THE PRIMARY STABILITY OF A CEMENTLESS HIP PROSTHESIS UNDER THE COMPRESSIVE LOADING

The objective of this research is to better understand the problems of primary stability of cementless hip prosthesis. The present study is aimed to develop a finite element model of the coupled system "femur-cementless prosthesis" which represents the implant in its environment particularly under the compressive loading. Its primary stability is investigated by quantifying the migration of the femoral stem in the femur and by analyzing the stress and strains engendered. We have made experimentations on ten fresh human femurs. A good agreement is observed between the experiments and the prediction by our finite element model for the prosthetic head displacement

Early outcomes of THA using uncemented dual-mobility cups with additional fixation screws

Background: The use of fixation screws with uncemented cups is controversial particularly for dual mobility (DM) cups where perforation of the articular surface could compromise implant longevity. We aimed to compare outcomes of total hip arthroplasty (THA) using uncemented DM cups with supplementary screw fixation versus simple press-fit fixation. Methods: From 235 consecutive THAs performed using uncemented DM cups, 203 were fixed by simple press-fit and 32 fixed with additional screws. The Oxford hip score (OHS) and EuroQol 5 Dimensions (EQ-5D) score were available at 3.3±1.1 years. To enable direct comparison, each screw fixation cup was matched to three simple press-fit cups using propensity scores, based on age, sex and bone quality. Results: The two groups had equivalent age, body mass index, gender distribution, femoral morphology and bone quality. Compared to the press-fit group (n=96), the screw fixation group had more surgical antecedents (p=0.032), higher femoral neck angles (p=0.028), and received slightly larger cups (p=0.036). Revision was required for two (6%) screw fixation cups (only one implant-related) and one (1%) press-fit cup (none implant-related). There were no differences between OHS (19±8 vs 18±7, p=0.682) nor EQ-5D (0.63±0.37, p=0.257). Conclusions: Revision rates were greater for DM cups fixed with additional screws than for those fixed by simple press-fit, but clinical scores were equivalent. There was only one implant-related revision (acetabular fracture) in the screw fixation group and it is unclear whether this is related to the additional screws or to patient/surgical factors

Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis

Time to Switch to Second-line Antiretroviral Therapy in Children With Human Immunodeficiency Virus in Europe and Thailand.

Background: Data on durability of first-line antiretroviral therapy (ART) in children with human immunodeficiency virus (HIV) are limited. We assessed time to switch to second-line therapy in 16 European countries and Thailand. Methods: Children aged <18 years initiating combination ART (≥2 nucleoside reverse transcriptase inhibitors [NRTIs] plus nonnucleoside reverse transcriptase inhibitor [NNRTI] or boosted protease inhibitor [PI]) were included. Switch to second-line was defined as (i) change across drug class (PI to NNRTI or vice versa) or within PI class plus change of ≥1 NRTI; (ii) change from single to dual PI; or (iii) addition of a new drug class. Cumulative incidence of switch was calculated with death and loss to follow-up as competing risks. Results: Of 3668 children included, median age at ART initiation was 6.1 (interquartile range (IQR), 1.7-10.5) years. Initial regimens were 32% PI based, 34% nevirapine (NVP) based, and 33% efavirenz based. Median duration of follow-up was 5.4 (IQR, 2.9-8.3) years. Cumulative incidence of switch at 5 years was 21% (95% confidence interval, 20%-23%), with significant regional variations. Median time to switch was 30 (IQR, 16-58) months; two-thirds of switches were related to treatment failure. In multivariable analysis, older age, severe immunosuppression and higher viral load (VL) at ART start, and NVP-based initial regimens were associated with increased risk of switch. Conclusions: One in 5 children switched to a second-line regimen by 5 years of ART, with two-thirds failure related. Advanced HIV, older age, and NVP-based regimens were associated with increased risk of switch

The evolution of osteoarthritis in 103 patients with ACL reconstruction at 17 years follow-up

AIM: To evaluate the functional and radiological outcome of a bone-tendon-bone anterior cruciate ligament reconstruction, at long-term follow-up. METHODS: A retrospective study of 148 patients, of which 103 were available for long-term follow-up. Complete functional and radiological evaluation (International Knee Documentation Committee scale) were performed in 89 out of the 103 patients [Anderson AF. Rating scales. In: Fu FH, Harner CD, Vince KG, (Eds.). Knee Surgery, Baltimore, Williams and Wilkins vol. 1, 1994; 12, pp. 275-296]. RESULTS: The mean follow-up time was 17.4 years. Subjectively, 88% of the patients were very satisfied or satisfied. According to the IKDC score 55% had type A symptoms, 29% type B, 12% type C, and 4% type D. The IKDC ligament evaluation showed 14.9% type A, 44.8% type B, 35.8% type C, and 4.5% type D. At the review 22.7% had a narrowing 50% (D). Onset of osteoarthritis showed an association with the status of the medial meniscus. Knees with a preserved (healthy or sutured) medial meniscus had a significantly (p &#60; 0.05) better radiological outcome. Among these, 9% had a joint space narrowing 50% (D). Medial meniscectomy, residual laxity, and femoral chondral defects were associated with osteoarthritis. CONCLUSION: The outcome of anterior cruciate ligament reconstruction plus extra-articular tenodesis is good in the very long term, particularly in knees with a preserved medial meniscus