Technical Note Fresh Osteochondral Resurfacing of the Patellofemoral Joint Pablo Eduardo Gelber, M.D., Ph.D., Eduard Ramírez-Bermejo, M.D., Maximiliano Ibañez, M.D., Alex Grau-Blanes, M.D., Oscar Fariñas, M.D., and Juan Carlos Monllau, M.D., Ph.D. Abstract: Large osteochondral lesions of the knee in young patients continue to be a challenge for orthopaedic surgeons and the focus of continual research. This is particularly true if the injury is a consequence of a dysplastic trochlea and involves both articular surfaces of the biomechanically complex patellofemoral joint. To obtain a healthy and congruent patellofemoral joint, the use of a bipolar fresh osteochondral allograft transplantation of the patella and trochlea is one of the few options to biologically treat these injuries. This would achieve a replacement of the entire articular surface of the patellofemoral joint with a high number of viable chondrocytes and respect the unique structural characteristics of the cartilage. The aim of this study was to obtain symptomatic and functional improvements while delaying the timing of prosthetic surgery. We present a reproducible although demanding surgical technique to perform a bipolar fresh osteo- chondral allograft transplantation of the patella and trochlea. T reatment of osteochondral knee injuries in young and active patients continues to be a challenge for the orthopaedic surgeon and the focus of continual options for patellofemoral chondral lesions range from simple arthroscopic debridement and microfracture to more invasive procedures5 such as osteochondral research. Chondral lesions on the patella and trochlea autograft transplantation,6 osteochondral allograft are particularly difficult to manage because of their (OCA) transplantation, autologous chondrocyte biomechanical characteristics, shape, and size.1-4 implantation,7 matrix-induced autologous chondrocyte The goal of surgical treatment is to correct the implantation,8 and patellofemoral arthroplasty.9 biomechanical alterations and anatomic deformities When the defect is focal and localized in an area with and to treat the chondral lesions in accordance with good stability, thus with better integration, osteochon- their location, extension, and depth.1,2 The treatment dral grafts can be of a relatively small size. In the case of large or multifocal lesions, particularly with a highly dysplastic trochlea, full osteochondral resurfacing of the From the Department of Orthopaedic Surgery, Hospital de la Santa Creu i patellofemoral joint would not only approach the Sant Pau (P.E.G., E.R-B., A.G-B.), and ICATMEeHospital Universitari cartilage defect but also address the cause of the Dexeus (P.E.G., M.I., J.C.M.), Universitat Autònoma de Barcelona; and injury.10 Barcelona Tissue BankeBanc de Sang i Teixits (O.F.), Barcelona, Spain. Having viable chondrocytes guarantees the viability of The authors report the following potential conflicts of interest or sources of funding: P.E.G. is a consultant for ConMed. J.C.M. receives grants/grants the graft after transplantation.11 Among all the different pending from Spanish Ministerio de Economia,Industria y Competitividad tissue bank storage techniques, fresh allografts are the (National Programme for Research Aimed at the Challenges of Society), and only ones that provide for the long-term viability of the payments for lectures from Smith & Nephew. Full ICMJE author disclosure chondrocytes.12 However, the allografts must be forms are available for this article online, as supplementary material. transplanted within 14 to 28 days after procurement for Received June 1, 2019; accepted July 18, 2019. Address correspondence to Pablo Eduardo Gelber, M.D., Ph.D., Department maximum chondrocyte viability.13 of Orthopaedic Surgery, Hospital de la Santa Creu i Sant Pau, Universitat Most authors have reported osteochondral trans- Autònoma de Barcelona, C/Sant Quintí 89, 08041 Barcelona, Spain E-mail: plantation of the trochlea using large plugs. Even so, a personal@drgelber.com dysplastic trochlea must be addressed differently. A Ó 2019 by the Arthroscopy Association of North America. Published by trochleoplasty is performed for patellofemoral insta- Elsevier. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). bility. However, it is contraindicated in the presence of 2212-6287/19708 large cartilage defects. Therefore, a combination of a https://doi.org/10.1016/j.eats.2019.07.017 large cartilage injury and a dysplastic trochlea can only Arthroscopy Techniques, Vol 8, No 11 (November), 2019: pp e1395-e1401 e1395 e1396 P. E. GELBER ET AL. be biologically treated by a total resurfacing osteo- between 4 C and 8 C. Once in the local authorized chondral transplantation. tissue bank, preparation and cleaning of the grafts are The purpose of this technical note is to present a performed in a class A clean room. This consists of the reproducible technique to address large osteochondral evaluation of the cartilage surface, removal of the soft defects of the patellofemoral joint with a fresh OCA tissue and periosteum, shaping of the grafts, and high- transplantation in the presence of a dysplastic trochlea. pressure pulsatile lavage irrigation with sterile saline This technique aims to reduce the symptoms and to solution. The finals grafts are subjected to a decon- delay the need for a prosthetic implant in an otherwise tamination process consisting of dry centrifugation, healthy young patient. followed by centrifugation with sterile phosphate- buffered saline solution. Microbiological tests are then Indication carried out on the grafts and on the last wash solution. Fresh osteochondral transplantation of both complete Finally, the allografts are submerged in a preservative articular surfaces of the patella and trochlea is indicated solution consisting of lactated Ringer solution and an in subjects younger than 50 years. They will have an antibiotic cocktail that includes amphotericin (125 mg/ extensive cartilage or osteochondral lesion in the mL), tobramycin (3 mg/mL), vancomycin (50 mg/mL), patella and trochlea (kissing lesion) with Dejour type C and co-trimoxazole (160 mg/mL). After 5 days, new or D trochlear dysplasia that cannot be treated with microbiological tests are performed on the allografts other, less aggressive techniques. Only patients with and on the preservative solution. From its arrival at the severe chronic pain that limits their daily activities and tissue bank until the time of implantation in the patient, without reasonable improvement with conservative the allograft is kept refrigerated between 4 C and 8 C. treatment are candidates for this option. Currently, the estimated risk of infectious disease The main exclusion criteria are advanced osteoar- transmission is 1 case in 420,000 donations for hepatitis thritis of other compartments of the knee and general C virus, 1 in 175,000 for human immunodeficiency conditions such as infections, tumors, locally aggressive virus, and 1 in 100,000 for hepatitis B virus.14 Allograft rheumatic disease, diabetes, and vasculitis. Relative sizing is performed in accordance with a preoperative contraindications are a body mass index greater than 30 computed tomography scan (both of the patient and of and age older than 50 years, although a clear age cutoff the graft) and anthropometric agreement between the has not yet been defined. Smoking must be stopped donor and recipient. 30 days prior to the surgical procedure and abstained from for at least 6 months after the operation. Surgical Technique Preoperative Study Positioning All patients undergo the following radiologic The patient is placed in the supine position with a evaluation: support for the foot and a lateral support for the thigh  A long-standing radiograph, with lateral and axial to maintain the knee at around 45 of flexion. The views of both knees contralateral limb is placed in full extension.  Magnetic resonance imaging to assess the chondral or Donor Graft Preparation subchondral status of the patellofemoral joint, as well The distal femoral and patellar grafts are first warmed as to look for any potential concomitant injuries up to room temperature and then inspected to ensure  A computed tomography scan to provide the most the absence of macroscopic damage. The articular side accurate information on bone loss and allow for of the patella is resected using a standard cutting measurement of the defect and disorders of the patellar guide such as that used in total knee arthro- patellofemoral joint plasty (Fig 1). Only 6 to 8 mm of the subchondral bone tissue is resected with the guide. This step is of utmost Fresh Allograft Harvesting importance because the thicker the bone tissue of the The local authorized tissue bank supplied the graft, the greater the possibility of an immunoreaction allografts and performed the preoperative graft pro- and bone resorption. In addition, osteochondral inte- cessing. The fresh OCA should be obtained from donors gration is only achieved because of the creeping younger than 45 years. The limit for harvesting fresh substitution phenomenon in the first 8- to 12-mm layer grafts is within the first 12 hours of death. However, the of bone tissue.15 It is crucial to minimize any potential period can be extended by an extra 12 hours if the immunologic reaction by removing all the remaining donor’s body is kept refrigerated at 4 C for the first 4 to soft tissue and by washing with a 6-L high-pressure 6 hours after death. pulsatile lavage irrigation system inside a proper tube- The harvested OCA is placed into transport medium like recipient. Lavage is performed for at least (lactated Ringer solution) and preserved refrigerated 15 minutes. A mark is made at the proximal and lateral PATELLOFEMORAL OSTEOCHONDRAL TRANSPLANTATION e1397 that there are no excluding criteria that may have been overlooked preoperatively. Any anatomic deformity or biomechanical alteration of the patellofemoral joint must be corrected to avoid further cartilage degradation of the graft. These corrections may be addressed either in a previous operation or, preferably, concomitantly with the procedure. Receiving Area Preparation A longitudinal midline incision is used, and either a standard medial parapatellar approach or a subvastus approach can be performed. Dissection of soft tissues is performed to allow for patellar eversion, with care Fig 1. Right patellar graft preparation. The articular side of taken not to excessively remove tissue from the Hoffa the patella is resected using a standard patellar guide such as fat pad because it is a source of vascularization for the that used in total knee arthroplasty. knee extensor apparatus. The knee is fully extended and the patella is kept part of the patellar graft with a sterile skin marker to aid everted by twisting it with 2 atraumatic clamps at the in its proper placement later in the recipient area. level of the insertions of the patellar and quadriceps The articular side of the trochlear graft is outlined tendons. Careful measurement of the patellar thickness with the sterile skin marker. Three 3 Kirschner wires, is performed with a caliper. Superior-inferior and on each lateral side of the trochlear joint surface ori- medial-lateral measures are also assessed to check that ented to 45 toward the center of the trochlea from they match the donor’s size and to avoid any instability anterior to posterior (Fig 2), serve as cutting guides. The or pain due to mismatching or overhang. Circumfer- articular side of the trochlea is then resected with a saw ential denervation on the medial, lateral, and proximal and chisels. It is also crucial to remove all the unnec- aspects of the patella is performed to decrease post- essary soft tissue and perform high-pressure pulsatile operative anterior knee pain. lavage irrigation with sterile saline solution to decrease At this point, using the same cutting guide and saws graft immunogenicity. used to prepare the patellar allograft, the articular side of the patella is resected (Fig 3). It is crucial that the Arthroscopic Assessment resected thickness is never less than that of the allograft; The tourniquet is now inflated. An arthroscopic otherwise, an overstuffed patella might increase the evaluation of all compartments of the knee is first patellofemoral joint pressure. performed to reconfirm that bipolar fresh OCA trans- plantation of the patella and trochlea is suitable and Fig 2. Right trochlear graft preparation. The articular side of the trochlea is outlined with a sterile skin marker. The Fig 3. Medial view of right knee. The patellar osteotomy is osteotomy will be performed guided by 3 K-wires placed on performed using a standard cutting guide. Care is also taken to each side of the joint surface and oriented to 45 toward the position the cutting guide to eliminate only 6 to 8 mm of the center of the trochlea from anterior to posterior. subchondral bone tissue. e1398 P. E. GELBER ET AL. trochlea using a sterile skin marker (Fig 4). Preparation of the trochlea’s resection is performed by the same technique used to prepare the trochlear allograft. Meticulous trimming and smoothing of both the recipient and donor subchondral bones must be per- formed to ensure a perfect match and full bone contact. Graft Placement When the best position for the trochlear transplant is determined, fixation is accomplished with two 3.5-mm headless titanium compression screws with various thread pitches (Acutrak Standard; Acumed, Hillsboro, OR) to provide strong fixation. This is complemented with three or four 2-mm-diameter by 20- to 25-mm-long absorbable pins (SmartNail; ConMed, Largo, FL) (Fig 5). Once the best position for the patellar transplant is visually determined, temporarily fixing it with two 1.8- mm K-wires positioned on the dorsal aspect of the patella (anterior to posterior) is recommended while care is taken to avoid cartilage tissue piercing (Fig 6). After that, final fixation of the graft can be carried out. Absorbable pins, 1.5 mm in diameter by 16 to 20 mm long (SmartNail), positioned in an anterograde manner through the cartilage surface (from posterior to ante- Fig 4. Frontal view of right knee. The knee is flexed at 45 rior), are recommended to minimize chondral damage and the patella is everted, exposing the trochlea. The shape and allow for postoperative magnetic resonance and size of the allograft’s trochlea are reproduced in the pa- tient’s trochlea using a sterile skin marker. imaging evaluation. We suggest using 4 absorbable pins at the level of each corner of the patella to give proper Subsequently, the knee is flexed at 45 and the patella stability without damaging the cartilage surface impli- cated in gliding over the trochlear groove. Fixation from is everted, exposing the trochlea. The shape and size of the dorsal aspect of the patella with small metal screws the allograft’s trochlea are reproduced in the patient’s can also be performed as an alternative. Once the patellar graft is fixed, the K-wires are removed (Fig 7). Fig 6. Temporary fixation of the patellar graft is accomplished Fig 5. Frontal view of right knee. Trochlear allograft fixation with two 1.8-mm K-wires positioned on the dorsal aspect of is accomplished with two 3.5-mm headless titanium the patella (anterior to posterior) while care is taken to avoid compression screws. cartilage tissue piercing. PATELLOFEMORAL OSTEOCHONDRAL TRANSPLANTATION e1399 Discussion The treatment of large, symptomatic chondral defects of dysplastic patellofemoral joints in young patients with full bipolar fresh OCA transplantation of the patella and trochlea provides a high number of vital chondrocytes within the extracellular matrix of the cartilage while restoring the normal patellofemoral shape and biomechanics. It permits achieving symptomatic and functional improvement with the possibility of delaying or eliminating the need for prosthetic surgery. Table 1. Step-by Step Fresh Osteochondral Allograft Resurfacing of Patella and Trochlea Step Description 1 The patient is positioned supine on the operating table, with 45 of knee flexion, using a distal foot support and a lateral support for the thigh. An arthroscopic evaluation of all compartments of the knee is first performed to reconfirm that bipolar fresh osteochondral allograft transplantation of the patella and trochlea is suitable. 2 A standard medial parapatellar approach or a subvastus approach can be used. Fig 7. Frontal view of right knee. Final disposition of patellar 3 The knee is extended and the patella is kept everted by and trochlear grafts. twisting it with 2 atraumatic clamps at the level of the insertions of the quadriceps and patellar tendons. 4 Careful measurement of the patellar thickness is performed Intra-articular drainage is left in place, and the inci- with a caliper to maintain the offset of the patellofemoral sion is closed. Special attention should be paid to joint. 5 An osteotomy is performed using a standard patellar guide respecting the synovium and the capsular layer. If such as that used in total knee arthroplasty. Care is also needed, the vastus medialis muscle may be partially taken to position the cutting guide to eliminate only 6 to advanced over the patella to decrease lateral facet 8 mm of the subchondral bone tissue. pressure. The knee is finally immobilized in a brace 6 Circumferential denervation of the patella is finally locked in full extension. performed to decrease postoperative anterior knee pain. 7 The graft is cut to a thickness that is the same as or slightly A step-by-step description of the surgical technique is less than that of the tissue removed from the patient’s summarized in Table 1. Table 2 provides pearls and patella to maintain the patellofemoral offset. With a sterile pitfalls of performing this procedure. Video 1 shows the skin marker, short lines are drawn on the proximal and whole technique in detail. lateral part of the graft to aid in its proper placement. 8 Once the most appropriate position for the transplant is visually determined, fixation is achieved with two to three 1.8-mm K-wires positioned on the dorsal aspect of the Rehabilitation Protocol patella (anterior to posterior) while care is taken to avoid cartilage tissue piercing Controlled continuous passive motion is started 9 The use of 4 absorbable pins at the level of each corner of the within the first hours after the intervention and is used patella is suggested to give absolute stability without for more than 6 hours per day during the first 6 weeks. damaging the cartilage surface implicated in gliding over Full range of motion is allowed from the beginning. the trochlear groove. Once the graft is fixed, the K-wires Isometric strengthening of the quadriceps and are removed and patellofemoral tracking, as well as implant stability, is tested again. hamstring muscles is also recommended starting from 10 The articular side of the trochlear allograft is outlined with a the first days after graft implantation. Full weight sterile skin marker. The preparation of the trochlea’s bearing is allowed but only with a brace locked in full allograft is performed by fixing 3 K-wires on each lateral extension during the first 6 weeks. At that point, side of the joint surface oriented 45 toward the center of rehabilitation focuses on restoring full range of motion the trochlea from anterior to posterior. 11 The articular side of the trochlea is resected with a saw and and strengthening. chisels, following the guide of the K-wires. The preparation Pivoting and strenuous activities are not recom- of the trochlea’s receiving area resection is performed using mended. It is imperative that the patient be made aware the same technique used to prepare the trochlear allograft. of such limitations before OCA transplantation of the 12 The approach is closed with attention paid to respecting the patella and trochlea is considered. synovium and the capsular layer. e1400 P. E. GELBER ET AL. Table 2. Pearls, Pitfalls, and Risks Some tricks and pearls that help to diminish the degree Pearls of immunoreaction in the transplant are (1) the use of Obtaining osteochondral tissue from donors aged >45 yr is not high-pressure pulsatile lavage irrigation with sterile recommended. saline solution to help to eliminate any trace of blood, Allograft sizing is performed in accordance with a preoperative CT scan (both of the patient and of the graft) and anthropometric (2) careful removal of remnant soft tissue, and (3) agreement between the donor and recipient. transplanting a graft with a bone layer no thicker than 6 The tourniquet should only be inflated once the graft preparation to 10 mm. In addition, osteochondral integration is only has been finished. achieved owing to the creeping substitution phenom- Care should be taken to position the cutting guide to eliminate enon in this thin layer of bone. The bone will be only 6-8 mm of the subchondral bone tissue. This step is of utmost importance because the thicker the bone tissue, the subjected to a necrosis process with subsequent greater the possibility of an immunoreaction. revascularization during the healing progress.15 Correction of any anatomic deformity or biomechanical alteration Correction of any anatomic deformity or of the patellofemoral joint is mandatory to avoid further cartilage biomechanical alteration of the patellofemoral joint is degradation of the graft. Any preoperative TT-TG distance can be mandatory to avoid further cartilage degradation of the used as a guide, but one should consider substantial changes after the new trochlea has been transplanted. graft. Special attention must be paid to the tibial To help diminish some degree of immunoreaction, the surgeon tuberosityetrochlear groove distance because the should carefully remove remnant soft tissue, use a high-pressure transplanted trochlea will modify the preoperative pulsatile irrigation system to eliminate any trace of blood, and value. Subsequently, a proper intraoperative assess- transplant a graft with the least amount of bone possible. ment of patellofemoral tracking must be performed. Suction drainage is used to minimize the risk of hematoma. Circumferential denervation of the patella further helps in Any obvious maltracking with a high Q angle can be preventing residual anterior knee pain. corrected with tibial tuberosity medialization. Pitfalls and risks Studies on bipolar OCA transplantation of the patella There are no cutting guides for the trochlea. This is a demanding and trochlea are few and have been limited to fewer technique. than 20 patients. In addition, most of them have There is a risk of distal osteochondral fracture while preparing the trochlear recipient area near the intercondylar notch. reported surgical techniques using bone plugs instead of Perfect matching can take several steps by trimming and the described resurfacing technique. Risk of failure is smoothing the subchondral bone. increased because of the size of the joint. However, Should the graft, by any chance, fall on the floor, we recommend a patients with surviving allografts showed significant new washing process with the high-pressure pulsatile irrigation system for no less than 20 min, with subsequent immersion in vancomycin solution, 1 g/100 mL, for 10 min. Athletic activity should be limited to light sports. Pivoting and Table 3. Advantages and Limitations strenuous activities are not recommended. Advantages Potentially, the procedure can lead to some degree of The treatment is biological. immunoreaction. The procedure is indicated in young subjects with extensive CT, computed tomography; TT-TG, tibial tuberosityetrochlear cartilage or osteochondral lesions in the patella and trochlea groove. (kissing lesions) with Dejour type C or D trochlear dysplasia that cannot be treated with other, less aggressive techniques. Good results are achieved when performed with a surgical Preventing the migration of multipotent cells from the technique that follows a few standard steps to maintain the long- subchondral bone of the host is achieved by the lack of term viability of the graft. chondral tissue vascularization and the hard consis- Fresh osteochondral allografts are biomechanically and tency of its matrix. Thus, a graft with the best chon- histologically comparable with autografts and retain viable chondrocytes. drocyte viability is the best option.16 Fresh-frozen and Implantation of a patellofemoral arthroplasty is prevented. cryopreservation storage techniques have the advan- Limitations tage of being widely available and allowing for the The use of fresh allografts carries considerable logistic limitations, preservation of the graft for several months. However, and this material is not easily available worldwide. it has been shown that these techniques affect the The main exclusion criteria are advanced osteoarthritis of other compartments of the knee and general conditions such as biomechanics and viability of the chondral layer of the infections, tumors, locally aggressive rheumatic disease, diabetes, graft in an irreversible manner.17 and vasculitis. Conversely, fresh OCAs are biomechanically and Relative contraindications are BMI >30 and age >50 yr. Smoking histologically comparable with autografts and retain must be stopped 30 d before surgery and abstained from for at viable chondrocytes.18 Thus, fresh allografts are least 6 mo after the operation. Only patients who have severe chronic pain that limits their daily preferred. The downside of fresh allografts is the logistic activities and see no improvement with rehabilitative treatment limitation because the storage time is limited to a few are candidates for this treatment. weeks from harvesting.13,19 The technique is not intended for patients seeking to return to A list including the main advantages and disadvan- demanding pivoting activities. tages of the described technique is shown in Table 3. BMI, body mass index. PATELLOFEMORAL OSTEOCHONDRAL TRANSPLANTATION e1401 improvements in functional outcomes, pain relief, and posttraumatic knee defects: Long-term followup. Clin range of motion.20-25 Orthop Relat Res 2008;466:1863-1870. 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