Return-to-play and performance after operative treatment of Achilles tendon rupture in elite male athletes: a scoping review

Molecular dissection of tendon development and healing: Insights into tenogenic phenotypes and functions

Tendon is a dense connective tissue that transmits contraction forces from skeletal muscles to bones. Adult tendon injury is a significant clinical problem because it occurs frequently with a high recurrence rate, and damaged tendon is rarely restored to full function. The main barrier to improving recovery outcomes is our incomplete understanding of the molecular mechanisms underlying the biological alterations following tendon injury in vivo. In this review, we specifically highlight the cellular dynamism of fibrotic tendon wound healing and the roles of mechanical loading. In particular, we document how tendon stem/progenitor cells expressing the tendon-specific transcription factor Scleraxis (Scx) play a role in fibrotic tendon wound healing, and describe novel experimental systems such as lineage cell tracing and single-cell analysis, both of which can shed light on tendon cell behavior and fate decisions during the tendon wound healing process.

Effects of Speed, Orthosis, and Load on Calf Muscle Electromyography Signal During Treadmill Walking

BACKGROUND

Achilles tendon rupture rehabilitation protocols often emphasize two key factors, namely plantar flexion and load restriction during the early recovery stages. However, we hypothesize that variations in walking speed also play a significant role in affecting the load on the Achilles tendon. This study aims to explore the combined impact of plantar flexion angle and walking speed on the surface electromyography (EMG) activity of the calf muscles.

METHODS

Surface EMG measurements on 24 healthy volunteers assessed the activity of the calf muscles (gastrocnemius lateralis, gastrocnemius medialis, and soleus). Participants walked on a treadmill using two designs of ankle foot orthoses set at three different angles of the ankle joint (mainly 0°, 15°, or 30° plantar flexion), as well as barefoot and in sports shoes. The tests were performed at full loads of 1, 2 and 4 km/h or with additional measurements at 1 and 2 km/h with a partial load of 20 kg. The walking speed of 4 km/h in sports shoes was used as reference, corresponding to the maximum load on the calf muscles during walking.

RESULTS

Both orthoses demonstrated a significant reduction in EMG activity by more than half even at a 0° setting and 1 km/h compared to walking barefoot or in sports shoes. However, as walking speed increased to 2 km/h and especially to 4 km/h, EMG activity significantly increased, approaching the level of walking with sports shoes at 1 km/h. The results indicated that even minor changes in walking speed had a significant impact on muscle activity, underscoring the importance of this parameter.

CONCLUSIONS

This study suggests that walking speed should be considered a crucial factor in rehabilitation protocols for Achilles tendon ruptures, alongside plantar flexion and load restrictions, to optimize recovery outcomes.

No significant impact of platelet-rich plasma on recovery after Achilles tendon surgery: A double-blind randomized controlled trial

Purpose

Double-blind, randomized, placebo-controlled trials evaluating the efficacy and safety of Platelet-rich plasma (PRP) in the treatment of Achilles tendon rupture (ATR) have been scant. This study examines the therapeutic impact of PRP injection 3 weeks after surgery in middle-aged males.

Methods

This double-blind, randomized, placebo-controlled trial included consecutive ATR patients who satisfied the inclusion criteria and was conducted from 5 September 2018 to 24 June 2021. Three weeks after surgery using the side-locking loop technique, PRP or saline was injected at the suture site under ultrasound guidance. Evaluations were conducted at predetermined intervals (6, 10, 12, 16 and 24 weeks and 1 and 2 years) after surgery. The primary outcome was the period needed to perform a bilateral heel raise, and the important secondary outcomes were the periods needed to perform a single heel raise and 20 unilateral heel raises, respectively.

Results

There were seven participants in the PRP group and seven in the saline group. Demographically, both groups exhibited comparable characteristics. No complications were reported. At 6 weeks after surgery, all participants achieved bilateral heel raise. The PRP and saline groups averaged 12.3 ± 2.7 and 15.7 ± 5.9 weeks to achieve a single heel raise and 14.3 ± 2.7 and 17.7 ± 4.5 weeks to achieve 20 unilateral heel raises, respectively, with no significant differences between both groups. Moreover, no substantial disparities in clinical scores, period of jogging initiation and magnetic resonance imaging tendon assessments were noted.

Conclusions

PRP did not offer a distinct advantage over saline in terms of recovery from ATR in middle-aged males. This finding underscores the need to reassess the post-operative significance of PRP and highlights the importance of further research to determine its potential advantages and risks.

Level of Evidence

Level I.

Economic and Performance Analysis of Achilles Tendon Rupture in the National Basketball Association

Background

Achilles tendon ruptures are common and potentially career-ending injuries for National Basketball Association (NBA) players. Many studies have reviewed the impact of Achilles tendon ruptures on return to play (RTP) and performance, but there are no studies on their economic significance.

Purpose/Hypothesis

This study aimed to analyze the economic and performance consequences of Achilles tendon ruptures usingthe cost of recovery (COR) for NBA franchises as well as preinjury salary/career success. It was hypothesized that players with higher preinjury salaries or performance would have an increased COR, higher rates of RTP, and more career success after their injury.

Study Design

Descriptive epidemiology study.

Methods

Publicly available data of NBA players who sustained an Achilles tendon rupture between 1990 and 2023 were analyzed. Data were retrospectively gathered by R software code to include players' ages, positions, salaries, pre- and postinjury player efficiency rating, time missed after injury, and RTP. Performance impact was measured by advanced statistics: player efficiency rating, Win Shares per 48 Minutes, and Value Over Replacement Player. Two groups of 3 cohorts were created: All-Star, Starter, and Reserve versus group A (<$3,999,999), group B (≥$3,999,999 to ≤$8,999,999), and group C (>$8,999,999). Analysis of variance with post hoc Tukey tests for continuous data and Fisher exact tests for categorical data was used. Significance levels were set at P < .05.

Results

A total of 37 players met the inclusion criteria and played between the years of 1992 through 2019. The mean COR that NBA teams faced was $4 million per player. The cumulative economic loss from Achilles tendon ruptures in the NBA between 1992 and 2019 was $117,578,851. Overall RTP was 78.38%, and 31.03% of players who returned to play were out of the NBA within 3 years. RTP to the highest playing level was highest in group B (45.5%), followed by group A (40%) then group C (12.5%). The COR of All-Star players, Starter players, and Reserve players averaged $5.7 million, $3.4 million, and $3 million, respectively.

Conclusion

This study investigated the financial and performance implications of Achilles tendon ruptures among NBA athletes. Most players struggled to restore their preinjury performance, except for Reserve players. The findings provide valuable insights into the complexities of COR and postinjury performance.

Epidemiology of Sports-Related Tendon Ruptures Presenting to Emergency Departments in the United States

BACKGROUND

Participation in recreational and competitive sports can predispose people to musculoskeletal injuries. Chronic overuse with insufficient recovery, overloading, and direct contact can result in acute primary tendon ruptures. There is scarce literature regarding the epidemiology of sports-related acute primary tendon ruptures in the United States (US).

PURPOSE

To identify the incidence rate (IR) of sports-related acute primary tendon ruptures presenting to US emergency departments using the National Electronic Injury Surveillance System (NEISS) database and describe the trends in the IR from 2001 to 2020.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

The NEISS database was queried using injury case narratives; cases with a clear diagnosis of an acute primary tendon rupture were included in the final analysis. National estimates, estimated IRs (reported as per 1,000,000 person-years at risk), and temporal trends in the annual IR (reported as average annual percent change) of acute primary tendon ruptures were calculated using NEISS sample estimates and US Census Bureau population estimates.

RESULTS

An estimated total of 141,382 patients (95% confidence interval [CI], 107,478-175,286) presented to US emergency departments with a sports-related tendon rupture over the study period (IR, 22.9 person-years at risk [95% CI, 17.4-28.3]). The mean age was 37.7 years (95% CI, 37.0-38.5). Of all cases of a tendon rupture identified from 2001 to 2020, 60.1% were secondary to exercise/sports-related injury mechanisms. An Achilles tendon rupture was the most common injury, representing 55.9% of cases. Basketball was the most common sports-related injury mechanism, accounting for 36.6% of cases. The overall injury rate in male patients was 7.7 times that of female patients (IR ratio, 7.7 [95% CI, 4.4-13.5]; P < .05). The annual incidence of all sports-related tendon ruptures in the US increased significantly from 2001 to 2020 (average annual percent change, 1.9 [95% CI, 1.0-2.8]; P < .01).

CONCLUSION

Recreational/competitive sports participation accounted for a large proportion of acute primary tendon ruptures in the US during the study period.

Rehabilitation and Return to Sports after Achilles Tendon Repair

Rehabilitation protocols post-Achilles tendon repair vary widely, particularly regarding weight bearing (WB) and immobilization duration, impacting recovery trajectories significantly. This commentary focuses on rehabilitation strategies following acute Achilles tendon repair (ATR), emphasizing early mobilization and progressive loading. Techniques such as blood flow restriction training (BFRT) and progressive loading to restore strength and tendon mechanical properties are discussed in the context of optimizing recovery, minimizing tendon elongation and facilitating safe return to sport (RTS). This manuscript highlights current evidence and clinical insights to guide practitioners in optimizing rehabilitation protocols for athletes recovering from ATR, aiming to improve functional outcomes and support safe return to athletic activity.

Open vs. Percutaneous Achilles Tendon Repair: Experience of Single Orthopedic Institute with Long-Term Follow-Up

Background and Objectives: There are numerous techniques for the surgical treatment of Achilles tendon lesions described in the literature, and it is possible to distinguish repair techniques as either open surgery or percutaneous repair techniques. Both approaches have advantages and disadvantages. With this retrospective study, we aim to analyze the incidence of re-ruptures and other complications, return to sport and overall quality of life at a long-term follow-up in the treatment of acute ATRs, comparing the results of percutaneous repair with those of open repair. Materials and Methods: This is a retrospective study on a consecutive series of patients with complete tear of the AT who were managed through a surgical approach by the Operative Unit of Orthopaedics and Traumatology of Sant'Anna University Hospital (Ferrara, Emilia-Romagna, Italy) between April 2014 and December 2021. Patients were treated with a percutaneous or an open technique according to the surgeon's preference without randomization. Results: We considered 155 patients who met the established inclusion criteria. Of these, 103 (66.45%) patients underwent percutaneous treatment with the Tenolig® system, and 52 (33.55%) underwent open surgery, with an average ATRS in the first group of 92.5 compared to an average ATRS value of 82 in patients treated with the open technique. Conclusions: In our experience, following overlapping rehabilitation protocols in all patients included, we observed that the Tenolig® repair system led to a better ATRS at long-term follow-up, with comparable complication rates to open surgery.

[Acute rupture of the Achilles tendon : Diagnostics, treatment and aftercare]

With up to 50 incidents per 100,000 inhabitants, Achilles tendon ruptures are among the most frequent tendon injuries encountered in orthopedics and trauma surgery. Apart from high-risk forms of sport, degenerative processes are primarily responsible for weakening and ultimately rupture. In addition to assessing the typical clinical signs with inability to perform powerful plantar flexion, the diagnostics include easy to earn examination techniques, such as the Thompson test and ultrasound as the imaging gold standard. Conservative and surgical treatment are available depending on the constitution, age and requirements of the patient. The latter option is divided into conventional open, minimally invasive or percutaneous procedures. Good to very good results can be expected regardless of the form of treatment, provided that early functional rehabilitation is carried out. The average rerupture rate is 5% and the return to sport rate is around 80%.

The effect of extracorporeal shock-wave therapy on pain in patients with various tendinopathies: a systematic review and meta-analysis of randomized control trials

OBJECTIVES

Tendinopathy is a common condition that affects the body's tendon structures, causing discomfort, restricted movement, and reduced functionality. In this study, we looked at how extracorporeal shock wave therapy (ESWT) affected pain levels in individuals with various forms of tendinopathy around the world.

DESIGN

This study is a comprehensive review and meta-analysis of previously published randomized controlled trials. To gather relevant data, the researchers performed keyword searches in international databases, including PubMed (Medline), Scopus, Web of Sciences, Cochrane Central Register of Controlled Trials (CENTRAL), Research Registers of ongoing trials (ClinicalTrials.gov), as well as Embase. The search was conducted up until March 2023. The quality of the selected articles was assessed using the Cochrane risk-of-bias method for randomized trials (RoB2).

RESULTS

Based on the results of the meta-analysis, which included 45 clinical studies, the use of ESWT was found to have a significant impact on reducing pain in various conditions. The standardized mean difference (SMD) in patients with plantar fasciitis (PF) was reduced by 1.63 (SMD: -1.63, 95% CI: -3.04, -0.21; I2: 77.36%; P heterogeneity: 0.0001). For lateral epicondylitis (LE), the SMD was 0.63 (SMD: -0.63, 95% CI: -1.11, -0.16; I2: 67.50%; P heterogeneity: 0.003). In the case of chronic Achilles tendinopathy, the SMD was 1.38 (SMD: -1.38, 95% CI: -1.66, -1.10; I2: 96.44%; P heterogeneity: 0.0001). Additionally, in individuals with rotator cuff tendinopathy, the SMD for pain reduction was 2.37 units (SMD: -2.37, 95% CI: -3.58, -1.15; I2: 98.46%; P heterogeneity: 0.0001).

CONCLUSION

This study suggests that ESWT can be a highly effective therapy option for relieving pain in people with tendinopathy. Nonetheless, it is encouraged to make additional recommendations based on high-quality clinical research and more accurate information in order to define the optimal therapeutic options for each type of tendinopathy.

Postoperative Return to Play and the Role of Imaging

Return to play (RTP) following surgery is a complex subject at the interface of social and internal pressures experienced by the athlete, psychological readiness, and intrinsic healing of the surgically repaired structures. Although functional testing, time from surgery, clinical examination, and scoring metrics can help clarify an athlete's readiness to return to sport, imaging can allow for a more direct assessment of the structures in question. Because imaging is often included in the diagnostic work-up of pain following surgery, the radiologist must be familiar with the expected postsurgical imaging appearance, as well as the associated complications. We briefly review such findings following anterior cruciate ligament reconstruction, Achilles tendon repair, syndesmotic fixation, and ulnar collateral ligament reconstruction in the context of the athlete, highlighting issues related to RTP.

Risk factors and clinical characteristics of surgical site infections in athletes undergoing Achilles tendon repair surgery

Achilles tendon ruptures are common in athletes, requiring surgical intervention. However, the risk of surgical site infections (SSIs) post-surgery poses significant challenges. This study aims to analyse the risk factors and microbial aetiology associated with SSIs in athletes undergoing Achilles tendon repair. A comprehensive retrospective analysis was conducted from May 2021 to July 2023. The study included 25 patients with SSIs (case group) and 50 patients without SSIs (control group) post Achilles tendon repair surgery. Inclusion criteria encompassed patients with medically confirmed Achilles tendon ruptures who underwent surgical repair. Exclusion criteria included prior tendon pathologies and significant chronic illnesses. Diagnostic criteria for SSIs involved symptoms like elevated body temperature and localized tenderness, along with laboratory confirmations such as positive microbiological cultures. The study utilized VITEK® 2 for bacterial identification and involved statistical analyses like univariate and multivariate logistic regression. The study identified Staphylococcus aureus as the primary pathogen in SSIs. Significant risk factors included lack of prophylactic antibiotic use, presence of diabetes, open wounds and prolonged surgery duration. Univariate analysis revealed stark contrasts in these factors between infected and non-infected groups, while multivariate analysis underscored their importance in SSI development. S. aureus emerged as the predominant pathogen in SSIs post Achilles tendon repair. Critical risk factors such as absence of prophylactic antibiotics, diabetes, open wounds and extended surgery duration play a vital role in SSIs. Addressing these factors is essential for better postoperative outcomes in Achilles tendon repair surgeries.

Tendon Elongation and Function After Delayed or Standard Loading of Surgically Repaired Achilles Tendon Ruptures: A Randomized Controlled Trial

BACKGROUND

Achilles tendon ruptures often result in long-term functional deficits despite accelerated (standard) rehabilitation.

PURPOSE/HYPOTHESIS

The purpose of this study was to investigate if delayed loading would influence functional, clinical, and structural outcomes of the muscles and tendon 1 year after a surgical repair. It was hypothesized that delaying the loading would reduce the heel-rise height deficit 1 year after Achilles tendon rupture.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

In total, 48 patients with a surgically repaired Achilles tendon rupture were randomized to 2 groups: the standard group received the currently accepted rehabilitation, and the delayed group received the same rehabilitation except that initial loading was delayed by 6 weeks. The primary outcome was the heel-rise height difference between the injured and uninjured sides at 1 year. The secondary outcomes were (1) tendon length measured with magnetic resonance imaging, (2) muscle fascicle length and pennation angle of the gastrocnemius medialis muscle, (3) Doppler activity measured with ultrasonography, (4) Achilles tendon Total Rupture Score (ATRS), and (5) isometric muscle strength.

RESULTS

The mean heel-rise height deficits for the standard and delayed groups were -2.2 cm and -2.1 cm, respectively (P = .719). The soleus part of the tendon was already elongated 1 week after surgery in both groups without a between-group difference (side-to-side difference: standard, 16.3 mm; delayed, 17.5 mm; P = .997) and did not change over 52 weeks. The gastrocnemius tendon length was unchanged at 1 week but elongated over time without a between-group difference (side-to-side difference at 52 weeks: standard, 10.5 mm; delayed, 13.0 mm; P = .899). The delayed group had less Doppler activity at 12 weeks (P = .006) and a better ATRS (standard, 60 points; delayed, 72 points; P = .032) at 52 weeks.

CONCLUSION

Delayed loading was not superior to standard loading in reducing the heel-rise height difference at 1 year. The data indirectly suggested reduced inflammation in the initial months and a better patient-reported outcome at 1 year in the delayed group. The soleus part of the tendon was already markedly elongated (35%) 1 week after surgery, while the length of the gastrocnemius tendon was unchanged at 1 week but was 6% elongated at 1 year. Together, these data indirectly suggest that the delayed group fared better, although this finding needs to be confirmed in future investigations.

REGISTRATION

NCT04263493 (ClinicalTrials.gov identifier).

Cell Sheet Technology: An Emerging Approach for Tendon and Ligament Tissue Engineering

Tendon and ligament injuries account for a substantial proportion of disorders in the musculoskeletal system. While non-operative and operative treatment strategies have advanced, the restoration of native tendon and ligament structures after injury is still challenging due to its innate limited regenerative ability. Cell sheet technology is an innovative tool for tissue fabrication and cell transplantation in regenerative medicine. In this review, we first summarize different harvesting procedures and advantages of cell sheet technology, which preserves intact cell-to-cell connections and extracellular matrix. We then describe the recent progress of cell sheet technology from preclinical studies, focusing on the application of stem cell-derived sheets in treating tendon and ligament injuries, as well as highlighting its effects on mitigating inflammation and promoting tendon/graft-bone interface healing. Finally, we discuss several prerequisites for future clinical translation including the selection of appropriate cell source, optimization of preparation process, establishment of suitable animal model, and the fabrication of vascularized complex tissue. We believe this review could potentially provoke new ideas and drive the development of more functional biomimetic tissues using cell sheet technology to meet the needs of clinical patients.

Application of Nondegradable Synthetic Materials for Tendon and Ligament Injury

Tendon and ligament injuries, prevalent requiring surgical intervention, significantly impact joint stability and function. Owing to excellent mechanical properties and biochemical stability, Nondegradable synthetic materials, including polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE), have demonstrated significant potential in the treatment of tendon and ligament injuries. These above materials offer substantial mechanical support, joint mobility, and tissue healing promotion of the shoulder, knee, and ankle joint. This review conclude the latest development and application of nondegradable materials such as artificial patches and ligaments in tendon and ligament injuries including rotator cuff tears (RCTs), anterior cruciate ligament (ACL) injuries, and Achilles tendon ruptures.

Return-to-performance in elite soccer players after Achilles tendon ruptures: a study using a weighted plus/minus metric and matched-control analysis

PURPOSE

Studies have shown decreased match participation and shortened careers in athletes suffering Achilles tendon ruptures (ATRs), but assessment using a true performance metric is lacking. Plus/minus (PM) metrics provide a practical and objective approach to player performance assessment and are commonly used in other sports. This study aimed to quantify and compare individual player performance variations in elite football league players who sustained ATRs and returned to play within 1 year compared to those without ATRs, using a PM metric.

METHODS

Player and team data were sourced from Transfermarkt.com. Male players sustaining ATRs between 2007 and 2018 were identified through injury reports. A control group (CTRL) was matched by position, age, height, and league, with a 6:1 ratio of controls to ATR subjects. The day of injury was considered "time zero". Year -1 corresponds to the 360 days preceding injury, and Year 1 to the interval between 360 and 720 days after. Performance in the player's main team was evaluated using a previously validated weighted PM metric. Only data from Year -1 and Year 1 were used for ATR versus CTRL group comparisons. Statistical significance was set at p < 0.05.

RESULTS

The ATR group included 125 athletes. Data from more than 76,000 matches were analyzed. No statistically significant differences in net weighted PM metric between Year -1 and Year 1 were found.

CONCLUSION

No differences were found between athletes suffering from ATRs and controls regarding the weighted PM metric.

LEVEL OF EVIDENCE

III.

Successful restoration of failed Achilles tendon surgery with semitendinosus and gracilis tendon graft: a case report

Objective

This case presentation aims to highlight the challenges and outcomes associated with a partial tear of the Achilles tendon (AT) in an elite marathon runner. The objective was to restore tendon anatomy and optimize strength recovery through surgical intervention.

Method

We present the case of a marathon runner who suffered a partial AT tear and underwent an initial surgery that failed. A revision surgery was then performed using a semitendinosus and gracilis tendon graft.

Results

The patient underwent surgery 14 weeks after the initial AT injury, but unfortunately experienced a complete AT tear after 6 months. However, the novel aspect of this case is the successful restoration of the failed double-row suture technique through the utilization of a semitendinosus and gracilis tendon graft. Notably, the graft remained intact even under high tendon loading during the 2-year follow-up period.

Conclusion

Differential diagnosis should consider partial tears of the AT as a possible diagnosis in the patients with heel pain. Furthermore, it is crucial to prioritize a well-paced post-surgical rehabilitation process in AT surgeries. In cases of failed AT surgery, the utilization of gracilis and semitendinosus tendon grafts can serve as viable options for repairing reruptures.

Prim-O-glucosylcimifugin ameliorates aging-impaired endogenous tendon regeneration by rejuvenating senescent tendon stem/progenitor cells

Adult tendon stem/progenitor cells (TSPCs) are essential for tendon maintenance, regeneration, and repair, yet they become susceptible to senescence with age, impairing the self-healing capacity of tendons. In this study, we employ a recently developed deep-learning-based efficacy prediction system to screen potential stemness-promoting and senescence-inhibiting drugs from natural products using the transcriptional signatures of stemness. The top-ranked candidate, prim-O-glucosylcimifugin (POG), a saposhnikovia root extract, could ameliorate TPSC senescent phenotypes caused by long-term passage and natural aging in rats and humans, as well as restore the self-renewal and proliferative capacities and tenogenic potential of aged TSPCs. In vivo, the systematic administration of POG or the local delivery of POG nanoparticles functionally rescued endogenous tendon regeneration and repair in aged rats to levels similar to those of normal animals. Mechanistically, POG protects TSPCs against functional impairment during both passage-induced and natural aging by simultaneously suppressing nuclear factor-κB and decreasing mTOR signaling with the induction of autophagy. Thus, the strategy of pharmacological intervention with the deep learning-predicted compound POG could rejuvenate aged TSPCs and improve the regenerative capacity of aged tendons.

Video analysis of Achilles tendon ruptures in professional male football (soccer) reveals underlying injury patterns and provides strategies for injury prevention

PURPOSE

In professional football (soccer), Achilles tendon ruptures are severe injuries. Video analysis promotes a better understanding of the underlying situational and biomechanical patterns, and provides a roadmap for future research to improve the management and prevention of Achilles tendon ruptures. The purpose of this study was to identify injury patterns contributing to acute Achilles tendon ruptures in professional male football players.

METHODS

Professional male football players with an acute Achilles tendon rupture were identified using an online database. For every in-competition injury, the corresponding football match was detected. Video footage of the injury was accessed using Wyscout.com or publicly available video databases. Situational patterns and injury biomechanics of the injury frame were independently analysed by two reviewers using a standardised checklist and a motion analysis software. Finally, consensus was reached to describe the main injury patterns of Achilles tendon ruptures in professional male football players.

RESULTS

The search identified video footage of 80 Achilles tendon ruptures in 78 players. Most injuries (94%) occurred through indirect or non-contact mechanisms. The kinematic analysis revealed characteristic joint positions at the time of injury consisting of hip extension, knee extension, ankle dorsiflexion, foot abduction, and foot pronation in most cases. The underlying direction of movement was from flexion to extension (knee) and from plantarflexion to dorsiflexion (ankle). Player actions identified as main injury patterns were stepping back (26%), landing (20%), running/sprinting (18%), jumping (13%), and starting (10%).

CONCLUSION

Most Achilles tendon ruptures in professional male football players are closed-chain indirect or non-contact injuries. Sudden loading to the plantarflexor musculotendinous unit remains to be the main component for most cases. By achieving a better understanding of underlying injury mechanisms, this study provides new strategies for the prevention of Achilles tendon ruptures.

LEVEL OF EVIDENCE

Level IV.

Energy-Supporting Enzyme-Mimic Nanoscaffold Facilitates Tendon Regeneration Based on a Mitochondrial Protection and Microenvironment Remodeling Strategy

Tendon injury is a tricky and prevalent motor system disease, leading to compromised daily activity and disability. Insufficient regenerative capability and dysregulation of immune microenvironment are the leading causes of functional loss. First, this work identifies persistent oxidative stress and mitochondrial impairment in the regional tendon tissues postinjury. Therefore, a smart scaffold incorporating the enzyme mimicry nanoparticle-ceria nanozyme (CeNPs) into the nanofiber bundle scaffold (NBS@CeO) with porous, anisotropic, and enhanced mechanical properties is designed to innovatively explore a targeted energy-supporting repair strategy by rescuing mitochondrial function and remodeling the microenvironment favoring endogenous regeneration. The integrated CeNPs scavenge excessive reactive oxygen species (ROS), stabilize the mitochondria membrane potential (ΔΨm), and ATP synthesis of tendon-derived stem cells (TDSCs) under oxidative stress. In a rat Achilles tendon defect model, NBS@CeO reduces oxidative damage and accelerates structural regeneration of collagen fibers, manifesting as recovering mechanical properties and motor function. Furthermore, NBS@CeO mediates the rebalance of endogenous regenerative signaling and dysregulated immune microenvironment by alleviating senescence and apoptosis of TDSCs, downregulating the secretion of senescence-associated secretory phenotype (SASP), and inducing macrophage M2 polarization. This innovative strategy highlights the role of NBS@CeO in tendon repair and thus provides a potential therapeutic approach for promoting tendon regeneration.