Reconstruction of the mandible by prefabricated autogenous bone grafts. An experimental study in minipigs

Sensory systems that detect weak electric fields initially evolved as a primitive vertebrate character and have subsequently been lost and 're-evolved' a number of times in various taxa. As such, they provide unique examples of evolutionary parallelism and convergence in vertebrate sensory systems. Electrosensory systems have additionally proven to be admirable models for investigating the fundamental strategies by which nervous systems interpret environmental signals as the basis for organizing behaviors.     

Esophageal reconstruction with free jejunal grafts: an experimental study

Replacement of a long segment of esophagus for esophageal atresia or severe stenosis remains a special problem in children. The following studies were designed to test the hypothesis that a section of small bowel without serosa could survive as a free autologous transplant to replace part of the mediastinal esophagus. Laparotomy was performed in 20 adult cats, a loop of small bowel was resected and an end-to-end jejunojejunostomy was completed. The serosa of the resected bowel was removed and the mucosa-muscularis graft was used to replace a segment of the middle esophagus that was resected via a right thoracotomy. The interposed graft was entirely wrapped with adjacent skeletal muscle flaps. Postoperative studies include barium swallow and cine esophagograms, histology and blood vessel casts. Results are presented which show anatomical and functional survival of 16 grafts without blood vessel anastomoses or intrinsic vascular pedicles.     

Vascularized bone flaps versus nonvascularized bone grafts for mandibular reconstruction: an outcome analysis of primary bony union and endosseous implant success

We present a patient with a lesion of the mesial frontal cortex, including the supplementary motor areas bilaterally, who on clinical examination revealed no spontaneous movements, although neurophysiological examination indicated integrity of the corticospinal tract to thenar and tibialis anterior muscles bilaterally. The patient was alert, speech was hesitant, and he was able to move his hands only on command. The role of the supplementary motor areas in planning, setting, and execution of skillful voluntary movements has been previously established by direct cortical electrical stimulation and studies of regional cerebral blood flow. The findings in our patient support the role of the supplementary motor areas in initiating movements. The presence of motor evoked potentials after acute insults to the brain is considered to be associated with a good functional outcome. This is in contrast to our patient who did not show improvement in motor performance, despite preserved motor evoked potentials. Hence, in the case of bilateral lesions to the supplementary motor areas sparing the corticospinal tract, the presence of motor evoked potentials may not predict functional recovery.     

Mandibular fracture after endosseous implant placement in conjunction with inferior alveolar nerve transposition: a patient treatment report

A patient with a severely atrophic right posterior mandible had three endosseous implants placed in conjunction with transposition of the inferior alveolar nerve. Three weeks following implant placement surgery, the patient experienced a spontaneous fracture of the mandible involving the two anterior implants. The two implants were removed, and the fracture was treated with open reduction and fixation with titanium mesh. The fracture healed, and the posterior implant integrated. This report suggests that the buccolingual and superior-inferior position of the mandibular canal can increase the possibility of mandibular fracture by increasing the size of the buccal cortical plate that is removed to expose the nerve during surgery.     

The viability of cryopreserved onlay cranial bone allografts: a comparative experimental study versus fresh autografts

It is well known that calvarial bone autografts are the bone grafts that are the least reabsorbent and have the best long-term evolution in craniofacial surgery. However, they do have certain limitations: (1) reabsorption results in repeated surgery and the need for new donor areas, (2) a limited amount of autogenous cranial bone is available (due to avoiding areas close to cranial sutures and venous sinuses, and because the temporal bone is very fragile and the cranium has not fully developed in children), and (3) graft extraction increases surgical time and morbidity. Because of this, we present an alternative to calvarial bone autografts: cryopreserved allografts. This paper is an experimental prospective study carried out on sheep with the following goals: (1) to assess the behavior of calvarial onlay bone grafts cryopreserved at -80 degrees C, using fresh autografts implanted under the same conditions as controls; (2) to compare reabsorption percentages statistically over time; and (3) to study qualitatively any histological variations. The results obtained are (1) more reabsorption of allografts when compared to autografts (at 90 days, 21.97% versus 20.21% of grafted volume), although this difference is not statistically significant; (2) a reduction in height in all onlay grafts as a consequence of the loss of the dipl?e; (3) the absence of any type of inflammation caused by a reaction to cryopreserved allografts; and (4) bone substitution performed using frozen allografts is histologically similar to that using fresh autografts.     

Guided bone regeneration for immediate non-submerged implant placement using bioabsorbable materials in Beagle dogs

The aim of the present study was to evaluate the combined application of different bioabsorbable materials for healing of residual peri-implant defects after placement of non-submerged implants into fresh extraction sockets. Second and third mandibular premolars were extracted from 10 Beagle dogs, the coronal part of the distal sockets were surgically enlarged and this was followed by immediate placement of specially designed hollow-screw non-submerged dental implants. For each animal, the coronal peri-implant defects were further treated with one of the 4 following procedures: 1) no treatment, control site; 2) grafting with porous hydroxyapatite (HA); 3) collagen membrane tightly secured around the implant and over the defect and 4) grafting with HA covered with a collagen membrane. After 16 weeks of healing, specimens were removed from the mandibule and prepared for a histomorphometric evaluation. The bone-to-implant contact length (BIC) was measured and compared amongst the different treatment modalities. In the defect area, the irregular bone regeneration was similar between all the treatment procedures (P > 0.10). In the sites covered with a collagen membrane alone, the total BIC (47%) was greater than in control sites (28.7%, P < 0.05) or sites grafted with HA (22.2%, P < 0.02). Total BIC in sites treated with the HA-membrane combination (43%) was only significantly different from sites treated with HA (P < 0.05). It is concluded that the use of bioabsorbable materials results in a limited increase of osseointegration when used in conjunction with immediate placement of non-submerged implants, although the principle of the one stage surgical approach can be maintained.     

Prefabricated osteomusculocutaneous flaps using calvarial bone: experimental study

Prefabricated osteomusculocutaneous flaps using free calvarial bone were examined and evaluated in a rat model. The animals were divided into two groups according to prefabrication time: 14 days in Group 1 (n = 10) and 28 days in Group 2 (n = 10). Nine of 10 preparations demonstrated neovascularization in Group 1, and all flaps showed neovascularization in Group 2. One flap was lost in Group 1 as a result of infection. Each group was evaluated histopathologically before the second stage of the experiment. Muscles without atrophy and osteocytes were noted in Group 1; however, Group 2 animals had both muscle atrophy and nonviable bone. The prefabricated osteomusculocutaneous flaps were then transferred as both island and free flaps. Flap viability was assessed on postoperative day 7 by macroscopic observation. Although all flaps survived in the island-flap group, two flaps failed to survive due to technical error in the free-flap group. Neovascularization was clearly evident by 2 weeks in the osteomusculocutaneous flaps; after 4 weeks, complete atrophy of the muscle meant that the flaps could no longer be characterized as osteomusculocutaneous. Clinically, it might be possible to use the outer table alone, in which case both thin skin and bone would be desirable. This study may provide a model for this approach.     

Regeneration of defects in articular cartilage with callus and cortical bone grafts. An experimental study

Luteal-phase estrogen and progesterone concentrations were measured every other day and used to monitor the corpus luteum activity. The patterns of estrogen and progesterone concentrations were compared relative to the day of endogenous human chorionic gonadotropin (hCG) detection (defined as the day of implantation). The relationship between estrogen and progesterone and hCG concentrations was studied in 71 viable pregnancies, 12 clinical abortions, five preclinical abortions and 84 non-pregnant cycles after IVF/ET. Although all patients received luteal-phase progesterone support (25-50 mg/ml), low late luteal-phase progesterone concentrations of < 30 ng/ml from day + 11 to day + 15 were found in 64 patients (17% of viable pregnancies, 33.3% of clinical abortions, 60% of preclinical abortions and 53.6% of non-pregnant cycles) day + 1 was the day of retrieval). Implantation always occurred before or on day + 13 and 86% of pregnant cycles implanted on day + 8 to day + 11. Viable pregnancies had significantly higher mean progesterone concentrations on day + 3 to day + 7 (pre-implantation) and on day + 9 to day + 15 (postimplantation) than those of non-pregnant cycles or abortions. On the day of implantation, the mean +/- standard of deviation of estrogen (pg/ml) and progesterone (ng/ml) levels for viable pregnancies, clinical abortion and preclinical abortions were 314 +/- 210, 40.5 +/- 25; 226.7 +/- 246, 48.7 +/- 31; and 39.6 +/- 24.5, 28.6 +/- 24.5, respectively. On the same day, 73.2% of viable pregnancies, 41.7% of clinical abortions, and 20% preclinical abortions had a progesterone concentration > 30 ng/ml; 73.2% of viable pregnancies, 41.7% of clinical abortions and 20% of preclinical abortions had an estrogen concentration > 100 pg/ml. Although not precluding implantation completely, late luteal-phase hormonal deficiencies may impair endometrial growth and might ultimately lead to failure or abnormal implantation. A viable pregnancy requires not only a functional corpus luteum in the early luteal phase to develop a receptive endometrium, but also a responsive corpus luteum in the late luteal phase to support pregnancy. The time of implantation is critical. Implantation that occurs before the demise of the corpus luteum will facilitate a normal pregnancy.     

Morphology and function of preserved microvascular arterial grafts: an experimental study in rats

The aim of this study is to examine the morphology and function and small-caliber, arterial grafts after preservation in the University of Wisconsin solution (UW). Rat carotid arteries were stored in UW (n = 10) or in phosphate-buffered saline (PBS) (n = 10) for 1, 3, 7, and 14 days and were examined with light microscopy (LM) and scanning electron microscopy (SEM). Rat aortic preparations were stored in UW or PBS for 1 hour, 24 hours, 72 hours, 7 days, and 14 days and assessed for functional responses (stimulated contraction and endothelium-dependent relaxation). Segments (5 mm) of rat carotid arteries were stored in UW or PBS for 3 days, 7 days, and 14 days and orthotopically implanted as autografts and allografts. No immunosuppressive or anticoagulant agents were used. After 28 days of implantation, the grafts were assessed for patency and excised for LM and SEM. In UW, the endothelial layer remained intact up to 9 days of storage. In PBS, the endothelial layer showed deterioration after 1 day and was completely lost after 3 days. Functional responses were demonstrated to exist for as long as 7 days storage in UW. In PBS, no responses could be evoked after 24 hours storage. Autografts preserved in UW for 3 days (n = 6), 7 days (n = 6), and 14 days (n = 6) showed patency rates of 83.3%, 66.6%, and 66.6%, respectively, whereas patency rates of allografts were 66.6%, 33.3%, and 33.3%, respectively. Autografts stored in PBS for 3 days (n = 6), 7 days (n = 6), and 14 days (n = 6) showed patency rates of 33.3%, 33.3%, and 50%, respectively, whereas patency rates of allografts were 16.7%, 0%, and 33.3%, respectively. The UW preserved autografts showed normal morphology. All other groups showed vessel wall degeneration which in the allograft groups, were accompanied by lymphocellular infiltration. In conclusion, the endothelial layer and vessel wall of arteries are adequately preserved in UW. Functional responses are retained up to 14 days storage in UW, but, are lost after 24 hours storage in PBS. Autograft implantation studies accordingly show good performance of arterial segments preserved in UW, whereas allografts are subject to degradation as a result of rejection.     

Bone augmentation at titanium implants using autologous bone grafts and a bioresorbable barrier. An experimental study in the rabbit tibia

The aim of the present investigation was to compare the effect of using autologous bone particles covered with a bioresorbable matrix barrier with the use of bone particles alone on bone augmentation at titanium implants installed in the rabbit tibia. Two Br?nemark System implants, one in each tibia, were inserted in each of 9 rabbits in such a way that 5 threads were not covered with bone. Autologous bone particles were harvested from the skull and placed over the exposed implant surfaces on each tibia. The bone graft on one tibia was covered with a Guidor Matrix Barrier, while the bone graft on the other tibia served as a control. After a healing period of 12 weeks, the animals were sacrificed and specimens taken for histomorphometrical analyses. The analyses showed that a significantly larger volume of augmented bone tissue had formed at the test sites. There were, however, no differences in the amount of mineralized bone. In fact, the difference in tissue volume was due to an increased amount of bone marrow at the test sites. The degree of mineralized bone to implant contact as well as the degree of mineralized bone within the threads at the test implants were similar to that at the controls. In conclusion, it was found that the coverage of particulate autologous bone grafts with a bioresorbable barrier resulted in a larger volume of augmented bone than the use of bone grafts not covered with a barrier.     

Long-term assessment of early alveolar bone grafts using three-dimensional computer-assisted tomography: a pilot study

Fifteen patients with complete unilateral cleft lip and palate who had primary alveolar bone grafting were studied with computer-assisted tomography at a mean age of 12 years. Keeping the maxillary alveolar crest parallel to the plane of the scan, 1.5-mm cuts of the maxilla were made from the infraorbital rim to the gingival third of the crowns of the teeth. A single operator reformatted the data into three-dimensional images using the Maxiview 3200 computer workstation. This allowed examination of the position, size, and spatial relationship of the grafted area and quantification of the amount of bone coverage of root surface and bone height of the alveolus in or adjacent to the graft site. Ten patients showed a lateral incisor in the line of the cleft. The average bony coverage of these tooth roots was 76.5 percent. In the five patients in whom there was lateral incisor agenesis, the canine root had average bony coverage of 82.6 percent. The average height of bone at the lateral incisor was 8.7 mm; at the canine, 14.1 mm. In two patients in whom there was only 42 percent tooth root coverage, the teeth were still viable, stable, and without mobility. Computed tomographic (CT) scans of the 15 patients demonstrated good graft survival with adequate volume. The functional and aesthetic status of the dentition in the area of the cleft also was demonstrated.     

Laparoscopic inguinal hernia repair by an intraperitoneal onlay mesh technique using expanded PTFE: a prospective study

BACKGROUND: Colonoscopy is the gold standard for the detection of colon polyps and cancers, but failed detections can occur and the reasons are incompletely understood. METHODS: During a retrospective evaluation of the sensitivity of barium enema and colonoscopy in 20 Indiana Hospitals, we encountered 47 cases of colorectal cancer in which a colonoscopy performed within 3 years of the diagnosis had not detected the cancer. Cases were reviewed for location of tumor, extenuating factors, pathologic features, delay in diagnosis from failed detection, and who performed the examination. RESULTS: Failed detection was more likely when colonoscopy was performed by a nongastroenterologist than a gastroenterologist (odds ratio 5:36, 95% CI [2.94,9.77]). Twenty-seven cancers were "missed," and 20 were estimated to be not reached. However, the location of missed tumors and a general absence of adequate documentation of cecal intubation suggested that some cecal and ascending colon cancers recorded as missed may actually have been not reached. Variation in sensitivity among gastroenterologists suggested that meticulous examination is also important in maximizing sensitivity. CONCLUSIONS: These cases suggest several factors that might improve the quality and sensitivity of colonoscopy: (1) examiners should receive adequate training, (2) cecal intubation rates should be high, (3) cecal intubation should be verified by specific landmarks in all cases, (4) failure to reach the cecum should be followed by prompt barium enema, and (5) meticulous examination would appear to improve sensitivity for cancer detection.     

Guided osteogenesis using synthetic membranes: an experimental pilot study

The purpose of this investigation was to examine lower arch alignment in the long term following treatment by second molar extraction. Thirty subjects, treated by extraction of four second permanent molars at an average age of 13.9 years, were examined five and ten years after extractions. None had any mechanical treatment in the lower arch. Twenty had some simple upper arch treatment, including, in five cases, extraction of first premolars. The changes in lower arch alignment were measured on study models. There was a small average decrease in lower arch crowding in the first five years following extraction, and little or no change in alignment in the next five years.     

Tendon repair using flexor tendon splints: an experimental study

Mechanical strength of tendon repair using Dacron tendon splints across the laceration site were evaluated in human cadaver profundus tendons; the splints were placed both on the dorsal surface and internally within the tendon substance. Comparison was made to modified Kessler, Becker, and Savage repair techniques. Ultimate tensile strength was 2.55 kgf for the Kessler, 3.00 kgf for the Becker, 8.29 kgf for the Savage, 8.46 kgf for the internal tendon splint, and 8.10 kgf for the dorsal tendon splint; the Savage and both Tendon Splints techniques had significant higher tensile strength than the Kessler and Becker. Gap strength was 1.44 kgf for the Kessler, 2.22 kgf for the Becker, 2.45 kgf for the Savage, 2.05 kgf for internal tendon splint, and 3.15 kgf for the dorsal tendon splint. The dorsal tendon splint technique showed significant greater gap strength than the other four techniques. There was no significant difference in the magnitude of the gap during cyclic testing of these techniques; however, three of seven Kessler repairs failed and one of six Becker repairs failed. The results of these cadaver studies suggest that both tendon splint repair techniques are comparable to the Savage and may have sufficient strength to allow postoperative active motion against minimal resistance. Further in vivo testing is in order.     

Cell adhesion and short-term patency in human endothelium preseeded 1.5-mm polytetrafluoroethylene vascular grafts: an experimental study

It has been shown that endothelialization improves short-term patency of 1.5-mm expanded polytetrafluoroethylene vascular grafts. A model for endothelialization of 1.5-mm expanded polytetrafluoroethylene vascular grafts with human endothelial cells is described. In this model, the adherence of endothelial cells was increased significantly in grafts coated with serum proteins and collagen. By means of this protocol, graft patency was tested after implantation in two animal models: the rat aorta and the rabbit common carotid artery. Anastomosis was performed with a 3M Precise Microvascular Anastomotic System. In both animal models, no significant loss of endothelial cells in the precoated grafts (rat, n = 8) were noted 1 hour after blood flow restoration. All uncoated grafts showed significant endothelial cell loss. In the rabbit model, all nonendothelialized grafts (n = 8) clotted 5 to 25 minutes after flow restoration. Seven (n = 8) endothelialized grafts showed no clotting during 1 hour's observation: one clotted immediately for a patency rate of 87.5 percent. These results indicate that endothelialization of 1.5-mm grafts is practical. Furthermore, adhesion of endothelial cells to the graft walls is not affected by short-term, pulsatile, high-pressure blood flow.     

Prediction of bone loss in patients with primary hyperparathyroidism using quantitative bone SPECT

Bone loss is a major complication of primary hyperparathyroidism (PHPT), and it has significant implications in the treatment of this disease. Bone turnover was measured in patients with PHPT, using quantitative bone SPECT (QBS), to determine if the rate of bone loss could be predicted before a significant decrease in bone mass occurs. METHODS: Forty-six patients were included in the study. QBS and bone mineral density (BMD) of the lumbar spine (LS) and femoral neck (FN) were done at baseline. The percent deviation of QBS in patients with PHPT from the values in normal matched controls was calculated. BMD was measured again after a mean of 17.5 mo in 38 patients, and in 29 patients a repeat BMD study was done after a mean of 41.4 mo. The change in BMD in patients with high and normal QBS values was compared using the nonparametric Mann-Whitney test. Regression analysis tested the correlation between baseline QBS values and BMD changes over time. RESULTS: For the FN, there was a statistically significant difference in the BMD change between patients with high and normal QBS values for short-term follow-up (-2.82%+/-4.80% versus 1.45%+/-4.67%, p < 0.05) and for long-term follow-up (-3.53%+/-5.34% versus 0.92%+/-2.40, p < 0.02). There was a negative correlation in the FN, r=-0.48 between QBS values and the percentage of change in BMD. There was no significant difference between the percentage of change in BMD in the LS in patients with high and normal QBS values for either short- or long-term follow-up. CONCLUSION: The results of this study show that QBS can predict bone loss in the FN in patients with PHPT. QBS can thus indicate the need for surgery at an early stage of the disease to prevent bone loss.     

Time course of histomorphometric alterations in nerve grafts without connection to a muscle target organ: an experimental study in sheep

In 15 adult sheep, the saphenous nerve (28 +/- 1.8 cm) was used for ipsilateral or for cross-nerve grafting and was sutured to the proximal stump of the cut, motor-nerve branch of the vastus muscle. The distal end of the nerve graft was left without a target organ. Semi-thin cross sections of normal vastus nerves and saphenous grafts and of the distal ends of the grafts were analyzed by computer-assisted planimetry, 3, 6, 9, 12, and 18 months after the nerve-grafting procedure. Electronmicroscopy was also performed on specimens from the distal ends of the nerve grafts. Comparing the total number of myelinated nerve fibers in the distal end of the graft, the ipsilateral group showed an increase with time elapsed since nerve grafting, while the cross-over group showed a maximum after 3 and 6 months, and fewer fibers after longer periods of regeneration. Independent of the time passed since nerve grafting, the diameters of the myelinated nerve fibers were homogeneously thin in both experimental groups. Most interesting, the cross-nerve grafts did more poorly than the ipsilateral ones, even before they were influenced by the target muscle. With ultrastructural investigation, the ends of the grafts containing only a few myelinated fibers also showed a low number of unmyelinated fibers, but an increase of collagen fibers. The results have consequences for the clinical application of cross-nerve grafting.     

Effects of primary bone grafting on facial development in patients with unilateral complete cleft lip and palate

The study is based on an anthropometric assessment of X-ray films obtained in 22 adult males with complete unilateral cleft lip and palate treated during childhood with primary bone grafts and in 32 males with the same type of cleft without bone grafting. In the series with bone grafts was recorded a more marked reduction of maxillary depth associated with a larger retrusion than in the series without bone grafts. This deviation was therapeutically compensated by a larger displacement of the mandible backwards which contributes to the increase of mandibular posterior rotation. This provided the possibility to attain an edge to edge bite. Our results confirmed the unfavourable effects of primary bone grafting on maxillary growth and development.     

Fibrillogenesis in tendon healing: an experimental study

The aim of this study was the histochemical, immunohistochemical and ultrastructural analysis of reparative fibrillogenesis in experimental lesions of Achilles' tendon. Subtotal tenotomy of Achilles' tendon was performed in twenty Wistar rats. The scar tissue was analysed 2, 4, 7, 14, 21, 30, 45 and 60 days post-operatively. Histochemical, (resorcin-fuchsin, aldehyde-fuchsin, iron haematoxylin and Fullmer and Lillie's methods) immunohistochemical (antibody against collagen I, II and elastin) and ultrastructural analyses were performed. Three phases in the healing process were distinguished: 1) inflammatory, 2) proliferative, and 3) remodelling phase. The inflammatory phase was characterised by haematoma, fibrin deposition, inflammatory cells, fibroblasts, beginning of collagen fibrillogenesis (200-400 A ? fibrils) and oxytalan fibrils. The proliferative phase was characterised by angiogenesis and fibroblast proliferation. Collagen fibres displayed a random arrangement and had a diameter of 400-600 A. Immature elastic fibres reached maximum tissutal concentration. In the remodelling phase, hypocellularity, normal vascularisation, tendon crimps, collagen fibres (800-1,000 A ?), elastic fibres with increased elastin deposition and reduction in oxytalan fibres were observed. In the course of the healing process collagen and elastic fibre fibrillogenesis exhibited consistent quantitative and qualitative variations (i.e. differences in the type and diameter of fibrils). The present study suggests that, together with other matrix macromolecules, also elastic fibres (oxytalan, elaunin and mature) are synthesised in significantly higher amounts during reparative fibrillogenesis and play a role in cell-matrix interaction.