42 ORTHOPEDICS | Healio.com/Orthopedics n sports medicine update T he first report of compres- sion of the suprascapular nerve was by Schilf in 1952. 1 Since then, the understanding of this neuropathy and its pos- sible etiologies has improved substantially. Those thought to be at highest risk include athletes engaging in repetitive overhead activity, especially tennis and volleyball play- ers. 2-6 Nerve compression has been attributed to a stenotic notch, an ossified transverse scapular ligament, soft tissue or bone tumors, cysts second- ary to capsulolabral pathol- ogy, and fractures. Several authors have described su- prascapular nerve palsy in patients with a massive rota- tor cuff tear associated with fatty infiltration or muscle at- rophy. 7-10 At times, anatomic variants of the neurovascular structures may lead to com- pression of the suprascapular nerve; however, this has been sparsely described in previous literature. 8,11 The current ar- ticle describes one such com- pressive etiology and reviews the literature on vascular anomalies at the suprascapu- lar and spinoglenoid notches. CASE REPORT A 52-year-old man who had undergone 2 previous failed shoulder surgeries for presumed rotator cuff tear pre- sented with pain and progres- sive weakness of forward ele- vation, abduction, and external rotation of his left shoulder. No rotator cuff tear was seen during the previous surgeries, and a subacromial decompres- sion with acromioplasty was performed. Although he ini- tially reported being unable to play basketball and participate in weight lifting, his symp- toms progressed to limiting his ability to work. Electromyography and nerve conduction studies dem- onstrated mild denervation in the infraspinatus and supraspi- natus muscles. Physical thera- py failed to improve his weak- ness or discomfort, which he localized to the posterior scapular region, and some atrophic changes were seen on inspection of the periscapular muscles. Magnetic resonance arthography demonstrated edema and moderate atrophy within the supraspinatus and infraspinatus muscles consis- tent with acute-on-chronic de- nervation, but no evidence of a tear. No lesion was identified within the suprascapular notch (Figure 1). A second electromyogram and nerve conduction study obtained 12 weeks after the first studies showed dysfunc- tion of the suprascapular nerve at or proximal to the suprascapular notch, with the supraspinatus and infraspina- tus demonstrating evidence of both acute and ongoing denervation and chronic changes. The decision was made to proceed with supra- scapular nerve decompression at the suprascapular notch. With the patient in the beach-chair position, a thor- ough diagnostic arthroscopy was performed. Evidence existed of a previous ac- romioplasty and some scar- ring of bursal tissues, but no Abstract: The vascular anatomy at the spinoglenoid and su- prascapular notches appears to be more variable than previ- ously thought. In patients presenting with signs of suprascap- ular nerve compression, vascular causes must be considered. Especially when considering percutaneous or arthroscopic treatment, awareness of these entities may help to guide treat- ment decisions, aid in identification of the anatomy, and pre- vent unwanted vascular insult. The authors are from the Highland Clinic (CH). Shreveport, Louisiana; and the Methodist Center for Sports Medicine (PCM), The Methodist Hospital, Houston, Texas. The authors have no relevant financial relationships to disclose. Correspondence should be addressed to: Carlton Houtz, MD, Highland Clinic, 1455 E Bert Kouns Industrial Loop, Ste 210, Shreveport, LA 71105 ([email protected]). doi: 10.3928/01477447-20121217-07 Suprascapular Vascular Anomalies as a Cause of Suprascapular Nerve Compression Carlton Houtz, MD; Patrick C. McCulloch, MD
Transcript
42 ORTHOPEDICS | Healio.com/Orthopedics
n sports medicine update
The first report of compres-sion of the suprascapular
nerve was by Schilf in 1952.1 Since then, the understanding of this neuropathy and its pos-sible etiologies has improved substantially. Those thought to be at highest risk include athletes engaging in repetitive overhead activity, especially tennis and volleyball play-ers.2-6 Nerve compression has been attributed to a stenotic notch, an ossified transverse scapular ligament, soft tissue
or bone tumors, cysts second-ary to capsulolabral pathol-ogy, and fractures. Several authors have described su-prascapular nerve palsy in patients with a massive rota-tor cuff tear associated with fatty infiltration or muscle at-rophy.7-10 At times, anatomic variants of the neurovascular structures may lead to com-pression of the suprascapular nerve; however, this has been sparsely described in previous literature.8,11 The current ar-
ticle describes one such com-pressive etiology and reviews the literature on vascular anomalies at the suprascapu-lar and spinoglenoid notches.
Case RepoRtA 52-year-old man who
had undergone 2 previous failed shoulder surgeries for presumed rotator cuff tear pre-sented with pain and progres-sive weakness of forward ele-vation, abduction, and external rotation of his left shoulder. No rotator cuff tear was seen during the previous surgeries, and a subacromial decompres-sion with acromioplasty was performed. Although he ini-tially reported being unable to play basketball and participate in weight lifting, his symp-toms progressed to limiting his ability to work.
Electromyography and nerve conduction studies dem-onstrated mild denervation in the infraspinatus and supraspi-natus muscles. Physical thera-py failed to improve his weak-ness or discomfort, which he localized to the posterior scapular region, and some
atrophic changes were seen on inspection of the periscapular muscles. Magnetic resonance arthography demonstrated edema and moderate atrophy within the supraspinatus and infraspinatus muscles consis-tent with acute-on-chronic de-nervation, but no evidence of a tear. No lesion was identified within the suprascapular notch (Figure 1).
A second electromyogram and nerve conduction study obtained 12 weeks after the first studies showed dysfunc-tion of the suprascapular nerve at or proximal to the suprascapular notch, with the supraspinatus and infraspina-tus demonstrating evidence of both acute and ongoing denervation and chronic changes. The decision was made to proceed with supra-scapular nerve decompression at the suprascapular notch.
With the patient in the beach-chair position, a thor-ough diagnostic arthroscopy was performed. Evidence existed of a previous ac-romioplasty and some scar-ring of bursal tissues, but no
Abstract: The vascular anatomy at the spinoglenoid and su-prascapular notches appears to be more variable than previ-ously thought. In patients presenting with signs of suprascap-ular nerve compression, vascular causes must be considered. Especially when considering percutaneous or arthroscopic treatment, awareness of these entities may help to guide treat-ment decisions, aid in identification of the anatomy, and pre-vent unwanted vascular insult.
The authors are from the Highland Clinic (CH). Shreveport, Louisiana; and the Methodist Center for Sports Medicine (PCM), The Methodist Hospital, Houston, Texas.
The authors have no relevant financial relationships to disclose.Correspondence should be addressed to: Carlton Houtz, MD, Highland
Clinic, 1455 E Bert Kouns Industrial Loop, Ste 210, Shreveport, LA 71105 ([email protected]).
doi: 10.3928/01477447-20121217-07
Suprascapular Vascular Anomalies as a Cause of Suprascapular Nerve Compression Carlton Houtz, MD; Patrick C. McCulloch, MD
JANUARY 2013 | Volume 36 • Number 1 43
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evidence existed of a rota-tor cuff tear. A lateral view-ing portal was established in the subacromial space. The coracoacromial ligament was identified and followed down to the base of the coracoid. A straight medial Nevasier portal was made under direct vision with a spinal needle, similar to the technique de-scribed by Lafosse et al.12
Just medial to the conoid ligament, the transverse scap-ular ligament was identified, and both the suprascapular ar-tery and nerve were identified passing beneath the ligament. Two smaller branches of the suprascapular artery originat-ing proximal to the ligament were traveling with the main trunk of the suprascapular artery under the ligament. These 3 arterial vessels were compressing the nerve within the notch (Figure 2).
A narrow arthroscopic bit-er was then used to divide and resect the transverse scapular ligament. However, the artery was still tethered medially by the smallest of the branch-es (Figure 3). This branch was cauterized using an ar-
throscopic cautery device and then divided. The artery then lifted superiorly off the nerve, leaving the nerve freely mo-bile in the notch (Figure 4).
Six months postopera-tively, the patient had no pain, full range of motion, and 5/5 rotator cuff strength. Electromyography demon-strated significant interval improvement with no signs of active denervation, normal recruitment, and a full 100% interference pattern. At 1-year follow-up, the patient re-mained symptom free and had returned to manual labor.
DisCussionThe suprascapular nerve
has contributions from C4-C6 via the upper trunk of the brachial plexus. It is a mixed nerve with sensory branches to the acromioclavicular joint, coracoacromial ligament, and glenohumeral joint capsule and has 2 motor branches that innervate the supraspinatus muscle. The nerve descends through the posterior triangle of the neck before passing beneath the superior trans-verse scapular ligament in the suprascapular notch. The superior transverse scapular
ligament is approximately 1.3 cm posterior to the poste-rior aspect of the clavicle, 2.9 cm medial to the acromiocla-vicular joint, and 4 cm deep to the skin surface.13 The nerve then courses approximately 3 cm medial to the supragle-noid tubercle and 1.8 cm me-dial from the posterior glenoid rim at the base of the scapular spine.14 The distance from the palpable posterolateral corner of the acromion to the base of the scapular spine is approxi-mately 4.5 cm.15 It then trav-els beneath the inferior trans-verse scapular ligament in
Figure 1: Sagittal magnetic resonance imaging anatomy sequence showing mild decreased muscle bulk and early fatty change of the supra- and infraspinatus consistent with acute-on-chronic changes (A). Fat-suppressed, fluid-sensitive sequence showing significant interstitial edema of muscles consistent with acute denervation changes (B).
1A 1B
Figure 2: Arthroscopic image of the suprascapular artery passing under the transverse scapular ligament.
2Figure 3: Arthroscopic image after release of the ligament showing the pulsatile artery in the notch, tethered by a small medial branch.
3Figure 4: Arthroscopic image of ligation of the smallest branch allowing the artery to lift superi-orly out of the notch, exposing the nerve.
4
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the spinoglenoid notch before innervating the infraspinatus muscle via 2 or more motor branches.14,15
Suprascapular nerve inju-ries are common in repetitive overhead athletes, such as ten-nis, volleyball, and throwing athletes, for 2 main reasons. First, this nerve is vulnerable to stretch injuries because it takes a circuitous course and can become tethered in several places, such as the suprascapu-lar and spinoglenoid notches. Second, those sports are often associated with labral pathol-ogy, which can lead to nerve compression from paralabral cysts. The resultant loss of rota-tor cuff strength can cause de-creased performance, and the pain can lead to the inability to participate.
Suprascapular nerve com-pression causing posterior shoulder pain can be attributed to previous cadaveric findings of sensory branches to the gle-nohumeral joint, acromiocla-vicular joint, coracoacromial ligament, and skin.14,15 Some evidence indicates that the nerve may supply up to 70% of the sensation of the shoulder.16 Vorster et al17 demonstrated a glenohumeral sensory branch in 87% of 31 cadavers and an acromial sensory branch in 74%.
The suprascapular artery is a branch of the thyrocervical trunk of the subclavian artery. It passes downward and later-ally across the scalenus ante-rior muscle and phrenic nerve before running behind and par-allel to the clavicle and subcla-vius muscle. It then crosses the suprascapular notch above the
superior transverse scapular ligament, after which it typi-cally gives off branches that supply the supraspinatus mus-cle. The artery then continues distally, traveling beneath the inferior transverse scapular ligament before forming an anastamosis with the scapular circumflex artery and descend-ing branch of the transverse cervical artery.18
The most common ana-tomic arrangement at the su-prascapular notch is that the artery travels superior to the transverse scapular ligament while the nerve travels under it. This spawned the classic teaching pneumonic that when faced with an obstacle, “the Army [artery] goes over and the Navy [nerve] goes under the bridge.” However, previous cadaveric work showed that the suprascapular artery has a subligamentous course in up to 2.5% of dissections.19-21
In the first clinical re-port on the subject, Reineck and Krishnan11 reported finding a subligamentous artery with evidence of su-prascapular nerve compres-sion in 3 of 100 patients undergoing arthroscopic su-prascapular nerve release. They reported that the liga-ment was released but offered no follow-up results. They did not trace the artery back to its origin and therefore may have been visualizing a branch of the suprascapular artery prop-er as opposed to the main ar-tery itself; they suggested that an anterior approach, rather than a lateral approach, may be preferable for better visu-alization of the suprascapular
notch to avoid placing the ar-tery at risk.11
Recently, Yang et al22 dis-sected 103 cadaveric shoulders and found a single suprascapu-lar artery that passed under the superior transverse supra-scapular ligament in 26.2% of the shoulder specimens. They noted that the venous anatomy was more variable, with 21.3% having multiple veins, and all of the vessels passing superior to the ligament only 59.4% of the time. The same vascular arrangement described in the current case (with the supra-scapular vein crossing over the transverse scapular ligament and the artery running under) occurred in 10.9% of their ca-daveric specimens.22
Although venous compres-sion at the suprascapular notch has not been reported, venous compression at the spinogle-noid notch has been reported. Carroll et al8 were the first to report enlarged spinogle-noid notch veins as a cause of compression leading to pain and infraspinatus weakness. They identified 6 patients, 3 of whom underwent surgery, and all showed clinical improve-ment. The inferior transverse scapular ligament was divided in all patients, and 1 also had a varicosity ligated. Not all fluid signal seen in the notch on magnetic resonance imaging is a ganglion, and they stressed the importance of recognizing this entity when considering percutaneous aspiration.8 This has also been described in a patient with varicose veins in the lower extremity who de-veloped a large varix in the spinoglenoid notch resulting
in nerve compression.23 The patient underwent an open vessel ligation and resection with good clinical improve-ment. They noted that the ad-dition of intravenous contrast when performing magnetic resonance imaging may help to differentiate this from the more common ganglion cyst.23
The vascular anatomy at the spinoglenoid and supra-scapular notches appears to be more variable than previously thought. In patients presenting with signs of suprascapular nerve compression, vascular causes must be considered. Especially when considering percutaneous or arthroscopic treatment, awareness of these entities may help to guide treatment decisions, aid in identification of the anatomy, and prevent unwanted vascular insult.
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