This study employed longitudinal measures of evoked spinal reflex responses (Hoffman reflex, V wave) to investigate changes in the activation of muscle and to determine if there are "linked" neural adaptations in the motor pathway following isometric resistance training. Twenty healthy, sedentary males were randomly assigned to either the trained (n = 10) or control group (n = 10). The training protocol consisted of 12 sessions of isometric resistance training of the plantar flexor muscles over a 4-wk period. All subjects were tested prior to and after the 4-wk period. To estimate changes in spinal excitability, soleus Hoffman (H) reflex and M wave recruitment curves were produced at rest and during submaximal contractions. Recruitment curves were analyzed using the slope method (Hslp/Mslp). Modulation of efferent neural drive was assessed through evoked V wave responses (V/Mmax) at 50, 75, and 100% maximal voluntary contraction (MVC). After 4 weeks, MVC torque increased 20.0 +/- 13.9% (mean +/- SD) in the trained group. The increase in MVC was accompanied by significant increases in the rate of torque development (42.5 +/- 13.3%), the soleus surface electromyogram (60.7 +/- 30.8%), voluntary activation (2.8 +/- 0.1%), and the rate of activation (48.7 +/- 24.3%). Hslp/Mslp was not altered by training; however, V/Mmax increased 57.3 +/- 34.2% during MVC. These results suggest that increases in MVC observed in the first few days of isometric resistance training can be accounted for by an increase in the rate of activation at the onset of muscle contraction. Augmentation of muscle activation may be due to increased volitional drive from supraspinal centers.

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Keywords:taper corrosion taper design trunnionosis metal-on-polyethylene total hip arthroplasty This study examines how taper design affects corrosion and fretting at the head trunnion surface. All hip prostheses retrieved between 1999 and 2013 with 28 mm/+0 heads were selected, resulting in 44 cobalt-chrome-onpolyethylene implants, representing six taper designs. Mean implantation time: 8.9 ± 3.7 years. The femoral head tapers were scored for fretting and corrosion using the Goldberg scale as both a combined score and by three zones (apex, central and base). There was no difference in age (P = 0.34), BMI (P = 0.29), or implantation time (P = 0.19) between taper groups. The 11/13 taper had the highest combined corrosion and fretting score, but no difference (P = 0.22) between groups for combined scores (P = 0.22 for corrosion, P = 0.19 for fretting). In a zone-specific analysis, the 11/13 taper had highest corrosion score at base zone (P = 0.02). Taper design had a significant effect on corrosion at base of trunnion.Crown

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We hypothesized that if reduced spinal excitability contributes to central activation failure, then a caffeine-induced increase in spinal excitability would enhance postfatigue maximal voluntary activation and maximal voluntary contraction (MVC). Ten male volunteer subjects attended two laboratory sessions separated by at least 1 week. Contractile and electrical properties were assessed before, and 1 h after oral administration of caffeine (6 mg/kg) or placebo (all-purpose flour), and again following a fatigue protocol. The slope of the H reflex recruitment curve, normalized to that of the M wave (H(slp)/M(slp)), was used to estimate spinal excitability. Maximal voluntary activation was assessed using maximal EMG (EMG(max)) and twitch interpolation. Postfatigue, MVC torque declined (P<0.05) to 75.2+/-12.7 and 70.2+/-9.3% of the prefatigue values in the placebo (PL) and caffeine (CF) trials, respectively, and remained depressed throughout the recovery period. This was accompanied by a decline in % activation (P<0.05) from 99.6+/-0.3% (PL) and 99.8+/-0.3% (CF) to 94.8+/-3.5% (PL) and 95.3+/-5.0% (CF), indicating the presence of central activation failure. Caffeine offset the decline in H(slp)/M(slp )observed in the placebo trial (P<0.05), but it did not prevent the decline in maximal voluntary activation or MVC torque. Furthermore, although the decline in spinal excitability was correlated to the decline in EMG(max) (r=0.55, P<0.05) it was not correlated with the decline in % activation or MVC torque. Thus a fatigue-induced decline in spinal excitability did not limit maximal activation.

Background: The goal of the study was to compare radiographic and functional outcomes between conventional closed syndesmotic reduction and screw fixation with open reduction, direct repair of the anterior inferior tibiofibular ligament (AiTFL) and screw fixation. We hypothesized that open reduction with restoration of the AiTFL would provide an improved reduction with better radiographic and functional outcomes. Methods: Fifty consecutive patients with OTA 44-C ankle fractures were enrolled. Treatment was nonrandomized and based on surgeon preference. Patients were treated with either open reduction, suture-anchor AiTFL repair, and screw fixation (ART group), or conventional closed reduction of the syndesmosis followed by screw fixation (CR group). The primary outcome measure was anteroposterior (AP) displacement of the fibula on CT scan at 3 months postoperatively. Secondary outcome measures included the Maryland Foot Score, the American Orthopaedic Foot & Ankle Society (AOFAS) Ankle Hindfoot Score, and the Foot and Ankle Outcome Score (FAOS). Results: Mean AP difference between injured and noninjured ankles was decreased in the ART group compared with the CR group (0.7 ± 0.3 mm vs 1.5 ± 0.3 mm, P = .008). No differences were observed between groups in overall scores for secondary outcome measures. The ART group displayed a significant difference in Maryland Foot Shoe subscore at 12 months (ART = 9.5 vs CR = 8.3, P = .03) and FAOS Quality of Life subscore at 12 months (64.1 compared to 38.3, P = .04). Conclusions: Open anatomic syndesmotic repair resulted in improved radiographic outcomes compared with closed reduction. Cosmesis was worse at 6 weeks compared to the CR group; however, quality of life and shoewear were improved in the ART group at 1 year postoperatively. Level of Evidence: Level II, prospective comparative study.

This biomechanical study assessed the influence of changing antegrade cephalomedullary nail insertion point from anterior to neutral to posterior locations relative to the tip of the greater trochanter with or without anterior cortical perforation in the distal femur. Artificial osteoporotic femurs and cephalomedullary nails were used to create 5 test groups each with 8 specimens: intact femur without a nail or perforation, anterior nail insertion point without perforation, neutral nail insertion point without perforation, posterior nail insertion point without perforation, and posterior nail insertion point with perforation. Nondestructive biomechanical tests were done at 250 N in axial, coronal 3-point bending, sagittal 3-point bending, and torsional loading in order to measure overall stiffness and bone stress. The intact femur group vs. all femur/nail groups had lower stiffness in all loading modes ( p ≤ 0.018 ), as well as higher bone stress in the proximal femur ( p ≤ 0.027 ) but not in the distal femur above the perforation ( p = 0.096 ). Compared to each other, femur/nail groups only showed differences in sagittal 3-point bending stiffness for anterior and neutral vs. posterior nail insertion points without ( p ≤ 0.025 ) and with perforation ( p ≤ 0.047 ). Although it did not achieve statistical significance ( p ≥ 0.096 ), moving the nail insertion point from anterior to neutral to posterior to posterior with perforation did gradually increase bone stress by 45% (proximal femur) and 46% (distal femur). No femur or hardware failures occurred. Moving the nail insertion point and the presence of a perforation had little effect on stiffness, but the increased bone stress may be important as a predictor of fracture. Based on current bone stress results, surgeons should use anterior or neutral nail insertion points to reduce the risk of anterior cortical perforation.

Tribocorrosion at the head-neck taper interface - so-called 'taperosis' - may be a source of metal ions and particulate debris in metal-on-polyethylene total hip arthroplasty (THA). We examined the effect of femoral head length on fretting and corrosion in retrieved head-neck tapers in vivo for a minimum of two years (mean 8.7 years; 2.6 to 15.9). A total of 56 femoral heads ranging from 28 mm to 3 mm to 28 mm + 8 mm, and 17 femoral stems featuring a single taper design were included in the study. Fretting and corrosion were scored in three horizontally oriented concentric zones of each taper by stereomicroscopy. Head length was observed to affect fretting (p = 0.03), with 28 mm + 8 mm femoral heads showing greater total fretting scores than all other head lengths. The central zone of the femoral head bore taper was subject to increased fretting damage (p = 0.01), regardless of head length or stem offset. High-offset femoral stems were associated with greater total fretting of the bore taper (p = 0.04). Increased fretting damage is seen with longer head lengths and high-offset femoral stems, and occurs within a central concentric zone of the femoral head bore taper. Further investigation is required to determine the effect of increased head size, and variations in head-neck taper design.