Platelet rich fibrin matrix effects on skeletal muscle lesions: an experimental study.

Even though muscle injuries are very common, few scientific data on their effective treatment exist. Growth Factors (GFs) may have a role in accelerating muscle repair processes and a currently available strategy for their delivery into the lesion site is the use of autologous platelet-rich plasma (PRP). The present study is focused on the use of Platelet Rich Fibrin Matrix (PRFM), as a source of GFs. Bilateral muscular lesions were created on the longissimus dorsi muscle of Wistar rats. One side of the lesion was filled with a PRFM while the contralateral was left untreated (controls). Animals were sacrificed at 5, 10, 40 and 60 days from surgery. Histological, immunohistochemical and histomorphometric analyses were performed to evaluate muscle regeneration, neovascularization, fibrosis and inflammation. The presence of metaplasia zones, calcifications and heterotopic ossification were also assessed. PRFM treated muscles exhibited an improved muscular regeneration, an increase in neovascularization, and a slight reduction of fibrosis compared with controls. No differences were detected for inflammation. Metaplasia, ossification and heterotopic calcification were not detected. This preliminary morphological experimental study shows that PRFM use can improve muscle regeneration and long-term vascularization. Since autologous blood products are safe, PRFM may be a useful and handy product in clinical treatment of muscle injuries.

Long-range interactions in turbulence and the energy decay problem.

We discuss the long-range interactions that arise in homogeneous turbulence as a consequence of the Biot-Savart law. We note that, somewhat surprisingly, these long-range correlations are very weak in decaying, isotropic turbulence, and we argue that this should also be true for magnetohydrodynamic, rotating and stratified turbulence. If this is indeed the case, it is possible to make explicit predictions for the rate of decay of energy in these anisotropic systems, and it turns out that these predictions are consistent with the available numerical and experimental evidence.

Evolution of localized blobs of swirling or buoyant fluid with and without an ambient magnetic field.

We investigate the evolution of localized blobs of swirling or buoyant fluid in an infinite, inviscid, electrically conducting fluid. We consider the three cases of a strong imposed magnetic field, a weak imposed magnetic field, and no magnetic field. For a swirling blob in the absence of a magnetic field, we find, in line with others, that the blob bursts radially outward under the action of the centrifugal force, forming a thin annular vortex sheet. A simple model of this process predicts that the vortex sheet thins exponentially fast and that it moves radially outward with constant velocity. These predictions are verified by high-resolution numerical simulations. When an intense magnetic field is applied, this phenomenon is suppressed, with the energy and angular momentum of the blob now diffusing axially along the magnetic field lines, converting the blob into a columnar structure. For modest or weak magnetic fields, there are elements of both types of behavior, with the radial bursting dominating over axial diffusion for weak fields. However, even when the magnetic field is very weak, the flow structure is quite distinct to that of the nonmagnetic case. In particular, a small but finite magnetic field places a lower bound on the thickness of the annular vortex sheet and produces an annulus of counter-rotating fluid that surrounds the vortex core. The behavior of the buoyant blob is similar. In the absence of a magnetic field, it rapidly develops the mushroomlike shape of a thermal, with a thin vortex sheet at the top and sides of the mushroom. Again, a simple model of this process predicts that the vortex sheet at the top of the thermal thins exponentially fast and rises with constant velocity. These predictions are consistent with earlier numerical simulations. Curiously, however, it is shown that the net vertical momentum associated with the blob increases linearly in time, despite the fact that the vertical velocity at the front of the thermal is constant. As with the swirling blob, an imposed magnetic field inhibits the formation of a vortex sheet. A strong magnetic field completely suppresses the phenomenon, replacing it with an axial diffusion of momentum, while a weak magnetic field allows the sheet to form, but places a lower bound on its thickness. The magnetic field does not, however, change the net vertical momentum of the blob, which always increases linearly with time.

Identifying turbulent energy distributions in real, rather than fourier, space.

It has been suggested that the equilibrium-range properties of high-Reynolds number turbulence are more readily observed in spectral space, using E(k) or T(k), than in real space, using second- or third-order structure functions. For example, the -5/3 law is usually easier to see in experimental data than the equivalent 2/3 law. We argue that this is not an implicit feature of a real-space description of turbulence. Rather, it is because the second-order structure function mixes small and large-scale information. To remedy this problem we adopt a real-space function, the signature function, which plays the role of an energy density, somewhat analogous to E(k). In this Letter we determine the form of the signature function in a variety of turbulent flows. We find that dissipation-range phenomena, such as the so-called bottleneck effect, are evident in the signature function, while absent in the structure function.

Rotator cuff repair tension as a determinant of functional outcome.

This study evaluated the effect of rotator cuff repair tension on surgical outcome. A total of 67 consecutive rotator cuff repairs for full-thickness tendon tears were prospectively evaluated. Rotator cuff repair tension was quantified by means of an intraoperative calibrated tensiometer after cyclic loading. The point of maximum repair tension was measured. Patients were evaluated for pain and improvement before and after surgery through use of Constant scores, American Shoulder and Elbow Surgeons' functional criteria, isokinetic strength-testing, and visual analog scale scores. Increased repair tension correlated with lesser gains in postoperative Constant score, a decrease in perceived improvement, decreased isokinetic strength measurements, and increased pain. Tension on repaired rotator cuff tendons should be minimized. High-tension repairs--those greater than 8 lb--are associated with poor subjective and objective outcomes and are not recommended.

Anterior-inferior (5 o'clock) portal for shoulder arthroscopy.

The present study describes an anterior-inferior portal for arthroscopic shoulder instrumentation at the 5 o'clock position along the glenoid rim. An anterior-inferior portal was established in 14 cadaver shoulders. The portal was created in an inside-to-outside fashion, with the humerus maximally adducted, directing the guide rod as far lateral as possible. Using the described technique, a 5 o'clock portal travels through the subscapularis and lateral to the conjoined tendon. Distance between the portal and the musculocutaneous nerve was 22.9 +/- 4.9 mm (mean +/- SD), and 24.4 +/- 5.7 mm between the portal and the axillary nerve. Previously described portals were either at, or above the 3 o'clock position, resulting in an acute, difficult angle of approach to the glenoid neck. Through a combination of proper arm positioning and rod insertion technique, the 5 o'clock portal can be created safely and is of great potential utility for arthroscopic shoulder stabilization procedures.

Functional anatomy of the flexor pronator muscle group in relation to the medial collateral ligament of the elbow.

To describe the relationship of the pronator teres, flexor carpi radialis, flexor digitorum superficialis, and flexor carpi ulnaris muscles to the medial collateral ligament at 30 degrees, 90 degrees, and 120 degrees of elbow flexion, we dissected 11 cadaveric specimens. The flexor carpi ulnaris muscle is the predominant musculotendinous unit overlying the medial collateral ligament in the majority of cases and is the only one at 120 degrees of elbow flexion. The flexor digitorum superficialis muscle is the only other significant contributor. The medial collateral ligament is the primary stabilizer of the medial elbow with elbow flexion greater than 30 degrees, as in throwing. The flexor carpi ulnaris muscle, because of its position directly over the medial collateral ligament, and the flexor digitorum superficialis muscle, with its near proximity and relatively large bulk, are the specific muscles best suited to provide medial elbow support. This is especially relevant to overhand throwing athletes who encounter extreme valgus force across the elbow during the cocking and acceleration phases of the throwing motion. Exercise and conditioning of the medial elbow musculature, specifically the flexor digitorum superficialis muscle and the flexor carpi ulnaris muscle, may prevent injury or assist in rehabilitation of medial elbow instability, especially in overhand throwing athletes.

Radial head fracture. A potentially complex injury.

A prospective study was undertaken on 50 acute, consecutive fractures of the radial head. Clinical examination and stress testing were performed on each patient. A valgus stress radiograph, in conjunction with clinical stress testing, was used to assess competence of the medial elbow ligaments. Axial stability of the radius was determined by the axial stress test. Eleven patients (22%) sustained a comminuted radial head fracture; all had instability either to valgus or axial stress. Seventeen patients (34%) had a displaced vertical shear type fracture or an impacted fracture of the radial neck. All sustained some injury to the medial collateral ligament, with variable degrees of valgus elbow instability. Twenty-two (44%) of the fractures were minimally or nondisplaced. All 22 were stable. Radial head fracture morphology can be used to assess the likelihood of associated soft-tissue injury.