Association Between Longitudinal Changes in Patellar Tendon Abnormality and Land-Jump Biomechanics in Male Collegiate Basketball Players.

Background: The relationship between self-reported symptoms and the severity of patellar tendon abnormality (PTA) as seen on magnetic resonance imaging and ultrasound is unclear, but biomechanical testing may resolve this. Purpose: To (1) compare land-jump limb biomechanics between pre- and postseason timepoints, (2) assess whether seasonal changes in biomechanics are associated with seasonal changes in PTA and symptom severity, and (3) explore models that identify seasonal changes in PTA and symptoms with seasonal changes in biomechanics in collegiate basketball players. Study Design: Cohort study; Level of evidence, 2. Methods: Victorian Institute of Sport Assessment Scale - Patellar Tendon (VISA-P) scores and bilateral measurements from 18 National Collegiate Athletic Association Division I and II male basketball players (n = 36 limbs) at the preseason (visit 1) and postseason (visit 2) timepoints were collected. PTA was graded with ultrasound and magnetic resonance imaging morphology measurements proximally and distally, and 3-dimensional lower extremity sagittal kinematics and kinetics were measured during a land-jump test. Multivariate and chi-square analyses assessed timepoint differences. The association of seasonal (Δ = visit 2 - visit 1) biomechanics with seasonal morphology (ΔPTA: no change/worsened) and symptoms (ΔVISA-P: improved/no change/worsened) was tested with multivariate models. Logistic regressions modeled the accuracy of seasonal biomechanics to classify seasonal PTA and symptoms. Results: Three athletes (6 limbs) at visit 1 and 2 athletes (4 limbs) at visit 2 were symptomatic. VISA-P scores were not significantly different between preseason and postseason. Regarding PTA, multivariate analyses found differences among grouped ground-reaction force variables (P < .05); univariate analyses found that worsened PTA was associated with seasonal decreases in peak vertical jumping force and with seasonal increases in knee flexion velocity at contact and maximum knee flexion velocity (P < .05 for all). Regarding VISA-P scores, multivariate analyses found differences among grouped hip (P < .01) and ankle (P < .05) kinematic variables; univariate analyses found that worsened VISA-P was associated with seasonal increases in hip (P < .01) and knee (P < .01) flexion velocity at contact and seasonal increases in ankle range of motion (P < .05). Conclusion: The findings demonstrated an association between seasonal changes in dynamic lower extremity biomechanics and seasonal changes in patellar tendon imaging signals as well as self-reported symptoms.

Association Between Patellar Tendon Abnormality and Land-Jump Biomechanics in Male Collegiate Basketball Players During the Preseason.

Background: Patellar tendinopathy is a degenerative condition that predominantly affects jumping athletes. Symptoms may be subtle or nonexistent at preseason, but structural abnormalities may be present. Assessing patellar tendon abnormality (PTA) through magnetic resonance imaging (MRI) and ultrasound (US) and classifying symptoms using the Victorian Institute for Sport Assessment-Patellar tendon (VISA-P) may provide useful insights if combined with biomechanics measurements. Purpose: To (1) assess whether land-jump biomechanical patterns are associated with clinically pertinent PTA as seen on imaging and through VISA-P scores and (2) model the contributing risk and accuracy of biomechanics to classify PTA and symptomatic observations. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 26 National Collegiate Athletic Association Division I and II male basketball players (n = 52 limbs) were recruited during the preseason. We collected VISA-P scores, bilateral PTA through US and MRI morphology measurements, and bilateral 3-dimensional lower extremity kinematics and kinetics measurements from a land-jump test from an 18-inch-high (45.7-cm-high) box. Statistically, each limb was treated independently. The association of biomechanics with PTA and symptoms (VISA-P score <80) was tested with multivariate models and post hoc tests. Logistic regression modeled relative risk and accuracy of biomechanical variables to classify PTA and symptomatic limbs. Results: There were 19 to 24 limbs with PTA depending on US and MRI measurements. Differences in hip and knee kinematic strategies and ground-reaction loads were associated with PTA and symptomatic limbs. Peak landing vertical ground-reaction force was significantly decreased (169 ± 26 vs 195 ± 29 %body weight; P = .001), and maximum hip flexion velocity was significantly increased (416 ± 74 vs 343 ± 94 deg/s; P = .005) in limbs with versus without PTA on imaging. Knee flexion at the initial contact was decreased in symptomatic versus healthy limbs (17°± 5° vs 21°± 5°, respectively; P = .045). Regression models classified PTA limbs and symptomatic limbs with 71.2% to 86.5% accuracy. Hip and knee maximum flexion velocity and vertical ground-reaction force variables were most common across models observing clinically pertinent PTA. Conclusion: Our findings suggested that functional kinematic and kinetic biomechanical strategies at the hip and knee were associated with PTA, identified on imaging, and symptomatic limbs.

Assessment of a two-mass ground reaction force model applied to indoor overground running in adult recreational runners.

Outdoor running kinetic measurements like vertical ground reaction force (vGRF) need simple and accurate models. A previous study assessed a two mass model (2MM) on an athletic adult population during treadmill running, but not recreational adults during overground running. The objectives were to compare accuracy of the overground 2MM and an optimized version to the reference study and force platform (FP) measurements. Overground vGRF, ankle position, and running speed were collected on 20 healthy subjects in a laboratory. The subjects ran at three self-selected speeds and with an opposite foot strike strategy. Reconstructed 2MM vGRF curves were calculated with the original parameter values (Model1), with parameters optimized each strike (ModelOpt), and with group-based optimal parameters (Model2). Root mean square error (RMSE), optimized parameters, and ankle kinematics were compared to the reference study; peak force and loading rate were compared to FP measurements. The original 2MM showed decreased accuracy with overground running. ModelOpt overall RMSE was lower than Model1 (p > 0.001, d = 3.4). ModelOpt overall peak force was different but most like FP signals (p < 0.01, d = 0.7) and Model1 was most different (p < 0.001, d = 1.3). ModelOpt overall loading rate was similar to FP signals and Model1 was different (p < 0.001, d = 2.1). Optimized parameters were different (p < 0.001) from the reference study. 2MM accuracy was largely attributable to curve parameter choice. These may be dependent on extrinsic factors like running surface and protocol and intrinsic factors like age and athletic caliber. Rigorous validation is needed if the 2MM is to be used in the field.

Body mass affects kinetic symmetry and inflammatory markers in adolescent knees during gait.

BACKGROUND: Early-onset osteoarthritis has been attributed to pro-inflammatory factors and biomechanical changes in obesity. However, research has yet to explore whether knee joint moments are asymmetrical in children with obesity and could precede the onset of knee osteoarthritis. The present study compares knee moment asymmetry between adolescents with and without obesity and examines the relationship between asymmetries and inflammatory biomarkers. METHODS: Twenty-eight adolescents (13-16 years) were classified as with (n = 12) or without (n = 16) obesity. Lower extremity kinetics were measured using three-dimensional motion analysis. Bilateral knee joint moments were analyzed in the sagittal, frontal, and transverse planes across stance phase. Kinetic asymmetry was calculated between the right and left sides and represented by the R2 value. Enzyme-linked immunosorbent assays analyzed serum 25-hydroxy vitamin D, interferon gamma, tumor nercrosis factor alpha, interleukin-6, and C-reactive protein levels. Parametric and non-parametric tests determined significant group differences in asymmetries and biomarkers, respectively. Spearman's correlations identified relationships between biomarkers and asymmetries with statistically significant group differences. FINDINGS: Adolescents with obesity had greater sagittal (loading, midstance) and frontal (midstance, pre-swing) plane kinetic knee asymmetry and higher concentrations of interleukin-6 and C-reactive protein. A moderately negative correlation existed between C-reactive protein and sagittal (loading, midstance) plane asymmetry, and also between interleukin-6 and frontal (pre-swing) plane asymmetry. INTERPRETATION: Inflammatory response increases with greater knee joint asymmetry, suggesting knee joint damage and altered joint loading co-exist in adolescents with obesity. Increased risk to joint health may exist in sub-phases where knee joints are improperly loaded.

Knee Kinetics and Kinematics in Patients With Ankle Arthroplasty and Ankle Arthrodesis.

Background: Previous literature suggests that patients treated with total ankle arthroplasty (TAA) versus ankle arthrodesis (AA) may have better function and lower risk for adjacent joint arthritis in the foot. Little is known on how these interventions affect proximal joints such as the knee. Questions: We sought to assess whether patients with TAA and AA exhibited altered biomechanics linked to the onset and progression of knee osteoarthritis (KOA). We used the knee adduction moment (KAM), a surrogate measure for the mechanical load experienced at the medial tibiofemoral compartment, because it is linked with the onset and progression of KOA. Methods: At a minimum of 2 years postoperatively, instrumented 3-dimensional walking gait was recorded in 10 TAA and 10 AA patients at self-selected walking speeds. TAA patients had either a Salto Talaris or INBONE prosthesis. Average first and second peak KAMs (Nm/kg), KAM impulse (Nm-s/kg), and range-of-motion (ROM, °) were calculated on both the affected and unaffected limbs for each patient. Results: There were no significant differences in the KAM's first and second peaks, impulse, or knee ROM in any plane between the unaffected and affected limbs, or between TAA and AA. Conclusion: TAA and AA may not meaningfully affect ipsilateral knee kinetics and KAMs in short-term follow-up. This study highlights the importance of continuing to study these parameters in larger cohorts of patients with longer follow-up to determine how our treatment of end-stage ankle arthritis may affect the incidence or progression of ipsilateral KOA.

Dynamic Assessment of Femoroacetabular Impingement Syndrome Hips.

PURPOSE: The purpose of our study was to compare lower extremity rotational kinematics and kinetics (angles, torques, and powers) and hip muscle electromyography (EMG) activity between cam-type femoroacetabular impingement syndrome (FAIS) and age- and sex-matched controls during walking, fast walking, stair ascent, stair descent, and sit-to-stand. METHODS: This study included 10 males with unilateral FAIS and 10 control males with no FAIS. We measured kinematics, kinetics, and electromyographic signals during stair ascent/descent, sit-to-stand, self-selected walk, and fast walk. Peak signal differences between groups were compared with independent t-tests with statistical significance when P < .05. RESULTS: FAIS hips showed significant differences compared to controls, including increased hip flexion during walking (+4.9°, P = .048) and stair ascent (+7.8°, P =.003); diminished trunk rotation during stair ascent (-3.4°; P = .015), increased knee flexion during self-selected walking (+5.1°, P = .009), stair ascent (+7.4°, P = .001), and descent (+5.3°, P = .038); and increased knee valgus during fast walking (+4.7°, P = .038). gMed and MedHam showed significantly decreased activation in FAIS during walking (gMed: -12.9%, P = .002; MedHam: -7.4%, P = .028) and stair ascent (gMed: -16.7%, P = .036; MedHam: -13.0%, P = .041); decreased gMed activation during sit-to-stand (-8.8%, P = .004) and decreased MedHam activation during stair descent (-8.0%, P = .039). CONCLUSIONS: Three-dimensional motion analysis and EMG evaluation of functional kinematics and kinetics in subjects with symptomatic unilateral cam-type FAIS across a spectrum of provocative tasks demonstrated significant differences compared to controls in hip flexion, trunk rotation, knee flexion, and valgus. FAIS hips had significantly decreased gMed and MedHam activity. These findings may explain altered torso-pelvic, hip, and knee mechanics in FAIS patients and suggest that evaluation of FAIS should include the patient's hip, knee, and torso-pelvic relationships and muscle function. CLINICAL RELEVANCE: The clinical and functional manifestation of FAIS hip pathomechanics is not entirely understood, and previous literature to date has not clearly described the alterations in gait and functional movements seen in patients with cam-type FAIS. The current study used 3D motion analysis and EMG evaluation of functional kinematics and kinetics to identify a number of differences between FAIS and control hips, which help us better understand the lower extremity kinematics and kinetics and muscle activation in FAIS.

Differences in Gait and Stair Ascent After Total Ankle Arthroplasty and Ankle Arthrodesis.

BACKGROUND: Ankle arthrodesis has historically been the standard of care for end-stage ankle arthritis; however, total ankle arthroplasty (TAA) is considered a reliable alternative. Our objective was to compare 3-dimensional foot and ankle kinetics and kinematics and determine the ankle power that is generated during level walking and stair ascent between TAA and ankle arthrodesis patients. METHODS: Ten patients who underwent TAA with a modern fixed-bearing ankle prosthesis and 10 patients who previously underwent ankle arthrodesis were recruited. Patients were matched for age, sex, body mass index, time from surgery, and preoperative diagnosis. A minimum of 2-year follow-up was required. Patients completed instrumented 3D motion analysis while walking over level ground and during stair ascent. Between-group differences were assessed with a 2-tailed Mann-Whitney exact test for 2 independent samples. RESULTS: Sagittal ankle range of motion (ROM) was significantly higher in the TAA group (21.1 vs 14.7 degrees, P = .003) during level walking. In addition, forefoot-tibia motion (25.3±5.9 degrees vs 18.6±5.1 degrees, P = .015) and hindfoot-tibia motion (15.4±3.2 degrees vs 12.2±2.5 degrees, P = .022) were significantly greater in the TAA group. During stair ascent, sagittal ankle ROM (25 vs 17.1 degrees, P = .026), forefoot-tibia motion (27.6 vs 19.6 degrees, P = .017), and hindfoot-tibia motion (16.8 vs 12 degrees, P = .012) was greater. CONCLUSION: There were significant differences during level walking and stair ascent between patients with TAA and ankle arthrodesis. TAA patients generated greater peak plantarflexion power and sagittal motion within the foot and ankle compared to patients with an ankle arthrodesis. Further investigation should continue to assess biomechanical differences in the foot and ankle during additional activities of daily living. LEVEL OF EVIDENCE: Level III, comparative study.

Biomechanical and Functional Improvements Gained by Proximal Tibia Osteotomy Correction of Genu Varum in Patients with Knee Pain.

BACKGROUND: Mechanical axis malalignment contributes to abnormal forces across the knee joint. Genu varum, or increased medial mechanical axis deviation (MAD), increases force transmission and contact pressures to the medial compartment. With increasing MAD and femoral-tibial mechanical axis angle (MAA), contact forces within the medial or lateral compartment of the knee significantly increase with increasing deformity. This may lead to knee pain, further deformity, and medial compartment degenerative joint disease, which can interfere with participation in sports and diminish quality of life. PURPOSES/QUESTIONS: We sought to evaluate patients with knee pain with bilateral genu varum and determine the effect of bilateral proximal tibial osteotomies on knee biomechanics, deformity correction, and functional outcomes. METHODS: This was a single-center, prospective study of eight limbs in four patients. Consecutive patients presenting with knee pain and bilateral genu varum originating from the proximal tibia were included. All patients underwent staged bilateral proximal tibial osteotomies with gradual deformity correction with an external fixator. Subjects underwent a three-dimensional (3D) instrumented motion analysis during level walking. A 3D lower extremity model was built and bilateral knee frontal plane kinematics and kinetics during the stance phase of gait were determined. Radiographic analysis was performed including assessment of MAD, MAA, and medial proximal tibial angle (MPTA). Functional outcomes were assessed with the Knee Injury and Osteoarthritis Outcome Score (KOOS), the 36-item Short-Form Survey (SF-36), the Lower Limb Questionnaire (LLQ), and a visual analog scale (VAS) for pain. RESULTS: The average time in the external fixator for a single limb was 97 days. The average follow-up period was 310 days. All biomechanical outcomes significantly improved, including knee adduction angle (7.8° to 1.8°), knee adduction moments (first peak, - 0.450 to - 0.281 nm/kg, and second peak, - 0.381 to - 0.244 nm/kg), and knee adduction moment impulse (- 0.233 to - 0.150 nm s/kg). There was a significant improvement in MAA, MAD, and MPTA. All patients showed qualitative improvement in mean scores on VAS (11.8 to 0.0), LLQ (77 to 93), KOOS (64 to 84), and SF-36 (71 to 88). CONCLUSION: These findings suggest that bilateral proximal tibial osteotomy may be effective in improving knee biomechanics during gait and correcting mechanical alignment in patients with bilateral genu varum. Patients also demonstrated improvement in functional outcome scores. This technique should thus be considered in patients with varus knee osteoarthritis in the setting of genu varum to alleviate symptoms and potentially decrease further clinical deterioration.

Comparing First Metatarsophalangeal Joint Flexibility in Hallux Rigidus Patients Pre- and Postcheilectomy Using a Novel Flexibility Device.

BACKGROUND: Hallux rigidus (HR) is a common pathology of the first metatarsophalangeal (MTP) joint causing pain and stiffness. However, severity of symptoms and radiographic findings are not always concordant. A novel flexibility device, which measures the mobility of the MTP joint through its arc of motion, has been validated. This study compares flexibility in patients before and after cheilectomy (with or without proximal phalanx osteotomy) for HR. METHODS: This is a single-center study of adult patients with HR who were indicated for cheilectomy or cheilectomy and Moberg (dorsiflexion closing wedge) osteotomy of the proximal phalanx based on symptoms and radiographs from 2013 to 2015. Pre- and postoperatively, patients underwent testing with a validated flexibility protocol to generate flexibility curves. Parameters included early and late flexibility, laxity torque, and laxity angle. Patients completed Foot and Ankle Outcomes Scores (FAOS) pre- and postoperatively. Twelve operative patients underwent preoperative testing, with 9 completing postoperative testing (mean age, 53.0 years; 67% female; mean 2.8-year follow-up). RESULTS: Patients had significant improvements in early sitting and standing flexibility, sitting and standing laxity angles, standing laxity torque, and both sitting and standing maximum dorsiflexion after surgery (all P < .05). While preoperative early flexibility, laxity angle, and maximum dorsiflexion all differed significantly between patients and controls (P < .015), postoperative early flexibility was similar to controls (P > .279). FAOS scores for pain, symptoms, sport, and quality improved significantly after surgery. CONCLUSION: Surgical treatment with cheilectomy was associated with significant improvements in nearly all flexibility parameters for sitting and standing positions. However, most postoperative flexibility parameters did not improve to the level of normal controls. Regardless, patients still experienced significant improvements in outcomes. This study demonstrated that surgical correction is associated with significant biomechanical and clinical results. The flexibility device can be used in further studies to assess outcomes after other HR procedures. LEVEL OF EVIDENCE: Level II, prospective comparative study.

What Are the Effects of Capsular Plication on Translational Laxity of the Glenohumeral Joint: A Study in Cadaveric Shoulders.

BACKGROUND: Surgical treatment for shoulder instability generally involves labral repair with a capsular plication or imbrication. Good results are reported in both open and arthroscopic procedures, but there is no consensus on the amount or location of capsular plication that is needed to achieve stability and anatomic anterior, posterior, and inferior translation of the joint. QUESTIONS/PURPOSES: (1) What are the separate and combined effects of increasing plication magnitude and sequential additive plications in the anterior, posterior, and inferior locations of the joint capsule on glenohumeral joint translation in the anterior, posterior, and inferior directions? (2) What plication location and magnitude restores anterior, posterior, and inferior translation to a baseline level? METHODS: Fourteen cadaveric shoulders were dissected down to the glenohumeral capsule and underwent instrumented biomechanical testing. Each shoulder was loaded with 22 N in anterior, posterior, and inferior directions at 60° abduction and neutral rotation and flexion and the resulting translation were recorded. Testing was done over baseline (native), stretched (mechanically stretched capsule to imitate a lax capsule), and 5-mm, 10-mm, and 15-mm plication conditions. Individually, for each of the 5-, 10-, and 15-mm increments, plications were done in a fixed sequential order starting with anterior plication at the 3 o'clock position (Sequence I), then adding posterior plication at the 9 o'clock position (Sequence II), and then adding inferior plication at the 6 o'clock position (Sequence III). Each individual sequence was tested by placing 44 N (10 pounds) of manual force on the humerus directed in an anterior, posterior, and inferior direction to simulate clinical load and shift testing. The effect of plication magnitude and sequence on translation was tested with generalized estimating equation models. Translational differences between conditions were tested with paired t-tests. RESULTS: Translational laxity was highest with creation of the lax condition, as expected. Increasing plication magnitude had a significant effect on all three directions of translation. Plication location sequence had a significant effect on anterior and posterior translation. An interaction effect between plication magnitude and sequence was significant in anterior and posterior translation. Laxity in all directions was most restricted with 15-mm plication in anterior, posterior, and inferior locations. For anterior translational laxity, at 10-mm and 15-mm plication, there was a progressive decrease in translation magnitude (10-mm plication anterior only: 0.46 mm, plus posterior: 0.29 mm, plus inferior, -0.12 mm; and for 15-mm anterior only: -0.53 mm, plus posterior: -1.00 mm, plus inferior: -1.66 mm). For posterior translational laxity, 10-mm and 15-mm plication also showed progressive decrease in magnitude (10-mm plication anterior only: 0.46 mm, plus posterior: -0.25 mm, plus inferior: -1.94; and for 15-mm anterior only: 0.14 mm, plus posterior: -1.54 mm, plus inferior: -3.66). For inferior translational laxity, tightening was observed only with magnitude of plication (anterior only at 5 mm: 0.31 mm, at 10 mm: -1.39, at 15 mm: -3.61) but not with additional plication points (adding posterior and inferior sequences). To restore laxity closest to baseline, 10-mm AP/inferior plication best restored anterior translation, 15-mm anterior plication best restored posterior translation, and 5 mm posterior with or without inferior plication best restored inferior translation. CONCLUSIONS: Our results suggest that (1) a 10-mm plication in the anterior and posterior or anterior, posterior, and inferior positions may restore anterior translation closest to baseline; (2) 10-mm anterior and posterior or 15-mm anterior plications may restore posterior translation closest to baseline; and (3) 5-mm anterior and posterior or anterior, posterior, and inferior plications may restore inferior translation closest to baseline. Future studies using arthroscopic techniques for plication or open techniques via a true surgical approach might further characterize the effect of plication on glenohumeral translation. CLINICAL RELEVANCE: This study found that specific combinations of plication magnitude and location can be used to restore glenohumeral translation from a lax capsular state to a native state. This information can be used to guide surgical technique based on an individual patient's degree and direction of capsular laxity. In vivo testing of glenohumeral translation before and after capsular plication will be needed to validate these cadaveric results.

Lateralizing Calcaneal Osteotomies and Their Effect on Calcaneal Alignment: A Three-Dimensional Digital Model Analysis.

BACKGROUND: Few authors have directly compared multiple types of lateralizing calcaneal osteotomies (LCOs) in terms of their ability to achieve deformity correction. The aim of this research was to use a digital model of a varus hindfoot to compare 4 different LCOs in terms of deformity correction and amount of tuberosity lateralization required. The authors hypothesis was that osteotomies involving a wedge resection would achieve greater correction with less lateralization. METHODS: A weightbearing computed tomographic scan of a patient with a varus hindfoot deformity was used to construct a 3-dimensional digital model of the hindfoot, preserving weightbearing alignment. Four different LCOs were modeled: a standard oblique osteotomy, a Dwyer osteotomy, a modified Dwyer osteotomy involving lateralization in addition to wedge resection, and a Malerba Z-type osteotomy with wedge resection and lateralization. Incremental corrections were performed with each osteotomy type, and amount of correction was assessed with a vertical hindfoot angle and measurement of the lateral translation of the most inferior aspect of the calcaneus. Calcaneal length and osteotomy contact surface area were also measured. RESULTS: The modified Dwyer osteotomy led to the greatest improvements in the vertical hindfoot angle and lateral translation, followed by the Malerba osteotomy. The standard and Malerba osteotomies allowed the most preservation of calcaneal length; the Malerba and Dwyer osteotomies had the greatest contact surface area. CONCLUSION: LCOs that involve wedge resection as well as lateralization were able to achieve the greatest correction of hindfoot varus. CLINICAL RELEVANCE: For the surgical treatment of cavovarus foot deformities, osteotomies with wedge resection in addition to lateralization enable more powerful correction.

Mapping glenohumeral laxity: effect of capsule tension and abduction in cadaveric shoulders.

BACKGROUND: Shoulder capsular plication aims to restore the passive stabilization of the glenohumeral capsule; however, high reported recurrence rates warrant concern. Improving our understanding of the clinical laxity assessment across 2 dimensions, capsular integrity and shoulder position, can help toward the standardization of clinical tools. Our objectives were to test and describe glenohumeral laxity across 5 capsular tension levels and 4 humeral position levels and describe tension-position interplay. METHODS: We tested 14 dissected cadavers for glenohumeral laxity in 5 directions: anterior, posterior, and inferior translation, and internal and external axial rotation. Laxity was recorded across capsule tension (baseline, stretched, 5 mm, 10 mm, and 15 mm of plication) and position (0°, 20°, 40°, 60° of scapular abduction). Repeated-measures analysis of variance with post hoc contrasts tested the effect of tension, position, and composite tension × position on laxity. RESULTS: Capsule tension, position, and composite interplay had a statistically significant, although unequal, effect on laxity in each direction. Laxity was consistently overconstrained in 15-mm plication and was overall greatest in 20° and lowest in 60°. Restoration occurred most in 10 mm, but this depended on the position. The composite effect was significant for external and internal rotation and inferior laxity, but laxity at the middle range (20° or 40°) was different than at the end range (0° or 60°) for all directions. CONCLUSIONS: On average, laxity was restored to baseline tension after 10-mm plication, but this determination varied depending on shoulder position. Middle-range laxity behaved differently than end-range laxity across plication tensions. This information is useful in understanding the unstable shoulder as well as for standardizing clinical laxity assessment.

Measuring Joint Flexibility in Hallux Rigidus Using a Novel Flexibility Jig.

BACKGROUND: The flexibility of the first metatarsophalangeal (MTP) joint in patients with hallux rigidus (HR) has not been studied. Compared to measuring range of motion alone, measures of joint flexibility provide additional information that may prove useful in the assessment of HR. The purpose of this study was to assess the flexibility of the hallux MTP joint in patients with HR compared to controls using a novel flexibility device. METHODS: Fifteen patients with Coughlin stage II or III HR and 20 healthy controls were recruited prospectively. Using a custom flexibility jig, each of 2 raters performed a series of seated and standing tests on each subject. Dorsiflexion angle and applied torque were plotted against each other to generate 5 different parameters of flexibility. Differences between (1) HR patients and controls and (2) the sitting and standing testing positions were assessed with t tests. Intrarater test-retest reliability, remove-replace reliability, and interrater reliability were assessed with intraclass correlation coefficients (ICCs). RESULTS: Patients in the HR group were older than patients in the control group ( P < .001) and had lower maximum dorsiflexion ( P < .001). HR patients were less flexible as measured by 3 of the 5 flexibility parameters: early flexibility (first 25% of motion; P = .027), laxity angle ( P < .001), and torque angle ( P = .002). After controlling for age, only laxity angle differed significantly between HR patients and controls ( P < .001). Generally, patients were more flexible when seated compared to standing, with this effect being more marked in HR patients. All parameters had good or excellent intra- and interrater reliability (ICC ≥ 0.60). CONCLUSIONS: Hallux MTP joint flexibility was reliably assessed in HR patients using a flexibility device. Patients with HR had decreased flexibility of the hallux MTP joint compared to control patients. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Changes in Lower Extremity Kinematics and Temporal Parameters of Adolescent Baseball Pitchers During an Extended Pitching Bout.

BACKGROUND: Few studies have investigated detailed 3-dimensional lower extremity kinematics during baseball pitching in adolescent athletes during extended play. Changes in these parameters may affect performance outcomes. PURPOSE: To investigate whether adolescent baseball pitchers experience changes in lower extremity kinematics and event timing during a simulated game-length pitching bout. STUDY DESIGN: Descriptive laboratory study. METHODS: Twelve male adolescent pitchers (aged 14-16 years) threw 6 sets of 15 fastball pitches from an artificial pitching mound to a target at regulation distance. Joint angles and angular velocities at the hip, knee, and ankle of both legs were collected throughout the phases of the pitching cycle as well as stride length, pelvis orientation, pitch duration, timing of foot contact and ball release, ball speed, and pitching accuracy. Paired t tests ( P < .05) were used to compare the dependent variables between the last 5 pitches of the second (baseline) and sixth (final) sets. RESULTS: During the stride phase, decreased maximum angular excursions for hip extension (baseline: 14.7° ± 9.8°; final: 11.6° ± 10.3°; P < .05) and ankle plantar flexion (baseline: 30.2° ± 14.5°; final: 24.2° ± 15.3°; P < .05) as well as maximum angular velocity for knee extension (baseline: 144.9 ± 63.3 deg·s-1; final: 121.7 ± 62.0 deg·s-1; P < .05) were observed between sets in the trailing leg. At foot contact, pitchers had decreased hip flexion (baseline: 69.5° ± 10.1°; final: 66.5° ± 11.8°; P < .05) and increased hip abduction (baseline: 20.7° ± 8.9°; final: 25.4° ± 6.0°; P < .05) in the leading leg in the final set. Compared with the baseline set, ball speed significantly decreased in the final set (29.5 ± 2.5 m·s-1 vs 28.3 ± 2.5 m·s-1, respectively; P < .05). CONCLUSION: Kinematic changes and decreased ball speeds observed in the final set suggest that adolescent pitchers are unable to maintain lower extremity kinematics and performance as a result of extended play. CLINICAL RELEVANCE: The results from this study may warrant further investigation into how altered lower extremity kinematics may affect trunk and upper extremity function, performance, and risk of injuries during pitching in adolescent athletes, particularly during actual game play.

An Investigation of Structure, Flexibility, and Function Variables that Discriminate Asymptomatic Foot Types.

It has been suggested that foot type considers not only foot structure (high, normal, low arch), but also function (overpronation, normal, oversupination) and flexibility (reduced, normal, excessive). Therefore, this study used canonical regression analyses to assess which variables of foot structure, function, and flexibility can accurately discriminate between clinical foot type classifications. The feet of 61 asymptomatic, healthy adults (18-77 years) were classified as cavus (N = 24), rectus (N = 54), or planus (N = 44) using standard clinical measures. Custom jigs assessed foot structure and flexibility. Foot function was assessed using an emed-x plantar pressure measuring device. Canonical regression analyses were applied separately to extract essential structure, flexibility, and function variables. A third canonical regression analysis was performed on the extracted variables to identify a combined model. The initial combined model included 30 extracted variables; however 5 terminal variables (malleolar valgus index, arch height index while sitting, first metatarsophalangeal joint laxity while standing, pressure-time integral and maximum contact area of medial arch) were able to correctly predict 80.7% of foot types. These remaining variables focused on specific foot characteristics (hindfoot alignment, arch height, midfoot mechanics, Windlass mechanism) that could be essential to discriminating foot type.

Surgical Treatments for Scapholunate Advanced Collapse Wrist: Kinematics and Functional Performance.

PURPOSE: The purpose of this investigation was to compare kinematic motion and functional performance during 2 tasks in patients following 4-corner fusion (4CF) or proximal row carpectomy (PRC) and to compare these data with those from healthy asymptomatic individuals. METHODS: Twenty men (10 4CFs and 10 PRCs, ages, 43-82 y) were recruited for 3-dimensional wrist motion analysis testing. Kinematic coupling (the ratio of wrist flexion/extension to radial-ulnar deviation), kinematic path length (a measure of total angle distance), clinical measures, and performance measures were collected during 2 tasks: dart throwing and hammering. For each outcome, between-group comparisons employed a 1-way analysis of variance with post hoc analysis using the Fisher least significant difference test. RESULTS: All clinical measures (flexion-extension, radial-ulnar deviation, and grip strength) were decreased for 4CF and PRC patients compared with healthy subjects. Coupling, kinematic path length, and performance were all significantly reduced in 4CF and PRC patients compared with healthy subjects during both tasks. Reduced coupling and a shorter kinematic path length are indicative of less global and combined wrist motion. There were no differences identified in coupling patterns or performance between the surgical groups for the dart-throwing task. However, in hammering, the kinematic path length and performance (time and total strikes) were worse in 4CF than in PRC. CONCLUSIONS: Differences in wrist kinematics and performance were identified between the groups. PRC subjects performed better on kinematic and performance variables. As expected, both groups demonstrated decreased wrist kinematic motion and functional performance compared with individuals with normal wrists. These results require confirmation and while they cannot be used to determine the benefits of one procedure over the other, they are an important step in quantifying differences in motion and function between procedures. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic II.

The effect of wrist surgery on the kinematic consistency of joint axis reconstruction in a static posture.

Three-dimensional analysis of wrist motion is a growing focus in orthopedic research, however, our understanding of its validity (accuracy and reliability) remains limited. Nine human cadavers were tested to estimate wrist joint axes alignment in a postural static pose. The objective was to investigate a rater's ability to reliably align three skin- tracked wrist joint coordinate system (WJCS) definitions across baseline and reconstructive wrist states (intact, mid-carpal arthrodesis, and proximal-row carpectomy). Two WJCSs (legacy, anatomic) were based on palpated bony landmarks and the third (functional) was based on both landmarks and passive flexion-extension motion. A coordinate frame based on the anatomic definition was tracked with bone pins and served as a reference. Each WJCS was tested in each wrist state and in three forearm position (45° pronation, neutral, 45° supination). The angular offset about each axis of the WJCS frames were calculated with respect to the reference in flexion-extension, radial-ulnar deviation, and pronation-supination for every iteration. Reliability and root mean square deviation values were analyzed across wrist states. Our data suggest that no WJCS is uniformly more reliable than another. The functional WJCS definition was most consistent across intact and post-operative states for pronation-supination offset, but this was dependent on rater interpretation. It still however offers the practical benefit of requiring fewer landmarks.

The effect of torsional shoe flexibility on gait and stability in children learning to walk.

PURPOSE: To examine the effects of different torsional flexibilities of shoes on gait and stability in children who are newly walking. METHODS: Twenty-five children walking 5 months or less were evaluated barefoot and in 4 shoes with different torsional flexibilities (UltraFlex, MidFlex, LowFlex, and Stiff). Gait pattern was assessed using GaitMatII. Stability was determined by the number of stumbles/falls during functional tasks. RESULTS: Stance time was shorter barefoot compared with all shoe conditions (P = .000). Stance time was shorter in UltraFlex than in LowFlex (P = .000). Step width was wider in UltraFlex than in MidFlex and LowFlex (P = .028). Velocity, step length, and the number of stumbles/falls did not differ significantly across shoe conditions. Children walking for 2 months or less had significantly more stumbles and falls than children walking more than 2 months (P = .003). CONCLUSIONS: Stance time and step width differ across shoe conditions. Stability does not differ across shoe conditions.

Development of an anatomical wrist joint coordinate system to quantify motion during functional tasks.

The purpose of this study was to develop a three-dimensional (3D) motion analysis based anatomical wrist joint coordinate system for measurement of in-vivo wrist kinematics. The convergent validity and reliability of the 3D motion analysis implementation was quantified and compared with manual and electrogoniometry techniques on 10 cadaveric specimens. Fluoroscopic measurements were used as the reference. The 3D motion analysis measurements (mean absolute difference [MAD] = 3.6°) were significantly less different (P < .005) than manual goniometry (MAD = 5.7°) but not (P = .066, power = 0.45) electrogoniometry (MAD = 5.0°) compared with fluoroscopy. The intraclass correlation coefficient (ICC[2,1]) was highest for 3D motion analysis compared with manual and electrogoniometry, suggesting better reliability for this technique. To demonstrate the utility of this new wrist joint coordinate system, normative data from 10 healthy subjects was obtained while throwing a dart.

Wrist kinematic coupling and performance during functional tasks: effects of constrained motion.

PURPOSE: To quantify the coupled motion of the wrist during selected functional tasks and to determine the effects of constraining this coupled motion using a radial-ulnar deviation blocking splint on performance of these tasks. METHODS: Ten healthy, right-handed men performed 15 trials during selected functional tasks with and without a splint, blocking radial and ulnar deviation. The following tasks were performed: dart throwing, hammering, basketball free-throw, overhand baseball and football throwing, clubbing, and pouring. Kinematic coupling parameters (coupling, kinematic path length, flexion-extension range of motion, radial-ulnar deviation range of motion, flexion-extension offset, and radial-ulnar deviation offset) and performance were determined for each functional task. A generalized estimation equation model was used to determine whether each kinematic coupling parameter was significantly different across tasks. A repeated-measures generalized estimation equation model was used to test for differences in performance and kinematic coupling parameters between the free and splinted conditions. RESULTS: Wrist motion exhibited linear coupling between flexion-extension and radial-ulnar deviation, demonstrated by R(2) values from 0.70 to 0.99. Average wrist coupling and kinematic path lengths were significantly different among tasks. Coupling means and kinematic path lengths were different between free and splinted conditions across all tasks other than pouring. Performance was different between wrist conditions for dart throwing, hammering, basketball shooting, and pouring. CONCLUSIONS: Wrist kinematic coupling parameters are task specific in healthy individuals. Functional performance is decreased when wrist coupling is constrained by an external splint. CLINICAL RELEVANCE: Surgical procedures that restrict wrist coupling may have a detrimental effect on functional performance as defined in the study. Patients may benefit from surgical reconstructive procedures and wrist rehabilitation protocols designed to restore kinematic coupling.