Dynamic knee valgus in competitive alpine skiers: Observation from youth to elite and influence of biological maturation

Numerous studies investigated the association between dynamic knee valgus and injury risk in post-pubertal and elite athletes; however, normative reference scores for competitive alpine skiers and observations on the development process throughout and beyond athletes' growth spurt are lacking. Thus, the aim of this study was to describe the dynamic knee valgus of competitive alpine skiers during drop jump landings (DJ) and single-leg squats (SLS) with respect to sex, sportive level, and biological maturation. Thirty-seven elite and 104 youth competitive alpine skiers around the growth spurt (U15) were examined for their maximal medial knee displacement (MKD) during DJ and SLS by a marker-based 3D motion analysis evaluating dynamic knee valgus. Additionally, skiers' age, anthropometry and biological maturation were assessed. MKD of youth and elite alpine skiers during DJ was comparable and did not improve with increasing training age. Female U15 skiers (on average further matured) had significantly larger MKD values during DJ than male U15 skiers (less matured) (P < .01). Moreover, MKD during DJ was directly associated with the athlete's individual biological maturation status. MKD values obtained from DJ significantly differed from those obtained during SLS (P < .01). The gender-specific difference in MKD values during DJ and their relationship with maturity offset highlight the fundamental changes to the neuromuscular control system during the growth spurt. Thus, biological maturation needs to be considered as a confounding factor for knee valgus screening. Caution is required when evaluating MKD by using high- and low-dynamic tasks, as corresponding information can differ.     

Age-related differences in vastus lateralis fascicle behavior during fast accelerative leg-extension movements

Leg-extensor rate of power development (RPD) decreases during aging. This study aimed to identify the underlying mechanism of the age-related decline in RPD during a fast acceleration in terms of in vivo vastus lateralis (VL) fascicle shortening behavior. Thirty-nine men aged between 25 and 69 years performed three maximal isokinetic leg-extensor tests with a fixed initial acceleration of 45° knee extension in 150 ms until 340°/s knee angular velocity. RPD, VL activity, and ultrasound images were recorded to assess (relative) fascicle shortening and mean shortening velocity for the phases of electromechanical delay, pretension, and acceleration. Our findings show that fascicle shortening and mean shortening velocity during a fast action increase with aging (0.002 per year, P = .035 and 0.005 s⁻¹ per year, P = .097, respectively), mainly due to a higher amount of shortening in the phase of electromechanical delay. The ratio of VL fascicle length over upper leg length at rest showed a negative correlation (r = −.46, P = .004) with RPD/body mass, while pennation angle at rest showed a trend toward a positive correlation (r = .28, P = .089). To conclude, our findings indicate that the ability to reach high VL fascicle shortening velocities in vivo is not reduced in older men while performing preprogrammed fast accelerations. The greater amount of fascicle shortening in old age is probably the result of age-related differences in the tendinous properties of the muscle-tendon complex, forcing the fascicles to shorten more in order to transmit the muscle force to the segment.     

Investigation of Drug Delivery in Rats via Subcutaneous Injection: Case Study of Pharmacokinetic Modeling of Suspension Formulations

With the rising cost of drug research, “do more with less” has become a new emphasis in the pharmaceutical industry. Consequently, the early analysis of pharmacokinetic/pharmacodynamic, efficacy, and safety parameters for a new drug target is critical for ensuring informed decision-making as soon as possible during the drug discovery process. When absorption, distribution, metabolism, and excretion properties of compounds are suboptimal which is especially true during the early stages of drug discovery, obtaining the desired exposure can be challenging via the most common routes (oral, intravenous). Therefore, subcutaneous (SC) injection is often explored as an alternate route of delivery. Although SC injection is used widely in the industry, information about how to model and predict the absorption of drugs administered via SC injection is not readily available. In the current research, we analyzed the absorption behavior of 12 model compounds covering a wide range of physicochemical properties following SC injection. We introduced a compound-specific parameter, the absorption factor from single SC injections of suspension doses of each compound, to aid in modeling and predicting of drug absorption profiles. The pharmacokinetic models derived in this study are capable of describing and predicting the absorption properties of SC injection for individual compounds.     

Post-operative delay in return of function following guided growth tension plating and use of corrective physical therapy

Purpose

Guided growth has long been used to treat growth deformities, but the Eight-Plate^® system has recently become more widely used by pediatric orthopaedists. Because the current literature lacks evaluation of functional status in the immediate post-operative period, we investigated functional status following use of the Eight-Plate^® system.

Methods

We evaluated post-operative delay in return of function following treatment with the Eight-Plate^® system at two weeks after surgery. Fifty-one consecutive patients with a growth deformity were treated with the Eight-Plate^® system. Patients were comprised of 32 male and 19 female patients with an average age of 11 years (range 2–17.9 years).

Results

Among study participants, 19 patients (37.3 %) had post-operative delay of function. The rate of delayed function for patients 10 years of age or younger and 11 years of age or older was respectively 11.8 and 50 % (P = 0.002). Six of the 19 patients were treated with four or more plates, of which five patients (83.3 %) developed delayed return of function. The rate of delayed function in patients with at least one femoral plate compared to no femoral plate was respectively 45 and 9.1 % (P = 0.006). Bilateral operations were associated with a 66.7 % rate of delayed function compared to 25 % with unilateral operations (P = 0.004). When patients with delay of function were treated with physical therapy, 12 of 13 patients (92.3 %) had complete resolution of their symptoms.

Conclusion

Statistical significance demonstrated that patients at the greatest risk were 11 years of age or older, with four or more plates, with femoral plates, or with bilateral operations. Patients with delayed function were readily corrected by physical therapy.     

Changes in Bone Mineral Density of Both Proximal Femurs after Total Knee Arthroplasty

Background

This study investigated the effects of total knee arthroplasty (TKA) on bone mineral density (BMD) of the proximal femur in patients who underwent the procedure.

Methods

Forty-eight patients scheduled to undergo unilateral TKA because of primary knee osteoarthritis were included in this study, which was conducted at a medical center between October 2006 and October 2009. In these 48 patients, 96 hips were evaluated. Measurement of BMD was performed preoperatively and one month, three months, six months, and one year after unilateral TKA. Repeated measured analysis of variance and paired t-tests for comparison of two repeated samples were used to compare differences between time points (preoperation, one, three, six, and 12 months) and between the operative and nonoperative sides.

Results

Preoperatively, BMD of the femoral neck, trochanter, and total hip on the operative side were lower than on the nonoperative side; however, there was no statistical difference. BMD of both femoral neck areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both trochanter areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both total hips was significantly lower than preoperative BMD at three months after TKA. However, no statistical differences of changes in BMD were observed between the operative and nonoperative sides at each measurement time.

Conclusions

According to our results, TKA was found to affect both proximal femurs during the acute period. However, TKA did not affect a change in BMD of the proximal femur during one year postoperative.