Penile Transplantation in Gender Affirmation Surgery: A Theoretical Feasibility Study.

BACKGROUND: It can be argued that individuals in the transgender and gender nonbinary (TGNB) community suffer from a similar impact on quality of life in the face of gender dysphoria, with psychosocial and physical consequences. Indications for penile allotransplantation for patients wishing to undergo gender affirmation surgery have yet to be elucidated, but technical lessons for feasibility can be gleaned from penis transplants that have already been performed on cisgender males to date. METHODS: This study investigates the theoretical feasibility for penile-to-clitoral transplantation, prior penile transplants, and current multidisciplinary gender affirmation health care modalities. RESULTS: Penile allotransplantation offers a potential solution for individuals in the TGNB community for a more aesthetic penis, improved erectile function without the need of a prosthesis, optimal somatic sensation, and improved urethral outcomes. CONCLUSION: Questions remain about ethics, patient eligibility, and immunosuppressive sequelae. Before these issues are addressed, feasibility of this procedure must be established.

Penile Transplantation: Lessons Learned and Technical Considerations.

PURPOSE: Penile vascularized composite allotransplantation is a powerful tool for penile reconstruction. Traditional methods of reconstruction utilizing free tissue and prostheses have well-known complications, can require reoperation and cannot truly emulate the natural form or function of the penis. While vascularized composite allotransplantation may alleviate these difficulties, penile transplantation carries its own ethical, surgical and medical complications. To date, the procedure has only been attempted 5 times. Broader use of this procedure requires unique surgical considerations. We present the first comprehensive, detailed review of this procedure in order to present lessons learned from both our own and the global experience. MATERIALS AND METHODS: A review of published reports of penile transplant methods and outcomes was conducted to compile lessons learned from these cases. RESULTS: Five penile transplant cases have been reported in literature, 4 with published methodology and outcomes data. All 4 detailed unique surgical approaches and postoperative immunosuppressive regimens. Three of these cases resulted in successful sensory and functional outcomes. CONCLUSIONS: Though all 4 analyzed cases employed unique anastomotic and immunosuppressive approaches, 3 resulted in successful recovery of penile urinary and sexual function. Still, specific approaches used by different teams circumvented otherwise common complications, and these differences should guide future research and penile transplant cases.

The Baltimore Criteria for an ethical approach to penile transplantation: a clinical guideline.

Significant advances and increasing acceptance of vascularized composite allotransplantation (VCA) have contributed to emerging success of penile transplantation. The aims of penile transplantation are fourfold: adequate urinary function, enabling natural erections, restoration of erogenous sensation and appearance of external male genitalia. Successful penile transplantation also requires limiting risks and managing complications of lifelong immunosuppression. Given the limited experience with this procedure, potential recipients must understand that penile transplantation is not currently standard of care and long-term functional outcomes are unknown. Moreover, these transplants are associated with complex ethical issues. Nevertheless, as the efficacy and safety of penile transplantation are being evaluated, clear indications for transplant are needed. Although preliminary recommendations have been proposed, a more comprehensive framework is needed. We performed a literature review for English language publications related to penile transplantation and ethics. Based on the results of the search, a review of prior recommendations, and our experience performing the first whole male genital allotransplantation including penis, scrotum and abdominal wall; screening and identifying potential donors and recipients for the procedure; and addressing the associated ethical issues, we propose guidelines for responsible penile transplantation: The Baltimore Criteria for an Ethical Approach to Penile Transplantation.

A novel rat microsurgical model to study the immunological characteristics of male genital tissue in the context of penile transplantation.

Penis transplantation represents an exciting new avenue for restoration of male genitalia and function after devastating tissue loss. This animal model is designed to fill a critical void to study immunologic aspects related to reconstructive transplantation of male genitalia. A rat penile graft dissection was designed based on the internal pudendal arteries and dorsal penile vein and includes the skin of the prepuce. A nonsuture cuff technique was used to anastomose the graft vessels to the recipient superficial epigastric and femoral vessels. Seventy-seven penile transplantations were performed. Graft design yields suitable caliber and length of vessels at the radix of the penis. Anastomosis of the dorsal penile vein and the internal pudendal arteries insures optimal graft perfusion. The nonsuture cuff technique allows for successful microvascular anastomosis by a single surgeon with an average overall operative time of 2.5 h. Long-term graft survival (>30 days) was observed in syngeneic transplants. We have established a robust murine model with ideal vascular perfusion of penile tissue to study the unique immunobiology of male genitourinary allotransplantation. Heterotopic inset further allows for visual monitoring of graft viability, while the native penis serves as an optimal control.

Postoperative Complications of Panniculectomy and Abdominoplasty: A Retrospective Review.

BACKGROUND: Recent studies of panniculectomy outcomes have reported variable complication rates ranging from 8.65% to 56%. Meanwhile, reported abdominoplasty complication rates are considerably lower (~4%). This discrepancy may be attributable to inaccurate inclusion of abdominoplasty patients in panniculectomy cohorts. We performed the current study to better characterize panniculectomy complication rates at a large tertiary care center. METHODS: We performed a retrospective review of patients who underwent abdominoplasty or panniculectomy at the Johns Hopkins Hospitals between 2010 and 2017. Patients were identified by Common Procedural Terminology codes (15847/17999, 15830) confirmed via the operative note. We examined postoperative complication rates including surgical site infection, seroma formation, wound dehiscence, readmission/reoperation, and postoperative length of stay (LOS). We used parametric and nonparametric methods to determine differences between abdominoplasty and panniculectomy outcomes, as well as logistic regression analysis to evaluate factors associated with patient outcomes following panniculectomy. RESULTS: Of the 306 patients included, 103 underwent abdominoplasty while 203 underwent panniculectomy. Initial complication rates following abdominoplasty and panniculectomy were 1.94% and 12.8%, respectively (P = 0.002). Thirty-day complication rates were 9.7% for abdominoplasty and 21.2% for panniculectomy (P = 0.012). The median LOS was 1 day (interquartile range, 0-1 day) for abdominoplasty and 2 days (interquartile range, 1-4 days) for panniculectomy (P = 0.002). No statistically significant differences in complication rates at 6 months and 1 year were observed. CONCLUSIONS: Panniculectomy offers many functional benefits including improved hygiene and enhanced mobility. However, this study demonstrates that panniculectomy patients may have significantly higher complication rates initially and 30 days postoperatively and longer LOS than individuals undergoing abdominoplasty.

Comparison of arterial and venous implantable Doppler postoperative monitoring of free flaps: Systematic review and meta-analysis of diagnostic test accuracy.

BACKGROUND: Early detection of vascular compromise following free flap microsurgical reconstruction is essential. This can lead to timely reoperations and flap salvage. Both arteries and veins are monitored postoperatively with implantable ultrasound Dopplers based on surgeon preference with no consensus as to which method is best. This systematic review and meta-analysis compared arterial to venous implantable Dopplers for postoperative monitoring of microsurgical free flap reconstruction. METHODS: Five databases (MEDLINE via PubMed, EMBASE, Cochrane Library, Web of Science, and Scopus) were systematically and independently searched. PRISMA and Cochrane guidelines were strictly followed. Clinical characteristics, donor and recipient sites, specific arterial or venous vessels, diagnostic data, outcomes, and complications were recorded. RESULTS: The seven studies included in the meta-analysis were published from 1994 to 2018, with results from 38 of the possible 64 outcomes and complications queried. A total of 763 flaps with implantable Doppler probes on 527 arteries and 388 veins were included in the study. Compared to patients monitored with venous implantable Dopplers, arterial monitoring was associated with a risk of false-positives reduced by 74% (RR:0.26, 95% CI:0.12, 0.55, I2 = 40%, p = .0004) and risk of signal loss reduced by 63% (RR:0.37, 95% CI:0.24, 0.59, I2 = 26%, p < .0001). Patients being monitored with a venous implantable Doppler did not show significantly different sensitivities, specificities, true-positives, false-negatives, true-negatives, positive predictive values, negative predictive values, time to signal loss, take-backs, salvage rates, flap failures, flap failure rates, arterial, venous, vascular, and hematoma compromise compared to an arterial implantable Doppler. CONCLUSION: These findings suggest arteries may be the best vessels to monitor when using an implantable Doppler following free flap microsurgical reconstruction. Caution is advised when interpreting these findings for clinical significance due to no significant differences in take-backs, SR, flap failures, and FFR.

Keloid Excision and Adjuvant Treatments: A Network Meta-analysis.

BACKGROUND: Keloid disease treatment continues to be unsatisfactory with high recurrence rates. We evaluated the literature regarding the effectiveness of keloid excision with various adjuvant treatments following surgery and assessed recurrence rates. METHODS: We systematically searched databases through November 2016. We performed pairwise meta-analyses and Bayesian network meta-analyses on the number of recurrences. RESULTS: Following screening, 14 studies including 996 patients with various types of keloids were eligible for inclusion. Patients were categorized based on the receipt of surgery and the type of adjuvant treatment employed afterward. Paired meta-analysis (6 meta-analyses) showed that "excision + 1 adjuvant drug" led to statistically significantly higher odds of recurrence compared to "excision + radiation" (odds ratio [OR], 3.22; 95% confidence interval [CI], 1.35-7.67). Based on the network meta-analyses, the ORs of keloid recurrence following various treatments compared to no excision were as follows: "excision + pressure, 0.18 (95% CI, 0.01-7.07); excision + 2 adjuvants drugs, 0.47 (95% CI, 0.02-12.82); excision + radiation, 0.39 (95% CI, 0.04-3.31); excision + skin grafting, 0.58 (95% CI, 0.00-76.10); excision + 1 adjuvant drug, 1.76 (95% CI, 0.17-21.35); and excision only, 2.17 (95% CI, 0.23-23.95). CONCLUSIONS: According to our results, "excision + radiation" had significantly better outcomes than excision alone. "Excision + pressure" had better outcomes than excision + any other treatment modality, and excision + nonradiation adjuvant therapies were also better than "excision only," although these findings did not reach statistical significance.

Delayed Breast Reconstruction on Patients With Upper Extremity Lymphedema: A Systematic Review of the Literature and Pooled Analysis.

BACKGROUND: Breast cancer-related lymphedema (BCRL) is a debilitating condition with morbidity, hindered quality of life, and increased health-related costs. Experimental studies support the use of musculocutaneous flaps for managing animal models with lymphedema. Although vascularized lymph node transfer (VLNT) and lymphovenous anastomosis are used to surgically treat patients with lymphedema, it is not known whether musculocutaneous or adipocutaneous flaps (eg, delayed autologous breast reconstruction) are effective for treating refractory upper extremity BCRL. We conducted a systematic review and pooled analysis to assess the impact of delayed breast reconstruction on developed BCRL. METHODS: Following PRISMA guidelines, we systematically searched PubMed, Scopus, EMBASE, and Google Scholar databases for relevant studies published through November 11, 2016. We screened 934 unique articles. Of these, we conducted full-text and reference screening on 37 articles. We then performed a pooled and sensitivity analysis using random effects. RESULTS: Eight studies met our inclusion criteria. One study was a case report; 7 studies were case series with sample sizes ranging from 3 to 38 patients. According to our pooled analysis 58% of patients reported improvement after breast reconstruction with or without VLNT. Sensitivity analysis revealed that 84% (95% confidence interval, 0.74-0.95) of patients who underwent breast reconstruction and VLNT reported improvement, whereas only 22% (95% confidence interval, 0.12-0.32) of those who had breast reconstruction alone reported improvement. CONCLUSIONS: Our review summarizes the current evidence regarding the effect of delayed breast reconstruction on established lymphedema. The VLNT component of the autologous breast reconstruction procedures may be the largest contributing factor leading to lymphedema improvement.

The Ethics of Hand Transplantation: A Systematic Review.

PURPOSE: We conducted a systematic review to document ethical concerns regarding human upper extremity (UE) allotransplantation and how these concerns have changed over time. METHODS: We performed a systematic review of 5 databases to find manuscripts addressing ethical concerns related to UE allotransplantation. Inclusion criteria were papers that were on the topic of UE allotransplantation, and related ethical concerns, written in English. We extracted and categorized ethical themes under the 4 principles of bioethics: Autonomy, Beneficence, Nonmaleficence, and Justice. We assessed theme frequency by publication year using Joinpoint regression, analyzing temporal trends, and estimating annual percent change. RESULTS: We identified 474 citations; 49 articles were included in the final analysis. Publication years were 1998 to 2015 (mean, 3 publications/y; range, 0-7 publications/y). Nonmaleficence was most often addressed (46 of 49 papers; 94%) followed by autonomy (36 of 49; 74%), beneficence (35 of 49; 71%), and justice (31 of 49; 63%). Of the 14 most common themes, only "Need for More Research/Data" (nonmaleficence) demonstrated a significant increase from 1998 to 2002. CONCLUSIONS: Upper extremity transplantation is an appealing reconstructive option for patients and physicians. Its life-enhancing (vs life-saving) nature and requirement for long-term immunosuppression have generated much ethical debate. Availability of human data has influenced ethical concerns over time. Our results indicate that discussion of ethical issues in the literature increased following publication of UE transplants and outcomes as well as after meetings of national societies and policy decisions by regulatory agencies. CLINICAL RELEVANCE: Because UE transplantation is not a life-saving procedure, much ethical debate has accompanied its evolution. It is important for UE surgeons considering referring patients for evaluation to be aware of this discussion to fully educate patients and help them make informed treatment decisions.

Penile transplantation: an emerging option for genitourinary reconstruction.

Penile transplantation is an emerging option for patients with severe genital defects not amenable to traditional reconstructive options. In this article, we discuss the burgeoning problem of severe male genitourinary trauma in the military, the limitations of traditional reconstructive options in addressing these problems, and the potential for penile transplantation to provide improved outcomes. We also review the preclinical research and limited worldwide experience with penile transplantation to date, including lessons learned, and discuss the many important technical, logistical, and ethical considerations pertaining to penile transplantation that must be addressed to maximize the likelihood of successful implementation.

Pyoderma Gangrenosum After Breast Surgery: Diagnostic Pearls and Treatment Recommendations Based on a Systematic Literature Review.

BACKGROUND: Pyoderma gangrenosum (PG) is a rare cutaneous disorder that poses a diagnostic challenge in the postoperative period. A systematic literature review was performed to determine distinguishing characteristics of PG in the setting of breast surgery that can facilitate timely diagnosis and appropriate treatment. METHODS: PubMed, EMBASE, Scopus, and Web of Science databases were systematically searched for articles with cases of PG occurring after breast surgery. Forty-three relevant articles, including 49 case reports, were identified. RESULTS: PG manifested bilaterally in 30 of 34 cases (88%) in which bilateral surgery was performed. Abdominal wounds were present in 6 of 7 cases in which an abdominal donor site was used for breast reconstruction. Nipples were spared from wound involvement in 33 of 37 cases (89%) in which nipples were present after surgery. Presence of fever was noted in 27 cases (55%) and leukocytosis in 21 cases (43%). A total of 33 patients (67%) underwent wound debridement. Successful medical treatment most commonly involved steroids (41 cases, 84%) and cyclosporine (10 cases, 20%). CONCLUSIONS: Pertinent clinical features were identified that may aid in timely diagnosis and treatment of PG after breast surgery. Appearance of discrete wounds involving multiple surgical sites that surround but spare the nipples should raise suspicion for PG rather than infection or ischemia, even with concomitant fever and leukocytosis. Wound debridement should be minimized and skin grafting considered only after medical therapy is initiated. Cognizance of these features may enable prompt therapeutic intervention that minimizes morbidity and improves outcomes.

Functional abdominal wall reconstruction using an innervated abdominal wall vascularized composite tissue allograft: a cadaveric study and review of the literature.

BACKGROUND: Large, composite abdominal wall defects represent complex problems requiring a multidisciplinary approach for reconstruction. Abdominal wall vascularized composite allotransplantation (AW-VCA) has been successfully performed in 21 patients, already receiving solid organ transplants, to provide immediate abdominal closure. The current study aims to establish a novel anatomic model for AW-VCA that retains motor and sensory function in an effort to preserve form and function while preventing complications. METHODS: Three fresh cadaver torsos were obtained. Dissection was started in the midaxillary line bilaterally through the skin and subcutaneous fascia until the external oblique was encountered. The thoracolumbar nerves were identified and measurements were obtained. A peritoneal dissection from the costal margin to pubic symphysis was performed and the vascular pedicle was identified for subsequent microsurgical anastomosis. RESULTS: The mean size of the abdominal wall graft harvested was 615 ± 120 cm(2). The mean time of abdominal wall procurement was ∼150 ± 12 minutes. The mean number of thoracolumbar nerves identified was 5 ± 1.4 on each side. The mean length of the skeletonized thoracolumbar nerves was 7.8 ± 1.7 cm. The cross-sectional diameter of all nerves as they entered the rectus abdominis was greater than 2 mm. CONCLUSIONS: Motor function and sensory recovery is expected in other forms of vascularized composite allotransplantation, such as the hand or face; however, this has never been tested in AW-VCA. This study demonstrates feasibility for the transplantation of large, composite abdominal wall constructs that potentially retains movement, strength, and sensation through neurotization of both sensory and motor nerves.

Diagnosing skin rejection in vascularized composite allotransplantation: advances and challenges.

Refinements in microsurgical techniques coupled with advances in immunosuppressive and immunomodulatory protocols have enabled broader clinical application of vascularized composite allotransplantation (VCA) with encouraging immunological, functional, and esthetic results. However, skin rejection remains a significant obstacle and a serious complication for VCA recipients. Clinical and histopathological features of rejection in VCA have been described in a number of studies, which led to the development of an international consensus on the classification guidelines of rejection in the context of VCA. Nevertheless, currently available diagnostic modalities still have several limitations and shortcomings that can pose a significant diagnostic challenge, particularly when signs of rejection are found to be equivocal. In this review, we provide a critical analysis of these advances and challenges in diagnosing skin rejection. Specifically, we highlight the gaps in understanding of rejection mechanisms, the shortfalls in correlating cellular, molecular, and clinicopathologic markers with rejection grades, deficiencies in defining chronic rejection, and antibody-mediated rejection after VCA, as well as providing an outlook on novel concepts, such as the utilization of advanced computational analyses and cross-disciplinary diagnostic approaches.

Upper-extremity transplantation using a cell-based protocol to minimize immunosuppression.

OBJECTIVE: To minimize maintenance immunosuppression in upper-extremity transplantation to favor the risk-benefit balance of this procedure. BACKGROUND: Despite favorable outcomes, broad clinical application of reconstructive transplantation is limited by the risks and side effects of multidrug immunosuppression. We present our experience with upper-extremity transplantation under a novel, donor bone marrow (BM) cell-based treatment protocol ("Pittsburgh protocol"). METHODS: Between March 2009 and September 2010, 5 patients received a bilateral hand (n = 2), a bilateral hand/forearm (n = 1), or a unilateral (n = 2) hand transplant. Patients were treated with alemtuzumab and methylprednisolone for induction, followed by tacrolimus monotherapy. On day 14, patients received an infusion of donor BM cells isolated from 9 vertebral bodies. Comprehensive follow-up included functional evaluation, imaging, and immunomonitoring. RESULTS: All patients are maintained on tacrolimus monotherapy with trough levels ranging between 4 and 12 ng/mL. Skin rejections were infrequent and reversible. Patients demonstrated sustained improvements in motor function and sensory return correlating with time after transplantation and level of amputation. Side effects included transient increase in serum creatinine, hyperglycemia managed with oral hypoglycemics, minor wound infection, and hyperuricemia but no infections. Immunomonitoring revealed transient moderate levels of donor-specific antibodies, adequate immunocompetence, and no peripheral blood chimerism. Imaging demonstrated patent vessels with only mild luminal narrowing/occlusion in 1 case. Protocol skin biopsies showed absent or minimal perivascular cellular infiltrates. CONCLUSIONS: Our data suggest that this BM cell-based treatment protocol is safe, is well tolerated, and allows upper-extremity transplantation using low-dose tacrolimus monotherapy.

Current concepts and systematic review of vascularized composite allotransplantation of the abdominal wall.

INTRODUCTION: Abdominal wall vascularized composite allotransplantation (AW-VCA) is a rarely utilized technique for large composite abdominal wall defects. The goal of this article is to systematically review the literature and current concepts of AW-VCA, outline the challenges ahead, and provide an outlook for the future. METHODS: Systematic review of the literature was performed using MEDLINE, EMBASE, and PubMed to identify relevant articles discussing results of AW-VCA. Cadaver and animal studies were excluded from the systematic review, but selectively included in the discussion. RESULTS: The resultant five papers report their results on AW-VCA(Transplantation, 85, 2008, 1607; Am J Transplant, 7, 2007, 1304; Transplant Proc, 41, 2009, 521; Transplant Proc, 36, 2004, 1561; Lancet, 361, 2003, 2173). These papers represent the result of two study groups in which a total of 18 AW-VCA were performed in 17 patients. Two different operative approaches were used. Overall flap/graft survival was 88%. No mortality related to the transplant was reported. One cadaver study and two animal models were identified and separately presented (Transplant Proc, 43, 2011, 1701; Transplantation, 90, 2010, 1590; Journal of Surgical Research, 162, 2010, 314). CONCLUSION: Literature review reports AW-VCA is technically feasible with low morbidity and mortality. Functional outcomes are not reported and minimally considered. With advancements in vascularized composite allotransplantation research and decreasing toxicity of immunosuppression therapies and immunomodulatory regimens, AW-VCA can be applied in circumstances beyond conjunction with visceral transplantation.

Near-infrared lymphography as a minimally invasive modality for imaging lymphatic reconstitution in a rat orthotopic hind limb transplantation model.

Wider application of vascularized composite allotransplantation (VCA) is limited by the need for chronic immunosuppression. Recent data suggest that the lymphatic system plays an important role in mediating rejection. This study used near-infrared (NIR) lymphography to describe lymphatic reconstitution in a rat VCA model. Syngeneic (Lewis-Lewis) and allogeneic (Brown Norway-Lewis) rat orthotopic hind limb transplants were performed without immunosuppression. Animals were imaged pre- and postoperatively using indocyanine green (ICG) lymphography. Images were collected using an NIR imaging system. Co-localization was achieved through use of an acrylic paint/hydrogen peroxide mixture. In all transplants, ICG first crossed graft suture lines on postoperative day (POD) 5. Clinical signs of rejection also appeared on POD 5 in allogeneic transplants, with most exhibiting Grade 3 rejection by POD 6. Injection of an acrylic paint/hydrogen peroxide mixture on POD 5 confirmed the existence of continuous lymphatic vessels crossing the suture line and draining into the inguinal lymph node. NIR lymphography is a minimally invasive imaging modality that can be used to study lymphatic vessels in a rat VCA model. In allogeneic transplants, lymphatic reconstitution correlated with clinical rejection. Lymphatic reconstitution may represent an early target for immunomodulation.

Successful replantation of an amputated midfacial segment: technical details and lessons learned.

Successful microvascular replantation of amputated facial tissues has been sporadically reported in the literature, although most of these reports have concerned the reattachment of relatively small and segmental portions of the nose or nasal tip. We report the successful replantation of a traumatically amputated composite piece of tissue comprising the entire nose, most of the upper and lower lips, and the nasal boney and cartilaginous complex based on microvascular repair of the labial arteries and glabellar veins and discuss the results and implications of this experience.

The impact of COVID-19 pandemic on free tissue transfer outcomes: A NSQIP analysis.

BACKGROUND: The COVID-19 pandemic significantly impacted hospital resources and patient care, although its effect on free tissue transfer procedures is poorly understood. We conducted the current study to investigate the potential impact of COVID-19 and its accompanying system shut-downs on the surgical outcomes of patients undergoing free flap procedures. METHODS: Patients undergoing free tissue transfer procedures were identified from the National Surgical Quality Improvement Program (NSQIP) database from 2016 to 2020. We used 2016-2019 as baseline (pre-pandemic) data to compare with 2020 (peri-pandemic). We divided the patients into the following 3 groups: all patients undergoing free tissue transfer, breast reconstruction free tissue transfer, and non-breast free tissue transfer cases. Outcomes of interest included patient morbidity/mortality, time to surgery, time to takeback, and length of hospital stay. We used Pearson's chi-square and Fisher's exact tests to assess categorical variables. Wilcoxon's ranked sign tests and ANOVA tests were used for non-parametric and parametric continuous variables, respectively. Significance was set at alpha < 0.05. RESULTS: When comparing peri-pandemic to pre-pandemic rates, patient morbidity and mortality and unplanned primary or secondary takeback operations were both significantly higher in all 3 groups peri-pandemic. Median time to primary or secondary takeback operation was also significantly greater peri-pandemic. CONCLUSION: Patients undergoing flap procedures peri-pandemic had an overall increase in median morbidity and mortality, unplanned primary or secondary takebacks, and median number of days to takebacks compared to the pre-pandemic period. This is concerning given that any future protocols instituted can have detrimental effects on patients who receive a free tissue transfer procedure.