Effect of stochastic resonance on proprioception and kinesthesia in anterior cruciate ligament reconstructed patients.

Low amplitude mechanical noise vibration has been shown to improve somatosensory acuity in various clinical groups with comparable deficiencies through a phenomenon known as Stochastic Resonance (SR). This technology showed promising outcomes in improving somatosensory acuity in other clinical patients (e.g., Parkinson's disease and osteoarthritis). Some degree of chronic somatosensory deficiency in the knee has been reported following anterior cruciate ligament (ACL) reconstruction surgery. In this study, the effect of the SR phenomenon on improving knee somatosensory acuity (proprioception and kinesthesia) in female ACL reconstructed (ACLR) participants (n = 19) was tested at three months post-surgery, and the results were compared to healthy controls (n = 28). Proprioception was quantified by the measure of joint position sense (JPS) and kinesthesia with the threshold to detection of passive movement (TDPM). The results based on the statistical analysis demonstrated an overall difference between the somatosensory acuity in the ACLR limb compared to healthy controls (p = 0.007). A larger TDPM was observed in the ACLR limb compared to the healthy controls (p = 0.002). However, the JPS between the ACLR and healthy limbs were not statistically significantly different (p = 0.365). SR significantly improved JPS (p = 0.006) while the effect was more pronounced in the ACLR cohort. The effect on the TDPM did not reach statistical significance (p = 0.681) in either group. In conclusion, deficient kinesthesia in the ACLR limb was observed at three months post-surgery. Also, the positive effects of SR on somatosensory acuity in the ACL reconstructed group warrant further investigation into the use of this phenomenon to improve proprioception in ACLR and healthy groups.

Cross-Modality Validation of Acetabular Surface Models Using 3-D Ultrasound Versus Magnetic Resonance Imaging in Normal and Dysplastic Infant Hips.

Current imaging diagnosis of developmental dysplasia of the hip (DDH) in infancy relies on 2-D ultrasound (US), which is highly operator-dependent. 3-D US offers more complete, and potentially more reliable, imaging of infant hip geometry. We sought to validate the fidelity of acetabular surface models obtained by 3-D US against those obtained concurrently by magnetic resonance imaging (MRI). 3-D US and MRI scans were performed on the same d in 20 infants with normal to severely dysplastic hips (mean age, 57 d; range 13-181 d). 3-D US was performed by two observers using a Philips VL13-5 probe. Coronal 3-D multi-echo data image combination (MEDIC) magnetic resonance (MR) images (1-mm slice thickness) were obtained, usually without sedation, in a 1.5 T Siemens unit. Acetabular surface models were generated for 40 hips from 3-D US and MRI using semi-automated tracing software, separately by three observers. For each hip, the 3-D US and MRI models were co-registered to overlap as closely as possible using Amira software, and the root mean square (RMS) distances between points on the models were computed. 3-D US scans took 3.2 s each. Inter-modality variability was visually minimal. Mean RMS distance between corresponding points on the acetabular surface at 3-D US and MRI was 0.4 ± 0.3 mm, with 95% confidence interval <1 mm. Mean RMS errors for inter-observer and intra-observer comparisons were significantly less for 3-D US than for MRI, while inter-scan and inter-modality comparisons showed no significant difference. Acetabular geometry was reproduced by 3-D US surface models within 1 mm of the corresponding 3-D MRI surface model, and the 3-D US models were more reliable. This validates the fidelity of 3-D US modeling and encourages future use of 3-D US in assessing infant acetabulum anatomy, which may be useful to detect and monitor treatment of hip dysplasia.

ACL/MCL transection affects knee ligament insertion distance of healing and intact ligaments during gait in the Ovine model.

The objective of this study was to assess the impact of combined transection of the anterior cruciate and medial collateral ligaments on the intact and healing ligaments in the ovine stifle joint. In vivo 3D stifle joint kinematics were measured in eight sheep during treadmill walking (accuracy: 0.4+/-0.4mm, 0.4+/-0.4 degrees ). Kinematics were measured with the joint intact and at 2, 4, 8, 12, 16 and 20 weeks after either surgical ligament transection (n=5) or sham surgery without transection (n=3). After sacrifice at 20 weeks, the 3D subject-specific bone and ligament geometry were digitized, and the 3D distances between insertions (DBI) of ligaments during the dynamic in vivo motion were calculated. Anterior cruciate ligament/medial collateral ligament (ACL/MCL) transection resulted in changes in the DBI of not only the transected ACL, but also the intact lateral collateral ligament (LCL) and posterior cruciate ligament (PCL), while the DBI of the transected MCL was not significantly changed. Increases in the maximal ACL DBI (2 week: +4.2mm, 20 week: +5.7mm) caused increases in the range of ACL DBI (2 week: 3.6mm, 20 week: +3.8mm) and the ACL apparent strain (2 week: +18.9%, 20 week: +24.0%). Decreases in the minimal PCL DBI (2 week: -3.2mm, 20 week: -4.3mm) resulted in increases in the range of PCL DBI (2 week: +2.7mm, 20 week: +3.2mm). Decreases in the maximal LCL DBI (2 week: -1.0mm, 20 week: -2.0mm) caused decreased LCL apparent strain (2 week: -3.4%, 20 week: -6.9%). Changes in the mechanical environment of these ligaments may play a significant role in the biological changes observed in these ligaments.

Alterations in knee joint laxity during the menstrual cycle in healthy women leads to increases in joint loads during selected athletic movements.

BACKGROUND: It has been speculated that the hormonal cycle may be correlated with higher incidence of ACL injury in female athletes, but results have been very contradictory. HYPOTHESIS: Knee joint loads are influenced by knee joint laxity (KJL) during the menstrual cycle. STUDY DESIGN: Controlled laboratory study. METHODS: Serum samples and KJL were assessed at the follicular, ovulation, and luteal phases in 26 women. Knee joint mechanics (angle, moment, and impulse) were measured and compared at the same intervals. Each of the 26 subjects had a value for knee laxity at each of the 3 phases of their cycle, and these were ordered and designated low, medium, and high for that subject. Knee joint mechanics were then compared between low, medium, and high laxity. RESULTS: No significant differences in knee joint mechanics were found across the menstrual cycle (no phase effect). However, an increase in KJL was associated with higher knee joint loads during movement (laxity effect). A 1.3-mm increase in KJL resulted in an increase of approximately 30% in adduction impulse in a cutting maneuver, an increase of approximately 20% in knee adduction moment, and a 20% to 45% increase in external rotation loads during a jumping and stopping task (P < .05). CONCLUSION: Changes in KJL during the menstrual cycle do change knee joint loading during movements. Clinical Relevance Our findings will be beneficial for researchers in the development of more effective ACL injury prevention programs.

Changing hormone levels during the menstrual cycle affect knee laxity and stiffness in healthy female subjects.

BACKGROUND: Whether knee laxity varies throughout the menstrual cycle remains controversial. As increased laxity may be a risk factor for anterior cruciate ligament (ACL) injury, further research is warranted. HYPOTHESIS: Variation in estradiol and progesterone levels during the menstrual cycle influences knee laxity and stiffness. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: The serum estradiol and progesterone levels of 26 healthy female subjects were recorded in the follicular phase, ovulation, and the luteal phase. Knee joint laxity was assessed using a standard knee arthrometer at the same intervals. Stiffness changes in the load-displacement curve were determined. Hormone levels across the cycle were compared between responders and nonresponders, defined by whether changes in knee laxity at 89 N occurred. RESULTS: Greater laxity at 89 N during ovulation was observed (ovulation: 5.13 +/- 1.70 mm vs luteal: 4.55 +/- 1.54 mm, P = .012). In knee laxity testing at manual maximum load, greater laxity was noticed during ovulation (14.43 +/- 2.60 mm, P = .018), as compared with the follicular phase (13.35 +/- 2.53 mm). A reduction in knee stiffness of approximately 17% (ovulation: 12.48 +/- 5.46 N/mm vs luteal: 15.02 +/- 7.71 N/mm, P = .042) during ovulation was observed. However, there were no differences in hormone levels between responders and nonresponders at 89 N. CONCLUSION: Female hormone levels are related to increased knee joint laxity and decreased stiffness at ovulation. To understand subject variations in knee joint laxity during the menstrual cycle in female athletes, further investigation is warranted.

Dynamic in vivo three-dimensional (3D) kinematics of the anterior cruciate ligament/medial collateral ligament transected ovine stifle joint.

The objective of this study was to use an ovine stifle joint model to assess the impact of combined transection of the anterior cruciate and medial collateral ligaments on three-dimensional (3D) joint motion serially over 20 weeks after transection. In vivo 3D kinematics were measured in the right hind limb of eight sheep while walking on a treadmill (accuracy, 0.4 mm +/- 0.4 mm, 0.4 degrees +/- 0.4 degrees ). Five sheep received surgical ligament transection and three sheep received sham surgery without transection. At 2 weeks after transection, average joint flexion at hoof strike was significantly increased (8.9 degrees +/- 3.0 degrees ), and the tibial position was significantly shifted in the anterior direction relative to the femur during midstance (4.9 mm +/- 0.9 mm). By 20 weeks after transection, joint flexion had normalized, but the tibial position was significantly adducted (0.5 degrees +/- 0.7 degrees ) and shifted in the medial (2.5 mm +/- 1.2 mm), anterior (5.8 mm +/- 1.9 mm), and superior directions (1.6 mm +/- 0.4 mm). At 2 and 20 weeks after surgical intervention, the maximal anterior tibial position was significantly increased during mid-stance in the transected group (4.9 mm +/- 0. 9 mm and 5.8 mm +/- 1.9 mm) compared to the sham operated group (0.2 mm +/- 0.2 mm and -0.1 +/- 0.1 mm). Although the anterior tibial shift was observed in all transected sheep, a high degree of variability existed between sheep, in the initial joint position, the magnitude of the early change, the change over time, and the change at 20 weeks. In this situation statistics must be interpreted carefully, and in future studies, individual changes should be assessed in the context of individual pathological changes in order to investigate potential clinical significance.

Clinical impact of optical imaging with 3-D reconstruction of torso topography in common anterior chest wall anomalies.

BACKGROUND: Standard modalities to assist in determining the extent of chest wall developmental deformities in patients include x-ray and computed tomography (CT). The purpose of this study is to describe an optical imaging technique that provides accurate cross-sectional images of the chest, and to compare these with standard CT-derived images of chest wall abnormalities. PATIENTS AND METHODS: Ten patients (5 pectus excavatum and 5 pectus carinatum) underwent imaging that included limited CT and optical cross-sectional imaging. Severity indices of the deformity using the standard Haller index (HI) were calculated from CT scans. A similar severity measurement of deformity was derived from the outline of torso cross sections (ie, from skin to skin measurements) obtained from optical images. To assess the severity of carinatum defects, a modified pectus index was derived, which measures the anterior chest protrusion from the central chord of the chest cross section. We performed regression analyses, comparing the indices obtained from CT and optical imaging methodologies. RESULTS: Optical measures of cross-sectional deformities correlated well with standard HI (r2 = 0.94) and even better with the modified pectus index (r2 = 0.96). Adaptation of the HI for pectus carinatum deformity evaluation was effective, and consistent with the torso surface deformity measures. CONCLUSIONS: Torso models from optical imaging offer 3-D images of the chest wall deformity with no radiation exposure. This preliminary study showed promising results for the use of torso surface measurement as an alternative index of pectus deformities; if validated in larger studies, these measures may be useful for following chest wall abnormalities, using repeated studies in patients.