T

Technical Note

Arthroscopic Decompression of a Bony Suprascapular Foramen

Vivek Agrawal, M.D.

Abstract: Arthroscopic decompression of the suprascapular nerve by transection of the trans-verse scapular ligament has only recently been described. Arthroscopic decompression of a bonysuprascapular notch foramen has not been previously reported. This article presents a case report andoutlines an arthroscopic technique to safely decompress a bony suprascapular notch. In the subacro-mial space, a lateral portal is used for viewing and a posterior portal for instrumentation. The medialwall of the subacromial bursa located behind the acromioclavicular joint is debrided with the shaverfacing laterally and superiorly. The posterior acromioclavicular artery is routinely coagulated. Asuperomedial portal is now established using spinal needle localization. A smooth 5.5-mm cannulais placed in this portal and the coracoclavicular ligaments (trapezoid and conoid) are followed to thecoracoid. The smooth cannula serves nicely to sweep and retract the suprascapular artery andassociated fibrofatty tissue from the field of view while allowing instrumentation and visualization ofthe suprascapular notch. The course of the suprascapular nerve and morphology of the notch isconfirmed. A Kerrison punch rongeur, routinely used in spine surgery, is introduced through thesuperomedial portal and a notchplasty is performed safely, allowing decompression of the supras-capular nerve. Key Words: Arthroscopic technique— Shoulder pain —Suprascapular foramen—Suprascapular nerve—Suprascapular notch.

lease of the transverse scapular ligament, further raisingawareness of SN entrapment as an overlooked cause ofchronic shoulder pain.3-6 Arthroscopic decompression ofa bony SSN foramen has not been previously reported.We present a case report and outline a technique topermit the arthroscopic surgeon to safely address bonystenosis of the SN at the SSN.

SURGICAL TECHNIQUE

A 41-year-old woman was referred to our shoulderclinic with a 7-year history of persistent shoulder painthat started after she jerked her shoulder pulling on acart loaded with books. She had been evaluated bymultiple orthopaedic surgeons over the past 7 yearsand had 4 previous shoulder operations without reliefof her postinjury pain. Initial examination of the pa-tient at our clinic was significant for posterior andsuperior shoulder pain without evidence of cervicalpathology, instability, or labrum pathology. Suspi-cious of occult suprascapular neuropathy, an electro-

he suprascapular notch (SSN), located medial to the

coracoid at the anterior and superior border of thescapula, is a potential site of compression of the supra-scapular nerve (SN). First described in 1936 by Thom-as,1 it continues to be an often overlooked cause ofshoulder pain and dysfunction. Many etiologies havebeen associated with SN entrapment, including blunttrauma, rotator cuff tear, instability, compressive lesionssuch as ganglion cysts, passage of the suprascapularartery through the SSN, crutch use, repetitive tractioninjury in athletics, and variations in SSN morphology,including a bony foramen.2 Multiple reports have onlyrecently described techniques for minimally invasive re-

From The Shoulder Center, Zionsville, Indiana,

U.S.A.The author reports no conflict of interest.

conoid) are identified. The conoid ligament is visu-alized and followed inferiorly to its attachment tothe coracoid. Frequently, this can be done with agentle sweeping motion along these ligaments. Thecoracoid insertion of the transverse scapular liga-ment is seen perpendicular to the coracoid insertionof the conoid ligament. Use of the shaver and ra-diofrequency device are restricted to the space lat-eral to the medial border of the coracoid to avoidinjury to the suprascapular artery. Blunt dissectioncan often proceed inferiorly and medially from thecoracoid while maintaining contact with bone, al-lowing the SSN, suprascapular artery, and SN to bevisualized and safely retracted without directly dis-turbing these structures. The morphology of theSSN is now defined (Fig 2). In most cases, thetransverse scapular ligament is easily transected viathe SM portal using arthroscopic scissors. For abony or stenotic SSN foramen, as in the presentcase, a Kerrison punch rongeur is introducedthrough the SM portal to perform a foraminotomy.The superior and lateral walls of the SSN are de-compressed in a controlled manner.11 Kerrison ron-geurs are routinely used for bone removal in spinesurgery and are available in multiple sizes andconfigurations in most facilities. Upon completionof the SSN decompression, a probe is used to con-firm mobility of the SN by lifting it out of the SSN.Postoperatively, the patient reported resolution ofher longstanding posterior and superior shoulderpain and was extremely pleased with her outcome.

DISCUSSION

Although the prevalence of suprascapular compres-sion neuropathy is thought to be rare, its role in

FIGURE 1. Lateral decubitus position with portals for suprascap-ular notch approach outlined. (A, anterior portal; L, lateral portal;P, posterior portal; SM, superomedial portal.)

diagnostic study of her upper extremity along with anmagnetic resonance arthrogram were recommended.The electrodiagnostic study confirmed neuropathy ofthe SN at both the SSN and spinoglenoid notch(SGN), consistent with a “double crush” phenome-non.7 To further confirm the diagnosis, the patient wasreferred for a confirmatory selective SN block. TheSN block provided excellent but transient relief of herpain. After reviewing the risks, benefits, and optionsfor treatment, including our arthroscopic approach toSN decompression, she wished to proceed with arthro-scopic treatment.

The SN was decompressed at the SGN by transect-ing the spinoglenoid ligament as described byPlancher.8 Our approach to visualize the SSN is sim-ilar to the approach described by Lafosse,6 with sev-eral modifications. We use a semilateral decubitusposition for shoulder arthroscopy (Fig 1). The anat-omy and vascularity of the subacromial space hasbeen elegantly described and is helpful in planningapproaches to the SN and medial wall of the subacro-mial bursa.9 After completing glenohumeral evalua-tion and treatment, the arthroscope is introduced intothe subacromial space via the posterior portal. Ananterolateral portal is established for outflow using aninside-outside technique, ensuring that both portalsare within the subacromial bursa. A lateral portal withspinal needle localization is used to ensure an optimalangle of approach. An arthroscopic shaver is intro-duced through the lateral portal, and the posterior wallof the subacromial bursa is removed to improve visu-

326 V. AGRAWAL

alization. The arthroscope is switched to the lateralportal for viewing and the shaver and radiofrequencydevice are introduced from the posterior portal. Thecoracoacromial (CA) ligament is visualized and fol-lowed medially. The acromioclavicular (AC) joint islocalized but not exposed. The medial wall of thesubacromial bursa is now removed to allow access tothe SSN. The posterior AC artery is located immedi-ately posterior to the AC joint and is routinely coag-ulated. A modified superomedial (SM) portal is nowestablished under direct visualization using spinal nee-dle localization.10 A smooth 5.5-mm cannula is in-troduced, and the shaver and radiofrequency deviceare used for further dissection via the SM portal.The CA ligament is followed towards the coracoid.The coracoclavicular ligaments (trapezoid and

gachary et al.,2 Natsis et al.15 examined 423 scapulasand noted an 8% incidence of a bony foramen (typesIV and V).

From May 2007 to May 2008, 2 of the 44 patientsseen at our tertiary care shoulder clinic for arthro-scopic SN decompression at the SSN had a bony SSNforamen. To establish the diagnosis of suprascapularneuropathy, we request electrodiagnostic studies aftera detailed clinical evaluation to confirm the diagnosisand predict an expected outcome for treatment.16 Inour experience, electrodiagnostic studies of the shoul-der girdle are highly variable in diagnostic quality.Therefore, a single experienced examiner familiarwith the electrodiagnostic criteria for SN pathologyperformed most of the studies.16 For patients withisolated SN lesions, we often use a selective SN blockas a further diagnostic and confirmatory measure be-fore proceeding with arthroscopy.

Several techniques for arthroscopic transverse scapu-lar ligament release along with early clinical results havebeen recently reported.3-6,10 In the preliminary clinicalseries of 10 patients reported by Lafosse et al.,6 nonehad SN compression as a result of bony stenosis.However, he recommended using an arthroscopic burrto address bony stenosis.6

This technique has several advantages: the SM por-tal is a safe distance from the SN and relativelyfamiliar to most arthroscopic surgeons.10 The SMportal allows a more direct approach to dissection ofthe deep surface of coracoclavicular ligaments and theSSN, and the smooth cannula in this portal servesnicely as a soft tissue retractor avoiding the need for

another portal. Kerrison punch rongeurs are specifi-cally designed for decompression of spinal stenosisand uniquely suited to arthroscopic decompression ofsuprascapular nerve stenosis. For our initial case witha bony SSN foramen, we started with a burr as sug-gested by Lafosse; however, given the proximity ofthe neurovascular structures, we felt that the Kerrisonpunch offered a greater margin of safety and control.We completed the case with the Kerrison punch andused it exclusively for the second patient with a bonySSN. The technique is adaptable and appropriate forvariations in SSN anatomy.

Arthroscopic decompression of the suprascapularnerve with a bony SSN foramen has not been previ-ously reported. This technique provides the arthro-scopic surgeon another approach to safely decompressthe suprascapular nerve at the SSN in cases of bonystenosis using commonly available instruments.

FIGURE 2.(A) Right shoulder with bony suprascapular notchforamen. (B) Left shoulder with more commonly encounteredsuperior transverse scapular ligament. (A, suprascapular artery; N,suprascapular nerve; STSL, superior transverse scapular ligament;SSN, suprascapular notch.)

shoulder pain and dysfunction is probably underap-preciated. The morphology, particularly a stenotic orbony notch of the SSN, may be associated with apredilection to suprascapular nerve injury.2 The trans-verse scapular ligament, despite connecting 2 regionsof the same bone, has been shown to have fibrocarti-lage entheses, indicating that it experiences both com-pressive and tensile loading.12 Consistent with thesefindings, bony bridges at the SSN are also seen morefrequently with increasing age.13 Of the 700 speci-mens examined by Edelson,14 11.8% had a completelyor partially ossified transverse scapular ligament. In arecent update to the classification proposed by Ren-

327DECOMPRESSION OF A BONY SUPRASCAPULAR FORAMEN

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