Optimal blocking screw placement for retrograde IM nail fixation of distal femur fracture: a standardized biomechanical study of "osteoporotic" synthetic bone.

PURPOSE: Intramedullary (IM) nail use for metaphyseal fracture management is problematic in long bones like the femur because the larger medullary cavity allows increased fracture motion and potentially increased implant failure and malunion/nonunion risk; Achieving effective distal femur fracture fixation is even more difficult in osteoporotic bone. Blocking screws to control IM nail movement are known to be effective for tibia fracture management. Few studies have evaluated IM nail and blocking screw use efficacy for distal femur fracture fixation in osteoporotic bone. METHODS: This study used an osteoporosis simulation synthetic bone model to evaluate retrograde IM nail fixation of a standardized non-comminuted, extra-articular distal femur fracture with and without blocking screws. The hypothesis was that use of one or two blocking screws would increase IM nail fixation stability as evidenced by greater peak IM nail load and lesser movement. A servohydraulic device under displacement control collected loading force versus movement deflection data. Shapiro-Wilk tests confirmed data normality. One-way analysis of variance and Tukey post hoc tests were used to compare condition specific loading force and movement differences. RESULT: In the coronal plane, blocking screw conditions displayed greater loading ranges (38.3 ± 2 vs. 19.1 ± 2 N, 100.5% difference) (p < 0.0001) and lesser movement (2.0 ± 0.3 vs. 6.86 ± 0.4 mm, 243% difference) (p < 0.0001). In the sagittal plane, the two blocking screw condition displayed a significantly greater loading magnitude (29.9 ± 6 vs. 20.8 ± 2.3 N, 43.8% difference) than the identical control condition without blocking screws (p = 0.018); however, movements were comparable (p = 0.82). Long-axis rotational loading failed to reveal load magnitude differences (p = 0.28); however, two different blocking screw conditions displayed decreased movement (1.32 ± 0.2 vs. 2.05 ± 0.3 mm, 53.8% difference) compared to other conditions (p ≤ 0.018). CONCLUSIONS: Use of one or two blocking screws on the medial and lateral sides of the IM nail decreased coronal plane movement in the intramedullary canal. Combining retrograde IM nail implantation with blocking screws reduced medial-lateral IM nail movement and increased fracture stability. These characteristics may help prevent fixation failure, malunion, and even nonunion in patients with a distal femur fracture in osteoporotic bone.

Return to sports bridge program improves outcomes, decreases ipsilateral knee re-injury and contralateral knee injury rates post-ACL reconstruction.

PURPOSE: To present the results of a return to sports bridge program designed to reduce knee injuries following ACL reconstruction and physical therapy. METHODS: One hundred and fifty (male = 83, female = 67) patients participated in a whole body neuromuscular control, progressive resistance strength and agility training program. Post-program testing included functional movement form, dynamic knee stability, lower extremity power, agility, and sports skill assessments. Participants completed the Knee Outcome Survey-Sports Activity Scale (KOS-SAS) before and after program initiation. Pre-participation scores were re-estimated following program completion. RESULTS: Global rating KOS-SAS score at program entry was 75 ± 13. Post-program global rating and calculated KOS-SAS were 91.0 ± 9.8 and 90.9 ± 9.7, respectively (p < 0.0001). Pre-participation KOS-SAS score re-estimates at program completion were 54.5 ± 23.3 and 57.3 ± 18.5, respectively. The approximately 20% lower pre-program KOS-SAS score re-estimates (p < 0.0001) observed at program completion suggests that subjects had inaccurately high sports readiness perceptions at program entry. Perceived overall sports activity knee function ratings improved from 2.9 ± 0.6 (abnormal) at program entry to 1.3 ± 0.5 (normal) at completion (p < 0.0001). Most subjects returned back to sports at or above their pre-injury performance skill/performance level (84%, 126/150). By 6.8 ± 3.2 years (range = 2-13 years) post-surgery, ten subjects had sustained an ipsilateral knee re-injury or contralateral knee injury (6.7%). The 2.7% non-contact contralateral and 1.3% non-contact ipsilateral knee injury rates observed were significantly lower than those cited in previous reports. CONCLUSION: Supplementing primary ACL reconstruction and standard physical therapy with a return to sports bridge program prior to release to unrestricted sports performance was effective at improving patient outcomes and decreasing ipsilateral knee re-injury and contralateral knee injury rates. LEVEL OF EVIDENCE: II.

Leptin resistance elicits depressive-like behaviors in rats.

There is a growing appreciation that the complications of obesity extend to the central nervous system (CNS) and include increased risk for development of neuropsychiatric co-morbidities such as depressive illness. The neurological consequences of obesity may develop as a continuum and involve a progression of pathological features which is initiated by leptin resistance. Leptin resistance is a hallmark feature of obesity, but it is unknown whether leptin resistance or blockage of leptin action is casually linked to the neurological changes which underlie depressive-like phenotypes. Accordingly, the aim of the current study was to examine whether chronic administration of a pegylated leptin receptor antagonist (Peg-LRA) elicits depressive-like behaviors in adult male rats. Peg-LRA administration resulted in endocrine and metabolic features that are characteristic of an obesity phenotype. Peg-LRA rats also exhibited increased immobility in the forced swim test, depressive-like behaviors that were accompanied by indices of peripheral inflammation. These results demonstrate that leptin resistance elicits an obesity phenotype that is characterized by peripheral immune changes and depressive-like behaviors in rats, supporting the concept that co-morbid obesity and depressive illness develop as a continuum resulting from changes in the peripheral endocrine and metabolic milieu.

Sports involvement following ACL reconstruction is related to lower extremity neuromuscular adaptations, subjective knee function and health locus of control.

PURPOSE: This retrospective study compared the influence of perceived sports involvement on lower extremity neuromuscular adaptations during single-leg countermovement jumping (CMJ), perceived knee function and internal health locus of control (HLOC) scores at a minimum 2-year post-anterior cruciate ligament reconstruction. The hypothesis was that subjects with higher-level sports involvement would display significant differences compared to subjects with lower-level sports involvement. METHODS: Uninvolved and involved lower extremity EMG amplitude (1,000 Hz), vertical ground reaction force (VGRF) (500 Hz) and kinematic (60 Hz) displacement differences were determined during single-leg CMJ. These data and International Knee Documentation Committee subjective knee survey scores, Multidimensional Health Locus of Control Survey internal HLOC subscale scores and sports activity characteristics were compared by sports involvement level. RESULTS: Subjects that regarded themselves as only sporting sometimes (Group 3, n = 26) had lower IKDC survey and internal HLOC scores, were more likely to decrease sports activities by two intensity levels than highly competitive (Group 1, n = 20) and well-trained/frequently sporting (Group 2, n = 24) subjects, and had greater peak landing VGRF differences suggesting decreased involved lower extremity loading compared to Group 2. During propulsion, Group 1 had greater gluteus maximus (GM) and gastrocnemius (G) EMG differences than Groups 2 and 3. Groups 1 and 2 had decreased vastus medialis (VM) EMG differences during propulsion than Group 3. During landing, Group 1 had greater GM and G EMG differences than Group 3. CONCLUSION: Subjects with higher-level sports involvement up-regulated involved lower extremity GM and G activation and down-regulated VM activation. This adaptation may enable continued higher-level sports participation while minimizing knee joint forces. Perceived higher-level sports involvement was related to neuromuscular adaptations, better subjective knee function, a more internal HLOC and higher sports activity intensity. LEVEL OF EVIDENCE: Therapeutic case series, level IV.

Mechanisms involved in the p62-73 idiopeptide-modulated delay of lupus nephritis in SNF(1) mice.

The F(1) progeny of the (SWR × NZB) cross develop a lupus-like disease with high serum titers of autoantibodies, and increased frequency and severity of immune complex-mediated glomerulonephritis in females. In previous work, we found that an idiotypic peptide corresponding to aa62-73 (p62-73) of the heavy chain variable region of autoantibody 540 (Id(LN)F(1)) induced the proliferation of p62-73 idiotype-reactive T cell clones. Further, monthly immunization of pre-nephritic SNF(1) female mice with p62-73 resulted in decreased nephritis and prolonged life spans. Here we show that this treatment modulated proliferative responses to Id(LN)F(1) antigen, including a reduction in the population of idiopeptide-presenting antigen-presenting cells (APCs), as early as two weeks after immunization (10 weeks of age). Th1-type cytokine production was increased at 12 weeks of age. The incidence and severity of nephritis was reduced by 14 weeks compared to controls. Clinical indicators of nephritis, specifically histological evidence of glomerulonephritis and urine protein levels, were reduced by 20 weeks. Together these data suggest that events involved in the mechanism(s) whereby p62-73 immunization delayed nephritis occurred early after immunization, and involved modulation of APCs, B and T cell populations.

ACL microtrauma: healing through nutrition, modified sports training, and increased recovery time.

PURPOSE: Sports injuries among youth and adolescent athletes are a growing concern, particularly at the knee. Based on our current understanding of microtrauma and anterior cruciate ligament (ACL) healing characteristics, this clinical commentary describes a comprehensive plan to better manage ACL microtrauma and mitigate the likelihood of progression to a non-contact macrotraumatic ACL rupture. METHODS: Medical literature related to non-contact ACL injuries among youth and adolescent athletes, collagen and ACL extracellular matrix metabolism, ACL microtrauma and sudden failure, and concerns related to current sports training were reviewed and synthesized into a comprehensive intervention plan. RESULTS: With consideration for biopsychosocial model health factors, proper nutrition and modified sports training with increased recovery time, a comprehensive primary ACL injury prevention plan is described for the purpose of better managing ACL microtrauma, thereby reducing the incidence of non-contact macrotraumatic ACL rupture among youth and adolescent athletes. CONCLUSION: Preventing non-contact ACL injuries may require greater consideration for reducing accumulated ACL microtrauma. Proper nutrition including glycine-rich collagen peptides, or gelatin-vitamin C supplementation in combination with healthy sleep, and adjusted sports training periodization with increased recovery time may improve ACL extracellular matrix collagen deposition homeostasis, decreasing sudden non-contact ACL rupture incidence likelihood in youth and adolescent athletes. Successful implementation will require compliance from athletes, parents, coaches, the sports medicine healthcare team, and event organizers. Studies are needed to confirm the efficacy of these concepts. LEVEL OF EVIDENCE: V.

Distal thigh compression garment improves knee control and safety perceptions during single leg triple-hop for distance.

INTRODUCTION: Frontal plane knee control is essential to athletic knee injury prevention. AIM: To evaluate knee valgus frontal plane projection angle (FPPA), knee safety, and sports movement capability confidence during single leg triple hop for distance (SLTHD) under knee sleeve, distal thigh compression garment (DTCG), and no device (control) conditions. METHODS: A single-session, experimental study was performed using a within-subject design, and randomized device order. Two-dimensional FPPA measurements were collected during the final SLTHD landing of 18 healthy female college athletes for each condition. Sports movement capability and knee safety confidence were measured using 10-cm visual analog scale questions. One-way ANOVA assessed group differences, and Pearson correlations delineated FPPA, knee safety and sports movement capability confidence relationships (p < 0.05). RESULTS: The DTCG group had less valgus FPPA than the control group. The knee sleeve group had greater knee safety confidence than the control group. The DTCG (r = 0.48) had a moderate positive relationship between mean SLTHD and knee safety confidence. The DTCG group also had a moderate relationship between maximum SLTHD and knee safety confidence (r = 0.52). The DTCG and knee sleeve groups displayed moderate direct, and moderate inverse relationships between FPPA and sports movement capability confidence (r = 0.48 and r = -0.44, respectively). CONCLUSION: Reduced FPPA and relationships between maximum SLTHD magnitude and knee safety confidence, and between FPPA magnitude and sports movement capability confidence suggests that the DTCG may enhance pelvic deltoid kinesthetic acuity and dynamic knee stability through iliotibial tract compression. CLINICAL RELEVANCE: The DTCG was superior to the standard knee sleeve or control conditions for displaying characteristics that might better prevent knee injury, while still enabling effective sports movement capability.

Biomechanical and tissue handling property comparison of decellularized and cryopreserved tibialis anterior tendons following extreme incubation and rehydration.

Little is known regarding the biomechanical profiles and tissue handling properties of decellularized and cryopreserved human tibialis anterior tendons prepared as allografts for ACL reconstruction. This study compared allografts prepared using two extremes of the same cryoprotectant incubation and rehydration technique with a standardly prepared control group. Porcine tibiae with similar apparent BMD were randomly divided into three groups of ten specimens. Paired tendons were randomly divided into two experimental groups: Group 1 = 8 h incubation/15 min rehydration; Group 2 = 2 h incubation/1 h rehydration. Group 3 (control) consisted of ten standardly prepared tendons with 20 min rehydration. Tissue handling properties were graded during allograft preparation using a modified visual analog scale. Similar diameter allografts were fixed in matched diameter extraction drilled tibial tunnels with 35 mm long, 1 mm > tunnel diameter bioabsorbable interference screws. Potted constructs were mounted in a servo hydraulic device, pretensioned between 10-50 N at 0.1 Hz (10 cycles), and isometric pretensioned at 50 N for 1 min, prior to 500 submaximal loading cycles (50-250 N) at 0.5 Hz, and load to failure testing (20 mm/min). Constructs prepared under extreme conditions generally displayed comparable biomechanical properties to the control condition. Group 1 (8 h incubation/15 min rehydration)(-34 +/- 35 ms) and Group 2 (2 h incubation/1 h rehydration) (-22 +/- 38 ms) displayed smaller mean displacement-load peak phase timing differences over the initial ten cycles compared to Group 3 (control)(-42 +/- 49 ms), P = 0.004, suggesting greater relative construct stiffness. Group 1 (8 h incubation/15 min rehydration) (234.9 +/- 34 N/mm) and Group 2 (2 h incubation/1 h rehydration)(231.3 +/- 43 N/mm) displayed lower construct stiffness during load to failure testing than Group 3 (control)(284.5 +/- 25.2 N/mm), P = 0.003. Group 1 (8 h incubation/15 min rehydration) differed from Group 2 (2 h incubation/1 h rehydration) and Group 3 (control) for perceived tensile stiffness (2.4 +/- 2.0 vs. 7.0 +/- 0.5 and 7.9 +/- 0.3, respectively), compressive resilience (1.7 +/- 0.8 vs. 5.9 +/- 1.0 and 7.8 +/- 0.4, respectively), handling ease (2.8 +/- 1.0 vs. 6.5 +/- 0.5 and 7.0 +/- 0.7, respectively), color (2.6 +/- 0.8 vs. 4.7 +/- 0.7 and 5.1 +/- 0.3, respectively) and texture (4.0 +/- 0.8 vs. 6.2 +/- 0.8 and 6.8 +/- 0.8, respectively) (P < 0.0001). Group 2 (2 h incubation/1 h rehydration)(6.0 +/- 0.7 and 5.9 +/- 1.0, respectively) also differed from Group 3 (control)(6.8 +/- 0.8 and 7.8 +/- 0.4, respectively) for general "feel" and compressive resilience (P < 0.0001). Tensile stiffness and compressive resilience displayed moderate and weak relationships, respectively with displacement during submaximal cyclic loading (r2 = 0.78 and 0.58, respectively), stiffness (r2 = 0.33 and 0.44, respectively) and load at failure (r2 = 0.59 and 0.37, respectively) for Group 3 (control), but not for experimental Group 1 (8 h incubation/15 min rehydration) or Group 2 (2 h incubation/1 h rehydration). Knee surgeons should be aware that soft tissue tendon decellularization and cryopreservation may change the biomechanical stiffness, tissue handling properties, and relationships between these variables compared to standardly prepared allograft tissue.

Sports hernias: a systematic literature review.

This review summarises the existing knowledge about pathogenesis, differential diagnosis, conservative treatment, surgery and post-surgical rehabilitation of sports hernias. Sports hernias occur more often in men, usually during athletic activities that involve cutting, pivoting, kicking and sharp turns, such as those that occur during soccer, ice hockey or football. Sports hernias generally present an insidious onset, but with focused questioning a specific inciting incident may be identified. The likely causative factor is posterior inguinal wall weakening from excessive or high repetition shear forces applied through the pelvic attachments of poorly balanced hip adductor and abdominal muscle activation. There is currently no consensus as to what specifically constitutes this diagnosis. As it can be difficult to make a definitive diagnosis based on conventional physical examination, other methods, such as MRI and diagnostic ultrasonography are often used, primarily to exclude other conditions. Surgery seems to be more effective than conservative treatment, and laparoscopic techniques generally enable a quicker recovery time than open repair. However, in addition to better descriptions of surgical anatomy and procedures and conservative and post-surgical rehabilitation, well-designed research studies are needed, which include more detailed serial patient outcome measurements in addition to basing success solely on return to sports activity timing. Only with this information will we better understand sports hernia pathogenesis, verify superior surgical approaches, develop evidence-based screening and prevention strategies, and more effectively direct both conservative and post-surgical rehabilitation.

Biomechanical comparison between CentraLoc and Intrafix fixation of quadrupled semitendinosus-gracilis allografts in cadaveric tibiae with low bone mineral density.

Supplementary or back-up tibial tunnel fixation of a quadruple semitendinosus-gracilis (STG) graft is often performed when the knee surgeon questions the integrity of intra-tunnel fixation. Back-up fixation devices such as staples however may contribute to increased knee pain and dysfunction. Both primary extra-tunnel and intra-tunnel fixation devices may provide sufficient quadruple STG graft fixation in a tibial tunnel to preclude the need for back-up fixation. This biomechanical study compared the fixation of quadruple STG allografts in standard drilled tunnels prepared in low apparent bone mineral density (BMD) cadaveric tibiae using either an Intrafix device with primary intra-tunnel fixation in a region of predominantly cancellous trabecular bone, or a CentraLoc device with primary extra-tunnel fixation in a region of predominantly cortical bone. The study hypothesis was that the CentraLoc device would display superior fixation in these low apparent BMD cadaveric tibiae. Matched pair tibiae and quadruple STG allografts were divided into two groups of seven specimens each. Extraction drilled tunnels matched allograft diameter. Constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles and isometric pretensioned at 50 N for 1 min prior to undergoing 500 loading cycles (50-250 N) and load to failure testing (20 mm/min). The CentraLoc group displayed superior load at failure (448.4+/-171 N vs. 338.4+/-119 N, P=0.04) and survived more loading cycles (410+/-154 cycles vs. 196+/-230 cycles, P=0.04) than the Intrafix group. Most CentraLoc group specimens (6/7, 85.7%) failed by device pullout with intact quadruple STG allograft strands while all Intrafix group specimens (7/7, 100%) failed by slippage of one or more strands (P=0.005).

Preserving knee function following osteoarthritis diagnosis: a sustainability theory and social ecology clinical commentary.

To sustain natural systems, there must be an ongoing balance between environmental, social, and economic considerations. A key element of sustainability theory is to identify the most vulnerable surroundings. The most vulnerable knee tissue is the articular cartilage as it is the last line of osteoarthritis (OA) defense. This tissue has a poor capacity for healing. Based on sustainability theory and social ecology concepts we propose that several key factors contribute to knee function preservation. Factors include health history, genetic predisposition, personal behaviors, and socio-environmental factors in addition to local-regional-global physiological system function. Addressing only some of these factors or any one factor in isolation may lead to less than optimal treatment effectiveness. The purpose of this commentary is to introduce a medical, surgical and rehabilitation management approach for patients with knee OA that considers more than physical function improvement. This approach also considers social, emotional, and environmental factors to better ensure patient satisfaction, fulfilled expectations and successful outcomes. A clinical care pathway is presented for a 57-year-old patient with medial compartment knee OA who is contemplating early arthroplasty versus a knee function preservation treatment approach. Early arthroplasty refers to high revision likelihood based on a minimum 15 year prosthesis life-expectancy.

Electromyographic timing analysis of forward and backward cycling.

PURPOSE: Backward walking to running progressions are becoming a popular, nontraditional component of functional knee rehabilitation programs. The purpose of this electromyographic (EMG) and motion analysis study was to compare the activation duration of the vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, lateral hamstring, tibialis anterior, and gastrocnemius muscles during forward and backward cycling. We hypothesized that the hamstrings would demonstrate greater activation duration during backward cycling. METHODS: The right lower extremity of 12 healthy subjects (6 male and 6 female) was instrumented with surface EMG electrodes and retroreflective markers to confirm lower extremity kinematic consistency between conditions. RESULTS: Statistical analysis of hip, knee, and ankle kinematics (200 Hz sampling rate) and gender failed to reveal significant differences between conditions (P > 0.05). Quadrant analysis of muscle activation duration with Bonferroni corrections for multiple comparisons revealed that medial and lateral hamstring activation duration was greater during the early recovery phase (quadrant III) of backward cycling than forward cycling (P < 0.00156). Rectus femoris activation duration was greater in the early propulsive phase of backward cycling (quadrant 1) (P < 0.00156) and in the early recovery phase of forward cycling (quadrant III) (P < 0.00156). CONCLUSIONS: These findings lend support for the use of backward cycling during the early recovery phase (quadrant III) to achieve a selective hamstring muscle response of relatively decreased patellofemoral stress and anterior cruciate ligament strain.

Shoulder proprioception: latent muscle reaction times.

PURPOSE: The purpose of this study was to identify electromyographic (EMG) differences in the latent muscle reaction timing (LMRT) of the rotator cuff between trained overhead throwers and control subjects in response to sudden internal rotation perturbation (P < or = 0.05). METHODS: Subjects included 15 trained overhead throwers (male intercollegiate baseball players) and 15 untrained subjects (males not active in competitive throwing sports). Subjects were tested while seated, with their dominant glenohumeral joint positioned in 90 degrees abduction/external rotation (scapular plane), their elbow flexed to 90 degrees, and their forearm placed in the perturbation device. Rotator cuff LMRT was assessed as they tried to decelerate a variably timed, sudden internal rotation force. EMG sampling (2000 Hz, 2-s duration) began immediately before perturbation. RESULTS: Trained throwers had slower infraspinatus (P = 0.011) and teres minor (P = 0.024) LMRT and decreased supraspinatus (P = 0.001) and posterior deltoid (P = 0.0001) muscle activation duration compared with control subjects. CONCLUSIONS: These results suggest that the rotator cuff muscles of trained throwers may be downregulated in response to sudden internal rotation perturbation. Although these adaptations would enable greater internal rotation velocities during overhead throwing, they may also contribute to glenohumeral joint pathology. The identification of changes in rotator cuff LMRT in response to sudden internal rotation perturbation suggests an area of acquired neuromuscular imbalance warranting consideration by those involved in the rehabilitation and conditioning of the overhead throwing athlete.

The effect of a geographic lateral bone bruise on knee inflammation after acute anterior cruciate ligament rupture.

We prospectively evaluated 40 patients who had knee inflammation after isolated anterior cruciate ligament rupture with or without an associated "geographic" bone bruise/subchondral fracture of the lateral femoral condyle. All patients with acute ruptures documented by magnetic resonance imaging within 1 week of injury were evaluated for a geographic bone bruise/subchondral fracture of the lateral femoral condyle. Two groups of 20 patients each (bone bruise versus no bone bruise) were then enrolled. Variables measured at 1, 2, 3, and 4 weeks after injury included pain, range of motion, effusion, and number of days with an antalgic gait. Patients with a bone bruise had increased size and duration of effusion, increased number of days required to nonantalgic gait without external aids, increased days to achieve normal range of motion, and increased pain scores at measured time intervals. This study confirms results of previous clinical and histologic studies showing an associated articular cartilage lesion, otherwise known as bone bruise/subchondral fracture, is clinically significant. There appears to be an association between a geographic bone bruise and increased disability in patients with acute anterior cruciate ligament ruptures. Patients with a geographic bone bruise may require longer to reach normal homeostasis (range of motion, pain, neuromuscular control) before undergoing anterior cruciate ligament reconstruction.

Medial patellar taping changes the peak plantar force location and timing of female basketball players.

Subtle changes in patellofemoral joint biomechanics may influence lower extremity function. The McConnell method of patellar taping has become an increasingly popular method of managing patients with various patellofemoral joint disorders. The purpose of this order effect controlled study was to assess medial patellar taping (McConnell Method) for changes in peak plantar force location and timing while running and dribbling a basketball prior to the performance of a basketball lay-up. Sixteen non-impaired, right hand dominant members of a female junior varsity basketball team (age=14.6 +/- 2 years) participated in this study. Subject bodyweight and height were 607.8 +/- 99 N and 1.67 +/- 0.10 m, respectively. All data were collected from the preferred stance limb. A series of two way analysis of variance (ANOVA) (condition, trial) were used to determine statistical significance (P < or = 0.05). During medial patellar taping, subjects displayed a more forefoot directed peak plantar force location 89.9 +/- 18 versus 81.3 +/- 21 mm and delayed peak plantar force onset 141 +/ - 23 versus 130 +/- 29 ms following initial ground contact. Medial-lateral peak plantar force location and peak plantar force magnitude did not differ between conditions, however, medial-lateral peak plantar force location displayed significant trial sequence influences with the latter trials displaying more lateral center of plantar force locations (30.4 +/- 2 vs. 32.5 +/- 3 mm). The results of this study suggest that medial patellar taping influences distal lower extremity function by shifting peak plantar force location toward the forefoot, and delaying its onset. These changes with consideration for known synergistic ankle plantar flexor-subtalar joint invertor and knee extensor function during weight bearing suggest the presence of increased muscular stiffness acting through a more rigid foot to improve the impact force attenuating capability of the lower extremity.

Femoral anteversion influences vastus medialis and gluteus medius EMG amplitude: composite hip abductor EMG amplitude ratios during isometric combined hip abduction-external rotation.

This prospective study evaluated differences in vastus medialis (VM) and gluteus medius (GM) EMG amplitude:composite hip abductor (gluteus maximus, gluteus medius, tensor fascia lata) EMG amplitude ratios among subjects with low or high relative femoral anteversion. Data were collected during the performance of a non-weight bearing, non-sagittal plane maximal volitional effort isometric combined hip abduction-external rotation maneuver. Eighteen nonimpaired athletically active females participated in this surface EMG study. Medial hip rotation (relative femoral anteversion estimate) was measured with a handheld goniometer. Subjects were grouped by medial hip rotation displacement (group 1 < or = 42 degrees =36.1+/-7 degrees and group 2 > 42 degrees =52.7+/-7 degrees ) for statistical analysis (Mann Whitney U-tests, p < 0.05). Group 2 had decreased VM (42+/-23% vs. 69+/-30%, U=19, p=0.034) and GM (62+/-25% vs. 96+/-39%, U=19, p=0.034) normalized mean peak EMG amplitude:composite mean peak hip abductor EMG amplitude ratios compared to group 1. Decreased normalized VM (-27%) and GM (-34%) EMG amplitudes among subjects with increased relative femoral anteversion suggest reduced dynamic frontal and transverse plane femoral control from these muscles, possibly contributing to the increased incidence of non-contact knee injury observed among athletic females.

Posterior cruciate ligament reconstruction (double bundle) using anterior tibialis tendon allograft.

Posterior cruciate ligament (PCL) reconstruction using a double-bundle technique has been described. However, reconstruction with a cryopreserved anterior tibialis tendon allograft and bioabsorbable fixation has not been described. The purpose of this article is to present this surgical technique with discussion and rationale for its indication and use in patients with PCL-deficient knees.

Review of the afferent neural system of the knee and its contribution to motor learning.

Understanding the afferent neural system of the knee is considered to be vital to rehabilitation planning. An intricate relationship exists involving the afferent neural receptors in the inert and contractile tissues of the knee. Traditional rehabilitation strategies may not exploit this extensive afferent neural system. Closed kinetic chain functional training (CKCFT) may provide a method for more effectively rehabilitating an injured or reconstructed knee. The rationale for CKCFT has traditionally focused on mechanical aspects. Sensorimotor integration through motor learning is believed to be an important component of CKCFT. The purposes of this review are to discuss: 1) the afferent neural system of the knee with emphasis on the mechanoreceptors, 2) the influence of the afferent neural system of the knee on motor learning, and 3) how CKCFT uses the afferent neural system of the knee and motor learning during knee rehabilitation. This review reinforces the use of CKCFT in knee rehabilitation plans.

The ankle ligaments: consideration of syndesmotic injury and implications for rehabilitation.

Injury to the distal tibiofibular syndesmosis (DTFS) may be more common than previously reported. This injury is typically caused by external forces which produce sudden ankle dorsiflexion or plantar flexion in combination with external rotation of the foot. Common mechanisms include direct contact with another player or uneven physical terrain. Improper diagnosis of this injury may greatly delay the return to normal functional status and promote the development of chronic instability, degenerative joint changes, and pain. The purpose of this clinical commentary is to review the ligamentous anatomy of the ankle and the incidence of injury to the lateral ligaments of the ankle, with emphasis on DTFS injury. Special tests which enhance the recognition of DTFS injury, such as the external rotation stress test and the distal tibiofibular compression test, and a rehabilitation progression are presented.

Effects of a 2-hour cheerleading practice on dynamic postural stability, knee laxity, and hamstring extensibility.

STUDY DESIGN: One group; pretest, posttest design. OBJECTIVE: To assess the effect of a 2-hour cheerleading practice on the anterior knee laxity, hamstring extensibility, and dynamic postural stability (preferred stance leg during vision-denied unilateral stance) of 17 nonimpaired members of a college cheerleading team (8 females, 9 males; 18-25 years old). BACKGROUND: Anterior knee laxity and hamstring extensibility increase following exercise. The relationship between exercise induced anterior knee laxity, hamstring extensibility, and dynamic postural stability, however, has not been examined. METHODS AND MEASURES: Pre- and postpractice measurements were compared using paired t tests and Bonferroni's correction for multiple comparisons. A 3 x 2 analysis of variance (force level applied to the arthrometer by condition) and Tukey honest significant difference post hoc test were used to evaluate specific arthrometer force level by condition effects (P < .05). RESULTS: Mean laxity at 133 N and hamstring extensibility increased (mean +/- SD) 1.5 +/- 1 mm and 3 +/- 4 degrees, respectively, following practice. Mean medial-lateral stabiliometer platform angulation (frontal plane position) moved medially following practice (2.9 +/- 3 degrees) and produced a weak correlation with increased knee laxity (r = 0.58). Hamstring extensibility did not significantly relate to stabiliometry or knee laxity variables. CONCLUSIONS: The relationship between the medially directed platform angulation and the increase in anterior knee laxity following cheerleading practice suggests a relationship between subtalar joint position and anterior cruciate ligament strain.