Rotator Cuff Repair With Magnesium Pin

Rotator cuff tears are one of the most common conditions encountered in orthopaedic practice leading to significant shoulder pain and functional deficit. The incidence of rotator cuff tears increases with age and previous trauma. Arthroscopic rotator cuff repair (ARCR) is a surgical procedure to reattach the torn edge of the tendon to the underlying bone, which can improve the clinical symptoms of patients. However, the retear rate after arthroscopic repair is as high as 94% (1). The high re-tear rate following cuff repair is due to the lack of a strong tendon to bone integration. The natural healing responses after surgical reattachment are too weak to regenerate strong tendon insertion, primarily owing to insufficient osteogenesis. To enhance the bone-tendon interface (BTI) healing, the investigators have developed a magnesium pin that can be applied to the cuff repair site to improve the BTI healing.This study is a single-center, randomized controlled trial to investigate the effect of using magnesium pin as a suture to augment rotator cuff repair. The intervention groups receives treated using magnesium pin additional to the suture anchor used routinely in clinical practice, whereas the control group receives routine suture anchor for the treatment-as-usual (TAU). The investigators hypothesize the magnesium pin applied in arthroscopic rotator cuff tears can promote BTI healing and reduce the cumulative retear rate with better functional outcomes.

Mechanical enhancement is a direct approach to enhance the bone-tendon interface (BTI) healing, which includes surgical techniques that seek to improve BTI healing through better fixation device. Favourable results would be achieved in the non-massively torn cases, improvement in the structural integrity and shoulder function were reported in the clinical studies. However, despite the improved initial biomechanical strength, high retear rate were still reported among the massive-teared patients, which indicates that enhancing the mechanical enhancement alone may not enough to promote the overall healing outcome. Other novel adjuvants to aid rotator cuff healing to promote bone tendon junction healing include growth factor supplementation, stem cells or biophysical intervention (5,6,7).

Tissue engineering is a promising strategy that would combine modern engineering techniques with novel biomaterials, cell therapy, growth factors, bioactive molecular. Enhancement of BTI healing with biomaterial, such as magnesium, may promote osteogenesis and thus improve the surgical outcome. These various approaches have been investigated in pre-clinical animal models of rotator cuff repair, yet further investigation to translate these into clinical practice is needed (8).

We have developed a magnesium pin that can be applied to the cuff repair site to improve the BTI healing.

The use of biodegradable materials as implants to stimulate healing has been developed in orthopaedics for decades. Our team and others reported that Mg-based interference screw or suture anchors could upregulate the expression of osteogenic and angiogenic factors experimentally, yet further investigation is still required to translate into clinical practice. However, the potential insufficient mechanical strength of Mg-based implants over the degradation period may result in a loss of fixation or failure of repair, which limits its clinical application. Herein, our novel magnesium pin showed good mechanical properties to be used to enhance the suture anchor commonly used for RCT repair in clinical practice. This can incorporate the benefit of an Mg-based component for its degradation and release of osteogenic and angiogenic by-products, but without the risk of compromising the integrity of the RCT repair site or the potentially osteoporotic bone at the repair site.

40 patients with rotator cuff tear scheduled for arthroscopic rotator cuff repair (ARCR) will be recruited from the Li Ka Shing Orthopaedic Specialist clinic at the Prince of Wales Hospital (PWH) Hong Kong.

Oral and written consents will be obtained from individuals who agree to participate in the study.

The recruitment period will last for 12 months and the whole project period is 2 years in total. Basic demographics, MRI assessment and Outcome Measurement Questionnaires will be carried out.

The intervention groups receive treated using magnesium pin in additional to the suture anchor used routinely in clinical practice, whereas the control group receives routine suture anchor for the treatment-as-usual (TAU). Both treatments are conducted in clinical practices that are randomly allocated to either the intervention or the control condition. Participants are therefore randomized as their allocation depends on their practice being an intervention or a control practice.

Assessments including anthropometric measurement, range of motion, shoulder muscle strength assessment, inflammation test and questionnaires will be conducted.

Eligibility Criteria:
Inclusion Criteria:

* Subject requires Arthroscopic rotator cuff repair (ARCR) and amenable to repair.
* Subject is \> 40 years of age (no upper limit);
* Subject provides written informed consent for study participation using an Independent Ethical Committee (IEC) / Institutional Review Board (IRB) approved consent form;
* Subject is willing and able to participate in required follow-up visits and is able to complete study activities.

Exclusion Criteria:

* Subjects who are unable to tolerate magnetic resonance imaging (MRI), due to psychiatric or medical contraindications;
* Subjects with Samilson-Prieto osteoarthritis \> 2;
* Subjects with current or prior infection of the ipsilateral shoulder;
* Subjects with known inflammatory arthropathy, history of inflammatory arthropathy, or chronic joint disease;
* Subjects with prior shoulder surgery (not including rotator cuff repair (revision repair subject group only), biceps tenodesis/tenotomy, distal clavicle excision (DCE), ubacromial decompression);
* Subjects with an irreparable or partially reparable rotator cuff tear;
* Subjects with a subscapularis tear requiring repair;
* Subjects requiring a concomitant labral fixation procedure;
* Subjects requiring a concomitant os acromiale fixation procedure
* Subjects with glenohumeral joint instability (multiple dislocations/subluxations);
* Subjects with a subacromial or intra-articular injection within 3 months prior to surgery;
* Subjects with condition(s) that contraindicate or complicate outcomes of ARCR e.g., \> Hamada 3 rotator cuff arthropathy on X-ray, Goutallier atrophy \> Grade 3, proximal humeral fracture or scapular fracture, avascular necrosis of the humeral head or glenoid, history of immunodeficiency disorders, history of chronic inflammatory disorders, oral or injected steroid use in last 4 weeks;
* Pregnancy or possibility of pregnancy
* Patient's inability to understand written and spoken Chinese, Mandarin or English.