Background: Shoulder proprioception in patients with glenohumeral osteoarthritis and the effect of total shoulder arthroplasty (TSA) on proprioception have been evaluated previously. Measuring proprioception with an active angle reproduction (AAR) test, proprioception remained unchanged or deteriorated in a short follow-up period after shoulder replacement. Therefore, the purpose of this prospective study was to evaluate the influence of the preoperative Constant score (CS) on postoperative proprioceptive outcome after TSA in patients with primary osteoarthritis to address the question of whether the preoperative state of shoulder function influences postoperative proprioceptive outcome.
Methods: Twenty-four patients who received total shoulder arthroplasty (TSA) (n = 24) for primary osteoarthritis of the shoulder were enrolled. After retrospectively analyzing the preoperative CS for 120 patients with primary osteoarthritis of the shoulder who received TSA, the patient group was divided into three subgroups according to preoperative functional assessment of the shoulder using the CS. Group one consisted of patients with CS < 20, group two patients with CS 20-30, and group three patients with the best preoperative CS (>30). In all patients proprioception was examined 1 day before the operation and 3 months after surgery by 3D motion analysis with an AAR test and also CS.
Results: Postoperatively, proprioception in group one (CS < 20) deteriorated significantly from 5.2° (SD 2.2) to 8.1° (SD 1.8); p = 0.018. In group two, there were no significant changes from preoperative to postoperative status [8.7° (SD 2.1) vs. 9.3° (SD 2.7) (p = 0.554)], likewise in group three [6.3° (SD 2.3) preoperatively vs. 6.9° (SD 3.3) postoperatively (p = 0.617)]. Comparing the postoperative results, the best proprioception [6.9° (SD 3.3)] was found in the group that had the best preoperative CS (group three, CS > 30).
Conclusion: In conclusion, a low preoperative CS is a negative predictive factor for postoperative proprioception after TSA. We should keep that in mind when determining the best timepoint for shoulder replacement in patients with glenohumeral osteoarthritis.