Periprosthetic infection is the major indication for TKA revision - experiences from a university referral arthroplasty center.

BACKGROUND: We hypothesized, that periprosthetic joint infection (PJI) accounts for the major proportion of first (primary) and repeated (secondary) Total Knee Arthroplasty revisions at our university referral arthroplasty center. METHODS: One thousand one hundred forty-three revisions, performed between 2008 and 2016 were grouped into primary (55%) and secondary (45%) revisions. The rate of revision indications was calculated and indications were categorized by time after index operation. The odds ratios of the indications for primary versus secondary revision were calculated. RESULTS: In the primary revision group PJI accounted for 22.3%, instability for 20.0%, aseptic loosening for 14.9% and retropatellar arthrosis for 14.2%. PJI (25.6%) was the most common indication up to 1 year after implantation, retropatellar arthrosis (26.8%) 1-3 years and aseptic loosening (25.6%) more than 3 years after implantation. In the secondary revision group PJI accounted for 39.7%, aseptic loosening for 16.2% and instability for 13.2%. PJI was the most common indication at any time of revision with 43.8% up to one, 35.4% 1-3 years and 39.4% more the 3 years after index operation. The odds ratios in repeated revision were 2.32 times higher (p = 0.000) for PJI. For instability and retropatellar arthrosis the odds ratios were 0.60 times (p = 0.006) and 0.22 times (p = 0.000) lower. CONCLUSIONS: PJI is the most common indication for secondary TKA revision and within one year after primary TKA. Aseptical failures such as instability, retropatellar arthrosis and aseptical loosening are the predominant reasons for revision more than one year after primary TKA.

[Osteotomies of the distal tibia]. / Distale Tibiaosteotomien.

OBJECTIVE: Restoration of physiological alignment of the distal tibia and thereby restoration of physiological loading of the ankle joint; joint preservation in asymmetric degenerative arthritis of the ankle. INDICATIONS: Congenital deformities of the distal tibia; acquired deformities of the distal tibia; asymmetric degenerative arthritis with partially preserved cartilage. CONTRAINDICATIONS: Absolute contraindications comprise severe nicotine abuse, Charcot arthropathy, peripheral polyneuropathy, relevant peripheral arterial vessel disease, poor local soft tissue condition, acute infection and extensive cartilage damage grade 3-4 in the Outerbridge classification in the complete joint. SURGICAL TECHNIQUE: Medial and lateral open and closed wedge osteotomies and dome osteotomies of the distal tibia are used, and shortening, lengthening and derotating osteotomies of the fibula. POSTOPERATIVE MANAGEMENT: For 6 weeks, 15-20 kg partial weight-bearing in a below knee cast or a walker orthosis; full weight-bearing depending on osseous healing after 9-12 weeks postoperatively. RESULTS: Between July 2012 and May 2017, 15 patients (10 men, 5 women) underwent a supramalleor osteotomy. Average age was 41.8 years (range 17-63 years) and the retrospective average follow-up was 28.7 months (range 3-47 months). Mean preoperative AOFAS (American Orthopaedic Foot and Ankle Society) hindfoot score was 54.3 (range 26-86) and postoperatively a mean of 74.2 (44-100). Preoperatively, 9 patients had varus malalignment and 6 patients valgus malalignment; overall, 4 patients developed complications requiring surgical intervention (26.7%). Osteosynthetic material was removed in 60% of the patients.

Acetabular defect classification in times of 3D imaging and patient-specific treatment protocols.

Parallel to the rising number of revision hip procedures, an increasing number of complex periprosthetic osseous defects can be expected. Stable long-term fixation of the revision implant remains the ultimate goal of the surgical protocol. Within this context, an elaborate preoperative planning process including anticipation of the periacetabular defect form and size and analysis of the remaining supporting osseous elements are essential. However, detection and evaluation of periacetabular bone defects using an unsystematic analysis of plain anteroposterior radiographs of the pelvis is in many cases difficult. Therefore, periacetabular bone defect classification schemes such as the Paprosky system have been introduced that use standardized radiographic criteria to better anticipate the intraoperative reality. Recent studies were able to demonstrate that larger defects are often underestimated when using the Paprosky classification and that the intra- and interobserver reliability of the system is low. This makes it hard to compare results in terms of defects being studied. Novel software tools that are based on the analysis of CT data may provide an opportunity to overcome the limitations of native radiographic defect analysis. In the following article we discuss potential benefits of these novel instruments against the background of the obvious limitations of the currently used native radiographic defect analysis.

[Treatment of acetabular bone defects in revision hip arthroplasty using the Revisio-System]. / Defektadaptierte Versorgung azetabulärer Knochendefekte mit dem Revisio-System.

BACKGROUND: Many different systems for the management of primary and secondary acetabular defects are available, each with its inherent advantages and disadvantages. The Revisio-System is a press-fit oval mono-block implant that makes a defect-oriented reconstruction and restoration of the center of rotation possible. MATERIAL AND METHODS: In this study, we retrospectively reviewed the outcome of 92 consecutive patients treated with this oval press-fit cup due to periacetabular bone loss. The average follow-up was 58.2 months. Defects were classified according to D'Antonio. There were 39 type II, 38 Type III, and 15 type IV defects. After an average of 4.9 years, the implant survival rate was 94.6% with cup revision as the end point and 89.1% with revision for any reason as the end point. The Harris Hip Score increased from 41.1 preoperatively to 62.3 postoperatively. The mean level of pain measured with the Visual Analogue Scale (VSA) was reduced from 6.9 preoperatively to 3.8 postoperatively. RESULTS: The Revisio-System represents a promising toolbox for defect-orientated reconstruction of acetabular bone loss in revision hip arthroplasty. Our results demonstrate that the implantation of the Revisio-System can result in a good mid-term clinical outcome.

[Gracilis tendon augmented reconstruction of the medial patellofemoral ligament with soft tissue fixation at the patellar insertion site]. / Ersatz des medialen patellofemoralen Ligaments durch autologe Gracilissehne mit implantat- und bohrkanalfreier patellarer Fixation.

OBJECTIVE: Reconstruction of the medial patellofemoral ligament with autologous tendon augmentation and soft tissue fixation at the patellar insertion with resorbable suture material. INDICATIONS: Patellofemoral instability due to insufficiency of the medial passive stabilizers and dysplastic trochlea. CONTRAINDICATIONS: Primary traumatic dislocation of the patella without risk factors for patellar redislocation, severe osteoarthritis of the patellofemoral joint, infection. SURGICAL TECHNIQUE: Diagnostic arthroscopy to evaluate cartilage and shape of trochlea and to treat associated injuries. Harvesting of the gracilis tendon and arming with resorbable suture material. Transfer of the tendon through the medial capsule in the anatomical layer of the MPFL and weaving in u-shape through the capsule and periosteum near the patella. Soft tissue fixation with resorbable suture material. Anatomical reconstruction of the femoral insertion site. Femoral fixation with interference screw. POSTOPERATIVE TREATMENT: For 4 weeks, partial (20 kg) weight bearing with crutches; cast with physiotherapy (limited ROM extension, flexion 0-0-90°). Thereafter free range of motion and full weight bearing. RESULTS: 27 patients (age 12-45 years) with patellofemoral instability underwent reconstruction of the medial patellofemoral ligament. Clinical follow-up was assessed up to 12 months postoperatively. After 1 year, the Kujala and Flandry scores increased from preoperatively 72 points to 95 points and 65.7 points to 89.9 points, respectively. One redislocation was observed. Patient satisfaction was significantly increased at 6 months postoperatively. Reconstruction of the medial patellofemoral ligament shows good clinical results after 12 months.

[Sliding osteotomy of the tibial tuberosity in patellofemoral instability]. / Verschiebeosteotomie der Tuberositas tibiae bei patellofemoraler Instabilität.

OBJECTIVE: The development of a stable patellofemoral joint by distal realignment with normal positioning of the patella. INDICATIONS: Patellofemoral instability with increased tibial tubercle to trochlear groove (TT-TG) distance ≥ 20 mm and higher Caton-Deschamps patellar height index ≥ 1.3. CONTRAINDICATIONS: Open epiphyseal and apophyseal plates of the proximal tibia, normal TT-TG distance with normal patellar height, and high-grade chondral lesions of the patellofemoral joint (ICRS grades 3 and 4). SURGICAL TECHNIQUE: Examination of the knee joint under anesthesia and evaluation of stability and mediolateral translation of the patella. Diagnostic knee arthroscopy and treatment of chondral or osteochondral lesions. Lateral approach to the tibial tuberosity with soft tissue mobilization and exposure of the patellar tendon. Osteotomy is performed in the frontal plane, creating a fragment at least 6 cm long. The tuberosity is slid into the desired position, medially and distally, if necessary, according to preoperative analysis and planning, followed by careful drilling of the posterior tibial cortex and lag screw osteosynthesis. POSTOPERATIVE MANAGEMENT: Partial weight-bearing of 20 kg in a MECRON knee brace for 6 weeks. Mobilization 0/0/90° from the MECRON knee brace without active knee extension. Isometric training of the thigh muscles with the knee fully extended. RESULTS: With meticulous planning and implementation, and in cases of severe trochlear dysplasia combined with medial patellofemoral ligament reconstruction, the technique of sliding osteotomy of the tibial tuberosity has a high success rate.

[Individualized total knee arthroplasty]. / Individualendoprothetik am Kniegelenk.

This article describes the rationale and the surgical technique of patient-specific uni-, bi-, or three-compartmental knee arthroplasty using the second generation (G2) of ConforMIS™ technology. The patient-individual implants and instruments are designed and fabricated based on data from a preoperative computed tomography of the lower limb. The disposable patient-specific drill guides and cutting-jigs are manufactured under consideration of the anatomical and biomechanical axes of the knee joint and mediate efficient pre-navigation of the saw-cuts on the femoral and tibial bone without the need for an additional navigation or balancing device. The surgical technique for all types of knee resurfacement comprises the steps of cartilage removal, knee balancing in extension and flexion, sparing bony cuts, final preparation of femur and tibia, trialling, cementing of components and final choice of tibial insert. The use of individualized three-dimensional image-derived resurfacing implants, as well as personalized single-use instrumentation, facilitates the surgeon to perform an almost anatomical knee resurfacement that has the potential to restore almost normal knee kinematics. The limited data on this novel technology is promising, however long-term clinical data is needed for final evaluation of this technology.

[Damage to implants due to high-frequency electrocautery : analysis of four fractured hip endoprostheses shafts]. / Implantatschädigung durch Einsatz eines Hochfrequenzmessers : Analyse von vier Hüftendoprothesenschaftbrüchen.

In revision surgery of joints, high-frequency electrocauterization instruments are used for homeostasis and dissection of soft tissue. If there is contact of these instruments with the metal implants, flashover can occur. This can lead to thermal microstructural changes in the material and as a consequence may reduce the fatigue strength of the implant. Four cases of hip revision surgeries were analysed. In all cases flashovers occurred and secondarily, the titanium hip endoprosthesis stem broke in the neck section of the prosthesis. The conducted investigations showed that contact between the high-frequency instrument and the anterolateral aspect of the endoprosthesis neck had occurred. Electrothermal implant damage was found in the broken area. If in hip revision surgery the stem is not to be replaced, contact between high-frequency instruments and the metal implant should be avoided.

[Minimally invasive hip arthroplasty - what must be spared?]. / Minimal-invasive Hüftendoprothetik - was muss geschont werden?

The classical surgical approach to the hip joint has been modified in recent years. The development of minimally invasive surgical techniques promised a particularly gentle soft-tissue preparation with significant benefits in postoperative recovery and intraoperative blood loss for patients undergoing total hip arthroplasty (THA). Exact knowledge of the anatomy of the hip joint and the surrounding structures at risk are essential to avoid complications. Each of the main minimally invasive approaches for THA implicates very specific advantages and disadvantages. Knowing these factors, minimally invasive hip surgery can be performed in a soft tissue-friendly manner. The resulting advantages have to be checked for significant clinical evidence.

[Painful hip arthroplasty: a diagnostic algorithm]. / Schmerzhafte Hüftendoprothetik: Ein diagnostischer Algorithmus.

The number of implantations of hip prostheses in Germany is now approximately 190,000 per year. By improving the implants and the development of modern surgical techniques and instruments the revision rate has been significantly reduced. The survival rate of the implants could be further increased in recent years, however, up to 22% of patients complain about persistent pain after hip arthroplasty. The diagnosis of existing pain after total joint replacement of the hip joint to achieve a causal therapy needs a systematic approach because of the heterogeneity of the symptoms and diseases. The etiology of the pain can be joint-associated and also hip joint independent. Often the causes of pain are multifactorial so that a standardized assessment should be conducted using an algorithm. The clarification of pain begins with the history, inspection and palpation followed by a clinical examination. It is then useful to perform radiological imaging followed by invasive procedures if necessary. The exploratory revision is nowadays considered to be obsolete in the literature.

[Total hip replacement in developmental dysplasia: anatomical features and technical pitfalls]. / Hüftgelenkendoprothetik bei kongenitaler Dysplasie: Anatomische Besonderheiten und technische Stolpersteine.

Total hip arthroplasty is the procedure of choice for most patients with advanced, symptomatic osteoarthritis due to congenital dysplasia of the hip. However, the complexity of arthroplasty is significantly increased because of anatomic abnormalities associated with dysplasia of the hip. In addition the relatively young age of patients may affect survival of the implant. From a biomechanical standpoint the primary surgical objective is reconstruction of the anatomical center of rotation. Independent of the pelvic bone stock the socket should be located as near as possible to the anatomical acetabular location. There are various operative strategies to ascertain sufficient stability of the socket. The anterolateral deficiency of the acetabulum can be reconstructed by bulk femoral autografting or bone impaction grafting. Furthermore controlled perforation of the medial wall or implantation of reinforcement rings and oval sockets have been described. Cementless, biological socket fixation shows superior long-term results compared to cemented cups, especially in these young patients. The location of the reconstructed acetabulum and the desired leg length influence the type of femoral reconstruction and in some cases femoral shortening is required. In this article endoprosthetic reconstructive options for developmental dysplasia of the hip are discussed depending on the femoral and acetabular deformity.

[Periprosthetic fractures after total hip arthroplasty : classification, diagnosis and therapy strategies]. / Periprothetische Frakturen bei Hüftendoprothese : Klassifikation, Diagnostik und Therapiestrategien.

The number of periprosthetic fractures following hip replacement is increasing due to longer life expectancy and the rising number of joint replacements. The main causes of periprosthetic fractures include trauma, implant specific factors or loosening of the endoprosthesis. When planning therapy, surgeons should consider specific and general implant- and patient-related risk factors to ensure the best possible treatment. Established classification systems can facilitate preoperative planning. At present, the Vancouver classification system probably comes closest to the ideal, as it considers fracture configuration, stability of the implant and quality of the bone stock. Depending on these factors, therapeutic options include conservative treatment, fracture stabilisation or replacement of the endoprosthesis. The problems associated with periprosthetic fractures of varying etiology and the available treatment options are discussed against the background of the established classification systems.

[Replacement of femoral hip prostheses]. / Femoraler Hüftprothesenwechsel.

Femoral revision of total hip arthroplasty is a technically demanding procedure. Therefore, accurate preoperative planning is essential for good clinical results. With many reconstruction methods available, the decision-making process can be complex. Well established classification systems can facilitate preoperative planning. At the time of revision surgery appropriate implants and instruments have to be available ensuring the possibility of managing operative complications. Primary goals of revision arthroplasty are restoration of the physiological joint biomechanics and primary stable fixation of the revision implant. In consideration of possible repeat revision surgery, cementless stem fixation should be preferred. Modular stems provide significant flexibility in restoring the center of rotation. Depending on the pre-existing femoral defect, osseous grafts can be necessary.The scope and classification systems of femoral osseous defects in revision arthroplasty will be discussed and different treatment options will be outlined, which guide the surgeon in selecting an appropriate method of reconstruction.

Transforming growth factor beta1 and laminin-111 cooperate in the induction of interleukin-16 expression in synovial fibroblasts from patients with rheumatoid arthritis.

OBJECTIVES: In synovial tissues of patients with rheumatoid arthritis (RA), strong expression of laminins and integrins co-localises with increased expression of inflammatory cytokines. Synovial fibroblasts (SF) contribute to the pathogenesis of RA through increased expression of cytokines and chemoattractant factors, one of which is interleukin-16 (IL16). A study was undertaken to investigate the regulatory pathways of IL16 in SF from patients with RA (RA-SF) and osteoarthritis (OA-SF). METHODS: SF were seeded in laminin-coated flasks and activated by the addition of cytokines. The expression of IL16 was investigated by quantitative RT-PCR, immunoblotting and ELISA; its biological activity was determined by a cell migration assay. Cell-matrix interactions were investigated by cell binding and attachment assays. Relevant intracellular signalling pathways were studied by immunoblotting and with pharmacological blocking reagents. RESULTS: Stimulation of SF with transforming growth factor beta(1)(TGF-beta(1)) and growth on laminin-111 (LM-111) significantly increased the expression of IL16. Binding to LM-111 induced significantly more IL16 mRNA in RA-SF than in OA-SF (p<0.05). The IL16 cytokine was detected in supernatants of TGF-beta(1)-activated and in LM-111+TGF-beta(1)-activated RA-SF (38 to 62 pg/ml), but not in supernatants of OA-SF. This IL16 regulation involved p38MAPK, ERK1/2 and SMAD2 signalling, but not NFkappaB. CONCLUSIONS: Binding of RA-SF to LM-111 in the presence of TGF-beta(1) triggers a significant IL16 response and thus may contribute to the infiltration of CD4+ lymphocytes into synovial tissues. This mode of IL16 induction represents a novel pathway leading to IL16 production in RA-SF but not in OA-SF, which operates independently of NFkappaB signalling.

Generation and characterization of a human acellular meniscus scaffold for tissue engineering.

Meniscus tears are frequent indications for arthroscopic evaluation which can result in partial or total meniscectomy. Allografts or synthetic meniscus scaffolds have been used with varying success to prevent early degenerative joint disease in these cases. Problems related to reduced initial and long-term stability, as well as immunological reactions prevent widespread clinical use so far. Therefore, the aim of this study was to develop a new construct for tissue engineering of the human meniscus based on an acellular meniscus allograft. Human menisci (n = 16) were collected and acellularized using the detergent sodium dodecyl sulfate as the main ingredient or left untreated as control group. These acellularized menisci were characterized biomechanically using a repetitive ball indentation test (Stiffness N/mm, residual force N, relative compression force N) and by histological (hematoxylin-eosin, phase-contrast) as well as immunohistochemical (collagen I, II, VI) investigation. The processed menisci histologically appeared cell-free and had biomechanical properties similar to the intact meniscus samples (p > 0.05). The collagen fiber arrangement was not altered, according to phase-contrast microscopy and immunohistochemical labeling. The removal of the immunogenic cell components combined with the preservation of the mechanically relevant parts of the extracellular matrix could make these scaffolds ideal implants for future tissue engineering of the meniscus.

[Metal-on-metal hybrid hip resurfacing. Development and current state]. / Der Metall-Metall-Hybridoberflächenersatz des Hüftgelenks. Entwicklung und aktueller Stand.

Worldwide the employment of surface replacements using metal-on-metal components as an option, particularly for the young and active patient, has gained broad acceptance. Part of the attraction for hip resurfacing is its conservative nature as a prosthetic solution for hip arthritis. It is anatomical, replicating the normal hip and limb length, preserving proximal femoral bone, and is a truly minimally bone invasive approach with excellent outcome of joint function. The purpose of this article is to show the data of 1,000 Conserve(c) Plus hybrid metal-on-metal prostheses in a consecutive study of 1,140 patients with a follow-up of 5.6 years. The current Kaplan and Meier survival estimates of the prosthesis, using any conversion to total hip replacement as the end point, were 98.1% at 3 years [95% confidence interval (CI): 96.8-98.9%], 96.7% at 4 years (95% CI: 94.8-97.8%), and 95.2% at 5 years (95% CI: 93.0-96.8%). The mean postoperative Harris hip score was 93.3. The current state of metal-on-metal surface replacement is positive. The new generation of hip resurfacing has a lot of improvements. The purpose of this review of the procedure is to point out the definite improvements from earlier designs using polyethylene as well as to highlight the overall results and durability achieved by one surgeon's extensive experience and to assess the results from other series and centers. We also want to point out the areas where further investigation is needed.

[Heel pain]. / Von der Achillessehnen-Tendinitis bis zur Knochenzyste. Fersenschmerz--was steckt dahinter?

Upper and plantar heel pains are differentiated from one another. Plantar heel pain is usually caused by plantar fasciitis. A heel spur is a side effect and is not related to the cause of the symptoms. Upper heel pain is mostly caused by tendonitis of the Achilles tendon or Haglund exostosis. Only through an exact diagnosis is an adequate and usually conservative therapy possible. If the conservative therapy should fail, it is nevertheless important to clarify the indication for surgery to prevent the problems from becoming chronic.

[Expression analysis of different collagens and cytokines in cartilage cells derived from arthrotic hip and knee joints]. / Expressionsanalyse verschiedener Kollagene und Zytokine in Knorpelzellen aus arthrotisch veränderten Hüft- und Kniegelenken.

AIM: Osteoarthritis (OA) is characterized by an irreversible destruction of articular cartilage. This is associated with a multiplicity of factors, causing an increased catabolic metabolism in cartilage. However, the prevalence of the OA is very variable in different joints. Therefore , we conducted a comparative analysis of chondrocytes derived from knee and hip joints with respect to their expression of inflammatory factors, such as IL-1beta, IL-1beta-receptorantagonist, iNOS, components of cartilage matrix (collagen I, II, and VI) as well as vimentin. METHODS: Different cytokines and proteins were detected by immune-histochemical staining of cartilage samples ex vivo. Further, chondrocytes were isolated from OA knee and hip joints, expanded in vitro and gene expression patterns were investigated by quantitative RT-PCR. RESULTS: Chondrocytes from knee and hip joints of OA patients express collagenes I, II and VI, IL-1beta and IL-1beta-RA, iNOS as well as Vimentin. A significant difference in gene expression patterns was not found in chondrocytes from the hip joints versus the knee joint ex vivo or in primary culture cells in vitro. However, in vitro the expression of type I collagen exceeded the expression of type II collagen. The IL-1beta-expression was high ex vivo, remained low during primary culture but was significantly elevated after primary culture in hip chondrocytes. CONCLUSION: Osteoarthritic gene expression patterns in cells derived from hip or knee joints ex vivo and in primary culture were not significantly different. We conclude that the rather frequent occurrence of OA in these joints in comparison to the ankle joint may be associated with a close physiological relation of cells in these joints. However, future studies which will include ankle cartilage must be investigated in further detail.

[Characterisation of human meniscus cells]. / Charakterisierung von humanen Meniskuszellen.

AIM: The meniscus of the human knee joint has an important function for the shock absorption, stability and power transmission from the upper to the lower leg. After meniscus injury often a partial or complete resection is necessary. Only injuries in the outer third may heal spontaneously or upon primary suture due to the vascularisation in these segments. After partial or total meniscectomy osteoarthritis of the knee joint is common in a large number of patients. The goal of our investigations was to establish meniscus cell cultures and to characterise the fibrochondrocytes (meniscus cells) in vitro. METHODS: We examined the expression of different growth factors, cytokines and proteins in human menisci from surgical preparations using immunohistochemistry and RT-PCR analysis. RESULTS: Human meniscus cells express the collagens I , II, III, and VI, the matrix metalloproteinases-1, -2, -3, -8, and -13, BMP-2, and -4, TGFbeta1, VEGF, IGF-I, and -II, FGF-2, endostatin, iNOS, vimentin, TIMP-1, and -2, aggrecan, IL-1beta, IL-6, and IL-18. Staining with the monoclonal antibody AS.02 in all examined cells confirmed their mesenchymal origin. CONCLUSION: New strategies for the treatment of meniscus damage can be derived from these results and further advances for the tissue engineering of meniscus tissue can be obtained.

Cell-based treatment of osteochondral defects in the rabbit knee with natural and synthetic matrices: cellular seeding determines the outcome.

INTRODUCTION: Matrix-associated transplantation of cartilage constructs is an appealing method in cartilage repair. Three different matrices seeded with allogenic chondrocytes were compared in an osteochondral defect model in the rabbit. An investigation was conducted to identify the best matrix for cell-based treatment of osteochondral defects in the rabbit knee joint. MATERIALS AND METHODS: Osteochondral defects (diameter 3 mm) were created in the trochlea and the femoral condyles of 33 New Zealand White rabbits, which were then treated with bioartificial cartilage constructs. The cartilage constructs were created in vitro using three different resorbable carrier materials (two fleece matrices: one of PLLA, and one composite of polydioxanon/ polyglactin, as well as one consisting of lyophilized dura) cultured with isolated allogenic chondrocytes. The defects were evaluated macroscopically, by histological and immunhistological techniques, and by scanning electron microscopy after 6 weeks, 6 months, and 12 months. The chondrocyte-seeded constructs were compared to defects treated with carrier material alone as well as to untreated control defects. RESULTS: There was a significant improvement in defect repair quality in the transport materials, which were cultured with chondrocytes prior to implantation (P < 0.0005). No significant differences were observed between the three carrier matrices, and no significant differences were seen between the unseeded matrices and the untreated control defects. CONCLUSION: There is no difference in the outcome between the three tested matrices in the treatment of osteochondral defects in the rabbit knee. The results of this in vitro experiment are promising and with refinement may lead to useful clinical therapies.