The Anatomy of the Dorsal Cutaneous Branch of the Ulnar Nerve – a Safe Zone for Positioning of the 6r Portal in Wrist Arthroscopy

Safe zones in dorsal portals for wrist arthroscopy: a cadaveric study

The standard dorsal portals are the most commonly used in wrist arthroscopy. This cadaveric study aims to determine safe zones, by quantitatively describing the neurovascular relationships of the dorsal wrist arthroscopy portals: 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar. The neurovascular structures of twenty-one fresh frozen human cadaveric upper limbs were exposed, while the aforementioned portals were established with needles through portal sites. The minimum distance between portals and: dorsal carpal branch of radial artery, superficial branch of radial nerve, posterior interosseous nerve and dorsal branch of ulnar nerve, were measured accordingly with a digital caliper, followed by statistical analysis of the data. The median and interquartile range for each portal to structures at risk were determined and a safe zone around each portal was established. Free of any neurovascular structure safe zones surrounding 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals were found at 0.46mm, 2.33mm, 10.73mm, 11.01mm, 10.38mm, 5.95mm and 0.64mm respectively. Results of statistical analysis from comparisons between 1-2, 3-4 and midcarpal radial portals, indicated that 1-2 was the least safe. The same analysis among 3-4, midcarpal radial, midcarpal ulnar and 4-5 portals indicated that midcarpal portals were safer, while 3-4 was the least safe. Results among midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals indicated that 6-radial and specifically 6-ulnar were the least safe. This study provides a safe approach to the dorsal aspect of the wrist, enhancing established measurements and further examining safety of the posterior interosseous nerve.

Complications after arthroscopic triangular fibrocartilage complex (TFCC) surgery

Wrist arthroscopy is a valuable and widely utilized tool in the treatment of triangular fibrocartilage complex (TFCC) injuries. These procedures include synovectomy alone, peri-capsular or transosseous repair, and arthroscopic-assisted reconstruction, and each are associated with specific complications. This review describes the types of complications and their rates in different types of arthroscopic TFCC surgery reported in the literature and in our centre. Across the spectrum of arthroscopic TFCC surgery, complication rates and the learning curve increase with surgical complexity. Relevant anatomy, prevention and management of complications including nerve injury and irritation, extensor tendon injury and tendinitis, fracture, stiffness, and persistence of symptoms or instability are discussed. Vigilance to anatomical details and careful dissection can help to reduce complications that may result in disturbing pain and functional loss.

The Risk of Injury in Wrist Arthroscopy Portals: A Cadaveric Study

During wrist arthroscopy, the wrist joint can be visualized from almost every perspective through a combination of standard dorsal and volar arthroscopic portals. This cadaveric study aims to compare all wrist portals described in terms of their safety in order to rank them according to the distance from the nearest structure at risk for arthroscopic wrist procedures. Twenty-nine cadaveric formalin-embellished upper limbs were examined. Needles were inserted at dorsal and volar portal sites to perform the measurements. During the subsequent dissection, distances were measured as the shortest possible distance from the nearest structure at risk for each portal. Safe zones were determined for all portals, and the safety classification of arthroscopic wrist portals was proposed, ranking them from the safest to the most perilous. Applying the proposed safety classification to arthroscopic practice, wrist arthroscopy can be performed with a lower risk of iatrogenic complications arising from the implementation of the wrist portals.

Subcutaneous Dorsomedial Triangle of Forearm: Surgical Anatomy and Clinical Implication

Background The purpose of the study was to provide a practical landmark for localizing the dorsal branch of the ulnar artery and nerve, to approach for microsurgical flaps, for harvesting nerve grafts and also to avoid these nerves during insertion of wrist arthroscopy portals. Material and methods Forty adult cadaveric upper limbs (20 right and 20 left) were dissected for localizing the dorsal branches of the ulnar artery and nerve. The ramification patterns of the nerve were mapped. The wrist arthroscopy portals are located radial and ulnar to the tendon of extensor carpi ulnaris at the level of the wrist joint, and their designated names are '6R & 6U', respectively. The distance of branches of the nerve from the 6U and 6R portals for wrist arthroscopy was recorded. Results The present study has delineated a subcutaneous dorsomedial triangular area in the distal forearm. The construction of this triangle uses palpable landmarks, i.e. pisiform bone, styloid process and subcutaneous border of the ulna. The measure of the sides of the triangle uses proportion rather than absolute measurements and hence is person specific. The dorsal branches of the ulnar nerve and artery are consistently given off in the triangle's upper third and middle third, respectively. Four branching patterns have been mapped, with one dominant pattern in 67.5% of limbs. In three-fourths of cases, one branch of the dorsal branch of the ulnar nerve consistently overlies the 6U portal and hence runs a higher risk of injury. Conclusion The study suggests more practical, accurate, reliable and consistent surface landmarks for the localization of the dorsal branch of the ulnar artery and nerve for reconstructive microsurgery for distal hand defects.

Causes of Dorsal Cutaneous Branch of the Ulnar Nerve Neuropathy Among Patients Undergoing Electrodiagnostic Studies: A Series of 14 Patients

BACKGROUND

Isolated neuropathy of the dorsal cutaneous branch of the ulnar nerve (DCBUN) is rare and most cases are secondary to trauma, often iatrogenic. The topography of sensory abnormalities and abnormal electrodiagnostic (EDX) findings are crucial in confirming DCBUN neuropathy.  Materials and methods: This is a retrospective study of patients with isolated involvement of the DCBUN from among patients referred for EDX studies for upper extremity symptoms. All patients underwent a focused neurological examination followed by EDX studies. Ultrasound (US) studies were performed in two patients.  Results: Of the 14 patients with DCBUN neuropathy, decreased pinprick sensation in the distribution of the DCBUN was noted in 11 (78%) patients. DCBUN sensory nerve action potential (SNAP) was not recordable in 13 (92%) patients. In one patient who had a recordable SNAP, the latency was prolonged, and the amplitude was decreased. Four (28%) patients had incidental EDX abnormalities suggestive of entrapment of the median nerve at the carpal tunnel. The most common cause of DCBUN neuropathy was trauma in 13 (92%) patients, of which eight were iatrogenic. No specific etiology was detected in one patient (7%). Of the two patients who underwent US studies, one had increased cross-sectional area (CSA) at the wrist with prominent fascicles and hyperechoic scar tissue, while the CSA was normal in the other patient.

CONCLUSIONS

Although rare, DCBUN neuropathy can be readily confirmed by typical clinical features and EDX findings. Surgeons should be aware of the anatomy and clinical features of DCBUN neuropathy and avoid injuring the nerve during surgical procedures at the wrist and forearm.

Failed Triangular Fibrocartilage Complex Repair and Reconstruction

Unsuccessful triangular fibrocartilage complex (TFCC) repair or reconstruction is poorly defined, often stemming from multiple causes, both patient and surgeon-related. Complete evaluation of the patient's psychosocial status and involvement in any litigation claims is essential, as is a thorough history, physical examination, and imaging workup to accurately diagnose TFCC injury, along with any concomitant wrist pathology. Awareness of common complications and technical errors is critical, and preventive treatment strategies should be implemented to minimize these events.

Complications of Wrist and Hand Arthroscopy

Arthroscopy of the wrist continues to evolve and advance as a valuable clinical technique in hand surgery. This article aims to address safety of wrist arthroscopy and provide an overview of the known iatrogenic complications. Ultimately, the likelihood of associated injuries during wrist arthroscopy is dependent on the surgeon's ability and understanding of the equipment. Case volume and duration of experience directly correlate with mitigating iatrogenic injury and optimizing patient outcomes.

Incidence of Posterior Interosseous Nerve Trauma During Creation of the 3-4 Wrist Arthroscopy Portal in Cadavers

PURPOSE

To describe histologic evidence of nerve trauma during the creation and use of the 3-4 portal.

METHODS

Fourteen fresh-frozen cadaveric wrists were mounted on a custom-built frame that simulated a wrist arthroscopy traction tower. After the 3-4 portal was created in the usual manner, the skin was dissected off to identify possible trauma to the posterior interosseous nerve (PIN). Specimens were categorized into those where there was clearly no trauma to the PIN and those where trauma was possible. In the cases where trauma was possible, we harvested the PIN with a cuff of the proximal edge of the portal and examined the cross-sectional histology of the most distal sections for the presence of neural tissue.

RESULTS

There was clearly no trauma to the PIN in 3 of the wrists during the creation of the 3-4 portal. In the remaining 11 wrists with possible trauma to the PIN, we identified axonal tissue on histologic examination at the proximal edge of the 3-4 portal in 7 of these specimens. In summary, 50% (7 of 14) of our specimens had visual and histologic evidence of trauma to the PIN.

CONCLUSIONS

Based on the findings of this study, there may be more instances of trauma to the PIN during routine wrist arthroscopy than have been previously reported.

CLINICAL RELEVANCE

Findings suggest that transection or injury to this nerve may not lead to any clinical sequelae. However, if there is an instance where a patient has persistent, otherwise unexplained, dorsal wrist pain after a wrist arthroscopy procedure, iatrogenic neuroma of the PIN may be responsible and should be considered.

Assessment of the structures at risk during wrist arthroscopy: a cadaveric study and systematic review

We assessed the proximity of neurological structures to arthroscopic portals in a cadaveric study and through a systematic review. Arthroscopy was performed on ten cadaveric wrists. Subsequently the specimens were dissected to isolate the superficial branch of the radial nerve, the dorsal branch of the ulnar nerve, the posterior interosseous nerve and the extensor tendons. We measured the distances from the nerves to common portals. For the systematic review Pubmed and EMBASE were searched on the 31 May 2014 for cadaveric studies reporting the proximity of neurological structures to any arthroscopic wrist portal. In the cadaveric study, partial injuries were seen to six extensor tendons and one posterior interosseous nerve; it was assumed this was due to creation of the portals. Seven published studies were included in the systematic review. The dorsal sensory branch of the ulnar nerve was found to be at risk by performing the 6 Ulnar, 6 Radial and ulnar midcarpal portals, the sensory branch of the radial nerve by the 1-2 and 3-4 portals and the posterior interosseous nerve by the 3-4 and 4-5 portals.

LEVEL OF EVIDENCE

V.

The Anatomical Relationship Between the Dorsal Cutaneous Branch of the Ulnar Nerve and the Ulnar Styloid Process with Variations in Forearm Position

BACKGROUND

There are significant variations in the anatomy of the dorsal cutaneous branch of the ulnar nerve (DCBUN). The DCBUN is at risk for iatrogenic injury during surgeries around the ulnar side of the wrist. The purpose of this study was to demonstrate the relationship between the ulnar styloid process and the DCBUN and to confirm the DCBUN's change in location with different forearm positions.

METHODS

We examined 9 fresh frozen cadaveric limbs to establish the course of this nerve. The DCBUN was dissected and traced around the ulnar border of the wrist. The distance from the tip of the ulnar styloid process to the origin of the DCBUN was measured. The distances from the ulnar styloid process to the DCBUN were measured in supination, pronation, and in a neutral position of the forearm.

RESULTS

The DCBUN originated on average 4.92 cm proximal to the ulnar styloid process. In all cases, the DCBUN crossed the ulnar distal to ulnar styloid process and it moved more closely to the ulnar styloid process with a forearm position change from supination to pronation.

CONCLUSIONS

We recommend making a skin incision on the ulnar side around the styloid process with the forearm in supination or neutral position was another method to avoid injury of DCBUN.

Risk of Injury to the Dorsal Sensory Branch of the Ulnar Nerve With Percutaneous Pinning of Ulnar-Sided Structures

PURPOSE

To assess the risk of injury to the dorsal sensory branch of the ulnar nerve (DSBUN) with percutaneous pinning of commonly stabilized ulnar-sided structures.

METHODS

Eleven fresh-frozen cadaveric upper extremities were assessed. Percutaneous pinning of the fifth metacarpal base and neck, lunotriquetral joint, ulnar styloid, and distal radioulnar joint (DRUJ) with 1.4-mm Kirschner wires was performed under fluoroscopic guidance. Each specimen was then carefully dissected and the distance from each pin to the DSBUN was measured using a digital caliper. Direct injury to the DSBUN and pins found immediately adjacent to the nerve were recorded.

RESULTS

Mean distance from the pin to the DSBUN at the fifth metacarpal neck was 5.0 ± 1.5 mm; fifth metacarpal base, 2.3 ± 2.2 mm; lunotriquetral joint, 1.8 ± 1.6 mm; ulnar styloid, 0.8 ± 1.1 mm; and DRUJ, 3.1 ± 0.9 mm. Two of 11 ulnar styloid pins and 1 of 11 lunotriquetral pin directly penetrated the DSBUN, whereas 4 of 11 ulnar styloid pins, 3 of 11 fifth metacarpal base pins, and 2 of 11 lunotriquetral pins were directly adjacent to the DSBUN. There was an increased overall risk of DSBUN injury (risk of direct injury and risk of adjacent pin) with pinning of the ulnar styloid compared with fifth metacarpal neck and DRUJ pinning.

CONCLUSIONS

The current study demonstrates the risk of iatrogenic injury to the DSBUN with percutaneous pinning of the ulnar styloid, lunotriquetral joint, and fifth metacarpal base.

CLINICAL RELEVANCE

We recommend identifying and protecting the nerve to mitigate the risk of iatrogenic injury when performing ulnar-sided pinning of structures from the ulnar styloid to the fifth metacarpal base.

Anatomical study of the dorsal cutaneous branch of the ulnar nerve (DCBUN) and its clinical relevance in TFCC repair

The aim of this study was to define a detailed description of the dorsal cutaneous branch of the ulnar nerve (DCBUN) in particular in relevance to triangular fibrocartilage complex (TFCC) repairs. In 20 formalin-embalmed arms, the DCBUN was dissected, and the course in each arm was mapped and categorized. Furthermore, the point of origin of the DCBUN, that is, from the ulnar nerve in association with the ulnar styloid process, was defined. Finally, the distance between the ulnar styloid process and the branching of the radial-ulnar communicating branch (RUCB) and the first branch of DCBUN was measured. The distance between the origin of the DCBUN in relation to the ulnar styloid process ranges from 55 to 111 mm (mean 87 mm; STD 14 mm). The distance between the ulnar styloid process and the RUCB ranges from 1 to 54 mm (mean 19 mm; STD 12 mm). Finally, the distance between the ulnar styloid process and the lateral distal branch shows a range of -6 to 28 mm (mean 10 mm; STD 9 mm). In general, three dorsal digital nerves (medial, intermediate, and lateral branch), run at the dorsal ulnar aspect of the hand. The RUCB is often less abundant and shows a large amount of variation. No complete safe zone could be identified; the course of the DCBUN suggests a longitudinal incision for the 6R portal. In fact, a more dorsal incision also prevents damage to the main branches of the DCBUN.

Anatomical relationships and branching patterns of the dorsal cutaneous branch of the ulnar nerve

PURPOSE

To describe the variable branching patterns of the dorsal cutaneous branch of the ulnar nerve (DCBUN) relative to identifiable anatomical landmarks on the ulnar side of the wrist.

METHODS

We dissected the ulnar nerve in 28 unmatched fresh-frozen cadavers to identify the DCBUN and its branches from its origin to the level of the metacarpophalangeal joints. The number and location of branches of the DCBUN were recorded relative to the distal ulnar articular surface. Relationships to the subcutaneous border of the ulna, the pisotriquetral joint, and the extensor carpi ulnaris tendon were defined in the pronated wrist.

RESULTS

On average, 2 branches of the DCBUN were present at the level of the distal ulnar articular surface (range, 1-4). On average, 2.2 branches were present 2 cm distal to the ulnar articular surface (range, 1-4). At least 1 longitudinal branch crossed dorsal to the extensor carpi ulnaris tendon prior to its insertion at the base of the fifth metacarpal in 23 of 28 specimens (82%). In 27 of 28 specimens (96%), all longitudinal branches of the DCBUN coursed between the dorsal-volar midpoint of the subcutaneous border of the ulna and the pisotriquetral joint. In 20 of 28 specimens (71%), a transverse branch of the DCBUN to the distal radioulnar joint was present.

CONCLUSIONS

During exposure of the dorsal and ulnar areas of the wrist, identification and protection of just a single branch of the DCBUN are unlikely to ensure safe dissection because multiple branches normally are present. The 6U, 6R, and ulnar midcarpal arthroscopy portals may place these branches at risk. In the pronated forearm, the area between the DCBUN and the pisotriquetral joint contained all longitudinal branches of the DCBUN in 96% of specimens.

CLINICAL RELEVANCE

During surgery involving the dorsal and ulnar areas of the wrist, multiple longitudinal branches and a transverse branch of the DCBUN are normally present and must be respected.

Anatomical study of the dorsal cutaneous branch of the ulnar nerve using ultrasound

OBJECTIVES

To determine whether ultrasound allows precise assessment of the course and relations of the dorsal cutaneous branch of the ulnar nerve (DCBUN).

METHODS

This work, initially undertaken in cadavers, was followed by high-resolution ultrasound study in 20 healthy adult volunteers (40 nerves) by two musculoskeletal radiologists in consensus. Location and course of the DCBUN and its relations to adjacent anatomical structures were analysed.

RESULTS

The DCBUN was consistently identified along its entire course by ultrasound. Mean cross-sectional area of the nerve was 1.6 mm(2) (range 1.1-2.2). The level at which the DCBUN branches from the ulnar nerve was located a mean of 57 mm (range 40-80) proximal to the ulnar styloid process and 11 mm (range 7-15) radial to the medial border of the ulna. The DCBUN then crossed the medial border of the ulna a mean of 14 mm (range 6-25) proximal to the ulnar styloid process.

CONCLUSION

The DCBUN is clearly depicted by ultrasound. Precise mapping of its anatomical course could have significant clinical applications, such as preventing injury during surgery of the ulnar side of the wrist or helping in the diagnosis of chronic pain of the ulnar side of the hand.

KEY POINTS

• The dorsal cutaneous branch of the ulnar nerve (DCBUN) is often injured. • The DCBUN originates from the ulnar nerve in the distal third of the forearm. • It can be clearly depicted by ultrasound. • The level at which the DCBUN crosses the ulna is variable. • Precise mapping of its anatomical course could have significant clinical applications.

The anatomy of the dorsal cutaneous branch of the ulnar nerve

We investigated the anatomy of the dorsal cutaneous branch of the ulnar nerve in 32 upper limbs in cadavers. The dorsal cutaneous branch of the ulnar nerve originated on average 5.1 cm proximal to the ulnar styloid process and 1.9 cm palmar and radial to the subcutaneous border of the ulna. It crossed the subcutaneous border 0.2 cm proximal to the ulnar styloid process. In all cases it displaced further away in full pronation. We recommend cautious dissection when approaching within 2.5 cm of the ulnar styloid process. We also recommend making the initial incision in full pronation and just along the dorsal aspect of the subcutaneous border of the ulna.

High origin of dorsal branch of the ulnar nerve and variations in its branching pattern and distribution: a case report

Introduction

Ulnar nerve is a branch of the brachial plexus. In the front of the forearm, normally near the wrist joint, it gives a dorsal cutaneous branch which supplies the skin of the dorsum of the hand.

Case presentation

The present case reports a very rare finding, the dorsal branch of the ulnar nerve along with the main nerve trunk originated between the two heads of the flexor carpi ulnaris muscle, after descending along the medial border of the forearm extensor surface, on the dorsal aspect of the wrist it is divided into three branches, one medial and two lateral. The medial most division received a communicating branch from the superficial ramus of the ulnar nerve and continued as the medial proper digital nerve of the little finger. The lateral two divisions became cutaneous on the medial half of the dorsum of the hand along the medial three digits i.e. radial and ulnar side of little, ring and middle finger.

Conclusion

The site, extent of injury, variations and the delay in the treatment, significantly influences the outcome of ulnar nerve repair. Thus, an adequate knowledge of all possible variations in the ulnar nerve may be important for clinicians and may help to explain uncommon symptoms.

Anatomic relation of dorsal wrist arthroscopy portals and superficial nerves: a cadaveric study

PURPOSE

The aim of this cadaveric study was to assess and compare the distance of commonly used dorsal wrist portals to the dorsal ulnar and radial superficial nerves and their branches.

METHODS

Twenty embalmed cadaveric upper limbs were dissected, exposing the nerves and tendons, and wrist arthroscopy portal sites were marked with pins. The horizontal distance between the portals and closest nerve branch was measured with a digital caliper. Statistical analysis of the data was performed with SPSS software for Windows (version 11.5; SPSS, Chicago, IL) by use of Friedman tests and Wilcoxon signed rank tests.

RESULTS

The median distance of the nearest nerve branch to portal 1-2 was 1.82 mm; portal 3-4, 4.85 mm; portal 4-5, 16.13 mm; portal 6U, 2.47 mm; and midcarpal radial portal (MCP), 6.65 mm. The 4-5 portal was safer than the 1-2 portal (P < .0001), 3-4 portal (P = .015), MCP (P = .001), and 6U portal (P < .0001). The MCP was safer than the 1-2 portal (P = .01), 3-4 portal (P = .019), and 6U portal (P = .003).

CONCLUSIONS

The 4-5 portal is further away from a nerve branch than any other portal, followed by the MCP.

CLINICAL RELEVANCE

The results of this study may be of use in the planning of wrist arthroscopy.

Anatomic course of the superficial branch of the radial nerve in the wrist and its location in relation to wrist arthroscopy portals: a cadaveric study

PURPOSE

The aim of this study was to assess the course of the superficial branch of the radial nerve (SBRN) at the level of the wrist and its branches in relation to wrist arthroscopy portals.

METHODS

Dissections were performed on 11 hands from 6 cadavers in the section starting from the point where the SBRN begins to emerge and ending at the terminal branches of the dorsal hand. The distribution of the SBRN, the distance from the superficial branch to the dorsal portals used in wrist arthroscopy, and the distance from the superficial branch to the anatomic determinants (styloid process of the radius, Lister tubercle) were studied.

RESULTS

At the level of the wrist, the nerve bifurcated into 2 branches in 8 of 11 wrists (73%) and into 3 branches in 3 of 11 wrists (27%). The mean distance from the SBRN where it was first detected proximal to the Lister tubercle was 73 mm. The mean distance between the styloids was 52 mm; the distance between the Lister tubercle and styloid process of the radius was 23 mm. At the wrist level, the distance from the branch closest to the radial side to the Lister tubercle was 28 mm (L-D1), 21 mm (L-D2/3), and 7 mm (RS-D1). The distance of the closest nerve branch to the 3-4 portal was 9 mm. The distances of the other portals were 5 mm (1-2RMC-D1), 8 mm (1-2RMC-D2/3), 8 mm (1-2P-D1), and 9 mm (1-2P-D2/3).

CONCLUSIONS

The limited size of the area where portals can be positioned and the anatomic variations between individuals are major obstacles in developing a guideline for reducing the risk of SBRN injury in wrist arthroscopy.

CLINICAL RELEVANCE

Great care must be taken when using the 1-2 portal. We suggest making a skin-only incision for this portal and then using blunt dissection to help prevent injury to the SBRN.

Relocation of painful neuromas in Zone III of the hand and forearm

Painful nerves are a difficult and complex clinical problem. We describe the result of treatment by proximal relocation of 51 painful end neuromas and scarred nerves of the forearm in 33 patients. The relocated nerves included 29 superficial radial nerves, 16 lateral antebrachial cutaneous nerves, two medial cutaneous nerves and four posterior cutaneous nerves. These relocations achieved no, or only mild, pain in 100% of nerves at the original site and 94% of nerves at the relocation site. It also achieved no, or only mild, hypersensitivity in 96% of nerves at the original site and 98% of nerves at the relocation site. The technical difficulties encountered in this region, in particular on the radial aspect of the wrist, are discussed.

Visualisation of the pisotriquetral joint through standard portals for arthroscopy of the wrist

Disorders of the pisotriquetral joint are well recognised as the cause of pain on the ulnar side of the wrist. The joint is not usually examined during routine arthroscopy because it is assumed to have a separate joint cavity to the radiocarpal joint, although there is often a connection between the two.

We explored this connection during arthroscopy and in fresh-frozen cadaver wrists and found that in about half of the cases the pisotriquetral joint could be visualised through standard wrist portals. Four different types of connection were observed between the radiocarpal joint and the pisotriquetral joint. They ranged from a complete membrane separating the two, to no membrane at all, with various other types of connection in between.

We recommend that inspection of the pisotriquetral joint should be a part of the protocol for routine arthroscopy of the wrist.