The accuracy of subacromial injections: a prospective randomized magnetic resonance imaging study.
OBJECTIVE
To assess the accuracy of shoulder infiltrations in the subacromial bursa (SAB) by a posterior or an anteromedial approach. Magnetic resonance imaging (MRI) and clinical outcome were used for evaluation.


METHODS
A prospective randomized study.


METHODS
Thirty-three patients (22 women, 11 men; average age, 46 years; range, 25 to 64 years) with clinical signs of subacromial impingement were infiltrated with a mixture of bupivacaine, methylprednisolone, and gadolinium-DTPA directly followed by MRI to determine the actual site of injection. The SAB was randomly infiltrated posteriorly (n = 17) or anteromedially (n = 16). Injection confidence of the surgeon and body-mass index of the patient were recorded. Follow-up consisted of the Constant Score, Simple Shoulder Test, and visual analog scale score for pain taken within 24 hours and 6 weeks after infiltration.


RESULTS
Thirteen injections (76%) were in the SAB with a posterior approach and 10 (69%) with an anteromedial approach. Many surrounding structures were hit as well, especially the rotator cuff. A positive correlation between the injection confidence of the orthopaedic surgeon and the MRI was found in 66%. Only injection of the SAB alone resulted in a significant decrease of the pain (P = .004) and an increase in the functional scores. Injection in the bursa and rotator cuff muscle showed a significant increase in pain (P = .032) but no change in clinical scores. The body mass index had no influence on the scores.


CONCLUSIONS
Injections in the SAB are inaccurate, despite the confident feeling of the clinician. The finding that many different structures can be infiltrated with 1 injection can create both false-positive and -negative results.


METHODS
Level II.
Henkus
Hans-Erik
HE
Department of Orthopaedics, Medisch Centrum Haaglanden, The Hague, The Netherlands. HHenkus@Planet.nl
Cobben
Lodewijck P J
LP
Coerkamp
Emile G
EG
Nelissen
Rob G H H
RG
van Arkel
Ewoud R A
ER
D000174:Acromion; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000627:therapeutic use; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D002045:Bupivacaine / Q000008:administration & dosage* / Q000627:therapeutic use; D002061:Bursa, Synovial; D003287:Contrast Media / Q000008:administration & dosage; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D019786:Gadolinium DTPA / Q000008:administration & dosage; D006801:Humans; D015552:Injections, Intralesional; D008279:Magnetic Resonance Imaging; D008297:Male; D008775:Methylprednisolone / Q000008:administration & dosage* / Q000627:therapeutic use; D008875:Middle Aged; D011446:Prospective Studies; D000070636:Rotator Cuff Injuries; D019534:Shoulder Impingement Syndrome / Q000150:complications*; D020069:Shoulder Pain / Q000175:diagnosis* / Q000188:drug therapy / Q000209:etiology
D000779:Anesthetics, Local; D000893:Anti-Inflammatory Agents; D003287:Contrast Media; D019786:Gadolinium DTPA; D008775:Methylprednisolone; D002045:Bupivacaine