Migration responses of outer and inner meniscus cells to applied direct current electric fields

Injuries to the inner regions of the knee meniscus do not heal and can result in degenerative changes to the articular surface, ultimately leading to osteoarthritis. A possible stimulus to enhance meniscus healing is to use electric fields that induce galvanotaxis. In this study, a novel characterization of the effects of direct current electric fields on migration characteristics of meniscus cells was performed. Primary and passaged inner and outer meniscus cells were exposed to varying electric field strengths from 0 to 6 V/cm. Cell migration was tracked using time lapse digital photography, and cell displacement and cathodal direct velocity were quantified. Cytoskeletal staining was performed to examine actin distribution and nuclear content. Cell adhesion strength was quantified as a function of wall shear stress. Meniscus cells exhibited cathodal migration and cell elongation perpendicular to the applied electric field accompanied by actin reorganization. Outer meniscus cells migrated quicker and exhibited lower adhesion strengths when compared to inner meniscus cells. Passaged cells exhibited higher migration characteristics when compared to primary cells. Overall, this study demonstrated that electric fields can significantly enhance and direct meniscus cell migration and suggests the potential for their incorporation in strategies of meniscus repair and tissue engineering.

Bipolar radiofrequency in the human meniscus. Comparative study between patients younger and older than 40 years of age

PURPOSE

To morphohistologically evaluate the effect of four increasing intensities of bipolar radiofrequency (RF) on the human meniscus and to compare the changes seen in the menisci from patients younger and older than 40 years old.

METHODS

Thirty fresh menisci were divided in two groups. Group 1: 12 menisci from patients younger than 40 y.o.; Group 2: 18 menisci from patients older than 40 y.o. Groups 1 and 2 were divided in four zones and subjected in vitro, for 3 s, to four intensities of bipolar RF energy. The samples were studied macroscopically, and microscopically.

RESULTS

Thermal changes were present between 0 and 4000 microm from the meniscal surface, with an average of 1699 microm (S.D. 740), and was significantly higher on the ablation than the coagulation group (p<0.001). We found a significant difference between the depth of thermal changes in the menisci from patients younger and older than 40 years old at medium intensities of RF energy (p=0.038 and p=0.044).

CONCLUSIONS

Although bipolar RF can cause deep thermal changes (up to 4000 microm) on the human meniscus, this effect depends on the magnitude of the energy applied. When comparing the effect between younger and older patients, the changes were deeper in the older group when RF was applied at medium intensities.

CLINICAL RELEVANCE

Based on our findings, we recommend to exert precaution when applying RF energy at medium intensities in the degenerative meniscus, due to a deeper thermal effect in this group.

Meniscal debridement with an arthroscopic radiofrequency wand versus an arthroscopic shaver: comparative effects on menisci and underlying articular cartilage

PURPOSE

Meniscal debridement with an arthroscopic radiofrequency (RF) wand versus an arthroscopic shaver and their comparative effects on menisci and underlying articular cartilage were studied.

METHODS

When repair is not feasible, degenerative or post-traumatic meniscal tears often need debridement. Six fresh bovine knees were harvested, the tibial plateau was dissected free from the femoral articulation and placed in a saline bath at 28 degrees C, with 10% to 15% of the posterior horn of menisci debrided arthroscopically, and the surfaces debrided using a basket punch plus shaver, punch plus RF wand, RF wand alone, and untreated control. Treatment time of each case was 24 seconds at wand power 7. We characterized an injury zone, as well as viability and metabolic activity of meniscal cells and tibial articular cartilage chondrocytes.

RESULTS

Chondrocyte viability of the tibial articular surface was 96% to 98%. We saw no differences in viability or injury zone (0 to 150 microm) among debrided groups or versus the control for any experimental surface, with no significant difference in metabolic activity in menisci debrided surfaces versus control. Meniscal viability was variable with analyses showing substantial levels (150 to 500 microm) of cell death in debrided and control groups. Metabolic activity in treated meniscus was lower than in cartilage specimens. No significant differences were observed among treatment groups versus control.

CONCLUSIONS

Focal areas of chondrocyte cell death were not seen. Meniscal samples showed cell death (150 to 500 mum) throughout the tissue.

CLINICAL RELEVANCE

Debridement of menisci with a bipolar RF wand produces levels of cell injury and death similar to those of debridement with a basket punch mechanical shaver. The RF wand did not harm underlying articular surfaces and produced a precise cut to the meniscal surface.

Sutureless avascular meniscal repair with a photoactive naphthalimide compound: a preliminary animal study

PURPOSE

The purpose of this study was to evaluate the ability of 2 new photoactive naphthalimide compounds to repair a lesion in the avascular zone of the meniscus.

TYPE OF STUDY

In vivo animal study.

METHODS

Ten Barbados sheep were used as the animal model. Under anesthesia, the left knee joint was opened and 2 identical lesions were produced in the avascular zone of the medial meniscus. The posterior horn lesion was left alone and used as the control and the lesion in the anterior horn was repaired using the photoactive laser technique. The photoactive laser technique involved placing small amounts of a naphthalimide compound into the lesion and then irradiating the site with a laser (457 nm and 1.8 W/cm2) for 6 minutes. Two different versions of the naphthalimide compound were produced and divided between the 10 animals. The joint was then flushed with normal saline and closed in layers with resorbable sutures. Four animals were euthanized at the end of 1 month and 6 animals were euthanized at the end of 3 months. After death, the medial meniscus was exposed, dissected free, and then placed in 10% buffered formalin for histologic preparation and staining.

RESULTS

At 1 month, the control lesions grossly showed no repair and the photochemically repaired lesions appeared to be bonded. The photochemically repaired lesions showed some bridging by an eosinophilic amorphous-appearing substance. The previous cleft within the fibrocartilaginous structure had disappeared, and early formation of connective tissue fibers was identified. However, some reduction in cellularity was seen in these tissue sections. At 3 months, again the control lesions did not show any repair response, while the photochemically repaired lesions showed results similar to the animals at 1 month, but with a less consistent pattern of tissue bonding and remodeling. The reduced tissue cellularity was still noted. There was no discernible difference between the naphthalimide compounds.

CONCLUSIONS

These preliminary results demonstrate the potential usefulness of this photochemical bonding for the treatment of avascular meniscal lesions. Additional research will be necessary to fully understand the mechanism of this repair and optimize its use before any human trials.

CLINICAL RELEVANCE

This is a preliminary animal study investigating the short-term in vivo effects of a novel photochemical compound for the repair of meniscal lesions. This repair may someday be valuable in the repair of avascular meniscal lesions.

Photochemical tissue bonding using monomeric 4-amino-1,8-naphthalimides

Certain substituted naphthalimides have been shown to produce, on photochemical activation, mechanically viable bonds between a variety of tissue surfaces. It is believed that these compounds act as photochemically activated oxidants, catalyzing the formation of reactive intermediates in the extracellular matrices of approximated tissue surfaces. The condensation of these intermediates results in the formation of crosslinks between the intimate surfaces. Of particular interest is the application of this technique to the repair of tears in the typically unrepairable avascular zone of menisci. The menisci are collagen-rich fibrocartilaginous tissues that support up to 90% of the load across the knee joint and participate in important functions including shock absorption, joint stabilization, hyperextension prevention, and lubrication of the knee. Preliminary ex vivo and in vivo work in our laboratories has demonstrated that photochemically activated naphthalimides have significant potential for the repair of meniscal lesions. We describe preliminary ex vivo studies assessing the relative abilities of a variety of water-soluble monomeric 4-amino-1,8-naphthalimides to bond bovine knee meniscal tissue on visible light irradiation.

Prolonged central motor conduction time of lower limb muscle in spinocerebellar ataxia 6

We investigated the function of corticospinal tract in spinocerebellar ataxia 6 (SCA6) by measuring the central motor conduction time (CMCT). Motor evoked potentials (MEP) of tibialis anterior (TA) muscle were elicited by magnetic stimulation to motor cortex and spinal cord in 9 SCA6 patients and 10 normal height- and age-matched subjects. CMCT in lower limb of SCA6 patients (18.1+/-1.9 ms) was significantly prolonged than that of the normal subjects (15.0+/-1.0 ms) ((p < 0.001). The prolonged CMCT was well correlated with the duration of disease (p = 0.005), but MEP amplitudes and stimulation intensities were not significantly different. These results indicate that the corticospinal tract function is also impaired and correlate with the disease duration in SCA6.

Radiofrequency thermal effects on the human meniscus. An in vitro study of systems with monopolar and bipolar electrodes

BACKGROUND

No data exist on the cutting efficiency of monopolar versus bipolar radiofrequency energy application systems on human meniscal tissue.

PURPOSE

To compare the effects of monopolar and bipolar thermal energy systems on human meniscal tissue.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fresh-frozen menisci were cut in cross-section into 180 pie-shaped specimens. A specially designed jig was used to consistently apply radiofrequency energy to the tissue under a constant 30-g force. Three different systems were tested at the low, middle, and high ranges, with application times of 1 and 3 seconds. Thermal effects were measured by image analysis microscopy.

RESULTS

No significant differences in thermal effects were found with respect to energy output for each system. Both the individual system tested and the application time had statistically significant effects on thermal damage, with the individual system tested having a greater effect. The mean depths of thermal change produced by the Mitek (bipolar) device were 564 and 648 microm at 1 and 3 seconds applications, respectively. The Arthrocare device (bipolar) produced depths of 1444 and 1697 microm at 1 and 3 seconds. The Oratec device (monopolar) produced depths of 895 and 1057 microm, respectively.

CONCLUSIONS

A differential thermal effect was created in the meniscal tissue by three commercially available radiofrequency systems. Within the parameters of the experiment, all three systems limited thermal damage to a depth of less than 2 mm. The results appeared to depend more on the particular system used, not whether it had monopolar or bipolar electrodes.

CLINICAL RELEVANCE

These data imply reasonably safe (less than 2 mm) thermal changes in the meniscus after radiofrequency energy application from these three systems.

The effects of radiofrequency bipolar thermal energy on human meniscal tissue

This study performed the first in vitro histological analysis of the effects of bipolar thermal energy on human meniscal tissue. Sixteen fresh human menisci were mounted on a cutting block and placed in a water bath simulating an arthroscopic environment. Each specimen was divided into four sections and randomized to one of four treatment options: 1. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power 3 setting); 2. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power setting 7); 3. resection with a scalpel blade; and 4. resection with a motorized 4.5 full-radius resector. Six micron sections were cut and stained with Hematoxylin and Eosin and Masson's trichrome stain. Menisci were evaluated for the contour of the cut edge: straight, jagged, frayed, or combined. The zone of thermal necrosis and zone of thermal alteration were determined by examining the differential staining of the connective tissue and measuring the affected area. Menisci treated with the bipolar thermal probe were noted to have a smoother contoured edge in comparison to motorized cutters. The zone of thermal penetration for the Arthrocare power setting 3 averaged 0.18 mm (range: 0.09 to 0.20; SD 0.04) and for Arthrocare power setting 7 averaged 0.33 mm (range: 0.26 to 0.36; SD 0.03). The difference in thermal penetration between Arthrocare power settings 3 and 7 was 0.15 mm. This was statistically significant at p < 0.0001 (95% CI: 0.11 to 0.19 mm). The zone of thermal penetration was non-existent for the shaver and scalpel groups. This study provides the first histological description of the effects of bipolar radiofrequency energy on meniscal tissue. It demonstrates that there is intra-substance thermal penetration and alteration of the meniscal tissue. Its clinical significance is unclear and further in vivo studies are needed to address its clinical applicability.

Radiofrequency thermal effects on the human meniscus: an in vitro analysis

PURPOSE

The purpose of this study was to evaluate the thermal effects produced in meniscal tissue with different radiofrequency (RF) energy levels and exposure times using a bipolar device.

TYPE OF STUDY

An anatomic in vitro analysis of the thermal effects of an RF device.

METHODS

A specially designed jig was used to apply RF energy under a constant force to cadaveric menisci. Three different energy levels were applied for 4 different contact times.

RESULTS

The overall mean depth of thermal change was 547 microm (range, 468 to 650 microm). There were no significant differences or trends when contact time and energy were varied.

CONCLUSIONS

These data suggest that increased contact times and energy outputs are not associated with increased thermal change in the meniscus. The submillimeter thermal denaturation was consistent with published reports using other thermal devices, such as laser.

Histological and magnetic resonance imaging alterations after irradiation of meniscus using Holmium:YAG laser

OBJECTIVE

The authors performed an experimental and a prospective clinical study to evaluate the histological and magnetic resonance imaging (MRI) alterations after irradiation of meniscus using holmium:YAG (Ho:YAG) laser VersaPulse Select 60 watts and InfraTome Delivery Systems 30 degrees Handpiece (spot size at fiber tip 0.4 mm; Coherent Medical, Palo Alto, CA).

BACKGROUND DATA

Recently, some authors reported a few cases with articular cartilage damage or paraarticular osteonecrosis following arthroscopic knee surgery in which the laser was used to assist in the treatment of meniscal pathology.

METHODS

Meniscus specimens in saline immersion were exposed to Ho:YAG laser irradiation. The laser wavelength was 2.1 microm and pulse duration was 250 microsec. Power settings were 1-1.5 joules per pulse and 10-15 Hz. Total laser energy used in these procedures was 2, 3.5, and 6 K joules. Eight patients with meniscal problems underwent arthroscopic partial meniscectomy using Ho:YAG laser. Total laser energy used for these surgeries was 1.5-2.5 K joules. MRI was performed preoperatively and at 6 months postoperatively.

RESULTS

At higher energy levels (more than 3 K joules), separation of the gap between the collagen fibers, and a three-dimensional dispersion in the striation were observed on electron microscopic evaluation of meniscus specimens. No patient had abnormal signals in MRI (a sign of articular cartilage damage or osteonecrosis) following arthroscopic laser surgery.

CONCLUSION

When higher energy level is required, conventional instruments should be preferred in the treatment of meniscal lesions. Laser should be reserved for the posteriorly located and smaller meniscal lesions.

Reactions of meniscal tissue after arthroscopic laser application: an in vivo study using five different laser systems

In many clinical and in vitro studies, the effect of laser radiation on meniscal tissue was examined. Clinical studies referred to clinical criteria like swelling, effusion, and pain to evaluate laser effects. In vitro studies showed the laser effect in the moment of cutting the tissue. But the effect of laser radiation on biological tissue also depends on the vital reaction of the tissue. So, the real extent of tissue damage caused by laser irradiation can only be examined in long-term in vivo studies. This was the purpose of this study. Seventy-two knees of pigs underwent arthroscopic meniscal cuts in the anterior horn of the medial meniscus. The pigs were divided into 6 groups: The first 5 groups were operated with 5 different laser systems: Neodym: YAG 1,440-nm wavelength; Nd:YAG 1,064-nm wavelength, Excimer, Holmium:YAG, and CO2. The sixth group was operated with mechanical punches. From each group, the menisci of the pigs were examined macroscopically and by light-microscope after survival periods of 0, 2, 6, 12 weeks. Results were as follows. (1) All laser systems caused greater damage to the meniscal tissue than mechanical instruments. (2) This damage was a biological reaction of the tissue, characterized by a necrotic zone surrounding the meniscus cut. (3) This necrotic zone was not visible intraoperatively but only 2, 6 and 12 weeks after operation. The diameter of the necrotic zone ranged between 1.5 nm and 9 mm. (4) Meniscus cuts with mechanical instruments showed no necrotic zone in the surrounding tissue. (5) Laser cuts in the meniscus caused more extensive healing reaction than cuts with mechanical instruments. (6) The quality of this healing reaction varied with the different laser systems: the Nd:YAG 1,064-nm, Ho:YAG, and CO2 laser caused only an incomplete healing because the tissue repair showed by tissue growing from the synovial edge into the defect only. The Nd:YAG 1,440-nm wavelength and Excimer led to tissue growing from the synovial edge and to remodeling of original meniscal tissue, recognizable by reduction of the necrotic zone. Arthroscopic surgeons should be aware that the damage to meniscus tissue caused by a laser is much greater than can be seen intraoperatively and is much greater than the damage caused by mechanical punches. The healing reaction of the tissue is more extensive after laser application than after use of mechanical instruments. Results of in vitro studies on the tissue damage caused by lasers are insufficient to describe the whole extent of laser effects on living tissue.

308 nm excimer laser ablation of cartilage

This article reports the investigation of the XeCl excimer laser as a cutting-ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800-microns fiber with the laser delivering a range of fluences (40-190 mJ/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on depth per pulse, a set of measurements was made at a constant fluence of 60 mJ/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis of preserved specimens was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10-70 microns). The excimer laser achieved ablation rates adequate for arthroscopic applications.

Macroscopic and microscopic findings after excimer laser treatment of different tissue

In reported tests, the interaction of excimer laser radiation with bone, meniscus, and tendon tissue was observed. Depending on various laser parameters, different tissue reactions were observed in all procedures. Ablation was performed in a liquid medium to ensure extended carbonizations even at low application energy and repetition rate. Our studies revealed that the longer the pulse, the lower the destruction rate of fibers. However, a longer pulse caused lower ablation rates than a shorter one. An increase of repetition rate instead of an increase of application energy resulted in higher heat accumulation in the adjacent tissue. Differentiation of the single parameters on various tissue allows flexibility of thermal effects from the laser procedure.

Evaluation of electrosurgical meniscectomy in rabbits

Recently, electrosurgical cutting instruments utilizing radiofrequency energy have been designed as arthroscopic devices for cutting meniscal tissue. This study attempted to determine the in vivo gross and microscopic effects of radiofrequency energy on meniscal tissue in rabbits. Twelve adult New Zealand white rabbits (48 menisci) underwent bilateral knee arthrotomies. Ten rabbits (40 menisci) underwent partial meniscectomies in which one half of each meniscus in the longitudinal plane was removed with the electrosurgical generator. Two control rabbits underwent arthrotomy without resection of meniscal tissue. At specific time intervals, the rabbits were killed, and the menisci were removed. The gross specimens were photographed, and microscopic sections of each meniscus were fixed and stained. Specimens were evaluated to determine the cellular and vascular response to the electrosurgical cut edge of each meniscus. The microscopic specimens revealed that the radiofrequency cutting instruments produced a small degree of direct thermal damage to the cut meniscus. A tissue response producing a hypercellular dense collagen matrix was present for approximately 3 months. The spontaneous repair of tissue was complete by 6 months, and the histologic 6-month specimens could not be distinguished from the 6-month control specimens except with respect to the overall width of the specimens.