Vladan Stevanovic

Symmetry of zinc oxide nanostructures.

The full geometrical symmetry groups of zinc oxide nanowires, nanotubes, nanosprings and nanorings are found and some physical properties which can be deduced from the symmetry are discussed: conserved quantum numbers and band degeneracies; dynamical representations, Raman and infrared active modes; piezoelectric tensor.

Hamstring Regeneration Following Harvest for Anterior Cruciate Ligament Reconstruction

The semitendinosus (ST) and gracillis (Gr) tendons are commonly used as a replacement graft during the anterior cruciate ligament (ACL) reconstruction. There are many advantages of using the hamstrings tendons, including the ease of harvesting, suitable morphology for use as a graft, lower donor site morbidity, early rehabilitation, and patient satisfaction.

The efficacy and safety of autologous conditioned serum (ACS) injections compared with betamethasone and placebo injections in the treatment of chronic shoulder joint pain due to supraspinatus tendinopathy: a prospective, randomized, double-blind, controlled study.

AIMS Autologous conditioned serum (ACS; marketed as Orthokine®) is an autologous blood product that has previously shown efficacy in treatment of joint osteoarthritis, spinal radiculopathy, tendon and muscle injuries in randomized controlled trials. In this 24-week, randomized, double-blind study, we compared the efficacy and safety of ACS with glucocorticoid (betamethasone) injections in chronic supraspinatus tendinopathy patients. MATERIAL AND METHODS Thirty-two patients with chronic supraspinatus tendinopathy were enrolled in the study. The ACS group received four ACS injections once weekly over four weeks and the glucocorticoid group received three betamethasone injections once weekly over three weeks with a placebo (saline) injection at week 4 into the enthesis and paratenon of the supraspinatus tendon. Study endpoints were pain intensity (VAS) and Constant Shoulder Score (CSS) assessed at weeks 0, 4 and 24. RESULTS Shoulder pain intensity improved after 4 weeks and significantly improved after 24 weeks in patients treated with ACS compared with those treated with glucocorticoids (pain intensity week 4: ACS=22.0, glucocorticoid=32.0; week 24: ACS=15.0, glucocorticoid=40.0). CSS improved to a similar extent in both groups after 4 weeks. After 24 weeks, ACS patients exhibited significantly greater CSS improvements than glucocorticoid patients. Adverse events (n=8) were reported in betamethasone patients. CONCLUSIONS Compared with betamethasone, ACS therapy improved joint function and reduced shoulder pain more effectively after 4 weeks of treatment; these improvements were sustained to week 24. Combined with its favorable safety profile, ACS appears to be a more effective treatment than glucocorticoids and could enhance the quality of life in patients with chronic rotator cuff tendinopathy.

A Method for Prediction of Femoral Component of Hip Prosthesis Durability due to Aseptic Loosening by Using Coffin/Manson Fatigue Model

The purpose of this work is to develop a new model estimate of the fatigue life of a hip prosthesis due to aseptic loosening as a multifactorial phenomenon. The formula developed here is a three-parameter model based on Basquins law for fatigue, eccentric compression formula for the compressive stress and torsion in the prosthesis due to the horizontal components of the contact force. With our model, we can accurately predict the durability of a hip prosthesis due to the following four parameters: body weight, femoral offset, duration, and intensity of daily physical activities of a patient. The agreement of the prediction with the real life of the prosthesis, observed on 15 patients, is found to be adequate. Based on the formula derived for a particular implant, there was a high degree of concurrence between the model-predicted and actual values of aseptic loosening (durability) proved by the Mann–Whitney U test. By virtue of the validated model, it is possible to predict, quantitatively, the influence of various factors on the hip life. For example, we can conclude that a 10% decrease of a patients body mass, with all other conditions being the same, causes 5% increase of the hip fatigue life.

Stress Fractures in Sport (ICL 5)

Stress fractures arise from the inability of bone to tolerate repeated mechanical loading and are characterized by damage to the bone’s micro-architecture. Repeated mechanical loading can cause an uncoupling of osteoblast bone formation and osteoclast bone resorption [1]. This can lead to bone loss and subsequent micro-damage that can result in localized bone weakening, resulting in stress fracture development. The etiology of stress fractures is multifactorial. The rate of occurrence depends on the bone composition, vascular supply, surrounding muscle attachments, systemic factors, and type of athletic activity. From a biomechanical standpoint, stress fractures may be the result of muscle fatigue, which leads to the transmission of excessive forces to the underlying bone. Muscles may also contribute to stress injuries by concentrating forces across a localized area of bone, thus causing mechanical insults that exceed the stress-bearing capacity of the bone (Table 5.1) [2, 3].

Discoid Lateral Meniscus Incidence During Knee Arthroscopy

Abstract Discoid meniscus is a morphological anomaly of the lateral meniscus that appears in 1–5% of meniscectomies. A precise diagnosis remains difficult to make, and many dilemmas hinder effective treatment. To evaluate the incidence of discoid meniscus in patients who underwent knee arthroscopy, as well as the discoid meniscus type, follow-up problems, combined knee lesions, and postoperative results. This retrospective study included 1357 patients who received knee arthroscopy during the period between January 2007 and December 2013. We analysed the discoid meniscus incidence, sex distribution, type distribution (Monllau classification), noted preoperative symptomatology, rupture incidence and type (O’Connor classification), anomaly presence and other intra-articular lesion correlations. The IKDC score was used to evaluate the operative treatment results. The DLM incidence was 1.03%. The most common type of discoid meniscus was complete 5 (35.71 %). The dominant symptom was pain, which was reported by 12 (85.71%) patients. Eleven (78.57 %) patients exhibited ruptures, and the most common type was horizontal, which was reported in 4 (36.36%) cases. The number of ruptures was significantly higher in patients older than 18 (9 patients; 90%), compared to those younger than 18 (2 patients; 40%). Operative treatment resulted in an improvement for all patients in terms of subjective symptom reduction. The incidence of DLM in our study was 1.03%, and the dominant symptom was pain in the knee (85.71%). The most common lesion of the meniscus was a horizontal split, primarily in patients older than 18 years. Patients also presented with joint intra-articular lesions; the most common type was ACL rupture. In all patients, an improved postoperative IKDC score was reported.

Periprosthetic Femoral Fractures in Total Knee Arthroplasty

Total joint arthroplasty has greatly improved the treatment of knee arthrosis, but still is not without complications. Supracondylar fractures above total knee replacements are an uncom‐ mon complication (incidence 0,3% to 2.5%), occuring more frequently in patients older than 60 years with osteoporotic bone. The rate of these fractures is expected to increase in the future because of the growing number of total knee replacements and greater level of acitivity among elderly patients. The timing of such fractures has been reported to range from early in the postoperative period to more than a decade after surgery, with a mean of 2 to 4 years. During the past two decades authors were not agreed in the definition of periprosthetic supracondylar region: the lower 3 inches (7cm) of the femur [1]; 9 cm proximal to the knee joint line [2]; all fractures within 15 cm proximal to the knee joint line [3]. Generally, based on the older literature, supracondylar periprosthetic fractures were those within 15 cm of the joint line, or in the case of stemmed component, within 5 cm of the proximal end of the implant. Never‐ theless, the most important is understanding that these fractures occur in regions of stress concentration adjacent to a prosthetic component, and that the presence of the prosthesis has a significant effect on fracture treatment. So, we suggest that fractures above total knee replacement should be considered supracondylar fractures if they extend within 7 cm of the prosthetic joint line or if they are within 2 cm of the femoral prosthetic flange.