UW Shoulder and Elbow Academy: Failure of healing after cuff repair

The normal attachment of the rotator cuff tendons to the bone of the tuberosity is through a complicated transition from flexible tendon, to unmineralized fibrocartilage, to mineralized fibrocartilage to bone (see Assembly, maturation, and degradation of the supraspinatus enthesis)

This progressive transition from flexible tendon to stiff bone enables the insertion to manage the twisting, traction and compression loads to which it is exposed throughout life. Nature's strategy is similar to that used in the construction of an electrical plug, with progressive transition from stiff to flexible with the goal of minimizing wire breakage with use.

When we attempt to repair a torn rotator cuff, our approximation of the edge of the torn tendon to bone does not re-establish a normal enthesis; thus our repair is inferior to the normal insertion and, as such, vulnerable to failure. "Healing and repair of an injured and degenerated supraspinatus enthesis remain a challenge, as the original graded transitional tissue of the fibrocartilaginous insertion is not re-created after the tendon is surgically reattached to bone. Instead, mechanically inferior and disorganized tissue forms at the healing site because of scar tissue formation."

In addition there are other factors that challenge the durable healing of a rotator cuff repair:

1. the tendon and bone are relatively avascular

2. tears often occur in tendons that have degenerated with compromised quantity and quality increasing the risk of sutures puling through the tendon

3. approximation of the retracted tendon to the repair site puts it under tension

4. it is difficult to completely immobilize the shoulder to protect the repair

5. the repair site is bathed in joint fluid that contain enzymes that can interfere with the healing response such as

*elastase (breaks down elastin and collagen fibers),

*plasmin (degrades fibrin clots, breaks down proteins and extracellular matrix)

*collagenases (break down collagen),

*matrix metalloproteinases (degrade components of the extracellular matrix)

*phospholipases (break down phospholipids, important components of cell membranes)

*cathepsin B and cathepsin D (breakdown of proteins)

As pointed out in Failure With Continuity in Rotator Cuff Repair "Healing" even when it appears that the cuff repair has healed by MRI, the tendon edge may not have actually healed to bone.

It is generally believed that early repair of acute traumatic cuff tears provides the highest chance of healing. However, the authors of Factors associated with healing failure after early repair of acute, trauma-related rotator cuff tears, found that even in this situation, healing failure occurred in more than 1 in 3 cases. They sought to identify factors associated with healing failure in 62 previously asymptomatic patients (median age 61 years, range 42 to 75) with trauma-related rotator cuff tears treated with early arthroscopic repair verified by MRI. Fatty infiltration (FI) was analyzed as global index, as well as in individual muscles separately. Surprisingly, only 79% of the individuals had a normal index for global FI preoperatively despite the fact that their cohort comprised trauma related tears in individuals without any history of shoulder dysfunction. 57 of these patients (92%) completed a 1-year follow-up and had repair integrity assessed on MR images according to Sugaya.

In spite of the fact that these patients seemed to have optimal conditions for successful repair - traumatic tears repaired within 6 weeks of injury - 37% of the repairs were not intact at one year after surgery.

Risk factors for healing failure were a high degree of fatty infiltration of the supraspinatus muscle, disruption of rotator cable integrity, and older age. Histopathologic degeneration of the tendon at the time of repair was not significantly associated with healing failure.

Another recent study illustrates again the difficult in achieving durable integrity of the cuff tendon attachment to bone.. The authors of Massive Rotator Cuff Tears With Short Tendon Length Can Be Successfully Repaired Using Synthetic Patch Augmentation. They evaluated 15 patients having massive cuff tears with good muscle quality but short tendon length (mean age 57 years, 86.7% male) at a mean follow-up of 43.8 months (27-55 months) after repair with patch augmentation. By MRI, there were three Sugaya grade 4 and five Sugaya grade 5 re-ruptures resulting in a re-tear rate of 53%.

On the the other hand, Harryman et al (Repairs of the rotator cuff. Correlation of functional results with integrity of the cuff) evaluated the results of 105 open repairs of tears of the rotator cuff in eighty-nine patients at an average of five years postoperatively. They correlated the functional result with the integrity of the cuff, as determined by ultrasonography. Eighty per cent of the repairs of a tear involving only the supraspinatus tendon were intact at the time of the most recent follow-up, while more than 50 per cent of the repairs of a tear involving more than the supraspinatus tendon had a recurrent defect. Older patients and patients in whom a larger tear had been repaired had a greater prevalence of recurrent defects. At the time of the most recent follow-up, most of the patients were more comfortable and were satisfied with the result of the repair, even when they had sonographic evidence of a recurrent defect. The shoulders in which the repaired cuff was intact at the time of follow-up had better function during activities of daily living and a better range of active flexion compared with the shoulders that had a large recurrent defect. Similar correlations were noted for the range of active external and internal rotation and for strength of flexion, abduction, and internal rotation. In the shoulders in which the cuff was not intact, the degree of functional loss was related to the size of the recurrent defect.

The anatomic results of rotator cuff repair reported in 2023 do not seem to be much of an improvement on these results published 32 years ago

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