The Micromechanical Environment of the Impinged Achilles Tendon.

Although tendon predominantly experiences longitudinal tensile forces, transverse forces due to impingement from bone are implicated in both physiological and pathophysiological processes. However, prior studies have not characterized the micromechanical strain environment in the context of tendon impingement. To address this knowledge gap, mouse hindlimb explants are imaged on a multiphoton microscope, and image stacks of the same population of tendon cells are obtained in the Achilles tendon before and after dorsiflexion-induced impingement by the heel bone. Based on the acquired images, multiaxial strains are measured at the extracellular matrix (ECM), pericellular matrix (PCM), and cell scales. Impingement generated substantial transverse compression at the matrix-scale, which led to longitudinal stretching of cells, increased cell aspect ratio, and enormous volumetric compression of the PCM. These experimental results are corroborated by a finite element model, which further demonstrated that impingement produces high cell surface stresses and strains that greatly exceed those brought about by longitudinal tension. Moreover, in both experiments and simulations, impingement-generated microscale stresses and strains are highly dependent on initial cell-cell gap spacing. Identifying factors that influence the microscale strain environment generated by impingement could contribute to a more mechanistic understanding of impingement-induced tendinopathies.

Decorin and/or biglycan knockdown in aged mouse patellar tendon impacts fibril morphology, scar area, and mechanical properties.

Small leucine-rich proteoglycans, such as decorin and biglycan, play pivotal roles in collagen fibrillogenesis during development, healing, and aging in tendon. Previous work has shown that the absence of decorin and biglycan affects fibril shape and mechanical properties during tendon healing. However, the roles of decorin and biglycan in the healing process of aged tendons are unclear. Therefore the objective of this study was to evaluate the differential roles of decorin and biglycan during healing of patellar tendon injury in aged mice. Aged (300 days old) female Dcn+/+/Bgn+/+ control (WT, n = 52), Dcnflox/flox (I-Dcn-/-, n = 36), Bgnflox/flox (I-Bgn-/-, n = 36), and compound Dcnflox/flox/Bgnflox/flox (I-Dcn-/-/Bgn-/-, n = 36) mice with a tamoxifen-inducible Cre were utilized. Targeted gene expression, collagen fibril diameter distributions, mechanical properties, and histological assays were employed to assess the effects of knockdown of decorin and/or biglycan at the time of injury. Knockdown resulted in alterations in fibril diameter distribution and scar area, but surprisingly did not lead to many differences in mechanical properties. Biglycan played a larger role in early healing stages, while decorin is more significant in later stages, particularly in scar remodeling. This study highlights some of the differential roles of biglycan and decorin in the regulation of fibril structure and scar area, as well as influencing gene expression during healing in aged mice.

Dexamethasone treatment influences tendon healing through altered resolution and a direct effect on tendon cells.

Inflammation, corticosteroids, and loading all affect tendon healing, with an interaction between them. However, underlying mechanisms behind the effect of corticosteroids and the interaction with loading remain unclear. The aim of this study was to investigate the role of dexamethasone during tendon healing, including specific effects on tendon cells. Rats (n = 36) were randomized to heavy loading or mild loading, the Achilles tendon was transected, and animals were treated with dexamethasone or saline. Gene and protein analyses of the healing tendon were performed for extracellular matrix-, inflammation-, and tendon cell markers. We further tested specific effects of dexamethasone on tendon cells in vitro. Dexamethasone increased mRNA levels of S100A4 and decreased levels of ACTA2/α-SMA, irrespective of load level. Heavy loading + dexamethasone reduced mRNA levels of FN1 and TenC (p < 0.05), while resolution-related genes were unaltered (p > 0.05). In contrast, mild loading + dexamethasone increased mRNA levels of resolution-related genes ANXA1, MRC1, PDPN, and PTGES (p < 0.03). Altered protein levels were confirmed in tendons with mild loading. Dexamethasone treatment in vitro prevented tendon construct formation, increased mRNA levels of S100A4 and decreased levels of SCX and collagens. Dexamethasone during tendon healing appears to act through immunomodulation by promoting resolution, but also through an effect on tendon cells.

Scapular morphology does not predict supraspinatus tendon tear propagation following an individualised exercise therapy programme.

Purpose: To determine whether scapular morphology could predict isolated supraspinatus tendon tear propagation after exercise therapy. We hypothesised that a larger critical shoulder angle (CSA) and type III acromial morphology predict a positive change in tear size. Methods: Fifty-nine individuals aged 40-70 years with isolated symptomatic high-grade partial or full-thickness supraspinatus tendon tears were included. Individuals participated in a structured, individualised 12-week exercise therapy programme and underwent ultrasound to measure tear size at baseline and 12 months following therapy. Computed tomography images were segmented to create three-dimensional subject-specific bone models and reviewed by three trained clinicians to measure CSA and to determine acromion morphology based on the Bigliani classification. A binary logistic regression was performed to determine the predictive value of CSA and acromion morphology on tear propagation. Results: The CSA was 30.0 ± 5.4°. Thirty-one individuals (52.5%) had type II acromial morphology, followed by type III and type I morphologies (25.4% and 22.0%, respectively); 81.4% experienced no change in tear size, four (6.8%) individuals experienced tear propagation and seven (11.9%) individuals had a negative change in tear size. No significant difference in tear propagation rates based on CSA or acromion morphology (not significant [NS]) was observed. The model predicted tear size status in 81.4% of cases but only predicted tear propagation 8.3% of the time. Overall, CSA and acromion morphology only predicted 24.3% (R 2 = 0.243) of variance in tear propagation (NS). Conclusions: CSA and acromion morphology were NS predictors of tear propagation of the supraspinatus tendon 12 months following an individualised exercise therapy programme. Level of Evidence: II.

[Click phenomenon in acquired Jaensch-Brown syndrome and trigger finger/thumb: the Notta syndrome]. / "Klick"-Phänomen beim erworbenen Jaensch-Brown-Syndrom und schnellenden Finger/Daumen: dem Notta-Syndrom.

CLINICAL FEATURES: The click phenomenon occurs when an acquired mechanical restriction of the elevation in adduction of the eye or of the extension of the finger/thumb, is forcefully overcome. The common cause is a nodule either of the superior oblique tendon posterior to the trochlea in the case of a Jaensch-Brown syndrome or of the digital flexor tendon anterior to the A1 annular pulley in the case of a trigger finger. Both locations share similar anatomical conditions for the development of the nodule and the pathomechanism of the click. RESULTS: From these identical findings in the eye and the hand in small children it can be assumed that the results from the studies of the hand in newborns and infants with a trigger thumb/finger are also applicable to the situation of the eye. 1. This motility disorder is not congenital. This is most likely due to an incomplete development at the time of birth of the sliding factors needed for a free passage of the tendon through the trochlea and the A1 annular pulley. 2. A distinction must be made between stages 0-3: stage 0 = no more restriction of the motility and no click phenomenon; stage 1 = forced active extension/elevation possible; stage 2 = only passive extension/elevation, each with a click phenomenon; stage 3 = no extension/elevation possible and no click phenomenon. 3. In most cases in early childhood there is a spontaneous complete recovery (75% after 6-7 years). In the eye this spontaneous course can only limitedly be shortened with motility exercises in combination with segmental occlusion. CONCLUSION: The click phenomenon is a symptom of stages 1 and 2 of an acquired mechanical restriction of the elevation in adduction of the eye or the extension of the finger/thumb. It should not be called a syndrome.

The roles and mechanisms of the NF-κB signaling pathway in tendon disorders.

Both acute and chronic tendon injuries are the most frequently occurring musculoskeletal diseases in human and veterinary medicine, with a limited repertoire of successful and evidenced-based therapeutic strategies. Inflammation has been suggested as a key driver for the formation of scar and adhesion tissue following tendon acute injury, as well as pathological alternations of degenerative tendinopathy. However, prior efforts to completely block this inflammatory process have yet to be largely successful. Recent investigations have indicated that a more precise targeted approach for modulating inflammation is critical to improve outcomes. The nuclear factor-kappaB (NF-κB) is a typical proinflammatory signal transduction pathway identified as a key factor leading to tendon disorders. Therefore, a comprehensive understanding of the mechanism or regulation of NF-κB in tendon disorders will aid in developing targeted therapeutic strategies for human and veterinary tendon disorders. In this review, we discuss what is currently known about molecular components and structures of basal NF-κB proteins and two activation pathways: the canonical activation pathway and the non-canonical activation pathway. Furthermore, we summarize the underlying mechanisms of the NF-κB signaling pathway in fibrosis and adhesion after acute tendon injury, as well as pathological changes of degenerative tendinopathy in all species and highlight the effect of targeting this signaling pathway in tendon disorders. However, to gain a comprehensive understanding of its mechanisms underlying tendon disorders, further investigations are required. In the future, extensive scientific examinations are warranted to full characterize the NF-κB, the exact mechanisms of action, and translate findings into clinical human and veterinary practice.

Effects of Preoperative Abnormality of Posterior Tibial Tendon on the Surgical Outcomes of Medial Osteochondral Lesion of the Talus.

BACKGROUND: Although surgical treatment for osteochondral lesion of the talus (OLT) can obtain good clinical outcomes, the rate of return to sports is variable. It is reported that medial OLT unrelated to trauma has abnormal structures in the medial aspect, which may induce the medial OLT due to the medial instability. The posterior tibial tendon (PTT) plays an important role in the stabilization of the foot, and high mechanical stress may be added to the PTT to compensate for medial instability in medial OLT. We investigated whether abnormal PTT findings on preoperative magnetic resonance imaging (MRI) in patients with OLT affect clinical outcomes after surgery.  Methods: Eighty-one ankles in 74 patients who were treated surgically for OLT were included in this study (41 men and 33 women; mean age, 26.0 years). Abnormalities of the PTT were evaluated using preoperative MRI. The Japanese Society for Surgery of the Foot (JSSF) scale, arch height, and ankle activity score (AAS) on standing plain radiogram were compared between patients with and those without preoperative PTT abnormalities. RESULTS: Twenty-five ankles (30.9%) had PTT abnormalities on preoperative MRI. All patients with preoperative PTT abnormalities were medial OLT. There were no significant differences in the preoperative JSSF scale in the procedures for OLT. The postoperative JSSF scale and arch height were significantly lower in patients with preoperative PTT abnormalities than those without them. AAS in patients with preoperative abnormalities significantly decreased at the final follow-up.  Conclusion: PTT abnormalities on preoperative MRI may affect clinical outcomes even in preoperative asymptomatic patients in the medial OLT unrelated to trauma.

Ultrashort echo time magnetic resonance elastography for quantification of the mechanical properties of short T2 tissues via optimal control-based radiofrequency pulses.

The aim of the current study is to demonstrate the feasibility of radiofrequency (RF) pulses generated via an optimal control (OC) algorithm to perform magnetic resonance elastography (MRE) and quantify the mechanical properties of materials with very short transverse relaxation times (T2 < 5 ms) for the first time. OC theory applied to MRE provides RF pulses that bring isochromats from the equilibrium state to a fixed target state, which corresponds to the phase pattern of a conventional MRE acquisition. Such RF pulses applied with a constant gradient allow to simultaneously perform slice selection and motion encoding in the slice direction. Unlike conventional MRE, no additional motion-encoding gradients (MEGs) are needed, enabling shorter echo times. OC pulses were implemented both in turbo spin echo (OC rapid acquisition with refocused echoes [RARE]) and ultrashort echo time (OC UTE) sequences to compare their motion-encoding efficiency with the conventional MEG encoding (classical MEG MRE). MRE experiments were carried out on agar phantoms with very short T2 values and on an ex vivo bovine tendon. Magnitude images, wave field images, phase-to-noise ratio (PNR), and shear storage modulus maps were compared between OC RARE, OC UTE, and classical MEG MRE in samples with different T2 values. Shear storage modulus values of the agar phantoms were in agreement with values found in the literature, and that of the bovine tendon was corroborated with rheometry measurements. Only the OC sequences could encode motion in very short T2 samples, and only OC UTE sequences yielded magnitude images enabling proper visualization of short T2 samples and tissues. The OC UTE sequence produced the best PNRs, demonstrating its ability to perform anatomical and mechanical characterization. Its success warrants in vivo confirmation in further studies.

Oxidative stress induces ferroptosis in tendon stem cells by regulating mitophagy through cGAS-STING pathway.

Tendinopathy is one of the most prevalent sports injury diseases in orthopedics. However, there is no effective treatment or medicine. Recently, the discovery of tendon stem cells (TSCs) provides a new perspective to find new therapeutic methods for Tendinopathy. Studies have shown that oxidative stress will inevitably cause TSCs injury during tendinopathy, but the mechanism has not been fully elucidated. Here, we report the oxidative damage of TSCs induced by H2O2 via ferroptosis, as well, treatment with H2O2 raised the proportion of mitochondria engulfed by autophagosomes in TSCs. The suppression of mitophagy by Mdivi-1 significantly attenuates the H2O2-induced ferroptosis in TSCs. Mechanically, H2O2 actives the cGAS-STING pathway, which can regulate the level of mitophagy. Interfering with cGAS could impair mitophagy and the classical ferroptotic events. In the rat model of tendinopathy, interference of cGAS could relieve tendon injury by inhibiting ferroptosis. Overall, these results provided novel implications to reveal the molecular mechanism of tendinopathy, by which pointed to cGAS as a potential therapeutic target for the treatment of tendinopathy.

Dynamic ultrasound assessment for insertional achilles tendinopathy: the COcco-RIcci (CORI) sign.

OBJECTIVE: To describe a novel, dynamic ultrasound assessment of the Achilles tendon at the calcaneal insertion taking advantage of the effusion within the deep retrocalcaneal bursa as a natural contrast agent. MATERIALS AND METHODS: Positioning the ultrasound transducer in a longitudinal plane over the Achilles tendon at the calcaneal insertion, manual compression of the deep retrocalcaneal bursa can be performed using the other hand. Dynamically shifting the anechoic effusion from the proximal to the distal compartment of the bursa, the undersurface of the Achilles tendon is lifted from the underlying cortical bone of the superior facet of the calcaneal tuberosity. RESULTS: Pushing the anechoic effusion from the bursal cavity toward the undersurface of the Achilles tendon, an eventual focal injury of its deep fibers can be visualized dynamically during the maneuver as a "black crescent" within the tendon-i.e., the COcco-RIcci (CORI) sign. Otherwise, the gliding of the posteroinferior wedge of the Kager's fat pad inside the tendon-bone interface can be observed in normal conditions. CONCLUSION: The CORI sign is a novel sonographic sign to further enhance the diagnostic accuracy of dynamic ultrasound imaging in patients with insertional Achilles tendinopathy especially to detect focal injury involving the deep fibers of the tendon.

Immersive virtual reality in orthopedic hand therapy.

Emerging advances in immersive virtual reality incorporating optical hand-tracking present promising potential for application in orthopedic hand therapy. The system is designed to analyze hand movements, enabling users to "use" their hands virtually in any fabricated setting. This article, supplemented with videos, examines practical applications of immersive virtual reality in routine hand therapy and provides a scientific presentation of the interaction of immersive virtual reality with our physiological and neurological systems. Indications for immersive virtual reality use, critical evaluations and recommendations are comprehensively discussed. Immersive virtual reality has the potential to evolve into a standard treatment modality in orthopedic hand therapy.

Heteronymous feedback from quadriceps onto soleus in stroke survivors.

Background: Recent findings suggest increased excitatory heteronymous feedback from quadriceps onto soleus may contribute to abnormal coactivation of knee and ankle extensors after stroke. However, there is lack of consensus on whether persons post-stroke exhibit altered heteronymous reflexes and, when present, the origin of increased excitation (i.e. increased excitation alone and/or decreased inhibition). This study examined heteronymous excitation and inhibition from quadriceps onto soleus in paretic, nonparetic, and age-matched control limbs to determine whether increased excitation was due to excitatory and/or reduced inhibitory reflex circuits. A secondary purpose was to examine whether heteronymous reflex magnitudes were related to clinical measures of lower limb recovery, walking-speed, and dynamic balance. Methods: Heteronymous excitation and inhibition from quadriceps onto soleus were examined in fourteen persons post-stroke and fourteen age-matched unimpaired participants. Heteronymous feedback was elicited by femoral nerve and quadriceps muscle stimulation in separate trials while participants tonically activated soleus at 20% max. Fugl-Myer assessment of lower extremity, 10-meter walk test, and Mini-BESTest were assessed in stroke survivors. Results: Heteronymous excitation and inhibition onsets, durations, and magnitudes were not different between paretic, nonparetic or age-matched unimpaired limbs. Quadriceps stimulation elicited excitation that was half the magnitude of femoral nerve stimulation. Femoral nerve elicited paretic limb heteronymous excitation was positively correlated with walking speed but did not reach significance because only a subset of paretic limbs exhibited excitation (n = 8, Spearman r = 0.69, P = 0.058). Conclusions: Heteronymous feedback from quadriceps onto soleus assessed in a seated posture was not impaired in persons post-stroke. Despite being unable to identify whether reduced inhibition contributes to abnormal excitation reported in prior studies, our results indicate quadriceps stimulation may allow a better estimate of heteronymous inhibition in those that exhibit exaggerated excitation. Heteronymous excitation magnitude in the paretic limb was positively correlated with self-selected walking speed suggesting paretic limb excitation at the higher end of a normal range may facilitate walking ability after stroke. Future studies are needed to identify whether heteronymous feedback from Q onto SOL is altered after stroke in upright postures and during motor tasks as a necessary next step to identify mechanisms underlying motor impairment.

Endothelial cells-derived exosomes-based hydrogel improved tendinous repair via anti-inflammatory and tissue regeneration-promoting properties.

Tendon injuries are common orthopedic ailments with a challenging healing trajectory, especially in cases like the Achilles tendon afflictions. The healing trajectory of tendon injuries is often suboptimal, leading to scar formation and functional impairment due to the inherent low metabolic activity and vascularization of tendon tissue. As pressing is needed for effective interventions, efforts are made to explore biomaterials to augment tendon healing. However, tissue engineering approaches face hurdles in optimizing tissue scaffolds and nanomedical strategies. To navigate these challenges, an injectable hydrogel amalgamated with human umbilical vein endothelial cells-derived exosomes (HUVECs-Exos) was prepared and named H-Exos-gel in this study, aiming to enhance tendon repair. In our research involving a model of Achilles tendon injuries in 60 rats, we investigated the efficacy of H-Exos-gel through histological assessments performed at 2 and 4 weeks and behavioral assessments conducted at the 4-week mark revealed its ability to enhance the Achilles tendon's mechanical strength, regulate inflammation and facilitate tendon regeneration and functional recovery. Mechanically, the H-Exos-gel modulated the cellular behaviors of macrophages and tendon-derived stem cells (TDSCs) by inhibiting inflammation-related pathways and promoting proliferation-related pathways. Our findings delineate that the H-Exos-gel epitomizes a viable bioactive medium for tendon healing, heralding a promising avenue for the clinical amelioration of tendon injuries.

Recurrent cyclops lesion after primary resection of fibroreactive nodule following anterior cruciate ligament reconstruction.

In this case report featured in World Journal of Orthopedics, Kelmer et al describe a rare finding of a 28-year-old female patient who presented with a recurrent fibroreactive nodule 7 months following the resection of a primary cyclops lesion, suggesting recurrent cyclops syndrome. The patient had undergone an initial anterior cruciate ligament reconstruction for a non-contact right knee injury and reported successful recovery. Two years later, the patient sustained a repeat right knee injury followed by a positive McMurray test and acute pain with terminal extension. Arthroscopic synovectomy confirmed magnetic resonance imaging (MRI) finding of a cyclops lesion, which was surgically removed. Seven months postoperatively, the patient reported stiffness and difficulty with terminal extension. Repeat MRI indicated a recurrent cyclops lesion, which was surgically resected. Following resection of the second lesion, the patient underwent physical therapy and achieved full range of motion, maintaining complete recovery 19 months postoperatively. Recurrent cyclops lesions have rarely been reported in the literature, and this article is novel in its report of recurrent cyclops syndrome following a bone-patellar tendon-bone allograft. The presentation of this unusual finding exposes a need for further investigation of cyclops lesion pathology, which will aid its prevention and treatment.

Collagen-Type Composition in the Semitendinosus, Quadriceps, and Patellar Tendons of a 22-Year-Old Patient: A Case Report.

Graft failure is a common postoperative complication after anterior cruciate ligament (ACL) reconstruction. Recently, a theory has emerged that histological and microstructural factors of autografts may be related to graft failure. We simultaneously collected the semitendinosus tendon (ST), quadriceps tendon (QT), and patellar tendon (PT) from a 22-year-old patient to provide insights into the differences in the collagen-type composition of the three tendons in skeletally mature patients. These findings may serve as a basis for selecting autografts for ACL to reduce graft failure rates. The patient was a 22-year-old female who required the removal of artificial ligament, screws, and washers and medial patellofemoral ligament (MPFL) reconstruction with an ST autograft after two surgeries for recurrent dislocation of the left patella. The ST, QT, and PT obtained during necessary intraoperative procedures were used as samples. The tissues were processed and immunostained; this was followed by confocal microscopy. Evaluation was performed by calculating the percentage of areas positive for collagen types I and III.The percentage of type I collagen in the ST, QT, and PT groups was 88%, 85%, and 88%, respectively.The collagen-type composition was examined following simultaneous collection of the ST, QT, and PT. The results revealed no significant differences in the content of physically strong type I collagen, which supports previous findings showing that the clinical outcomes after ACL reconstruction do not vary with the autograft used.

Achilles tendon complications of fluoroquinolone treatment: a molecule-stratified systematic review and meta-analysis.

Purpose: The association between fluoroquinolone intake and Achilles tendinopathy (AT) or Achilles tendon rupture (ATR) is widely documented. However, it is not clear whether different molecules have the same effect on these complications. The purpose of this study was to document Achilles tendon complications for the most prescribed fluoroquinolones molecules. Methods: A literature search was performed on Pubmed, Cochrane, Embase, and Web of Science databases up to April 2023. Inclusion criteria: studies of any level of evidence, written in English, documenting the prevalence of AT/ATR after fluoroquinolone consumption and stratifying the results for each type of molecule. The Downs and Black's 'Checklist for Measuring Quality' was used to evaluate the risk of bias. Results: Twelve studies investigating 439,299 patients were included (59.7% women, 40.3% men, mean age: 53.0 ± 15.6 years). The expected risk of AT/ATR was 0.17% (95% CI: 0.15-0.19, standard error (s.e.): 0.24) for levofloxacin, 0.17% (95% CI: 0.16-0.19, s.e.: 0.20) for ciprofloxacin, 1.40% (95% CI: 0.88-2.03, s.e.: 2.51) for ofloxacin, and 0.31% (95% CI: 0.23-0.40, s.e.: 0.77) for the other molecules. The comparison between groups documented a significantly higher AT/ATR rate in the ofloxacin group (P < 0.0001 for each comparison). Levofloxacin and ciprofloxacin showed the same risk (P = n.s.). The included studies showed an overall good quality. Conclusion: Ofloxacin demonstrated a significantly higher rate of AT/ATR complications in the adult population, while levofloxacin and ciprofloxacin showed a safer profile compared to all the other molecules. More data are needed to identify other patient and treatment-related factors influencing the risk of musculoskeletal complications.

Histological differences in cartilage layer growth at various tendon and ligament insertions in rabbits.

Objectives: Histological differences in cartilage layer growth in Achilles tendon (AT), quadriceps tendon (QT), patellar tendon (PT), and anterior cruciate ligament (ACL) insertion are unclear. Therefore, this study aimed to investigate the differences in cartilage layer growth in AT, QT, PT, and ACL insertions. Materials and Methods: Forty-eight male Japanese white rabbits were used. Six animals were euthanized at different stages (day 1 and 1, 2, 4, 6, 8, 12, and 24 weeks). Safranin O-stained glycosaminoglycan (GAG) production area, chondrocyte count, and insertion width were investigated. Results: A two-way analysis of variance (ANOVA) revealed a significant difference in the main effects of time and insertion for all parameters. In addition, the time × insertion interaction was significant. Multiple comparisons showed a significant difference between the ACL insertion and all other variables; however, the GAG production area was not significantly different for the QT, PT, and AT insertions. AT insertions were significantly different from all other groups; however, the number of chondrocytes and insertion width were not significantly different for ACL, QT, and PT insertions. Conclusion: Cartilage layer growth differed between the AT, QT, PT, and ACL insertions. The differences between the insertions may also be due to the differences in their structures, locations, and mechanical environments.

Central slip defect reconstruction utilizing partial ulnar side of flexor digitorum superficial tendon for chronic boutonniere deformity: A case report.

Background: Post-traumatic central slip injuries, resulting in boutonniere deformity, are a complex issue that can significantly impact hand function and quality of life. The deformity should be easily reducible in the acute phase, but if left untreated, it shortens the oblique retinacular ligament, leading to chronic contracture. This is a challenging issue in hand surgery, as chronic central slip defects cannot be sutured like other tendon. Various methods for reconstructing central slips have been discussed, but the best method for subacute or chronic injuries remains unclear. This case presents a case of chronic traumatic boutonniere deformity with central slip defect reconstruction. Case report: A 65-year-old male patient presented with swelling and boutonniere deformity on the digiti III of the right hand. The patient had previously fallen from a motorcycle, and the patient's right middle finger got was by a motorcycle six months ago. After the incident, the patient's right middle finger cannot be fully extended. The patient's right hand showed edema with flexion of the interphalangeal (PIP) joint and hyperextension of the distal interphalangeal (DIP) joint. The Range of Motion (ROM) of the PIP joint right middle finger was 45-110 degrees. The X-ray of the right hand AP/oblique showed no bone involvement in the deformity. The patient underwent central slip defect reconstruction utilizing the partial ulnar side of the flexor digitorum superficial tendon. A PIP joint extension splint was applied for 2 weeks. Active and passive exercise of the ROM of the PIP joint began after 2 weeks of PIP extension joint splinting. The patient's ROM of the PIP joint (0-90 degrees) significantly improved 1 month after surgery. The patient's ROM of the PIP joint returned to normal after 2 months after surgery. The function of the patient's right hand is evaluated with the DASH score, which improves significantly from 50 to 4.2. Conclusion: Central slip defect reconstruction utilizing the partial ulnar side of the flexor digitorum superficial tendon is a reliable method for traumatic chronic boutonniere deformity and results in great functional outcomes after 2 months of follow-up. Central slip defect reconstruction utilizing the partial ulnar side of the flexor digitorum superficial tendon is a simple and cost-effective method compared to other methods.

Machine learning used to determine features of importance linked to overnight stay after patellar tendon repair.

Purpose: The purpose of this study is to determine if machine learning is an effective method to identify features of patients who may need a longer postoperative stay following a patellar tendon repair. Methods: The American College of Surgeons National Quality Improvement Program (ACS-NSQIP) was used to collect 1173 patients who underwent patellar tendon repair. Machine learning (ML) was then applied to determine features of importance in this patient population. Several algorithms were used: Random Forest, Artificial Neural Network, Gradient Boosting, and Support Vector Machine. These were then compared to the American Society of Anesthesiologists (ASA) classification system based logistic regression as a control. Results: Random Forest (RF) was determined to be the best performing algorithm, with an AUC of 0.72, accuracy of 77.66 %, and precision of 0.79, and recall of 0.96. All other algorithms performed similarly to the control. RF gave the highest permutation feature importance to age (PFI 0.25), BMI (PFI 0.19), ASA classification (PFI 0.14), hematocrit (PFI 0.12), and height (PFI 0.11). Conclusions: This study shows that machine learning can be used as a tool to identify features of importance for length of postoperative stay in patients undergoing patellar tendon repair. RF was found to be a better performing model than logistic regression at determining patients predisposed to longer length of stay as determined by AUC. This supported the study's hypothesis that ML can provide an effective method for identifying features of importance in patients requiring a longer postoperative stay after patellar tendon repair.