Kim L. Bennell

Risk Factors for Stress Fractures in Track and Field Athletes A Twelve-Month Prospective Study

The aim of this 12-month prospective study was to investigate risk factors for stress fractures in a cohort of 53 female and 58 male track and field athletes, aged 17 to 26 years. Total bone mineral content, regional bone density, and soft tissue composition were meas ured using dual-energy x-ray absorptiometry and an thropometric techniques. Menstrual characteristics, current dietary intake, and training were assessed us ing questionnaires. A clinical biomechanical assess ment was performed by a physical therapist. The inci dence of stress fractures during the study was 21.1%, with most injuries located in the tibia. Of the risk factors evaluated, none was able to predict the occurrence of stress fractures in men. However, in female athletes, significant risk factors included lower bone density, a history of menstrual disturbance, less lean mass in the lower limb, a discrepancy in leg length, and a lower fat diet. Multiple logistic regression revealed that age of menarche and calf girth were the best independent predictors of stress fractures in women. This bivariate model correctly assigned 80% of the female athletes into their respective stress fracture or nonstress frac ture groups. These results suggest that it may be pos sible to identify female athletes most at risk for this overuse bone injury.

Physical Therapy for Patellofemoral Pain A Randomized, Double-Blinded, Placebo-Controlled Trial

Background Although physical therapy forms the mainstay of nonoperative management for patellofemoral pain, its efficacy has not been established. Hypothesis Significantly more pain relief will be achieved from a 6-week regimen of physical therapy than from placebo treatment. Study Design Multicenter, randomized, double-blinded, placebo-controlled trial. Methods Seventy-one subjects, 40 years of age or younger with patellofemoral pain of 1 month or longer, were randomly allocated to a physical therapy or placebo group. A standardized treatment program consisted of six treatment sessions, once weekly. Physical therapy included quadriceps muscle retraining, patellofemoral joint mobilization, and patellar taping, and daily home exercises. The placebo treatment consisted of sham ultrasound, light application of a nontherapeutic gel, and placebo taping. Results Sixty-seven participants completed the trial. The physical therapy group (N = 33) demonstrated significantly greater reduction in the scores for average pain, worst pain, and disability than did the placebo group (N = 34). Conclusions A six-treatment, 6-week physical therapy regimen is efficacious for alleviation of patellofemoral pain.

Intra-rater and inter-rater reliability of a weight-bearing lunge measure of ankle dorsiflexion

This study aimed to evaluate the inter-rater and intra-rater reliability of a weight-bearing dorsiflexion (DF) lunge in 13 healthy subjects. Our raters with varying clinical experience tested all subjects in random order. Two of the raters repeated the measurements one week later. Two methods were used to assess the DF lunge: (i) the distance from the great toe to the wall and (ii) the angle between the tibial shaft and the vertical using an inclinometer. The average of three trials was used in data analysis. Intra-rater intraclass correlation coefficients (iccs) ranged from 0.97 to 0.98. Inter-rater ICC values were 0.97 (angle) and 0.99 (distance). results indicate excellent reliability for both methods of assessing a DF lunge.

The Incidence and Distribution of Stress Fractures in Competitive Track and Field Athletes A Twelve-Month Prospective Study

The incidence and distribution of stress fractures were evaluated prospectively over 12 months in 53 female and 58 male competitive track and field athletes (age range, 17 to 26 years). Twenty athletes sustained 26 stress fractures for an overall incidence rate of 21.1%. The incidence was 0.70 for the number of stress frac tures per 1000 hours of training. No differences were observed between male and female rates (P > 0.05). Twenty-six stress fractures composed 20% of the 130 musculoskeletal injuries sustained during the study. Although there was no difference in stress fracture incidence among athletes competing in different events (P > 0.05), sprints, hurdles, and jumps were associated with a significantly greater number of foot fractures; middle- and long-distance running were as sociated with a greater number of long bone and pelvic fractures (P < 0.05). Overall, the most common sites of bone injuries were the tibia with 12 injuries (46%), followed by the navicular with 4 injuries (15%), and the fibula with 3 injuries (12%). The high incidence of stress fractures in our study suggests that risk factors in track and field athletes should be identified.

Higher dynamic medial knee load predicts greater cartilage loss over 12 months in medial knee osteoarthritis

Objective Mechanical factors, in particular increased medial knee joint load, are believed to be important in the structural progression of knee osteoarthritis. This study evaluated the relationship of medial knee load during walking to indices of structural disease progression, measured on MRI, in people with medial knee osteoarthritis. Methods A longitudinal cohort design utilising a subset of participants (n=144, 72%) enrolled in a randomised controlled trial of lateral wedge insoles was employed. Medial knee load parameters including the peak knee adduction moment (KAM) and the KAM impulse were measured at baseline using three-dimensional gait analysis during walking. MRI at baseline and at 12 months was used to assess structural indices. Multiple regression with adjustment for covariates assessed the relationship between medial knee load parameters and the annual change in medial tibial cartilage volume. Binary logistic regression was used for the dichotomous variables of progression of medial tibiofemoral cartilage defects and bone marrow lesions (BML). Results A higher KAM impulse, but not peak KAM, at baseline was independently associated with greater loss of medial tibial cartilage volume over 12 months (β=29.9, 95% CI 6.3 to 53.5, p=0.01). No significant relationships were seen between medial knee load parameters and the progression of medial tibiofemoral cartilage defects or BML. Conclusion This study suggests knee loading, in particular the KAM impulse, may be a risk factor for loss of medial tibial cartilage volume. As knee load is modifiable, load-modifying treatments may potentially slow disease progression.

Risk Factors for Stress Fractures

Preventing stress fractures requires knowledge of the risk factors that predispose to this injury. The aetiology of stress fractures is multifactorial, but methodological limitations and expediency often lead to research study designs that evaluate individual risk factors. Intrinsic risk factors include mechanical factors such as bone density, skeletal alignment and body size and composition, physiological factors such as bone turnover rate, flexibility, and muscular strength and endurance, as well as hormonal and nutritional factors. Extrinsic risk factors include mechanical factors such as surface, footwear and external loading as well as physical training parameters. Psychological traits may also play a role in increasing stress fracture risk. Equally important to these types of analyses of individual risk factors is the integration of information to produce a composite picture of risk.The purpose of this paper is to critically appraise the existing literature by evaluating study design and quality, in order to provide a current synopsis of the known scientific information related to stress fracture risk factors. The literature is not fully complete with well conducted studies on this topic, but a great deal of information has accumulated over the past 20 years. Although stress fractures result from repeated loading, the exact contribution of training factors (volume, intensity, surface) has not been clearly established. From what we do know, menstrual disturbances, caloric restriction, lower bone density, muscle weakness and leg length differences are risk factors for stress fracture.Other time-honoured risk factors such as lower extremity alignment have not been shown to be causative even though anecdotal evidence indicates they are likely to play an important role in stress fracture pathogenesis.

Effectiveness of targeted falls prevention programme in subacute hospital setting: randomised controlled trial

Abstract Objective To assess the effectiveness of a targeted, multiple intervention falls prevention programme in reducing falls and injuries related to falls in a subacute hospital. Design Randomised controlled trial of a targeted multiple intervention programme implemented in addition to usual care compared with usual care alone. Setting Three subacute wards in a metropolitan hospital specialising in rehabilitation and care of elderly patients. Participants 626 men and women aged 38 to 99 years (average 80 years) were recruited from consecutive admissions to subacute hospital wards. Intervention Falls risk alert card with information brochure, exercise programme, education programme, and hip protectors. Main outcome measures Incidence rate of falls, injuries related to falls, and proportion of participants who experienced one or more falls during their stay in hospital. Results Participants in the intervention group (n = 310) experienced 30% fewer falls than participants in the control group (n = 316). This difference was significant (Peto log rank test P = 0.045) and was most obvious after 45 days of observation. In the intervention group there was a trend for a reduction in the proportion of participants who experienced falls (relative risk 0.78, 95% confidence interval 0.56 to 1.06) and 28% fewer falls resulted in injury (log rank test P = 0.20). Conclusions A targeted multiple intervention falls prevention programme reduces the incidence of falls in the subacute hospital setting.

Epidemiology and site specificity of stress fractures

Clinically, stress fractures appear to be a common overuse injury among athletes and in military recruits undertaking basic training; however, there is a lack of sound epidemiologic studies describing stress fracture occurrence in athletes. Few have directly compared stress fracture rates between sports to establish which poses the greatest risk for this injury. Furthermore, incidence rates, expressed in terms of exposure, have rarely been reported for stress fractures in athletes. Nevertheless, available data suggest that runners and ballet dancers are at relatively high risk for stress fractures. Although a gender difference in rates is clearly evident in military populations, this is less apparent in athletes. Other participant characteristics, such as age and race, may also influence stress fracture risk. The most common site of stress fracture in athletes is the tibia, although the site reflects the nature of the load applied to the skeleton. Stress fracture morbidity, expressed as the time until return to sport or activity, varies depending on the site. Generally, a period of 6 to 8 weeks is needed for healing; however, stress fractures at certain sites, such as the navicular and anterior tibial cortex, are often associated with protracted recovery and, in some cases, termination of sporting pursuits.

A systematic review of physical interventions for patellofemoral pain syndrome

ObjectivePhysical interventions (nonpharmacological and nonsurgical) are the mainstay of treatment for patellofemoral pain syndrome (PFPS). Physiotherapy is the most common of all physical interventions and includes specific vastus medialis obliquus or general quadriceps strengthening and/or realignment procedures (tape, brace, stretching). These treatments appear to be based on sound theoretical rationale and have attained widespread acceptance, but evidence for the efficacy of these interventions is not well established. This review will present the available evidence for physical interventions for PFPS. Data SourcesComputerized bibliographic databases (MEDLINE, Current Contents, CINAHL) were searched, including the keywords “patellofemoral,” “patella,” and “anterior knee pain,” combined with “treatment,” “rehabilitation,” and limited to clinical trials through October 2000. Study SelectionThe critical eligibility criteria used for inclusion were that the study be a controlled trial, that outcome assessments were adequately described, and that the treatment was a nonpharmacological, nonsurgical physical intervention. ResultsOf the 89 potentially relevant titles, 16 studies were reviewed and none of these fulfilled all of the requirements for a randomized, controlled trial. Physiotherapy interventions were evaluated in eight trials, and the remaining eight trials examined different physical interventions. Significant reductions in PFPS symptoms were found with a corrective foot orthosis and a progressive resistance brace, but there is no evidence to support the use of patellofemoral orthoses, acupuncture, low-level laser, chiropractic patellar mobilization, or patellar taping. Overall the physiotherapy interventions had significant beneficial effects but these interventions were not compared with a placebo control. There is inconclusive evidence to support the superiority of one physiotherapy intervention compared with others. ConclusionsThe evidence to support the use of physical interventions in the management of PFPS is limited. There appears to be a consistent improvement in short-term pain and function due to physiotherapy treatment, but comparison with a placebo group is required to determine efficacy, and further trials are warranted for the other interventions.

Bone mass and bone turnover in power athletes, endurance athletes, and controls: A 12-month longitudinal study

Strain magnitude may be more important than the number of loading cycles in controlling bone adaptation to loading. To test this hypothesis, we performed a 12 month longitudinal cohort study comparing bone mass and bone turnover in elite and subelite track and field athletes and less active controls. The cohort comprised 50 power athletes (sprinters, jumpers, hurdlers, multievent athletes; 23 women, 27 men), 61 endurance athletes (middle-distance runners, distance runners; 30 women, 31 men), and 55 nonathlete controls (28 women, 27 men) aged 17-26 years. Total bone mineral content (BMC), regional bone mineral density (BMD), and soft tissue composition were measured by dual-energy X-ray absorptiometry. Bone turnover was assessed by serum osteocalcin (human immunoradiometric assay) indicative of bone formation, and urinary pyridinium crosslinks (high-performance liquid chromatography) indicative of bone resorption. Questionnaires quantified menstrual, dietary and physical activity characteristics. Baseline results showed that power athletes had higher regional BMD at lower limb, lumbar spine, and upper limb sites compared with controls (p < 0.05). Endurance athletes had higher BMD than controls in lower limb sites only (p < 0.05). Maximal differences in BMD between athletes and controls were noted at sites loaded by exercise. Male and female power athletes had greater bone density at the lumbar spine than endurance athletes. Over the 12 months, both athletes and controls showed modest but significant increases in total body BMC and femur BMD (p < 0.001). Changes in bone density were independent of exercise status except at the lumbar spine. At this site, power athletes gained significantly more bone density than the other groups. Levels of bone formation were not elevated in athletes and levels of bone turnover were not predictive of subsequent changes in bone mass. Our results provide further support for the concept that bone response to mechanical loading depends upon the bone site and the mode of exercise.