CASE REPORT
Infraspinatus muscle atrophy from suprascapular nerve compression Christopher B. Cordova, MPAS, PA-C; Brett D. Owens, MD
ABSTRACT Muscle weakness without pain may signal a nerve compression injury. Because these injuries should be identified and treated early to prevent permanent muscle weakness and atrophy, providers should consider suprascapular nerve compression in patients with shoulder muscle weakness. Keywords: infraspinatus muscle atrophy, suprascapular nerve compression, posterior labral tear, paralabral cyst, spinoglenoid notch, orthopedics
CASE A 21-year-old man presented to the orthopedic clinic for evaluation and treatment of right shoulder weakness that started about 3 weeks ago and occurred during weight lifting. The patient was referred by his physical therapist when the infraspinatus muscle atrophy was identified. The patient had no recent traumatic events to his shoulder or neck, although he recalled a right-shoulder subluxation during a wrestling match when he was in high school. He said the pain subsided after 3 weeks and he did not seek treatment. The patient was right-hand dominant and otherwise healthy. He reported constant pain localized to the superior aspect of his shoulder, which he rated as a 1 on a 0 to 10 pain intensity rating scale. He denied any numbness or tingling in either upper extremity. A thorough review of symptoms was noncontributory. A detailed physical examination revealed a generally healthy, young man. Visual inspection of his shoulder girdles revealed decreased musculature of his right infraspinatus muscle when compared with the contralateral side (Figure 1). His active and passive range of motion was full in all ranges compared with his unaffected limb. The
Christopher B. Cordova practices orthopedics at Keller Army Community Hospital in West Point, N.Y. Brett D. Owens is a professor of surgery (orthopedics) for the John A. Feagin Jr. Sports Medicine Fellowship, and chief of orthopedic surgery at Keller Army Community Hospital. The authors have indicated no relationships to disclose relating to the content of this article. DOI: 10.1097/01.JAA.0000442701.87975.42 Copyright © 2014 American Academy of Physician Assistants
FIGURE 1. Clinic image demonstrating infraspinatus atrophy
strength testing revealed 4/5 strength with resisted external rotation with the arm at the patient’s side. All other strength testing was unremarkable. A shoulder stability examination revealed a significant posterior load-shift as well as posterior apprehension. The working diagnosis was suprascapular nerve compression with a posterior labral tear and a paralabral cyst. Given the patient’s history of subluxation and physical examination findings of infraspinatus muscle atrophy and weakness and posterior instability, the posterior labral tear most likely occurred from the subluxation. This labral tear formed a paralabral cyst that progressively increased in size, compressing the suprascapular nerve at the spinoglenoid notch. Initial radiographs revealed a relatively high posterior positioned humeral head and a clinically insignificant os acromiale. A noncontrast MRI of the right shoulder was ordered to confirm a compressing lesion on the suprascapular nerve. MRI revealed a large paralabral cyst within the spinoglenoid notch with an associated posterior labral tear (Figures 2 to 4). The MRI confirmed the diagnosis of posterior labral tear with a large paralabral cyst in the spinoglenoid notch. The presence of the cyst confirmed the cause of the infraspinatus atrophy. The patient was referred to orthopedic surgery for surgical decompression of his paralabral cyst and posterior labral repair.
JAAPA Journal of the American Academy of Physician Assistants
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
www.JAAPA.com
33
CASE REPORT
Key points With the patient undressed, visually inspect the shoulder girdle muscles for atrophy. Confirm the diagnosis with MRI. Early operative treatment and postoperative rehabilitation support a return to full function.
FIGURE 2. Axial proton-density weighted image of the right
shoulder demonstrating a paralabral cyst (arrow) in the spinoglenoid notch
FIGURE 3. Coronal proton-density weighted image of the right
shoulder demonstrating a cyst in the spinoglenoid notch
FIGURE 4. Sagittal proton-density weighted image of the right
shoulder demonstrating a cyst in the spinoglenoid notch 34
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After operative consent was obtained, the patient was examined under general anesthesia. The examination revealed a grade 3 posterior load-shift with a grade 1+ anterior load-shift. Using arthroscopic technique, the cyst was decompressed and a capsulolabral repair was performed using suture anchors (Figures 5 and 6). Finally, an arthroscopic load-shift was performed to confirm elimination of pathologic translation. The patient completed a 6-month postoperative rehabilitation program under the guidance of a physical therapist. He was reevaluated periodically, and at his 6-month follow-up evaluation noted no pain or weakness. His examination revealed no infraspinatus atrophy or weakness with resisted external rotation, and a stable load-shift. DISCUSSION The true frequency of suprascapular nerve compression was not clearly defined in the literature. Suprascapular nerve compression at the spinoglenoid notch was first recognized and described in 1981.1 Over the subsequent decade (1982 through 1991), nine more cases were reported in the literature.2 Additionally, a review of the literature revealed that suprascapular nerve compression at the spinoglenoid notch secondary to compression from a paralabral cyst is not a common injury.3,4 Ferretti and Cummins both describe their findings of infraspinatus muscle atrophy in competitive athletes caused by a traction mechanism from repetitive overhead motions.3,4 This finding could warrant future epidemiologic investigation. The suprascapular nerve has a circuitous route through the shoulder girdle, originating from the superior trunk of the brachial plexus and traversing through the scapular and spinoglenoid notches. The nerve terminates with branches to the supraspinatus and infraspinatus muscles.5 Although the nerve anatomy in the upper extremity can be intimidating, when muscle atrophy is present, a diagnosis must be clearly identified. Nerve compression injuries should be identified and treated early. Visual inspection of the affected area must be performed. When a nerve compression injury is severe, the presenting patient complaint is usually muscle weakness not accompanied by pain. Advanced imaging should be ordered to accompany physical examination findings. If the imaging is not helpful in a diagnosis, consider electroVolume 27 • Number 2 • February 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Infraspinatus muscle atrophy from suprascapular nerve compression
FIGURE 5. Arthroscopic visualization of cyst decompression
myography. Early diagnosis and treatment can prevent permanent muscle weakness and atrophy. When considering differential diagnoses for patients presenting for shoulder muscle weakness, suprascapular nerve compression should always be included. JAAPA REFERENCES 1. Ganzhorn RW, Hocker JT, Horowitz, M, Switzer HE. Suprascapular-nerve entrapment. J Bone Joint Surg Am. 1981;63(3): 492-494.
FIGURE 6. Arthroscopic visualization of the posterior labral
repair 2. Liveson JA, Bronson MJ, Pollack, MA. Suprascapular nerve lesions at the spinoglenoid notch: report of three cases and review of the literature. J Neurol Neurosurg Psychiatry. 1991;54(3):241-243. 3. Ferretti A, De Carli A, Fontana M. Injury of the suprascapular nerve at the spinoglenoid notch. Am J Sports Med. 1998;26(6): 759-763. 4. Cummins CA, Bowen M, Anderson K, Messer T. Suprascapular nerve entrapment at the spinoglenoid notch in a professional baseball pitcher. Am J Sports Med. 1999;27(6):810-812. 5. Bigliani LU, Dalsey RM, McCann PD, April EW. An anatomical study of the suprascapular nerve. Arthroscopy. 1990;6(4):301-305.
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Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Infraspinatus muscle atrophy from suprascapular nerve compression Christopher B. Cordova, MPAS, PA-C; Brett D. Owens, MD
ABSTRACT Muscle weakness without pain may signal a nerve compression injury. Because these injuries should be identified and treated early to prevent permanent muscle weakness and atrophy, providers should consider suprascapular nerve compression in patients with shoulder muscle weakness. Keywords: infraspinatus muscle atrophy, suprascapular nerve compression, posterior labral tear, paralabral cyst, spinoglenoid notch, orthopedics
CASE A 21-year-old man presented to the orthopedic clinic for evaluation and treatment of right shoulder weakness that started about 3 weeks ago and occurred during weight lifting. The patient was referred by his physical therapist when the infraspinatus muscle atrophy was identified. The patient had no recent traumatic events to his shoulder or neck, although he recalled a right-shoulder subluxation during a wrestling match when he was in high school. He said the pain subsided after 3 weeks and he did not seek treatment. The patient was right-hand dominant and otherwise healthy. He reported constant pain localized to the superior aspect of his shoulder, which he rated as a 1 on a 0 to 10 pain intensity rating scale. He denied any numbness or tingling in either upper extremity. A thorough review of symptoms was noncontributory. A detailed physical examination revealed a generally healthy, young man. Visual inspection of his shoulder girdles revealed decreased musculature of his right infraspinatus muscle when compared with the contralateral side (Figure 1). His active and passive range of motion was full in all ranges compared with his unaffected limb. The
Christopher B. Cordova practices orthopedics at Keller Army Community Hospital in West Point, N.Y. Brett D. Owens is a professor of surgery (orthopedics) for the John A. Feagin Jr. Sports Medicine Fellowship, and chief of orthopedic surgery at Keller Army Community Hospital. The authors have indicated no relationships to disclose relating to the content of this article. DOI: 10.1097/01.JAA.0000442701.87975.42 Copyright © 2014 American Academy of Physician Assistants
FIGURE 1. Clinic image demonstrating infraspinatus atrophy
strength testing revealed 4/5 strength with resisted external rotation with the arm at the patient’s side. All other strength testing was unremarkable. A shoulder stability examination revealed a significant posterior load-shift as well as posterior apprehension. The working diagnosis was suprascapular nerve compression with a posterior labral tear and a paralabral cyst. Given the patient’s history of subluxation and physical examination findings of infraspinatus muscle atrophy and weakness and posterior instability, the posterior labral tear most likely occurred from the subluxation. This labral tear formed a paralabral cyst that progressively increased in size, compressing the suprascapular nerve at the spinoglenoid notch. Initial radiographs revealed a relatively high posterior positioned humeral head and a clinically insignificant os acromiale. A noncontrast MRI of the right shoulder was ordered to confirm a compressing lesion on the suprascapular nerve. MRI revealed a large paralabral cyst within the spinoglenoid notch with an associated posterior labral tear (Figures 2 to 4). The MRI confirmed the diagnosis of posterior labral tear with a large paralabral cyst in the spinoglenoid notch. The presence of the cyst confirmed the cause of the infraspinatus atrophy. The patient was referred to orthopedic surgery for surgical decompression of his paralabral cyst and posterior labral repair.
JAAPA Journal of the American Academy of Physician Assistants
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
www.JAAPA.com
33
CASE REPORT
Key points With the patient undressed, visually inspect the shoulder girdle muscles for atrophy. Confirm the diagnosis with MRI. Early operative treatment and postoperative rehabilitation support a return to full function.
FIGURE 2. Axial proton-density weighted image of the right
shoulder demonstrating a paralabral cyst (arrow) in the spinoglenoid notch
FIGURE 3. Coronal proton-density weighted image of the right
shoulder demonstrating a cyst in the spinoglenoid notch
FIGURE 4. Sagittal proton-density weighted image of the right
shoulder demonstrating a cyst in the spinoglenoid notch 34
www.JAAPA.com
After operative consent was obtained, the patient was examined under general anesthesia. The examination revealed a grade 3 posterior load-shift with a grade 1+ anterior load-shift. Using arthroscopic technique, the cyst was decompressed and a capsulolabral repair was performed using suture anchors (Figures 5 and 6). Finally, an arthroscopic load-shift was performed to confirm elimination of pathologic translation. The patient completed a 6-month postoperative rehabilitation program under the guidance of a physical therapist. He was reevaluated periodically, and at his 6-month follow-up evaluation noted no pain or weakness. His examination revealed no infraspinatus atrophy or weakness with resisted external rotation, and a stable load-shift. DISCUSSION The true frequency of suprascapular nerve compression was not clearly defined in the literature. Suprascapular nerve compression at the spinoglenoid notch was first recognized and described in 1981.1 Over the subsequent decade (1982 through 1991), nine more cases were reported in the literature.2 Additionally, a review of the literature revealed that suprascapular nerve compression at the spinoglenoid notch secondary to compression from a paralabral cyst is not a common injury.3,4 Ferretti and Cummins both describe their findings of infraspinatus muscle atrophy in competitive athletes caused by a traction mechanism from repetitive overhead motions.3,4 This finding could warrant future epidemiologic investigation. The suprascapular nerve has a circuitous route through the shoulder girdle, originating from the superior trunk of the brachial plexus and traversing through the scapular and spinoglenoid notches. The nerve terminates with branches to the supraspinatus and infraspinatus muscles.5 Although the nerve anatomy in the upper extremity can be intimidating, when muscle atrophy is present, a diagnosis must be clearly identified. Nerve compression injuries should be identified and treated early. Visual inspection of the affected area must be performed. When a nerve compression injury is severe, the presenting patient complaint is usually muscle weakness not accompanied by pain. Advanced imaging should be ordered to accompany physical examination findings. If the imaging is not helpful in a diagnosis, consider electroVolume 27 • Number 2 • February 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Infraspinatus muscle atrophy from suprascapular nerve compression
FIGURE 5. Arthroscopic visualization of cyst decompression
myography. Early diagnosis and treatment can prevent permanent muscle weakness and atrophy. When considering differential diagnoses for patients presenting for shoulder muscle weakness, suprascapular nerve compression should always be included. JAAPA REFERENCES 1. Ganzhorn RW, Hocker JT, Horowitz, M, Switzer HE. Suprascapular-nerve entrapment. J Bone Joint Surg Am. 1981;63(3): 492-494.
FIGURE 6. Arthroscopic visualization of the posterior labral
repair 2. Liveson JA, Bronson MJ, Pollack, MA. Suprascapular nerve lesions at the spinoglenoid notch: report of three cases and review of the literature. J Neurol Neurosurg Psychiatry. 1991;54(3):241-243. 3. Ferretti A, De Carli A, Fontana M. Injury of the suprascapular nerve at the spinoglenoid notch. Am J Sports Med. 1998;26(6): 759-763. 4. Cummins CA, Bowen M, Anderson K, Messer T. Suprascapular nerve entrapment at the spinoglenoid notch in a professional baseball pitcher. Am J Sports Med. 1999;27(6):810-812. 5. Bigliani LU, Dalsey RM, McCann PD, April EW. An anatomical study of the suprascapular nerve. Arthroscopy. 1990;6(4):301-305.
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Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
