Altered knee kinematics after posterior cruciate ligament single-bundle reconstruction-a comprehensive prospective biomechanical in vivo analysis

Purpose: Passive tibiofemoral anterior-posterior (AP) laxity has been extensively investigated after posterior cruciate ligament (PCL) single-bundle reconstruction. However, the PCL also plays an important role in providing rotational stability in the knee. Little is known in relation to the effects of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity. Gait biomechanics after PCL reconstruction are even less understood. The aim of this study was a comprehensive prospective biomechanical in vivo analysis of the effect of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity, passive anterior-posterior laxity, and gait pattern. Methods: Eight patients undergoing PCL single-bundle reconstruction (seven male, one female, mean age 35.6 ± 6.6 years, BMI 28.0 ± 3.6 kg/m2) were analyzed preoperatively and 6 months postoperatively. Three of the eight patients received additional posterolateral corner (PLC) reconstruction. Conventional stress radiography was used to evaluate passive translational tibiofemoral laxity. A previously established rotometer device with a C-arm fluoroscope was used to assess passive tibiofemoral rotational laxity. Functional gait analysis was used to examine knee kinematics during level walking. Results: The mean side-to-side difference (SSD) in passive posterior translation was significantly reduced postoperatively (12.1 ± 4.4 mm vs. 4.3 ± 1.8 mm; p < 0.01). A significant reduction in passive tibiofemoral rotational laxity at 90° knee flexion was observed postoperatively (27.8° ± 7.0° vs. 19.9° ± 7.5°; p = 0.02). The range of AP tibiofemoral motion during level walking was significantly reduced in the reconstructed knees when compared to the contralateral knees at 6-month follow-up (16.6 ± 2.4 mm vs. 13.5 ± 1.6 mm; p < 0.01). Conclusion: PCL single-bundle reconstruction with optional PLC reconstruction reduces increased passive tibiofemoral translational and rotational laxity in PCL insufficient knees. However, increased passive tibiofemoral translational laxity could not be fully restored and patients showed altered knee kinematics with a significantly reduced range of tibiofemoral AP translation during level walking at 6-month follow-up. The findings of this study indicate a remaining lack of restoration of biomechanics after PCL single-bundle reconstruction in the active and passive state, which could be a possible cause for joint degeneration after PCL single-bundle reconstruction.

Quantification of morning stiffness to assess disease activity and treatment effects in rheumatoid arthritis

OBJECTIVES

The clinical parameter of morning stiffness is widely used to assess the status of RA, but its accurate quantitative assessment in a clinical setting has not yet been successful. This lack of individual quantification limits both personalized medication and efficacy evaluation in the treatment of RA.

METHODS

We developed a novel technology to assess passive resistance of the MCP III joint (stiffness) and its passive range of motion (PRoM). Within this pilot study, 19 female postmenopausal RA patients and 9 healthy controls were examined in the evening as well as the morning of the following day. To verify the specificity of the biomechanical quantification, 11 patients with RA were assessed both prior to and ∼3 h after glucocorticoid therapy.

RESULTS

While the healthy controls showed only minor changes between afternoon and morning, in RA patients the mean PRoM decreased significantly by 18% (s.d. 22) and stiffness increased significantly by 20% (s.d. 18) in the morning compared with the previous afternoon. We found a significant positive correlation between RA activity and biomechanical measures. Glucocorticoids significantly increased the mean PRoM by 16% (s.d. 11) and reduced the mean stiffness by 23% (s.d. 22).

CONCLUSION

This technology allowed mechanical stiffness to be quantified in MCP joints and demonstrated high sensitivity with respect to disease status as well as medication effect in RA patients. Such non-invasive, low-risk and rapid assessment of biomechanical joint stiffness opens a novel avenue for judging therapy efficacy in patients with RA and potentially also in other non-RA inflammatory joint diseases.

Longitudinal changes in location-specific cartilage thickness and T2 relaxation-times after posterior cruciate ligament reconstruction for isolated and multiligament injury

BACKGROUND

Knee cartilage undergoes pathological changes after anterior cruciate ligament rupture. However, little is known about the development and progression of structural pathology after posterior cruciate ligament (PCL) injury. This study aimed to determine the location-specific longitudinal changes in knee cartilage morphology (thickness) and composition (T2 relaxation-times) after PCL rupture and reconstruction (PCLR) and compare these to uninjured controls.

METHODS

Fifteen adults (mean age 39 years (standard deviation 10), 12 men) with PCLR for isolated and multiligment injury had MRIs acquired at a minimum 5 years post-PCLR and 1 year later. Location-specific changes in knee cartilage thickness and T2 relaxation-times were determined quantitatively after segmentation, and compared with annualised cartilage changes in 13 active controls (mean age 45 years (standard deviation 4), 6 men).

FINDINGS

Following PCLR, the annual loss of cartilage thickness was greatest in the medial femoral condyle (mean -4.0%, 95% confidence interval [95% CI] -6.7, -1.4), medial tibia (mean -3.7%, 95% CI -6.1, -1.3), and patella (mean -3.2%, 95% CI -4.7, -1.6). In the medial femoral condyle and trochlea, the PCLR group lost significantly more cartilage thickness than uninjured controls (mean difference -3.7%, 95% CI -0.9, -6.5; and -1.8%, 95% CI -0.1, -3.6, respectively). Deep and superficial zone T2 relaxation-times were relatively constant over time, without longitudinal differences between PCLR and control knees.

INTERPRETATION

PCL reconstructed knees displayed substantially greater rates of cartilage loss in the medial tibiofemoral and patellofemoral compartments compared to uninjured controls, highlighting that the process of degeneration remains active many years after injury.

Association between changes in molecular biomarkers of cartilage matrix turnover and changes in knee articular cartilage: a longitudinal pilot study

Background

An early detection of Osteoarthritis is urgently needed and still not possible until today. The aim of the study was to assess whether molecular biomarkers of cartilage turnover are associated with longitudinal change in knee cartilage thickness during a 2 year period in individuals with increased risk of developing knee osteoarthritis. A secondary aim was to assess whether prior knee injury or subjective patient-reported outcomes at baseline (BL) were associated with articular cartilage changes. Nineteen volleyball players (mean age 46.5 ± 4.9 years, 47% male) with a 30-year history of regular high impact training were recruited. The serum biomarkers Cpropeptide of type II procollagen (CPII), cartilage oligomeric matrix protein (COMP), collagenase generated carboxy-terminal neoepitope of type II collagen (sC2C), cartilage intermediate layer protein 2 (CILP-2), and the urine biomarkers C-telopeptide of type II collagen (CTX-II) and collagenase-generated peptide(s) of type II collagen (C2C-HUSA) were assessed at BL and at 2 year follow up (FU). Femorotibial cartilage thinning, thickening and absolute thickness change between BL and FU was evaluated from magnetic resonance imaging. Subjective clinical status at BL was evaluated by the International Knee Documentation Committee Subjective Knee Form and the Short-Form 36 Physical Component Score.

Results

CILP-2 was significantly higher at FU and linearly associated with the absolute cartilage thickness change during the experimental period. Prior injury was a predictor of increased absolute cartilage thickness change.

Conclusion

Measuring the change in the cartilage biomarker CILP-2 might be a valid and sensitive method to detect early development of knee osteoarthritis as CILP-2 appears to be related to cartilage thickness loss in certain individuals with increased risk of developing knee osteoarthritis. Prior knee injury may be predictive of increased articular cartilage thickness change.

Modifications of femoral component design in multi-radius total knee arthroplasty lead to higher lateral posterior femoro-tibial translation

PURPOSE

As the aims of changes in total knee arthroplasty (TKA) designs are to reinstate more natural kinematics, the current study evaluated the in vivo kinematics in patients who underwent a cruciate retaining gradually changing femoral radius ("G-CURVE") against a cruciate retaining conventional changing femoral radius ("J-CURVE") geometry TKA design. The hypothesis of the study is that the G-CURVE design would allow a substantial increase in the femoral rollback compared to the J-CURVE design.

METHODS

Retrospective study design. Thirty patients were included (G-CURVE, n = 20; J-CURVE, n = 10). Single-plane fluoroscopic analysis and marker-based motion capture gait analysis was performed to analyse dynamic tibiofemoral motion during weight-bearing and unloaded activities at 24 month after index surgery.

RESULTS

The analysis of the medial and lateral points on the tibia plateau during the unloaded flexion-extension and the weight-bearing lunge activities revealed a significant difference in femoral rollback in G-CURVE TKA above 60° (p = 0.001) and 30° (p = 0.02) of knee flexion, respectively. Moreover, the lateral condyle of the G-CURVE showed a higher extent of femoral rollback while the lateral condyle of the J-CURVE rolled forward.

CONCLUSION

At 2 years post-operative, the G-CURVE TKA showed significant differences in femoro-tibial translation in comparison with the J-CURVE system, in vivo. The G-CURVE resulted in an increased lateral rollback and simultaneously in an elimination of the paradoxical medial roll-forward present in the J-CURVE design. Moreover, knee kinematics analysis showed significant differences between unloaded and weight-bearing conditions revealing the impact of load and muscle force. The analysis conducted in this study contributes to further understand the principal movement characteristics in widely used older designs in comparison with recently developed concepts to get a better overview on their potential benefits on in vivo kinematics.

LEVEL OF EVIDENCE

III.

Degenerative changes after posterior cruciate ligament reconstruction are irrespective of posterior knee stability: MRI-based long-term results

INTRODUCTION

Posterior cruciate ligament reconstruction (PCLR) is advocated to prevent an early onset of osteoarthritis. We hypothesized that posterior instability after PCLR correlates with degenerative changes.

MATERIALS AND METHODS

MRIs of 42 (12 female/30 male; 39 ± 9 years) patients were enrolled with a minimum 5-year follow-up (FFU) after PCLR. In addition, 25 contralateral and 15 follow-up MRIs (12 months after baseline) were performed. Degenerative changes were graded using WORMS. Posterior tibial translation (PTT) was measured using posterior stress radiographs. Outcome parameters included WORMS/cartilage subscore for the whole joint, patellofemoral (PFJ), medial (MFTJ), and lateral femorotibial joint (LFTJ).

RESULTS

Final follow-up was 101 (range 68-168) months. WORMS reached 41.5 [18.5-56.8]. Regional WORMS for PFJ was significantly higher than MFTJ and LFTJ. Cartilage subscore yielded 7 [2.8-15]. MFTJ and PFJ were significantly higher than LFTJ. Primary outcome parameters were significantly higher than the contralateral knee (P < 0.0001) and significantly increased within 12 months (P = 0.0002). There was a significant correlation between the intraoperative degree of cartilage injury and WORMS (P < 0.0001 with r = 0.64) and between the number of previous surgery and the cartilage subscore (P = 0.03 with r = 0.32). Meniscal surgery led to a significantly higher WORMS (P = 0.035). Combined risk models revealed that women below the mean age had significantly lower WORMS (P = 0.001) and cartilage subscores (P = 0.003).

CONCLUSIONS

Patients undergo degenerative changes after PCLR, which are significantly higher compared to the contralateral knee. These occur predominantly at PFJ/MFTJ and are irrespective of posterior stability. Concomitant meniscus/cartilage injuries and a high number of previous surgeries are further risk factors.

Longitudinal change in patellofemoral cartilage thickness, cartilage T2 relaxation times, and subchondral bone plate area in adolescent vs mature athletes

OBJECTIVE

Patellofemoral cartilage changes have been evaluated in knee trauma and osteoarthritis; however, little is known about changes in patellar and trochlear cartilage thickness, T2 relaxation-time and subchondral bone plate area (tAB) during growth. Our prospective study aimed to explore longitudinal change in patellofemoral cartilage thickness, T2 and tAB in adolescent athletes, and to compare these data with those of mature (i.e., adult) athletes.

MATERIALS AND METHODS

20 adolescent (age 16±1years) and 20 mature (46±5years) volleyball players were studied over 2-years (10 men and 10 women each group). 1.5T MRI 3D-VIBE and multi-echo spin-echo sequences were acquired at baseline and 2-year follow-up. Using manual segmentation and 3D reconstruction, longitudinal changes in patellar and trochlear cartilage thickness, patellar cartilage T2 (mono-exponential decay curve with five echoes [9.7-67.9ms]), and patellar and trochlear tAB were determined.

RESULTS

The annual increase in both patellar and trochlear cartilage thickness was 0.8% (95% confidence interval [CI] 0.6, 1.0) and 0.6% (0.3, 0.9), for adolescent males and females respectively; the longitudinal gain in patellar and trochlear tAB was 1.3% (1.1, 1.5) and 0.5% (0.2, 0.8), and 1.6% (1.1, 2.2) and 0.8% (0.3, 0.7) for adolescent males and females, respectively (no significant between-sex differences). Mature athletes showed smaller gains in tAB, and loss of <1% of cartilage thickness annually. While no significant sex-differences existed in adolescent patellar T2 changes, mature males gained significantly greater T2 than mature females (p=0.002-0.013).

CONCLUSIONS

Patellar and trochlear cartilage thickness and tAB were observed to increase in young athletes in late adolescence, without significant differences between sexes. Mature athletes displayed patellar cartilage loss (and T2 increases in mature males), potentially reflecting degenerative changes.

MRI findings of knee abnormalities in adolescent and adult volleyball players

Background

To longitudinally and cross-sectionally evaluate knee abnormalities by sex and age in adolescent and adult volleyball athletes over 2 years using magnetic resonance imaging (MRI).

Methods

Thirty-six high-level volleyball athletes (18 adolescents: 56% female, mean age 16.0 ± 0.8 years; and 18 adults: 50% female, mean age 46.8 ± 5.1 years) were imaged by MRI at BL and at 2-year follow-up (FU). Prevalence and severity of cartilage lesions, subarticular bone marrow lesions (BMLs), subarticular cysts, osteophytes, and ligament and meniscus integrity were evaluated by sex and by age cohort (adolescents and adults) using the whole-organ MRI score (WORMS).

Results

There were no significant longitudinal changes in any of the features within any of the sex or age groups. No significant differences were found in overall prevalence or severity of any of the features between males and females, although at FU, males had a significantly higher prevalence of osteophytes in the medial femorotibial joint (MFTJ) than females (p=0.044). Compared to adolescents, adult volleyball players had a significantly greater prevalence and severity of cartilage lesions (p<0.001 for both), BMLs (p=0.0153 and p=0.005), and osteophytes (p≤0.003 and p<0.001), and more severe meniscal lesions (p≤0.021).

Conclusion

We found significant differences in the prevalence and severity of knee abnormalities between adolescent and adult volleyball players, but no overall differences by sex. These findings lay the groundwork for further investigations with larger cohorts and longer FU times to determine whether or not these knee abnormalities are associated with the development of OA.

Differences in biomarkers of cartilage matrix turnover and their changes over 2 years in adolescent and adult volleyball athletes

BACKGROUND

This study aimed the feasibility to assess longitudinal changes in biomarkers of cartilage turnover and to determine their relationship with patient-rated outcomes over 2 years in volleyball athletes.

METHODS

Thirty-seven athletes were studied: 18 adolescents (age 15.9 ± 0.64 years) in a 2-year intensive volleyball training program and 19 adult recreational volleyball players (age 46.5 ± 4.9 years). Blood and serum samples were taken at baseline (BL) and 2-year follow-up (FU). Subjects completed the International Knee Documentation Committee (IKDC) Subjective Knee Form and the Short-Form 36 (SF-36) at BL.

RESULTS

Thirteen adolescents (72%) had open growth plates at BL (BL open adolescents), the rest had closed growth plates at BL (BL closed adolescents), and all but one adolescent had closed growth plates at FU as assessed by MRI. BL open and closed adolescents had greater levels of the cartilage degradation-based biomarkers 45 mer collagenase peptide of type II collagen (C2C-HUSA) and C-telopeptide of type II collagen (CTX-II) than adults. BL open adolescents showed decreases in C2CHUSA, collagen synthesis marker C-propeptide of type II procollagen (CPII), and CTXII, and adults showed increases in cartilage intermediate layer protein 2 (CILP-2) and C2C-HUSA. In adolescents, IKDC scores were correlated with CPII changes. In adults, SF-36 Physical Component Scores were correlated with cartilage oligomeric matrix protein (COMP) changes.

CONCLUSION

Significant differences in biomarker levels over time show the feasibility to assess their changes. Greater levels of C2C-HUSA and CTX-II in adolescents than in adults may reflect increased cartilage turnover in response to higher joint loading. CPII and COMP may be more reflective of subjective patient outcomes. These biomarkers may thus be useful in assessing mechanical loading-induced cartilage changes, their associated symptoms, and Osteoarthritis risk in athletes.

Longitudinal bone, muscle and adipose tissue changes in physically active subjects - sex differences during adolescence and maturity

OBJECTIVES

To explore changes in bone, muscle and adipose tissue composition in athletes with high physical activity levels at different stages of life.

METHODS

Thigh MRIs were acquired at baseline and 2-year follow-up for 20 young (16±1 years) and 20 mature (46±5 years) athletes (10 males, 10 females, respectively). Longitudinal changes in cross-sectional areas (CSAs) of femoral bone, quadriceps muscle, and thigh subcutaneous (SCF) and intermuscular (IMF) adipose tissue were evaluated.

RESULTS

Adolescent males displayed significant muscle (+5.0%, 95%CI: 0.8, 9.2) and bone growth (+2.9%, 95%CI: 1.3, 4.5), whereas adolescent females did not (muscle: +0.8%, 95%CI: -2.2, 3.8; bone: +1.9%, 95%CI: -2.1, 5.6). Adolescent and mature females showed significant SCF increases (+11.0%, 95%CI: 0.9, 21.1 and +6.0%, 95%CI: 0.6, 11.4, respectively), whereas adolescent and mature males did not (+7.2%, 95%CI: -8.0, 22.5 and +1.5%, 95%CI: -9.7, 11.8, respectively). Muscle and bone changes were highly correlated in adolescent males (r=0.66), mature males (r=0.75) and mature females (r=0.68) but not in adolescent females (r=-0.11).

CONCLUSIONS

The results suggest sex-specific patterns of age-related change in bone, muscle and adipose tissue, and tight coupling of bone and muscle growth. Sex-specific bone-muscle-adipose tissue relationships may have implications for understanding sex differences in fracture risk.

The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction

While the anterior cruciate ligament (ACL) is considered one of the most important ligaments for providing knee joint stability, its influence on rotational laxity is not fully understood and its role in resisting rotation at different flexion angles in vivo remains unknown. In this prospective study, we investigated the relationship between in vivo passive axial rotational laxity and knee flexion angle, as well as how they were altered with ACL injury and reconstruction. A rotometer device was developed to assess knee joint rotational laxity under controlled passive testing. An axial torque of ±2.5Nm was applied to the knee while synchronised fluoroscopic images of the tibia and femur allowed axial rotation of the bones to be accurately determined. Passive rotational laxity tests were completed in 9 patients with an untreated ACL injury and compared to measurements at 3 and 12 months after anatomical single bundle ACL reconstruction, as well as to the contralateral controls. Significant differences in rotational laxity were found between the injured and the healthy contralateral knees with internal rotation values of 8.7°±4.0° and 3.7°±1.4° (p = 0.003) at 30° of flexion and 9.3°±2.6° and 4.0°±2.0° (p = 0.001) at 90° respectively. After 3 months, the rotational laxity remained similar to the injured condition, and significantly different to the healthy knees. However, after 12 months, a considerable reduction of rotational laxity was observed towards the levels of the contralateral controls. The significantly greater laxity observed at both knee flexion angles after 3 months (but not at 12 months), suggests an initial lack of post-operative rotational stability, possibly due to reduced mechanical properties or fixation stability of the graft tissue. After 12 months, reduced levels of rotational laxity compared with the injured and 3 month conditions, both internally and externally, suggests progressive rotational stability of the reconstruction with time.

Muscle and tendon adaptation in adolescent athletes: A longitudinal study

There is evidence that a non-uniform adaptation of muscle and tendon in young athletes results in increased tendon stress during mid-adolescence. The present longitudinal study investigated the development of the morphological and mechanical properties of muscle and tendon of volleyball athletes in a time period of 2 years from mid-adolescence to late adolescence. Eighteen elite volleyball athletes participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis, medialis and intermedius morphology, and patellar tendon mechanical and morphological properties in mid-adolescence (16 ± 1 years) and late adolescence (18 ± 1 years). Muscle strength, anatomical cross-sectional area (CSA), and volume showed significant (P < 0.05) but moderate increases of 13%, 6%, and 6%, respectively. The increase of patellar tendon CSA (P < 0.05) was substantially greater (27%) and went in line with increased stiffness (P < 0.05; 25%) and reduced stress (P < 0.05; 9%). During late adolescence, a pronounced hypertrophy of the patellar tendon led to a mechanical strengthening of the tendon in relation to the functional and morphological development of the muscle. These adaptive processes may compensate the unfavorable relation of muscle strength and tendon loading capacity in mid-adolescence and might have implications on athletic performance and tendon injury risk.

Longitudinal analysis of MR spin-spin relaxation times (T2) in medial femorotibial cartilage of adolescent vs mature athletes: dependence of deep and superficial zone properties on sex and age

OBJECTIVE

Cartilage spin-spin magnetic resonance imaging (MRI) relaxation time (T2) represents a promising imaging biomarker of "early" osteoarthritis (OA) known to be associated with cartilage composition (collagen integrity, orientation, and hydration). However, no longitudinal imaging studies have been conducted to examine cartilage maturation in healthy subjects thus far. Therefore, we explore T2 change in the deep and superficial cartilage layers at the end of adolescence.

METHODS

Twenty adolescent and 20 mature volleyball athletes were studied (each 10 men and 10 women). Multi-echo spin-echo (MESE) images were acquired at baseline and 2-year follow-up. After segmentation, cartilage T2 was calculated in the deep and superficial cartilage layers of the medial tibial (MT) and the central, weight-bearing part of the medial femoral condyle (cMF), using five echoes (TE 19.4-58.2 ms).

RESULTS

16 adolescent (6 men, 10 women, baseline age 15.8 ± 0.5 years) and 17 mature (nine men, eight women, age 46.5 ± 5.2 years) athletes had complete baseline and follow-up images of sufficient quality to compute T2. In adolescents, a longitudinal decrease in T2 was observed in the deep layers of MT (-2.0 ms; 95% confidence interval (CI): [-3.4, -0.6] ms; P < 0.01) and cMF (-1.3 ms; [-2.4, -0.3] ms; P < 0.05), without obvious differences between males and females. No significant change was observed in the superficial layers, or in the deep or superficial layers of the mature athletes.

CONCLUSION

In this first pilot study on quantitative imaging of cartilage maturation in healthy, athletic subjects, we find evidence of cartilage compositional change in deep cartilage layers of the medial femorotibial compartment in adolescents, most likely related to organizational changes in the collagen matrix.

Automatic initial contact detection during overground walking for clinical use

The division of gait into cycles is crucial for identifying deficits in locomotion, particularly to monitor disease progression or rehabilitative recovery. Initial contact (IC) events are often used to separate movement into repetitive cycles yet automatic methods for IC identification in pathological gait are limited in both number and capacity. The aim of this work was to develop a more precise algorithm in IC detection. A projected heel markers distance (PHMD) algorithm is presented here and compared for accuracy to the high pass algorithm (HPA) in IC identification. Kinematic gait data from two clinical cohorts were analyzed and processed automatically for IC detection: (1) unilateral total hip arthroplasty (THA) patients (n=27) and (2) cerebral palsy pediatric (CPP) patients (n=20). IC events determined by the two algorithms were benchmarked against the IC events detected manually and from force plates. The PHMD method detected 96.6% IC events in THA patients and 99.1% in CPP patients with an average error of 5.3 ms and 18.4 ms. The HPA method detected 99.1% IC events in THA patients and 97.3% IC events in CPP patients, with an average error of 57.5 ms and 10.2 ms. PHMD identified no superfluous IC events, whereas 51.5% of all THA IC and 47.6% of CPP IC were superfluous events requiring manual deletion with HPA. With the superior comparison against the current gold standard, the PHMD algorithm appears valid for a wide spectrum of clinical data sets and allows for precise, fully automatic processing of kinematic gait data without additional sensors, triggers, or force plates.

Evidence of imbalanced adaptation between muscle and tendon in adolescent athletes

Adolescence may be regarded as a critical phase of tissue plasticity in young growing athletes, as the adaptation process of muscle-tendon unit is affected by both environmental mechanical stimuli and maturation. The present study investigated potential imbalances of knee extensor muscle strength and patellar tendon properties in adolescent compared with middle-aged athletes featuring long-term musculotendinous adaptations. Nineteen adolescent elite volleyball athletes [(A), 15.9 ± 0.6 years] and 18 middle-aged competitively active former elite volleyball athletes [(MA), 46.9 ± 0.6 years] participated in magnetic resonance imaging and ultrasound-dynamometry sessions to determine quadriceps femoris muscle strength, vastus lateralis morphology and patellar tendon mechanical and morphological properties. There was no significant age effect on the physiological cross-sectional area of the vastus lateralis and maximum knee extension moment (P > 0.05) during voluntary isometric contractions. However, the patellar tendon cross-sectional area was significantly smaller (A: 107.4 ± 27.5 mm(2) ; MA: 121.7 ± 39.8 mm(2) ) and the tendon stress during the maximal contractions was significantly higher in adolescent compared with the middle-aged athletes (A: 50.0 ± 10.1 MPa; MA: 40.0 ± 9.5 MPa). These findings provide evidence of an imbalanced development of muscle strength and tendon mechanical and morphological properties in adolescent athletes, which may have implications for the risk of tendon overuse injuries.

Longitudinal change in femorotibial cartilage thickness and subchondral bone plate area in male and female adolescent vs. mature athletes

Little is known about changes in human cartilage thickness and subchondral bone plate area (tAB) during growth. The objective of this study was to explore longitudinal change in femorotibial cartilage thickness and tAB in adolescent athletes, and to compare these data with those of mature former athletes. Twenty young (baseline age 16.0 ± 0.6 years) and 20 mature (46.3 ± 4.7 years) volleyball athletes were studied (10 men and 10 women in each group). Magnetic resonance images were acquired at baseline and at year 2-follow-up, and longitudinal changes in cartilage thickness and tAB were determined quantitatively after segmentation. The yearly increase in total femorotibial cartilage thickness was 0.8% (95% confidence interval [CI]: -0.5; 2.1%) in young men and 1.4% (95% CI: 0.7; 2.2%) in young women; the gain in tAB was 0.4% (95% CI: -0.1; 0.8%) and 0.7% (95% CI: 0.2; 1.2%), respectively (no significant difference between sexes). The cartilage thickness increase was greatest in the medial femur, and was not significantly associated with the variability in tAB growth (r=-0.19). Mature athletes showed smaller gains in tAB, and lost >1% of femorotibial cartilage per annum, with the greatest loss observed in the lateral tibia. In conclusion, we find an increase in cartilage thickness (and some in tAB) in young athletes toward the end of adolescence. This increase appeared somewhat greater in women than men, but the differences between both sexes did not reach statistical significance. Mature (former) athletes displayed high rates of (lateral) femorotibial cartilage loss, potentially due to a high prevalence of knee injuries.

Anterior cruciate ligament-deficient patients with passive knee joint laxity have a decreased range of anterior-posterior motion during active movements

BACKGROUND

Although instability of the knee joint is known to modify gait patterns, the amount that patients compensate for joint laxity during active movements remains unknown.

PURPOSE

By developing a novel technique to allow the assessment of tibiofemoral kinematics, this study aimed to elucidate the role of passive joint laxity on active tibiofemoral kinematics during walking.

STUDY DESIGN

Controlled laboratory study.

METHODS

Using motion capture, together with combinations of advanced techniques for assessing skeletal kinematics (including the symmetrical axis of rotation approach [SARA], symmetrical center of rotation estimation [SCoRE], and optimal common shape technique [OCST]), a novel noninvasive approach to evaluate dynamic tibiofemoral motion was demonstrated as both reproducible and repeatable. Passive and active anterior-posterior translations of the tibiofemoral joint were then examined in 13 patients with anterior cruciate ligament (ACL) ruptures that were confirmed by magnetic resonance imaging and compared with those in their healthy contralateral limbs.

RESULTS

Passive tibial anterior translation was significantly greater in the ACL-ruptured knees than in the contralateral healthy controls. However, the femora of the ACL-ruptured knees generally remained more posterior (~3 mm) relative to the tibia within a gait cycle of walking compared with the healthy limbs. Surprisingly, the mean range of tibiofemoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL-ruptured knees than in the healthy joints (P = .026). A positive correlation was detected between passive laxity and active joint mobility, but with a consistent reduction in the range of tibiofemoral anterior-posterior translation of approximately 3 mm in the ACL-deficient knees.

CONCLUSION

It seems that either active stabilization of tibiofemoral kinematics or anterior subluxation of the tibia reduces joint translation in lax knees. This implies that either a muscular overcompensation mechanism or a physical limitation due to secondary passive stabilizers occurs within the joint and thus produces a situation that has a reduced range of active motion compared with knees with physiological stability.

CLINICAL RELEVANCE

The reduced range of active tibiofemoral translation suggests overloading of the passive structures in passively lax knees, either through excessive muscular action or joint subluxation, and could provide a plausible mechanism for explaining posttraumatic degeneration of cartilage in the joint.

Optical measurement of adipose tissue thickness and comparison with ultrasound, magnetic resonance imging, and callipers

Near-infrared spectroscopy is used to quantify the subcutaneous adipose tissue thickness (ATT) over five muscle groups (vastus medialis, vastus lateralis, gastrocnemius, ventral forearm and biceps brachii muscle) of healthy volunteers (n=20). The optical lipid signal (OLS) was obtained from the second derivative of broad band attenuation spectra and the lipid absorption peak (lambda=930 nm). Ultrasound and MR imaging as well as mechanical calliper readings were taken as reference methods. The data show that the OLS is a good predictor for ATT (<16 mm) with absolute and relative errors of <0.8 mm and <24%, respectively. The optical method compares favourably with calliper reading. The finding of a non-linear relationship of optical signal vs. ultrasound is explained by a theoretical two-layer model based on the diffusion approximation for the transport of photons. The crosstalk between the OLS and tissue hemoglobin concentration changes during an incremental cycling exercise was found to be small, indicating the robustness of OLS. Furthermore, the effect of ATT on spatially-resolved spectroscopy measurements is shown to decrease the calculated muscle hemoglobin concentration and to increase oxygen saturation.

Fluorescence tomography technique optimized for noninvasive imaging of the mouse brain

In vivo molecular fluorescence tomography of brain disease mouse models has two very specific demands on the optical setup: the use of pigmented furry mice does not allow for a purely noncontact setup, and a high spatial accuracy is required on the dorsal side of the animal due to the location of the brain. We present an optimized setup and tomographic scheme that meet these criteria through a combined CW reflectance-transmittance fiber illumination approach and a charge-coupled device contactless detection scheme. To consider the anatomy of the mouse head and take short source detector separations into account, the forward problem was evaluated by a Monte Carlo simulation input with a magnetic resonance image of the animal. We present an evaluation of reconstruction performance of the setup under three different condition. (i) Using a simulated dataset, with well-defined optical properties and low noise, the reconstructed position accuracy is below 0.5 mm. (ii) Using experimental data on a cylindrical tissue-simulating phantom with well-defined optical properties, a spatial accuracy of about 1 mm was found. (iii) Finally, on an animal model with a fluorescent inclusion in the brain, the target position was reconstructed with an accuracy of 1.6 mm.