Safety and Effectiveness of a Perturbation-based Neuromuscular Training Program on Dynamic Balance in Adolescent Females: A Randomized Controlled Trial.

BACKGROUND: Adolescent females are at much greater risk for ACL injury than their male counterparts when participating in the same sports. Preventative and pre-operative rehabilitation neuromuscular (NM) exercise programs are often recommended to improve knee function and reduce injury rates. The effectiveness of perturbation-based NM training program has been established in an adult population but has yet to be investigated in the at-risk adolescent female population. PURPOSE: To determine the effectiveness of a perturbation-based NM exercise program in a group of physically active adolescent females. STUDY DESIGN: Prospective randomized trial. METHODS: Twenty-four healthy and an exploratory group of 10 ACL-injured females (ages 12-18) were equally randomized into a perturbation-based NM training or control group and evaluated before and after a five-week intervention period. The primary outcome of dynamic balance was measured using the Y-Balance test (YBT); secondary outcome measures included lower limb strength, proprioception, and flexibility. RESULTS: The perturbation-based NM training intervention was safely completed by all participants but had no significant effect on YBT scoring, lower limb strength, proprioception or flexibility in either the healthy or ACL-injured groups. CONCLUSIONS: Perturbation-based NM training is safe, but may offer little preventative benefit for healthy or pre-operative rehabilitation benefit for ACL-injured adolescent females. Future research should examine whether the effectiveness of perturbation-based NM training is influenced by the length of the training intervention, training intensity, or when it is combined with other forms of prophylactic or pre-surgical rehabilitation frequently used with at-risk adolescent females who regularly participate in sport. LEVEL OF EVIDENCE: Level 3.

Lower Extremity Kinematics of the Y-Balance Test in Healthy and ACL Injured Adolescent Females.

BACKGROUND: Adolescent females are at significant risk for sustaining an ACL injury. The Y-Balance Test (YBT) is frequently used to evaluate neuromuscular control and lower extremity function. However, few studies have quantified 2D lower extremity kinematics during performance of the YBT, and there is an absence of kinematic data specific to at-risk adolescent females. PURPOSE: To examine lower extremity joint kinematics during execution of the YBT by healthy and ACL-injured adolescent females. STUDY DESIGN: Prospective cohort. METHODS: Twenty-five healthy and ten ACL-injured (mean time from injury 143 days) adolescent females were assessed using the YBT. Sagittal and frontal plane knee and ankle motion was video recorded during execution of the YBT anterior reach movement. Ankle dorsi-flexion, knee flexion, and knee valgus angles were quantified via kinematic analysis. ANOVAs with a post hoc Bonferroni correction were used to compare YBT scoring (%LL) and kinematic data between groups. Pearson product-moment correlations determined the relationship between kinematic data and YBT scoring. RESULTS: Healthy and ACL-injured subjects demonstrated similar YBT scores and lower extremity kinematic data. Healthy subjects demonstrated a weak positive correlation between ankle dorsiflexion and YBT scoring, and a weak negative correlation between knee valgus and YBT scoring. These relationships did not exist for ACL-injured subjects. Kinematic data for both groups also demonstrated a large degree of variability, regardless of YBT score. CONCLUSIONS: Adolescent females frequently utilize a variety of lower extremity movement strategies when performing a functional movement task, and scoring on the YBT offers limited insight regarding lower extremity joint kinematics and ACL-injury risk in a physically active adolescent female population. LEVEL OF EVIDENCE: Level 3.

Associations between concussion and risk of diagnosis of psychological and neurological disorders: a retrospective population-based cohort study.

OBJECTIVE: To investigate associations between concussion and the risk of follow-up diagnoses of attention-deficit hyperactivity disorder (ADHD), mood and anxiety disorders (MADs), dementia and Parkinson's disease. DESIGN: A retrospective population-based cohort study. SETTING: Administrative health data for the Province of Manitoba between 1990-1991 and 2014-2015. PARTICIPANTS: A total of 47 483 individuals were diagnosed with a concussion using International Classification of Diseases (ICD) codes (ICD-9-CM: 850; ICD-10-CA: S06.0). All concussed subjects were matched with healthy controls at a 3:1 ratio based on age, sex and geographical location. Associations between concussion and conditions of interest diagnosed later in life were assessed using a stratified Cox proportional hazards regression model, with adjustments for socioeconomic status and pre-existing medical conditions. RESULTS: 28 021 men (mean age ±SD, 25±18 years) and 19 462 women (30±21 years) were included in the concussion group, while 81 871 men (25±18 years) and 57 159 women (30±21 years) were included in the matched control group. Concussion was associated with adjusted hazard ratios of 1.39 (95% CI 1.32 to 1.46, p<0.001) for ADHD, 1.72 (95% CI 1.69 to 1.76; p<0.001) for MADs, 1.72 (95% CI 1.61 to 1.84; p<0.001) for dementia and 1.57 (95% CI 1.41 to 1.75; p<0.001) for Parkinson's disease. CONCLUSION: Concussion was associated with an increased risk of diagnosis for all four conditions of interest later in life.

The Effects of Acute Anaerobic Exercise on the Cardiovascular and Metabolic Response to the Cold Pressor Test in Healthy Adult Males.

Little is known about the physiological response to the cold pressor test (CPT) when in a clinically-induced state of autonomic nervous system (ANS) imbalance, despite its utility in various disease- and injury-states. To date, research in this area is limited to acute aerobic and isometric exercise, with a paucity of research investigating the effects of anaerobic exercise on the physiological response to the CPT. Therefore, the purpose of our study was to assess the effects of the Wingate anaerobic cycle test (WAT) on cardiovascular (CV) and metabolic recovery following the CPT in a group of healthy adult males. A pre-post intervention study was conducted, whereby 10 healthy adult males (age = 29 ± 4 years, height = 182 ± 7 cm, mass = 83 ± 9 kg) completed a baseline cold pressor test (CPT-only) and a follow-up cold pressor test preceded by a Wingate anaerobic exercise test (WAT+CPT). Recovery slopes for various CV and metabolic variables, including heart rate (HR), blood pressure (BP), and relative oxygen consumption (V̇O2) were analyzed using single-subject analysis, with celeration line slopes calculated for all participants in the CPT-only and WAT+CPT testing sessions. Celeration line slopes were compared between testing sessions using paired t-tests. No differences were identified for recovery slopes for HR (p = .295), diastolic BP (p = .300), and relative V̇O2 (p = .176) when comparing CPT-only and WAT+CPT testing sessions. Our results suggest that the CPT elicits a CV and metabolic response beyond that elicited solely by an acute bout of anaerobic exercise. As such, the CPT may be able to serve as a surrogate test for anaerobic exercise for individuals where high-intensity exercise may be contraindicated. Future research is warranted however, as the specific physiological mechanisms governing the observed responses have yet to be elucidated.

Evaluation of Early Submaximal Exercise Tolerance in Adolescents with Symptomatic Sport-related Concussion.

PURPOSE: This study aimed to compare cardiorespiratory response to a graded aerobic exercise challenge between adolescents with symptomatic sport-related concussion (SSRC) and healthy control subjects. METHODS: A quasiexperimental nonrandomized study at a multidisciplinary pediatric concussion program was conducted. Thirty-four adolescents with SSRC (19 males and 15 females) and 40 healthy control subjects (13 males and 27 females) completed the Buffalo Concussion Treadmill Testing (BCTT) until either symptom exacerbation or volitional fatigue. Main outcome measures included heart rate (HR), oxygen consumption (V˙O2), carbon dioxide production (V˙CO2), and minute ventilation (V˙E) at rest and at test termination, and change from rest in variables (ΔHR, ΔV˙O2, ΔV˙CO2, and ΔV˙E) during the first five stages of the BCTT. Main outcomes were analyzed using three-way mixed-model ANOVA, with group status (control vs SSRC) and sex (male vs female) as between-subject factors, and time (BCTT stage) as the within-subject factor. RESULTS: No group differences in resting HR, systolic and diastolic blood pressure, ΔV˙O2, V˙CO2, and V˙E were observed. During the first five stages of the BCTT, no group differences in ΔV˙O2, V˙CO2, and V˙E were observed; however, SSRC patients demonstrated higher RPE (P < 0.0005) compared with control subjects. No sex-based differences were observed among SSRC patients on measures collected at rest and during early stages of BCTT. CONCLUSIONS: Although SSRC patients exhibited higher RPE during a graded aerobic exercise challenge, no differences in cardiorespiratory response were observed compared with control subjects exercising at equivalent workloads. Further work is needed to elucidate the physiological mechanisms underlying exercise intolerance after SSRC.

Radiostereometric analysis of keeled versus pegged glenoid components in total shoulder arthroplasty: a randomized feasibility study.

BACKGROUND: This study aimed to assess differences in the fixation and functional outcomes between pegged and keeled all-polyethylene glenoid components for standard total shoulder arthroplasty. METHODS: Patients were randomized to receive a keeled or pegged all-polyethylene glenoid component. We used model-based radiostereometric analysis (RSA) to assess glenoid fixation and subjective outcome measures to assess patient function. Follow-up examinations were completed at 6 weeks and 6, 12 and 24 months after surgery. Modifications to the RSA surgical, imaging and analytical techniques were required throughout the study to improve the viability of the data. RESULTS: Stymied enrolment resulted in only 16 patients being included in our analyses. The RSA data indicated statistically greater coronal plane migration in the keeled glenoid group than in the pegged group at 12 and 24 months. Functional outcome scores did not differ significantly between the groups at any follow-up. One patient with a keeled glenoid showed high component migration after 24 months and subsequently required revision surgery 7 years postoperatively. CONCLUSION: Despite a small sample size, we found significant differences in migration between glenoid device designs. Although clinically these findings are not robust, we have shown the feasibility of RSA in total shoulder arthroplasty as well as the value of a high-precision metric to achieve objective results in a small group of patients.

CONTEXTE: Cette étude avait pour objet d'évaluer les différences sur le plan de la fixation et des résultats fonctionnels entre les composants glénoïdiens à plots et à quille, tous deux en polyéthylène, dans une arthroplastie totale traditionnelle de l'épaule. MÉTHODES: La répartition des composants glénoïdiens en polyéthylène à plots et à quille a été faite de façon aléatoire. Nous nous sommes servis de modèles d'analyses radiostéréométriques (ARS) pour évaluer la fixation glénoïdienne et les indicateurs de résultats subjectifs, ce qui nous a ainsi permis d'évaluer les résultats fonctionnels des patients. Quatre examens de suivi ont été réalisés après la chirurgie : à 6 semaines, puis à 6 mois, à 12 mois et à 24 mois. Tout au long de l'étude, des ajustements ont été apportés aux modèles d'ARS de la chirurgie, de l'imagerie et des analyses afin d'améliorer la viabilité des données. RÉSULTATS: Des problèmes liés au recrutement ont fait en sorte que nous n'avons retenu que 16 patients dans le cadre de nos analyses. Les données d'ARS ont montré une migration statistiquement plus grande du plan frontal dans le groupe quille que dans le groupe plots à 12 et à 24 mois. Les résultats fonctionnels étaient sensiblement les mêmes d'un groupe à l'autre, peu importe le moment du suivi. Un patient du groupe quille a présenté une migration très importante du composant après 24 mois; il a dû subir une chirurgie de révision 7 ans après la chirurgie initiale. CONCLUSION: Malgré la petite taille de l'échantillon, nous avons observé des différences significatives dans la migration des composants, selon le type utilisé. Même si ces observations ne permettent pas d'arriver à des conclusions robustes d'un point de vue clinique, nous avons montré qu'il est possible d'avoir recours aux ARS en contexte d'arthroplastie totale de l'épaule et démontré la valeur associée à l'utilisation de mesures de haute précision pour l'obtention de résultats objectifs chez un petit groupe de patients.

Fibrosis, low vascularity, and fewer slow fibers after rotator-cuff injury.

INTRODUCTION: Rotator-cuff injury (RCI) represents 50% of shoulder injuries, and prevalence increases with age. Even with successful tendon repair, muscle and joint function may not return. METHODS: To explore the dysfunction, supraspinatus and ipsilateral deltoid (control) muscles were biopsied during arthroscopic RCI repair for pair-wise histological and protein-expression studies. RESULTS: Supraspinatus showed fiber atrophy (P < 0.0001), fibrosis (by Sirius Red, P = 0.05), reduced vascular density (P < 0.001), and a lower proportion of slow fibers (P < 0.0001) compared with the ipsilateral control muscle. There were also higher levels of atrogin-1 (P = 0.05), vascular endothelial growth factor (VEGF, P < 0.01), and dystrophin (P < 0.008, relative to fiber diameter) versus control. CONCLUSIONS: Adaptive changes in vascular endothelial growth factor and dystrophin were likely associated with reduced vascular supply, fatigue resistance, and fibrosis, accompanied by disuse atrophy from mechanical unloading of supraspinatus after tendon tear. Treatment to promote growth and vascularity in atrophic supraspinatus muscle may help improve functional outcome after surgical repair. Muscle Nerve 55: 715-726, 2017.

Altered Satellite Cell Responsiveness and Denervation Implicated in Progression of Rotator-Cuff Injury.

BACKGROUND: Rotator-cuff injury (RCI) is common and painful; even after surgery, joint stability and function may not recover. Relative contributions to atrophy from disuse, fibrosis, denervation, and satellite-cell responsiveness to activating stimuli are not known. METHODS AND FINDINGS: Potential contributions of denervation and disrupted satellite cell responses to growth signals were examined in supraspinatus (SS) and control (ipsilateral deltoid) muscles biopsied from participants with RCI (N = 27). Biopsies were prepared for explant culture (to study satellite cell activity), immunostained to localize Pax7, BrdU, and Semaphorin 3A in satellite cells, sectioning to study blood vessel density, and western blotting to measure the fetal (γ) subunit of acetylcholine receptor (γ-AchR). Principal component analysis (PCA) for 35 parameters extracted components identified variables that contributed most to variability in the dataset. γ-AchR was higher in SS than control, indicating denervation. Satellite cells in SS had a low baseline level of activity (Pax7+ cells labelled in S-phase) versus control; only satellite cells in SS showed increased proliferative activity after nitric oxide-donor treatment. Interestingly, satellite cell localization of Semaphorin 3A, a neuro-chemorepellent, was greater in SS (consistent with fiber denervation) than control muscle at baseline. PCAs extracted components including fiber atrophy, satellite cell activity, fibrosis, atrogin-1, smoking status, vascular density, γAchR, and the time between symptoms and surgery. Use of deltoid as a control for SS was supported by PCA findings since "muscle" was not extracted as a variable in the first two principal components. SS muscle in RCI is therefore atrophic, denervated, and fibrotic, and has satellite cells that respond to activating stimuli. CONCLUSIONS: Since SS satellite cells can be activated in culture, a NO-donor drug combined with stretching could promote muscle growth and improve functional outcome after RCI. PCAs suggest indices including satellite cell responsiveness, atrogin-1, atrophy, and innervation may predict surgical outcome.

Atrophy, inducible satellite cell activation, and possible denervation of supraspinatus muscle in injured human rotator-cuff muscle.

The high frequency of poor outcome and chronic pain after surgical repair of shoulder rotator-cuff injury (RCI) prompted this study to explore the potential to amplify muscle regeneration using nitric oxide (NO)-based treatment. After preoperative magnetic resonance imaging (MRI), biopsies of supraspinatus and ipsilateral deltoid (as a control) were collected during reparative surgery for RCI. Muscle fiber diameter, the pattern of neuromuscular junctions observed with alpha-bungarotoxin staining, and the γ:ε subunit ratio of acetylcholine receptors in Western blots were examined in tandem with experiments to determine the in vitro responsiveness of muscle satellite cells to activation (indicated by uptake of bromodeoxyuridine, BrdU) by the NO-donor drug, isosorbide dinitrate (ISDN). Consistent with MRI findings of supraspinatus atrophy (reduced occupation ratio and tangent sign), fiber diameter was lower in supraspinatus than in deltoid. ISDN induced a significant increase over baseline (up to 1.8-fold), in the proportion of BrdU+ (activated) Pax7+ satellite cells in supraspinatus, but not in deltoid, after 40 h in culture. The novel application of denervation indices revealed a trend for supraspinatus muscle to have a higher γ:ε subunit ratio than deltoid (P = 0.13); this ratio inversely with both occupancy ratio (P < 0.05) and the proportion of clusters at neuromuscular junctions (P = 0.05). Results implicate possible supraspinatus denervation in RCI and suggest NO-donor treatment has potential to promote growth in atrophic supraspinatus muscle after RCI and improve functional outcome.

Long-term follow-up of ACL reconstruction with hamstring autograft.

PURPOSE: To investigate the differences in the incidence and severity of knee osteoarthritis (OA), joint space narrowing, knee laxity, and knee flexion and extension strength between an anterior cruciate ligament (ACL)-reconstructed knee and the contralateral non-reconstructed limb. METHODS: Retrospective case series of patients from a single surgeon that had an ACL reconstruction with a semitendinosus/gracilis autograft more than 12 years ago. Outcome measures included radiographic analysis, International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC), KT-1000, Tegner Activity Level Scale, Lysholm Knee Score, ACL quality of life score (ACL-QOL) and knee flexor/extensor strength. RESULTS: Seventy-four patients consented and sixty-eight (43 male, 25 female) were included for analysis. Average age (SD) at the time of surgery was 31.2 (±9.1) years. At follow-up of 14.6 (1.9) years, 9% had re-ruptured their ACL, whereas 5% ruptured the contralateral ACL. Reconstructed knees had a greater incidence and severity of OA (P < 0.01). Medial meniscus surgery was a strong predictor of OA. Seventy-five per cent scored a normal or nearly normal knee on the IKDC. The mean Lysholm score was 75.8% and Tegner Activity Level Scale scores decreased (P < 0.001) from the time of surgery. Knee extension strength was greater in the contralateral knee at speeds of 60°/s (P = 0.014) and 150°/s (P = 0.012). CONCLUSIONS: Reconstructed knees have a greater incidence and severity of OA than non-reconstructed knees, which suggests degenerative changes are secondary to ACL rupture. Medial meniscus surgery is a strong predictor of OA. Despite this, 75% of patients reported good outcomes.

Accuracy and reliability of determining the isometric point of the knee for multiligament knee reconstruction.

PURPOSE: To compare the accuracy and reliability of the anatomic and radiographic techniques for identifying the isometric point of the knee. METHODS: Only four specimens were used; however, eight experienced multiligament knee injury surgeons were recruited to address this limitation. Surgeons estimated the isometric point (EIP) on the medial and lateral sides using an anatomic and radiographic method. The x and y coordinates of the EIP were compared to the true isometric point (TIP). T-tests and interclass correlation coefficients (ICC) were performed to determine the accuracy and reliability between the methods. RESULTS: There was no difference in placement of the EIP on the medial side of the knee in the anterior/posterior (x; p = n.s.) and superior/inferior direction (y; p = n.s). The EIP was anterior (p = 0.001) to the TIP with the radiographic method on the lateral side and approached significance (p = 0.05) in the superior/inferior direction. The ICC (95% CI) for identifying the EIP on the medial side in the anterior/posterior direction using the anatomic method was 0.64 (0.28-0.96) and 0.11 (-0.06 to 0.77) in the superior/inferior direction. Using the radiographic method, the ICC in the anterior/posterior and superior/inferior direction was 0.49 (0.14-0.94) and 0.15 (-0.47 to 0.81), respectively. On the lateral side, the ICC for the anatomic method was 0.84 (0.56-0.99) in the anterior/posterior direction and 0.36 (0.05-0.90) in the superior/inferior direction. Using the radiographic method, the ICC in the anterior/posterior and superior/inferior direction was 0.61 (0.26-0.96) and 0.89 (0.67-0.99), respectively. CONCLUSIONS: There was no difference in accuracy on the medial side of the knee. On the lateral side, the anatomic method was more accurate in the anterior/posterior direction. Reliability was greater in the anterior/posterior direction on both sides of the knee. Surgeons were most likely to place the isometric point anterior and superior to the TIP on both the medial and lateral sides of the knee with either method which has the potential to cause graft lengthening. This should be taken into consideration during reconstruction/repair of the MCL/PMC and LCL/PLC.

The internal validity of arthroscopic simulators and their effectiveness in arthroscopic education.

PURPOSE: The purpose of this systematic review was to identify standard procedures for the validation of arthroscopic simulators and determine whether simulators improve the surgical skills of users. METHODS: Arthroscopic simulator validation studies and randomized trials assessing the effectiveness of arthroscopic simulators in education were identified from online databases, as well as, grey literature and reference lists. Only validation studies and randomized trials were included for review. Study heterogeneity was calculated and where appropriate, study results were combined employing a random effects model. RESULTS: Four hundred and thirteen studies were reviewed. Thirteen studies met the inclusion criteria assessing the construct validity of simulators. A pooled analysis of internal validation studies determined that simulators could discriminate between novice and experts, but not between novice and intermediate trainees on time of completion of a simulated task. Only one study assessed the utility of a knee simulator in training arthroscopic skills directly and demonstrated that the skill level of simulator-trained residents was greater than non-simulator-trained residents. CONCLUSIONS: Excessive heterogeneity exists in the literature to determine the internal and transfer validity of arthroscopic simulators currently available. Evidence suggests that simulators can discriminate between novice and expert users, but discrimination between novice and intermediate trainees in surgical education should be paramount. International standards for the assessment of arthroscopic simulator validity should be developed to increase the use and effectiveness of simulators in orthopedic surgery.

Lower body positive pressure: an emerging technology in the battle against knee osteoarthritis?

BACKGROUND: Knee osteoarthritis (OA) is the most prevalent medical condition in individuals over the age of 65 years, and is a progressive joint degenerative condition with no known cure. Research suggests that there is a strong relationship between knee pain and loss of physical function. The resulting lifestyle modifications negatively impact not only disease onset and progression but also overall health, work productivity, and quality of life of the affected individual. PURPOSE: The goal of this investigation was to examine the feasibility of using an emerging technology called lower body positive pressure (LBPP) to simulate weight loss and reduce acute knee pain during treadmill walking exercise in overweight individuals with radiographically confirmed symptomatic knee OA. DESIGN: Prospective case series. METHODS: Twenty-two overweight individuals with knee OA completed two 20-minute treadmill walking sessions (one full weight bearing and one LBPP supported) at a speed of 3.1 mph, 0% incline. Acute knee pain was assessed using a visual analog scale, and the percentage of LBPP support required to minimize knee pain was evaluated every 5 minutes. Knee Osteoarthritis Outcome Scores were used to quantify knee pain and functional status between walking sessions. The order of testing was randomized, with sessions occurring a minimum of 1 week apart. RESULTS: A mean LBPP of 12.4% of body weight provided participants with significant pain relief during walking, and prevented exacerbation of acute knee pain over the duration of the 20-minute exercise session. Patients felt safe and confident walking with LBPP support on the treadmill, and demonstrated no change in Knee Osteoarthritis Outcome Scores over the duration of the investigation. CONCLUSION: Results suggest that LBPP technology can be used safely and effectively to simulate weight loss and reduce acute knee pain during weight-bearing exercise in an overweight knee OA patient population. These results could have important implications for the development of future treatment strategies used in the management of at-risk patients with progressive knee OA.

Intrinsic stresses on bone and cartilage in the normal and anterior cruciate ligament-reconstructed knee before and after a half marathon: a magnetic resonance imaging analysis.

OBJECTIVE: To investigate intrinsic changes of the anterior cruciate ligament-reconstructed and control (contralateral) knees after a half marathon. DESIGN: Prospective case series. SETTING: Sports Medicine Clinic. PARTICIPANTS: Eight runners were included in the analysis. INTERVENTIONS: Magnetic resonance imaging (MRI) of both knees within 48 hours before and after competition. Participants completed the Tegner Activity Level Scale and a Knee Demographic Questionnaire before the preevent MRI scan. MAIN OUTCOME MEASURES: The incidence of MRI-identified cartilage, ligament, bone, and meniscus pathology in the ACL-reconstructed and control knees. RESULTS: The control knees of 5 runners (63%) demonstrated cartilage lesions, but no change was evident on postevent MRI. Preevent MRI in ACL-reconstructed knees demonstrated Grade IV meniscal lesions (4 of 8), Grades II (2 of 8) and IV cartilage lesions (4 of 8), and Type I bony edema (4 of 8). Although not significant, ACL-reconstructed knees demonstrated a strong trend (P = 0.01) toward a greater incidence of bone marrow edema on postevent MRIs compared with control knees. CONCLUSIONS: This is the first study to compare the effects of running on intrinsic structures of a normal and ACL-reconstructed knee. Reconstructed knees demonstrated a greater incidence of bone marrow edema on postevent scans, but knee pathology evident on preevent scans did not progress in either control or ACL-reconstructed knees.

Nitric oxide and voluntary exercise together promote quadriceps hypertrophy and increase vascular density in female 18-mo-old mice.

Age-related sarcopenia reduces the size, strength, and function of muscle, and the diameter of muscle fibers. It also disrupts the dystrophin-glycoprotein complex, dislocating nitric oxide synthase 1 (NOS-1) and reducing sarcolemmal integrity. This study of quadriceps muscle in 18-mo-old mice showed that NO-donor treatment with isosorbide dinitrate (I) for 6 wk, in combination with voluntary exercise for 3 wk, increased muscle mass by 25% and stimulated cell proliferation. The resulting fiber hypertrophy was accompanied by a lower ratio of protein:DNA, consistent with myogenic-cell hyperplasia. Treatment enhanced the ratio of NOS-1:ß-dystroglycan in correlation with fiber diameter, improved sarcolemmal integrity, and increased vascular density after an increase in vascular endothelial growth factor protein at 3 wk. Results demonstrate that age-related muscle refractoriness to exercise can be overcome with NO-donor treatment. Since activation of muscle stem cells and vascular perfusion are limiting factors in the maintenance, regeneration, and growth of aged muscle, results suggest the feasibility of using NO-donor drugs to combat atrophy and muscle ischemia. Improved function and quality of life from the NO-amplified effects of exercise may be useful in aging and other conditions such as disuse, insulin resistance, or microgravity.

Exercise-induced muscle growth is muscle-specific and age-dependent.

INTRODUCTION: Sarcopenia, and the importance of satellite cells (SCs) in muscle growth led us to examine the effects of exercise and age on SC activation and gene expression. METHODS: Eight- and 18-month-old mice were either sedentary or underwent 3 weeks of exercise (N = 24). Body mass, distance traveled, and grip strength were recorded at weekly intervals. The extensor digitorum longus (EDL), tibialis anterior (TA), gastrocnemius (GAST), and quadriceps (QUAD) muscles were analyzed along with muscle fiber area, SC activation, neuronal nitric oxide synthase (NOS-I), MyoD, and myostatin protein content. RESULTS: Older mice demonstrated decreased body mass, grip strength, and fiber area, but these changes were not affected by exercise. The QUAD muscle from young mice demonstrated an exercise-induced increase in SC activation and NOS-I and downregulation of myostatin. CONCLUSIONS: Exercise-induced activation of SCs and regulation of gene expression are muscle-specific and age-dependent. Perturbed sensitivity to exercise in older mice provides insight into sarcopenia and potential treatments.

Novel application of lower body positive-pressure in the rehabilitation of an individual with multiple lower extremity fractures.

OBJECTIVE: Lower extremity fractures, if not treated appropriately, can increase the risk of morbidity. Partial weight-bearing after surgical repair is recommended; however, current methods of partial weight-bearing may cause excessive loads through the lower extremity. A new rehabilitation tool that uses lower body positive-pressure is described, that may allow partial weight-bearing while preventing excessive loads, thereby improving functional outcomes. METHODS: A patient with multiple lower extremity fractures underwent a 6-month rehabilitation programme using bodyweight support technology 3 times per week, post-surgery. RESULTS: The patient experienced a reduction in pain and an improvement in ankle range of motion (p=0.002), walking speed (p>0.05) and physical function (p=0.004), as assessed by the Foot and Ankle Module of the American Academy of Orthopaedic Surgeons Lower Limb Outcomes Assessment Instrument. Training did not appear to affect fracture healing, as was evident on radiograph. The effect of lower body positive-pressure on effusion, which has not previously been reported in the literature, was also investigated. No significant difference in effusion of the foot and ankle when using lower body positive-pressure was found. CONCLUSION: Initial results suggest that this new technology may be a useful rehabilitation tool that allows partial weight-bearing during the treatment of lower extremity injuries.

Reliability of tunnel angle in ACL reconstruction: two-dimensional versus three-dimensional guide technique.

PURPOSE: To compare the reliability of tibial tunnel position and angle produced with a standard ACL guide (two-dimensional guide) or Howell 65° Guide (three-dimensional guide) in the coronal and sagittal planes. In the sagittal plane, the dependent variables were the angle of the tibial tunnel relative to the tibial plateau and the position of the tibial tunnel with respect to the most posterior aspect of the tibia. In the coronal plane, the dependent variables were the angle of the tunnel with respect to the medial joint line of the tibia and the medial and lateral placement of the tibial tunnel relative to the most medial aspect of the tibia. METHODS: The position and angle of the tibial tunnel in the coronal and sagittal planes were determined from anteroposterior and lateral radiographs, respectively, taken 2-6 months postoperatively. The two-dimensional and three-dimensional guide groups included 28 and 24 sets of radiographs, respectively. Tibial tunnel position was identified, and tunnel angle measurements were completed. Multiple investigators measured the position and angle of the tunnel 3 times, at least 7 days apart. RESULTS: The angle of the tibial tunnel in the coronal plane using a two-dimensional guide (61.3 ± 4.8°) was more horizontal (P < 0.05) than tunnels drilled with a three-dimensional guide (64.7 ± 6.2°). The position of the tibial tunnel in the sagittal plane was more anterior (P < 0.05) in the two-dimensional (41.6 ± 2.5%) guide group compared to the three-dimensional guide group (43.3 ± 2.9%). CONCLUSION: The Howell Tibial Guide allows for reliable placement of the tibial tunnel in the coronal plane at an angle of 65°. Tibial tunnels were within the anatomical footprint of the ACL with either technique. Future studies should investigate the effects of tibial tunnel angle on knee function and patient quality of life. LEVEL OF EVIDENCE: Case-control retrospective comparative study, Level III.

Bilateral femoral neck fractures resulting from a grand mal seizure in an elderly man with Down syndrome.

Simultaneous bilateral hip fractures are exceedingly rare and usually occur following a seizure. To our knowledge, only 22 cases of such injuries have been reported in the literature during the past forty years and the majority of fractures are treated with open reduction and internal fixation. We present a case of a 66-year old man with Down syndrome and severe dementia who was diagnosed with bilateral displaced femoral neck fractures following an epileptic seizure. He was treated with single staged bilateral uncemented monopolar hemi-arthroplasties through lateral Hardinge approaches. The treatment choice was governed by fracture displacement, the lack of pre-existing osteoarthritis, length of time to diagnosis, the patient's age, ambulatory status and mental impairment, with the intention to minimize post-operative complications such as avascular necrosis, non-union and hip dislocation.

Satellite cells are increasingly refractory to activation by nitric oxide and stretch in aged mouse-muscle cultures.

Age-related muscle atrophy or sarcopenia results in progressive loss of muscle function and satellite cells in aging muscle are increasingly refractory to activation that could mitigate atrophy. We know that nitric oxide release triggered by mechanical stretch of skeletal muscle, initiates satellite cell activation in vitro in single fiber, single cell and whole-muscle cultures, and in vivo in animals. This study examined muscle cell activation using tritiated-thymidine incorporation into the DNA of muscle cells in cultured muscles from female mice between 6 weeks and 18 months-of-age. Experiments examined age-related changes in activation by mechanical stretch and/or NO treatments (with the substrate of nitric oxide synthase (l-arginine), a nitric oxide donor (isosorbide dinitrate) and/or nitric oxide synthase inhibition). Activation without stretch was highest at 8 months. Stretching muscles by 10% more than doubled activation in muscles at 6 weeks of age and only a 20% stretch similarly activated cells in cultured 6-month-old muscles. Only treatment with ISDN in combination with a 20% stretch activated cell proliferation in muscles from 8-month-old mice. A nitric-oxide donor drug rescued muscle satellite cells in adult, 8-month-old mice from being refractory to mechanical stretch, apparently by overcoming an ineffective release of nitric oxide during stretch. Results suggest that treatment with nitric oxide has the potential to enhance the effectiveness of exercise in preventing the onset of age-related muscle atrophy in adult muscle.