SUPERIOR SUBLUXATION OF THE HUMERAL HEAD AFTER TOTAL SHOULDER REPLACEMENT IN RHEUMATOID PATENTS

Abstract

To identify the incidence and timing of superior subluxation following total shoulder replacement (TSR) and any associated change in pain, activities of daily living and ranges of movement. Forty-six TSR in rheumatoid patients with more than 5years follow-up were identified from a prospectively compiled database held by the senior author (ANS). Modified Constant scores (excluding the power component) were measured and recorded prospectively every 2years. Pre-operative and complete follow-up scores were available for 35 joints (27 patients). A Mann-Whitney U test was used to compare patients with subluxation and those without, with regard to the changes in the components of the Constant score at last follow-up compared with the pre-operative score. Superior subluxation of the humeral head was defined as when the lower third of the humeral head had migrated level or superior to the midpoint of the glenoid component as measured on the AP radiograph. An independent observer reviewed AP radiographs, taken at each 2 yearly review, at random with identity hidden and in no particular date order. Twenty-three patients developed superior subluxation since surgery, of which 87% occurred after 5years. Of the 35 joints with both clinical and radiological follow-up, 16 had evidence of subluxation. There was no statistically significant difference between the changes in the activities of daily living (Mann-Whitney U=106, p=0.1) and range of movement (U=140, p=0.7) components of the Constant score. However, patients without subluxation had a greater improvement in their pain scores (U=80, p=0.02). Approximately half of rheumatoid patients with TSR will demonstrate radiological changes of superior subluxation, in the majority after 5 years. This change is not associated with deterioration in activities of daily living or ranges of movement. However, pain relief persists irrespective of subluxation but is better maintained in those without subluxation.