Sleeve Fracture Research Articles

Medial sleeve fractures in elite-athletes: A heterogeneous group, anatomical and case-based considerations.

The purpose of this study is to provide a detailed description of the anatomy and radiology of the medial sleeve and present an approach in its management among elite athletes. Five cases of elite athletes who underwent treatment for a medial sleeve injury of which the diagnosis was confirmed through physical examination and additional magnetic resonance imaging scan are described in this study. Two patients presented with isolated medial sleeve injuries, while the other three patients suffered from concomitant ankle injuries. Non-operative treatment consisted of relative rest, soft cast immobilization and mobilization in a walking boot or kinesiotape which was successful in four of the cases with regard to the medial sleeve. One patient underwent surgery due to syndesmotic instability. Another patient presented with combined medial and lateral ankle instability which was treated surgically with an open medial and lateral ligament repair. All patients were able to return to their pre-injury sports and at the time of the last follow-up were still playing in their pre-injury level of competition. Medial sleeve injuries of the ankle in elite athletes should be considered in the differential diagnosis for athletes presenting with medial ankle pain. Inherent knowledge regarding anatomy is essential when guiding the management of these injuries which can be treated successfully with a non-operative approach consisting of relative rest, immobilization, kinesiotape and physical therapy. In case of persistent medial instability or rotational instability, surgical repair is a viable treatment option. Both modalities allow athletes to return to the pre-injury level of competition. However, early diagnosis is crucial to minimize the delay of appropriate treatment and avoid potential residual symptoms. Level IV.

Patellar Sleeve Fracture: An Update of Literature

Patellar sleeve fractures, though relatively rare, present unique challenges in diagnosis and management. This review aims to provide a comprehensive overview of the current understanding of patellar sleeve fractures, focusing on their epidemiology, clinical presentation, imaging, and management strategies. Epidemiologically, these fractures are uncommon, representing approximately 1% of all fractures in pediatric patients, yet they account for 50% of all patella fractures in this population. They predominantly affect adolescents, with a peak incidence around 12.7 years of age, and are more common in boys, occurring at a ratio of 3 to 5:1. Understanding these demographic patterns is crucial for early recognition and appropriate management. Clinically, patellar sleeve fractures typically present with the sudden onset of severe pain, often associated with explosive activities such as jumping. However, diagnosis can be challenging, particularly in cases with minimal displacement or where alternative muscle groups compensate for the injury. Differential diagnosis is essential, and clinicians should be vigilant for signs such as palpable gaps at the lower pole of the patella and patella alta. Imaging modalities play a vital role in diagnosis, with plain X-rays often revealing no bony damage. Ultrasonography may offer a cost-effective alternative, especially in cases where radiographic findings are inconclusive. Advanced imaging techniques such as MRI can assist in characterizing the extent of the injury and assessing for associated complications. Management strategies encompass a spectrum of approaches, ranging from conservative measures such as immobilization and physical therapy to surgical interventions, including open reduction and internal fixation or arthroscopic surgery. The choice of treatment depends on various factors, including the fracture pattern, displacement, patient age, activity level, and associated injuries. Despite advancements in diagnosis and treatment, the optimal management of patellar sleeve fractures remains a clinical challenge. Further research is warranted to elucidate optimal algorithms for diagnosis and treatment, with the ultimate goal of improving outcomes and reducing the risk of long-term complications associated with this rare but clinically significant knee injury.

Injuries of the knee extensor complex in children

Fractures of the knee extensor complex are relatively rare injuries in children. We distinguish between apure tendon rupture and ruptures with bony avulsions. A mid-substance tear in children is arelatively rare injury, whereas bony avulsions due to skeletal immaturity are seen more often. Sole bony fractures of the patella also only account for alow number of paediatric related fractures. Sleeve fractures are characterized by an avulsion of cartilage and, usually, bone pulled off from the distal patella pole. Avulsion fractures of the tibia tubercle are found in the group of sportive adolescents. Especially dislocated fractures should be conveyed to surgical therapy to avoid excessive bone callus. Timely diagnostics and an efficient and consistent treatment are recommended. Deformities and dislocated avulsions will regularly not remodel spontaneously during further growth. Therefore, it is mandatory to reconstruct the articular surface and the knee extensor complex to avoid future complications such as osteoarthritis or elongation of the knee extensors.

Risk of fractures following bariatric surgery with Roux-en-Y gastric bypass or sleeve gastrectomy: a Danish population-based cohort study.

We examined the association between Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) and fracture risk, including major osteoporotic fractures (MOF), and the use of anti-osteoporosis medication (AOM). While RYGB is associated with impaired bone health and increased fracture risk, it remains uncertain whether SG has a similar impact and whether this risk is primarily due to MOF or any fracture. We conducted a nationwide cohort study covering patients treated with RYGB (n = 16 121, 10.2-year follow-up) or SG (n = 1509, 3.7-year follow-up), from 2006 to 2018, comparing them with an age- and sex-matched cohort (n = 407 580). We computed incidence rates and adjusted hazard ratios (HRs) with 95% CIs, using Cox regression for any fracture, MOF, and use of AOM with adjustment for comorbidities. Compared with the general population cohort, RYGB was associated with an increased risk of any fracture (HR 1.56 [95% CI, 1.48-1.64]) and MOF (HR 1.49 [1.35-1.64]). Sleeve gastrectomy was associated with an increased risk of any fracture (HR 1.38 [1.13-1.68]), while the HR of MOF was 1.43 (0.97-2.12). The use of AOM was low but similar in all cohorts (approximately 1%). Bariatric surgery increased the risk of any fracture and MOF to similar extend. Risks were similar for RYGB and SG. However, SG had a shorter follow-up than RYGB, and the cohort size was rather small. More research is needed for long-term SG fracture risk assessment. The use of AOM was low in all cohorts.

Thumb Metacarpal Periosteal Sleeve Avulsion: A Case Report.

Periosteal sleeve fractures, or avulsions of cartilage and/or periosteum with or without an osseous fragment in skeletally immature individuals, are notoriously easy to miss and a high index of suspicion is necessary for accurate diagnosis and treatment. While periosteal sleeve avulsion fractures are classically reported in the patella, they have also been reported in the shoulder, clavicle, and elsewhere in the knee. However, no published reports exist for a periosteal sleeve avulsion fracture in the hand. This case details the first reported instance of such an injury involving a thumb metacarpal in a 3-year-old boy, treated with open reduction and percutaneous pinning of the thumb metacarpal.

Patient Characteristics and Postoperative Outcomes of Surgically Treated Inferior Pole Patellar Sleeve Fractures.

Despite representing over half of all pediatric patella fractures, inferior pole patellar sleeve fractures (PSFs) are a relatively uncommon pediatric injury. As a result, existing literature on PSFs is limited to case reports and small case series. The purpose of this study was to evaluate the radiographic and clinical characteristics of operatively treated PSFs as well as outcomes following surgical management. A retrospective review of all inferior pole PSFs requiring surgery from 2007 to 2023 was performed at a single urban tertiary care children's hospital. Cases were identified using diagnostic and billing codes. Patient demographics, injury characteristics, surgical techniques, and postoperative rehabilitation practices were recorded. Regional skeletal maturity, fracture characteristics, and postreduction patellar height were recorded. Postoperative complications were recorded and categorized using the modified Clavien-Dindo Classification System (CDS). Thirty-eight inferior pole PSFs were identified meeting study criteria. The majority of patients were male (86.8%), and the mean age at injury was 11.0 years (range: 7.2 to 15.0). Mean BMI was 21.1. Radiographically, the majority of patients were Epiphyseal Fusion Stage 0 (nonunion), with a median postreduction Caton-Deschamps index (CDI) of 1.2 (IQR: 1.1 to 1.3). These fractures were predominantly treated with suture-based fixation (84%). Postoperative immobilization varied within the cohort, and the initiation of knee ROM was permitted at a median of 3.5 (IQR: 2.0 to 4.6) weeks. All patients regained full range of motion and straight leg raise without extensor lag, and return-to-sport was achieved by a median of 17.6 weeks (IQR: 12.8 to 30.3). Complications occurred in 10 (26.3%) patients, with 3 (7.9%) requiring a return to the OR (CDS Grade III). Inferior pole PSFs appear to occur most commonly among prepubertal males of normal BMI and normal patellar height. Despite variable rehabilitation protocols, operative management resulted in restoration of extensor mechanism function. Eight percent of patients experienced complications requiring unplanned surgery. This large series improves our understanding of the epidemiology, injury characteristics, and postoperative outcomes of an operatively treated cohort of a rare injury pattern. Level IV.

Management and subsequent outcomes of patellar sleeve injuries: A retrospective case series of 90 pediatric and adolescent patients.

This study aims to report the epidemiology of patellar sleeve injuries, describe diagnostic findings and treatment, and assess functional outcomes following different treatments. A medical database was queried from 1990 to 2016 to identify patients ≤18 years presenting to a single pediatric institution with a patellar sleeve injury. Patients with significant comorbidities or previously operatively treated for ipsilateral knee injuries were excluded. Standard demographic data, mechanism of injury, skeletal maturity, injury-related radiographic parameters, along with treatment paradigms, post-treatment clinical and radiographic findings, and patient-reported outcomes were collected. A total of 90 patients, mean age of 10.7 years (range: 7-17) was included, of which 69 (77%) were male. Seventy-three percent of all injuries occurred while playing sports (particularly football/basketball/soccer), with "direct blow" or "landing" being the most prevalent mechanisms of injury. Twenty-six (29%) underwent operative treatment, with transosseous suture fixation being the most popular surgical technique (73%). Of the 64 (71%) non-operatively treated patients, 18 (39%) were placed in a hinged knee brace locked in extension with the remainder split between casting and standard knee immobilizer. Compared to the non-operative cohort, a higher percentage of the operative group had a pre-treatment extensor lag (p < 0.001) and greater fragment displacement (p < 0.001) with patella alta (p < 0.001) on imaging. There was no difference in outcome scores (Pedi-IKDC/Lysholm) or patella alta on radiographs between groups. Post-treatment surveys indicated no difference in residual pain or ability to return to sport. This large case series provides valuable epidemiologic, clinical, and radiographic data describing patellar sleeve fractures, along with outcomes following non-operative and operative treatments. IV.

Patellar Sleeve Avulsion Fracture Repair: Suture Anchor Technique With Suture Cerclage Augmentation

Patella sleeve fractures are rare injuries that occur in pediatric patients. For minimally displaced fractures, nonoperative treatment with immobilization is possible. When fractures are displaced, surgical repair is indicated. Previously described operative techniques include transosseous sutures and tension band wiring. We describe a surgical technique to repair distal pole and patella sleeve avulsion fractures in pediatric patients using intraosseous suture anchors with suture cerclage augmentation.

273 Open Split Fracture of the Patella in a 14-Year-Old Child: An Unusual Occurrence

Abstract Background Patella fractures in children are rare, accounting for approximately 1 % of all paediatric fractures. Due to resilience and adequate flexibility, transverse patellar fractures are extremely rare. This case accounts for less than 10 cases of open transverse or split patellar fracture reported in literature among the paediatric population. Case Presentation A 14-year-old boy was brought in as a pediatric trauma call following a fall and collision of his right knee against a concrete wall on a turf ground while playing football. He had Crohn's disease (on Prednisolone). No history of bone or joint pain, fever, rashes, or juvenile idiopathic arthritis was noted. On clinical examination, a 5cm open horizontal wound in the right knee with no visible bony fragments was noted. Imaging showed a split fracture of the right patella with wide separation of the superior and inferior fragments. Adjacent gas locules and haematoma which extended into the joint space were noted. Clinical outcomes Tension band wiring was done and the patient was placed in a full weight-bearing hinge knee brace with initial range of motion(ROM) of 0-30 degrees followed by an increase of 30 degrees at every 2 weeks. Discussion While sleeve fractures of the patella is more common, a transverse or split pattern is rather unusual and an open fracture in the paediatric population is rare. Other anomalies of the knee joint should be always excluded. The treatment protocol for children is the same as for adults. Restoring the extensor mechanism and realigning the articular surface is essential.

Patellar Sleeve Fracture: An Important Consideration for Pediatric Knee Pain.

Patellar Sleeve Fracture: An Important Consideration for Pediatric Knee Pain.

Mechanical properties of large-diameter semi-grouted sleeve connections for railway platform canopies

To study the mechanical properties of a large-diameter semi-grouted sleeve of a railway platform canopy under a construction environment in winter, this study designed five groups of specimens for unidirectional tensile loading tests based on different curing conditions and freeze–thaw deterioration. The ultimate bearing capacity, strain distribution, failure mode, and grouting material damage were compared and analyzed under different working conditions. Based on the theory of thick-walled cylinders and the constraint analysis model, formulas for calculating the bond strength of grouted sleeve joints were developed to predict the bond strength of joints. Finally, a finite element model was established to study the effects of the steel bar embedded length, grouting material saturation, sleeve type, and steel bar diameter on the mechanical properties and damage of the specimens. The results indicate that the failure modes of GSCs include steel bar fracturing, steel bar slippage, sleeve fracturing, and screw thread failure. The ultimate bearing capacity of the GSC increased by 1.1% when the curing temperature increased from −5 to + 5 °C in the freeze–thaw group. Compared with the condition without freeze–thaw cycles, the short-term low-temperature curing freeze–thaw cycles increased the bond-strength of the grouted sleeve by 1.3%, whereas the high-temperature curing freeze–thaw cycles reduced the bond-strength by 3.5%. The maximum error between the proposed formula and the test result was less than 2%, which could be used to effectively predict the bond strength of a grouted sleeve joint. In addition, the ultimate bearing capacity of the GSCs decreased with decreases in the steel bar embedded length, grouting material saturation, and steel bar and sleeve diameter. When the steel bar embedded length and grouting material saturation decreased from 7d to 6.5d, the ultimate bearing capacity decreased by 9.4% and 2.5%, respectively, and the failure mode changed from steel bar to sleeve fracturing. Two methods, involving an increased wall thickness and a combined sleeve, are proposed for sleeve fracture defects. They effectively solve the problem of reduction in the ultimate bearing capacity owing to the increase in local stress caused by the insufficient length of the steel bar embedment and grouting material.

Clinical and Radiographic Differentiation of Pediatric Patellar Sleeve Fractures and Other Inferior Pole Pathologies

Background: Inferior pole patellar sleeve fractures (PSFs) are rare injuries that occur in skeletally immature patients that may be missed or falsely diagnosed as an inferior pole fracture (IPF) or Sinding-Larsen-Johansson syndrome (SLJS). Purpose: The objective of this study was to evaluate and compare clinical and radiographic features of patients with PSF, IPF, and SLJS. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Retrospective review of skeletally immature patients diagnosed with PSF, IPF, and SLJS between 2011 and 2019 at a single urban academic center was performed. Chart and radiographic review was completed. Between-group differences were assessed using analysis of variance, Kruskal-Wallis test, and Fisher exact test, as appropriate to variable distributions. Results: In total, 125 patients (82% male) were included, with a mean (SD) age of 10.7 (2) years (16 PSF, 51 IPF, 58 SLJS). There were no significant differences in patient characteristics between the 3 groups. One hundred percent of the patients with PSF (P < .001) and IPF (P < .001) had acute trauma, compared with 24% of patients with SLJS. Fewer patients with PSF had an intact straight leg raise (38%) compared with those with IPF (94%; P < .001) and SLJS (98%; P < .001). Fewer patients with SLJS had knee swelling (41%) compared with those with PSF (93%; P < .001) and IPF (94%; P < .001). More patients with PSF had knee effusion (81%) compared with those with IPF (37%; P = 0.011) and SLJS (3%; P < .001). More patients with SLJS were able to bear weight (88%) compared with those with IPF (12%; P < .001) and PSF (0; P < .001). Radiographically, compared with those with IPF and SLJS, patients with PSFs had increased mean prepatellar swelling (6.1 [P < .001] and 6.5 [P < .001] vs 12.9 mm), intra-articular effusion (6.1 [P = .014] and 4.9 [P = .001] vs 9.2 mm), maximum fragment size (26 [P = .004] and 17.7 [P < .001] vs 45.3 mm), and maximum fragment displacement (1.24 [P = .002] and 1.45 [P = .003] vs 13.30 mm), respectively. Compared with those with SLJS (1.10), patients with PSF (1.92; P < .001) and IPF (1.22; P < .001) had patella alta with higher mean Insall-Salvati ratios >1.2. Conclusion: Differences in clinical features such as ability to straight leg raise, knee swelling, knee effusion, ability to bear weight, and radiographic features, such as prepatellar swelling, intra-articular effusion, fragment displacement/size/shape/location, and patellar height, can all be helpful in recognizing rare pediatric inferior patellar pathology, thus increasing efficiency in indicating for higher-level imaging to reach a prompt diagnosis and provide appropriate treatment.

Sleeve Fracture of the Superior Pole of Patella

Sleeve Fracture of the Superior Pole of Patella

Knee Trauma.

Knee Trauma.

Knee Avulsion Injuries: What can I Get From a CT?

Acute bone and soft-tissue injuries to the knee are commonly seen in emergency departments as well as in the outpatient clinic. Most commonly, these injuries result from a direct blow, a fall, or a twisting injury. Prompt and accurate diagnosis relies heavily on imaging and is mandatory to facilitate adequate management and prevent potential complications [1]. Radiographs are usually the initial imaging modality in the evaluation of the acutely injured knee but have a low yield. Computed Tomography (CT) may be performed as the next imaging study for the evaluation of suspected radiographically occult fractures. In patients with radiographic diagnosis of knee fracture, CT is frequently performed for further classification and characterization of the fracture severity and for prediction or diagnosis of associated meniscal and ligamentous injuries [12]. The knee has numerous tendinous, ligamentous, and meniscal attachments, which make it particularly vulnerable to avulsion injuries after trauma. These include avulsions of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), Segond (small bony avulsion of the anterolateral ligament at the lateral tibial rim that indicates a ACL tear) and reverse Segond (small medial tibial avulsion fracture that indicates a PCL tear) fractures, fibular head avulsion fracture, arcuate complex avulsion, fracture avulsions of the medial collateral ligament, iliotibial band avulsion, avulsions of the semimembranosus, and quadriceps tendons, and patellar sleeve fractures. In the setting of acute twisting trauma to the knee, CT scan has high sensitivity and specificity in detecting bony avulsion fractures and a high negative predictive value for excluding ligamentous injuries (e.g.: ACL avulsion fracture) [3] (Figure 1). Radiologists should recognize the pattern of these injuries and their underlying mechanism to understand the substantial damage that it frequently represents. This presentation will outline the imaging appearances of common knee avulsion fractures. Specific examples will be used to highlight clinical relevance and learning points.

Clinical and Radiographic Differentiation of Pediatric Patellar Sleeve Fractures and Other Inferior Pole Pathologies (165)

Objectives:Inferior pole patellar sleeve fractures (PSF) are rare injuries that occur in skeletally immature patients with sparse literature on the diagnosis, management, and outcomes of this injury. Diagnosis of PSF can be difficult based on radiographs alone, as only a small bony fragment is often seen. Consequently, PSFs may be missed or falsely diagnosed as an inferior pole fracture (IPF) or Sinding-Larson-Johansson syndrome (SLJS) possibly leading to improper treatment and poor outcomes (Figure 1). The objective of this study was to evaluate and compare clinical and radiographic features of patients with PSF, IPF and SLJS to help improve diagnostic accuracy.Methods:This was a retrospective review of skeletally immature patients diagnosed with inferior pole patellar pathology between 2011-2019 at a single urban academic center. Patients were identified using both International Classification of Diseases 9th and 10th edition (ICD-9 and ICD-10) codes and Current Procedural Terminology (CPT) codes. Data from medical records (demographics, injury mechanism and physical exam) and lateral knee radiographs (fragment size, fragment displacement, number of fragments, Insall-Salvati, Caton-Deschamps, pre-patellar effusion, intra-articular effusion) was collected. ANOVA, Student’s t-test and Fisher’s exact test were used for comparisons between the three groups. Statistical significance was determined at p<0.05. This study was approved by our institutional review board.Results:A total of 125 patients were included: 82% male, average age 10.7 years (SD 2), 16 PSF, 51 IPF, 58 SLJS patients. There were no significant differences in patient demographics between the three groups (Table 1). Only 24% of SLJS patients presented with acute trauma compared to 100% of the PSF and IPF patients. Fewer PSF patients had an intact straight leg raise (37.5%) compared to IPF (94.1%) and SLJS (98.3%) (p<0.001). SLJS patients were less likely to present with knee swelling (41.4%) compared to PSF (93.8%) and IPF (94.1%) (p<0.001) . Knee effusion was more frequently seen in PSF (81.2%) compared to IPF (37.3%) and SLJS (3.4%) (p<0.001). More patients with SLJS were able to bear weight (87.9%) compared to IPF (11.8%) and PSF (0%) (p<0.001) (Table 2). Radiographically, compared to those with IFP and SLJS, patients with PSFs had increased mean prepatellar swelling (6.1 and 6.5 versus 12.9mm, p<0.001), intra-articular effusion (6.1 and 4.9 versus 9.2mm, p<0.001), maximum fragment size (26 and 17.7 versus 45.3mm, p<0.001) and maximum fragment displacement (1.24 and 1.45 versus 13.30mm, p<0.003) respectively. Compared to SLJS, PSF and IPF patients had higher patella alta with mean Insall-Salvati ratios > 1.2 (Table 3).Conclusions:Differences in clinical features such as straight leg raise, knee swelling, knee effusion, ability to bear weight and radiographic features such as prepatellar swelling, intra-articular effusion, fragment displacement/size/shape/location can all be helpful in improving the accuracy of diagnosing inferior pole injuries in pediatric patients.

The Role of Rock Matrix Permeability in Controlling Hydraulic Fracturing in Sandstones

A concomitant effect of a hydraulic fracturing experimenting is frequently fluid permeation into the rock matrix, with the injected fluid permeating through the porous rock matrix (leak-off) rather than contributing to the buildup of borehole pressure, thereby slowing down or impeding the hydro-fracturing process. Different parameters, such as low fluid viscosity, low injection rate and high rock permeability, contribute to fluid permeation. This effect is particularly prominent in highly permeable materials, therefore, making sleeve fracturing tests (where an internal jacket separates the injected fluid in the borehole from the porous rock matrix) necessary to generate hydraulic fractures. The side effect, however, is an increase in pressure breakdown, which results in higher volume of injected fluid and in higher seismic activity. To better understand this phenomenon, we report data from a new comparative study from a suite of micro-hydraulic fracturing experiments on highly permeable and on low-permeability rock samples. Experiments were conducted in both sleeve fracture and direct fluid fracture modes using two different injection rates. Consistent with previous studies, our results show that hydraulic fracturing occurred only with low permeation, either due to the intrinsic low permeability or due to the presence of an inner silicon rubber sleeve. In particular, due to the presence of quasi-impermeable inner sleeve or borehole skin in the sleeve fracturing experiment, fracturing occurs, with the breakdown pressure supporting the linear elastic approach considering poroelastic effects, therefore, with low stress drop and consequently low microseismicity. Rock matrix permeability also controls the presence of precursory Acoustic Emission activity, as this is linked to the infiltration of fluids and consequent expansion of the pore space. Finally, permeability is shown to mainly control fracturing speed, because the permeation of fluid into the newly created fracture via the highly permeable rock matrix slows down its full development. The application of these results to the field may help to reduce induced seismicity and to conduct well stimulation in a more efficient way.

Effects of the geometry and material properties on the mechanical strength and failure modes of water hydraulic artificial muscles

To develop high-strength water hydraulic artificial muscle (WHAM) and ensure its reliability, the failure mechanism and the main effect factors of WHAM’s strength were studied. WHAM’s failure modes consist of end fitting slipping out, fibre sleeve loosening, the end of rubber tube breaking, rubber tube coming out from fibre sleeve and fibre fracture. It can be preliminarily confirmed that the strength of WHAM is mainly related to fibre sleeve, rubber tube and end fitting structure. Therefore, effects of structure and material properties on WHAM’s strength and failure modes were analysed. The structure parameters contain the initial braid angle, the number of fibre bundles, the rubber tube wall thickness, the diameter of crimping rings, and the number of crimping rings. The fibre spacing was optimized according to the analysis of the ratio of fibre sleeve coverage area to rubber tube outer wall area. The number of end fitting’s barbs and the crimping rings were improved by strength test. Moreover, it can be confirmed that the initial braid angle, fibre sleeve material, rubber tube wall thickness and deformation of rubber tube have strong effects on WHAM’s strength. Aiming to obtain the level of significance for effect factors and an appropriate set of structure parameters, the orthogonal experiment with four factors and two levels was designed. The structure parameters of high-strength WHAM were obtained according to the orthogonal analysis, which can provide theoretical guidance for high-strength WHAM design. The tests results show that the improved structure can effectively avoid the failure modes of end fitting slipping out, fibre sleeve loosening, and rubber tube coming out from fibre sleeve. Finally, only two kinds of failure modes, the end of rubber tube breaking and fibre fracture, occurred. The reliability of WHAM can be improved by studying the WHAM’s strength and failure modes.

Stress due to interfacial slip causing sleeve fracture in shrink-fitted work roll

The rolls are classified into two types; one is a single-solid type, and the other is a shrink-fitted construction type consisting of a sleeve and a shaft. The bimetallic work rolls are widely used in the roughing stands of hot rolling stand mills. Regarding a shrink-fitted construction type, the interfacial slip sometimes appears between the shaft and the shrink-fitted sleeve. This interfacial slip can be regarded as the relative displacement between the sleeve and the shaft. In this paper, the stress due to the interfacial slip is studied because the stress may cause the sleeve fracture. It is found that the stress in the shrink-fitted surface is slightly decreased with increasing number of rotations [Formula: see text]. Therefore, the stress obtained by the simulation at [Formula: see text] can be used to estimate the fatigue strength.

Narrative Review - Knee Pain in the Pediatric Athlete.

This review article seeks to highlight common youth athlete knee conditions due to overuse or trauma and elucidate differences from the adult populations. Overuse conditions presented include apophysitis, osteochondritis dissecans plica syndrome, and discoid meniscus. Traumatic conditions presented include patellar instability, patellar sleeve fracture, and patellofemoral osteochondral fractures. Knee injuries affect a significant proportion of youth athletes. These injuries place athletes at higher risk of chronic pain and potentially osteoarthritis. We have reviewed common overuse and traumatic knee injuries and differentiating factors between the adult population to improve and expedite the diagnosis, treatment, and prognosis for youth athletes with knee injuries.