Rehabilitation following microfracture for chondral injury in the knee

Full-thickness chondral defects in the knee are common, and these articular cartilage lesions may present in various clinical settings and at different ages. Articular cartilage defects that extend full thickness to subchondral bone rarely - by providing a suitable environment for new tissue formation and takes advantage of the body's own healing potential. Proper surgical technique and rehabilitation improve the success rate of the microfracture procedure. The goals are to alleviate the pain and disability that can result from chondral lesions and restore joint conformity, thereby preventing late degenerative changes in the joint.

Effect of lateral heel wedges on sagittal and transverse plane kinematics of trotting Shetland ponies and the influence of feeding and training regimes

REASONS FOR PERFORMING STUDY

Lateral heel wedges are used to treat horses and ponies with patella fixation or bone spavin. However, these therapies are purely empirically based and lack scientific evidence.

OBJECTIVES

Lateral heel wedges would change joint motion in the sagittal, but mainly in the transversal planes, in healthy horses. This effect would be increased by restricted feeding and decreased by extra training.

METHODS

A group of 24 Shetland ponies age 3 years was used, as foals had been assigned to restricted and ad libitum (ad lib) feeding, and low and high level training groups of 6 animals each. An experienced judge evaluated passive patella luxation in the square standing pony, using a score of 0 (normal) to 4 (stationary patella luxation). The motion of the markers, glued to the skin covering skeletal landmarks on the left fore- and hindlimbs, was recorded 3 dimensionally at a frequency of 300 Hz using a modified CODA-3 apparatus while trotting on a treadmill at a speed of 3.0 m/sec, before and directly after 5 degrees lateral heel wedges had been applied to the hindlimbs. After data analysis, the kinematic variables in the sagittal and transversal plane, under these 3 conditions (wedge, feeding, training), were compared statistically using a multivariate repeated measures analysis, general linear model (P < 0.05).

RESULTS

In the sagittal plane, an acute change in hind hoof conformation resulted in a less animated trot with a less protracted forelimb and less hindlimb flexion. This is similar, although less pronounced, to the decrease in limb flexion reported previously as a result of restricted feeding. More specifically, lateral heel wedges resulted in significant changes in the transversal plane angles of all joints in the hindlimb. The stifle joint became maximally 1.8 degrees more adducted just before the end of the stance phase, while the tarsal joint was 2.9 degrees and fetlock joint 4.7 degrees more abducted (P < 0.05). In the restricted feeding group, stifle joint adduction was 85 degrees and tarsal joint abduction 5.6 degrees larger than in the ad libitum feeding group (P < 0.05). The patella luxation score was also significantly higher in this group (1.8) compared to ponies fed ad libitum (0.9).

CONCLUSIONS

The acute effects of lateral heel wedges on the equine locomotor system in the transversal plane movement relieve tension from the medial patellar ligament and decrease pressure on the medial side of the tarsal joint. However, the fetlock joint experiences considerably more out of plane stress. Poor body condition resulted in a 2x worse patella luxation score, while the effect on stifle and tarsal joint movement in the transversal plane was almost 5x and 2x larger, respectively, than a lateral wedge.

POTENTIAL RELEVANCE

The clinical importance of general body condition for maintaining lateral stability in the equine hindlimbs is established, but future research may prove that wedges are beneficial to treat patella fixation and bone spavin in the long term.

Evaluation of bone-tendon junction healing using water jet ultrasound indentation method

The re-establishment of bone-tendon junction (BTJ) tissues with the junction, characterized as a unique transitional fibrocartilage zone, is involved in many trauma and reconstructive surgeries. Experimental and clinical findings have shown that a direct BTJ repair requires a long period of immobilization, which may be associated with a postoperative weak knee. Therefore, it is necessary to evaluate the morphologic and mechanical properties of BTJ tissues in situ to better understand the healing process for the purpose of reducing the adverse effects of immobilization. We previously reported a noncontact ultrasound water jet indentation system for measuring and mapping tissue mechanical properties. The key idea was to utilize a water jet as an indenter as well as the coupling medium for high-frequency ultrasound. In this article, we used ultrasound water jet indentation to evaluate the BTJ healing process. The system's capability of measuring the material elastic modulus was first validated using tissue-mimicking phantoms. Then it was employed to assess the healing of the BTJ tissues after partial patellectomy over time on twelve 18-week-old female New Zealand White rabbits. It was found that in comparison with the normal control samples, the elastic modulus of the fibrocartilage of the postoperative samples was significantly smaller, while its thickness increased significantly. Among the postoperative sample groups, the elastic modulus of the fibrocartilage of the samples harvested at week 18 was significantly higher than those harvested at week 6 and week 12, which was even comparable with the value of the control samples at the same sacrifice time. The results suggested that the noncontact ultrasound water jet indentation system provided a nondestructive way to evaluate the material properties of small animal tissues in situ and thus had the ability to evaluate the healing process of BTJ.

Efficacy and tolerability of eperisone in patients with spastic palsy: a cross-over, placebo-controlled dose-ranging trial

BACKGROUND AND OBJECTIVES

Central muscle relaxants are a clinical option in patients with spastic palsy. Eperisone is a central muscle relaxant used in several conditions, but its therapeutic potential in spastic palsy needs to be verified. This dose-ranging trial compares two doses of eperisone in patients with spastic palsy associated to cerebral or spinal diseases.

PATIENTS AND METHODS

In this randomized, placebo-controlled, double-blind, three-way cross-over study, patients (18-75 years) with spastic palsy received eperisone 150 mg/day, eperisone 300 mg/day, or placebo for 8 weeks. Treatment periods lasted for 14 days. Objective clinical parameters (intensity of spasticity and physiological reflexes) and functional parameters (walking capability, capability to climb stairs, rigidity) were measured. Tolerability was also evaluated.

RESULTS

Eighteen patients were enrolled. The reduction in the intensity of spasticity versus the beginning of each treatment cycle was significant with eperisone 300 mg/day (p = 0.004). Similar findings were observed in the evaluation of patellar reflex (p = 0.01), while the other reflexes were not significantly different. Walking capability was significantly improved with eperisone 300 mg/day (p < 0.05). No significant differences were observed in the capability to climb stairs and in rigidity. A trend towards a reduction in pain was noted with eperisone 300 mg/day versus placebo. The incidence of adverse events was similar in all groups.

DISCUSSION

Eperisone 300 mg/day might be an effective and well-tolerated treatment for spastic palsy. Larger studies are required to further characterize the efficacy of eperisone in this therapeutic area.

The structural properties of the lateral retinaculum and capsular complex of the knee

Although lateral retinacular releases are not uncommon, there is very little scientific knowledge about the properties of these tissues, on which to base a rationale for the surgery. We hypothesised that we could identify specific tissue bands and measure their structural properties. Eight fresh-frozen knees were dissected, and the lateral soft tissues prepared into three distinct structures: a broad tissue band linking the iliotibial band (ITB) to the patella, and two capsular ligaments: patellofemoral and patellomeniscal. These were individually tensile tested to failure by gripping the patella in a vice jaw and the soft tissues in a freezing clamp. Results: the ITB–patellar band was strongest, at a mean of 582 N, and stiffest, at 97 N/mm. The patellofemoral ligament failed at 172 N with 16 N/mm stiffness; the patellomeniscal ligament failed at 85 N, with 13 N/mm stiffness. These structural properties suggest that most of the load in-vivo is transmitted to the patella by the transverse fibres that originate from the ITB.

Treating patellar tendinopathy with Fascial Manipulation

According to Fascial Manipulation theory, patellar tendon pain is often due to uncoordinated quadriceps contraction caused by anomalous fascial tension in the thigh. Therefore, the focus of treatment is not the patellar tendon itself, but involves localizing the cause of this incoordination, considered to be within the muscular fascia of the thigh region. Eighteen patients suffering from patellar tendon pain were treated with the Fascial Manipulation technique. Pain was assessed (in VAS) before (VAS 67.8/100) and after (VAS 26.5/100) treatment, plus a follow-up evaluation at 1 month (VAS 17.2/100). Results showed a substantial decrease in pain immediately after treatment (p<0.0001) and remained unchanged or improved in the short term. The results show that the patellar tendon may be only the zone of perceived pain and that interesting results can be obtained by treating the muscular fascia of the quadriceps muscle, whose alteration may cause motor incoordination and subsequent pathology.

Synovial mesenchymal stem cells accelerate early remodeling of tendon-bone healing

Tendon-bone healing is important for the successful reconstruction of the anterior cruciate ligament by using the hamstring tendon. Mesenchymal stem cells (MSCs) have attracted much interest because of their self-renewing potential and multipotentiality for possible clinical use. We previously reported that MSCs derived from synovium had a higher proliferation and differentiation potential than the other MSCs that we examined. The purpose of this study was to investigate the effect and mechanism of the implantation of the synovial MSCs on tendon-bone healing in rats. Half of the Achilles' tendon grafts of rats were inserted into a bone tunnel from the tibial plateau to the tibial tuberosity with a suture-post fixation. The bone tunnel was filled with MSCs labeled with fluorescent marker DiI or without MSCs as the control. The tendon-bone interface was analyzed histologically, and collagen fibers were quantified. At 1 week, the tendon-bone interface was filled with abundant DiI-positive cells, and the proportion of collagen fiber area was significantly higher in the MSC group than in the control group. By 2 weeks, the proportion of oblique collagen fibers, which appeared to be Sharpey's fibers, was significantly higher in the MSC group than in the control group. At 4 weeks, the interface tissue disappeared, and the implanted tendon appeared to attach to the bone directly in both groups. DiI-labeled cells could no longer be observed. Implantation of synovial MSCs into bone tunnel thus accelerated early remodeling of tendon-bone healing, as shown histologically.

The responses of extrinsic fibroblasts infiltrating the devitalised patellar tendon to IL-1beta are different from those of normal tendon fibroblasts

In order to clarify the role of cytokines in the remodelling of the grafted tendon for ligament reconstruction we compared the responses to interleukin (IL)-1beta, platelet-derived growth factor (PDGF)-BB and transforming growth factor (TGF)-beta1 of extrinsic fibroblasts infiltrating the frozen-thawed patellar tendon in rats with that of the normal tendon fibroblasts, in regard to the gene expression of matrix metalloproteinase (MMP)-13, using Northern blot analysis. We also examined, immunohistologically, the local expression of IL-1beta, PDGF-BB, and TGF-beta1 in fibroblasts infiltrating the frozen-thawed patellar tendon. Northern blot analysis showed that fibroblasts derived from the patellar tendon six weeks after the freeze-thaw procedure in situ showed less response to IL-1beta than normal tendon fibroblasts with respect to MMP-13 mRNA gene expression. The immunohistological findings revealed that IL-1beta was over-expressed in extrinsic fibroblasts which infiltrated the patellar tendon two and six weeks after the freeze-thaw procedure in situ, but neither PDGF-BB nor TGF-beta1 was over-expressed in these extrinsic fibroblasts. Our findings indicated that IL-1beta had a close relationship to matrix remodelling of the grafted tendon for ligament reconstruction, in addition to the commencement of inflammation during the tissue-healing process.

The anisotropic compressive mechanical properties of the rabbit patellar tendon

In this study, we examine the transverse and longitudinal compressive mechanical behavior of the rabbit patellar tendon. The anisotropic compressive properties are of interest, because compression occurs where the tendon attaches to bone and where the tendon wraps around bone leading to the development of fibro-cartilaginous matrices. We quantified the time dependent viscoelastic and anisotropic behavior of the tendon under compression. For both orientations, sections of patellar tendon were drawn from mature male white New Zealand rabbits in preparation for testing. The tendons were sequentially compressed to 40% strain at strain rates of 0.1, 1 and 10% strain(s) using a computer-controlled stepper motor driven device under physiological conditions. Following monotonic loading, the tendons were subjected to stress relaxation. The tendon equilibrium compressive modulus was quantified to be 19.49+/-11.46 kPa for the transverse direction and 1.11+/-0.57 kPa for the longitudinal direction. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain(s) in the transverse orientation were 13.48+/-2.31, 18.24+/-4.58 and 20.90+/-8.60 kPa, respectively. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain/s in the longitudinal orientation were 0.19+/-0.11, 1.27+/-1.38 and 3.26+/-3.49 kPa, respectively. The modulus values were almost significantly different for the examination of the effect of orientation on the equilibrium modulus (p=0.054). Monotonic loading of the tendon showed visual differences of the strain rate dependency; however, no significant difference was shown in the statistical analysis of the effect of strain rate on compressive modulus. The statistical analysis of the effect of orientation on compressive modulus showed a significant difference. The difference shown in the orientation analysis validated the anisotropic nature of the tendon.

Gender-specific in vivo measurement of the structural and mechanical properties of the human patellar tendon

Human patellar tendon stress (sigma), strain (epsilon), stiffness (K), and tensile or Young's modulus (E), are determined in vivo through voluntary isometric contractions monitored with B-mode ultrasonography. The limitations in previous studies are: (1) they have generally not accounted for the fact that the distal attachment of the patellar tendon (the tibial tuberosity) also displaces; thus, they have underestimated epsilon (and, hence, injury risk) while overestimating K; (2) no gender effect has been studied despite the fact that females are seen to have higher incidences of tendon-related injuries. The current investigation therefore aimed to determine the gender specific values of sigma, epsilon, K, and E of the patellar tendon while also accounting for distal displacement of the patellar tendon. Healthy young males (aged 23.1 +/- 1.3 years, n = 10) and females (aged 21.3 +/-0.9 years, n = 10) were tested. The maximal epsilon of the young males was approximately 5-10% higher than that reported in earlier literature. Average female versus male values for epsilon, sigma, K, and E, taken at the same force level as the males for comparison purposes, were respectively 10.6 +/- 1.0 versus 9.0 +/- 1.0%, 36.9 +/- 1.4 versus 28.9 +/- 0.9 MPa, 1053 +/- 108 versus 1652 +/- 216 N x mm(-1), and 0.61 +/- 0.08 versus 0.68 +/- 0.10 GPa (p < 0.05). There are gender differences in tendon structural and mechanical properties. The current methodology may be useful in a clinical context where early prediction of injury risk and/or monitoring of reconstructed tendon needs to be an accurate, objective, and reliable method if optimal functionality is to be achieved.

Region specific patellar tendon hypertrophy in humans following resistance training

AIM

To examine if cross-sectional area (CSA) differs along the length of the human patellar tendon (PT), and if there is PT hypertrophy in response to resistance training.

METHODS

Twelve healthy young men underwent baseline and post-training assessments. Maximal isometric knee extension strength (MVC) was determined unilaterally in both legs. PT CSA was measured at the proximal-, mid- and distal PT level and quadriceps muscle CSA was measured at mid-thigh level using magnetic resonance imaging. Mechanical properties of the patellar tendons were determined using ultrasonography. Subsequently, subjects performed 12 weeks of heavy resistance knee extension training with one leg (Heavy-leg), and light resistance knee extension training with the other leg (Light-leg).

RESULTS

The MVC increased for heavy-leg (15 +/- 4%, P < 0.05), but not for light-leg (6 +/- 4%). Quadriceps CSA increased in heavy-legs (6 +/- 1%, P < 0.05) while unchanged in light-legs. Proximal PT CSA (104 +/- 4 mm(2)) was smaller than the mid-tendon CSA (118 +/- 3 mm(2)), which again was smaller than distal tendon CSA (127 +/- 2 mm(2), P < 0.05). Light-leg PT CSA increased by 7 +/- 3% (P < 0.05) at the proximal tendon level, but was otherwise unchanged. Heavy-leg PT CSA increased at the proximal and distal tendon levels by 6 +/- 3% and 4 +/- 2% respectively (P < 0.05), but was unchanged at the mid tendon level. PT stiffness increased in heavy-legs (P < 0.05) but was unchanged in light-legs. Modulus remained unchanged in both legs.

CONCLUSIONS

To our knowledge, this study is the first to report tendon hypertrophy following resistance training. Further, the data show that the human PT CSA varies along the length of the tendon.

Time course of muscular, neural and tendinous adaptations to 23 day unilateral lower-limb suspension in young men

Muscles and tendons are highly adaptive to changes in chronic loading, though little is known about the adaptative time course. We tested the hypothesis that, in response to unilateral lower limb suspension (ULLS), the magnitude of tendon mechanical adaptations would match or exceed those of skeletal muscle. Seventeen men (1.79 +/- 0.05 m, 76.6 +/- 10.3 kg, 22.3 +/- 3.8 years) underwent ULLS for 23 days (n = 9) or acted as controls (n = 8). Knee extensor (KE) torque, voluntary activation (VA), cross-sectional area (CSA) (by magnetic resonance imaging), vastus lateralis fascicle length (L(f)) and pennation angle (), patellar tendon stiffness and Young's modulus (by ultrasonography) were measured before, during and at the end of ULLS. After 14 and 23 days (i) KE torque decreased by 14.8 +/- 5.5% (P < 0.001) and 21.0 +/- 7.1% (P < 0.001), respectively; (ii) VA did not change; (iii) KE CSA decreased by 5.2 +/- 0.7% (P < 0.001) and 10.0 +/- 2.0% (P < 0.001), respectively; L(f) decreased by 5.9% (n.s.) and 7.7% (P < 0.05), respectively, and by 3.2% (P < 0.05) and 7.6% (P < 0.01); (iv) tendon stiffness decreased by 9.8 +/- 8.2% (P < 0.05) and 29.3 +/- 11.5% (P < 0.005), respectively, and Young's modulus by 9.2 +/- 8.2% (P < 0.05) and 30.1 +/- 11.9% (P < 0.01), respectively, with no changes in the controls. Hence, ULLS induces rapid losses of KE muscle size, architecture and function, but not in neural drive. Significant deterioration in tendon mechanical properties also occurs within 2 weeks, exacerbating in the third week of ULLS. Rehabilitation to limit muscle and tendon deterioration should probably start within 2 weeks of unloading.

Modified pre-curved patellar basket plate, reconstruction of the proper length and position of the patellar ligament--a biomechanical analysis

Biomechanical properties of basket plate fixation for fracture dislocation in the distal part of the patella were studied on 22 fresh-frozen lower extremities (human cadaveric knees). The patella and the patellar ligament with the proximal tibia were removed. A comminuted fracture of the distal part of the patella was created with a chisel. The fractured patella, patellar ligament and tibial tuberosity of each specimen were fixed with a basket plate and mounted into the jaws of the testing machine. The measured load to failure was 421.66+/-45.90 N, which is approximately 70% higher than the results in other studies. The results of the measurements verified the results of finite element analysis. The modified precurved patellar basket plate developed in this study showed improved performance compared to the pre-existing fixation methods.

Current Concepts on Anatomy and Biomechanics of Patellar Stability

This review describes anatomic features of the patellofemoral joint that relate to the stability and function of the joint. The role of the geometry of the articular surfaces, particularly the trochlear groove, it's depth and orientation, are described. The stabilizing actions of the medial and lateral retinaculae, that tether the patella from either side to guide it into the trochlear groove in the early phase of knee flexion, are related to the specific structures, the medial patellofemoral ligament, and the fibers originating from the ilio-tibial tract laterally. The quadriceps muscles have different orientations, and converge onto the patella not only from either side but also from posteriorly, thus pulling the patella onto the anterior aspect of the trochlea. Finally, these local factors are discussed in relation to overall limb alignment, which leads to the mechanical logic of more extensive surgical procedures such as femoral rotational osteotomy or tibial tuberosity medialization.

Effect of habitual exercise on the structural and mechanical properties of human tendon, in vivo, in men and women

We examined whether long-term habitual training (a) was associated with differences in structural and mechanical properties in tendon in women and (b) yielded different tendon properties in men and women. Ten male runners, 10 female runners and 10 female non-runners were tested. Tendon cross-sectional area (CSA) and length of the patellar and Achilles tendon were determined with MRI. Ultrasonography-based measurement of tendon elongation and force during isometric contractions provided mechanical properties. Distal patellar and Achilles tendon CSAs were greater than the proximal part in all three groups (P<0.05). Weight-normalized Achilles tendon CSA were similar in trained (2.78+/-0.17 mm(2)/kg(3/4)) and untrained women (2.60+/-0.13 mm(2)/kg(3/4)), while that in trained men (3.77+/-0.27 mm(2)/kg(3/4)) was greater compared with trained women (P<0.01). Patellar tendon CSA were comparable in trained and untrained women, while that in trained men was greater compared with trained women (P<0.01). Patellar tendon stiffness was greater in male runners (3528+/-773 N/mm) compared with female runners (2069+/-666 N/mm) and non-runners (2477+/-381 N/mm), (P<0.01), but patellar tendon deformation, stress, strain and modulus were similar. These data indirectly suggest that the ability of Achilles and patellar tendons to adapt in response to habitual loading such as running is attenuated in women.

Resonance frequency in patellar tendon

The aim of this study was to the measure resonance frequency of the patellar tendon in order to determine whether the resonance frequency exists in the soft tissue of the human body. A vibrator was attached to the medial aspect of the tibia of 10 healthy subjects to provide different frequencies of vibration, and an accelerometer was attached to the patellar tendon to measure the vibration of the patellar tendon. Measurements were obtained at 0 degrees , 60 degrees and 90 degrees of knee flexion. A mean resonance frequency of 22.5+/-0.8, 23.0+0.7 and 24.0+0.8 Hz was produced in the right patellar tendon when the knee joint was at 0 degrees , 60 degrees and 90 degrees of flexion, respectively. The increase in resonance frequency from 0 degrees to 60 degrees was not statistically significant. However, the increase from 60 degrees to 90 degrees was significant (P<0.05). No differences in the measured parameters were evident for the left and right patellar tendons. These results indicate that resonance frequencies exist in soft tissues of the body and that this characteristic may be useful in detecting changes in soft tissue physical properties.

Biomechanical analysis of the single-leg decline squat

BACKGROUND

The single-leg squat on a 25 degrees decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. Several assumptions have been made about its working mechanism on patellar load and patellofemoral forces, but these are not substantiated by biomechanical evaluations.

AIM

To investigate knee moment and patellofemoral contact force as a function of decline angle in the single-leg squat.

METHODS

Five subjects performed single-leg eccentric squats at decline angles of 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees and 25 degrees (with/without a backpack of 10 kg), and 30 degrees on a board that was placed over a forceplate. Kinematic and forceplate data were recorded by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics.

RESULTS

Knee moment increased by 40% at decline angles of 15 degrees and higher, whereas hip and ankle moment decreased. Maximum knee and ankle angles increased with steeper decline. With a 10 kg backpack at 25 degrees decline, the knee moment was 23% higher than unloaded. Both patellar tendon and patellofemoral forces increased with higher decline angles, but beyond 60 degrees, the patellofemoral force rose steeper than the tendon force.

CONCLUSIONS

All single-leg squats at decline angles >15 degrees result in 40% increase in maximum patellar tendon force. In knee flexions >60 degrees, patellofemoral forces increase more than patellar tendon forces. Higher tendon load can be achieved by the use of a backpack with extra weight.

The tensile properties of collagen fascicles harvested from regenerated and residual tissues in the patellar tendon after removal of the central third

The central one-third portion of the patellar tendon (PT) is commonly used for the reconstruction of the anterior cruciate ligament. For better understanding of the healing mechanisms of the PT, tensile properties of collagen fascicles harvested from the healing PT were studied. A rectangular defect was made at the central third portion in each right PT in the skeletally mature rabbit. At 6 and 12 weeks, tensile tests were performed on fascicles from the tissue regenerated in the defect and the non-resected, residual tissue. The elastic modulus and tensile strength of fascicles from the regenerated tissue gradually increased in a fashion similar to the bulk regenerated tissue. The properties of fascicles from the residual tissue were similar to those from normal tendons, which was very much different from those of the bulk residual tissue that were greatly deteriorated by the removal of the central portion.

Proprioception in the ACL-ruptured knee: the contribution of the medial collateral ligament and patellar ligament. An in vivo experimental study in the cat

In the absence of anterior cruciate ligament (ACL), secondary restraints such as menisci, ligaments, and tendons restrict anterior knee laxity. Strain detection at these sites could define the contribution of this alternative signalling system to knee proprioception after ACL injury. The hypothesis in this study questions if measurements of anterior tibial translation (ATT) from surface strain gauges on the insertions of the medial collateral ligament (MCL) and the patellar tendon (PT) are sufficiently sensitive and specific to differentiate normal, stable knees from acutely unstable knees due to ACL section. Twelve cats received miniaturized strain gauges on the surface of MCL and PT distal insertions. A purpose-made receiver transformed into measurements any voltage variation obtained during passive knee flexion-extension and anterior tibial translation manoeuvres. Variables under evaluation included first peak latency, normalized amplitude, and slope of voltage along time. Femorotibial displacements were video recorded, digitized, and used as the ATT reference. The proposed system detected significant changes in the slope of the voltage/time signal, with higher specificity and sensitivity during ATT after experimental ACL section. Changes were not significant during flexion or extension. It was found that a pattern of earlier and more intense strain in MCL and PT distal insertions was found during ATT in the ACL deficient knee. Enhanced pattern recognition learning from these structures could be a future target for proprioceptive training after ACL injury.

In vivo changes in the human patellar tendon moment arm length with different modes and intensities of muscle contraction

The purpose of this study was to examine the effect of different muscle contraction modes and intensities on patellar tendon moment arm length (d(PT)). Five men performed isokinetic concentric, eccentric and passive knee extensions at an angular velocity of 60 deg/s and six men performed gradually increasing to maximum effort isometric muscle contractions at 90( composite function) and 20( composite function) of knee flexion. During the tests, lateral X-ray fluoroscopy imaging was used to scan the knee joint. The d(PT) differences between the passive state and the isokinetic concentric and extension were quantified at 15( composite function) intervals of knee joint flexion angle. Furthermore, the changes of the d(PT) as a function of the isometric muscle contraction intensities were determined during the isometric knee extension at 90( composite function) and 20( composite function) of knee joint flexion. Muscle contraction-induced changes in knee joint flexion angle during the isometric muscle contraction were also taken into account for the d(PT) measurements. During the two isometric knee extensions, d(PT) increased from rest to maximum voluntary muscle contraction (MVC) by 14-15%. However, when changes in knee joint flexion angle induced by the muscle contraction were taken into account, d(PT) during MVC increased by 6-26% compared with rest. Moreover, d(PT) increased during concentric and eccentric knee extension by 3-15%, depending on knee flexion angle, compared with passive knee extension. These findings have important implications for estimating musculoskeletal loads using modelling under static and dynamic conditions.

Time-of-day effect on patella tendon stiffness alters vastus lateralis fascicle length but not the quadriceps force–angle relationship

AIM

To examine the time-of-day (TOD) effect on torque-force/angle, fibre length (FL), tendon stiffness (K), stress, and strain using the quadriceps muscle-tendon complex as a model.

METHODS

Twelve healthy young men (aged 27+/-2.0 years) were studied at AM (7h45) and PM (5h45). Maximal isometric contractions were carried out on an isokinetic dynamometer, with real-time recordings of vastus lateralis (VL) FL and patella tendon K using B-mode ultrasonography. Percutaneous electrical twitch doublets superimposed on maximal torque were used to test for muscle activation capacity (AC).

RESULTS

At PM, torque and force increased by 16+/-3.0% (P<0.01) over 30-90 degrees knee angles. Where the load was standardised (at 250N) in order to discriminate between torque generation capacity and tendon K changes, PM relative to AM, there were 8% and 13% (P<0.01) reductions in relaxed and contracted FL, respectively. Average K decreased by 21% (P<0.001) and the maximal stress and strain were increased at PM by 11% and 16%, respectively (P<0.01). No TOD effect on AC was seen.

CONCLUSION

The quadriceps torque or force-angle relationships shift upwards at PM vs. AM, with no shift in the position of the optimal knee angle. This torque or force increase appears not to be centrally modulated. Although K decreases with TOD thereby potentially shortening the working length of the sarcomeres, these changes overall do not affect the ability of the muscle to produce greater torque in the evening.

Adductor T and H reflexes in humans

In the belief that changes in the adductor reflex (AR) may be helpful in evaluating lumbar root and plexus lesions, expression of the AR was studied in 43 healthy human subjects. ARs elicited with an electronic reflex hammer were recorded from the inner side of the proximal thigh using needle and surface electrodes, and patellar reflexes (PRs) were recorded simultaneously. These reflexes were obtained by tapping the ipsilateral medial aspect of the knee, the contralateral patellar tendon, the ipsilateral and contralateral anterior superior iliac spines, and the Achilles tendon. The H reflex of the obturator nerve was also evaluated in 17 cases. ARs were evoked consistently by tapping the ipsilateral medial aspect of the knee and by contralateral patellar tap, and by tapping ipsilateral and contralateral anterior superior iliac spines when a needle recording electrode was used. Sometimes an Achilles tendon tap also elicited the AR ipsilaterally. By contrast, the PR could only be elicited by a tap to the ipsilateral patellar tendon. ARs have somewhat different features than other well-known tendon reflexes such as the PR and are recorded consistently when a needle electrode is used, being elicited from both distal and proximal areas of the legs by tapping the Achilles tendon or anterior superior iliac spines unilaterally or bilaterally. Their role in evaluating lumbar root disease and monitoring adductor spasticity merits investigation.

The 3D patellar tendon moment arm: quantified in vivo during volitional activity

The patellar tendon moment arm is a critical quantity in that it defines the quadriceps ability to generate a moment on the tibia. Thus, the primary purpose of this study was to establish the first in vivo three-dimensional measures of the patellar tendon moment arm, measured non-invasively and in vivo during dynamic activity in a large normative population (n=34) using a dynamic MRI technique (fast-PC MRI). The magnitude of the moment arm was defined as the shortest distance between the finite helical axis and the patellar tendon line of action. Using these data, the hypothesis that the patellar tendon moment arm is independent of gender was tested. In general, the moment arm increased from 20 to 50 mm during knee extension. There were significant differences (P<0.05) in the moment arm between gender, but these differences were eliminated when the moment arm was scaled by the femoral epicondylar width. This study took a large step forward towards the ultimate goal of defining how pathology may alter joint dynamics through alteration in moment arms by establishing the first in vivo normative data base for the patellar tendon moment arm using non-invasive measures during volitional activity in a relatively large population (n=34). The fact that the scaled moment arm was independent of gender may lend insights into impairments that tend to be gender specific, such as patellar maltracking. The next steps will be to quantify the patellar tendon moment arm in populations with specific pathologies.

No deterioration of kinematics and cruciate function 10 years after medial unicompartmental arthroplasty

The mechanisms of failure for unicompartmental arthroplasty are poorly understood. There is some suggestion that long term ligament degeneration, particularly of the anterior cruciate ligament (ACL), may affect long term survivorship. This study evaluated whether the cruciate mechanism remained functional in the long term (10 years) following UKA. Two separate cohorts of patients who had undergone St Georg Sled medial compartmental arthroplasty had knee kinematics assessed using an established fluoroscopic technique. One group (early) was assessed at a mean of 46 months (3.8 years) since surgery, whilst the other (late) was assessed at a mean of 125 months (10.4) following surgery. No significant difference was found in the sagittal plane kinematics between the two groups or in comparison to the control normal knee. The results suggest that after fixed bearing UKA the cruciate mechanism remains intact over time and the ligaments continue to function similarly to those of the normal knee.

Kinematic quantitation of the patellar tendon reflex using a tri-axial accelerometer

We designed a simple procedure based on the angular speed of the knee joint for quantitating the patellar tendon reflex. The angular speed of the knee joint is calculated from acceleration data generated in response to the tapping force applied to the patellar tendon with a customized tendon hammer and measured using a tri-axial accelerometer placed at the ankle joint. Data were collected and processed using a signal analyzer and a notebook PC. The results obtained using standard equipment were similar to those generated by more elaborate devices. For instance, the time delay (29.6+/-6.0 ms) and the acceleration time (150.8+/-19.5 ms) of the speed response were quite constant for all participants within the range of tapping forces normally applied during physical examinations. Representative relationships between the peak tapping force and the peak angular speed also closely fit with the exponential model (the average coefficient of determination, 0.70; range, 0.43-0.97). In contrast, the mean asymptotic value of the peak angular speed (Omega(pas)) was 160+/-67 degrees/s for spastic individuals, compared with only 72+/-21 degrees/s for healthy individuals. The important features of this method are portability, ease of use, and non-constraint of solicited reflex responses.