Anatomic Description of the Origin of the Proximal Hamstring.

PURPOSE: To define the topographic anatomy of the footprint of the hamstrings origin on the ischium. METHODS: Dissection of the hamstrings origin in 6 cadaveric pelvises was performed. The hamstrings origin was isolated with sharp dissection, and it was noted whether the semimembranosus had a separate attachment or whether there was one confluent tendon attached at the footprint. The common hamstrings tendon was then sharply dissected from the ischium, and the footprint was outlined with surgical marker followed by radiopaque paint. Paint was prepared by mixing 0.25 g Daler-Rowney acrylic artists ink scarlet no. 567 (Daler-Rowney, Bracknell, England) per gram of EZ-HD 98% v/w barium sulfate (E-Z-EM Inc, Lake Success, NY). The paint was then applied to the area of the footprint, and the specimen underwent a 0.5-mm-slice computed tomographic (CT) scan of the pelvis with 3-dimensional (3D) reconstructions. Vitrea (Vital Images, Minnetonka, MN) software was used to determine the surface area of the ligament footprint as well as the distance from the ischial tuberosity to the center of the footprint. The thickness of the bone underlying the footprint was measured. Data are presented as means ± standard error. RESULTS: Five of 6 specimens had a common hamstrings tendon, whereas one had a separate attachment for the semimembranosus. The semimembranosus joined the common hamstrings tendon 2.33 ± 0.61 cm distal to the footprint. The average surface area of the hamstrings footprint measured 10.19 ± 0.75 cm(2). The distance from the tip of the ischial tuberosity to the center of the hamstrings footprint measured 3.73 ± 0.22 cm. The average thickness of the bone deep to the footprint was 3.77 ± 0.9 cm. CONCLUSIONS: This study provides a topographic description of the origin of the hamstrings footprint and may assist surgeons in performing anatomic reattachment of this tendon. CLINICAL RELEVANCE: Our data will assist surgeons in performing anatomic repair of proximal hamstrings avulsions.

Upper extremity hemodynamics and sensation with backpack loads.

Heavy backpacks are often used in extreme environments, for example by military during combat, therefore completion of tasks quickly and efficiently is of operational relevance. The purpose of this study was to quantify hemodynamic parameters (brachial artery Doppler and microvascular flow by photoplethysmography; tissue oxygenation by near-infrared spectroscopy; arterial oxygen saturation by pulse oximeter) and sensation in upper extremities and hands (Semmes-Weinstein monofilament test and 2-point discrimination test) while wearing a loaded backpack (12 kg) in healthy adults for 10 min. All values were compared to baseline before wearing a backpack. Moderate weight loaded backpack loads significantly decreased upper extremity sensation as well as all macrovascular and microvascular hemodynamic values. Decreased macrovascular and microvascular hemodynamics may produce neurological dysfunction and consequently, probably affect fine motor control of the hands.

Footprint of the lateral ligament complex of the ankle.

BACKGROUND: We describe the topographic anatomy of the lateral ligament complex of the ankle using 3-dimensional (3D) computed tomography (CT) imaging. METHODS: Dissection of the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL) was performed on 8 unpaired fresh-frozen cadaver feet. Ligaments were sharply dissected from bone, and the footprint was outlined with radio-opaque paint. The specimen underwent a 0.625-mm slice CT scan of the ankle with 3D reconstructions. Software was used to determine the surface area of the ligament footprint as well as measure the distance from the peroneal tubercle to the center of the CFL footprint. Data are presented as mean ± standard error. RESULTS: Six specimens had a bifid ATFL. Seven ankles had a bifid ATFL footprint on the talus. All specimens had intact CFL fibers. The intact superior and inferior limbs of the ATFL measured 19.7 ± 1.2 mm and 16.7 ± 1.1 mm. The CFL measured 24.8 ± 2.4 mm. The area of the footprints of the superior ATFL and inferior ATFL on the talus measured 1.5 ± 0.26 cm(2) and 0.90 ± 0.07 cm(2). The CFL and ATFL origins on the fibula were continuous and measured 3.48 ± 0.39 cm(2). The CFL insertion on the calcaneus measured 2.68 ± 0.20 cm(2). The CFL was found 27.1 ± 1.0 mm posterior and superior from the peroneal tubercle. CONCLUSIONS: In presumably uninjured specimens, both the ATFL and its footprint on the talus were bifid. The CFL and ATFL origins have a single confluent footprint on the anterior border of the distal fibula. The CFL footprint on the calcaneus is almost 3 cm posterior and superior to the peroneal tubercle. CLINICAL RELEVANCE: This study may assist surgeons in anatomically reconstructing the lateral ligament complex of the ankle.

Leg intramuscular pressures and in vivo knee forces during lower body positive and negative pressure treadmill exercise.

Quantifying muscle and joint forces over a broad range of weight bearing loads during exercise may provide data required to improve prosthetic materials and better protect against muscle and bone loss. Collectively, leg intramuscular pressure (IMP), ground reaction force (GRF), and the instrumented tibial tray force measurements provide a comprehensive assessment of leg muscle and joint biomechanical effects of gravity during exercise. Titration of body weight (BW) by lower body negative pressure (LBNP) and lower body positive pressure (LBPP) can reproducibly modulate IMP within leg muscle compartments. In addition, previous studies document peak tibial forces during various daily activities of 2.2 to 2.5 BW. The study objective was to determine the IMPs of the leg, axial compressive force on the tibia in vivo, vertical GRF, and knee range of motion during altered BW levels using LBPP and LBNP treadmill exercise. We hypothesize that peak GRF, peak tibial forces, and peak IMPs of the leg correlate linearly with percent BW, as generated across a broad range of upright LBPP and supine LBNP exercise. When running at 2.24 m/s the leg IMPs significantly increased over the loading range of 60% to 140% BW with LBPP and LBNP (P < 0.001); as expected, leg IMPs were significantly higher when running compared with standing (P < 0.001). During upright LBPP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s (R(2) = 0.90) and 1.34 m/s (R(2) = 0.98). During supine LBNP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s (R(2) = 0.98) and 1.34 m/s (R(2) = 0.91). The present study is the first to measure IMPs and peak tibial forces in vivo during upright LBPP, upright LBNP, and supine LBNP exercise. These data will aid the development of rehabilitation exercise hardware and prescriptions for patients and astronauts.

The effect of backpacks on the lumbar spine in children: a standing magnetic resonance imaging study.

STUDY DESIGN: This study is a repeated measures design to measure the lumbar spine response to typical school backpack loads in healthy children. The lumbar spine in this setting was measured for the first time by an upright magnetic resonance imaging (MRI) scanner. OBJECTIVE: The purpose of this study is to measure the lumbar spine response to typical school backpack loads in healthy children. We hypothesize that backpack loads significantly increase disc compression and lumbar curvature. SUMMARY OF BACKGROUND DATA: Children commonly carry school backpacks of 10% to 22% bodyweight. Despite growing concern among parents about safety, there are no imaging studies which describe the effect of backpack loads on the spine in children. METHODS: Three boys and 5 girls, age 11 +/- 2 years (mean +/- SD) underwent T2 weighted sagittal and coronal MRI scans of the lumbar spine while standing. Scans were repeated with 4, 8, and 12 kg backpack loads, which represented approximately 10%, 20%, and 30% body weight for our sample. Main outcome measures were disc compression, defined as post- minus preloading disc height, and lumbar asymmetry, defined as the coronal Cobb angle between the superior endplates of S1 and L1. RESULTS: Increasing backpack loads significantly compressed lumbar disc heights measured in the midline sagittal plane (P < 0.05, repeated-measures analysis of variance [ANOVA]). Lumbar asymmetry was: 2.23 degrees +/- 1.07 degrees standing, 5.46 degrees +/- 2.50 degrees with 4 kg, 9.18 degrees +/- 2.25 degrees with 8 kg, and 5.68 degrees +/- 1.76 degrees with 12 kg (mean +/- SE). Backpack loads significantly increased lumbar asymmetry (P < 0.03, one-way ANOVA). Four of the 8 subjects had Cobb angles greater than 10 degrees during 8-kg backpack loads. Using a visual-analogue scale to rate their pain (0-no pain, 10-worst pain imaginable), subjects reported significant increases in back pain associated with backpack loads of 4, 8, and 12 kg (P < 0.001, 1-way ANOVA). CONCLUSION: Backpack loads are responsible for a significant amount of back pain in children, which in part, may be due to changes in lumbar disc height or curvature. This is the first upright MRI study to document reduced disc height and greater lumbar asymmetry for common backpack loads in children.

Inelastic compression legging produces gradient compression and significantly higher skin surface pressures compared with an elastic compression stocking.

The purposes of this study were to (1) investigate compression levels beneath an inelastic legging equipped with a new pressure-adjustment system, (2) compare the inelastic compression levels with those provided by a well-known elastic stocking, and (3) evaluate each support's gradient compression production. Eighteen subjects without venous reflux and 12 patients with previously documented venous reflux received elastic and inelastic compression supports sized for the individual. Skin surface pressures under the elastic (Sigvaris 500, 30-40 mm Hg range, Sigvaris, Inc., Peachtree City, GA) and inelastic (CircAid C3 with Built-in-Pressure System [BPS], CircAid Medical Products, San Diego, CA) supports were measured using a calibrated Tekscan I-Scan device (Tekscan, Inc., Boston, MA). The elastic stocking produced significantly lower skin surface pressures than the inelastic legging. Mean pressures (+/- standard error) beneath the elastic stocking were 26 +/- 2 and 23 +/- 1 mm Hg at the ankle and below-knee regions, respectively. Mean pressures (+/- standard error) beneath the inelastic legging with the BPS were 50 +/- 3 and 38 +/- 2 mm Hg at the ankle and below-knee regions, respectively. Importantly, our study indicates that only the inelastic legging with the BPS produces significant ankle to knee gradient compression (p = .001).

Hertel curve: orbital volume increment and proptosis in a cadaver model.

PURPOSE: This study examined the relation between effective orbital volume increment and proptosis induced by an inflatable orbital implant in a human cadaver orbit. METHODS: A 25-ml inflatable latex balloon was inserted between the periorbita and orbital floor in 15 human cadavers. Hertel measurements were taken for each milliliter over a total 7-ml volume increment. Five trials per orbit for 15 cadavers resulted in 525 data points. RESULTS: Average exophthalmos per milliliter of volume increment was plotted over 7 ml, using 1-ml volume increments. The resultant curve, which was termed a Hertel curve, was linear over 7 ml (R > 99%) and had a slope of 0.62 mm per milliliter of volume increment. CONCLUSIONS: An inflatable orbital implant is an effective tool for introducing a specified amount of volume in the cadaver orbit. The predictable relation between proptosis and volume increment (Hertel curve) may be a useful tool for surgeons in planning the size of an implant required to surgically correct enophthalmos.