Does sterilization with fractionated electron beam irradiation prevent ACL tendon allograft from tissue damage?

PURPOSE: Allografts are frequently used for anterior cruciate ligament (ACL) reconstruction. However, due to the inherent risk of infection, a method that achieves complete sterilization of grafts is warranted without impairing their biomechanical properties. Fractionation of electron beam (FEbeam) irradiation has been shown to maintain similar biomechanical properties compared to fresh-frozen allografts (FFA) in vitro. Therefore, aim of this study was to evaluate the biomechanical properties and early remodelling of grafts that were sterilized with fractionated high-dose electron beam irradiation in an in vivo sheep model. METHODS: ACL reconstruction was performed in 18 mature merino mix sheep. Sixteen were reconstructed with allografts sterilized with FEbeam irradiation (8 × 3.4 kGy) and two with FFA. Eight FFA from prior studies with identical surgical reconstruction and biomechanical and histological analyzes served as controls. Half of the animals were sacrificed at 6 and 12 weeks, and biomechanical testing was performed. Anterior-posterior laxity (APL) was assessed with an AP drawer test at 60° flexion, and load to failure testing was carried out. Histological evaluation of mid-substance samples was performed for descriptive analysis, cell count, crimp and vessel density. For statistical analysis a Kruskal-Wallis test was used for overall group comparison followed by a Mann-Whitney U test for pairwise comparison of the histological and biomechanical parameters. RESULTS: Biomechanical testing showed significantly decreased stiffness in FEbeam compared to FFA at both time points (p ≤ 0.004). APL was increased in FEbeam compared to FFA, which was significant at 6 weeks (p = 0.004). Median of failure loads was decreased in FEbeam grafts, with 12 reconstructions already failing during cyclic loading. Vessel density was decreased in FEbeam compared to FFA at both time points, with significant differences at 12 weeks (p = 0.015). Crimp length was significantly shorter in FEbeam compared to FFA at both time points (p ≤ 0.004) and decreased significantly in both groups from 6 to 12 weeks (p ≤ 0.025). CONCLUSION: ACL reconstruction with fractionated Ebeam sterilization significantly alters the biomechanical properties and the early remodelling process of treated grafts in vivo. Therefore, this sterilization method cannot be recommended for clinical application. As substantial changes in the remodelling are inherent in this study, care in the rehabilitation of even low-dose sterilized allografts, used for ACL reconstruction, is recommended.

The histological analysis of the anterior cruciate ligament of canine after radiofrequency shrinkage.

OBJECTIVE: Radiofrequency (RF) shrinkage has been widely conducted in clinical practice and the anterior cruciate ligament (ACL) laxity is regarded as one of the indications. However, basic researches regarding the postoperative histological changes were still insufficient. The study aimed to investigate postoperative histological changes of different areas of ACL for further identifying the optimal area for RF shrinkage. MATERIALS AND METHODS: A total of 29 healthy canine (16.5 ± 2.2 kg, 4.1 ± 0.7 years) were recruited, 24 of which were randomly divided into group A and group B. The epiphyseal arrest was confirmed by X-ray examination in all animals. On one canine, an ACL's vascular perfusion model was established by the ink-perfusion method to observe the blood supply of the ACL. The mid-portion of ACL was conducted by RF in group A while the amph-portions of ACL were conducted in group B. Two legs of each canine were sub-divided into fixation group (group A1 and B1) and non-fixation group (group A2 and B2). 8 ACLs were separated from the rest 4 canine. 2 ACLs were sent for the histological examination after RF shrinkage and the rest 6 ACLs were served as blank controls. Masson staining and hematoxylin-eosin (H-E) staining were applied to observe the features of inner fibrous changes of ACL, cell count and vascular density. RESULTS: According to the Masson staining, collagenous tissues were observed in area after RF shrinkage, which was more evident among group B1 than the others. The cellar density in both group A and B was found lower at 12 weeks postoperatively than that at 6 weeks postoperatively (p < 0.05). In addition, the cellar density in B1 group was found higher than that in A1 group at both 6 and 12 weeks postoperatively (p < 0.05). The density of subsynovial vessel in B1 group was found higher than that in A1 group at 6 weeks postoperatively (p < 0.05) and the density of subsynovial vessel in both A1 and B1 groups was found lower at 12 postoperatively weeks than that at 6 weeks postoperatively (p < 0.05). In both A2 and B2 groups, all ACLs were found ruptured at 12 weeks postoperatively. CONCLUSIONS: The postoperative revascularization pattern of RF-treated ACL was permeating from the synovium to the RF-treated areas, and the best area for the RF shrinkage treatment was the amph-portions of the ACL. Moreover, the application of postoperative external fixation to restrict the movement of injured limb was necessary.

[Thermal shrinkage of anterior cruciate ligament--if it works?]. / Termiczne skrócenie wiezadla krzyowego przedniego--czy to dziala?

UNLABELLED: Common used method of treatment of anterior cruciate ligament deficiency is reconstructive surgery. But in cases of incomplete tear of ligament or graft failure one of the treatment options is thermal shrinkage of remain tissue. Although this method is widespread among clinicians, still there are a lot of controversies. Some studies showed good short and midterms outcomes, but others authors described failure of this method in long term observations in form of secondary laxation of the ligament or its spontaneous rupture. The aim of this study was to investigate outcomes of thermal shrinkage of lax, partially torn anterior cruciate ligament or its graft. MATERIALS AND METHODS: In years 2006-2012 was conducted twenty five operations of thermal shrinkage of anterior cruciate ligament or its graft. Full data was obtained from twenty individuals. Anterior stability was assessed by stabilometric side to side tests with Telos Stress Device and Rolimeter. Patients was asked to complete a Lysholm questionnaire. Arthritic changes was assessed by X-Ray scans using Lawrence-Kellgren scale. To made a statistic analysis MS Excel was used. RESULTS: Among twenty individuals failure of treatment was found in eight cases (40%). Remaining twelve patients (60%) at control examination stated that they feel improvement after surgical treatment. Mean Lysholm score was 87 pts and its comparable to other authors investigations. We have to keep in mind that subjective outcome may be affected by associated injuries. CONCLUSIONS: Thermal shrinkage of anterior cruciate ligament may in some cases find a place as a therapeutic option. The effect of shortening the ligament and improvement of the subjective feeling of instability is noticeable in the short term follow-up, but due to reports in the literature, patients require further observation.

Comparison of light-emitting diode wavelength on activity and migration of rabbit ACL cells.

The purpose of this study was to evaluate the biological response and gene expression of New Zealand White Rabbit anterior cruciate ligament (ACL) fibroblasts for different wave lengths of light-emitting diode (LED) irradiation. In other words, this study was undertaken to evaluate the effects of different wavelengths of LED irradiation on cell growth, expression of extracellular matrix and growth factors, migration, and expression of actin and integrin. Proliferation assay showed that red (630 nm, 9.5 J/cm(2)) and green LED (530 nm, 9.8 J/cm(2)) irradiated cells were more increased than control group but there was no difference between the control group and the blue LED (460 nm, 27 J/cm(2)) irradiated group. Moreover, the expression of insulin-like growth factor, transforming growth factor-beta (TGF-ß1), and collagen I were significantly increased in the red and green LED-irradiated group, but the expression of collagen was decreased in the blue LED-irradiated group. The results of staining showed that collagen and TGF-ß1 were weaker in the control group and blue LED-irradiated cells, but stronger in the red and green LED-irradiated cells. Also, in the red and green LED-irradiated group, the expression of actin and integrin was not changed compared to the control group, but the expression of actin and integrin was decreased in the blue irradiated group. This study revealed that irradiation with a wavelength of 460 nm (blue LED) is cytotoxic to ACL cells, but irradiation with nontoxic fluencies of 530 (green LED) and 630 nm (red LED) wavelengths induced cell growth in cultured ACL cells.

Effects of phototherapy on cartilage structure and inflammatory markers in an experimental model of osteoarthritis.

The aim of this study was to evaluate the effects of laser phototherapy on the degenerative modifications on the articular cartilage after the anterior cruciate ligament transection (ACLT) in the knee of rats. Eighty male rats (Wistar) were distributed into four groups: intact control group (IG), injured control group (CG), injured laser treated group at 10 J/cm(2) (L10), and injured laser treated group at 50 J/cm(2) (L50). Animals were distributed into two subgroups, sacrificed in 5 and 8 weeks postsurgery. The ACLT was used to induce knee osteoarthritis in rats. After 2 weeks postsurgery, laser phototherapy initiated and it was performed for 15 and 30 sessions. The histological findings revealed that laser irradiation, especially at 10 J/cm(2), modulated the progression of the degenerative process, showing a better cartilage structure and lower number of condrocytes compared to the other groups. Laser phototherapy was not able to decrease the degenerative process measured by Mankin score and prevent the increase of cartilage thickness related to the degenerative process. Moreover, it did not have any effect in the biomodulation of the expression of markers IL1ß, tumor necrosis factor-α, and metalloprotein-13. Furthermore, laser irradiated animals, at 50 J/cm(2) showed a lower amount of collagen type 1.

Short-term effects of radiofrequency shrinkage treatment for anterior cruciate ligament relaxation on proprioception.

OBJECTIVE: Radiofrequency (RF) shrinkage is used in anterior cruciate ligament (ACL) reconstruction. The present study investigated the therapeutic effects of RF on ACL relaxation and the probable influencing factors. METHODS: Patients with ACL relaxation were included. Participants were randomly divided into two groups: a treatment group, in which patients were treated with RF shrinkage (RF group); a control group, in which patients received conventional surgical treatment. Thermal shrinkage was performed on ACL using an ArthroCare® CAPSure® wand. Lysholm scores, proprioceptive testing and Tegner activity scores were evaluated before and after treatment (at 6 and 12 months). RESULTS: A total of 38 patients were included. The mean ± SD Lysholm score of those in the RF group at 12 months' post-treatment was significantly higher than in controls. The angle of deviation of the knee joint in RF group was significantly larger than in the control group at 6 months' post-treatment. CONCLUSIONS: RF shrinkage treatment for ACL laxity could improve knee scores, and may affect proprioception and recovery of activity after surgery.

Bony incorporation of soft tissue anterior cruciate ligament grafts in an animal model: autograft versus allograft with low-dose gamma irradiation.

BACKGROUND: The effect of low-dose gamma irradiation on healing of soft tissue allografts remains largely unknown. HYPOTHESIS: The authors hypothesized that soft tissue allograft healing to bone would be delayed compared with that of autograft tissue and that low-dose (1.2 Mrad) gamma irradiation would not affect the healing response of allograft tissue after anterior cruciate ligament (ACL) reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight New Zealand White rabbits underwent bilateral ACL reconstructions with semitendinosus tendon graft. Sixteen rabbits were reconstructed with autografts and the remainder with allografts. The 32 allograft rabbits each received 1 irradiated allograft (1.2 Mrad), with the contralateral leg receiving a nonirradiated allograft. Animals were euthanized at 2 weeks or 8 weeks postoperatively. Tensile stiffness, maximum load, and displacement at maximum load were measured. Tibial and femoral segments were sectioned perpendicular to the tunnel axis allowing for histologic and histomorphometric analyses at the tendon-bone interface. RESULTS: There were no significant differences between the maximum load or stiffness values among all groups at 8 weeks. At 2 weeks, autograft exhibited significantly (P < .01) lower maximum load than did the nonirradiated grafts. Regarding histology, at both 2- and 8-week time points, autograft tendon displayed more advanced degenerative and remodeling processes in comparison with irradiated allograft and nonirradiated allograft. DISCUSSION: The maximum load and stiffness of a healing tendon allograft in ACL reconstruction appear to be unaltered by low-dose (1.2 Mrad) irradiation. At 8 weeks, there were no biomechanical differences in tendon-bone healing of allografts when compared with autograft controls. Histologic analyses suggested a faster remodeling response in autograft specimens in comparison with allografts at both time points. CLINICAL RELEVANCE: The findings support the contention that low-dose gamma irradiation is safe for sterilization of ACL soft tissue allografts without compromise of graft properties at early time points.

Sterilization with electron beam irradiation influences the biomechanical properties and the early remodeling of tendon allografts for reconstruction of the anterior cruciate ligament (ACL).

Although allografts for anterior cruciate ligament (ACL) replacement have shown advantages compared to autografts, their use is limited due to the risk of disease transmission and the limitations of available sterilization methods. Gamma sterilization has shown detrimental effects on graft properties at the high doses required for sufficient pathogen inactivation. In our previous in vitro study on human patellar tendon allografts, Electron beam (Ebeam) irradiation showed less detrimental effects compared to gamma sterilization (Hoburg et al. in Am J Sports Med 38(6):1134-1140, 2010). To investigate the biological healing and restoration of the mechanical properties of a 34 kGy Ebeam treated tendon allograft twenty-four sheep underwent ACL replacement with either a 34 kGy Ebeam treated allograft or a non-sterilized fresh frozen allograft. Biomechanical testing of stiffness, ultimate failure load and AP-laxity as well as histological analysis to investigate cell, vessel and myofibroblast-density were performed after 6 and 12 weeks. Native sheep ACL and hamstring tendons (HAT, each n = 9) served as controls. The results of a previous study analyzing the remodeling of fresh frozen allografts (n = 12) and autografts (Auto, n = 18) with the same study design were also included in the analysis. Statistics were performed using Mann-Whitney U test followed by Bonferroni-Holm correction. Results showed significantly decreased biomechanical properties during the early remodeling period in Ebeam treated grafts and this was accompanied with an increased remodeling activity. There was no recovery of biomechanical function from 6 to 12 weeks in this group in contrast to the results observed in fresh frozen allografts and autografts. Therefore, high dose Ebeam irradiation investigated in this paper cannot be recommended for soft tissue allograft sterilization.

The effect of low-level laser to apoptosis of chondrocyte and caspases expression, including caspase-8 and caspase-3 in rabbit surgery-induced model of knee osteoarthritis.

The purpose of this study was to observe the effect of 810-nm low-level laser to apoptosis of chondrocyte and related proteins, including caspase-3 and caspase-8, in rabbit surgery-induced model of knee osteoarthritis. A total of 24 New Zealand White rabbits were randomly assigned into 3 groups: test group, model group, and normal group. The rabbits in test group and model group received anterior cruciate ligament transection in the right knee. Six weeks after transection, the rabbits in test group were given 10-session 810-nm laser illumination. Eight weeks after transection, all animal were killed. Modified Mankin Score was made for histological assessment. The caspases expressions and chondrocytes apoptosis were tested using the immunohistochemistry and TUNEL assessment, respectively. The modified Mankin Score of test group was significantly lower than model group (P < 0.01) and higher than normal group (P < 0.01). The caspase-8 expression of test group was lower than model group and higher than normal group, but no significant difference was found (P > 0.05). This study revealed that the 810-nm low-level laser can improve cartilage structure, prevent articular cartilage degradation and significantly decrease the expression of caspase-3 in this surgery-induced OA model. Further studies are needed.

Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation.

PURPOSE: Irradiation >30 kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20 kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization. METHODS: Forty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34 kGy of ebeam (2) 34 kGy gamma (3) 34 kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing. RESULTS: Fractionation of ebeam irradiation resulted in significantly higher failure loads (1,327 ± 305) than with one-time ebeam irradiation (1,024 ± 204; P = 0.008). Compared to gamma irradiation, significantly lower strain (2.9 ± 1.5 vs. 4.6 ± 2.0; P = 0.008) and smaller cyclic elongation response (0.3 ± 0.2 vs. 0.6 ± 0.4; P = 0.05), as well as higher failure loads (1,327 ± 305 vs. 827 ± 209; P = 0.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation. CONCLUSIONS: In this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.

In vivo effects of partial electrothermal shrinkage on mechanical properties of the anterior cruciate ligament in rabbits.

BACKGROUND: No studies have been conducted to clarify an in vivo remodeling of the radiofrequency-treated lesion of the anterior cruciate ligament. The purpose was to determine in vivo effects of radiofrequency shrinkage on mechanical properties of the anterior cruciate ligament. METHODS: Thirty skeletally mature rabbits were used. In each group, radiofrequency energy set at non-ablative levels was applied to the posterolateral bundle of the anterior cruciate ligament with a bipolar radiofrequency generator. All animals were sacrificed at 0, 6, and 12 weeks after surgery, respectively. In each group, 7 and 3 out of the 10 specimens were used for biomechanical and histological evaluations. FINDINGS: After shrinkage treatment, the anterior-posterior translation of the knee and the length of the posterolateral bundle were significantly reduced immediately after surgery, but that this effect disappeared at 6 weeks. The tensile strength and the tangent modulus of the treated bundle were significantly lower than that of the normal control bundle at each period. In addition, the tensile strength and the tangent modulus measured at 12 weeks were significantly lower than that at 0 week. Histological examination showed granulation-like tissues with numerous plump fibroblasts and inflammatory cells were dominantly found in the midsubstance of the posterolateral bundle at 12 weeks. INTERPRETATIONS: This result suggested that the anterior cruciate ligament tissue shortened with the radiofrequency treatment is elongated gradually over time. The mechanical properties of the posterolateral bundle of the anterior cruciate ligament reduced by the radiofrequency shrinkage are not restored in vivo, but significantly deteriorated with time.

The impact of radiofrequency shrinkage on the mechanical and histologic properties of the elongated anterior cruciate ligament in a sheep model.

PURPOSE: Shrinkage of the elongated anterior cruciate ligament (ACL) and its grafts with radiofrequency (RF) energy has become increasingly popular as an alternative to ACL reconstruction in the field of knee surgery. Although there have been a few clinical studies on the outcome and complications of RF shrinkage of the elongated ACL, there is a substantial lack of in vivo basic science studies to evaluate the mechanical and histologic changes of such treated tissue. Therefore, it was the aim of this study to simulate an ACL elongation in an animal model, treat this pathology with RF shrinkage, and analyze the mechanical and histologic changes at 6 months after initial treatment. TYPE OF STUDY: Experimental in vivo animal study. METHODS: A chronic elongation of the ACL was simulated in 16 mature female merino sheep. In group A, no treatment was applied; in group B, RF shrinkage was used. For biomechanical testing anteroposterior (AP) laxity was measured at time zero and 24 weeks. A load-to-failure test was also performed at 24 weeks. For histologic analysis, cell number and crimp pattern were measured by conventional histologic examination and the vascular status by immunohistochemical histologic examination. RESULTS: The initial reduction of AP laxity after RF shrinkage could not be maintained at 24 weeks. A significant reduction in ultimate load was found at 24 weeks in the RF-treated group B compared with the untreated group A. At 24 weeks, an intensive process of tendon remodeling was ongoing in the RF-treated group that differed substantially from the untreated elongated ACLs and the intact ACL. CONCLUSIONS: The treatment of an elongated ACL with RF energy resulted in a significant impairment of its ultimate load and induced a process of intensive remodeling that was not completed at 24 weeks. Therefore, strong caution is warranted during the time of rehabilitation, considering the impaired ligamentous structure. CLINICAL RELEVANCE: This study provides insights into the consequences of RF shrinkage of the ACL that will guide the clinician in the appropriate rehabilitation of patients and informs of possible complications associated with this procedure.

Injured rabbit ACL treated by radiofrequency. Effects of cyclic loading.

BACKGROUND: Radiofrequency treatment is increasingly used to treat shoulder instability. Patients are asked to restrain their physical activities after this treatment but there is no precise information concerning the necessity for the restrain. METHODS: There were two groups of ten specimens each. Treatment group specimens were stretched to subfailure injury, treated by a radiofrequency probe, and then cyclically loaded. Control group specimens were stretched to the same subfailure injury, Sham treated, and then cyclically loaded. Between each step of the experiment in both groups there was a relaxation test to examine the ligament viscoelastic properties. At the end, each ligament was stretched to failure and the load-elongation curve obtained. FINDINGS: Relaxation forces decreased after the subfailure injury in both groups (average 76% and 81% of intact state, in treatment and control groups, respectively). In the treatment group, the relaxation forces first increased after the radiofrequency treatment (average 99% of intact state), and then decreased after the cyclic loading (average 50% of intact state). The treated ligaments failed at lower loads and smaller deformations than the controls. INTERPRETATION: The radiofrequency treatment restored viscoelastic properties of the injured ligaments, but cyclic loading degraded these. Protection of the treated ligament is advised during the immediate post-operative period.

Thermal modification of the lax anterior cruciate ligament using radiofrequency: efficacy or catastrophe?

Alchemists dream of using energy to turn base metal to gold. "Shrinkers" use energy to transform laxity to stability. While alchemists search for the mechanism to achieve their goal, shrinkers have thermal energy (heat) and scientific ground for their pursuit. Without doubt, application of heat to collagen using radiofrequency (RF) results in tissue shrinkage. However, with regard to thermal shrinkage of a lax anterior cruciate ligament (ACL) or ACL graft, indications and techniques, rehabilitation and outcomes require review. Such is the purpose of this article.

Thermal effects after anterior cruciate ligament shrinkage using radiofrequency technology: a porcine cadaver study.

The effects of thermal energy on an anterior cruciate ligament (ACL) are unknown. This study was undertaken to know the immediate and direct effects of thermocoagulation on normal ACL. Thermocoagulation was generated by monopolar radiofrequency (RF) at 67 degrees C and 40 W of energy and applied with use of a commercial jig in a porcine cadaveric model, and biomechanical and histological changes were evaluated immediately. Thermocoagulation caused significant shrinkage of ACL without immediate effects on ligament biomechanical properties, including stiffness and maximal failure force. However, histological analysis demonstrated a decrease in number of dense elongated cells and blood vessels within the epiligamentous tissue, loss of areolar spaces, decrement in the periodicity of collagen waveform, and shortening and pyknotic nuclear changes of cells within the fascicular region. RF-generated thermocoagulation resulted in ACL shortening with significant changes on histological findings but not on initial biomechanical properties.

The effect of electrothermal shrinkage on the biomechanical properties of the anterior cruciate ligament: an experimental study.

PURPOSE: The purpose of this study was to determine the acute effects of electrothermal shrinkage on the biomechanical properties of the anterior cruciate ligament (ACL). TYPE OF STUDY: Randomized trial. METHODS: Fifty fresh femur-ACL-tibia complexes harvested from fully matured pigs were used. The femur-anteromedial bundle-tibia complex specimens were randomly divided into 5 groups of 10 specimens each. In each group, radiofrequency energy set at nonablative levels was applied to the anteromedial bundle of the ACL with a bipolar radiofrequency generator. In groups I and II, radiofrequency treatment was applied to the ACL using 28 W and 45 W power, respectively, for 30 seconds. In groups III and IV, radiofrequency treatment was applied to the ACL using 28 W and 45 W power, respectively, for 60 seconds. In group V, no treatment was applied in order to obtain normal control data. The treatment was performed in physiological saline solution under a 1-N load. In each group, 8 of the 10 specimens were used for biomechanical evaluation, and the remaining 2 were used for histologic observation. RESULTS: Concerning the length of the anteromedial bundle after the treatment, the analysis of variance (ANOVA) showed a significant difference among the 5 groups. The length in groups I, II, III, and IV was significantly shorter than that of group V. In tensile testing, the stiffness was 120, 116, 113, 89, and 156 N/mm in groups I, II, III, IV, and V, respectively. The ANOVA showed a significant difference among the groups. Groups I, II, III, and IV were significantly lower than group V, respectively. Histologic examination showed diffuse collagenous denaturation and pyknotic nuclear changes in fibroblasts at the treated portion. The collagen crimp pattern was not present in the treated area. CONCLUSIONS: Application of RF energy to the specimens caused both shortening and weakening according to the magnitude and duration of the application. CLINICAL RELEVANCE: These results may explain one of the causes of the poor results reported in some clinical studies. This study warns against a too optimistic application of electrothermal shrinkage to the ACL as a clinical treatment.

["Shrinkage of cruciate ligaments"--a biomechanical study. Shrinkage of elongated cruciate ligaments using an application of radiofrequency energy]. / 'Kreuzbandschrumpfung"--eine biomechanische Studie. Schrumpfung von elongierten Kreuzbändern unter Anwendung von Radiofrequenzenergie.

The aim of this study was to evaluate structural properties of native and elongated bovine anterior cruciate ligaments after the application of bipolar radiofrequency. Using a material testing machine typical load-elongation curves were used to determine the initial strength of untreated (group 1, n = 20) and elongated cruciate ligaments (group 2, n = 20) after treatment with bipolar radiofrequency (ArthroCare). After the application of a cyclic loading protocol (1000 x 400 N) elongation, yield load, maximal load, and stiffness were determined. Native ligaments served as a control group (group 3, n = 20). In both groups 4 mm reduction in length was caused by the application of radiofrequency. Elongation was significantly higher; yield load, maximal load, and stiffness of cruciate ligaments treated with radiofrequency (groups 1 and 2) were significantly reduced after the application of a cyclic loading protocol in comparison to the control group (p < 0.05). Group 2 ligaments showed the lowest values. The application of radiofrequency weakens the biomechanical properties of native and elongated cruciate ligaments significantly. When radiofrequency energy is used to shrink elongated cruciate ligaments, a nonaggressive rehabilitation protocol should be applied.

Anterior cruciate ligament rupture after thermal treatment in a canine model.

BACKGROUND: The use of radiofrequency energy to treat damaged anterior cruciate ligaments is gaining popularity. However, complete rupture of the ligament after treatment has been reported. PURPOSE: To evaluate the effect of thermal energy applied arthroscopically to normal, intact anterior cruciate ligaments in mature dogs. STUDY DESIGN: Controlled laboratory study. METHODS: Monopolar radiofrequency energy was applied to the normal anterior cruciate ligament of 1 knee in 18 dogs. The contralateral anterior cruciate ligament (also normal) was sham treated. Force-plate gait analysis was performed preoperatively and at 4, 8, 12, 16, 26, and 36 weeks after surgery. Anterior cruciate ligament rupture was detected by a sudden onset of nonweightbearing and a positive drawer sign. RESULTS: All treated ligaments ruptured approximately 55 days after surgery (mean, 55 days; standard error, 1.6). CONCLUSIONS: Although monopolar radiofrequency energy may have some potential in the treatment of lax anterior cruciate ligaments, in the application described here the result was a highly predictable deterioration and rupture of all treated anterior cruciate ligaments. CLINICAL RELEVANCE: On the basis of these findings, we strongly recommend that strict selection and application criteria be used when considering use of this modality on anterior cruciate ligaments that are stretched or partially disrupted, or both. Use of this modality should be followed by adherence to a highly conservative rehabilitation protocol.

Monopolar thermal treatment of symptomatic anterior cruciate ligament instability.

Patients with anterior cruciate ligament instability resulting from incomplete tears or elongation in continuity without ligament detachment historically have been treated conservatively or by graft replacement. The literature is sparse regarding alternative treatments. The current study presents experience using monopolar thermal repair on 28 consecutive knees with partial anterior cruciate ligament tears all symptomatically unstable. All lesions were less than 6 months old (average, 77 days; range, 7-180 days) and with a difference of 6 mm or more (average, 9 mm; range, 6-13 mm) when comparing both knees using KT-1000 evaluation. Incomplete tears of the anterior cruciate ligament were seen at arthroscopic evaluation. The rehabilitation protocol included use of a brace for at least 6 weeks and progressive weightbearing. A 2-year minimum followup (range, 24-35 months) was done in all patients following the International Knee Documentation Committee guidelines. The overall outcome was normal or nearly normal in 96% of the patients. One failure occurred at 8 weeks. Twenty-six knees had a KT-1000 difference between 0 and 2 mm (average, 1.9 mm). Because thermal application causes death to some of the cells directly treated, it should be taken into account in selection and application. Immediately after thermal use, the anterior cruciate ligament, although thicker and tighter, is at first weaker than normal. Rehabilitation and compliance are critical during early ligament healing. This procedure seems to be a reasonable alternative to anterior cruciate ligament grafting in selected patients.

A comparison of joint stability between anterior cruciate intact and deficient knees: a new canine model of anterior cruciate ligament disruption.

Transection of the canine anterior cruciate ligament (ACL) is a well-established osteoarthritis (OA) model. This study evaluated a new method of canine ACL disruption as well as canine knee joint laxity and joint capsule (JC) contribution to joint stability at two time points (16 and 26 weeks) after ACL disruption (n=5/time interval). Ten crossbreed hounds were evaluated with force plate gait analysis and radiographs at intervals up to 34 weeks after monopolar radiofrequency energy (MRFE) treatment of one randomly selected ACL. Each contralateral ACL was sham treated. The MRFE treated ACLs ruptured approximately eight weeks (mean 52.5 days, SEM+/-1.0, range 48-56 days) after treatment. Gait analysis and radiographic changes were consistent with established canine ACL transection models of OA. Anterior-posterior (AP) translation and medial-lateral (ML) rotation were measured in each knee at 30 degrees, 60 degrees, and 90 degrees of flexion with and then without JC with loads of 40 N in AP translation and 4 Nm in ML rotation. A statistically significant interaction in AP translation included JC by cruciate (P=0.02), and there was a trend for a cruciate by time (P=0.07) interaction. Significant interactions in ML rotational testing included the presence of joint capsule (P=0.0001) and angle by cruciate (P=0.0012). This study describes a model in which canine ACLs predictably rupture approximately eight weeks after arthroscopic surgery and details the contribution of JC to canine knee stability in both ACL intact and deficient knees. The model presented here avoids the introduction of potential surgical variables at the time of ACL rupture and may contribute to studies of OA pathogenesis and inhibition. This model may also be useful for insight into the pathologic changes that occur in the knee as the ACL undergoes degeneration prior to rupture.