Use of injectable collagen in partial-thickness tears of the
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Partial-thickness rotator cuff tear (PTRCT) is one of the most common shoulder injuries. The supraspinatus (SSP) tendon is the most affected in PTRCT.

A 55-year-old right-handed housewife visited while complaining of pain and functional limitation in the left shoulder, lasting 2 months. Patient was habitually practising free-body gymnastics twice a week and had already treated the shoulder pain with rest, non-steroidal anti-inflammatory drugs and physical therapy, without improvements.

Based on physical examination left SSP tendon involvement was suspected. Shoulder ultrasonography, revealed a partial-thickness tear of the articular surface of the SSP tendon (Grade II according to Ellman classification). It was decided to treat the patient with a series of four US-guided intratendineous injections of 2-ml porcine type I collagen at weekly intervals in combination with physical therapy.

Injections were performed using an anterior approach. The patient was seated on a chair with the arm in internal rotation in order to expose as much of the SSP tendon as possible. This position was best achieved by placing the patient’s arm behind her back. A 22-gauge needle was directed towards the tear of the SSP tendon as guided by US until the tip of the needle was seen in the correct position and then the collagen was injected slowly.

Physiokinesitherapy was performed starting from the first injection and during 4 weeks, three times a week, 30 minutes per session and consisted of motor re-education and proprioceptive exercises, with the aim to recover range of motion and strength of the shoulder.

The patient was evaluated at the time of enrolment (T0), right before the third injection (T1), and 1 month (T2), 3 months (T3) and 18 months (T4) after the last injection by means of the Constant–Murley (CM) score and the Disability of the Arm, Shoulder and Hand (DASH) questionnaire.

US assessment was performed at T0, T3 and T4 by the same expert radiologist. Longitudinal US of the SSP tendon at T0 showed a well-defined hypoechoic area, indicating partial-thickness tear of the articular surface of the tendon, without retraction (Grade II according to Ellman classification). Three months following the last injection, the partial-thickness tear became smaller and less defined (Grade I according to Ellman classification). Eventually, the T4 US assessment no longer showed tear within the tendon, which in addition appeared quite regular and isoechoic. No adverse events have been described after collagen injections.

In conclusion, the tear healing, the improvement in the tendon structure, the clinical and functional positive outcomes and the absence of side effects allow us to propose collagen injections as a valid option for the treatment of PTRCTs. A regenerative effect of collagen injections on tendon structure may be assumed to account the results achieved.