Muscle atrophy, fibrosis and fatty infiltration (FI) are commonly seen in rotator cuff tears (RCT), which are critical factors that directly determine the clinical outcomes for patients with this injury. Therefore, improving muscle quality after RCT is crucial in improving the clinical outcome of tendon repair. In recent years, it has been discovered that adults have functional beige/brown adipose tissue (BAT) which can secrete batokines to promote muscle growth. PRDM16, a PR-domain containing protein, was discovered with the ability to determine the brown fat cell fate and stimulate its development. Thus, the goal of this study is to discover the role of PRDM16 in improving muscle function after massive tendon tears using a transgenic mouse model with an elevated level of PRDM16 expression. Transgenic aP2 driven PRDM16 overexpression mice and C57BL/6J mice underwent unilateral supraspinatus (SS) tendon transection and suprascapular nerve transection (TTDN) as described previously (N=8 in each group). DigiGait was performed to evaluate forelimb function at 6 weeks post the TTDN injury. Bilateral SS muscles, interscapular brown fat, epididymal white fat, and inguinal beige fat were harvested for analysis. The expression of PRDM16 in adipose tissue was detected by Western Blot. Masson's trichome staining was conducted to evaluate the muscle fibrosis and Oil Red O staining was used to determine the fat infiltration. Muscle fiber type was determined by MHC expression via immunostaining. All data was presented in the form of mean±SD. T-test and two-way ANOVA analysis was performed to determine a statistically significant difference between groups. Significance was considered when P<0.05. Western blot data showed an increased expression of PRDM16 protein in both white and brown fat in PRDM16-overexpression mice compared to wild-type (WT) mice. Even though PRDM16 overexpression had no effect on increasing muscle weight, it significantly improved the forelimbs function with longer brake, stance and stride time, larger stride length and paw area in mice after RCT. Additionally, PRDM16 overexpression mice showed no difference in amount of fibrosis when compared to WT mice, however, they had significantly reduced area of fatty infiltration. These mice also exhibited abundant MHC-IIx fiber percentage in supraspinatus muscle after TTDN. Overexpression of PRDM16 significantly improved muscle function and reduced fatty infiltration after rotator cuff tears. Promoting BAT activity is beneficial in improving rotator cuff muscle quality and shoulder function after RCT.

Background: Rotator cuff (RC) tears are among the most common causes of shoulder dysfunction in sports medicine. Muscle atrophy and degeneration are important risk factors for RC tendon retearing and suboptimal recovery of shoulder function after tendon repair. Although blood flow restriction (BFR) can stimulate muscle regeneration after lower extremity trauma and anterior cruciate ligament reconstruction, the mechanisms that underlie BFR remain unknown, and its application to RC tears has not yet been explored. Hypothesis: The authors hypothesized that BFR induces transfer of mitochondria from intramuscular fibro-adipogenic progenitors (FAPs) to myocytes, enhances muscle regeneration, and improves shoulder function after RC injury. Study Design: Controlled laboratory study. Methods: To assess mitochondrial transfer after BFR, the authors used Prrx1-Cre/MitoTag reporter mice, in which FAP mitochondria are labeled. Mice underwent unilateral forelimb BFR, and supraspinatus (SS) muscles were collected at baseline and days 1, 2, 3, 5, and 7 for histology. To model massive RC tears, mice received unilateral SS and infraspinatus tendon transection with denervation (TT+DN) and then were randomized to a BFR (every 3 days) or control group. At 2 or 6 weeks after surgery, SS muscles were analyzed for mitochondrial transfer, fiber size, and fiber-type distribution. Additionally, forelimb gait and weightbearing were captured using the Blackbox system. Results: BFR was associated with increased FAP-mediated mitochondrial transfer in healthy SS muscle as early as 1 day after BFR treatment and lasted for up to 3 days after BFR. The authors observed an enhanced effect of BFR-induced FAP mitochondrial transfer in SS muscle after RC injury, compared with the control, at both 2 and 6 weeks after TT+DN. BFR-treated mice had significantly reduced muscle atrophy, fatty infiltration, and fibrosis after RC injury. They also observed a significant improvement in forepaw weightbearing ratio and ipsilateral forepaw stride length at 6 weeks after injury in BFR-treated mice compared with controls. Conclusion: BFR significantly improves muscle quality and shoulder function after RC injury. These effects occur alongside increased mitochondrial transfer from FAPs to myocytes. Clinical Relevance: Understanding the mechanism of BFR by which BFR enhances muscle regeneration could pave the way for its use as a novel rehabilitation strategy to improve recovery in patients with RC injuries and other muscle-related conditions.

Background: Acute compartment syndrome (ACS) is a limb-threatening complication of pediatric tibial tubercle fractures. Despite its severity, the incidence of ACS in pediatric cases has been largely unexplored. Purpose: We sought to examine the incidence and risk factors of ACS and associated fasciotomies in pediatric patients with tibial tubercle fractures. Methods: We conducted a retrospective cohort study using data from the Pediatric Health Information System, a comprehensive inpatient and outpatient nationwide database. Inclusion criteria specified patients 18 years of age or younger with tibial tubercle fracture ( International Classification of Disease, 10th Revision (ICD-10) diagnosis code, S82.151-156) between October 1, 2015, and June 30, 2023. Exclusion criteria were patients with a positive hematologic or immunologic flag and patients with a positive congenital or genetic defect flag. Patients with tibial tubercle fractures were stratified into 3 categories: (1) patients with a diagnosis code for ACS and/or a fasciotomy procedure code; (2) patients with a diagnosis code for ACS and a fasciotomy code; and (3) patients exclusively with a fasciotomy procedure code. Results: Of the 6830 included patients with tibial tubercle fractures, 4% had a code for ACS and/or fasciotomy, 1% had a code for ACS and a procedure code for fasciotomy, and 2.9% had a code for fasciotomy only. Univariate analysis revealed that older and male patients had higher rates of ACS and fasciotomies without any corresponding diagnosis of ACS, compared to their counterparts; White patients had higher rates of ACS than patients of other races. Multivariate analysis showed that age was the only significant predictor of ACS across all groups. Conclusion: This retrospective database study suggests that ACS is a rare complication of pediatric tibial tubercle fractures and that fasciotomies without any evidence of ACS—interpreted as prophylactic fasciotomies—occur at a higher rate than formally diagnosed ACS. Level of Evidence: Level IV: Retrospective Cohort Study.

Background/Objectives: Wearable activity monitors and sensor-based devices are increasingly used to quantify mobility, load, and recovery in orthopaedic patients, yet clinicians lack practical guidance on selection, implementation, and interpretation. This qualitative expert consensus study synthesized real-world experiences from leaders in orthopaedics, rehabilitation, biomechanics, and digital health who implemented wearables at scale. Methods: Semi-structured interviews were conducted with 16 experts (64% response rate) recruited via hybrid purposive and snowball sampling. Participants included orthopaedic surgeons and research scientists with 124 cumulative years of wearable experience across over 9000 monitored patients. Interviews addressed device selection, clinical workflow, data management, and adoption barriers. Data were charted into a structured extraction matrix and analyzed using Inductive Thematic Analysis and a Framework Approach, reported per COREQ guidelines. Results: Experts utilized diverse sensor platforms across arthroplasty, trauma, spine, and sports medicine. Four key themes emerged: (1) device selection prioritized usability and patient compliance over technical sophistication; (2) workflow required defined team roles to manage data volume and avoid clinical burden; (3) patient engagement favored simplified, actionable feedback amid divergent views on data transparency; (4) future outlook anticipated AI-driven proactive risk prediction. Conclusions: No single wearable suits all orthopaedic practices; success hinges on aligning sensor placement with clinical questions, rigorous data quality checks, and integration into care plans. This study offers a practical checklist and roadmap for point-of-care adoption.

Depression is highly prevalent among patients with lumbar degenerative disease and is associated with worse postoperative outcomes. However, a significant proportion of affected individuals remain undiagnosed. We aimed to evaluate the utility of PROMIS Depression scores in identifying patients with undiagnosed depression undergoing lumbar spine surgery and to characterize their clinical outcomes relative to patients with diagnosed and no depression. This retrospective cohort study included patients undergoing 1- or 2-level lumbar decompression or fusion between March 2019 and November 2021. Patients were stratified into three cohorts: diagnosed depression (PDD), no depression (NDD), and at-risk for undiagnosed depression (ARUD), defined as PROMIS Depression ≥55 without an ICD-10 diagnosis. Patient-reported outcomes were assessed preoperatively and at 6, 12, and 24 months postoperatively. Between group comparisons and baseline-adjusted ANCOVA models were performed, including subgroup analyses by procedure type (fusion vs. decompression) and revision status. Of 286 ICD-10-negative patients, 24.1% (n=69) met criteria for ARUD. Patient-reported outcome scores across all domains in the ARUD cohort mirrored those of the PDD group and were significantly worse than those of the NDD cohort at all timepoints (p<.001). PROMIS Depression showed a strong correlation with Anxiety (ρ>0.77) and moderate correlations with other domains. No significant difference was observed in outcomes between treated and untreated PDD patients. Older age was associated with reduced likelihood of diagnosis, while substance abuse history, pain clinic enrollment, and retired status predicted higher risk of undiagnosed depression. PROMIS Depression scores can identify patients with undiagnosed depression who experience similar impairments and postoperative outcomes as those with diagnosed depression. These findings support the routine use of PROMIS Depression as a screening tool to enhance preoperative psychiatric assessment in spine surgery patients.