Dorsal Cutaneous Nerve Research Articles

Anterolateral and accessory anterolateral portals are safe to avoid subcutaneous nerve injury during subtalar arthroscopy-Definition of safe zones for standard lateral portals.

Injury to the superficial peroneal nerve (SPN) or the sural nerve (SN) is a common complication in subtalar arthroscopy. The purpose of this anatomical study was to evaluate the distance to surrounding subcutaneous nerves in the vicinity of three standard arthroscopic portals for subtalar joint arthroscopy and through actual portal placement for arthroscopic procedures, in order to define anatomical safe zones. Forty paired fresh-frozen foot-and-ankle specimens were used. Subtalar arthroscopy using a three-portal technique (anterolateral [AL], posterolateral [PL] and accessory anterolateral [AAL] portals) was performed. After completion of subtalar arthroscopy, the portals were marked, and all surrounding subcutaneous nerves, that is, the branches of the SPN and SN, were dissected. The distance of the nearest nerve at the level of the respective portal was measured and potential injury was recorded. The nearest nerve at the level of the AL portal was the intermediate dorsal cutaneous nerve at a mean of 15.4 ± 5.1 mm medial to the portal. The nearest nerve at the level of the AAL portal was the lateral dorsal cutaneous nerve at a mean of 17.7 ± 4.8 mm, being lateral to the portal. The nearest nerve at the level of the PL portal was the SN at a mean of 6.7 ± 4.7 mm anterior to the portal. Based on the measurements, safe zones were defined. Placement of the AL and AAL portals in subtalar arthroscopy is saved using standard anatomical landmarks and a thorough surgical technique. At the level of the PL portal, the SN is the most endangered structure in subtalar arthroscopy. Surgeons should be aware of the proximity of the SN to the PL portal and take the utmost care during portal placement and instrument insertion to avoid iatrogenic injury. The risk of nerve damage during portal placement may be reduced when positioning the portals in the defined safe zones. Not applicable.

ANATOMICAL VARIATIONS IN A FINITE ELEMENT NERVE MODEL OF THE HUMAN FOOT

The nerves in the foot offer a significant role in controlling the movement and correct loading of the foot by providing continuous feedback to the central nervous system. The health importance in the anatomical variations of nerves, such as the locations, the lengths, the communicating branches, and the distance between the adjacent nerve terminals between individuals have given prominence to anatomists as well as physiologists. A previously developed one-dimensional (1D) model of the nerve was extended to determine different anatomical variations in the nerves of the foot, as a realistic anatomical-based variant nerve model of the human foot is not available. The model was verified against experimental data from the literature for communicating branches and distances of various area of the human foot. For instance, the simulated distances of the communicating branches of the plantar nerves and medial dorsal cutaneous nerve (MDCN) division proximal to the first digital space were found to be 43.3 mm and 112.3 mm, respectively, which was in general agreement with the experimental distances of 8-56 mm and 96-116.74 mm, respectively. The developed nerve variant model provides a platform for future studies of the various geometrical and efficient concerns of neurovascular diseases such as diabetic neuropathies by determining the parameters of nerve conduction studies.

Anatomical Structures at Risk in Percutaneous Distal Bunionette Correction

Introduction/Purpose: Bunionette deformity affects 23% of the population and has numerous surgical options, including a minimally invasive approach (MIA) to decrease complications. Percutaneous surgery is favored by patients as it decreases pain, inflammation, and noticeable incision sites. Three possible osteotomy sites have been identified: proximal, diaphyseal, and distal. The study investigates the anatomic structures at risk during distal osteotomy of bunionette deformity using a Shannon burr. The distal osteotomy site was on average greater than 8mm from the extensor digitorum longus and adductor digiti minimi while it was 1.64mm from the lateral dorsal cutaneous nerve. The study highlighted the challenges posed by minimally invasive approaches to treating bunionette deformity and the need for cautious consideration when utilizing percutaneous methods. Methods: Eleven fresh frozen below-knee amputated foot and ankle cadavers were used for this study. Cadavers were allowed to thaw for 12 hours at room temperature before performing any tissue handling. All cadavers were visually inspected for evidence of gross pathology. Fluoroscopic radiographs were used to inspect for evidence of preexisting pathology of the fifth metatarsal. All cadavers with gross pathology or radiographic fifth metatarsal pathology were excluded from the study. All procedures were performed by a fellowship trained orthopaedic foot and ankle surgeon. Results: All eleven cadavers met the inclusion criteria for this study. The average age of the patients was 66.6 +/- 20.1 years. There were five female feet and six male feet. There were seven right feet and four left feet. Distance from the percutaneous access site was measured to structures at potential risk. The closest structure at risk was the lateral dorsal cutaneous nerve (LDCN) (1.64 mm), which was contacted 2/11 times and transected both times. The extensor digitorum longus (EDL) and abductor digiti minimi (ADM) had no instances of contact during the procedure. Dissection allowed for the identification of structures at risk and the assessment of osteotomy. All procedures resulted in a complete osteotomy. Conclusion: Overall, distal percutaneous bunionette osteotomy is largely safe. Structures pertinent to the surgery were identified with ease and were intact after osteotomy with a Shannon burr. Anatomic variations of LDCN can present challenges to the procedure. Meticulous dissection and judicious use of fluoroscopy can help prevent further damage. Surgeons should be aware of anatomic variations in order to proceed safely.

Medial dorsal cutaneous nerve entrapment following inversion ankle sprain

The medial dorsal cutaneous nerve is one of the terminal branches of the superficial peroneal nerve that provides sensory innervation to the dorsum of the foot. It may be prone to injury by direct blow, iatrogenic surgical lesion or in rare situations secondary to ankle sprains. The authors report a case of persistent ankle pain in a female patient caused by a post- traumatic compressive neuropathy of the medial dorsal cutaneous nerve secondary to an ankle sprain which was successfully surgically treated with complete resolution of the symptoms.

Comparison of Neurovascular Structures at Risk During Ankle Arthroscopy: A Cadaveric Study.

Arthroscopy has become increasingly common for diagnosis and treatment of ankle joint pathology. The four most common portals used for ankle arthroscopy are the anteromedial, anterolateral, posteromedial, and posterolateral. Anatomy of neurovascular structures along the ankle can significantly vary. The distance of neurovascular structures was compared with anatomical landmarks of ankle arthroscopic portals to verify safe zones for scope insertion. Twenty-six fresh frozen cadavers were used, with dissection of standard anatomical landmarks and neurovascular structures. Portals were made and verified with a 2.7-mm arthroscope. Significant differences were found in mean distances between anatomical landmarks except for the peroneus tertius tendon to the intermediate dorsal cutaneous nerve (P = .181; all others, P < .0001). In quantifying a scope space, the anteromedial and anterolateral portals had the largest margin of error at 0.82 cm and 1.04 cm, respectively. The saphenous nerve and vein were an average of 1.39 cm and 1.23 cm, respectively, from the anteromedial portal. The peroneus tertius tendon was an average of 0.23 cm from the intermediate dorsal cutaneous nerve. The tibialis anterior tendon was an average of 1.10 cm lateral to the medial gutter; the peroneus tertius tendon, 1.31 cm medial to the lateral gutter; and the Achilles tendon, 0.94 and 0.73 cm from the medial and lateral gutters, respectively. Among common ankle arthroscopic approaches, the anterolateral portal features the highest anatomic variability. These data support the standard protocol of beginning with the anteromedial portal to facilitate visualization of lateral-sided anatomy before anterolateral portal placement.

Ultrasound-guided injection of the ankle joint: cadaveric investigation of the anterolateral approach.

Injection of the tibiotalar (TT) joint is commonly performed in clinical practice under ultrasound (US) guidance using an anteromedial approach. However, in some patients, this approach may be technically challenging due to post-traumatic and/or degenerative bony changes. Therefore, the aim of this cadaveric investigation was to demonstrate the feasibility of the ultrasound-guided (USG) injection of the ankle joint via the anterolateral sulcus (ALS) by confirming the dye placement/distribution inside the articular space. Likewise, the safety of the procedure has also been evaluated by measuring the distance between the needle and the intermediate dorsal cutaneous nerve of the foot. A descriptive laboratory study with eight embalmed cadaveric ankles using the Fix for Life (F4L) method was performed at the setting of an academic institution. The interventional technique and the related anatomical findings were illustrated. During the injection, the needle was advanced into the TT joint through the ALS under US guidance, i.e., in-plane anterior-to-posterior approach. With the objective to confirm its correct placement, the needle was kept in situ and-to demonstrate the location of the dye inside the articular space-all eight ankles were injected with 3 mL of green color dye. Thereafter, a layer-by-layer anatomical dissection was performed on all four cadavers. The position of the needle's tip within the ALS was confirmed in all specimens. Accurate placement of the dye inside the articular space of the ankle was confirmed in seven of the eight cadaveric ankles, with 87.5% of accuracy. Herewith, unintentional spilling of the dye within the superficial soft tissues was reported in two of the eight ankles (25.0%). The mean distance between the needle and the intermediate dorsal cutaneous nerve of the foot, measured in all eight procedures, was 3 cm. USG injection of the ALS using the in-plane, anterior-to-posterior approach can accurately place the injectate inside the articular space. This cadaveric investigation described the accuracy and potential pitfalls of USG injection of the ankle via the anterolateral approach which represents an alternative technique in patients with reduced accessibility of the anteromedial recess due to degenerative and/or post-traumatic bony changes.

Minimally invasive subtalar joint and talonavicular joint preparation for hindfoot arthrodesis: A Cadaveric study evaluating structures at risk

Minimally invasive surgery (MIS) is growing in popularity due to smaller incisions, faster recovery times with less post-operative pain, and measurable decreases in morbidity. Our center performed an MIS hindfoot joint preparation about the talonavicular and subtalar joints and defined structures at risk in order to make this procedure more reproducible. Using ten fresh frozen cadaver limbs, we created a medial and lateral portal for talonavicular joint (TN) access, and an additional portal for subtalar joint (STJ) access to prepare the subtalar joint. After denuding the aforementioned joints of cartilage, the specimens were dissected to identify nearby anatomical structures. We documented the position of the peroneal sheath and sural nerve relative to the STJ portal, and the position of the dorsalis pedis artery (DP), medial dorsal cutaneous nerve (MDCN), extensor hallucis longus (EHL), extensor digitorum longus (EDL), tibialis anterior (TA), and tibialis posterior (TP) tendons relative to the TN portals. The average distance of the sural nerve and the peroneal sheath from the STJ portal was 34.21 mm and 14.12 mm respectively. The average distance of the DP, MDCN, and deep peroneal nerve from the medial and lateral TN portals were 13.31 mm, 11.54 mm, and 17.14 respectively. No neurovascular structures were transected throughout joint preparation. To our knowledge this is the first study looking into structures at risk for this specific procedure.

Anatomical landmarks for ankle block

We aimed to describe anatomical landmarks to accurately locate the five nerves that are infiltrated to accomplish anaesthesia of the foot in an ankle block. Twenty-four formaldehyde-fixed cadaveric ankles were studied. Photographs of cross sections of the frozen legs, cut at a horizontal plane across the most prominent points of the medial and lateral malleoli, were analysed. The curvilinear distance from the most prominent point of the closest malleolus to each of the five cutaneous nerves and their depth from the skin surface were measured. Sural, tibial, deep peroneal, saphenous and medial dorsal cutaneous nerves were located 5.2 ± 1.3, 9.2 ± 2.4, 7.4 ± 1.9, 2.8 ± 1.1, 2.1 ± 0.6 mm deep to the skin surface. The curvilinear distances from the medial malleolus to the tibial, deep peroneal and saphenous nerves were 32.5 ± 8.9, 62.8 ± 11.1 and 24.4 ± 7.9 mm, respectively. The curvilinear distances from the lateral malleolus to the sural and medial dorsal cutaneous branches of superficial peroneal nerves were 27.9 ± 6.3 and 52.7 ± 7.3 mm, respectively. The deep peroneal nerve was found between the tendons of the extensor hallucis longus and the extensor digitorum longus in the majority of specimens, while the medial dorsal cutaneous nerve was almost exclusively found on the extensor digitorum longus tendon. The sural and tibial nerves were located around halfway between the most prominent point of the relevant malleolus and the posterior border of the Achilles tendon. In conclusion, this study describes easily identifiable, palpable bony and soft tissue landmarks that could be used to locate the nerves around the ankle.

Connection between medial dorsal cutaneous nerve and saphenous nerve: case report.

There are no data on the connection of the saphenous nerve (SN), located on the medial side of the foot, with the terminal branches of the superficial fibular nerve. The aim of this study is to reveal the variation that surgeons should pay attention to for anesthesia applied in foot surgeries. In this study, the left foot of a 70-year-old female cadaver fixed with formalin was dissected. The distance to the medial malleolus and the incision line was recorded using digital caliper to determine the reference points in the resulting variation. It was observed that a branch from the SN, which arose from the SN and proceeded anteriorly to the upper part of the medial malleolus and continued towards the dorsum of the foot, hooked with a branch from the medial dorsal cutaneous nerve (MDCN). The branches arising from this hook were distributed on the medial edge of the foot up to the proximal metatarsophalangeal joint I. The distance of this nerve connection to the medial malleolus is 91.14mm, and the distance to the incision line is 15.76mm. It is suggested that the case presented as an unusual SN variation, which may affect the success of local anesthesia in invasive procedures to the medial part of the foot and could be considered in the evaluation of sensory loss after anteromedial surgical approach to the ankle, should be included in the classification of the cutaneous innervation pattern of the foot.

Cutaneous Squamous Cell Carcinoma of the Hand Presenting as Clinical Perineural Invasion

Cutaneous squamous cell carcinoma of the hand with clinical perineural invasion is uncommon. This article describes a case of a 70-year-old female who presented with a small painful nodule on the dorsum of the left hand with minor skin surface changes who underwent excisional biopsy. A deep long subcutaneous cord was palpable extending proximally from the nodule. Intraoperative findings showed a tumour growing 2.5 cm along the dorsal cutaneous nerve of the hand, and histopathological examination revealed a primary well-differentiated squamous cell carcinoma with perineural invasion. This case highlights the importance of considering malignancy as a differential diagnosis when dealing with atypical lesions.

The effect of intraoperative nerve identification technique on distally-based dorsal fasciocutaneous flap for thumb and fingertip reconstruction

IntroductionThumb and fingertip resurfacing continues to be a challenge for hand surgeons, as the treatment varies widely. Being donor nerves in the flap for sensory restoration, the dorsal cutaneous nerves in hand have been widely described in the literature. However, their applications in providing anatomical information to sufficiently harvest the longitudinal axis of a robust flap are usually underestimated. This study reports reconstruction of thumb and fingertip defects with the distally based dorsal fasciocutaneous (DDF) flap and explores the effect of intraoperative nerve identification technique on clinical outcomes. HypothesisThe nerve identification technique can contribute considerably to the improvement of flap circulation, with less risk of poor venous return. Materials and methodsA retrospective study was conducted in 89 patients who had thumb or fingertip defects treated with the DDF flap from February 2014 to June 2020. Patients were divided into two groups based on whether intraoperative nerve identification technique was used. Flap survival was evaluated. The follow-up was conducted by using smartphone or by face-to-face visit. Time for complete wound healing, time to return to work, hand performance, the total active motion of the joints and static two-point discrimination of flaps were analyzed. ResultsThe 46 flaps (group A) that underwent intraoperative nerve identification technique had an 8.7% venous congestion rate versus a 27.9% venous congestion rate in the 43 flaps (group B) without using nerve identification technique (p=0.018). The mean follow-up was 11.08 (range 6–26) months. Time for complete wound healing and time to return to work were significantly shorter in group A (p=0.026 and p=0.012). Michigan Hand Outcomes Questionnaire (MHQ) scores were similar between groups. In the face-to-face follow-up, there was no significant difference in the total active motion of the injured fingers and static two-point discrimination between the two groups (p=0.657 and p=0.182). DiscussionThe use of nerve identification technique could decrease the odds of postoperative venous congestion in DDF flap for thumb and fingertip reconstruction, and result in improved outcomes in terms of time for complete wound healing and time to return to work. Level of evidenceIII; retrospective comparative study.

Anatomical Variations in the Course and Level of Termination of Superficial Peroneal Nerve- A Cadaveric Study

Introduction: Several variations in the course and branching pattern of the Superficial Peroneal Nerve (SPN) have been reported. Knowledge of the different course of SPN is essential in reducing the risk of iatrogenic injury during the orthopaedic foot and ankle surgery and various other procedures. Aim: To observe any variations in the course, and level of termination of SPN. Materials and Methods: This descriptive analytical study was conducted on 50 lower limb specimens in the Department of Anatomy, Bangalore Medical College and Research Institute Bengaluru from January 2013 to January 2016. Dissection kit was used for dissection, digital camera was used for photography of specimens, measuring tape was used to measure the distance at which the SPN became cutaneous with respect to the tip of lateral malleolus and the distance at which SPN terminated into medial and Intermediate Dorsal Cutaneous Nerve (IDCN) with reference to the tip of lateral malleolus. Descriptive statistics was used and results were expressed as Mean±SD. Results: It was observed that the distance at which SPN became cutaneous with respect to tip of lateral malleolus was 10±2.82 cm. The level of termination of SPN into Medial Dorsal Cutaneous Nerve (MDCN) and IDCN with reference to tip of lateral malleolus was 4.7±2.08 cm. In 5 (10%) of 50 specimens the SPN terminated at a higher level before piercing the deep fascia. Out of these 5 specimens, it was observed that in one specimen the SPN terminated above the head of fibula before piercing Peroneus Longus (PL) muscle. In another specimen, the SPN terminated near the head of fibula before piercing PL muscle. In one of the specimens SPN terminated near head of fibula after piercing PL, in two specimens SPN terminated in upper third of the leg after piercing PL muscle and their terminal branches pierced the deep fascia and emerged out at different level with respect to tip of lateral malleolus. Conclusion: SPN became cutaneous and terminated in the distal third of the leg in most cases. This knowledge is very helpful to surgeons and orthopaedists in performing fasciotomy, and ankle arthroscopy to prevent iatrogenic injury to the nerve.

Identification of portals and evaluation of their safeness for MIS arthrodesis of the 1st tarsometatarsal joint

There has been a growing trend towards the use of minimally invasive surgical techniques in foot and ankle surgery. The aim of this study is to identify portal sites for minimally invasive arthrodesis of the 1st TMT joint and determine the safeness of each portal to the surrounding structures. 10 cadavers were utilized. 3 portal sites were utilized in preparing the 1st TMT joint which included dorsomedial, plantar medial and dorsolateral portals at the level of the 1st TMT joint. Fluoroscopic guided joint prep was performed. After joint prep, each specimen was dissected to evaluate structures at risk which included the deep peroneal nerve, dorsalis pedis artery, EHL Tendon, medial dorsal cutaneous nerve and medial marginal vein. In 1 specimen, there was noted to be disruption of the deep peroneal nerve, dorsalis pedis artery and partial tear of the EHL through the dorsolateral portal. No damage to any vital structures was noted at the dorsomedial or plantar medial portals. All but 1 specimen was determined to be underprepped with the dorsolateral aspect of the joint being the most common area. Additionally, upon open dissection to evaluate the joint prep, there was noted to be some small pieces of cartilage remaining despite thorough irrigation. The three-portal approach for the MIS 1st TMTJ arthrodesis is a relatively low risk procedure, with low risk of injury to the surround neurovasculature and tendon structures. However, care should be taken at each portal site with resecting cartilage to ensure no damage to surrounding vital structures occurs while also ensuring adequate joint preparation.

Variations in Innervation Pattern to Dorsum of Foot by Medial Dorsal Cutaneous Nerve, Intermediate Dorsal Cutaneous Nerve, Lateral Dorsal Cutaneous Nerve with Surgical and Clinical Correlations: A Cadaveric Dissection Based Study

The complete reconstruction of any soft tissue defect includes even the sensory recovery which is very significant aspect pertaining to prognosis. Superficial nerves in the vicinity of the vascular axis can be considered as vascular relays and neuroskin grafts can be constructed on them. Variations in innervation to various part of the dorsum of the foot by this nerve should be kept in mind while making these grafts. Authors dissected 50 formalinized cadaveric feet and studied normal anatomy and variations in origin, course, branching pattern, communications, and any other variations in medial, intermediate and lateral dorsal cutaneous nerve. The intermediate dorsal cutaneous nerve was innervating larger area of the skin around 3rd and 4th web spaces in 60% of cadaveric feet. The 2nd web space was innervated by medial dorsal cutaneous nerve in 92% of cadaveric feet. In 52% of cadaveric feet communicating branches were found between intermediate dorsal cutaneous nerve and lateral dorsal cutaneous nerve. In 63% cadaveric feet communicating branches were found between medial dorsal cutaneous nerve and branch of deep peroneal nerve to 2nd web space. The mean distance between lateral malleolus and intermediate dorsal cutaneous nerve was 4.05cm. These all observations can provide anatomical basis at the time of preparing medial dorsal cutaneous nerve flaps and intermediate dorsal cutaneous nerve flaps and also can minimize morbidity at donor site. KEY WORDS: Medial Dorsal Cutaneous Nerve, Intermediate Dorsal Cutaneous Nerve, Lateral Dorsal Cutaneous Nerve, Medial Dorsal Cutaneous Nerve Flap, Intermediate Dorsal Cutaneous Nerve Flap, Soft Tissue Defects, Open Reduction And Internal Fixation Of Fibula, Arthroscopy, Local Anesthetic Block, First Dorsal Metatarsal Artery Flap, Defects In Distal Dorsalis Pedis, Compression And Entrapment Neuropathies.

A retrospective study of electrodiagnostically evaluated ulnar neuropathies with special guidelines for ulnar neuropathies at elbow

BackgroundThe diagnosis of type, severity of ulnar neuropathy based on symptoms and clinical tests are unsatisfactory. This study aimed to retrospectively analyze ulnar neuropathies at different sites evaluated through electrodiagnostic studies (EDx), especially for ulnar neuropathy at elbow (UNE).ResultsTotal 270 ulnar neuropathy patients’ data were recruited from laboratory record over a five-year period (2016–2021).Their demographic data, clinical history and EDx parameters were analyzed focusing on etiology, nerve lesion types, 5th-digit sensory, dorsal ulnar cutaneous nerve (DUCN) conduction, motor nerve conduction velocity (NCV) across elbow along with EMG of ADM, FDI, FCU, FDP muscles. The patients grouped into traumatic injuries—27.8% (T) and 72.2% non-traumatic (NT) had varied sensory-motor symptoms: pain—10%, altered sensation—28.1%, pain-paresthesia—14.8%, atrophy—25.2% and clawing—8.9%. UNE was the most prevalent (82.75%-NT, 66.67% -T) with < 50 m/s motor and sensory NCV across elbow. Compound muscle action potential (CMAP) amplitude > 50% drop across elbow was seen in 55.17%-NT and 54.16%-T groups. Abnormal DUCN and short-segment inching NCV were less frequently noted. In EMG, ADM (T-83.33% and NT-65.51%) and FDI (T-70.83% and NT-68.96%) muscles were evaluated the most and FDP the least.ConclusionUNE was the most common followed by forearm and wrist. NCV and CMAP across elbow are stronger EDx parameters for UNE. Neuropathy was irrespective of gender and prevalent at early of middle age. The EDx could be considered as one of the most valuable tests in confirming the localization, severity and type of ulnar nerve lesion, which favors management and prognosis of patient.

An Anatomic Study of the Lateral Dorsal Cutaneous Nerve Using 3-Tesla MRI: A Comparison to Cadaveric Data With Surgical Applications.

The lateral dorsal cutaneous nerve (LDCN) and the anastomotic branch of the sural nerve (AB) are cutaneous sensory nerves at risk of iatrogenic injury during lateral foot surgery. This study is the first to use a large cohort of high-resolution magnetic resonance images (MRIs) of the ankle to better describe the course of these nerves in vivo in order to aid surgeons intraoperatively. Our study intends to build on the "high and inside" approach to the proximal 5MT by accounting for variations in course of the LDCN and AB. One hundred twenty-five 3-tesla (T) MRI studies of the ankle were analyzed. Three reviewers measured the distance from the LDCN and AB to landmarks including the most proximal aspect of the fifth metatarsal tuberosity (5MT) and the peroneus brevis tendon (PBT). Mean vertical distance from the LDCN to the 5MT was 0.8 ± 0.2 cm. Presence of an AB was visualized in 59 of 125 studies (47.2%) and was found 2.2 ± 0.5 cm dorsal to the 5MT. The AB was found to become superior to PBT at a horizontal distance 1.9 ± 0.5 cm proximal to the 5MT. The LDCN was found superior to the PBT at its insertion onto the 5MT in approximately 10% (n = 12) of our studies. During these instances, the LDCN was located an average of 0.3 cm dorsal to the PBT. Our proposed "safe zone" for the approach to the proximal 5MT remains superior to the LDCN and inferior to the AB and avoids crossing directly over either nerve in >95% of analyzed MRI studies. This incision begins 1.5 cm dorsal to the most proximal aspect of the 5MT and extends no more than 1 cm posteriorly. Careful dissection and identification of the LDCN and possible AB is necessary prior to further extension of incision. Level IV, case series.

Lateral Dorsal Cutaneous Nerve and Anastomotic Branch to the Intermediate Dorsal Cutaneous Nerve: A Review of Cadaveric Data and Comparison with 3 Tesla MRI

Category:Other; HindfootIntroduction/Purpose:The lateral dorsal cutaneous nerve (LDCN) and anastomotic branch to the intermediate dorsal cutaneous nerve (AICN) can be injured during foot and ankle surgery. Cadaveric specimen studies are limited by small sample size.1-11 We sought to use high-field 3-tesla (3T) magnetic resonance imaging (MRI) to examine a significantly larger cohort and obtain a more representative sample of the course of the LDCN and AICN. A more generalizable understanding of the course and position of these structures will aid surgeons intraoperatively in avoiding iatrogenic injury when performing the sinus tarsi approach, as well as during percutaneous intramedullary fixation of the 5th metatarsal.Methods:High-field 3T MRI studies performed between January 2015 to January 2020 were reviewed. Three blinded reviewers at a single academic center measured the coronal distances of LDCN and AICN from the fifth metatarsal styloid (5MS). Intraclass correlation coefficients (ICC) were calculated to assess reviewer reliability. Foot and ankle MRIs with major structural abnormalities, such as tumor or the presence of hardware, were excluded.Results:A total of 125 foot and ankle 3T MRIs were identified. Intraclass correlation coefficient was excellent at 0.87 for LDCN to 5MS and 0.88 for AICN to 5MS. The mean distance of the LDCN to the 5MS was 0.8 cm (range 0.3-1.4 cm, CI 0.8-0.8 cm) and that from the AICN to the 5MS was 2.1 cm (range 1.6-3.2 cm, CI 2.0-2.2 cm. Height had no significant correlation with the nerves' distance from bony landmarks with r values of 0.14 and 0.29 for the LDCN and AICN, respectively. Similarly, we did not find BMI to significantly correlate, with r values of 0.10 and 0.30 for the LDCN and AICN, respectively.Conclusion:Our study demonstrated the LDCN and AICN can be found on average 0.8 cm and 2.1 cm, respectively, above the 5MS with no clear association to patient height or BMI. Literature studying the range of distances the LDCN is found from the 5MS is scarce, but one study noted the range to be 0.7-1.2 cm, which is significantly smaller than our range of 0.3-1.4 cm.3 To our knowledge, our study is first to note the range of distances the AICN can be found from the 5MS, which is 1.6-3.2 cm.

Risk of Injury to the LDCN and IACN During Surgical Approaches to the Foot and Ankle: an Anatomical Study using 3-Tesla Magnetic Resonance Imaging

Category:Ankle; OtherIntroduction/Purpose:The dorsomedial branch of the lateral dorsal cutaneous nerve (dmLDCN) and anastomotic branch to the intermediate dorsal cutaneous nerve (AICN) are at risk during foot and ankle surgery. Prior studies of the distal sural nerve on cadaveric specimens are limited by small sample size.1-7 We sought to use high-field 3-tesla (3T) magnetic resonance imaging (MRI) to examine a significantly larger cohort and obtain a more representative sample of the course of the dmLDCN and AICN. A more generalizable understanding of the course and position of these structures will aid surgeons intraoperatively in avoiding iatrogenic injury when performing the dorsomedial approach to the fifth metatarsal, as well as the sinus tarsi and extended sinus tarsi approaches for calcaneal fractures and subtalar/calcaneocuboid fusions.Methods:High-field 3T MRI studies performed between January 2015 to January 2020 were reviewed. Three blinded reviewers at a single academic center measured the coronal distances of dmLDCN and AICN from the fifth metatarsal styloid (5MS). Intraclass correlation coefficients (ICC) were calculated to assess reviewer reliability. We analyzed the upper and lower quartile ranges to evaluate the risk of iatrogenic nerve injury with standard surgical approaches.Results:A total of 125 foot and ankle 3T MRIs were measured. Intraclass correlation coefficient was excellent at 0.87 for dmLDCN to 5MS and 0.88 for AICN to 5MS. 1st and 4th quartile range for the dmLDCN to the 5MS was 0.5-0.7 cm and 0.9-1.4 cm, respectively. 1st and 4th quartile range for the AICN to the 5MS was 1.6-1.9 cm and 2.3-3.2 cm respectively. The AICN was identified in 47.2% of the images.Conclusion:The dmLDCN, AICN, and SN are vulnerable to iatrogenic injury during surgical approaches to the fifth metatarsal and calcaneus. Our 1st quartile range for the dmLDCN to the 5MS of 0.5-0.7 cm suggests that nearly 25% of our values measured by 3T MRI were lower than the reported range of 0.7-1.2 cm by Fansa, suggesting iatrogenic injury to the dmLDCN with the 'high and inside approach' to the fifth metatarsal may be higher than previously thought. The 4th quartile range of the AICN's distance from the 5MS of 2.3-3.2cm places it at risk with the sinus tarsi approach.

MTP Arthrodesis: Percutaneous Interfragmentary Screw Placement and Nerve Injury

Category:Basic Sciences/Biologics; Midfoot/ForefootIntroduction/Purpose:Iatrogenic cutaneous nerve injury is the most common complication encountered in foot and ankle surgery with limited evidence to inform surgeons on neuroprotective techniques. The purpose of this study was to assess risk for injury to the dorsomedial cutaneous nerve (DCN) during insertion of percutaneous interfragmentary screws used in metatarsophalangeal (MTP) arthrodesis.Methods:Ten mid-tibia fresh frozen cadaver specimens were obtained for execution of this study. All cadavers were grossly and radiographically inspected for any evidence of existing pathology or prior operative intervention. Percutaneous placement of interfragmentary screw in both distal to proximal and proximal to distal fashion was performed. Only the skin was incised before reaming and screw placement. After screw placement, dissection of the great toe was conducted. The distance between the screws and the DCN was obtained. The DCN was also inspected for injury.Results:A total of 10 cadavers were included. The average age of our population was 64 (+- 12.6). Males represented 80% of our included specimens. Injury to the DCN was not reported using the proximal to distal screw fixation. The mean distance from the dorsal cutaneous nerve using proximal to distal interfragmentary screw fixation was 7.45+- 3.85 mm compared to 4.30+-2.71 mm in the distal to proximal screw. Distal to proximal screw fixation was associated with 10% risk of nerve injury with no nerve injuries occurring at the site of proximal to distal screws.Conclusion:In our cadaver study, proximal to distal screw fixation seems to offer neuroprotection in the setting of MTP arthrodesis. The DCN is known to have many anatomic variants, and DCN injuries can be a pretext for painful neuroma formation. Surgeons should consider careful dissection to the joint capsule in effort to decrease the risk of neurogenic injury when placing interfragmentary screws in MTP arthrodesis.

A combined functional dorsal nerve model of the foot.

The nerves in the skin surface of the foot are comprised of unmyelinated smaller somatic nerves and larger myelinated sensory nerves. Current diagnostic methods are unable to evaluate combined nerve conduction velocity (NCV) from both unmyelinated smaller somatic nerve (USSN) and myelinated larger nerves (MLN) respectively. Computational models may provide an alternative tool to determine the NCV of the combined nerve. Therefore, a combined functional dorsal nerve model (CFDNM) of the various dorsal nerves along with its associated nerve ending of the human foot is proposed and constructed. The combined dorsal nerve model consists of synthetic USSN (SUSSN) and dorsal MLN of the foot. The unmyelinated as well as myelinated electrophysiological nerve models were used to simulate selected SUSSN and MLN of the foot by injecting an external stimulus at the most distal part of SUSSN of the foot through the use of bidomain model. Results from our work demonstrated that the action potential propagated from the most distal part to proximal part of distinct dorsal nerves of the foot, e.g., the simulated NCV of the combined intermediate dorsal cutaneous nerve (IDCN) of the foot was 28.4 m s-1. The CFDNM will provide a vital tool for diagnosis initially small fibre neuropathy (SFN) by computing NCV in the prospective studies.