Redefining the "Arcade of Struthers"

PURPOSE: To define the anatomy and presence of the arcade of Struthers, its anatomic variations, and potential sites of compression of the ulnar nerve. METHODS: In 11 fresh specimen dissections, the ulnar nerve was followed from the brachial plexus through the anterior compartment into the posterior compartment through the intermuscular septum and the arcade of Struthers on to the cubital tunnel. The arcade was identified, dissected, measured, and photographed. All anatomic variations were documented. RESULTS: The arcade of Struthers and intermuscular septum were present in all 11 specimens. The arcade was not merely an opening in the septum nor was it a short band as typically described: the arcade was better described as a fibrous canal with an average length of 5.7 cm. Its openings at either end were 3.9 and 9.6 cm proximal to the medial epicondyle. The structural components of the canal consisted of the fibrous tissue of the intermuscular septum, the internal brachial ligament, the deep fascia of the triceps, and the epimysium of the triceps muscle itself. The ulnar nerve was bound tightly within the entire canal in one case. In all specimens the nerve had an hourglass indentation at the proximal opening of the canal between the intermuscular septum and the internal brachial ligament. CONCLUSIONS: The arcade of Struthers consists of a fibrous canal. The tightest point is the proximal end of the canal at the intermuscular septum that represents the clinically relevant site of entrapment or compression of the ulnar nerve.     

肘管综合征的应用解剖学研究

目的 研究肘管综合征中尺神经的卡压因素,为临床手术提供解剖学依据.方法 采用解剖学方法对16具(32侧)成人尸体上肢标本进行解剖,观测造成尺神经卡压的Struthers弓形组织、内侧肌间隔和肘管,测量肘管内尺神经的面积、肘管的面积和肘管的长度,测量弓状韧带的长、宽和厚度.观测尺神经的营养血管及伴行长度,观测尺神经的尺侧腕屈肌肌支.结果 32侧上肢标本中12侧存在腱性Struthers弓形组织,10侧有肌性Struthers弓形组织,存在率为68.8%.尺神经在内上髁上方[(11.02±1.16)cm,小x±s.下同]处穿内侧肌间隔,尺神经肘管内面积与肘管面积之比为1:3.86,肘管长度为(1.96±0.18)cm.尺神经伴行血管有尺侧上副动脉和尺侧返动脉后支,尺神经在内上髁下方1cm左右发出尺侧腕屈肌肌支.结论 尺神经在肘管处最容易受压,手术治疗肘管综合征时向上的切口长度约为11.02cm,同时切除Struthers弓形组织和内侧肌间隔;尺神经前置手术时,注意保留与神经伴行的尺侧返动脉后支.     

The innervation of the medial humeral epicondyle: implications for medial epicondylar pain

The purpose of this study was identification of the innervation of the medial humeral epicondyle which has not been described before. In 20 patients, the medial intermuscular septum was evaluated histopathologically: the nerve was identified in 15 specimens without S-100 staining, and in the remaining 5 with S-100 staining. In six fresh cadavers, bilateral dissections identified the source of this nerve as the radial nerve in the axilla, coursing adjacent to the ulnar nerve in the upper arm, then moving laterally to be superficial to, or within, the medial intermuscular septum, until the nerve terminated in the periosteum of the medial humeral epicondyle, at the origin of the flexor-pronator muscle mass. In one specimen, a branch from the ulnar nerve in the axilla contributed to this nerve to the medial humeral epicondyle.     

The V-sling: a modified medial intermuscular septal sling for anterior transposition of the ulnar nerve

Subcutaneous anterior ulnar nerve transposition has been advocated by many surgeons as simple and effective. Techniques to maintain the nerve anterior to the medial epicondyle include subcutaneous pocket, subcutaneous-fascia tunnel, and fascial and fasciodermal sling. We describe a modified technique that uses the medial intermuscular septum as a sling to allow a more gentle transition of the ulnar nerve as it enters into the flexor carpi ulnaris muscle belly.     

Latrogenic snapping of the medial head of the triceps after ulnar nerve transposition

We postulate an iatrogenic cause for snapping of the medial head of the triceps. A patient whose ulnar nerve and triceps did not dislocate over the medial epicondyle preoperatively had snapping of a portion of the medial triceps after submuscular transposition of the ulnar nerve. We believe that release of the brachial fascia and excision of the medial intermuscular septum removed the restraint to anterior translation of the medial aspect of the triceps, permitting dislocation of a portion of the medial head of the triceps with elbow flexion in this case. Previous reports of snapping of the triceps resulting after ulnar nerve transposition occurred in patients whose ulnar nerve dislocated preoperatively; in these cases, the triceps was thought to have dislocated preoperatively (along with the ulnar nerve) but was not recognized. Careful intraoperative assessment of the triceps after ulnar nerve transposition should prevent medial triceps instability as a postoperative concern.     

An anatomic factor significant in transposition of the ulnar nerve

Anterior subcutaneous or submuscular transposition of the ulnar nerve are recommended treatments for the cubital tunnel syndrome. Commonly encountered findings at submuscular transposition are the presence of a distinct fibrous septum within the main flexor-pronator origin, which arises from the proximal ulna and medial epicondyle and requires release to accomplish the transposition. Cadaver dissections were conducted to study the intermuscular fascial anatomy of the flexor-pronator origin. The surgical findings were confirmed. The fascial structure is the common aponeurosis between the flexor digitorum superficialis of the ring finger and the humeral head of the flexor carpi ulnaris. Failure to release this structure from the proximal ulna caused kinking and tethering of the nerve when transposition was attempted.     

肘部尺神经卡压的定位诊断和电生理学研究

目的：对肘部尺神经卡压进行精确定位和电生理学研究。方法：对４６例临床诊断为肘部尺神经卡压患者，除进行常规ＥＭＧ、ＮＣＶ、和尺神经混合神经动作电位（ＭＮＡＰ）测定以外，还进行尺神经短段传导时间（ｓｈｏｒｔｓｅｇｍｅｎｔｃｏｎｄｕｃｔｉｏｎｔｉｍｅ，ＳＳＣＴ）测定。结果：４６例经ＳＳＣＴ测定，发现了卡压最常发生的４个部位，即肱骨内上髁后神经沟、肱尺弓、尺侧腕屈肌的出口和内侧肌间隔。结论：和传统的电生理测定方法相比较，ＳＳＣＴ技术可以更精确地对尺神经卡压进行定位诊断     

Predicting ulnar nerve location in pinning of supracondylar humerus fractures

Thirty-four consecutive patients with displaced supracondylar humerus fractures were treated with reduction and percutaneous pinning. The precise location of the ulnar nerve to the medial pin was determined by intraoperative nerve stimulation. In 22 of the 34 patients, the authors attempted to predict the location of the ulnar nerve by palpation and placing a mark on the skin. They also recorded the ability to feel the anatomic landmarks for pin fixation, including the medial epicondyle and ulnar nerve. The average distance from the medial pin to the predicted location was 9.3 mm, whereas the actual distance measured 7.6 mm, for a significant difference of 1.7 mm. Statistically, the authors could not accurately predict the location of the ulnar nerve prior to blind percutaneous crossed K-wire fixation of supracondylar humerus fractures. However, clinically they were fairly close in their prediction and documented safe insertion and distance from the nerve. Intraoperative nerve stimulation may assist in localizing the nerve prior to placement of the medial pin. Stimulation of the pin itself following insertion is another technique to ensure safe pin placement and decrease the risk of injury.     

Quantitative Anatomy of Medial Femoral Perforators of the Distal Thigh

The purpose of the study was to quantitatively examine the anatomical organization of medial femoral perforators. Mini-incision approaches to total knee arthroplasty are being used more often; however, no studies have examined the quantitative anatomy of perforating vessels into the distal intermuscular septum. Fourteen embalmed cadaveric knees were dissected to identify where vascular perforators pierced the medial intermuscular septum. Quantitative measurements were made from the perforators to the medial epicondyle of the femur. The mean measurements from the medial epicondyle to each of the vascular perforators were 7.1, 10.5, and 13.5 cm. The closest perforator to the medial epicondyle was found at a distance of 5.5 cm. During mini-incision approaches to the knee, vascular perforators are at potential risk of injury when dissection proceeds 5 cm proximal to the medial epicondyle.     

Radial and axillary nerves. Anatomic considerations for humeral fixation

Because the axillary and radial nerves can be injured during operative exposure and fixation of the humerus, accurate delineation of their location is vital to avoid complications. The authors investigated the relationship of the radial and axillary nerves for radiographically and surgically identifiable bony landmarks. Fifty fresh human cadaveric upper extremities were dissected to identify the nerves as they crossed the lateral intermuscular septum and the humeral surgical neck, respectively. Longitudinal distances between the nerves and the superior aspect of the humeral head, the surgical neck, the superior extent of the olecranon fossa, and the distal aspect of the trochlea were measured with calipers. The average distance from the axillary nerve to the proximal humerus was 6.1 +/- 0.7 cm (range, 4.5-6.9 cm) and 1.7 +/- 0.8 cm (range, 0.7-4.0 cm) from the surgical neck. The radial nerve traversed the lateral intermuscular septum 17 +/- 2.3 cm (range, 13-22 cm) from the proximal humerus, 12 +/- 2.3 cm (range, 7.4-16.6 cm) from the olecranon fossa, and 16 +/- 0.4 cm (range, 9.0-20.5 cm) from the distal humerus, representing the approximate midpoint of the bone. Anteroposterior locking screws placed into the proximal humerus endanger the axillary nerve because it lies directly over the posterior cortex as little as 0.7 cm from the surgical neck. As the radial nerve crosses the lateral intermuscular septum more proximal than generally was thought, it is at risk during implant insertion in the distal half of the humerus. Using measurements calculated from preoperative and intraoperative imaging, the approximate position of the nerve could be determined to better plan fixation method and implant location.     

Low incidence of ulnar nerve injury with crossed pin placement for pediatric supracondylar humerus fractures using a mini-open technique

OBJECTIVES: Several recent studies have suggested that medial pinning in pediatric supracondylar humerus fractures leads to increased rates of ulnar nerve injury. The purpose of this study was to determine the risk of iatrogenic ulnar nerve injury in a consecutive series of supracondylar fractures treated using a standardized technique of crossed pin placement. DESIGN: Single cohort retrospective. SETTING: Metropolitan university tertiary care center. PATIENTS AND PARTICIPANTS: Seventy-one consecutive children with Gartland type II or type III supracondylar humerus were treated surgically by 2 pediatric orthopaedic surgeons at 1 institution between 1995 and 2000 using a medial mini-open and cross-pinning technique. Sixty-five patients were available for follow-up (92%). INTERVENTION: Patients were treated with a combination of medial and lateral pins using a mini-incision technique. MAIN OUTCOME MEASUREMENTS: Outcomes analyzed included ulnar nerve injury and clinical and radiographic evidence of healing. RESULTS: The study group consisted of 65 patients, of whom 29 (45%) presented with Gartland type III fractures, and the remaining 36 (55%) presented with a type II fracture. There were no ulnar nerve motor injuries. One patient was noted to have transient sensory changes in the ulnar nerve distribution postoperatively, which resolved by the 1-week follow-up visit. All patients were noted to have normal ulnar motor and sensory nerve function at final follow-up (average 4.5 months). No cases of nonunion, malunion, or infection were identified during the follow-up period. CONCLUSIONS: The rate of iatrogenic ulnar nerve injury with this specific technique of crossed pin placement for extension-type supracondylar humerus fractures was extremely low in this series. A single case of transient ulnar sensory neuropraxia occurred. Our series demonstrates that crossed pin fixation can be performed safely and reliably and is an appropriate treatment option for unstable supracondylar humerus fractures.     

Subcutaneous anterior transposition of the ulnar nerve for failed decompression of cubital tunnel syndrome

The current literature universally suggests that submuscular anterior transposition is the standard operative treatment for recurrent cubital tunnel syndrome. Regardless of the type of initial failed procedure, including submuscular transposition, 20 patients underwent anterior subcutaneous transposition of the ulnar nerve. All patients were monitored for a minimum of 2 years after surgery. The most common sites of compression were the medial intermuscular septum and the flexor-pronator aponeurosis. Fifteen patients had a good or excellent outcome; 5 patients had a fair or poor outcome. Relief of pain and paresthesias were the most consistent favorable results. Fair and poor outcomes were significantly associated with increasing age and the number of previous surgeries. Subcutaneous anterior transposition of the ulnar nerve proved to be an effective treatment for recurrent cubital tunnel syndrome.     

The failed ulnar nerve transposition. Etiology and treatment

Various procedures have been recommended for the treatment of cubital tunnel syndrome. Simple decompression in situ, medial epicondylectomy, subcutaneous transposition, intramuscular transposition, and submuscular transposition all have their advocates. The results of the surgical treatment for cubital tunnel syndrome are related to the severity of the compressive neuropathy at the time of diagnosis and to the adequate decompression of the nerve at all sites of potential compression at the time of surgical treatment. Fourteen patients who had previously undergone surgical treatment for cubital tunnel syndrome were evaluated because of persistent pain, paresthesia, numbness, and motor weakness. All patients had documented persistent compression of the ulnar nerve on clinical and electromyographic evaluation. The indication for repeat surgical exploration in all patients was unremitting pain despite nonoperative treatment. All patients had been treated by neurolysis and submuscular transposition of the ulnar nerve as described by Learmonth. The causes of continued pain after initial surgery included retention of the medial intermuscular septum, dense perineural fibrosis of the nerve after intramuscular and subcutaneous transposition, adhesions of the nerve to the medial epicondylectomy site, and recurrent subluxation of the nerve over the medial epicondyle after subcutaneous transposition. Revision surgery was found to be highly successful for relief of pain and paresthesias; however, the recovery of motor function and return of sensibility were variable and unpredictable.     

Effect of submuscular versus intramuscular placement of ulnar nerve: experimental model in the primate

A primate model was developed to study the effect of submuscular versus intramuscular placement upon the development of ulnar nerve fibrosis. No significant adherence was found in either location between the ulnar nerve and the flexor-pronator muscle mass. There was no significant difference in the mean nerve fibre diameter or in the percent neural tissue between the ulnar nerves in the two different locations. It is suggested that it is the interaction of the transposed ulnar nerve with other fibrous anatomical structures proximal to, across, and distal to the elbow that causes failure in ulnar nerve transposition procedures, rather than an adverse reaction between the incised flexor-pronator muscle mass and the ulnar nerve.     

Recurrent cubital tunnel syndrome. Etiology and treatment.

Controversy surrounds the treatment of recurrent cubital tunnel syndrome after previous surgery. Irrespective of the surgical technique, namely pure decompression in the ulnar groove and the cubital tunnel distal of the medial epicondyle, and the different methods of volar transposition (subcutaneous, intramuscular, and submuscular), the results of surgical therapy of cubital tunnel syndrome are often not favorable, especially in cases of long-standing symptoms and severe deficits. Twenty-two patients who had previously undergone surgical treatment for ulnar nerve entrapment at the elbow were evaluated because of persistent or recurrent pain, paresthesia, numbness, and motor weakness. Ten patients had undergone a nerve transposition, 5 patients underwent a simple decompression of the ulnar nerve, and 7 patients experienced two previous operations with different surgical techniques. Two patients underwent surgery at our hospital, whereas 20 patients underwent their primary surgery at other institutions. Various surgical techniques were used during the subsequent surgery, such as external neurolysis, subcutaneous anterior transposition, and subsequent transfer of the nerve back into the sulcus. The causes of continued or recurrent symptoms after initial surgery included dense perineural fibrosis of the nerve after subcutaneous transposition, adhesions of the nerve to the medial epicondyle and retention of the medial intermuscular septum. The average follow-up after the last procedure was 7 months (2 - 20 months). All 7 patients with subsequent transfer of the ulnar nerve back into the sulcus became pain-free, whereas only 11 of 15 patients who had external neurolysis or subcutaneous transposition became free of pain or experienced reduced pain. The recovery of motor function and return of sensibility were variable and unpredictable. In summary, reoperation after primary surgery of cubital tunnel syndrome gave satisfactory results in 18 of 22 cases. Subsequent transfer of the ulnar nerve back into the sulcus promises to be useful in cases in which subcutaneous transposition had not been successful.     

The dorsal branch of the ulnar nerve: an anatomic study

The dorsal branch of the ulnar nerve was dissected in 24 cadavers. The nerve arose from the medial aspect of the ulnar nerve at an average distance of 6.4 centimeters from the distal aspect of the head of the ulna and 8.3 centimeters from the proximal border of the pisiform. Its mean diameter at origin was 2.4 millimeters. The nerve passed dorsal to the flexor carpi ulnaris and pierced the deep fascia. It became subcutaneous on the medial aspect of the forearm at a mean distance of 5.0 centimeters from the proximal edge of the pisiform. The nerve gave an average of five branches with diameters between 0.7 and 2.2 millimeters. A better understanding of the anatomy of this nerve may help prevent nerve injury during surgical procedures, and can help in locating the nerve for repair of lacerations or administration of local anesthetics for regional nerve blocks.     

程序化操作在尺神经皮下前置术中的应用

目的 探讨程序化手术操作在尺神经皮下前置术中的应用效果.方法 我院自2017年1月至2019年12月采用尺神经松解皮下前置术治疗肘管综合征病人34例.所有病人均采用程序化操作处理前臂内侧皮神经、Struthers弓、内侧肌间隔、Osborne韧带、尺侧腕屈肌两头、指浅屈肌筋膜、尺神经伴行血管、尺侧屈腕肌肌支及关节支、屈...     

Open medial placement of Kirschner wires for supracondylar humeral fractures in children

PURPOSE: To assess the efficacy of our protocol for treatment of displaced Gartland type-3 supracondylar fractures of the humerus in children. METHODS: Records of 43 children with displaced Gartland type-3 supracondylar fractures of the humerus admitted from October 1997 to October 2003 were reviewed. Patients were treated within 12 hours of admission by closed reduction (n=33) or open reduction (n=10). Crossed medial and lateral Kirschner wires through a medial approach were used in all patients. A 3-cm incision was made medially to identify the correct entry point of the medial wire, and thus prevent ulnar nerve injury. The incision was extendable for open reduction if closed reduction was unsuccessful. RESULTS: The mean age of the 43 patients was 7.2 years (range, 2-14 years). The mean follow-up period was 48 months (range, 12-84 months). 83% of the fractures occurred in boys. All fractures were closed, extension type, with 28 (65.1%) involved the right elbow. No patient had iatrogenic ulnar nerve injury. All patients showed satisfactory results according to Flynn criteria. CONCLUSION: If closed reduction is unsuccessful, open reduction and open medial placement of crossed Kirschner wires can provide reliable results. The small medial incision provides a viewing point for entry of the wire and prevents iatrogenic injury of the ulnar nerve. It is cosmetically more acceptable and can be extended to facilitate open reduction.     

前臂内侧皮神经后支与肘管综合征手术切口的解剖关系

目的 观察肘部前臂内侧皮神经(medial antebrachial cutaneous nerve,MACN)后支的解剖特征,探讨在肘管综合征松解手术中防止其医源性损伤的方法.方法 解剖10具(20侧)成人上肢标本,并对12例肘管综合征手术患者,在肱骨内上髁远、近各8 cm范围内,观察NACN后支的数目、横跨角度并测定其与手术切口(内上髁前1 cm)的交汇部位.结果 32侧肢体共记录到62支MACN 后支,平均每侧肢体为1.9支.其中1支者8侧(25.0%,均位于内上髁远侧),2支者19侧(59.4%),3支者4侧(12.5%),4支者1侧(3.1%).位于内上髁下方者37支(59.7%),内上髁上方者25支(40.3%).这些后支与切口线的交角均大于45°,即皮神经是横向跨过切口线的.所有标本(100%)均至少有1支后支从内上髁远侧跨过切口线,其距内上髁的平均距离为[(2.9±2.3)cm,x-±s,下同];在68.8%的标本中至少有1支后支从内上髁近侧跨过切口线,其距内上髁的平均距离为(2.1±1.8)cm.结论 MACN后支至少有1支横跨肘管综合征的手术切口线,了解其位置关系并在皮下组织中仔细解剖分出保护,有助于避免误伤.     

Ultrasound‐Assisted Precise In Situ Decompression for Cubital Tunnel Syndrome

ObjectiveTo explore the effect of locating the ulnar nerve compression sites and guiding the small incision so as to decompress the ulnar nerve in situ on the elbow by high‐frequency ultrasound before operation.MethodsA retrospective analysis was conducted on 56 patients who underwent ultrasound‐assisted in situ decompression for cubital tunnel syndrome from May 2018 to August 2019. The patients'' average age was 51.13 ± 7.35 years, mean duration of symptoms was 6.51 ± 1.96 months, and mean postoperative follow‐up was 6.07 ± 0.82 months. Nine patients had Dellon''s stage mild, 39 had stage moderate, and eight had stage severe. Ultrasound and electromyography were completed in all patients before operation. The presence of ulnar nerve compressive lesion, the specific location, and the reason and extent of compression were determined by ultrasound. A small incision in situ surgery was given to decompress the ulnar nerve according to the pre‐defined compressive sites.ResultsAll patients underwent in situ decompression. The compression sites around the elbow were as follows: two in the arcade of Struthers, one in the medial intermuscular septum, four in the anconeus epitrochlearis muscle, five beside the cyst of the proximal flexor carpi ulnaris (FCU), and the remaining 44 cases were all from the compression between Osborne''s ligament to the two heads of the FCU. The compression localizations diagnosed by ultrasound were confirmed by operations. Preoperative ultrasound confirmed no ulnar nerve subluxation in all cases. The postoperative outcomes were satisfactory. There was no recurrence or aggravation of symptoms in this group of patients according to the modified Bishop scoring system; results showed that 43 cases were excellent, 10 were good, and three were fair.ConclusionsHigh‐frequency ultrasound can accurately and comprehensively evaluate the ulnar nerve compression and the surrounding tissues, thus providing significant guidance for the precise minimally invasive treatment of ulnar nerve compression.