Recent Advances in Upper Extremity Microsurgery: From Traditional to Perforator Flaps

The upper extremity has unique functional and aesthetic requirements. Reconstruction of upper extremity soft tissue defects should ideally provide coverage for vital structures, facilitate early mobilization, be thin and pliable to match its slim contour, and reestablish sensation. Perforator flaps can be raised on the superficial fascia, which creates a thin and pliable yet durable and supple flap option to match the contour and functional needs of the upper extremity. Comparisons to traditional reconstructive methods should be performed to assess whether these innovations in microsurgical reconstruction of upper extremity defects provide an improved functional and aesthetic benefit over traditional methods.

Quantifying Nipple-Areolar Complex Shape and Location After Transmasculine Top Surgery: A Study of Postoperative Photographs Posted on Social Media and Surgeons' Professional Websites

Purpose

The transgender community utilizes online platforms to view and share postoperative masculinizing top surgery photographs. However, the quantitative and qualitative nature of these photographs is unknown. We aimed to conduct an analysis of postoperative online photographs for nipple-areolar complex (NAC) shape and location, and compare social media platforms to World Professional Association for Transgender Health (WPATH) surgeons' websites and published cis-male chest proportions.

Methods

In a cross-sectional analysis (April to May 2019), social media (Instagram and Reddit) and WPATH surgeon website postoperative top surgery photographs were analyzed. Areola height (AH):areola width (AW), NAC horizontal (inter-nipple distance [IND]:chest width [CW]) and vertical placement (sternal notch to nipple line [SN-NL]:sternal notch to umbilicus [SN-U]), and vertical scar placement (sternal notch to scar line [SN-SL]:SN-U) ratios were assessed on MATLAB. Data were compared to published cis-male proportions. Photograph skin color, soft tissue redundancy, and scar location were also analyzed.

Results

We analyzed 304 social media and 192 surgeons' website photographs qualitatively, and 139 social media and 189 surgeons' photographs quantitatively. Means (standard deviation) for postoperative photographs were AH:AW 1.12±0.24, IND:CW 0.68±0.07, SN-NL:SN-U 0.37±0.06. Most ratios significantly differed from published cis-male ratios (p<0.001). Photographs from WPATH surgeons' websites differed from social media platforms in SN-NL:SN-U and SN-SL:SN-U (p<0.001), and in scar location and soft tissue redundancy (p=0.012).

Conclusion

Postoperative top surgery photographs on online platforms showed more vertically oval, caudally positioned, and in many cases wider-spaced NACs than cis-male proportions. Our study highlights variability in results of masculinizing top surgery as it relates to an emerging source of information; online photographs.

Merging Humans and Neuroprosthetics through Regenerative Peripheral Nerve Interfaces

Limb amputations can be devastating and significantly affect an individual's independence, leading to functional and psychosocial challenges in nearly 2 million people in the United States alone. Over the past decade, robotic devices driven by neural signals such as neuroprostheses have shown great potential to restore the lost function of limbs, allowing amputees to regain movement and sensation. However, current neuroprosthetic interfaces have challenges in both signal quality and long-term stability. To overcome these limitations and work toward creating bionic limbs, the Neuromuscular Laboratory at University of Michigan Plastic Surgery has developed the Regenerative Peripheral Nerve Interface (RPNI). This surgical construct embeds a transected peripheral nerve into a free muscle graft, effectively amplifying small peripheral nerve signals to provide enhanced control signals for a neuroprosthetic limb. Furthermore, the RPNI has the potential to provide sensory feedback to the user and facilitate neuroprosthesis embodiment. This review focuses on the animal studies and clinical trials of the RPNI to recapitulate the promising trajectory toward neurobionics where the boundary between an artificial device and the human body becomes indistinct. This paper also sheds light on the prospects of the improvement and dissemination of the RPNI technology.

Utilization Trends of Nerve Autograft Alternatives for the Reconstruction of Peripheral Nerve Defects

BACKGROUND

Autologous nerve grafting is the time-honored reconstruction method for peripheral nerve gaps. However, it is associated with donor site morbidities. A growing number of studies have demonstrated the effective use of decellularized nerve allograft and synthetic conduits, which are convenient options with no donor deficit. The specific aim of this study was to characterize changes in practice trends for peripheral nerve defect reconstruction.

METHODS

We queried the 2015-2020 Truven MarketScan database for patients who underwent nerve autograft, allograft, synthetic conduit, and/or vein graft reconstruction. Patient demographic data (i.e. location, indication) and hospital characteristics (i.e. facility, provider type) were recorded. Regression analysis identified changes in trends over the study period.

RESULTS

4331 patients underwent one or more nerve gap reconstructive procedures over the study period. Since the introduction of allograft CPT code in 2018, segmented mixed effect longitudinal modeling revealed allograft utilization significantly increased from 21.5% to 29.6% after 2018 (p<0.001), whereas nerve autograft utilization decreased from 18.6% to 15.8% and conduit utilization decreased from 60% to 54.7% (p=0.09 and p=0.03, respectively). When stratifying autograft by size, use of autograft ≥4cm significantly decreased from 10.6% to 7.7% after 2018 (p=0.03), and autograft >4cm did not. When stratifying by state, there is heterogeneity in utilizati.

CONCLUSION

After creation of a designated allograft CPT code in 2018, there was an increase in allograft use with concomitant decrease in conduit and short length autograft use, suggesting that allograft replaced a portion of procedures used in short nerve gap reconstruction.

Noninferiority Trial Design: Opportunities and Challenges

Defining treatment effectiveness is the foundation of evidence-based practice. Most studies comparing the effectiveness of treatment options involve superiority designs in which a treatment is compared against a placebo, standard care, or an alternative treatment. However, in scenarios in which it is not ethical to consider these options, noninferiority designs can be considered. Noninferiority (NI) trials aim to demonstrate that a new treatment is not unacceptably worse than a standard treatment. Noninferiority is determined relative to a noninferiority margin, which is the difference between the test and active control treatment that is not unacceptably clinically inferior. However, there are important considerations with respect to the design, analysis, and interpretation of NI studies, which differ from superiority trials. This review will outline the key components of NI trials, how to interpret the findings, and understand their nuances and potential limitations.

Extended Abdominal Pedicled Flap Using a Modified Abdominoplasty Incision for Reconstruction of an Extensive Forearm Defect

Extensive upper extremity traumatic defects are challenging to reconstruct. Regional flaps are often too small or have pedicles in the zone of injury. Free microvascular flaps are not ideal options in the presence of extensive vascular injuries and in patients who cannot tolerate long procedures. We present a case featuring an extended abdominal flap using abdominoplasty-like incisions that facilitated simultaneous abdominoplasty and soft tissue coverage of an extensive, traumatic defect of the forearm and hand in a patient who was not a candidate for free flap.

Sensory nerve regeneration and reinnervation in muscle following peripheral nerve injury

Sensory afferent fibers are an important component of motor nerves and compose the majority of axons in many nerves traditionally thought of as "pure" motor nerves. These sensory afferent fibers innervate special sensory end organs in muscle, including muscle spindles that respond to changes in muscle length and Golgi tendons that detect muscle tension. Both play a major role in proprioception, sensorimotor extremity control feedback, and force regulation. After peripheral nerve injury, there is histological and electrophysiological evidence that sensory afferents can reinnervate muscle, including muscle that was not the nerve's original target. Reinnervation can occur after different nerve injury and muscle models, including muscle graft, crush, and transection injuries, and occurs in a nonspecific manner, allowing for cross-innervation to occur. Evidence of cross-innervation includes the following: muscle spindle and Golgi tendon afferent-receptor mismatch, vagal sensory fiber reinnervation of muscle, and cutaneous afferent reinnervation of muscle spindle or Golgi tendons. There are several notable clinical applications of sensory reinnervation and cross-reinnervation of muscle, including restoration of optimal motor control after peripheral nerve repair, flap sensation, sensory protection of denervated muscle, neuroma treatment and prevention, and facilitation of prosthetic sensorimotor control. This review focuses on sensory nerve regeneration and reinnervation in muscle, and the clinical applications of this phenomena. Understanding the physiology and limitations of sensory nerve regeneration and reinnervation in muscle may ultimately facilitate improvement of its clinical applications.

The Current State of Fat Grafting in the Hand: A Systematic Review for Hand Diseases

Autologous fat grafting (AFG) has traditionally been used for facial rejuvenation and soft tissue augmentation, but in recent years, its use has expanded to treat diseases of the hand. Autologous fat grafting is ideal for use in the hand because it is minimally invasive, can restore volume, and has regenerative capabilities. This review summarizes the emerging evidence regarding the safety and efficacy of AFG to the hand in several conditions, including systemic sclerosis, Dupuytren disease, osteoarthritis, burns, and traumatic fingertip injuries. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant literature search on the use of AFG in hand pathologies was performed on October 8, 2020, in Ovid MEDLINE, Elsevier Embase, Clarivate Web of Science, and Wiley Cochrane Central Register of Controlled Trials. The retrieved hits were screened and reviewed by 2 independent reviewers and a third reviewer adjudicated when required. Reviewers identified 919 unique hits. Screening of the abstracts identified 22 manuscripts which described the use of AFG to treat an identified hand condition. Studies suggest AFG in the hands is a safe, noninvasive option for the management of systemic sclerosis, Dupuytren contracture, osteoarthritis, burns, and traumatic fingertip injuries. While AFG is a promising therapeutic option for autoimmune, inflammatory, and fibrotic disease manifestations in the hand, further studies are warranted to understand its efficacy and to establish more robust clinical guidelines. Studies to date show the regenerative, immunomodulatory, and volume-filling properties of AFG that facilitate wound healing and restoration of hand function with limited complications.

"Decreasing Postamputation Pain with the Regenerative Peripheral Nerve Interface (RPNI)"

Over 185,000 limb amputations are performed in the United States annually, many of which are due to the sequelae of peripheral vascular disease. Symptomatic neuromas remain a significant source of postamputation morbidity and contribute to both phantom limb (PLP) and residual limb pain (RLP). While many interventions have been proposed for the treatment of symptomatic neuromas, conventional methods lead to a high incidence of neuroma recurrence. Furthermore, these existing methods do not facilitate an ability to properly interface with myoelectric prosthetic devices. The Regenerative Peripheral Nerve Interface (RPNI) was developed to overcome these limitations. The RPNI consists of an autologous free muscle graft secured around the end of a transected nerve. The muscle graft provides regenerating axons with end organs to reinnervate, thereby preventing neuroma formation. We have shown that this simple, reproducible, and safe surgical technique successfully treats and prevents neuroma formation in major limb amputations. In this paper, we describe RPNI surgery in the setting of major limb amputation and highlight the promising results of RPNIs in our animal and clinical studies.

Evolution of Cranioorbital Shape in Nonsyndromic, Muenke, and Saethre-Chotzen Bilateral Coronal Synostosis: A Case-Control Study of 2-Year Outcomes

BACKGROUND

The purpose of this study was to quantify change in cranioorbital morphology from presentation, after fronto-orbital advancement, and at 2-year follow-up.

METHODS

Volumetric, linear, and angular analyses were performed on computed tomographic scans of consecutive bilateral coronal synostosis patients. Comparisons were made across three time points, between syndromic and nonsyndromic cases, and against normal controls. Significance was set at p < 0.05.

RESULTS

Twenty-five patients were included: 11 were nonsyndromic, eight had Saethre-Chotzen syndrome, and six had Muenke syndrome. Total cranial volume was comparable to normal, age-matched control subjects before and 2 years after surgery despite an expansion during surgery. Axial and sagittal vector analyses showed advancement and widening of the lower forehead beyond control values with surgery and comparable anterior position, but increased width compared to controls at 2 years. Frontal bossing decreased with a drop in anterior cranial height and advanced lower forehead position. Middle vault height was not normalized and turricephaly persisted at follow-up. Posterior fossa volume remained lower at all three time points compared to control subjects. Supraorbital retrusion relative to anterior corneal position was overcorrected by surgery, with values comparable to those of control subjects at 2 years because of differential growth. There was no difference at 2 years between syndromic and nonsyndromic groups.

CONCLUSIONS

Open fronto-orbital advancement successfully remodels the anterior forehead but requires overcorrection to be comparable to normal at 2 years. Although there are differences in syndromic cases at presentation, they do not result in significant morphometric differences on follow-up. Posterior fossa volume remains lower at all time points.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Shoulder Release and Tendon Transfer following Neonatal Brachial Plexus Palsy: Gains, Losses, and Midline Function

BACKGROUND

Shoulder release and tendon transfer is frequently performed to address persistent weakness from neonatal brachial plexus palsy. Although postoperative improvements in motion are well described, associated deficits are poorly documented, and functional assessments are lacking. Loss of ability to reach midline can occur with surgery and may result in impairment. The purpose of this study was to comprehensively assess the gains, losses, functional changes, and patient-reported outcome associated with the authors' surgical approach.

METHODS

Consecutive patients undergoing surgery with 2-year follow-up were included (n = 30). Prospectively recorded assessments by therapists were reviewed. Changes were assessed by t test and Wilcoxon rank sum (p < 0.05).

RESULTS

Active external rotation and abduction improved and internal rotation diminished. Aggregate modified Mallet score increased with improvements in all subscales, except that hand to spine was unchanged and hand to belly decreased. Functional assessment using the Brachial Plexus Outcome Measure revealed an increase of aggregate score, with no decline in any subscales. Improvements were in hand to back of head, forward overhead reach, holds plate with palm up, opening large container, and strings bead. Aggregate patient self-report of appearance and function increased (from 18 to 23). Loss of ability to reach midline occurred in three patients (10 percent) who had extended Erb or total palsy and preoperative limitations of internal rotation.

CONCLUSIONS

Secondary reconstruction rebalances shoulder motion by increasing external rotation and abduction and reducing internal rotation. In this study, a conservative surgical approach results in overall improvement in task-based abilities and self-reported outcomes and preservation of internal rotation within a functional range.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Orexinergic modulation of serotonin neurons in the dorsal raphe of a diurnal rodent, Arvicanthis niloticus

The hypothalamic neuropeptide, orexin (or hypocretin), is implicated in numerous physiology and behavioral functions, including affective states such as depression and anxiety. The underlying mechanisms and neural circuits through which orexin modulates affective responses remain unclear. The objective of the present study was to test the hypothesis that the serotonin (5-HT) system of the dorsal raphe nucleus (DRN) is a downstream target through which orexin potentially manifests its role in affective states. Using a diurnal rodent, the Nile grass rat (Arvicanthis niloticus), we first characterized the expression of the orexin receptors OX1R and OX2R in the DRN using in situ hybridization. The results revealed distinct distributions of OX1R and OX2R mRNAs, with OX1R predominantly expressed in the dorsal and lateral wings of the DRN that are involved in affective processes, while OX2R was mostly found in the ventral DRN that is more involved in sensory-motor function. We next examined how the orexin-OX1R pathway regulates 5-HT in the DRN and some of its projection sites using a selective OX1R antagonist SB-334867 (10 mg/kg, i.p.). A single injection of SB-334867 decreased 5-HT-ir fibers within the anterior cingulate cortex (aCgC); five once-daily administrations of SB-334867 decreased 5-HT-ir not only in the aCgC but also in the DRN, oval bed nucleus of the stria terminalis (ovBNST), nucleus accumbens shell (NAcSh), and periaqueductal gray (PAG). HPLC analysis revealed that five once-daily administrations of SB-334867 did not affect 5-HT turnover to any of the five sites, although it increased the levels of both 5-HT and 5-HIAA in the NAcSh. These results together suggest that orexinergic modulation of DRN 5-HT neurons via OX1Rs may be one pathway through which orexin regulates mood and anxiety, as well as perhaps other neurobiological processes.

Attenuated orexinergic signaling underlies depression-like responses induced by daytime light deficiency

Light has profound effects on mood, as exemplified by seasonal affective disorder (SAD) and the beneficial effects of bright light therapy. However, the underlying neural pathways through which light regulates mood are not well understood. Our previous work has developed the diurnal grass rat, Arvicanthis niloticus, as an animal model of SAD (Leach et al., 2013a,b). By utilizing a 12:12-h dim light:dark (DLD) paradigm that simulates the lower light intensity of winter, we showed that the animals housed in DLD exhibited increased depression-like behaviors in the forced swim test (FST) and sweet solution preference (SSP) compared to animals housed in bright light during the day (BLD). The objective of the present study was to test the hypothesis that light affects mood by acting on the brain orexinergic system in the diurnal grass rat model of SAD. First, orexin A immunoreactivity (OXA-ir) was examined in DLD and BLD grass rats. Results revealed a reduction in the number of OXA-ir neurons in the hypothalamus and attenuated OXA-ir fiber density in the dorsal raphe nucleus of animals in the DLD compared to those in the BLD group. Then, the animals in BLD were treated systemically with SB-334867, a selective orexin 1 receptor (OX1R) antagonist, which led to a depressive phenotype characterized by increased immobility in the FST and a decrease in SSP compared to vehicle-treated controls. Results suggest that attenuated orexinergic signaling is associated with increased depression-like behaviors in grass rats, and support the hypothesis that the orexinergic system mediates the effects of light on mood.

Depression-like responses induced by daytime light deficiency in the diurnal grass rat (Arvicanthis niloticus)

Seasonal Affective Disorder (SAD) is one of the most common mood disorders with depressive symptoms recurring in winter when there is less sunlight. The fact that light is the most salient factor entraining circadian rhythms leads to the phase-shifting hypothesis, which suggests that the depressive episodes of SAD are caused by misalignments between the circadian rhythms and the habitual sleep times. However, how changes in environmental lighting conditions lead to the fluctuations in mood is largely unknown. The objective of this study is to develop an animal model for some of the features/symptoms of SAD using the diurnal grass rats Arvichantis niloticus and to explore the neural mechanisms underlying the light associated mood changes. Animals were housed in either a 12∶12 hr bright light∶dark (1000lux, BLD) or dim light∶dark (50lux, DLD) condition. The depression-like behaviors were assessed by sweet-taste Saccharin solution preference (SSP) and forced swimming test (FST). Animals in the DLD group showed higher levels of depression-like behaviors compared to those in BLD. The anxiety-like behaviors were assessed in open field and light/dark box test, however no significant differences were observed between the two groups. The involvement of the circadian system on depression-like behaviors was investigated as well. Analysis of locomotor activity revealed no major differences in daily rhythms that could possibly contribute to the depression-like behaviors. To explore the neural substrates associated with the depression-like behaviors, the brain tissues from these animals were analyzed using immunocytochemistry. Attenuated indices of 5-HT signaling were observed in DLD compared to the BLD group. The results lay the groundwork for establishing a novel animal model and a novel experimental paradigm for SAD. The results also provide insights into the neural mechanisms underlying light-dependent mood changes.

Orexinergic signaling mediates light-induced neuronal activation in the dorsal raphe nucleus

Seasonal affective disorder (SAD), a major depressive disorder recurring in the fall and winter, is caused by the reduction of light in the environment, and its depressive symptoms can be alleviated by bright light therapy. Both circadian and monoaminergic systems have been implicated in the etiology of SAD. However, the underlying neural pathways through which light regulates mood are not well understood. The present study utilized a diurnal rodent model, Arvicanthis niloticus, to explore the neural pathways mediating the effects of light on brain regions involved in mood regulation. Animals kept in constant darkness received light exposure in early subjective day, the time when light therapy is usually applied. The time course of neural activity following light exposure was assessed using Fos protein as a marker in the following brain regions/cells: the suprachiasmatic nucleus (SCN), orexin neurons in the perifornical-lateral hypothalamic area (PF-LHA) and the dorsal raphe nucleus (DRN). A light-induced increase in Fos expression was observed in orexin neurons and the DRN, but not in the SCN. As the DRN is densely innervated by orexinergic inputs, the involvement of orexinergic signaling in mediating the effects of light on the DRN was tested in the second experiment. The animals were injected with the selective orexin receptor type 1 (OXR1) antagonist SB-334867 prior to the light exposure. The treatment of SB-334867 significantly inhibited the Fos induction in the DRN. The results collectively point to the role of orexin neurons in mediating the effects of light on the mood-regulating monoaminergic areas, suggesting an orexinergic pathway that underlies light-dependent mood fluctuation and the beneficial effects of light therapy.