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Robert S Heidt

Publications and source records attributed to Robert S Heidt.

7 recordsLinked to original sources
PubMed2006

Comparison of in-shoe foot loading patterns on natural grass and synthetic turf.

Synthetic playing surfaces with rubber or sand infill are now used on many athletic fields such as soccer, football and rugby. Although these surfaces may come closer to the mechanical characteristics of a true grass playing surface than the older turf designs, their potential effects on lower extremity biomechanics and related injury rates necessitate further study. The purpose of this study was to examine the effects of two surfaces (natural grass versus turf) on in-shoe foot loading patterns during cutting. Seventeen male football players were tested on a slalom course. An in-shoe pressure distribution measurement insole was used in the right shoe (14 stud, molded cleat) of each athlete. Individual cutting steps were extracted from each slalom trial and peak pressure and relative load calculated in nine distinct plantar regions of the foot. The turf condition had significantly higher peak pressures within the central forefoot (turf: 646.6+/-172.6 kPa, grass: 533.3+/-143.4 kPa, P=0.017) and lesser toes (turf: 429.3+/-200.9 kPa, grass: 348.1+/-119.0 kPa, P=0.043) compared to grass. In contrast, the relative load within the medial forefoot (turf: 27.2+/-5.3%, grass: 30.2+/-6.6%, P=0.031) and lateral midfoot (turf: 3.4+/-1.8%, grass: 4.1+/-2.3%, P=0.029) were higher during the grass condition. No differences between the grass and turf were found in maximal effort sprint times performed prior to the testing trials. This study demonstrates that playing surface significantly affects plantar loading during sport related activities. Further epidemiological investigation is warranted to determine the effects of playing surfaces on sport specific injury mechanisms.

Athletic Injuries↗
PubMed2005

Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective study.

BACKGROUND: Female athletes participating in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than do male athletes. HYPOTHESIS: Prescreened female athletes with subsequent anterior cruciate ligament injury will demonstrate decreased neuromuscular control and increased valgus joint loading, predicting anterior cruciate ligament injury risk. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: There were 205 female athletes in the high-risk sports of soccer, basketball, and volleyball prospectively measured for neuromuscular control using 3-dimensional kinematics (joint angles) and joint loads using kinetics (joint moments) during a jump-landing task. Analysis of variance as well as linear and logistic regression were used to isolate predictors of risk in athletes who subsequently ruptured the anterior cruciate ligament. RESULTS: Nine athletes had a confirmed anterior cruciate ligament rupture; these 9 had significantly different knee posture and loading compared to the 196 who did not have anterior cruciate ligament rupture. Knee abduction angle (P<.05) at landing was 8 degrees greater in anterior cruciate ligament-injured than in uninjured athletes. Anterior cruciate ligament-injured athletes had a 2.5 times greater knee abduction moment (P<.001) and 20% higher ground reaction force (P<.05), whereas stance time was 16% shorter; hence, increased motion, force, and moments occurred more quickly. Knee abduction moment predicted anterior cruciate ligament injury status with 73% specificity and 78% sensitivity; dynamic valgus measures showed a predictive r2 of 0.88. CONCLUSION: Knee motion and knee loading during a landing task are predictors of anterior cruciate ligament injury risk in female athletes. CLINICAL RELEVANCE: Female athletes with increased dynamic valgus and high abduction loads are at increased risk of anterior cruciate ligament injury. The methods developed may be used to monitor neuromuscular control of the knee joint and may help develop simpler measures of neuromuscular control that can be used to direct female athletes to more effective, targeted interventions.

Adolescent↗
PubMed2003

Physiologic axial load, frictional resistance, and the football shoe-surface interface.

The purpose of this investigation was to report on the interaction between different types of athletic shoes and playing surfaces using physiologic loads of 40 and 220 lbs. This is a continuation of our previous report using a load of 25 lbs. Nine shoes by three manufacturers were characterized as turf, court, molded cleat, or traditional cleat and tested on both natural grass and synthetic turf. A specially designed pneumatic testing device was used in order to measure translational resistance and rotational torque of the shoe-surface interface. Measurements were acquired for 1) force-X describing translational loading, 2) moment-Y describing the torque generated by linear translation, and 3) moment-Z describing the moment generated by axial rotation, and data were analyzed using repeated measures analysis of variance and Tukey's post-hoc comparison. It was found that increased the axial loads from 40 to 220 lbs significantly increased the frictional resistance (p < .05) between the shoe and the artificial turf surface in a nonlinear fashion. Turf shoes demonstrated the most frictional resistance of any group for this condition. Increases in the forces generated in linear translation from the axial load of 40 to 220 lbs produced the most significant increases of any resistance test on the turf surface. The cleated shoes (both traditional and molded) generated the highest frictional and torsional resistance on the grass surface when compared to the other categories of shoes. Grass generated higher peak moments than turf for the cleated shoes. These results demonstrate the considerable differences between laboratory and physiologic conditions and that the increase in frictional resistance is nonlinear with increasing loads.

Ankle↗
PubMed2003

Simultaneous ACL and PCL reconstruction.

The results of 11 patients who underwent simultaneous arthroscopically assisted anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction for acute (n=7) or chronic (n=4) multiligamentous knee injuries were reviewed. Seven patients were treated with a bone-patellar tendon-bone (BPTB) autograft for the ACL reconstruction and an Achilles allograft for the PCL reconstruction, three patients with ipsilateral/contralateral BPTB autografts, and one patient with BPTB allograft for ACL and Achilles allograft for PCL. Seven patients were operated on acutely (<3 months postinjury), and 4 were treated for chronic conditions. At follow-up, all patients were subjectively and functionally evaluated with a Lysholm Knee Scoring Scale. Average patient age at surgery was 29 years, and average postoperative follow-up was 28.4 months. Average postoperative Lysholm score was 87.7 (range: 49-100). Four of 11 patients reported occasional mild pain, 2 occasional swelling, and 4 infrequent instability. No patient required a postoperative manipulation to regain his or her range of motion and 10 of the 11 returned to their previous activity level postoperatively. Of the 10 patients able to return for clinical examination, 2 demonstrated a loss of flexion <5 degrees compared to the other side, 7 demonstrated a mild postoperative posterior drawer at 90 degrees (6 at 1+, 1 at 2+), 3 demonstrated a positive Lachman (grade 1), whereas no patient demonstrated any posterior lateral corner instability. The average anterior active difference on KT-1000 was 2.6 (range: 0-6). Simultaneous reconstruction of the ACL and PCL, although technically difficult, is feasible and yields good to excellent functional results.

Anterior Cruciate Ligament↗
PubMed2002

Effects of iontophoretic versus injection administration of dexamethasone.

PURPOSE: Sixty-eight skeletally mature New Zealand white rabbits were used to study the effects of iontophoresis- and injection-delivered sodium phosphate dexamethasone (DX) on the morphologic, histologic, microscopic, and biomechanical properties of uninjured rabbit patellar tendons over an initial 14-d period. METHODS: Three control (untreated, placebo iontophoresis, and placebo injection) groups and two treatment (iontophoresis and injection) groups underwent serum, ELISA tendon, histology, electron microscopy, and biomechanical analysis. RESULTS: Serum DX levels were detectable and quantifiable in both treatment groups at 1 h but were significantly greater (P < 0.05) in the injected group (11.29 ng.mL-1) compared with the iontophoresis group (6.34 ng.mL-1). The most significant histologic finding was a lack of a cellular inflammatory response in the DX-treated groups at 24 h. Ultrastructural analysis produced no significant differences between size or size ratio of collagen fibrils among any groups. Morphologic examination revealed only injection puncture marks seen in appropriate tendons. Biomechanical testing produced disruption at the patellar insertion in 81% of the specimens. No injected tendon failed at the injection site. Normalized biomechanical properties included: 1) Stiffness increased in control and iontophoresis groups from 1 to 24 h, then gradually declined; the DX-injected specimens showed a similar but delayed effect. 2) Peak load at failure for iontophoresis and control groups was greatest at 24 h. The DX-injected group again showed a delayed response. 3) In general, total energy to failure revealed no significant differences between groups at any time period. CONCLUSION: It appears that iontophoresis or injection-delivered DX may produce anti-inflammatory effects without significantly altering ultrastructural or biomechanical characteristics of the rabbit patellar tendon within an initial 14-d period.

Analysis of Variance↗
PubMedDate not supplied

Arthroscopic laser-assisted capsular shift in the treatment of patients with multidirectional shoulder instability.

BACKGROUND: In recent years, various investigators have begun using lasers in the treatment of shoulder instability. HYPOTHESIS: Arthroscopic laser-assisted capsular shift is an effective treatment for patients with multidirectional shoulder instability. STUDY DESIGN: Retrospective cohort study. METHODS: We retrospectively identified 28 patients (30 shoulders) with multidirectional shoulder instability who were unresponsive to nonoperative management and who had undergone the laser-assisted capsular shift procedure. Twenty-five patients (27 shoulders) with an average follow-up of 28 months were available for review. All patients underwent a physical examination and completed a general questionnaire; the University of California, Los Angeles, shoulder rating scale; the Western Ontario Shoulder Instability Index; and the Short-Form 36 quality of life index. RESULTS: In 22 shoulders, results of the procedure were considered a success because the patients had no recurrent symptoms and at latest follow-up had required no further operative intervention. In five shoulders, results were considered a failure because of recurrent pain or instability and the need for an open capsular shift procedure. With recurrent instability as a measure of failure, the overall success rate was 81.5%. CONCLUSIONS: Our results with laser-assisted capsular shift are comparable with the results of other open and arthroscopic techniques in relieving pain and returning athletes to their premorbid function.

Adolescent↗