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FAILURE TO RECOVER MRI MUSCLE BULK AND QUALITY AFTER SUBACROMIAL DECOMPRESSION

Dept of Radiology, Nottingham City Hospital and Nottingham Shoulder and Elbow Unit, Nottingham, UK

Sub-Acromial Decompression (SAD) for impingement has a failure rate of 5–20%. We used MRI to see whether SAD failure is associated with muscle wasting or fatty degeneration in the rotator cuff. Fifty one patients with impingement were assessed using MRI pre- and post-op. Following arthroscopic SAD, seven patients with cuff tears were excluded. This study reviews the pre-op and 6 month post-op MRIs of the remaining 44 patients (25 males; 19 females) and also 17 additional MRIs obtained at three years post-op. MRI assessment was performed by an experienced radiologist using Zanetti’s muscle bulk assessment with values expressed as standard deviations from an age matched mean and Goutallier’s fatty degeneration assessment graded 0 to 4. There was a wide range of pre-op muscle bulk values (SupraSpinatus minus;2.4 to +3.4; SubScapularis minus;2.1 to +4.8; and InfraSpinatus/ Teres Minor minus;1.1 to +5.7). Comparing post-op with pre-op there was a gradual trend towards a reduced muscle bulk for each muscle after surgery but to a limited extent only (<0.5SD). Pre-op fatty degeneration of SS and IS was grade 2 in about a half with a mild increase with time post-op (SS pre=50%, 6/12 and 3 years=59%; IS pre=45%, 6/12=43% and 3 years=59%). There was a similar age distribution for grades 1 and 2. Only three of the patients were a clinical failure at 6 months but this increased to five of the 17 patients scanned at 3 years. Predicting these failures was not possible based on the pre-op MRI data. The high initial success of SAD was not accompanied by an overall increase in muscle bulk or quality of the muscle at 6 months. The progressive loss of muscle bulk and quality over 3 years was accompanied by an increased clinical failure rate.

The abstracts were prepared by Cormac Kelly. Correspondence should be addressed to The Secretary, British Elbow and Shoulder Society, Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE