Radiofrequency Microtenotomy for Elbow Epicondylitis: Midterm Results.

We conducted a prospective, nonrandomized, single-center clinical study to evaluate the safety and midterm effectiveness of microtenotomy using a radiofrequency probe to treat chronic tendinosis of the elbow. All patients had failed conservative treatment for 6 months. The radiofrequency-based microtenotomy was performed using the Topaz Microdebrider (ArthroCare). Patients were followed annually for up to 9 years postoperatively. Pain status was documented using a visual analog scale self-reported measure. Eighty consecutive patients with tendinosis of the elbow were enrolled; 69 patients were treated for lateral epicondylitis and 11 for medial epicondylitis. The duration of follow-up ranged from 6 months to 9 years (mean, 2.5 years). Ninety-one percent of the patients reported a successful outcome. Within the lateral epicondylitis group, the preoperative visual analog scale improved from 6.9 to 1.3 postoperatively and demonstrated an 81% improvement (P ≤ .01). For the medial epicondylitis patients, the preoperative visual analog scale improved from 6.1 to 1.3 after surgery, a 79% improvement (P ≤ .01). No complications were reported. Radiofrequency-based microtenotomy is a safe and effective procedure for elbow epicondylitis. The results are durable with successful outcomes observed at 9 years after surgery.

Osteochondral allograft transplantation in cartilage repair: Graft storage paradigm, translational models, and clinical applications.

The treatment of articular cartilage injury and disease has become an increasingly relevant part of orthopaedic care. Articular cartilage transplantation, in the form of osteochondral allografting, is one of the most established techniques for restoration of articular cartilage. Our research efforts over the last two decades have supported the transformation of this procedure from experimental "niche" status to a cornerstone of orthopaedic practice. In this Kappa Delta paper, we describe our translational and clinical science contributions to this transformation: (1) to enhance the ability of tissue banks to process and deliver viable tissue to surgeons and patients, (2) to improve the biological understanding of in vivo cartilage and bone remodeling following osteochondral allograft (OCA) transplantation in an animal model system, (3) to define effective surgical techniques and pitfalls, and (4) to identify and clarify clinical indications and outcomes. The combination of coordinated basic and clinical studies is part of our continuing comprehensive academic OCA transplant program. Taken together, the results have led to the current standards for OCA processing and storage prior to implantation and also novel observations and mechanisms of the biological and clinical behavior of OCA transplants in vivo. Thus, OCA transplantation is now a successful and increasingly available treatment for patients with disabling osteoarticular cartilage pathology.

Radiofrequency stimulation for potential healing of meniscal injuries in the avascular zone.

We conducted this study to evaluate the effect of radiofrequency (RF) stimulation with suture repair on the healing of tears in the meniscal white-white zone. Fifty-four New Zealand white rabbits underwent surgically induced meniscal injuries within the white-white region. RF was applied using a 0.8-mm TOPAZ MicroDebrider RF wand (ArthroCare) at level 4 for 500 milliseconds. Rabbits were sacrificed at 28 and 84 days for gross and histologic analysis by 3 blinded observers and at 9, 28, and 84 days for biochemical examination. Biochemical analyses included evaluation of cell proliferation (3H-thymidine), as well as mitogenic (IGF-1, bFGF) and angiogenic (VEGF, αV) factors. Of specimens repaired with RF combined with suture, 19 (58%) showed a degree of gross morphologic and histologic healing. No significant healing was seen in specimens with either no repair or repair with suture alone. We observed a 40% increase in cellular proliferation when RF supplementation was used (P<.05). With regards to mitogenic and angiogenic markers (IGF-1, bFGF, VEGF, and αV), there was a significant increase in groups treated with RF at 9 and 28 days (P>0.05). RF supplementation of avascular zone meniscal repairs may lead to an increased healing response.

Development of a Comprehensive Osteochondral Allograft MRI Scoring System (OCAMRISS) with Histopathologic, Micro-Computed Tomography, and Biomechanical Validation.

OBJECTIVE: To describe and apply a semi-quantitative MRI scoring system for multi-feature analysis of cartilage defect repair in the knee by osteochondral allografts, and to correlate this scoring system with histopathologic, micro-computed tomography (µCT), and biomechanical reference standards using a goat repair model. DESIGN: Fourteen adult goats had two osteochondral allografts implanted into each knee: one in the medial femoral condyle (MFC) and one in the lateral trochlea (LT). At 12 months, goats were euthanized and MRI was performed. Two blinded radiologists independently rated nine primary features for each graft, including cartilage signal, fill, edge integration, surface congruity, calcified cartilage integrity, subchondral bone plate congruity, subchondral bone marrow signal, osseous integration, and presence of cystic changes. Four ancillary features of the joint were also evaluated, including opposing cartilage, meniscal tears, synovitis, and fat-pad scarring. Comparison was made with histological and µCT reference standards as well as biomechanical measures. Interobserver agreement and agreement with reference standards was assessed. Cohen's kappa, Spearman's correlation, and Kruskal-Wallis tests were used as appropriate. RESULTS: There was substantial agreement (κ>0.6, p<0.001) for each MRI feature and with comparison against reference standards, except for cartilage edge integration (κ=0.6). There was a strong positive correlation between MRI and reference standard scores (ρ=0.86, p<0.01). OCAMRISS was sensitive to differences in outcomes between the types of allografts. CONCLUSIONS: We have described a comprehensive MRI scoring system for osteochondral allografts and have validated this scoring system with histopathologic and µCT reference standards as well as biomechanical indentation testing.

Use of platelet-rich plasma to enhance tendon function and cellularity.

Clinical studies have shown inconsistent healing with subjective improvement after use of platelet-rich plasma (PRP) for tendinosis and partial tendon tears. We conducted a study to assess changes after injecting PRP into an intact rabbit patellar tendon (PT) model. In the study group (n = 10), an incision was made over the PT and PRP was injected into multiple sites on the PT. The control group (n = 8) was injected with saline. PTs were harvested 7 and 28 days after injection. Hematoxylin-eosin staining showed hypercellularity in the PRP group at 7 days, but the effect was not as marked at 28 days. At 7 days, polarized microscopy showed increased crimp density of collagen in the PRP group, compared with the control group, demonstrating up-regulation in collagen matrix. Cellular proliferation measured by tritiated thymidine was also significantly increased (P = .02) in the PRP group, compared with the control group, but the difference was not as significant at 28 days. At 7 and 28 days, there were no significant changes in basic fibroblast growth factor, insulin-like growth factor, vascular endothelial growth factor, or platelet-derived growth factor with 2B chains. Injection of PRP into rabbit PT enhances collagen remodeling and hypercellularity with increased metabolic activity, which could have a positive effect on healing.

Treatment of articular cartilage defects in the goat with frozen versus fresh osteochondral allografts: effects on cartilage stiffness, zonal composition, and structure at six months.

BACKGROUND: Understanding the effectiveness of frozen as compared with fresh osteochondral allografts at six months after surgery and the resultant consequences of traditional freezing may facilitate in vivo maintenance of cartilage integrity. Our hypothesis was that the state of the allograft at implantation affects its performance after six months in vivo. METHODS: The effect of frozen as compared with fresh storage on in vivo allograft performance was determined for osteochondral allografts that were transplanted into seven recipient goats and analyzed at six months. Allograft performance was assessed by examining osteochondral structure (cartilage thickness, fill, surface location, surface degeneration, and bone-cartilage interface location), zonal cartilage composition (cellularity, matrix content), and cartilage biomechanical function (stiffness). Relationships between cartilage stiffness or cartilage composition and surface degeneration were assessed with use of linear regression. RESULTS: Fresh allografts maintained cartilage load-bearing function, while also maintaining zonal organization of cartilage cellularity and matrix content, compared with frozen allografts. Overall, allograft performance was similar between fresh allografts and nonoperative controls. However, cartilage stiffness was approximately 80% lower (95% confidence interval [CI], 73% to 87%) in the frozen allografts than in the nonoperative controls or fresh allografts. Concomitantly, in frozen allografts, matrix content and cellularity were approximately 55% (95% CI, 22% to 92%) and approximately 96% (95% CI, 94% to 99%) lower, respectively, than those in the nonoperative controls and fresh allografts. Cartilage stiffness correlated positively with cartilage cellularity and matrix content, and negatively with surface degeneration. CONCLUSIONS: Maintenance of cartilage load-bearing function in allografts is associated with zonal maintenance of cartilage cellularity and matrix content. In this animal model, frozen allografts displayed signs of failure at six months, with cartilage softening, loss of cells and matrix, and/or graft subsidence, supporting the importance of maintaining cell viability during allograft storage and suggesting that outcomes at six months may be indicative of long-term (dys)function. CLINICAL RELEVANCE: Fresh versus frozen allografts represent the "best versus worst" conditions with respect to chondrocyte viability, but "difficult versus simple" with respect to acquisition and distribution. The outcomes described from these two conditions expand the current understanding of in vivo cartilage remodeling and describe structural properties (initial graft subsidence), which may have implications for impending graft failure.

The in vivo performance of osteochondral allografts in the goat is diminished with extended storage and decreased cartilage cellularity.

BACKGROUND: Currently, osteochondral allografts (OCA) are typically used after 4°C storage for prolonged durations (15-43 days), which compromises chondrocyte viability, especially at the articular surface. The long-term in vivo performance of these fresh-stored allografts, in association with variable cellularity, is unknown. PURPOSE: To determine the effect of 4°C storage duration (14, 28 days) versus the best (fresh) and worst (frozen) conditions of chondrocyte viability on structure, composition, and function of cartilage in the goat and the association of retrieved chondrocyte cellularity with those tissue properties. STUDY DESIGN: Controlled laboratory study. METHODS: The effect of allograft storage on in vivo repair outcomes was determined for OCA transplanted into 15 recipient goats and analyzed at 12 months. Repair outcomes were assessed by examining cartilage structure (gross, histopathology), composition (cellularity by depth, matrix fixed charge), and biomechanical function (stiffness). Relationships between cellularity and structural scores, matrix fixed charge, and stiffness were assessed by linear regression. RESULTS: Repair outcomes in 4°C-stored OCA were similar after 14 and 28 days of storage, and both were inferior to fresh OCA and were accompanied by diminished cellularity at the surface, matrix fixed charge, and histopathological structure. Overall, cellularity by depth and matrix fixed charge in cartilage of fresh OCA were similar to nonoperated controls. However, cellularity at the articular surface and matrix fixed charge in 4°C-stored OCA were lower than fresh, by ~55% (95% confidence interval [CI], 32%-76%) and ~20% (CI, 9%-30%), respectively. In frozen OCA, cellularity and matrix fixed charge were lower than 4°C-stored OCA, by ~93% (CI, 88%-99%) and ~22% (CI, 10%-35%), respectively. Cellularity correlated negatively with cartilage health indices, including structural scores, and positively with matrix fixed charge and stiffness. CONCLUSION: Reduced cellularity at the articular surface, resulting from 4°C storage, was associated with variable long-term outcomes versus consistently good repair by fresh allografts. Cellularity at the articular surface was an important index of biological performance. CLINICAL RELEVANCE: Normal chondrocyte density in vivo, especially in the superficial region of cartilage, is important for maintaining long-term cartilage function and matrix content. In human cartilage, containing cells at ~3 to 5 times lower density than goat, repair outcomes may be related to absolute minimum number of cells rather than density.

Augmentation of tendon healing with butyric acid-impregnated sutures: biomechanical evaluation in a rabbit model.

BACKGROUND: Butyric acid (BA) has been shown to be angiogenic and to enhance transcriptional activity in tissue. These properties of BA have the potential to augment biological healing of a repaired tendon. PURPOSE: To evaluate this possibility both biomechanically and histologically in an animal tendon repair model. STUDY DESIGN: Controlled laboratory study. METHODS: A rabbit Achilles tendon healing model was used to evaluate the biomechanical strength and histological properties at 6 and 12 weeks after repair. Unilateral tendon defects were created in the middle bundle of the Achilles tendon of each rabbit, which were repaired equivalently with either Ultrabraid BA-impregnated sutures or control Ultrabraid sutures. RESULTS: After 6 weeks, BA-impregnated suture repairs had a significantly increased (P < .0001) Young's modulus and ultimate tensile strength relative to the control suture repairs. At 12 weeks, no statistical difference was observed between these measures. The histological data at 6 weeks demonstrated significantly increased (P < .005) vessel density within 0.25 mm of the repair suture in the BA-impregnated group. There was also an associated 42% increase in the local number of myofibroblasts in the BA samples relative to the controls at this time. By 12 weeks, these differences were not observed. CONCLUSION: Tendons repaired with BA-impregnated sutures demonstrated improved biomechanical properties at 6 weeks relative to control sutures, suggesting a neoangiogenic mechanism of enhanced healing through an increased myofibroblast presence. CLINICAL RELEVANCE: These findings demonstrate that a relatively simple alteration of suture material may augment early tendon healing to create a stronger repair construct during this time.

A biomechanical assessment of tendon repair after radiofrequency treatment.

After acute tendon injury, rapid mobilization prevents adhesions and improves the ultimate strength of the repair. Radiofrequency (RF) ablation is proposed to enhance angiogenesis in the early stages of healing. The mechanism and effect of RF have not yet been described in an animal model of tendon injury. To investigate the biomechanical effect of bipolar RF on acute injury in a rabbit model of partial Achilles tendon transection and suture repair, RF-treated tendon repairs were compared to untreated tendons. Cross-sectional area, Young's modulus, and ultimate tensile strength were determined. At 6 and 12 weeks after repair, RF-treated tendons had significant increases in cross-sectional area (P<.001; P< .0001) and ultimate tensile strength (P<.0001; P<.01). Young modulus of RF-treated tendons was increased at 6 weeks but not at 12 weeks (P<.01) Compared with untreated tendons, RF-treated tendons showed faster return to mechanical integrity. This may allow earlier rehabilitation.

The effect of butyric acid on normal tendons: a potential stimulus for extracellular matrix expression.

We propose comparing angiogenic effects of butyric acid (BA)-impregnated suture vs control suture on an aged tendon model. Twenty-four 3-year-old rabbits underwent bilateral Achilles tendon exposure. BA-impregnated orthopedic suture was sutured into one side, and a control orthopedic suture into the contralateral side similarly. The rabbits were sacrificed at 7, 30, and 45 days and the tendons harvested for gross, histologic, and biochemical study. Histologically, there was increased vascularity/cell migration at all time points in the BA-treated tendons; proteoglycan expression (ie, safranin O staining) increased at 30 and 45 days. DNA concentration was significantly (P = .05) higher in the BA-treated tendon group relative to the control group at 7 days but was unchanged at 30 and 45 days. Similarly, messenger RNA (mRNA) expression of vascular endothelial growth factor (VEGF) was significantly (P = .05) higher in the BA-treated tendon at 7 days. A trend (P = .12) for higher expression in the BA group also was found at 30 days.

Effect of light-emitting diode (LED) therapy on the development of osteoarthritis (OA) in a rabbit model.

OBJECTIVE: The objective of this study was to evaluate whether light-emitting diodes (LEDs) could be effective in a noninvasive, therapeutic device for the treatment of osteoarthritic (OA) knee joints. DESIGN: Five weeks following the anterior cruciate ligament transection (ACLT) of mature New Zealand White rabbits, the animal knees were exposed to LED stimulation at intervals of 10 min/day, 5 days/week for 5 weeks in the experimental group (n=7). The device used high intensity red and infrared (IR) LEDs with a total amount of energy delivered to the skin of 2.4 J/cm(2). Animals were sacrificed at 9 weeks postoperatively. Femoral surface gross morphology was evaluated with a modified Outerbridge classification and mRNA expression of catabolic and anabolic markers from femoral condyle cartilage and synovial tissue was assessed using RT-PCR. A control group was harvested 9 weeks following untreated ACLT. RESULTS: Gross morphometry of the control group showed four Grade II, two Grade III and one Grade IV (average 2.6) condyles macroscopically. The experimental group showed two Grade I and five Grade II (average 1.7) (Table 1). mRNA expression of aggrecan in the cartilage showed no difference between the groups, however type II collagen expression increased in the experimental group compared with control. TNF-α expression was significantly decreased in the experimental group compared to control. CONCLUSIONS: There was general preservation of the articular surface and decreased levels of inflammation in the osteoarthritic joints with the application of LED therapy. This may provide potential application as a noninvasive treatment.

Etanercept enhances preservation of osteochondral allograft viability.

BACKGROUND: Osteochondral allografts are an increasingly popular treatment for the repair of articular cartilage lesions. Current tissue bank protocols require bacteriological testing that takes from 21 to 28 days to process. During this time, tumor necrosis factor-alpha (TNF-α, a proapoptotic cytokine) is upregulated, resulting in loss of chondrocyte viability. To date, etanercept (a cytokine inhibitor) has not been studied in the current storage paradigm with the intention of preserving cell viability. PURPOSE: This study was undertaken to assess whether the addition of etanercept can improve the chondrocyte viability ofosteochondral allograft during storage. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral allografts were harvested from 8 Boer goat femurs and placed into storage media and stored at 4°C for 28 days. The experimental group was supplemented with 10 µg/mL of etanercept. After storage, cell viability was assessed by live/dead staining and confocal microscopy. Specimens were also analyzed histologically and underwent histomorphologic analysis. TNF-α expression was measured with semiquantitative polymerase chain reaction. RESULTS: At 28 days, the percentage viability of the superficial zone in etanercept-treated allografts was maintained at significantly higher levels than those measured in the untreated group (69.3 ± 9.4 compared with 47.8 ± 19.1, P = .01). No difference was found histologically between the etanercept and the untreated group (ie, safranin O staining for glycosaminoglycan expression). Histomorphologic assessment showed no difference in indentation stiffness or roughness between groups. TNF-α expression was significantly decreased in the etanercept group compared to the untreated group. CONCLUSION: Etanercept was able to maintain cell viability of osteochondral allografts significantly better than the current storage paradigm after 28 days of storage. CLINICAL RELEVANCE: Maintaining the viability of the superficial zone will benefit outcomes by facilitating joint articulation via improved lubrication. Additionally, maintaining the cellular viability for increased periods of time may allow a greater window of time in which a suitable recipient may be found.

The effects of exogenous basic fibroblast growth factor on intrasynovial flexor tendon healing in a canine model.

BACKGROUND: Studies have demonstrated that flexor tendon repair strength fails to increase in the first three weeks following suturing of the tendon, a finding that correlates closely with the timing of many clinical failures. The application of growth factors holds promise for improving the tendon-repair response and obviating failure in the initial three weeks. METHODS: The effects of basic fibroblast growth factor on flexor tendon healing were evaluated with use of a canine model. Operative repair followed by the sustained delivery of basic fibroblast growth factor, at two different doses, was compared with operative repair alone. Histological, biochemical, and biomechanical methods were used to evaluate the tendons twenty-one days after repair. RESULTS: Vascularity, cellularity, and adhesion formation were increased in the tendons that received basic fibroblast growth factor as compared with the tendons that received operative repair alone. DNA concentration was increased in the tendons that received 1000 ng of basic fibroblast growth factor (mean and standard deviation, 5.7 ± 0.7 µg/mg) as compared with the tendons that received 500 ng of basic fibroblast growth factor (3.8 ± 0.7 µg/mg) and the matched control tendons that received operative repair alone (4.5 ± 0.9 µg/mg). Tendons that were treated with basic fibroblast growth factor had a lower ratio of type-I collagen to type-III collagen, indicating increased scar formation compared with that seen in tendons that received operative repair alone (3.0 ± 1.6 in the group that received 500-ng basic fibroblast growth factor compared with 4.3 ± 1.0 in the paired control group that received operative repair alone, and 3.4 ± 0.6 in the group that received 1000-ng basic fibroblast growth factor compared with 4.5 ± 1.9 in the paired control group that received operative repair alone). Consistent with the increases in adhesion formation that were seen in tendons treated with basic fibroblast growth factor, the range of motion was reduced in the group that received the higher dose of basic fibroblast growth factor than it was in the paired control group that received operative repair alone (16.6° ± 9.4° in the group that received 500 ng basic fibroblast growth factor, 13.4° ± 6.1° in the paired control group that received operative repair alone, and 29.2° ± 5.8° in the normal group [i.e., the group of corresponding, uninjured tendons from the contralateral forelimb]; and 15.0° ± 3.8° in the group that received 1000 ng basic fibroblast growth factor, 19.3° ± 5.5° in the paired control group that received operative repair alone, and 29.0° ± 8.8° in the normal group). There were no significant differences in tendon excursion or tensile mechanical properties between the groups that were treated with basic fibroblast growth factor and the groups that received operative repair alone. CONCLUSIONS: Although basic fibroblast growth factor accelerated the cell-proliferation phase of tendon healing, it also promoted neovascularization and inflammation in the earliest stages following the suturing of the tendon. Despite a substantial biologic response, the administration of basic fibroblast growth factor failed to produce improvements in either the mechanical or functional properties of the repair. Rather, increased cellular activity resulted in peritendinous scar formation and diminished range of motion.

Can osteochondral grafting be augmented with microfracture in an extended-size lesion of articular cartilage?

BACKGROUND: Both microfracture and osteochondral autografting procedures have been useful in treating osteochondral lesions. HYPOTHESIS: Combining microfracture and osteochondral autografting procedures can extend the size of lesions that can be treated with either technique. STUDY DESIGN: Descriptive laboratory study. METHODS: Eight adult goats underwent osteochondral autograft transfer of a 4.5-mm femoral trochlea plug into an 8-mm full-thickness chondral defect. Microfracture was performed in the gap region surrounding the autograft. The animals were allowed normal activity until the end of the experiment at 6 months. At harvest, the knees were assessed grossly, and then evaluation was performed by histology, histomorphometry, biochemistry, and biomechanics. RESULTS: The osteochondral plugs healed well, with integration of the bone and preservation of the chondral cap. The chondral gap between the host site articular cartilage and the transferred plug had decreased from 3 mm at implant to less than 0.1 mm. Histologic analysis demonstrated regions of variable cartilage repair, with integration of the cartilage layer at some sites but incomplete healing at others. Histomorphometry demonstrated filling of the chondral gap to 75% to 85% of the normal volume. Biochemical analysis revealed greater than 90% type II collagen at most sites, with some areas containing 80% type II collagen. Biomechanical indentation testing indicated that the repaired area had variable thickness and stiffness, with a trend of increased stiffness in the bulk graft and decreased softness at the proximal microfracture interface site. CONCLUSION: The performance of a combined microfracture and osteochondral autograft transfer procedure to resurface a large chondral defect appears promising. CLINICAL RELEVANCE: This combined technique shows promise for treatment of large chondral defects with a single operative procedure with autogenous tissue that is safe and potentially would have a shorter period of rehabilitation, similar to that of osteochondral transfers and microfracture, in a cost-effective setting.

Changes in condylar coefficient of friction after osteochondral graft transplantation and modulation with hyaluronan.

PURPOSE: To better understand the changes in the cartilage coefficient of friction (COF) after an osteochondral repair, an assessment of dynamic loads has been developed using a goat knee model. The application of hyaluronan (HA) was also assessed for its lubricative properties and the resulting COF of the knee after osteochondral repair. METHODS: A total of 18 caprine knees were dissected and mounted into an Instron load frame (Instron, Norwood, MA) for testing. The COF was measured in 10 knees relative to the normal, unaltered joint and then calibrated to account for friction of the system. These experimental knees were tested in 5 modes: normal; empty 4.5-mm defect; and osteochondral repairs that were elevated, flush, or depressed relative to the cartilage surface. Saline solution lavage kept the knees moist during testing. The effect of HA was evaluated after mechanical testing. Eight knees were used to study the effect of lavage on the joints because of the significant increase in the COF that it produced. RESULTS: Whereas all modes increased the COF from normal levels, the most significant changes occurred when there was proud placement. Increases of 4 times the normal friction levels were measured. Increases in the COF were also associated with saline solution lavage (0.006 to 0.046). There was a significant reduction in friction after HA injection, which reduced the COF to near-normal levels. CONCLUSIONS: There is a significant increase in the COF associated with saline solution lavage and an osteochondral plug being left proud, which can be temporarily reduced with a lubricative material such as HA. CLINICAL RELEVANCE: Dramatic increases in the COF can potentially damage chondrocytes when the patient begins articulating the joint after surgery. Such injuries may affect the ability of the cartilage to heal fully. Reducing the elevated COF with lubricating materials, such as HA, is recommended based on the results of this study.

Enhanced flexor tendon healing through controlled delivery of PDGF-BB.

A fibrin/heparin-based delivery system was used to provide controlled delivery of platelet derived growth factor BB (PDGF-BB) in an animal model of intrasynovial flexor tendon repair. We hypothesized that PDGF-BB, administered in this manner, would stimulate cell proliferation and matrix remodeling, leading to improvements in the sutured tendon's functional and structural properties. Fifty-six flexor digitorum profundus tendons were injured and repaired in 28 dogs. Three groups were compared: (1) controlled delivery of PDGF-BB using a fibrin/heparin-based delivery system; (2) delivery system carrier control; and (3) repair- only control. The operated forelimbs were treated with controlled passive motion rehabilitation. The animals were euthanized at 7, 14, and 42 days, at which time the tendons were assessed using histologic (hyaluronic acid content, cellularity, and inflammation), biochemical (total DNA and reducible collagen crosslink levels), and biomechanical (gliding and tensile properties) assays. We found that cell activity (as determined by total DNA, collagen crosslink analyses, and hyaluronic acid content) was accelerated due to PDGF-BB at 14 days. Proximal interphalangeal joint rotation and tendon excursion (i.e., tendon gliding properties) were significantly higher for the PDGF-BB-treated tendons compared to the repair-alone tendons at 42 days. Improvements in tensile properties were not achieved, possibly due to suboptimal release kinetics or other factors. In conclusion, PDGF-BB treatment consistently improved the functional but not the structural properties of sutured intrasynovial tendons through 42 days following repair.

Variation of mesenchymal cells in polylactic acid scaffold in an osteochondral repair model.

OBJECTIVE: To achieve osteochondral regeneration utilizing transplantation of cartilage-lineage cells and adequate scaffolds, it is essential to characterize the behavior of transplanted cells in the repair process. The objectives of this study were to elucidate the survival of mesenchymal cells (MCs). In a polylactic acid (PLA) scaffold and assess the possibility of MC/PLA constructs for osteochondral repair. DESIGN: Bone marrow from mature male rabbits was cultured for 2 weeks, and fibroblast-like MCs, which contain mesenchymal stem cells (MSCs), were obtained. A cell/scaffold construct was prepared with one million MCs and a biodegradable PLA core using a rotator device. One week after culturing, the construct was transplanted into an osteochondral defect in the medial femoral condyle of female rabbits and the healing process examined histologically. To examine the survivability of transplanted MCs, the male-derived sex-determining region Y (SRY) gene was assessed as a marker of MCs in the defect by polymerase chain reaction (PCR). RESULTS: In the groups of defects without any treatment, and the transplantation of PLA without cells, the defects were not repaired with hyaline cartilage. The cartilaginous matrix by safranin O staining and type II collagen by immunohistochemical staining were recognized, however the PLA matrix was still present in the defects at 24 weeks after transplantation of the construct. During the time passage, transplanted MCs numbers decreased from 7.8 x 105 at 1 week, to 3.5 x 105 at 4 weeks, and to 3.8 x 104 at 12 weeks. Transplanted MCs were not detectable at 24 weeks. CONCLUSIONS: MCs contribute to the osteochondral repair expressing the cartilaginous matrix, however the number of MCs were decreasing with time (i.e. 24 weeks). These results could be essential for achieving cartilage regeneration by cell transplantation strategies with growth factors and/or gene therapy.

Use of bone morphogenic protein-7 as a treatment for osteoarthritis.

Osteoarthritis is a degenerative disorder resulting from breakdown of articular cartilage. Previous work has shown bone morphogenic protein-7 has a potential protective effect on cartilage during the development of osteoarthritis. The purpose of this study was to determine whether bone morphogenic protein-7 could decrease the amount of cartilage degradation in preexisting osteoarthritis. The rabbit ACLT model was used as a model of osteoarthritis. Bone morphogenic protein-7 was delivered via Alzet osmotic pump to the joint 4 weeks after anterior cruciate ligament transection; thus cartilage injury was preexisting. The experimental group showed less cartilage degradation than the controls, with an average Outerbridge score of 1.9 versus 2.6 for the controls. Histomorphometry showed a trend toward less cartilage degradation in the bone morphogenic protein-7 group when compared with controls. Semiquantitative real-time polymerase chain reaction showed a considerably greater expression of aggrecan in the bone morphogenic protein-7-treated cartilage when compared with controls and less expression of matrix metalloproteinase-3 and matrix metalloproteinase-13, important catabolic mediators. The synovial tissue of the experimental group also showed considerably less expression of matrix metalloproteinase-3, matrix metalloproteinase-13, and aggrecanase. These results indicate bone morphogenic protein-7 may reduce degradation of articular cartilage in osteoarthritis.

Controlled-release kinetics and biologic activity of platelet-derived growth factor-BB for use in flexor tendon repair.

PURPOSE: Surgically repaired intrasynovial tendons are at greatest risk of failure in the first 3 weeks after surgery. Attempts to improve the strength of repair by modifying rehabilitation parameters have not always been successful. Manipulation of the biological environment of the sutured tendon holds great promise for accelerating the repair process. The goals of this study were to examine (1) the range of conditions (eg, dosage, delivery system formulation, presence of cells) over which delivery of platelet-derived growth factor-BB (PDGF-BB) can be sustained from fibrin matrices using a heparin-binding delivery system (HBDS) and (2) the biological activity of the PDGF-BB released from this system on canine tendon fibroblasts in vitro. METHODS: We examined in vitro release kinetics from cellular and acellular fibrin matrices using enzyme-linked immunosorbent assays. We examined the biologic activity of the PDGF-BB in vitro by measuring cell proliferation (ie, total DNA) and collagen synthesis (ie, proline incorporation). RESULTS: The acellular release kinetics of PDGF-BB was modulated by varying the ratio of PDGF-BB to heparin (PDGF-binding sites) or the dose of PDGF-BB in the presence of the delivery system. In the presence of canine tendon fibroblasts, the delivery system prolonged the duration of PDGF-BB release from fibrin matrices, thus demonstrating that cells are able to liberate PDGF-BB retained by the HBDS. Sustained delivery of PDGF-BB promoted increased cell proliferation at doses of 0.125 microg/mL and 1.25 microg/mL compared to fibrin without delivery system. Collagen synthesis was enhanced by PDGF-BB at doses of 0.125 microg/mL and 1.25 microg/mL; however, there was an enhancement over fibrin without the delivery system only at the lower dose. CONCLUSIONS: These results demonstrate that the PDGF-BB released from fibrin matrices containing an HBDS is biologically active and can modulate both cell proliferation and extracellular matrix synthesis, both of which are key factors in the process of tendon repair.

Effects of biglycan deficiency on myocardial infarct structure and mechanics.

Biglycan, a small leucine-rich proteoglycan, has been shown to interact with extracellular matrix (ECM) collagen and may influence fibrillogenesis. We hypothesized that biglycan contributes to post-myocardial infarction (MI) scar development and that the absence of biglycan would result in altered scar structure and mechanics. Anterior MI was induced in biglycan hemizygous null and wild-type mice by permanent ligation of the left coronary artery. The initial extent of ischemic injury was similar in the two groups, as was the infarct size after 30 days, although there was some tendency toward reduced expansion in the biglycan-null. Electron microscopy revealed that collagen fibrils had a smaller average diameter and a narrower range in the biglycan-null scar, as well as appearing more densely packed. In vivo strain analysis showed that biglycan-null scars were stiffer than the wild-type. Remote LV collagen concentration tended to be reduced in biglycan-null hearts, but the difference was not statistically significant. Null-expression of biglycan may alter collagen fibril ultrastructure, and thereby influence scar mechanics and remodeling.