Abstract
Interest in the treatment of articular cartilage lesions has grown in recent decades because of promising results obtained with the development of new therapeutic options. Whereas reparative treatments are mostly directed at the recruitment of bone marrow cells to obtain potential cartilage precursors and allow formation of only a fibrous-cartilaginous tissue, 25,27 the bioengineered approach aims to regenerate the damaged tissue and restore a biologically and biomechanically valid articular surface.
The clinical use of autologous chondrocyte transplantation has yielded encouraging clinical results, especially in the femoral condyle, 31 which have to be weighed against the number of problems that can be observed with the standard autologous chondrocyte implantation methods, such as surgical complexity and biological problems related to the cell culture. 16 To address these problems, the so-called second-generation autologous chondrocyte implantation technique was developed, based on the use of biodegradable polymers as temporary scaffolds for the in vitro growth of living cells and their subsequent transplantation into the defect site. However, the results obtained for the treatment of cartilage lesions are still controversial. A satisfactory clinical outcome 18 at a medium-term follow-up has been reported for second-generation autologous chondrocyte implantation, which aims to represent a valid option for mediumwide lesions or salvage procedures where the classic techniques easily fail, even though there is no agreement to date on its effective superiority compared with a nonregenerative approach. 11,12
Moreover, whereas good results are obtained in traumatic lesions of the femoral condyle, the treatment of other kinds of cartilage lesions is more problematic. In the case of osteochondritis dissecans, or osteochondral lesions, a more complex surgical procedure is required; for deep damage, the full thickness of the defect needs to be replaced to restore the joint surface, which also involves surgical time for the bone reconstruction before autologous chondrocyte implantation. 32 Other difficulties are related to the treatment of the patellofemoral joint, where anatomic and biomechanical factors contribute to the worst results reported. 5,6,30 Last, the worst clinical outcome was observed in patients with osteoarthritis. The presence of osteoarthritis is a variable that significantly correlates with clinical outcome, and the majority of graft failures occur in salvage procedures performed in an attempt to delay arthroplasty. 21
The possibility of treating complex defects is very attractive for cases wherein tissue damage extends to the subchondral bone and involves 2 tissues characterized by different intrinsic healing capacities.
For the repair of all osteochondral units, several authors have highlighted the need for biphasic scaffolds to reproduce the biological and functional requirements for guiding the growth of the 2 tissues. 10,20,35 Following this rationale, we performed a clinical experimentation on a recently developed composite scaffold that mimics the biochemical and biophysical properties of the different layers of native osteochondral structures. 15 The osteochondral nanostructured biomimetic scaffold tested (Fin-Ceramica Faenza SpA, Faenza, Italy) has a porous, 3-dimensional composite, trilayered structure, to reproduce the cartilaginous layer, the tide mark, and the subchondral bone. In previous in vitro and animal studies, 15,17,37 we tested this novel biomaterial and obtained good results with cartilage and bone tissue formation. We observed the same macroscopic, histologic, and radiographic results when implanting scaffolds loaded with autologous chondrocytes or scaffolds alone. The scaffold in the animal model was able to induce an in situ regeneration, through stem cells coming from the surrounding bone marrow. Thus, we applied this innovative scaffold without cells to clinical practice.
The primary purpose of this experimental study was to evaluate the safety and feasibility of this osteochondral surgical treatment approach. The secondary aim was to analyze the clinical results of the newly developed scaffold in the treatment of chondral or osteochondral lesions to evaluate the real potential of this new approach for replacing the articular surface with the advantages of a 1-step surgery, cost reduction, and simplified procedure.
Materials and Methods
Scaffold Preparation
As mentioned, the osteochondral biomimetic scaffold (Fin-Ceramica Faenza SpA) has a porous, 3-dimensional, composite, trilayered structure that mimics the whole osteochondral anatomy. The cartilaginous layer, consisting of type I collagen, has a smooth surface. The intermediate layer (tide mark–like) consists of a combination of type I collagen (60%) and hydroxyapatite (40%), whereas the lower layer consists of a mineralized blend of type I collagen (30%) and hydroxyapatite (70%) reproducing the subchondral bone layer (Figure 1). Detailed description of the scaffold preparation method and its characteristics was reported in previous studies. 14,15,17,37
Three-gradient multilayer scaffold that mimics the articular osteochondral compartment.
Patient Selection
In this prospective pilot study, 30 consecutive patients were enrolled and treated in our institute in 2007. Among these patients, 28 were prospectively evaluated at 6, 12, and 24 months of follow-up, and 2 were lost to follow-up. The 28 evaluated patients (34 defect sites) were 19 males and 9 females, with a mean age of 35.3 ± 10.2 years (range, 16-51 years). The inclusion criteria of the study were patients with clinical symptoms such as knee pain or swelling, and having grade III-IV chondral and osteochondral lesions of the knee (International Cartilage Repair Society evaluation package). The exclusion criteria were noncorrected axial deviation and knee instability, as evaluated clinically and via radiographic examination. The patients with an ACL lesion at the time of surgery underwent the associated surgical procedure of ACL reconstruction in the same surgical session as the osteochondral grafting. Patients with infectious, neoplastic, metabolic, and inflammatory pathologic changes were excluded from the study. All patients gave informed consent, and treatment was approved by the local ethics board.
The sites of the defects were the following: 8 medial femoral condyles, 5 lateral femoral condyles, 12 patellas, 7 trochleas, and 2 lateral tibial plateaus. The average size of the defects was 2.9 ± 1.3 cm2 (range, 1.5-6.0 cm2). The cause of injury was traumatic in 5 cases and microtraumatic/degenerative in 17 cases, and 6 patients were affected by osteochondritis dissecans. Seventeen patients were athletically active, being well trained or practicing sports at a competitive level, whereas 11 patients were less active, practicing sports at only an amateur level or not practicing any type of sport. Eight patients were operated on for the first time, whereas 20 patients had undergone previous surgery (11 patients had cartilage surgery): 7 meniscectomies, 4 ACL reconstructions, 2 lateral releases, 9 shavings of chondral lesions, 1 microfracturing, 1 refixation of an osteochondritis dissecans fragment, 1 patellar realignment, 1 bursectomy, 2 synovial fold removals, 1 loose body removal, and 3 tibial plateau reconstructions. In 15 patients, other associated procedures were performed during the same operation: 4 osteotomies, 3 patellar realignments, 2 lateral releases, 1 patellar tendon suturing, 1 ACL reconstruction, 1 meniscectomy, 1 meniscal allograft, 1 patellar lateral facet removal, 1 lateral tibial plateau elevation, 1 external distractor implantation, and 1 hardware removal (see the Appendix, available in the online version of this article at http://ajs.sagepub.com/supplemental/).
Surgical Procedure
The surgical procedure was performed according to that previously described. 14 The lesions were exposed through an arthrotomic parapatellar approach and prepared using a specifically designed drill. The sclerotic subchondral bone was eliminated, and 9-mm-deep areas with stable shoulders were created in which to place the scaffolds. Templates of the lesions were made with aluminum foil to obtain the size of the grafts, which were then implanted press fit (Figure 2). Cyclic bending of the knee, both before and after tourniquet removal, allowed testing of implant stability.
Surgical view: A, chondral lesion of the trochlea; B, lesion preparation; C, osteochondral scaffold implant.
Management of postoperative pain aimed for early mobilization to facilitate faster resolution of swelling, promote healing and joint nutrition, and prevent adhesions. On the second postoperative day, self-assisted mobilization of the knee or continuous passive motion for 6 hours daily with 1 cycle per minute was recommended until 90° of flexion was reached. Patients did not usually require more than 2 weeks of continuous passive motion, which was reduced and delayed for those who experienced fever or marked swelling postoperatively. Early isometric and isotonic exercises and controlled mechanical compression were performed. Muscular voluntary contraction and neuromuscular electrical stimulation were indicated and could be started at patient discharge. In the third or fourth week, weight touchdown with crutches was allowed, and the patient could then move gradually toward full weightbearing, usually reached at 6 to 8 weeks. Active functional training was then started, aiming to return to a correct running pathway by proprioceptive, strength, and endurance exercises and aerobic training. When rehabilitation progressed without complications, this stage ended within 7 to 8 months after surgery. The remainder of rehabilitation was dedicated to the return to previous sports activity, as allowed no earlier than 10 to 12 months after surgery.
Patient Evaluation
The clinical outcome of all patients was analyzed using the Cartilage Standard Evaluation Form as proposed by the International Cartilage Repair Society. 9 Effusion, passive motion deficit, and ligament examination were used to determine the knee functional grade (normal, nearly normal, abnormal, or severely abnormal). 9 Return to sports was evaluated with the Tegner score 38 and compared with preoperative and preinjury levels.
For ethical reasons, we performed only 3 biopsies. As previously reported, 14 6 months after treatment, 1 patient underwent biopsy during hardware removal and 1 during meniscectomy. At 2-year follow-up, second-look macroscopic and microscopic findings of the repair tissue were analyzed in 1 patient who was reoperated on for hardware removal.
MRI Evaluation
Examinations were carried out with a 1.5-T superconducting magnet (General Electric Co, Fairfield, Connecticut) with a dedicated quadrature detection knee coil (Quadknee; diameter, 18 cm). As in the previous study, 14 the following sequences were used:
sagittal fast spin echo, proton density weighted with fat saturation (repetition time [TR], 3200 milliseconds; echo time [TE], 22 milliseconds; echo train, 8; field of view [FOV], 160 mm; matrix, 512 × 256; slice thickness, 3.5 mm; gap, 0.5 mm; number of excitations, 2; number of slices, 22) and
sagittal dual fast spin echo (TR, 2850 milliseconds; TE, 100 and 44 milliseconds [T2 weighted and proton density weighted, respectively]; echo train, 8; FOV,160 mm; matrix, 512 × 256; slice thickness, 3.5 mm; gap, 0.5 mm; number of excitations, 2).
For the femoral condyle defects, we performed
3A.sagittal fast imaging employing steady-state acquisition,
4A.coronal 3-dimensional gradient echo with fat suppression (TR, 40 milliseconds; TE, 5 milliseconds; flip angle 45°; FOV, 160 mm; matrix, 256 × 256; slice thickness, 2.0 mm; number of excitations, 3), and
5A.coronal fast spin echo proton density-weighted with fat saturation (TR, 3200 milliseconds; TE, 22 milliseconds; echo train, 8; FOV, 160 mm; matrix, 512 × 256; slice thickness, 3.5 mm; gap 0.5 mm; number of excitations, 2; number of slices, 22).
For the trochlear and patellar defects, we performed
3B.axial fast imaging employing steady-state acquisition,
4B.axial 3-dimensional gradient echo with fat suppression (TR, 40 milliseconds; TE, 5 milliseconds; flip angle 45°; FOV, 160 mm; matrix, 256 × 256; slice thickness, 2.0 mm; number of excitations, 3), and
5B.axial fast spin echo, proton density weighted with fat saturation (TR, 3200 milliseconds; TE, 22 milliseconds; echo train, 8; FOV, 160 mm; matrix, 512 × 256; slice thickness, 3.5 mm; gap, 0.5 mm; number of excitations, 2; number of slices, 22).
For the description and evaluation of the graft maturation, an MRI scoring system was employed: MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue). 22,23 Twenty-four patients underwent MRI at 24 months of follow-up. Two experienced musculoskeletal radiologists evaluated the images. After an initial independent analysis, images were reviewed in consensus.
Statistical Analysis
All statistical analyses were carried out with SPSS 13.0 (IBM, Chicago, Illinois). A P value of less than .05 was considered statistically significant. The results were expressed as mean ± SD. The Kolmogorov-Smirnov test was done to assess normal data distribution. The paired t test (for normally distributed data) and the Wilcoxon test (for nonnormally distributed data) were used to measure significant differences between baseline and various follow-up measurements. The 1-way analysis of variance test (for normally distributed and homoskedastic data) and the Mann-Whitney and Kruskal-Wallis tests were used to measure significant differences between and among groups. Pearson, Spearman ρ, and Kendall τ were used to assess correlation between continuous and ranking data.
Results
Ten patients had adverse events. Swelling during the first month was observed in 6 patients. One patient experienced bleeding during the first 3 days after surgery. Two patients developed a fever during the first 3 weeks. All adverse events resolved within 1 month after surgery, with the exception of 2 patients with joint stiffness who were reoperated on arthroscopically, one at 2 months and the other at 5 months. One patient affected by multiple lesions had loosening of one of the grafts, which was removed, and another patient was reoperated for graft hypertrophy.
A statistically significant improvement of all clinical scores was obtained from basal evaluation to the 6-, 12-, and 24-month follow-up points. The International Knee Documentation Committee (IKDC) objective score changed from 50.0% normal and nearly normal knees before treatment (14 B, 8 C, 6 D) to 96.4% at the 6-month follow-up (17 A, 10 B, 1 D), 96.4% at 12 months (20 A, 7 B, 1 C), and 85.7% at 24 months (21 A, 3 B, 3 C, 1 D), showing a statistically significant improvement (P < .0005) at all follow-up times with respect to the baseline level. The improvement obtained at 6 months of follow-up remained stable at the further evaluations. From 12 to 24 months of follow-up, we observed a worsening in the objective evaluation in 3 cases: a 36-year-old woman treated for a patellar lesion lost some degree of extension; a 27-year-old man treated for a condylar lesion lost some degree of flexion; and a 24-year-old man treated for a trochlear lesion went back to high-level sports activity and was evaluated with a knee effusion. The IKDC subjective score improved markedly from the baseline evaluation to the 6- and 12-month follow-ups (P < .0005), and a further improvement was documented from the 12- to the 24-month follow-up (P = .02) (Figure 3). The mean Tegner score was 5.2 ± 2.5 preinjury, 1.6 ± 1.1 preoperative, 4.0 ± 1.6 at the 12-month follow-up, and 4.0 ± 1.8 after 2 years.
International Knee Documentation Committee subjective score: improvement from the preoperative level to 6, 12, and 24 months of follow-up.
These results showed a statistically significant improvement (P < .0005) from the preoperative level to the 1- and 2-year follow-ups, and the results remained stable over time; however, the new level of sports activity was significantly lower with respect to the preinjury level (P = .003 and P = .007 at 12 and 24 months of follow-up, respectively) (Figure 4).
Comparison of Tegner scores before the injury, before the treatment, and at the 1-year and final follow-ups.
Further analysis was performed to determine the parameters that influenced clinical outcome. The 10 patients who initially experienced adverse events had a slower recovery; in fact, they had poorer results at the 6- and 12-month follow-ups (P = .04 and P= .018, respectively) but achieved the same outcome of the other patients at 24 months (Figure 5). A slower recovery was seen in older patients, who presented with the worst results (ρ = −.386, P = .043) and a smaller improvement (ρ = −.438, P = .02) at the initial follow-up at 6 months. The same trend was observed in the patients who underwent previous surgery and in cases of patellar lesions. A tendency toward worse results was shown by the objective evaluation at the 12-month follow-up in the 20 cases of previous surgery (P = .06), and an even significantly worse objective evaluation was observed in the 11 patients who were previously treated for cartilage lesions (P = .029). The lesion site influenced the earlier results, with less improvement observed at 6 and 12 months of follow-up in cases of the 12 patellar lesions (P = .037 and P = .05, respectively), whereas no significant differences were observed at the 2-year follow-up (Figure 6). In contrast, a faster recovery was observed in active patients. In fact, the 17 athletically active patients had better subjective results (τ = .321, P = .034) and a greater improvement at the 12-month follow-up evaluation (τ = .344, P = .023) (Figure 7). Other factors—such as sex, defect size (probably due to the homogeneity of the group treated), and associated surgery—did not significantly influence the clinical outcome. Twenty-four patients (30 lesions) were evaluated with high-resolution MRI at 24 months after the scaffold implantation (Figure 8). The mean total MOCART score obtained was 79.2 (range, 40-95). The analysis of the individual parameters showed the following: (1) complete filling of the cartilage was shown in 70% of the lesions, (2) complete integration of the graft was detected in 70% of cases, (3) the repair tissue surface was intact in 53.3%, (4) the structure of the repair tissue was homogeneous in 37%, and (5) the graft signal intensity score was isointense with the adjacent native cartilage in 40% and 63% of the cases in dual T2-weighted fast spin echo and 3-dimensional gradient echo fat suppression sequences, respectively. Moreover, the subchondral lamina was considered intact in 7% of the cases, and subchondral bone changes (edema, granulation tissue, cysts, sclerosis) were observed in 53% of the cases. Finally, adhesion and effusion were shown in 0% and 23.3% of the cases, respectively (Table 1). Analyzing the correlation between MRI findings and clinical evaluation, we found that the total MOCART score was not statistically correlated to the IKDC subjective evaluation or the Tegner score. Further analysis showed more effusion in patients who underwent associated surgery (P = .007), less edema in case of patellofemoral lesions (P = .024), and a more homogeneous tissue in case of smaller lesions (P = .03).
International Knee Documentation Committee subjective evaluation. Patients who initially experienced adverse events had slower recoveries but similar results at the 2-year follow-up.
International Knee Documentation Committee subjective evaluation. Lesion site influences the recovery time.
International Knee Documentation Committee subjective evaluation. Patients participating in sports had a faster improvement with respect to nonactive patients.
MRI of a trochlear lesion preoperatively (A and B) and at 2 years of follow-up after osteochondral reconstruction (C and D).
MOCART Scores of the 24 Patients Evaluated at the 2-Year Follow-Up a
MOCART, Magnetic Resonance Observation of Cartilage Repair Tissue. n = 30 lesions.
Out of 30.
Histologic analysis of the biopsy specimens harvested at the 2-year follow-up showed complete biomaterial reabsorption and a hyaline-like tissue with a strong proteoglycan content and presence of collagen type II (Figure 9).
A, cartilaginous tissue with high proteoglycan content. The superficial layer is regular. Chondrocytes are regularly distributed inside extracellular matrix. Safranin O/fast green staining (magnification, 50 µm). B, immunohistochemical analysis for type II collagen of cartilaginous sample. The positivity is located at the extracellular matrix level (magnification, 200 µm). C, immunohistochemical analysis for type I collagen of cartilaginous sample. The specimen shows a positivity localized at intracellular (magnification, 200 µm). D, immunohistochemical analysis for caspase 3 of the cartilaginous biopsy sample (negative) (magnification, 50 µm).
Discussion
In recent years, there has been an increasing interest in and awareness of the importance of subchondral bone, for its role in the etiopathogenetic processes of articular surface damage and for the careful consideration of it needed in treatment. Certain defects—such as those resulting from osteochondritis dissecans, osteonecrosis, and trauma—may in fact be osteochondral in nature with involvement of the subchondral bone. 1,13,29 Moreover, the subchondral bone may be involved in the previously mentioned pathologic entities. In large cartilage lesions, the subchondral bone is involved in the degenerative process as well, and focal chondral defects, if left untreated, may even increase in size over time and present with concomitant changes of the underlying subchondral bone plate, either overgrowth or bone loss. 7,8,40 In fact, the functional conditions of articular cartilage and its supporting bone are tightly coupled because injuries of either type adversely affect the entire joint mechanical environment. The biomechanical perturbations caused by osteochondral alterations substantially alter the pattern and magnitude of contact pressure and cartilage strain in the joint. 36 As such, they have the potential to contribute to the initiation and development of osteoarthritis.
Surgical goals should always include reestablishment of the joint surface in the most anatomic way possible, restoring the physiologic properties of the entire osteochondral unit to achieve a more predictable repair tissue that closely resembles the native articular surface and remains durable over time. However, most bioengineered tissues used in clinical practice present the problem of promoting only the cartilage layer and not bone regeneration.
Many new scaffolds with osteochondral regenerative potential have therefore been developed and evaluated with promising preliminary results. Niederauer et al 28 experimented with a multiphase implant prototype using poly(D,L)lactide-co-glycolide for the treatment of osteochondral defects in goats. Qualitative evaluations showed a high percentage of hyaline cartilage, good bony restoration, new tissue integration with the native cartilage, and no difference in healing with the addition or omission of cells. Jiang et al 10 developed a biphasic porous plug of DL-poly-lactide-coglycolide, with its lower body impregnated with B-tricalciumphosphate as the osseous phase, and they found good scaffold integration but hyaline cartilage regeneration only in the minipigs with cell-seeded scaffolds. Nagura et al 26 tested a PLG bioabsorbable porous material on full-thickness osteochondral defects in rabbits and noted scaffold absorption with osteochondral regeneration. Schlichting et al 34 reported osteochondral defect healing using a polylactide-co-glycolide copolymer with a calcium sulfate scaffold in sheep. Schagemann et al 33 carried out a study on osteochondral repair treated with implantation of an alginate-gelatin biopolymer hydrogel in sheep. Defects treated with hydrogel plus autologous chondrocytes were restored with smooth, hyaline-like neocartilage and trabecular subchondral bone, whereas the cell-free gel treatment produced a slightly inferior regenerate cartilage.
However, despite all the preclinical studies reported, only one scaffold used for osteochondral regeneration is largely commercialized for clinical application. This is a bilayer porous PLGA calcium-sulfate biopolymer (TruFit). Although preclinical experimentation is promising, there are no systematic controlled studies, and only isolated reports have shown favorable results after implantation of these osteochondral substitutes. The MRI information at 12 months still demonstrated heterogeneous repair of cartilage tissue, and information on the long-term durability is not available. 24,39
To improve the attainable results in the treatment of chondral and osteochondral damage and to avoid problems and limits related to the existing procedures, this bicomposite, multilayer, biomimetic scaffold was developed that can mimic the osteocartilaginous anatomical structure in all its components. The structure of the scaffold, composed of type I collagen and nanostructured hydroxyapatite, was conceived with the aim of confining bone formation to the deepest portion of the construct without involving any superficial layer, where the process of cartilaginous-like connective tissue formation should begin. In vitro and animal studies have shown good results in terms of cartilage and bone tissue formation. 15,17,37 Moreover, the same macroscopic, histologic, and radiographic results were observed when implanting scaffold loaded with autologous chondrocytes or scaffold alone, suggesting an in situ regeneration through differentiation in osteogenic and chondrogenic lineages of stem cells coming from the surrounding bone marrow. These findings are thus consistent with previously proposed concepts, 3 and a recent study advocated the relevant contribution of mesenchymal stem cells attracted from the bone marrow toward autologous matrix-induced chondrogenesis. 19 Thus, this new osteochondral scaffold was introduced into clinical practice as a cell-free approach: technique note and early stability evaluation of the first 13 patients of this pilot study were documented in an earlier publication, with promising preliminary results. 14
The 2-year follow-up of this initial clinical study showed an improvement of all the parameters evaluated. The objective evaluation showed an improvement at 6 months of follow-up that remained stable over time. The subjective evaluation presented an improvement at 6 months that increased at the 12- and 24-month follow-ups. The mean Tegner score improved from the preoperative level at the 1- and 2-year follow-ups, and the results achieved remained stable over time, although significantly lower with respect to the preinjury level. Among patients, different trends have been detected in clinical outcome; in fact, some parameters have been identified as being responsible for the delay of functional recovery. Patients who initially experienced adverse events had a slower recovery. A slower improvement was also seen in older patients, in patients who underwent previous surgery, and in patients with patellar lesions. However, these factors only delayed the results, with lower scores obtained at 12 months, but they did not affect the final outcome; in fact, no significant differences were observed at the 2-year follow-up. In contrast, a faster recovery was observed in active patients. These data confirm our clinical findings 4 on the positive influence of sports activity on the clinical outcome of the patients treated with second-generation autologous chondrocyte implantation. We can suppose that a higher activity level can provide the mechanical stimulation necessary for the osteochondral regeneration.
Interestingly, in this study, patellar lesions had a slower recovery but achieved the same results at the 2-year follow-up. This result seems to be in contradiction with the common findings of inferior results in the patellofemoral joint with respect to other locations. 2,5,6,30 However, we believe that this result is biased by the high number of previous surgeries and the complexity of the lesions treated in the other areas of the joint. In fact, many of these operations can be considered as salvage procedures, and this knowledge can explain and increase the importance of the results obtained.
Finally, good results have been obtained with MRI. The MOCART evaluation showed a complete filling of the defect and integration of the border zone in 70% of cases and an intact surface of the new cartilage tissue in 70%. The structure of the repair tissue was homogeneous in 37% of the cases, and the graft signal intensity score in both sequences was predominantly isointense or moderately hyperintense with the adjacent native cartilage. However, the subchondral lamina and bone were considered intact in a minority of cases (7% and 47%, respectively). Further analysis showed more effusion in patients who underwent associated surgery (P = .007), less edema in cases of patellofemoral lesions (P = .024), and a more homogeneous tissue in cases of smaller lesions (P = .03). The overall MOCART score did not have a significant correlation with the subjective IKDC score. This lack of correlation can be explained by the low number of patients evaluated and by the fact that the MOCART score was designed for MRI evaluation of cartilage treatments. In fact, our approach involves the reconstruction of all osteochondral units, thus making the MOCART score not highly appropriate for the evaluation of and correlation with the clinical outcome of this treatment.
For practical and ethical reasons, we did not perform a histologic study. We performed 2 biopsies at 6 months of follow-up for 2 patients, who underwent hardware removal in one case and meniscectomy in the other, which showed the formation of subchondral bone without the presence of biomaterial and with cartilage repair tissue still engaged in ongoing maturation, as reported in a previous study. 14 The histologic analysis of a patient who underwent hardware removal at 2 years of follow-up showed complete biomaterial reabsorption and the presence of hyaline-like cartilage.
The clinical and MRI evaluations demonstrated good results, showing that this approach for replacing articular surface—with the advantages of 1-step surgery, potentially reduced costs, and a simplified procedure—may be successfully applied for the treatment of chondral and osteochondral lesions of the knee. Moreover, because of the plasticity of the graft, large osteochondral lesions can be treated through minor incisions.
The limitations of our study include the lack of a control group, the short follow-up, the scarcity of the cases evaluated through histologic study, and the low number and heterogeneity of the patients treated, with a high percentage of associated surgery, which may confound the results obtained. These limitations make it difficult to compare the results obtained with historical controls of other cartilage restoration techniques. In fact, the final outcome includes results from the treatment of different patient populations—such as those with patellofemoral, condylar, or tibial plateau lesions; those with varying ages and activity levels; and those with lesions of different origins. Moreover, in a high number of associated operations and complex cases, the treatment could be considered a salvage procedure. With this in consideration, our results seem to be in line with those previously reported in the literature with other techniques—with good clinical and MRI findings at 2 years and a slower improvement in patellofemoral lesions, as well as in less active and older patients 4-6,8,18,25 —but the separate evaluation reduces the number of patients in each subgroup, thus hampering a proper, deeper analysis and comparison with the literature.
However, despite these limitations, the present pilot study highlighted the safety and potential of the graded biomimetic osteochondral scaffold in promoting, by itself, bone and cartilage tissue restoration with good clinical and MRI results at 2-year follow-up. Further randomized studies with a larger number of homogeneous patients and a longer follow-up time are needed to confirm these preliminary findings, compare the promising results obtained with those of other available treatments, and confirm the potential of this therapy in regenerating the osteochondral unit and treating focal chondral defects and osteochondral lesions or wide areas of articular surface degeneration.
Footnotes
Acknowledgements
The authors thank A. Montaperto, G. Altadonna, F. Balboni, S. Bassini, Rizzoli Orthopaedic Institute, Bologna, Italy, for tecnical support; E. Pignotti, Rizzoli Orthopaedic Institute, Bologna, Italy, for statistical analysis; B. Grigolo, G. Desando, Rizzoli Orthopaedic Institute, Bologna, Italy, for histologic analysis; and Fin-Ceramica Faenza SpA, Faenza, Italy, for providing the osteochondral scaffolds.
Presented at the 36th annual meeting of the AOSSM, Providence, Rhode Island, July 2010
One or more of the authors has declared the following potential conflict of interest or source of funding: The osteochondral scaffolds were supplied by Fin-Ceramica Faenza SpA, Faenza, Italy.
References
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