Ortho-oncoplastic surgery in foot and ankle: A narrative overview on reconstruction of soft-tissue defects after oncologic resections.

INTRODUCTION: Malignant tumors of the foot are rare, and treatment strategies are challenging considering the complex anatomy of this area. In recent years, dramatic advances in technology and collaborations between different specialties (such as orthopedic, oncology, radiology, plastic, and vascular surgery) significantly changed the approach to complex malignant tumors without resorting to limb removal. The combination of the strengths of both orthopedic surgery and plastic surgery constitutes the modern definition of "orthoplasty." The aim of this review article is to provide treatment strategies that are available for reconstruction of foot and ankle in limb-salvage surgery after tumor resection, with a specific focus on microsurgical techniques in plastic surgery. METHODS: We conducted a comprehensive search for relevant papers across PubMed, Scopus, Embase, and Web of Science. We included patient-based studies reporting on procedures for soft-tissue reconstruction with small and large soft tissue defects. Indications, pros and cons, and technique tips are discussed for each type of reconstructive technique. RESULTS: The search was done using literature of the past 30 years (from 1990 to date), resulting in about 725 articles describing over 2000 cases. Cutaneous flaps included lateral supramalleolar flap, medial plantar flap, reverse sural neurocutaneous island flap, medial leg flap, and lateral leg flap. Free flaps included anterolateral thigh flap, radial forearm flap, latissimus dorsi flap, gracilis muscle flap, lateral arm flap, and rectus abdominis flap. CONCLUSIONS: The orthoplastic approach in musculoskeletal oncology is a collaborative model of orthopedic and plastic surgeons working together, resulting in a higher rate of successful limb salvage in patients at risk for amputation. Protocols, biologic substitutes, and surgical techniques are largely improved in the last decades increasing the possibility of functional reconstruction. Microsurgical strategies represent the new frontiers in these demanding reconstructions.

Blood supply to the superficial fascia of the abdomen: An anatomical study.

The aim of this study was to examine data demonstrating that Scarpa's fascia, a superficial fascia of the anterior abdominal wall, is a vascularized tissue. Specimens of the fascia of seven volunteers undergoing abdominoplasty surgical procedures at the Plastic Surgery Unit of the University of Padova Medical Center were collected. Fractal analysis and quantitative assessment of the vascular network of the fascia was carried out, exploiting the presence of blood in the vessels. Each sample was divided and processed for histological/immunohistochemical analysis (into 5 micron-paraffin embedded sections and cryo-sectioned free-floating samples) as well as for electron microscopy study. A rich vascular pattern forming a fine, dense meshwork with an area percentage of 6.20% ± 2.10% von Willebrand factor stained vessels was noted in all the specimens of the fascia examined; the area percentage of the αSMA-stained vessels was 2.93% ± 1.80%. The diameters of the vessels fell between the 13 and 65 µm range; the network was composed of arteries, veins, capillaries and lymphatic segments. Topological results showed that the vascular network within Scarpa's fascia is well branched (segments: 6615 ± 3070 and 8.40 ± 3.40 per mm2 ; crossing points: 3092 ± 1490 and 3.40 ± 1.90 per mm2 ). Fractal analysis (fractal dimension = 1.063 ± 0.10; lacunarity = 0.60 ± 0.10) revealed that this particular vascular network has an optimal spatial distribution and homogeneity occupying the entire space of the superficial fascia. These findings could undoubtedly be useful to plastic surgeons as well as to pain management specialists.

Detection of Mast Cells in Human Superficial Fascia.

The recent findings showed that the superficial fascia is a fibrous layer in the middle of hypodermis, richly innervated and vascularized, and more complex than so far demonstrated. This study showed the presence of mast cells in the superficial fascia of the human abdomen wall of three adult volunteer patients (mean age 42 ± 4 years; 2 females, 1 male), by Toluidine Blue and Safranin-O stains and Transmission Electron Microscopy. Mast cells are distributed among the collagen bundles and the elastic fibers, near the vessels and close to the nerves supplying the tissue, with an average density of 20.4 ± 9.4/mm2. The demonstration of the presence of mast cells in the human superficial fascia highlights the possible involvement of the tissue in the inflammatory process, and in tissue healing and regeneration processes. A clear knowledge of this anatomical structure of the hypodermis is fundamental for a good comprehension of some fascial dysfunctions and for a better-targeted clinical practice.

Bridging Gaps in Peripheral Nerves: From Current Strategies to Future Perspectives in Conduit Design.

In peripheral nerve injuries (PNI) with substance loss, where tensionless end-to-end suture is not achievable, the positioning of a graft is required. Available options include autografts (e.g., sural nerve, medial and lateral antebrachial cutaneous nerves, superficial branch of the radial nerve), allografts (Avance®; human origin), and hollow nerve conduits. There are eleven commercial hollow conduits approved for clinical, and they consist of devices made of a non-biodegradable synthetic polymer (polyvinyl alcohol), biodegradable synthetic polymers (poly(DL-lactide-ε-caprolactone); polyglycolic acid), and biodegradable natural polymers (collagen type I with/without glycosaminoglycan; chitosan; porcine small intestinal submucosa); different resorption times are available for resorbable guides, ranging from three months to four years. Unfortunately, anatomical/functional nerve regeneration requirements are not satisfied by any of the possible alternatives; to date, focusing on wall and/or inner lumen organization/functionalization seems to be the most promising strategy for next-generation device fabrication. Porous or grooved walls as well as multichannel lumens and luminal fillers are the most intriguing options, eventually also including the addition of cells (Schwann cells, bone marrow-derived, and adipose tissue derived stem cells) to support nerve regeneration. This review aims to describe common alternatives for severe PNI recovery with a highlight of future conduits.

Deep inferior epigastric perforator flap preoperative planning: A comparative analysis between dynamic infrared thermography, computerized tomography angiography, and hand-held Doppler.

INTRODUCTION: Hand-held Doppler (HHD) sonography and computerized tomography angiography (CTA) are the common assessment tools for deep inferior epigastric perforator (DIEP) flap preoperative planning. CTA is considered the gold standard method for preoperative perforator mapping but necessitates contrast medium and X-ray exposure. Dynamic infrared thermography (DIRT) does not have these drawbacks and allows the detection of hot and cold spots on a given body area. Our study aimed to compare DIRT, HHD, and CTA in perforator mapping for breast reconstruction using DIEP flap. PATIENTS AND METHODS: From March to September 2020, 12 consecutive patients scheduled for DIEP flap breast reconstruction were preoperatively investigated with HHD, CTA, and DIRT. The patients' mean age was 53 and the mean BMI was 29.23 kg/m2 . All the reconstructions were due to breast cancer. The results of preoperative perforator mapping on the lower abdomen were compared among the three techniques. All the evidence was compared to the intraoperative findings, during flap harvesting, to establish if the techniques were able to correctly locate the perforator. RESULTS: We detected 178 perforators intraoperatively, 178 with CTA, 178 with DIRT, and 125 with HHD. The latter revealed a lower number of perforator vessels for each patient (10.42 ± 3.58), compared with CTA (14.83 ± 3.04) and DIRT (14.83 ± 4.76). DIRT resulted superior to HHD (p < .05), while no statistically significant difference (p > .05) was found between DIRT and CTA. We calculated a mean sensitivity of 93.87% for CTA, 69.02% for HHD, and 92.06% for DIRT. CONCLUSION: DIRT is a useful tool in the preoperative planning of DIEP flaps, as it provides information about the location of perforators and the hemodynamic properties of angiosomes. It is easy to use, and it does not involve ionizing radiation. DIRT could represent an innovative and promising implementation of CTA and HHD techniques for preoperative perforator mapping in DIEP breast reconstruction.

Distal nerve transfer from the median nerve lumbrical fibers to the distal ulnar nerve motor branches in the palm: An anatomical cadaveric study.

BACKGROUND: The aim of the current study is to investigate the first and second lumbrical nerves as potential fibers donors to the deep motor branch of the ulnar nerve to avoid intrinsic atrophy in high ulnar nerve injuries. METHODS: Sixteen fresh frozen cadaveric hands were dissected, the radial lumbrical nerves accessed, and a coaptation, either in reverse end-to-side or in double end-to-side through a bridge nerve graft, was created to the deep motor branch of ulnar nerve. Semithin sections were taken from samples of donor and recipient nerves for qualitative (nerve architecture) and quantitative studies (fiber count and donor/recipient ratio). RESULTS: The first lumbrical showed a robust trunk and a superior axon density (9,126.50 ± 2,923.41 axons/mm2 ) to the ulnar motor branch (7,506.50 ± 1,137.50 axons/mm2 distal to the opponens tunnel and 7,947.75 ± 1,741.24 axons/mm2 before its terminal branching); the ulnar motor branch showed a higher axon number (2,633.51 ± 410.00 distal to the opponens tunnel and 2,345.75 ± 2,101.56 before its terminal branching) than the first lumbrical (1,410.56 ± 823.89); section areas occupied by axons were higher in proximal (0.20 ± 0.16) and distal (0.26 ± 0.20) ulnar samples than the first lumbrical (0.17 ± 0.16). Donor/recipient ratio first lumbrical/deep motor branch of the ulnar nerve were 1:1.86 (distal to the opponens tunnel) and 1:1.67 (at its terminal branching); data about the second lumbrical were ruled out because of bias. CONCLUSIONS: A transfer from the first lumbrical nerve to the deep motor branch of the ulnar nerve in palm is suitable to avoid intrinsic atrophy.

Radiological anatomy of the perforators of the gluteal region: The "radiosome" based anatomy.

BACKGROUND: The superior (SGA) and the inferior gluteal artery (IGA) perforator flaps are widely used in pressure-sore repair and in breast reconstruction. The aim was to exhaustively depict the topographical anatomy of the whole system of perforators in the buttock. METHODS: Eighty lower-extremity computed tomographic angiography (CTA) of patients (20 males/20 females, mean age 61-years old, range 38-81) were considered. The source artery, location, type, and caliber of gluteal perforators were analyzed. The location of perforators was reproduced using a standardized two-dimensional grid on the coronal plane, centered onto defined bone landmarks. We defined "radiosome" the cutaneous vascular territory of a source artery inferred through the representation of its whole perforator system at the exit point through the deep fascia. RESULTS: A mean number of 25.6 ± 5.7 perforators in the gluteal region was observed, distributed as follows: 11.6 ± 4.8(45.2%) from SGA; 7.9 ± 4.5(30.8%) from IGA; 1.5 ± 0.8(5.8%) from fifth lumbar artery; 1.2 ± 0.8(4.7%) from internal pudendal artery; 1.2 ± 1(4.8%) from lateral circumflex femoral artery; 0.3 ± 0.7(1.2%) from circumflex iliac superficial artery. At least one large (internal diameter > 1 mm) SGA septocutaneous perforator was present in 77.5% of patients. CONCLUSIONS: The gluteal region is vascularized by perforators of multiple source arteries. Septocutaneous perforators of SGA and IGA were planned along a curve drawn from the posterior-superior border of the iliac crest to the greater trochanter. The lumbar artery perforators are clustered over the apex of the iliac crest; the internal pudendal artery perforators are clustered medially to the ischiatic tuberosity. Contributions can also come from the sacral and superficial circumflex iliac arteries.

Hand fasciae innervation: The palmar aponeurosis.

There are few data in the scientific literature about the innervation of fasciae of the hand. The present study first elucidates the density and location of nervous structures in the palmar aponeurosis and, for comparison, in the flexor retinaculum (both can be considered specializations of the deep fascia of the upper limbs). Second, it compares nonpathological with pathological palmar aponeurosis. Samples of nonpathological fascia were taken from the flexor retinaculum and palmar aponeurosis of 16 upper limbs of unembalmed cadavers. Samples of pathological palmar aponeurosis were taken from seven patients with Dupuytren's disease. All samples were stained immunohistochemically with anti-S100 and anti-tubulin antibodies, and analyzed quantitatively and qualitatively by microscopy. The palmar aponeurosis showed higher median density than the retinacula of free nerve endings (22 and 20 elements/cm2 , respectively), Pacinian corpuscles (2 and 0 elements/cm2 ) and Golgi-Mazzoni corpuscles (1.0 and 0.5 element/cm2 ). Some corpuscles were located at the intersections of the fibers in the three directions. Free nerve endings were denser in pathological palmar aponeurosis (38 elements/cm2 ). The results indicate that the palmar aponeurosis is central to proprioception of the hand and that surgery should therefore avoid injuring it. The higher density of free nerve endings in pathological samples indicates that the nervous structures are implicated in the amplified fibrosis of Dupuytren's disease. Clin. Anat. 31:677-683, 2018. © 2018 Wiley Periodicals, Inc.

Rectus abdominis muscle innervation: an anatomical study with surgical implications in diep flap harvesting.

PURPOSE: To improve the current knowledge of rectus abdominis innervation, so as to identify a safe area where the vascular pedicle should be dissected to reduce the risk of nerve damage during deep inferior epigastric perforator (DIEP) flap harvesting. METHODS: Ten abdominal wall dissections were performed. Perforating arteries were identified and classified into nerve-related perforators and non-nerve-related perforators depending on the presence of nerve branches crossing vessels. The width of rectus abdominis and the distance between perforators and lateral edge of rectus abdominis muscle were measured. In contralateral hemi-abdomen, full-thickness specimens were sampled for microscopical analysis. RESULTS: Nerves enter the rectus sheath piercing the lateral edge (60% of cases) or the posterolateral surface of the sheath (40% of cases). They enter the rectus abdominis muscle at a mean distance of 4.3 cm from the lateral margin of the sheath. Within rectus abdominis, nerves have a mean thickness of 200.3 µm and split into 2-4 sensitive and 2-4 muscular branches. Close relationship between muscular branches and deep inferior epigastric artery perforators were shown. The mean distance between nerve-related perforators and the lateral edge of the rectus abdominis was of 3.26 ± 0.88 cm. The mean distance between non-nerve-related perforators and the lateral edge of the rectus abdominis was of 6.26 ± 0.90 cm. CONCLUSIONS: To spare nerves and reduce donor-site complications, a perforator located beyond an imaginary line of 3.26 ± 0.88 cm far from the lateral edge of rectus abdominis muscle should be included in the DIEP flap.

Evaluation of the effectiveness of the prepectoral breast reconstruction with Braxon dermal matrix: First multicenter European report on 100 cases.

We report the outcomes of the European prospective study on prepectoral breast reconstruction using preshaped acellular dermal matrix for complete breast implant coverage. Seventy-nine patients were enrolled between April 2014 and August 2015 all over Europe using a single protocol for patient selection and surgical procedure, according to the Association of Breast Surgery and British Association of Plastic Reconstructive and Aesthetic Surgeons joint guidelines for the use of acellular dermal matrix in breast surgery. The preshaped matrix completely wraps the breast implant, which is placed above the pectoralis major, without detaching the muscle. A total of 100 prepectoral breast reconstructions with complete implant coverage were performed. This series, with mean follow-up of 17.9 months, had two cases of implant loss (2.0%) including one necrosis of the nipple and one wound breakdown (1.0% respectively). No implant rotations were observed. Good cosmetic outcomes were obtained with natural movement of the breasts and softness to the touch; none of the patients reported experiencing pain or reduction in the movements of the pectoralis major muscle postoperatively. The use of preshaped acellular dermal matrix for a complete breast implant coverage in selected patients is safe and gives satisfactory results, both from the aesthetic view point and the low postoperative complication rates. Further studies reporting long-term outcomes are planned.

Extraskeletal Myxoid Chondrosarcoma of the Foot Clinically Mimicking Plantar Fibromatosis.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue sarcoma usually presenting in proximal extremities of middle-aged men. The authors discuss a unique case of EMC, localized in the plantar foot of a 76-year-old woman, clinically suspected as plantar fibromatosis. It is important to avoid misdiagnosis of EMC because of their propensity for late recurrence and their metastatic potential.

Radiological and histological analysis of two replaced interphalangeal joints with active subchondral bone resorption in erosive hand osteoarthritis: a novel mechanism?

The aim of this study was to describe the histological features of erosive hand osteoarthritis (EHOA), which is considered an aggressive subset of hand osteoarthritis (OA) characterized by severe local inflammation and degeneration of the distal and proximal interphalangeal joints. Two patients with EHOA underwent replacement with a cement-free press fit ceramic prosthesis of a proximal interphalangeal joint (PIPJ). Clinical and radiological data were collected and histological examination was performed. Radiological examination with histological correlation showed complete erosion of the articular cartilage with focal presence of peripheral fibrocartilaginous resurfacing, sclerosis, and remodeling of the exposed bone, osteoclastic activity with resorptive lacunae in the subchondral bone and around degenerative fibromyxoid pseudocysts, coarse trabeculation of the cancellous bone, and marginal osteophytes. The synovial membrane showed non-specific mild hypertrophy and mildly cellular fibromyxoid stroma. The histological findings in patients with EHOA suggest a pathogenesis of cartilage resorption from the subchondral bone, via osteoclastic-mediated activity and formation of periarticular reactive fibrocartilaginous proliferation with partial resurfacing of the articular surface.

The cubital tunnel: a radiologic and histotopographic study.

Entrapment of the ulnar nerve at the elbow is the second most common compression neuropathy in the upper limb. The present study evaluates the anatomy of the cubital tunnel. Eighteen upper limbs were analysed in unembalmed cadavers using ultrasound examination in all cases, dissection in nine cases, and microscopic study in nine cases. In all cases, thickening of the fascia at the level of the tunnel was found at dissection. From the microscopic point of view, the ulnar nerve is a multifascicular trunk (mean area of 6.0 ± 1.5 mm(2) ). The roof of the cubital tunnel showed the presence of superimposed layers, corresponding to fascial, tendineous and muscular layers, giving rise to a tri-laminar structure (mean thickness 523 ± 235 µm). This multilayered tissue was hyperechoic (mean thickness 0.9 ± 0.3 mm) on ultrasound imaging. The roof of the cubital tunnel is elastic, formed by a myofascial trilaminar retinaculum. The pathological fusion of these three layers reduces gliding of the ulnar nerve during movements of the elbow joint. This may play a role in producing the symptoms typical of cubital tunnel syndrome. Independent from the surgical technique, decompression should span the ulnar nerve from the triceps brachii muscle to the flexor carpi ulnaris fascia.

Evaluating Arterialized Vein in Thumb Replantation using Indocyanine Green Angiography: A Case Report.

BACKGROUND The absence of valid vessels for the anastomosis constitutes a contraindication to replantation, but the need for arterial vessels in good condition has recently been questioned and some authors have proposed the arterialization of the veins with promising results. However, this method is not routine in replantation and it is unclear what conditions can establish venous congestion and loss of the replanted segment. CASE REPORT We detail a case where indocyanine green aids in evaluating arterialization of a vein during thumb replantation in a 40-year-old smoker following a crush injury. Multiple attempts to anastomose the princeps pollicis and its collateral vessel failed due to a thrombus formation, leaving the finger non-perfused despite urokinase treatment. To confirm the absence of reperfusion, we administered 0.3 mg/kg of indocyanine green through an upper limb peripheral vein. Observing no reperfusion, we located a suitable radial dorsal vein and performed an arteriovenous anastomosis at the proximal phalanx level. Indocyanine Green Angiography (IGA) revealed a slightly delayed reperfusion but a effective venous outflow. We did not consider it necessary to perform additional venous anastomoses other than the single dorsal radial venous anastomosis. CONCLUSIONS This single case report shows the potential of indocyanine green as a valid aid to evaluate the perfusion of the replantation and also any early venous congestion, being able to modify the operative plan accordingly.

The multiple strategies adopted in a complex case of calcium extravasation in a child: a case report.

Extravasation of calcium solution is a common adverse event in children in intensive care units. The lack of adequate and timely treatment can lead to important functional sequelae. Here, we report the case of calcium extravasation in a child and we discuss the multiple therapeutic strategies adopted.

The profunda artery perforators: Anatomical study and radiological findings using computed tomography angiography in patients undergoing PAP flap breast reconstruction.

BACKGROUND: The popularity of the profunda femoris artery perforator (PAP) flap is increasing; however, knowledge concerning the standardization of radiological findings and their clinical implications is limited. We evaluated the radiological architecture of posterior thigh perforators using Computed Tomography Angiography (CTA) to identify landmarks to facilitate flap dissection. METHODS: A retrospective study was conducted on 35 patients who underwent unilateral breast reconstruction with a PAP flap. The preoperative CTA scans were analyzed, and the perforator characteristics were evaluated. The perforators were mapped using a Cartesian coordinate system. Data were normalized by anatomical landmarks and overlapped. Perioperative and postoperative results were analyzed. Radiological and intraoperative were compared. RESULTS: Two CTA scans were excluded; 66 thighs were examined. The mean perforator number was 3.2. The mean diameter of chosen perforators was 2.7 mm (DS ± 0.6 mm) at the origin, 2.2 mm (DS ± 0.4 mm) at the adductor space midpoint, and 1.7 mm (DS ± 0.3 mm) at the deep fascia. The mean adipose tissue thickness was 3.35 cm (DS ± 0.94) at the deep fascia and 3.59 cm (DS ± 1.19) at the adductor space midpoint. Intraoperatively, the perforator was located 3.22 cm (DS ± 0.87) from the posterior border of the gracilis muscle and 8.98 cm (DS ± 1.44) from the inferior gluteal crease. A radiological area located 9.33 cm (DS ± 4.81) from the y-axis and 7.48 cm (DS ± 1.88) from the x-axis was identified. CONCLUSIONS: CTA using the volume-rendering technique is a valuable method to study in vivo the radiological anatomy of the posterior thigh perforators.

Fascia redefined: anatomical features and technical relevance in fascial flap surgery.

Fascia has traditionally been thought of as a passive structure that envelops muscles, and the term "fascia" was misused and confusing. However, it is now evident that fascia is a dynamic tissue with complex vasculature and innervation. A definition of fascia as an integral tissue has been provided here, highlighting the main features of the superficial and deep fasciae. Wide anatomic variations and site-specific differences in fascial structure are described, coupled with results of our extensive investigations of fascial anatomy. This will enable surgeons to make better decisions on selecting the appropriate fascia in the construction of fascial flaps. The use of the superficial or deep fasciae in the creation of a fascial flap cannot be selected at random, but must be guided by the anatomical features of the different types of fasciae. In particular, we suggest the use of the superficial fascia, such as the parascapular fascio-cutaneous free flap or any cutaneous flap, when a well-vascularized elastic flap, with the capacity to adhere to underlying tissues, is required, and a fascio-cutaneous flap formed by aponeurotic fascia to resurface any tendon or joints exposures. Moreover, the aponeurotic fascia, such as the fascia lata, can be used as a surgical patch if the plastic surgeon requires strong resistance to stress and/or the capacity to glide freely. Finally, the epimysial fascia, such as in the latissimus dorsi flap, can be used with success when used together with the underlying muscles. Clearly, extensive clinical experience and judgment are necessary for assessment of their potential use.

The origins of the camper's chiasm asymmetry: a cadaveric study and clinical implications for flexor tendons surgery.

The Camper's chiasm (CC) originates from the decussation of tendon fibers of the flexor digitorum superficialis at the level of the proximal phalanx. Previous studies described several conformations of the CC, but none has studied the asymmetry pattern for each finger. We lack studies about the relationship between the vincula tendinum and the morphology of the CC. We aimed to study the precise pattern of asymmetry and the aforementioned relationship in a cadaveric study. We studied the fingers of 9 fresh frozen human hands (thumb excluded). We observed the distribution of the fibers and categorized each CC according to the Gonzalez classification. Finally, we recorded the inset point of the vincula longa superficiales (VLS) according to Schmidt. We found 7 symmetrical CCs, while the remaining 29 showed an asymmetrical pattern that matched with the site of insertion of the VLS. For the index and long fingers, we detected a dominance of the ulnar slip. For the ring and little finger, we found a higher radial dominance. The inset point of the VLS always coincided with the side of slip dominance, whereas in symmetrical CCs, the VLS was symmetrical as well. Since the vascular role of the vincula tendinum, we speculate that the asymmetry of the CC may be of vascular origin.

Topography of the deep branch of the ulnar nerve between genders: a cadaveric study with potential clinical implications.

The lack of meticulous knowledge concerning the topographical anatomy of the deep branch of the ulnar nerve (DUN) may pose difficulties, leading to a delay or a misdiagnosis of a DUN injury. Identification of the DUN is quite difficult without precise anatomical landmarks as reference points. The current study investigates the topography of the DUN between genders, taking as a reference point a well-known landmark, the Kaplan line, used in hand surgery for carpal tunnel release. Twenty-two (15 males and 7 female) fresh frozen adult cadaveric hands were dissected by using magnifying loupes (3.5 and 5.0 x). We marked values proximal to the Kaplan line as positive (+), while we marked distal ones as negative (-). The mean distance DUN-Kaplan line was 1.69 ± 4.45 mm. In male hands, the mean distance was 4.17 ± 1.88 mm, distal to the Kaplan line, while in females, the mean distance was -4.92 ± 0.69 mm proximal to the Kaplan line. Gender dimorphism was detected, with higher statistically significant values in male hands (p = 0.001). Cadaveric studies of the DUN topography, course, and distribution pattern are uncommon. The current study provides an accurate description of the DUN topography, taking the Kaplan line as a reference point, emphasizing gender differences. The DUN is located distally in males and proximally in females. Knowledge of these predictable anatomical relations may help hand surgeons intraoperatively when dealing with a DUN lesion, because of hand trauma or during the decompression of the DUN.