Biomedical subjects

Gerald Smith

Publications and source records attributed to Gerald Smith.

5 recordsLinked to original sources

PubMed2006

Estimating 3D joint kinematics from video sequences of running and cutting maneuvers--assessing the accuracy of simple visual inspection.

Videos of sports injuries can potentially provide valuable information on non-contact ACL injuries. However, only the un-validated simple visual inspection approach has, so far, been used. Therefore, the purpose of this study was to test the accuracy and precision of researchers in estimating kinematics from video sequences of situations that typically lead to ACL injuries. We also tested if accuracy and precision could be improved through a training program. Using a routine surface marker based infrared, 240 Hz, 3D motion analysis system, we recorded running and cutting trials from three test subjects. Six observers were asked to provide estimates of kinematic variables from 27 video composites from one, two or three ordinary cameras, systematically varying viewing angles and time point of analysis. The observers thereafter went through a training program where 35 similar composites were analyzed, and feedback on the kinematics, as measured by the 3D motion analysis system, was provided on a group basis. Finally, the test was repeated to assess accuracy and precision. The mean error for knee flexion was -19 degrees, indicating a consistent underestimation. Hip flexion was underestimated by 7 degrees, but the standard deviation between the observers was 18 degrees on average, indicating poor consistency. Substantial errors were also found in the accuracy and precision of the other estimates. Only small group effects were seen from our training program. Based on these findings, results from studies using a simple visual inspection approach to describe joint motion must be interpreted with caution.

Adult↗

PubMed2006

Mechanisms of anterior cruciate ligament injury in basketball: video analysis of 39 cases.

BACKGROUND: The mechanisms of anterior cruciate ligament injury in basketball are not well defined. PURPOSE: To describe the mechanisms of anterior cruciate ligament injury in basketball based on videos of injury situations. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Six international experts performed visual inspection analyses of 39 videos (17 male and 22 female players) of anterior cruciate ligament injury situations from high school, college, and professional basketball games. Two predefined time points were analyzed: initial ground contact and 50 milliseconds later. The analysts were asked to assess the playing situation, player behavior, and joint kinematics. RESULTS: There was contact at the assumed time of injury in 11 of the 39 cases (5 male and 6 female players). Four of these cases were direct blows to the knee, all in men. Eleven of the 22 female cases were collisions, or the player was pushed by an opponent before the time of injury. The estimated time of injury, based on the group median, ranged from 17 to 50 milliseconds after initial ground contact. The mean knee flexion angle was higher in female than in male players, both at initial contact (15 degrees vs 9 degrees , P = .034) and at 50 milliseconds later (27 degrees vs 19 degrees , P = .042). Valgus knee collapse occurred more frequently in female players than in male players (relative risk, 5.3; P = .002). CONCLUSION: Female players landed with significantly more knee and hip flexion and had a 5.3 times higher relative risk of sustaining a valgus collapse than did male players. Movement patterns were frequently perturbed by opponents. CLINICAL RELEVANCE: Preventive programs to enhance knee control should focus on avoiding valgus motion and include distractions resembling those seen in match situations.

Adolescent↗

PubMed2005

Ski skating technique and physiological responses across slopes and speeds.

Appropriate technique choice may affect ski performance. V2 ski skating technique has in recent years become more widely applied on uphill terrain where V1 technique has typically been used. This investigation compared physiological responses of skiers using V1 and V2 techniques during uphill treadmill roller-skiing. Part 1: six skiers from B-level national ski teams participated in technique comparisons performed under six uphill conditions (3, 4, 5, 6, 7, and 8 degrees) with speeds selected so external work was approximately constant for each slope. The 12 trials of 5-min steady-state skating were randomly distributed across two test sessions of six trials each. Heart rate (HR), oxygen consumption (VO(2)), blood lactate concentration (La) and rating of perceived exertion (RPE) were measured. Part 2: 15 skiers from A-level and B-level national ski teams participated in V1-V2 technique comparison on constant slope (5 degrees) with five speeds ranging from 2.25 to 3.25 m s(-1). In two test sessions of V1 or V2 skating (randomly assigned for 2 days) similar characteristics as Part 1 were measured. Across all variables consistent responses were observed for both the experimental parts. As slope increased, V2 skating became increasingly costly compared to V1 skating. At constant slope across the range of speeds, V2 was more costly than V1 skating. This suggests that it may be disadvantageous for skiers to use V2 instead of V1 skating technique on moderate to steep uphill terrain. Doing so may result in elevated HR, La, and VO(2) compared to V1 skating at the same speed.

Adolescent↗

PubMed2005

Reliability estimation of grouped functional imaging data using penalized maximum likelihood.

We analyzed grouped fMRI data and developed a reliability analysis for such data using the method of penalized maximum likelihood (ML). Specifically, this technique was applied to a somatosensory paradigm that used a mechanical probe to provide noxious stimuli to the foot, and a paradigm consisting of four levels of graded peripheral neuromuscular electrical stimulation (NMES). In each case, reliability maps of activation were generated. Receiver operating characteristic (ROC) curves were constructed in the case of the graded NMES paradigm for each level of stimulation, which revealed an increase in the specificity of activation with increasing stimulation levels. In addition, penalized ML was used to determine whether the grouped reliability maps obtained from one stimulus level were significantly different from those obtained at other levels. The results show a significant difference (P < 0.01) in the reliability of activation from one stimulation level to the next. These results are in agreement with those obtained using generalized linear modeling (GLM). While the reliability maps generated are not directly comparable, they are qualitatively similar to those obtained by controlling the expected false discovery rate (FDR). The proposed methodology can be used to objectively compare activation maps between groups, as well as to perform reliability assessments. Furthermore, this method potentially can be used to assess the longitudinal effect of treatment therapies within a group.

Analysis of Variance↗

PubMed2005

Effect of intraarticular hyaluronan injection on vertical ground reaction force and progression of osteoarthritis after anterior cruciate ligament transection.

OBJECTIVE: To determine if intraarticular (IA) injection of hyaluronan (HA) into the canine knee after anterior cruciate ligament transection (ACLT) alters the progression of osteoarthritis (OA) and the perception of pain in this model. METHODS: OA was induced in 30 adult dogs of mixed breed by ACLT. The dogs were divided into 3 groups and given 5 weekly IA injections into the unstable knee during Weeks 1-5 and 13-17. The prophylactic treatment group received HA in the first series and saline during the second series. The therapeutic group received saline in the first series and HA in the second series. The control group received saline during both injection series. The progression of joint damage of OA was evaluated by arthroscopy 12 weeks after ACLT and by gross examination 32 weeks after ACLT. Histologic and biochemical changes of OA were evaluated. Loading of the unstable limb during gait was determined by force-plate analysis before surgery, after each series of injections, and the week before euthanasia. RESULTS: Arthroscopic examination 12 weeks after ACLT revealed OA changes in the cruciate-deficient knees. Chondropathy scores ranged from 0 to 8 (possible range 0-65). The mean chondropathy score was 2.5 +/- 1.3 (mean +/- SD) for the controls, 2.5 +/- 2.5 for the therapeutic group, and 2.1 +/- 1.3 for the prophylactic group. At the termination of the experiment 32 weeks after ACLT, the gross chondropathy scores were 14.0 +/- 5.2 for controls, 17.6 +/- 6.8 for the therapeutic group, and 13.3 +/- 5.0 for the prophylactic group. There were no significant differences among the means of the gross scores, the histologic scores, or biochemical composition of articular cartilage. The peak vertical ground reaction force (VGRF) generated by the unstable limb was reduced by ~60% after ACLT, and slowly increased to ~75% of the baseline value over the 32 weeks after ACLT. HA injection had no effect on the VGRF or on the pathologic changes of OA. CONCLUSION: Intraarticular HA injection did not alter the progression of OA in the cruciate-deficient canine knee or alter the loading of the unstable limb.

Adjuvants, Immunologic↗