Skeletal system: biomechanical concepts and relationships to normal and abnormal conditions

Green nanotechnology-based drug delivery systems for osteogenic disorders

Introduction: Current treatments for osteogenic disorders are often successful, however they are not free of drawbacks, such as toxicity or side effects. Nanotechnology offers a platform for drug delivery in the treatment of bone disorders, which can overcome such limitations. Nevertheless, traditional synthesis of nanomaterials presents environmental and health concerns due to its production of toxic by-products, the need for extreme and harsh raw materials, and their lack of biocompatibility over time.Areas covered: This review article contains an overview of the current status of treating osteogenic disorders employing green nanotechnological approaches, showing some of the latest advances in the application of green nanomaterials, as drug delivery carriers, for the effective treatment of osteogenic disorders.Expert opinion: Green nanotechnology, as a potential solution, is understood as the use of living organisms, biomolecules and environmentally friendly processes for the production of nanomaterials. Nanomaterials derived from bacterial cultures or biomolecules isolated from living organisms, such as carbohydrates, proteins, and nucleic acids, have been proven to be effective composites. These nanomaterials introduce enhancements in the treatment and prevention of osteogenic disorders, compared to physiochemically-synthesized nanostructures, specifically in terms of their improved cell attachment and proliferation, as well as their ability to prevent bacterial adhesion.

Effects of age and rate of twist on torsional fracture patterns in infant porcine femora

OBJECTIVE

Long bone fractures are a common injury in the pediatric population. Differentiation between abusive, or non-accidental trauma, and accidental trauma in children remains challenging for forensic practitioners. A recent clinical-based study was able to separate pediatric abusive from accidental trauma based on femoral fracture pattern using the ratio of fracture length over bone diameter (fracture ratio), as determined from radiographic analysis of this fractured bone. The forensic literature indicates more cases of abuse in younger pediatric victims than accidental cases. While this was the case in the clinical study, the effect was not shown to be statistically significant. Furthermore, while speed of trauma was not considered in the clinical study, a laboratory study with an immature bovine model indicates rotational speed influences fracture pattern, but specimen age was not varied in that study. Therefore, the objective of the current study was to use immature porcine femora to investigate the effects of age and rate of twist on a modified version of this fracture ratio parameter.

METHODS

Fifteen pairs of porcine femora with various ages were twisted until observable failure using a custom-built torsional fixture. The left femur of each pair was twisted to failure at a rate of 3 deg/s, while the right femur was twisted at a rate of 90 deg/s. The torque and angle of rotation were recorded at a sampling rate of 10,000 Hz. Fracture ratio was defined as total fracture length divided by bone diameter.

RESULTS

Fracture ratio increased with specimen age, with specimens under the low rate of twist yielding a consistently lower fracture ratio than those from specimens under the high rate of twist. The results showed that both specimen age and rate of twist were significant factors influencing fracture ratio.

CONCLUSION

The determination of abusive from accidental trauma in criminal cases, based on the pattern of long bone fracture alone, may need to include additional data on the specific age of the pediatric victim and the potential speed of the traumatic event.

Risk of hysterectomy and salpingectomy or oophorectomy compared to repair after pelvic gynecologic trauma

PURPOSE

Pelvic gynecologic trauma (PGT) includes injury to the uterus, ovaries or fallopian tubes. We hypothesized Injury Severity Score (ISS) ≥ 25, hypotension on admission and age ≥ 51 (average age for menopause) would be independent risk factors for resection compared to repair.

METHODS

A retrospective analysis of the National Trauma Data Bank was performed between 2007 and 2015.

RESULTS

Of 2,040,235 female patients, 1938 (< 0.1%) presented with PGT with the majority sustaining injury to the ovary or fallopian tubes (52.9%). Most patients were managed nonoperatively (77.1 vs 22.9%). On multivariable analysis, in patients with injury to the uterus, ISS ≥ 25 (OR 3.52, CI 1.67-7.48, p < 0.05) was associated with higher risk for hysterectomy compared to repair. In patients with injury to the ovaries or fallopian tubes, gunshot wound (OR 3.73, CI 1.43-9.68, p < 0.05) was associated with a higher risk for salpingectomy or oophorectomy compared to repair. Age ≥ 51 and hypotension on admission were not independent risk factors for resection in patients with PGT. Operative treatment was associated with a lower risk for mortality in patients with an injury to the uterus (OR 0.27, CI 0.14-0.51, p < 0.001) or ovaries/fallopian tubes (OR 0.37, CI 0.19-0.72, p < 0.001) compared to those managed nonoperatively.

CONCLUSION

In the largest study reported, PGT occurred in < 0.1% of traumas involving women. Patients with ISS ≥ 25 have higher risk for hysterectomy compared to repair. Gunshot injuries have higher risk for salpingectomy or oophorectomy compared to repair. Hypotension on arrival or age ≥ 51 are not independent risk factors for resection in PGT. Operative management is associated with lower risk of mortality in PGT patients.

Hypothesis about an existent biomechanical cause-effect relationship between Schëuermann's kyphosis and scoliosis

Schëuermanńs kyphosis is usually observed with a mild idiopathic scoliosis, and there is parity between these two diseases. The aim of this work is to establish a hypothesis about the existence of a biomechanical causal relationship between Schëuermann's kyphosis and scoliosis. To achieve this, a literature review was conducted. A simple mechanical model of the passive thoracolumbar subsystem was created to support part of the discussion. This mechanical model describes the passive thoracolumbar subsystem under ideal conditions of equilibrium. After giving consideration to the system under these conditions, some of the geometrical changes that may be found in Schëuermanńs kyphosis are considered. Next, this work discusses the evolution of the spine, taking into account its relationship with stable equilibrium, which the passive subsystem tends toward. We hypothesized about the postural response of the body to compensate for possible situations of imbalance. In conclusion, it can be found that a change in the alignment of the spine may occur due to the postural adaptation of the body to an inadequate mechanical situation that may lead to scoliotic deformity of the spine.

Effective therapeutic exercise prescription: the right exercise at the right dose

The prescription of an effective therapeutic exercise program requires the right dosage of the right exercise, at the right time for that patient. The therapist must understand and apply training principles effectively in the presence of pathology, injury, or otherwise unhealthy tissue. The intervention goal is to close the gap between current performance and the desired goal or capacity. Although there may be a preferred linear path from current performance to optimal outcome, complexities of the human body, internal factors, and external variables may create barriers to this direct path. Successful programs include key program design considerations such as ensuring a stable baseline before progression, treating the right impairments and activity limitations, understanding contextual factors, considering the principles of specificity and optimal loading, and applying dosing principles. Program progression can be achieved through increases in total exercise volume and/or through manipulation of exercise challenges at the same exercise volume. Effective application of these principles will guide patients toward their goals as quickly and efficiently as possible.

Influence of cryosurgery on treatment outcome of low-grade chondrosarcoma

Successfully managing low-grade chondrosarcomas with margins considered less than wide would minimize the need for extensive reconstruction. We report our experience using cryotherapy as an adjuvant to treat patients with low-grade intracompartmental chondrosarcomas. Ten consecutive patients had intralesional resections including curettage, cryo-surgery, and polymethylmethacrylate application. Eight of these patients required prophylactic skeletal stabilization. We retrospectively reviewed the outcomes for tumor recurrence, disease progression, and complications. The Musculo-skeletal Tumor Society rating scale was used to evaluate functional outcome, and the mean score was 27 points (range, 25-30 points). The mean age of the patients was 54.4 years (range, 29-83 years), and the average followup was 38.5 months (range, 24-60 months). Patients were treated for lesions of the femur (n = 3), humerus (n = 3), scapula (n = 2), tibia (n = 1), and acetabulum (n = 1). There was no evidence of recurrence or metastases. At the latest followup, all patients were well, however, one patient had hardware loosening. In this small group of patients, intralesional resection with adjuvant cryoablation provided an alternative to more radical procedures for low-grade intracompartmental chondrosarcoma.

Evaluation of axial and flexural stresses in the vertebral body cortex and trabecular bone in lordosis and two sagittal cervical translation configurations with an elliptical shell model

BACKGROUND

Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare.

OBJECTIVE

To calculate and compare combined axial and flexural stresses in lordosis versus cervical configurations in anterior and vertical sagittal head translated positions.

DESIGN

Digitized measurements from lateral cervical radiographs of 3 different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2-C7.

METHODS

An elliptical shell model was used to model horizontal cross-sections of the vertebral bodies of C2 through T1. Axial and flexural stresses were calculated with short compression block equations. Elliptical shell modeling permitted separation of stresses into cortical and inner medullary regions. Digitized radiographic points were used to create polynomials representing the shape of the sagittal cervical curvatures from C1 to T1. To calculate bending moments at each vertebral segment, moment arms from a vertical line through C1 were determined from digitizing.

RESULTS

Compared with the normal lordosis, stresses on the anterior vertebral body cortical margins of C5-T1 in the sagittal translated postures are compression rather than tension. At the posterior vertebral bodies in the anteriorly translated position and vertically translated postures, the stresses change from compression to tension at C5 through T1. In absolute value (ABS) compared with values at the same segments in a normal lordosis, the magnitude of the combined anterior stresses in the sagittal postures are higher at C5-C7 (eg, ABS[sigma(straight)/sigma(normal)] approximately 1.25 to 4.25).

CONCLUSIONS

Vertebral body stresses are reversed in direction at C5-T1 in sagittal translated postures compared to a normal lordosis. Stress analysis, with implications for bone remodeling, indicates that both sagittal head translation postures, anterior head carriage, and vertical head translation, are undesirable configurations in the cervical spine.

Comparison of axial and flexural stresses in lordosis and three buckled configurations of the cervical spine

OBJECTIVE

To calculate and compare combined axial and flexural stresses in lordosis versus buckled configurations of the sagittal cervical curve.

DESIGN

Digitized measurements from lateral cervical radiographs of four different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2-C7.Background. Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare.

METHODS

Center of gravity of the head (inferior-posterior sella turcica) and vertebral body margins were digitized on four different lateral cervical radiographs: lordosis, kyphosis, and two "S"-shapes. Polynomials (seventh degree) and stress concentrations on the concave and convex margins were derived for the shape of the sagittal cervical curvatures from C1 to T1. Moments of inertia were determined from digitizing and the use of an elliptical shell model of cross-section. Moment arms from a vertical line through the center of gravity of the head to the atlas and scaled neck extensor moment arms from the literature were used to compute the vertical component of extensor muscle effort. Segmental lever arms were calculated from a vertical line through C1 to each vertebra.

RESULTS

In lordosis, anterior and posterior stresses in the vertebral body are nearly uniform and minimal. In kyphotic areas, combined stresses changed from tension to compression at the anterior vertebral margins and were very large (6-10 times as large in magnitude) compared to lordosis. In kyphotic areas at the posterior vertebral body, the combined stresses changed from compression (in lordosis) to tension.

CONCLUSIONS

The stresses in kyphotic areas are very large and opposite in direction compared to a normal lordosis. This analysis provides the basis for the formation of osteophytes (Wolff's Law) on the anterior margins of vertebrae in kyphotic regions of the sagittal cervical curve. This indicates that any kyphosis is an undesirable configuration in the cervical spine. Relevance. Osteophytes and osteoarthritis are found at areas of altered stress and strain. Axial and flexural stresses at kyphotic areas in the sagittal cervical spine are abnormally high.