Endoscopic Excision of Supracondylar Humeral Spur for Decompression of the Median Nerve and Brachial Artery

Abstract

The humeral supracondylar process and Struthers ligament comprise a relatively rare but well-known anatomic variant. They are usually asymptomatic but may produce clinical symptoms related to compression of the median nerve or brachial artery below the ligament. Previously, surgery has been performed with an open ligament release and supracondylar process excision. This article reports on the use of endoscopic findings and the method of ligament release and process excision. Endoscopy is a minimally invasive technique that provides excellent visualization and enables the surgeon to perform dissection with magnification and precision. It allows the surgeon to introduce open surgical techniques into the depths of the wound in a controlled manner. Because of the dead space created, there is a risk of hematoma formation. Many of the concepts used in open surgery are now being used for endoscopic surgery, and vice versa. The barriers and differences among endoscopic, arthroscopic, and open procedures are being broken down. We report another endoscopic technique, which is part of the ongoing evolution of musculoskeletal surgery.

The supracondylar spur or process was noted by Tiedmann¹ in 1818 and described further by Struthers in 1848² as a bony projection on the anteromedial humerus approximately 5 cm proximal to the medial epicondyle. It occurs in 0.4% to 2.7% of the worldwide population.³

The supracondylar process is a normal anatomic variant that represents the embryologic vestigial remnant of the latissimo-condyloideus, a muscle that is still present in climbing animals, many reptiles, and cats. In humans this muscle is usually represented as a fibrous band between the tendons of the latissimus dorsi and coracobrachialis.³ The bone formation starts from a broad base, about 7 cm proximal to the medial epicondyle, and is directed distally, its beak-like apex giving rise to the ligament of Struthers that inserts on the medial epicondyle.

The constellation of symptoms associated with entrapment of the brachial artery and median nerve beneath the ligament of Struthers is known as “supracondylar process syndrome.” Symptoms include paresthesia, weakness, and muscle wasting related to the median nerve. Vascular symptoms related to the brachial artery include ischemic pain and claudication in the forearm. The symptoms are typically exacerbated by extension and pronation of the forearm, as well as repetitive activities.⁴ However, most supracondylar processes are asymptomatic and are incidentally identified on humeral radiographs. Therefore correlation of the radiologic and clinical findings is important. The differential diagnosis includes an osteochondroma and myositis ossificans of the humerus, which have characteristic radiographic appearances that differ from a supracondylar spur. On clinical assessment, it is important to rule out other sources of nerve compression both proximal and distal to the elbow. The spur is usually palpable, and a positive Tinel sign may be elicited just distal to the prominence. Symptoms may be reproduced by provocative maneuvers.

Plain radiographs will show the supracondylar process (Fig 1A), and a computed tomography arteriogram is valuable to understand the relation of the brachial artery and the supracondylar process (Fig 1B). In the presented case the nerve conduction studies were equivocal and an ultrasound scan confirmed the median nerve to be beneath the process. Conservative treatment with splinting, activity modification, and physiotherapy was unsuccessful; hence surgical decompression was performed.

Fig 1.

(A) Anteroposterior radiograph of an elbow showing a supracondylar spur pointing downward, present at the medial aspect of the distal humerus. (B) Computed tomography arteriogram of the upper limb showing the brachial artery passing and kinking under the supracondylar spur. © 2016 Gregory Bain. All Rights Reserved.

In the presence of persistent symptoms failing nonoperative modalities or in the presence of muscle wasting or weakness, surgical decompression should be considered. This usually involves open surgical excision of the supracondylar process with the overlying periosteum⁵ and resection of the associated ligament of Struthers. We describe a minimally invasive endoscopic technique for excision of the supracondylar process and decompression of the median nerve and brachial artery, adapted from our experience performing endoscopic surgery around the elbow.6, 7, 8, 9

Surgical Technique

Setup

Under general anesthesia, a pneumatic tourniquet is applied and the patient is positioned supine with the operative arm in 90° of shoulder abduction on a standard hand table (Video 1). The upper extremity is draped to allow full mobility of the arm. The surgeon flexes the elbow and externally rotates the shoulder to optimize the orientation of the operative field. A sterile roll comprising a sheet may be placed under the elbow to elevate the arm.

Exposure

A 3-cm skin incision is made just distal to the palpable supracondylar process over the medial supracondylar ridge. An endoscopic working space is created between the forearm fascia and the subcutaneous tissue for approximately 5 cm distally and proximally. This is created initially with blunt dissection, until the deep fascia is identified, and is then expanded with the assistance of retractors and tunneling forceps. The deep fascia is incised, and a hooded 4.0-mm 30° arthroscope (Karl Storz, Tuttlingen, Germany) is inserted into the working space. The median nerve and the brachial artery are identified and are traced proximally, which directs the surgeon to the supracondylar spur and the ligament of Struthers. The ligament of Struthers is a taut thick fibrous band that spans from the process, over the brachial artery and median nerve, to the medial epicondyle (Fig 2). The humeral head of the pronator teres is attached to the medial aspect of the ligament.

Fig 2.

Intraoperative photograph showing the median nerve under the supracondylar spur. The inset shows the relation of the Struthers ligament (lig) with the median nerve (n), brachial artery (a), and ulnar nerve. © 2016 Gregory Bain. All Rights Reserved.

Endoscopic Decompression

The exact orientations of the ligament, process, and neurovascular structures are identified. The neurovascular structures are decompressed by incising the Struthers ligament with scissors (Fig 3A). The ligament and process are then excised with a Kerrison rongeur to minimize the chance of the ligament re-forming (Fig 3B). Under endoscopic vision, the neurovascular structures are released proximally and distally, including the arch of the flexor digitorum superficialis. The tourniquet is released, and hemostasis is achieved under endoscopic vision.

Fig 3.

Intraoperative photographs showing excision of Struthers ligament with scissors (A) and excision of supracondylar spur with Kerrison rongeur (B). © 2016 Gregory Bain. All Rights Reserved.

Postoperative Care

After surgery, the patient is given a sling and is advised that he or she can remove the sling and mobilize the arm as comfort allows. The patient can be discharged the same day but should be assessed before discharge to ensure that there is no excessive bleeding or hematoma. The patient then undergoes a review in the clinic 1 week later to ensure that he or she is making a satisfactory recovery and that the neurologic symptoms are recovering.

Tips and Tricks

Table 1 presents tips and tricks on performing our technique.

Table 1.

Tips and Tricks

Because of the temperature difference between the soft-tissue space and the lens of the arthroscope, condensation on the arthroscope lens is not uncommon. Wiping the lens with an alcohol swab or immersing the arthroscope tip in warm saline solution before starting the procedure can minimize condensation.

During the procedure, the view can become compromised with blood, debris, or condensation on the arthroscope lens. The lens can be dabbed on the surrounding fat, which cleans the arthroscope and minimizes the recurrence of condensation. If this is unsuccessful, the arthroscope can be removed and lens wiped with an alcohol wipe or glycerin.

In case of blood obscuring the field of view, washing with 5 mL of saline solution through the side valve of the arthroscope and then aspirating with suction or a chondrotome are helpful.

The hooded arthroscope works like a tent post, elevating the subcutaneous tissues, to maintain the endoscopic space.

Discussion

Endoscopic assessment provides an amazing view of the soft tissues around the elbow. The advantages include the following: Such assessment provides a magnified view of the anatomy so that the specific details of each structure can be appreciated and the release can be performed with precision. It provides a new insight into the anatomy. Hoffmann and Lubahn⁹ identified that the deep surface of the flexor carpi ulnaris muscle had a thickened fascial layer. In our case the detail of the vascular anatomy provided new insight into the venous system of the region.

This technique provides another extension of the new concepts of endoscopic surgery around the elbow. Hoffmann and Lubahn¹⁰ initially described using a hooded arthroscope or speculum to visualize the ulnar nerve and then divide the cubital retinaculum with scissors to release the ulnar nerve. Bipolar cautery was used to obtain hemostasis. In our technique the Struthers ligament is divided with scissors, and the Kerrison rongeur is used to resect the supracondylar spur. However, there have been other endoscopic advances in recent times that included the following:

• •Anterior interosseous nerve¹¹—using scissors to release the pronator teres entrapment of the anterior interosseous nerve.
• •Olecranon bursa⁹—creating a second working portal to introduce instruments to resect the olecranon bursa, with instruments such as a motorized shaver and pituitary rongeur.
• •Ulnar nerve transposition⁷—introducing a second port to retract the ulnar nerve to allow an artery clip to safely be placed onto the free edge of the medial intermuscular septum so that it can be resected and then introducing a nylon tape through a third portal to control the position of the ulnar nerve so that it can be transposed.
• •Endoscopic-assisted biceps tendon repair⁸—using a Wissinger rod to create a second portal and performing an endoscopic-assisted distal biceps tendon repair, which includes debriding the tendon footprint with a motorized shaver, drilling the radius, and advancing sutures through the radius.

The endoscopic procedures are minimally invasive techniques that are performed with magnification, which allows dissection to be performed with precision. In our experience, these tend to use less soft-tissue dissection, to cause less postoperative bruising, and to allow a faster rehabilitation. Many of the concepts used in open surgery are now being used for endoscopic surgery, and vice versa. The barriers among endoscopic, arthroscopic, and open procedures are being broken down. We report another advanced endoscopic technique, which is part of the evolution of musculoskeletal surgery.

Supplementary Data

Video 1

Technique for endoscopic exposure with retractors, tunneling forceps, and hooded arthroscope. Magnified 30° endoscopy provides a crystal-clear view of the soft tissues, vessels, and tissue planes, which allows the soft-tissue dissection to be performed with precision and usually with minimal bleeding. The median nerve and brachial artery are identified and lead the surgeon to the Struthers ligament and the supracondylar process. The exact neurovascular anatomy is confirmed; the ligament is then divided with scissors, and the process is resected with a Kerrison rongeur. Once the median nerve and brachial artery have been decompressed, the arthroscope is advanced proximally and distally to ensure that no other sites of compression exist. With the arthroscope still in the forearm, the tourniquet is released and hemostasis obtained.

© 2016 Gregory Bain. All Rights Reserved.