Lag-screw fixation of anterior mandibular fractures using biodegradable polylactide screws: a preliminary report

Mechanical Properties and Corrosion Rate of ZnAg3 as a Novel Bioabsorbable Material for Osteosynthesis

Osteosynthesis in fracture treatment typically uses hardware that remains in the patient's body, which brings a permanent risk of negative side effects such as foreign body reactions or chronic inflammation. Bioabsorbable materials, however, can degrade and slowly be replaced by autologous bone tissue. A suitable material is requested to offer great biocompatibility alongside excellent mechanical properties and a reasonable corrosion rate. Zinc-silver alloys provide these characteristics, which makes them a promising candidate for research. This study investigated the aptitude as a bioabsorbable implant of a novel zinc-silver alloy containing 3.3 wt% silver (ZnAg3). Here, the tensile strength as well as the corrosion rate in PBS solution (phosphate buffered solution) of ZnAg3 were assessed. Furthermore, shear tests, including fatigue and quasi-static testing, were conducted with ZnAg3 and magnesium pins (MAGNEZIX®, Syntellix AG, Hannover, Germany), which are already in clinical use. The detected corrosion rate of 0.10 mm/year for ZnAg3 was within the proposed range for bioabsorbable implants. With a tensile strength of 237.5 ± 2.12 MPa and a shear strength of 144.8 ± 13.2 N, ZnAg3 satisfied the mechanical requirements for bioabsorbable implants. The fatigue testing did not show any significant difference between ZnAg3 and magnesium pins, whereas both materials withstood the cyclic loading. Thus, the results support the assumption that ZnAg3 is qualified for further investigation.

An overview of translational research in bone graft biomaterials

Natural bone healing is often inadequate to treat fractures with critical size bone defects and massive bone loss. Immediate surgical interventions through bone grafts have been found to be essential on such occasions. Naturally harvested bone grafts, although are the preferred choice of the surgeons; they suffer from serious clinical limitations, including disease transmission, donor site morbidity, limited supply of graft etc. Synthetic bone grafts, on the other hand, offer a more clinically appealing approach to decode the pathways of bone repair through use of tissue engineered biomaterials. This article critically retrospects the translational research on various engineered biomaterials towards bringing transformative changes in orthopaedic healthcare. The first section of the article discusses about composition and ultrastructure of bone along with the global perspectives on statistical escalation of bone fracture surgeries requiring use of bone grafts. The next section reviews the types, benefits and challenges of various natural and synthetic bone grafts. An overview of clinically relevant biomaterials from traditionally used metallic, bioceramic, and biopolymeric biomaterials to new generation composites have been summarised. Finally, this narrative review concludes with the discussion on the emerging trends and future perspectives of the promising bone grafts.

Resorbable Versus Titanium Rigid Fixation for Pediatric Mandibular Fractures: A Systematic Review, Institutional Experience and Comparative Analysis

Study Design

Pediatric mandible fractures mandate special consideration because of unerupted teeth, mixed dentition, facial growth and the inability to tolerate maxillomandibular fixation. No consensus exists as to whether resorbable or titanium plating systems are superior with regards to clinical outcomes.

Objective

This study aims to systematically review and compare the outcomes of both material types in the treatment of pediatric mandible fractures.

Methods

After PROSPERO registration, studies from 1990-2020 publishing on outcomes of ORIF of pediatric mandible fractures were systematically reviewed according to PRISMA guidelines. An additional retrospective review was conducted at a pediatric level 1 trauma center.

Results

1,144 patients met inclusion criteria (30.5% resorbable vs. 69.5% titanium). Total complication rate was 13%, and 10% required a second, unplanned operation. Complication rates in the titanium and resorbable groups were not significantly different (14% vs. 10%; P = 0.07), and titanium hardware was more frequently removed on an elective basis (P < 0.001). Condylar/sub-condylar fractures were more often treated with resorbable hardware (P = 0.01); whereas angle fractures were more often treated with titanium hardware (P < 0.001). Within both cohorts, fracture type did not increase the risk of complications, and comparison between groups by anatomic level did not demonstrate any significant difference in complications.

Conclusions

Pediatric mandible fractures requiring ORIF are rare, and hardware-specific outcomes data is scarce. This study suggests that titanium and resorbable plating systems are equally safe, but titanium hardware often requires surgical removal. Surgical approach should be tailored by fracture anatomy, age-related concerns and surgeon preference.

Resorbable Versus Titanium Hardware for Rigid Fixation of Pediatric Upper and Midfacial Fractures: Which Carries a Lower Risk Profile?

PURPOSE

Titanium associated risks have led to interest in resorbable hardware for open reduction and internal fixation (ORIF) of pediatric facial fractures. This study aims to systematically review and compare the outcomes of titanium/resorbable hardware used for ORIF of upper/midfacial fractures to determine which hardware carries a higher complication rate in the pediatric patient.

METHODS

Studies published between 1990 and 2020 on the ORIF of pediatric upper/midfacial fractures were systematically reviewed. A retrospective institutional review was also conducted, and both arms were compiled for final analysis. The primary predictor value was the type of hardware used and the primary outcome was the presence of a complication. Fisher's exact test and 2-proportion 2-tailed z-test calculations were used to determine statistical significance, which was defined as a P value < .05. The low quality of published evidence precluded meta-analysis.

RESULTS

Systematic review of 23 studies identified 659 patients, and 77 patients were identified in the institutional review. A total of 736 patients (299 resorbable, 437 titanium) were included in the final analysis. Total complication rate was 22.8%. The titanium group had a higher complication rate (27 vs 16.7%; P < .01), and more often underwent elective hardware removal (87.3 vs 0%, P < .01). In each hardware subgroup, the incidence of complications was analyzed by fracture site. In the titanium group, complication incidence was higher when treating maxillary fractures (32.8 vs 22.9%, P = .03). When comparing the 2 hardware groups by fracture site, maxillary fractures had a higher rate of complications when treated by titanium hardware compared with resorbable hardware (32.8 vs 18%, P < .01).

CONCLUSIONS

Upper/midfacial pediatric fractures requiring ORIF, especially maxillary fractures, may be best treated with resorbable hardware. Additional hardware-specific outcomes data is encouraged.

Change in Pull-Out Force during Resorption of Magnesium Compression Screws for Osteosynthesis of Mandibular Condylar Fractures

BACKGROUND

Magnesium has been used as degradable fixation material for osteosynthesis, but it seems that mechanical strength is still a current issue in these fixations. The aim of this study was to evaluate the axial pull-out force of compression headless screws made of magnesium alloy during their resorption.

METHODS

The tests included screws made for osteosynthesis of the mandible head: 2.2 mm diameter magnesium alloy MgYREZr (42 screws) and 2.5 mm diameter polylactic-co-glycolic acid (PLGA) (42 pieces, control). The screws were resorbed in Sørensen's buffer for 2, 4, 8, 12, and 16 weeks, and force was measured as the screw was pulled out from the polyurethane block.

RESULTS

The force needed to pull the screw out was significantly higher for MgYREZr screws than for PLGA ones (p < 0.01). Within eight weeks, the pull-out force for MgYREZr significantly decreased to one third of its initial value (p < 0.01). The dynamics of this decrease were greater than those of the pull-out force for PLGA screws (p < 0.05). After these eight weeks, the values for metal and polymer screws equalized. It seems that the described reduction of force requires taking into account when using magnesium screws. This will provide more stable resorbable metallic osteosynthesis.

Bioabsorbable Osteofixation Materials for Maxillofacial Bone Surgery: A Review on Polymers and Magnesium-Based Materials

Clinical application of osteofixation materials is essential in performing maxillofacial surgeries requiring rigid fixation of bone such as trauma surgery, orthognathic surgery, and skeletal reconstruction. In addition to the use of titanium plates and screws, clinical applications and attempts using bioabsorbable materials for osteofixation surgery are increasing with demands to avoid secondary surgery for the removal of plates and screws. Synthetic polymeric plates and screws were developed, reaching satisfactory physical properties comparable to those made with titanium. Although these polymeric materials are actively used in clinical practice, there remain some limitations to be improved. Due to questionable physical strength and cumbersome molding procedures, interests in resorbable metal materials for osteofixation emerged. Magnesium (Mg) gained attention again in the last decade as a new metallic alternative, and numerous animal studies to evaluate the possibility of clinical application of Mg-based materials are being conducted. Thanks to these researches and studies, vascular application of Mg-based biomaterials was successful; however, further studies are required for the clinical application of Mg-based biomaterials for osteofixation, especially in the facial skeleton. The review provides an overview of bioabsorbable osteofixation materials in maxillofacial bone surgery from polymer to Mg.

Use of Transgingival Lag Screw Osteosynthesis in the Management of Alveolar Process Fracture

The purpose of this study is to check the efficacy of transgingival lag screw osteosynthesis in alveolar process fractures of maxilla and mandible. A single-arm nonrandomized observational study was performed for the treatment of alveolar process fractures of maxilla and mandible. In this study, 20 mixed age group patients with alveolar process fracture were included. All the patients were treated by a 2.0-mm transgingival screw fixation under local or general anesthesia. All the patients were evaluated for fracture stability, anatomical reduction, bone loss and bone resorption of alveolar process, tooth loss, and wound infection at 3 months of follow-up. A simple descriptive statistical analysis was done to evaluate the parameters and it was shown that the treatment of alveolar process fracture with two or three lag screws provides adequate fracture stability and anatomical reduction with no signs of bone loss and tooth loss, and wound infections were noted post lag screw fixation. The study concludes that transgingival lag screw fixation is a suitable alternative for alveolar process fractures in all the age groups and two to three lag screws are generally sufficient to fix fractured alveolar process either under local anesthesia or general anesthesia.

Application of biodegradable plates for treating pediatric mandibular fractures

OBJECTIVE

We assessed the clinical results of a biodegradable plate system for the internal fixation of mandibular fractures in children, and observed the imaging features of fracture healing and bone changes around the biodegradable plates and screws during follow-up.

PATIENTS AND METHODS

We enrolled 39 patients (22 male, 17 female, average age 4 years 10 months) with different mandibular fractures. We used 2.0-mm resorbable plates to repair the fractures. Postoperative follow-up ranged from 6 months to 5 years; average follow-up was 1 year 2 months. The outcome measures identified and assessed included facial symmetry, mouth opening, occlusal relationship, infection, nonunion, malunion, and plate dehiscence.

RESULTS

We fixed 42 fractures with 43 resorbable plates; the fracture site of one patient (aged 11 years 3 months) was fixed with two plates. Two patients developed small fistulas at the intraoral incision 2 months after surgery; the fistulas healed after 1 month without special treatment. In the other patients, the incision healed well, there was facial symmetry, mouth opening was >35 mm, and occlusion was good. Follow-up computed tomography examination data were available for 20 cases, and revealed different degrees of radiolucency indicating that osteolysis had occurred. Radiolucency was observed around the resorbable plates 1 month after the surgery. The extent and depth of the radiolucent region were obvious within 1 year of surgery. In the second year, there were obvious repairs, with the bony defect areas becoming shallower. After 2 years, the bony defect areas had almost disappeared.

CONCLUSION

Biodegradable fixation devices are safe and efficient for treating pediatric mandibular fractures. Osteolysis commonly follows biodegradable fixation of pediatric mandibular fractures, and has no adverse effect on fracture healing.

Comparative evaluation of bite forces in patients after treatment of mandibular fractures with miniplate osteosynthesis and internal locking miniplate osteosynthesis

Aims and Objectives:

The aim of present study was to compare the stability of fractured mandibular fragments under functional load, when fixed with conventional miniplate and internal locking miniplate.

Materials and Methods:

Bite force (in kg) recorded in twenty mandible fractured patients and fifty normal healthy individuals. Bite force was measured at incisor and molar regions. Comparative evaluation of bite force generated was performed between 10 cases treated with conventional miniplates and 10 cases treated with internal locking miniplates. Bite force generated by patients in mandibular fracture between symphysis and the angle of mandible was recorded in incisor and molar regions preoperatively. The fracture fragments were fixed using the above fixation techniques. Then same recording was undertaken on the 7^th, 14^th, 21^st, 28^th, and 90^th days postoperatively.

Results:

Bite force generated by patients treated with locking plates at the 7^th, 14^th, 21^st, 28^th, and 90^th postoperative days was significantly higher as compared to those in patients treated with miniplates.

Conclusion:

It was observed in our study that the locking plate/screw system offers significant advantages over the conventional plating system. There are no intraoperative difficulties associated with placement of the plate.

Bioabsorbable fixation devices in trauma and bone surgery: current clinical standing

Bioabsorbable fixation devices are increasingly used in trauma, orthopedic and craniomaxillofacial surgery. The devices are essentially made of polylactic acid and/or polyglycolic acid polymers. Ultra-high-strength implants are manufactured from such polymers using self-reinforcing techniques. Implants are available for stabilization of fractures, osteotomies, bone grafts and fusions, as well as for reattachment of ligaments, tendons, meniscal tears and other soft tissue structures. As these implants are completely absorbed, the need for a removal operation is overcome and long-term interference with tendons, nerves and the growing skeleton is avoided. The risk of implant-associated stress shielding, peri-implant osteoporosis and infections is reduced. Implants do not interfere with clinical imaging. Current clinical use of bioabsorbable devices is reviewed.

Anchor lag screw vs conventional lag screw in mandibular fractures: A series of 30 cases

Lag screw osteosynthesis is a well proven technique. Its application is limited by the fact that the spherical head of the screw act as wedge. Combining this screw with a bioconcave washer has broadened the range of applications for lag screw osteosynthesis in the maxillofacial region.

PURPOSE

The aim of the study was to compare the efficacy of anchor lag screw with conventional lag screw in anterior mandibular fractures.

PATIENTS AND METHOD

Thirty patients with anterior mandible fractures with no concomitant fractures, infection or extraoral communication, who visited our outpatient Department of Oral and Maxillofacial Surgery, were included in the study after obtaining their informed consent. Patients were randomly divided into two groups; where Group A underwent fixation using conventional lag screw and Group B anchor lag screw. The fixation system used included 2 mm titanium lag screws of sizes 25 mm, 27 mm and 30 mm and 3 mm titanium bioconcave washer. At each follow up visit, clinical data was collected detailing clinical presentation of healing and radiographic findings.

RESULTS

Radiographic features at post surgery evaluation indicated loss of bone contact around the screw head and bone resorption in five patients of Group A, thus causing loosening of lag screw whereas none of the patient in Group B, was found to have any such complication.

CONCLUSIONS

The findings support the hypothesis that bioconcave washer aids in holding up the farthest fragment at the interface of the fracture fragment. Application of bioconcave washer provides easy loading of lag screw.

Crystallization study and comparative in vitro-in vivo hydrolysis of PLA reinforcement ligament

In the present work, the crystallization behavior and in vitro-in vivo hydrolysis rates of PLA absorbable reinforcement ligaments used in orthopaedics for the repair and reinforcement of articulation instabilities were studied. Tensile strength tests showed that this reinforcement ligament has similar mechanical properties to Fascia Latta, which is an allograft sourced from the ilio-tibial band of the human body. The PLA reinforcement ligament is a semicrystalline material with a glass transition temperature around 61 °C and a melting point of ~178 °C. Dynamic crystallization revealed that, although the crystallization rates of the material are slow, they are faster than the often-reported PLA crystallization rates. Mass loss and molecular weight reduction measurements showed that in vitro hydrolysis at 50 °C initially takes place at a slow rate, which gets progressively higher after 30-40 days. As found from SEM micrographs, deterioration of the PLA fibers begins during this time. Furthermore, as found from in vivo hydrolysis in the human body, the PLA reinforcement ligament is fully biocompatible and after 6 months of implantation is completely covered with flesh. However, the observed hydrolysis rate from in vivo studies was slow due to high molecular weight and degree of crystallinity.

Skeletal stability and morbidity with self-reinforced P (L/DL) LA resorbable osteosynthesis in bimaxillary orthognathic surgery

INTRODUCTION

We present a retrospective study of 30 consecutive cases of bimaxillary orthognathic surgery with biodegradable self-reinforced poly-L/DL-lactide plates and tacks, for the same indication of Angle class III malocclusion. We reported the skeletal stability and morbidity at 1 year after surgery.

PATIENTS AND METHODS

All patients underwent bimaxillary procedure. We used self-reinforced poly-L/DL lactic acid copolymer. Stabilization of Lefort I osteotomy was achieved by four plates L-shaped. Sagittal split osteotomies were fixed by two straight-plates. Lateral cephalograms were taken before (T0), soon after (T1) and more than 1 year after surgery (T2). Eight standard landmarks and four angular measurements were taken into account. All differences of the landmarks and angles were measured at T1 and T2. The regular clinical follow-up was scheduled for a minimum period of 1 year.

RESULTS

The mean advanced maxillary was 3.33 mm and the mean mandibular setback was 6.13 mm. The mean mandibular relapse was 2.2 mm (non-significant). Horizontal maxilla mean variation was 0.8 mm at 1 year at A-point. Vertical maxilla stability depends on maxillary movements: impaction stability is better as an isolated advancement or associated with pull-down movement. We found six inflammatory reactions and two of them need the removal of the plates.

CONCLUSION

Bimaxillary orthognathic procedure with bioresorbable osteosynthesis is a reliable and reproducible method. Angle class III malocclusions could be entirely and successfully managed with bioresorbable osteosynthesis. The stability and suites at 1 year are comparable to titanium osteosynthesis.

Use of resorbable implants for mandibular fixation: a systematic review

Titanium plating is recognized as the criterion standard for the treatment of mandibular fractures and osteotomies. Use of resorbable implants is well documented in the literature for a range of craniofacial fractures. However, no clear review exists of the use of resorbable implants on the mandible. In this systematic review, we searched MEDLINE/PubMed and the Cochrane Database for studies of resorbable mandibular fixation. Two independent reviewers analyzed the search results using specific inclusion/exclusion criteria. Twenty-two articles detailing 19 studies, including 1 randomized controlled trial were analyzed in this study. These studies included fixation of mandibular fractures at various locations or fixation of bilateral sagittal split osteotomies. Overall, we found a total of 326 patients treated with resorbable plates and screws and 112 patients treated with resorbable screws alone. Analysis of these studies indicates that several material types are used in resorbable mandibular implants, including poly-L-lactic acid (PLLA) and 70% poly-L-lactic acid/30% poly-D,L-lactic acid (PLLA 70/PDLLA 30), coming from at least 10 different manufacturers. Mean follow-up ranged from 3 to 348 weeks. Based on the reported data, we found a total of 14 to 15 infections, 2 foreign body reactions, 7 malocclusions, 8 malunions, and 8 to 10 premature removals in the plate group and 1 foreign body reaction and 2 malocclusions in the screws-only group. These results should be interpreted in the context of the patient selection criteria in the studies. This systematic review demonstrates the need for further randomized controlled trials in this area and concludes with such a study design.

Fixation properties of a biodegradable "free-form" osteosynthesis plate

The Inion FreedomPlate, a "free-form" osteosynthesis plate, is a biodegradable plate with just pilot holes for drilling. The construction of the plate allows the surgeon a placement of screws in optimal position. The screw heads can either be countersunk into the plate or cut off. Furthermore, the plate can be cut and contoured to match the bone. The aim of this study was to determine the mechanical properties of the Inion FreedomPlate compared to a conventional biodegradable plate. Acrylic pipes were fixed together with plates and screws. Tensile and cantilever bending tests were performed to measure the fixation properties. In the tensile test, the samples were loaded with a constant speed of 5 mm/min until failure of fixation. The yield load, maximum failure load, and initial stiffness were recorded, and the failure mode was visually determined. In the cantilever bending test, the samples were loaded with a constant speed of 50 mm/min (with a moment arm of 45 mm) until failure of fixation. The yield bending moment and initial stiffness were recorded, and the failure mode was determined. The results of the study show that the new free-form plate provides at least as strong fixation as the tested conventional biodegradable plate. No clinically relevant difference was found between free-form plates fixed with into-the-plate countersunk screws and those fixed with screws without heads.

Indications and limitations in resorbable P(L70/30DL)LA osteosyntheses of displaced mandibular fractures in 4.5-year follow-up

BACKGROUND

This study evaluates prospective 4.5-year follow-up of available poly(l-lactide-co-dl-lactide) [P(L70/30DL)LA] resorbable plate osteosyntheses in displaced traumatic and pathological mandibular fractures.

METHODS

P(L70/30DL)LA miniplates and screws were used to fixate 50 displaced fractures in 30 patients, aged 1 to 83 years, with their informed consent. There were 15 traumatic paramedian, seven corpus, 11 angle, and 10 condyle fractures, and seven pathological fractures due to atrophy, osteomyelitis, or third molar osteotomy. Double osteosyntheses were preferred, with one monocortical plate at the dentoalveolar basis (6-mm screws) and a second plate at the inferior margin (8-mm screws).

RESULTS

The average follow-up was 31 months (range, 6 to 53 months). Fifteen (100 percent) traumatic paramedian, seven (100 percent) corpus, 10 (91 percent) angle, 10 (100 percent) condylar, and three (43 percent) pathological fractures healed primarily. Two mandibular angle fractures, traumatic and pathological, each initially healed, but 6 weeks postoperatively the first fracture re-dislocated on removal of a dental impression by the family dentist, and the second re-dislocated after mastication of hard food. One atrophic corpus fracture developed a rigid fibrous union in an 83-year-old patient; a preexistent osteomyelitis and fracture progressed to further bone loss and finally required preformed fibula reconstruction.

CONCLUSIONS

Use of the tested resorbable plates can be encouraged in multiple displaced mandibular fractures in children and likewise in highly compliant dentate adolescents and adults with doubled osteosyntheses; traumatic mandibular angle and pathological fractures, however, remain critical for nonunion. These necessitate evaluation with future smaller, more rigid, and, it is hoped, more economical fixations.

Biodegradable fixation of mandibular fractures in children: stability and early results

OBJECTIVE

The aim of this study was to assess the safety and efficiency of biodegradable self-reinforced (SR-PLDLA) bone plates and screws in open reduction and internal fixation of mandible fractures in children.

STUDY DESIGN

Thirteen patients (5 female, 8 male; mean age 12 years, range 5-16 years) were operated on various fractures of the mandible (2 symphyseal, 6 parasymphyseal, 4 body, 3 angle, 1 ramus, 2 condylar fractures). The mean follow-up time was 26.4 months (range 10.9-43.4 months). Intermaxillary fixation was applied in cases with concomitant condylar fractures up to 3 weeks.

RESULTS

Primary healing of the fractured mandible was observed in all patients. Postoperative complications were minor and transient. The outcome of the operations was not endangered. Adverse tissue reactions to the implants, malocclusion, and growth restrictions did not occur during the observation period.

CONCLUSIONS

Pediatric patients benefit from the advantages of resorbable materials, especially from faster mobilization and the avoidance of secondary removal operations. Based on these preliminary results, self-reinforced fixation devices are safe and efficient in the treatment of pediatric mandible fractures. However, further clinical investigations are necessary to evaluate the long-term reliability.

Resorbable poly(D,L)lactide plates and screws for osteosynthesis of condylar neck fractures in sheep

We made osteotomies in the condylar neck in 12 adult sheep to simulate fractures, and joined the two ends with 2 poly(D,L)lactide (PDLLA) plates and 8 PDLLA screws 2mm in diameter. The animals were killed after 2, 6, and 12 months and bony healing was assessed macroscopically and histologically. The plates and screws remained intact and there was no displacement of the bony ends. The degrading plates, which were still visible in the specimens after 6 months, had been replaced by bone. At 12 months the PDLLA had been resorbed with no foreign body reaction and no resorption of underlying bone. The articular discs showed no signs of degeneration.

Immediate mechanical stability of sagittal split ramus osteotomy fixed with resorbable compared with titanium bicortical screws in mandibles of sheep

Ten fresh mandibles from adult sheep were stripped of all soft tissues and sectioned in the midline. We did sagittal split osteotomies and 5 mm advancement on all the 20 hemimandibles. Ten hemimandibles were fixed with three 2.0 mm x 13 mm titanium bicortical screws, and the other 10 were fixed with three 2.0 mm x 13 mm poly-l-lactic acid/polyglycolic acid (PLLA/PGA) bicortical screws in an inverted L pattern. All the hemimandibles were then mounted in a servohydraulic testing unit and tested to permanent deformation. Maximum forces that the mandibles resisted before breaking, maximum displacements, and the displacement values under 20, 60, 120, and 150 N were compared using the Mann-Whitney U-test. There were no significant differences in stability between the bones fixed with titanium and those fixed with resorbable screws.

Changes in condylar long axis and skeletal stability after bilateral sagittal split ramus osteotomy with poly-l-lactic acid or titanium plate fixation

This study was designed to assess skeletal stability after bilateral sagittal split ramus osteotomy (BSSO) and fixation with a poly-l-lactic acid (PLLA) plate, as compared to that after BSSO and fixation with a titanium plate, and to analyze the change in the condylar long axis after these procedures. The study group comprised 40 patients who had mandibular prognathism (20, titanium group; 20, PLLA group). The groups were randomized to show similar distributions of preoperative SNB. All patients underwent BSSO setback by the Obwegeser method. Fixation was done with bent titanium plates or bent PLLA plates, applied in a similar manner. Lateral, frontal, and submental-vertical cephalograms were analyzed preoperatively and postoperatively. The maximum mouth opening range and the incidence of temporomandibular disorders were also evaluated. There was no significant difference in the right condylar angle or width between the two groups, but the left condylar angle and width, gonial angle, and ramus inclination differed significantly between them (P<0.05). SNA, SNB, and ANB were similar in both groups. There was no significant difference between the groups in maximum mouth opening range or temporomandibular disorders. We conclude that the change in condylar angle after BSSO and fixation with a titanium plate is greater than that after BSSO and fixation with a PLLA plate, but skeletal stability related to the occlusion is similar for the two procedures.

Stability of Biodegradable Implants in Treatment of Mandibular Fractures

BACKGROUND

Biodegradable implants have not been used on a large scale for internal fixation of mandibular fractures because of presumed inferior mechanical properties. This prospective clinical trial was designed to elucidate the stability and biocompatibility of self-reinforced poly-L/D-lactide plates and screws used to stabilize a variety of mandible fractures by open reduction and internal fixation.

METHODS

Sixty-six consecutive patients (22 female, 44 male; mean age, 23.9 years) with a total of 89 fractures at various sites of the mandible were included in the study. Stability of plates and screws and bone healing were observed by clinical and radiographic assessment. Intermaxillary fixation was applied in eight patients with concomitant condylar fractures for 2 to 3 weeks.

RESULTS

The self-reinforcement technique provided sufficient mechanical stability of the implants for primary healing of these high-load mandibular bone areas. Postoperative complications were transient and limited to wound dehiscence and localized wound infection (two patients). In some patients, hypesthesia (three patients) or slight pain (10 patients) was reported at the 1-year recall examination, but implant-related serious adverse tissue reactions were not observed during the follow-up (mean, 24.4 months; range 6.4 to 44.3 months).

CONCLUSIONS

On the basis of these preliminary results, the authors conclude that biodegradable self-reinforced implants show efficient stability during initial bone healing and promise a high potential for successful use in osteofixation of mandibular fractures.

Assessment of material- and technique-related complications following sagittal split osteotomies stabilized by biodegradable polylactide screws

OBJECTIVE

The aim of this retrospective clinical study was to determine whether there are any material-related problems and increased occurrence of postoperative mandibular nerve and temporomandibular joint dysfunctions in connection with the use of biodegradable self-reinforced poly-L-lactide (SR-PLLA) screws for bone fixation after bilateral sagittal split osteotomies (BSSO).

STUDY DESIGN

Forty consecutive patients who underwent BSSO and mandibular advancement that included fragment fixation using SR-PLLA screws were monitored for an average of 2.2 years postoperatively.

RESULTS

The osteotomy sites healed uneventfully with no adverse reactions. The incidence of postoperative sensory disturbances of the inferior alveolar nerve was 27%. Symptoms of temporomandibular joint disorders (TMJD) observed preoperatively in 73% of patients were reduced to 48% after surgery.

CONCLUSION

The occurrence of postoperative sensory disturbances and TMJD symptoms in this study did not deviate strikingly from that of other studies using conventional osteosynthesis. No specific complications related to the screw material were observed.

A retrospective evaluation of rigid fixation in orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polyactide

OBJECTIVE

This study was designed to evaluate clinical and radiological evidence of osteotomy site healing in orthognathic surgery after rigid fixation using a biodegradable plating system.

STUDY DESIGN

A follow up of 30 patients who underwent orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polylactide plating system was presented. The follow-up schedule for all patients consisted of regular appointments at 1-180 days after surgery. Clinical evaluation involved notation of any abnormal swelling, infection, discoloration, or discharge at the osteotomy sites. Stability was evaluated by manual palpation. For radiographic evaluation, panoramic radiographs were taken immediately after surgery, and again at 7-180 days. The radiographs were analyzed for any visual changes in osteotomy fragments, resorptive changes in osteotomy fragments, callus formation, and union of the osteotomy segments.

RESULTS

No clinical complications and no radiological changes in the osteotomy sites were observed. Regarding the clinical usefulness of the biodegradable fixation system, fixation at the time of operation was considered as excellent in all 30 cases.

CONCLUSIONS

The conclusions of this study were that self-reinforced (70L:30DL) polylactide was considered to be comparable to other forms of rigid internal fixation for orthognathic surgery.

Successful Use of Biosorb Osteofixation Devices in 165 Cranial and Maxillofacial Cases: A Multicenter Report

Bioabsorbable osteofixation devices were developed to avoid problems associated with metals. Bioabsorbable devices are mostly made of the polymers polylactide, polyglycolide, and their copolymers [polyglycolide-co-polylactide and P(L/DL)LA]. Using the technique of self-reinforcement of bioabsorbable materials, it is possible to manufacture osteofixation devices with ultra high strength. Self-reinforced polyglycolide-co-polylactide 80/20 was selected to make devices (Biosorb PDX) for this study because of its favorable degradation characteristics. The aim of this study was to evaluate the efficacy of using self-reinforced polyglycolide-co-polylactide 80/20 (Biosorb) plates and screws in the fixation of osteotomies in craniomaxillofacial surgery. In a prospective study, 165 patients (161 children and 4 adults) were operated on in four European Union centers (Paris, Innsbruck, London, and Oulu) from May 1, 1998 to January 31, 2002. Indications included correction of dyssynostotic deformities (n = 159), reconstruction of bone defects after trauma (n = 2), tumor removal (n= 2), and treatment of encephalocele (n = 2). Plates used were 0.8, 1, or 1.2 mm thick, and screws had an outer (thread) diameter of 1.5 or 2 mm and a length of 4, 6, or 8 mm. Tacks had an outer diameter of 1.5 or 2 mm and a length of 4 or 6 mm. During surgery, the devices were easy to handle and apply and provided stable fixation apart from 2 cases. Postoperative complications occurred in 12 cases (7.3%), comprising infection (n = 6), bone resorption (n = 4), diabetes insipidus (n = 1), delayed skin wound healing/skin slough (n = 2), and liquorrhea (n = 1). Accordingly, self-reinforced polyglycolide-co-polylactide 80/20 (Biosorb) plates and screws can be used safely and with a favorable outcome in corrective cranioplasties, especially in infants and young children.

Comparison of stability of absorbable and titanium plate and screw fixation for sagittal split ramus osteotomy

Six unembalmed adult sheep mandibles were stripped of all soft tissues and sectioned at the midline. Each side had a sagittal split ramus osteotomy (SSRO) and was advanced 5 mm. Six of the hemimandibles were fixed with four-hole extended titanium miniplates and titanium screws, and the other six were fixed with four-hole extended absorbable plates and absorbable screws. All specimens were mounted in a servohydraulic testing unit, and a range of forces (0-140 N) was applied. Displacement of each proximal segment was recorded at 10 N increments from 0 to 140 N. Values for the two groups were compared using the Mann-Whitney U-test, and significant differences in displacement were seen only at loads between 10 and 50 N. The results indicate that when absorbable miniplates are used intermaxillary fixation may be necessary to stabilise the bony fragments in the early postoperative period.

Self-reinforced bioresorbable poly-L/DL-Lactide [SR-P(L/DL)LA] 70/30 miniplates and miniscrews are reliable for fixation of anterior mandibular fractures: A pilot study

OBJECTIVE

Bioresorbable osteofixation devices are being increasingly used in orthognathic surgery and in cases of trauma to avoid problems associated with conventional metal osteofixation devices. The aim of this clinical study was to assess the reliability and efficacy of bioresorbable self-reinforced poly-L/DL-lactide (SR-P(L/DL)LA 70/30) plates and screws in the fixation of mandibular fractures in adults.

STUDY DESIGN

Ten patients (20 to 49 years old) with isolated anterior mandibular parasymphyseal fractures were treated by means of open reduction and internal fixation using SR-P(L/DL)LA 70/30 bioresorbable plates and screws.

RESULTS

During the minimum of 6 months of follow-up, no problems were encountered except for 1 case where a plate became exposed intraorally and infected. This required debridement and later excision of the exposed part of the plate. Despite this setback the fractured bone healed well.

CONCLUSIONS

SR-P(L/DL)LA 70/30 plates and screws are reliable for internal fixation of anterior mandibular fractures in adults. Proper soft tissue coverage should be ensured to avoid plate exposure. Should implant exposure occur, it might be necessary to excise the exposed part after fracture healing (6-8 weeks postoperatively).

The early tissue response to titanium and LactoSorb screws

Fractures of the maxillofacial region are common in the elderly people. Titanium and LactoSorb screws are the widely accepted materials for use in the maxillofacial fractures. This study was undertaken to evaluate the early tissue response following the insertion of both titanium and LactoSorb screws composed of 82% PLLA and 18% PGA in an elderly animal model. In this study, 22 titanium and 22 LactoSorb screws were applied to calvaria of 44 guinea pigs that were 10-11 months old. Animals were sacrificed on postoperative days 3, 7, 14, 30 and 60. Screws were retrieved with surrounding bone tissue and the specimens were prepared for routine histologic examination. All the specimens were evaluated by light microscopy. Histometric analysis revealed that there was no significant difference between LactoSorb and titanium screws for the new bone formation. The biodegradation of LactoSorb screws was not complete by the end of day 60. In conclusion, both materials were well tolerated and induced bone formation without causing adverse tissue response in an elderly animal model. Our results suggest that both LactoSorb and titanium miniplates and screws can be used safely, regardless of the increasing age. However, LactoSorb may be the first choice as it does not require a second operation for removal and has late biodegradation in elderly that keeps its support for a relatively longer time during fracture healing.

Resorbable plate osteosynthesis of dislocated or pathological mandibular fractures: a prospective clinical trial of two amorphous L-/DL-lactide copolymer 2-mm miniplate systems

The purpose of this study was to evaluate the indication for resorbable miniplates in traumatic and pathological mandibular fractures. Two resorbable miniplate systems, the 2.0-mm MacroSorb (Macropore, San Diego, Calif.) and the PolyMax (Synthes, Oberdorf, Switzerland), were prospectively used in 24 mandibular osteosyntheses. Made from amorphous 70:30 poly-L/DL-lactide, amorphous copolymer plates have not yet been evaluated for mandibular osteosyntheses. The main advantage of the amorphous copolymer-structure is continuous hydrolysis through water penetration into the implant body during the first 6 months. Hydrolysis breaks the copolymer chains into smaller particles that later become degraded through phagocytotic cells. Twelve patients, aged 13 to 83 years, were treated after providing informed consent. Fourteen dentate patients with moderately dislocated traumatic fractures and two edentulous atrophic and dislocated traumatic mandibular fractures were treated. Two patients with pathological fractures due to osteomyelitis received osteosynthesis after sequestrectomy. Histological specimens of the plates, screws, and surrounding soft tissues were taken after 3, 6, 9, and 12 months in secondary dental implant operations. A total of 22 osteosyntheses healed well without clinical or radiological signs of dislocation, insufficient or excess formation of callus, pseudarthrosis, or plate fracture. The follow-up time ranged from 4 to 22 months. One patient with osteomyelitis worsened because of widespread osseous infection, and one with atrophic fracture developed a bland fibrous pseudarthrosis. The histological specimens showed a moderate inflammatory foreign body reaction. No sinuous drainage or clinically apparent inflammation occurred. The presented osteosynthesis systems showed reliable stability for mandibular osteosynthesis in cooperative patients; however, two treatment failures occurred (8 percent). Disadvantages of the resorbable osteosyntheses were costs, greater diameter, screw breakage, and the need to place the screws vertically to the plate. The use of resorbable osteosyntheses in dislocated fractures should be further evaluated in controlled studies.

Fixation of mandibular fractures with biodegradable plates and screws

OBJECTIVE

Little data exist regarding the use of biodegradable plates and screws for the internal fixation of human mandibular fractures. The purpose of this study was to evaluate the stability of biodegradable, self-reinforced poly-L-lactide plates and screws for the internal fixation of fractures of the human mandible.

STUDY DESIGN

Twenty-two individuals (14 male, 8 female; average age, 26.3 years) with a variety of fracture patterns of the mandible underwent management with a biodegradable fixation system. After surgery, maxillomandibular fixation was applied in 3 cases. Images (panoramic radiograph, computed tomographic scan) were taken immediately after surgery and at the 4-week, 8-week, 12-week, and 24-week intervals. The follow-up period averaged 49.1 weeks (range, 22 to 78 weeks).

RESULTS

Mucosal dehiscences over the resorbable devices were present in 2 patients. In 1 of these 2 cases, the material had to be replaced with titanium plates. Mucosal healing and consolidation of the fracture were normal in all other patients.

CONCLUSION

Self-reinforced biodegradable osteosynthesis materials provide a reliable and sufficient alternative to conventional titanium plate systems.

The use of bioabsorbable osteofixation devices in craniomaxillofacial surgery

Because of problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, bioabsorbable devices have presented an appealing alternative. Devices made of the polymers polyglycolide (PGA) and polylactide (PLA) and their copolymers (PLGA and PLDLA) are currently the most commonly used. Strong implants can be manufactured from these polymers with a self-reinforcing technique and used in the treatment of fractures and osteotomies. Self-reinforced devices have been studied for nearly 2 decades by our multidisciplinary research group for internal fixation of the bone in both experimental and clinical settings. In craniomaxillofacial fractures and osteotomies they have been used for as long as 10 years with no significant clinical problems. Because of more favored degradation characteristics, currently the copolymer devices (PLDLA and PLGA) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. By using bioabsorbable devices, several problems associated with conventional biostable devices can be avoided, especially in children. New techniques that are not possible with biostable devices can be developed by using bioabsorbable devices, too. Our experience with and research on self-reinforced devices are shared here.

Posttraumatic craniofacial reconstruction using combined resorbable and nonresorbable fixation systems

The facial skeleton consists of high-stress-bearing buttresses and low-stress-bearing curved surfaces. The buttresses are like trusses made of beams, struts, and columns. They resist tensile, compressive, and shear loading. The thin, curved, planar surfaces provide for the support and partitioning of the soft tissue. The trusses are strong and one-dimensional whereas the planes are weak and two-dimensional. Ideally, strong one-dimensional fixation systems should be used for the former; weaker, two-dimensional systems should be used for the latter. The authors report their clinical experience of using such combined approaches to the treatment of facial fractures using rigid, titanium mini-plates and screws for the buttresses and polymeric resorbable meshes for the curved planes. For an 11-month period (August 2000 to June 2001), nine patients (7 males and 2 females) with a mean age of 33.7 years were treated in this fashion. The resorbable meshes were deployed for the reconstitution of the orbital walls and the anterior wall of the maxillary sinus. No enophthalmos, globe dystopia, or diplopia occurred during the short mean follow-up of 10 months (4-17 months). There were no infections or sterile abscess formations. This type of combined use of fixation systems appears to be safe and effective. More patients and more extensive follow-ups are obviously needed.

Developments in craniomaxillofacial surgery: use of self-reinforced bioabsorbable osteofixation devices

Because of the problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, absorbable devices present an appealing alternative. Devices made of the polymers polylactide, polyglycolide, and their copolymers (PLGA and P[L/DL]LA) are currently the most commonly used. Ultrahigh-strength implants can be manufactured from these polymers with the self-reinforcing technique. Over the authors' almost two decades of study, both in experimental and clinical settings, self-reinforced devices have proved to be biocompatible, easy to handle, and mechanically strong, even for the fixation of femoral neck fractures. In craniomaxillofacial surgery, the authors have used self-reinforced devices for over 8 years without complications. Because of the more favored degradation characteristics, currently the copolymeric self-reinforced devices (P[L/DL]LA, Biosorb FX and PLGA, Biosorb PDX; Elite Performance Technologies, Solana Beach, Calif.) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. The authors' share their experience and their studies of self-reinforced devices, which possess the highest strength and ductility of all bioabsorbable products.

Self-adapting washer system for lag screw fixation of mandibular fractures. Part II: In vitro mechanical characterization of 2.3 and 2.7 mm lag screw prototypes and in vivo removal torque after healing

The aim of this study was to mechanically characterize self-tapping 2.3 and 2.7 mm titanium lag screw prototypes which are part of the newly developed 'self-adapting washer' maxillofacial lag screw osteosynthesis system. In vitro in a screw testing machine the insertion torque, maximum locking torque and axial force and the ultimate torsional strength were assessed. In vivo in six miniature pigs using a mandibular symphyseal fracture model, the removal torques after 3 and 6 months of healing were measured. Additionally the bone-metal contact (BMC) of the screws was assessed histometrically. The maximum insertion torque (0.185 Nm) was far below the mechanical limits of the screws (2.3 mm = 0.96 Nm, 2.7 mm = 1.6 Nm). A tightening of the 2.7 mm screw with an axial force of 1000 N and of the 2.3 mm screw with 500-550 N leaves a safety margin of approximately one-third on the ultimate torsional strength. Clinically these values permit the use of two 2.3 mm lag screws or one 2.7 mm lag screw in mandibular symphysis fractures since 1000 N tensile axial force are required in this indication. During screw removal after 6 months healing, torque levels close to the mechanical limits of the screws were recorded and screw failures were observed. This failure rate may have been due to the BMC of 49.8% which was in the range of titanium dental implants. Accordingly the screw heads were reinforced to prevent fractures.

Fixation of mandibular body osteotomies using biodegradable amorphous self-reinforced (70L:30DL) polylactide or metal lag screws: an experimental study in sheep

Mandibular body osteotomies were fixed in nine sheep using new totally amorphous (70L:30DL), self-reinforced, polylactide (SR-PLA) lag screws and in nine sheep using standard stainless steel lag screws. No intermaxillary fixation was used. During follow-up, radiological, histological and microradiological studies were undertaken at 3, 6, 12 and 24 weeks. In both groups, all osteotomies consolidated at similar rates and no adverse reaction to the screws was seen. However, displacements of the fixed osteotomy fragments were common in both groups during the first 3 weeks. The biocompatibility of SR-PLA during the follow-up period was found to be good. Only initial signs of biodegradation were seen. The results of this study indicate that (70L:30DL) SR-PLA has potential for use as a fixation screw material in oral and maxillofacial surgery, and that further studies using this material are justified.