Experimental analysis of the quadriceps muscle force and patello-femoral joint reaction force for various activities

Strains on the human femur after revision total knee arthroplasty: An in vitro study using digital image correlation

Pain at the tip of the stem of a knee prosthesis (End-of-Stem Pain) is a common problem in revision total knee arthroplasty (TKA). It may be caused by a problematic interaction between stem and bone, but the exact biomechanical correlate is still unknown. On top of this, there is no biomechanical study investigating End-of-Stem Pain at the distal femur using human specimens. Aim of this study was to find out whether the implantation of a revision total knee implant leads to high femoral surface strains at the tip of the stem, which the authors expect to be the biomechanical correlate of End-of-Stem Pain. We implanted 16 rotating hinge knee implants into 16 fresh-frozen human femora using the hybrid fixation technique and comparing two reaming protocols. Afterwards, surface strains on these femora were measured under dynamic load in two different load scenarios (climbing stairs and chair rising) using digital image correlation (DIC) and fracture patterns after overcritical load were analysed. Peak surface strains were found at the tip of the stem in several measurements in both load scenarios. There were no significant differences between the two compared groups (different trial sizes) regarding surface strains and fracture patterns. We conclude that implantation of a long intramedullary stem in revision TKA can lead to high surface strains at the tip of the stem that may be the correlate of femoral End-of-Stem Pain. This finding might allow for a targeted development of future stem designs that can lead to lower surface strains and therefore might reduce End-of-Stem Pain. Digital Image Correlation proved valid for the measurement of surface strains and can be used in the future to test new stem designs in vitro.

Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) Scores > 55 at 6 Months Postoperative Predict Ability to Achieve Patient Acceptable Symptomatic State at Minimum 1 Year Postoperative Following Autologous Chondrocyte Implantation for Grade IV Chondral Defects About the Patellofemoral Joint

PURPOSE

The primary aim is to evaluate the relationship between MOCART scores and patient satisfaction, as evaluated by achievement of (1) the Patient Acceptable Symptomatic State (PASS) and (2) the minimal clinically important difference (MCID) for Knee Injury and Osteoarthritis Score Quality of Life (KOOS QoL), for patients undergoing autologous chondrocyte implantation (ACI) for focal Grade IV patellofemoral chondral defects. The secondary aim is to determine the threshold MOCART score which predicts the ability to meet the PASS and the MCID for KOOS QoL.

METHODS

Patients undergoing ACI for grade IV patellofemoral chondral defects by a single surgeon from 2017 to 2020 were identified by search of the EMR. To determine PASS status, patients were asked, "Do you consider your current level of symptoms to be acceptable?" KOOS QoL scores were also collected. Patients with 6-month postoperative knee MRI, PASS scores, and minimum 2-year follow-up data were included. Paired t tests and Wilcoxon Rank-Sum tests were used to evaluate the relationship between MOCART scores and (1) PASS achievement and (2) achievement of the MCID for KOOS QoL (12.8).

RESULTS

Thirty-four patients were included, with a median age of 35.1 years [IQR: 24.6, 37.1], and BMI of 24.0 kg/m2 [IQR: 21.5, 28.1]. The median time to postoperative MRI was 6.7 months [IQR: 5.8, 7.9], and average follow-up time was 3.7 ± 1.2 years. Twenty-five patients (74%) achieved PASS, and 18 patients (out of 27 who had postop KOOS QoL Scores, 67%) achieved the MCID for KOOS QoL. Patients who achieved PASS had higher average MOCART scores (61.8 ± 16.0) than those who did not achieve PASS (45.0 ± 12.8, p=0.011), whereas patients who achieved the MCID for KOOS QoL did not have higher MOCART scores than those who did not achieve the MCID (61.9 ± 18.3 versus 53.3 ± 17.1, P = 0.25). There was no relationship between age, sex, lesion size, and lesion location and ability to achieve PASS or MCID for KOOS QoL (p>0.05). A threshold MOCART value of 55 was associated with the highest AUC on ROC analysis for likelihood of achieving PASS (0.778) and MCID for KOOS QoL (0.667).

CONCLUSION

Higher MOCART scores are associated with an increased likelihood of achieving PASS following patellofemoral ACI. Moreover, MOCART scores > 55 predict the ability to achieve PASS and the MCID for KOOS QoL following patellofemoral ACI.

LEVEL OF EVIDENCE

IV.

Morphology and transverse alignment of the patella have no effect on knee gait characteristics in healthy Chinese adults over the age of 40 years

Background: The influence of patella morphology and horizontal alignment on knee joint kinematics and kinetics remains uncertain. This study aimed to assess patella morphology and transverse alignment in relation to knee kinetics and kinematics in individuals without knee conditions. A secondary objective was to investigate the impact of femur and tibia alignment and shape on knee gait within this population. Patients and methods: We conducted a prospective collection of data, including full-leg anteroposterior and skyline X-ray views and three-dimensional gait data, from a cohort comprising 54 healthy individuals aged 40 years and older. Our study involved correlation and logistic regression analyses to examine the influence of patella, femur, and tibia morphology and alignment on knee gait. Results: The patellar tilt angle or the patella index did not show any significant relationships with different aspects of gait in the knee joint, such as velocity, angle, or moment (p > 0.05, respectively). Using multivariate logistic regression analysis, we found that the tibiofemoral angle and the Q angle both had a significant effect on the adduction angle (OR = 1.330, 95%CI 1.033-1.711, p = 0.027; OR = 0.475, 95%CI 0.285-0.792, p = 0.04; respectively). The primary variable influencing the knee adduction moment was the tibiofemoral angle (OR = 1.526, 95% CI 1.125-2.069, p = 0.007). Conclusion: In healthy Chinese individuals aged over 40, patella morphology and transverse alignment do not impact knee gait. However, the femoral-tibial angle has a big impact on the knee adduction moment.

Evolution in the Management of Patella Fractures

Patella fractures usually occur as a result of direct trauma to the anterior knee joint, indirect injury as a result of eccentric muscle contraction, or rapid knee flexion against a contracted quadriceps muscle. The patella functions as part of the extensor mechanism of the knee, where large forces are transmitted, and its subcutaneous nature has made treatment of patella fractures a challenge. In this review article, we evaluate how the management of these fractures has evolved over time and the advantages associated with the various treatment techniques. There are few comparative studies looking at the different treatment types for fractures of the patella, with the goal of achieving a functional extensor mechanism with low rates of post-traumatic arthritis and metal-work irritation.

Gradual loaded exercise of knee extension muscles using an orthosis after wide resection of a femoral sarcoma and quadriceps muscle: a case report

BACKGROUND

Details of improved gait ability after wide resection of soft tissue sarcomas that necessitate removal of portions of the quadricep muscle have not yet been reported. We describe a patient with improved gait ability following a rehabilitation program after wide resection of a soft tissue sarcoma that included four components of the quadricep muscle.

CASE PRESENTATION

An 85-year-old Japanese man underwent wide resection of an undifferentiated pleomorphic sarcoma that included portions of the quadriceps femoris muscle. The rectus femoris, vastus medialis, sartorius, and vastus intermedius were separated in the maximally bulging region of the tumour. Three weeks postoperatively, gait exercise was initiated using a rigid knee orthosis with a dual-adjustable lock knee. The contraction loading of the knee extension muscle was controlled by adjusting the hinge motion range of the orthosis as follows: fully extended, fixed knee 0°-30°, and free range. Under this regimen, he could walk independently without a rigid orthosis within 5 weeks postoperatively but could not sit on his heels during daily living activities. At six months, there was no clinical evidence of recurrent tumours or complications.

CONCLUSIONS

Postoperative gait ability might be affected by not only the number of resected muscles but also by the function of the separated muscles and the cross-sectional area of the remaining muscle. Gradually loaded exercise of the knee extension muscles using an orthosis could result in an improved gait motion for patients who undergo wide resection of a sarcoma that includes four components of the quadriceps femoris.

Exoskeletons: A challenge for development

The development of exoskeletons is currently a lengthy process full of challenges. We are proposing a framework to accelerate the process and make the resulting exoskeletons more user-centered. The needed accomplishments in science are described in an effort to lay the foundation for future research projects. Since the early 2000s, exoskeletons have been discussed as an emerging technology in industrial, medical, or military applications. Those systems are designed to support people during manual tasks. At first, those systems lacked broad acceptance. Many models found their niches in ongoing developments and more diverse systems entering the market. There are still applications that are in dire need of such assistance. Due to the lack of experience with body-worn robotics, the development of such systems has been shaped by trial and error. The lack of legacy products results in longer development times. In this paper, a process to generate a framework is presented to display the required research to enable future exoskeleton designers. Owing to their proximity to the user's body, exoskeletons are highly complex systems that need sophisticated subsystems, such as kinematic, control, interaction design, or actuators, to be accepted by users. Due to the wide variety of fields and high user demands, a synchronized multidisciplinary effort is necessary. To achieve this, a process to develop a modular framework for exoskeleton design is proposed. It focuses on user- and use-case-centered solutions for matching kinematics, actuation, and control. To ensure the usefulness of the framework, an evaluation of the incorporated solutions is required.

Patellar tendon lengthening and augmentation with quadriceps tendon graft for treatment of severe patella infera

BACKGROUND

Patella infera represents a permanent abnormally low position of the patella with three characteristics: distal position of the patella in the femoral trochlea, permanent shortening of the patellar tendon, and decreased distance between the inferior pole of the patella and the articular surface of the tibia. Several surgical techniques have been described to resolve this disabling condition with varying outcomes.

HYPOTHESIS

Lengthening of the shortened patellar tendon with augmentation using a quadriceps tendon graft in combination with excessive intra-articular release improve knee function in patients presenting with severe and permanent patella infera.

METHODS

Nine patients (four males, five females) with significant patella infera were treated between 2004 and 2020. The low position of the patella was documented using the Caton-Deschamps index. The Tegner Lysholm knee scoring scale and the Numerical Rating Scale (NRS) for pain were used as outcome measures before surgery and at follow up. Complete data were available in 100% of cases at 12 months follow up, and in 78% at final follow up.

RESULTS

The average follow up was 4.2 years (range, 1-16 years). The Tegner Lysholm score improved from a mean preoperative score of 43.8 to a mean postoperative score of 80.5. The median NRS status decreased from an average of 6.7 (range, 5-8) to 2.3 (range, 1-7). The median preoperative flexion was 103.3° (range, 40-125°), rising to 126.6° (range, 40-145°). The median preoperative Caton-Deschamps ratio of 0.32 (range, 0-0.6) improved to 0.99 (range, 0.9-1.1) at final follow up. Two patients needed additional surgical treatment (arthroscopic scar tissue removal and proximalisation of the tibial tuberosity).

CONCLUSION

Lengthening of a shortened patellar tendon with augmentation using a quadriceps tendon graft combined with excessive intra-articular release is an individually adapted surgical salvage procedure to treat permanent patella infera. It improves knee function and yields good to excellent results in most cases.

Causal associations of obesity related anthropometric indicators and body compositions with knee and hip arthritis: A large-scale genetic correlation study

Backgrounds

Epidemiological studies have repeatedly investigated the association between obesity related anthropometric indicators and body compositions and osteoarthritis (OA). However, the results have remained inconsistent. This work aimed to investigate the genetic correlation and causal associations of obesity related anthropometric indicators and body compositions with knee and hip OA.

Methods

Single-nucleotide polymorphisms associated with the exposures were searched from the recent genome-wide association studies (GWAS) to obtain full statistics. Summary-level results of knee and hip OA were from the UK Biobank and arcOGEN. First, linkage disequilibrium score regression (LD score regression) was applied to detect the genetic correlation (rg). We further performed a series of sensitivity analyses as validation of primary mendelian randomization (MR) results and the specific evidence of potential causal effects was defined.

Results

We found that genetic components in OA had significant correlation with obesity related traits, except waist-to-hip ratio. In the univariable MR analysis, with the exception of waist-to-hip ratio, obesity related anthropometric indicators were causally associated with increased risks of knee and hip OA. For obesity related body compositions, higher fat-free mass in arm, leg, and whole body increased the risk of knee OA but only fat-free mass in leg showed a significant association with hip OA. Meanwhile trunk fat mass and trunk fat percentage, were associated with knee but not with hip OA. Higher fat mass, and fat percentage in arm, leg, and whole body increased the risk of both knee and hip OA. After adjusting for BMI, the multivariable MR showed maintained results in knee OA. However, in hip OA, only fat mass and fat-free mass in arm, leg, trunk and whole body were significantly associated with the risk of hip OA.

Conclusion

The present study suggests genetic evidence for certain causal associations of obesity related anthropometric indicators and body compositions with knee and hip OA, which may provide important insights for the prevention and treatment on OA.

Study on the Role of MicroRNA-214 in the Rehabilitation of Cartilage in Mice with Exercise-Induced Traumatic Osteoarthritis

This study aimed to explore the possible relationship between the expression of Micro RNA-214 (miR-214) and the pathogenesis and recovery in mice with post-traumatic osteoarthritis (PTOA). In this study, 40 male C57BL/6 mice were randomly divided into five groups: model control (MC) group, model (M) group, rehabilitation control (RC) group, model + rehabilitation (M + R) group, and model + convalescent (M + C) group. Four weeks of high-intensity treadmill exercise (HITE) and 4 weeks of moderate-intensity treadmill exercise (MITE) were implemented for PTOA modeling and rehabilitation, respectively. In vitro, 10% elongation mechanical strain was used for IL-1β stimulated chondrocytes. We found that compared with the MC group, there was a significant increase in the aspect of inflammation and catabolism while a dramatic fall in miR-214 expression was observed in the M group. After the 4 weeks of MITE, the level of inflammation and metabolism, as well as miR-214 expression, was partially reversed in the M + R group compared with the M + C group. The expression of miR-214 decreased dramatically after chondrocyte stimulation by IL-1β and then increased significantly after 10% strain was applied to IL-1β-treated cells. These results suggest that a suitable mechanical load can increase the expression of miR-214, and that miR-214 may play a chondroprotective effect in the development of OA.

Suture tension band fixation vs. metallic tension band wiring for patella fractures - A biomechanical study on 19 human cadaveric patellae

PURPOSE

Traditional tension band fixation of patella fracture is associated with high reoperation rates. The purpose of the study was to assess strength of fixation in patella fractures treated with either a non-metallic all suture-based technique or traditional metallic tension band wiring.

METHODS

Ten paired human cadaveric specimens were included. A transverse fracture was created, reduced and fixated with a non-metallic or metallic approach. Non-metallic fixation was done according to a previously published technique, metallic fixation was done according to AO description. Specimens were fixed in 90° of flexion and underwent 200 cycles of loading by pulling the Quadriceps tendon to 300 Newton. Fracture displacement was optically monitored. Primary outcome was fracture displacement after 200 cycles compared to the first cycle. Subsequently, load-to-failure was assessed by a monotonic pull to 1000 N.

RESULTS

For cyclic loading analysis, one specimen from each group was excluded due to machine synchronization, resulting in a total population of 18 specimens. Median (min-max) fracture displacement was 0.65 mm (0.06-1.3) in the non-metallic group and 0.68 mm (0-1.23), (p=0.931) in the metallic group. No difference in displacement was found between the two groups in the repeated measures analysis of variance (p=0.5524). For load-to-failure analysis one specimen was excluded due to machine synchronization, resulting a total population of 19 specimens. 2/9 specimens failed in the non-metallic group (at 979 and 635 N) and 2/10 failed in the metallic group (745 and 654 N).

CONCLUSION

Non-metallic technique is a biomechanically viable alternative to traditional tension band fixation and it can hopefully lead to fewer implant-related complications.

Anterior Knee Pain: State of the Art

Anterior knee pain (AKP) is one of the most common conditions to bring active young patients to a sports injury clinic. It is a heterogeneous condition related to multiple causative factors. Compared to the general population, there appears to be a higher risk of development of patellofemoral osteoarthritis in patients with AKP. AKP can be detrimental to the patient’s quality of life and, in the larger context, significantly burdens the economy with high healthcare costs. This study aims to present a comprehensive evaluation of AKP to improve clinical daily practice. The causes of AKP can be traced not only to structures within and around the knee, but also to factors outside the knee, such as limb malalignment, weakness of specific hip muscle groups, and core and ligamentous laxity. Hence, AKP warrants a pointed evaluation of history and thorough clinical examination, complemented with relevant radiological investigations to identify its origin in the knee and its cause. Conservative management of the condition achieves good results in a majority of patients with AKP. Surgical management becomes necessary only when it is deemed to provide benefit—when the patient has well-characterized structural abnormalities of the knee or limb that correlate with the AKP clinically or in situations where the patient does not obtain significant or sustained relief from symptoms. AKP has a multifactorial etiology. The treatment strategy must be individualized to the patient based on the patient profile and specific cause identified. Hence, treatment of AKP warrants a pointed evaluation of history and thorough clinical examination complemented with relevant radiological investigations to identify the condition’s origin and its cause. A holistic approach focused on the patient as a whole will ensure a good clinical outcome, as much as a focus on the joint as the therapeutic target.

Modelling and in vivo evaluation of tendon forces and strain in dynamic rehabilitation exercises: a scoping review

OBJECTIVES

Although exercise is considered the preferred approach for tendinopathies, the actual load that acts on the tendon in loading programmes is usually unknown. The objective of this study was to review the techniques that have been applied in vivo to estimate the forces and strain that act on the human tendon in dynamic exercises used during rehabilitation.

DESIGN

Scoping review.

DATA SOURCES

Embase, PubMed, Web of Science and Google Scholar were searched from database inception to February 2021.

ELIGIBILITY CRITERIA

Cross-sectional studies available in English or Spanish language were included if they focused on evaluating the forces or strain of human tendons in vivo during dynamic exercises. Studies were excluded if they did not evaluate tendon forces or strain; if they evaluated running, walking, jumping, landing or no dynamic exercise at all; and if they were conference proceedings or book chapters.

DATA EXTRACTION AND SYNTHESIS

Data extracted included year of publication, study setting, study population characteristics, technique used and exercises evaluated. The studies were grouped by the types of techniques and the tendon location.

RESULTS

Twenty-one studies were included. Fourteen studies used an indirect methodology based on inverse dynamics, nine of them in the Achilles and five in the patellar tendon. Six studies implemented force transducers for measuring tendon forces in open carpal tunnel release surgery patients. One study applied an optic fibre technique to detect forces in the patellar tendon. Four studies measured strain using ultrasound-based techniques.

CONCLUSIONS

There is a predominant use of inverse dynamics, but force transducers, optic fibre and estimations from strain data are also used. Although these tools may be used to make general estimates of tendon forces and strains, the invasiveness of some methods and the loss of immediacy of others make it difficult to provide immediate feedback to the individuals.

Dynamic versus static medial patellofemoral ligament reconstruction technique in the treatment of recurrent patellar dislocation: a randomized clinical trial protocol

BACKGROUND

The redislocation rate of conservatively treated patella instability is high. One of the leading surgical strategies is medial patellofemoral ligament reconstruction. Over-tensioning is one of the most challenging complications in static medial patellofemoral ligament reconstruction as the graft used for reconstruction is isometric and the anatomical MPFL is a mostly dynamic structure. As an alternative to established static reconstruction techniques, dynamic graft techniques have been introduced for stabilizing the patella with the aim of providing a more physiological reconstruction of the medial patellofemoral ligament. To date, data on clinical outcomes are scarce and on biomechanical outcomes of the dynamic MPFL reconstruction are lacking. Here, we present the protocol of a randomized clinical trial for comparing clinical and biomechanical outcomes of dynamic versus static medial patellofemoral ligament reconstruction.

METHODS

This study is a prospective, single blinded, randomized, multicenter, multimodal (clinical and biomechanical) clinical trial. Patients with recurrent patella dislocation requiring isolated MPFL reconstruction will be recruited and randomized to the dynamic or static reconstruction technique. Participants will be followed up for 2 years with a total of five follow-ups. Preoperative magnetic resonance imaging, upright radiographs, surgical reports and patient records will be evaluated, and clinical and functional outcomes will be measured. Patient-reported knee function and anterior knee pain as assessed with the Kujala score will serve as primary outcome. For biomechanical outcome, pre- and postoperative evaluations will be performed to assess isokinetic muscle strength, gait asymmetry, joint kinematics and kinetics, and timing of muscle activity.

DISCUSSION

The results of the study will clarify whether the reported surgery success for patella stabilization via dynamic MPFL reconstruction is due to muscle contraction or to the passive tenodesis effect combined with clinical outcome measures. With this study, we will provide much needed information on knee biomechanics after dynamic versus static MPFL reconstruction to provide evidence to support orthopedic surgeons in evidence-based decision-making in their quest for surgical techniques most favorable for their patients. Trial registration The study protocol was registered at clinicaltrials.gov (NCT04849130). Registered 19 April 2021, https://clinicaltrials.gov/ct2/show/NCT04849130 .

Techniques to determine knee joint contact forces during squatting: A systematic review

This review article provides an overview of techniques used to determine human knee joint contact forces during squatting. The main two approaches are experimental and theoretical. Thigh calf contact has a significant effect on knee forces and should not be neglected. In this study, data were searched electronically and organized by techniques to find knee joint contact force during squatting theoretically and experimentally. There was a large variation in peak tibiofemoral (CV = 0.45) and patellofemoral (CV = 0.38) contact forces predicted theoretically. However, very little variation was observed between peak tibiofemoral contact forces (CV = 0.12) measured in vivo experimentally but measured knee joint force is available up to a limited knee flexion angle. There was a reduction in knee joint contact forces due to thigh calf contact. Literature of knee joint contact force prediction theoretically during squatting incorporating thigh calf contact force is very limited.

A staged procedure for the treatment of chronic patellar tendon ruptures after total knee arthroplasty

The management of extensor mechanism lesions after total knee replacement is still associated with an unacceptably high complication rate, especially in its chronic setting. In this study, we report on 4 patients with chronic (> 3 months) patellar tendon rupture after knee arthroplasty, who were treated with a novel procedure of staged patella advancement prior to reconstruction with autografts. Initially, a unilateral frame was applied connecting the patella with the tibial shaft. The construct allowed for gradual distal advancement of the patella based on the Ilizarov principles. After achieving the desired patella height, the frame was removed, and the patellar tendon was reconstructed with hamstrings. All four patients experienced a significant improvement in extensor lag by a mean of 38.0°, while Knee society scores increased by a mean of 38.5 units. No substantial loss in active knee flexion was observed. Our findings suggest that our technique yields favorable outcomes in patients with patellar tendon disruption in the setting of a total knee arthroplasty.

The Wheelchair Propulsion Wheel Rotation Angle Function Symmetry in the Propelling Phase: Motion Capture Research and a Mathematical Model

The movement of a wheelchair with manual propulsion depends on the kinematics of the human body and the forces exerted by the muscles. To design innovative wheelchair propulsion systems, the biomechanical parameters resulting from human interaction in this anthropotechnical system must be formalised. The research objectives were thus adopted: an analysis of the propulsion wheel angle of rotation resulting from the hand movement’s trajectory and the mathematical formalisation of the propulsion wheel angle of rotation described as a function of the propelling phase’s duration. The research was carried out using three variants of manually propelled wheelchairs on a group of 10 patients representing the same group (C50) of anthropometric dimensions. The research demonstrated that the function of the propulsion wheel angle of rotation shows the features of central symmetry occurring at an angle of rotation of φ 52° and a propelling phase duration of 58%. Moreover, the measurements were averaged and a mathematical model of the propulsion wheel rotation function during the propulsion phase was developed, depending on the percentage of duration.

Obesity impacts the mechanical response and biochemical composition of patellofemoral cartilage: An in vivo, MRI-based investigation

Obesity is a primary risk factor for osteoarthritis. While previous work has addressed relationships between in vivo cartilage mechanics, composition, and obesity in the tibiofemoral joint, there is limited information on these relationships in the patellofemoral joint. The purpose of this study was to compare the patellofemoral cartilage mechanical response to walking in participants with normal and obese body mass indices (BMIs). Additionally, patellar cartilage T1rho relaxation times were measured before exercise to characterize the biochemical composition of the tissue. Fifteen participants (eight with normal BMI and seven with obese BMI) underwent baseline magnetic resonance imaging (MRI) of their right knee. They then walked on a treadmill for 20 min at a speed normalized to their leg length before a second MRI scan. Subsequently, three-dimensional models of the bones and articular surfaces of the patellofemoral joint were created via manual segmentation of the pre- and post-exercise MR images to compute cartilage thickness and strain. Strain was defined as the change in patellofemoral cartilage thickness normalized to the baseline thickness. Results showed that participants with an obese BMI exhibited significantly increased patellofemoral cartilage strain compared to those with a normal BMI (5.4 ± 4% vs. 1.7 ± 3%, respectively; p = 0.003). Furthermore, patellar cartilage T1rho values were significantly higher in participants with obese versus normal BMIs (95 ms vs. 83 ms, respectively; p = 0.049), indicative of decreased proteoglycan content in those with an obese BMI. In summary, the altered patellofemoral cartilage strain and composition observed in those with an obese BMI may be indicative of cartilage degeneration.

May the force be with you: understanding how patellofemoral joint reaction force compares across different activities and physical interventions-a systematic review and meta-analysis

OBJECTIVE

To systematically review and synthesise patellofemoral joint reaction force (PFJRF) in healthy individuals and those with patellofemoral pain and osteoarthritis (OA), during everyday activities, therapeutic exercises and with physical interventions (eg, foot orthotics, footwear, taping, bracing).

DESIGN

A systematic review with meta-analysis.

DATA SOURCES

Medline, Embase, Scopus, CINAHL, SportDiscus and Cochrane Library databases were searched.

ELIGIBILITY CRITERIA

Observational and interventional studies reporting PFJRF during everyday activities, therapeutic exercises, and physical interventions.

RESULTS

In healthy individuals, the weighted average of mean (±SD) peak PFJRF for everyday activities were: walking 0.9±0.4 body weight (BW), stair ascent 3.2±0.7 BW, stair descent 2.8±0.5 BW and running 5.2±1.2 BW. In those with patellofemoral pain, peak PFJRF were: walking 0.8±0.2 BW, stair ascent 2.5±0.5 BW, stair descent 2.6±0.5 BW, running 4.1±0.9 BW. Only single studies reported peak PFJRF during everyday activities in individuals with patellofemoral OA/articular cartilage defects (walking 1.3±0.5 BW, stair ascent 1.6±0.4 BW, stair descent 1.0±0.5 BW). The PFJRF was reported for many different exercises and physical interventions; however, considerable variability precluded any pooled estimates.

SUMMARY

Everyday activities and exercises involving larger knee flexion (eg, squatting) expose the patellofemoral joint to higher PFJRF than those involving smaller knee flexion (eg, walking). There were no discernable differences in peak PFJRF during everyday activities between healthy individuals and those with patellofemoral pain/OA. The information on PFJRF may be used to select appropriate variations of exercises and physical interventions.

Moderate-intensity treadmill running relieves motion-induced post-traumatic osteoarthritis mice by up-regulating the expression of lncRNA H19

BACKGROUND

The purpose of this study was to explore whether moderate-intensity exercise can alleviate motion-induced post-traumatic osteoarthritis (PTOA) and the expression change of lncRNA H19 during this progression.

METHODS

Twenty-week-old male C57BL/6 mice were randomly divided into five groups: model control group (MC group, n = 6), treadmill model group (M group, n = 6), rehabilitation control group (RC group, n = 6), treadmill model + rehabilitation training group (M + R group, n = 6) and treadmill model + convalescent group (M + C group, n = 6). Paraffin sections were used to observe the pathological changes in the mouse knee joint in each group. A micro-CT was used to scan the knee joint to obtain the morphological indexes of the tibial plateau bone. Real-time PCR was used to detect the mRNA levels of inflammatory factors, synthetic and catabolic factors in cartilage.

RESULTS

After high-intensity exercise for 4 weeks, the inflammation and catabolism of the mouse knee cartilage were enhanced, and the anabolism was weakened. Further study showed that these results were partially reversed after 4-week moderate-intensity training. The results of hematoxylin-eosin staining confirmed this finding. Meanwhile, high-intensity exercise reduced the expression of lncRNA H19 in cartilage, while the expression of lncRNA H19 increased after 4 weeks of moderate-intensity exercise.

CONCLUSION

High-intensity treadmill running can cause injury to the knee cartilage in C57BL/6 mice which leads to PTOA and a decrease of lncRNA H19 expression in cartilage. Moderate-intensity exercise can relieve PTOA and partially reverse lncRNA H19 expression.

Knee extension moment arm variations relate to mechanical function in walking and running

The patellofemoral joint plays a crucial mechanical role during walking and running. It increases the knee extensor mechanism's moment arm and reduces the knee extension muscle forces required to generate the extension moment that supports body weight, prevents knee buckling and propels the centre of mass. However, the mechanical implications of moment arm variation caused by patellofemoral and tibiofemoral motion remain unclear. We used a data-driven musculoskeletal model with a 12-degree-of-freedom knee to simulate the knee extension moment arm during walking and running. Using a geometric method to calculate the moment arm, we found smaller moment arms during running than during walking in the swing phase. Overall, knee flexion causes differences between running and walking moment arms as increased flexion causes a posterior shift in the tibiofemoral rotation axis and patella articulation with the distal femur. Moment arms were also affected by knee motion direction and best predicted by separating by direction instead of across the entire gait cycle. Furthermore, we found high inter-subject variation in the moment arm that was largely explained by out-of-plane motion. Our results are consistent with the concept that shorter moment arms increase the effective mechanical advantage of the knee and may contribute to increased running velocity.

Patella Fractures: Approach to Treatment

Patellar fracture morphology varies based on the mechanism of injury. Most fractures are either a result of direct impact or through an indirect eccentric extensor contraction injury. Each fracture pattern requires appropriate preoperative planning and individualization of the fixation method. Displaced fractures affect the extension apparatus, and often require surgical fixation. Surgical treatment is recommended in fractures with any of the following features: articular step-off > 2 mm, > 3 mm of fracture displacement, open fractures, and displaced fractures affecting the extensor mechanism. Meticulous handling of the soft-tissue envelope is of the utmost importance, given the patella's tenuous blood supply and limited soft-tissue envelope. Incongruent articular surface can result in detrimental long-term effects; therefore, surgical treatment is directed toward anatomic reduction and fixation. The evolution of patellar fracture fixation continues to maximize options to balance rigid fixation with low-profile fixation constructs. Improving functional outcomes, minimizing soft-tissue irritation, and limiting postoperative complications are possible by using the therapeutic principles of rigid anatomical fixation and meticulous soft-tissue handling.

Patella fractures treated with suture tension band fixation

BACKGROUND

Patella fractures requiring surgery are traditionally treated using metallic implants, which are associated with high re-operation rates, mainly due to implant prominence. To overcome the problem of prominent metallic implants, we present a technique based purely on braided sutures.

METHODS

This technique is described in a step-wise, standardised way based on our findings on six patients treated at our institution.

RESULTS

This technique can be adapted to all types of patella fractures. The described suture configuration allows maintenance of inter-fragmentary reduction until bony union without symptoms from the suture material.

CONCLUSIONS

We believe that this technique is a safe and promising alternative to traditional metallic fixation methods.

Technique for Fixation of Semitendinosus to the Patella in Patellar Tendon Reconstruction

Chronic patellar tendon injuries are rare yet challenging to treat. Timing of surgery and graft choices are debatable. Many techniques and methods of fixation have been described with pros and cons. Functional impairment of the extensor mechanism and postoperative complications triggers the quest for finding the ideal technique. In this Technical Note, we use distally based semitendinosus (ST) looped over 2 ETHIBOND sutures. The ETHIBOND is passed through 2 vertical tunnels in the patella and retrieved proximally, docking the ST in a blind tunnel created in the lower pole of the patella. The whip-stitched free ST end is passed through a tunnel behind the tibial tubercle and sutured back to its base. A polyester tape is used to augment the repair in a circumferential manner. Postoperatively full weight bearing is allowed as tolerated in a hinged knee brace locked in extension with only passive range of motion of 0-90° allowed for 6 weeks.

Comminuted patellar fractures: The role of biplanar fixed angle plate constructs

Background

Comminuted patellar fractures represent a challenging clinical problem. Treatment aims to restore the integrity of the extensor mechanism and the congruity of patellofemoral joint. Controversy exists regarding the ideal fixation method. Metallic constructs aiming to convert pulling forces on the anterior aspect of the patella into compression forces across the fracture site are the standard of care. More recently, low profile plates have been described in the management of comminuted patellar fractures. The aims of this study were to (1) develop a novel unstable patellar fracture model and (2) to compare biomechanically three different constructs for fixation comminuted patellar fractures. We hypothesized that an orthogonal biplanar disposition of the screws within an anteriorly placed locking plate provides the best biomechanical properties in the management of comminuted fractures.

Methods

Six-part complex AO 34–C3 patella fractures were simulated in 18 human cadaveric knees by means of osteotomies including comminution around the distal patellar pole. The specimens were randomly assigned to 3 fixation techniques (n ​= ​6) for either anterior plating, antero-lateral plating, or tension band wiring (TBW). Biomechanical testing was performed over 5000 cycles in active extension and passive flexion, followed by ultimate destructive quasi-static testing. Interfragmentary movements were captured by means of optical motion tracking.

Results

Displacement between the proximal and distal medial patella fragments was lower after anterior plating compared to both antero-lateral plating (P ​= ​0.084) and TBW (P ​< ​0.001). Moreover, displacement between the proximal and distal lateral fragments was significantly lower after anterior plating compared to both other techniques (P ​≤ ​0.032). In addition, it was significantly lower for antero-lateral plating versus TBW (P ​< ​0.001). Rotation around the medio-lateral axis between the proximal and distal medial fragments was significantly lower after anterior plating compared to TBW (P ​= ​0.017).

Conclusions

Anterior mesh plating with biplanar placement of locking screws provides superior stability for fixation of comminuted patellar fractures when compared to both antero-lateral mesh plating and TBW. The latter is associated with considerably inferior performance.

Integration and Testing of a Three-Axis Accelerometer in a Woven E-Textile Sleeve for Wearable Movement Monitoring

This paper presents a method to integrate and package an accelerometer within a textile to create an electronic textile (e-textile). The smallest commercially available accelerometer sensor (2 mm × 2 mm × 0.95 mm) is used in the e-textile and is fully integrated within the weave structure of the fabric itself, rendering it invisible to the wearer. The e-textile forms the basis of a wearable woven sleeve which is applied to arm and knee joint bending angle measurement. The integrated e-textile based accelerometer sensor system is used to identify activity type, such as walking or running, and count the total number of steps taken. Performance was verified by comparing measurements of specific elbow joint angles over the range of 0° to 180° with those obtained from a commercial bending sensor from Bend Labs and from a custom-built goniometer. The joint bending angles, measured by all three sensors, show good agreement with an error of less than ~1% of reading which provides a high degree of confidence in the e-textile sensor system. Subsequently, knee joint angles were measured experimentally on three subjects with each being tested three times on each of three activities (walking, running and climbing stairs). This allowed the minimum and maximum knee joint angles for each activity to be determined. This data is then used to identify activity type and perform step counting.

Patellofemoral joint kinetics in females when using different depths and loads during the barbell back squat

Back squats are a common strengthening exercise for knee and hip musculature. However, repetitive loaded movements like backs squats result in high patellofemoral joint loading and therefore may contribute to the development of common overuse injuries. Thus, it is important to understand how changing parameters such as squat depth or load influences patellofemoral loading. This study investigated differences in patellofemoral loading when experienced female lifters squatted to three depths (above parallel, parallel, and below parallel) and with three loads (unloaded, 50%, and 85% of depth-specific one repetition maximums). Patellofemoral joint reaction forces (pfJRF) and stresses (pfJS) were calculated from biomechanical models incorporating knee extensor moments (KEM) and joint angles. Peak KEMs displayed a depth-by-load interaction such that within each depth, as load increased so did peak KEM. However, within each load, the effects of depth were different. Peak pfJRF also increased with load and was higher at below parallel than above or parallel depths. Peak pfJS also displayed a depth-by-load interaction, increasing with load within a given depth, and being greatest at the below parallel depths within a given load. If patellofemoral joint loading is a concern, clinicians or coaches should carefully monitor the depth and load combinations being used.

A musculoskeletal modelling approach to explain sit-to-stand difficulties in older people due to changes in muscle recruitment and movement strategies

By 2050 the proportion of over 65s is predicted to be 20% of the population. The consequences of an age-related reduction in muscle mass have not been fully investigated and, therefore, the aim of the present study was to quantify the muscle and joint contact forces using musculoskeletal modelling, during a sit-to-stand activity, to better explain difficulties in performing everyday activities for older people. A sit-to-stand activity with and without the use of arm rests was observed in ninety-five male participants, placed into groups of young (aged 18-35 years), middle-aged (aged 40-60 years) or older adults (aged 65 years and over). Older participants demonstrated significantly lower knee extensor and joint forces than the young when not using arm rests, compensating through elevated hip extensor and ankle plantarflexor muscle activity. The older group were also found to have higher shoulder joint contact forces whilst using arm rests. This tendency to reorganise muscle recruitment to include neighbouring groups or other parts of the body could make everyday activities more susceptible to age-related functional decline. Reductions in leg strength, via age- or atrophy- related means, creates increased reliance on the upper body and may result in further lower limb atrophy through disuse. The eventual decline of upper body function reduces strength reserves, leading to increased vulnerability, dependence on others and risk of institutionalisation.

Design Evaluation of a Novel Multicompartment Unloader Knee Brace

Knee osteoarthritis (OA) is a significant problem in the aging population, causing pain, impaired mobility, and decreased quality of life. Conservative treatment methods are necessary to reduce rapidly increasing rates of knee joint surgery. Recommended strategies include weight loss and knee bracing to unload knee joint forces. Although weight loss can be beneficial for joint unloading, knee OA patients often find it difficult to lose weight or begin exercise due to knee pain, and not all patients are overweight. Unicompartment offloader knee braces can redistribute joint forces away from one tibiofemoral (TF) compartment; however, <5% of patients have unicompartmental tibiofemoral osteoarthritis (TFOA), while patients with isolated patellofemoral or multicompartmental OA are much more common. By absorbing body weight (BW) and assisting the knee extension moment using a spring-loaded hinge, sufficiently powerful knee-extension-assist (KEA) braces could be useful for unloading the whole knee. This paper (1) describes the design of a spring-loaded tricompartment unloader (TCU) knee brace intended to provide unloading in all three compartments of the knee while weight-bearing, (2) measures and compares the force output of the TCU against the only published and commercially available KEA brace, and (3) calculates the static unloading capacity of each device. The TCU and KEA braces delivered maximum assistive moments equivalent to reducing BW by approximately 45 and 6 lbs, respectively. The paper concludes that sufficiently powerful spring-loaded knee braces show promise in a new class of multicompartment unloader knee orthoses, capable of providing a clinically meaningful unloading effect across all three knee compartments.

[Patellar fractures]

Patellar fractures are a relatively rare entity with an prevalence of 1%. Preoperative computed tomography has gained a significant role as a diagnostic tool for patellar fractures in recent years. It enables an exact assessment of the fracture and helps in the decision making for the correct treatment procedure. Therapeutically, the armamentarium was supplemented by angle stable plate fixation, which potentially enables a better reconstruction of the patella than the conventional tension band fixation. In this context, the results of angle stable plate fixation are promising in terms of functional outcome and lower complication rates. The proven tension band fixation using K‑wires or cannulated screws continues to be widespread in clinical practice and retains significance for simple patellar fractures. The use of polyethylene thread material instead of steel wire has shown advantages in biomechanical studies but the clinical application is more restrained.

Biomechanical Comparison of Tension Band Fixation of Patella Transverse Fracture: Headless Screws Versus Headed Screws

OBJECTIVE

This study aimed to investigate the stability and strength of tension band wire fixation using headless compression screws versus headed screws for transverse patella fractures.

METHODS

Six matched pairs of fresh-frozen cadaveric knees with transverse osteotomies created at the midpoint of the patella were surgically fixed, with one knee randomly receiving fixation with headless screws (Acumed Acutrak 4/5) and the other with headed screws (Synthes 4.0 partially threaded cannulated screws). The specimens were mounted onto a servohydraulic load frame in a 45-degree flexed position and loaded through the quadriceps tendon. Interfragmentary movement was recorded with a motion analysis system. The initial fixation stiffness, range of interfragmentary motion, and strength of the headless screw construct were compared with the headed screw construct. Failure was defined as either a sudden drop in applied tendon force or 2 mm of separation on the anterior surface of the patella (ie, clinical failure), whichever occurred first.

RESULTS

Mean primary interfragmentary motion was 0.31 ± 0.28 degrees for the headed screws and 0.10 ± 0.06 degrees for headless screws under 150 N load (P = 0.03). Mean construct stiffness was 277 ± 243 N/degrees for the headed screws and 510 ± 362 N/degrees for the headless screws (P = 0.03). None of the constructs from either group displayed structural failure before reaching the clinical failure gap of 2 mm. The mean clinical failure strength was 808 ± 183 N for the headless screws construct and 520 ± 241 N for the headed screws construct (P = 0.03).

CONCLUSIONS

Headless screw tension band fixation demonstrated superior biomechanical behaviors over standard headed screw fixation with higher construct rigidity, smaller interfragmentary motion, and greater fixation strength.

Treatment of Extensor Tendon Disruption After Total Knee Arthroplasty: A Systematic Review

BACKGROUND

Patellar or quadriceps tendon ruptures after total knee arthroplasty constitute a devastating complication with historically poor outcomes. With advances in soft tissue reconstruction and repair techniques, treatment has become more nuanced. Numerous graft options for reconstruction and suture techniques for repair have been described but there is no consensus regarding optimal treatment.

METHODS

A search of PubMed, MEDLINE, Embase, and Scopus was conducted. Articles meeting inclusion criteria were reviewed. Type of intervention performed, type of injury studied, outcome measures, and complications were recorded. Quantitative and qualitative analyses were performed.

RESULTS

Twenty-eight articles met inclusion criteria. The complication rate after repair of patellar tendon (63.16%) was higher than the complication rate after repair of quadriceps tendon (25.37%). However, the complication rate for patellar and quadriceps tendon tears after autograft, allograft, or mesh reconstruction was similar (18.8% vs 19.2%, respectively). The most common complication after extensor mechanism repair or reconstruction was extension lag of 30° or greater (45.33%). This was followed by re-rupture and infection (25.33% and 22.67%, respectively). Early ruptures had a higher overall complication rate than late injuries.

CONCLUSION

Extensor mechanism disruption after total knee arthroplasty is a complication with high morbidity. Reconstruction of patellar tendon rupture has a much lower complication rate than repair. Our findings support the recommendation of patellar tendon reconstruction in both the early and late presentation stages. Quadriceps rupture can be treated with repair in early ruptures or with reconstruction in the late rupture or in the case of revision surgery.

Patellar tendon stress between two variations of the forward step lunge

BACKGROUND

Patellar tendinopathy (PT) or "jumper's knee" is generally found in active populations that perform jumping activities. Graded exposure of patellar tendon stress through functional exercise has been demonstrated to be effective for the treatment of PT. However, no studies have compared how anterior knee displacement variations during the commonly performed forward step lunge (FSL) affect patellar tendon stress.

METHODS

Twenty-five subjects (age: 22.69 ± 0.74 years; height: 169.39 ± 6.44 cm; mass: 61.55 ± 9.74 kg) performed 2 variations of an FSL with the anterior knee motion going in front of the toes (FSL-FT) and the knee remaining behind the toes (FSL-BT). Kinematic and kinetic data were used with an inverse-dynamics based static optimization technique to estimate individual muscle forces to determine patellar tendon stress during both lunge techniques. A repeated measures multivariate analysis was used to analyze these data.

RESULTS

The peak patellar tendon stress, stress impulse, quadriceps force, knee moment, knee flexion, and ankle dorsiflexion angle were significantly greater (p < 0.001) during the FSL-FT as compared to the FSL-BT. The peak patellar tendon stress rate did not differ between the FSL-FT and FSL-BT.

CONCLUSION

The use of an FSL-FT as compared to an FSL-BT increased the load and stress on the patellar tendon. Because a graded exposure of patellar tendon loading with other closed kinetic chain exercises has proven to be effective in treating PT, consideration for the prescription of variations of the FSL and further clinical evaluation of this exercise is warranted in individuals with PT.

Bioelectrical Activity of Vastus Medialis and Rectus Femoris Muscles in Recreational Runners with Anterior Knee Pain

Patellofemoral pain syndrome (PFPS), the most common source of knee pain among physically active individuals, is defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peri-patellar pathology. Differences in the activation and endurance of the quadriceps components, causing an imbalance in the forces controlling patellar tracking during flexion and extension in the knee joint, appear to be the most commonly reported risk factors for PFPS. The aim of this study was to determine the differences in bioelectric activity of vastus medialis and rectus femoris muscles during half knee bend position in runners with PFPS. The sample comprised 20 recreational runners (15 males, 5 females; aged 27 ± 5 years) reporting knee pain and diagnosed with PFPS. The age- and sex-matched control group consisted of recreational runners who did not report knee pain. The myon electromyographic system was used to determine the changes in the electromyographic median frequency during a half squat position. The decrease in the median frequency of vastus medialis and rectus femoris muscles was significantly greater in runners with PFPS in comparison to the control group (p < 0.01 for right and left vastus medialis and right rectus femoris; p < 0.05 for left rectus femoris). There is a relationship between knee pain related to PFPS and the imbalance of bioelectric activity of vastus medialis and rectus femoris muscles. Achieving the muscular balance within the thigh muscles can be an important factor in the rehabilitation process of PFPS.

The influence of compressive forces across the patellofemoral joint on patient-reported outcome after bi-cruciate stabilized total knee arthroplasty

AIMS

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome.

PATIENTS AND METHODS

This prospective study included 42 patients (42 knees) with varus-type osteoarthritis who underwent a bi-cruciate stabilized total knee arthroplasty and in whom the planned alignment was confirmed on 3D CT. Of the 42 patients, 36 were women and six were men. Their mean age was 72.3 years (61 to 87) and their mean body mass index (BMI) was 24.4 kg/m ² (18.2 to 34.3). After implantation of the femoral and tibial components, the compressive force across the patellofemoral joint was measured at 10°, 30°, 60°, 90°, 120°, and 140° of flexion using a load cell (Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) manufactured in the same shape as the patellar implant. Multiple regression analyses were conducted to investigate the relationship between intraoperative patellofemoral compressive force and patient-reported outcome two years after implantation.

RESULTS

No patient had anterior knee pain after total knee arthroplasty. The compressive force across the patellofemoral joint at 140°of flexion was negatively correlated with patient satisfaction (R ² = 0.458; β = -0.706; p = 0. 041) and Forgotten Joint Score-12 (FJS-12; R ² = .378; β = -0.636; p = 0. 036). The compressive force across the patellofemoral joint at 60° of flexion was negatively correlated with the patella score (R ² = 0.417; β = -0.688; p = 0. 046).

CONCLUSION

Patient satisfaction, FJS-12, and patella score were affected by the patellofemoral compressive force at 60° and 140° of flexion. Reduction of the patellofemoral compressive forces at 60° and 140° of flexion angle during total knee arthroplasty may improve patient-reported outcome, but has no effect on anterior knee pain.

Ultrasonographic assessment of articular cartilage of the femoral condyle in patients with an increased Q-angle

Introduction

The patella is a sesamoid for the quadriceps, which increases its power during knee extension and thus transfers considerable forces. The etiology of patellofemoral pain is multifactorial. In the absence of injury, the commonly accepted hypothesis is associated with increased compression of articulating surfaces.

Aim

The aim of the study was to perform an ultrasound evaluation of the thickness of articular cartilage covering the medial and lateral femoral condyle in patients with an increased Q-angle.

Materials and methods

The study included 26 women aged between 35 and 45 years. A total of 13 patients with Q >15° were included in the study group, and 13 patients with Q ≤15° were included in the control group. A goniometer was used for Q-angle measurement. The thickness of articular cartilage covering the medial and lateral femoral condyle of the femoral bone was measured using a HONDA HS-2200 ultrasound with a linear HLS-584M transducer. The Shapiro–Wilk test was used for the assessment of data distribution normality; the distribution was normal. The differences in the measured parameters were assessed with the ANOVA test for independent samples. The Bonferroni test was used for a multiple comparison.

Results

The statistical analysis showed statistically significantly reduced thickness of articular cartilage on the lateral femoral condyle (p = 0.00) in the Q >15° group. No statistically significant differences were demonstrated for the thickness of articular cartilage on the medial femoral condyle (p = 0.47).

Conclusions

The thickness of the articular cartilage on the lateral femoral condyle is lower than that of the medial femoral condyle in women aged between 35 and 45 years with the Q-angle >15°.

Treatment of Patella Fractures

Patella fractures comprise 1% of all fractures. Treatment options vary based on fracture displacement, classification, and patient factors. Traditionally, nonoperative treatment has been reserved for nondisplaced fractures. Many operative treatments are available with differing indications and levels of success. Tension band constructs have been the most commonly employed approach to fixation, with cerclage wiring for comminuted fractures. Recently, plate fixation of patella fractures has become more popular. Plating constructs offer a low-profile design with stable fixation, allowing for earlier mobilization and potentially improved functional outcomes. Data regarding the long-term outcomes of plating techniques are limited, and further studies are needed. [Orthopedics. 2018; 41(6):e747-e755.].

Axial-Oblique Versus Standard Axial 3-T Magnetic Resonance Imaging for the Detection of Trochlear Cartilage Lesions: A Prospective Study

Background:

Imaging of the femoral trochlea has been inherently difficult because of its convex anatomy.

Purpose/Hypothesis:

The purpose of this study was to compare the diagnostic utility of a standard axial magnetic resonance imaging (MRI) sequence with an axial-oblique MRI sequence of the knee for the detection of trochlear articular cartilage lesions on a high-field 3-T MRI scanner. We hypothesized that axial-oblique MRI scans of the knee obtained along the true axis of the trochlea would significantly improve the detection of high-grade cartilage lesions.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

Patients who underwent MRI and subsequent surgery for any indication were prospectively enrolled into this study between June 2014 and February 2015. The articular cartilage of the trochlea was evaluated independently by 3 raters on axial and axial-oblique MRI and compared with arthroscopic findings (gold standard). The interrater and intrarater reliability of mild (International Cartilage Repair Society [ICRS] grades 1 or 2) and severe (ICRS grades 3 or 4) lesions on MRI were assessed as well as the sensitivity, specificity, positive predictive value, and negative predictive value.

Results:

A total of 99 knees in 96 patients were included in the study. Interrater and intrarater agreement for the identification of severe lesions were moderate to good on the proximal trochlea and fair to moderate on the distal trochlea. No significant differences in sensitivity were found between axial and axial-oblique scans for any grade of lesion (55% vs 51%, respectively; P = .700) or for severe lesions (61% vs 52%, respectively; P = .289). Similarly, specificity for detecting severe lesions was not significantly different between axial and axial-oblique scans (95% vs 87%, respectively; P = .219). Last, no significant differences in sensitivity or specificity were found between MRI sequences when separately evaluating proximal and distal trochlear lesions (all P > .05).

Conclusion:

The axial-oblique sequence was unable to improve the sensitivity of MRI in detecting articular cartilage lesions on the trochlea. Both conventional axial and axial-oblique sequences, reviewed independently of the complete MRI series, had low sensitivity in detecting trochlear articular cartilage lesions. For this reason, clinicians should utilize all MRI planes to evaluate the articular cartilage of the trochlea. Future studies should focus on improving MRI techniques for detecting and characterizing cartilage lesions of the trochlea.

Development of intraoperative plantar pressure measuring system considering weight bearing axis

PURPOSE

Surgical reconstructions in three dimensions are needed for treatment of foot and ankle deformities. However, surgical results might be influenced by the skill and experience of doctors which complement the limited information for reconstructions in three dimensions. To solve these, studies were carried out to measure plantar pressure distribution during surgery. Though, it was impossible to accurately measure plantar pressure distribution accurately during operation. Therefore, we proposed an intraoperative plantar pressure measurement (IPPM) device that enables proper navigation in the push direction.

METHODS

For this purpose, first, we investigated how the physiological load axis passes through the human body to identify the pushing direction of the pressure sensor of the device toward the patient's foot. In particular, we hypothesized that the physiological load axis passes through the femoral head center and we evaluated this in a measurement experiment with nine healthy subjects. Second, based on these results, we developed the IPPM device that has two force sensors to identify the pushing direction toward the femoral head center and a conductive ink sensor to measure plantar pressure distribution. Finally, we conducted the experiments with nine healthy subjects and two users.

RESULTS

From the first experimental results, the physiological load axis was found to pass through the femoral head center in normal standing posture. From the evaluation experiment, there are no significant differences statistically in plantar pressure distributions between the conditions of using IPPM device and without using it for both a medical student and a surgeon. However, in some cases the plantar pressure distribution can be reproduced similarly to that of the standing posture, and also from the evaluation experiment concerning the relation between CoP position and NCC, the NCC tends to increase when the position of the CoP is closer to that at the standing posture.

CONCLUSION

The IPPM device has possibility to reproduce the plantar pressure distribution during surgery and prevent the recurrence of surgical complications.

Effects of Anterior Knee Displacement During Squatting on Patellofemoral Joint Stress

CONTEXT

Squatting is a common rehabilitation training exercise for patellofemoral pain syndrome (PFPS). Patellofemoral joint stress (PFJS) during squatting with more anterior knee displacement has not been systematically investigated.

OBJECTIVE

To compare PFJS during squatting using 2 techniques: squat while keeping the knees behind the toes (SBT) and squat while allowing the knees to go past the toes (SPT).

SETTING

University research laboratory.

PARTICIPANTS

Twenty-five healthy females (age: 22.69 (0.74) y; height: 169.39 (6.44) cm; mass: 61.55 (9.74) kg) participated.

MAIN OUTCOME MEASURES

Three-dimensional kinematic and kinetic data were collected at 180 and 1800 Hz, respectively. A musculoskeletal model was used to calculate muscle forces through static optimization. These muscle forces were used in a patellofemoral joint model to estimate PFJS.

RESULTS

The magnitudes of PFJS, reaction force, and quadriceps force were higher (P < .001) during SPT compared with the SBT technique. Knee flexion, hip flexion, and ankle dorsiflexion angles were reduced when using the SBT technique.

CONCLUSIONS

Findings provide some general support for minimizing forward knee translation during squats for patients that may have patellofemoral pain syndrome.

[Jumper's Knee]

Zusammenfassung. Sportliche Aktivitäten mit Sprungabläufen stellen für die Kniegelenke eine mechanische Herausforderung dar. Häufig projizieren sich chronisch auftretende, atraumatische Beschwerden auf den Patellaunterpol, welcher pathomorphologisch eine patellare Tendinopathie entspricht. Extrinsische und intrinsische Risikofaktoren können unterschieden werden. In der klinischen Untersuchung zeigt sich ein meist unauffälliges Knie mit einer Druckdolenz am kaudalen Teil der Kniescheibe beim Übergang zum Ligamentum patellae. In der Bildgebung ist sonografisch ein degenerierter Sehnenanteil der tiefen Patellarsehne zu erkennen, der magnettomografisch mit Hyperintensität des Hoffa-Körpers einhergehen kann. Abhängig von der klinischen Entwicklung wird das Jumper’s Knee nach Blazina Grad I–IV eingeteilt. Bis zu 90 % der Patienten können konservativ therapiert werden. Operativ stehen offene und arthroskopische Verfahren mit ordentlichem Resultat zur Verfügung.

The coupled effects of crouch gait and patella alta on tibiofemoral and patellofemoral cartilage loading in children

BACKGROUND

Elevated tibiofemoral and patellofemoral loading in children who exhibit crouch gait may contribute to skeletal deformities, pain, and cessation of walking ability. Surgical procedures used to treat crouch frequently correct knee extensor insufficiency by advancing the patella. However, there is little quantitative understanding of how the magnitudes of crouch and patellofemoral correction affect cartilage loading in gait.

METHODS

We used a computational musculoskeletal model to simulate the gait of twenty typically developing children and fifteen cerebral palsy patients who exhibited mild, moderate, and severe crouch. For each walking posture, we assessed the influence of patella alta and baja on tibiofemoral and patellofemoral cartilage contact.

RESULTS

Tibiofemoral and patellofemoral contact pressures during the stance phase of normal gait averaged 2.2 and 1.0 MPa. Crouch gait increased pressure in both the tibofemoral (2.6-4.3 MPa) and patellofemoral (1.8-3.3 MPa) joints, while also shifting tibiofemoral contact to the posterior tibial plateau. For extended-knee postures, normal patellar positions (Insall-Salvatti ratio 0.8-1.2) concentrated contact on the middle third of the patellar cartilage. However, in flexed knee postures, both normal and baja patellar positions shifted pressure toward the superior edge of the patella. Moving the patella into alta restored pressure to the middle region of the patellar cartilage as crouch increased.

CONCLUSIONS

This work illustrates the potential to dramatically reduce tibiofemoral and patellofemoral cartilage loading by surgically correcting crouch gait, and highlights the interaction between patella position and knee posture in modulating the location of patellar contact during functional activities.

The Feasibility and Usability of RunningCoach: A Remote Coaching System for Long-Distance Runners

Studies have shown that about half of the injuries sustained during long-distance running involve the knee. Cadence (steps per minute) has been identified as a factor that is strongly associated with these running-related injuries, making it a worthwhile candidate for further study. As such, it is critical for long-distance runners to minimize their risk of injury by running at an appropriate running cadence. In this paper, we present the results of a study on the feasibility and usability of RunningCoach, a mobile health (mHealth) system that remotely monitors running cadence levels of runners in a continuous fashion, among other variables, and provides immediate feedback to runners in an effort to help them optimize their running cadence.

Biomechanical comparison of pin and tension-band wire fixation with a prototype locking plate fixation in a transverse canine patellar fracture model

Objective: To compare a locking plate (LP) with pin and tension-band wire (pin/TBW) for fixation of mid-patellar transverse fractures.

Materials and methods: Cadaveric canine stifle joints from 10 adult mixed breed dogs (23–36 kg) were used. Mid-patellar transverse osteotomies were randomly stabilized (in pairs) with either pin/TBW or a prototype LP. Cyclic loads (1 Hz, 500 cycles) at 100% body weight (90°-135° stifle joint extension), were applied. Survival or failure of constructs was defined as <2 mm fracture gap distraction at 500 cycles, or ≥ 2 mm fracture gap distraction at the number of cycles sustained, respectively. Number of cycles at failure and distraction gap were compared with a paired Student’s t-test, and a survival analysis performed with a Mantel-Cox test. All constructs that survived cyclic testing were tested in single cycle load to failure (1.0 mm/sec; 110° stifle joint extension); yield strength was compared with a Wilcoxon rank sum test. Significance was set at p <0.05.

Results: All 10/10 LP and three out of 10 pin/ TBW fixations survived cyclic testing. Survival analysis, number of cycles at failure, and distraction gap all were significantly different between the two groups (p = 0.0011, p = 0.0013, and p <0.0001, respectively). Construct yield strength was not significantly different (p = 0.1273).

Conclusions: The failure mode with pin/TBW was consistently similar to failures observed clinically. The LP demonstrated consistent, reliable and stable fixation.

This work was performed at the Biomechanics Orthopedic Research Laboratory, Cummings School of Veterinary Medicine at Tufts University, North Grafton, MA, USA.

Biomechanical evaluation of the tension band wiring principle. A comparison between two different techniques for transverse patella fracture fixation

PURPOSE

The aim of this study was to investigate the validity of the dynamic compression principle of tension band wiring in two techniques for patella fracture treatment.

METHODS

Twelve human cadaveric knees with simulated transverse patella fractures were assigned to two groups for treatment with tension band wiring using either Kirschner (K-) wires or cannulated screws. Biomechanical testing was performed over three knee movement cycles between 90° flexion and 0° full extension. Pressure distribution in the fracture gap and fracture site displacement were evaluated at the 3^rd cycle in 15° steps, namely 90°-75°-60°-45°-30°-15°-0° extension phase and 0°-15°-30°-45°-60°-75°-90° flexion phase.

RESULTS

Mean anterior / posterior interfragmentary pressure in the groups with K-wires and cannulated screws ranged within 0.16-0.40MPa / 0.12-0.35MPa and 0.37-0.59MPa / 0.10-0.30MPa, respectively. These changes remained non-significant for both groups and loading phases (P≥0.171). Mean anterior / posterior fracture site displacement for K-wires and cannulated screws ranged within -0.01-0.53mm / 0.11-0.74mm and 0.11-0.55mm / -0.10-0.50mm, respectively. Anterior displacement remained without significant changes for both groups and loading phases (P≥0.112). However, posterior displacement underwent a significant increase in the course of knee extension for K-wires (P≤0.047), but not for cannulated screws (P≥0.202). Significantly smaller displacement at the posterior fracture site was detected in the group with cannulated screws compared to K-wires at 60° and 75° extension phase (P≤0.017), as well as at 45°, 60° and 75° flexion phase (P≤0.018). The critical value of 2mm displacement at the posterior fracture site was not reached for any specimen and fixation technique. Knee extension was accompanied by synchronous increase in quadriceps pulling force.

CONCLUSIONS

Tension band wiring fulfills from a biomechanical perspective the requirements for sufficient stability of transverse patella fracture fixation. It should, however, rather be considered as a static fixation principle than a dynamic one. Tension band wiring with cannulated screws was found advantageous over Kirschner wires in terms of interfragmentary movements at the posterior fracture site.

Severity and distribution of cartilage damage and bone marrow edema in the patellofemoral and tibiofemoral joints in knee osteoarthritis determined by MRI

The aim of the present study was to analyze the distribution and severity of cartilage damage (CD) and bone marrow edema (BME) of the patellofemoral and tibiofemoral joints (PFJ and TFJ, respectively) in patients with knee osteoarthritis (OA), and to determine whether a correlation exists between BME and CD in knee OA, using magnetic resonance imaging (MRI). Forty-five patients diagnosed with knee OA (KOA group) and 20 healthy individuals (control group) underwent sagittal multi-echo recalled gradient echo sequence scans, in addition to four conventional MR sequence scans. Knee joints were divided into 15 subregions by the whole-organ MRI scoring method. MRIs of each subregion were analyzed for the presence of CD, CD score and BME score. The knee joint activity functional score was determined using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) in the KOA group. Statistical analyses were used to compare the CD incidence; CD score and BME score between the PFJ and TFJ. Whether a correlation existed among body mass index, BME score, WOMAC pain score and CD score was also examined. Among the 675 subregions analyzed in the KOA group, 131 exhibited CD (CD score, 1-6). These 131 subregions were primarily in the PFJ (80/131, 61.07%), with the remainder in the TFJ (51/131, 38.93%). Thirty-three subregions had a CD score of 1, including 24 PFJ subregions (72.73%) and 9 TFJ subregions (27.27%). Among the 103 subregions with BME, the PFJ accounted for 60 (58.25%) and the TFJ for 43 (41.75%). A significant positive correlation was found between the BME and CD scores. In conclusion, CD and BME occurred earlier and more often in the PFJ compared to the TFJ in knee OA, and BME is an indirect sign of CD.

The Influence of Knee Pain Location on Symptoms, Functional Status, and Knee-related Quality of Life in Older Adults With Chronic Knee Pain: Data From the Osteoarthritis Initiative

OBJECTIVE

To evaluate whether knee pain location can influence symptoms, functional status, and knee-related quality of life in older adults with chronic knee pain.

MATERIALS AND METHODS

A total of 2959 painful knees from the Osteoarthritis Initiative database were analyzed. Trained interviewers recorded patient-reported location of knee pain. Painful knees were divided into 3 groups of patellofemoral only pain, tibiofemoral only pain, and combined pain. Self-reported knee-specific symptoms, functional status, and knee-related quality of life were assessed using the Knee Injury and Osteoarthritis Outcome Score.

RESULTS

The most common knee pain pattern was tibiofemoral only pain (62%), followed by patellofemoral only pain (23%), and combined pain (15%). The combined pain pattern was associated with greater odds of reporting pain, symptoms, sports, or recreational activity limitations and lower knee-related quality of life compared with either isolated knee pain patterns, after adjusting for demographics and radiographic disease severity. Individual item analysis further revealed that patients with combined pain had greater odds of reporting difficulty with daily weight-bearing activities that required knee bending compared with tibiofemoral or patellofemoral only pain patterns. Furthermore, symptoms, functional status, and knee-related quality of life were comparable between patients with patellofemoral and tibiofemoral only pain patterns, after adjusting for demographics and radiographic disease severity.

DISCUSSION

Combined patellofemoral and tibiofemoral pain is associated with poorer clinical presentation compared with isolated knee pain from either location. In addition, patellofemoral pain in isolation may be as important as tibiofemoral pain in causing symptoms and functional limitation in older adults with chronic knee pain.

Patella instability in children and adolescents

Patellar instabilities are the most common knee pathologies during growth. Congenital dislocations are rare. Extensive, early soft tissue releases relocate the extensor mechanism and may enable normal development of the femoro-patellar anatomy.Conservative management is the preferred strategy after a 'first-time' traumatic dislocation. In cases with concomitant anatomical predisposing factors such as trochlear dysplasia, malalignment, malrotation or ligamentous laxity, surgical reconstruction must be considered. The same applies to recurrent dislocations with pain, a sense of instability or re-dislocations which may also lead to functional compensatory mechanisms (quadriceps-avoiding gait in knee extension) or cartilaginous lesions with subsequent patello-femoral osteoarthritis. The decision-making process guiding surgical re-alignment includes analysis with standard radiographs and MRI of the trochlear groove, joint cartilage and medial patello-femoral ligament (MPFL). Careful evaluation of dynamic and static stabilisers is essential: the medial patello-femoral ligament provides stability during the first 20° of flexion, and the trochlear groove thereafter.Excessive femoral anteversion, general ligamentous laxity with increased femoro-tibial rotation, patella alta and increased distance between the tibial tuberosity and the trochlear groove must also be taken into account and surgically corrected.In cases with ongoing dislocations during skeletal immaturity, soft tissue procedures must suffice: reconstruction of the medial patello-femoral ligament as a standalone procedure or in conjuction with more complex distal realignment of the quadriceps mechanism may lead to a permanent stable result, or at least buys time until a definitive bony procedure is performed. Cite this article: Hasler CC, Studer D. Patella instability in children and adolescents. EFORT Open Rev 2016;1:160-166. DOI: 10.1302/2058-5241.1.000018.

Role of Piezo Channels in Joint Health and Injury

Cartilage is an intrinsically mechanically sensitive tissue composed of chondrocytes as the only cell type. Chondrocyte mechanotransduction is not well understood, but recently we identified critical components of the mechanotransduction machinery demonstrating how mechanical stimulation of these cells can be converted into cellular calcium signals. Physiologic mechanical cues induce anabolic responses of (post-mitotic) chondrocytes via transient receptor potential vanilloid 4 ion channels, whereas injurious mechanical stress is transduced by Piezo1 jointly with Piezo2 ion channels. This chapter sheds light on the latter discovery and provides a rationale for follow-up questions, such as the nature of interaction between Piezo1 and Piezo2, and their tethering to the cytoskeleton. These recent insights can be leveraged toward translational medical progress to benefit diagnosis and treatment of osteoarthritis, representing a large and growing unmet medical need in the United States and large parts of the world.