Soft Tissue to Bone Healing in Rotator Cuff Repair - Structural Interfaces and Attachments in Biology - page 254

12.4.5 Medical Comorbidities
A number of animal studies have been utilized to ascertain the effects of various
medical comorbidities commonly seen in humans. Beason et al. performed a study
evaluating the healing characteristics of a patellar tendon defect in aged mice with
hypercholesterolemia compared to controls [ 35 ]. The tendons in the aged mice
with hypercholesterolemia had a higher than expected rupture rate as well as a
decreased elastic modulus, suggesting a negative cumulative effect of cholesterol.
Furthermore, patients with rotator cuff tears had higher total cholesterol,
triglycerides, and low density lipoproteins compared to an age matched control
group [ 36 ]. High-density lipoproteins were lower in the cuff tear group. These
results suggest that serum cholesterol may have a significant effect on the develop-
ment of rotator cuff tears, and this may represent a viable therapeutic target for
clinical management.
Non-steroidal anti-inflammatory medications are commonly used for pain relief
in the setting of tendon degeneration or injury. Animal studies have suggested that a
certain level of inflammation is necessary for normal tendon healing and
remodeling. A study investigating the effects of NSAIDs on rotator cuff healing in
a rat model found that both indomethacin, a cyclooxygenase 1 and 2 inhibitor, as
well as celecoxib, a specific cyclooxygenase 2 inhibitor, had detrimental effects on
tendon healing [ 37 ]. Histologic findings revealed a less organized tissue at the
healing site in comparison to controls, as well as persistent osteoclasts. Biomechani-
cal testing showed lower load to failure in both NSAID-treated groups. Most
clinicians recommend that patients not use these medications in the immediate
postoperative period, although further studies are necessary to determine the exact
period of time and dosing regimen after which it is safe to resume these medications.
Diabetes is another common medical comorbidity that may have an effect on
rotator cuff healing. Diabetes is known to affect microvascular environment of
tissues. A study utilizing a rodent model of induced diabetes was used to investigate
the effect of diabetes on rotator cuff healing [ 38 ]. Diabetes was induced preopera-
tively. Short-term results at 2 weeks showed reduced load-to-failure in the diabetic
group compared to the control group. This study may underestimate the effects of
diabetes compared to the chronically ill patients; longer term studies are necessary
to come to a definitive conclusion. No long-term healing studies exist to answer this
question in the human population.
Decreased bone mineral density is also associated with a higher failure rate after
rotator cuff repair. In a study of 272 patients evaluated by either computed tomog-
raphy or ultrasonography for rotator cuff integrity an average of 13 months after
repair, decreased BMD and fatty infiltration were associated with unhealed cuffs
[ 39 ]. These results are substantiated by a rat study in which the failure stress at the
supraspinatus insertion was evaluated [ 40 ]. The study compared female rats after
ovariectomies, half treated with bisphosphonates to improve bone density. Improv-
ing bone density improved the failure stress. These studies highlight the role of the
bone in the process of degeneration and repair.