Comparison of fresh osteochondral autografts and allografts: a canine model

BACKGROUND: Osteochondral autografts and allografts have been widely used in the treatment of isolated grade IV articular cartilage lesions of the knee. However, the authors are not aware of any study that has prospectively compared fresh osteochondral autografts to fresh allografts with regard to imaging, biomechanical testing, and histology. HYPOTHESIS: The imaging, biomechanical properties, and histologic appearance of fresh osteochondral autograft and fresh allograft are similar with respect to bony incorporation into host bone, articular cartilage composition, and biomechanical properties. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen adult dogs underwent bilateral knee osteochondral graft implantation after creation of an Outerbridge grade IV cartilage defect. One knee received an autograft, and the contralateral knee received a fresh allograft. Nine dogs were sacrificed at 3 months, and 9 dogs were sacrificed at 6 months. Graft analysis included gross examination, radiographs, magnetic resonance imaging, biomechanical testing, and histology. RESULTS: Magnetic resonance imaging demonstrated excellent bony incorporation of both autografts and allografts. Biomechanical testing demonstrated no significant difference between autografts versus allografts versus control at 3 or 6 months (P = .36-.91). A post hoc calculation showed 80% power to detect a 30% difference between allograft and control. Histologic examination showed normal cartilage structure for both autografts and allografts. CONCLUSION: Fresh osteochondral autograft and fresh allograft tissues are not statistically different with respect to bony incorporation, articular cartilage composition, or biomechanical properties up to 6 months after implantation. CLINICAL RELEVANCE: The use of fresh allograft tissue to treat osteochondral defects eliminates morbidity associated with harvesting autograft tissue without compromising the results of the surgical procedure.     

Mechanical behavior of articular cartilage after osteochondral autograft transfer in an ovine model

BACKGROUND: Grafting of autologous hyaline cartilage and bone for articular cartilage repair is a well-accepted technique. Although encouraging midterm clinical results have been reported, no information on the mechanical competence of the transplanted joint surface is available. HYPOTHESIS: The mechanical competence of osteochondral autografts is maintained after transplantation. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral defects were filled with autografts (7.45 mm in diameter) in one femoral condyle in 12 mature sheep. The ipsilateral femoral condyle served as the donor site, and the resulting defect (8.3 mm in diameter) was left empty. The repair response was examined after 3 and 6 months with mechanical and histologic assessment and histomorphometric techniques. RESULTS: Good surface congruity and plug placement was achieved. The Young modulus of the grafted cartilage significantly dropped to 57.5% of healthy tissue after 3 months (P < .05) but then recovered to 82.2% after 6 months. The aggregate and dynamic moduli behaved similarly. The graft edges showed fibrillation and, in some cases (4 of 6), hypercellularity and chondrocyte clustering. Subchondral bone sclerosis was observed in 8 of 12 cases, and the amount of mineralized bone in the graft area increased from 40% to 61%. CONCLUSIONS: The mechanical quality of transplanted cartilage varies considerably over a short period of time, potentially reflecting both degenerative and regenerative processes, while histologically signs of both cartilage and bone degeneration occur. CLINICAL RELEVANCE: Both the mechanically degenerative and restorative processes illustrate the complex progression of regeneration after osteochondral transplantation. The histologic evidence raises doubts as to the long-term durability of the osteochondral repair.     

Weightbearing ovine osteochondral defects heal with inadequate subchondral bone plate restoration: implications regarding osteochondral autograft harvesting

Purpose

It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal. Contact pressure and edge loading at donor sites may play a role in the healing process. It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges, resulting in incomplete and irregular repair of the subchondral bone plate.

Methods

To simulate edge loading, large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles. After killing at 3 and 6?months, osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restoration.

Results

Osteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition. Unfilled area decreased significantly from 3 to 6 months (P?=?0.004), whereas bone content increased (n.s.). Complete but irregular subchondral bone plate restoration occurred in ten animals. In fourteen animals, an incomplete subchondral bone plate was found. Further common findings included cavitary lesion formation, degenerative cartilage changes and cartilage and subchondral bone collapse.

Conclusions

Osteochondral defect healing starts with subchondral bone plate restoration. However, after 6 months, incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common. Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically, as similar changes are also present in humans.

Level of evidence

Prognostic study, Level III.     

Fresh osteochondral allografting

The treatment of articular cartilage defects in the knee is a difficult challenge. Fresh, small-fragment osteochondralallografting is a technique involving the transplantation of articular (hyaline) cartilage into the defective joint surface. The graft, a composite of living cartilage and a thin layer of underlying subchondral bone, provides a mature matrix with viable chondrocytes along with an osseous component that provides a surface for fixation and integration with the host. Fresh allografting is particularly useful in larger lesions (greater than 2 cms) or when associated osseous defects are present. Clinical experience with fresh osteochondral allografts now extends over 2 decades. Up to 90% of individuals treated for femoral condyle lesions are improved. The allograft tissue appears well tolerated by the host, with documented long-termsurvival of chondrocytes and intact matrix. Successful clinical outcomes have established fresh osteochondrall allografting as an appropriate alternative in the treatment of chondral and osteochondral lesions of the knee.     

Disease-specific clinical problems associated with the subchondral bone

The subchondral bone is involved in a variety of diseases affecting both the articular cartilage and bone. Osteochondral defects in distinct locations and of variable sizes are the final results of different etiologies. These include traumatic osteochondral defects, osteochondritis dissecans, osteonecrosis, and osteoarthritis. Traumatic osteochondral defects are caused by osteochondral fractures, separating an osteochondral fragment that includes articular cartilage and both subchondral and trabecular bone from the joint surface. In osteochondritis dissecans, the disease originates in the subchondral bone and secondarily affects the articular cartilage. Location, stage, size, and depth of osteochondral lesions play a role in the treatment of traumatic osteochondral defects and osteochondritis dissecans. Surgical options include fragment refixation, transplantation of osteochondral autografts, or bone restoration by impacted cancellous bone grafts combined with autologous chondrocyte transplantation. An insufficiency fracture of the subchondral bone may be the initiating factor of what was formerly believed to be a spontaneous osteonecrosis of the knee (SPONK). Recent histopathological studies suggest that each stage of SPONK reflects different types of bone repair reactions following a fracture of the subchondral bone plate. Osteoarthritis is a disease that does affect not only the articular cartilage, but also the subchondral bone. Reconstructive surgical techniques aim at preserving joint function, inducing fibrocartilaginous repair, and at correcting malalignment. This review summarizes the current status of the clinical treatment of traumatic osteochondral defects, osteochondritis dissecans, osteonecrosis, and osteoarthritis as they affect the subchondral bone region and its adjacent structures.     

Biomechanical and histological evaluation of osteochondral transplantation in a rabbit model

BACKGROUND: Biomechanical and histological properties of osteochondral transplantation have not been extensively examined. HYPOTHESIS: Osteochondral grafts have properties similar to native articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: A 2.7 mm (diameter) x 4.0 mm (depth) osteochondral defect was created in 17 New Zealand white rabbit knees. An osteochondral graft, harvested from the contralateral knee, was transplanted into the defect. Eight rabbits were sacrificed each at 6 and 8 weeks. RESULTS: The 12-week grafts (1213.6 +/- 309.0 N/mm) had significantly higher stiffness than the 6-week grafts (483.1 +/- 229.1 N/mm; P <.001) and of normal cartilage (774.8 +/- 117.1 N/mm; P <.003). Stiffness of the 6-week grafts was significantly lower than normal cartilage (P <.036). At all time points, full-thickness defects had significantly lower stiffness than normal cartilage (P <.001). Histologically, transplanted grafts scored significantly higher than the full-thickness defects (P <.001). The defects showed inconsistent, fibrocartilage healing. The grafts demonstrated cartilage viability, yet with a persistent cleft between the graft and host. CONCLUSIONS: Osteochondral transplants undergo increased stiffness in the short term, with evidence of structurally intact grafts. Clinical Relevance: Osteochondral transplantation may be a viable treatment option; however, long-term investigation on graft function is necessary.     

The use of a single osteochondral autograft plug in the treatment of a large osteochondral lesion in the femoral condyle: an experimental study in sheep

BACKGROUND: The use of osteochondral autograft plugs can be restricted because of limited amount of donor material. HYPOTHESIS: A small osteochondral autograft plug placed in the center of a large defect in a sheep femoral condyle will yield results superior to either an untreated or a bone-grafted defect. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve adult sheep underwent bilateral hindlimb surgery. On 1 limb, a 6-mm circular osteochondral autograft plug was placed in the center of a 10-mm circular defect in the medial femoral condyle. The gap between the plug and the condyle was filled with bone graft. On the contralateral side, the defect was either left untreated or filled with bone graft (control specimens). Animals were studied at 6 and 12 months under gross examination, high-resolution radiography, and histologic evaluation. RESULTS: At 6 months, 4 of 6 plugs healed and showed good maintenance of the joint surface and cartilage viability in the plugs. One plug fractured and resorbed, and 1 plug settled but healed. At 1 year, all 5 plugs healed, 1 having settled slightly (1 animal died earlier). The plug specimens showed better maintenance of the condyle contour at both times, and the central plug had hyaline-appearing cartilage. The control specimens were more irregular, had a fibrocartilage fill, and appeared flatter, although no gross cavitation or collapse was indicated. Composite cartilage scores on histologic evaluation were significantly higher for the plug specimens after 6 months (P = .02) and 1 year (P = .036) compared with controls. CONCLUSION: At 6 months and 1 year, a 6-mm osteochondral plug placed in a 10-mm defect better preserved the articular surface and contour of the condyle compared to untreated or bone-grafted defects. CLINICAL RELEVANCE: Osteochondral autograft plugs may be able to treat larger articular lesions without complete fill of the defect.     

Epidemiology and imaging of the subchondral bone in articular cartilage repair

Articular cartilage and the subchondral bone act as a functional unit. Following trauma, osteochondritis dissecans, osteonecrosis or osteoarthritis, this intimate connection may become disrupted. Osteochondral defects—the type of defects that extend into the subchondral bone—account for about 5% of all articular cartilage lesions. They are very often caused by trauma, in about one-third of the cases by osteoarthritis and rarely by osteochondritis dissecans. Osteochondral defects are predominantly located on the medial femoral condyle and also on the patella. Frequently, they are associated with lesions of the menisci or the anterior cruciate ligament. Because of the close relationship between the articular cartilage and the subchondral bone, imaging of cartilage defects or cartilage repair should also focus on the subchondral bone. Magnetic resonance imaging is currently considered to be the key modality for the evaluation of cartilage and underlying subchondral bone. However, the choice of imaging technique also depends on the nature of the disease that caused the subchondral bone lesion. For example, radiography is still the golden standard for imaging features of osteoarthritis. Bone scintigraphy is one of the most valuable techniques for early diagnosis of spontaneous osteonecrosis about the knee. A CT scan is a useful technique to rule out a possible depression of the subchondral bone plate, whereas a CT arthrography is highly accurate to evaluate the stability of the osteochondral fragment in osteochondritis dissecans. Particularly for the problem of subchondral bone lesions, image evaluation methods need to be refined for adequate and reproducible analysis. This article highlights recent studies on the epidemiology and imaging of the subchondral bone, with an emphasis on magnetic resonance imaging.     

Aspects of Magnetic Resonance in the surgical treatment of osteochondral lesions of the knee

AIM: To assess the magnetic resonance (MR) appearance of knee cartilage chondroplasty procedures and their evolution in order to evaluate the usefulness of the method in monitoring postoperative rehabilitation. MATERIALS AND METHODS: Sixty-two patients treated with knee chondroplasty for high-grade cartilage injuries (Noyes' stages II and III) were examined with MR. Forty patients were treated with abrasion chondroplasty, fifteen with osteochondral graft in the injury site and seven with the matrix-induced autologous chondrocyte transplant technique. All patients were operated on by the same orthopaedic team and examined with the same MR protocol. The MR follow-up was performed six months and one year after surgery in the patients treated with abrasion chondroplasty and osteochondral graft, and one week, three months and one year after surgery in the patients treated with cartilage transplant. In the patients treated with abrasion chondroplasty we assessed the fibrocartilage repair and the subchondral bone features, in the patients treated with osteochondral graft we examined the cartilage, the subchondral bone and the graft borders, while in the patients treated with cartilage transplant we evaluated the features and the evolution of the transplant and the subchondral bone. Arthrosynovitis was assessed in all patients. In seven patients a cartilage repair biopsy was performed in arthroscopy. RESULTS: In all the patients MR imaging proved useful in monitoring the chondroplasty. In the patients treated with abrasion chondroplasty the cartilage repair appeared as a hypointense non-homogeneous irregular strip of tissue that replaced the articular surface. The subchondral bone was sclerotic with some geodes. In the later examination the repair was unchanged. In the patients treated with osteochondral graft the articular cartilage was similar to the adjacent hyaline cartilage, although more non-homogeneous. The subchondral bone was sclerotic and in three cases oedematous. In four cases the graft extended beyond the articular border. In the cartilage transplant the matrix appeared as a hypointense stripe after a week due to hydration and it had thinned with signal reduction in the later follow-ups. In the cases with unfavourable clinical evolution the subchondral bone was oedematous and sclerotic in the later examinations. In the cases with unfavourable clinical evolution there was moderate arthrosynovitis, regardless of the chondroplasty technique performed. CONCLUSIONS: MR imaging is useful for monitoring the maturation and the integration of knee chondroplasty and can be proposed as a replacement of arthroscopy for the assessment of postoperative rehabilitation.     

Large osteochondral defects of the femoral condyle: press-fit transplantation of the posterior femoral condyle (MEGA-OATS)

BACKGROUND AND AIMS: Large osteochondral defects in the weight-bearing zone of the knee remain a challenging therapeutic problem. Surgical options include drilling, microfracturing, and transplantation of osteochondral plugs but are often insufficient for the treatment of large defects of the femoral condyle. PATIENTS AND METHODS: Large osteochondral defects of the femoral condyle (mean defect size 7.2 cm(2) range 3-20) were treated by transplantation of the autologous posterior femoral condyle. Between 1984 and 2000, 29 patients were operated on: in 22 the medial, in 6 the lateral femoral condyle, and in one the trochlear groove was grafted. Thirteen patients underwent simultaneous high tibial valgus osteotomy. In the first series (1984-1999) the graft was temporarily fixed with a screw ( n=12), but from 1999 we used a newly developed press-fit technique ( n=17) avoiding screw fixation of the graft. The operative technique comprising graft harvest, defect preparation, transplantation, and fixation is described. Patients were clinically evaluated using the Lysholm score, and magnetic resonance imaging with intravenous contrast was performed 6 and 12 weeks after surgery (mean follow-up 17.7 months (range 3-46). RESULTS: Pain and swelling were reduced in 26 patients. Three patients of the first series reported persistent problems and were subjectively not satisfied. The mean Lysholm score rose from preoperatively 52 to 77 points after 3 months, 74 after 6, 88 after 12, and 95 after 18. Magnetic resonance imaging showed good graft viability in all cases. We saw one arthrofibrosis after 6 months but noted no problems related to the loss of the missing posterior condyle. CONCLUSION: Large osteochondral defects of the femoral condyle can be treated by transplantation of the autologous posterior femoral condyle. The use of only one osteochondral piece renders better approximation of the femoral cartilage curvature and thus joint congruence than in mosaic plasty. However, whether loss of the posterior condyle has a long-term negative impact on the knee joint remains to be elucidated.     

Effects of small incongruities in a sheep model of osteochondral autografting

BACKGROUND: Exact reconstruction of an osteochondral defect by autogenous transplantation (mosaicplasty) is difficult given the variation in joint surface contour. Clinical and experimental studies do not show the extent to which incongruity can be tolerated in autografting. HYPOTHESIS: Grafted articular cartilage will hypertrophy to correct the incongruity created by recession of the transplanted surface. STUDY DESIGN: Controlled laboratory study. METHODS: To test the response of grafts to incongruities, osteochondral autografts were transplanted from the trochlea to the femoral condyle in adult male sheep stifle joints. In groups of 6 animals, graft surfaces were placed flush, countersunk 1 mm or countersunk 2 mm, then histologically analyzed 6 weeks after surgery. Cartilage thickness, condition of the articular surfaces, and preservation of hyaline characteristics were the primary features compared. RESULTS: Bony union, vascularization, and new bone formation were present in all grafts. Cartilage-to-cartilage healing did not occur. In flush specimens, cartilage changed minimally in thickness and histologic architecture. The specimens countersunk 1 mm demonstrated significant cartilage thickening (54.7% increase, P <.05). Chondrocyte hyperplasia, tidemark advancement, and vascular invasion occurred at the chondroosseous junction, and the surface remained smooth. Cartilage necrosis and fibrous overgrowth were observed in all grafts countersunk 2 mm. CONCLUSIONS: Minimally countersunk autografts possess a capacity for remodeling that can correct initial incongruities while preserving hyaline characteristics. Grafts placed deeper do not restore the contour or composition of the original articular surface. CLINICAL RELEVANCE: If preservation of normal hyaline cartilage is the objective, thin grafted articular cartilage can remodel, but the tolerance for incongruity is limited and probably less than that reported for an intra-articular fracture.     

Histological evaluation of juvenile osteochondritis dissecans of the knee: a case series

Osteochondritis dissecans (OCD) is an acquired, potentially reversible idiopathic disease of subchondral bone resulting in delamination and sequestration. Although juvenile-type OCD lesions typically appear stable on superficial examination, conservative treatment results in cure in approximate 50% of patients. We hypothesized that juvenile-type OCD lesions exhibit an underlying instability despite stability at the articular surface and this underlying instability might underlie the lack of effectiveness of conservative treatment. In this study, osteochondral cylindrical tissue samples obtained from stable juvenile OCD lesions located at the medial femoral condyle (classical site) were examined. Eight patients with symptomatic juvenile-type OCD at the classical site underwent arthroscopy. Osteochondral cylindrical tissue samples were obtained from the central portion using a biopsy needle. The samples underwent macroscopic and microscopic examination. All cylindrical samples demonstrated macroscopic separation. On microscopic examination, no degenerative changes in articular cartilage and no bone necrosis were observed. Histological examination revealed two distinct patterns in the samples: (1) thick homogeneous hyaline cartilage alone with little fibrous tissue surrounding areas of separation and (2) nearly normal, thin hyaline cartilage above a mixed layer of hyaline cartilage and subchondral trabeculae and fibrous/fibro-cartilaginous tissue at the areas of separation, indicating delayed or nonunion. Pathological findings in stable juvenile OCD lesions indicate an underlying instability at deeper layers of articular cartilage and poor healing at areas of separation. Improved knowledge of the histology of juvenile-type OCD lesions may support surgical treatment. Early marrow stimulation and/or fixation may be the treatment of choice to promote healing even in macroscopically stable juvenile-type OCD lesions.     

Autologous chondrocyte implantation: Prospective MRI evaluation with clinical correlation

PURPOSE: This study was done to assess the progression of cartilage repair after autologous chondrocyte implantation (ACI) with magnetic resonance imaging (MRI) and to correlate the findings with the clinical outcome. MATERIALS AND METHODS: Forty-one patients (mean age 30 years) affected by chondral defects of the knee (27 patients) and ankle joint (14 patients) who underwent arthroscopic autologous osteochondral grafting were studied 6 months and 1 year postoperatively with MRI. Cartilage repair after chondrocyte implantation was studied by assessing the degree of defect filling, graft integration, graft signal intensity, integrity of the subchondral lamina and trabecular oedema underneath the graft. MR findings were correlated with clinical data. RESULTS: Postoperative MRI evaluation at 6 months demonstrated complete filling of the osteochondral defect in 12/41 cases, complete integration in 18/41, mild hyperintensity in 28/41, intact subchondral lamina in 38/41 and trabecular oedema in 11/41. Postoperative MRI evaluation at 1 year demonstrated complete filling of the osteochondral defect in 9/41 patients, complete integration in 22/41, mild hyperintensity in 23/41, intact subchondral lamina in 36/41 and trabecular oedema in 8/41. Filling of the osteochondral defect and incomplete integration, nonintact subchondral lamina, high signal intensity and absence of oedema were found to correlate with worse clinical-functional outcomes. CONCLUSIONS: MRI shows direct prognostic signs of the clinical outcome of ACI.     

Treatment algorithm for osteochondral injuries of the knee

The treatment of osteochondral fractures and OCD lesions in the knee is controversial. Many new procedures and techniques have been developed recently to address osteochondral lesions, indicating that no single procedure is accepted universally. Our treatment algorithm is based on the age of the patient, skeletal maturity, and the presence of adequate subchondral bone attached to the chondral lesion. Most nondisplaced lesions in the patient with open physes will heal with conservative treatment. The onset of skeletal maturity indicates a need for a more aggressive treatment approach. If adequate cortical bone is attached to the fragment, drilling of stable lesions, or drilling with fixation of unstable or loose fragments is appropriate. Autologous bone graft can be necessary to stimulate healing and properly reconstruct the subchondral bony contour. For failed fixation attempts or lesions not amenable to fixation, each treating surgeon must be proficient and comfortable with an articular surface reconstruction technique. The goal for the reconstructive procedure, to produce a smooth gliding articular surface of hyaline or hyaline-like cartilage, is possible using current techniques including mosaicplasty, osteochondral allograft transplantation, and autologous chondrocyte transplantation. Débridement, drilling, microfracture, and abrasion chondroplasty have been shown to result in fibrocartilage with inferior mechanical properties when compared with hyaline cartilage. No long-term studies have been published, however, to confirm the benefits of replacing osteochondral defects with hyaline cartilage rather than fibrocartilage. Although the results of many reconstructive procedures are quite encouraging with early follow up, the ultimate goal is to prevent long-term degenerative arthritis. Only well-designed prospective studies with long-term follow up will determine the adequacy of these procedures in reaching the ultimate goal. This treatment algorithm is based on the senior author's (WGC) experience with the complex dilemma of osteochondral lesions of the knee.     

Osteochondral autograft transplantation for osteochondritis dissecans of the elbow in juvenile baseball players: minimum 2-year follow-up

BACKGROUND: Osteochondral autografts have recently become popular to treat articular cartilage defects, and they are used for unstable osteochondritis dissecans lesions as a means of biological fixation. PURPOSE: To evaluate the clinical results of osteochondral autograft transfer for osteochondritis dissecans of the elbow. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Osteochondral autograft transfer was performed on 18 baseball players (mean age, 13.6 years) with osteochondritis dissecans of the elbow. These included 9 lesions that were grade 3 (separated but in situ) and 9 lesions that were grade 4 (displaced fragment with osteochondral defect) based on magnetic resonance imaging. All patients were evaluated with a scoring system, radiographs, and magnetic resonance imaging, with the mean follow-up at 3.5 years. RESULTS: In patients with grade 3 lesions, the subjective score was increased, but the objective score did not change. Six of 9 patients returned to their previous sports performance levels. One quit baseball because of academic reasons, 1 changed his position, and 1 changed to softball. In patients with grade 4 lesions, both subjective and objective scores were increased significantly. All but 1 patient returned to their previous sports performance levels. In the 3 grade 4 lesions with a wide osteochondral defect, the irregularity of the articular surface remained on magnetic resonance imaging. CONCLUSION: Osteochondral autograft transplantation is a useful treatment for reattachment of the lesion as well as osteochondral resurfacing of elbow osteochondritis dissecans.     

A cadaveric analysis of contact stress restoration after osteochondral transplantation of a cylindrical cartilage defect

Osteochondral transplantation is a successful treatment for full-thickness cartilage defects, which without treatment would lead to early osteoarthritis. Restoration of surface congruency and stability of the reconstruction may be jeopardized by early mobilization. To investigate the biomechanical effectiveness of osteochondral transplantation, we performed a standardized osteochondral transplantation in eight intact human cadaver knees, using three cylindrical plugs on a full-thickness cartilage defect, bottomed on one condyle, unbottomed on the contralateral condyle. Surface pressure measurements with Tekscan pressure transducers were performed after five conditions. In the presence of a defect the border contact pressure of the articular cartilage defect significantly increased to 192% as compared to the initially intact joint surface. This was partially restored with osteochondral transplantation (mosaicplasty), as the rim stress subsequently decreased to 135% of the preoperative value. Following weight bearing motion two out of eight unbottomed mosaicplasties showed subsidence of the plugs according to Tekscan measurements. This study demonstrates that a three-plug mosaicplasty is effective in restoring the increased border contact pressure of a cartilage defect, which may postpone the development of early osteoarthritis. Unbottomed mosaicplasties may be more susceptible for subsidence below flush level after (unintended) weight bearing motion.     

Autologous osteochondral grafts in the treatment of cartilage defects of the knee joint

Autologous osteochondral grafting (mosaicplasty) was performed on 18 patients with grade IV cartilage defects of the knee joint. The average age of these 12 men and 6 women was 36 years, follow-up time was 27.2 months and defect size was 252 mm² (18×14 mm). After plain anteroposterior and lateral radiographs and MRI (STIR sequence) examination, diagnostic arthroscopy was performed, followed by autologous osteochondral grafting, avoidance of weight bearing for 6–8 weeks, physiotherapy and continuous passive motion. All patients showed, radiologically (MRI), a full coverage of the defect with articular surface congruity postoperatively. The postoperative ICRS score was normal for 12 and nearly normal for 6 patients. Seven patients showed early persistent joint effusion for an average of 5.3 months. Hyaline-like cartilage coverage was found in four patients on second-look arthroscopy. The transplantation of autologous osteochondral grafts is being applied in an effort to reconstruct the affected articular surface with properties similar to those of hyaline cartilage. This method retains the integrity and function of a damaged joint, providing promising results in terms of preventing the development of early arthritis in young patients.     

MR imaging of osteochondral grafts and autologous chondrocyte implantation

Surgical articular cartilage repair therapies for cartilage defects such as osteochondral autograft transfer, autologous chondrocyte implantation (ACI) or matrix associated autologous chondrocyte transplantation (MACT) are becoming more common. MRI has become the method of choice for non-invasive follow-up of patients after cartilage repair surgery. It should be performed with cartilage sensitive sequences, including fat-suppressed proton density-weighted T2 fast spin-echo (PD/T2-FSE) and three-dimensional gradient-echo (3D GRE) sequences, which provide good signal-to-noise and contrast-to-noise ratios. A thorough magnetic resonance (MR)-based assessment of cartilage repair tissue includes evaluations of defect filling, the surface and structure of repair tissue, the signal intensity of repair tissue and the subchondral bone status. Furthermore, in osteochondral autografts surface congruity, osseous incorporation and the donor site should be assessed. High spatial resolution is mandatory and can be achieved either by using a surface coil with a 1.5-T scanner or with a knee coil at 3 T; it is particularly important for assessing graft morphology and integration. Moreover, MR imaging facilitates assessment of complications including periosteal hypertrophy, delamination, adhesions, surface incongruence and reactive changes such as effusions and synovitis. Ongoing developments include isotropic 3D sequences, for improved morphological analysis, and in vivo biochemical imaging such as dGEMRIC, T2 mapping and diffusion-weighted imaging, which make functional analysis of cartilage possible.     

移植基质诱导的自体软骨细胞修复关节软骨缺损临床研究

 目的 探讨基质诱导的自体软骨细胞移植修复关节软骨缺损的方法与疗效.方法 2004年11月～2006年11月,对7例膝关节软骨炎患者行关节镜取软骨、基质诱导自体软骨细胞移植(Matrix-induced Autologous chondrocyte implantation,MACI)膜植入术.对患者行MRI检查确定损伤位置,并进行IKDC2000评分.术后按照特定的康复计划进行循序渐进的功能锻炼.结果 随访时间6个月到24个月.术后半年多数患者各项症状逐渐消失,IKDC2000评分大部分增高.复查MRI和关节镜,显示原来缺损的关节软骨已基本修复,并伴有软骨下骨的修复.结论 与传统自体软骨细胞移植(Autologous chondrocyte implantation,ACI)技术相比,利用MACI技术修复软骨缺损具有术后恢复时间短、操作简便、创伤小、生成更多透明软骨等优点,具有良好的应用前景.