photograph showing use of special reduction forceps. Drill holes in buccal cortical bone were made through two small transbuccal tunnels, and trocar was used. Drill holes should be roughly central between superior border of alveolar process and inferior border of mandible. Reduction forceps were introduced through same transbuccal tunnels. Drill holes should penetrate only cortical bone to avoid nerve damage.
The follow-up schedule involved clinical examination 2 weeks after operation and clinical and radiologic examination (panoramic and Towne views of the mandible) 6 weeks and 3 months after surgery. During follow-up visits clinical signs relating to stability/instability of osteosynthesis, infection, occlusion, and mental-nerve function were recorded. Mental nerve function was evaluated in the same way as before operation by stroking the skin in the region of the mental nerve and chin with cotton wool and by pricking the same area with a dental probe. The subjective sensations of the patient were recorded. On radiologic evaluation positioning of repositioned fragments (displacement/no displacement) and bone healing (visibility of fracture gap and external callus) were assessed by one surgeon in the study group. Additional visits were arranged when needed.
RESULTS Postoperative radiographs revealed anatomic reduction without detectable displacement in LSF fractures in 21 (88%) cases. In two (8%) cases displacement was slight (1 to 2 mm). In one (4%) case osteosynthesis had broken down. There were no signs that the screws had engaged the mandibular canal or roots of the teeth in any patient.
Follow-up was complete within 3 months in 19 (86%) of 22 patients with LSF in place on leaving hospital. During follow-up clinical signs relating to instability of fixation and infection were noted in one (5%) patient and to infection in an additional two (9%) (see Complications). After surgery slight occlusal adjustment was needed in five (23%) patients (6, 7, 11, 16, and 23). In patients with only parasymphyseal fracture (13) no neurosensory disturbances (anesthesia, hypesthesia, or paresthesia) were noted before surgery. After surgery there were disturbances in eight (68%) patients in the region of the mental nerve, chin, or both. All of these recovered within 5.4 weeks on average (range 38 weeks). In three patients who underwent parasymphyseal LSF one-sided angular fractures were fixed with means other than lag-screws. Before surgery all had neurosensory disturbance on the same side as the angle fracture. After surgery two also had disturbances in the contralateral mental region. Disturbances evident before surgery resolved in 4 and 6 months except in one case, in which total anesthesia was still evident after 10 months. Disturbances caused by the operation resolved within 6 to 12 weeks.
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Fig. 3. Steps in performing lag screw fixation with AO/ASIF standard equipment. 1. Above, left. Drilling of near cortex with 2.7 mm drill bit. 2. Above, right. Countersinking. 3. Center, right. Drilling through entire bone with 2 mm drill bit with centering drill guide. 4. Center, left. Measuring screw length with depth gauge. 5. Below, right. Tapping. 6. Below, left. Screw in place.
In patients with angular fracture fixed with lagscrews there were neurosensory disturbance in two (29%) cases before surgery. They recovered after surgery in between 4 and 16 weeks. One (14%) patient with an angular fracture who had no preoperative disturbances had development of anesthesia in the ipsilateral mental-nerve region. It resolved in 19 weeks. In another four (57%) patients with angular fixation no postoperative disturbances occurred. No displacement of repositioned fragments or screws from previous positions was noted on radiologic evaluation during follow-up except in patient 12 (5%). At 6 weeks the fracture line was more visible in seven (37%) patients than it had been in the immediate postoperative radiograph. In six (32%) patients the appearance was exactly the same as in the postoperative view. In two (10%) patients the fracture gap was considered to have narrowed. In four (21%) it was invisible. At 3 months all fracture gaps were less visible than at 6 weeks, In 10 (53%) cases the fracture line could no longer be detected. No external callus formation was seen in any radiograph.
COMPLICATIONS Two (9%) complications occurred during surgery and in the immediate postoperative period. In one patient (11) the parasymphyseal and right-sided angular fractures were to be fixed with lag-screws. In both locations on drilling the outer cortex with a 2 m m drill bit, the bit fractured and remained inside the mandible. Preparation in relation to the parasymphyseal fracture was accomplished with a new drill bit, and LSF was performed in the normal way. In the angle the lag-screw did not provide adequate stability in relation to the fracture line. The screw was removed and the fracture line stabilized with a miniplate along the external oblique ridge. In another patient (14) postoperative radiographs revealed that the right angular L S F had broken after 3 days, although it had been considered to be stable during operation. The patient was taken to the operating department, the screw was removed, and the fracture was reduced and fixed with a miniplate along the external oblique ridge. Bone healing was subsequently uneventful. Slight mental nerve neurosensory
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Fig. 4. Postoperative radiograph shows perfect reductions and lag-screw fixations. deficit apparent before surgery disappeared in 4 weeks. During follow-up complications were noted in three (14%) cases. Three weeks after surgery patient 17 presented with swelling and discharge of pus around the left lower canine tooth in the fracture line. During primary operation the apex of this tooth had been found to be extensively exposed in the fracture gap. Local incision, peroral antibiotics, and root canal therapy resolved the situation. Subsequent healing was uneventful. Patient 12 presented 4 weeks after surgery with fever, pain, and massive swelling in the left cheek area. The left angular fracture with LSF was found to be unstable. The abscess was incised through a left submandibular incision, the screw was removed, and the fracture was restabilized with an 11hole AO/ASIF 2.7 m m reconstruction plate. An impacted left third molar was also removed. The postoperative course was uneventful, and the fracture went to union. Patient 11 had left angular pain 4 months after surgery. On clinical evaluation slight swelling and pain on palpation were noted in the left angular region, buccally. On radiologic evaluation resorption was detected in this region around the fractured drill bit. The drill bit was removed. The postoperative course was uneventful, with cessation of all symptoms and no permanent neurosensory deficit.
DISCUSSION Our first experience with LSF in treating mandibular-angle fractures was mixed. Although in five patients rigid osteosynthesis leading to good bone union was achieved, there were three failures that could be accounted for by instability. It would seem important
to manipulate fixation forcefully to check for instability after releasing M M F as recommended by Ellis and Ghali. 5 If stability is doubtful, it is better to remove the screw and stabilize the fracture with, for example, a miniplate instead of subjecting the patient to MMF. The most crucial factor in achieving sound compression is screw angulation in the anteroposteriot direction, which should be almost sagittal. 5 There is a tendency to drill the screw canal in a lingual direction, which results in the screw bit failing to hold in the thin lingual cortical bone. When drilling is then directed in an almost sagittal plane, it is difficult to find enough bone in the buccal cortex to hold the screw head after countersinking. The biomechanical validity of this fixation method has been shown in vitro. 16 There have been reports of success with LSF in angular fractures. In 50 patients Niederdellman and Shetty 4 reported that only 4% of patients needed major intervention because of complications resulting from infection. Ellis and Ghali 5 reported that 13% of their 30 patients needed similar interventions. In contrast to these findings, our early results were disappointing. It could be that this method is not practical for extensive use. Surgeons using this procedure should have a strong interest in and significant experience of LSF in fracture treatment. Our results with LSF used to treat mandibular parasymphyseal fractures were, however, promising. We saw two complications necessitating further procedures but not affecting fracture healing. One was a local infection related to a devitalized tooth in the fracture line and could not be related to the type of osteosynthesis. Nonvitality of teeth in dislocated fracture lines with exposure of the apex is high. 17 The
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other c o m p l i c a t i o n was related to faulty technique w h e n drilling, initially with a 2 m m bit. W e f o u n d that it is m a n d a t o r y to use sharp drill bits and to w i t h d r a w and a d v a n c e the bit at times to resist the t e n d e n c y o f the bit to c l o g in the far cortex. It is obvious that in creating e x t e n s i v e burr canals in bone that cooling and rinsing actions o f the c o o l a n t liquid are r e d u c e d at the far side o f the canal. It is also i m p o r t a n t in perf o r m i n g L S F in anterior fractures to a d v a n c e the 2 m m drill bit v e r y s l o w l y f r o m the m e d u l l a r y c a v i t y into the outer cortex; o t h e r w i s e the drill bit will slip along the inner surface o f the outer cortex and be f o r c e d into the angular region. In their study o f 41 patients subjected to L S F , Ellis and G h a l i 11 r e c o r d e d two p o s t o p e r a t i v e infections. O n e led to sequestrectomy, the other to r e m o v a l o f the fracture-line tooth and screw. External pin fixation was u n d e r t a k e n after surgery. In 1993, Assael118 r e p o r t e d a high i n c i d e n c e o f t e c h n i q u e - r e l a t e d failures w h e n surgeons w e r e perf o r m i n g L S F in a teaching l a b o r a t o r y setting during A O / A S I F courses. In our study w e saw no failures l e a d i n g to m a l p o s i t i o n i n g o f fragments or s e v e r a n c e o f n e u r o v a s c u l a r structures or teeth. This result is in a c c o r d a n c e with the clinical results o f Ellis and G h a li. l i In our patients p o s t o p e r a t i v e n e u r o s e n s o r y deficit was p r o b a b l y c a u s e d b y stretching o f the mental nerve and soft tissues during operation. Such disturbances w e r e transient in e v e r y case. It is usually practical to a p p l y one screw first along the b u l k y inferior b o r d e r o f the anterior m a n d i b l e and the s e c o n d at the level b e t w e e n the f o r m e r and the apexes o f the teeth. L i k e Ellis and G h a l i 11 w e b e l i e v e that the orthopedic principl e d e m a n d i n g p l a c e m e n t o f lagscrews a l o n g a course that bisects the angle b e t w e e n the outer cortex and the line o f fracture with the tip o f the screw penetrating the inner cortex 19 can be neg l e c t e d in p e r f o r m i n g L S F in m a n d i b u l a r p a r a s y m p h y s e a l fractures. W e p l a c e d screws from the b u c c a l outer c o r t e x across the fracture line in e v e r y case exc e p t one to repenetrate the b u c c a l outer cortex on the o p p o s i t e side o f the fracture. The centers o f the screws were situated r o u g h l y on the fracture line. The obliqueness o f the fracture line was not taken into account in directing drill bits. T h e r e always s e e m e d to b e so m a n y interdigitations in the fracture surfaces in this area that w e saw no t e n d e n c y o f fragments to override. P l a c i n g screws in a crisscross m a n n e r can be valuable, i f there is a d a n g e r o f there being insufficient b o n e left after c o u n t e r s i n k i n g two points o f entry b e s i d e each other. H o w e v e r , screws inserted in a crisscross m a n n e r take l o n g e r to r e m o v e than screws not inserted in this way. The c o n s i d e r a b l e d e g r e e o f c o m p r e s s i o n a c h i e v e d
with l a g - s c r e w s b e c o m e s e v i d e n t on tightening the screws during operation. In a p e r f e c t l y r e p o s i t i o n e d fracture the fracture line a l m o s t c o m p l e t e l y vanishes. It is important to understand that the stability o f this k i n d o f osteosynthesis relies solely on c o m p r e s s i o n b e t w e e n the fragments. I f there is fragmentation, this single stabilizing factor is lost, and the fracture m u s t be treated with b o n e plates and screws in a neutral position. It m i g h t be s u p p o s e d that c o m p r e s s i o n caused b y the screws w o u l d b e too extensive, resulting in b o n e necrosis and m a l i g n m e n t and l e a d i n g to m a l o c c l u sion. H o w e v e r , w e f o u n d no a b n o r m a l i t i e s o f b o n e healing on clinical or r a d i o l o g i c evaluation. Occlusal a d j u s t m e n t in the f o r m o f o c c l u s a l grinding was n e e d e d in five patients. A l l h a d c o n c o m i t a n t m a n d i b ular or m i d - f a c e fractures. It was not p o s s i b l e to determine reasons for m a l o c c l u s i o n in these patients. Ellis and Ghali 11 f o u n d no p o s t o p e r a t i v e realocclusion in 41 patients, 29 o f w h o m had associated m a n d i b u l a r fractures. F e a r o f i m p a i r e d b o n e healing and p o s t o p e r a t i v e m a l o c c l u s i o n w o u l d s e e m to be unjustified. CONCLUSIONS L a g - s c r e w fixation o f m a n d i b u l a r p a r a s y m p h y s e a l fractures is a practical and effective w a y o f fixing such fractures internally. It leads to g o o d b o n e healing without p e r m a n e n t n e u r o s e n s o r y deficit or inc r e a s e d risk o f m a l o c c l u s i o n . In m a n d i b u l a r angle fractures L S F is l i k e l y to b e too technique-sensitive to a l l o w its e x t e n s i v e use. REFERENCES
1. Bruce R, Fonseca RJ. Mandibular fractures. In: Fonseca RJ, Walker RV, editors. Oral and maxillofacial trauma. Philadelphia: WB Saunders Company, 1991:359-417. 2. Spiessl B. Rigid internal fixation of the mandible. A manual of AO/ASIF principles. Berlin, Germany: Springer Verlag, 1989. 3. Champy M, Lodde JP, Schmit R, et al. Mandibular osteosynthesis by miniature screwed plates via buccal approach. J Maxillofacial Surg 1978;6:14-21. 4. Niederdellmann H, Shetty V. Solitary lag screw osteosynthesis in the treatment of fractures of the angle of mandible: a retrospective study. Plast Reconstr Surg 1987;80:688-74. 5. Ellis E, Ghali G. Lag screw fixation of mandibular angle fractures. J Oral Maxillofac Surg 1991;49:234-43. 6. Farris P, Dierks E. Single oblique lag screw fixation of mandibular angle fractures. Laryngoscope 1992;102:1070-2. 7. Kitayama S. A new method of intra oral open reduction using a screw applied through the mandibular crest of condylar fractures. J Craniomaxillofac Surg 1989; 17:16-23. 8. Eckelt U. Zugscraubenosteosynthese bei Unterkiefergelenkfortsatzfracturen. Dtsch Z Mund Kiefer GesichtsChir 1991; 15:5!-7. 9. Krenkel C. Axial "anchor screw" (lag screw with biconcave washer) or "slanted screw" plate for osteosynthesis of fractures of the mandibular condylar process. J Craniomaxillofac Surg 1992;20:348-53.
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10. Kallela I, Soderholm A-L, Paukku P, Lindqvist C. Lag-screw osteosynthesis of mandibular condyle fractures: a clinical and radiological study. J Oral Maxillofac Surg 1995 ;53:1397-404. 11. Ellis E, Ghali G. Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 1991 ;49:13-21. 12. 12. Muller ME, Allg6ver M, Schneider R, Willenegger H. Manual of internal fixation. 3rd ed. Berlin: Springer-Verlag, 1995. 13. Iizuka T, Lindqvist C, Hallikainen D, Paukku P. Infection after rigid internal fixation of mandibular fractures. A clinical and radiological study. J Oral Maxillofac Surg 1991;49:58593. 14. Nishioka G, Van Sickels J. Transoral plating of mandibular angle fractures: a technique. Oral Surg 1988;66:531-5. 15. Niederdellmann H, Akuam oa-boateng E, Uhlig G. Lag-screw osteosynthesis: a new procedure for treating fractures of the mandibular angle. J Oral Surg 1981;9:938-40. 16. Shetty V, Caputo A. Biomechanical validation of the solitary lag screw technique for reducing mandibular angle fractures. J Oral Maxillofac Surg 1992;50:603-7. 17. Kamboozia A, Punnia-Moorthy A. The fate of teeth in mandibular fracture lines. A clinical and radiological follow-up study. Int J Oral Maxillofac Surg 1993;22:97-101. 18. Assael L. Evalution of rigid internal fixation of mandible fractures performed in the teaching laboratory. J Oral Maxillofac Surg 1993;51:1315-9.
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 1996 19. Leonard M. The use of lag screws in mandibular fractures. Otolaryngol Clin North Am 1987;20:479-93.
Reprint requests: Ilkka Kallela, MD, DDS Departmem of Maxillofacial Surgery Helsinki University Central Hospital Kasarmikatu 11-13, SF-00130 Helsinki, Finland
CORRECTION
In the article "Gingival mass as the primary manifestation of multiple myeloma: Report of two cases," which appeared in the July 1996 issue (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:75-9), the authors were Shiou-Hwei Lee, DDS, Jane-Jane Huang, DDS, Whei-Lin Pan, DDS, and Chin-Po Chan, DDS from Chang-Gang Memorial Hospital in Taipei, Taiwan.
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