The ulnar collateral ligament responds to stress in professional pitchers.

BACKGROUND: Our purpose with this study was to determine the response of the ulnar collateral ligament (UCL) in professional pitchers after exposure to a season of pitching and to rest during an off-season. METHODS: In a prospective study supported by Major League Baseball, all pitchers within a single professional baseball club were enrolled. An ultrasound of the ligament was then performed by a single fellowship-trained ultrasonographer at the beginning of the season (T1), the end of the season (T2), and the beginning of the following season (T3). We measured the UCL thickness and ulnotrochlear joint opening at 30° of flexion with and without stress. Two ultrasound images were saved. Inter- and intra-rater reliability were determined. A multivariable analysis was conducted. RESULTS: A total of185 total pitchers were included: 94 pitchers at T1, 83 at T2, and 118 at T3. These pitchers had 12 [7, 15] (median [interquartile range]) years of pitching experience and had a peak velocity of 95 [93, 97] miles/hour. Intra- and inter-rater reliability were excellent. The baseline UCL thickness was associated with peak velocity (P = .031) and prior UCL reconstruction (P = .024). After accounting for pitching experience, peak velocity, and prior UCL reconstruction, thickness increased during the season (P = .002) and decreased during the off-season (P = .001). After accounting for these same variables, valgus laxity at 30° increased during the season (P = .002) and decreased during the off-season (P = .029). CONCLUSION: The UCL responds to stress in professional pitchers by becoming thicker and more lax, and responds to rest by becoming thinner and less lax.

Importance of radar gun inclusion during return-to-throwing rehabilitation following ulnar collateral ligament reconstruction in baseball pitchers: a simulation study.

BACKGROUND: Rehabilitation following elbow ulnar collateral ligament reconstruction in baseball pitchers relies on a progression of pitching activities to ensure protection and gradual strengthening of the reconstructed ligament. The purpose of this study was to determine the medial elbow torque associated with pitches at various effort levels and determine whether radar gun assistance improves players' abilities to accurately match partial-effort pitches with true references based on maximum pitch velocity. METHODS: Thirty-seven healthy high school and collegiate baseball pitchers were included in this study. Participants were excluded if they were injured, recovering from injury, or otherwise not currently pitching at full effort. Pitch parameters were collected using a validated wearable sensor. Participants threw 5 pitches at 50%, 75%, and 100% subjective effort. Pitchers then threw 5 pitches at 50% maximum velocity and 75% maximum velocity, as measured by a radar gun. RESULTS: Thirty-seven pitchers completed this study. Pitches thrown at 50% and 75% partial effort were significantly faster and generated higher elbow torque than did pitches thrown at 50% and 75% velocity, respectively (P < .001). A 10% decrease in percentage of maximum velocity was associated with a 13% decrease in percentage of maximum elbow torque (ß coefficient = 1.3, R2 = 0.81, P < .001). CONCLUSION: Pitchers generate higher-than-intended forces when throwing at 50% and 75% effort during a subjective partial-effort throwing protocol. Use of a radar gun to guide partial-effort throwing during throwing rehabilitation programs may protect the reconstructed elbow from excess medial torque.

The biomechanical evaluation of a novel 3-strand docking technique for ulnar collateral ligament reconstruction in the elbow.

BACKGROUND AND HYPOTHESIS: The original 2-strand docking technique for elbow ulnar collateral ligament reconstruction has recently been modified to use a 3-strand graft. To date, no biomechanical study has compared the 2 techniques. We hypothesized that the 3-strand docking technique would restore valgus laxity to its native state, with comparable load-to-failure characteristics to the 2-strand docking technique. MATERIALS AND METHODS: Sixteen fresh cadaveric elbows were matched to the corresponding contralateral side from the same individual to create 8 matched pairs and were then randomized to undergo ulnar collateral ligament reconstruction using either the 2- or 3-strand technique. Valgus laxity and rotation measurements were quantified using a MicroScribe 3DLX digitizer at various flexion angles for the native state, transected state, and 1 of the 2 tested reconstructed ligaments. Each reconstruction was then tested to failure. RESULTS: Valgus laxity for the intact state at elbow flexion angles of 30°, 60°, 90°, and 120° was 7° ± 2°, 7° ± 2°, 6° ± 1°, and 5° ± 2°, respectively. These values were similar to those of both reconstruction techniques. On load-to-failure testing, there was no significant difference in any parameter recorded. Yield torques for the 3- and 2-strand reconstructions were 13.4 ± 4.80 N/m and 11.8 ± 4.76 N/m, respectively (P = .486). The ultimate torques were 15.7 ± 6.10 N/m and 14.4 ± 5.58 N/m for the 3- and 2-strand techniques, respectively (P = .582). CONCLUSION: The 3-strand docking technique was able to restore valgus laxity to the native state, with similar load-to-failure characteristics to the 2-strand docking technique.

Functional Outcome and Graft Retention in Patients With Septic Arthritis After Anterior Cruciate Ligament Reconstruction: A Systematic Review.

PURPOSE: To provide a comprehensive review of clinical and functional outcomes after treatment for septic arthritis after anterior cruciate ligament reconstruction. METHODS: A systematic review of the literature was performed. Two reviewers assessed and confirmed the methodologic quality of each study. Studies that met the inclusion criteria were assessed for pertinent data, and when available, similar outcomes were combined to generate frequency-weighted means. RESULTS: Nineteen studies met the inclusion and exclusion criteria for this review, reporting on a total of 203 infected knees. The mean age was 27.5 years and the mean length of follow-up was 44.2 months, with male patients comprising 88% of the population. Hamstring and bone-patellar tendon-bone autografts were used in 63% and 33% of patients, respectively, with 78% of patients retaining their grafts. The studies reported mean flexion and extension deficits of 5.8° and 1.0°, respectively, and laxity testing showed a mean difference of 1.9 mm. The studies reported mean Lysholm, International Knee Documentation Committee, and Tegner scores of 82.1, 68.2, and 5.6, respectively. Of the patients, 83% reported an ability to return to activities of daily living whereas 67% reported a return to their preinjury level of athletics. Evidence of new degenerative changes was seen in 22% of patients. CONCLUSIONS: Septic arthritis after anterior cruciate ligament reconstruction remains a very infrequent event, affecting 0.5% of patients. On average, outcomes in these patients are comparable with those in patients in whom infection does not develop, including postoperative range of motion, residual instability, Lysholm scores, and return to preinjury level of activity. These patients do exhibit decreased International Knee Documentation Committee scores compared with patients without septic arthritis, however. The impact of this differential is not clear, but this scoring difference suggests that septic arthritis may be associated with more severe symptoms and reduced functional outcomes. In addition, there is limited evidence suggesting that septic arthritis leads to early degenerative changes found on imaging. LEVEL OF EVIDENCE: Level IV, systematic review of Level III and IV studies.

Retrograde headless compression screw fixation of olecranon stress fractures in throwing athletes: a novel technique.

Background: An olecranon stress fracture (OSF) is a rare injury most commonly seen in high-level overhead throwing athletes with no clear consensus on surgical treatment. The most common surgical treatment described in the literature is cannulated screw fixation but there have been high rates of reported hardware irritation and need for subsequent hardware removal. Hypothesis/Purpose: This study describes a novel surgical technique in the treatment of OSFs in high-level throwing athletes using retrograde headless compression screws. We hypothesized that patients would have excellent outcomes and decreased rates of hardware irritation postoperatively. Methods: A retrospective review of competitive-level throwing athletes who sustained OSFs that were treated operatively using a novel technique using retrograde cannulated headless compression screws to avoid disruption of the triceps tendon. Postoperative outcome measures obtained included the Disabilities of the Arm, Shoulder and Hand score, Mayo Elbow Performance Score, Simple Elbow Test score, Single Assessment Numerical Evaluation score, Visual Analog Scale, arch of motion, and time to return to sport as well as level returned to. Radiographs were obtained routinely at 2-week, 6-week, 12-week, 6-month, 1-year, and 2-year follow-up. Results: Five of 5 patients who met inclusion criteria were available for final follow-up. Mean age at time of surgery was 20 years (range 17-24). Mean follow-up was 17 months (range 4-33). All patients were baseball players, 4 of which were pitchers and 1 position player. All patients were able to return to sport at the same level or higher at a mean of 5.8 months (range 3-8). Postoperatively, mean arch of motion was 138°, Visual Analog Scale score was 0, Single Assessment Numerical Evaluation score was 90, Disabilities of the Arm, Shoulder and Hand score was 2.0, Mayo Elbow Performance Score was 100, and Simple Elbow Test score was 12. There was no incidence of hardware removal. Conclusion: This study presents a novel surgical technique in the treatment of OSFs in high-level throwing athletes. The results presented demonstrate that this technique is safe and effective for getting athletes back to play quickly without any complications of hardware irritation which has previously shown to be a significant problem in prior literature.

Management of septic arthritis following anterior cruciate ligament reconstruction: a review of current practices and recommendations.

Septic arthritis following anterior cruciate ligament reconstruction is a rare and potentially devastating complication that often leads to articular destruction and adverse clinical outcomes. Because of its rare occurrence, best practices for diagnosis and management have yet to be established. However, graft retention and favorable outcomes are possible with early diagnosis, surgical intervention, and appropriate antibiotic management. Clinicians must be familiar with the diagnostic criteria and management options for septic arthritis. Most patients require multiple procedures to effectively eradicate infection. When the original reconstructed graft cannot be salvaged, a staged anterior cruciate ligament reconstruction revision is required.

Proximal humerus and humeral shaft nonunions.

The rate of nonunion is estimated to be 1.1% to 10% following closed treatment of proximal humerus fracture and 5.5% following closed treatment of humeral shaft fracture. Surgical management should be considered for fractures that demonstrate no evidence of progressive healing on consecutive radiographs taken at least 6 to 8 weeks apart during the course of closed treatment. In the case of proximal humerus nonunion, recent series have demonstrated union in >90% of patients treated with reconstruction using locking plates and autogenous bone graft. Shoulder arthroplasty is reserved as a salvage option in cases in which the humeral head is not viable or the proximal fragment will not support osteosynthesis. For humeral shaft nonunions, open reduction and internal fixation with compression plating and bone graft remains the standard of care, with a >90% rate of union and good functional outcomes. Recent studies support the use of locked compression plates, dual plating, and cortical allograft struts in patients with osteopenic bone.

Healthy younger and older adults control foot placement to avoid small obstacles during gait primarily by modulating step width.

BACKGROUND: Falls are a significant problem in the older population. Most falls occur during gait, which is primarily regulated by foot placement. Variability of foot placement has been associated with falls, but these associations are inconsistent and generally for smooth, level flooring. This study investigates the control of foot placement and the associated gait variability in younger and older men and women (N=7/group, total N=28) while walking at three different speeds (slow, preferred, and fast) across a control surface with no obstacles and surfaces with multiple (64) small (10 cm long ×13 mm high) visible and hidden obstacles. RESULTS: Minimum obstacle distance between the shoe and nearest obstacle during each footfall was greater on the visible obstacles surface for older subjects because some of them chose to actively avoid obstacles. This obstacle avoidance strategy was implemented primarily by modulating step width and to a lesser extent step length as indicated by linear regressions of step width and length variability on minimum obstacle distance. Mean gait speed, step length, step width, and step time did not significantly differ by subject group, flooring surface, or obstacle avoidance strategy. CONCLUSIONS: Some healthy older subjects choose to actively avoid small obstacles that do not substantially perturb their gait by modulating step width and, to a lesser extent, step length. It is not clear if this obstacle avoidance strategy is appropriate and beneficial or overcautious and maladaptive, as it results in fewer obstacles encountered at a consequence of a less efficient gait pattern that has been shown to indicate increased fall risk. Further research is needed on the appropriateness of strategy selection when the environmental demands and/or task requirements have multiple possible completion strategies with conflicting objectives (i.e. perceived safety vs. efficiency).

Management of articular cartilage defects of the knee.

Articular cartilage injuries of the knee present a difficult clinical dilemma and their treatment is controversial. Hyaline articular cartilage is an avascular, low-friction, and wear-resistant weightbearing surface that has limited capacity for self-repair. The optimal treatment for cartilage lesions has yet to be established. Various treatment methods are employed to reestablish a stable cartilage surface, including microfracture, autologous and allograft osteochondral transplantation, autologous chondrocyte implantation, matrix-associated chondrocyte implantation, and scaffold-assisted methods. Treatment algorithms help to guide physicians' decision making in the care of these injuries. In this article, results from outcomes studies as well as prospective randomized clinical trials comparing treatment methods are reviewed, and current practice guidelines are summarized.

Advanced technologies for intuitive control and sensation of prosthetics.

The Department of Defense, Department of Veterans Affairs and National Institutes of Health have invested significantly in advancing prosthetic technologies over the past 25 years, with the overall intent to improve the function, participation and quality of life of Service Members, Veterans, and all United States Citizens living with limb loss. These investments have contributed to substantial advancements in the control and sensory perception of prosthetic devices over the past decade. While control of motorized prosthetic devices through the use of electromyography has been widely available since the 1980s, this technology is not intuitive. Additionally, these systems do not provide stimulation for sensory perception. Recent research has made significant advancement not only in the intuitive use of electromyography for control but also in the ability to provide relevant meaningful perceptions through various stimulation approaches. While much of this previous work has traditionally focused on those with upper extremity amputation, new developments include advanced bidirectional neuroprostheses that are applicable to both the upper and lower limb amputation. The goal of this review is to examine the state-of-the-science in the areas of intuitive control and sensation of prosthetic devices and to discuss areas of exploration for the future. Current research and development efforts in external systems, implanted systems, surgical approaches, and regenerative approaches will be explored.

Major League Baseball Pitching Performance After Tommy John Surgery and the Effect of Tear Characteristics, Technique, and Graft Type.

BACKGROUND: Return to play and player satisfaction have been quite high after ulnar collateral ligament reconstruction (UCLR); however, there has been little reported on how outcomes are affected by surgical technique, graft type, and tear characteristics. PURPOSE: To evaluate surgical techniques, graft type, and tear characteristics on Major League Baseball (MLB) performance after UCLR. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: MLB pitchers who underwent primary UCLR at a single institution were included. Tear characteristics included tear location, tear grade, and acuity. Surgical technique and graft type were also collected. Pitching performance statistics, including earned run average (ERA), walks and hits per innings pitched (WHIP), innings pitched, and fastball velocity were evaluated 3 years before and after UCLR. RESULTS: Forty-six MLB pitchers were identified as having primary UCLR. Return to play was 96%, with 82% returning to MLB play. Technique performed showed no difference in performance. As compared with pitchers with gracilis grafts, pitchers with palmaris grafts were younger ( P = .043), played longer after surgery ( P = .012), and returned to play at 100% (35 of 35) versus 82% (9 of 11, P = .010). When compared with pitchers with proximal tears, pitchers with distal tears pitched at higher velocity (93.0 vs 90.6 mph, P = .023) and had better performance before surgery (ERA, P = .003; WHIP, P = .021); however, those with proximal tears improved to match this performance and velocity after reconstruction. As compared with those having partial tears, pitchers with complete tears played longer after surgery (5.9 vs 4.0 years, P = .033), had a better ERA before injury ( P = .041), and had better WHIP ( P = .037) and strikeouts per 9 innings ( P = .025) after reconstruction. Pitchers with chronic tears had a significant improvement in postoperative ERA, from 4.49 to 3.80 ( P = .040). CONCLUSION: Technique performed and graft type used did not affect performance; however, pitchers with palmaris grafts returned at a higher rate than those with gracilis grafts. Distal tears occurred in pitchers with greater velocity and better performance before injury, yet pitchers with proximal tears matched this performance after reconstruction. Pitchers with complete tears played longer after reconstruction. Pitchers who had partial tears had worse performance before injury and after reconstruction, and those with chronic tears saw a significant improvement in ERA with reconstruction.

Relationship Between Glenohumeral Internal Rotation Deficit and Medial Elbow Torque in High School Baseball Pitchers.

BACKGROUND: Alterations in throwing mechanics have been identified as a risk factor for overuse injuries in baseball players. Glenohumeral internal rotation deficit (GIRD) has been found to adversely affect throwing mechanics, but the effect of GIRD on medial elbow torque is unclear. PURPOSE: To investigate the relationship between GIRD and medial elbow torque in high school-aged baseball pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: High school baseball pitchers (14-18 years old) were recruited for participation in this study. Players' height, weight, body mass index, and arm measurements were recorded as well as shoulder and elbow range of motion measurements. GIRD was calculated from the difference between dominant and nondominant shoulder internal rotation. Participants then pitched 5 fastballs at maximum effort while wearing a wireless sensor that recorded elbow torque, arm slot, arm speed, shoulder rotation, and ball velocity. Principal component analysis was performed to determine which variables were associated with elbow torque or ball velocity. RESULTS: Twenty-three high school pitchers participated in this study; 35% (n = 8) of participants exhibited GIRD of at least 20°. The mean GIRD was 15.3°± 11.2° and was not a predictor of medial elbow torque (P = .205) or ball velocity (P = .333). Ball velocity, age, and height were predictors of medial elbow torque (P = .012, P = .003, and P = .024, respectively). CONCLUSION: In high school baseball pitchers, GIRD was not associated with medial elbow torque during the pitching motion. Instead, ball velocity, player age, and player height carried greater significance. CLINICAL RELEVANCE: This study suggests that high school pitchers with GIRD do not have an inherently greater risk for increased medial elbow torque during the throwing motion. It is recommended that pitchers instead assess their ball velocity to evaluate for relative differences in medial elbow torque.

Treatment Retention Among Patients Participating in Coordinated Specialty Care for First-Episode Psychosis: a Mixed-Methods Analysis.

Young adults experiencing first-episode psychosis have historically been difficult to retain in mental health treatment. Communities across the United States are implementing Coordinated Specialty Care to improve outcomes for individuals experiencing first-episode psychosis. This mixed-methods research study examined the relationship between program services and treatment retention, operationalized as the likelihood of remaining in the program for 9 months or more. In the adjusted analysis, male gender and participation in home-based cognitive behavioral therapy were associated with an increased likelihood of remaining in treatment. The key informant interview findings suggest the shared decision-making process and the breadth, flexibility, and focus on functional recovery of the home-based cognitive behavioral therapy intervention may have positively influenced treatment retention. These findings suggest the use of shared decision-making and improved access to home-based cognitive behavioral therapy for first-episode psychosis patients may improve outcomes for this vulnerable population.

The effects of age and step length on joint kinematics and kinetics of large out-and-back steps.

BACKGROUND: Maximum step length (MSL) is a clinical test that has been shown to correlate with age, various measures of fall risk, and knee and hip joint extension speed, strength, and power capacities, but little is known about the kinematics and kinetics of the large out-and-back step utilized. METHODS: Body motions and ground reaction forces were recorded for 11 unimpaired younger and 10 older women while attaining maximum step length. Joint kinematics and kinetics were calculated using inverse dynamics. The effects of age group and step length on the biomechanics of these large out-and-back steps were determined. FINDINGS: Maximum step length was 40% greater in the younger than in the older women (P<0.0001). Peak knee and hip, but not ankle, angle, velocity, moment, and power were generally greater for younger women and longer steps. After controlling for age group, step length generally explained significant additional variance in hip and torso kinematics and kinetics (incremental R2=0.09-0.37). The young reached their peak knee extension moment immediately after landing of the step out, while the old reached their peak knee extension moment just before the return step liftoff (P=0.03). INTERPRETATION: Maximum step length is strongly associated with hip kinematics and kinetics. Delays in peak knee extension moment that appear to be unrelated to step length, may indicate a reduced ability of older women to rapidly apply force to the ground with the stepping leg and thus arrest the momentum of a fall.

A case of factitious subfascial emphysema.

A 44-year-old woman with a history of borderline personality disorder, Hepatitis C, and multiple hospital admissions for cellulitis and cutaneous abscesses presented with pain of several days duration in her left upper extremity following getting her left arm "stuck" in a subway turnstile. The pain and swelling had progressively worsened following the injury. At the time of presentation the patient's temperature was 98.6 degrees F, heart rate was 82 beats/minute, blood pressure of 116/60, and an oxygen saturation of 98% on room air. The left upper extremity was diffusely swollen but minimally tender throughout. Crepitus was noted along the left arm, elbow and forearm areas. No open wounds were visualized during the examination. Radiographs and computed tomography revealed diffuse subcutaneous emphysema extending from the left axillary region to the wrist, as well as gas beneath the fascia extending between multiple muscles in both the upper and lower areas of her left upper extremity. The possibility of necrotizing fasciitis or gas gangrene prompted immediate operative exploration. No evidence of infection was found during the exploration. Stat gram stains sent during the procedure revealed no organisms. Aerobic, anaerobic, fungal, and acid-fast bacteria cultures taken during the operation revealed no final growth. The patient was stable throughout the hospitalization, remaining afebrile with a normal white blood cell count. The gas in the subcutaneous and subfascial layers was not caused by infection but presumably was due to factitious self-injection of air.

Self-reported shoulder function following massive rotator cuff tear reconstruction using a triceps brachii interposition flap.

This retrospective study evaluated patient shoulder function and general health at a minimum of two-years following massive rotator cuff reconstruction using the long head of the triceps brachii muscle. Fourteen patients completed the Disabilities of the Arm, Shoulder, and Hand scale (DASH), the Shoulder Pain and Disability Index (SPADI), and Medical Outcomes Survey Short Form 36 (SF-36). Five others provided shoulder function and pain relief satisfaction data. Mean DASH score was 15.6 (SD: 12.1). Greatest disability was with placing an object on an overhead shelf, heavy household chores, carrying an object > 4.54 kg (10 lbs), and recreational activities with upper extremity impact or free movements. Mean SPADI disability score was 15.7 (SD: 16.3). Greatest disability was with placing an object on a high shelf, carrying a 4.54 kg (10 lb) object, and washing the back. Patients were satisfied, but disability remained with overhead tasks, carrying heavy objects, sudden upper extremity movements and impact forces.

A kinematic analysis of the rapid step test in balance-impaired and unimpaired older women.

Little is known about the kinematic and kinetic determinants that might explain age and balance-impairment alterations in the results of volitional stepping performance tests. Maximal unipedal stance time (UST) was used to distinguish "balance-impaired" old (BI, UST<10s, N=15, mean age=76 years) from unimpaired old (O, UST>30s, N=12, mean age=71 years) before they and healthy young females (Y, UST>30s, N=13, mean age=23 years) performed the rapid step test (RST). The RST evaluates the time required to take volitional front, side, and back steps of at least 80% maximum step length in response to verbal commands. Kinematic and kinetic data were recorded during the RST. The results indicate that the initiation phase of the step was the major source of age- and balance impairment-related delays. The delays in BI were primarily caused by increased postural adjustments prior to step initiation, as measured by center-of-pressure (COP) path length (p<0.003). The Step landing phase showed similar, but non-significant, temporal trends. Step length and peak center-of-mass (COM) deceleration during the Step-Out landing decreased in O by 18% (p=0.0002) and 24% (p=0.001), respectively, and a further 12% (p=0.04) and 18% (p=0.08) in BI. We conclude that the delay in BI step initiation was due to the increase in their postural adjustments prior to step initiation.

Maximum step length: relationships to age and knee and hip extensor capacities.

BACKGROUND: Maximum Step Length may be used to identify older adults at increased risk for falls. Since leg muscle weakness is a risk factor for falls, we tested the hypotheses that maximum knee and hip extension speed, strength, and power capacities would significantly correlate with Maximum Step Length and also that the "step out and back" Maximum Step Length [Medell, J.L., Alexander, N.B., 2000. A clinical measure of maximal and rapid stepping in older women. J. Gerontol. A Biol. Sci. Med. Sci. 55, M429-M433.] would also correlate with the Maximum Step Length of its two sub-tasks: stepping "out only" and stepping "back only". These sub-tasks will be referred to as versions of Maximum Step Length. METHODS: Unimpaired younger (N=11, age=24[3]years) and older (N=10, age=73[5]years) women performed the above three versions of Maximum Step Length. Knee and hip extension speed, strength, and power capacities were determined on a separate day and regressed on Maximum Step Length and age group. Version and practice effects were quantified and subjective impressions of test difficulty recorded. Hypotheses were tested using linear regressions, analysis of variance, and Fisher's exact test. FINDINGS: Maximum Step Length explained 6-22% additional variance in knee and hip extension speed, strength, and power capacities after controlling for age group. Within- and between-block and test-retest correlation values were high (>0.9) for all test versions. INTERPRETATION: Shorter Maximum Step Lengths are associated with reduced knee and hip extension speed, strength, and power capacities after controlling for age. A single out-and-back step of maximal length is a feasible, rapid screening measure that may provide insight into underlying functional impairment, regardless of age.

A new measure of trip risk integrating minimum foot clearance and dynamic stability across the swing phase of gait.

Minimum toe clearance (MTC) is thought to quantify the risk of the toe contacting the ground during the swing phase of gait and initiating a trip, but there are methodological issues with this measure and the risk of trip-related falls has been shown to also be associated with gait speed and dynamic stability. This paper proposes and evaluates a new measure, trip risk integral (TRI), that circumvents many issues with MTC as typically calculated at a single point by considering minimum foot clearance across the entire swing phase and taking into account dynamic stability to estimate risk of falling due to a trip rather than risk of the foot contacting the floor. Shoes and floor surfaces were digitized and MTC and TRI calculated for unimpaired younger (N=14, age=26±5), unimpaired older (N=14, age=73±7), and older adults who had recently fallen (N=11, age=72±5) walking on surfaces with no obstacles, visible obstacles, and hidden obstacles at slow, preferred, and fast gait speeds. MTC and TRI had significant (F≥5, p≤0.005) but differing effects of gait speed and floor surface. As gait speed increased (which increases risk of trip-related falls) MTC indicated less and TRI greater risk, indicating that TRI better quantifies risk of falling due to a trip. While MTC and TRI did not differ by subject group, strong speed-related effects of TRI (F≥8, p≤0.0007) resulted in improved TRI for fallers due to their slower self-selected preferred gait. This demonstrates that slower gait is both an important covariate and potential intervention for trip-related falls.

Can initial and additional compensatory steps be predicted in young, older, and balance-impaired older females in response to anterior and posterior waist pulls while standing?

The initiation of a single compensatory step in response to balance perturbations has been predicted with accuracies of up to 71%. We sought to determine whether similar methods also could be used to predict the onset of additional compensatory steps in both healthy and balance-impaired older females. Anterior and posterior waist pulls of five different magnitudes were applied to 13 unimpaired young (mean age 23 years), 12 unimpaired older (mean age 71 years), and 15 balance-impaired older (mean age 76 years) women. Body segment kinematic data were recorded at 100 Hz. A step was predicted when the time for the center-of-mass to reach the vertical projection of the boundary of the base-of-support fell below a certain threshold. The results show that 83% of all steps and non-steps were correctly predicted at an optimal time-to-boundary threshold (tau(opt)) of 0.78 s. Step prediction accuracy did not differ significantly by group: 86% of steps and non-steps by young, 84% by unimpaired old, and 82% by balance-impaired old women were correctly predicted at tau(opt) of 0.58, 0.67, and 0.78 s, respectively. Anterior steps and non-steps were predicted more accurately than posterior ones (94% vs. 79% correct at tau(opt) of 0.52 and 0.84 s, respectively) and initial steps were better predicted than additional ones (87% vs. 81% correct at tau(opt) of 0.77 and 0.34 s, respectively). We conclude that this step prediction method reasonably predicts initial and additional steps in the anterior and posterior direction by all three subject cohorts.