Effect of diet-induced vitamin D deficiency on rotator cuff healing in a rat model

Biomechanical, Histologic, and Micro-Computed Tomography Characterization of Partial-Width Full-Thickness Supraspinatus Tendon Injury in Rats

PURPOSE

Partial rotator cuff tears can cause shoulder pain and dysfunction and are more common than complete tears. However, few studies examine partial injuries in small animals and, therefore a robust, clinically relevant model may be lacking. This study aimed to fully characterize the established rat model of partial rotator cuff injury over time and determine if it models human partial rotator cuff tears.

METHODS

We created a full-thickness, partial-width injury at the supraspinatus tendon-bone interface bilaterally in 31 Sprague-Dawley rats. Rats were euthanized immediately, and at 2-, 3-, 4-, and 8-weeks after surgery. Fourteen intact shoulders were used as controls. Samples were assessed biomechanically, histologically, and morphologically.

RESULTS

Biomechanically, load to failure in controls and 8 weeks after injury was significantly greater than immediately and 3 weeks after injury. Load to failure at 8 weeks was comparable to control. However, the locations of failure were different between intact shoulders and partially injured samples. Bone mineral density at 8 weeks was significantly greater than that at 2 and 3 weeks. Although no animals demonstrated propagation to complete tear and the injury site remodeled histologically, the appearance at 8 weeks was not identical to that in the controls.

CONCLUSIONS

The biomechanical properties and bone quality decreased after the injury and was restored gradually over time with full restoration by 8 weeks after injury. However, the findings were not equivalent to the intact shoulder. This study demonstrated the limitations of the current model in its application to long-term outcome studies, and the need for better models that can be used to assess chronic partial rotator cuff injuries.

CLINICAL RELEVANCE

There is no small animal model that mimics human chronic partial rotator cuff tears, which limits our ability to improve care for this common condition.

A Diagnosis of Vitamin D Deficiency Is Associated With Increased Rates of Primary Patellar Instability and Need for Recurrent Surgical Stabilization

BACKGROUND

Vitamin D has been proven experimentally to affect musculoskeletal health. The purpose of this study was to identify the relationship between vitamin D deficiency and patellar instability.

HYPOTHESIS

Vitamin D deficiency is associated with an increased risk of experiencing primary patellar instability and recurrent patellar dislocation after primary surgical stabilization.

STUDY DESIGN

Retrospective comparative study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A 1:1 matched retrospective study of 328,011 patients diagnosed with vitamin D deficiency was performed using the PearlDiver database. Incidence of primary patellar instability was calculated according to sex and age. Rates of primary patellar instability and surgical stabilization for recurrent dislocation were calculated with sex- and age-specific stratifications. Multivariable logistic regression was used to compare the rates of primary injury and recurrent stabilization while controlling for demographics and medical comorbidities.

RESULTS

A total of 656,022 patients were analyzed. The overall 1-year incidence rate of patellar instability in patients with vitamin D deficiency was 82.6 per 100,000 person-years (95% CI, 73.2-92.9), compared with 48.5 (95% CI, 41.4-56.5) in the matched control. Women were significantly more likely to experience primary patellar instability within 1 (adjusted odds ratio [aOR] = 1.45; 95% CI, 1.12-1.88) and 2 years (aOR, 1.31; 95% CI, 1.07-1.59) of hypovitaminosis D diagnosis. Patients aged 10 to 25 years with hypovitaminosis D were at greater risk of requiring recurrent patellar stabilization for both men (aOR, 2.48; 95% CI, 1.06-5.80) and women (aOR, 1.77; 95% CI, 1.04-3.02).

CONCLUSION

Patients diagnosed with vitamin D deficiency experienced higher rates of primary patellar instability and have greater risk of requiring recurrent surgical stabilization for subsequent dislocations.

CLINICAL RELEVANCE

These results suggest that monitoring and proactively treating vitamin D deficiency in the physically active patient may lower the risk of suffering primary patellar instability or recurrence after surgical stabilization.

Exploring the impact of vitamin D on tendon health: a comprehensive review

Tendons are vital components of the musculoskeletal system, facilitating movement and supporting mechanical loads. Emerging evidence suggests that vitamin D, beyond its well-established role in bone health, exerts significant effects on tendon physiology. The aim of this manuscript is to review the impact of vitamin D on tendons, focusing on its mechanisms of action, clinical implications, and therapeutic applications. A comprehensive search of scientific electronic databases was conducted to identify articles on the effects of vitamin D on tendon health. Fourteen studies were included in this review. Five studies were performed in vitro, and nine studies were conducted in vivo. Despite some conflicting results, the included studies showed that vitamin D regulates collagen synthesis, inflammation, and mineralization within tendons through its interaction with vitamin D receptors. Epidemiological studies link vitamin D deficiency with tendon disorders, including tendinopathy and impaired healing. Supplementation with vitamin D shows promise in improving tendon strength and function, particularly in at-risk populations such as athletes and the elderly. Future research should address optimal supplementation strategies and explore the interplay between vitamin D and other factors influencing tendon health. Integrating vitamin D optimization into clinical practice could enhance tendon integrity and reduce the burden of tendon-related pathologies.

Rotator cuff tears

Rotator cuff tears are the most common upper extremity condition seen by primary care and orthopaedic surgeons, with a spectrum ranging from tendinopathy to full-thickness tears with arthritic change. Some tears are traumatic, but most rotator cuff problems are degenerative. Not all tears are symptomatic and not all progress, and many patients in whom tears become more extensive do not experience symptom worsening. Hence, a standard algorithm for managing patients is challenging. The pathophysiology of rotator cuff tears is complex and encompasses an interplay between the tendon, bone and muscle. Rotator cuff tears begin as degenerative changes within the tendon, with matrix disorganization and inflammatory changes. Subsequently, tears progress to partial-thickness and then full-thickness tears. Muscle quality, as evidenced by the overall size of the muscle and intramuscular fatty infiltration, also influences symptoms, tear progression and the outcomes of surgery. Treatment depends primarily on symptoms, with non-operative management sufficient for most patients with rotator cuff problems. Modern arthroscopic repair techniques have improved recovery, but outcomes are still limited by a lack of understanding of how to improve tendon to bone healing in many patients.

A Diagnosis of Vitamin D Deficiency Is Associated With Increased Rates of Anterior Cruciate Ligament Tears and Reconstruction Failure

PURPOSE

To characterize the association between a diagnosis of hypovitaminosis D and primary anterior cruciate ligament (ACL) tear, primary anterior cruciate ligament reconstruction (ACLR), and revision ACLR in different sex and age cohorts.

METHODS

In this retrospective cohort study of the PearlDiver claims database, records were queried between January 1, 2011, and October 31, 2018 for all patients aged 10 to 59 years who received a diagnosis of hypovitaminosis D. Rates of primary ACL tears, primary reconstruction, and revision reconstruction were calculated for sex- and age-specific cohorts and compared with a control of patients without a diagnosis of hypovitaminosis D. Incidence rates for primary ACL injuries were calculated, and multivariable logistic regression was used to compare rates of ACL injury, primary reconstruction, and revision reconstruction while controlling for age, sex, Charlson Comorbidity Index, and several other comorbidities.

RESULTS

Among the 328,011 patients (mean age 41.9 ± 12.6 years, 65.8% female) included in both the hypovitaminosis D and control cohorts, the incidence of ACL tears was 115.2 per 100,000 person-years (95% confidence interval [CI] 107.2-123.7) compared with 61.0 (95% CI 55.2-67.2) in the demographic- and comorbidity-matched control cohort. The study cohort was significantly more likely to suffer an ACL tear over a 1- (aOR 1.67, 95% CI 1.41-1.99, P < .001) and 2-year (aOR 1.81, 95% CI 1.59-2.06, P < .001) period. This trend remained for both male patients at the 1- (aOR 1.66, 95% CI 1.29-2.14, P < .001) and 2-year (aOR 1.68, 95% CI 1.37-2.06, P < .001) mark and female patients at the 1- (aOR 1.69, 95% CI 1.33-2.14, P < .001) and 2-year (aOR 1.80, 95% CI 1.51-2.14, P < .001) mark. Finally, patients with vitamin D deficiency had a significantly increased likelihood of undergoing a revision ACLR within 2 years of a primary reconstruction (aOR 1.28, 95% CI 1.05-1.55, P = .012).

CONCLUSIONS

This study reports an association between patients previously diagnosed with hypovitaminosis D and significantly increased rates of both index ACL tears (81% increase within 2 years of diagnosis) and revision ACLR (28% within 2 years). These results identify a population with increased odds of injury and provide valuable knowledge as we expand our understanding of the relationship between vitamin D and musculoskeletal health.

LEVEL OF EVIDENCE

Level III, retrospective database study.

Preoperative vitamin D supplementation is a cost-effective intervention in arthroscopic rotator cuff repair

BACKGROUND

This study investigates the potential role of preoperative 25(OH)D supplementation as a cost-effective strategy to decrease revision rotator cuff repair (RCR) rates and lower the total health care burden from patients undergoing primary arthroscopic RCR. Previous literature has emphasized the importance of vitamin D on bone health maintenance, soft tissue healing, and outcomes in RCR. Inadequate preoperative vitamin D levels may increase revision RCR rates following primary arthroscopic RCR. Although 25(OH)D deficiency is common in RCR patients, serum screening is not routinely performed.

METHODS

A cost-estimation model was developed to determine the cost-effectiveness of both preoperative selective and nonselective 25(OH)D supplementation in RCR patients in order to reduce revision RCR rates. Prevalence and surgical cost data were obtained from published literature through systematic reviews. Cost of serum 25(OH)D assay and supplementation were obtained from public-use data. Mean and lower and upper bounds of 1-year cost savings were calculated for both the selective and nonselective supplementation scenarios.

RESULTS

Preoperative 25(OH)D screening and subsequent selective 25(OH)D supplementation was calculated to result in a mean cost savings of $6,099,341 (range: -$2,993,000 to $15,191,683) per 250,000 primary arthroscopic RCR cases. Nonselective 25(OH)D supplementation of all arthroscopic RCR patients was calculated to result in a mean cost savings of $11,584,742 (range: $2,492,401-$20,677,085) per 250,000 primary arthroscopic RCR cases. Univariate adjustment projects that selective supplementation is a cost-effective strategy in clinical contexts where the cost of revision RCR exceeds $14,824.69 and prevalence of 25(OH)D deficiency exceeds 6.67%. Additionally, nonselective supplementation is a cost-effective strategy in clinical scenarios where revision RCR cost is ≥$4216.06 and prevalence of 25(OH)D deficiency is ≥1.93%.

CONCLUSIONS

This cost-predictive model promotes the role of preoperative 25(OH)D supplementation as a cost-effective mechanism to reduce revision RCR rates and lower the overall health care burden from arthroscopic RCR. Nonselective supplementation appears to be more cost-effective than selective supplementation, likely due to the lower cost of 25(OH)D supplementation compared to serum assays.

Evaluation of Vitamin D-enriched Bone Graft in Surgically-induced Critical-sized Bone Defects: An Experimental Study

BACKGROUND

Restoration of bone defects in the craniac vault may require the use of autografts, allografts, xenografts, or synthetic grafts. There are promising data that vitamin D may play a positive role in graft incorporation. The purpose of the present study is the evaluation of the impact of vitamin D addition to human-derived bone grafts in the healing of critical-sized bone defects in porcine skulls.

MATERIALS AND METHODS

Four identical critical-sized defects were created in the calvaria of 8 adult Landrace Large White pigs. The first defect was left blank as control, the second defect was filled with human-derived bone graft, the third defect was filled with human-derived bone graft enriched with a low concentration of vitamin D (2 mg/mL), and the fourth defect was filled with human-derived bone graft enriched with a high concentration of vitamin D (10 mg/mL). The animals were sacrificed after 12 weeks. Harvested tissue specimens were qualitatively evaluated by histology. New bone formation (bone volume/tissue volume) was quantitatively measured by histomorphometry.

RESULTS

Signs of bone formation were evident in all bone sockets. Mean values of the bone volume/tissue volume of the 4 defects were 10.91%, 11.05%, 10.40% and 10.87% respectively, at 12 weeks. In 5 animals, high concentration of vitamin D caused a significant improvement in bone formation in relation to controls. In 3 animals, a high concentration of vitamin D was associated with decreased bone formation compared with controls. No statistical difference was observed in the graft healing among the 4 graft sites ( P > 0.05).

CONCLUSIONS

The results of this study have shown that the addition of vitamin D to human-derived bone grafts does not have a significant effect on bone formation and graft incorporation in critical-sized bone defects of the porcine calvaria. Further high-quality studies are needed to fully elucidate the role of vitamin D in bone formation and bone graft union.

Tailored modulation of S100A1 and RASSF8 expression by butanediamide augments healing of rotator cuff tears

Objectives

This investigation sought to elucidate promising treatment modalities for rotator cuff tears (RCTs) by delving into the molecular machinations instigating the affliction. The focus was on differentially expressed genes (DEGs) linked to RCTs, and the exploration of their roles and operative pathways.

Methods

DEGs were discerned from GEO datasets, followed by the establishment of a protein-protein interaction (PPI) network. Subsequently, the network's core genes were determined employing a Venn diagram. Enrichment analysis facilitated the unveiling of the biological roles and signal transduction pathways of these pivotal genes, thus shedding light on molecular strategies for RCT-targeted treatment. The Discovery Studio 2019 software was employed to sift through FDA-sanctioned drugs targeting these essential proteins. Moreover, the efficaciousness of these FDA-endorsed drugs vis-à-vis RCTs was corroborated by the construction of an in vivo animal model of the injury and the in vitro cultivation of tendon-derived stem cells.

Results

Bioinformatics outcomes revealed a significant overexpression of S100A1 and RASSF8 in RCT patients. The FDA drug repository indicated that Butanediamide has a selective affinity for S100A1 and RASSF8. Subsequent in vivo and in vitro experimentation demonstrated that Butanediamide could suppress S100A1 expression and bolster TDSC proliferation, thereby facilitating RCT healing.

Conclusions

S100A1 and RASSF8 are pivotal genes implicated in RCTs, and their roles have been elucidated. The FDA-approved compound, Butanediamide, may represent a prospective therapeutic agent for RCTs by targeting S100A1 and RASSF8, respectively.

Influence of Vitamin D Deficiency on the Expression of Genes and Proteins in Patients With Medium Rotator Cuff Tears

BACKGROUND

Whether vitamin D deficiency is related to rotator cuff muscle and tendon physiology is controversial.

PURPOSE

To assess the relationship between vitamin D deficiency and various gene expression patterns in patients with rotator cuff tears.

STUDY DESIGN

Controlled laboratory study.

METHODS

During arthroscopic surgery, samples from the supraspinatus muscle, deltoid muscle, and supraspinatus tendon were acquired from 12 patients with vitamin D deficiency (serum 25-hydroxyvitamin D concentration <20 ng/dL) and 12 patients with sufficient vitamin D levels (control group, serum 25-hydroxyvitamin D concentration ≥30 ng/dL) who were matched for age, sex, and tear size. Alterations in the expression of genes and proteins associated with myogenesis, muscle atrophy, adipogenesis, inflammation, and apoptosis, as well as in vitamin D receptor expression, were assessed using quantitative reverse transcription polymerase chain reaction, Western blotting, and immunohistochemistry and were compared between the 2 groups.

RESULTS

Vitamin D receptor gene expression in the deltoid muscle was significantly lower in the vitamin D deficiency group than in the control group (P = .043). Additionally, in the deltoid muscle, myoDgene expression levels were lower and atrogin levels were higher in the vitamin D deficiency group than in the control group (P = .034 and P = .011, respectively). However, in the supraspinatus muscle, no differences were observed between groups in the expression of myogenesis- or atrophy-related genes (all P > .05). The expression of inflammation-related genes (interleukin (IL)-1β and IL-6) was significantly higher in the vitamin D deficiency group, in both the deltoid and supraspinatus muscles (all P < .05). The supraspinatus tendon tissue did not show any significant differences in any gene expression evaluated (all P > .05). A correlation between gene and protein expression was observed for atrogin and IL-1β in the deltoid muscle (P = .019 and P = .037, respectively) and for IL-6 in the supraspinatus muscle (P = .044).

CONCLUSION

Vitamin D deficiency was not associated with the expression of myogenesis-related or muscle atrophy-related genes in the supraspinatus muscle of patients with rotator cuff tears, unlike in the deltoid muscle; rather, vitamin D deficiency was associated with increased proinflammatory cytokine expression.

CLINICAL RELEVANCE

In patients with rotator cuff tears, vitamin D deficiency was observed to be associated with increased levels of proinflammatory cytokines in the rotator cuff muscles, without significant changes in gene expression related to myogenesis or muscle atrophy.

Anatomical and Interpositional Bursa Preservation Showed Similar Improved Tendon to Bone Healing Compared With the Bursa Removal in a Rat Rotator Cuff Tear Model

PURPOSE

To compare the effects of anatomical preservation (AP) and interpositional preservation (IP) of subacromial bursa tissue on tendon-to-bone healing in a rat model of rotator cuff tear.

METHODS

In this study, 48 male Sprague-Dawley rats (average weight 283 g) underwent bilateral supraspinatus tendons severed by sharp incision and repaired immediately. The subacromial bursa tissues were completely removed in 16 rats, who served as the control (CON) group. The other 32 rats were randomly divided into 2 groups AP and IP between tendon and bone. Eight rats of each group were sacrificed for bilateral shoulders at 3 and 9 weeks after the operation, including 5 rats for biomechanical tests and 3 for histologic analysis.

RESULTS

No significant differences in terms of biomechanical properties were observed among the groups 3 weeks after surgery. At 9 weeks, the maximum load and stiffness of the AP (32.95 ± 6.33 N, P = .029; 12.49 ± 3.17 N/mm, P < .001; respectively) and IP (33.58 ± 8.47 N, P = .015; 11.63 ± 2.84 N/mm, P = .010, respectively) groups were significantly superior to that of the CON group (26.59 ± 4.47 N; 8.42 ± 2.33 N/mm, respectively). More organized collagen and more mature tendon insertion were observed in AP and IP groups at the interface at 9 weeks, which means better tendon-to-bone healing compared with the CON group.

CONCLUSIONS

The subacromial bursa plays a positive role in tendon-bone healing. Either anatomical preservation or interpositional preservation between tendon and bone can similarly facilitate the process of healing.

CLINICAL RELEVANCE

Considering the additional surgical time and surgical manipulation, preserving the subacromial bursa at the anatomical position seems to be a better way to promote rotator cuff healing.

Effect of PARP-1 Inhibition on Rotator Cuff Healing: A Feasibility Study Using Veliparib in a Rat Model of Acute Rotator Cuff Repair

BACKGROUND

PARP-1 (poly[ADP-ribose]) was shown to influence the inflammatory response after rotator cuff tear, leading to fibrosis, muscular atrophy, and fatty infiltration in mouse rotator cuff degeneration. So far, it is not known how PARP-1 influences enthesis healing after rotator cuff tear repair.

HYPOTHESIS/PURPOSE

This study aimed to examine the feasibility of oral PARP-1 inhibition and investigate its influence on rat supraspinatus enthesis and muscle healing after rotator cuff repair. The hypothesis was that oral PARP-1 inhibition would improve enthesis healing after acute rotator cuff repair in a rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 24 Sprague-Dawley rats, the supraspinatus tendon was sharply detached and immediately repaired with a single transosseous suture. The rats were randomly allocated into 2 groups, with the rats in the inhibitor group receiving veliparib with a target dose of 12.5 mg/kg/d via drinking water during the postoperative recovery period. The animals were sacrificed 8 weeks after surgery. For the analysis, macroscopic, biomechanical, and histologic methods were used.

RESULTS

Oral veliparib was safe for the rats, with no adverse effects observed. In total, the inhibitor group had a significantly better histologic grading of the enthesis with less scar tissue formation. The macroscopic cross-sectional area of the supraspinatus muscles was 10.5% higher (P = .034) in the inhibitor group, which was in agreement with an 8.7% higher microscopic muscle fiber diameter on histologic sections (P < .0001). There were no statistically significant differences in the biomechanical properties between the groups.

CONCLUSION

This study is the first to investigate the influence of PARP-1 inhibition on healing enthesis. On the basis of these findings, we conclude that oral veliparib, which was previously shown to inhibit PARP-1 effectively, is safe to apply and has beneficial effects on morphologic enthesis healing and muscle fiber size.

CLINICAL RELEVANCE

Modulating the inflammatory response through PARP-1 inhibition during the postoperative healing period is a promising approach to improve enthesis healing and reduce rotator cuff retearing. With substances already approved by the Food and Drug Administration, PARP-1 inhibition bears high potential for future translation into clinical application.

Serum Vitamin D Level Correlations With Tissue Vitamin D Level and Muscle Performance Before and After Rotator Cuff Repair

BACKGROUND

There is a lack of studies about serum and tissue vitamin D levels of the rotator cuff muscle on muscle power, fatty degeneration, and healing failure after rotator cuff repair (RCR). Furthermore, no studies have evaluated vitamin D receptor proteins in the rotator cuff that show a close association with serum vitamin D levels.

PURPOSE

To evaluate the correlations between serum vitamin D and tissue vitamin D as well as perioperative variables of arthroscopic RCR.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From March 2017 to October 2017, a total of 36 patients who underwent RCR were prospectively enrolled, and supraspinatus muscle tissue was obtained during surgery to analyze tissue vitamin D levels. Serum vitamin D levels were checked preoperatively and at 6 months and 1 year postoperatively. Tissue vitamin D levels were assessed using liquid chromatography, and the vitamin D receptor was measured by western blotting. Isokinetic muscle performance test (IMPT; peak torque and torque deficiency compared with the opposite shoulder) results and fatty degeneration of the rotator cuff using the Goutallier classification were assessed preoperatively and at 1 year after surgery. The American Shoulder and Elbow Surgeons score and Constant score were collected at 2 years after surgery. Healing failure of the repaired rotator cuff was analyzed by magnetic resonance imaging at 1 year after surgery.

RESULTS

Overall, only three patients (8.3%) had serum vitamin D sufficiency (>20 ng/mL). Among 36 patients, 26 patients returned for their 1-year follow-up. Lower preoperative serum vitamin D levels resulted in lower serum vitamin D levels at 6 months and 1 year postoperatively (all P < .05). Lower preoperative and 1-year postoperative serum vitamin D levels resulted in more torque deficiency on the IMPT in abduction than higher preoperative and 1-year postoperative serum vitamin D levels (all P < .05). Tissue vitamin D levels had a strong correlation with preoperative serum vitamin D levels (P = .001). Lower tissue vitamin D levels were associated with lower peak torque on the IMPT in abduction (P = .043) and a tendency of lower peak torque on the IMPT in external rotation (P = .077) at 1 year postoperatively. There was no correlation between tissue and serum vitamin D levels and functional outcomes, fatty degeneration, and healing failure after surgery (all P > .05). The vitamin D receptor showed no correlation with any variables (all P > .05).

CONCLUSION

Lower preoperative serum vitamin D levels had a strong correlation with lower tissue vitamin D levels and lower serum vitamin D levels at 1 year after surgery. Furthermore, the patients with lower serum vitamin D levels showed more weakness of muscle power perioperatively. The results of this study emphasized the association between vitamin D levels and rotator cuff muscle power.

Is Curcumine Useful in the Treatment and Prevention of the Tendinopathy and Myotendinous Junction Injury? A Scoping Review

Physical activity in general and sports in particular, is a mechanism that produces stress and generates great force in the tendon and in the muscle-tendon unit, which increases the risk of injury (tendinopathies). Eccentric and repetitive contraction of the muscle precipitates persistent microtraumatism in the tendon unit. In the development of tendinopathies, the cellular process includes inflammation, apoptosis, vascular, and neuronal changes. Currently, treatments with oral supplements are frequently used. Curcumin seems to preserve, and even repair, damaged tendons. In this systematic review, we focus more especially on the benefits of curcumin. The biological actions of curcumin are diverse, but act around three systems: (a) inflammatory, (b) nuclear factor B (NF-κB) related apoptosis pathways, and (c) oxidative stress systems. A bibliographic search is conducted under the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) as a basis for reporting reliable systematic reviews to perform a Scoping review. After analysing the manuscripts, we can conclude that curcumin is a product that demonstrates a significant biological antialgic, anti-inflammatory, and antioxidant power. Therefore, supplementation has a positive effect on the inflammatory and regenerative response in tendinopathies. In addition, curcumin decreases and modulates the cell infiltration, activation, and maturation of leukocytes, as well as the production of pro-inflammatory mediators at the site of inflammation.

Assessment of a Synergistic Effect of Platelet-Rich Plasma and Stem Cell-Seeded Hydrogel for Healing of Rat Chronic Rotator Cuff Injuries

Outcomes after repair of chronic rotator cuff injuries remain suboptimal. Type-1 collagen-rich tendon hydrogel was previously reported to improve healing in a rat chronic rotator cuff injury model. Stem cell seeding of the tendon hydrogel improved bone quality in the same model. This study aimed to examine whether there was a synergistic and dose-dependent effect of platelet-rich plasma (PRP) on tendon-bone interface healing by combining PRP with stem cell-seeded tendon hydrogel. Human cadaveric tendons were processed into a hydrogel. PRP was prepared at two different platelet concentrations: an initial concentration (initial PRP group) and a higher concentration (concentrated PRP group). Tendon hydrogel was mixed with adipose-derived stem cells and one of the platelet concentrations. Methylcellulose, as opposed to saline, was used as a negative control due to comparable viscosity. The supraspinatus tendon was detached bilaterally in 33 Sprague-Dawley rats (66 shoulders). Eight weeks later, each detached tendon was repaired, and a hydrogel mixture or control was injected at the repair site. Eight weeks after repair, shoulder samples were harvested and assigned for biomechanical testing (n = 42 shoulders) or a combination of bone morphological and histological assessment (n = 24 shoulders). Biomechanical testing showed significantly higher failure load and stiffness in the concentrated PRP group than in control. Yield load in the initial and concentrated PRP groups were significantly higher than that in the control. There were no statistically significant differences between the initial and concentrated PRP groups. The addition of the highly concentrated PRP to stem cells-seeded tendon hydrogel improved healing biomechanically after chronic rotator cuff injury in rats compared to control. However, synergistic and dose-dependent effects were not seen.

Vitamin D Metabolic Pathway Components in Orthopedic Patientes-Systematic Review

Vitamin D takes part in the functioning of many processes that ensure the homeostasis of the body. In orthopedics, it is indicated as an inseparable element ensuring proper bone growth and functioning, and its deficiencies are indicated in various diseases, mainly in the proper structure and function of the skeleton. In this review, we focus on the most important components of the vitamin D metabolic pathway, in correlation with selected orthopedic conditions. Records were obtained from the PubMed database in a timeline of 2010-2022. The keywords were as follows: vitamin D/cholesterol/vitamin D binding protein/ VDBP/Cytochrome/CYP24A1/CYP 27B1/Vitamin D receptor/VDR/ + diseases (ACL reconstruction, rotator cuff, arthroplasty knee/hip/shoulder). The recent original studies were analyzed, discussed, and the most important data were shown. The vast majority of articles concern the metabolite of vitamin D (25(OH)D), which is measured as a standard in diagnostic laboratories. Even though there is a lot of valuable information in the literature, we believe that the other elements of the vitamin D pathway also deserve attention and suggest their research in correlation with orthopedic disorders to supplement the missing knowledge on this topic.

Association of Preoperative Vitamin D Deficiency With Retear Rate and Early Pain After Arthroscopic Rotator Cuff Repair: A Retrospective Cohort Study

Background

Although the function of vitamin D in bone metabolism has been well studied, the question remains whether vitamin D deficiency impairs tendon healing after rotator cuff repair.

Purpose

To investigate the correlation between preoperative vitamin D deficiency and the retear rate and pain after arthroscopic rotator cuff repair.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients with full-thickness rotator cuff tears who underwent arthroscopic rotator cuff repair between January 2018 and August 2019 were enrolled. Included patients were divided into a control group (vitamin D level ≥20 μg/L) and a deficiency group (vitamin D level <20 μg/L). We investigated the association between preoperative vitamin D level and patient characteristics, MRI findings, pain and function scores (visual analog scale [VAS] for pain; Constant-Murley; University of California, Los Angeles; and American Shoulder and Elbow Surgeons scores), and healing status using the Pearson or Spearman correlation coefficient. The clinical characteristics were compared between the groups using the chi-square test or Fisher exact test.

Results

Included were 89 patients (control group, 44 patients; deficiency group, 45 patients). The mean vitamin D levels were 25.07 ± 5.38 and 14.61 ± 3.43 μg/L in the control and deficiency groups, respectively (P < .001); otherwise, there were no significant differences between the groups in the variables under study. Vitamin D levels were not related to age, symptom duration, tear size, extent of retraction, VAS pain score preoperatively and at 6 and 24 months postoperatively, or any function scores. Supraspinatus fatty infiltration and VAS scores at 1 and 3 months postoperatively were significantly associated with vitamin D level (r = -0.360, -0.362, and -0.316, respectively; P < .05 for all). VAS scores were significantly lower in the control group than in the deficiency group at postoperative 1 month (1.09 ± 0.56 vs 1.47 ± 0.66, respectively) and 3 months (1.14 ± 0.77 vs 1.44 ± 0.66) (P < .05 for both). The retear rate was significantly lower in the control group than in the deficiency group (9.09% vs 26.67%, respectively; P < .05).

Conclusion

Our study revealed that preoperative vitamin D deficiency was associated with a higher retear rate and early pain (1 and 3 months) after arthroscopic rotator cuff repair.

Abaloparatide Improves Rotator Cuff Healing via Anabolic Effects on Bone Remodeling in a Chronic Rotator Cuff Tear Model of Rat With Osteoporosis: A Comparison With Denosumab

BACKGROUND

Because of poor clinical outcomes, rotator cuff healing in patients with osteoporosis has recently gained attention. Antiresorptive therapy for osteoporosis has been reported to improve healing after repair. However, the comparative effectiveness of anabolic and antiresorptive agents has not been investigated.

HYPOTHESIS

Anabolic therapy with abaloparatide (ABL) would outperform antiresorptive therapy with denosumab (Dmab) to improve rotator cuff healing in the osteoporotic status.

STUDY DESIGN

Controlled laboratory study.

METHODS

A chronic rotator cuff tear model was established in ovariectomy-induced postmenopausal osteoporotic rats. Then, bilateral rotator cuff repairs were conducted in all experimental rats, which were randomly divided into control (CON), Dmab, and ABL groups to receive the corresponding subcutaneous injections. The rats sacrificed at 2 weeks (the early healing period) were used to detect osteoblast and osteoclast activities, related gene expression (osteoclastogenesis, osteogenesis, and chondrogenesis), new bone formation, and mineralization. In the rats sacrificed at 4 and 8 weeks, the bone mineral density and bone architecture at the repaired site were assessed by micro-computed tomography, and rotator cuff healing was evaluated using histological and biomechanical analyses.

RESULTS

At 8 weeks, significantly higher failure load and stiffness were observed in the ABL (25.13 ± 3.54 N, P < .001; 21.65 ± 3.08 N/mm, P < .001; respectively), and Dmab (21.21 ± 2.55 N, P < .001; 16.15 ± 2.07 N/mm, P = .008; respectively) groups than in the CON group (13.36 ± 1.70 N; 11.20 ± 2.59 N/mm; respectively), whereas the ABL treatment provided better failure load and stiffness than Dmab (P = .019; P = .003). Although tendon-to-bone healing was improved by Dmab, the most mature tendon insertion at the interface was observed in the ABL group, including a more organized collagen and fibrocartilage and higher bone quality. ABL significantly promoted bone remodeling via coupling between osteoclasts and osteoblasts (osteoblast to osteoclast ratio: 4.80 ± 0.39; P = .022), thereby stimulating more new bone formation and mineralization at the tendon-to-bone healing interface than Dmab (osteoblast to osteoclast ratio: 3.21 ± 0.75) at 2 weeks. Moreover, ABL had significant effects on gene expression [Runt-realted transcription factor 2 (Runx2, collagen type I-alpha 1 (Col1A1]), and sclerostin for osteogenesis; aggrecan and collagen type II (Col2) for chondrogenesis] in mineralized tissues, indicative of enhanced bone and fibrocartilage formation when compared with the CON and Dmab groups.

CONCLUSION

ABL promoted rotator cuff healing in osteoporotic rats by significantly increasing the mineralized tissue quality and collagen maturity at the reattachment site, leading to improved biomechanical properties, and was superior to Dmab in both biomechanical and histological analyses.

CLINICAL RELEVANCE

Anabolic therapy with ABL may outperform antiresorptive therapy with Dmab in improving outcomes after rotator cuff repair in osteoporotic patients.

Use of biologics in rotator cuff disorders: Current concept review

Poor tendon to bone healing following rotator cuff repair has led to the continued interest and investigation into biological augmentation. The biology of tendinopathy is not fully understood and consequently the availability of disease modifying therapeutic targets is limited. A ceiling of benefit has been reached by mechanical optimisation of rotator cuff repair and thus, in order to improve healing rates, a biological solution is required. This review focuses on the strategies to biologically augment rotator cuff disorders with an emphasis on rotator cuff repair. Leucocyte rich platelet rich plasma has been shown to improve healing rates without clinically relevant improvements in outcome scores. Similarly, improved healing rates have also been reported with bone marrow stimulation and in long-term follow-up with bone marrow concentrate. Extracellular matrix (ECM) and synthetic scaffolds can increase healing through mechanical and or biological augmentation. A potential third category of scaffold is bio-inductive and has no mechanical support. Studies involving various scaffolds have shown promising results for augmentation of large to massive tears and is likely to be most beneficial when tendon quality is poor, however level I evidence is limited.

Possible Roles of Vitamin D in Bone Grafting

Bone grafting is one of the most commonly used options to treat large bone defects. Evidence has shown that vitamin D may affect osseointegration, a major component for successful bone grafting. In vitro studies have proved that implants coated with activated vitamin D stimulate bone production and reduce bone resorption around implants. Animal studies have noticed that oral administration of vitamin D may stimulate bone formation as well as strengthen and support the interaction between bone and implants. Vitamin D insufficiency may affect negatively the cortical peri-implant bone formation, suggesting a negative effect in graft incorporation. Few clinical studies have observed that vitamin D administration enhanced graft incorporation and bone formation, while severe vitamin D deficiency is associated with failed implant osseointegration. Even though there are encouraging results of vitamin D supplementation on graft incorporation in animal studies, the use of vitamin D as an adjuvant in bone grafting procedures cannot be fully supported at the moment. However, there is theoretical support in the use of vitamin D after surgery and the use of bone grafts to support the bone structure, relieve pain and increase graft absorption. Further experimental and clinical studies are required to support the administration of vitamin D and its analogues in such cases.

Osteoporosis Screening Is Often Indicated but Overlooked Prior to Rotator Cuff Repair

Purpose

To (1) report the percentage of patients undergoing rotator cuff repair (RCR) who were appropriately screened with dual-energy X-ray absorptiometry testing prior to surgery, if indicated, and (2) determine the percentage of patients properly prescribed osteoporosis medications within 6 months of surgery.

Methods

Consecutive patients aged 50 years or older who underwent elective RCR at a single tertiary-care center over a 1-year period were reviewed. Fracture risk was estimated using the Fracture Risk Assessment Tool (FRAX) with and without bone mineral density. The U.S. National Osteoporosis Foundation (NOF) criteria for screening and treatment were applied. Patients with acute fractures or revision surgery were excluded.

Results

Of the 218 patients included, 129 were women (58.1%). The mean age was 61.5 ± 7.2 years. One hundred thirty-one RCRs (60.1%) occurred within 3 months of injury. A total of 69 patients (31.7%) met the NOF criteria for bone mineral density screening. Of these patients, 23 (33.3%) were appropriately screened with a dual-energy X-ray absorptiometry scan. Primary care providers initiated bone health assessment in 18 of the 23 appropriately screened patients, with orthopaedic providers initiating the workup in 3 patients (13.0%). Thirty-two patients (14.7%) met the NOF criteria for pharmacologic management of osteoporosis. Of these patients, 5 (15.6%) were treated. Patients meeting the medication criteria were older (69.1 ± 7.7 years vs 60.2 ± 6.3 years, P < .001), had a lower body mass index (28.8 ± 6.1 vs 31.5 ± 6.5, P = .028), and had chronic rotator cuff tears (P = .015).

Conclusions

Patients aged 50 years or older undergoing RCR are often not appropriately screened for osteoporosis. Even when appropriately screened, only 15.6% of patients meeting the indications for pharmacologic intervention for bone health optimization were prescribed appropriate medications. Although bone health optimization may or may not affect surgical timing, patient encounters related to rotator cuff tears can be used as an opportunity for providers to initiate osteoporosis screening and treatment protocols.

Level of Evidence

Level IV, therapeutic case series.

Proximal muscle strength as a predictor of vitamin D insufficiency in elderly

OBJECTIVES

This study aims to evaluate the association of serum vitamin D level with proximal muscle strength, tone, elasticity, and stiffness in elderly.

PATIENTS AND METHODS

Between September 2017 and January 2018, a total of 109 participants (21 males, 88 females; mean age: 71.2±4.6 years; range, 65 to 85 years) were included in the study. The proximal muscle strength was evaluated by MicroFET® 3 device. The muscle tone, elasticity, and stiffness were measured using the MyotonPRO® digital palpation device. Serum 25-hydroxyvitamin D [25(OH)D] level was tested by high-performance liquid chromatography. A receiver operating characteristic (ROC) curve was performed to evaluate the potential role of MicroFET® 3-measured proximal muscle strength in the quantification of vitamin D status.

RESULTS

Vitamin D sufficient participants had a higher proximal muscle strength (p<0.001). Quadriceps and hamstring elasticity at the non-dominant site were significantly higher in vitamin D sufficient group (p<0.05). The ROC analysis indicated that the deltoid muscle strength had the potential of determining vitamin D insufficiency with moderate accuracy (area under the curve=0.744; 95% confidence interval: 0.643-0.845; p<0.001).

CONCLUSION

Proximal muscle strength, elasticity, and physical performance are associated with vitamin D status. Proximal muscle strength measured by a hand-held dynamometer can be used as a predictor of hypovitaminosis D in elderly.

Vitamin D deficiency and total shoulder arthroplasty complications

INTRODUCTION

The primary objective of this study was to examine the relationship between vitamin D deficiency and implant-related and medical complications following total shoulder arthroplasty.

METHODS

Using the PearlDiver database, patients who underwent total shoulder arthroplasty from 2005 to 2016 with vitamin D deficiency were identified. These were compared to a 3:1 control group matched by age, sex, and presence of a concomitant osteoporosis diagnosis. Primary outcome measures were implant-related complications (loosening, periprosthetic fracture, periprosthetic joint infection, and revision total shoulder arthroplasty) in addition to medical complications within 90 days of surgery. A multivariable logistic regression analysis was utilized to control for patient demographics and comorbidities.

RESULTS

One thousand and six hundred and seventy-four patients with vitamin D deficiency were identified and compared to 5022 controls. There was a significantly higher rate of revision total shoulder arthroplasty in the vitamin D deficient patients compared to controls (2.3% versus 0.8%, odds ratio 3.3, p < 0.0001). After controlling for confounding variables, there were no significant differences in any of the remaining implant-related or medical complications with the exception of higher rates of urinary tract infections in patients with vitamin D deficiency.

CONCLUSIONS

Vitamin D deficiency is associated with a higher rate of all-cause revision total shoulder arthroplasty but not medical complications compared to controls.Level of evidence: Level III case control study.

Prevalence of and Risk Factors for Hypovitaminosis D in Patients with Rotator Cuff Tears

Backgroud

It has been reported that vitamin D may play an important role in rotator cuff tears. However, there has been limited information about the prevalence of and risk factors for hypovitaminosis D in patients with rotator cuff tears. Therefore, the purpose of current study was to investigate the prevalence of and risk factors for hypovitaminosis D in patients with rotator cuff tears.

Methods

One hundred seventy-six patients (age, 61.9 ± 8.90 years) who underwent arthroscopic rotator cuff repair for a full-thickness tear were enrolled in this retrospective study. Preoperative serum vitamin D levels (25-hydroxyvitamin D) were measured. Hypovitaminosis D was defined as a serum concentration of 25-hydroxyvitamin D < 20 ng/mL. We investigated whether age, sex, height, weight, body mass index, bone mineral density, alcohol consumption, smoking status, and outdoor occupation were associated with hypovitaminosis D.

Results

The prevalence of hypovitaminosis D in patients with rotator cuff tears was 44.3% (78/176). The mean serum concentration of 25-hydroxyvitamin D of total patients was 24.7 ± 13.7 ng/mL. A higher serum level of vitamin D was significantly associated with older age (p < 0.001). Young age was an independent risk factor for hypovitaminosis D. The prevalence of hypovitaminosis D was also lower in patients with an outdoor occupation than in those with an indoor occupation (19.0% vs. 31.4%, p = 0.001).

Conclusions

The prevalence of hypovitaminosis D in patients with rotator cuff tears was 44.3%. Age had a significant positive correlation with the serum concentration of 25-hydroxyvitamin D. Young age and indoor working were independent risk factors for hypovitaminosis D in patients with rotator cuff tears. Therefore, the possibility of hypovitaminosis D should be considered for young and indoor working patients who have rotator cuff tears.

Application of Autogenous Urine-Derived Stem Cell Sheet Enhances Rotator Cuff Healing in a Canine Model

BACKGROUND

A repaired rotator cuff (RC) often heals with interposed scar tissue, making repairs prone to failure. Urine-derived stem cells (USCs), with robust proliferation ability and multilineage differentiation, can be isolated from urine, avoiding invasive and painful surgical procedures for harvesting the cells. These advantages make it a novel cell source for autologous transplantation to enhance RC healing.

HYPOTHESIS

Implantation of an autogenous USC sheet to the injury site will enhance RC healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

USCs isolated from urine were cultured using ascorbic acid and transforming growth factor β3 to form a cell sheet. Sixteen male mature beagles underwent bilateral shoulder surgery. The right shoulder underwent infraspinatus tendon (IT) insertion detachment and repair only, and the other was subjected to IT insertion detachment and repair, followed by autogenous USC sheet implantation. Among the animals, 3 received a Dil (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate)- labeled USC sheet implant in the right shoulder and were sacrificed at postoperative 6 weeks for cell tracking. The other animals were sacrificed at postoperative 12 weeks, and the IT-humerus complexes were harvested for gross observation, micro-computed tomography evaluation and histological analysis (n = 5), and mechanical testing (n = 8). Additionally, 13 unpaired canine cadaveric shoulders were included as native controls.

RESULTS

Micro-computed tomography analysis showed that the USC sheet group had a significant increase in bone volume/total volume and trabecular thickness at the RC healing site when compared with the control group (P < .05 for all). Histologically, the Dil-labeled USC sheet was still visible at the RC healing site, which suggested that the implanted USCs remained viable at postoperative 6 weeks. Meanwhile, the healing interface in the USC sheet group regenerated significantly more enthesis-like tissue than did that of the control group (P < .05). Additionally, the healing interface in the USC sheet group presented a larger fibrocartilage area, more proteoglycan deposition, and higher collagen birefringence than did that of the control group (P < .05 for all). Biomechanically, the USC sheet group showed significantly higher failure load and stiffness versus the control group (P < .05 for all).

CONCLUSION

A USC sheet was able to enhance RC healing in a canine model.

CLINICAL RELEVANCE

The findings of the study showed that USC sheet implantation could serve as a practical application for RC healing.

Vitamin D and the athlete-patient: state of the art

Vitamin D deficiency is common in athletes. The conventional measurement of vitamin D levels provides a general indicator of body stores. However, there are nuances in its interpretation as values of 25(OH)D do not correlate absolutely with the amount of 'bioavailable' vitamin to the cells. Vitamin D should be regarded as a hormone and influences between 5% and 10% of our total genome. Determining the precise effect of the vitamin, isolated from the actions of other cofactors, is not straightforward and restricts our complete understanding of all of its actions. Deficiency has harmful effects on not only bone and muscle but also wider areas, including immunity and respiratory and neurological activities. More caution should be applied regarding the ability of supranormal vitamin D levels to elevate athletic performance. Hopefully, future research will shed more light on optimal levels of vitamin D and supplementation regimes, and improved understanding of its intracellular control of our genetic mechanisms and how extrinsic influences modify its activity.

Pleiotropic actions of Vitamin D in composite musculoskeletal trauma

Composite tissue injuries are the result of high energy impacts caused by motor vehicle accidents, gunshot wounds or blasts. These are highly traumatic injuries characterized by wide-spread, penetrating wounds affecting the entire musculoskeletal system, and are generally defined by frank volumetric muscle loss with concomitant segmental bone defects. At the tissue level, the breadth of damage to multiple tissue systems, and potential for infection from penetration, have been shown to lead to an exaggerated, often chronic inflammatory response with subsequent dysregulation of normal musculoskeletal healing mechanisms. Aside from the direct effects of inflammation on myogenesis and osteogenesis, frank muscle loss has been shown to directly impair fracture union and ultimately contribute to failed wound regeneration. Care for these injuries requires extensive surgical intervention and acute care strategies. However, often these interventions do not adequately mitigate inflammation or promote proper musculoskeletal injury repair and force amputation of the limb. Therefore, identification of factors that can promote tissue regeneration and mitigate inflammation could be key to restoring wound healing after composite tissue injury. One such factor that may directly affect both inflammation and tissue regeneration in response to these multi-tissue injuries may be Vitamin D. Beyond traditional roles, the pleiotropic and localized actions of Vitamin D are increasingly being recognized in most aspects of wound healing in complex tissue injuries - e.g., regulation of inflammation, myogenesis, fracture callus mineralization and remodeling. Conversely, pre-existing Vitamin D deficiency leads to musculoskeletal dysfunction, increased fracture risk or fracture non-unions, decreased strength/function and reduced capacity to heal wounds through increased inflammation. This Vitamin D deficient state requires acute supplementation in order to quickly restore circulating levels to an optimal level, thereby facilitating a robust wound healing response. Herein, the purpose of this review is to address the roles and critical functions of Vitamin D throughout the wound healing process. Findings from this review suggest that careful monitoring and/or supplementation of Vitamin D may be critical for wound regeneration in composite tissue injuries.

The Effect of Patient Characteristics and Comorbidities on the Rate of Revision Rotator Cuff Repair

PURPOSE

To describe the national rates of failed primary rotator cuff repair (RCR) requiring revision repair, using numerous patient characteristics previously defined in orthopaedic literature, including smoking history, diabetes mellitus (DM), hyperlipidemia (HLD), vitamin D deficiency, and osteoporosis to determine which factors independently affect the success of primary RCR.

METHODS

A combined public and private national insurance database was searched from 2007 to 2016 for all patients who underwent RCR. Current Procedural Terminology codes were used to identify RCRs. Laterality modifiers for the primary surgery were used to identify subsequent revision RCRs. All patients who did not have a linked laterality modifier for the RCR Current Procedural Terminology code were excluded from the study. Basic demographics were recorded. International Classification of Diseases Ninth Revision codes were used to identify patient characteristics including Charlson Comorbidity Index, smoking status, DM, obesity, HLD, vitamin D deficiency, and osteoporosis. Patient age categorized as <60, 60-69, 70-74, or 75+ years old. Dichotomous data were analyzed with χ² testing. Multivariable logistic regression was used to characterize independent associations with revision RCR.

RESULTS

Included in the study were 41,467 patients (41,844 shoulders, 52.7% male patients) who underwent primary arthroscopic RCR. Of all arthroscopic RCRs, 3072 patients (3463 shoulders, 53.5% male patients) underwent revision RCR (8.38%). In both primary and revision RCR, patients age 60 to 69 years were most prevalent, accounting for 38.4% and 37.6% of the cohorts, respectively. The average time from primary RCR to revision was 414.9 days (median 214.0 days). Increasing age and male sex (odds ratio [OR] 1.10, P = .019, 95% confidence interval [CI] 1.02-1.19) were significantly predictive of revision RCR. Of the remaining patient characteristics, smoking most strongly predicted revision RCR (OR 1.36, P < .001, CI 1.23-1.49). Obesity (OR 1.32, P < .001, CI 1.21-1.43), hyperlipidemia (OR 1.09, P = .032, CI 1.01-1.18), and vitamin D deficiency (OR 1.18, P < .001, CI 1.08-1.28) also increased risk of revision RCR significantly. DM was found to be protective against revision surgery (OR 0.84, P < .001, CI 0.76-0.92). Overall comorbidity burden as measured by the Charlson Comorbidity Index was not predictive of revision RCR.

CONCLUSIONS

Smoking, obesity, vitamin D deficiency, and HLD are shown to be independent risk factors for failure of primary RCR requiring revision RCR. However, despite the suggestions of previous studies, DM, osteoporosis, and overall comorbidity burden did not demonstrate independent associations in this study.

LEVEL OF EVIDENCE

IV, Case Series.

Low vitamin D levels in post-menopausal women are associated with complex regional pain syndrome type I in surgically treated distal radius fractures

BACKGROUND

Complex regional pain syndrome type I (CRPS I) is a chronic devastating condition and a relatively common complication of distal radius fractures (DRF). The purpose of this study was to investigate the relationship of vitamin D levels in surgically treated post-menopausal women with CRPS I occurrence in DRF.

METHODS

From February 2016 to March 2017, 158 surgically treated post-menopausal patients with DRF were enrolled. Exclusion criteria were (1) patients who had been taking vitamin D or osteoporosis medication at the time of injury; (2) patients with medical factors that may affect vitamin D levels; (3) patients who were reluctant to enroll in the study; and (4) patient with additional fractures, ligamentous injuries, or neuropathy. A total of 107 patients were available for final analysis. We compared the serum vitamin D levels in post-menopausal women with DRF with CRPS I (group 1) and without CRPS I (group 2). Bone mineral density (BMD) of the femur and spine, osteocalcin, alkaline phosphatase (ALP), body mass index (BMI) were also measured.

RESULTS

The average age at the time of surgery was 66.5 years (range, 39-86 years). The mean follow-up period was 16.3 months after surgery. Among the 107 surgically treated DRF patients, 19 (18%) met the Budapest criteria for CRPS I during the follow-up period. The mean serum vitamin D level in group 1 (15.2 ng/ml) was significantly lower than that in group 2 (20.5 ng/ml, p = 0.027). The mean values of osteocalcin, ALP, BMI, and BMD were not significantly different between the groups.

CONCLUSION

Lower vitamin D levels in post-menopausal women can increase CRPS I occurrence in distal radius fractures.

Encapsulation of vitamin D3 in gum arabic to enhance bioavailability and stability for beverage applications

Delivery of vitamin D₃ (VD₃ ) in foods should exhibit desirable physicochemical characteristics and improves absorption. In this study, gum arabic (GA) was investigated as a VD₃ carrier to encapsulate VD₃ . VD₃ dissolved in 5 mL ethanol corresponding to 0.3 to 6.0% mass of GA, was blended in 5.0% w/v GA solution, followed by freeze drying. The encapsulation efficiency decreased while loading capacity increased with an increased amount of VD₃ . At the highest VD₃ level, the loading capacity (3.47%) was the highest, and the encapsulation efficiency (61.24%) was satisfactory, and the treatment was further studied. The magnitude of negative zeta-potential increased from 3.1 to 31.0 mV at pH 2.0 to 7.4. During the 100-day storage at 3 °C of capsules reconstituted at pH 2.0 to 7.4, the hydrodynamic diameter decreased at all pH conditions, most evident for reduction to 81.3 nm at pH 7.4, and no precipitation was observed, indicating the significance of steric repulsion on capsule stability. Bioaccessibility of VD₃ in capsules (95.76%) was significantly higher than the nonencapsulated VD₃ (68.98%). The in vivo pharmacokinetic study in Sprague-Dawley rats after a single-dose of 300 µg VD₃ showed the area-under-curve of serum 25(OHD) level in 48 hr of the encapsulation treatment was 4.32-fold of the nonencapsulated VD₃ and more than twice higher than the VD₃ -GA physical mixture. During 2-week supplementation of 60 µg VD₃ /d, rats receiving capsules or physical mixture had 25(OH)D levels of at least 81 ng/mL higher than that of the nonencapsulated VD₃ group. The studied encapsulation system holds great potential as a value-added ingredient to supplement VD₃ in beverages with a wide pH range. PRACTICAL APPLICATION: The findings of this study demonstrated the improved dispersion stability and absorption of vitamin D₃ after encapsulation in gum arabic. The capsules exhibited good dispersion stability across a pH range between 2.0 and 7.4, showing potential application in beverages. Furthermore, the enhanced absorption of VD₃ after encapsulation highlights the nutritional benefits of the studied encapsulation system.

Factors Influencing the Reparability and Healing Rates of Rotator Cuff Tears

PURPOSE OF THE REVIEW

To discuss tear- and patient-related factors that influence the healing potential of rotator cuff tears and to clarify the terminology surrounding this topic.

RECENT FINDINGS

Over the last few years, further insight has been gained regarding rotator cuff tear features that are associated with poor healing rates after rotator cuff repair. Some of these features have been incorporated in prediction models developed to accurately predict rotator cuff healing rates utilizing preoperative risk factors weighted by importance. Rotator cuff tears may be considered functionally irreparable based on their size, chronicity, absence of adequate tendon length, atrophy, and fatty infiltration. Furthermore, advanced age, use of tobacco products, diabetes, and other patient-related factors may impair tendon healing. Careful analysis and discussion of all these factors with patients is essential to determine if surgical repair of a rotator cuff tear should be recommended, or if it is best to proceed with one of the several salvage procedures reviewed in this topical collection, including augmentation of the repair, superior capsular reconstruction, tendon transfers, and other.

Zoledronic Acid Substantially Improves Bone Microarchitecture and Biomechanical Properties After Rotator Cuff Repair in a Rodent Chronic Defect Model

BACKGROUND

Bone mineral density at the humeral head is reduced in patients with chronic rotator cuff tears. Bone loss in the humeral head is associated with repair failure after rotator cuff reconstruction. Bisphosphonates (eg, zoledronic acid) increase bone mineral density.

HYPOTHESIS

Zoledronic acid improves bone mineral density of the humeral head and biomechanical properties of the enthesis after reconstruction of chronic rotator cuff tears in rats.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 male Sprague-Dawley rats underwent unilateral (left) supraspinatus tenotomy with delayed transosseous rotator cuff reconstruction after 3 weeks. All rats were sacrificed 8 weeks after rotator cuff repair. Animals were randomly assigned to 1 of 2 groups. At 1 day after rotator cuff reconstruction, the intervention group was treated with a single subcutaneous dose of zoledronic acid at 100 µg/kg bodyweight, and the control group received 1 mL of subcutaneous saline solution. In 12 animals of each group, micro-computed tomography scans of both shoulders were performed as well as biomechanical testing of the supraspinatus enthesis of both sides. In 4 animals of each group, histological analyses were conducted.

RESULTS

In the intervention group, bone volume fraction (bone volume/total volume [BV/TV]) of the operated side was higher at the lateral humeral head (P = .005) and the medial humeral head (P = .010) compared with the control group. Trabecular number on the operated side was higher at the lateral humeral head (P = .004) and the medial humeral head (P = .001) in the intervention group. Maximum load to failure rates on the operated side were higher in the intervention group (P < .001). Cortical thickness positively correlated with higher maximum load to failure rates in the intervention group (r = 0.69; P = .026). Histological assessment revealed increased bone formation in the intervention group.

CONCLUSION

Single-dose therapy of zoledronic acid provided an improvement of bone microarchitecture at the humeral head as well as an increase of maximum load to failure rates after transosseous reconstruction of chronic rotator cuff lesions in rats.

CLINICAL RELEVANCE

Zoledronic acid improves bone microarchitecture as well as biomechanical properties after reconstruction of chronic rotator cuff tears in rodents. These results need to be verified in clinical investigations.

Paternal Resistance Training Modulates Calcaneal Tendon Proteome in the Offspring Exposed to High-Fat Diet

The increase in high-energy dietary intakes is a well-known risk factor for many diseases, and can also negatively impact the tendon. Ancestral lifestyle can mitigate the metabolic harmful effects of offspring exposed to high-fat diet (HF). However, the influence of paternal exercise on molecular pathways associated to offspring tendon remodeling remains to be determined. We investigated the effects of 8 weeks of paternal resistance training (RT) on offspring tendon proteome exposed to standard diet or HF diet. Wistar rats were randomly divided into two groups: sedentary fathers and trained fathers (8 weeks, three times per week, with 8–12 dynamic movements per climb in a stair climbing apparatus). The offspring were obtained by mating with sedentary females. Upon weaning, male offspring were divided into four groups (five animals per group): offspring from sedentary fathers were exposed either to control diet (SFO-C), or to high-fat diet (SFO-HF); offspring from trained fathers were exposed to control diet (TFO-C) or to a high-fat diet (TFO-HF). The Nano-LC-MS/MS analysis revealed 383 regulated proteins among offspring groups. HF diet induced a decrease of abundance in tendon proteins related to extracellular matrix organization, transport, immune response and translation. On the other hand, the changes in the offspring tendon proteome in response to paternal RT were more pronounced when the offspring were exposed to HF diet, resulting in positive regulation of proteins essential for the maintenance of tendon integrity. Most of the modulated proteins are associated to biological pathways related to tendon protection and damage recovery, such as extracellular matrix organization and transport. The present study demonstrated that the father’s lifestyle could be crucial for tendon homeostasis in the first generation. Our results provide important insights into the molecular mechanisms involved in paternal intergenerational effects and potential protective outcomes of paternal RT.

The role of biologic agents in the management of common shoulder pathologies: current state and future directions

The field of orthopedic surgery has seen a rapid increase in the use of various biologic agents for the treatment of common musculoskeletal injuries. Most biologic agents attempt to harness or mimic naturally occurring growth factors, cytokines, and anti-inflammatory mediators to improve tissue healing and recovery. The most commonly used biologic agents are platelet-rich plasma and cells derived from bone marrow aspirate and adipose tissue. These agents have become increasingly popular despite a relative dearth of clinical data to support their use. Much confusion exists among patients and physicians in determining the role of these agents in treating common shoulder pathologies, such as glenohumeral osteoarthritis, rotator cuff tears, and tendinopathy. This article reviews the basic science and clinical evidence for the most commonly used biologic agents in the management of common shoulder pathology.

Restoration of Cellular Proliferation and Characteristics of Human Tenocytes by Vitamin D

Vitamin D (Vit D) increases calcium absorption in the intestine after binding to the Vit D receptor (VDR). The VDR has also been identified in muscle cells. Vit D supplementation resulted in improved muscle strength. However, there is a paucity of studies of the role of Vit D on tenocytes. We investigated the effects of Vit D on damaged tenocytes. Human tenocytes were treated with dexamethasone (Dex) to induce cell injury. Expression of the tenocyte-related markers tenomodulin (Tnmd), tenascin C (Tnc), scleraxis (Scx), mohawk (Mkx), and collagen (Col) 1 and 3 were measured. Then, tenocytes were cotreated with Vit D. 1-α-Hydroxylase and VDR were explored in tenocytes. With 10 μM Dex, the growth of tenocytes was significantly inhibited, and the gene expression of Tnmd, Tnc, Scx, Mkx, Col 1 and 3 also decreased. When tenocytes were cotreated with Vit D, cell proliferation recovered in a dose-dependent manner, and the expression of TNMD and Col 1 improved. When studying the mechanisms of the effects of Vit D on tenocytes, reactive oxygen species produced by Dex decreased with Vit D, and the phosphorylation of extracellular signal-regulated kinase and p38 was stimulated by Vit D cotreatment. 1-α-Hydroxylase and VDR were found in tenocytes, indicating that the cells have the ability to use an inactive form of Vit D and interact with it. Vit D is known to perform diverse actions and its protective effects on tenocytes suggest its beneficial role in tendon in addition to muscle and bone. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2241-2248, 2019.

Human Tendon-Derived Collagen Hydrogel Significantly Improves Biomechanical Properties of the Tendon-Bone Interface in a Chronic Rotator Cuff Injury Model

PURPOSE

Poor healing of the tendon-bone interface (TBI) after rotator cuff (RTC) tears leads to high rates of recurrent tear following repair. Previously, we demonstrated that an injectable, thermoresponsive, type I collagen-rich, decellularized human tendon-derived hydrogel (tHG) improved healing in an acute rat Achilles tendon injury model. The purpose of this study was to investigate whether tHG enhances the biomechanical properties of the regenerated TBI in a rat model of chronic RTC injury and repair.

METHODS

Tendon hydrogel was prepared from chemically decellularized human cadaveric flexor tendons. Eight weeks after bilateral resection of supraspinatus tendons, repair of both shoulders was performed. One shoulder was treated with a transosseous suture (control group) and the other was treated with a transosseous suture plus tHG injection at the repair site (tHG group). Eight weeks after repair, the TBIs were evaluated biomechanically, histologically, and via micro-computed tomography (CT).

RESULTS

Biomechanical testing revealed a larger load to failure, higher stiffness, higher energy to failure, larger strain at failure, and higher toughness in the tHG group versus control. The area of new cartilage formation was significantly larger in the tHG group. Micro-CT revealed no significant difference between groups in bone morphometry at the supraspinatus tendon insertion, although the tHG group was superior to the control.

CONCLUSIONS

Injection of tHG at the RTC repair site enhanced biomechanical properties and increased fibrocartilage formation at the TBI in a chronic injury model.

CLINICAL RELEVANCE

Treatment of chronic RTC injuries with tHG at the time of surgical treatment may improve outcomes after surgical repair.

Tendinopathy: Pathophysiology, Therapeutic Options, and Role of Nutraceutics. A Narrative Literature Review

Tendinopathies are very common in general population and a huge number of tendon-related procedures take place annually worldwide, with significant socio-economic repercussions. Numerous treatment options are commonly used for tendon disorders. Besides pharmacological and physical therapy, nutrition could represent an additional tool for preventing and treating this complex pathology that deserve a multidisciplinary approach. In recent years, nutraceutical products are growing up in popularity since these seem to favor the prevention and the healing processes of tendon injuries. This narrative literature review aims to summarize current understanding and the areas of ongoing research about the management of tendinopathies with the help of oral supplementation.

Preoperative Vitamin D Deficiency Is Associated With Higher Postoperative Complications in Arthroscopic Rotator Cuff Repair

INTRODUCTION

Rotator cuff tears are one of the most common injuries worldwide, yet it is difficult to predict which patients will have poor outcomes after arthroscopic rotator cuff repair (RCR). The purpose of this study was to identify an association between preoperative vitamin D (25D) levels and postoperative complications in arthroscopic RCR.

METHODS

From a national claims database, patients undergoing arthroscopic RCR with preoperative 25D levels were reviewed. Patients were stratified into 25D-sufficient (≥20 ng/dL) or 25D-deficient (<20 ng/dL) categories and examined for development of postoperative complications. Multivariate logistic regression was performed using age, sex, and Charlson Comorbidity Index (CCI) as covariates. From this, risk-adjusted odds ratios (ORs) were calculated comparing complications between the two groups.

RESULTS

One thousand eight hundred eighty-one patients with measured preoperative 25D levels were identified; 229 patients were 25D deficient (12.2%). After adjusting for age, sex, and Charlson Comorbidity Index, 25D-deficient patients had increased odds of revision RCR (OR 1.54, 95% confidence interval 1.21 to 1.97, P < 0.001) and stiffness requiring manipulation under anesthesia (OR 1.16, 95% confidence interval 1.03 to 2.03, P = 0.035).

CONCLUSIONS

Vitamin D deficiency is associated with a greater risk of postoperative surgical complications after arthroscopic RCR and may be a modifiable risk factor. Further investigation on preoperative vitamin D repletion is warranted.

Surgical Considerations in Managing Osteoporosis, Osteopenia, and Vitamin D Deficiency During Arthroscopic Rotator Cuff Repair

Osteopenia and osteoporosis are common in older adults and are associated with increased risk of fragility fractures. Vitamin D deficiency caused by chronic disease, poor nutrition, and inadequate sun exposure affects bone quality. Chronic rotator cuff tears can deteriorate the bone mineral density of the greater tuberosity and have been linked to reduced anchor pullout strength and high re-tear rate after repair especially in older patients with larger tear size. This article summarizes the current evidence on rotator cuff tear and bone quality and provides treatment strategies for rotator cuff repair in patients with poor bone quality.

Current concepts in vitamin D and orthopaedic surgery

INTRODUCTION

Vitamin D plays an important role in the musculoskeletal system of the human body. Here, we review the most current literature on vitamin D as it relates to orthopaedic surgery and the musculoskeletal system, focusing largely on non-fracture applications.

MATERIALS AND METHODS

A literature review was performed on the basic science of vitamin D metabolism, epidemiology of vitamin D levels, role of vitamin D within the musculoskeletal system, and the correlation of vitamin D with injuries and orthopaedic surgical outcomes.

RESULTS

The existing literature suggests vitamin D plays multiple roles in the musculoskeletal system. Recent research has shed light on the importance of vitamin D in the setting of soft tissue healing and recovery in addition to affecting postoperative outcomes after common orthopaedic procedures.

CONCLUSIONS

Given the widespread prevalence of vitamin D deficiency, orthopaedic surgeons should be aware of the current evidence regarding clinical implications in patients with musculoskeletal complaints.

Perioperative Serum 25-Hydroxyvitamin D Levels Affect Revision Surgery Rates After Arthroscopic Rotator Cuff Repair

PURPOSE

To examine any association between perioperative serum 25-hydroxyvitamin D levels and failure of arthroscopic rotator cuff repair (RCR) requiring revision surgery.

METHODS

Using a private-payer national insurance database, patients who underwent arthroscopic RCR with perioperative serum 25-hydroxyvitamin D levels recorded were included. Patients were stratified into groups of (1) serum 25-hydroxyvitamin D deficiency (<20 ng/mL), (2) insufficiency (20-30 ng/mL), or (3) sufficient (>30-<150 ng/mL). The primary outcome measure was ipsilateral revision rotator cuff surgery, including revision repair, debridement, or reverse shoulder arthroplasty. A multivariable logistic regression analysis was used to control for patient demographics and comorbidities during comparisons.

RESULTS

A total of 982 patients were included in the study. The rate of revision rotator cuff surgery was significantly higher in patients in the serum 25-hydroxyvitamin D-deficient group (5.88%) compared with the serum 25-hydroxyvitamin D-sufficient control group (3.7%) (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.6-5.8; P = .007). Patients with serum 25-hydroxyvitamin D deficiency (5.88%) also had a significantly higher incidence of revision surgery compared with patients with serum 25-hydroxyvitamin D insufficiency (OR, 2.4; 95% CI, 1.5-3.9; P = .011). There was no significant difference in the incidence of revision surgery in the serum 25-hydroxyvitamin D-insufficient group (4.97%) compared with the serum 25-hydroxyvitamin D-sufficient control group (3.7%) (OR, 1.4; 95% CI, 0.8-2.3; P = .250). The absolute risk reduction of revision surgery for 25-hydroxyvitamin D-deficient patients compared with controls was 2.2%, corresponding to a number needed to treat to avoid 1 revision surgery of 46 patients, relative risk reduction = 0.59.

CONCLUSIONS

Although the present study found a significant statistical association between serum 25-hydroxyvitamin D deficiency and insufficiency and the rate of revision rotator cuff surgery after primary arthroscopic RCR, the absolute differences of these revision rates are minimal and are accompanied with overlapping confidence intervals limiting the clinical significance of these findings.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

High prevalence of vitamin D insufficiency in professional handball athletes

OBJECTIVES

Vitamin D affects multiple body functions through the regulation of gene expression. In sports medicine, its influence on musculoskeletal health and performance is of particular interest. Vitamin D insufficiency might decrease athletic performance and increase the risk of musculoskeletal injuries. Several studies have demonstrated vitamin D deficiency in professional athletes; however, the prevalence of vitamin D insufficiency in professional handball players is yet unknown.

METHODS

The study was planned as a prospective, non-interventional study. We examined 70 male elite handball athletes (first league) in a pre-competition medical assessment in July. Age, height, weight, body mass index, 25-OH vitamin D, calcium, and parathyroid hormone were evaluated, and a sun exposure score was calculated. Players were then divided into two groups of vitamin D levels: insufficient (<30 ng/mL) and sufficient (≥30 ng/mL).

RESULTS

The mean 25-OH vitamin D level of the 70 players was 33.5 ± 10.9 ng/mL (median 32.2, IQR 26.5-38.9 ng/mL). Thirty-nine (55.7%) had sufficient and 31 (44.3%) insufficient levels. Athletes with sufficient vitamin D levels had significantly lower parathyroid hormone levels than athletes with insufficiency (24.9 ± 12.1 vs. 33.5 ± 15.1 ng/mL, p = 0.02). All other parameters evaluated demonstrated no significant difference between the two groups.

CONCLUSION

Vitamin D insufficiency is a common finding in professional handball athletes even in summer, which might negatively affect physical performance. Furthermore, it might lead to an increased risk of musculoskeletal injuries and infections. This should be evaluated in further studies.

Orthobiologics for Bone Healing

Orthobiologics are a group of biological materials and substrates that promote bone, ligament, muscle, and tendon healing. These substances include bone autograft, bone allograft, demineralized bone matrix, bone graft substitutes, bone marrow aspirate concentrate, platelet-rich plasma, bone morphogenetic proteins, platelet-derived growth factor, parathyroid hormone, and vitamin D and calcium. Properties of orthobiologics in bone healing include osteoconduction, osteoinduction, and osteogenesis. This article discusses the important properties of orthobiologics in bone healing, many of the orthobiologics currently available for bone healing, the related literature, their current clinical uses in sports medicine, and systemic factors that inhibit bone healing.

An asymmetric chitosan scaffold for tendon tissue engineering: In vitro and in vivo evaluation with rat tendon stem/progenitor cells

The poor healing capacity and typically incomplete regeneration of injured tendons has made tendon repair as a primary clinical concern. Several methods for repairing injured tendons have been developed in the last decade. Tendon regeneration using current tissue engineering techniques requires advanced biomaterials to satisfy both microstructural and mechanical criteria. In this study, a novel chitosan (CS)-based scaffold with asymmetric structure was fabricated using a self-deposition technique. The fabricated scaffolds were assessed with regard to the microstructural and mechanical demands of cell ingrowth and the prevention of peritendinous adhesion. In vitro studies showed that rat tendon stem/progenitor cells (TSPCs) seeded onto the CS scaffold displayed higher levels of tenogenic specific genes expression and protein production. Four and six weeks after the implantation of CS scaffolds on full-site Achilles tendon defects, in vivo tendon repair was evaluated by histology, immunohistochemistry, immunofluorescence, and mechanical measurements. The production of collagen I (COL1) and collagen III (COL3) demonstrated that the CS scaffolds were capable of inducing conspicuous tenogenic differentiation, higher tenomodulin (TNMD) production, and superior phenotypic maturity, compared with the empty defect group. The introduction of TSPCs into the CS scaffold resulted in a synergistic effect on tendon regeneration and yielded better-aligned collagen fibers with elongated, spindle-shaped cells. These findings indicated that the application of TSPC-seeded CS scaffolds would be a feasible approach for tendon repair.

STATEMENT OF SIGNIFICANCE

The poor healing capacity of injured tendons and inevitable peritendinous adhesion has made tendon regeneration a clinical priority. In this study, an asymmetric chitosan scaffold was developed to encapsulate rat tendon stem/progenitor cells (TSPCs), which could induce higher levels of tenogenic specific genes and protein expression. Remarkably, the introduction of TSPCs into the asymmetric chitosan scaffold generated a synergistic effect on in vivo tendon regeneration and lead to better-aligned collagen fibers compared with asymmetric chitosan scaffold alone. This work can provide new guidelines for the structure and property design of cell-seeded scaffolds for tendon regeneration.

Biomechanic and histologic analysis of fibroblastic effects of tendon-to-bone healing by transforming growth factor β1 (TGF-β1) in rotator cuff tears

PURPOSE

To evaluate the effect of transforming growth factor β1 (TGF-β1) on tendon-to-bone reconstruction of rotator cuff tears.

METHODS

Seventy-two rat supraspinatus tendons were transected and reconstructed in situ. At 8 and 16 weeks, specimens of three groups; that is control, L-dose (low dose), and H-dose (high dose) were harvested and underwent a biomechanical test to evaluate the maximum load and stiffness values. Histology sections of the tendon-to-bone interface were identified by hematoxylin-eosin or Masson trichrome stain. Collagen type III was observed by picric acid sirius red staining under polarized light. The level of insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF) was measured by the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

Collagen type III of the H-dose group had a significant difference in histology structure compared with the L-dose group (P<0.05). The maximum load and stiffness decreased significantly in the control group compared with the values of the L-dose and H-dose groups. The stiffness among the three groups differed significantly at the same postoperative time (P<0.05). Interestingly, progressive reestablishment of collagen type III affected tendon-to-bone healing significantly in the later stages.

CONCLUSION

The H-dose was associated with an increased collagen type III morphology stimulated by TGF-β1.

The biology of rotator cuff healing

Despite advances in surgical reconstruction of chronic rotator cuff (RC) tears leading to improved clinical outcomes, failure rates of 13-94% have been reported. Reasons for this rather high failure rate include compromised healing at the bone-tendon interface, as well as the musculo-tendinous changes that occur after RC tears, namely retraction and muscle atrophy, as well as fatty infiltration. Significant research efforts have focused on gaining a better understanding of these pathological changes in order to design effective therapeutic solutions. Biological augmentation, including the application of different growth factors, platelet concentrates, cells, scaffolds and various drugs, or a combination of the above have been studied. It is important to note that instead of a physiological enthesis, an abundance of scar tissue is formed. Even though cytokines have demonstrated the potential to improve rotator cuff healing in animal models, there is little information about the correct concentration and timing of the more than 1500 cytokines that interact during the healing process. There is only minimal evidence that platelet concentrates may lead to improvement in radiographic, but not clinical outcome. Using stem cells to biologically augment the reconstruction of the tears might have a great potential since these cells can differentiate into various cell types that are integral for healing. However, further studies are necessary to understand how to enhance the potential of these stem cells in a safe and efficient way. This article intends to give an overview of the biological augmentation options found in the literature.

The Effect of Purified Human Bone Marrow-Derived Mesenchymal Stem Cells on Rotator Cuff Tendon Healing in an Athymic Rat

PURPOSE

To evaluate the ability of purified human bone marrow-derived mesenchymal stem cells (MSCs) to augment healing of an acute small- to medium-sized rotator cuff repair in a small-animal model, evaluating the structure and composition of the healing tendon-bone interface with histologic and biomechanical analyses.

METHODS

Fifty-two athymic rats underwent unilateral detachment and transosseous repair of the supraspinatus tendon augmented with either fibrin glue (control group) or fibrin glue with 10⁶ human MSCs (experimental group) applied at the repair site. Flow cytometry verified the stem cell phenotype of the cells as CD73⁺, CD90⁺, CD105⁺, CD14^-, CD34^-, and CD45^-. Rats were killed at 2 and 4 weeks, with 10 from each group used for biomechanical testing and 3 for histologic analysis.

RESULTS

Safranin O staining identified increased fibrocartilage formation at the repair site at 2 weeks in the human MSC group (18.6% ± 2.9% vs 9.1% ± 1.6%, P = .026). Picrosirius staining identified decreased energy (36.88 ± 4.99 J vs 54.97 ± 8.33 J, P = .04) and increased coherence in the human MSC group (26.96% ± 15.32% vs 14.53% ± 4.10%, P = .05), indicating improved collagen orientation. Biomechanical testing showed a significant increase in failure load (11.5 ± 2.4 N vs 8.5 ± 2.4 N, P = .002) and stiffness (7.1 ± 1.2 N/mm vs 5.7 ± 2.1 N/mm, P < .001) in the experimental group compared with the control group at 2 weeks. These effects dissipated by 4 weeks, with no significant differences in fibrocartilage formation (35% ± 5.0% vs 26.6% ± 0.6%, P = .172) or biomechanical load to failure (24.6 ± 7.1 N vs 21.5 ± 4.1 N, P = .361) or stiffness (13.5 ± 3.1 N/mm vs 16.1 ± 5.6 N/mm, P = .384). All failures occurred at the bone-tendon interface.

CONCLUSIONS

Rotator cuff repair augmentation with purified human MSCs improved early histologic appearance and biomechanical strength of the repair at 2 weeks, although the effects dissipated by 4 weeks with no significant differences between groups.

CLINICAL RELEVANCE

Human MSCs may improve early rotator cuff healing during the first 2 weeks after repair.

Icariin Promotes Tendon-Bone Healing during Repair of Rotator Cuff Tears: A Biomechanical and Histological Study

To investigate whether the systematic administration of icariin (ICA) promotes tendon-bone healing after rotator cuff reconstruction in vivo, a total of 64 male Sprague Dawley rats were used in a rotator cuff injury model and underwent rotator cuff reconstruction (bone tunnel suture fixation). Rats from the ICA group (n = 32) were gavage-fed daily with ICA at 0.125 mg/g, while rats in the control group (n = 32) received saline only. Micro-computed tomography, biomechanical tests, serum ELISA (calcium; Ca, alkaline phosphatase; AP, osteocalcin; OCN) and histological examinations (Safranin O and Fast Green staining, type I, II and III collagen (Col1, Col2, and Col3), CD31, and vascular endothelial growth factor (VEGF)) were analyzed two and four weeks after surgery. In the ICA group, the serum levels of AP and OCN were higher than in the control group. More Col1-, Col2-, CD31-, and VEGF-positive cells, together with a greater degree of osteogenesis, were detected in the ICA group compared with the control group. During mechanical testing, the ICA group showed a significantly higher ultimate failure load than the control group at both two and four weeks. Our results indicate that the systematic administration of ICA could promote angiogenesis and tendon-bone healing after rotator cuff reconstruction, with superior mechanical strength compared with the controls. Treatment for rotator cuff injury using systematically-administered ICA could be a promising strategy.

Vitamin D and the immunomodulation of rotator cuff injury

Tendon-to-bone healing after rotator cuff repair surgery has a failure rate of 20%–94%. There has been a recent interest to determine the factors that act as determinants between successful and unsuccessful rotator cuff repair. Vitamin D level in patients is one of the factors that have been linked to bone and muscle proliferation and healing, and it may have an effect on tendon-to-bone healing. The purpose of this article is to critically review relevant published research that relates to the effect of vitamin D on rotator cuff tears and subsequent healing. A review of the literature was conducted to identify all studies that investigate the relationship between vitamin D and tendon healing, in addition to its mechanism of action. The data were then analyzed in order to summarize what is currently known about vitamin D, rotator cuff pathology, and tendon-to-bone healing. The activated metabolite of vitamin D, 1α,25-dihydroxyvitamin D₃, affects osteoblast proliferation and differentiation. Likewise, vitamin D plays a significant role in the tendon-to-bone healing process by increasing the bone mineral density and strengthening the skeletal muscles. The 1α,25-dihydroxyvitamin D₃ binds to vitamin D receptors on myocytes to stimulate growth and proliferation. The form of vitamin D produced by the liver, calcifediol, is a key initiator of the myocyte healing process by moving phosphate into myocytes, which improves function and metabolism. Investigation into the effect of vitamin D on tendons has been sparse, but limited studies have been promising. Matrix metalloproteinases play an active role in remodeling the extracellular matrix (ECM) of tendons, particularly deleterious remodeling of the collagen fibers. Also, the levels of transforming growth factor-β3 positively influence the success of the surgery for rotator cuff repair. In the tendon-to-bone healing process, vitamin D has been shown to successfully influence bone and muscle healing, but more research is needed to delve into the mechanisms of vitamin D as a factor in skeletal tendon health and healing.