"Risk" factors for progression of cuff tears - association vs causation

The natural course of and risk factors for tear progression in conservatively treated full-thickness rotator cuff tears

These authors retrospectively evaluated tear progression in 48 non-operatively treated rotator cuff tears using magnetic resonance imaging (MRI) with the goal of identifying risk factors for tear progression >5 mm over 22 months (range, 12-65 months). 

26 of these tears (54%)  showed medial-lateral (M-L) progression while 20 (41%) showed anterior-posterior (A-P) tear progression on MRI follow-up. 

Multivariate analysis revealed that MRI follow-up duration, diabetes mellitus, and infraspinatus muscle atrophy were associated with progression in the A-P plane. A high critical shoulder angle and supraspinatus and infraspinatus muscle atrophy were risk were associated with with M-L tear progression.

 Comment: This is not a study of "risk factors" a phrase that implies causation; rather it is a study of associations.  Following shoulders for longer periods of time does not increase the risk of cuff tear progression, for example.

The assertion that an increased "critical shoulder angle" is a risk factor for cuff tear progression, suggests that a five degree change in this angle from 33 to 38 degrees would be causative.

It seems at least equally likely that the change in CSA is not a cause, but rather the result of cuff disease. Note in the example below that the CSA measurement is increased by drawing a line from the inferior glenoid to the edge of a thin calcification on the lateral acromion, a change that may well arise from increased loading of the coracoacromial arch in shoulders with failing rotator cuffs.

The distinction between "association" and "causation" is important in that a surgeon convinced that an increased lateral extension of the acromion causes cuff tear progression, might be tempted to cut off the lateral acromion as was done in the case below.

There is a temptation in some corners to measure angles on the AP x-ray and attribute great clinical significance to small differences.

 

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Rotator cuff tears - does activity relate to progression?

Shoulder activity level and progression of degenerative cuff disease

These authors examined the relationship of shoulder activity with the risks of tear progression and pain development in 346 subjects (mean age 62 yrs) with an asymptomatic degenerative rotator cuff tear followed for a median duration of 4.1 years.

As determined by sequential interpretation of annual ultrasound reports, tear enlargement was seen in 177 shoulders (51.2%) and pain developed in 161 shoulders (46.5%) over time. 

Tear progression was defined as tear enlargement or conversion to a more severe tear type (partial to full thickness tear or control to partial or full-thickness tear). Partial and full-thickness cuff tears were considered enlarged if the tear size increased 5 mm or greater in any dimension compared with baseline.

Of note is the fact that the median duration of study follow-up was almost twice as long for the shoulders with tears that enlarged (6.0 years; IQR, 3.1-8.9 years) compared with the shoulders with stable tears (3.1 years; IQR, 2.0-5.0 years; P < .001).

Shoulder activity level and occupational demand level were not predictive of tear enlargement. Interestingly, patients who developed shoulder pain were less active than patients who did not.

Tear enlargement and pain development in asymptomatic tears were more common with involvement of the dominant shoulder. 

Comment: This is an interesting report of a large natural history study. It seems to indicate that in patients with asymptomatic rotator cuff tendon failure, tear size can progress with time independent of the shoulder's activity level. Of note, the authors do not suggest that the risk of tear progression is an indication for cuff repair.

This is surely good news for those of us with unoperated supraspinatus tears who continue to be active (and who avoided what would have been a painful 6 months of post-repair down time)!

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Progression of asymptomatic degenerative rotator cuff tears - is the 'cable' relevant?

Patterns of tear progression for asymptomatic degenerative rotator cuff tears

These authors studied 139  full-thickness rotator cuff tears with a mean subject age of 63.3 years and follow-up duration of 6.0 years/

Ninety-six (69.1%) of the tears demonstrated integrity of the anterior 3 mm of the supraspinatus tendon (the 'cable').

Fifty (52.1%) of the tears with intact anterior 3 mm of the supraspinatus tendon showed >5mm progression of tear width at a median of 3.2 years from enrollment. 

Twenty nine (67.4%) of tears with disruption of anterior 3 mm of the supraspinatus tendon showed >5mm progression of tear width at a median of 2.2 years from enrollment.

They concluded that the integrity of the anterior 3 mm of the supraspinatus had no effect on the magnitude of enlargement.

Comment: It is not surprising that degenerative cuff tears continue to degenerate. The significance of the 'anterior rotator cuff cable' remains undefined. 

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Degenerative (atraumatic) rotator cuff tears are usually bilateral and continue to degenerate with age.

Prospective Longitudinal Analysis of the Risk of Tear Progression for Asymptomatic Degenerative Rotator Cuff Tears

These authors identified that of 224 subjects with a painful rotator cuff tear in one shoulder were often found to have an asymptomatic tear on the opposite side:  118 had full-thickness and 56 had partial thickness asymptomatic tears.

These subjects were followed annually with shoulder ultrasonography, radiographs and clinical evaluations. The study also included 50 control subjects.  The mean age of the control subjects (60.7 +/- 10 yrs) and those with partial-thickness (59.4 +/- 10 yrs) was less than those with full-thickness tears (63.8 +/- 9 yrs, p=0.01).

38% of control subjects developed a tear and 46% of partial-thickness and 53% of full-thickness tears demonstrated tear enlargement.

Age was associated with enlargement for partial-thickness tears (62.5 +/-10 yrs enlarged vs. 55.8 +/- 10 yrs stable, p=0.01) but not for controls (p=0.52) or full-thickness tears (p=0.70).

Twenty percent of controls, 36% of partial-thickness and 42% of full-thickness tears developed pain regardless of tear enlargement. Interestingly the development of pain did not correlate with tear enlargement for the controls (p=0.47), partial-thickness (p=0.69) or full-thickness tears (p=0.80).

Survivorship analysis for the entire cohort with tear progression as the end point was 96% at one year, 74% at three years and 59% at five years.

Comment: This study documents well that the issue with atraumatic cuff tears is the progressive loss of the quality of the tendon. This progressive degeneration was observed in over 1/3 of the control subjects as well as in those individuals with existing cuff tears. Pain is not a reliable indicator of the progressive deterioration of the cuff tendon.

This study helps explain the high failure rate of rotator cuff repair that has remained constant despite many different approaches used in an attempt to reattach the degenerated tendon to bone.

As H.L.McLaughlin stated in 1962, "the wise surgeon, realizing that he may find little but rotten cloth to sew, will operate only by necessity and make a carefully guarded prognosis."
It has yet to be demonstrated that suturing degenerated tendon results in improvement in the quality of the tendon.
Bottom line: it matters if the cuff fails because of tear or wear

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Asymptomatic rotator cuff tears - natural history

The Natural History of Asymptomatic Rotator Cuff Tears: A Three-Year Follow-up of Fifty Cases

The authors report on 50 patients with initially asymptomatic full-thickness rotator cuff tears followed clinically, sonographically, and by magnetic resonance imaging over three years.

These patients were part of a prior study by the same authors of 420 asymptomatic volunteers aged between 50 and 79 years. In that study, full-thickness tears of the rotator cuff were detected in 32 subjects (7.6%). The prevalence increased with age as follows: 50 to 59 years, 2.1%; 60 to 69 years, 5.7%; and 70 to 79 years, 15%. The mean size of the tear was less than 3 cm and tear localisation was limited to the supraspinatus tendon in most cases (78%). The strength of flexion was reduced significantly in the group with tears (p = 0.01). The authors concluded that asymptomatic tears of the rotator cuff should be regarded as part of the normal ageing process in the elderly.

In the new study, eighteen of fifty tears developed symptoms during follow-up. There was a significantly larger (11mm) increase in the mean tear size in the newly symptomatic group ( when compared with the still-asymptomatic group (3 mm). The rate of fatty degeneration was significantly higher (35%) in the newly symptomatic group when compared with the still-asymptomatic group (4%). The rate of pathology of the long head of the biceps tendon was significantly higher (33%) in the newly symptomatic group  when compared with the still-asymptomatic group (6%).

During a relatively short-term follow-up, a substantial percentage of asymptomatic rotator cuff tears became symptomatic and underwent anatomic deterioration. Increase in tear size and decrease of muscle quality were correlated to the development of symptoms.

The authors caution that there may not be a direct cause-and-effect relationship between tear progress and the development of symptoms: 3 of 18  newly symptomatic subjects developed symptoms even though the tear did not progress, while 12 of 32 subjects remained asymptomatic although they had deterioration of the rotator cuff.

We would add the caution that the observation that tears progressed with time in some of these patients does not demonstrate that these patients would have fared better if their asymptomatic tears had been surgically repaired.

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