Combustion Synthesis Porous Nitinol for Biomedical Applications.

Porous Nitinol with a three-dimensional anisotropic interconnective open pore structure has been successfully produced by the combustion synthesis (CS) of elemental Ni and Ti powders. The resulting product can be tailored to closely match the stiffness of cancellous bone to minimize stress shielding. The average elastic modulus was approximately 1 GPa for a porosity of 60 vol% and the average pore size of 100-500 µm. The low elastic modulus meets the basic demand for orthopedic bone ingrowth applications. Furthermore, porous Nitinol was composed of cubic (austenitic) and monoclinic (martensitic) NiTi compounds without the presence of Ni metal or Ni-rich phases. The resulting product exhibits excellent corrosion resistance with breakdown potentials above 750mV. An ovine study in cortical sites of the tibia demonstrated rapid osseointegration into the porous strucutre as early as two weeks and complete bone growth across the implant at six weeks. A separate ovine study showed complete through-growth of bone at four months using a lumbar interbody fusion model, substantiating the use of porous Nitinol as an implant material for applications in the spine. Porous Nitinol is thus a promising biomaterial with proven biocompatibility and exceptional osseointegration performance which may enhance the healing process and promote long-term fixation, making it a strong candidate for a wide range of orthopedic implant applications.

Two-year outcome of arthroscopic bankart repair and electrothermal-assisted capsulorrhaphy for recurrent traumatic anterior shoulder instability.

PURPOSE: Arthroscopic treatment of chronic anterior shoulder instability in active athletes is reportedly less successful than open techniques. We performed arthroscopic stabilization for confirmed capsulolabral avulsions and followed-up patients prospectively for a minimum of 24 months. TYPE OF STUDY: Prospective nonrandomized study. METHODS: We studied 42 patients (mean age, 26 years) with recurrent traumatic anterior dislocations. They reported an average of 9 dislocations preoperatively. An average of 69 months elapsed from initial dislocation to surgery. The shoulders underwent arthroscopic capsulolabral repair with either a suture anchor and horizontal mattress suture, or an absorbable tack. Each shoulder also was treated with a monopolar radiofrequency probe for thermal shrinkage of the middle, anteroinferior, and posteroinferior glenohumeral ligaments. Patients were evaluated prospectively for pain, motion, stability, and function using the modified Rowe score. RESULTS: At a mean of 28 months postoperatively, 38 patients had returned to their preinjury sports. Three patients (7%) had a traumatic redislocation. Using the modified Rowe score, statistically significant improvements were noted for pain, stability, and function. There was no significant change in motion. The overall modified Rowe score improved from 38 points preoperatively to 89 points at final evaluation (P <.001). CONCLUSIONS: These results indicate that arthroscopic treatment of patients with recurrent traumatic anterior instability yields results comparable to open procedures, including athletes involved in high-level contact and collision sports. We believe that addressing capsular laxity surgically is critical, particularly when dealing with chronic instability. This procedure allows the surgeon to reliably correct the labral detachment and the capsular redundancy while preserving motion and minimizing morbidity.

Monopolar radiofrequency energy for arthroscopic treatment of shoulder instability in the athlete.

Monopolar radiofrequency energy is increasingly being used in the treatment of shoulder instability. Basic science studies and early clinical results have shown that application of thermal energy can result in successful shrinkage of the shoulder capsule. This procedure is useful in treating certain traumatic and recurrent instability conditions of the shoulder especially in the athlete where range of motion is preserved, recovery is faster than with open procedures, and there, is little disruption or alteration of inherent anatomy. The procedure is technically easy to perform, and the complication rate is low. Success, however, depends on proper patient selection, attention to the rehabilitation program, and patient compliance. Long-term follow-up will be necessary to determine if results for this procedure will deteriorate over time, especially in patients with multidirectional instability.

The effect of monopolar radiofrequency treatment pattern on joint capsular healing. In vitro and in vivo studies using an ovine model.

The purpose of this study was to compare joint capsular healing after two delivery patterns of monopolar radiofrequency energy: 1) uniform treatment of the joint capsule (paintbrush pattern) and 2) multiple single linear passes (grid pattern). First, an in vitro study was performed to compare the percent shrinkage of these two treatment patterns using the femoropatellar joints (stifles) of six sheep. Monopolar radiofrequency energy (settings, 70 degrees C/15W) was applied to the lateral joint capsule; the treated area was approximately 10 x 10 mm. There was no significant difference in shrinkage between the grid (27% +/- 8.7%) and paintbrush (29% +/- 7.9%) patterns. In the in vivo study, stifles of 24 sheep were randomly assigned to the paintbrush or the grid pattern groups and treatment was performed arthroscopically. Sheep were sacrificed immediately after surgery, or at 2, 6, or 12 weeks after surgery. At 6 weeks after surgery, confocal microscopy demonstrated that treated areas had almost completely repaired in the grid group; some nonviable areas were still present in the paintbrush group. Mechanical testing at 6 weeks indicated that joint capsule in the grid group had better mechanical properties than capsule in the paintbrush group. This study revealed that radiofrequency treatment of joint capsule in a grid pattern allowed faster healing than tissue treated in a paintbrush pattern.

The effect of monopolar radiofrequency energy on partial-thickness defects of articular cartilage.

PURPOSE: To evaluate the effect of monopolar radiofrequency (RF) energy on partial-thickness defects of articular cartilage, comparing the outcome of partial-thickness defects treated with monopolar RF energy with that of treatment by conversion of partial-thickness defects to full-thickness defects by curettage and microfracture. TYPE OF STUDY: Randomized trial using adult female sheep. MATERIALS AND METHODS: Thirty-six sheep were used in this study. Both stifles in each animal were randomly assigned to 1 of the following 3 procedures: (1) partial-thickness defect without any treatment to serve as a sham-operated control, (2) partial-thickness defect with RF energy treatment, and (3) partial-thickness defect treated by conversion of the defect to a full-thickness defect by curettage and microfracture. Nine sheep were euthanized at 0, 2, 12, and 24 weeks after surgery (n = 6 per group). After euthanasia, cartilage samples were harvested from the defect sites, and chondrocyte viability was analyzed by confocal laser microscopy using a triple-labeling technique. Cartilage samples also were decalcified and stained with hematoxylin and eosin and safranin-O for histologic analysis. Surface properties of cartilage samples were analyzed using scanning electron microscopy. RESULTS: The analysis of chondrocyte viability showed that RF treatment caused death of almost all chondrocytes in the defect. Histologic analysis showed that RF treatment caused detrimental effects to chondrocytes and proteoglycan concentration that progressed over time, and that full-thickness defects were repaired by fibrocartilage by 24 weeks after surgery. Scanning electron microscopy analysis indicated that RF-treated groups were significantly smoother and less irregular than control groups at 2, 12, and 24 weeks after surgery. CONCLUSIONS: This study showed that monopolar RF energy caused long-term damage to cartilage in this sheep model and did not appear to have the beneficial effects reported in a previous study that evaluated application of this technique using a bipolar RF probe.

Arthroscopic monopolar radiofrequency thermal stabilization for chronic lateral ankle instability: a preliminary report on 10 cases.

This study represents a preliminary review of 10 patients having undergone arthroscopic monopolar thermal stabilization for ankle instability from October 1996 to June 1998. All patients in this study expressed mild to moderate chronic ankle instability complaints and were dissatisfied with their attempts at conservative care. Subjective clinical results were evaluated in all patients having undergone this procedure utilizing a modified version of the American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale. In addition, eight of these patients underwent pre- and postoperative stress radiographs. The average age of the patient population in this study was 34.5 +/- 9.26 years. The preoperative AOFAS scores averaged 58.3 +/- 8.96 and the postoperative were 88.1 +/- 11.09 points. Patients returned to full activities on the average of 3 months. Postoperative ankle varus stress test reduced on the average of 2.8 degrees +/- 2.77 degrees, while the anterior drawer measurements reduced 4.8 +/- 1.83 mm. The reduction in anterior drawer test amounted to an approximate 60% decrease in talar excursion postoperatively. All patients who underwent this procedure achieved ankle stability and commented that they would undergo the procedure again.

Comparative effects of laser and radiofrequency energy on joint capsule.

The study compared the effects of laser and monopolar radiofrequency energy on thermal and architectural properties of joint capsular tissue in an in vitro ovine model. Sheep glenohumeral joint capsular specimens were treated with laser (5, 10, 15 W) or radiofrequency energy (55 degrees, 65 degrees, 75 degrees C) (n = six per group). Energy application caused significant tissue shrinkage and decreased surface area in all laser and radiofrequency treatment groups. Tissue thickness significantly increased in all treatment groups except for radiofrequency 55 degrees C. Tissue shrinkage, surface area, and thickness each correlated significantly with the delivered laser energy per tissue area or mean radiofrequency probe temperature. There were no significant differences among laser 10 W, laser 15 W, and radiofrequency 75 degrees C treatment groups for these three architectural parameters. Tissue temperature was elevated significantly in the laser 10 W, laser 15 W, radiofrequency 65 degrees C, and radiofrequency 75 degrees C groups when compared with the control. Tissue temperature changes between the laser 10 W and radiofrequency 75 degrees C groups were similar; however, laser treatment produced a steeper temperature increase accompanying its peak temperature. Despite different mechanisms, laser and radiofrequency energy can achieve similar and predictable tissue modification, which is temperature dependent. Additional in vivo studies must be performed to evaluate the applicability of these techniques to clinical use.

Effects of monopolar radiofrequency energy on ovine joint capsular mechanical properties.

Radiofrequency energy may provide a relatively noninvasive method to stabilize joints with excessive laxity by thermally shrinking redundant joint capsular tissue. The authors determined the percentage of shrinkage associated with five radiofrequency treatment temperatures and evaluated the effect of this energy on the structural properties of joint capsular tissue in vitro. First, 36 adult sheep femoropatellar joint capsular specimens were treated with one of five treatment temperatures (n = 6 per group) or served as a control to determine tissue shrinkage. An additional 24 specimens were treated with three temperatures that resulted in different shrinkage: 45 degrees C, 65 degrees C, and 85 degrees C. Tissue stiffness, relaxation, and failure strength were determined for each specimen (n = 6 per group). Tissue shrinkage was correlated significantly with treatment temperature. There was a significant decrease in tensile stiffness in the 65 degrees C and 85 degrees C treatment groups. There were no significant differences between stress relaxation before treatment and after treatment. Relaxation properties after treatment were not different from each other or from control values either normalized to pretreatment values or expressed as raw data. Failure strength was not affected significantly at any temperature.

The biologic response to laser thermal modification in an in vivo sheep model.

The purpose of this study was to evaluate the effect of nonablative laser energy on mechanical, histologic, ultrastructural, and biochemical properties of joint capsular tissue in an in vivo sheep model. Femoropatellar joint capsule was treated with the holmium:yttrium-aluminum-garnet laser via an arthroscope, and tissues were harvested immediately after surgery, or at 3, 7, 14, 30, 60, 90, and 180 days after surgery (n = 8/group). Laser treatment caused significant decreases in tissue stiffness from 0 to 7 days after surgery, then stiffness gradually increased after 14 days. Tissue strength was lowest 3 days after laser treatment. Histologic examination revealed immediate collagen hyalinization and cell necrosis, followed by active cellular response characterized by extensive fibroblast migration and capillary sprouting. Tissue appeared to be normal histologically 60 days after surgery; however, collagen fibrils remained uniformly small. This study showed an active tissue response secondary to thermal modification with concomitant recovery of mechanical properties by 30 days after surgery. Whether the shrinkage or joint stability was maintained with time remains to be evaluated. To clarify the advantages and disadvantages of this technique, a carefully controlled clinical trial with long term followup should be performed.

The mechanism of joint capsule thermal modification in an in-vitro sheep model.

The purpose of this study was to understand the mechanism responsible for joint capsule shrinkage after nonablative laser application in an in-vitro sheep model. Femoropatellar joint capsular tissue specimens harvested from 20 adult sheep were treated with one of three power settings of a holmium:yttrium-aluminum-garnet laser or served as a control. Laser treatment significantly shortened the tissue and decreased tissue stiffness in all three laser groups, whereas failure strength was not altered significantly by laser treatment. Transmission electron microscopic examination showed swollen collagen fibrils and loss of membrane integrity of fibroblasts. A thermometric study revealed nonablative laser energy caused tissue temperature to rise in the range of 64 degrees C to 100 degrees C. Electrophoresis after trypsin digestion of the tissue revealed significant loss of distinct alpha bands of Type I collagen in laser treated samples, whereas alpha bands were present in laser treated tissue without trypsin digestion. The results of this study support the concept that the primary mechanism responsible for the effect of nonablative laser energy is thermal denaturation of collagen in joint capsular tissue associated with unwinding of the triple helical structure of the collagen molecule.

Monopolar radiofrequency energy effects on joint capsular tissue: potential treatment for joint instability. An in vivo mechanical, morphological, and biochemical study using an ovine model.

The purpose of this study was to evaluate the thermal effect of monopolar radiofrequency energy, a potential treatment means for joint instability, on the mechanical, morphologic, and biochemical properties of joint capsular tissue in an in vivo ovine model. The energy was applied arthroscopically to the synovial surface of the femoropatellar joint capsule of 24 sheep. The sheep were sacrificed at 0, 2, 6, and 12 weeks after surgery (6 per group). Monopolar radiofrequency energy initially caused a significant decrease in tissue stiffness and an increase in tissue relaxation properties, followed by gradual improvement in the tissue's mechanical properties by 6 weeks after surgery. Microscopic examination illustrated that radiofrequency energy initially caused collagen hyalinization and cell necrosis, followed by active tissue repair. Biochemical analysis revealed that treated collagen was significantly more trypsin-susceptibile than untreated collagen at 0 and 2 weeks after surgery, indicating early collagen denaturation. This study demonstrated that this treatment initially caused a significantly deleterious effect on the mechanical properties of the joint capsule, which was associated with partial denaturation of joint capsular tissue. This was followed by gradual improvement of the mechanical, morphologic, and biochemical properties of the tissue over time.

Histologic evaluation of the glenohumeral joint capsule after the laser-assisted capsular shift procedure for glenohumeral instability.

Glenohumeral joint capsule obtained from 42 patients who had undergone an arthroscopic laser-assisted capsular shift procedure was evaluated histologically. A total of 53 samples from the anterior inferior glenohumeral ligament of the joint capsule were collected before and at various times after the procedure (range, 0 to 38 months). Despite glenohumeral instability, joint capsule of the patients before the procedure showed no significant histologic lesions. Laser treatment significantly altered the histologic properties of the tissue as evidenced by hyalinization of collagen and necrotic cells (time 0). Tissues sampled during the short-term period (3 to 6 months) after the procedure demonstrated fibrous connective tissue with reactive cells and vasculature. Collagen and cell morphology returned to normal in the middle- to long-term period (7 to 38 months) after the procedure, while the number of fibroblasts remained elevated. Joint capsule collected from the shoulders of six patients who experienced stiffness after the procedure showed persistent synovial, cellular, and vascular reaction even after 1 year postoperatively, the cause of which is unclear. This study revealed histologic evidence of robust tissue healing and maturation after thermal treatment by the laser-assisted capsular shift procedure, although mechanical and biochemical characterization of the tissue was not evaluated. Correlation with clinical follow-up must be performed to further clarify the advantages and disadvantages of this procedure.

Arthroscopic treatment of shoulder instability: current concepts and techniques.

The incidence of glenohumeral joint instability is estimated to effect between 2 and 8% of the population. It represents at least one third of all shoulder related emergency room visits. When one considers the spectrum of shoulder instability, including transient subluxation, the true incidence of glenohumeral instability is probably grossly under-reported. Although any age group can be affected, shoulder instability is primarily a disease of the young. The occurrence of instability is inversely proportional to the age of the patient and the time of original injury. A patient who dislocates for the first time as a teen can expect a redislocation rate approaching 90% in his or her lifetime. Therefore, many authors recommend early surgical treatment to repair the lesion.

The thermal effect of monopolar radiofrequency energy on the properties of joint capsule. An in vivo histologic study using a sheep model.

The purpose of this in vivo study was to analyze the short-term tissue response of joint capsule to monopolar radiofrequency energy and to compare the effects of five power settings at 65 degrees C on heat distribution in joint capsule. In 12 mature Hampshire sheep, the medial and lateral aspects of both stifles were treated with monopolar radiofrequency energy under arthroscopic control in a single uniform pass to the synovial surface. The radiofrequency generator power settings were 0, 10, 15, 20, 25, and 30 watts (N = 8/group). The electrode tip temperature was 65 degrees C. Histologic analysis at 7 days after surgery revealed thermal damage of capsule at all radiofrequency power settings. The lesion's cross-sectional area, depth, vascularity, and inflammation were commensurate with radiofrequency power. Tissue damage was indicated by variable inflammatory cell infiltration, fusion of collagen, pyknosis of fibroblasts, myonecrosis, and vascular thrombosis, whereas synovial hyperplasia, fibroblast proliferation, and rowing of sarcolemmal nuclei demonstrated regenerative processes. This study revealed that radiofrequency power settings and heat loss through lavage solution play a significant role in heat distribution and morphologic alterations in joint capsule after arthroscopic application of monopolar radiofrequency energy.

The effect of radiofrequency energy on the ultrastructure of joint capsular collagen.

This study evaluated the effect of radiofrequency energy on the histological and ultrastructural appearance of joint capsular collagen. Femoropatellar joint capsular specimens from adult sheep were treated with one of three treatment temperatures (45 degrees C, 65 degrees C, and 85 degrees C) with a radiofrequency generator or served as control in a randomized block design. Twenty-four specimens (n = 6) were processed for histological examination as well as ultrastructural analysis using transmission electron microscopy. A computer-based area determination program was used to calculate the area affected in histological samples. Histological changes consisted of thermal tissue damage characterized by collagen fiber fusion and fibroblastic nuclear pyknosis at all application temperatures with clear demarcations between treated and untreated tissue. Mean tissue affected ranged from 50.4% for 85 degrees C to 22.5% for 45 degrees C. There was a strong correlation between treatment temperature and percent area affected (P < .001, R2 = .65). Ultrastructural alterations included a general increase in cross-sectional fibril diameter and loss of fibril size variation with increasing treatment temperature. Longitudinal sections of collagen fibrils showed increased fibril diameter and the loss of cross-striations in the treated groups. Thermally induced ultrastructural collagen fibril alteration is likely the predominant mechanism of tissue shrinkage caused by application of radiofrequency energy.

Postoperative epidural injection of saline can shorten postanesthesia care unit time for knee arthroscopy patients.

BACKGROUND AND OBJECTIVES: The goal of this prospective, double-blind study was to ascertain if the postanesthesia care unit (PACU) stay of outpatients receiving epidural anesthesia for knee arthroscopy is decreased by injection of epidural saline at the end of the case. METHODS: Twenty healthy patients undergoing knee arthroscopy received lumbar epidural anesthesia with 2% lidocaine. At the end of surgery, in a double-blind design, group 1 patients (intervention group) received 20 mL 0.9% saline injected into the epidural catheter. Patients in group 2 (control group) had 1 mL 0.9% saline injected into the epidural catheter. In the PACU, the epidural catheter was removed, and motor block was assessed at 15-minute intervals according to the Bromage scale. Standard discharge criteria for our ambulatory surgery center were followed. RESULTS: Patients who received 20 mL epidural 0.9% saline remained in phase I (intensive nursing) 83 +/- 8 minutes compared with control patients who stayed 110 +/- 8 minutes (P < .01). Nonmedical issues related to the unavailability of the patients transportation or waiting for medications to be issued from the pharmacy delayed discharge from phase II (non-nursing) in 70% of group 1 patients and 60% of group 2 patients. Time to actual hospital dismissal for group I was 119 +/- 14 minutes, compared with 159 +/- 13 minutes (P < .05) for group 2. CONCLUSION: Patients receiving epidural anesthesia for knee arthroscopy had a shorter PACU stay if they received an injection of saline into the epidural space at the end of surgery.

The effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule.

The purpose of this in vitro study was to evaluate the effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule in a sheep model. Dissected glenohumeral joint capsules were placed in a 37 degrees C tissue bath and treated with radiofrequency energy at temperature settings of 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C. Pretreatment and posttreatment tissue length was measured, and tissue temperature changes were recorded at distances of 0.0, 0.5, 1.0, 1.5 mm away from the probe path. Tissue shrinkage was found to be less than 4% for treatments below 65 degrees C, and increased to 14% for treatments at 80 degrees C. Posttreatment lengths of tissues treated at 65 degrees, 70 degrees, 75 degrees, 80 degrees C were significantly shorter than pretreatment lengths. The maximum tissue temperatures directly below the probe were observed to be 3.7 degrees to 6.7 degrees C lower than the set temperatures. As the distance from the probe was increased, the tissue temperature was found to decrease, reaching a value of less than 45 degrees C at 1.5 mm for all five treatment temperature settings. This study provided basic information on temperature settings, tissue shrinkage, and tissue temperature distribution of radiofrequency treatment.

Arthroscopy of the calcaneocuboid and talonavicular joints.

The authors describe the anatomy, portal placement, technique, indications, and preliminary results of seven cases of calcaneocuboid or talonavicular joint pathology that underwent elective investigational diagnostic or therapeutic arthroscopy with a follow up of 3-14 months. All patients had failed available conservative therapy. Results of treatment were five excellent and two good cases. Two patients required arthrotomy. There were no complications associated with portal placement, arthroscopic technique, or instrumentation. Arthroscopy of the calcaneocuboid and talonavicular joints has proven to be a relatively safe and valuable diagnostic and therapeutic tool. It is hoped that advances in small joint arthroscopy application will encourage further technological evolution in arthroscopic instrumentation and establish a foundation for further arthroscopic exploration of the small joints of the foot.

[Shoulder arthroscopy using the holmium-YAG laser method. State of the art 1994]. / Schulterarthroskopie unter Verwendung des Holmium:YAG-Lasers. Stand 1994.

The Ho:YAG laser has been found to be a safe and efficacious adjunct to many arthroscopic shoulder procedures. The curved, thin handpieces are easily manipulated around the surfaces of the joint. Postoperative inflammation is minimized, and a versatile instrument that can cut, coagulate, ablate, and cauterize has obvious benefit where optimal visualization is required. The potential for chondral contouring and bone resection is currently being studied, and the use of laser-induced thermal contraction of soft tissue collagen may add some exciting possibilities to the treatment of joint instabilities.