The aim of this manuscript is to present a modification of the current arthroscopic implantation technique of a biodegradable subacromial spacer. This modified ultrasound-guided technique was intended to maximally reduce the invasiveness of the procedure. The ultrasound technique was used to measure the subacromial space for an optimal fit and to verify subacromial spacer placement in the sagittal and frontal planes. This finding is of particular importance for patients with contraindications to general or regional anesthesia. The follow-up (5 months) of subacromial spacer implantation using ultrasound in a patient with an irreparable rotator cuff tear showed correct spacer placement.