Non-Adherence to Pain Medication Increases Risk of Postoperative Frozen Shoulder

Postoperative frozen shoulder (FS) or adhesive capsulitis is a relatively frequent complication (5-20%), even after simple arthroscopic shoulder surgeries. The pathophysiology is still unclear, but psychological factors may play a pivotal role. From clinical experience, we hypothesized that patients, who are reluctant to take medications, particularly "pain-killers," have an increased incidence of postoperative FS.

We identified twenty patients who underwent limited arthroscopic operations of the shoulder and developed postoperative FS. Twenty patients with matching type of surgery, age, and gender served as control group (n = 20). All patients were at least one year postoperative and asymptomatic at the time of examination. Demographic data, the patient's adherence to self-medication (including self-medicating scale, SMS), development the Quality of life (QoL), and depression scale (PHQ-4-questionnaire) were assessed.

Patients with FS had a 2-fold longer rehabilitation and 3-fold longer work inability compared to the patients without FS (P < 0.009 and P < 0.003, respectively). Subjective shoulder value SSV (P = 0.075) and post-operative improvement of QoL (P = 0.292) did not differ among the groups. There was a trend-but not significant-toward less coherence to self-medication in the FS-group (26.50 vs. 29.50; P = 0.094). Patients with postoperative FS significantly more often stated not to have "taken pain-killers as prescribed" (P = 0.003).

Patients reporting unwillingness to take the prescribed pain medications had a significantly higher incidence of postoperative FS. It remains unclear whether the increased risk of developing FS is due to reduced postoperative analgesia or a critical attitude toward taking medication. However, patients who are reluctant to take painkillers should strongly be encouraged to take medications as prescribed.