Biomechanics of Subcutaneous Locked Plating Versus Burke Plate and External Fixator for Comminuted Distal Radius Fractures.

Background External fixators that span the wrist have been the historical norm in treating distal radius fractures. We have modified a dorsal distraction approach by using a subcutaneously applied locked bridge plate through two small incisions superficial to the extensor tendons and outside the extensor compartment. The purpose of this study was to biomechanically evaluate this modified method of fixation for comminuted distal radius fractures in comparison with two established constructs. Methods Matched cadaver specimens were used to model an AO Type 23-C3 distal radius fracture. Biochemical testing for stiffness during axial compressive loading was done on three constructs: a conventional Burke distraction plate, the subcutaneous internal fixation plating technique, and an external fixator. All specimens were cyclically loaded for 3000 cycles and then retested. Results The modified construct was found to be stiffer than the external fixator (p=0.013). When compared to the Burke plate, the modified construct was significantly less stiff before axial cycling (p=0.025). However, the difference was not maintained after cycling, and the post-axial loading stiffness difference was non-significant (p=0.456). Conclusion Our data demonstrate the biomechanical integrity of the subcutaneous plating technique for the fixation of comminuted distal radius fractures. It is stiffer than an external fixator and has the theoretical advantage of avoiding pin-tract infections. In addition, it is subcutaneous and not a cumbersome external construct. Our construct is minimally invasive, and it does not violate the dorsal extensor compartments. This allows for finger movement even while the construct is in place.

The Effect of Ambient Temperature and Implantation Time on the Material Properties of Two Viscosity-Differing Cements Using American Society of Testing and Materials Methodology.

Ambient temperature and time to implantation can affect the material properties of polymethylmethacrylate bone cement, and cement intrusion depth has been shown to affect implant fixation. The purpose of this study was to examine the effects of ambient temperature and time to implantation on depth of intrusion, and the effect of ambient temperature on setting time. Two types of cements were evaluated: cement A (Simplex P,medium Q7 viscosity) and cement B (Palacos R, high viscosity). Dough, working and setting times were determined, as well as intrusion depth, at different temperatures per American Society of Testing and Materials (ASTM) protocol F451. A vacuum mixer was used in a temperature- and humidity-controlled environment at 60, 65, and 70°F. At each temperature, the cement was placed into an intrusion mold at 0, 50, and 100% of working time. Increasing ambient temperature resulted in a significant decrease in dough and working and setting times for both cements (p = 0.038 - < 0.001). At each working time point and temperature, cement A showed significantly more intrusion than cement B (p = 0.044 - < 0.001). There was no effect of temperature on intrusion depth regardless of working time to implantation for either cement with the exception of cement B when comparing 60 versus 70°F at 0% working time (p = 0.004). Both cements showed a significant decrease in intrusion as time to implantation increased (p < 0.001). In conclusion, there are large inherent differences in properties of commercially available cements, and these properties are affected by such variables as time to implantation and ambient temperatures. An understanding of these properties may aid the surgeon in optimizing surgical outcomes.

An Epidemiological Comparison of Elbow Injuries Among United States High School Baseball and Softball Players, 2005-2006 Through 2014-2015.

BACKGROUND: Pitching is a common mechanism of injury in baseball, with known risk factors for elbow injuries among adolescent pitchers. HYPOTHESIS: Elbow injury rates and mechanisms will differ between high school baseball and softball players. STUDY DESIGN: Descriptive epidemiology study. LEVEL OF EVIDENCE: Level 3. METHODS: Baseball- and softball-related injury data from the 2005-2006 through 2014-2015 academic years were collected from the High School Reporting Information Online (RIO) Internet-based data collection tool. Athlete-exposure (AE) and injury data were collected by certified athletic trainers. Rate ratios (RRs) were calculated comparing injury rates in the 2 populations. Injury proportion ratios (IPRs) comparing elbow injuries in pitchers and nonpitchers were calculated as the proportion of all elbow injuries in pitchers divided by the proportion of all elbow injuries in nonpitchers. RESULTS: A total of 214 elbow injuries in male baseball players occurred over 2,327,774 AEs, for an overall elbow injury rate of 0.92 per 10,000 AEs. A total of 75 elbow injuries were reported in female softball players over 1,731,644 AEs, for an overall rate of 0.43 per 10,000 AEs. The rate of elbow injury was significantly higher for baseball than softball (RR, 2.12; 95% CI, 1.64-2.77). A significantly greater proportion of elbow injuries in baseball were pitching-related compared with those from softball, with 50.2% occurring while pitching in baseball versus 11.0% in softball (IPR, 4.58; 95% CI, 2.35-8.93). If all injuries occurring during pitching were removed from both sports, the difference in elbow injury rate for baseball and softball would no longer be significant (RR, 1.19; 95% CI, 0.88-1.62). CONCLUSION: The rate of elbow injuries is significantly higher in baseball than softball. This is attributable to differences in rates of pitching-related injuries between these 2 groups. CLINICAL RELEVANCE: These results demonstrate that overhand pitching increases risk of elbow injury in high school athletes.

Are the Current Little League Pitching Guidelines Adequate? A Single-Season Prospective MRI Study.

BACKGROUND: Little League throwing guidelines have recently been implemented in an attempt to lessen the growing number of elbow injuries occurring in youth baseball players. HYPOTHESIS/PURPOSE: The purpose of this study was to examine pre- and postseason changes seen on magnetic resonance imaging (MRI) in youth baseball players' elbows in an attempt to identify risk factors for pain and MRI abnormalities, with a particular focus on the current Little League guidelines. We hypothesized that MRI abnormalities would be common in pitchers with high pitch counts and poor guideline compliance. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A prospective study of Little League players aged 10 to 13 years was performed. Players were recruited prior to the start of the season and underwent bilateral elbow MRI as well as a physical examination and completed a questionnaire addressing their playing history and arm pain. At the end of the season, a repeat MRI and physical examination were performed. MRIs were read by blinded radiologists. During the season, player statistics including innings played, pitch counts, and guideline compliance were recorded. Physical examination findings and player statistics were compared between subjects with and without MRI changes utilizing chi-square and analysis of variance techniques. RESULTS: Twenty-six players were enrolled. Despite 100% compliance with pitching guidelines, 12 players (48%) had abnormal MRI findings, and 28% experienced pain during the season. There was a significant difference in distal humeral physeal width measured pre- to postseason (1.54 vs 2.31 mm, P < .001). There was a significant loss of shoulder internal rotation during the season, averaging 11°. While pitch counts, player position, and throwing curveballs/sliders were not significantly associated with changes seen on MRI, year-round play was associated with abnormalities (P < .05). Much lower compliance (<50%) was observed with nonenforced guidelines, including avoidance of single-sport specialization, year-round play, and throwing curveballs/sliders. CONCLUSION: Arm pain and MRI abnormalities of the medial elbow are common in Little League baseball players who comply with the Little League throwing guidelines, especially those playing year-round.

Does cortisol acting via the type II glucocorticoid receptor mediate suppression of pulsatile luteinizing hormone secretion in response to psychosocial stress?

This study assessed the importance of cortisol in mediating inhibition of pulsatile LH secretion in sheep exposed to a psychosocial stress. First, we developed an acute psychosocial stress model that involves sequential layering of novel stressors over 3-4 h. This layered-stress paradigm robustly activated the hypothalamic-pituitary-adrenal axis and unambiguously inhibited pulsatile LH secretion. We next used this paradigm to test the hypothesis that cortisol, acting via the type II glucocorticoid receptor (GR), mediates stress-induced suppression of pulsatile LH secretion. Our approach was to determine whether an antagonist of the type II GR (RU486) reverses inhibition of LH pulsatility in response to the layered stress. We used two animal models to assess different aspects of LH pulse regulation. With the first model (ovariectomized ewe), LH pulse characteristics could vary as a function of both altered GnRH pulses and pituitary responsiveness to GnRH. In this case, antagonism of the type II GR did not prevent stress-induced inhibition of pulsatile LH secretion. With the second model (pituitary-clamped ovariectomized ewe), pulsatile GnRH input to the pituitary was fixed to enable assessment of stress effects specifically at the pituitary level. In this case, the layered stress inhibited pituitary responsiveness to GnRH and antagonism of the type II GR reversed the effect. Collectively, these findings indicate acute psychosocial stress inhibits pulsatile LH secretion, at least in part, by reducing pituitary responsiveness to GnRH. Cortisol, acting via the type II GR, is an obligatory mediator of this effect. However, under conditions in which GnRH input to the pituitary is not clamped, antagonism of the type II GR does not prevent stress-induced inhibition of LH pulsatility, implicating an additional pathway of suppression that is independent of cortisol acting via this receptor.

Does the type II glucocorticoid receptor mediate cortisol-induced suppression in pituitary responsiveness to gonadotropin-releasing hormone?

Stress-like elevations in plasma cortisol suppress LH pulse amplitude in ovariectomized ewes by inhibiting pituitary responsiveness to GnRH. Here we sought to identify the receptor mediating this effect. In a preliminary experiment GnRH and LH pulses were monitored in ovariectomized ewes treated with cortisol plus spironolactone, which antagonizes the type I mineralocorticoid receptor (MR), or with cortisol plus RU486, which antagonizes both the type II glucocorticoid receptor (GR) and the progesterone receptor (PR). Cortisol alone reduced LH pulse amplitude, but not pulsatile GnRH secretion, indicating that it reduced pituitary responsiveness to endogenous GnRH. RU486, but not spironolactone, reversed this suppression. We next tested whether RU486 reverses the inhibitory effect of cortisol on pituitary responsiveness to exogenous GnRH pulses of fixed amplitude, frequency, and duration. Hourly GnRH pulses were delivered to ovariectomized ewes in which endogenous GnRH pulses were blocked by estradiol during seasonal anestrus. Cortisol alone reduced the amplitude of LH pulses driven by the exogenous GnRH pulses. RU486, but not an antagonist of PR (Organon 31710), prevented this suppression. Thus, the efficacy of RU486 in blocking the suppressive effect of cortisol is attributed to antagonism of GR, not PR. Together, these observations imply that the type II GR mediates cortisol-induced suppression of pituitary responsiveness to GnRH.