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PubMed1996

Variables affecting pedicle screw plate fixation of an unstable L3-L4 defect.

Fresh frozen human cadaveric spinal specimens (T8-S1) were subjected to pure flexion extension bending moment and pure axial torque loadings while intervertebral rotations were recorded at the L3-L4, L2-L3, and Ll-L2 discs. A standardized unstable defect was created at the L3-L4 disc, and loading tests were repeated after application of bilateral Steffee plates in 2 configurations: a short plate with 2 pedicle screws (spanning the defect) and a longer plate with 3 pedicle screws (spanning the defect and 1 disc above). Each plating configuration was tested in the unlocked state (nuts compressing the plate down onto the spine) and locked state (nuts above and below the plate tightened against each other to clamp the plate to the screws). Locking the plates to the screws had no effect on any intervertebral rotation at any disc level. Use of a longer plate that also spanned the disc above the defect offered no advantage in controlling flexion extension rotations at the defect site. However, mean torsional rotation at the defect site with the 3-screw plate was approximately 50% of the mean for a 2-screw plate. Extension and torsional rotations at the L2-L3 disc (1 level above the defect site) were unaffected by application of a 2-screw plate; flexion rotation at this level increased slightly after plating. All motions at the L2-L3 disc were reduced (as would be expected) when the 3-screw plate spanned this uninjured disc. Plating the defect had no effect on disc rotations at the L1-L2 disc (2 levels above the fracture site).

Aged↗
PubMed1997

Regeneration of diaphyseal bone defects using resorbable poly(L/DL-lactide) and poly(D-lactide) membranes in the Yucatan pig model.

OBJECTIVES: To determine the effects of tubular resorbable polymer membranes on the healing of a segmental diaphyseal bone defect. DESIGN: A randomized prospective study using the minipig model. Animals were evaluated with in vivo roentgenograms on a biweekly basis until explanted at twelve weeks. SETTING: After surgery, animals were allowed unrestricted activity and weight bearing between twenty-four and forty-eight hours. ANIMALS: Fifteen yearling Yucatan minipigs. INTERVENTION: A 2.5- to 3.0-centimeter mid-diaphyseal defect was created in the middle third of the radius. Animals were assigned in groups of three to receive the following implants: (a) poly(L/DL-lactide), (b) poly(L/DL-lactide)-CaCO3, (c) poly(D-lactide), (d) poly(D-lactide)-CaCO3, and (e) an untreated defect. No adjunctive internal or external fixation was used as the ulna was left intact. MAIN OUTCOME MEASURES: The limbs were studied with in vivo anterior-posterior and lateral radiographs at biweekly intervals for the presence and pattern of bone formation. All limbs were explanted at twelve weeks postimplantation for methyl-methacrylate embedding and histologic and microradiographic study. RESULTS: The bone defects covered with membranes were completely reconstituted by six to eight weeks. Untreated defects healed with less bone formation and in a more disorganized pattern. Histologic evaluation of the implants demonstrated that the entire lumen of the implant was filled with bone, with some periosteal bone formation occurring on the outer surface of the membrane. There was direct apposition of bone onto the membrane surface or minimal fibrous tissue interposition between membrane and new bone. There was no foreign body or adverse reaction to the membrane. Untreated defects showed woven bone formation with clefts and irregularly shaped margins occupied by fibrous tissues or surrounding muscle tissues. CONCLUSIONS: This study supports the concept that a membrane enhances bone defect healing by excluding nonosseous tissues from a defect and providing structural scaffolding for periosteal and endosteal bone regeneration.

Absorption↗
PubMed2006

Simultaneous treatment of tibial bone and soft-tissue defects with the Ilizarov method.

OBJECTIVES: To evaluate the potential for limb salvage using the Ilizarov method to simultaneously treat bone and soft-tissue defects of the leg without flap coverage. DESIGN: Retrospective study. SETTING: Level I trauma centers at 4 academic university medical centers. PATIENTS/PARTICIPANTS: Twenty-five patients with bone and soft-tissue defects associated with tibial fractures and nonunions. The average soft-tissue and bone defect after debridement was 10.1 (range, 2-25) cm and 6 (range, 2-14) cm respectively. Patients were not candidates for flap coverage and the treatment was a preamputation limb salvage undertaking in all cases. INTERVENTION: Ilizarov and Taylor Spatial Frames used to gradually close the bone and soft-tissue defects simultaneously by using monofocal shortening or bifocal or trifocal bone transport. MAIN OUTCOME MEASUREMENTS: Bone union, soft-tissue closure, resolution or prevention of infection, restoration of leg length equality, alignment, limb salvage. RESULTS: The average time of compression and distraction was 19.7 (range, 5-70) weeks, and time to soft-tissue closure was 14.7 (range, 3-41) weeks. Bony union occurred in 24 patients (96%). The average time in the frame was 43.2 (range, 10-82) weeks. Lengthening at another site was performed in 15 patients. The average amount of bone lengthening was 5.6 (range, 2-11) cm. Final leg length discrepancy (LLD) averaged 1.2 (range, 0-5) cm. Use of the trifocal approach resulted in less time in the frame for treatment of large bone and soft-tissue defects. There were no recurrences of osteomyelitis at the nonunion site. All wounds were closed. There were no amputations. All limbs were salvaged. CONCLUSIONS: The Ilizarov method can be successfully used to reconstruct the leg with tibial bone loss and an accompanying soft-tissue defect. This limb salvage method can be used in patients who are not believed to be candidates for flap coverage. One also may consider using this technique to avoid the need for a flap. Gradual closure of the defect is accomplished resulting in bony union and soft-tissue closure. Lengthening can be performed at another site. A trifocal approach should be considered for large defects (>6 cm). Advances in technique and frame design should help prevent residual deformity.

Debridement↗
PubMed1997

Management of large infected tibial defects with antibiotic beads local therapy and staged fibular osteoseptocutaneous free transfer.

Fifteen patients with tibial fractures complicated by large infected tibial defects were treated with a two-stage protocol. In the first stage, antibiotic-impregnated polymethylmethacrylate bead chains were used to obliterate the debrided osseous defect, and a meshed porcine skin was used for temporary wound coverage. In the second stage, the bead chains were removed, and the defects were reconstructed with a microvascularized fibular osteoseptocutaneous free transfer. The time between the first and second stages of treatment was 2 to 6 weeks. The bone defects ranged from 6 to 16 cm, and the skin defect areas ranged from 10 to 82 cm2. Wound healing and bony union were achieved in all 15 cases. An additional muscle flap or skin graft was required for only three patients with a large skin defect. Minor pin tract infections were seen in two patients. Stress fractures in three cases were successfully managed with bracing, external skeletal fixation or plating, and cancellous bone grafting. All of the most recent roentgenograms showed good consolidation and hypertrophy of grafted fibular bones. No recurrence of osteomyelitis was observed during an average follow-up period of 50 months (range, 36-86 months). We therefore conclude that this treatment protocol provides rapid recovery from osteomyelitis. The fibular osteoseptocutaneous graft is a useful method for the reconstruction of a large tibial defect, and it also offers the unique advantage of simultaneously reconstructing a moderate skin defect.

Adult↗
PubMed1999

Progressive visual field defects from experimental glaucoma: measurements with white and colored stimuli.

PURPOSE: Our purpose was to study the effects of using monochromatic test stimuli to measure the relative rate of progression of visual field defects caused by experimental glaucoma. METHODS: Visual field measurements were obtained by static perimetry from trained macaque monkeys with laser-induced, unilateral glaucoma. The visual field defects were assessed by perimetric (global) indices derived from comparisons of experimental visual fields to the expected normal fields of monkeys. Three types of perimetry stimuli were used, the conventional white Goldmann III and two monochromatic (460 and 620 nm) Goldmann V test stimuli. The relationships between field defects with white and monochromatic stimuli were investigated by linear regression of the Z-scores for the perimetric indices. RESULTS: The correlations between the mean deviation global indices for chromatic vs. white stimuli were high (r > 0.9) and linear throughout the period of progression of field defects. The slopes of the regression lines typically were greater than unity, indicating that statistical significance was higher for visual field defects measured with chromatic stimuli than with white light stimuli. The higher significance level for defects measured with chromatic stimuli was not explained by a difference in visual thresholds, because the thresholds with chromatic and white light were highly correlated across the full range of visual field defects, from initial-onset to end-state. This result also suggests that the early detection of glaucomatous visual defects with monochromatic stimuli does not reflect a selective loss of retinal ganglion cells. CONCLUSIONS: Although these experiments do not suggest an alternative neural mechanism for the clinical utility of perimetry with chromatic light for the early detection of glaucoma, it is very likely that the combinations of neural and/or analytical factors that explain the utility of perimetry with chromatic stimuli will also provide an explanation for the higher sensitivities in identifying early glaucoma reported for other prototype stimuli.

Animals↗
PubMed2000

Interdental distraction osteogenesis and rapid orthodontic tooth movement: a novel approach to approximate a wide alveolar cleft or bony defect.

The closure of a wide alveolar cleft and fistula in cleft patients and the reconstruction of a maxillary dentoalveolar defect in traumatic patients are challenging for both orthodontists and surgeons. This is due to the difficulty in achieving complete closure by using local attached gingiva and the great volume of bone required for the graft. In this article, the authors propose using interdental distraction osteogenesis to create a segment of new alveolar bone and attached gingiva for the complete approximation of a wide alveolar cleft/fistula and the reconstruction of a maxillary dentoalveolar defect. They performed this procedure on one patient with a traumatic maxillary dentoalveolar defect and 10 patients with unilateral or bilateral cleft lips and palates who had varied dentoalveolar clefts/fistulas. Interdental and maxillary osteotomies were performed on one side of the dental arch by the cleft or defect. After a latency period of 3 days, the osteotomized distal segment of the dental arch was then distracted and transported toward the cleft or defect by using a toothborne intraoral distraction device. The alveoli and gingivae on both ends of the cleft or defect were approximated after distraction osteogenesis. The need for extensive alveolar bone grafting was eliminated. A segment of new edentulous alveolus and attached gingiva was created interdentally at a site distant to the cleft or defect. In the cleft patients, teeth were moved orthodontically into the regenerate (newly formed alveolar bone) dental crowding 1 week after distraction. The orthodontic tooth movement was rapidly completed in 3 months, and the edentulous space was eliminated. Interdental distraction osteogenesis minimizes an alveolar cleft/fistula and helps reconstruct a maxillary dentoalveolar defect by approximating the native alveoli and gingivae; it also creates new alveolar bone and gingiva for rapid orthodontic tooth movement.

Alveolar Process↗
PubMed2002

Reconstruction of through-and-through cheek defects involving the oral commissure, using chimeric flaps from the thigh lateral femoral circumflex system.

Repairing full-thickness cheek defects involving the oral commissure in the head and neck regions after tumor resection is a challenge for reconstructive surgeons. First, they are usually relatively large defects. Second, the axes of the cheek and intraoral lining are different from each other. Third, the shape and volume of the defect and the oral sphincter should be considered individually. Lateral femoral circumflex perforator flaps with at least two independent cutaneous perforators are suitable for reconstruction of such a defect in one stage. In this study, between January and December of 1999, a total of nine patients underwent reconstruction with chimeric lateral femoral circumflex perforator flaps immediately after resection of their oral cancers. The average age of the patients was 61 years (range, 42 to 74 years). The oral lining defects were between 5 x 5 cm and 6 x 12 cm in size, whereas the cheek defects were between 5 x 6 and 8 x 12 cm. Fifteen flaps were supplied by one perforator, and three flaps were supplied by two perforators. There were nine single arterial anastomoses, eight single venous anastomoses, and one double venous anastomosis. There were no total flap failures. One case of postoperative venous congestion was successfully treated by a second venous anastomosis. The average duration of hospitalization was 31.8 days (range, 18 to 49 days). The median follow-up time was 8.6 months, and all patients were alive at the time of evaluation. Six of nine patients had satisfactory or good contours of the cheek. Five of nine patients had normal deglutition. Six of nine patients had adequate oral continence. Compared with other free flaps, use of the combined (chimeric) lateral femoral circumflex perforator flaps for the reconstruction of cheek through-and-through defects involving the oral commissure has several advantages: (1) easy three-dimensional insetting, (2) a unique character suitable for the requirements of the oral lining and cheek skin to achieve good aesthetic appearance, (3) functional preservation of the oral sphincter and the resistance of gravity by use of the tensor fasciae latae, (4) minimal donor-site morbidity, (5) economic design, and (6) no need for microsurgical fabrication, because major vascular branches such as the transverse branch, the ascending branch, and the feeding branch to the rectus femoris muscle are not sacrificed in the procedure. The disadvantages of these flaps include (1) the complicated anatomy of the perforators, (2) the learning-curve requirement for their use, and (3) the occasional need for secondary venous drainage and shifts to double flaps. Although there are some difficulties, it was concluded that use of the chimeric lateral femoral circumflex perforator flaps in the selected cases is one of the good options available for the reconstruction of cheek through-and-through defects involving the oral commissure.

Adult↗
PubMed2002

Transport distraction osteogenesis: a new method to heal adult calvarial defects.

Popularized by Gavril Ilizarov in the 1960s, monofocal distraction osteogenesis has become a well-established method of endogenous bone engineering. This revolutionary surgical technique has significantly augmented the available reconstructive orthopedic and craniomaxillofacial procedures. Bifocal distraction osteogenesis, or bone transportation, is a modification of monofocal distraction that involves moving a free segment of living bone to fill an intercalary bone defect. Bifocal distraction has been applied successfully to reconstruct complex mandibular and long bone defects. Because traumatic or postsurgical calvarial defects do not spontaneously heal in humans older than 18 to 24 months of age, we hypothesized that bifocal distraction osteogenesis could be applied to the skull to close critical size calvarial defects. Critical size (15 x 15 mm) calvarial defects were created in eight New Zealand White rabbits. Next, a 15-mm x 10-mm calvarial box osteotomy was created just anterior to the skull defect. This osteotomy created a free bone segment that could be transported. A custom-made transport distraction device was fixed into place and the skin incision was closed. After a 4-day latency period, the distraction device was activated (0.5 mm once daily for 30 days) in seven animals; the distraction device in one animal was not activated and served as a control. All animals underwent 30 days of consolidation and were then killed. Radiographs and computed tomographic scans were performed at the following time points: end of latency period (postoperative day 4), mid-distraction (postoperative day 19), and end of consolidation period (postoperative day 64). Gross and histologic analysis was performed to evaluate the quality of the bony regenerate. The control animal healed with a fibrous union. Complete closure of the skull defects was observed in five of seven rabbits at the end of the consolidation period. One animal was removed from the study because of an early loosening of the distraction device, and one was removed because of device failure. Of the remaining five animals that completed the distraction protocol, radiographs and computerized tomographic scans showed successful ossification in all five rabbits at the end of the consolidation period. This study suggests that transport distraction osteogenesis is a promising technique that may be applied to a variety of commonly encountered craniofacial problems such as nonhealing calvarial defects.

Age Factors↗
PubMed2002

The free latissimus dorsi flap revisited: a primary option for coverage of wide recurrent lumbosacral defects.

In comparison with other regions of the trunk, defects located in the lumbosacral region are infrequent. However, these particular lesions sometimes present difficulties in reconstruction, arising from the quality of the surrounding tissue and the width of the defects. In this area, the skin adheres strongly to subcutaneous tissue and is difficult to mobilize. Attempts to perform local or regional flaps for covering defects of this area often end in necrosis of the flaps, with subsequent risk of infection and unstable wounds. The consequence is larger defects and the need for a wide, tension-free coverage, which can be performed after a wide debridement. The authors report on 10 patients presenting with wide, recurrent (and in some cases, infected) defects of the lumbosacral region, after already having undergone several reconstructive local or regional operations. In all cases, the authors harvested a free latissimus dorsi flap, lengthening the pedicle by means of an arteriovenous suralis loop connected to the thoracodorsal vessels (lumbar defect) or the femoral vessels (sacral defect). The procedure, already described in the past by others, has been revisited by the authors' group and used as the technique of choice in selected cases, that is, in the presence of wide, recurrent, and infected lesions; radiation; and scarring injuries. The authors thus obtained stable coverage with well-vascularized tissue and were able to save the patients any further operations. The authors suggest, therefore, that this procedure can be used in cases of wide and recurrent defects where other conventional procedures have failed. Advantages, disadvantages, and technical features of the method used are discussed in this article.

Back↗
PubMed1995

Relationship between premacular cortical vitreous defects and idiopathic premacular fibrosis.

PURPOSE: To investigate the relationship between the defect in the premacular cortical vitreous detached from the retina and the development of idiopathic premacular fibrosis. METHODS: One hundred six consecutive patients (106 eyes) with posterior vitreous detachment but no other ocular disorders were prospectively studied. All follow-up periods were longer than 6 months. The vitreous condition was studied using an aspherical, +58.6-diopter preset lens with a slit-lamp. RESULTS: The detached premacular cortical vitreous was a continuous, unbroken sheet in 93 (88%) of the 106 eyes; in 13 (12%) eyes, the detached premacular cortical vitreous had an oval or round defect ranging from 4 to 7 disc diameters over the macula. At the study's conclusion, 36 (34%) of the 106 eyes had idiopathic premacular fibrosis; 70 (66%) eyes did not. The defect in the detached premacular vitreous was observed in 9 (25%) of the 36 eyes that eventually developed idiopathic premacular fibrosis and in 4 (6%) of the 70 eyes that did not undergo such development. The incidence of the defect in the detached premacular cortical vitreous was significantly higher in eyes with idiopathic premacular fibrosis than in eyes without (P = 0.011). Nine (69%) of thirteen eyes with the defect in the detached premacular cortical vitreous developed premacular fibrosis, whereas only 25% of eyes without the defect developed it. Twenty-seven (75%) of thirty-six eyes with premacular fibrosis did not have a defect in the detached premacular cortical vitreous. CONCLUSIONS: The defect in the detached premacular cortical vitreous probably occurs because the premacular cortical vitreous remains attached to the internal limiting lamina when a posterior vitreous detachment develops. The vitreous that remains attached to the macula may be related to the development of idiopathic premacular fibrosis.

Adult↗
PubMed2000

Study of the contralateral eye in patients with glaucoma and a unilateral perimetric defect.

PURPOSE: To study the unaffected fellow eye in patients with glaucoma and unilateral visual field defect, using conventional automated achromatic perimetry, blue-yellow short-wavelength automated perimetry (SWAP), and a nerve fiber layer analyzer (GDx; Laser Diagnostic Technologies, San Diego, CA). METHODS: Eighteen patients in whom a unilateral visual field defect was detected on conventional computerized threshold perimetry were selected. The contralateral eyes of these patients were studied with normal conventional threshold perimetry using blue-yellow perimetry and also were studied with the nerve fiber layer analyzer. Also, 18 eyes of 18 sex- and age- (+/-3 years) matched persons without glaucoma were selected as a control group. RESULTS: Of the 18 contralateral eyes, seven (38.8%) showed a visual field defect on blue-yellow conventional perimetry, and 10 (55.5%) showed a defect of the nerve fiber layer when evaluated with the nerve fiber analyzer. Of the 10 eyes with abnormal visual fields on the nerve fiber analyzer, six (60.0%) also showed a defect on blue-yellow perimetry. In the control group, no eyes showed visual field defect on SWAP, but three eyes (16.6% false positive rate) showed a visual field defect on the nerve fiber layer analyzer. CONCLUSION: These findings suggest that what appeared to be unilateral visual field defects may in fact have been bilateral in at least 33.3% of our patients (n = 6) for whom there was agreement between results of SWAP and the nerve fiber layer analyzer.

Aged↗
PubMed2006

Reconstruction of the lateral mandibulectomy defect: management based on prognosis and location and volume of soft tissue resection.

OBJECTIVE: To examine how the accompanying soft tissue resection of the oral cavity, oropharynx, neck, or face affects the reconstructive management of the lateral mandibulectomy defect. STUDY DESIGN: Retrospective review of 76 consecutive patients. METHODS: Patient and tumor variables were extracted from the medical records. Outcomes that were examined included method of reconstruction, medical complications, flap complications, and survival. RESULTS: Age greater than 70 years (P = .03), moderate or severe comorbidity (P = .01), and tumor involvement of the base of tongue (P = .03) were significantly associated with decreased use of a free flap and with decreased 3-year survival rates. For choice of free (osteocutaneous radial forearm free flap or fibula vs. rectus abdominis) and regional flaps (pectoralis or cervicodeltopectoral), lateral defects could be classified into one of three types: type 1 (n = 60), lateral defect with a soft tissue resection limited to the oral cavity and oropharynx; type 2 (n = 11), lateral defect with a through and through defect of the lower one third of the face (skin overlying the mandible) or neck; and type 3 (n = 5), lateral defect with an associated large-volume resection of the midface, parotid, or cheek skin. CONCLUSION: When the lateral mandible is resected with an accompanying large soft tissue defect of the neck or face (type 2 or type 3 defect), the reconstructive challenge becomes the determination of how best to cover the planned bony reconstruction or whether to perform only a soft tissue reconstruction. When placed in the context of expected prognosis, the proposed classification system based on the location and volume of the associated soft tissue resection can help guide the reconstructive options for these decisions.

Aged↗
PubMed2004

Primary closure of radial forearm flap donor defects with a bilobed flap based on the fasciocutaneous perforator of the ulnar artery.

To primarily repair a series of radial forearm flap donor defects, a total of 10 bilobed flaps based on the fasciocutaneous perforator of the ulnar artery were designed at the Chang Gung Memorial Hospital in Kaohsiung in the period from January of 2002 to January of 2003. All patients were male, with ages ranging from 36 to 67 years. The forearm donor defects ranged in size from 5 x 6 cm to 8 x 8 cm, with the average defect being 47 cm. One to three sizable perforators from the ulnar artery were consistently observed in the distal forearm and were most frequently located 8 cm proximal to the pisiform, which could be used as a pivot point for the bilobed flap. The bilobed flap consisted of two lobes, one large lobe and one small lobe. With elevation and rotation of the bilobed flap, the large lobe of the flap was used to repair the radial forearm donor defect and the small lobe was used to close the resultant defect from the large lobe. All bilobed flaps survived completely, without major complications, and no skin grafting was necessary. Compared with conventional methods for reconstruction of radial forearm donor defects, such as split-thickness skin grafting, the major advantage of this technique is its ability to reconstruct the donor defect with adjacent tissue in a one-stage operation. Forearm donor-site morbidity can be minimized with earlier hand motion, and better cosmetic results can be obtained. Furthermore, because a skin graft is not used, no additional donor area is necessary. However, this flap is suitable for closure of only small or medium-size donor defects. A lengthy postoperative scar is its major disadvantage.

Adult↗
PubMed2004

A 1-year study of osteoinduction in hydroxyapatite-derived biomaterials in an adult sheep model: part II. Bioengineering implants to optimize bone replacement in reconstruction of cranial defects.

The present study investigated hydroxyapatite biomaterials implanted in critical-size defects in the calvaria of adult sheep to determine the optimal bioengineering of hydroxyapatite composites to facilitate bone ingrowth into these materials. Five calvarial defects measuring 16.8 mm in diameter were made in each of 10 adult sheep. Three defects were filled with cement paste composites of hydroxyapatite and beta-tricalcium phosphate as follows: (1) 100 percent hydroxyapatite-cement paste, (2) 60 percent hydroxyapatite-cement paste, and (3) 20 percent hydroxyapatite-cement paste. One defect was filled with a ceramic composite containing 60 percent hydroxyapatite-ceramic, and the fifth defect remained unfilled. One year after implantation, the volume of all biomaterials was determined by computed tomography, and porosity and bone replacement were determined using backscatter electron microscopy. Computed tomography-based volumetric assessment 1 year after implantation demonstrated that none of the unfilled cranial defects closed over the 1-year period, confirming that these were critical-size defects. There was a significant increase in volume in both the cement paste and ceramic implants containing 60 percent hydroxyapatite (p < 0.01). There was no significant change in volume of the remaining cement paste biomaterials. Analysis of specimens by backscatter electron microscopy demonstrated mean bone replacement of 4.8 +/- 1.4 percent (mean +/- SEM) in 100 percent hydroxyapatite-cement paste, 11.2 +/- 2.3 percent in 60 percent hydroxyapatite-cement paste, and 28.5 +/- 4.5 percent in 20 percent hydroxyapatite-cement paste. There was an inverse correlation between the concentration of hydroxyapatite and the amount of bone replacement in the cement paste for each composite tested (p < 0.01). Bone replacement in 60 percent hydroxyapatite-ceramic composite (13.6 +/- 2.0 percent) was not significantly different from that in 60 percent hydroxyapatite-cement paste. Of note is that the ceramic composite contained macropores (200 to 300 microm) that did not change in size over the 1-year period. All cement paste composites initially contained micropores (3 to 5 nm), which remained unchanged in 100 percent hydroxyapatite-cement paste. Cement paste implants containing increased tricalcium phosphate demonstrated a corresponding increase in macropores following resorption of the tricalcium phosphate component. Bone replacement occurred within the macropores of these implants. In conclusion, there was no significant bone ingrowth into pure hydroxyapatite-cement paste (Bone Source, Stryker-Leibinger Inc., Dallas, Texas) in the present study. The introduction of macropores in a biomaterial can optimize bone ingrowth for reconstruction of critical-size defects in calvaria. This was demonstrated in both the ceramic composite of hydroxyapatite tested and the cement paste composites of hydroxyapatite by increasing the composition of a rapidly resorbing component such as beta-tricalcium phosphate.

Animals↗
PubMed2006

Lower eyelid orbicularis oculi musculocutaneous flap for reconstruction of nasal tip and supratip defects.

BACKGROUND: In clinical practice, there are many ways to reconstruct nasal defects. Despite this fact, achieving a desirable image and better functional results is still a problem. Banner, bilobed, and dorsal nasal flaps have recently been used to reconstruct defects up to 2 cm. For defects larger than 2 cm, flaps raised from the frontal region and face are used. The major disadvantages of these flaps are the visible scar and the frequent need for a second session. METHODS: The authors used orbicularis oculi musculocutaneous flaps raised from the lower eyelid, containing branches of the angular artery and the infraorbital artery in its pedicle, to reconstruct nasal tip and supratip defects. Between February of 2002 and March of 2004, reconstruction with orbicularis oculi musculocutaneous island flaps raised from the lower eyelid was performed on 15 patients (eight men and seven women) with nasal tip and supratip defects. Thirteen defects were secondary to basal cell carcinoma and two were secondary to congenital melanocytic nevus. The diameter of the defects ranged between 2.1 and 3.1 cm (average diameter, 2.5 cm). Patients were between 25 and 72 years old (average age, 52 years). RESULTS: Patients were followed up for an average period of 6 months (range, 1 to 12 months). In two patients (13.3 percent), postoperative venous problems were seen but resolved in 3 days. Partial necrosis developed in one patient (6.6 percent). In one patient (6.6 percent), minimal scleral show was seen in tolerable ranges. Neither ectropion nor other eyelid deformities were seen. CONCLUSIONS: The authors believe that this flap is a good alternative for reconstruction of nasal defects because of its advantages, namely, the need for only a single session, minimal donor-site morbidity, better color and thickness match, and easy and faster surgery.

Adult↗
PubMed2003

Renal perfusion defects after endovascular repair of abdominal aortic aneurysms.

PURPOSE: To determine the prevalence of new renal perfusion defects and the association of these events with aneurysm neck atheroma during endovascular stent-graft repair of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: A retrospective review was performed of 50 patients who underwent AAA repair with bifurcated endovascular stent-grafts without suprarenal components between June 1998 and May 1999. Pre- and postprocedural computed tomographic (CT) angiograms were reviewed to determine the prevalence of new renal perfusion defects. The percent volume of atheroma of the aneurysm neck was determined by three-dimensional volumetric reformation and correlated with prevalence of new postprocedural renal perfusion defects. Follow-up CT angiography was performed between 6 months and 2 years after the procedure and used to evaluate the presence of residual defects and interval changes. RESULTS: Of 50 subjects, 18% (n = 9) had new perfusion defects presumed to be embolic in origin. Follow-up was available for four patients: scarring and cortical thinning consistent with infarction developed in two, whereas the defects resolved in the other two. Analysis of aneurysm neck revealed an average percentage of atheroma of 32% and a range of 0%-73%. In subjects with >/=40% neck atheroma, the prevalence of new renal perfusion defects was 45.4% (five of 11), compared to 10.3% (four of 39) in subjects with <40% neck atheroma. This difference was significant (P =.0170). CONCLUSIONS: In this series, the frequency of renal embolic events associated with AAA endovascular repair was 18%. Prevalence of renal embolic perfusion defects was shown to correlate with volume of aneurysm neck atheroma.

Angiography↗
PubMed2004

Ocular defects in photosensitive epilepsy.

Patients with photosensitive epilepsy are susceptible to seizures due to photoparoxysmal response (PPR). This response adversely precipitates factors that modify the functional status of the visual system. Such factors may or may not be evident superficially, but may lead to ocular defects due to trauma, hormonal imbalance, abnormal intraocular pressure (IOP), or any other reflex-inducing stimuli. The extent to which photosensitive epileptic patients suffer from PPR-related ocular defects has not been documented fully. In this investigation, ocular defects in patients with photosensitive epilepsy are studied using visual-evoked response (VER). A total of 212 photosensitive epileptic patients were studied to ascertain the magnitude and distribution of ocular defects using the changes in EEG and visual-evoked potential (VEP); 51% of the patients were female, the age range was 1-46 years. The major ocular defects and complications found were visual field defects, optic nerve abnormalities, nystagmus, cataracts, amblyopia, and migraine. These findings were analyzed according to age and sex. The relationship between the ocular abnormalities and the interpretations of the changes in the characteristics of the VEP indicated that optic-related atrophies, visual defects, optic neuritis, chiasmal compression, nystagmus, migraine headache, cataracts, and amblyopia were prevalent in photosensitive epileptic patients at varying degrees. The results showed that although ocular defects in photosensitive epilepsy may not be obvious differentially, VEP can be used in their diagnosis, contrary to earlier studies reporting that VEP is not of much value in epilepsy diagnosis.

Adolescent↗
PubMed2001

Computer simulation of topological defects around a colloidal particle or droplet dispersed in a nematic host.

We use molecular dynamics to study the ordering of a nematic liquid crystal around a spherical particle or droplet. Homeotropic boundary conditions and strong anchoring create a hedgehog (radial point defect) director configuration on the particle surface and in its vicinity; this topological defect is canceled by nearby defect structures in the surrounding liquid crystal, so as to give a uniform director field at large distances. We observe three defect structures for different particle sizes: a quadrupolar one with a ring defect surrounding the particle in the equatorial plane; a dipolar one with a satellite defect at the north or south pole; and a transitional, nonequatorial, ring defect. These observations are broadly consistent with the predictions of the simplest elastic theory. By studying density and order-parameter maps, we are able to examine behavior near the particle surface, and in the disclination core region, where the elastic theory is inapplicable. Despite the relatively small scale of the inhomogeneities in our systems, the simple theory gives reasonably accurate predictions of the variation of defect position with particle size.

Journal Article↗