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Biomedical subjects

Allen T Bishop

Publications and source records attributed to Allen T Bishop.

At least 19 recordsLinked to original sources
PubMed2007

Short-term immunosuppression and surgical neoangiogenesis with host vessels maintains long-term viability of vascularized bone allografts.

Currently available methods to reconstruct large skeletal defects have limitations. These include nonunion and stress fractures in structural allografts, and inability to match the size, shape, and/or strength of most recipient sites using vascularized fibular autografts. Prosthetic diaphyseal replacements may loosen or produce periprosthetic fractures. Transplantation of living allogenic bone would enable matching donor bone to the recipient site, combined with the desirable healing and remodeling properties of living bone. We propose a novel method by which the transplantation of such tissue might be done without the risks of life-long immunosuppression, using surgical neoangiogenesis to develop a new host-derived osseous blood supply. We performed vascularized femoral allografts from 86 female Dark Agouti donor rats to male Piebald Virol Glaxo recipients across a major histocompatibility (MHC) barrier. In addition to microvascular reconstruction of the nutrient vessel, we surgically implanted a host arteriovenous (AV) bundle into the medullary canal to promote host vessel neoangiogenesis. Independent variables included patency of the implanted AV bundle, and use of 2 weeks' FK-506 immunosuppression. After 18 weeks, bone blood flow was measured, and neoangiogenic capillary density quantified. Bone blood flow and capillary density were significantly greater in transiently immunosuppressed recipients with a patent AV pedicle. We conclude that neoangiogenesis from implanted host-derived AV-bundles, combined with short-term immunosuppression maintains blood flow in vascularized bone allografts, and offers potential for clinical application.

Anastomosis, Surgical↗
PubMed2007

Vascularized bone allotransplantation: current state and implications for future reconstructive surgery.

This article focuses on current advances in musculoskeletal tissue allotransplantation, including strategies for maintaining tissue viability in the face of histocompatibility mismatch and resulting acute and chronic rejection responses. In particular, it introduces a novel concept developed in the authors' laboratory and currently under evaluation that may obviate the problem of chronic rejection. The authors have used therapeutic angiogenesis to develop a host-derived neoangiogenic circulation that maintains blood flow regardless of rejection. The replacement of the allogeneic vessels together with bone remodeling from host-derived cells eventually may largely replace the allogeneic osteocytes and bone with native bone.

Animals↗
PubMed2006

Venous congestive flap salvage with subcutaneous rtPA.

Free-flap success has been the rule with technical advancements in microsurgery. Despite improvements, thrombosis and flap loss still occur occasionally. Salvaging a sick flap can be a harrowing experience, even in the most experienced hands. Thrombolysis using intravenous and intra-arterial urokinase, streptokinase, and/or tissue plasminogen activator (rtPA) administered through the flap vascular pedicle has been reported in free-flap salvages. In such situations, success depends on early diagnosis and emergent exploration. Recently, we successfully used rtPA subcutaneously to salvage a venous congested free transverse rectus abdominus myocutaneous (TRAM) flap. Here, we report on that case.

Adult↗
PubMed2006

The outcomes and complications of 1,2-intercompartmental supraretinacular artery pedicled vascularized bone grafting of scaphoid nonunions.

PURPOSE: Over the past decade vascularized bone grafts that use a 1,2-intercompartmental supraretinacular artery (1,2-ICSRA) pedicle have gained popularity in the treatment of scaphoid nonunions. The purpose of this study was to evaluate critically the outcome, complications, and failures of 1,2-ICSRA-based vascularized bone grafting at our institution to understand better the appropriate indications, methods, and possible contraindications. METHODS: From January 1994 through July 2003, 50 scaphoid nonunions in 49 patients were treated with 1,2-ICSRA-based vascularized bone grafts. A retrospective review of the clinical and radiographic information was performed. Two patients were lost to follow-up study. Nine female and 38 male patients averaging 24 years of age were followed-up for an average of 7.8 months. RESULTS: Thirty-four scaphoid nonunions went on to union at an average of 15.6 weeks after surgery. Complications occurred in 8 patients and consisted of graft extrusion, superficial infection, deep infection, and failure of fixation. Univariate risk factors for failure included older age, proximal pole avascular necrosis, preoperative humpback deformity, nonscrew fixation, tobacco use, and female gender. CONCLUSIONS: Although previous researchers have concluded that vascularized bone grafts based on the 1,2-ICSRA are efficacious in the treatment of scaphoid nonunions, we determined that a successful outcome is not universal and depends on careful patient and fracture selection and appropriate surgical techniques. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level IV.

Adolescent↗
PubMed2006

Dorsal distal radius vascularized pedicled bone grafts for scaphoid nonunions.

Fractures of the scaphoid, particularly its proximal pole, are at risk of progressing to nonunion because of the tenuous, retrograde blood supply. The overall incidence of scaphoid fractures developing nonunion ranges from 10% to 15%, whereas proximal pole fractures of the scaphoid can have up to a 30% incidence of nonunion. Avascular necrosis of these proximal pole fractures can occur in 14% to 39% of cases. Dorsal distal radius vascularized pedicled bone grafting is an alternative to conventional measures for the treatment of displaced proximal pole fractures, established nonunions, and avascular necrosis of the proximal fragment. This graft is based on the 1,2-intercompartmental supraretinacular artery, which has reliable anatomy and predictable course between the first and second extensor compartments. The graft can be harvested and inset into the prepared fracture site using a single-incision approach. The indications, contraindications, technique, and results of treatment are reviewed and detailed.

Bone Transplantation↗
PubMed2006

The use of massive bone allograft with intramedullary free fibular flap for limb salvage in a pediatric and adolescent population.

BACKGROUND: Long segmental bony defects after tumor extirpation can pose difficult problems for the reconstructive surgeon. Capanna and colleagues have described a technique that places a free fibular flap within the intramedullary canal of an allograft for reconstruction of large intercalary bony defects. This article describes the authors' long-term follow-up with this technique for the treatment of large segmental bone defects in a pediatric population. METHODS: Over a 6-year period, seven patients underwent bony reconstruction with an allograft and vascularized fibular construct. All reconstructions were performed for lower extremity salvage after tumor extirpation. Grafts were evaluated for viability with bone scans 10 days postoperatively. Radiologic and clinical evaluations were performed on all patients. Time to union was recorded through evaluation of plain radiographs. Patients' charts were evaluated for postoperative complications. RESULTS: There were two female and five male patients with an average age of 10.5 years. The average follow-up time was 36 months (range, up to 72 months). Limb salvage was 100 percent, with all bone scans positive at 10 days. Two nonunions at the allograft interface were treated successfully with a secondary bone graft. The average time to complete bony union of the fibula and allograft to the native bone was 9 months. There were no allograft fractures and no infections. One patient developed nonunion at the donor leg syndesmosis site. Average final knee motion was 110 degrees. All patients returned to ambulation. CONCLUSION: Intramedullary free fibular flaps in combination with massive bony allografts provide an excellent option in the pediatric population for reconstruction of large bony defects after tumor extirpation.

Adolescent↗
PubMed2006

Results of vascularized rib grafts in complex spinal reconstruction.

BACKGROUND: The application of vascularized rib grafts in spine surgery has been limited to the treatment of kyphosis with anterior placement of the rib graft to facilitate anterior spine arthrodesis. The outcomes following use of vascularized rib grafts in complex spinal reconstruction have not been adequately evaluated. The purpose of this study was to determine the results, including the time to osseous union and complications, following anterior or posterior placement of pedicled vascularized rib grafts for complex spinal reconstruction. METHODS: The medical records and images of all patients in whom a vascularized rib graft had been used for a multisegmental spine reconstruction at a single institution between 1994 and 2004 were retrospectively reviewed. Eighteen patients (mean age, 45.3 years) who had been followed for an average of 31.8 months were identified. Details regarding indications, the levels that were spanned, the graft length, the time to union, and complications were evaluated. RESULTS: The preoperative diagnoses included metastatic or primary tumor (thirteen patients) and progressive kyphosis secondary to chronic osteomyelitis (two), injury (one), congenital anomalies (one), or implant failure (one). On the average, 4.4 levels were fused and 1.9 vertebral bodies were excised. All eighteen arthrodeses included various forms of allograft and/or autograft material, and instrumentation was used, in addition to the vascularized rib graft, in twelve patients. The mean rib length was 16.1 cm, and a rib between the fifth and eleventh ribs, inclusive, was used, depending on the location of the spinal reconstruction. The average time to union was 6.8 months, and all rib grafts united. There were no complications specific to the rib-harvesting procedure. CONCLUSIONS: The use of a vascularized rib graft in complex spinal reconstruction adds little time to the overall procedure, is associated with low morbidity, and appears to offer substantial benefits to the patient.

Adolescent↗
PubMed2005

Clinical significance of suprascapular nerve mobilization.

The anatomy of the suprascapular nerve is important to surgeons when focal nerve lesions necessitate surgical repair. Recent experience with a patient who had a complete suprascapular nerve lesion in the retroclavicular region (combined with axillary and musculocutaneous nerve lesions) is presented to illustrate that successful direct nerve repair is possible despite resection of a neuroma. Specifically, we found that neurolysis and mobilization of the suprascapular nerve and release of the superior transverse scapular ligament provided the necessary nerve length to achieve direct nerve repair after the neuroma was removed. A combined supraclavicular and infraclavicular approach to the suprascapular nerve provided excellent visualization, especially in the retroclavicular region. Postoperatively, the patient recovered complete shoulder abduction and external rotation with the direct repair, an outcome uncommonly achieved with interpositional grafting. Based on our operative experience, we set out to quantify the length that the suprascapular nerve could be mobilized with neurolysis. Mobilization of the nerve and release of the superior transverse scapular ligament generated an average of 1.6 cm and 0.7 cm of extra nerve length respectively, totaling 2.3 cm of additional usable nerve length overall. The ability to expose the suprascapular nerve in the retroclavicular/infraclavicular region and to mobilize the suprascapular nerve for possible direct repair has not been previously emphasized and is clinically important. This surgical approach and technique permits direct nerve repair after resection of a focal neuroma in the retroclavicular or infraclavicular region, thus avoiding interpositional grafting, and improving outcomes.

Adult↗
PubMed2005

Gradual graft-cell repopulation with recipient cells following vascularized bone and limb allotransplantation.

Little is known about the fate of graft cells following vascularized bone allografting. This study was conducted to define the process of graft-cell repopulation with recipient cells. Sixty-five vascularized tibial bone and 50 limb allotransplantations were performed in rat sex-mismatched pairs. FK 506 was used for immunosuppression. The ratio of donor and recipient cells in the graft was evaluated by semiquantitative polymerase chain reaction, using the Y-chromosome primers. Allografted bones had no rejection episodes. In the vascularized bone allograft model, donor-derived cells were gradually replaced by cells of recipient origin, such that by 24 weeks, they comprised only 10% of total cells. In the limb allograft model, male recipient cells were detected in female grafts not at 1 week but at 48 weeks posttransplantation. The ratio of recipient cells was more than 10% in the femur and tibia. Recipient-derived cells gradually migrated into the grafted bone cells with the passage of time.

Animals↗
PubMed2005

Functioning free-muscle transfer for brachial plexus injury.

Functioning free-muscle transfers are now an important, even essential, tool in the current management of patients with brachial plexus injury. They are indicated for the restoration of elbow flexion in patients who delay presentation(those seen after 6 to 9 mo). Double free-muscle transfers provide the possibility of simple grasp function when combined with nerve transfers or grafts for restoration of shoulder motion, hand sensation, and triceps function.

Brachial Plexus↗
PubMed2005

The use of the 4 + 5 extensor compartmental vascularized bone graft for the treatment of Kienböck's disease.

PURPOSE: The use of vascularized bone grafts for the treatment of Kienböck's disease may prevent ongoing lunate collapse and provide relief of wrist symptomatology. This study examines our experience with the use of the 4 + 5 extensor compartmental artery (ECA) bone graft for the treatment of Kienböck's disease. METHODS: A retrospective review was performed of all patients having pedicled vascularized bone grafts for Kienböck's disease between 1991 and 2002. Only those patients who had reconstruction with a 4 + 5 ECA graft were included in the study. Presurgical and postsurgical measurements included range of motion, grip strength, and pain evaluation. Measurements of the radiolunate angle, radioscaphoid angle, Stahl's index, and carpal height ratio were taken from presurgical and final follow-up radiographs. Postsurgical magnetic resonance imaging scans were also examined to verify revascularization of the lunate. Statistical analysis was performed using Student's t test. A chi-square test was used to evaluate the effects of lunate revascularization on radiographic progression of disease. Twenty-six 4 + 5 ECA vascularized bone grafts were performed as treatment for Kienböck's disease. The average patient age was 32 years. At the time of surgery 12 patients were graded as stage II, 10 as IIIA, and 4 as IIIB. Mean follow-up time was 31 months. RESULTS: At a mean follow-up of 3 months, motion improved from 68% to 71% of the unaffected side, grip strength improved from 50% to 89% of the unaffected side, and 92% of patients had significant improvement in their pain. Satisfactory results were seen in 85% of patients based on the Lichtman outcome score. Seventy-seven percent of patients showed no further collapse on postsurgical radiographs. Sixty-five percent of patients had follow-up magnetic resonance imaging scans at a mean of 20 months after surgery. Seventy-one percent of patients showed evidence of revascularization with improvement in the T2 and/or T1 signal. CONCLUSIONS: The 4 + 5 ECA bone graft provides a reliable alternative for the treatment of Kienböck's disease and may aid in lunate revascularization.

Adolescent↗
PubMed2005

Acute coronal plane scaphoid fracture and scapholunate dissociation from an axial load: a case report.

Coronal fractures of the scaphoid are rare and can be difficult to diagnose. Axial load injuries that result in a complete coronal fracture of the scaphoid associated with an acute scapholunate dissociation are exceedingly rare. In our patient the radiographic finding of wide scapholunate dissociation was obvious; however, the coronal scaphoid fracture was not recognized initially nor suspected. During surgery the coronal scaphoid fracture was identified, reduced anatomically, and fixed with a compression screw. The scapholunate ligament also was repaired. A good result was obtained with return to sports with extension of 60 degrees and flexion of 70 degrees , grip strength equal to that of the uninjured wrist, and no radiographic problems (arthrosis, avascular necrosis, nonunion).

Adolescent↗
PubMed2005

Cell traffic between donor and recipient following rat limb allograft.

Although cell traffic from the graft into the recipient and from the recipient into the graft had been noticed in allogeneic organ transplantation, little is known following whole-limb allografting. This study was conducted to define cell migration between donor and recipient. Sixty-seven vascularized hind limb allotransplantations were performed in rat sex-mismatched pairs and the recipient animals were treated with FK506 immunosuppression. The ratio of donor and recipient cells was evaluated by semi-quantitative PCR using the specific primers of the Y-chromosome. Allografted limbs had no rejection episode until the final assessment. The male recipient cells were detected in female limb grafts not at 1 week but at 48 weeks after transplantation. The male donor cells were detected in the humerus and tibia in the female recipient but not in the gastrocnemius muscle and leg skin. Our results demonstrated that recipient-derived cells gradually migrated into the grafted bone, muscle and skin cells with the duration of time. Donor-derived cells migrated into the healthy bones but not into the healthy muscle and skin. Because active regeneration occurs in the grafted limb to compensate graft damage secondary to ischemia and operative intervention, recipient-derived cells may mediate a muscular and dermo-epidermal renewal.

Animals↗
PubMed2005

Vascularized free fibula transfer for oncologic reconstruction of the humerus.

UNLABELLED: Reconstruction of the humerus after oncologic resection is challenging. Vascularized free-fibula transfer allows the potential for rapid autograft incorporation in areas compromised by radiation, chemotherapy, and resection. A retrospective case series of vascularized free-fibula transfers for humeral reconstructions is reported. Fifteen patients were identified; nine had surgery for glenohumeral arthrodesis (three primary fusions, six salvage/revision), four had surgery for intercalary defects (three primary reconstructions, one salvage), one patient had an onlay graft for a pathologic fracture in irradiated bone, and one patient had an osteoarticular graft. Average followup was 68 months. One patient died from disease 41 months after surgery. Oncologic outcome was excellent with no local recurrence and preservation of all limbs. There were an average of 0.8 major complications (requiring reoperation) and 0.5 minor complications per patient. The most frequent complication was fracture, occurring in six of 15 patients. All patients went on to bony union except two patients with glenohumeral arthrodesis with asymptomatic fibrous unions. Mean time to union was 12 months. Vascularized free fibula transfer provides an effective and successful means of limb-preserving reconstruction after oncologic resection of the humerus. Healing time may be prolonged, and refracture and other complications commonly are encountered. LEVEL OF EVIDENCE: Therapeutic study, Level IV-1 (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Bone Neoplasms↗
PubMed2005

Adult traumatic brachial plexus injuries.

Adult traumatic brachial plexus injuries are devastating, and they are occurring with increasing frequency. Patient evaluation consists of a focused assessment of upper extremity sensory and motor function, radiologic studies, and, most important, preoperative and intraoperative electrodiagnostic studies. The critical concepts in surgical treatment are patient selection as well as the timing and prioritizing of restoration of function. Surgical techniques include neurolysis, nerve grafting, neurotization, and free muscle transfer. Results are variable, but increased knowledge of nerve injury and repair, as well as advances in microsurgical techniques, allow not only restoration of elbow flexion and shoulder abduction but also of useful prehension of the hand in some patients.

Adult↗
PubMed2004

Vascular endothelial growth factor (VEGF) gene transfer enhances surgical revascularization of necrotic bone.

Avascular necrosis of bone is a relatively common clinical condition caused by inflammatory conditions, steroid or other drug use, and trauma that affect many different sites in man. Revascularization of the necrotic bone is slow to occur, often resulting in bone resorption and eventual collapse of the involved bone. Rapid revascularization and subsequent bone remodeling may lead to improved outcomes. Surgical revascularization with arterovenous bundles (AV bundles) or vascularized bone grafts results in neoangiogenesis and bone remodeling. Gene transfer of an angiogenic factor to the vessel wall may be an additional strategy to further accelerate this process. In this study, we examined the effectiveness of vascular endothelial growth factor (VEGF) gene transfer to augment surgical revascularization of necrotic bone. An adenoviral vector, either with the VEGF gene (VEGF-A) or identical virus without the cDNA VEGF insert (ADV-DeltaE1) was used to transduce endothelial cells in rabbit saphenous arteries. The artery was then placed with its venae comitantes as an AV bundle into necrotic iliac crest bone in vivo. Angiogenesis in the necrotic bone was quantified by bone blood flow measurement and assessment of vessel density following microangiography. The extent of neoangiogenesis was significantly greater in the VEGF group than the control group at 1 week postoperatively.

Animals↗
PubMed2004

Gracilis free muscle transfer for restoration of function after complete brachial plexus avulsion.

OBJECT: The authors report the functional outcomes after functioning free muscle transfer (FFMT) for restoration of the upper-extremity movement after brachial plexus injury (BPI). METHODS: The authors conducted a retrospective review of 36 gracilis FFMT procedures performed in 27 patients with BPI between 1990 and 2000. Eighteen patients underwent a single gracilis FFMT procedure for restoration of either elbow flexion (17 cases) or finger flexion (one case). Nine patients underwent a double free muscle transfer for simultaneous restoration of elbow flexion and wrist extension (first muscle) and finger flexion (second muscle), combined with direct triceps neurotization. The results obtained in 29 cases of FFMT in which the follow-up period was 1 year are reported. Neurotization of the donor muscle was performed using the musculocutaneous nerve (one case), spinal accessory nerve (12 cases), or multiple intercostal motor nerves (16 cases). Two second-stage muscle flaps failed secondary to vascular insufficiency. Mean electromyography-measured reinnervation time was 5 months. At a minimum follow-up period of 1 year, five muscles achieved less than or equal to Grade M2, eight Grade M3, four Grade M4, and 12 Grade M5. Transfer for combined elbow flexion and wrist extension compared with elbow flexion alone lowered the overall results for elbow flexion strength. Seventy-nine percent of the FFMTs for elbow flexion alone (single transfer) and 63% of similarly innervated muscles transferred for combined motion achieved at least Grade M4 elbow flexion strength. CONCLUSIONS: Functioning free muscle transfer is a viable reconstructive option for restoration of upper-extremity function in the setting of severe BPI. It is possible to achieve good to excellent outcomes in terms of muscle grades with the simultaneous reconstruction of two functions by one FFMT, making restoration of basic hand function possible. More reliable results are obtained when a single FFMT is performed for a single function.

Adolescent↗