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Use of lag screws for fractures of the mandibular body
J Oral Maxillofac Surg 54:1314-1316, 1996
Use of Lag Screws for Fractures Mandibular Body EDWARD
ELLIS
of the
III, DDS, MS*
Purpose: This article presents the results of treating fractures of the mandibular body using lag screws alone or lag screws inserted through bone plates. Patients and Methods: Thirty-one patients treated for fractures of the mandibular body using lag screws within a 5.5year period were retrospectively studied for complications. Nine patients were treated with lag screws only and 22 with a lag screw inserted through a bone plate. No patient was placed into postsurgical maxillomandibular fixation. Results: There were no intraoperative or postoperative complications, except for one dental abscess. Conc/usions: Lag screw fixation of mandibular body fractures is a reliable technique when these is sufficient obliquity of the fracture.
Lag screws provide a useful method of rigid fixation for fractures of the mandible. The lag screw technique was first introduced to maxillofacial surgery by Brons and Boering’ in 1970, who cautioned that at least two screws are necessary to prevent rotational movement of the fragments in oblique fractures of the mandible.’ Others have similarly illustrated the versatility of lag screws for fractures of the mandibular symphysis and angle.2-6 Lag screws are less useful in the body of the mandible than elsewhere. This is because the fractures that occur in this region generally are not located in the sagittal plane, with splitting of the buccal and lingual cortices. When such fractures do occur, however, they readily lend themselves to treatment with two or three lag screws in the same manner as a sagittal ramus osteotomy (Fig 1). Most fractures in the body of the mandible occur between the roots of teeth and continue through the inferior border without much obliquity. Such fractures are much more amenable to bone plate fixation than fixation with lag screws. Occasionally, however, as the
fracture courses inferiorly from the dentition, obliquity occurs in the area of the inferior border. This sagittal splitting of the bone lends itself to the application of a lag screw. Unfortunately, there is rarely room for two screws because of the presence of the inferior alveolar neurovascular bundle. In such instances, an hybrid technique, applying concepts of both bone plating and a lag screw, can be used.7 The purpose of this study was to analyze treatment results after use of lag screws to stabilize fractures of the mandibular body. Technique After application of maxillary and mandibular arch bars, a vestibular incision was made, and a subperiosteal dissection was used to expose the fracture. Care was taken around the mental nerve, which usually was dissected from the periosteum to mobilize it more freely. Once exposed, the fracture was assessed for the amount and direction of obliquity. The fracture was reduced and the occlusion reestablished by placing the patient into maxillomandibular fixation (MMF). If enough obliquity for the application of at least two bone screws was present, lag screws were inserted, taking care to avoid the mandibular neurovascular canal and roots of the teeth (Fig 1). If obliquity was only present along the inferior border, a five-hole mandibular bone plate was adapted so that the it rested passively on the buccal cortex below the level of the inferior alveolar neurovascular bundle (Fig 2). The plate was
* Professor, Oral and Maxillofacial Surgery, The University of Texas Southwestern Medical Center, Dallas, TX. Supported by a grant from the Chalmers J. Lyons AcademyJames R. Hayward Research Fund. Address correspondence and reprint requests to Dr Ellis: University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-9109. 0 1996 American Association 0278.2391/96/5411-0009$3,00/O
of Oral and Maxillofacial
Surgeons
1314
EDWARD
FIGURE lar body
ELLIS
1315
III
1. Illustration of a sagittal fracture treated with three lag screws.
through
the mandibu-
removed and a hole was prepared for a lag screw in the area of obliquity. This involved drilling the buccal cortex to the external diameter of the screw and the lingual cortex to the internal diameter of the screw. The hole was drilled so that it was perpendicular to the fracture line in the area where it crossed the fracture. The bone plate was then replaced and the lag screw inserted through the center hole. When tightened, the lag screw compressed the bone plate toward the lingual cortex, with the buccal cortex in between (Fig 2). All other screw holes were then drilled through both buccal and lingual cortices in the “neutral” position (no axial compression). The two screws in the bone plate anterior and posterior to the lag screw acted to prevent rotation about the center (lag) screw. Patients
ers had a contralateral fracture of the angle, symphysis, or condyle that had been stabilized using plate or screw fixation. Nine of the 31 patients had their fracture treated with lag screws only. In five of these patients, three lag screws were used; in four patients, only two screws were inserted. The remaining 22 patients had the lag screw inserted through a bone plate. A tooth in the line of fracture was encountered in 24 patients. Three patients had the tooth in the line of fracture removed at surgery because of avulsion, fracture, or dental pathologic condition. Only three of the nine patients treated by lag screws without a bone plate had a tooth in the line of fracture. Intraoperatively, reductions were judged as excellent in all patients. No patient was placed into postsurgical MMF. Follow-up ranged from 6 to 174 weeks, with a mean of 24 weeks. All fractures were found to be stable at follow-up appointments. There were no postsurgical complications of the body fracture in any patient, except one, who required extraction of a tooth in the line of fracture 2 weeks after surgery because of an abscess. The fracture healed uneventfully. All patients had reestablishment of their pretraumatic occlusal relationship. Discussion Besides the many advantages that rigid fixation of mandibular fractures offer, the use of lag screws alone, has several unique advantages over bone plate fixation. The major advantage is that lag screws can be applied more rapidly, because the time-consuming task of adapting a bone plate is eliminated. This also allows a novice to achieve a more anatomically accurate re-
and Methods
All dentate patients treated for fractures of the mandibular body with lag screws between July 1, 1989 and December 3 1, 1994, who had at least 6 weeks of follow-up, were included in this study. For purposes of this study, fractures through or distal to the mental foramen and anterior to the third molar were classified as “body” fractures. The cases were evaluated for the following information: 1) additional fractures; 2) presence of a tooth in the line of fracture; 3) extraction of tooth in line of fracture; 4) complications during surgery; 5) postsurgical occlusal relationship, and; 6) postsurgical complications, which were defined as a need for further surgical intervention. Results Thirty-one patients were identified. Seven patients had isolated fractures of the mandibular body; all oth-
FIGURE 2. Illustration of a fracture through the mandibular body with sufficient obliquity for only one lag screw. In such circumstances, placement of the lag screw through a bone plate produces ideal fixation. The remaining screws are inserted in the “neutral” position (ie, no axial compression).
1316
duction, because it takes considerable skill to perfectly adapt a bone plate to the complex contours of the mandible. In our experience, displacement of bone fragments is much more common when using a bone plate, because the adequacy of plate contouring is not known until the screws are inserted, and the plate is drawn to the mandible. Displacement of bone segments almost never occurs while applying lag screw fixation when one adheres to the details previously described. Furthermore, lag screws permit the rapid application of fixation without a reduction in rigidity. This is especially evident when the screws are applied perpendicular to the fracture. The fracture gap frequently completely disappears from sight because of the great amount of compression imparted by the screws. Another advantage is the cost savings; screws cost little compared to with a bone plate. When insufficient obliquity is present to accommodate a minimum of two lag screws, one must resort to bone plate fixation if rigid internal stabilization is desired. However, with obliquity of the fracture along the inferior border, axial compression using a bone plate is contraindicated. Compression plating of such fractures causes overriding and displacement of the obliquely fractured cortices (Fig 3). In such fractures, using a noncompression plate is an option. However, more stability can be provided by applying a lag screw through a bone plate across the area of obliquity, and then using the other screws to prevent rotation (Fig 2). The results of this retrospective study and clinical experience show that lag screw fixation of mandibular body fractures is an extremely simple and successful method of rigidly securing the fragments, permitting active use of the mandible during healing. In this series of cases, only one minor complication was encountered that required secondary surgical intervention (extraction of a tooth). Unfortunately, as shown by the sample size of this study, most fractures of the body of the mandible do not readily lend themselves to fixation
USE
OF LAG
SCREWS
FOR
MANDIBULAR
BODY
FRACTURES
FIGURE 3. Illustration demonstrating why application of axial compression is contraindicated in oblique fractures. The obliquity of the fracture results in overriding and displacement of the fragments when axial compression is applied by compression plate osteosynthesis. This causes improper alignment of the fragments with resultant malocclusion, and premature loosening of the fixation.
with lag screws. However, it is worthwhile to keep these techniques in mind for situations in which they may apply. References 1. Brons R, Boering G: Fractures of the mandibular body treated by stable internal fixation: A preliminary report. J Oral Surg 28:407, 1970 2. Niederdellmann H, Schilli W, Dtiker J, et al: Osteosynthesis of mandibular fractures using lag screws. Int .I Oral Surg 5:117, 1976 3. Niederdellmann H, Akuamoa-Boateng E, Uhlig G: Lag-screw osteosynthesis: A new procedure for treating fractures of the mandibular angle. J Oral Surg 39:938, 1981 4. Leonard MS: The use of lag screws in mandibular fractures. Otolaryngol Clin North Am 20:479, 1987 5. Ellis E, Ghali GE: Lag screw fixation of mandibular angle fractures. J Oral Maxillofac Surg 49:234, 1991 6. Ellis E, Ghali GE: Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 49:13, 1991 7. Spiessl B: Internal Fixation of the Mandible. New York, NY, Springer-Verlag, 1989
Use of Lag Screws for Fractures Mandibular Body EDWARD
ELLIS
of the
III, DDS, MS*
Purpose: This article presents the results of treating fractures of the mandibular body using lag screws alone or lag screws inserted through bone plates. Patients and Methods: Thirty-one patients treated for fractures of the mandibular body using lag screws within a 5.5year period were retrospectively studied for complications. Nine patients were treated with lag screws only and 22 with a lag screw inserted through a bone plate. No patient was placed into postsurgical maxillomandibular fixation. Results: There were no intraoperative or postoperative complications, except for one dental abscess. Conc/usions: Lag screw fixation of mandibular body fractures is a reliable technique when these is sufficient obliquity of the fracture.
Lag screws provide a useful method of rigid fixation for fractures of the mandible. The lag screw technique was first introduced to maxillofacial surgery by Brons and Boering’ in 1970, who cautioned that at least two screws are necessary to prevent rotational movement of the fragments in oblique fractures of the mandible.’ Others have similarly illustrated the versatility of lag screws for fractures of the mandibular symphysis and angle.2-6 Lag screws are less useful in the body of the mandible than elsewhere. This is because the fractures that occur in this region generally are not located in the sagittal plane, with splitting of the buccal and lingual cortices. When such fractures do occur, however, they readily lend themselves to treatment with two or three lag screws in the same manner as a sagittal ramus osteotomy (Fig 1). Most fractures in the body of the mandible occur between the roots of teeth and continue through the inferior border without much obliquity. Such fractures are much more amenable to bone plate fixation than fixation with lag screws. Occasionally, however, as the
fracture courses inferiorly from the dentition, obliquity occurs in the area of the inferior border. This sagittal splitting of the bone lends itself to the application of a lag screw. Unfortunately, there is rarely room for two screws because of the presence of the inferior alveolar neurovascular bundle. In such instances, an hybrid technique, applying concepts of both bone plating and a lag screw, can be used.7 The purpose of this study was to analyze treatment results after use of lag screws to stabilize fractures of the mandibular body. Technique After application of maxillary and mandibular arch bars, a vestibular incision was made, and a subperiosteal dissection was used to expose the fracture. Care was taken around the mental nerve, which usually was dissected from the periosteum to mobilize it more freely. Once exposed, the fracture was assessed for the amount and direction of obliquity. The fracture was reduced and the occlusion reestablished by placing the patient into maxillomandibular fixation (MMF). If enough obliquity for the application of at least two bone screws was present, lag screws were inserted, taking care to avoid the mandibular neurovascular canal and roots of the teeth (Fig 1). If obliquity was only present along the inferior border, a five-hole mandibular bone plate was adapted so that the it rested passively on the buccal cortex below the level of the inferior alveolar neurovascular bundle (Fig 2). The plate was
* Professor, Oral and Maxillofacial Surgery, The University of Texas Southwestern Medical Center, Dallas, TX. Supported by a grant from the Chalmers J. Lyons AcademyJames R. Hayward Research Fund. Address correspondence and reprint requests to Dr Ellis: University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-9109. 0 1996 American Association 0278.2391/96/5411-0009$3,00/O
of Oral and Maxillofacial
Surgeons
1314
EDWARD
FIGURE lar body
ELLIS
1315
III
1. Illustration of a sagittal fracture treated with three lag screws.
through
the mandibu-
removed and a hole was prepared for a lag screw in the area of obliquity. This involved drilling the buccal cortex to the external diameter of the screw and the lingual cortex to the internal diameter of the screw. The hole was drilled so that it was perpendicular to the fracture line in the area where it crossed the fracture. The bone plate was then replaced and the lag screw inserted through the center hole. When tightened, the lag screw compressed the bone plate toward the lingual cortex, with the buccal cortex in between (Fig 2). All other screw holes were then drilled through both buccal and lingual cortices in the “neutral” position (no axial compression). The two screws in the bone plate anterior and posterior to the lag screw acted to prevent rotation about the center (lag) screw. Patients
ers had a contralateral fracture of the angle, symphysis, or condyle that had been stabilized using plate or screw fixation. Nine of the 31 patients had their fracture treated with lag screws only. In five of these patients, three lag screws were used; in four patients, only two screws were inserted. The remaining 22 patients had the lag screw inserted through a bone plate. A tooth in the line of fracture was encountered in 24 patients. Three patients had the tooth in the line of fracture removed at surgery because of avulsion, fracture, or dental pathologic condition. Only three of the nine patients treated by lag screws without a bone plate had a tooth in the line of fracture. Intraoperatively, reductions were judged as excellent in all patients. No patient was placed into postsurgical MMF. Follow-up ranged from 6 to 174 weeks, with a mean of 24 weeks. All fractures were found to be stable at follow-up appointments. There were no postsurgical complications of the body fracture in any patient, except one, who required extraction of a tooth in the line of fracture 2 weeks after surgery because of an abscess. The fracture healed uneventfully. All patients had reestablishment of their pretraumatic occlusal relationship. Discussion Besides the many advantages that rigid fixation of mandibular fractures offer, the use of lag screws alone, has several unique advantages over bone plate fixation. The major advantage is that lag screws can be applied more rapidly, because the time-consuming task of adapting a bone plate is eliminated. This also allows a novice to achieve a more anatomically accurate re-
and Methods
All dentate patients treated for fractures of the mandibular body with lag screws between July 1, 1989 and December 3 1, 1994, who had at least 6 weeks of follow-up, were included in this study. For purposes of this study, fractures through or distal to the mental foramen and anterior to the third molar were classified as “body” fractures. The cases were evaluated for the following information: 1) additional fractures; 2) presence of a tooth in the line of fracture; 3) extraction of tooth in line of fracture; 4) complications during surgery; 5) postsurgical occlusal relationship, and; 6) postsurgical complications, which were defined as a need for further surgical intervention. Results Thirty-one patients were identified. Seven patients had isolated fractures of the mandibular body; all oth-
FIGURE 2. Illustration of a fracture through the mandibular body with sufficient obliquity for only one lag screw. In such circumstances, placement of the lag screw through a bone plate produces ideal fixation. The remaining screws are inserted in the “neutral” position (ie, no axial compression).
1316
duction, because it takes considerable skill to perfectly adapt a bone plate to the complex contours of the mandible. In our experience, displacement of bone fragments is much more common when using a bone plate, because the adequacy of plate contouring is not known until the screws are inserted, and the plate is drawn to the mandible. Displacement of bone segments almost never occurs while applying lag screw fixation when one adheres to the details previously described. Furthermore, lag screws permit the rapid application of fixation without a reduction in rigidity. This is especially evident when the screws are applied perpendicular to the fracture. The fracture gap frequently completely disappears from sight because of the great amount of compression imparted by the screws. Another advantage is the cost savings; screws cost little compared to with a bone plate. When insufficient obliquity is present to accommodate a minimum of two lag screws, one must resort to bone plate fixation if rigid internal stabilization is desired. However, with obliquity of the fracture along the inferior border, axial compression using a bone plate is contraindicated. Compression plating of such fractures causes overriding and displacement of the obliquely fractured cortices (Fig 3). In such fractures, using a noncompression plate is an option. However, more stability can be provided by applying a lag screw through a bone plate across the area of obliquity, and then using the other screws to prevent rotation (Fig 2). The results of this retrospective study and clinical experience show that lag screw fixation of mandibular body fractures is an extremely simple and successful method of rigidly securing the fragments, permitting active use of the mandible during healing. In this series of cases, only one minor complication was encountered that required secondary surgical intervention (extraction of a tooth). Unfortunately, as shown by the sample size of this study, most fractures of the body of the mandible do not readily lend themselves to fixation
USE
OF LAG
SCREWS
FOR
MANDIBULAR
BODY
FRACTURES
FIGURE 3. Illustration demonstrating why application of axial compression is contraindicated in oblique fractures. The obliquity of the fracture results in overriding and displacement of the fragments when axial compression is applied by compression plate osteosynthesis. This causes improper alignment of the fragments with resultant malocclusion, and premature loosening of the fixation.
with lag screws. However, it is worthwhile to keep these techniques in mind for situations in which they may apply. References 1. Brons R, Boering G: Fractures of the mandibular body treated by stable internal fixation: A preliminary report. J Oral Surg 28:407, 1970 2. Niederdellmann H, Schilli W, Dtiker J, et al: Osteosynthesis of mandibular fractures using lag screws. Int .I Oral Surg 5:117, 1976 3. Niederdellmann H, Akuamoa-Boateng E, Uhlig G: Lag-screw osteosynthesis: A new procedure for treating fractures of the mandibular angle. J Oral Surg 39:938, 1981 4. Leonard MS: The use of lag screws in mandibular fractures. Otolaryngol Clin North Am 20:479, 1987 5. Ellis E, Ghali GE: Lag screw fixation of mandibular angle fractures. J Oral Maxillofac Surg 49:234, 1991 6. Ellis E, Ghali GE: Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 49:13, 1991 7. Spiessl B: Internal Fixation of the Mandible. New York, NY, Springer-Verlag, 1989