Obesity Impairs Enthesis Healing After Rotator Cuff Repair in a Rat Model

Biomechanical properties of various rat rotator cuff repair techniques

While rat models are frequently used to study tendon healing, there is a lack of research comparing various rotator cuff repair methods in this animal model. Determining the most effective method to begin with is pivotal for biological studies focused on healing augmentation. No study to date has shown the superiority of one repair over the other for rotator cuff repair in a rat model. We performed a biomechanic study using a rat model to study the strength of four common grasping techniques. We assessed if the bone tunnel trajectory influenced the early biomechanics of the repair at postoperative day 0 (POD0). Sixty cadaveric rat shoulders were divided equally into 6 groups; 4 groups were allocated for the biomechanical strength testing based on either a (1) modified Mason Allen (MM), (2) modified Kessler loop (MK), (3) horizontal mattress (HM), or a (4) simple interrupted stitch (SS) technique. The remaining 2 groups were used to evaluate two tunneling angles: a transverse tunnel (TT) that was perpendicular to the long humeral axis, or a longitudinal tunnel (LT) that was 30◦ angle to the humerus. MM had the highest mean failure load, followed by MK, HM, and SS. Pairwise comparison revealed that MM was stronger than SS and HM (P = 0.025 and P = 0.026, respectively), although similar to the MK (P = 0.881). MM was stiffer than MK (P < 0.001), HM (P = 0.008), and SS (P < 0.001). The TT and LT had similar loads to failure and stiffness. Our study suggests that the MM technique provides a stronger and stiffer rotator cuff repair than the others.

Leptin promotes tendon stem/progenitor cell senescence through the AKT-mTOR signaling pathway

Dysregulated adipokine production is an influencing factor for the homeostatic imbalance of tendons. High levels of serum leptin may be a potential link between increasing adiposity and tendinopathy, while the detailed mechanistic explanation was not well-defined. In this study, we investigated the regulatory role of leptin in the tendon stem/progenitor cells (TSPCs) and the molecular mechanism within, and determined the effect of high levels of leptin on tendon recovery. We demonstrated that leptin reduced the viability of isolated rat TSPCs in a dose-dependent way, accompanied with increased transdifferentiation and altered gene expression of a series of extracellular matrix (ECM) enzymatic modulators. Also, we found that leptin could dose-dependently promote TSPCs senescence, while exhibiting limited effect in apoptotic or autophagic induction. Mechanistic study evidenced that leptin treatment increased the AKT/mTOR signaling activity and elevated the expression of leptin receptor (LEPR) in TSPCs, without marked change in MAPK or STAT5 activation. Further, we confirmed that rapamycin treatment, but not AKT inhibition, effectively reduced the leptin-promoted TSPCs senescence. In a rat model with Achilles wounding, exposure to leptin profoundly delayed tendon healing, which was effectively rescued with rapamycin treatment. Our results suggested that leptin could cause intrinsic cellular deficits in TSPCs and impede tendon repair through the AKT/mTOR signaling pathway. These findings evidenced for an important role of elevated leptin levels in the care of tendinopathy and tendon tears.

Preoperative handgrip strength can predict early postoperative shoulder function in patients undergoing arthroscopic rotator cuff repair

BACKGROUND

Rotator cuff tears (RCTs) are a common musculoskeletal disorder, and arthroscopic rotator cuff repair (ARCR) is widely performed for tendon repair. Handgrip strength correlates with rotator cuff function; however, whether preoperative grip strength can predict functional outcomes in patients undergoing ARCR remains unknown. This study aimed to investigate the correlation between preoperative grip strength and postoperative shoulder function following ARCR.

METHODS

A total of 52 patients with full-thickness repairable RCTs were prospectively enrolled. Baseline parameters, namely patient characteristics and intraoperative findings, were included for analysis. Postoperative shoulder functional outcomes were assessed using the Quick Disabilities of the Arm, Shoulder, and Hand (QDASH) questionnaire and Constant-Murley scores (CMSs). Patients were followed up and evaluated at three and six months after ARCR. The effects of baseline parameters on postoperative outcomes were measured using generalized estimating equations.

RESULTS

At three and six months postoperatively, all clinical outcomes evaluated exhibited significant improvement from baseline following ARCR. Within 6 months postoperatively, higher preoperative grip strength was significantly correlated with higher CMSs (β = 0.470, p = 0.022), whereas increased numbers of total suture anchors were significantly correlated with decreased CMSs (β =  - 4.361, p = 0.03). Higher body mass index was significantly correlated with higher postoperative QDASH scores (β = 1.561, p = 0.03) during follow-up.

CONCLUSIONS

Higher baseline grip strength predicts more favorable postoperative shoulder function following ARCR. A preoperative grip strength test in orthopedic clinics may serve as a predictor for postoperative shoulder functional recovery in patients undergoing ARCR.

The Influence of Obesity on Outcomes Following Arthroscopic Rotator Cuff Repair: A Systematic Review and Meta-Analysis of 118,331 Patients Internationally

Background

Given the rising prevalence of obesity, the number of patients with obesity undergoing arthroscopic rotator cuff repair (RCR) will likely increase; however, there have been mixed results in the existing literature with regard to the effect of elevated body mass index (BMI) on functional outcomes and complications.

Methods

The patient-reported outcome measures included the visual analog scale (VAS) pain score, the American Shoulder and Elbow Surgeons (ASES) score, range of motion, and adverse events.

Results

Fourteen studies (118,331 patients) were included. There were significant decreases in VAS pain scores for both patients with obesity (mean difference, -3.8 [95% confidence interval (CI), -3.9 to -3.7]; p < 0.001) and patients without obesity (mean difference, -3.2 [95% CI, -3.3 to -3.1]; p < 0.001). There were also significant increases in ASES scores for both patients with obesity (mean difference, 24.3 [95% CI, 22.5 to 26.1]; p < 0.001) and patients without obesity (mean difference, 24.3 [95% CI, 21.4 to 26.0]; p < 0.001). There were also significant increases in ASES scores for both patients with obesity (mean difference, 24.3 [95% CI, 22.5 to 26.1]; p < 0.001) and patients without obesity (mean difference, 24.3 [95% CI, 21.4 to 26.0]; p < 0.001). However, there were no significant differences in final VAS pain scores, ASES scores, or range of motion between the groups. The mean rates of complications were higher among patients with obesity (1.2% ± 1.7%) than among patients without obesity (0.59% ± 0.11%) (p < 0.0001), and the mean rates of postoperative admissions were also higher among patients with obesity (5.9%) than patients without obesity (3.7%) (p < 0.0001). Although the mean rates of reoperation were similar between groups (5.2% ± 2.8% compared with 5.2% ± 4.2%), the meta-analysis revealed lower odds of reoperation in patients without obesity (odds ratio [OR], 0.76 [95% CI, 0.71 to 0.82]).

Conclusions

No significant or clinically important differences in postoperative pain, ASES scores, or range of motion were found between patients with and without obesity following arthroscopic RCR. However, populations with obesity had higher rates of complications, postoperative admissions, and reoperation following arthroscopic RCR.

Level of Evidence

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Bi-lineage inducible and immunoregulatory electrospun fibers scaffolds for synchronous regeneration of tendon-to-bone interface

Facilitating regeneration of the tendon-to-bone interface can reduce the risk of postoperative retear after rotator cuff repair. Unfortunately, undesirable inflammatory responses following injury, difficulties in fibrocartilage regeneration, and bone loss in the surrounding area are major contributors to suboptimal tendon-bone healing. Thus, the development of biomaterials capable of regulating macrophage polarization to a favorable phenotype and promoting the synchronous regeneration of the tendon-to-bone interface is currently a top priority. Here, strontium-doped mesoporous bioglass nanoparticles (Sr-MBG) were synthesized through a modulated sol-gel method and Bi-lineage Inducible and Immunoregulatory Electrospun Fibers Scaffolds (BIIEFS) containing Sr-MBG were fabricated. The BIIEFS were biocompatible, showed sustained release of multiple types of bioactive ions, enhanced osteogenic and chondrogenic differentiation of mesenchymal stem cells (MSCs), and facilitated macrophage polarization towards the M2 phenotype in vitro. The implantation of BIIEFS at the torn rotator cuff resulted in greater numbers of M2 macrophages and the synchronous regeneration of tendon, fibrocartilage, and bone at the tendon-to-bone interface, leading to a significant improvement in the biomechanical strength of the supraspinatus tendon-humerus complexes. Our research offers a feasible strategy to fabricate immunoregulatory and multi-lineage inducible electrospun fibers scaffolds incorporating bioglass nanoparticles for the regeneration of soft-to-hard tissue interfaces.

A high-fat diet has negative effects on tendon resident cells in an in vivo rat model

BACKGROUND

Tendinopathy is a major complication of diet-induced obesity. However, the effects of a high-fat diet (HFD) on tendon have not been well characterised. We aimed to determine: [1] the impact of a HFD on tendon properties and gene expression; and [2] whether dietary transition to a control diet (CD) could restore normal tendon health.

METHODS

Sprague-Dawley rats were randomised into three groups from weaning and fed either a: CD, HFD or HFD for 12 weeks and then CD thereafter (HF-CD). Biomechanical, histological and structural evaluation of the Achilles tendon was performed at 17 and 27 weeks of age. Tail tenocytes were isolated with growth rate and collagen production determined. Tenocytes and activated THP-1 cells were exposed to conditioned media (CM) of visceral adipose tissue explants, and gene expression was analysed.

RESULTS

There were no differences in the biomechanical, histological or structural tendon properties between groups. However, tenocyte growth and collagen production were increased in the HFD group at 27 weeks. There was lower SOX-9 expression in the HFD and HF-CD groups at 17 weeks and higher expression of collagen-Iα1 and matrix metalloproteinase-13 in the HFD group at 27 weeks. THP-1 cells exposed to adipose tissue CM from animals fed a HFD or HF-CD had lower expression of Il-10 and higher expression of Il-1β.

CONCLUSIONS

In this rodent model, a HFD negatively altered tendon cell characteristics. Dietary intervention restored some gene expression changes; however, adipose tissue secretions from the HF-CD group promoted an increased inflammatory state in macrophages. These changes may predispose tendon to injury and adverse events later in life.

The Effects Of Obesity On 1 Year Functional Outcomes Following Arthroscopic Rotator Cuff Tear Repair

Background

The purpose of our study was to examine the impact that an increased body mass index (BMI) has on arthroscopic rotator cuff repair (aRCR) outcomes.

Methods

We identified a sample of 313 patients who underwent aRCR at our institution from 2017 to 2020. Patients were classified into cohorts by BMI: normal BMI (<25), overweight (25-30), and obese (≥30). Patient-Reported Outcomes Measurement Information System (PROMIS) scores (Pain Interference, Pain Intensity, and Upper Extremity) and Clinical Global Impressions scale rating of pain and functional improvement after surgery were obtained at 1 year postoperatively. The significance of the BMI category as a predictor for outcomes was evaluated using multiple linear and multivariable logistic regressions. Receiver operating characteristic curve analysis with Youden’s J-statistic was used to determine optimal BMI cutoff for predicting likelihood of achieving minimum clinically important difference (MCID) and substantial clinical benefit (SCB) on the Clinical Global Impressions scales.

Results

Obesity was a significant predictor of reduced preoperative-to-postoperative improvement in the PROMIS Upper Extremity score (P = .04). However, BMI was not predictive of other preoperative-to-postoperative differences in outcome scores or the size and number of cuff tendons torn (P > .05). Optimal BMI cutoffs were determined for pain MCID (40.8), pain SCB (26.8), function MCID (27.4), and function SCB (26.8), but all cutoffs had low correct classification rates (≤13%).

Discussion and Conclusion

Obesity was not found to be an independent risk factor for increased rotator cuff tear size or tendon involvement but was nonetheless associated with worse upper extremity function and pain after aRCR.