Effects of unilateral strength training and detraining on bone mineral density and content in young women: a study of mechanical loading and deloading on human bones

Detraining among Athletes-Is Withdrawal of Adaptive Cardiovascular Changes a Hint for the Differential Diagnosis of Physically Active People?

An athlete's training aims to achieve the highest possible sports results by improving physical dispositions which lead to cardiac adaptive changes. The annual training cycle is divided into periods. The preparatory period begins with gradually increasing training intensity and volume until the competitive period occurs, when the athlete's maximum performance is expected. Finally, the athlete enters a phase of loss of fitness, which is called detraining. Detraining is a time of resting both physically and mentally from the training regime and usually lasts about 4 weeks for endurance athletes. We collected data from much research on athletes' detraining. According to these data, the earliest change after detraining seems to be a decrease in left ventricular wall thickness and left ventricular mass, followed by decreased performance parameters, diastolic diameter of the left ventricle and size of the left atrium. A reversal of adaptive changes affects the left heart chamber first, then the right atrium and, finally, the right ventricle. Training reduction is often proposed as a method of differentiating an athlete's heart from cardiomyopathies. The aim of this study is to consider the diagnostic value of detraining in differentiating athletes' hearts from cardiomyopathies. We suggest that detraining cannot be conclusive in differentiating the disease from adaptive changes. Although a withdrawal of the characteristic morphological, functional and electrocardiographic changes occurs in healthy athletes during detraining, it can also concern individuals with cardiomyopathies due to the lower expression of abnormal features after decreased training loads. Therefore, a quick diagnosis and individual assessments using imaging and genetic tests are essential to recommend a proper type of activity.

Position Statement: Exercise Guidelines for Osteoporosis Management and Fall Prevention in Osteoporosis Patients

BACKGROUND

The effectiveness of exercise for improving osteoporosis and fall prevention in patients diagnosed with osteoporosis or osteopenia has not been fully summarized. The Korean Society for Bone and Mineral Research and the Korean Society of Exercise Physiology has developed exercise guidelines for patients with osteoporosis or osteopenia and provide evidence-based recommendations.

METHODS

A systematic review identified randomized controlled trials (RCT) assessing the effect of resistance, impact, balance, aerobic training, and physical activity in osteoporosis and osteopenia on bone quality, physical performance, quality of life, and fall prevention. PubMed, Embase, KoreaMed, and RISS were searched from January 2000 to August 2022. Ten key questions were established to review the evidence and formulate recommendations.

RESULTS

The 50 RCTs reported that even with osteoporosis and osteopenia, resistance and impact training consistently maximized bone strength, improved body strength and balance, and eventually reduced fall incidences. Resistance exercise combining 3 to 10 types of free weight and mechanical exercise of major muscle groups performed with an intensity of 50% to 85% 1-repetition maximum, 5 to 12 repetitions/set, 2 to 3 days/week, for 3 to 12 months is recommended. Impact exercises such as jumping chin-ups with drop landings and jump rope performed 50 jumps/session for at least 6 months with 3 or more days/week are recommended.

CONCLUSIONS

A multi-component exercise mainly comprised of resistance and impact exercise seems to be an effective strategy to attenuate the risk factors of osteoporosis and osteopenia. The integration of exercise guidelines and individualized exercise plans has significant potential to reduce the morbidity and mortality of osteoporosis.

Effect of 6-month high-impact step aerobics and resistance training on BMD and tibial bending strength in sedentary premenopausal women

The rationale of this study was to examine the effectiveness of 6-month high-impact step aerobics (SA) or moderate-intensity resistance training exercise (RT) on bone mineral density (BMD) and bone bending strength in sedentary women. Results show that SA enhanced BMD in the heel, lower leg, and lumbar spine 2.

INTRODUCTION

To determine the effectiveness of 6 months of high-impact step aerobics (SA) or moderate-intensity resistance training (RT) on areal bone mineral density (aBMD) and tibial bending strength in sedentary premenopausal women.

METHODS

Sixty-nine women (20-35 years old) who were randomly assigned to RT (n = 22), SA (n = 26), or non-treatment control (CON, n = 21) groups completed the study. SA had a minimum of 50 high-impact landings each training session. RT had a periodized lower body resistance training program incorporating eight exercises (65-85% of 1 repetition maximum: 1-RM). Both RT and SA met 3 times weekly. aBMD was assessed using dual X-ray absorptiometry (DXA). Tibial bending strength was assessed using mechanical response tissue analysis (MRTA). Measurements at 6 months were compared to baseline using ANCOVA, adjusted for baseline measures and covariates with α = 0.05.

RESULTS

Calcaneus aBMD (0.0176 vs -0.0019 or -0.0009 g/cm² relative to RT, p < 0.004, and CON, p < 0.006, respectively), lower leg aBMD (0.0105 vs -0.0036 g/cm², relative to RT, p = 0.02), and lumbar spine 2 (L2) aBMD (0.0082 vs -0.0157 g/cm² relative to CON, p < 0.02) were significantly greater in the SA group after 6 months. Tibial bending strength and bone resorption biomarkers were unchanged in all three groups after 6 months.

CONCLUSION

Sedentary premenopausal women engaging in 6 months of high-impact aerobic exercise improved aBMD in the calcaneus, lower leg, and L2.

Detraining Effects on Musculoskeletal Parameters in Early Postmenopausal Osteopenic Women: 3-Month Follow-Up of the Randomized Controlled ACTLIFE Study

Periods of absence from supervised group exercise while maintaining physical activity might be a frequent pattern in adults' exercise habits. The aim of the present study was to determine detraining effects on musculoskeletal outcomes after a 3-month detraining period in early post-menopausal, osteopenic women. Due to the COVID-19 pandemic, we terminated the 18-month randomized controlled ACTLIFE exercise intervention immediately after the 13-month follow-up assessment. This put an abrupt stop to the high-intensity aerobic and resistance group exercise sessions undertaken three times per week by the exercise group (EG: n = 27) and the gentle exercise program performed once per week for the attention control group (CG: n = 27); but both groups were permitted to conduct individual outdoor activity for the 3-month lock-down period. Study endpoints were lean body mass (LBM), bone mineral density (BMD) at the lumbar spine (LS), maximum hip-/leg extension strength and power. Detraining-induced reductions of LBM, hip/leg strength and power (but not BMD-LS) were significantly greater (p < 0.001 to p = 0.044) compared with the CG. Significant exercise effects, i.e. differences between EG and CG, present after 13 months of exercise, were lost after 3 months of detraining for LBM (p = 0.157) and BMD-LS (p = 0.065), but not for strength (p < 0.001) and power (p < 0.001). Of note, self-reported individual outdoor activities and exercise increased by about 40% in both groups during the lock-down period. Three months' absence from a supervised group exercise protocol resulted in considerable detraining effects for musculoskeletal parameters. Thus, exercise programs for adults should be continuous rather than intermittent.Trial registration number: ClinicalTrials.gov: NCT04420806, 06.05.2020.

Body composition in professional female netball players within and between seasons: a cohort study

Background

There is limited information on the physique attributes of female netball players from the highest playing standards and the typical body composition changes that occur with training and competition in these athletes. The purpose of this study was to examine the body composition of professional female netball players and changes that occur within and between national premier netball seasons.

Methods

Dual-energy X-ray absorptiometry (DXA) assessments were conducted in 20 female netball players (age = 26.5 [4.7] years, body mass = 77.3 [9.7] kg, stature = 182.7 [9.5] cm) contracted to a Suncorp Super Netball team. Total body lean mass, fat mass, bone mass and bone mineral density were derived for 127 assessments collected over three seasons. Linear mixed effects modelling was used to examine changes in body composition measures within and between seasons.

Results

Goal circle players were heavier (12.3 [3.5] kg, p < 0.001, g = 1.51) and taller (15.0 [2.7] cm, p < 0.001, g = 2.30) than midcourt players, and midcourt players had greater lean mass (3.1 [1.6] %, p = 0.07, g = 0.85) and less fat mass (-3.3 [1.7] %, p = 0.06, g = -0.84) than goal circle players when values were normalised to body mass. Players achieved increases in lean mass (2,191 [263] g, p < 0.01, g = 0.45) and decreases in fat mass (-835 [351] g, p = 0.09, g = -0.16) following a preseason preparation period. There were no changes in lean mass (-394 [295] g, p = 0.54, g = 0.07) or fat mass (102 [389] g, p = 0.99, g = 0.04) from the start to the end of the 14-week competition period.

Conclusions

Professional female netball players achieve small changes in lean mass and fat mass during preseason preparation and maintain their physique over the competitive season. The results of this study can inform practitioners on the training content necessary to promote or maintain desired body composition changes in these athletes.

Detraining effects after 18 months of high intensity resistance training on osteosarcopenia in older men-Six-month follow-up of the randomized controlled Franconian Osteopenia and Sarcopenia Trial (FrOST)

PURPOSE

Detraining after dedicated exercise programs might be a frequent situation in older people's exercise patterns. The aim of the present study was thus to determine the effects of 6 months of detraining after 18 months of high intensity resistance exercise (HIT-RT) on musculoskeletal outcomes in older men with sarcopenia.

METHODS

Community-dwelling men aged 72 years and older with osteosarcopenia (n = 43) were randomly assigned to an 18-month HIT-RT (EG: n = 21) or a non-training control group (CG, n = 22). After the intervention, participants of the EG stopped HIT-RT for 6 months, but continued their habitual physical activity. Study outcomes were skeletal muscle mass index, bone mineral density (BMD) at the lumbar-spine and total-hip, maximum hip/leg-extensor strength, handgrip strength and gait velocity. We applied an intention-to-treat analysis with multiple imputation.

RESULTS

Changes in the HIT-RT were much more pronounced during the detraining period compared with the CG, although this effect was only significant for skeletal muscle mass index and hip-/leg-extensor strength (p = .002 and p = .013), but not for lumbar-spine BMD (p = .068), total-hip BMD (p = .069), handgrip strength (p = .066) or gait velocity (p = .067). Apart from total-hip BMD (p = .055), handgrip strength (p = .069) and gait velocity (p = .881) values of the HIT-RT group decreased significantly during detraining. However, after 24 months, overall effects (p < .001) were still observed for skeletal muscle mass index and hip-/leg-extensor strength.

CONCLUSION

Although unable to state from which point in time relevant detraining effects emerge, we conclude that health care providers should focus on continuous rather than intermitted exercise programs for older people. Clinical trial number: clinicalTrials.gov: NCT03453463; NCT04444661.

Regional changes in indices of bone strength of upper and lower limbs in response to high-intensity impact loading or high-intensity resistance training

It is well known that the bone response to physical activity is highly dependent on the nature of the loads imposed. Despite this, few direct comparisons of the effect of impact-style loading and resistance training on bone have been made. We therefore aimed to compare the effects of 10-month, twice-weekly, high-impact loading and 10-month, twice-weekly, high-intensity resistance training on indices of bone strength of both the upper and lower limbs of young adult women. Physically inactive, otherwise healthy, young adult women (18-30 years) with below average bone mass (T-score ≤ 0) were recruited as part of the OPTIMA-Ex trial. Testing included DXA- and pQCT-derived measures of bone mass and indices of bone strength and QUS-derived measures of bone quality of the dominant (D) and non-dominant (ND) upper (radius) and lower limbs (femoral neck, tibia, calcaneus). The present study examined those participants who completed the impact training (IT; n = 10) and resistance training (RT; n = 12) arms of the trial. Age differed between groups at baseline (IT = 23.2 ± 3.8 years, RT = 20.5 ± 1.8 years; p = 0.042). Compliance with the training programs did not differ (IT = 61.4 ± 15.1%, RT = 66.4 ± 11.2%, p = 0.381). Age and baseline differences in bone outcomes served as covariates for repeated measures and univariate ANCOVA conducted for dependent variables and percent change respectively. IT improved distal pQCT-derived bone mineral density (BMD) of the upper limb (ND radius: total BMD = 8.55 ± 2.26% versus 1.50 ± 2.04%, p = 0.040 and trabecular BMD = 1.86 ± 0.90% versus -1.30 ± 0.81%, p = 0.029) and lower limb (ND tibia trabecular BMD = 1.22 ± 0.55% versus -0.82 ± 0.50%, p = 0.017), more than RT. IT also improved upper limb bone strength index (BSI) (ND radius total BSI = 15.35 ± 2.83% versus 2.67 ± 2.55, p = 0.005) and lower limb BSI (D tibia total BSI = 5.16 ± 1.13% versus 0.37 ± 1.02%, p = 0.008; D tibia trabecular BSI = 3.93 ± 1.76% versus -2.84 ± 1.59, p = 0.014, ND tibia trabecular BSI = 3.57 ± 1.63% versus -3.15 ± 1.48%, p = 0.009) more than RT. Conversely, RT improved DXA-derived cortical volumetric BMD at the femoral neck more than IT (3.68 ± 1.99% versus -4.14 ± 2.20%, p = 0.021). Results suggest that IT and RT provide differing site-specific effects in both the upper and lower limbs, with superior bone responses observed at the distal segment from IT, while RT appeared to have greater effect on the shaft of the bone, on indices of bone-strength in young adult women.

The Assessment of the Supply of Calcium and Vitamin D in the Diet of Women Regularly Practicing Sport

INTRODUCTION

The appropriate intake of calcium and vitamin D in women's diet is significant for a proper maintenance of the skeletal system.

RESEARCH AIM

The aim of the research was to assess the calcium and vitamin D supply in a diet among women regularly practicing sport.

METHODOLOGY

The research was completed by 593 women at the age of 18-50 (median 25) who played sports regularly (at least 2 times a week). To assess the calcium and vitamin D intake, short Food Frequency Questionnaires for calcium and vitamin D (VIDEO-FFQ) were used. The examined group was provided with the questionnaires via social media. To assess intake levels, the authors applied the group-based cutoff point method (calcium norm was EAR 800 mg/day; vitamin D norm was AI 15 μg/day).

RESULTS

The median of calcium and vitamin D intake in a diet was 502 mg/day and 5.2 μg/day, respectively (Q25 and Q75 for calcium was 387 mg/day and 627 mg/day, respectively, and for vitamin D was 3.4 μg/day and 8.2 μg/day, respectively). In relation to the EAR norm for calcium and AI norm for vitamin D, 92.0% of the examined participants in a group demonstrated lower than recommended calcium intake levels and 97.3% showed lower than recommended vitamin D intake levels. Calcium and vitamin D supplementation was used by 13.1% (in this subgroup, 11.5% of the examined group members did not need it) and 56.8% of the examined women (in this subgroup, 2.4% of the examined group did not need it), respectively. After including the calcium and vitamin D intake, the supply median for the whole group was 535 mg/day and 28.8 μg/day, respectively (Q25 and Q75 for calcium was 402 mg/day and 671 mg/day, and for vitamin D was 6.3 µg/day and 55.7 μg/day, respectively); 87.5% of the examined participants did not meet the EAR norms for calcium and 42.0% did not meet the AI norm for vitamin D. Among the women supplementing calcium, 58.9% did not reach the reference intake value; however, all women supplementing vitamin D fulfilled the expected nutritional need.

CONCLUSIONS

It is important to educate women about the necessity to provide the body with proper calcium and vitamin D intake levels in a diet in order to avoid health problems resulting from the deficit of the nutrients.

Resorbable screw and sheath versus resorbable interference screw and staples for ACL reconstruction: a comparison of two tibial fixation methods

PURPOSE

The anterior cruciate ligament (ACL) reconstruction is one of the most performed and successful orthopaedic procedures. The results are considered independent by the choice of the graft and the fixation devices. A growing interest on resorbable non-metallic fixation devices versus standard metallic fixation devices has been noted over recent years with few clinical experiences reported in the literature. The aim of this study is to compare the clinical and radiological outcomes of patients undergoing ACL reconstruction using autologous hamstring tendons with tibial fixation by a centrally placed resorbable screw and sheath to a combination of an eccentrically placed resorbable interference screw and supplementary staple fixation.

METHODS

Ninety patients undergoing an isolated, single-bundle, primary ACL reconstruction with autologous hamstring tendons, using the same femoral fixation, were randomized to a tibial fixation with a centrally placed resorbable screw and sheath, BioIntrafix (group A), or an eccentrically placed resorbable interference screw, BioRCI, and two non-resorbable staples (group B). The latter has represented for many years our standard fixation method. Clinical evaluations (KOOS, IKDC, KT-2000™ side-to-side difference) and radiological analyses were conducted in both groups with a minimum follow-up of 2 years.

RESULTS

We assisted in a satisfactory pain relief and functional improvements, without significant clinical and radiological differences in both groups. No further surgery was needed in patients with the screw/sheath tibial fixation. Seven patients with the screw/staples tibial fixation needed the surgical removal of the fixation devices due to pes anserinus irritation or local infection years after the index operation. Other parameters such as the tunnel enlargement were not statistically different in the two groups.

CONCLUSIONS

Good clinical and radiological outcomes of ACL reconstruction by a screw/sheath tibial fixation have been reported showing comparable results with respect to screw/staples fixation. There were no failures associated with loss of fixation with either of tibial fixation methods. A fewer number of surgical removals of tibial devices were also recorded in patients treated by the screw/sheath fixation system, related to the absence of local intolerance or infection compared to subjects with a standard tibial fixation.

Hybrid Tibia Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction: A Systematic Review

BACKGROUND

Optimal fixation of soft tissue grafts in anterior cruciate ligament (ACL) reconstruction remains a controversial topic, and tibial-sided fixation is frequently cited as the "weak point" of the femur-graft-tibia construct. Some studies have recommended the use of hybrid fixation (combining intratunnel aperture fixation and extracortical suspensory fixation) on the tibial side to increase the strength of the reconstructed ACL and decrease the risk of graft slippage and subsequent failure. However, no consensus has emerged on the necessity or suitability of this technique, relative to single modes of fixation.

PURPOSE

This study sought answers to the following questions: (1) Does hybrid fixation result in stronger, stiffer initial fixation of soft tissue grafts? (2) Does hybrid fixation reduce side-to-side laxity differences in clinical practice? (3) Does hybrid fixation increase complication rates when compared with a single mode of tibial fixation?

STUDY DESIGN

Systematic review.

METHODS

A systematic keyword search of PubMed, EMBASE, the Cochrane Library of Systematic Reviews, and the PROSPERO International Prospective Register of Systematic Reviews was performed. Candidate articles were included if they compared biomechanical or clinical characteristics of tibial-sided hybrid fixation (defined as a combination of aperture and suspensory fixation methods) with single-mode fixation of soft tissue grafts in ACL reconstruction.

RESULTS

A total of 21 studies (15 biomechanical, 6 clinical) met criteria for inclusion. Most biomechanical studies reported significantly increased strength and stiffness with hybrid fixation versus single modes of fixation. Among clinical studies, 66% reported significantly decreased anterior-posterior laxity when hybrid fixation methods were employed, with the remainder showing no difference.

CONCLUSION

Hybrid methods of tibial-sided graft fixation in ACL reconstruction result in stronger initial fixation and less side-to-side laxity after healing but do not change patient-reported outcomes at 1- to 3-year follow-up.

REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews No. 42014015464.

Relationship of body composition, knee extensor strength, and standing balance to lumbar bone mineral density in postmenopausal females

[Purpose] This study aimed to investigate correlations between lumbar bone mineral density (BMD) and general characteristics of postmenopausal females, including body composition, knee extensor strength, standing balance, and femur BMD. [Subjects and Methods] A total of 40 postmenopausal females (55.6 ± 4.6 years) who were caregivers or guardians of patients in the K hospital were included in the study. The weight, height, body composition, left and right knee extensor strength, standing balance, femur BMD, and lumbar BMD measurements of the subjects were obtained. [Results] The effect of measurement variables on lumbar BMD was examined. Increases in age and menopausal duration were observed to significantly increase lumbar BMD, whereas an increase in height was found to significantly decrease lumbar BMD. An increase in soft lean mass, skeletal muscle mass, fat-free mass, and femur BMD was also associated with significantly decreased lumbar BMD. [Conclusion] Age, menopausal duration, soft lean mass, skeletal muscle mass, and fat-free mass were factors that decreased lumbar BMD in menopausal females. This study is expected to provide basic knowledge for osteoporosis prevention and treatment programs for postmenopausal females.

Early-phase musculoskeletal adaptations to different levels of eccentric resistance after 8 weeks of lower body training

PURPOSE

Eccentric muscle actions are important to the development of muscle mass and strength and may affect bone mineral density (BMD). This study's purpose was to determine the relative effectiveness of five different eccentric:concentric load ratios to increase musculoskeletal parameters during early adaptations to resistance training.

METHODS

Forty male subjects performed a supine leg press and calf press training program 3 days week(-1) for 8 weeks. Subjects were matched for pre-training leg press 1-repetition maximum strength (1-RM) and randomly assigned to one of five training groups. Concentric training load (% 1-RM) was constant across groups, but within groups, eccentric load was 0, 33, 66, 100, or 138% of concentric load. Muscle mass (dual energy X-ray absorptiometry; DXA), strength (1-RM), and BMD (DXA) were measured pre- and post-training. Markers of bone metabolism were assessed pre-, mid- and post-training.

RESULTS

The increase in leg press 1-RM in the 138% group (20 ± 4%) was significantly greater (P < 0.05) than the 0% (8 ± 3%), 33% (8 ± 5%) and 66% (8 ± 4%) groups, but not the 100% group (13 ± 6 %; P = 0.15). All groups, except the 0% group, increased calf press 1-RM (P < 0.05). Leg lean mass and greater trochanter BMD were increased only in the 138% group (P < 0.05).

CONCLUSIONS

Early-phase adaptations to eccentric overload training include increases in muscle mass and site-specific increases in BMD and muscle strength which are not present or are less with traditional and eccentric underload training. Eccentric overload provides a robust musculoskeletal stimulus that may benefit bedridden patients, individuals recovering from injury or illness, and astronauts during spaceflight.

Comparison of bioabsorbable suture anchor fixation on the tibial side for anterior cruciate ligament reconstruction using free soft tissue graft: experimental laboratory study on porcine bone

PURPOSE

The use of graft tissue fixation using bioabsorbable interference screws (BISs) in anterior cruciate ligament (ACL) reconstruction offers various advantages, but limited pullout strength. Therefore, additional tibial fixation is essential for aggressive rehabilitation. We hypothesized that additional graft tissue fixation using bioabsorbable suture anchors (BSA) would provide sufficient pull-out strength.

MATERIALS AND METHODS

Twenty four fresh frozen porcine distal femur and patellar tendon preparations were used. All specimens were divided into three groups based on additional fixation methods: A, isolated BIS; B, BIS and BSA; and C, BIS and post cortical screw. Tensile testing was carried out under an axial load. Ultimate failure load and ultimate failure load after cyclic loading were recorded.

RESULTS

The ultimate failure loads after load to failure testing were 166.8 N in group A, 536.4 N in group B, and 438 N in group C; meanwhile, the ultimate failure loads after load to failure testing with cyclic loading were 140 N in group A, 466.5 N in group B, and 400 N in group C. Stiffness after load to failure testing was 16.5 N/mm in group A, 33.5 N/mm in group B, and 40 N/mm in group C. An additional BSA fixation resulted in a significantly higher ultimate failure load and stiffness than isolated BIS fixation, similar to post screw fixation.

CONCLUSION

Additional fixation using a BSA provided sufficient pullout strength for ACL reconstruction. The ultimate failure load of the BSA technique was similar to that of post cortical screws.

Asymmetrical hip bone density in multiple sclerosis

As multiple sclerosis (MS) may affect one leg more than the other, we predicted that bone mineral density (BMD) would be lower in the limb self-identified as more affected. Therefore, the purpose of this study was to determine whether ambulatory individuals with MS displaying moderate-to-severe lower-extremity paresis exhibit asymmetrical femoral neck BMD. Dual-energy x-ray absorptiometry was used to assess proximal femoral neck BMD. Lower BMD was observed in the proximal femoral neck of the more paretic limb (P = .001) in a group (N = 23) of ambulatory individuals with relapsing-remitting MS (RRMS). Our preliminary findings suggest that bilateral hip screening may be important in the early detection of compromised bone health in ambulatory individuals with RRMS. Further research is warranted to fully characterize the factors and mechanisms associated with bone loss and identify effective strategies for optimizing bone health in people with MS.

Beneficial effects of judo training on bone mineral density of high-school boys in Korea

Bone mineralization is strongly stimulated by weight-bearing exercise during growth and development. Judo, an Olympic combat sport, is a well-known form of strenuous and weight-bearing physical activity. Therefore, the primary goal of this study was to determine the effects of Judo practice on the bone health of male high school students in Korea. The secondary goal of this study was to measure and compare the bone mineral density (BMD) of the hands of Judo players and sedentary control subjects. Thirty Judo players (JDP) and 30 sedentary high school boys (CON) voluntarily participated in the present study, and all of the sedentary control subjects were individually matched to the Judo players by body weight. BMD was determined by using dual-energy X-ray absorptiometry (Hologic, Bedford, MA, USA). The lumbar spine, femur and forearm BMD in the JDP group were significantly greater by 22.7%, 24.5%, and 18.3%, respectively, than those in the CON group. In addition, a significant difference in the CON group was observed between the dominant hand (DH) radius (0.710 ± 0.074 g/cm(2)) and the non-dominant hand (NDH) radius (0.683 ± 0.072 g/cm(2)), but this was not observed in the JDP group (DH = 0.819 ± 0.055 g/cm(2); NDH = 810 ± 0.066 g/cm(2)) (P < 0.05). Therefore, the results of this study suggest that Judo practice during the growth period significantly improves bone health in high school male students. In addition, it seems that Judo practice could eliminate the effect of increased BMD in the dominant hand.

Effectiveness of low-profile supplemental fixation in anterior cruciate ligament reconstructions with decreased bone mineral density

PURPOSE

The purpose of this study was to compare anterior cruciate ligament (ACL) fixation using a bioabsorbable interference screw (BIS) and a supplemental low-profile suture anchor (PushLock 4.5-mm polyetheretherketone anchor; Arthrex, Naples, FL) with a standard BIS fixation to determine if fixation methods were dependent on tibial bone mineral density (BMD).

METHODS

Ten matched pairs of fresh-frozen human female knee specimens (20 total) were harvested with specimen ages ranging from 40 to 65 years. The BMD for each specimen was determined with a dual-energy x-ray absorptiometry scanner. The specimens were divided into 2 groups, 1 with a BIS and the other with a BIS plus a PushLock. Tibial-sided ACL fixation with hamstring tendon grafts was performed on all the specimens. Then, load to failure and stiffness were biomechanically tested.

RESULTS

The BIS-plus-PushLock specimens had a significantly higher mean yield load compared with specimens with the BIS alone (702 N v 517 N, P = .047). However, in samples with lower bone density, there was no statistically significant difference in failure loads between fixation techniques (P = .8566 at BMD of 0.5 g/cm(2)). As the bone density of the samples increased, the failure loads increased for both techniques (P < .0001 for PushLock and P = .0057 for BIS). This BMD-associated increase was greater for the PushLock (P = .0148), resulting in a statistically significant difference in failure load at the upper range tested (P = .0293 at BMD of 0.9 g/cm(2)).

CONCLUSIONS

Supplemental fixation of ACL reconstructions with a PushLock is beneficial in persons with a normal BMD of the proximal tibia, but at a lower BMD, there was no difference in our study.

CLINICAL RELEVANCE

Individuals with normal BMDs may benefit from this supplemental fixation. However, caution should be used in postmenopausal women or individuals with chronic ACL injuries when using this fixation strategy.

Measurement of bone mineral density in the tunnel regions for anterior cruciate ligament reconstruction by dual-energy X-ray absorptiometry, computed tomography scan, and the immersion technique based on Archimedes' principle

PURPOSE

To determine, for anterior cruciate ligament (ACL) reconstruction, whether the bone mineral density (BMD) of the femoral tunnel was higher than that of the tibial tunnel, to provide objective evidence for choosing the appropriate diameter of interference screws.

METHODS

Two groups were enrolled. One group comprised 30 normal volunteers, and the other comprised 9 patients with ACL rupture. Dual-energy X-ray absorptiometry was used to measure the BMD of the femoral and tibial tunnel regions of the volunteers' right knees by choosing a circular area covering the screw fixation region. The knees were also scanned by spiral computed tomography (CT), and the 3-dimensional reconstruction technique was used to determine the circular sections passing through the longitudinal axis of the femoral and tibial tunnels. Grayscale CT values of the cross-sectional area were measured. Cylindrical cancellous bone blocks were removed from the femoral and tibial tunnels during the ACL reconstruction for the patients. The volumetric BMD of the bone blocks was measured using a standardized immersion technique according to Archimedes' principle.

RESULTS

As measured by dual-energy X-ray absorptiometry, the BMD of the femoral and tibial tunnel regions was 1.162 ± 0.034 g/cm(2) and 0.814 ± 0.038 g/cm(2), respectively (P < .01). The CT value of the femoral tunnel region was 211.7 ± 11.5 Hounsfield units, and the value of the tibial tunnel region was 104.9 ± 7.4 Hounsfield units (P < .01). The volumetric BMD of the bone block from the femoral tunnel (2.80 ± 0.88 g/cm(3)) was higher than the value from the tibial tunnel (1.88 ± 0.59 g/cm(3)) (P < .01). Comparing the data between male and female patients, we found no significant difference in both femoral and tibial tunnel regions.

CONCLUSIONS

For ACL reconstruction, the BMD of the femoral tunnel is higher than that of the tibial tunnel. This implies that a proportionally larger-diameter interference screw should be used for fixation in the proximal tibia than that used for fixation in the distal femur.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Physical activity as a strategy to reduce the risk of osteoporosis and fragility fractures

Childhood and adolescence are critical periods for the skeleton. Mechanical load has then been shown to be one of the best stimuli to enhance not only bone mass, but also structural skeletal adaptations, as both contributing to bone strength. Exercise prescription also includes a window of opportunity to improve bone strength in the late pre- and early peri-pubertal period. There is some evidence supporting the notion that skeletal gains obtained by mechanical load during growth are maintained at advanced age despite a reduction of physical activity in adulthood. The fact that former male athletes have a lower fracture risk than expected in their later years does not oppose the view that physical activity during growth and adolescence is important and it should be supported as one feasible strategy to reduce the future incidence of fragility fractures.

MECHANICAL ASPECTS OF A SINGLE-BUNDLE TIBIAL INTERFERENCE SCREW FIXATION IN A TENDON GRAFT ACL RECONSTRUCTION

Numerical methods applicable to the tibia bone and soft tissue biomechanics of an anterior cruciate ligament (ACL) reconstructed knee are presented in this paper. The aim is to achieve a better understanding of the mechanics of an ACL reconstructed knee. The paper describes the methodology applied in the development of an anatomically detailed three-dimensional ACL reconstructed knee model for finite element analysis from medical image data obtained from a computed tomography scan. Density segmentation techniques are used to geometrically define the knee bone structure and the encapsulated soft tissues configuration. Linear and nonlinear elastic constitutive material models are implemented to mechanically characterize the behavior of the biological materials. Preliminary numerical results for the model qualitative evaluation are presented.

Supplemental bio-tenodesis improves tibialis anterior allograft yield load in extremely low density tibiae

INTRODUCTION

Improved soft tissue tendon graft mechanical properties have led to their increased use for anterior cruciate ligament (ACL) reconstruction. Because they do not have an osseous component; however, there are greater concerns regarding tibial graft slippage during early postoperative rehabilitation and activities of daily living, particularly in patients with poor bone mineral density (BMD), such as older patients, women, smokers, and patients undergoing revision ACL reconstruction surgery.

METHODS

This in vitro biomechanical study attempted to determine the effectiveness of supplemental ACL graft fixation in low BMD tibiae. Eight paired knees (16 specimens) were harvested from female cadavers (mean age = 76, range = 60-88 years). Tibiae were assigned to either a combination bioabsorbable interference screw, bio-tenodesis screw group (Group 1, n = 8, apparent BMD = 0.44 ± 0.13 g/cm(2)) or a bioabsorbable interference screw group (Group 2, n = 8, apparent BMD = 0.44 ± 0.14 g/cm(2)). Double-strand (single loop) tibialis anterior tendon allografts were fixed in matched diameter tibial tunnels. Using a custom 6° of freedom jig, potted constructs were mounted on to a servo hydraulic device with the axial loading force aligned directly with the tibial tunnel. Constructs underwent progressive cyclic tensile loading from 10 to 150 N with a 25 N load increase every 20 cycles. This was followed by yield load to failure testing (20 mm/min).

RESULTS

Groups did not display displacement differences during progressive cyclic loading. Group 1 (312.7 ± 67.5 N) displayed 25% greater yield load at failure than Group 2 (235.0 ± 47.6 N), P = 0.045. Both groups displayed fixation levels well below the previously reported minimal safe threshold estimate for early unrestricted weight bearing, accelerated rehabilitation and activities of daily living.

CONCLUSION

Supplemental bio-tenodesis fixation may improve early tibial-soft tissue tendon graft fixation in patients that have poor tibial BMD, but study results suggest that both methods may require weightbearing, rehabilitation, and activity of daily living restrictions during the early postoperative period to prevent graft slippage.

Effects of high-impact training and detraining on femoral neck structure in premenopausal women: a hip structural analysis of an 18-month randomized controlled exercise intervention with 3.5-year follow-up

PURPOSE

This study evaluated the training effects of an 18-month exercise intervention and subsequent 3.5-year follow-up on femoral neck structure in premenopausal women.

METHODS

Of 98 women who participated in this randomized controlled study, 84 (39 trainees and 45 controls) completed the 18-month intervention. At both 18 months and 3.5 years, dual-energy X-ray absorptiometry data on 22 trainees and 22 control participants (ages 35-45 y) were available for hip structural analysis. The section modulus (Z), cross-sectional area (CSA), and subperiosteal width at the femoral neck were analyzed. Lower-leg explosive power and estimated maximal oxygen uptake (Vo(2)max) were assessed by vertical countermovement jump and standardized 2 km walking test, respectively. Progressive supervised high-impact exercises were done three times per week for 18 months.

RESULTS

Significant between-group differences in favour of trainees were observed after the 18-month intervention in Z (3.2%, p=0.047) and CSA (2.8%, p=0.043). At the 3.5-year follow-up point, the exercise-induced benefits in Z and CSA had diminished and were statistically insignificant. A between-group difference in favour of trainees was observed in lower-limb power after intervention (4.2%, p=0.002) and at 3.5-year follow-up (5.1%, p=0.003). A similar difference was seen in estimated Vo(2)max (5.6% after intervention, p=0.002, and 4.6% at 3.5-y follow-up, p=0.005).

CONCLUSION

The 18-month high-impact exercise intervention strengthened the femoral neck in premenopausal women by enhancing its structural properties; however, this benefit was not maintained at 3.5-year follow-up. In contrast, the exercise benefits on physical performance continued to be maintained 3.5 years after intervention.

Effect of short-term upper-body resistance training on muscular strength, bone metabolic markers, and BMD in premenopausal women

To examine the effect of a 10-week upper-body resistance training program on bone turnover markers and site-specific bone mineral density (BMD) in the wrist and distal half of the ulna and radius in untrained and healthy young premenopausal women.

Non-uniform decay in jumping exercise-induced bone gains following 12 and 24 weeks of cessation of exercise in rats

The effects of deconditioning on exercise-induced bone gains in rats were investigated in 12-week-old female WKY rats performing a standard jumping exercise regimen for either 8, 12 or 24 weeks, followed by sedentary periods of either 24, 12 or 0 weeks, respectively. Age-matched controls received no exercise over the same period. At the end of the training/sedentary period, the tibiae were harvested for analyses of bone parameters. Gains in tibial fat-free dry weight decayed within 12 weeks of deconditioning, but gains in tibial ultimate bending force (strength), maximum diameter and cortical area were still present at 12 weeks of deconditioning. With the exception of cortical area, all other exercise-induced bone gains decayed by the 24th week of deconditioning. It appears that the decay in exercise-induced bone gains in strength, physical and morphological properties is not uniform, and that gains in fat-free dry weight seem to decay earlier.

Osteoporosis: nonpharmacologic management

Osteoporosis is a chronic disorder of the skeleton causing increased bone fragility and fractures. In the second of our 3-part series, we discuss the beneficial effects of nonpharmacologic agents in the management of osteoporosis. We review the evidence supporting the use of exercise, whole-body vibration, hip protectors, low-intensity pulsed ultrasound, bracing, and vertebral augmentation procedures. The mechanism of action, precautions, and expected outcomes are discussed. Nonpharmacologic management of osteoporosis blends in very well with an overall exercise prescription. The nonpharmacologic interventions discussed are readily available and easy to implement. The use of such techniques demonstrates the important role of the physiatrist in the management of osteoporosis.

Sport and training influence bone and body composition in women collegiate athletes

This is a novel descriptive study to characterize off-season, preseason, and postseason bone and body composition measures in women collegiate athletes. From 2006 through 2008, 67 women collegiate athletes from 5 sports, softball (n = 17), basketball (n = 10), volleyball (n = 7), swimming (n = 16), and track jumpers and sprinters (n = 17) were scanned using dual energy X-ray absorptiometry (DXA) at 3 seasonal periods: (a) off-season = before preseason training, (b) preseason = after preseason training, and (c) postseason = after competitive season. Dual energy X-ray absorptiometry scans were analyzed for total body mass, lean mass (LM), fat mass (FM), percent body fat (%BF), bone mineral content, bone mineral density (BMD), arm BMD, leg BMD, pelvis BMD, and spine BMD. Data were analyzed between sports using analysis of variance (ANOVA) with Tukey post hoc follow-ups, and within each sport using repeated-measures ANOVA and LSD; alpha < 0.05. Significant off-season to preseason or postseason changes in %BF, LM, and BMD within each sport were as follows, respectively: softball, -7, +4, +1%; basketball, -11, +4, +1%; volleyball, unchanged, unchanged, +2%; swimming, unchanged, +2.5%, unchanged; track jumpers and sprinters, -7, +3.5, +1%. Comparisons among athletes in each sport showed bone measurements of swimmers averaged 4-19% lower than that of athletes in any other sport, whereas for track jumpers and sprinters, %BF and FM averaged 36 and 43% lower compared with other sports at all seasonal periods. Values for athletes playing basketball and volleyball were most similar, whereas softball athletes' values fell between all other athletes. These data serve as sport-specific reference values for comparisons at in-season and off-season training periods among women collegiate athletes in various sports.

BIOMECHANICAL TESTING PROCEDURES IN TENDON GRAFT RECONSTRUCTIVE ACL SURGERY

This paper, describes the biomedical testing of an Anterior Cruciate Ligament (ACL) reconstruction using an interference screw fixation on the bovine and porcine tissues. The harvesting procedure, experimental setup, mechanical testing, and evaluation of the tendon graft interference screw fixation are all presented throughout this study. A guideline has also been introduced to evaluate the basic mechanical properties of the bone components and the tendon graft.

Effects of a 1-year randomized controlled trial of resistance training on lower limb bone and muscle structure and function in older men

SUMMARY

A 1-year randomized controlled trial of resistance training compared with a control group was undertaken in 143 men aged 55-80 years. Although hip bone mineral density, lean body mass, and function increased in both groups, lean body mass and function but not bone density increased more in the resistance group.

INTRODUCTION

Previous studies have demonstrated a positive effect of resistance training on bone mineral density (BMD) in postmenopausal women, but the effect in men is unclear. The aim was to examine the effect of a 1-year resistance training program on bone and lean body mass in 143 men aged 55-80 years, randomized to either resistance training or active control.

METHODS

Resistance exercises were selected to provide loading at the hips. Measurements were taken at 0, 6, and 12 months for BMD (whole body, hip, and spine), lean body mass, strength, and functional fitness.

RESULTS

The intervention showed a significant increase in total hip BMD for both groups at 12 months (active control, 1,014-1,050 mg/cm(2); resistance, 1,045-1,054 mg/cm(2), p < 0.05) with no increased effect of resistance training compared to active control. However, compared to the active control group, the resistance group increased their lean body mass (active control, 0.1 +/- 2.1%; resistance, 1.5 +/- 2.7%, p < 0.05), fitness (active control, 4.6 +/- 11.1%; resistance, 13.0 +/- 13.4%, p < 0.05), and lower limb muscle strength (active control, 14.3 +/- 16.8%; resistance, 39.4 +/- 30.87%, p < 0.05).

CONCLUSIONS

In contrast to previous findings in older women, in older men, a resistance training program does not increase hip bone mass more than walking 30 min three times a week.

Stiffer fixation of the tibial double-tunnel anterior cruciate ligament complex versus the single tunnel: a biomechanical study

PURPOSE

The primary objective of this study was to evaluate the difference in graft pullout forces, stiffness, and failure mode of double-bundle anterior cruciate ligament (ACL) reconstruction of the tibial insertion by use of a single tunnel compared with a double-tunnel technique with interference screw fixation.

METHODS

ACL reconstruction on the tibial side was performed on 40 fresh-frozen porcine knees (mean bone mineral density of 0.64 g/cm(2) measured by dual-energy x-ray absorptiometry scan), randomly assigned to the single- or double-tunnel group. Interference screw fixation of the soft-tissue graft was used for both types of tibial reconstruction. Maximum failure load, stiffness, and failure mode were recorded.

RESULTS

There was no significant difference in maximum failure load between the single-tunnel group (400 +/- 26 N) and double-tunnel group (440 +/- 20 N). Stiffness of the tibial tunnel complex was significantly higher in the double-tunnel group (76 +/- 3 N/mm) than in the single-tunnel group (62 +/- 4 N/mm) (P = .013). All but 2 grafts (38 of 40) failed by slippage of the tendon past the interference screw.

CONCLUSIONS

There was significantly stiffer fixation of the tibial double-tunnel ACL complex when compared with the single tunnel. Our study did not show a different failure mode for the double-tunnel reconstruction compared with the single-tunnel reconstruction.

CLINICAL RELEVANCE

This study shows a biomechanical advantage with no potential deleterious side effects for fixation of the ACL with a double-tunnel technique on the tibial side.

Comparison between bovine bone and titanium interference screws for implant fixation in ACL reconstruction: a biomechanical study

INTRODUCTION

The application of interference screws for the fixation of bone-patellar tendon-bone (BPTB) grafts is a well-established technique in anterior-cruciate ligament reconstruction. Interference screws derived from bovine compact bone are a biological alternative to metallic or biodegradable polymer interference screws.

MATERIALS AND METHODS

In 60 porcine specimens, the tibial part of an anterior-cruciate ligament reconstruction was performed using a BPTB graft. To secure the graft, either an 8-mm titanium interference screw or a self-made bovine interference screw (BC), or a commercial bovine compact bone screw (Tutofix) was used. The maximum failure load was determined by means of a universal testing machine with computer interface at a testing speed of 50 mm/min. In a second test series, cyclic sub-maximal load was applied to the test specimen from 40 to 400 N with a number of 1,000 load cycles and a frequency of 1 Hz. Subsequently, the maximum failure load was determined. The stiffness of the test specimen was investigated in both test series. Each type of interference screw was tested 10 times.

RESULTS

A secure fixation of the grafts was achieved with all interference screws. In the experiments on the maximum load to failures, the titanium screws showed significantly higher failure loads than the Tutofix screws (P = 0.005). The stiffness of the grafts fixed with BC screws was significantly higher as compared to the fixation with Tutofix screws (P = 0.005). After cyclic sub-maximal loading, the maximum failure load of the titanium screws was significantly higher than that of the Tutofix screws (P = 0.033). The fixation of the BC screws showed a significantly higher failure load (P = 0.021) and stiffness (P = 0.032) than the Tutofix screw fixation. Except for two screw head fractures and two intra-tendinous graft ruptures, the failure mode was slippage in the interface between interference screw and bone plug.

CONCLUSION

Interference screws derived from bovine compact bone show similar good results as the titanium interference screws. Therefore, the safety and in vivo performance of products derived from xenogenic bone should be the focus of further investigations.

Stepwise increasing and decreasing fluid shear stresses differentially regulate the functions of osteoblasts

It is well accepted that osteoblasts respond to fluid shear stress (FSS) depending on the loading magnitude, rate, and temporal profiles. Although in vivo observations demonstrated that bone mineral density changes as the training intensity gradually increases/decreases, whether osteoblasts perceive such slow temporal changes in the strength of stimulation remains unclear. In this study, we hypothesized that osteoblasts can detect and respond differentially to the temporal gradients of FSS. In specific, we hypothesized that when the temporal FSS gradient is high enough, i) the increasing FSS inhibits the osteoblastic potential in supporting osteoclastogenesis and enhances the osteoblastic anabolic responses; ii) on the other hand, the deceasing FSS would have opposite effects on osteoclastogenesis and anabolic responses. To test the hypotheses, stepwise varying FSS was applied on primary osteoblasts and osteogenic and resorption markers were analyzed. The cells were subjected to FSS increasing from 5, 10, to 15 or decreasing from 15, 10, to 5 dyn/cm(2) at a step of 5 dyn/cm(2) for either 6 or 12 hours. In a subset experiment, the cells were stimulated with stepwise increasing or decreasing FSS at a higher step (10 dyn/cm(2)) for 12 hours. Our results showed that, with the step of 5 dyn/cm(2), the stepwise increasing FSS inhibited the osteoclastogenesis with a 3- to 4-fold decrease in RANKL/OPG gene expression versus static controls, while the stepwise decreasing FSS increased RANKL/OPG ratio by 2- to 2.5-fold versus static controls. Both increasing and decreasing FSS enhanced alkaline phosphatase expression and calcium deposition by 1.0- to 1.8 fold versus static controls. For a higher FSS temporal gradient (three steps of 10 dyn/cm(2) over 12 hour stimulation), the increasing FSS enhanced the expression of alkaline phosphatase expression and calcium deposition by 1.3 fold, while the decreasing FSS slightly inhibited them by -10% compared with static controls. Taken together, our results suggested that osteoblasts can detect the slow temporal gradients of FSS and respond differentially in a dose-dependent manner, which may account for the observed bone mineral density changes in response to the gradual increasing/decreasing exercise in vivo. The stepwise FSS can be a useful model to study bone cell responses to long-term mechanical usage or disuse. These studies will complement the short-term studies and provide additional clinically relevant insights on bone adaptation.

Early physical activity provides sustained bone health benefits later in childhood

PURPOSE

This study examined the potential effect of early childhood moderate and vigorous physical activity (MVPA) on later bone health.

METHODS

Three hundred and thirty-three children, participating in the Iowa Bone Development Study, were studied at ages 5, 8, and 11 yr. MVPA (min x d(-1)) was measured using an accelerometry-based physical activity monitor. Bone mineral content (BMC; g) of the whole body, lumbar spine, and hip was measured using dual-energy x-ray absorptiometry. Mixed regression models were used to test whether MVPA at age 5 yr had an effect on BMC at ages 8 and 11 yr after adjustment for concurrent height, weight, age, maturity, and MVPA. The analysis was repeated to control for bone outcomes at age 5 yr. Mixed-model least-squares mean values at the person level of covariates for age group were used to compare the BMC at ages 8 and 11 yr of children in the highest and lowest quartiles of MVPA at age 5 yr.

RESULTS

For boys and girls, MVPA at age 5 yr predicted BMC adjusted for concurrent height, weight, age, maturity, and MVPA at ages 8 and 11 yr (P < 0.05). When the analysis was repeated to also control for BMC at age 5 yr, the effect of MVPA at age 5 yr was significant for boys but not for girls. Boys and girls in the highest quartile of MVPA at age 5 yr had 4%-14% more BMC at ages 8 and 11 yr than those in the lowest quartile of MVPA at age 5 yr (P < 0.05).

CONCLUSIONS

These results provide support for the benefits of early MVPA on sustained bone health during childhood especially for boys. Results indicate the importance of increasing MVPA as a strategy to improve BMC later in childhood.

Torsional stability of interference screws derived from bovine bone--a biomechanical study

Background

In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws.

Methods

In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a commercial 8 mm interference screw (Tutofix^®). Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times.

Results

There was no statistically significant difference between the different 8 mm interference screws (p = 0.121). Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10^-5). Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079) and the 9 mm BC screw (p = 0.0079). Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15). During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn.

Conclusions

The BC screws show comparable torsional stability to Tutofix^® interference screws. As expected the torsional strength of the screws increases significantly with the diameter. The safety and in vivo performance of products derived from xenogeneic bone should be the focus of further investigations.

Is bone's response to mechanical signals dominated by gravitational loading?

During locomotion and exercise, bone is subjected to forces induced by gravitational loading and muscle loading. The inherent link between these modes of loading has confounded emergence of either one as the principal anabolic or anticatabolic signal in bone. A paradigm has emerged in the literature stipulating that muscle loading is the larger of the two, and therefore, bone morphology is predominantly determined by muscle loads. In spite of the intuitive appeal of a muscle-bone unit tuned to the magnitude of contractile forces, little evidence exists for the relatively few, large-magnitude muscle contractions arising during daily activities to dominate the mechanosensory input of bone. Moreover, a review of the literature raises several inconsistencies in this paradigm and indicates that the alternative--gravitational loading--can have a significant role in determining bone mass and morphology. Certainly, the relative contribution of each type of loading will depend on the specific activity, the location of the bone within the skeleton, and whether the bone is weight-bearing or not. Most likely, a more comprehensive paradigm for explaining sensitivity of bone to loading will have to include not only large-magnitude gravitational and muscle loads, but also other factors such as high-frequency, low-magnitude signals generated by the muscles during postural adjustments.

Biomechanical evaluation of different anterior cruciate ligament fixation techniques for hamstring graft

BACKGROUND

A number of anterior cruciate ligament (ACL) fixation techniques are currently in use. Slippage or failure of the graft by excessive loading or aggressive rehabilitation may result in an unstable knee. Load and slippage of the ACL graft varies according to the fixation technique used.

METHODS

Graft slippage, load to failure, and stiffness were evaluated using an animal model. Six soft tissue ACL fixation techniques and bone cement as a fixation device were tested: group A, Endo Button CL-Bio RCI; group B, Swing Bridge-Evolgate; group C, Rigidfix-Intrafix; group D, Bone Mulch-Washer Lock; group E, Transfix-Retroscrew; group F, Transfix-Deltascrew; group G, Kryptonite bone cement. Maximum failure load, stiffness, and slippage at the 1st and 1000th cycles and mode of failure were evaluated.

RESULTS

The maximum failure load was significantly higher in group B (1030 N) and significantly lower in group E (483 N) than in the others. The stiffness of group B (270 N/mm) was significantly higher than the others. As for the mode of failure, group C showed failure in the femoral side in all tests (four device ruptures and two tendon ruptures on the femoral side). All failures of the other groups occurred on the tibial side except one test in group A. All failures in group G were due to slippage of the tendons.

CONCLUSION

Load to failure and stiffness was significantly different between the ACL fixation techniques. All but one of the fixation techniques showed sufficient properties for adequate postoperative rehabilitation. Bone cement used as a fixation device in soft tissue grafts did not seem to provide adequate initial fixation suitable for early rehabilitation after ACL reconstruction.

Tibial fixation of anterior cruciate ligament allograft tendons: comparison of 1-, 2-, and 4-stranded constructs

BACKGROUND

In sum, 1-, 2-, and 4-stranded allografts are used for soft tissue anterior cruciate ligament reconstruction; however, the fixation properties of fixation devices are not well assessed.

HYPOTHESIS

There are no differences in the biomechanical characteristics of 1 (Achilles)-, 2 (posterior tibialis)-, and 4 (semitendinosus)-stranded allograft tibial fixation.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixty-three fresh-frozen porcine tibiae were used to evaluate the fixation of 1-, 2-, and 4-stranded human tendon allografts (Achilles, posterior tibialis, and semitendinosus) with 3 fixation devices (Delta, Intrafix, and Calaxo screws). With use of a materials testing system, each graft was subjected to 500 cycles of loading (50-250 N, 0.75 mm/sec) to determine displacement and cyclic stiffness, followed by a monotonic failure test (20 mm/min) to determine maximum load and pullout stiffness.

RESULTS

For each graft type, there were no significant biomechanical differences between fixation devices. However, the 1-stranded graft (Achilles) construct demonstrated significantly higher mean displacement (3.17 +/- 1.62 mm), lower cyclical stiffness (156 +/- 25 N/mm), lower load to failure (479 +/- 87 N), and lower pullout stiffness (140 +/- 28 N/mm). In comparison with the 2-stranded graft (posterior tibialis), the 4-stranded graft (semitendinosus) exhibited lower displacement (0.86 +/- 0.44 to 1.12 +/- 0.51 mm) and higher ultimate failure load (832 +/- 255 to 656 +/- 168 N). Numerous differences in fixation properties were noted when comparing a device to each of the 3 grafts.

CONCLUSION

The 1-stranded allograft demonstrated inferior biomechanical tibial fixation properties when compared with 2 (posterior tibialis)- and 4 (semitendinosus)-stranded allograft constructs for all fixation devices tested.

CLINICAL RELEVANCE

This study demonstrated that not all tibial fixation devices are designed to adequately accommodate different types of anterior cruciate ligament allografts. Biomechanical evidence suggests that caution is warranted when using an Achilles allograft fixated solely with an interference device.

Tendon graft fixation in ACL reconstructionIn vitro evaluation of bioabsorbable tenodesis screw

BACKGROUND

Conventional ACL reconstruction requires sufficient tibial bone quality for secure graft fixation. We evaluated the mechanical characteristics of a supplemental tenodesis screw in cadaveric specimens.

MATERIAL AND METHODS

One group of 7 specimens from 7-paired tibiae was randomly assigned to undergo tibialis anterior tendon graft-bone tunnel fixation with a bioabsorbable interference screw, using conventional ACL reconstruction techniques. The other group of 7 specimens underwent the same procedure supplemented with a bioabsorbable tenodesis screw. All specimens were subjected to pullout testing on a servo hydraulic device.

RESULTS

Specimens in the supplemental fixation group had double the load to failure (tenodesis = 467 (SD 184) N, control group = 223 (SD 66) N, p = 0.02) and were also one-third stiffer (tenodesis = 31 (SD 13) N/mm, control group = 21 (SD 6) N/mm, p = 0.03) than the specimens in the conventional fixation group.

INTERPRETATION

Supplemental bioabsorbable tenodesis screw fixation may be advantageous for primary reconstruction in patients with low tibial bone mineral density or during revision procedures. By providing secure soft tissue graft-tibia fixation during the early phase after ACL reconstruction, supplemental tenodesis fixation may enable patients to participate safely in more intense, early rehabilitation.

Post-operative analysis of ACL tibial fixation

The main aims of the study were to describe the mechanical behaviour of the bone and tendon graft in ACL reconstruction. We also wanted to evaluate the stresses upon the tendon and try to relate these to modes of healing observed in animal studies. An MRI scan of a knee from a 22-year-old male patient, 3 months post ACL reconstruction, was used to generate a finite element model for assessing the stresses on the tendon and bone. A 200 N force, equivalent to the force during normal gait, was placed on the graft and the stress distribution recorded. The maximum stress was found on the tendon graft at the proximal end of the tibial tunnel. Direct tendon healing, which has been observed in animal studies, maybe as a result of the increased stress in this area.

Minimum level of jumping exercise required to maintain exercise-induced bone gains in female rats

SUMMARY

This study determines the minimum level of exercise required to maintain 8 weeks of jumping exercise-induced bone gains in rats. It was found that the minimum level of exercise required for maintaining the different exercise-induced bone gains varied between 11% and 18% of the initial exercise intensity.

INTRODUCTION

This study ascertains the minimum level of follow-up exercise required to maintain bone gains induced by an 8-week jumping exercise in rats.

METHODS

Twelve groups of 12-week old rats (n = 10 rats per group) were given either no exercise for 8 (8S) or 32 weeks (32S), or received 8 weeks of standard training program (8STP) that consisted of 200 jumps per week, given at 40 jumps per day for 5 days per week, followed by 24 weeks of exercise at loads of either 40 or 20 or 10 jumps per day, for either 5, or 3, or 1 day/week. Bone mass, strength, and morphometric properties were measured in the right tibia. Data were analyzed using one-way analyses of variance.

RESULTS

Bone mass, strength, mid-shaft periosteal perimeter and cortical area were significantly (p < 0.05) higher in the rats given 8STP than that in the 8S group. The minimal level of exercise required to maintain the bone gains was 31, 36, 25, and 21 jumps per week for mass, strength, periosteal perimeter and cortical area, respectively.

CONCLUSIONS

Eight weeks of jumping exercise-induced bone gains could be maintained for a period of 24 weeks with follow-up exercise consisting of 11% to 18% of the initial exercise load.

Osteoporosis and Strength Training

Osteoporosis is a major public health problem. Mechanical strain, imparted by muscle action and ground reaction forces, regulates bone size, shape, mineral mass, and density and subsequently bone strength. Thus, physical activity is critical for bone development, bone health, and fracture risk reduction. Animal studies, in which strain can be manipulated and measured directly, consistently show bone responds to high-strain magnitudes and rates, and only a few repetitions are needed to elicit a response. Extrapolation to humans suggests resistance exercise may be effective for osteoporosis prevention. Indeed, strength-trained athletes have significantly higher bone mass and density than athletes and nonathletes who do not engage in similar training. Prospective studies also support the benefits of resistance exercise demonstrating slowed bone loss and often an increase of 1% to 3% in regional bone mineral density, especially in women. Although more work is needed to define the optimal dose and the effects of nonmechanical factors (eg, nutritional, endocrine, body composition) on the response, the effects of resistance exercise on muscle mass and strength, balance, and agility, in addition to direct skeletal benefits, underscore its importance for osteoporosis, falls, and fracture prevention.

Biomechanical and tissue handling property comparison of decellularized and cryopreserved tibialis anterior tendons following extreme incubation and rehydration

Little is known regarding the biomechanical profiles and tissue handling properties of decellularized and cryopreserved human tibialis anterior tendons prepared as allografts for ACL reconstruction. This study compared allografts prepared using two extremes of the same cryoprotectant incubation and rehydration technique with a standardly prepared control group. Porcine tibiae with similar apparent BMD were randomly divided into three groups of ten specimens. Paired tendons were randomly divided into two experimental groups: Group 1 = 8 h incubation/15 min rehydration; Group 2 = 2 h incubation/1 h rehydration. Group 3 (control) consisted of ten standardly prepared tendons with 20 min rehydration. Tissue handling properties were graded during allograft preparation using a modified visual analog scale. Similar diameter allografts were fixed in matched diameter extraction drilled tibial tunnels with 35 mm long, 1 mm > tunnel diameter bioabsorbable interference screws. Potted constructs were mounted in a servo hydraulic device, pretensioned between 10-50 N at 0.1 Hz (10 cycles), and isometric pretensioned at 50 N for 1 min, prior to 500 submaximal loading cycles (50-250 N) at 0.5 Hz, and load to failure testing (20 mm/min). Constructs prepared under extreme conditions generally displayed comparable biomechanical properties to the control condition. Group 1 (8 h incubation/15 min rehydration)(-34 +/- 35 ms) and Group 2 (2 h incubation/1 h rehydration) (-22 +/- 38 ms) displayed smaller mean displacement-load peak phase timing differences over the initial ten cycles compared to Group 3 (control)(-42 +/- 49 ms), P = 0.004, suggesting greater relative construct stiffness. Group 1 (8 h incubation/15 min rehydration) (234.9 +/- 34 N/mm) and Group 2 (2 h incubation/1 h rehydration)(231.3 +/- 43 N/mm) displayed lower construct stiffness during load to failure testing than Group 3 (control)(284.5 +/- 25.2 N/mm), P = 0.003. Group 1 (8 h incubation/15 min rehydration) differed from Group 2 (2 h incubation/1 h rehydration) and Group 3 (control) for perceived tensile stiffness (2.4 +/- 2.0 vs. 7.0 +/- 0.5 and 7.9 +/- 0.3, respectively), compressive resilience (1.7 +/- 0.8 vs. 5.9 +/- 1.0 and 7.8 +/- 0.4, respectively), handling ease (2.8 +/- 1.0 vs. 6.5 +/- 0.5 and 7.0 +/- 0.7, respectively), color (2.6 +/- 0.8 vs. 4.7 +/- 0.7 and 5.1 +/- 0.3, respectively) and texture (4.0 +/- 0.8 vs. 6.2 +/- 0.8 and 6.8 +/- 0.8, respectively) (P < 0.0001). Group 2 (2 h incubation/1 h rehydration)(6.0 +/- 0.7 and 5.9 +/- 1.0, respectively) also differed from Group 3 (control)(6.8 +/- 0.8 and 7.8 +/- 0.4, respectively) for general "feel" and compressive resilience (P < 0.0001). Tensile stiffness and compressive resilience displayed moderate and weak relationships, respectively with displacement during submaximal cyclic loading (r2 = 0.78 and 0.58, respectively), stiffness (r2 = 0.33 and 0.44, respectively) and load at failure (r2 = 0.59 and 0.37, respectively) for Group 3 (control), but not for experimental Group 1 (8 h incubation/15 min rehydration) or Group 2 (2 h incubation/1 h rehydration). Knee surgeons should be aware that soft tissue tendon decellularization and cryopreservation may change the biomechanical stiffness, tissue handling properties, and relationships between these variables compared to standardly prepared allograft tissue.

Sustainability of exercise-induced increases in bone density and skeletal structure

BACKGROUND

The prevalence of osteoporosis with related fragility fractures has increased during the last decades. As physical activity influences the skeleton in a beneficial way, exercise may hypothetically be used as a prophylactic tool against osteoporosis.

OBJECTIVE

This review evaluates if exercise-induced skeletal benefits achieved during growth remain in a long-term perspective.

DESIGN

PUBLICATIONS WITHIN THE FIELD WERE SEARCHED THROUGH MEDLINE (PUBMED) USING THE SEARCH WORDS: exercise, physical activity, bone mass, bone mineral content (BMC), bone mineral density (BMD) and skeletal structure. We based our inferences on publications with the highest level of evidence, particularly randomised controlled trials (RCT).

RESULTS

Benefits in BMD achieved by exercise during growth seem to be eroded at retirement, but benefits in skeletal structure may possibly be retained in a longer perspective. Recreational exercise seems to at least partially maintain exercise-induced skeletal benefits achieved during growth.

CONCLUSIONS

Exercise during growth may be followed by long-term beneficial skeletal effects, which could possibly reduce the incidence of fractures. Exercise during adulthood seems to partly preserve these benefits and reduce the age-related bone loss.

Exercise for optimising peak bone mass in women

Physical activity is one of the major non-pharmacological methods for increasing and maintaining bone mineral density (BMD) and geometry. As such, it has an important role in maintaining peak bone mass and strength, thus reducing the risk of future osteoporotic fracture. However, not all exercise is effective, so a prescription in terms of optimal type, intensity, frequency and duration is required. Studies using animal models suggest that loading that is high in magnitude, rapidly applied and novel is most effective, whilst duration is less important beyond a threshold number of cycles. In human subjects cross-sectional studies comparing different athletic populations suggest that those who participate in high- or odd-impact sports have higher BMD; whilst impact exercise, strength training and brief high-impact-jump training interventions increase BMD in premenopausal women. In order to further elucidate exercise recommendations to optimise bone health in this population, the usefulness of brief high-impact unilateral exercises has been evaluated. Brief hopping exercises were shown to be feasible for sedentary premenopausal women, producing ground-reaction forces as high as those from jumping. Regularly performing these hopping exercises over 6 months was found to increase femoral-neck BMD of the trained leg relative to the control leg. Unilateral high-impact exercise may therefore improve bone strength of the trained limb and provide a useful model for comparing exercise prescriptions to help define the most efficient and effective exercise recommendations for the bone health of premenopausal women.

Biomechanical comparison between CentraLoc and Intrafix fixation of quadrupled semitendinosus-gracilis allografts in cadaveric tibiae with low bone mineral density

Supplementary or back-up tibial tunnel fixation of a quadruple semitendinosus-gracilis (STG) graft is often performed when the knee surgeon questions the integrity of intra-tunnel fixation. Back-up fixation devices such as staples however may contribute to increased knee pain and dysfunction. Both primary extra-tunnel and intra-tunnel fixation devices may provide sufficient quadruple STG graft fixation in a tibial tunnel to preclude the need for back-up fixation. This biomechanical study compared the fixation of quadruple STG allografts in standard drilled tunnels prepared in low apparent bone mineral density (BMD) cadaveric tibiae using either an Intrafix device with primary intra-tunnel fixation in a region of predominantly cancellous trabecular bone, or a CentraLoc device with primary extra-tunnel fixation in a region of predominantly cortical bone. The study hypothesis was that the CentraLoc device would display superior fixation in these low apparent BMD cadaveric tibiae. Matched pair tibiae and quadruple STG allografts were divided into two groups of seven specimens each. Extraction drilled tunnels matched allograft diameter. Constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles and isometric pretensioned at 50 N for 1 min prior to undergoing 500 loading cycles (50-250 N) and load to failure testing (20 mm/min). The CentraLoc group displayed superior load at failure (448.4+/-171 N vs. 338.4+/-119 N, P=0.04) and survived more loading cycles (410+/-154 cycles vs. 196+/-230 cycles, P=0.04) than the Intrafix group. Most CentraLoc group specimens (6/7, 85.7%) failed by device pullout with intact quadruple STG allograft strands while all Intrafix group specimens (7/7, 100%) failed by slippage of one or more strands (P=0.005).

The reduction of physical activity reflects on the bone mass among young females: a follow-up study of 142 adolescent girls

Maintenance of positive effects of physical activity on growing bone is unknown. Physical activity was associated with increased BMC and BMD in a 7-year follow-up with 142 adolescent girls. Marked reduction in physical activity had an unfavorable effect on bone measurements, which is an important finding when the prevention of osteoporosis is considered.

INTRODUCTION

Environmental factors influence quality and durability of bone. Physical activity, with high-impact weight bearing activity during puberty in particular, has been shown to have a beneficial effect on growing bone. Only few studies have been published on the maintenance of these effects.

METHODS

At baseline, 142 girls aged 9-15 years participated in the present 7-year follow-up study. Growth and development, physical activity, and intakes of calcium and vitamin-D were recorded at intervals. BMC and BMD measurements were repeated using DXA. Based on the recording of physical activity during the follow-up measurements, the effect of the reduction in physical activity was examined with the bone measurements, and the measurements in the tertiles based on the amount of physical activity during the whole follow-up period were compared.

RESULTS

Physical activity was positively associated with the development of BMC and BMD during the follow-up. The mean BMC of the lumbar spine increased 1.69 g (3%) (p = 0.021) more among those girls who maintained the physical activity level as compared with those who reduced it during last 4 years. In the femoral neck, the corresponding difference was 0.14 g (4.6%) (p = 0.015) between the same two groups of girls. The mean increases in BMC at lumbar spine and femoral neck were more substantial among those girls having the highest physical activity levels during the 7-year follow-up (46.7% and 22.6%) as compared with those having the lowest physical activity levels (43.3% and 17.4%, respectively).

CONCLUSIONS

The findings of the present study show that regular physical activity is valuable in preserving the peak bone mass acquired at puberty in particular. Many of the girls who markedly reduced their activity levels lost bone in their femoral neck prior to their 25th birthday.