Moshe Ayalon

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.

Isokinetic strength and endurance after percutaneous and open surgical repair of Achilles tendon ruptures.

Background: Reports on complete spontaneous Achilles tendon ruptures and associated treatment have become more frequent in the literature in the past two decades, as has the request for treatments that enable the finest possible functional recovery. The best available treatment is a matter of considerable controversy in the literature. The purpose of this study was to compare the isokinetic strength and endurance of the plantarflexor muscle-tendon unit in subjects who sustained rupture of the Achilles tendon and underwent either open surgery or closed percutaneous repair of the Achilles tendon. Methods: Twenty patients (18 males, 2 females) with spontaneous ruptures of the Achilles tendon were included in this study. Ten patients were treated by open surgery, and 10 patients were treated percutaneously. All patients had ruptured their Achilles tendon more than 6 months before the study, and all of the ruptures occurred 3.5 years or less before the day of the testing. All patients underwent an oriented physical examination. An isokinetic Biodex dynamometer (Biodex Medical System, Shirley, NY) was used to measure ankle joint angle, and in plantarflexion to calculate the torque at the ankle joint (Newton/meter), and the average work (jouls) for both maximal power and endurance. Each measurement was compared to the normal ankle. Results: Biodex dynamometer evaluations at 90 deg/sec demonstrated a significant difference of maximal voluntary plantarflexor torque, endurance performance and range of motion at the ankle joint between the involved and uninvolved sides in patients treated by either mode of treatment. Yet, no statistically significant differences were revealed for the parameters mentioned above between the subjects that were treated either percutaneously or by an open surgery. Conclusions: In functional terms, the biomechanical outcomes of open surgery and percutaneous repair for acute ruptures of the Achilles tendon are both effective.

Reliability of isokinetic strength measurements of the knee in children with cerebral palsy

This study evaluates the reliability of isokinetic testing of the knee flexors and extensors in children with cerebral palsy (CP). Twelve children (seven girls, five boys), aged 9 to 15 years, participated in this study. The childrens strength was measured bilaterally, using a dynamometer. Each participant was tested twice at an interval of 1 week. During each session, the participant performed five consecutive cycles of knee extension and flexion. Testing velocity was set at 90°/s, and the range of motion was 80°, starting with the knee flexed at 80° and ending in full extension. The measured variable was the peak torque. Reliabilities were determined using intraclass coefficient (ICC) with two‐way ANOVA model. The ICCs for individual sessions range from 0.90 to 0.99. ICCs for the eight repetitions over the two sessions range from 0.95 to 0.98. The findings indicate that measuring isokinetic strength in the tested population is highly reliable and should be considered in rehabilitation protocols.

‘The Multiple-Sit-to-Stand’ Field Test for Older Adults: What Does It Measure?

Background: The need to predict decline in functional status in a large number of older adults has brought researchers and clinicians to develop easy-to-administer field tests. One of them is the ‘multiple-sit-to-stand’ (MSTS), which claims to measure leg strength. Objective: To assess the extent to which the MSTS is a leg strength, leg endurance or general endurance test. Methods: 49 independently functioning women (72.2 ± 6.4 years) were assessed on the MSTS, on a submaximal stress test, and on strength and endurance of knee extensors measured by isokinetics. The knee extensors were selected, more than in other muscle groups responsible for movement of the lower extremity, as the largest range of motion, and the largest torques required while performing activities of daily living (ADL) is found in this group. Results: The correlation of the MSTS with the stress test was moderate and significant but very low and nonsignificant with the isokinetic measurements. Conclusions: The MTST is not able to predict strength of knee extensors, the leading group of leg muscles in ADL. If at all, it predicts general endurance rather than any measure – muscle strength or muscle endurance – of lower extremities. Longitudinal studies assessing the potential of the MSTS to predict deterioration in ADL in older adults are recommended, as well as studies assessing other factors related to both MSTS and ADL, such as muscle-nerve coordination affecting multiple joint activities.

Subtalar kinematics following resection of tarsal coalition.

Background: Pain relief and functional improvement in the short term have been demonstrated in the majority of patients with tarsal coalition following resection. Recreation of normal subtalar kinematics is an important goal in these patients as well, and may have long term implications. The purpose of our study was to examine whether kinematic variables of foot motion are normalized following resection of tarsal coalition. Materials and Methods: This study compared three groups: nine candidates for resection of tarsal coalition, nine patients between 2 and 4 years after bar resection, and nine control subjects. Ankle hindfoot scoring was evaluated according to the AOFAS. Kinematic analysis of subtalar motion in the coronal plane and in the sagittal plane was performed using a computerized gait analysis system. Results: Significantly increased passive subtalar range of motion and AOFAS ankle hindfoot scoring were demonstrated in postoperative subjects relative to preoperative subjects (p = 0.000). However, the kinematic analysis performed during walking, revealed similar, severe restriction of the subtalar eversion-inversion motion in postoperative and preoperative subjects. Angular velocity of the subtalar motion was also similar in both coalition groups, and was significantly increased compared with control. Kinematic analysis of foot motion in the sagittal plain demonstrated improved motion in postoperative subjects, which was comparable with the control group. Conclusion: Foot kinematics are not recreated following tarsal coalition resection, despite the favorable clinical outcome observed. Clinical Relevance: Following resection of a tarsal coalition, patients continue to be subjected to increased loading and torque in their subtalar and adjacent articulations. This may promote further articular deterioration in the long term. Additional operative procedures or rehabilitation protocols should be examined to improve foot kinematics in this population. Level of Evidence: III, Retrospective Case Control Study

Analysis of Foot Structure in Athletes Sustaining Proximal Fifth Metatarsal Stress Fracture

Background: In the past, several studies provided anecdotal descriptions of high-arched feet in individuals sustaining proximal fifth metatarsal stress fractures. This relationship has never been supported by scientific evidence. Our objective was to examine whether athletes who sustained this injury had an exceptional static foot structure or dynamic loading pattern. Materials and Methods: Ten injured professional soccer players who regained full professional activity following a unilateral proximal fifth metatarsal stress fracture and ten control soccer players were examined. Independent variables included static evaluation of foot and arch structure, followed by dynamic plantar foot pressure evaluation. Each variable was compared between injured, contra-lateral uninjured, and control feet. Results: Static measurements of foot and arch structure did not reveal differences among the groups. However, plantar pressure evaluation revealed relative unloading of the fourth metatarsal in injured and uninjured limbs of injured athletes compared with control, while the fifth metatarsal revealed pressure reduction only in the injured limbs of injured athletes. Conclusion: Athletes who sustained proximal fifth metatarsal stress fracture were not characterized by an exceptional static foot structure. Dynamically, lateral metatarsal unloading during stance may either play a role in the pathogenesis of the injury, or alternately represent an adaptive process. Clinical Relevance: Footwear fabrication for previously injured athletes should not categorically address cushioning properties designed for high-arch feet, but rather focus on individual dynamic evaluation of forefoot loading, with less attention applied to static foot and arch characteristics. Level of Evidence: III, Retrospective Comparative Study

Is there an ACE ID-ACTN3 R577X polymorphisms interaction that influences sprint performance?

Functional R577X (rs.1815739) and ID (rs.5186) polymorphisms in the alpha-actinin-3 ( ACTN3) and the angiotensin converting enzyme (ACE) genes, respectively, have been associated with sprint performance. The aim of this study was to determine their effect on sprint performance among 81 Israeli sprinters and 240 healthy controls. Results revealed that the ACE II genotype+ ACTN3 R allele (P=0.003 for sprinters vs. controls), and the ACTN3 RR genotype +ACE I allele (P=0.001 for sprinters vs. controls) might be the genotype for sprinters. In the whole cohort the probability of ACTN3 RR genotype+ ACE I allele being a sprinter (odds ratio 2.67, 95% confidence interval 1.45-4.93) and of ACE II genotype+ ACTN3 R allele being a sprinter (odds ratio 3.57, 95% confidence interval 1.78-7.15) was significantly higher than that in the controls. In conclusion, the above data suggest that ACE ID/ ACTN3 R577X genotype combination is associated with sprint ability. However, ACE ID/ ACTN3 R577X genotype combination is not related to the level of performance.

The role of foot pronation in the development of femoral and tibial stress fractures: a prospective biomechanical study.

Objective:To examine whether dynamic parameters of foot pronation are risk factors for the development of stress fractures of the femur and tibia. Design:Observational prospective study. Setting:Infantry basic training course. Participants:473 recruits evaluated for stress fractures of the femur and tibia every 2 weeks during 14 weeks of infantry basic training. The final analysis included 405 recruits. Assessment of Risk Factors:Two weeks before commencement of training, the recruits were evaluated during treadmill walking for their subtalar joint kinematics. Five independent variables were measured bilaterally: maximal pronation angle during the stance, pronation range of motion, time from heel strike to maximum pronation, pronation mean angular velocity, and time to maximum pronation as a percent of the total stance time. Main Outcome Measurements:Stress fractures of the femur and tibia. These were considered positive only when proven by imaging. Results:Ten percent of the participants were diagnosed with stress fractures of the femur and tibia. Recruits with longer duration of foot pronation had reduced odds ratio to develop this injury. Conclusions and Clinical Relevance:Longer duration of foot pronation may have a protective effect from stress fractures of the femur and tibia. This finding may promote the understanding of stress fracture pathomechanism, assist in the identification of subjects with increased risk who need augmented monitoring throughout training, and assist in future planning of impact reducing aids.

Is the interaction between HIF1A P582S and ACTN3 R577X determinant for power/sprint performance?

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that regulates gene expression in response to hypoxia and has been associated with athletic performance. The aims of this study were (1) to determine the frequency distribution of HIF1A Pro582Ser (rs11549465) polymorphism among 155 Israeli athletes (sprinters and endurance athletes) and 240 healthy controls and (2) to analyze the influence of the interaction between HIF1A Pro582Ser and ACTN3 R577X (rs1815739) genotypes on sprint performance. There were no differences across the HIF1A genotype and allele frequencies among endurance athletes, sprinters, and controls. Similarly, no differences were found between the subgroups of top-level and national-level endurance athletes, or between top-level and national-level sprinters. Conversely, interaction effects were found between HIF1A Pro582Ser and ACTN3 R577X polymorphisms and sprinters. The proportion of HIF1A Pro/Pro + ACTN3 R/R genotypes was significantly higher in sprinters than in endurance athletes and healthy controls (P = .002). In addition, the odds ratio for HIF1A Pro/Pro + ACTN3 R/R genotype carriers being a sprinter was 2.25 (95% confidence interval, 1.24-4.1); and that for HIF1A Pro/Pro + ACTN3 R/R genotype carriers being an endurance athlete was 0.5 (95% confidence interval, 0.2-1.24). We conclude that HIF1A Pro582Ser polymorphism by itself is not critical in determining sprint performance. However, sprinter performance is determined by the interaction between the wild-type HIF1A Pro/Pro genotype and ACTN3 RR genotype.

Plantar pressure distribution in patients with Muller-Weiss disease

Background: Müller-Weiss disease (MWD) is a rare pathological entity of unclear etiology that occurs in middle aged individuals and is characterized by midfoot pain and typical radiographic findings of navicular compression between the talar head and lateral cuneiform. Pes planovarus is a hallmark of advanced disease. The purpose of this study was to characterize the plantar pressure distribution in patients with this diagnosis. Methods: Eight symptomatic feet in six patients with MWD, between the ages of 40 and 60 years, were compared to 18 feet of nine normal individuals. Midfoot scores were recorded according to the American Orthopaedic Foot and Ankle Society scale. Radiographic staging of navicular fragmentation and talar head displacement was done according to the Meary-Tomeno lines. Plantar pressure was measured during walking on a level floor at a natural preferred cadence. All subjects used the same shoe model, and plantar pressure data were collected over four cycles. For each step, the mean pressure and mean normalized pressure impulse were calculated for each of 10 foot zones. The mean of the four steps was computed for comparison between groups. Statistical analysis was performed using a t-test, and the level of significance was set at 0.05. Results: All patients with MWD had advanced radiographic characteristics, and their midfoot scores did not exceed 47 points. Plantar pressure measurements demonstrated significantly higher values (p < 0.05) in the midfoot segments of patients with MWD than the control group, while significantly lower values (p < 0.01) were recorded in the toe segments. Conclusions: Müller-Weiss disease is characterized by increased plantar pressures at the midfoot, combined with reduction in toe pressures. This abnormal pressure distribution may be at least partially responsible for patients’ pain and discomfort. Considering these foot characteristics in treatment plans may help choose appropriate nonoperative treatment (i.e. insoles, arch support, hard platform shoes), as well as operative alternatives (appropriate fusion procedures).