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Biomedical subjects

H C Vasconez

Publications and source records attributed to H C Vasconez.

13 recordsLinked to original sources
PubMed2001

Effect of a freeze-dried CMC/PLGA microsphere matrix of rhBMP-2 on bone healing.

The hypothesis of this research was that implants of poly(lactide-co-glycolide) (PLGA) microspheres loaded with bone morphogenetic protein-2 (rhBMP-2) and distributed in a freeze-dried carboxymethylcellulose (CMC) matrix would produce more new bone than would matrix implants of non-protein-loaded microspheres or matrix implants of only CMC. To test this hypothesis it was necessary to fashion microsphere-loaded CMC implants that were simple to insert, fit precisely into a defect, and would not elicit swelling. Microspheres were produced via a water-in-oil-in-water double-emulsion system and were loaded with rhBMP-2 by soaking them in a buffered solution of the protein at a concentration of 5.4 mg protein per gram of PLGA. Following recovery of the loaded microspheres by lyophilization, matrices for implantation were prepared by lyophilizing a suspension of the microspheres in 2% CMC in flat-bottom tissue culture plates. Similar matrices were made with 2% CMC and with 2% CMC containing blank microspheres. A full-thickness calvarial defect model in New Zealand white rabbits was used to assess bone growth. Implants fit the defect well, allowing for direct application. Six weeks postsurgery, defects were collected and processed for undecalcified histology. In vitro, 60% of the loaded rhBMP-2 released from devices or microspheres in 5 to 7 days, with the unembedded microspheres releasing faster than those embedded in CMC. In vivo, the rhBMP-2 microspheres greatly enhanced bone healing, whereas nonloaded PLGA microspheres in the CMC implants had little effect. The results showed that a lyophilized device of rhBMP-2/PLGA microspheres in CMC was an effective implantable protein-delivery system for use in bone repair.

Animals↗
PubMed2001

Enhancement of bone growth by sustained delivery of recombinant human bone morphogenetic protein-2 in a polymeric matrix.

PURPOSE: The purpose of this study was to develop a polymeric sustained delivery system for recombinant human bone morphogenetic protein-2 (BMP-2) and to evaluate local bone growth induced by the sustained release of BMP-2 in an animal model. METHODS: BMP-2 was incorporated in biodegradable poly(D,L-lactide-co-glycolide) (PLGA) microspheres to obtain different release rates. Two sustained and an immediate release implants were produced by suspending the BMP-2 loaded PLGA microspheres in aqueous sodium carboxymethylcellulose (CMC), lyophilizing, and cutting the dried materials to the size of the animal bone defects. The local in vivo release at the implantation site in rat calvarial defects was determined by gamma scintigraphy using radiolabeled BMP-2. The local bone induction in the critical size of rabbit calvarial defects was evaluated six weeks post implantation. RESULTS: The immediate release implant showed about 65% initial drug release within 24 h and the remaining BMP-2 quickly exhausted from the implantation site within 7 days. The sustained release implants, showing 45-55% initial release followed by a prolonged release for 21 days, released a greater amount of BMP-2 at the implantation site and maintained higher serum BMP-2 for the longer period of time compared to the immediate release implant. Significant bone growth was observed in all BMP-2 treated defects while the defects without treatment or with BMP-2-free implant showed minimal bone healing. 75-79% of rabbit calvarial defect area was healed with newly induced bone matrix by the sustained release implants in 6 weeks as compared to 45% recovery from the immediate release implant. CONCLUSION: The sustained delivery of BMP-2 based on the biodegradable PLGA microsphere system resulted in faster and more complete bone healing in the animal model.

Animals↗
PubMed1999

Skin contraction with pulsed CO2 and erbium:YAG laser.

The purpose of this study was to assess the physical response of skin to laser resurfacing in a real-time, quantitative fashion. The study was designed to assess skin contraction from two opposite standpoints. First, change in tension was measured during laser application while samples were held at constant length. Second, change in length of a sample under no tension was measured during laser treatment. These two disparate analyses represent the two possible extremes of the clinical situation in which skin exists under some tension with some laxity to allow for decrease in length. A custom apparatus with digital interface for skin tension measurements was used to produce single sample tracings of change in skin tension with laser treatment. Length change was measured for individual samples by continuous sonomicrometer readings. Individual sample data were then plotted in a time versus tension/length graph. Skin contracts immediately to a peak level and then relaxes to a sustained plateau level for both CO2 and erbium:YAG lasers. Increased contraction was noted when the beam penetrated into the dermis. Greater peak and plateau contraction is observed after the beam has penetrated into the dermis. Skin contraction varies directly with energy for CO2 and erbium:YAG laser. Findings were similar when skin tension was measured with the sample held at constant length and when length change was measured with the sample under no tension. Char left on the skin after a pass with CO2 laser substantially decreases skin contraction. High-density settings with CO2 laser yield pulse stacking, which effectively irradiates the same portion of tissue with char on it. Skin contraction varies inversely with computer pattern density settings for CO2 laser due to this pulse stacking effect. Density has little effect on skin contraction for the erbium:YAG laser because little char is generated. Histologic analysis identified a zone of coagulated dermis that correlates linearly with skin contraction.

Animals↗
PubMed1998

Two lyophilized polymer matrix recombinant human bone morphogenetic protein-2 carriers in rabbit calvarial defects.

We have developed a lyophilized bone morphogenetic protein (BMP) delivery device that can be formulated to control release over 2 to 8 weeks. Bioerodible poly (d,l lactide-co-glycolide) particles loaded with 90 micrograms recombinant human BMP-2 were suspended in either carboxymethylcellulose (CMC) or methylcellulose (MC) implants. Plain CMC and MC implants served as controls, as did a nonimplanted group. A total of 40 rabbits was evaluated histologically 2, 4, or 8 weeks after receiving circular full-thickness 15-mm calvarial defects. MC appeared to prevent prolapse of periosteum and dura into the defects and did not elicit bone growth. Addition of BMP improved the result. CMC implants appeared to encourage bone growth even in the absence of BMP. When BMP was added, new bone formed earlier. CMC may influence new bone formation because it is hydrophilic. MC is less hydrophilic and may cause undue inflammation. Either can be combined with BMP to produce unitary devices that are easy to make and use.

Animals↗
PubMed1997

Supraorbital roof fractures: a formidable entity with which to contend.

Supraorbital roof fractures are uncommon. The incidence has been quoted at between 1 and 5%. We believed that the incidence and morbidity of supraorbital roof fractures were actually higher. The charts of 621 inpatients with facial fractures between September 1993 and September 1995 were retrospectively reviewed. Parameters included patient characteristics; mechanism of injury; fracture characteristics; associated clinical, computed tomography, and operative findings; presence of associated skull and frontal sinus fractures; and complication rates. Fifty-eight patients (9.3%) had supraorbital roof fractures, making this one of the largest series. The average age was 31 years and the predominant mechanism of injury was motor vehicle accidents. Sixty-nine percent of the patients had associated skull fractures and 54% had frontal sinus fractures. Thirty-one of the cases were open and 32 cases were treated operatively. Dural tears were present in 14 patients, traumatic encephalocele in 3, proptosis in 6, pulsatile proptosis in 3, orbital apex syndrome in 1, persistent cerebrospinal fluid leak in 3, and meningitis in 5. A majority of the patients had associated intracranial bleeds. The incidence and morbidity of supraorbital roof fractures are much higher than previously thought. The treatment of cases should be individualized, taking into account displacement, association with skull and frontal sinus fractures, dural tears, and intracranial hemorrhage.

Adolescent↗
PubMed1994

Sequentially linked free flaps in head and neck reconstruction.

Free tissue transfer has become a useful technique for reconstructing complex three-dimensional defects following the extirpation of head and neck malignancies. This technique, however, may be limited by inadequate vascularity in the recipient site when a patient has been subjected to operative procedures or radiation therapy. The use of serial flaps, with the first flap connected sequentially to the second, reduces the need for dual recipient vessels in a surgical field when two flaps are required for reconstruction. Although this procedure is more technically demanding than more traditional approaches, it can provide a satisfactory, reliable one-stage composite reconstruction under these difficult circumstances. Results have been functionally and aesthetically superior to those achieved with pedicled one-flap reconstructive methods.

Carcinoma, Squamous Cell↗
PubMed1993

Soft-tissue coverage of the shoulder and brachium.

Injuries to the upper extremity often involve bone and soft-tissue elements, as do injuries to the lower extremity. Proper reconstruction of the soft-tissue deficits in concert with bone restoration is essential to final recovery. Better understanding of the blood supply and newer concepts of managing severely injured limbs has improved the ability to manage these challenging problems.

Arm↗
PubMed1991

Immediate closure of traumatic upper arm and forearm injuries with the latissimus dorsi island myocutaneous pedicle flap.

This paper reports the authors' experience with latissimus dorsi island pedicle flaps in the acute treatment of massive arm injuries. Seven patients with upper arm injuries and four patients with forearm injuries were treated with latissimus dorsi pedicle flaps. All cases involved massive soft-tissue loss and open fractures. Primary healing of wounds occurred without complications in 10 of 11 patients; the eleventh developed a wound infection. There were no instances of flap loss or vascular complications. This report compares and discusses surgical management options and details the importance of robust, immediate soft-tissue coverage for optimal functional recovery. Contrary to traditional thought, delay in definitive wound closure may be unnecessary when aggressive debridement is followed by acute flap closure.

Adolescent↗
PubMed1991

Management of extremity injuries with external fixator or Ilizarov devices. Cooperative effort between orthopedic and plastic surgeons.

Major advances in the last decade have improved the treatment and outcome of patients with moderate to severe lower extremity injuries. Better transport and emergency room facilities, which allow more prompt repair of injuries, advances in bone stabilization, and better methods of soft-tissue reconstruction have led to a significant decrease in amputation and infection rates. This article presents the Mangled Extremity Severity Score (MESS) index and Gustilo's classification to evaluate injuries. Orthopedic, plastic, and vascular surgeons collaborate to manage these injuries in five categories: limb viability, timing, debridement, fixation, and secondary reconstruction. Finally, two cases are presented to demonstrate practical application of these steps, and guiding principles are outlined.

Adult↗
PubMed1990

Maxillofacial trauma.

If a multiply injured patient with severe head injuries, intra-abdominal and intrathoracic injuries is admitted, the diagnosis and management of the facial fractures may be shunted into the background. With the tremendous methods of modern medicine at hand, we are adequately able to resuscitate, treat, and discharge those patients. If the maxillofacial injuries go undiagnosed or untreated, the patient is left with some fairly significant sequelae in function and appearance that are difficult to treat on a delayed basis. Initial management of those injuries can be done concomitantly with management of the other serious life-threatening injuries and a successful outcome achieved. The traditional approach of waiting "until all the swelling goes down" before definitive correction of bony or soft tissue problems are addressed, has been shown to produce inadequate and disabling results both from a structural and functional viewpoint. Following the first or at most second week after injury, the process of bone healing and scar formation have usually progressed quite quickly. This is especially true in children who normally have a very high metabolic rate. A displaced facial fracture not corrected during the initial "golden" period will require major manipulation and even refracture in order to adequately reduce the segments into the proper position and a less satisfactory result than acute management. Similar considerations with respect to the skin and soft tissues are also important. Once scar tissue has formed it becomes very difficult to restore normal or near-normal appearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMedDate not supplied

Mediastinal dissection and reconstruction for recurrent Hürthle cell carcinoma of the thyroid.

A 69-year-old man presented with recurrent Hürthle cell carcinoma of the thyroid. Successful surgical resection of the recurrent tumor included the larynx and trachea; skin, soft tissues, and lymph nodes of the neck; and the tissues of the anterior mediastinum, including upper sternum and clavicular heads. Coverage of the wound was accomplished with an inferiorly based parasternal fasciocutaneous flap and a long pectoralis myocutaneous flap. This represents the first reported case of Hürthle cell carcinoma treated with mediastinal dissection for extensive local disease. Radical surgical resection should be considered for any patient with Hürthle cell carcinoma of the thyroid in view of the ineffectiveness of nonsurgical modalities.

Adenocarcinoma↗