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Castel Guelfo di Bologna, Italy

Zaffagnini S.,Laboratorio Of Biomeccanica | Klos T.V.,ICONE Orthopaedics and Sports Traumatology | Bignozzi S.,Laboratorio Of Biomeccanica
Arthroscopy - Journal of Arthroscopic and Related Surgery | Year: 2010

In the last 15 years, computer-assisted surgery (CAS) has been used for many purposes during anterior cruciate ligament (ACL) reconstruction, such as tunnel positioning, joint laxity evaluation, and biomechanical studies. This article is an evidence-based literature review of the contribution of such technology to ACL surgery. A search of the PubMed and Medline databases was performed. Articles were classified according to the study design and to the research topic: anatomy, laxity, kinematics, and comparison of surgical techniques. An evidence-based approach was used to verify the clinical usefulness of CAS to ACL surgery. The use of CAS for research purposes was also evaluated. CAS was shown to improve femoral tunnel positioning, even if clinical outcomes showed no differences compared with manual techniques. CAS technology was found to be useful for research purposes in terms of providing a better comprehension of the effect of different ACL reconstructions and of the different bundles on joint laxity, as well as describing tunnel positioning in relation to native ACL insertion. CAS in ACL surgery can improve results at time 0 and can improve knowledge about ACL anatomy and kinematics. Its application remains limited mostly to research purposes because of the invasiveness of the system and the absence of improved clinical results at follow-up. © 2010 Arthroscopy Association of North America.

Affatato S.,Laboratorio Of Tecnologia Medica | Spinelli M.,Laboratorio Of Tecnologia Medica | Lopomo N.,Laboratorio Of Biomeccanica | Grupp T.M.,Aesculap AG | And 3 more authors.
Clinical Biomechanics | Year: 2011

Background: Modern unicompartmental knee prostheses represent a valid alternative to total knee replacement. It is known that variations in clinical alignment lead to altered biomechanics and abnormal wear. The aim of this study was to assess the influence, on wear behaviour, of two different cementing interfaces of the femoral components tested on a knee joint wear simulator. Methods: The wear tests were run in a knee wear simulator at a frequency of 1.1 Hz for 3 million cycles in accordance with ISO 14243-3. Twelve commercial mobile GUR 1020 UHMWPE meniscus specimens articulated in between 12 cobalt-chromium-molybdenum alloy femoral and tibial components covered by a multi-layer of chromium nitride and a final layer of zirconium nitride ceramic coating to prevent ion release from the substrate. Two wear tests were performed: in the first test, each femoral component was cemented into a custom made metallic-block shaped to perfectly host it. In the second test, synthetic composite femurs received the femoral components on the basis of guidelines used in current surgery. Findings: The two cementing interfaces showed a significantly different wear behaviour, quantified as mean weight loss (P < 0.001). Scanning electron microscope examinations of new and tested metallic components showed macro- and micro-pores of few microns on both configurations. Interpretation: The wear pattern observed at 3 million cycles showed differences between the two methods of fixation for the meniscus femoral components. © 2010 Elsevier Ltd. All rights reserved.

Lopomo N.,Laboratorio Of Biomeccanica | Sun L.,Institute of Traumatology and Orthopaedics | Zaffagnini S.,Laboratorio Of Biomeccanica | Giordano G.,Laboratorio Of Biomeccanica | Safran M.R.,Stanford University
Clinical Biomechanics | Year: 2010

Background: The hip joint center is a fundamental landmark in the identification of lower limb mechanical axis; errors in its location lead to substantial inaccuracies both in joint reconstruction and in gait analysis. Actually in Computer Aided Surgery functional non-invasive procedures have been tested in identifying this landmark, but an anatomical validation is scarcely discussed. Methods: A navigation system was used to acquire data on eight cadaveric hips. Pivoting functional maneuver and hip joint anatomy were analyzed. Two functional methods - both with and without using the pelvic tracker - were evaluated: specifically a sphere fit method and a transformation techniques. The positions of the estimated centers with respect to the anatomical center of the femoral head, the influence of this deviation on the kinematic assessment and on the identification of femoral mechanical axis were analyzed. Findings: We found that the implemented transformation technique was the most reliable estimation of hip joint center, introducing a - Mean (SD) - difference of 1.6 (2.7) mm from the anatomical center with the pelvic tracker, whereas sphere fit method without it demonstrated the lowest accuracy with 25.2 (18.9) mm of deviation. Otherwise both the methods reported similar accuracy (<3 mm of deviation). Interpretation: The functional estimations resulted in the best case to be in an average of less than 2 mm from the anatomical center, which corresponds to angular deviations of the femoral mechanical axis smaller than 1.7 (1.3)° and negligible errors in kinematic assessment of angular displacements. © 2009 Elsevier Ltd. All rights reserved.

Zaffagnini S.,Laboratorio Of Biomeccanica | Muccioli G.M.M.,Laboratorio Of Biomeccanica | Giordano G.,Laboratorio Of Biomeccanica | Bonanzinga T.,Laboratorio Of Biomeccanica | And 5 more authors.
Knee Surgery, Sports Traumatology, Arthroscopy | Year: 2012

Purpose: The purpose of this study is to report long-term outcomes of the arthroscopic modified Caspari technique compared to an open capsular shift surgery to treat post-traumatic anterior shoulder recurrent instability. The hypothesis was that the open surgery group would show higher degenerative changes than to the modified Caspari technique group after a follow-up from 10 to 17 years. Methods: One hundred and ten nonrandomized consecutive patients who underwent a surgical repair of recurrent unilateral anterior shoulder instability between 1990 and 1999 were retrospectively analyzed. Eighty-two patients were available for long-term follow-up. In particular, 49 patients (59.8%) (group A) were treated with arthroscopic transglenoid modified Caspari suturing technique (mean follow-up 13.7 ± 2.2 years), whereas 33 patients (40.2%) (group B) were treated with combined open capsular shift and Bankart repair (mean follow-up 15.7 ± 2.2 years). Patients were evaluated according to the failure rate (re-dislocation), Rowe, UCLA, and Constant scores. Radiological osteoarthritis changes were ranked according to Samilson score. Results: There were no statistically significant differences between the two groups concerning the failure rate (n.s.), Rowe (n.s.), UCLA (n.s.), and Constant (n.s.) scores. Group A: re-dislocation rate 12.5% (6 re-dislocations), Rowe 85.0 ± 22.6, UCLA 26.4 ± 4.8, and Constant 86.3 ± 16.7. Group B: re-dislocation rate 9% (3 re-dislocations), Rowe 83.2 ± 24.4, UCLA 26.9 ± 4.2, and Constant 87.4 ± 14.1. Radiographic findings of osteoarthritis: 2 severe (4%), 4 moderate (8%), and 12 mild (25%) in group A; 2 severe (6%), 4 moderate (12%), and 9 mild (27%) in group B; differences between groups were not statistically significant (n.s). Conclusions: The results after both techniques were good in majority of patients, with no significant differences in terms of re-dislocation and osteoarthritis development. Compared to the current literature, the recurrence rate was high in both groups. The modified Caspari technique could be an arthroscopic alternative for older, non-athletic shoulders. Level of evidence: Therapeutic Study-Retrospective Comparative Study, Level III. © 2011 Springer-Verlag.

Marchiori G.,Laboratorio Of Nanobiotecnologie Nabi | Lopomo N.,Laboratorio Of Biomeccanica | Lopomo N.,University of Brescia | Boi M.,Laboratorio Of Nanobiotecnologie Nabi | And 7 more authors.
Materials Science and Engineering C | Year: 2016

Realizing hard ceramic coatings on the plastic component of a joint prosthesis can be strategic for the mechanical preservation of the whole implant and to extend its lifetime. Recently, thanks to the Plasma Pulsed Deposition (PPD) method, zirconia coatings on ultra-high molecular weight polyethylene (UHMWPE) substrates resulted in a feasible outcome. Focusing on both the highly specific requirements defined by the biomedical application and the effective possibilities given by the deposition method in the perspectives of technological transfer, it is mandatory to optimize the coating in terms of load bearing capacity. The main goal of this study was to identify through Finite Element Analysis (FEA) the optimal coating thickness that would be able to minimize UHMWPE strain, possible insurgence of cracks within the coating and stresses at coating-substrate interface. Simulations of nanoindentation and microindentation tests were specifically carried out. FEA findings demonstrated that, in general, thickening the zirconia coating strongly reduced the strains in the UHMWPE substrate, although the 1 μm thickness value was identified as critical for the presence of high stresses within the coating and at the interface with the substrate. Therefore, the optimal thickness resulted to be highly dependent on the specific loading condition and final applications. © 2015 Elsevier B.V. All rights reserved.

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