Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.     

In vitro and clinical feasibility study with an over-the-wire delivery system for pulsed dye laser angioplasty.

The suitability of a pulsed dye laser (504 nm) in experimental and clinical angioplasty was investigated. In an experimental study, the ablation thresholds were 3 J/cm2 +/- 8 (mean +/- standard deviation) for fibrofatty plaque and 25 J/cm2 for calcified tissues under saline. At a radiant exposure of 10 J/cm2 the etch rates were 1.7 microns per pulse +/- 0.3 for media, 2.8 microns/pulse +/- 0.4 for normal intima, and 3.9 microns/pulse +/- 1.1 for fibrofatty plaque (P less than .05). Pressure wave effects with a separation of tissue layers were predominantly localized at the internal elastic lamina. Thermal injury with vacuolations extended 15 microns +/- 6 into adjacent tissue. For clinical study, laser-assisted balloon angioplasty was performed in 10 patients (64 years +/- 14) with occlusions of peripheral arteries using a 9-F multifiber ring catheter. Lesion length ranged from 2 to 12 cm (mean, 7 cm). Laser angioplasty with an 80 mJ/pulse decreased the mean stenosis from 100% to 58% +/- 12% (P less than .005). The ankle-brachial index rose from a median of 0.48 to 0.88 (P less than .001). In 33% of patients, there were subintimal dissections after laser angioplasty. After a mean follow-up of 10.2 months, the overall clinical success was 70% with a primary patency of 78%. The over-the-wire approach with a pulsed dye laser may constitute a safe and feasible tool in laser angioplasty.     

In vitro ablation of normal and diseased vascular tissue by a fiber-transmitted holmium laser

An in vitro study was performed to test the ablative potential of a fiber-transmitted pulsed holmium laser (2.1 microns) applied to normal vascular wall, lipomatous plaques, and calcified plaques. Different fluences per pulse of 42, 80, 205, and 315 J/cm2 were used. Ablation of normal tissue and lipomatous plaques was achieved with all power settings. Effective ablation of calcified plaques, however, occurred only after a minimum fluence of 205 J/cm2, and the effect was significantly less pronounced compared to ablation of soft lesions.     

Lineage plasticity and cell biology of fibrocartilage and hyaline cartilage: its significance in cartilage repair and replacement

Cartilage repair is a major goal of modern tissue engineering. To produce novel engineered implants requires a knowledge of the basic biology of the tissues that are to be replaced or reproduced. Hyaline articular cartilage and meniscal fibrocartilage are two tissues that have excited attention because of the frequency with which they are damaged. A basic strategy is to re-engineer these tissues ex vivo by stimulating stem cells to differentiate into the cells of the mature tissue capable of producing an intact functional matrix. In this brief review, the sources of cells for tissue engineering cartilage and the culture conditions that have promoted differentiation are discussed within the context of natural cartilage repair. In particular, the role of cell density, cytokines, load, matrices and oxygen tension are discussed.     

Holmium :YAG-laser-assisted arthroscopy versus conventional methods for treatment of the knee Two-year results of a prospective study

The results of 320 arthroscopic procedures are reported here, in which laser surgery using the holmium:YAG laser is compared with conventional mechanical methods. The patients were followed-up during a 2-year period and the data analyzed in a prospective study. The following knee injuries were included: meniscal lesion, chondromalacia, combined meniscal/cartilage lesion, rheumatoid synovialitis and patellofemoral pain syndrome. Because strict inclusion criteria were used, the patient collective is homogenous. Gender, age, injured side, intrasurgical diagnosis, and the initial values of the Lysholm score (modified after Klein) are congruous. After 2 years, the results of the laser collective were significantly improved, whereas the results for the conventional collective, especially for chondromalacia and synovialitis, did not show the same improvement. Analysis of the effect of various instruments and the laser system itself show differing results for the various knee disorders. The hemostatic effect of the holmium:YAG laser was excellent during surgery of all knee disorders, including surface treatment. Operating time for laser surgery was not prolonged, in contrast to what is often claimed. This study shows that chondromalacia, combined meniscal-cartilage lesions, and chronic rheumatoid synovialitis are treated more effectively and with better results with the holmium:YAG laser than with conventional arthroscopic methods. Furthermore, laser treatment of lateral retinacular release can be considered to be better than mechanical techniques. No significant advantage can be found for using the laser during meniscectomy. Lasers are useful for treating smaller, hard-to-reach joints and lower the risk of iatrogenic cartilage damage. The holmium:YAG laser is a suitable instrument for arthroscopic surgery. Received: 25 May 1996 Accepted: 1 March 1997     

Matrix assessment of the articular cartilage surface after chondroplasty with the holmium:yttrium-aluminum-garnet laser. A long-term study.

A long-term in vivo study was performed to assess biochemical changes after laser repair of articular cartilage. Forty New Zealand White rabbits were sacrificed 26 weeks after undergoing an articular cartilage chondroplasty with use of a holmium:yttrium-aluminum-garnet laser at 0.8 joules per pulse and a rate of 10 Hz. Glycosaminoglycan content in the repaired tissue decreased significantly with both perpendicular (19.59+/-5.6 microg hexosamin/mg of dry tissue) and tangential delivery (14.78+/-4.5 microg/mg) compared with the sham-treated tissue (39.6+/-5.0 microg/mg). Cellular viability was also significantly decreased. Sulfate incorporation was decreased to 203+/-142 cpm/mg of dry cartilage in the tangential mode and 461+/-209 cpm/mg in the tangential mode, compared with the sham at 1845 cpm/mg. Uptake of [3H]thymidine decreased to 463+/-473 cpm/mg of dry tissue and 455+/-170 cpm/mg in the tangential and perpendicular modes, respectively, compared with 2465 cpm/mg in the sham tissue. There were no significant differences between the tangential and perpendicular delivery modes in any assessments performed. The shortterm chondrocyte destruction previously noted in a 12-week study after laser treatment was not reversed during a longer-term 26-week study, and cellular viability was not recovered, suggesting that the loss of chondrocyte function may be permanent.     

MR imaging of Ho:YAG laser diskectomy with histologic correlation

Twelve cadaveric vertebral specimens were imaged after holmium yttrium aluminum garnet (Ho:YAG) laser diskectomy to determine the usefulness of magnetic resonance (MR) imaging in evaluating treatment outcome. The Ho:YAG laser was operated at 1.0-2.0 J per pulse, 5 Hz, and 250-usec pulse width. The total energy varied between 600 and 2,700 J. Two distinct patterns emerged on MR images. Tissue ablation at higher power (1.5 and 2.0 J per pulse) produced discrete signal voids that correlated with areas of laser-induced ablation identified at gross inspection. More subtle changes, characterized by a high-signal-intensity ring, were seen in the specimens lased at 1.0 J per pulse. The latter appearance corresponded to incomplete vaporization of diskal tissue, a broader zone of minimal thermal injury, and sparing of adjacent vertebral endplates. Total mass loss did not appear to be affected by the choice of power setting (1.0 vs 1.5 J per pulse), with total laser energy held constant.     

The effect of magnetization transfer in meniscal fibrocartilage

Magnetic resonance imaging of the knee was performed in 28 patients (ages 15–72 years), using a 1.5-T unit. Volume gradient echo (3D GRASS) acquisition with and without presaturation off-resonance RF pulse was used to evaluate magnetization transfer (MT) effects, determined by placing regions of Interest on muscle, fat, hyaline, and fibrocartilage; the percent change in signal intensity was calculated and compared using a paired two-sample t test. An in vitro study of the normal meniscus from a cadaver containing a scalpel cut extending to an articular surface was performed to observe the relative improvement in contrast in the presence of a small meniscal defect. MR imaging of the specimen was performed using an Omega CSI 2.0–T system (General Electric Medical Systems, Fremont, CA). Analysis of clinical images resulted in signal loss, compared to that of the identically timed and tuned non-MT images of 47 ± 5, 8 ± 5, 49 ± 5, and 57 ± 7% for muscle, fat, articular cartilage and fibrocartilage, respectively. Application of MT improved the depiction of the artificially introduced meniscal defect. Meniscal fibrocartilage demonstrates significant MT effect after application of off-resonance RF presaturation, which may improve visualization of meniscal defects.     

Meniscal repair following meniscectomy: mechanism and protective effect

Meniscal repair was studied to evaluate the mechanism and its potential protective effects on the articular cartilage in an experimental model consisting of 68 knees of adult dogs on which five different types of medial meniscectomy were performed. The results were assessed by macroscopic, microangiographic, and histological methods, after a sequential follow-up period of 10–450 days. Two different mechanisms of meniscal repair were observed, depending on whether meniscal section had been performed in vascular (total meniscectomy) or avascular (subtotal or partial meniscectomy) zones. It was also observed that the repaired meniscal tissue does not prevent articular cartilage degeneration. This is more closely related to the size of the meniscal fragment preserved at meniscectomy. Due to the biomechanical importance of the meniscus and the lack of functional relevance of the repaired meniscal tissue, the most conservative approach possible to meniscectomy is recommended.     

The holmium:YAG laserin knee arthroscopy

The Holmium:YAG (Ho:YAG) laser is effective in the arthroscopic treatment of common knee conditions, includingresection of inaccessible posterior meniscal tears, smoothing irregular chondral disease, and ablation of hypertrophic synovium. Understanding the multiple parameters that influence energy delivery will facilitate appropriate and effective use of the laser. Clinical outcome data does not demonstrate the laser to be superior to mechanical instrumentation. Complications of osteonecrosis and chondral sloughing have been reported after use of the holmium laser, but critical review suggests these may be a consequence of inappropriate surgical technique rather than the laser itself. When used properly, the holmium laser is safe and provides a convenient and multipurpose tool in the arthroscopic treatment of common conditions of the knee.     

The effects of time course after anterior cruciate ligament injury in correlation with meniscal and cartilage loss

In this study, 130 consecutive patients with anterior cruciate ligament insufficiency who were undergoing ligament reconstruction underwent arthroscopic examination at the time of reconstruction, and any loss of meniscal or chondral integrity was documented in a systematic fashion. In these patients, a greater proportion of the medial meniscus was lost compared with the lateral meniscus (16% versus 5%). On average, 6 cm2 of the articular cartilage was damaged (5.2 cm2) or lost (0.8 cm2), with the area of damage and loss greatest on the medial femoral condyle. Patients whose injuries had occurred more than 2 years before the examination had more than sixfold greater cartilage loss and damage compared with those whose injuries had occurred within the past 2 months. Meniscal loss was associated with a threefold increase in cartilage damage or loss. The group of patients with meniscal loss whose initial anterior cruciate ligament injury occurred more than 2 years before examination exhibited 18 times the amount of cartilage loss or damage as did the group that had no meniscal loss and whose injury occurred less than 1 month before examination.     

Long-term outcome for large meniscal defects treated with small intestinal submucosa in a dog model

BACKGROUND: Large meniscal defects are a common problem for which current treatment options are limited. HYPOTHESIS: Treatment of posterior medial meniscal defects in dogs with small intestinal submucosa is superior to partial meniscectomy in terms of clinical limb function, chondroprotection, and amount and type of new tissue in the defect. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 51 mongrel dogs underwent medial arthrotomy with creation of standardized meniscal defects. The dogs were divided into groups based on defect treatment: small intestinal submucosa meniscal implant (n = 29) or meniscectomy (n = 22). The dogs were assessed for lameness by subjective scoring after surgery and sacrificed at 3, 6, or 12 months and assessed for articular cartilage damage, gross and histologic appearance of the operated meniscus, amount of new tissue in the defect, equilibrium compressive modulus of meniscal tissue, and relative compressive stiffness of articular cartilage. RESULTS: Dogs in the meniscectomy groups were significantly (P < .001) more lame than dogs treated with small intestinal submucosa. Joints treated with small intestinal submucosa had significantly (P <.001) less articular cartilage damage, based on india ink staining, than did those treated with meniscectomy. Menisci receiving small intestinal submucosa had more tissue filling in the defects than did menisci receiving no implants, and this new tissue was more mature and meniscus-like and better integrated with remaining meniscus. CONCLUSION: Small intestinal submucosa scaffolds placed in large meniscal defects resulted in production of meniscus-like replacement tissue, which was consistently superior to meniscectomy in amount, type, and integration of new tissue; chondroprotection; and limb function in the long term. CLINICAL RELEVANCE: Small intestinal submucosa implants might be useful for treatment of large posterior vascular meniscal defects in humans.     

Meniscal substitutes – animal experience

Animal studies have shown that meniscus allografts and tendon autografts generally heal to the capsule, are revascularized and repopulated with host cells. In animals, neither meniscal allografts nor tendon or fat autografts gain the properties of a normal meniscus. Meniscus allografts and tendon autografts are promising as both seem to offer some protection to the cartilage of the tibial plateau. There is no evidence that meniscal transplantation can prevent cartilage degenerative changes, and the long-term effect of meniscal transplantation on articular cartilage remains unknown. Whether cellular repopulation of the meniscal allograft is sufficient to restore its biomechanical properties is unknown. Collagen scaffolds and tissue engineered grafts are still under investigation, showing promising results especially for the former. Viable meniscal allografts should be implanted within 1 to 2 weeks after harvesting, as the production of proteoglycans decreases after 2 weeks.     

Contribution of meniscal extrusion and cartilage loss to joint space narrowing in osteoarthritis.

OBJECTIVE: This study was undertaken to determine the contribution of meniscal extrusion and cartilage loss to joint space narrowing on conventional radiographs by correlation with magnetic resonance imaging (MRI). SUBJECTS AND METHODS: Sixty-two consecutive patients, 32 patients with osteoarthritis and 30 without osteoarthritis, over the age of 60 years that were referred for both radiographic and MRI of the knee were included in the study. In each case, relative joint space narrowing on conventional AP radiographs was assessed utilizing the Kellgren-Lawrence scoring system. Subsequently, the degree of meniscal extrusion and the integrity of articular cartilage were evaluated from MR in the same patients. RESULTS: Each of 30 patients with normal joint space (Kellgren Grade 0) were noted to have normal articular cartilage, grade 1 meniscal extrusion was identified in only three of these patients. In comparison, meniscal extrusion was identified in all 32 patients with joint space narrowing (Kellgren Grades 1-4). Definite thinning or loss of articular cartilage was identified in only 15 of the 32 cases. In 17 patients with radiographic joint space narrowing (Kellgren Grades 1-3) and meniscal extrusion, no loss of articular cartilage was observed. A statistically significant correlation (P<0.001) was observed between Kellgren Grade and degree of meniscal extrusion and cartilage thinning on MRI. CONCLUSION: Conventional radiographs are an unreliable method of evaluating for articular cartilage loss in patients with early osteoarthritis. Initial joint space narrowing on conventional radiographs is secondary to meniscal extrusion rather than thinning of articular cartilage in most cases.     

Lower Energy Endovenous Laser Ablation of the Great Saphenous Vein with 980 nm Diode Laser in Continuous Mode

Purpose To assess clinical outcomes, complication rates, and unit energy applied using 980 nm diode endovenous laser treatment at 11 watts for symptomatic great saphenous vein (GSV) incompetence and reflux disease. Methods Thirty-four consecutive ablation therapies with a 980 nm diode endovenous laser at 11 watts were studied. The diagnosis of GSV incompetence with reflux was made by clinical evaluation and duplex Doppler examinations. The treated GSVs had a mean diameter of 1.19 cm (range 0.5–2.2 cm). The patients were followed with clinical evaluation and color flow duplex studies up to 18.5 months (mean 12.19 months ± 4.18). Results Using 980 nm diode endovenous laser ablation in continuous mode, 100% technical success was noted. The mean length of GSVs treated was 33.82 cm (range 15–45 cm). The mean energy applied during the treatment was 1,155.81 joules (J) ± 239.50 (range 545.40–1620 J) for a mean treatment duration of 90.77 sec ± 21.77. The average laser fiber withdrawal speed was 0.35 cm/sec ± 0.054. The mean energy applied per length of GSV was 35.16 J/cm ± 8.43. Energy fluence, calculated separately for each patient, averaged 9.82 J/cm² ± 4.97. At up to 18.5 months follow-up (mean 12.19 months), 0% recanalization was noted; 92% clinical improvement was achieved. There was no major complication. Minor complications included 1 patient with hematoma at the percutaneous venotomy site, 1 patient with thrombophlebitis on superficial tributary varices of the treated GSV, 24% ecchymoses, and 32% self-limiting hypersensitivity/tenderness/“pulling” sensation along the treatment area. One patient developed temporary paresthesia. Four endovenous laser ablation treatments (12%) were followed by adjunctive sclerotherapies for improved cosmetic results. Conclusion Endovenous laser ablation treatment of GSV using a 980 nm diode laser at 11 watts in continuous mode appears safe and effective. Mean energy applied per treated GSV length of 35.16 J/cm or mean laser fluence of 9.82 J/cm² appears adequate, resulting in 0% recanalization and low minor complication rates.     

Meniscal transplant: bone blocktechnique for medial meniscus

The medial and lateral menisci significantly contribute to optimal knee mechanical function. When meniscusinjury and tearing occur and surgical resection is performed, then altered load-sharing and contact stress distribution can result in symptomatic dysfunction and articular cartilage degeneration. Post-meniscectomy patients who fail nonsurgical treatment may be candidates for meniscal tissue restoration through meniscal transplantation. The technique of medial meniscal transplantation using an allograft meniscal tissue and bone block composite to anchor the posterior and anterior horns has been shown to result in optimal fixation and healing. The arthroscopic-assisted approach to medial meniscal transplantation remains technically challenging particularly bond block insertion, passage and seating. Arthroscopic-assisted medial meniscal transplantation using fresh frozen allograft tissue and an osseous block technique is discussed. Operative pearls and technical tips that facilitate the procedure and postoperative care are described and illustrated.     

Meniscal allograft transplantation in the sheep knee: evaluation of chondroprotective effects

BACKGROUND: Early protection of articular cartilage, before degenerative changes appear on radiographs, should result in better long-term results, but scientific evidence regarding the effectiveness of meniscal transplantation is lacking. PURPOSE: To assess the chondroprotective effects of a new meniscal allograft transplantation animal model and evaluate a magnetic resonance imaging parameter, T2 mapping, in articular cartilage after meniscectomy and meniscal transplantation. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-five skeletally mature sheep were placed into 3 surgical groups: lateral meniscectomy (n = 24), meniscal allograft transplant (n = 17), and sham (n = 4). Animals were sacrificed at 2, 4, or 12 months. Cartilage was assessed by gross inspection, magnetic resonance imaging, T2 mapping, biomechanical testing, and semiquantitative histologic analysis. RESULTS: There were no differences between the sham operation and nonoperated control limbs. Compared with control limbs, meniscectomy resulted in significant increases in cartilage degeneration by all objective criteria (P < .01). Compared with meniscectomy, meniscal allograft transplantation resulted in significant decreases in cartilage degeneration (P < .02). There were significant correlations between T2-mapping data and all other traditional outcomes measures (P < .05, r(2) = 0.37-0.67). Compared with the nonoperated control limbs, allograft transplants demonstrated no significant differences at 2 months in any category, except magnetic resonance imaging data. By 4 months, nonoperated control limbs demonstrated significantly less wear compared to allograft limbs in all categories except modified Mankin scores. CONCLUSION: This model demonstrated significant chondroprotection compared with meniscectomy but demonstrated more cartilage wear at 4 months compared to control limbs. A high degree of allograft cell viability and vascular ingrowth was seen in allograft explants. T2 mapping may provide an accurate noninvasive measure of early cartilage degeneration after meniscectomy, as well as cartilage protection after meniscal allograft transplantation. CLINICAL RELEVANCE: This study establishes a reliable animal model for meniscal allograft transplantation and provides evidence for the utility of T2 mapping at clinically relevant magnetic resonance imaging field strengths for evaluation of early cartilage degeneration.     

Temperature requirements for altering the morphology of osteoarthritic and nonarthritic articular cartilage: in vitro thermal alteration of articular cartilage

BACKGROUND: Radiofrequency and laser thermal chondroplasty procedures are performed to debride and smooth fibrillated, articular cartilage. HYPOTHESIS: Temperature requirements necessary to achieve morphological change will be lower in fibrillated arthritic cartilage as compared with nonarthritic articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: A thermal cell-culture chamber was mounted on a stereoscopic microscope and coordinated with a custom temperature-control program. Nonarthritic and osteoarthritic articular cartilage specimens were sectioned into full-thickness slices. The articular sections were exposed to temperatures incrementally from 37 masculine C to 75 masculine C. Real-time, digital capture microscopy was used to visualize and analyze the morphological changes undergone by the articular cartilage specimens. RESULTS: Arthritic articular cartilage displayed morphological change at 56.5 +/- 1.7 masculine C. Loss of fibrillation was the initial morphological change visualized. Continued thermal exposure caused a shrinkage effect of the entire tissue section that was similar to the change seen in nonarthritic sections. Nonarthritic cartilage displayed morphological change at 60.9 +/- 1.9 masculine C. CONCLUSIONS: Consistent characteristic morphological changes were found at distinct temperatures in osteoarthritic and nonarthritic articular cartilage. CLINICAL RELEVANCE: This information begins to establish the thermal parameters required for morphological change of osteoarthritic articular cartilage.     

The long-term results of meniscus transplantation for articular cartilage defects in the knee joint

The purpose of this study was to examine the long-term clinical results of meniscus transplantation for articular cartilage defects in the knee joint. The type of study was case series. From October 1990 to June 1995, eight cases underwent allogenic or autogenic meniscus transplantations for articular cartilage defects, and seven cases were available for follow-up evaluations. The age at surgery ranged from 14 to 42 years of age (average 22.5). In one case, transplantation of tissue-engineered cartilage was performed due to pain 5 years after surgery. The other six cases were followed up for 8–13 years (average 10.1). The size of the cartilage defect ranged from 1.0 to 6.3 cm² (average 2.8 cm²). Patients were evaluated with the Lysholm score and MR images. We also performed arthroscopic examinations in three cases at the final evaluation. This study leads to the conclusion that meniscus transplantation for articular cartilage damage is not comparable to autologous chondrocyte transplantation. Two cases showed a good clinical outcome but the tissue remained as fibrocartilage tissue in the long-term.     

Meniscal allografts--where do we stand?

Meniscal transplantation has been recommended for selected meniscus-deficient patients in an effort to forestall progressive joint degeneration. Meniscal allograft transplantation may be considered for patients with symptoms (pain and swelling) due to meniscal deficiency in an effort to prevent progressive articular cartilage degeneration. Medial meniscal transplantation may also be considered during concomitant anterior cruciate ligament reconstruction, since absence of the medial meniscus results in increased forces in the anterior cruciate ligament graft. Contraindications for meniscal transplantation include advanced articular cartilage degeneration (especially on the flexion weightbearing zone of the condyle), axial malalignment, and flattening of the femoral condyle. Patient evaluation should include standing, long-leg radiographs for assessment of the mechanical axis and magnetic resonance imaging with appropriate pulse sequences for evaluation of hyaline cartilage thickness. Fresh-frozen and cryopreserved allografts are currently the most commonly used transplantation materials. Appropriate graft sizing is critical; most tissue banks size the meniscus based on radiographic tibial plateau measurements. Early results of meniscal transplantation indicate predictable improvements in pain, swelling, and knee function; however, no long-term results are available. Poor results have been reported in patients with advanced cartilage degeneration. Objective evaluations often demonstrate some degree of degeneration of the posterior horn of the transplant. Earlier transplantation should be considered for patients with known meniscal deficiency.