Do the vastus medialis obliquus and vastus medialis longus really exist? A systematic review

Topographical Anatomy of the Adductor Muscle Group in the Albino Rat (Rattus norvegicus)

In comparative anatomy, the adductor muscles are said to be quite variable and to often cause difficulty in separation. The arrangement of these muscles and the possible occurrence of the adductor minimus and obturator intermedius muscles in the albino rat has not been investigated. The aim of this study was to accurately describe the adductor muscles in the albino rat (Rattus norvegicus). We hypothesized that all adductor muscles are constantly present and can be separated in a constant manner, and that the adductor minimus and obturator intermedius muscles are constant structures. Both pelvic limbs of 30 formalin-embalmed male albino rats were carefully dissected. The identification of the individual muscles was made based on their position in relation to the two branches of the obturator nerve and by comparing our results with previous findings in other species including humans. All examined rats had two gracilis muscles. The adductor longus muscle was the most superficial and smallest individual. The adductor brevis split into two parts of insertion-the femoral and genicular parts. The adductor magnus and minimus muscles could be separated constantly. The obturator intermedius muscle was a constant structure next to the obturator externus muscle. The adductor muscles of the albino rat were constantly separable and could be clearly assigned to their names. Further research is needed to investigate these muscles, especially the obturator intermedius muscle, in other species including humans.

The Effect of Self-Myofascial Release on the Pennation Angle of the Vastus Medialis Oblique and the Vastus Lateralis in Athletic Male Individuals: An Ultrasound Investigation

Background

Maintenance of patellar stability requires a balance between the vastus medialis oblique (VMO) and the vastus lateralis (VL). The imbalance between these muscles is thought to be implicated in the etiology of patellofemoral pain (PFP). Where there is hypertrophy of the VL in PFP patients, self-myofascial release (SMR) may be utilized for its management. However, there is no current evidence regarding SMR and its effects on VMO and VL architecture. The aim of this study, therefore, was to use ultrasound to gain further understanding of the effects of a program of SMR on the fiber angles of the VMO and VL.

Hypothesis

There will be a significant decrease in the pennation angles of the VMO and VL after seven weeks of SMR using a foam roller.

Study Design

Cohort Study.

Methods

Twenty-five young, athletic, male participants were recruited to use a foam roller, along the full length of both anterior thighs, three times weekly, on three separate days, for seven weeks. Ultrasound was used to determine the initial and final VMO and VL pennation angles on both limbs. One eligible participant was chosen as an intra-rater control and did not partake in the SMR regimen.

Results

There was a statistically significant (p < 0.001) decrease in the pennation angles of the VMO and VL after the SMR regime. Mean combined right and left VL angle change was -6.65° (-18% mean change) and the mean combined right and left VMO angle change was -7.65° (-11.5% mean change). A weak negative correlation was found between initial VMO fiber angle and the angle change (Rsquared = -0.21), as well as moderate negative correlation for the VL (Rsquared = -0.51).

Conclusion

A program of SMR on the anterior thighs of young, asymptomatic males resulted in changes to the fiber angles of both the VMO and VL. There was a significant decrease in pennation angle after seven weeks of SMR using a foam roller.

The effect of stretching exercises on the fibre angle of the vastus lateralis and vastus medialis oblique: an ultrasound study

[Purpose] To investigate the effects of a seven-week quadriceps stretching program on the muscle fibre orientation of the vastus medialis oblique and vastus lateralis in the lower limbs by ultrasound imaging. [Participants and Methods] Twenty-seven healthy, physically fit, asymptomatic females and males (age 21.5 ± 1.3, Tegner activity level score ≥4) were recruited. Their initial vastus medialis oblique and vastus lateralis fibre angles were determined using ultrasound. They then undertook a seven-week quadriceps stretching program, 3 sets of stretches to be performed on both lower limbs, 3 times a week on 3 separate days. One volunteer was assigned as an intra-rater control and did not take part in the stretching program. The vastus lateralis and vastus medialis oblique fibre angles were measured again on completion of the exercise regime. [Results] A statistically significant decrease in muscle fibre angle was observed in both the right and left vastus medialis oblique, and the right and left vastus lateralis. [Conclusion] A 7-week stretching program can result in a significant decrease in muscle fibre angle in both the vastus medialis oblique and the vastus lateralis. This can help in understanding the effects of prescribed stretching exercises on athletic patients with PFP.

Innervation of the distal part of the vastus medialis muscle is endangered by splitting its muscle fibers during total knee replacement: an anatomical study using modified Sihler's technique

Background and purpose - The distal part of the vastus medialis muscle is an important stabilizer for the patella. Thus, knowledge of the intramuscular nerve course and branching pattern is important to estimate whether the muscle's innervation is at risk if splitting the muscle. We determined the intramuscular course of the nerve branches supplying the distal part of the vastus medialis muscle to identify the surgical approach that best preserves its innervation.Material and methods - 8 vastus medialis muscles from embalmed anatomic specimens underwent Sihler's procedure to make soft tissue translucent while staining the nerves to study their intramuscular course. After dissection under transillumination using magnification glasses all nerve branches were evaluated.Results - The terminal nerve branches were located in different layers of the muscle and ran mostly parallel but also transverse to the muscle fibers. In half of the cases, the latter formed 1 to 3 anastomoses and coursed close to the myotendinous junction. Additionally, most of the branches extended into the ventromedial part of the knee joint capsule.Interpretation - To preserve the innervation of the distal part of the vastus medialis muscle, any split of the muscle during surgical approaches to the knee joint should be avoided.

Triceps, quadriceps or pentaceps femoris? Need for proper muscle definition

INTRODUCTION

Over the last years, the definition of quadriceps femoris (QF) has evolved somewhat and some authors now define a fifth head: the tensor of vastus intermedius (TVI). Descriptions of the different components of QF in textbooks and recent findings remain confusing. Therefore, the aim of this study is to obtain more information on this possible fifth head.

MATERIALS AND METHODS

Twenty lower limbs of 10 embalmed cadavers, six females and four males, were investigated by macro-dissection. The dissection and separation of the different heads were performed with the fingers and a distinction between the different parts of the quadriceps was noted only if it was possible to separate the heads without scalpel to avoid artificial separation of muscle parts.

RESULTS

In 9 lower limbs we found a QF as classically described in textbook. TVI was found in only 7 limbs and in 4 cases we were not able to differentiate VI and VM or VI and VL (triceps femoris as described by Testut). These results, and the diversity of descriptions found in the literature have led us to review the definition of an isolated muscle.

CONCLUSION

In this study, the presence of TVI was not demonstrated in all limbs unlike previously published studies on the subject. Harmonisation of dissection techniques, but also a clear definition of a muscle is required in order to be able to compare studies and draw clear conclusions.

Towards a Dynamic Model of the Kangaroo Knee for Clinical Insights into Human Knee Pathology and Treatment: Establishing a Static Biomechanical Profile

There is limited understanding of how patella realignment or patellectomy to surgically manage patellofemoral pain (PFP) affects knee biomechanics. By analysing marsupials like kangaroos that lack an ossified patella, actionable biomimetic insight for the management of end-stage PFP could be gained. This study aimed to provide the foundation of a multi-stage approach, by establishing a static biomechanical profile of the kangaroo stifle that informs the inputs and factors requiring consideration for future dynamic analyses. Volumetric CT and MRI sequences were obtained for four hindlimbs from two Macropus giganteus specimens, from which three-dimensional models of the stifles were created. Two limbs were dissected to visualise the insertion points, origins and lines of action of the quadriceps muscles and the knee extensor mechanism. Static measurements were obtained from the three-dimensional models to establish the biomechanical profile. The results confirmed structural differences in the kangaroo stifle with lack of an ossified patella, a prominent tuberosity and a shorter femur, which functionally affect the mechanical advantage and the torque-generating capability of the joint. The data reported in this study can be used to inform the inputs and constraints of future comparative analyses from which important lessons can be learned for the human knee.

Influence of knee joint position and sex on vastus medialis regional architecture

Ultrasound imaging was used to investigate vastus medialis (VM) architecture in 10 males and 10 females at different knee angles. Increase in muscle thickness occurs predominantly when the knee angle is changed from 0° (full extension) and 45° (p < 0.05); increases in VM pennation angle can be predominantly observed between 45° and 90° (p < 0.05). Sex differences in the VM architecture can be observed in the distal (p < 0.01) but not in the proximal region of the muscle (p > 0.11).

Identification of regional activation by factorization of high-density surface EMG signals: A comparison of Principal Component Analysis and Non-negative Matrix factorization

In this study, we investigated whether principal component analysis (PCA) and non-negative matrix factorization (NMF) perform similarly for the identification of regional activation within the human vastus medialis. EMG signals from 64 locations over the VM were collected from twelve participants while performing a low-force isometric knee extension. The envelope of the EMG signal of each channel was calculated by low-pass filtering (8 Hz) the monopolar EMG signal after rectification. The data matrix was factorized using PCA and NMF, and up to 5 factors were considered for each algorithm. Association between explained variance, spatial weights and temporal scores between the two algorithms were compared using Pearson correlation. For both PCA and NMF, a single factor explained approximately 70% of the variance of the signal, while two and three factors explained just over 85% or 90%. The variance explained by PCA and NMF was highly comparable (R > 0.99). Spatial weights and temporal scores extracted with non-negative reconstruction of PCA and NMF were highly associated (all p < 0.001, mean R > 0.97). Regional VM activation can be identified using high-density surface EMG and factorization algorithms. Regional activation explains up to 30% of the variance of the signal, as identified through both PCA and NMF.

The interaction between the vastus medialis and vastus intermedius and its influence on the extensor apparatus of the knee joint

PURPOSE

Although the vastus medialis (VM) is closely associated with the vastus intermedius (VI), there is a lack of data regarding their functional relationship. The purpose of this study was to investigate the anatomical interaction between the VM and VI with regard to their origins, insertions, innervation and function within the extensor apparatus of the knee joint.

METHODS

Eighteen human cadaveric lower limbs were investigated using macro-dissection techniques. Six limbs were cut transversely in the middle third of the thigh. The mode of origin, insertion and nerve supply of the extensor apparatus of the knee joint were studied. The architecture of the VM and VI was examined in detail, as was their anatomical interaction and connective tissue linkage to the adjacent anatomical structures.

RESULTS

The VM originated medially from a broad hammock-like structure. The attachment site of the VM always spanned over a long distance between: (1) patella, (2) rectus femoris tendon and (3) aponeurosis of the VI, with the insertion into the VI being the largest. VM units were inserted twice-once on the anterior and once on the posterior side of the VI. The VI consists of a complex multi-layered structure. The layers of the medial VI aponeurosis fused with the aponeuroses of the tensor vastus intermedius and vastus lateralis. Together, they form the two-layered intermediate layer of the quadriceps tendon. The VM and medial parts of the VI were innervated by the same medial division of the femoral nerve.

CONCLUSION

The VM consists of multiple muscle units inserting into the entire VI. Together, they build a potential functional muscular complex. Therefore, the VM acts as an indirect extensor of the knee joint regulating and adjusting the length of the extensor apparatus throughout the entire range of motion. It is of clinical importance that, besides the VM, substantial parts of the VI directly contribute to the medial pull on the patella and help to maintain medial tracking of the patella during knee extension. The interaction between the VM and VI, with responsibility for the extension of the knee joint and influence on the patellofemoral function, leads readily to an understanding of common clinical problems found at the knee joint as it attempts to meet contradictory demands for both mobility and stability. Surgery or trauma in the anteromedial aspect of the quadriceps muscle group might alter a delicate interplay between the VM and VI. This would affect the extensor apparatus as a whole.

Origin and insertion of the medial patellofemoral ligament: a systematic review of anatomy

PURPOSE

The medial patellofemoral ligament (MPFL) is the major medial soft-tissue stabiliser of the patella, originating from the medial femoral condyle and inserting onto the medial patella. The exact position reported in the literature varies. Understanding the true anatomical origin and insertion of the MPFL is critical to successful reconstruction. The purpose of this systematic review was to determine these locations.

METHODS

A systematic search of published (AMED, CINAHL, MEDLINE, EMBASE, PubMed and Cochrane Library) and unpublished literature databases was conducted from their inception to the 3 February 2016. All papers investigating the anatomy of the MPFL were eligible. Methodological quality was assessed using a modified CASP tool. A narrative analysis approach was adopted to synthesise the findings.

RESULTS

After screening and review of 2045 papers, a total of 67 studies investigating the relevant anatomy were included. From this, the origin appears to be from an area rather than (as previously reported) a single point on the medial femoral condyle. The weighted average length was 56 mm with an 'hourglass' shape, fanning out at both ligament ends.

CONCLUSION

The MPFL is an hourglass-shaped structure running from a triangular space between the adductor tubercle, medial femoral epicondyle and gastrocnemius tubercle and inserts onto the superomedial aspect of the patella. Awareness of anatomy is critical for assessment, anatomical repair and successful surgical patellar stabilisation.

LEVEL OF EVIDENCE

Systematic review of anatomical dissections and imaging studies, Level IV.

Regionalization of the stretch reflex in the human vastus medialis

KEY POINTS

Regionalization of the stretch reflex, i.e. the notion that the activation of 1a afferents from a muscle region influences only the activation of motor units in the same region, has been demonstrated previously in animals but not in humans. Mechanical stretches applied to regions of vastus medialis as close as 10 mm apart resulted in recruitment of motor units localized topographically with respect to the location of the mechanical stretch. Stretch reflexes are regionalized in the human vastus medialis. The human spinal cord has the neuromuscular circuitry to preferentially activate motoneurones innervating muscle fibres located in different regions of the vastus medialis.

ABSTRACT

The localization of motor unit territories provides an anatomical basis to suggest that the CNS may have more independence in motor unit recruitment and control strategies than what was previously thought. In this study, we investigated whether the human spinal cord has the neuromuscular circuitry to independently activate motor units located in different regions of the vastus medialis. Mechanical taps were applied to multiple locations in the vastus medialis (VM) in nine healthy individuals. Regional responses within the muscle were observed using a grid of 5 × 13 surface EMG electrodes. The EMG amplitude was quantified for each channel, and a cluster of channels showing the largest activation was identified. The spatial location of the EMG response was quantified as the position of the channels in the cluster. In a subset of three participants, intramuscular recordings were performed simultaneously with the surface EMG recordings. Mechanical taps resulted in localized, discrete responses for each participant. The spatial location of the elicited responses was dependent on the location of the tap (P < 0.001). Recordings with intramuscular electrodes confirmed the regional activation of the VM for different tap locations. Selective stimulation of 1a afferents localized in a region of the VM results in reflex recruitment of motor units in the same region. These findings suggest that the human spinal cord has the neuromuscular circuitry to modulate spatially the motoneuronal output to vastus medialis regions, which is a neuroanatomical prerequisite for regional activation.

Is the firing rate of motor units in different vastus medialis regions modulated similarly during isometric contractions?

INTRODUCTION

Previous evidence suggests the fibers of different motor units reside within distinct vastus medialis (VM) regions. It remains unknown whether the activity of these motor units may be modulated differently. Herein we assess the discharge rate of motor units detected proximodistally from the VM to address this issue.

METHODS

Surface electromyograms (EMGs) were recorded proximally and distally from the VM while 10 healthy subjects performed isometric contractions. Single motor units were decomposed from surface EMGs. The smoothed discharge rates of motor units identified from the same and from different VM regions were then cross-correlated.

RESULTS

During low-level contractions, the discharge rate varied more similarly for distal (cross-correlation peak; interquartile interval: 0.27-0.40) and proximal (0.28-0.52) than for proximodistal pairs of VM motor units (0.20-0.33; P = 0.006).

DISCUSSION

The discharge rates of motor units from different proximodistal VM regions show less similarity in their variations than those of pairs of units either distally or proximally. Muscle Nerve 57: 279-286, 2018.

Regional activation within the vastus medialis in stimulated and voluntary contractions

This study examined the contribution of muscle fiber orientation at different knee angles to regional activation identified with high-density surface electromyography (HDsEMG). Monopolar HDsEMG signals were collected using a grid of 13 × 5 electrodes placed over the vastus medialis (VM). Intramuscular electrical stimulation was used to selectively activate two regions within VM. The distribution of EMG responses to stimulation was obtained by calculating the amplitude of the compound action potential for each channel; the position of the peak amplitude was tracked across knee angles to describe shifts of the active muscle regions under the electrodes. In a separate experiment, regional activation was investigated in 10 knee flexion-extension movements against a fixed resistance. Intramuscular stimulation of different VM regions resulted in clear differences in amplitude distribution along the columns of the electrode grid (P < 0.001); changes in knee angle resulted in consistent shifts along the rows (P < 0.01) and negligible shifts along the columns of the electrode grid. Regional VM activation was identified in dynamic movement, with distal shifts of the EMG distribution in the eccentric phase of the movement (P < 0.05) and at more flexed knee angles (P < 0.05). HDsEMG was used to describe regional activation across the VM that was not attributable to anatomic factors. Changes in muscle fiber orientation associated with knee joint angle mainly influence the amplitude distribution along the fiber direction. Future studies are needed to understand possible functional roles for regional activation within the VM in dynamic tasks.

Inter- and intramuscular differences in training-induced hypertrophy of the quadriceps femoris: association with muscle activation during the first training session

The purpose of this study was to examine whether inter- and intramuscular differences in hypertrophy induced by resistance training correspond to differences in muscle activation during the first training session. Eleven young men completed 12 weeks of training intervention for knee extension. Before and after the intervention, T1-weighted magnetic resonance (MR) images were recorded to determine the volume and anatomical cross-sectional area (CSA) along the length of the individual muscles of the quadriceps femoris. The T2-weighted MR images were also acquired before and immediately after the first training session. The T2 was calculated for each pixel within the quadriceps femoris, from which the muscle activation was evaluated as %activated volume and area. The results showed that the %activated volume after the first training session was significantly higher in the vastus intermedius than the vastus medialis. However, the relative change in muscle volume after the training intervention was significantly greater in the rectus femoris than the vasti muscles (vastus lateralis, intermedius and medialis). Within the rectus femoris, both the %activated area and relative increase in CSA were significantly greater in the distal region than the proximal region. In contrast, the %activated area and relative increase in CSA of the vasti were nearly uniform along each muscle. These results suggest that the muscle activation during the first training session is associated with the intramuscular difference in hypertrophy induced by training intervention, but not with the intermuscular difference.

Territory and fiber orientation of vastus medialis motor units: A Surface electromyography investigation

INTRODUCTION

The aim of this study was to determine whether muscle fibers innervated by single motor neurons are confined in small subvolumes of the vastus medialis (VM) and if motor unit fiber orientation depends on their position within the muscle.

METHODS

Single motor units were identified from a grid of surface electrodes. The size of their surface representation and fiber orientation were extracted using an algorithm validated on simulated signals.

RESULTS

The action potentials of 77 motor units were represented locally on the skin (10th-90th percentiles: 14-25 mm). According to simulations, this indicates territories smaller than 11.8-64.8 mm. Motor units in distal regions of VM had fibers at a greater angle than those in proximal regions (R = -0.54, P < 0.001).

CONCLUSION

Motor units with small territories and varying fiber orientations may be an anatomical predisposition to regulate how regions within VM apply forces to the patella. This could help to redistribute loads within the joint in painful conditions.

Quadriceps tendon autograft for anterior cruciate ligament reconstruction: a comprehensive review of current literature and systematic review of clinical results

PURPOSE

The autograft of choice for anterior cruciate ligament (ACL) reconstruction remains controversial. Recently, there has been an increase in interest in the quadriceps tendon as an autologous graft option for ACL reconstruction. The purposes of this study were to provide an in-depth review of quadriceps tendon anatomy, histology, and biomechanics and to synthesize reported clinical outcomes of ACL reconstructions using quadriceps tendon autografts. We hypothesize that (1) published studies on the anatomic, histologic, and biomechanical data regarding the quadriceps tendon support its use as a graft option for ACL reconstruction and (2) clinical outcomes of ACL reconstruction using quadriceps tendon autograft have similar clinical outcomes to bone-patellar tendon-bone autografts with less donor-site morbidity.

METHODS

We performed a comprehensive review of the literature regarding the anatomy, histology, and biomechanical studies of the quadriceps tendon, as well as a systematic review of clinical studies (Level of Evidence I-III) evaluating outcomes after ACL reconstruction using quadriceps tendon autograft. Stability outcomes, functional outcomes, range of motion, patient satisfaction, morbidity, and complications were comprised.

RESULTS

Fourteen studies were included in the review of clinical results, including 1,154 ACL reconstructions with quadriceps tendon autograft. Six studies directly compared quadriceps tendon autografts (n = 383) with bone-patellar tendon-bone autografts (n = 484). Stability outcomes (Lachman, pivot-shift, and instrumented laxity testing), functional outcomes (International Knee Documentation Committee and Lysholm scores), overall patient satisfaction, range of motion, and complications were similar between quadriceps tendon and other graft options. Less donor-site morbidity was seen in patients who underwent quadriceps tendon ACL reconstructions.

CONCLUSIONS

Use of the quadriceps tendon autograft for ACL reconstruction is supported by current orthopaedic literature. It is a safe, reproducible, and versatile graft that should be considered in future studies of ACL reconstruction.

LEVEL OF EVIDENCE

Level III, systematic review of Level I, II, and III studies.

Magnetic resonance imaging of the extensor mechanism

Anterior knee pain is associated with many different causes. The clinical diagnosis may be unclear when the patient initially presents for evaluation. Magnetic resonance (MR) imaging is a valuable modality with high diagnostic accuracy in the evaluation of extensor mechanism pathology, which commonly presents with anterior knee pain. The most common disorders include patellar fracture, patellofemoral tracking abnormalities, tendon trauma and degeneration. These injuries manifest with characteristic patterns on MR imaging. This article discusses normal anatomy, common injuries, and diagnostic pitfalls on MR imaging.

Prospective randomized comparison between ultrasound-guided saphenous nerve block within and distal to the adductor canal with low volume of local anesthetic

Background and Aims:

The anatomic site and the volume of local anesthetic needed for an ultrasound-guided saphenous nerve block differ in the literature. The purpose of this study was to examine the effect of two different ultrasound-guided low volume injections of local anesthetic on saphenous and vastus medialis nerves.

Materials and Methods:

Recruited patients (N = 48) scheduled for orthopedic surgery were randomized in two groups; Group distal adductor canal (DAC): Ultrasound-guided injection (5 ml of local anesthetic) distal to the inferior foramina of the adductor canal. Group adductor canal (AC): Ultrasound-guided injection (5 ml local anesthetic) within the adductor canal. Following the injection of local anesthetic, block progression was monitored in 5 min intervals for 15 min in the sartorial branches of the saphenous nerve and vastus medialis nerve.

Results:

Twenty two patients in each group completed the study. Complete block of the saphenous nerve was observed in 55% and 59% in Group AC and DAC, respectively (P = 0.88). The proportion of patients with vastus medialis weakness at 15 min in Group AC, 36%, was significantly higher than in Group DAC (0/22), (P = 0.021).

Conclusions:

Low volume of local anesthetic injected within the adductor canal or distally its inferior foramina leads to moderate success rate of the saphenous nerve block, while only the injection within the adductor canal may result in vastus medialis nerve motor block.

Menstrual cycle mediates vastus medialis and vastus medialis oblique muscle activity

PURPOSE

Sports medicine professionals commonly describe two functionally different units of the vastus medialis (VM), the VM, and the vastus medialis oblique (VMO), but the anatomical support is equivocal. The functional difference of the VMO is principle to rehabilitation programs designed to alleviate anterior knee pain, a pathology that is known to have a greater occurrence in women. The purpose of this study was to determine whether the motor units of the VM and VMO are differentially recruited and if this recruitment pattern has an effect of sex or menstrual cycle phase.

METHODS

Single motor unit recordings from the VM and VMO were obtained for men and women during an isometric ramp knee extension. Eleven men were tested once. Seven women were tested during five different phases of the menstrual cycle, determined by basal body temperature mapping. The recruitment threshold and the initial firing rate at recruitment were determined from 510 motor unit recordings.

RESULTS

The initial firing rate was lower in the VMO than that in the VM in women (P < 0.001) but not in men. There was no difference in recruitment thresholds for the VM and VMO in either sex or across the menstrual cycle. There was a main effect of menstrual phase on initial firing rate, showing increases from the early follicular to late luteal phase (P = 0.003). The initial firing rate in the VMO was lower than that in the VM during ovulatory (P = 0.009) and midluteal (P = 0.009) phases.

CONCLUSION

The relative control of the VM and VMO changes across the menstrual cycle. This could influence patellar pathologies that have a higher incidence in women.

Spinal reflex arc excitability corresponding to the vastus medialis obliquus and vastus medialis longus muscles

[Purpose] The gross morphology of the vastus medialis (VM) muscle has been thoroughly described. However, there is insufficient evidence of physiological differentiation between the VM obliquus (VMO) and VM longus (VML). To elucidate spinal reflex arc excitability in two divisions of the VM, we compared H-reflexes and T-waves in VMO and VML. [Subjects] Twenty-three healthy male volunteers participated in this study. [Methods] The H-reflex was evoked from the VMO and VML by electrical stimulation of the femoral nerve during knee extension at 10% maximal voluntary isometric contraction. Also, the patellar tendon was tapped by an examiner using an electrical tendon hammer, and a component of the compound muscle action potential (T-wave) was recorded. [Results] The configurations of the H-reflex and T-wave were sharp and slow in VMO and VML, respectively. No significant differences in the amplitudes of the H-reflexes and T-waves were observed between VMO and VML. The durations of VML H-reflexes and T-waves were significantly longer than those in VMO. [Conclusion] Spinal reflex arc excitability corresponding to VMO and VML was similar. However, the configurations and durations of the H-reflex and T-wave were differentiated with electromyography. On the basis of these findings, we suggest that VMO and VML are electrophysiologically distinct entities.

Innervation zone of the vastus medialis muscle: position and effect on surface EMG variables

The aim of this study was to investigate the position of the innervation zone (IZ) of the vastus medialis (VM) and its effect on the electromyographic (EMG) amplitude and mean frequency estimates. Eighteen healthy subjects performed maximal isometric knee extensions at three knee angles. Surface EMG signals were collected by using a 16 × 8 electrode grid placed on the VM muscle. The position of the IZ was estimated through visual analysis, and traditional bipolar signals were obtained from channels over and away from it; amplitude and mean frequency values were extracted and compared using an analysis of variance (ANOVA) with repeated measures. The IZ is shaped as a line running from the proximal-lateral to the distal-medial aspect of the VM muscle. The presence of an IZ under the electrodes lowered the EMG amplitude (P < 0.001, F = 58.11) and increased the EMG mean frequency (P < 0.001, F = 26.47); variations of these parameters due to the knee flexion angle were less frequently observed in EMG signals collected over than away from the IZ. Electrodes placed 'over the belly of the VM muscle' are likely to collect EMG signals influenced by the presence of the IZ, thus hindering the detection of changes in muscle activity.

Muscles within muscles: a tensiomyographic and histochemical analysis of the normal human vastus medialis longus and vastus medialis obliquus muscles

The aim of this study was to show the connection between structure (anatomical and histochemical) and function (muscle contraction properties) of vastus medialis obliquus (VMO) and vastus medialis longus (VML). The non-invasive tensiomyography (TMG) method was used to determine the contractile properties (contraction time; T(c)) of VML and VMO muscle, as a reflection of the ratio between the slow and fast fibers in two groups of nine young men. VML and VMO significantly (P < 0.01) differ in the proportion of type 1 (59.6: 44%) and type 2b (6.3: 15%) fibers. The VML muscle is almost entirely composed of type 1 and type 2a fibers. In many samples of this muscle no type 2b fibers were found. The proportion of slow-twitch type 1 fibers is nearly twice as high as the proportion of fast-twitch type 2a fibers. These observations indicate that VML is a slower and more fatigue-resistant muscle than VMO muscle. These characteristics correspond to the different functions of the VML, which is an extensor of the knee, and to the VMO, which maintains the stable position of the patella in the femoral groove. Our results obtained by TMG provided additional evidence that muscle fibers within the segments of VM muscle were not homogenous with regard to their contractile properties, thereby confirming the histochemical results. T(c) can be attributed to the higher percentage of slow-twitch fibers - type 1. The statistically shorter T(c) (P ≤ 0.001) of VMO (22.8 ± 4.0 ms) compared with VML (26.7 ± 4.0 ms) in our study is consistent with previously found differences in histochemical, morphological and electrophysiological data. In conclusion, the results of this study provide evidence that the VML and VMO muscles are not only anatomically and histochemically different muscles, but also functionally different biological structures.

The safety and feasibility of a less invasive distal femur closing wedge osteotomy technique: a cadaveric dissection study of the medial aspect of the distal femur

PURPOSE

To investigate the feasibility and safety of a less invasive surgical approach to the distal medial aspect of the femur in supracondylar medial closing wedge osteotomy for the treatment of lateral compartment osteoarthritis of the knee. The aim of a less invasive approach is to minimize soft tissue disruption, reduce damage to neurovascular structures and thereby prevent muscle atrophy and optimize bone healing potential.

METHODS

A human cadaver dissection study on the vascular and neural structures of the medial side of the distal femur was conducted. Surgical dissection (n = 4), cryomicrotomy and subsequent 3D reconstruction of the anatomy (n = 1), and surgical dissection after performance of a supracondylar osteotomy through a less invasive approach (n = 1) were performed in 6 legs in total.

RESULTS

The surgical dissection and 3D reconstruction showed that a branch of the femoral artery, the distal genicular artery, supplies the distal area of the vastus medialis (VM) muscle. This artery has several branching patterns; crucial in the presented less invasive approach is its musculo-articular branch, which has an oblique course through the VM to the superomedial pole of the patella. The femoral nerve and saphenous nerve innervate the VM. These structures are at risk in the traditional subvastus approach, whereas no major damage was observed in the leg in which a less invasive approach was performed.

CONCLUSIONS

In this cadaveric dissection study, a less invasive approach to the medial side of the distal femur proved to be feasible and safe. Damage to the VM and its neurovascular structures is minimized as compared to the traditional subvastus approach.

Alterations in in vivo knee joint kinematics following a femoral nerve branch block of the vastus medialis: Implications for patellofemoral pain syndrome

BACKGROUND

A potential source of patellofemoral pain, one of the most common problems of the knee, is believed to be altered patellofemoral kinematics due to a force imbalance around the knee. Although no definitive etiology for this imbalance has been found, a weak vastus medialis is considered a primary factor. Therefore, this study's purpose was to determine how the loss of vastus medialis obliquus force alters three-dimensional in vivo knee joint kinematics during a volitional extension task.

METHODS

Eighteen asymptomatic female subjects with no history of knee pain or pathology participated in this IRB approved study. Patellofemoral and tibiofemoral kinematics were derived from velocity data acquired using dynamic cine-phase contrast MRI. The same kinematics were then acquired immediately after administering a motor branch block to the vastus medialis obliquus using 3-5ml of 1% lidocaine. A repeated measures analysis of variance was used to test the null hypothesis that the post- and pre-injection kinematics were no different.

FINDINGS

The null hypothesis was rejected for patellofemoral lateral shift (P=0.003, max change=1.8mm, standard deviation=1.7mm), tibiofemoral lateral shift (P<0.001, max change=2.1mm, standard deviation=2.9mm), and tibiofemoral external rotation (P<0.001, max change=3.7°, standard deviation=4.4°).

INTERPRETATION

The loss of vastus medialis obliquus function produced kinematic changes that mirrored the axial plane kinematics seen in individuals with patellofemoral pain, but could not account for the full extent of these changes. Thus, vastus medialis weakness is likely a major factor in, but not the sole source of, altered patellofemoral kinematics in such individuals.

Patellar tilt correlates with vastus lateralis: vastus medialis activation ratio in maltracking patellofemoral pain patients

Patellofemoral (PF) pain is a common ailment of the lower extremity. A theorized cause for pain is patellar maltracking due to vasti muscle activation imbalance, represented as large vastus lateralis:vastus medialis (VL:VM) activation ratios. However, evidence relating vasti muscle activation imbalance to patellar maltracking is limited. The purpose of this study was to investigate the relationship between VL:VM activation ratio and patellar tracking measures, patellar tilt and bisect offset, in PF pain subjects and pain-free controls. We evaluated VL:VM activation ratio and VM activation delay relative to VL activation in 39 PF pain subjects and 15 pain-free controls during walking. We classified the PF pain subjects into normal tracking and maltracking groups based on patellar tilt and bisect offset measured from weight-bearing magnetic resonance imaging. Patellar tilt correlated with VL:VM activation ratio only in PF pain subjects classified as maltrackers. This suggests that a clinical intervention targeting vasti muscle activation imbalance may be effective only in PF pain subjects classified as maltrackers.

Between-day reliability of a method for non-invasive estimation of muscle composition

Tensiomyography is a method for valid and non-invasive estimation of skeletal muscle fibre type composition. The validity of selected temporal tensiomyographic measures has been well established recently; there is, however, no evidence regarding the method's between-day reliability. Therefore it is the aim of this paper to establish the between-day repeatability of tensiomyographic measures in three skeletal muscles. For three consecutive days, 10 healthy male volunteers (mean±SD: age 24.6 ± 3.0 years; height 177.9 ± 3.9 cm; weight 72.4 ± 5.2 kg) were examined in a supine position. Four temporal measures (delay, contraction, sustain, and half-relaxation time) and maximal amplitude were extracted from the displacement-time tensiomyogram. A reliability analysis was performed with calculations of bias, random error, coefficient of variation (CV), standard error of measurement, and intra-class correlation coefficient (ICC) with a 95% confidence interval. An analysis of ICC demonstrated excellent agreement (ICC were over 0.94 in 14 out of 15 tested parameters). However, lower CV was observed in half-relaxation time, presumably because of the specifics of the parameter definition itself. These data indicate that for the three muscles tested, tensiomyographic measurements were reproducible across consecutive test days. Furthermore, we indicated the most possible origin of the lowest reliability detected in half-relaxation time.