To evaluate bone destruction, upward migration, and medialisation of the glenohumeral (GH) joint in a cohort of 74 patients with seropositive and erosive rheumatoid arthritis followed up prospectively.
At the 15 year follow up 148 shoulders were radiographed by a standard method. Bone destruction in the GH joint was examined from the radiographs by four methods, of which three measured the migration and one the remodelling of the humeral head. The distances from the greater tuberosity of the humeral head to the coracoid process (medialisation distance (MD)) and to the articular surface of the humeral head (GA) have been previously developed to evaluate the preoperative offsets of the arthritic GH joint. Medial displacement index (MI) and upward migration index (UI) have been recently developed to evaluate the destructive pattern of the rheumatoid GH joint. Destruction of the GH joints was assessed by the Larsen method on a scale of 0 to 5. The relation between the measurements and the grade of destruction of the GH joints was examined. UI was compared with our previous measurements of the subacromial space.
Both the MI and the UI had a negative correlation with the GH joint destruction (Larsen grade), r=-0.49 (95% CI -0.36 to -0.60) and r=-0.58 (95% CI -0.46 to -0.68). The UI correlated significantly with the subacromial space, r=0.90 (95% CI 0.86 to 0.93). The mean MI and UI measurements of the non-affected joints were within the reported normal variation. The mean MD collapsed between Larsen grades 4 (83.0 mm) and 5 (65.5 mm). The morphology of the humeral head began to flatten and erode from the grade 3 onwards and medial head destruction was detected at grade 5.
Medialisation seems to be preceded by upward migration of the humeral head, indicating rotator cuff damage. Symptomatic Larsen grade 3 shoulders should be intensively followed up by clinical and radiological means. If a total shoulder arthroplasty is considered, an orthopaedic consultation is worthwhile at a sufficiently early stage (Larsen 3 and 4), when soft tissue structures responsible for function are still in proper condition and timing of the operative procedure can be well planned.