This is a prospective, single-center, placebo-controlled, non-comparative, phase II study to evaluate the influence of an adjuvant, intravenous therapy with zoledronic acid (single dose) on healing after arthroscopic repair of chronic rotator cuff tears.

The study including its financial support was approved by the medical director of the General Accident Insurance Institution (AUVA) , Dr. Roland Frank.

Hypothesis to prove: Adjuvant intravenous therapy with zoledronic acid does improve tendon healing after arthroscopic reconstruction of chronic rotator cuff tears compared to a control group without adjuvant therapy with zoledronic acid.,

Inclusion Criteria

• Age between 50 and 70 years
• Magnetic resonance imaging verified rotator cuff tear (within 6 month prior to surgery)
• Rupture size with a maximum diameter of 3 cm
• Willingness to participate in the study
• Willingness to participate in a unified physiotherapy with use of a shoulder abduction pad for four weeks postoperativel

Exclusion Criteria:

• Patients younger than 50 or older than 70 years of age
• Pregnancy
• Known allergy to zoledronic acid or other components of the medicinal product
• Previous fracture of the affected shoulder
• Previous surgery of the affected shoulder
• Previous or existing bacterial infection of the affected shoulder
• Rupture of more than two tendons in the affected shoulder (massive rotator cuff tear)
• Isolated subscapularis tendon tear
• Presence of glenohumeral osteoarthritis (Hamada type 3 or higher)
• Diabetes mellitus (fasting glucose ≥ 126 mg/dl, HbA1C ≥ ZORRO Version Draft1.0/09.05.2022 Page 6 of 42 6.5%)
• Malignant tumor disease
• Pathological dental status
• Known disease that interferes with bone metabolism
• Concomitant diseases that do not permit general anesthesia
• Previous therapy with anti-osteoporotic drugs (bisphosphonates, denosumab, teriparatide)
• Epilepsy
• Claustrophobia
• Chronic alcohol abuse
• Drug abuse

In this trial, zoledronic acid or placebo will be administered once immediately before arthroscopic rotator cuff repair.

Randomization will take place. immediately before surgery by the anesthesiologist using sealed envelopes. To simplify the study procedure, zoledronic acid 5 mg (Aclasta®), administered as single intravenous infusion (verum) or sodium chloride (physiological saline solution 0.9%), administered as single intravenous infusion (placebo) will be administered preoperatively by the anesthesiologist after induction of anesthesia. Thereby, patients and surgeons are blinded to the randomization process.