Impact of Environmental Factors on the ACL Injury Risk in Recreational Alpine Skiing

In recreational alpine skiing, an ACL injury represents the most common injury. Skiing is a complex activity where the skier interacts with the environment, such as weather, snow conditions, temperature, etc. Thus, the aim of this study was to evaluate the potential impact of environmental factors on ACL injury risk in recreational alpine skiers. Among a cohort of 392 ACL-injured skiers and 392 uninjured controls matched for sex and skiing skill, environmental factors were collected by questionnaire. Factors included weather conditions, snow conditions, perceived temperature, and slope difficulty at the time-point of the accident (ACL-injured skiers) or of questioning during the ski day (uninjured controls).Multiple logistic regression revealed that in addition to age, five environmental factors were significantly predictive of an ACL injury: fresh snow (OR 10.5), grippy snow (OR 7.8), icy slope condition (OR 12.4), very cold/cold perceived temperature (OR 1.6), and skiing on easy slopes (OR 6.9). In conclusion, besides age, environmental factors such as fresh and grippy snow, icy slope conditions, low temperatures, and flat slopes are associated with an increased ACL injury risk in recreational alpine skiing. Those factors are at least partly modifiable and should be taken into consideration for preventive strategies.

Developing a Cell-Microcarrier Tissue-Engineered Product for Muscle Repair Using a Bioreactor System

Fecal incontinence, although not life-threatening, has a high impact on the economy and patient quality of life. So far, available treatments are based on both surgical and nonsurgical approaches. These can range from changes in diet, to bowel training, or sacral nerve stimulation, but none of which provides a long-term solution. New regenerative medicine-based therapies are emerging, which aim at regenerating the sphincter muscle and restoring continence. Usually, these consist of the administration of a suspension of expanded skeletal-derived muscle cells (SkMDCs) to the damaged site. However, this strategy often results in a reduced cell viability due to the need for cell harvesting from the expansion platform, as well as the non-native use of a cell suspension to deliver the anchorage-dependent cells. In this study, we propose the proof-of-concept for the bioprocessing of a new cell delivery method for the treatment of fecal incontinence, obtained by a scalable two-step process. First, patient-isolated SkMDCs were expanded using planar static culture systems. Second, by using a single-use PBS-MINI Vertical-Wheel® bioreactor, the expanded SkMDCs were combined with biocompatible and biodegradable (i.e., directly implantable) poly(lactic-co-glycolic acid) microcarriers prepared by thermally induced phase separation. This process allowed for up to 80% efficiency of SkMDCs to attach to the microcarriers. Importantly, SkMDCs were viable during all the process and maintained their myogenic features (e.g., expression of the CD56 marker) after adhesion and culture on the microcarriers. When SkMDC-containing microcarriers were placed on a culture dish, cells were able to migrate from the microcarriers onto the culture surface and differentiate into multinucleated myotubes, which highlights their potential to regenerate the damaged sphincter muscle after administration into the patient. Overall, this study proposes an innovative method to attach SkMDCs to biodegradable microcarriers, which can provide a new treatment for fecal incontinence.

Association of personal and equipment-related factors on ACL injury risk in alpine skiers with cautious or risk-taking behaviour: A case-control study

Background

In recreational alpine skiing ACL injury risk depends on the interaction of individual characteristics and behaviours as well as on equipment-related factors.

Aim

to evaluate if and to what extent personal characteristics and equipment-related parameters are associated with ACL injury risk in cautious and risk-taking recreational alpine skiers.

Methods

A retrospective questionnaire-based, case-control study of ACL-injured and uninjured in a cohort of cautious as well as risk-taking recreational skiers was conducted. Participants self-reported their demographics, skiing skill level, and risk-taking behaviour. Ski length, side-cut radius, widths of the tip, waist, and tail were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding caliper, and a standing height ratio between the front and rear components was calculated. Ski boot sole abrasion at the toe and heel pieces was also measured with the digital sliding caliper.

Results

In total, 1068 recreational skiers (50.8% females) with a mean age of 37.8 ± 12.3 years participated, of whom 193 (22.0%) sustained an ACL injury, and 330 (30.9%) participants reported a risk-taking behaviour. Results of the multiple logistic regression analyses revealed that a higher age, a lower skill level, a higher standing height ratio, and greater ski boot sole abrasion at the toe as well as heel pieces were independently associated with an increased ACL injury risk in both the cautious and the risk-taking group. Among cautious skiers, a longer ski length was an additional significant risk factor for sustaining an ACL injury. In conclusion, the same personal and equipment related characteristics contribute to an increase in the ACL injury risk regardless of risk-taking behaviour, with the only difference that longer skis represent an additional risk factor in cautious skiers.

Skill-Specific Differences in Equipment-Related Risk Factors for ACL Injury in Male and Female Recreational Skiers

Background

In recreational alpine skiing, the anterior cruciate ligament (ACL) is affected in approximately 50% of serious knee injuries. There are established sex-based and skill-based differences in ACL injury risk, but the potential impact of equipment used (eg, skis, bindings, and boots) has not been evaluated.

Purpose

To evaluate individual and equipment-related risk factors for an ACL injury depending on sex and skill level.

Study Design

Case-control study; Level of evidence, 3.

Methods

This was a retrospective questionnaire-based, case-control study of female and male skiers with and without ACL injuries during 6 winter seasons (from 2014-2015 to 2019-2020). Demographic data, skill level, equipment specifications, risk-taking behavior, and ownership of ski equipment were recorded. Ski geometry (ski length; sidecut radius; and widths of the tip, waist, and tail) was taken from each participant's ski. The standing heights of the front and back part of the ski binding were measured using a digital sliding caliper, and the standing height ratio was calculated. Abrasion of the ski boot sole was also measured at the toe and heel. Participants were divided by sex into less and more skilled skiers.

Results

A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. A greater standing height ratio and more abrasion at the toe of the boot sole were associated with increased ACL injury risk in both sexes, independent of the skill level. Riskier behavior increased the injury risk only in male skiers, independent of the skill level, and longer skis increased the injury risk only in less skilled female skiers. Older age, the use of rented/borrowed skis, and more abrasion at the heel of the boot sole were independent risk factors for ACL injury in the more skilled skiers of both sexes.

Conclusion

Individual and equipment-related risk factors for an ACL injury partly differed according to skill level and sex. Consideration of the demonstrated equipment-related factors should be implemented in order to reduce ACL injuries in recreational skiers.

Might Gendering Ski Binding Settings be Helpful for the Prevention of ACL Injuries Among Female Recreational Alpine Skiers?

When interpreting sex differences in the injury risk during sport activities, potential gender effects are often overlooked. This might actually be the case with regard to the higher injury risk of the anterior cruciate ligament (ACL) in female skiers. A higher failure rate of ski binding releases has been suggested at least partly to explain the more frequent ACL injuries in female skiers. However, as males seem to be predominantly responsible for the development of standards for ski binding settings, one might speculate that they could rather make standards for males than females. If true, the inclusion of female engineers could actually represent an appropriate approach to reduce ACL injures in female recreational skiers.

A Comparison of ACL Injury Risk, Ski Geometry and Standing Height Parameters between Skiers with Rented and with Owned Skis

to evaluate if ACL injuries are associated with recreational skiers using rented skis and whether individual factors, ski geometry parameters and standing heights differ between skiers who rented or owned skis. A retrospective questionnaire-based, case-control study of ACL-injured and uninjured recreational skiers was conducted during six winter seasons. Age, sex, body height, body weight, nationality, ownership of skis, skill level, risk-taking behavior, ski length, side-cut radius, widths of the tip, waist, and tail, and the standing heights at the front and rear components of the ski binding were assessed. Additionally, ratios between ski widths and a standing height ratio were calculated. Altogether, 1780 skiers (48.9% females) with a mean age of 39.2 ± 13.0 years participated, of whom 22.0% sustained an ACL injury and 32.3% rented skis. ACL injury risk was significantly associated with rented skis (OR 3.2, 95% CI 2.5-4.0). Compared to skiers using own skis, participants who rented skis were more likely female, smaller and lighter, tourists, less skilled and more cautious. In comparison to owned skis, rented skis showed significantly lower mean values in ski length, side-cut radius, ski widths, and for the three ski widths ratios. Additionally, standing heights were significantly lower while standing height ratio was higher for rented skis. Beside individual factors, equipment-related factors should be considered when renting skis in order to reduce ACL injury risk.

Impact of ski geometry data and standing height ratio on the ACL injury risk and its use for prevention in recreational skiers

OBJECTIVES

To evaluate the impact of ski geometry data and standing height ratio on anterior cruciate ligament (ACL) injury risk of male and female recreational skiers.

METHODS

A retrospective questionnaire-based, case-control study of ACL-injured and uninjured recreational skiers was conducted during six consecutive winter seasons. Ski geometry data (ski length, side-cut radius, widths of the tip, waist and tail) were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding calliper, and the standing height ratio between the front and rear was calculated.

RESULTS

A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. Multiple logistic regression analysis indicates a higher age, a lower skill level and riskier behaviour as independent individual risk factors associated with an ACL injury. An increase in ski length, tip width of the ski, standing height at the rear ski binding component, and in standing height ratio were found to be independent equipment-related risk factors for an ACL injury.

CONCLUSION

Reduced ski length, narrower ski tip width, lower rear standing height and a lower standing height ratio (ie, rear component of the ski binding is more elevated compared with the front component) were associated with a reduced likelihood for ACL injury. When buying or renting skis, these parameters could be considered to reduce the likelihood of ACL injury in recreational skiers.

Ski-geometric parameters do not differ between ACL injury mechanisms in recreational alpine skiing

PURPOSE

It is not known so far if ski-equipment-related factors differ between the ACL injury mechanisms, potentially influencing the circumstances and causes of falling, finally resulting in ACL injury. More specifically focusing on the injury mechanisms will provide a deeper understanding of injury causation. The aim of the study was to evaluate whether ACL injury mechanisms in recreational alpine skiing differ with regard to ski-geometric parameters, self-reported circumstances and causes of accident and injury severity.

METHODS

Among a cohort of 392 ACL-injured (57.9% females) skiers, age, sex, height, weight, skill level, risk-taking behavior, circumstances and causes of accident, and ACL injury severity were collected by questionnaire. Additionally, patients had to recall their type of fall (ACL injury mechanism) by classifying forward and backward falls with and without body rotation. Ski length, side cut radius and widths of the tip, waist and tail were directly notated from the ski.

RESULTS

The forward fall with body rotation was the most common reported ACL injury mechanism (63%). A riskier behavior was associated with forward falls without body rotation. Ski-geometric parameters did not significantly influence the type of ACL injury mechanism. Regarding accident characteristics, catching an edge of the ski was more frequent (p < 0.001) the cause for forward falls (75% and 67%) when compared to the backward falls (46 and 15%) and executing a turn was the most frequent action in all falls (39-68%). A complete rupture of the ACL (66-70%) was more commonly reported than a partial tear (30-34%) among all four non-contact ACL injury mechanisms (n.s.).

CONCLUSION

In contrast to risk-taking behavior and accident characteristics, ski-geometric parameters and injury severity do not significantly differ between ACL injury mechanisms in recreational skiing. Thus, an individual skiing style seems to have more impact on ACL injury mechanisms than ski equipment. Future studies should evaluate potential effects of ski geometry on the incidence of ACL injury.

LEVEL OF EVIDENCE

III.

In recreational alpine skiing, the ACL is predominantly injured in all knee injuries needing hospitalisation

PURPOSE

The knee joint still represents the most frequent anatomical injury location accounting for about one-third of all injuries in recreational alpine skiers. However, comprehensive information on current knee injury patterns in this populations is sparse.

METHODS

During the winter seasons 2016/17 and 2019/20, this retrospective questionnaire-based study was conducted in an Austrian sportclinic situated in a large ski area. Among a cohort of 282 recreational skiers (51.8% females), all injuries were diagnosed by the use of magnetic resonance imaging. Additionally, data were recorded on anthropometric characteristics, the perceived speed at the moment of injury, type of fall, physical fitness, self-reported skill level and risk-taking behaviour.

RESULTS

The anterior cruciate ligament (ACL) was injured in all knee injuries recorded. Of the total study sample, 64.5% (n = 182) were ACL injuries with concomitant injuries and about 35.5% (n = 100) were isolated ACL injuries, not involving any other structures of the knee joint. In general, most common concomitant injury diagnoses among ACL-injured recreational alpine skiers were injuries of the medial collateral ligament (MCL) (n = 92, 50.5%), medial meniscus (MM) (n = 73, 40.1%) and lateral collateral ligament (LCL) (n = 41, 22.5%). No significant differences regarding additionally recorded characteristics were found between ACL-injured individuals with concomitant injuries and those with isolated ACL injury.

CONCLUSIONS

Whereas, before the introduction of carving skis, the MCL was reported being the most common injured part of the knee, currently, the majority of knee injuries are ACL injuries accompanied by injury of other knee joint structures, i.e. the MCL, MM and LCL.

LEVEL OF EVIDENCE

Level III.

Performance evaluation of a novel multi-pinhole collimator for dopamine transporter SPECT

There is a tradeoff between spatial resolution and count sensitivity in SPECT with conventional collimators. Multi-pinhole (MPH) collimator technology has potential for concurrent improvement of resolution and sensitivity in clinical SPECT of 'small' organs. This study evaluated a novel MPH collimator specifically designed for dopamine transporter (DAT) SPECT with a triple-head SPECT camera. Count sensitivity was measured with a ^99mTc point source placed on the lattice points of a 1 cm grid covering the whole field-of-view (FOV). Spatial resolution was assessed with a Derenzo type hot rod phantom. An anthropomorphic striatum phantom was scanned with total activity representative of a typical patient scan and different striatum-to-background activity concentration ratios. Recovery of striatum-to-background contrast was assessed by the contrast-recovery-coefficient. Measurements were repeated with double-head SPECT with fan-beam or low-energy-high-resolution-high-sensitivity (LEHRHS) collimators. A patient referred to DAT SPECT because of suspicion of Parkinson's disease was scanned with both LEHRHS and MPH collimators after a single tracer injection. The axial MPH sensitivity profile was approximately symmetrical around its peak, although it was shifted 7 cm towards the patient to simplify positioning. Peak sensitivity of the triple-head MPH system in the center of the FOV was 620 cps MBq^-1 compared to 225 cps MBq^-1 for the double-head fan-beam system. Sensitivity of the MPH system decreased towards the edges of the FOV. The full width of the sensitivity profile at 200 cps MBq^-1 was 21 cm transaxially and 11 cm axially. In MPH SPECT of the Derenzo phantom all rods with ≥ 5 mm diameter were clearly visible. MPH SPECT improved striatal contrast recovery by ≥ 20% compared to fan-beam SPECT. The patient scan demonstrated good image quality of MPH SPECT with almost PET-like delineation of putamen and caudate nucleus. SPECT with dedicated MPH collimators provides considerable improvement of the resolution-sensitivity tradeoff in DAT SPECT compared to SPECT with fan-beam or LEHRHS collimators.

Effectiveness of a Mini-Trampoline Training Program on Balance and Functional Mobility, Gait Performance, Strength, Fear of Falling and Bone Mineral Density in Older Women with Osteopenia

Purpose

To evaluate the effectiveness of a combined balance-, strength-, and jumping-exercise intervention on a mini-trampoline performed by older women with osteopenia on static balance and functional mobility, gait speed, strength of the upper and lower limbs, fear of falling, as well as to investigate its influence on bone mineral density (BMD).

Patient and methods

Using a randomized controlled study design, participants (range: 56-83 years) were assigned either to the intervention group (IG; n=20, mean age 69.6 ± 5.3 years) performing a specifically tailored intervention on a mini-trampoline or to the control group (CG; n=20, 67.4 ± 6.8 years), that did not undertake any intervention beyond regular osteopenia treatment. The intervention was performed twice a week for 12 weeks, each session lasting 45-60 mins and consisted of balance, strength and jumping exercises. Static balance and functional mobility was measured by one-leg stance (OLS) and timed up and go test (TUG). Upper and lower limb strength was evaluated by the arm curl test (ACT) and the 30-s chair stand test (CST) whereas gait speed was measured by the 6 m walking test (WT). Fear of falling was measured using the Falls Efficacy Scale - International (FES-I). BMD was measured at the lumbar spine and femoral neck using Dual-energy X-ray absorptiometry (DXA).

Results

Significant interactions (group x time) were found for all parameters (p<0.001) except for BMD, measured at the lumbar spine (p=0.064) and femoral neck (p=0.073). All test parameters of balance and functional mobility tests (OLS, TUG), strength tests (ACT, CST), WT, FES-I and BMD (femoral neck) showed significant improvement in the IG (p<0.05).

Conclusion

The combined 12-week intervention was highly effective in improving balance and functional mobility, strength, gait performance and fear of falling in patients with osteopenia.

Is ski boot sole abrasion a potential ACL injury risk factor for male and female recreational skiers?

Objectives

To evaluate the potential impact of ski boot sole abrasion on the ACL injury risk of recreational skiers.

Methods

During the past two winter seasons 2016/17 and 2017/18, this retrospective case‐control study was conducted in one Austrian ski area. Among a cohort of 148 ACL‐injured (51.4% females) and 455 uninjured recreational skiers (43.3% females), age, sex, height, weight, and self‐reported skill level were collected by questionnaire, ski length and sidecut radius were notated and sole abrasion of the toe and heel piece of the ski boot was measured using a digital caliper.

Results

ACL‐injured skiers showed a higher proportion of female (51.4% vs 43.3%, P < 0.001) and less skilled skiers (48.6% vs 20.9%, P < 0.001), and ski length to height ratio was higher (94.7 ± 3.7 vs 93.8 ± 5.0%, P = 0.019) compared to uninjured skiers. ACL‐injured skiers used ski boots of greater abrasion at the toe (4.8 ± 1.8 vs 2.4 ± 2.5 mm, P < 0.001) and heel piece (5.4 ± 1.8 vs 3.3 ± 2.3 mm, P < 0.001) compared to controls. Multivariate regression analysis revealed, beside female sex (OR 6.0, 95% CI, 3.1‐11.5, P < 0.001), lower skill level (OR 3.2, 95% CI, 1.9‐5.4, P < 0.001) and ski length to height ratio (OR 1.1, 95% CI, 1.0‐1.2, P < 0.001), sole abrasion at the toe (OR 1.8, 95% CI, 1.5‐2.1, P < 0.001) and heel piece (OR 1.4, 95% CI, 1.2‐1.6, P < 0.001) to be independently associated with an ACL injury among recreational alpine skiers.

Conclusions

Based on the underlying findings, ski boot sole abrasion was found to be an independent risk factor and may contribute to an increased ACL injury risk.

Impact of lowering ski binding settings on the outcome of the self-release test of ski bindings among female recreational skiers

Background and purpose

The ability to successfully self-release the ski binding can prevent skiing-related injuries of the lower extremities. Failure of binding release associated with a knee injury is significantly higher among females compared to males. The International Standards Organization ISO 11088 standard for binding setting values allows a lowering by 15% upon request of the skier. Thus, the aim of this study was to evaluate the impact of lowered ski binding settings by 15% on the outcome of the self-release test among female recreational skiers.

Materials and methods

In this randomized single-blinded study, a cohort of 20 females (24.5±2.7 years) performed the self-release test in the laboratory thrice with each leg under two conditions: 1) with an actual ISO 11088 setting and 2) with a setting lowered by 15%. For each attempt, torques calculated via the force plate were normalized to torques measured by a binding adjustment system (relative release torque, RRT).

Results

Among 240 trials in total, more females were significantly able to self-release their ski bindings with lowered binding settings when compared to their actual ISO settings (53% vs 9%, p<0.001). Thirteen females (65%) were able to release their bindings at least once with both legs with lowered binding settings compared to only three females (15%) with their actual binding settings (p<0.001). Mean RRT of all failure of binding release trials significantly differed between lowered and actual binding settings (58.6%±22.2% vs 50.5%±20.4%, p=0.003).

Conclusion

Four times more females were able to self-release their ski bindings at least once with both legs with a 15% lowered binding setting compared to their normal ISO 11088 setting. The fact that the ISO standard accepts a lowering by 15% upon request of the skier could represent an important measure to prevent knee injuries, especially for female recreational skiers.

[Are there Sex Differences Regarding Ski Length to Height Ratio, Ski Length to Weight Ratio, Sidecut Radius and Ski Boot Sole Abrasion among ACL Injured Male and Female Skiers?]

Introduction Female skiers suffer from knee injuries twice as much as male skiers, and the risk of an injury to the anterior cruciate ligament (ACL) is three times greater among females compared to males. The sex-specific ACL injury risk depends on internal (e. g. age, skiing skills, fitness level) and external (e. g. slope and weather conditions, ski equipment) factors. However, it is not clear whether male and female recreational skiers with an ACL injury differ regarding the sidecut radius and ski boot sole abrasion. Method This questionnaire-based study was conducted in the winter seasons 2014/15 and 2015/16. During those periods, data of ACL-injured skiers were collected at an Austrian ski clinic. The questionnaire included information about demographics, skiing skills, type of fall, binding release, and injury diagnosis. Furthermore, the ski length and sidecut radius were notated from the ski, and abrasion of ski boot sole was measured at the toe and heel piece of the ski boot using a caliper. Results In total 164 ACL-injured skiers (67 % females) with a mean age of 41.7 ± 11.5 years were recorded. Males used significantly longer skies compared to females (168.3 ± 6.6 vs. 157.5 ± 5.9 cm, p < 0.001), however the ski length to height ratio (94.0 ± 3.4 vs. 94.1 ± 3.3 %) showed no significant difference between the two sexes. The ski length to weight ratio was significantly different between females and males (2.5 ± 0.3 vs. 2.0 ± 0.2 cm/kg). The sidecut radius (13.5 ± 1.4 vs. 15.6 ± 2.6 m, p < 0.001) was significantly lower among ACL-injured females compared to ACL-injured males. No sex-specific differences were found regarding the abrasion of ski boot soles, neither at the toe piece (5.4 ± 1.2 vs. 5.5 ± 1.1 mm) nor at the heel piece (6.0 ± 1.7 vs. 6.0 ± 1.6 mm) between females and males. For both sexes the most common type of fall was the forward fall with body rotation (approximately 59 %). Failure of binding release was significantly more often reported by females compared to males (86 vs. 44 %, p < 0.001). Conclusion Female and male skiers with an ACL injury differ regarding the sidecut radius, the ski length to weight ratio, and the proportion of failure of binding release. Moreover, although no sex-specific differences were found regarding the abrasion of ski boot soles, the mean ski boot abrasion was beyond the ISO standard tolerances.

Factors associated with self-reported failure of binding release among ACL injured male and female recreational skiers: a catalyst to change ISO binding standards?

BACKGROUND

Female recreational skiers have twice the rate of knee injuries and three time the rate of ACL injuries compared with their male counterparts. Female skiers suffering from a knee injury reported a significantly higher proportion of failure of binding release than knee injured male skiers.

PURPOSE

To evaluate factors associated with failure of binding release among ACL injured male and female recreational skiers.

STUDY DESIGN

Cohort study.

METHODS

Among a cohort of 498 recreational skiers (68% females) suffering from an ACL injury (complete rupture or partial rupture), age, sex, height, weight, self-reported skill level and self-reported risk taking behaviour, gear origin, ski length, date of last binding adjustment, perceived speed at the moment of injury, type of fall, and failure of binding release of the ski of the injured knee, were collected by questionnaire.

RESULTS

Failure of binding release was reported within 78% of cases and was significantly higher for females compared to males (83 vs 66%, p<0.001) with an adjusted OR of 2.7 (95% CI 1.7 to 4.4). A higher perceived speed at the moment of injury was significantly associated with a decreasing proportion of failure of binding release. A slow perceived speed was independently associated with failure of binding release (adjusted OR 2.0; 95% CI 1.2 to 3.5). There was a significantly higher proportion of failure of binding release during backward falling compared to forward falling (87 vs 72%, p=0.002); similarly, a higher proportion of failure of binding release occurred in cases of complete rupture compared with a partial tear of the ACL (81 vs 64%, p=0.001), respectively.

CONCLUSIONS

Among this cohort of ACL-injured skiers, failure of binding release was significantly associated with female sex, a slow perceived speed at the moment of injury and complete rupture of the ACL.

[Impact of Self-Reported Fatigue on ACL Injuries in Alpine Skiing: A Sex Comparison]

INTRODUCTION

In recreational alpine skiing, about one third of all injuries affect the knee joint, and the most common diagnosis in adult male and female skiers is a tear of the anterior cruciate ligament (ACL), which makes up 15 - 21 % of all injuries. General preventive recommendations to reduce the incidence of ski injuries include avoiding fatigue. However, it seems unclear to what extent ACL injuries in male and female recreational skiers are related to perceived fatigue.

METHODS

This study was conducted as a prospective questionnaire-based investigation in two Austrian ski injury clinics during the five winter seasons between 2009/2010 and 2013/2014. In total, 588 skiers (67.9 % females) with a mean age of 42.1 ± 10.9 years were interviewed about demographics, skiing ability, skiing behaviour, fitness, day and time of accident, skiing duration and perceived fatigue at the moment of accident.

RESULTS

ACL injured males reported a significantly higher skiing ability and fitness level as well as a more risky behaviour on ski slopes compared to females. About one third of males and females injured their ACL within the first day of the ski trip and about 57 % within the first two days, with no sex differences. However, a significantly higher number of female skiers sustained an ACL injury during the first hour of skiing (28 vs. 17 %) as well as during the first two hours of skiing compared to males (52 vs. 44 %). About 81 % of males and females felt no fatigue or just a trace of fatigue in their legs at the time of accident, with no sex differences.

CONCLUSION

Based on the findings of this study, fatigue does not seem to be a major risk factor for an ACL injury among male and female recreational skiers.

Single-bundle anterior cruciate ligament reconstruction: a biomechanical cadaveric study of a rectangular quadriceps and bone--patellar tendon--bone graft configuration versus a round hamstring graft

PURPOSE

The purposes of this study were to investigate anterior tibial translation under loading conditions after single-bundle (SB) anterior cruciate ligament (ACL) reconstruction using a rectangular tunnel placement strategy with quadriceps and bone--patellar tendon--bone (BPTB) graft and to compare these data with a SB hamstring reconstruction with a round tunnel design.

METHODS

In 9 human cadaveric knees, the knee kinematics were examined with robotic/universal force-moment sensor testing. Within the same specimen, the knee kinematics under simulated pivot-shift and KT-1000 arthrometer (MEDmetric, San Diego, CA) testing were determined at 0°, 15°, 30°, 60°, and 90° of flexion under different conditions: intact knee, ACL-deficient knee, and SB ACL-reconstructed knee. For the SB ACL-reconstructed knee, 3 different SB reconstruction techniques were used: a rectangular tunnel strategy (9 × 5 mm) with quadriceps graft, a rectangular tunnel strategy with BPTB graft, and a round tunnel strategy (7 mm) with hamstring graft.

RESULTS

In a simulated Lachman test, a statistically significant difference was found at 0° and 15° of knee flexion between the rectangular reconstruction with quadriceps graft (5.1 ± 1.2 mm and 8.3 ± 2 mm, respectively) or BPTB graft (5.3 ± 1.5 mm and 8 ± 1.9 mm, respectively) and the reconstruction using hamstring graft (7.2 ± 1.4 mm and 12 ± 1.8 mm, respectively) (P = .032 and P = .033, respectively, at 0°; P = .023 and P = .02, respectively, at 15°). On the simulated pivot-shift test at 0° and 15°, rectangular ACL reconstruction with quadriceps graft (3.9 ± 2.1 mm and 6.5 ± 1.7 mm, respectively) or BPTB graft (4.2 ± 1.8 mm and 6.7 ± 1.7 mm, respectively) showed a significantly lower anterior tibial translation when compared with round tunnel reconstruction (5.5 ± 2.1 mm and 7.9 ± 1.9 mm, respectively) (P = .03 and P = .041, respectively, at 0°; P = .042 and P = .046, respectively, at 15°).

CONCLUSIONS

Under simulated Lachman testing and pivot-shift testing, a reconstruction technique using a rectangular tunnel results in significantly lower anterior tibial translation at 0° and 15° of flexion in comparison to knees reconstructed with a hamstring SB graft using a round tunnel strategy.

CLINICAL RELEVANCE

ACL reconstruction with a rectangular tunnel and BPTB and quadriceps tendon might result in better anterior knee stability at low flexion angles than ACL reconstruction with hamstring SB graft and a round tunnel in the clinical setting.

Outcome of surgery for recurrent patellar dislocation based on the distance of the tibial tuberosity to the trochlear groove

We evaluated the outcome in a series of patients with recurrent patellar dislocation who had either medial transfer of the tibial tuberosity and lateral release or an isolated lateral release as the primary treatment. The decision to use one or other procedure was based on a pre-operative distance between the tibial tuberosity to the trochlear groove (TTTG) of less than 10 mm to include the tibial tuberosity transfer in addition to the lateral release.

Between April 2002 and December 2006, 49 patients (63 knees) underwent one of these procedures. A total of 35 patients (46 knees) was evaluated at a mean of 38 months (13 to 71) post-operatively. Medial transfer of the tibial tuberosity was performed in 33 knees and isolated lateral release in the remaining 13. Evaluation included the International Knee Documentation Committee (IKDC), the Kujala and the Short-form 36 scores. From the tibial tuberosity group 23 knees also underwent radiological examination at follow-up.

There were further episodes of patellar dislocation in six of the 46 knees available for review. Further dislocation was noted in five of 33 knees (15.2%) in the tibial tuberosity transfer group and in one of 13 knees (7.7%) in the lateral release group. The mean subjective IKDC score was 80.4 (sd 11.6), the mean Kujala score 88 (sd 8.2) and the mean objective IKDC score was 79% normal and 21% nearly normal. The mean post-operative TTTG distance in the tibial tuberosity transfer group was 8.9 mm (3.2 to 15.7) compared with the mean pre-operative value of 16.8 mm (12.2 to 24.4).

Three dimensional motion analysis of within and between day repeatability of tibial rotation during pivoting

Activities that involve a change in direction apply a high rotational load to the knee joint. Biomechanical analysis of such activities may be useful for determining mechanisms that underlie knee injury and the success of ligament reconstruction surgery. However, the reliability of the measurement of tibial rotation remains unclear. The purpose of this study was to determine the reliability of tibial rotation measurements during a pivoting task, both between testing sessions conducted on the same day and between those made one week apart. Three-dimensional motion analysis was used to measure peak internal tibial rotation and rotational excursion during a stair descent and pivoting task in eleven healthy subjects (six female, five males). Intraclass correlation coefficients (ICC (3, 1)) and typical error analyses were used to examine within and between day reliability. Tibial rotational excursion had excellent reliability for within day (ICC=0.82) and between day sessions (ICC=0.76) whereas peak internal rotation had good reliability (within ICC=0.74; between ICC=0.68). Typical error was less than 2.4 degrees for within day measures and 2.9 degrees for between day measures. It was concluded that tibial rotation can be measured reliably during pivoting. Typical error values were less than the usual group differences in rotational excursion reported in the literature. The ability to reliably quantify tibial rotation during dynamic activities is important in determining the causes of persisting instability following anterior cruciate ligament reconstruction.

Suspensory fixation of grafts in anterior cruciate ligament reconstruction: a biomechanical comparison of 3 implants

PURPOSE

Our purpose was to evaluate the biomechanical difference between 2 new soft-tissue anterior cruciate ligament (ACL) fixation devices (RetroButton [Arthrex, Naples, FL] and ToggleLoc [Biomet, Warsaw, IN]) and a clinically established implant (EndoButton CL; Smith & Nephew, Andover, MA).

METHODS

In test session 1 biomechanical testing was performed by use of 48 porcine femora fixed to a material testing machine. In session 2 the implants were tested alone. Cyclic loading was carried out for 1,000 cycles, followed by a load-to-failure test. The tested devices were as follows: EndoButton CL, 20-mm and 40-mm loops; RetroButton, 12/20-mm and 12/40-mm loops; and ToggleLoc, 20-mm and 40-mm loops.

RESULTS

In test session 1 the EndoButton CL showed higher motion per cycle (0.30 +/- 0.09 mm for 20-mm loop and 0.43 +/- 0.03 mm for 40-mm loop) but lower plastic displacement values (0.66 +/- 0.19 mm for 20-mm loop and 0.50 +/- 0.13 mm for 40-mm loop) than the objects of comparison. The RetroButton devices were the stiffest (331.47 +/- 133.92 N/mm for 12/20-mm loop and 265.66 +/- 103.97 N/mm for 12/40-mm loop). The highest ultimate failure load, however, was shown by the EndoButton CL devices. In test session 2 the EndoButton CL oscillated the most. The ToggleLoc devices elongated more than the objects of comparison (0.66 +/- 0.12 mm for 20-mm loop and 0.76 +/- 0.06 mm for 40-mm loop). The RetroButton devices were both the stiffest among the respective implants (542.7 +/- 148.0 N/mm for 12/20-mm loop and 379.0 +/- 40.1 N/mm for 12/40-mm loop). The EndoButton CL showed the highest values for displacement to failure (3.6 +/- 0.4 mm for 20-mm loop and 6.4 +/- 0.4 mm for 40-mm loop). The ToggleLoc devices failed the latest on load-to-failure testing.

CONCLUSIONS

All tested implants could provide adequate fixation strength. Despite advantages in the design of the EndoButton CL regarding its handling, the 2 newly released products showed superior material properties.

CLINICAL RELEVANCE

Suspensory fixation of hamstring grafts in ACL reconstruction is frequently associated with bone tunnel enlargement. Material properties and implant design may limit graft-tunnel motion and result in enlargement of the femoral bone tunnel. With improved implant design, suspensory graft fixation may still be an attractive fixation technique in primary and revision ACL reconstruction.

Radiological aspects of injuries of avalanche victims

OBJECTIVE

Increasing numbers of avalanche victims with polytrauma have highlighted their need for radiological injury characterisation, which this study examines.

METHODS

People in Tirol injured by avalanche during 1994-2005 and admitted to the Innsbruck Medical University Hospital were included. Data for this retrospective study were obtained from the Austrian avalanche register and local electronic patient files archive.

RESULTS

During the observation period 94 avalanche victims in Tirol were admitted to our hospital, and a mean of 1.5 radiological methods were used per person at presentation. A mean of three diagnoses per victim were recorded, of which one was eligible for radiological examination only. Most victims (56%) were diagnosed with hypothermia, followed by unspecific contusion (54%), injuries of ligaments, tendons or muscles (26%) and fracture (23%); 21 victims died in hospital.

CONCLUSIONS

Emergency radiological examination can discover injuries otherwise not immediately apparent. However, initial use of radiological assessments such as computed tomography for people admitted under cardiopulmonary resuscitation does not always ensure an optimal outcome.

The immediate effect of navigation on implant accuracy in primary mini-invasive unicompartmental knee arthroplasty

The success of unicompartmental knee arthroplasty (UKA) is highly dependent on the accuracy of the component alignment. Objective of the present study was to evaluate the immediate effect of image-free computer navigation technology on implant accuracy in primary mini-invasive UKA. This study reviews 40 patients with primary isolated arthritis of the medial compartment of the knee that underwent unicompartmental knee arthroplasty through a minimally invasive approach. A cohort of the 20 most recent consecutive UKA's implanted with standard instrumentation was followed by a cohort of the very first 20 consecutive cases after conversion to the navigated technique. There was no variability regarding implant (Oxford meniscal unicompartmental knee system--Biomet Orthopedics, Inc., Warsaw, Indiana 46580, USA), surgeons and surgical technique, except for the use of the navigation system (Treon plus--Medtronic Inc., Minnesota, MI, USA). The axis alignment and accuracy of implant positioning was measured on postoperative long-leg standing radiographs and standard lateral X-rays with regard to the valgus angle and the coronal and sagittal component angle. In addition, preoperative deformities of the mechanical leg axis, tourniquet time, age, gender, and body mass index were correlated. Statistical analyses were performed using the SPSS 14.0 (SPSS Inc., Chicago, IL, USA) software package. Optimal implant alignment including all measurements in the desired angular range was significantly (P=0.041) higher in the navigated cohort. Navigation eliminated outliers in the frontal mechanical alignment and coronal orientation of the femoral component totally and significantly (P<0.02). Furthermore, navigation narrowed the range of outliers in all other planes of component orientation. There were no statistically significant differences in the mean numerical values between the cohorts, except for the frontal mechanical alignment (P<0.009) and coronal tibial alignment (P<0.037). The average tourniquet time was increased by 10.95 min in the navigated cohort. Our results indicate that navigation immediately improves accuracy of bone cuts and reduces the number of outliers with implementation in UKA.

Anterior cruciate ligament injury with simultaneous locked bucket-handle tears of both medial and lateral meniscus in a 19-year-old female professional ski racer: a case report

Acute anterior cruciate ligament deficiency combined with simultaneous locked bucket-handle tears of both medial and lateral menisci have rarely been observed. This case report describes the first case of such a combined knee injury in an athlete including injury mechanism, clinical symptoms, specific signs on MRI, and treatment options.

Prospective evaluation of patellar tendon graft fixation in anterior cruciate ligament reconstruction comparing composite bioabsorbable and allograft interference screws

PURPOSE

Bioabsorbable interference screws have proved to be biologically safe and to provide adequate graft fixation. Metallic interference screws have therefore been continuously replaced over the years. However, degradation times are highly variable, and bony replacement of the screw does not always occur in human beings. Composite interference screws have recently been introduced to enhance bony integration. We evaluated 2 different composite interference screws and compared them with an allograft interference screw over a 2-year period after anterior cruciate ligament (ACL) reconstruction with an autologous bone-patellar tendon-bone graft.

METHODS

Three groups of patients were prospectively evaluated. Poly-L-lactid acid/hydroxyapatite composite screws (BioRCI-HA; Smith & Nephew, Andover, MA) (group A), poly-L-lactid acid/beta-tricalcium phosphate composite screws (Bilok; Atlantech, Radevormwald, Germany) (group B), or allograft interference screws (CorlS; Regeneration Technologies, Alachua, FL) (group C) were used for tibial fixation of a patellar tendon autograft in ACL reconstruction. Each group consisted of 20 patients (mean age, 32.2 +/- 10.9 years in group A, 32.3 +/- 10.6 years in group B, and 31.1 +/- 6.6 years in group C) with no significant (P < .05) differences in age, sex, and time of follow-up. Subjective and clinical International Knee Documentation Committee parameters were evaluated preoperatively and at 3, 12, and 24 months postoperatively; computed tomography scans were obtained postoperatively and at 3, 12, and 24 months; and magnetic resonance imaging (MRI) scans were obtained at 3 and 24 months postoperatively.

RESULTS

Screw breakage during insertion occurred in 2 cases (1 in group A and 1 in group B). There was no significant (P < .05) difference in subjective and clinical results at any time of follow-up. No inflammatory response could be detected on MRI in any of the patients in all groups. Computed tomography scans documented complete bone block incorporation at 3 months in all groups. Both composite interference screws showed signs of degradation but were still clearly visible 24 months after ACL reconstruction. At 12 months, a sclerotic rim around the screw cavity could be outlined in group B only. No bony replacement had taken place up to 24 months postoperatively in group A or B. In group C the allograft bone screw was completely integrated and barely visible after 24 months.

CONCLUSIONS

All 3 screw types provided adequate graft fixation and were associated with excellent clinical results and no inflammatory response on MRI. Ultimately, a resorbable screw has to be replaced by bone to facilitate revision surgery. Formation of a sclerotic rim around the outline of the screw makes later bony replacement (group B) unlikely. After 24 months, complete bony integration had only taken place when allograft screws were used.

CLINICAL RELEVANCE

At 24 months, no advantage of composite screw materials over conventional bioabsorbable screws could be detected. If composite materials will be of any advantage with respect to bony replacement has to be observed with longer-term follow-up. The allograft bone screw was completely incorporated and replaced by cancellous bone after 24 months. Unfortunately, the screw's more complicated handling, higher cost, and limited availability impair the possibilities for its standard clinical use.

Bony and cartilaginous anatomy of the patellofemoral joint

The patella as the largest sesamoid bone of the human body forms the patellofemoral joint with the patellar groove of the femur. The patellofemoral joint is a complex articulation with high functional and biomechanical requirements. Several anatomical variants of both patella and the trochlea exist. Multiple clinical problems of the knee may be caused by anatomical and physiological abnormalities of this joint. Exact knowledge about the anatomy, the biomechanics and the function of the patellofemoral joint is therefore required to understand its wide range of pathology.

Vordere Kreuzbandplastik mit proximaler Endobutton-Fixation eines Lig.-patellae-Transplantats

BACKGROUND

Interference screw fixation in ACL reconstruction with bone-patellar tendon-bone graft (BPTB) is a potential source of intraoperative complications such as graft laceration. Further problems are artifacts on MRI and screw removal in revision surgery. These problems can be avoided by using distant fixation with the EndoButton. We designed this study to evaluate the clinical as well as the subjective outcome of ACL reconstruction with BPTB graft and femoral fixation with the EndoButton.

METHODS

A total of 51 patients (7 female, 44 male) were examined 2-5 years after ACL reconstruction with BPTB graft and femoral fixation with the EndoButton. We used the IKDC form, Lysholm score, Tegner activity score, and digital radiographs (AP, lateral, axial) for the evaluation.

RESULTS

Of all the patients included in the study, 87% showed a "normal" or "nearly normal" knee function according to the IKDC score, Lysholm score 94.2+/-7.9, Tegner score 6.4+/-1.2, and subjective IKDC 89.9+/-11.9. Radiological signs of arthritic changes could be seen in ten cases.

CONCLUSION

The clinical outcome of ACL reconstruction with EndoButton fixation is comparable to other studies on ACL reconstruction with interference screw fixation. However, since the EndoButton avoids potential problems of the interference screw fixation, we recommend this fixation technique for ACL reconstruction with BPTB graft.

Postoperative evaluation of femoral tunnel position in ACL reconstruction: plain radiography versus computed tomography

Inaccurate femoral tunnel placement has been identified as one of the most frequent errors in failed anterior cruciate ligament reconstructions. Most surgeons evaluate the femoral tunnel position on plain radiographs but in a lot of cases it is difficult to detect the femoral tunnel. The goal of this study was to compare plain digital radiographs and multiplanar computed tomography (CT) scans for the evaluation of femoral tunnel position. We examined 50 patients 24-60 months postoperatively, following an arthroscopically-assisted anterior cruciate ligament reconstruction with central third bone-patellar tendon-bone graft. Endobutton fixation was used on the femoral side and titanium interference screws on the tibial side. Standard antero-posterior and lateral X-rays and a CT scan were obtained from each patient. Sagittal and frontal reconstructions of the CT scan were used for the evaluation. We measured the height of the center of the tunnel in the notch in the frontal plane, and the position of the tunnel along Blumensaat's line (BL) in the lateral plane. Measurements are reported as percentages of total notch height and of the length of BL. On plain X-rays the tunnel was invisible in 46 cases in the anterior-posterior plane and in eight cases on the lateral plane. The average position in the frontal plane was 89.8%, and in the lateral plane 38.6%. In the CT scans, measurements were able to be done in 48 patients. The frontal-plane position averaged 90.5% and the lateral-plane position 34.1%. Pearson's correlation coefficient for the values in the lateral plane for CT and X-rays was low at 0.22, with p>0.05. In our group of 50 patients we were able to detect the femoral tunnel on both plains of standard X-rays in only four patients, whereas it was possible to take accurate measurements in 48 patients on reconstructed CT scans. We advocate the use of CT technology for the evaluation of femoral position whenever precise measurements are needed.

Effect of relaxation training on personal adjustment and perceptions of organizational climate

The chief aim of the present study was to investigate the effect of relaxation training on personal adjustment and perceptions of organizational climate. The Stern Activity Index and Organizational Climate Index along with the Bendig Manifest Anxiety Scale were administered to 71 volunteer Ss (28 males and 43 females) as pre- and post-test measures. The Ss were randomly assigned to three groups, seminar and relaxation training, seminar and a placebo condition, and no treatment. A one-way multivariate analysis showed a significant mean difference. Results obtained from t tests indicated a significant reduction in anxiety and an increase in personal adjustment. Changes in perceptions of organizational climate, although in the predicted direction, were not statistically significant.