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1.  Cementless Hydroxyapatite Coated Hip Prostheses 
BioMed Research International  2015;2015:386461.
More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality.
PMCID: PMC4352755  PMID: 25802848
2.  Clinical outcomes of minimally invasive versus open approach for one-level transforaminal lumbar interbody fusion at the 3- to 4-year follow-up 
European Spine Journal  2013;22(12):2857-2863.
Supporters of minimally invasive approaches for transforaminal lumbar interbody fusion (TLIF) have reported short-term advantages associated with a reduced soft tissue trauma. Nevertheless, mid- and long-term outcomes and specifically those involving physical activities have not been adequately studied. The aim of this study was to compare the clinical outcomes of mini-open versus classic open surgery for one-level TLIF, with an individualized evaluation of the variables used for the clinical assessment.
A prospective cohort study was conducted of 41 individuals with degenerative disc disease who underwent a one-level TLIF from January 2007 to June 2008. Patients were randomized into two groups depending on the type of surgery performed: classic open (CL-TLIF) group and mini-open approach (MO-TLIF) group. The visual analog scale (VAS), North American Spine Society (NASS) Low Back Pain Outcome instrument, Oswestry Disability Index (ODI) and the Short Form 36 Health Survey (SF-36) were used for clinical assessment in a minimum 3-year follow-up (36–54 months).
Patients of the MO-TLIF group presented lower rates of lumbar (p = 0.194) and sciatic pain (p = 0.427) and performed better in daily life activities, especially in those requiring mild efforts: lifting slight weights (p = 0.081), standing (p = 0.097), carrying groceries (p = 0.033), walking (p = 0.069) and dressing (p = 0.074). Nevertheless, the global scores of the clinical questionnaires showed no statistical differences between the CL-TLIF and the MO-TLIF groups.
Despite an improved functional status of MO-TLIF patients in the short term, the clinical outcomes of mini-open TLIF at the 3- to 4-year follow-up showed no clinically relevant differences to those obtained with open TLIF.
PMCID: PMC3843777  PMID: 23764765
Minimally invasive; TLIF; Lumbar fusion; Degenerative disc disease; Prospective
3.  Study of the Polycarbonate-Urethane/Metal Contact in Different Positions during Gait Cycle 
BioMed Research International  2014;2014:548968.
Nowadays, a growing number of young and more active patients receive hip replacement. More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients.
PMCID: PMC4163484  PMID: 25247180
4.  Male osteoporosis: A review 
World Journal of Orthopedics  2012;3(12):223-234.
Osteoporosis in men is a heterogeneous disease that has received little attention. However, one third of worldwide hip fractures occur in the male population. This problem is more prevalent in people over 70 years of age. The etiology can be idiopathic or secondary to hypogonadism, vitamin D deficiency and inadequate calcium intake, hormonal treatments for prostate cancer, use of toxic and every disease or drug use that alters bone metabolism.
Risk factors such as a previous history of fragility fracture should be assessed for the diagnosis. However, risk factors in men are very heterogeneous. There are significant differences in the pharmacological treatment of osteoporosis between men and women fundamentally due to the level of evidence in published trials supporting each treatment. New treatments will offer new therapeutic prospects. The goal of this work is a revision of the present status knowledge about male osteoporosis.
PMCID: PMC3557324  PMID: 23362466
Male osteoporosis; Skeleton involution; Etiology; Fracture risk; Osteoporosis; Non-pharmacological treatments; Pharmacological treatments
5.  A mechanical model for predicting the probability of osteoporotic hip fractures based in DXA measurements and finite element simulation 
Osteoporotic hip fractures represent major cause of disability, loss of quality of life and even mortality among the elderly population. Decisions on drug therapy are based on the assessment of risk factors for fracture, from BMD measurements. The combination of biomechanical models with clinical studies could better estimate bone strength and supporting the specialists in their decision.
A model to assess the probability of fracture, based on the Damage and Fracture Mechanics has been developed, evaluating the mechanical magnitudes involved in the fracture process from clinical BMD measurements. The model is intended for simulating the degenerative process in the skeleton, with the consequent lost of bone mass and hence the decrease of its mechanical resistance which enables the fracture due to different traumatisms. Clinical studies were chosen, both in non-treatment conditions and receiving drug therapy, and fitted to specific patients according their actual BMD measures. The predictive model is applied in a FE simulation of the proximal femur. The fracture zone would be determined according loading scenario (sideway fall, impact, accidental loads, etc.), using the mechanical properties of bone obtained from the evolutionary model corresponding to the considered time.
BMD evolution in untreated patients and in those under different treatments was analyzed. Evolutionary curves of fracture probability were obtained from the evolution of mechanical damage. The evolutionary curve of the untreated group of patients presented a marked increase of the fracture probability, while the curves of patients under drug treatment showed variable decreased risks, depending on the therapy type.
The FE model allowed to obtain detailed maps of damage and fracture probability, identifying high-risk local zones at femoral neck and intertrochanteric and subtrochanteric areas, which are the typical locations of osteoporotic hip fractures.
The developed model is suitable for being used in individualized cases. The model might better identify at-risk individuals in early stages of osteoporosis and might be helpful for treatment decisions.
PMCID: PMC3549900  PMID: 23151049
Osteoporosis; Osteoporotic fracture; Predictive model; Finite elements; Fracture risk; Fracture probability
6.  Applications of finite element simulation in orthopedic and trauma surgery 
World Journal of Orthopedics  2012;3(4):25-41.
Research in different areas of orthopedic and trauma surgery requires a methodology that allows both a more economic approach and the ability to reproduce different situations in an easy way. Simulation models have been introduced recently in bioengineering and could become an essential tool in the study of any physiological unity, regardless of its complexity. The main problem in modeling with finite elements simulation is to achieve an accurate reproduction of the anatomy and a perfect correlation of the different structures, in any region of the human body. Authors have developed a mixed technique, joining the use of a three-dimensional laser scanner Roland Picza captured together with computed tomography (CT) and 3D CT images, to achieve a perfect reproduction of the anatomy. Finite element (FE) simulation lets us know the biomechanical changes that take place after hip prostheses or osteosynthesis implantation and biological responses of bone to biomechanical changes. The simulation models are able to predict changes in bone stress distribution around the implant, so allowing preventing future pathologies. The development of a FE model of lumbar spine is another interesting application of the simulation. The model allows research on the lumbar spine, not only in physiological conditions but also simulating different load conditions, to assess the impact on biomechanics. Different degrees of disc degeneration can also be simulated to determine the impact on adjacent anatomical elements. Finally, FE models may be useful to test different fixation systems, i.e., pedicular screws, interbody devices or rigid fixations compared with the dynamic ones. We have also developed models of lumbar spine and hip joint to predict the occurrence of osteoporotic fractures, based on densitometric determinations and specific biomechanical models, including approaches from damage and fracture mechanics. FE simulations also allow us to predict the behavior of orthopedic splints applied to the correction of deformities, providing the recovering force-displacement and angle-moment curves that characterize the mechanical behavior of the splint in the overall range of movement.
PMCID: PMC3329620  PMID: 22550621
Finite element simulation; Hip prosthesis; Lumbar spine; Lumbar fixations; Osteoporotic fractures; Splints
7.  Perioperative and short-term advantages of mini-open approach for lumbar spinal fusion 
European Spine Journal  2009;18(8):1194-1201.
It has been widely reported a vascular and neurologic damage of the lumbar muscles produced in the classic posterior approach for lumbar spinal fusions. The purpose of this study is to demonstrate a better clinical and functional outcome in the postoperative and short term in patients undergoing minimal invasive surgery (“mini-open”) for this lumbar spinal arthrodesis. We designed a prospective study with a 30 individuals cohort randomized in two groups, depending on the approach performed to get a instrumented lumbar circumferential arthrodesis: “classic posterior” (CL group) or “mini-open” approach (MO group). Several clinical and functional parameters were assessed, including blood loss, postoperative pain, analgesic requirements and daily life activities during hospital stay and at the 3-month follow-up. Patients of the “mini-open approach” group had a significant lower blood loss and hospital stay during admission. They also had significant lower analgesic requirements and faster recovery of daily life activities (specially moderate efforts) when compared to the patients of the “classic posterior approach” group. No significant differences were found between two groups in surgery timing, X-rays exposure or sciatic postoperative pain. This study, inline with previous investigations, reinforces the concept of minimizing the muscular lumbar damage with a mini-open approach for a faster and better recovery of patients’ disability in the short term. Further investigations are necessary to confirm these findings in the long term, and to verify the achievement of a stable lumbar spinal fusion.
PMCID: PMC2899516  PMID: 19399538
Mini-invasive; Surgery; Lumbar fusion; Discopathy; Arthrodesis

Results 1-7 (7)