Exploring an innovative decellularization protocol for porcine nerve grafts: a translational approach to peripheral nerve repair.

Introduction: Peripheral nerves are frequently affected by lesions caused by traumatic or iatrogenic damages, resulting in loss of motor and sensory function, crucial in orthopedic outcomes and with a significant impact on patients' quality of life. Many strategies have been proposed over years to repair nerve injuries with substance loss, to achieve musculoskeletal reinnervation and functional recovery. Allograft have been tested as an alternative to the gold standard, the autograft technique, but nerves from donors frequently cause immunogenic response. For this reason, several studies are focusing to find the best way to decellularize nerves preserving either the extracellular matrix, either the basal lamina, as the key elements used by Schwann cells and axons during the regenerative process. Methods: This study focuses on a novel decellularization protocol for porcine nerves, aimed at reducing immunogenicity while preserving essential elements like the extracellular matrix and basal lamina, vital for nerve regeneration. To investigate the efficacy of the decellularization protocol to remove immunogenic cellular components of the nerve tissue and to preserve the basal lamina and extracellular matrix, morphological analysis was performed through Masson's Trichrome staining, immunofluorescence, high resolution light microscopy and transmission electron microscopy. Decellularized porcine nerve graft were then employed in vivo to repair a rat median nerve lesion. Morphological analysis was also used to study the ability of the porcine decellularized graft to support the nerve regeneration. Results and Discussion: The decellularization method was effective in preparing porcine superficial peroneal nerves for grafting as evidenced by the removal of immunogenic components and preservation of the ECM. Morphological analysis demonstrated that four weeks after injury, regenerating fibers colonized the graft suggesting a promising use to repair severe nerve lesions. The idea of using a porcine nerve graft arises from a translational perspective. This approach offers a promising direction in the orthopedic field for nerve repair, especially in severe cases where conventional methods are limited.

Current perspectives on peripheral nerve repair and management of the nerve gap.

From the first surgical repair of a nerve in the 6th century, progress in the field of peripheral nerve surgery has marched on; at first slowly but today at great pace. Whether performing primary neurorrhaphy or managing multiple large nerve defects, the modern nerve surgeon has an extensive range of tools, techniques and choices available to them. Continuous innovation in surgical equipment and technique has enabled the maturation of autografting as a gold standard for reconstruction and welcomed the era of nerve transfer techniques all while bioengineers have continued to add to our armamentarium with implantable devices, such as conduits and acellular allografts. We provide the reader a concise and up-to-date summary of the techniques available to them, and the evidence base for their use when managing nerve transection including current use and applicability of nerve transfer procedures.

Fingertip injuries and their reconstruction, focusing on nails.

The fingertip is a complex anatomical structure that is frequently injured, especially in manual workers. Different classifications have been reported, considering injury orientation, level and geometry. To optimize treatment planning, the area of soft-tissue defect should be considered. Treatment aims to conserve as long a finger as possible, restore sensation (S3 + or more) and ensure a pleasant esthetic appearance. When amputation occurs, the best treatment is replantation when conditions allow. When this is not possible, the fingertip should be used as a composite graft or the nail complex can be grafted and soft tissue reconstructed, according to the preferred method. In defect without amputation or if the distal part of the finger is not present or not useful, many reconstructive techniques have been described. Depending on the injury, patient characteristics and requirements and the surgeon's skills and experience, the treatments vary from secondary healing to free flaps. In this paper, the various treatment options are described and discussed. Nowadays, considering most variables, the best treatment in fingertip injury is secondary healing with occlusive or non-occlusive dressing, even in case of bone exposure. This simple solution is able to restore a nearly normal fingertip with good sensation without further injuring the hand.

Microsurgical reconstruction of the nail.

Very often, post-traumatic defects involve multiple tissues. Microsurgical techniques can reconstruct them with tissues taken from a toe: from the nail complex alone to compound osteo-onychocutaneous flaps. Several techniques have been reported since the 1980s. This paper describes techniques and indications for microsurgical nail reconstruction. Technique differs according to the deficit, and first and foremost whether only the nail complex is involved or whether other components of the fingertip important for the normal growth of the nail, such as the phalanx bone or the finger pad, are also missing (toenail flaps and the custom-made osteo-onychocutaneous flaps). For most patients the absence of a fingernail is an esthetic rather than functional concern, and the outcomes of microsurgical reconstruction are far from ideal in this regard. We prefer to reserve reconstruction for symptomatic patients with functional impairment.

Single-stage versus two-stage bone flap reconstruction in chronic osteomyelitis: Multicenter outcomes comparison.

BACKGROUND: Chronic osteomyelitis is an invalidating disease, and its severity grows according to the infection's particular features. The Cierny-Maiden criteria classify it according to the anatomical aspects (I to IV) and also by physiological class (A host being in good immune condition and B hosts being locally (L) or systemically (S) compromised). The surgical approach to chronic osteomyelitis involves radical debridement and dead space reconstruction. Two-stage management with delayed reconstruction is the most common surgical management, while one-stage treatment with concomitant reconstruction is a more aggressive approach with less available literature. Which method gives the best results is unclear. The purpose of this study is to compare single and two-stage techniques. METHODS: The authors carried out a retrospective multicentric cohort study to compare two primary outcomes (bone union and infection healing) in one versus two-stage reconstructions with vascularized bone flaps in 23 cases of limb osteomyelitis (22 patients, 23 extremities). Thirteen subjects (56.5%) sustained a single-stage treatment consisting of a single surgery of radical debridement, concomitant soft tissue coverage, and bone reconstruction. Ten cases (43.5%) sustained a two-stage approach: radical debridement, simultaneous primary soft tissue closure, and antibiotic PMMA spacers implanted in 7 patients. RESULTS: No statistical differences were observed between one- and two-stage approaches in bone union rate and infection recurrence risk. Even though bone union seems to be higher and faster in the two-stage than in the one-stage group, and all infection relapses occurred in the one-stage group, data did not statistically confirm these differences. Two of the six cases (33.3%) of bone nonunion occurred in compromised hosts (representing only 17.4% of our sample). The B-hosts bone union rate was 50.0%, while it reached 78.9% in A-hosts, but the difference was not statistically significant (p = .5392). Infection recurrence was higher in B-hosts than in A-hosts (p = .0086) and in Pseudomonas aeruginosa sustained infections (p = .0208), but in the latter case, the treatment strategy did not influence the outcome (p = .4000). CONCLUSIONS: Bone union and infection healing rates are comparable between one and two-stage approaches. Pseudomonas aeruginosa infections have a higher risk of infection relapse, with similar effectiveness of one- and two-stage strategies. B-hosts have a higher infection recurrence rate without comparable data between the two approaches. Further studies with a larger sample size are required to confirm our results and define B-hosts' best strategy. LEVEL OF EVIDENCE: Level III of evidence, retrospective cohort study investigating the results of treatments.

Lumbrical Muscles Neural Branching Patterns: A Cadaveric Study With Potential Clinical Implications.

BACKGROUND: Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles' absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles. MATERIALS: Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted. RESULTS: The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified. CONCLUSION: The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations.

Effect of unacylated ghrelin on peripheral nerve regeneration.

Ghrelin is a circulating peptide hormone released by enteroendocrine cells of the gastrointestinal tract as two forms, acylated and unacylated. Acylated ghrelin (AG) binds to the growth hormone secretagogue receptor 1a (GHSR1a), thus stimulating food intake, growth hormone release, and gastrointestinal motility. Conversely, unacylated GHR (UnAG), through binding to a yet unidentified receptor, protects the skeletal muscle from atrophy, stimulates muscle regeneration, and protects cardiomyocytes from ischemic damage. Recently, interest about ghrelin has raised also among neuroscientists because of its effect on the nervous system, especially the stimulation of neurogenesis in spinal cord, brain stem, and hippocampus. However, few information is still available about its effectiveness on peripheral nerve regeneration. To partially fill this gap, the aim of this study was to assess the effect of UnAG on peripheral nerve regeneration after median nerve crush injury and after nerve transection immediately repaired by means of an end-to-end suture. To this end, we exploited FVB1 Myh6/Ghrl transgenic mice in which overexpression of the ghrelin gene (Ghrl) results in selective up-regulation of circulating UnAG levels, but not of AG. Regeneration was assessed by both functional evaluation (grasping test) and morphometrical analysis of regenerated myelinated axons. Results obtained lead to conclude that UnAG could have a role in development of peripheral nerves and during more severe lesions.

Studying nerve transfers: Searching for a consensus in nerve axons count.

Axonal count is the base for efficient nerve transfer; despite its capital importance, few studies have been published on human material, most research approaches being performed on experimental animal models of nerve injury. Thus, standard analysis methods are still lacking. Quantitative data obtained have to be reproducible and comparable with published data by other research groups. To share results with the scientific community, the standardization of quantitative analysis is a fundamental step. For this purpose, the experiences of the Italian, Austrian, German, Greek, and Iberian-Latin American groups have been compared with each other and with the existing literature to reach a consensus in the fiber count and draw up a protocol that can make future studies from different centers comparable. The search for a standardization of the methodology was aimed to reduce all the factors that are associated with an increase in the variability of the results. All the preferential methods to be used have been suggested. On the other hand, alternative methods and different methods have been identified to achieve the same goal, which in our experience are completely comparable; therefore, they can be used indifferently by the different centers according to their experience and availability.

Experimental Methods to Simulate and Evaluate Postsurgical Peripheral Nerve Scarring.

As a consequence of trauma or surgical interventions on peripheral nerves, scar tissue can form, interfering with the capacity of the nerve to regenerate properly. Scar tissue may also lead to traction neuropathies, with functional dysfunction and pain for the patient. The search for effective antiadhesion products to prevent scar tissue formation has, therefore, become an important clinical challenge. In this review, we perform extensive research on the PubMed database, retrieving experimental papers on the prevention of peripheral nerve scarring. Different parameters have been considered and discussed, including the animal and nerve models used and the experimental methods employed to simulate and evaluate scar formation. An overview of the different types of antiadhesion devices and strategies investigated in experimental models is also provided. To successfully evaluate the efficacy of new antiscarring agents, it is necessary to have reliable animal models mimicking the complications of peripheral nerve scarring and also standard and quantitative parameters to evaluate perineural scars. So far, there are no standardized methods used in experimental research, and it is, therefore, difficult to compare the results of the different antiadhesion devices.

Long-term clinical results of 33 thumb replantations.

INTRODUCTION: Thumb replantation following complete amputation is a relatively frequent and well-established surgical procedure. In literature many studies report a discrepancy between the objective measurements and the subjective satisfaction of the patients. Nowadays, evaluation of the patient long-term benefit obtained by replantation is uncertain. The aim of this study was to consider the long-term results of 33 thumb replantation procedures. METHODS: The period considered is from January 1997 to December 2015, 33 subjects fulfilled the study inclusion criteria and were included in the study. We evaluated in each patient: ROM (performing Kapandji test), level and mechanism of amputation, force peak of three grips using Dexter dynamometer (five-handle, key, tri-digital grips), sensibility (using Disk-Criminator and aesthesiometers of Semmes-Weinstein) and subjective perception of disability (using DASH questionnaire). RESULTS: All patients were males, 94% of them returned to their previous occupation. Average follow-up was 9±4 years. The prevalent mechanism of injury was a combined amputation in 58% of cases. Levels involved in more than half of patients were interphalangeal joints and proximal phalanxes. Ratios of strength recovery were: for the five-handle grip equal to 0.90±0.28 kg (p=0.63), 0.78±0.30 kg (p=0.64) for key grip and 0.75±0.32 kg (p=0.78) for tri-digital grip. Results for Kapandji test was 8±2 and for DASH test was 16±21. The protective tactile threshold was recovered in 49% of patients; S2PD test resulted positive in 54% and D2PD test in 39% of cases. CONCLUSIONS: Results confirm and strengthen evidence of positive long-term functional outcomes of thumb replantation interventions.

Propeller Flaps for Hand and Digit Reconstruction.

The reconstruction of soft tissue defects of the hand, as seen often after trauma or tumor excision, is a challenge due to the great differentiation of tissues depending on the hand area involved. The classical intrinsic "workhorse flaps" of the hand are associated with a significant donor-site morbidity. Capturing perforator vessels in discrete donor areas can reduce the amount of soft tissue that has to be dissected and included in what now would be a perforator flap, while also insuring robust vascularization of those transferred tissues. Moreover, the presence of perforator vessels both on the dorsal and volar sides of the hand allows harvest of perforator flaps that will respect the like-with-like principle by maintaining the main characteristics of volar and dorsal skin as desired. However, the dissection of these flaps, especially those based on volar palmar and digital perforators, still requires microsurgical skills to preserve the fine vascularization of these flaps. These small flaps are also amenable for application of the propeller flap concept. This is an especially valuable means for preserving the length of an amputated finger where bone is exposed by using more proximal uninjured tissues. Although in general only a short dissection is required to raise a propeller flap in this region, most often the donor site will have to be closed by a skin graft.

Treatment of chronic Osteomyelitis with vascularized bone flaps in one-stage-procedure.

BACKGROUND: Chronic osteomyelitis is a long-standing infection of the bone. Treatment is often combined, using antibiotics and surgery (with radical debridement and secondary or concomitant reconstruction). One-stage management is an alternative approach, with few reported cases in literature. PATIENTS/MATERIAL AND METHODS: We carried out an observational retrospective multicenter study to evaluate the results of one-stage reconstructions with vascularized bone flaps. We assessed bone and infection healing in 14 cases, with a mean follow-up of 63.6 months. RESULTS: Bone union was obtained in 10 cases (71.4 %) in a mean period of 7.9 months. Nonunion occurred in 4 cases (28.6 %), 2 of them with infection persistence. Bone nonunion risk increases in polymicrobial infections (p = 0.0269) and in compromised hosts (p = 0.0110). Infection healing was achieved in 11 cases (78.6 %). Fistula recurred in 3 cases of forearm osteomyelitis (21.4 %) in 10 months on average. Infection recurrence is associated with polymicrobial infections (p = 0.0378) and is higher in internal fixation and compromised hosts with no statistically significant relation. CONCLUSIONS: One-stage surgical treatment seems to be an effective approach in selected patients, in particular when an important impairment of local soft tissue and bone exposure are present, and immediate bone coverage with vascularized soft tissue is needed. Most complications occurred in compromised hosts and in patients with polymicrobial cultures. Further research, with comparison between one and two-stage procedures, is needed in order to strengthen the level of evidence.

Critical analysis of the value of the rabbit median nerve model for biomedical research on peripheral nerve grafts.

The rabbit has been proposed to represent an animal model that allows studying peripheral nerve regeneration across extended gap lengths. We describe here our experiences with the rabbit median nerve model and the obstacles it comes along with. This short communication is meant to inform the community and to prevent other researcher from investing time and animal lives in a model with low translational power.

Prevention of symptomatic neuroma in traumatic digital amputation: A RAND/UCLA appropriateness method consensus study.

INTRODUCTION: The appearance of a symptomatic neuroma following finger amputation is a devastating consequence for patient's quality of life. It could be cause of chronic neuropathic pain. The prevention of neuroma formation is a challenging effort for hand surgeons. The biological mechanisms leading to neuroma formation are mostly unknown and different preventing procedures have been tried without certain results. In this paper, a panel of Italian hand surgeons have been asked to express appropriateness about potentially preventive techniques of neuroma formation following the RAND/UCLA appropriateness protocol. METHODS: A literature review was preliminarily performed identifying the most employed methods to reduce the pathologic nerve scar. Afterwards, the selected panelists were asked to score the appropriateness of each procedure in a double scenario: in case of a sharp amputation or in a tear injury. The appropriateness was evaluated according to RAND/UCLA protocol. RESULTS: Nine Italian hand surgeons were included in the panel. Of them 5 were orthopaedic surgeons, 4 plastic surgeons. The identified appropriate procedures were: revision amputation should be done in operating room, the neurovascular bundles should be identified and is mandatory to treat surrounding soft tissues. Only in case of clean-cut amputation, it is appropriate to perform a proximal extension of the dissection, to use diathermocoagulation and coverage with local flaps. Procedures such as shortening in tension of the nerve stump, bone shortening, implantation of the nerve end in the soft tissue, treatment in the emergency room and, in both scenarios, certain results are evaluated as uncertain. DISCUSSION: In order to prevent the formation of a distal stump neuroma few methods were judged appropriate. It is mandatory to identify the neurovascular bundles and treat also the surrounding tissues, but no certain results could be obtained with local flap, bone shortening and other ancillary surgical acts. Moreover, it is not possible to guarantee the non arising of neuroma in any cases, also when every procedure has been temped. CONLUSIONS: The prevention of distal neuroma is actually a challenge, without a well known strategy due to the variability of response of nervous tissue to injury.

Fibulo-scapho-lunate fusion after resection of the distal radius: Case series, review of the literature and critical analysis of bone fixation.

Fibulo-scapho-lunate fusion is a technique that allows residual movement in the wrist in case of wide bone resection replacing the distal radius by a vascularised fibular transfer. Some authors have used this technique with favourable results but the distal synthesis seems to not be standardised at all, many different osteosynthesis methods have been proposed. This paper reports a complete review of the present day literature about this subject and, evaluating the different proposed osteosynthesis techniques referred in literature, suggests a standardization of the synthesis methods with dorsal plating. We report some technical considerations and results of three cases operated with a stable dorsal osteosynthesis (twice with a double plate and once with a long plate). We evaluate the time of healing and the clinical result.

International microsurgery simulation society (IMSS) consensus statement on the minimum standards for a basic microsurgery course, requirements for a microsurgical anastomosis global rating scale and minimum thresholds for training.

INTRODUCTION: Microsurgery is a surgical technique that uses optical magnification as well as specific instruments to address necessary reconstructive procedures in different medical specialties. The apprenticeship of this technique requires overcoming a steep learning curve. There is a need for standardization of the training criteria in microsurgery. The International Microsurgery Simulation Society (IMSS) was born in 2011, since then its main objective has been to connect the main international specialists and educators of this sub-specialty to share and discuss the ethical and scientific basis of preclinical microsurgery teaching. METHODS: In order to achieve a consensus on the minimum standards for the organization of basic microsurgery training courses, the requirements for a microsurgical anastomosis global rating scale and minimum thresholds for training, a total of nineteen independent global experts participated in a formal consultative consensus development program. The agreement criteria for each statement was established when consensus of 65-100% was reached. RESULTS: There have been established six recommendations concerning minimum standards for a basic microsurgery course, one recommendation in relation to minimum thresholds for training and four recommendations regarding the global rating scale as gold standard for a microsurgical anastomosis assessment. The eleven defined recommendations reached the agreement threshold of 65-100%. CONCLUSIONS: The development of this consensus sets the minimum recommended requirements for conducting basic microsurgery training courses, as well as suggestions for objective assessment of the learning curve and skills of trainees.

A sequence of flaps and dissection exercises in the living model to improve the learning curve for perforator flap surgery.

INTRODUCTION: The training to learn how to perform perforator flaps requires practice on a living model to optimize dissection and to evaluate outcome. The purpose of this study was to describe a training model that optimizes the use of animals in order to perform the maximum number of exercises per animal. MATERIAL AND METHODS: The sequence has been planned and practiced by the first and last author, recorded perfected and implemented in a two-day surgical course. The sequence was then evaluated by the trainers and the trainees by means of a questionnaire. RESULTS: All students were able to complete the sequence of exercises before the end of the second day except two (8/10) who could not complete one exercise each. The students considered the Deep Superior Epigastric Artery Perforator flap the most difficult to perform, being the most technically demanding. The sequence of exercises was judged either easily reproducible or reproducible by all the students. Two students suggested to postpone the DSEAP flap to the second day, after some training, to optimize the experience with the most challenging and rewarding flap. CONCLUSIONS: The training sequence proposed offers a wide range of exercises and allows four trainees, divided in two teams, to work and learn on the same animal. They can perform a wide range of flaps and also harvest the internal mammary vessels. The living model allows for evaluation of the quality of the surgical performance, judged by the difficulties and complications encountered during dissection, and finally through the feedback of flap perfusion.

The surgical outcomes of radial artery forearm free-flap phalloplasty in transgender men: single-centre experience and systematic review of the current literature.

Radial artery forearm free-flap (RAFFF) phalloplasty is considered by most authors as the gold-standard technique for genital gender-affirming surgery (GGAS). RAFFF surgical complications have rarely been investigated, and the aim of this study and literature review is to analyse and focus on the surgical technique and its postoperative vascular complications. From May 2016 to January 2020, a consecutive series of 25 transgender men who underwent GGAS were enrolled in the present study. Age, BMI and smoking habits were recorded for all patients. Overall, vascular flap complications occurred in 20% of cases. Complete flap loss due to acute arterial thrombosis was recorded in a single case (4%). In 8% of cases, limited ventro-proximal arterial ischaemia was detected, while in the remaining 8% of cases, venous ventral ischaemia was reported. These results were compared with the current literature results. Indeed, from our analysis, the number of flap veins (<2) was the only predictive factor for vascular complications. In conclusion, RAFFF represents a reliable option for total phallic construction, leading to satisfactory results in terms of flap survival. To optimize the surgical outcomes, venous vascular drainage should be recommended.

Emergency toe-to-hand transfer for post-traumatic finger reconstruction: A multicenter case series.

BACKGROUND: The aim of this paper was to evaluate the outcomes of a homogenous series of emergency with a toe-to-hand transfer reconstructions with a different timing: immediate (same surgical step with the debridement), primary (in the first 24 h), early (24-72 h after the debridement) or delayed (72 h-7 days). MATERIALS AND METHODS: Between 2001 and 2011, 31 patients received an immediate reconstruction with a toe-to-hand transfer. Data on indications, timing, type of surgery, complications and outcomes (sensory and motor recovery, patient satisfaction) were extrapolated and recorded. RESULTS: Most of the procedures in our series (71%) were performed in the first 24 h. Survival rate was 100%. The only complications were 3 venous thrombosis (10%), solved with surgical re-exploration. Only 1 patient required secondary surgery for web deepening. No functional problems were recorded at the donor site. Sensibility recovery was acceptable in all patients; toe mobility was higher for the reconstructed thumb (85%) than for other digits (77%). Patient satisfaction was high with regard to functional results and lower but acceptable with regard to the aesthetic outcome. There was no difference in satisfaction rate of patients treated within 24 h or within 7 days. CONCLUSION: No conclusive evidence exists in favor of an immediate versus a primary, early or delayed emergency reconstruction. Emergency toe transfer for finger reconstruction is a safe procedure and its outcomes are comparable to those reported in the literature for secondary reconstruction. Immediate reconstruction has the advantage of an easier dissection, but early or delayed reconstruction gives more time to discuss with the patient and to plan surgery.