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Biomedical subjects

C Milgrom

Publications and source records attributed to C Milgrom.

At least 19 recordsLinked to original sources
PubMed2006

A prospective biomechanical study of the association between foot pronation and the incidence of anterior knee pain among military recruits.

Excessive foot pronation has been considered to be related to anterior knee pain. We undertook a prospective study to test the hypothesis that exertional anterior knee pain is related to the static and dynamic parameters of foot pronation. Two weeks before beginning basic training lasting for 14 weeks, 473 infantry recruits were enrolled into the study and underwent two-dimensional measurement of their subtalar joint displacement angle during walking on a treadmill. Of the 405 soldiers who finished the training 61 (15%) developed exertional anterior knee pain. No consistent association was found between the incidence of anterior knee pain and any of the parameters of foot pronation. While a statistically significant association was found between anterior knee pain and pronation velocity (left foot, p = 0.05; right foot, p = 0.007), the relationship was contradictory for the right and left foot. Our study does not support the hypothesis that anterior knee pain is related to excessive foot pronation.

Biomechanical Phenomena↗
PubMed2005

Exercise-induced strain and strain rate in the distal radius.

Strains applied to bone can stimulate its development and adaptation. High strains and rates of strain are thought to be osteogenic, but the specific dose response relationship is not known. In vivo human strain measurements have been performed in the tibia to try to identify optimal bone strengthening exercises for this bone, but no measurements have been performed in the distal radial metaphysis, the most frequent site of osteoporotic fractures. Using a strain gauged bone staple, in vivo dorsal metaphyseal radial strains and rates of strain were measured in ten female patients during activities of daily living, standard exercises and falls on extended hands. Push-ups and falling resulted in the largest compression strains (median 1345 to 3146 microepsilon, equivalent to a 0.1345% to 0.3146% length change) and falling exercises in the largest strain rates (18582 to 45954 microepsilon/s). On the basis of their high strain and/or strain rates these or variations of these exercises may be appropriate for distal radial metaphyseal bone strengthening.

Activities of Daily Living↗
PubMed2004

A comparison of bone strain measurements at anatomically relevant sites using surface gauges versus strain gauged bone staples.

Instrumented bone staples were first introduced as an alternative to surface-mounted strain gauges for use in human in vivo bone strain measurements because their fixation to bone is secure and requires not only minimally invasive surgery. Bench-top bone bending models have shown that the output from strain gauged bone staples compares favorably to that of traditional mounted gauges. However their within- and across-subject performance at sites typically instrumented in vivo has never been examined. This study used seven human cadaver lower extremities with an age range of 23-81 years old and a dynamic gait simulator to examine and compare axial strains in the mid tibial diaphysis and on the dorsal surface of the second metatarsal as measured simultaneously with strain gauged bone staples and with traditional surface-mounted gauges. Rosette configurations were used at the tibial site for deriving principal compression and tension, and shear strains. Axial outputs from the two gauge types demonstrated strong linear relationships for the tibia (r(2)=0.78-0.94) and the second metatarsal (r(2)=0.96-0.99), but coefficients (slopes) for the relationship were variable (range 7-20), across subjects and across sites. The apparent low reliability of strain gauged staples may be explained by the fact that both strain gauged staples and surface strain gauges are inexact to some degree, do not measure strains from exactly the same areas and strain gauged staples reflect surface strains as well as deformations within the cortex. There were no relationships for the principal tibia compression, tension or shear strain measurements derived from the two rosette gauge types, reflecting the very different anatomical areas measured by each of the constructs in this study. Strain gauged bone staples may be most useful in comparing relative axial intra-subject differences between activities, but inter-subject variability may require larger sample sizes to detect differences between populations.

Adult↗
PubMed2003

Are overground or treadmill runners more likely to sustain tibial stress fracture?

BACKGROUND: Repetitive high bone strain and/or strain rates, such as those that occur during running, contribute to stress fractures as well as promoting maintenance of or increase in bone mass. Kinematic differences are known to exist between overground and treadmill running and these may be reflected in different bone strains and strain rates during the two running techniques. AIM: To measure in vivo strains and strain rates in human tibia during treadmill and overground running and determine if there are significant differences in strain and strain rate levels between the two running techniques. METHODS: A strain gauged bone staple was mounted percutaneously along the axial direction in the mid diaphysis of the medial tibia in three subjects, and in vivo tibial strains were measured during treadmill and overground running at 11 km/h. RESULTS: Axial compression strains (p<0.0001), tension strains (p<0.001), compression strain rates (p<0.0001), and tension strain rates (p<0.0001) were 48-285% higher during overground running than during treadmill running. CONCLUSIONS: On the basis of lower in vivo strains and strain rates, treadmill runners are at lower risk of developing tibial stress fractures, but less likely to achieve tibial bone strengthening, than overground runners.

Adult↗
PubMed2003

Cold weather training: a risk factor for Achilles paratendinitis among recruits.

In a prospective study of risk factors for Achilles tendinopathy among four induction cycles of infantry recruits, 95 out of 1405 recruits, (6.8%) were found to suffer from Achilles tendinopathy. In more than 94% of the cases, the tendinopathy was considered to be paratendinitis. Training season had a statistically significant effect on the incidence of Achilles paratendinitis with 3.6% suffering in the summer and 9.4% in the winter (p = .001). This increased risk for Achilles paratendinitis in cold weather outdoor training can be explained by a fall in temperature of the Achilles paratenon whose membranes are rich in mucopolysaccharides and serve as a lubricant for gliding of the tendon and epitenon. Decreased temperature may increase the viscosity of the lubricant and thereby increases friction and risk for Achilles paratendinitis. This same relationship illustrates why "warming up" before exercising may be important in lowering the incidence of Achilles paratendinitis.

Achilles Tendon↗
PubMed2002

Metatarsal strains are sufficient to cause fatigue fracture during cyclic overloading.

Human in vivo tibial strains during vigorous walking have not been found to exceed 1200 microstrains. These values are below those found in ex vivo studies (>3000 microstrains) to cause cortical bone fatigue failure, suggesting that an intermediate bone remodeling response may be associated with tibial stress fractures. Metatarsal stress fractures, however, often develop before there is time for such a response to occur. Simultaneous in vivo axial strains were measured at the mid diaphysis of the second metatarsal and the tibia in two subjects. Peak axial metatarsal compression strains and strain rates were significantly higher than those of the tibia during treadmill walking and jogging both barefoot and with running shoes and during simple calisthenics. During barefoot treadmill walking metatarsal compression strains were greater than 2500 microstrains. During one- and two-leg vertical jumps and broad jumping, both metatarsal compression and tension strains were >3000 microstrains. Compression and tension strains in the metatarsus unlike those of the tibia may be sufficiently high even during moderate exertional activities to cause fatigue failure of bone secondary to the number of loading cycles without an intermediate bone remodeling response.

Adult↗
PubMed2001

A home exercise program for tibial bone strengthening based on in vivo strain measurements.

OBJECTIVE: To compare the strain and strain rates generated during lower limb calisthenics with walking, an exercise that has been found to have only minimal effect on bone mass. Strengthening of bone, while it still has adaptive ability, can be achieved by exercise. Mechanical loading during physical activity produces strains and strain rates within the bones. It is thought that strain and strain rates higher than the usual provide the stimulus for the bones' adaptation. DESIGN: Three strain-gauged bone staples were inserted percutaneously in a 30 degrees rosette pattern in the medial aspect of the midtibial diaphysis of two volunteers. The principal compression, tension, shear strains, and strain rates were measured during various lower limb calisthenics and compared with those of jogging and walking. RESULTS: Zig-zag hopping was in the grouping of exercises with the highest principal compression, tension, and shear strains and compression strain rates, whereas walking was in the lowest or next-to-the-lowest grouping for all principal strain or strain rates. CONCLUSION: Zig-zag hopping, based on the high strain and strain rates that it produces, may be an optimal tibial bone-strengthening exercise.

Adult↗
PubMed2001

The effect of shoe sole composition on in vivo tibial strains during walking.

To test the hypothesis that shoe sole composition can affect the level of bone strain and strain rates that contribute to the development of stress fractures, in vivo tibial strain measurements were made during treadmill walking while wearing four shoes which differed only in their sole composition. Soles of 65 Shore A polyurethane with an embedded heel air cell had significantly lower compression and shear strains and shear strain rates than soles of 65, 75 and a composite of 40/65 Shore A polyurethane with no embedded air cells. A sole composed of 65 Shore A polyurethane with an embedded air cell can potentially be protective against stress fracture in a walking shoe.

Adult↗
PubMed2000

[Pre-induction sport activity in prevention of stress fractures in elite infantry recruits].

Pre-induction sports participation of 392 elite infantry recruits was evaluated for correlation with incidence of stress fractures (SF) during 14 weeks of basic training. 23.7% developed lower extremity stress fractures. 72% of the recruits had participated in sports on a regular basis during the 2 years prior to induction. Their fitness as examined by the Bar-Or induction fitness test, was significantly better than that of those who had not trained. 14.9% of the soldiers who had previously participated in ball games (primarily basketball) as an only sport suffered stress fractures, compared to 31.0% of those whose only sport was running (p < 0.005). Training for only 6 months prior to induction had no effect on the incidence of SF. The reason for the difference between ball games and running is probably related to the higher strains and strain rates developed during ball games and to their multidirectional nature, as compared to running. These findings suggest that participation in a pre-induction program that includes activities that create strains, such as basketball, can reduce incidence of SF in infantry recruits. The training period has to last at least 2 years.

Fractures, Stress↗
PubMed2000

Do high impact exercises produce higher tibial strains than running?

BACKGROUND: Bone must have sufficient strength to withstand both instantaneous forces and lower repetitive forces. Repetitive loading, especially when bone strain and/or strain rates are high, can create microdamage and result in stress fracture AIM: To measure in vivo strains and strain rates in human tibia during high impact and moderate impact exercises. METHODS: Three strain gauged bone staples were mounted percutaneously in a rosette pattern in the mid diaphysis of the medial tibia in six normal subjects, and in vivo tibial strains were measured during running at 17 km/h and drop jumping from heights of 26, 39, and 52 cm. RESULTS: Complete data for all three drop jumps were obtained for four of the six subjects. No statistically significant differences were found in compression, tension, or shear strains with increasing drop jump height, but, at the 52 cm height, shear strain rate was reduced by one third (p = 0.03). No relation was found between peak compression strain and calculated drop jump energy, indicating that subjects were able to dissipate part of the potential energy of successively higher drop jumps by increasing the range of motion of their knee and ankle joints and not transmitting the energy to their tibia. No statistically significant differences were found between the principal strains during running and drop jumping from 52 cm, but compression (p = 0.01) and tension (p = 0.004) strain rates were significantly higher during running. CONCLUSIONS: High impact exercises, as represented by drop jumping in this experiment, do not cause higher tibial strains and strain rates than running and therefore are unlikely to place an athlete who is accustomed to fast running at higher risk for bone fatigue.

Adult↗
PubMed2000

In-vivo strain measurements to evaluate the strengthening potential of exercises on the tibial bone.

Mechanical loading during physical activity produces strains within bones. It is thought that these forces provide the stimulus for the adaptation of bone. Tibial strains and rates of strain were measured in vivo in six subjects during running, stationary bicycling, leg presses and stepping and were compared with those of walking, an activity which has been found to have only a minimal effect on bone mass. Running had a statistically significant higher principal tension, compression and shear strain and strain rates than walking. Stationary bicycling had significantly lower tension and shear strains than walking. If bone strains and/or strain rates higher than walking are needed for tibial bone strengthening, then running is an effective strengthening exercise for tibial bone.

Adult↗
PubMed1999

Prevention of stress fractures using custom biomechanical shoe orthoses.

In a prospective study of stress fractures the hypothesis that training with custom made biomechanical shoe orthoses could lessen the incidence of stress fractures in infantry recruits was tested. Recruits were assigned randomly to groups and given soft biomechanical orthoses or semirigid biomechanical orthoses and compared with a control group that did not train in biomechanical orthoses. All recruits wore infantry boots with soles designed like those of basketball shoes. Recruits were examined biweekly during 14 weeks of basic training. The incidence of stress fractures was 15.7% for the recruits with the semirigid biomechanical orthoses, 10.7% for the recruits with the soft biomechanical orthoses, and 27% for the control group. The soft biomechanical orthoses were tolerated better by the recruits than were the semirigid devices. Among trainees at high risk for stress fractures, prophylactic use of custom made biomechanical orthoses may be warranted.

Adult↗
PubMed1998

FRACAS: a system for computer-aided image-guided long bone fracture surgery.

This article describes FRACAS, a computer-integrated orthopedic system for assisting surgeons in performing closed medullary nailing of long bone fractures. FRACAS's goal is to reduce the surgeon's cumulative exposure to radiation and surgical complications associated with alignment and positioning errors of bone fragments, nail insertion, and distal screw locking. It replaces uncorrelated, static fluoroscopic images with a virtual reality display of three-dimensional bone models created from preoperative computed tomography and tracked intraoperatively in real time. Fluoroscopic images are used to register the bone models to the intraoperative situation and to verify that the registration is maintained. This article describes the system concept, software prototypes of preoperative modules (modeling, nail selection, and visualization), intraoperative modules (fluoroscopic image processing and tracking), and preliminary in vitro experimental results to date. Our experiments suggest that the modeling, nail selection, and visualization modules yield adequate results and that fluoroscopic image processing with submillimetric accuracy is practically feasible on clinical images.

Bone Nails↗
PubMed1998

A comparison of the effect of shoes on human tibial axial strains recorded during dynamic loading.

Percutaneous axial extensometers were mounted on the medial cortex of the midtibial diaphysis in seven male volunteers and the effect of three different shoes on in vivo peak-to-peak axial compression-tension strains measured during dynamic loading. Zohar shoes had lower axial strains and strain rates during treadmill walking than Nike Air Max running shoes or Israeli infantry boots. During running on a running track, there was no statistically significant difference between the axial strains or strain rates between the shoes tested. Shoe gear can modify tibial strains and strain rates that contribute to the development of tibial stress fractures.

Adult↗
PubMed1997

A method suitable for in vivo measurement of bone strain in humans.

Strain gages are the gold-standard for measurement of bone strains in vivo. The use of strain gages in humans, however, is limited by the need for surgery to implant them and by the use of cyanoacrylate adhesives to bond them to bone. Cyanoacrylate adhesives are not FDA approved for implantation in humans, making it difficult to justify their use in experimental procedures. To surmount this difficulty, a method was developed to bond strain gages to bone using an approved substance: polymethylmethacrylate (PMMA). The technique and the validating experiments are presented. The PMMA bonding method gave strain gage readings within an average of 0.25% (range 0-5%) of those found using cyanoacrylate bonding in a side by side comparison on cast acrylic. On bone, the PMMA bonding method produced results comparable to extensometer readings. This method of strain gage application is accurate and straightforward. It is currently being successfully used for in vivo strain measurements in both humans and animals for up to several days following gage application.

Biomechanical Phenomena↗
PubMed1996

In vivo measurement of human tibial strains during vigorous activity.

Our understanding of mechanical controls on bone remodeling comes from studies of animals with surgically implanted strain gages, but in vivo strain measurements have been made in a single human only once. That study showed that strains in the human tibia during walking and running are well below the fracture threshold. However, strains have never been monitored in vivo during vigorous activity in people, even though prolonged strenuous activity may be responsible for the occurrence of stress fractures. We hypothesized that strains > 3000 microstrain could be produced on the human tibial midshaft during vigorous activity. Strains were measured on the tibiae of two subjects via implanted strain gauges under conditions similar to those experienced by Israeli infantry recruits. Principal compressive and shear strains were greatest for uphill and downhill zigzag running, reaching nearly 2000 microstrain in some cases, about three times higher than recorded during walking. Strain rates were highest during sprinting and downhill running, reaching 0.050/sec. These results show that strain is maintained below 2000 microstrain even under conditions of strenuous activity. Strain rates are higher than previously recorded in human studies, but well within the range reported for running animals.

Analysis of Variance↗
PubMed1996

Anterior knee pain caused by overactivity: a long term prospective followup.

In a prospective study to determine the natural history of anterior knee pain caused by overactivity, 60 (15%) of 390 elite Israeli infantry recruits were found to have anterior pain in 77 knees during 14 weeks of basic training. At 6 years' followup, 3 years after returning to civilian life, half of the knees originally with anterior knee pain were still symptomatic, but in only 8% of the originally symptomatic knees was the pain severe, hindering physical activity. The long term prognosis of anterior knee pain caused by overactivity is much better than that reported previously for anterior knee pain in adolescents, but in a small percentage of cases the pain persists at a level that may prevent participation in exertional activities.

Adolescent↗