In vivo and in vitro degradation of a novel bioactive guided tissue regeneration membrane.

The aim of this study was to assess degradation of a novel bioactive guided tissue regeneration (GTR) membrane and to quantify the concurrent tissue responses. Pieces of membrane composed of poly-l-lactide, poly-d,l-lactide, trimethylenecarbonate and polyglycolide were dipped into an N-methyl-2-pyrroline (NMP) solution and implanted in the mandibles of 10 sheep. The animals were sacrificed at 6-104 weeks. Parallel in vitro degradation was analysed by measuring the inherent viscosity, water absorption and remaining mass. One of the 2 in vitro sets of membranes was prehandled with NMP. At 6-26 weeks in vivo, the gradually more degraded implants were surrounded by a fibrous network. At 52 and 104 weeks, the implants and fibrous networks were non-detectable. Foreign body granulomatous reactions were not observed. In vitro, the mass of the NMP-exposed membranes diminished linearly over the 2-year period down to 10%, while the non-NMP-exposed membrane maintained all their mass for the first 16 weeks. The membranes without NMP had absorbed significantly less water at weeks 4 and 8 than the other group. The inherent viscosity decreased relatively uniformly in the in vitro groups. In conclusion, the in vivo degradation was complete in 12 months with only mild histologic responses; the degradation in vitro may be slower. NMP accelerates the degradation.

Bioabsorbable plates and screws: Current state of the art in facial fracture repair.

BACKGROUND AND OBJECTIVES: The use of bioabsorbable materials in craniomaxillofacial surgery began a new era in fracture fixation. The purpose of this paper is to review the historical perspectives and the current concept of bioresorbable materials in fracture fixation. METHODS AND MATERIALS: The authors review the biochemistry and clinical characteristics of bioabsorbable polymers--polylactic acid (PLA), polyglycolic acid (PGA), polydioxanone (PDS), and their copolymers. Their use and clinical perspectives by the Helsinki (authors') group and other study groups are presented. RESULTS AND CONCLUSIONS: These materials have proven to be safe in clinical applications. When manufactured with current technology, they are easy to handle. Economically, they are nearly equal to similar metal devices. The materials have met clinical success throughout the world, first in orthognathic surgery, followed by treatment of fractures of the upper facial skeleton and the mandible. Today, most maxillofacial fractures and osteotomies may be adequately fixed with bioabsorbable materials.

Osteotomy site healing following mandibular sagittal split osteotomy and rigid fixation with polylactide biodegradable screws.

Follow-up of 47 patients, treated using mandibular bilateral sagittal split osteotomy and self-reinforced poly-L-lactide acid (SR-PLLA) screws for rigid internal fixation, is presented. The focus was on clinical and radiological osteotomy healing. The average follow-up time was 2.1 years (range 0.5-5 years). Clinical recovery and radiological osteotomy healing during follow-up were uneventful. Osteolytic changes were seen around the SR-PLLA screws in 27% of cases. The majority of the screw canals remained as radiolucent shadows without bony filling.

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.

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

PURPOSE: The purpose of this study was to evaluate the utility of biodegradable, self-reinforced poly-L-lactide screws (SR-PLLA) for lag-screw fixation of anterior mandibular fractures. PATIENTS AND METHODS: SR-PLLA lag-screws were used to stabilize anterior mandibular fractures in 11 patients. Maxillomandibular fixation was used to treat concomitant mandibular condyle fractures for 2 weeks in four patients and for 1 and 5 weeks in two patients. Clinical and radiologic follow-up lasted for 6 months in 36% of patients and for 1 year in 64%. RESULTS: Healing of all anterior fractures was uneventful, with no displacement or delay of bony union. No adverse reactions to the biodegradable screws were seen during follow-up. CONCLUSION: Biodegradable SR-PLLA screw fixation seems to be a new and promising way of treating anterior mandibular fractures.

Skeletal stability following mandibular advancement and rigid fixation with polylactide biodegradable screws.

Skeletal stability during the first year after mandibular advancement surgery and fixation using biodegradable self-reinforced poly-l-lactide (SR-PLLA) screws, without postoperative intermaxillary fixation, was studied in 25 patients by means of cephalometric measurements. The magnitude of advancement was on average, 3.88 mm at pogonion (PG) (range 1.25-6.5 mm) and 4.57 mm at B-point (range 2.75-7.5 mm). After one year a mean relapse backwards of 0.59 mm at the PG (15%) and 0.78 mm at the B-point (17%) was observed. Nineteen patients (76%) and 17 patients (68%) were stable at PG and B-point, respectively. SR-PLLA screws are considered to be comparable to other forms of rigid internal fixation for fixation of bilateral splitting osteotomies after mandibular advancement, as far as skeletal stability is concerned.

Lag-screw fixation of mandibular parasymphyseal and angle fractures.

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.

Lag-screw osteosynthesis of mandibular condyle fractures: a clinical and radiological study.

PURPOSE: This study evaluates the clinical and radiologic results after open reduction and lag-screw osteosynthesis of fractured mandibular condyles. MATERIALS AND METHODS: Eleven adult patients underwent surgery for displaced or dislocated mandibular condyle fractures via a submandibular approach. The repositioned fragments were fixed using lag screws designed by Krenkel or Eckelt. Maxillomandibular fixation was used postoperatively for 2.6 weeks on average (range, 1 to 4 weeks) in nine patients. RESULTS: Slight transient weakness of the mandibular branch of the facial nerve occurred in three cases. Occlusal adjustment was needed in another three cases. Radiologically, the fracture line disappeared at 22.5 weeks on average (range, 8 to 38 weeks). Three screws had to be removed because of loosening. There were signs that the screws had migrated caudally from their original position in seven cases. Twenty-one months on average after operation (range, 8 to 31 months), patients were satisfied with treatment. Clinically, all patients had a stable occlusion and symmetry of the face. All had greater than 5-mm symmetrical lateral jaw excursions. Ten patients had wide (> 40 mm) painless mouth opening. Healing in malposition occurred in four cases and there was considerable shortening of the mandibular ramus in four cases. CONCLUSIONS: Despite good clinical results, lag screws do not meet the needs for rigid internal fixation in the treatment of mandibular condyle fractures.

Blindness after maxillofacial blunt trauma. Evaluation of candidates for optic nerve decompression surgery.

Clinical and computerized tomography (CT) findings in 10 patients with post-traumatic blindness after maxillofacial blunt trauma were evaluated as potential candidates for optic nerve decompression surgery. The total number of blind eyes was 14. All patients suffered from midfacial fractures (isolated zygomatic fracture in 4 and Le Fort fracture in 6 cases) predominantly caused by road traffic accidents. CT scanning and clinical findings allowed location of damage to the optic nerve region in all patients. The most common CT finding was swelling of the optic nerve. Fracture in the optic canal wall was seen in only 3 cases. The clinical situations characteristic of this type of injury make diagnosis and early surgical intervention difficult. It was concluded that two of the 10 patients might have benefitted from optic nerve decompression.

Surgical treatment of ventricular septal defect secondary to myocardial infarction.

13 patients were operated on during 1974-88 for ventricular septal defect secondary to myocardial infarction. 7 infarctions were inferior and 6 anterior. At the time of operation 5 patients were in shock. Besides the correction of ventricular septal defect coronary artery by-pass grafting was performed in 6 patients and left ventricular aneurysmectomy in 3 patients. The operative mortality was 31%. The cause of death was low output syndrome in 3 cases and a new rupture through the left ventricular free wall in one case. Postoperative shunting was detected in 5 patients. During an average follow-up time of 6.3 years (range 0.5-15 years) 3 patients died from a new myocardial infarction. The mean performance levels of the patients still living was NYHA II. Prompt diagnosis of a ventricular septal defect due to myocardial infarction and its immediate surgical treatment is recommended. The results are poor in the presence of primary shock and for inferior infarction.