Matrix-Encapsulation Cell-Seeding Technique to Prevent Cell Detachment During Arthroscopic Implantation of Matrix-Induced Autologous Chondrocyte Implantation (MACI) (SS-46)

ABSTRACTS points preoperatively to 1.1⫾1.1 points at FU1 and 1.1⫾1.1 points at FU2. Conclusion: Arthroscopic repair or partial reconstruction is advisable even in patients with massive rotator cuff tears as it led to significant improvements in function, pain and patient satisfaction in active patients suffering from a symptomatic massive rotator cuff tear. Rotator Cuff Tears as a Complication of Portal Placement (SS-44). Scott Mair, MD, and Joel Hurt, MD An accessory trans-rotator cuff portal is commonly utilized in shoulder arthroscopy, primarily in the repair of SLAP lesions. This portal has become popular as it provides access to the superior glenoid and labrum. Improper placement of this portal can result in damage to the rotator cuff near its attachment to the greater tuberosity. We wish to stress the importance of proper placement of this portal and the potential for complications with its use. Six patients were referred to our clinic after previous shoulder arthroscopy with SLAP repair. Mean age of the patients was 34.4 years (range 17-44 years). There were five males and one female. ASES scores at time of presentation averaged 45.4 (range 34-60). 5 of 6 reported that their symptoms were worse after the index surgery. Review of operative notes showed that the rotator cuff had been described as normal in five patients at the time of the first surgery. The other patient was described as having a mild partial supraspinatus tear. All patients underwent repeat shoulder arthroscopy. Mean time period from the index to revision surgery was 15.0 months (range 10-22 months). All 6 patients were found to have significant rotator cuff tears associated with portal placement from their first surgery. Confirmation of the portal as the source of the rotator cuff tear was made by placing a spinal needle through the skin at the site of the previous portal. 3 of 6 patients underwent revision SLAP repair. All six were treated with rotator cuff repair: 3 with side to side repair, 3 with suture anchor repair to bone. All patients improved after revision surgery. Postoperative ASES scores averaged 90.5 (range 77-100). Mean follow-up was 16.0 months (range 8-36 months). A trans-rotator cuff portal is an accepted portal in shoulder arthroscopy. Its proper use involves careful placement in order to traverse the rotator cuff medial to the muscle-tendon junction. This report highlights the potential for injury to the rotator cuff tendons with improper placement of this portal. In patients with persistent pain after previous SLAP repair, where a trans-rotator cuff portal was used, consideration should be given to rotator cuff injury as the source of symptoms. Revision surgery with rotator cuff repair can provide improvement.

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Effects of Bipolar Radiofrequency on the Human Meniscus: A Comparative Study Between Patients Younger and Older Than 40 Years Old (SS-45). David Figueroa, MD, Rafael Calvo, Alejandro Vaisman, Miguel Carrasco, MD, Marcela Gallegos, Rodrigo Mardones, MD, and Iris Delgado Bipolar radiofrequency is frequently used in arthroscopic surgery. It provides excellent intraarticular hemostasis, debridement and shrinkage of soft tissues. Although extensively used in meniscal surgery, there are few studies that report the ultrastructural effect of bipolar radiofrequency on the human meniscus. Furthermore, it is not clear if there is any difference between applying the same amount of energy on younger versus older menisci. The main objective of our study was to evaluate the effects of bipolar radiofrequency applied to the human meniscus in 4 differents intensities and compare the results between patients younger and older than 40 y.o. Our study shows the effects of four different magnitudes of bipolar radiofrequency, commonly used in knee arthroscopic surgery: coagulation medium and high, vaporization intensities 5 and 7. Each magnitude was applied for 3 seconds on 30 human menisci resected from patients between 14 and 84 years old. The menisci were then divided in two groups: younger and older than 40 years old, and studied macroscopically, microscopically and by electronic microscopy. Thermal necrosis was found between m (D.S. 740) and␮m from the meniscal surface, with an average of 1700␮0 and 4000 was significantly higher on the vaporization than the coagulation group (p ⬍ 0.001). We found significative differences between patients younger or older than 40 years old in groups zone 2 and 3 (zone 2 p⫽0.038 and zone 3 p⫽0.044) We concluded that although bipolar radiofrequency can cause deep necrosis (up to m) on the human meniscus, this effect depends on the magnitude of the ␮4000 energy applied and is higher when we applied medium intensity in older patients. KEY WORDS: Radiofrequency – Knee arthroscopy – Meniscus. Matrix-Encapsulation Cell-Seeding Technique to Prevent Cell Detachment During Arthroscopic Implantation of Matrix-Induced Autologous Chondrocyte Implantation (MACI) (SS-46). Maria Masri, MVZ, MSC, DACVIM, German Lombardero, Cristina Velasquillo, Valentin Martinez, Rosario Neri, Hilda Villegas, PhD, and Clemente Ibarra, MD Arthroscopic implantation of matrix–induced autologous chondrocytes (MACI) can be limited by fluid flow that can affect cell attachment to the matrix. The goal of this study is to evaluate the efficiency to obtain a larger

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ABSTRACTS

number of viable cells in a construct, so that they will not detach by the high fluid flow during arthroscopic implantation. Results: Cells were alive throughout the cell culture procedure. Consistency of the polymer was ideal for implantation between 7 and 9 days. The cell-encapsulated polymer was recovered after implantation and viability of cells and attachment to the co-polymer was demonstrated. Good attachment was observed by ESEM before and after implantation. Discussion: Fluid flow during arthroscopic implantation affects the attachment of chondrocytes to the copolymer. Previous attempts to deliver chondrocyte-constructs were performed and no cells attached to the polymer were observed. The encapsulation technique appears to help maintain cells within the construct, an important consideration for arthroscopic implantation.

Tissue Engineered Arthroscopic Repair of Experimental Cartilage Lesions in Horses (SS-47). Clemente Ibarra, MD, German Lombardero, Valentin Martinez, Maria Masri, MVZ, MSC, DACVIM, Blanca Garcia, MD, Baltazar Reyes, MD, and Cristina Velasquillo Objective: To valuate by means of magnetic resonance imaging (MRI), arthroscopy and histology the repair tissue obtained after the arthroscopic implantation of an autologous chondrocyte-construct derived from cartilage and seeded onto a polyglycolic acid-polylactic acid (PGA-PLA) co-polymer attached to an experimental chondral lesion in the patello-femoral joint of the horse. Materials and methods: Five young horses were used. An osteochondral biopsy was obtained from the left femoral trochlea. Chondrocytes were isolated by collagenase digestion and expanded in culture. Cells were seeded (2x107) onto PGA/PLA discs and were implanted arthroscopically to repair 8mm diameter cartilage defects created in the right medial trochlea using an absorbable fixation device. At 8 weeks stifle joints were evaluated by MRI, arthroscopy and light microscopy (H&E, Safranin-O, Trichrome). Results: New tissue was integrated to normal surrounding tissue. Arthroscopic evaluation showed cartilage-like tissue in all defects. MRI showed a distinct difference among the tissue engineered repair and controls. Histology demonstrated very cellular fibrocartilage-like repair tissue, attached to subchondral bone. Discussion: Arthroscopic implantation of cell-polymer constructs was possible. Defects were filled by cartilage-like tissue by 8 weeks. MRI was useful to evaluate

repair. The equine model is extremely useful to test new techniques for potential human use. Suture Fixation of Biodegradable Nanofibrous PolyCaprolactone Scaffolds to Bovine Meniscus: A Novel Approach to Repairing Meniscal Tears (SS-48). Neil P. Sheth, MD, Robert L. Mauck, PhD., Wan-Ju Li, PhD, Rocky Tuan, PhD, Dawn Elliott, PhD, and G. Huffman, MD, MPH Purpose: We have designed a novel biodegradable, aligned nanofibrous scaffold for augmenting the repair of meniscal tears historically considered irreparable. As a first step in this endeavor, scaffold fixation to meniscal tissue was quantified by comparing suture pull-out from scaffolds and fixation strength to the native tissue. Methods: Two suture types: monofilament (Prolene) and braided (Ticron) of equal diameter; and, two knots: horizontal mattress (HM) and -caprolacone fiber aligned and ␧ vertical mattress (VM) were investigated. Polynon-aligned meshes were produced via electrospinning. Tensile testing to failure of the suture was carried out at 0.1% elongation/second. An “apparent” Young’s modulus was calculated from the stress-strain profile and scaffold geometry. Subsequently, circumferentially aligned bovine meniscal strips were sutured parallel to aligned scaffolds using single or double VM or HM with Ticron suture. Results: The apparent Young’s modulus was 15 MPa for the aligned group sutured with a Ticron HM compared to 5 MPa for the same scaffold sutured with a Prolene HM (Figure 1, left, p⬍0.01). There was no significant difference in the tensile strength between HM and VM knots. When sutured to native meniscus, double knots provided slightly stronger fixation (Figure 1, right). Conclusion: This study confirms that aligned scaffolds have superior tensile properties compared to nonaligned scaffolds and that a braided Ticron suture material provides a more stable fixation. Moreover, increasing number of VM Ticron knots were shown to improve the fixation strength of fiber-aligned scaffolds to the native tissue. Arthroscopic Glenoid Resurfacing with a Meniscal Allograft (SS-49). William T. Pennington, MD, and Brian Bartz, PA-C Purpose: The chronically painful arthritic glenohumeral joint recalcitrant to non-surgical treatment modalities generally has been treated with an open arthroplasty type of procedure. Certain patients may benefit from a less invasive surgical technique in which a meniscal