Debridement of cartilage lesions before autologous chondrocyte implantation by open or transarthroscopic techniques

Recent development in multizonal scaffolds for osteochondral regeneration

Osteochondral (OC) repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue. In contrast to the current surgical approaches which yield only short-term relief of symptoms, tissue engineering strategy has been shown more promising outcomes in treating OC defects since its emergence in the 1990s. In particular, the use of multizonal scaffolds (MZSs) that mimic the gradient transitions, from cartilage surface to the subchondral bone with either continuous or discontinuous compositions, structures, and properties of natural OC tissue, has been gaining momentum in recent years. Scrutinizing the latest developments in the field, this review offers a comprehensive summary of recent advances, current hurdles, and future perspectives of OC repair, particularly the use of MZSs including bilayered, trilayered, multilayered, and gradient scaffolds, by bringing together onerous demands of architecture designs, material selections, manufacturing techniques as well as the choices of growth factors and cells, each of which possesses its unique challenges and opportunities.

Subchondral Drilling Independent of Drill Hole Number Improves Articular Cartilage Repair and Reduces Subchondral Bone Alterations Compared With Debridement in Adult Sheep

BACKGROUND

Subchondral drilling is an established marrow stimulation technique for small cartilage defects, but whether drilling is required at all and if the drill hole density affects repair remains unclear.

HYPOTHESES

Osteochondral repair is improved when the subchondral bone is perforated by a higher number of drill holes per unit area, and drilling is superior to defect debridement alone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rectangular full-thickness chondral defects (4 × 8 mm) were created in the trochlea of adult sheep (N = 16), debrided down to the subchondral bone plate without further treatment as controls (no treatment; n = 7) or treated with either 2 or 6 (n = 7 each) subchondral drill holes (diameter, 1.0 mm; depth, 10.0 mm). Osteochondral repair was assessed at 6 months postoperatively by standardized (semi-)quantitative macroscopic, histological, immunohistochemical, biochemical, and micro-computed tomography analyses.

RESULTS

Compared with defect debridement alone, histological overall cartilaginous repair tissue quality (P = .025) and the macroscopic aspect of the adjacent cartilage (P≤ .032) were improved after both drilling densities. Only drilling with 6 holes increased type 2 collagen content in the repair tissue compared with controls (P = .038). After debridement, bone mineral density was significantly decreased in the subchondral bone plate (P≤ .015) and the subarticular spongiosa (P≤ .041) compared with both drilling groups. Debridement also significantly increased intralesional osteophyte sectional area compared with drilling (P≤ .034). No other differences in osteochondral repair existed between subchondral drilling with 6 or 2 drill holes.

CONCLUSION

Subchondral drilling independent of drill hole density significantly improves structural cartilage repair compared with sole defect debridement of full-thickness cartilage defects in sheep after 6 months. Subchondral drilling also leads to a better reconstitution of the subchondral bone compartment below the defects. Simultaneously, drilling reduced the formation of intralesional osteophytes caused by osseous overgrowth compared with debridement.

CLINICAL RELEVANCE

These results have important clinical implications, as they support subchondral drilling independent of drill hole number but discourage debridement alone for the treatment of small cartilage defects. Clinical studies are warranted to further quantify the effects of subchondral drilling in similar settings.

Small Ruminant Models for Articular Cartilage Regeneration by Scaffold-Based Tissue Engineering

Animal models play an important role in preclinical studies, especially in tissue engineering scaffolds for cartilage repair, which require large animal models to verify the safety and effectiveness for clinical use. The small ruminant models are most widely used in this field than other large animals because they are cost-effective, easy to raise, not to mention the fact that the aforementioned animal presents similar anatomical features to that of humans. This review discusses the experimental study of tissue engineering scaffolds for knee articular cartilage regeneration in small ruminant models. Firstly, the selection of these scaffold materials and the preparation process in vitro that have been already used in vivo are briefly reviewed. Moreover, the major factors influencing the rational design and the implementation as well as advantages and limitations of small ruminants are also demonstrated. As regards methodology, this paper applies principles and methods followed by most researchers in the process of experimental design and operation of this kind. By summarizing and comparing different therapeutic concepts, this paper offers suggestions aiming to increase the effectiveness of preclinical research using small ruminant models and improve the process of developing corresponding therapies.

Comparison of Human Articular Cartilage Tissue and Chondrocytes Isolated from Peripheral versus Central Regions of Traumatic Lesions

OBJECTIVE

Cellular and molecular events occurring in cartilage regions close to injury are poorly investigated, but can possibly compromise the outcome of cell-based cartilage repair. In this study, key functional properties were assessed for cartilage biopsies collected from the central part of traumatic joint lesions (central) and from regions surrounding the defect (peripheral). These properties were then correlated with the quality of the initial cartilage biopsy and the inflammatory state of the joint.

DESIGN

Cartilage samples were collected from knee joints of 42 patients with traumatic knee injuries and analyzed for cell phenotype (by reverse transcriptas-polymerase chain reaction), histological quality, cellularity, cell viability, proliferation capacity, and post-expansion chondrogenic capacity of chondrocytes (in pellet culture). Synovium was also harvested and analyzed for the expression of inflammatory cytokines.

RESULTS

Cartilage quality and post-expansion chondrogenic capacity were higher in peripheral versus central samples. Differences between these 2 parameters were more pronounced in joints with high inflammatory features characterized by >100-fold difference in the mRNA levels of IL6 and IL8 in the corresponding synovium. Peripheral chondrocytes isolated from good- versus bad-quality biopsies expressed higher levels of collagen II/I and aggrecan/versican and lower levels of MMP13 and ADAMTS5. They also exhibited reduced proliferation and enhanced cartilage-forming capacity.

CONCLUSIONS

Chondrocytes at the periphery of traumatic lesions better maintain properties of healthy cartilage compared to those isolated from the center, even when derived from bad-quality tissues harvested from highly inflamed joints. Future studies are necessary to investigate the change of functional properties of peripheral chondrocytes over time.

Cyst formation in the subchondral bone following cartilage repair

Subchondral bone cysts represent an early postoperative sign associated with many articular cartilage repair procedures. They may be defined as an abnormal cavity within the subchondral bone in close proximity of a treated cartilage defect with a possible communication to the joint cavity in the absence of osteoarthritis. Two synergistic mechanisms of subchondral cyst formation, the theory of internal upregulation of local proinflammatory factors, and the external hydraulic theory, are proposed to explain their occurrence. This review describes subchondral bone cysts in the context of articular cartilage repair to improve investigations of these pathological changes. It summarizes their epidemiology in both preclinical and clinical settings with a focus on individual cartilage repair procedures, examines an algorithm for subchondral bone analysis, elaborates on the underlying mechanism of subchondral cyst formation, and condenses the clinical implications and perspectives on subchondral bone cyst formation in cartilage repair.

Biological perspectives and current biofabrication strategies in osteochondral tissue engineering

Articular cartilage and the underlying subchondral bone are crucial in human movement and when damaged through disease or trauma impacts severely on quality of life. Cartilage has a limited regenerative capacity due to its avascular composition and current therapeutic interventions have limited efficacy. With a rapidly ageing population globally, the numbers of patients requiring therapy for osteochondral disorders is rising, leading to increasing pressures on healthcare systems. Research into novel therapies using tissue engineering has become a priority. However, rational design of biomimetic and clinically effective tissue constructs requires basic understanding of osteochondral biological composition, structure, and mechanical properties. Furthermore, consideration of material design, scaffold architecture, and biofabrication strategies, is needed to assist in the development of tissue engineering therapies enabling successful translation into the clinical arena. This review provides a starting point for any researcher investigating tissue engineering for osteochondral applications. An overview of biological properties of osteochondral tissue, current clinical practices, the role of tissue engineering and biofabrication, and key challenges associated with new treatments is provided. Developing precisely engineered tissue constructs with mechanical and phenotypic stability is the goal. Future work should focus on multi-stimulatory environments, long-term studies to determine phenotypic alterations and tissue formation, and the development of novel bioreactor systems that can more accurately resemble the in vivo environment.

Surgeon Ability to Appropriately Address the Calcified Cartilage Layer: An In Vitro Study of Arthroscopic and Open Techniques

BACKGROUND

Microfracture is a commonly utilized cartilage restoration technique for articular cartilage defects. While the removal of the calcified cartilage layer (CCL) has been shown to be critical with in vivo models, little is known with regard to surgeon reliability to adequately perform the technique.

PURPOSE

To evaluate surgeon reliability in removing the CCL utilizing open and arthroscopic techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eleven cadaveric knees were utilized to create four 12-mm diameter defects in the anterior and posterior medial femoral condyles. Eleven fellowship-trained surgeons were asked to perform the following procedures: remove the CCL open, retain the CCL open, remove the CCL arthroscopically, and retain the CCL arthroscopically. Samples underwent histologic staining and analysis with 3-dimensional micro-computed tomography. The latter was used to calculate the percentage of the CCL that was removed or retained across the entire defect.

RESULTS

When surgeons were asked to retain the CCL arthroscopically, 48% ± 41% (mean ± SD) remained. When surgeons were asked to remove the CCL arthroscopically, 24% ± 35% remained. There was no statistical difference between these groups (P > .05). When the CCL was retained during open preparation, 60% ± 39% remained. During attempts to remove the CCL in an open manner, 19% ± 28% remained. There was a significant difference in the amount of CCL remaining between the open removal and open retaining groups (P = .03). There were no significant differences in the percentage of CCL remaining between the open and arthroscopic preservation groups and between the open and arthroscopic removal groups.

CONCLUSION/CLINICAL RELEVANCE

This study highlights the significant variability in surgeon ability to reliably retain or remove the CCL. However, there appears to be improved ability of surgeons to more reliably remove or retain the CCL in an open fashion as compared with the arthroscopic approach.

Arthroscopic Cartilage Lesion Preparation in the Human Cadaveric Knee Using a Curette Technique Demonstrates Clinically Relevant Histologic Variation

PURPOSE

To examine the quality of arthroscopic cartilage debridement using a curette technique by comparing regional and morphologic variations within cartilage lesions prepared in human cadaveric knee specimens for the purpose of cartilage repair procedures. A secondary aim was to compare the histologic properties of cartilage lesions prepared by surgeons of varying experience.

METHODS

Standardized cartilage lesions (8 mm × 15 mm), located to the medial/lateral condyle and medial/lateral trochlea were created within 12 human cadaver knees by 40 orthopaedic surgeons. Participants were instructed to create full-thickness cartilage defects within the marked area, shouldered by uninjured vertical walls of cartilage, and to remove the calcified cartilage layer, without violating the subchondral plate. Histologic specimens were prepared to examine the verticality of surrounding cartilage walls at the front and rear aspects of the lesions, and to characterize the properties of the surrounding cartilage, the cartilage wall profile, the debrided lesion depth, bone sinusoid access, and the bone surface profile. Comparative analysis of cartilage wall verticality measured as deviation from perpendicular was performed, and Spearman's rank correlation analysis was used to examine associations between debrided wall verticality and surgeon experience.

RESULTS

Mean cartilage wall verticality relative to the base of the lesion was superior at the rear aspect of the lesion compared to the front aspect (12.9° vs 29.2°, P < .001). Variability was identified in the morphology of the surrounding cartilage (P < .001), cartilage wall profile (P = .016), debrided lesion depth (P = .028), bone surface profile (P = .040), and bone sinusoid access (P = .009), with sinusoid access identified in 42% of cases. There was no significant association of cartilage lesion wall verticality and surgeon years in practice (r_s = 0.161, P = .065) or arthroscopic caseload (r_s = -0.071, P = .419).

CONCLUSIONS

Arthroscopic cartilage lesion preparation using standard curette technique in a human cadaveric knee model results in inferior perpendicularity of the surrounding cartilage walls at the front aspect of the defect, compared to the rear aspect. This technique has shown significant variability in the depth of debridement, with debridement depths identified as either too superficial or too deep to the calcified cartilage layer in more than 60% of cases in this study. Surgeon experience does not appear to impact the morphologic properties of cartilage lesions prepared arthroscopically using ring curettes. CLINICAL RELEVANCE: To optimize restoration of hyaline-like cartilage tissue, careful attention to prepared cartilage lesion morphology is advised when arthroscopically performing cartilage repair, given the tendency for standard curette technique to create inferior verticality of cartilage walls at the front of the lesion, and the variable depth of debridement achieved.

Morphologic Properties of Cartilage Lesions in the Knee Arthroscopically Prepared by the Standard Curette Technique Are Inferior to Lesions Prepared by Specialized Chondrectomy Instruments

BACKGROUND

Cartilage lesion preparation is an important component to cartilage repair procedures, given the effect of prepared lesion morphology on the formation of durable and well-integrated repair tissue.

PURPOSE

To compare the quality of arthroscopic cartilage lesion debridement performed by (1) the standard curette (SC) technique and (2) specialized chondrectomy (CM) instruments, to provide technical guidance for optimization of cartilage lesion preparation in the setting of arthroscopic cartilage repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Articular cartilage lesions of standardized size (8 × 15 mm) were demarcated within the trochlea and femoral condyles of 20 human cadaver knee specimens. Orthopaedic surgeons performed arthroscopic lesion preparation using 2 techniques that consisted of SC preparation and preparation by CM instruments. A histologic comparative analysis was performed within each treatment group and between treatment groups to evaluate the morphology of prepared cartilage defects.

RESULTS

The mean angle deviation from perpendicular of the cartilage wall at the front of the prepared cartilage lesions was significantly greater in the SC group versus the CM group (29.8° ± 21.4° vs 7.7° ± 7.6°, P < .001). In lesions prepared via the SC technique, the cartilage walls at the front of the prepared lesions were significantly less perpendicular than the cartilage walls at the rear of the lesions (29.8° ± 21.4° vs 11.0° ± 10.3°, P < .001), whereas lesions prepared by the CM technique demonstrated comparable verticality of surrounding cartilage walls at the front and rear aspects of the lesions (7.7° ± 7.6° vs 9.4° ± 12.3°, P = .827). Depth of lesion debridement was accomplished to the target level by the CM technique in 86% of prepared lesions, compared with 34% of lesions in the SC group. The prepared cartilage wall profile was characterized as the most ideal morphology in 55% of prepared lesions in the CM group, as opposed to 10% in the SC group.

CONCLUSION

Arthroscopic cartilage lesion preparation with SC instruments results in superior perpendicularity of surrounding cartilage walls to subchondral bone and greater consistency of debrided lesion depth, as compared with the standard debridement technique with curettes.

CLINICAL RELEVANCE

Arthroscopic preparation using standard curette technique leads to suboptimal morphologic characteristics of prepared lesions that likely affect the quality of repair tissue, compared to preparation using specialized chondrectomy instruments.

Surgical Preparation for Articular Cartilage Regeneration in the Osteoarthritic Knee Joint

PURPOSE

Autologous chondrocyte implantation (ACI) is a treatment option even in early osteoarthritis (OA). Surgical preparation for ACI should avoid penetration of the subchondral bone plate to prevent hemorrhage, fibrin clot formation, and subsequent activation of the inflammatory response.

HYPOTHESIS

Current surgical procedures with ring curettes preserve the integrity of the subchondral bone plate, even in patients with OA.

METHODS

Subchondral femoral bone plates ( n = 40) of OA knees undergoing total knee arthroplasty were prepared in vivo using standard, non-brute-force debridement for ACI. To approach regular wear/early OA, only cartilage with maximally grade 3A International Cartilage Repair Society score was prepared. Effects were analyzed by light microscopy.

RESULTS

In 87.5% of the specimens (35/40), standard debridement did not violate the tide mark, except for occasional minor openings with a smooth edge (diameter approximately 20 µm). In contrast, 5/40 samples (12.5%) showed one large area with a missing bone plate and an open bone marrow space. Twenty-eight specimens (70%) showed at least remnants of uncalcified cartilage.

CONCLUSION

On the basis of size/fine structure, the occasional minor openings are likely due to increased vascular penetration through the tide mark in the pathologically altered bone-cartilage interface in OA. The consequences of limited hemorrhage through minor openings or selected large defects following in vivo debridement are still unknown. Thus, standard debridement appears suitable for cartilage regeneration even in OA defects.

Effect of a Rapidly Degrading Presolidified 10 kDa Chitosan/Blood Implant and Subchondral Marrow Stimulation Surgical Approach on Cartilage Resurfacing in a Sheep Model

Objective This study tested the hypothesis that presolidified chitosan-blood implants are retained in subchondral bone channels perforated in critical-size sheep cartilage defects, and promote bone repair and hyaline-like cartilage resurfacing versus blood implant. Design Cartilage defects (10 × 10 mm) with 3 bone channels (1 drill, 2 Jamshidi biopsy, 2 mm diameter), and 6 small microfracture holes were created bilaterally in n = 11 sheep knee medial condyles. In one knee, 10 kDa chitosan-NaCl/blood implant (presolidified using recombinant factor VIIa or tissue factor), was inserted into each drill and Jamshidi hole. Contralateral knee defects received presolidified whole blood clot. Repair tissues were assessed histologically, biochemically, biomechanically, and by micro-computed tomography after 1 day ( n = 1) and 6 months ( n = 10). Results Day 1 defects showed a 60% loss of subchondral bone plate volume fraction along with extensive subchondral hematoma. Chitosan implant was resident at day 1, but had no effect on any subsequent repair parameter compared with blood implant controls. At 6 months, bone defects exhibited remodeling and hypomineralized bone repair and were partly resurfaced with tissues containing collagen type II and scant collagen type I, 2-fold lower glycosaminoglycan and fibril modulus, and 4.5-fold higher permeability compared with intact cartilage. Microdrill holes elicited higher histological ICRS-II overall assessment scores than Jamshidi holes (50% vs. 30%, P = 0.041). Jamshidi biopsy holes provoked sporadic osteonecrosis in n = 3 debrided condyles. Conclusions Ten kilodalton chitosan was insufficient to improve repair. Microdrilling is a feasible subchondral marrow stimulation surgical approach with the potential to elicit poroelastic tissues with at least half the compressive modulus as intact articular cartilage.

Joint Preservation Techniques in Orthopaedic Surgery

CONTEXT

With increasing life expectancy, there is growing demand for preservation of native articular cartilage to delay joint arthroplasties, especially in younger, active patients. Damage to the hyaline cartilage of a joint has a limited intrinsic capacity to heal. This can lead to accelerated degeneration of the joint and early-onset osteoarthritis. Treatment in the past was limited, however, and surgical treatment options continue to evolve that may allow restoration of the natural biology of the articular cartilage. This article reviews the most current literature with regard to indications, techniques, and outcomes of these restorative procedures.

EVIDENCE ACQUISITION

MEDLINE and PubMed searches relevant to the topic were performed for articles published between 1995 and 2016. Older articles were used for historical reference. This paper places emphasis on evidence published within the past 5 years.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 4.

RESULTS

Autologous chondrocyte implantation and osteochondral allografts (OCAs) for the treatment of articular cartilage injury allow restoration of hyaline cartilage to the joint surface, which is advantageous over options such as microfracture, which heal with less favorable fibrocartilage. Studies show that these techniques are useful for larger chondral defects where there is no alternative. Additionally, meniscal transplantation can be a valuable isolated or adjunctive procedure to prolong the health of the articular surface.

CONCLUSION

Newer techniques such as autologous chondrocyte implantation and OCAs may safely produce encouraging outcomes in joint preservation.

Allografts: Osteochondral, Shell, and Paste

There is an increasing need for articular cartilage restoration procedures. Hyaline cartilage lacks intrinsic healing capacity. Persistent osteochondral defects can lead to early and rapid degenerative changes. Microfracture and autologous chondrocyte implantation provide reasonable outcomes for smaller defects without bone loss. However, these techniques have limited effectiveness for lesions greater than 4 cm² or with significant bony involvement. Ostochondral allografts provide an option for these lesions. This article reviews osteochondral allografts for articular defects. Emerging options provide different approaches to difficult cartilage defects. We discuss current screening, procurement, and storage methods, surgical techniques, outcomes, and bacterial/viral transmission.

Early loss of subchondral bone following microfracture is counteracted by bone marrow aspirate in a translational model of osteochondral repair

Microfracture of cartilage defects may induce alterations of the subchondral bone in the mid- and long-term, yet very little is known about their onset. Possibly, these changes may be avoided by an enhanced microfracture technique with additional application of bone marrow aspirate. In this study, full-thickness chondral defects in the knee joints of minipigs were either treated with (1) debridement down to the subchondral bone plate alone, (2) debridement with microfracture, or (3) microfracture with additional application of bone marrow aspirate. At 4 weeks after microfracture, the loss of subchondral bone below the defects largely exceeded the original microfracture holes. Of note, a significant increase of osteoclast density was identified in defects treated with microfracture alone compared with debridement only. Both changes were significantly counteracted by the adjunct treatment with bone marrow. Debridement and microfracture without or with bone marrow were equivalent regarding the early cartilage repair. These data suggest that microfracture induced a substantial early resorption of the subchondral bone and also highlight the potential value of bone marrow aspirate as an adjunct to counteract these alterations. Clinical studies are warranted to further elucidate early events of osteochondral repair and the effect of enhanced microfracture techniques.

Dry Arthroscopic Single-Stage Cartilage Repair of the Knee Using a Hyaluronic Acid-Based Scaffold With Activated Bone Marrow-Derived Mesenchymal Stem Cells

Cartilage lesions of the knee are a frequent finding; however, treatment options that are capable of restoring hyaline-like tissue are not routinely used. Cell-based technology such as autologous chondrocyte implantation may in some cases provide durable cartilage repair, but availability of this procedure is often restricted due to cost constraints. There have been promising outcomes reported with the use of scaffolds seeded with activated bone marrow aspirate concentrate in cases of chondral injury. There are clear advantages to cell-based cartilage repair techniques that are performed as a single-stage procedure, particularly when the repair technology can be used in a minimally invasive manner. We present an arthroscopic technique of cartilage repair using a hyaluronic acid-based scaffold associated with activated bone marrow aspirate concentrate. This technique is a cost-effective, minimally invasive, single-stage procedure that has the potential for routine use in a wide range of cartilage lesion types and locations.

Cartilage defect repair in horses: Current strategies and recent developments in regenerative medicine of the equine joint with emphasis on the surgical approach

Chondral and osteochondral lesions due to injury or other pathology are highly prevalent conditions in horses (and humans) and commonly result in the development of osteoarthritis and progression of joint deterioration. Regenerative medicine of articular cartilage is an emerging clinical treatment option for patients with articular cartilage injury or disease. Functional articular cartilage restoration, however, remains a major challenge, but the field is progressing rapidly and there is an increasing body of supportive clinical and scientific evidence. This review gives an overview of the established and emerging surgical techniques employed for cartilage repair in horses. Through a growing insight in surgical cartilage repair possibilities, surgeons might be more stimulated to explore novel techniques in a clinical setting.

Small-Diameter Awls Improve Articular Cartilage Repair After Microfracture Treatment in a Translational Animal Model

BACKGROUND

Microfracture is the most commonly applied arthroscopic marrow stimulation procedure.

HYPOTHESIS

Articular cartilage repair is improved when the subchondral bone is perforated by small-diameter microfracture awls compared with larger awls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Standardized rectangular (4 × 8 mm) full-thickness chondral defects (N = 24) were created in the medial femoral condyle of 16 adult sheep and debrided down to the subchondral bone plate. Three treatment groups (n = 8 defects each) were tested: 6 microfracture perforations using small-diameter awls (1.0 mm; group 1), large-diameter awls (1.2 mm; group 2), or without perforations (debridement control; group 3). Osteochondral repair was assessed at 6 months in vivo using established macroscopic, histological, immunohistochemical, biochemical, and micro-computed tomography analyses.

RESULTS

Compared with control defects, histological cartilage repair was always improved after both microfracture techniques (P < .023). Application of 1.0-mm microfracture awls led to a significantly improved histological overall repair tissue quality (7.02 ± 0.70 vs 9.03 ± 0.69; P = .008) and surface grading (1.05 ± 0.28 vs 2.10 ± 0.19; P = .001) compared with larger awls. The small-diameter awl decreased relative bone volume of the subarticular spongiosa (bone volume/tissue volume ratio: 23.81% ± 3.37% vs 30.58% ± 2.46%; P = .011). Subchondral bone cysts and intralesional osteophytes were frequently observed after either microfracture treatment. Macroscopic grading, DNA, proteoglycan, and type I and type II collagen contents as well as degenerative changes within the adjacent cartilage remained unaffected by the awl diameter.

CONCLUSION

Small-diameter microfracture awls improve articular cartilage repair in the translational sheep model more effectively than do larger awls.

CLINICAL RELEVANCE

These data support the use of small microfracture instruments for the surgical treatment of cartilage defects and warrant prolonged clinical investigations.

Large animal models in experimental knee sports surgery: focus on clinical translation

Large animal models play a crucial role in sports surgery of the knee, as they are critical for the exploration of new experimental strategies and the clinical translation of novel techniques. The purpose of this contribution is to provide critical aspects of relevant animal models in this field, with a focus on paediatric anterior cruciate ligament (ACL) reconstruction, high tibial osteotomy, and articular cartilage repair. Although there is no single large animal model strictly replicating the human knee joint, the sheep stifle joint shares strong similarities. Studies in large animal models of paediatric ACL reconstruction identified specific risk factors associated with the different surgical techniques. The sheep model of high tibial osteotomy is a powerful new tool to advance the understanding of the effect of axial alignment on the lower extremity on specific issues of the knee joint. Large animal models of both focal chondral and osteochondral defects and of osteoarthritis have brought new findings about the mechanisms of cartilage repair and treatment options. The clinical application of a magnetic device for targeted cell delivery serves as a suitable example of how data from such animal models are directly translated into in clinical cartilage repair. As novel insights from studies in these translational models will advance the basic science, close cooperation in this important field of clinical translation will improve current reconstructive surgical options and open novel avenues for regenerative therapies of musculoskeletal disorders.

Chondroinduction Is the Main Cartilage Repair Response to Microfracture and Microfracture With BST-CarGel: Results as Shown by ICRS-II Histological Scoring and a Novel Zonal Collagen Type Scoring Method of Human Clinical Biopsy Specimens

BACKGROUND

Current cartilage repair histological scoring systems are unable to explain the relationship between collagen type II deposition and overall repair quality.

PURPOSE/HYPOTHESIS

The purpose of this study was to develop a novel zonal collagen type (ZCT) 5-point scoring system to measure chondroinduction in human clinical biopsy specimens collected after marrow stimulation. The hypothesis was that the ZCT scores would correlate with the International Cartilage Repair Society-II (ICRS-II) overall histological repair assessment score and glycosaminoglycan (GAG) content.

STUDY DESIGN

Descriptive laboratory study.

METHODS

After optimizing safranin O staining for GAG and immunostaining for human collagen type II and type I (Col2 and Col1, respectively), serial sections from clinical osteochondral repair biopsy specimens (13 months after microfracture or microfracture with BST-CarGel; n = 39 patients) were stained and 3 blinded readers performed histomorphometry for percentage of staining, ICRS-II histological scoring, polarized light microscopy (PLM) scoring, and 5-point ZCT scoring based on tidemark morphology, zonal distribution of Col2 and Col1, and Col1 percentage stain. Because 1 biopsy specimen was missing bone, 38 biopsy specimens were evaluated for ICRS-II, PLM, and ZCT scores.

RESULTS

Chondroinduction was identified in 21 biopsy specimens as a Col2 matrix fused to bone that spanned the deep-middle-superficial zones ("full-thickness hyaline repair"), deep-middle zones, or deep zone ("stalled hyaline") that was covered with a variable-thickness Col1-positive matrix, and was scored, respectively, as ZCT = 1 (n = 4 biopsy specimens), ZCT = 2 (n = 6) and ZCT = 3 (n = 11). Other biopsy specimens (n = 17) were fibrocartilage (n = 9; ZCT = 4), fibrous tissue (n = 4, ZCT = 5), or non-marrow derived (n = 4; ZCT = 0). Non-marrow derived tissue had a mean mature tidemark score of 84 out of 100 versus a regenerating tidemark score of 24 for all other biopsy specimens (P = .005). Both "stalled hyaline" repair and fibrocartilage had the same mean Col2 percentage stain; however, fibrocartilage was distinguished by heavy Col1 deposits in the deep zone, a 2-fold higher mean Col1 percentage stain (P = .001), and lower surface integrity (P = .03). ZCT scores correlated with GAG content and the ICRS-II overall assessment score, especially when combined with the PLM score for collagen organization (R = 0.82). Histological scores of the deep zone strongly predicted the ICRS-II overall assessment score (R = 0.99).

CONCLUSION

The ICRS-II overall repair assessment score and GAG content correlated with the extent of Col2 deposition free of fibrosis in the deep/middle zone rather than bulk accumulation of Col2.

CLINICAL RELEVANCE

Biopsy tissue from the BST-CarGel randomized clinical trial (microfracture without and with BST-CarGel, as treatment groups were not unblinded) showed regenerated tissue consistent with a chondroinduction mechanism in at least half of the treated lesions.

Instruments for reproducible setting of defects in cartilage and harvesting of osteochondral plugs for standardisation of preclinical tests for articular cartilage regeneration

Background

Standardisation is required in research, so are approval procedures for advanced therapy medical products and other procedures for articular cartilage therapies. The process of creating samples needs to be reproducible.

The aim of this study was to design, create and validate instruments (1) to create reproducible and accurate defects and (2) to isolate samples in the shape of osteochondral cylinders in a quick, reliable and sterile manner.

Methods

Adjustable instruments were created: a crown mill with a resolution of 0.05 mm and a front mill to create defects in articular cartilage and subchondral bone. The instruments were tested on knee joints of pigs from the slaughterhouse; 48 defects were created and evaluated. A punching machine was designed to harvest osteochondral plugs. These were validated in an in vivo animal study.

Results

The instruments respect the desired depth of 0.5 and 1.5 mm when creating the defects, depending on whether the person using the instrument is highly experienced (0.451 mm; confidence interval (CI): 0.390 mm; 0.512 mm and 1.403 mm; CI: 1.305 mm; 1.502 mm) or less so (0.369 mm; CI: 0.297 mm; 0.440 mm and 1.241 mm; CI: 1.141 mm; 1.341 mm). Eighty samples were taken from knee joints of Göttingen Minipigs with this punching technique. The time needed for the harvesting of the samples was 7.52 min (±2.18 min), the parallelism of the sides of the cylinders deviated by −0.63° (CI: −1.33°; 0.08°) and the surface of the cartilage deviated from the perpendicularity by 4.86° (CI: 4.154°; 5.573°). In all assessed cases, a sterile procedure was observed.

Conclusions

Instruments and procedures for standardised creation and validation of defects in articular cartilage and subchondral bone were designed. Harvesting of samples in the shape of osteochondral cylinders can now be performed in a quick, reliable and sterile manner. The presented instruments and procedures can serve as helpful steps towards standardised operating procedures in the field of regenerative therapies of articular cartilage in research and for regulatory requirements.

Small subchondral drill holes improve marrow stimulation of articular cartilage defects

BACKGROUND

Subchondral drilling is an established marrow stimulation technique.

HYPOTHESIS

Osteochondral repair is improved when the subchondral bone is perforated with small drill holes, reflecting the physiological subchondral trabecular distance.

STUDY DESIGN

Controlled laboratory study.

METHODS

A rectangular full-thickness chondral defect was created in the trochlea of adult sheep (n = 13) and treated with 6 subchondral drillings of either 1.0 mm (reflective of the trabecular distance) or 1.8 mm in diameter. Osteochondral repair was assessed after 6 months in vivo by macroscopic, histological, and immunohistochemical analyses and by micro-computed tomography.

RESULTS

The application of 1.0-mm subchondral drill holes led to significantly improved histological matrix staining, cellular morphological characteristics, subchondral bone reconstitution, and average total histological score as well as significantly higher immunoreactivity to type II collagen and reduced immunoreactivity to type I collagen in the repair tissue compared with 1.8-mm drill holes. Analysis of osteoarthritic changes in the cartilage adjacent to the defects revealed no significant differences between treatment groups. Restoration of the microstructure of the subchondral bone plate below the chondral defects was significantly improved after 1.0-mm compared to 1.8-mm drilling, as shown by higher bone volume and reduced thickening of the subchondral bone plate. Likewise, the microarchitecture of the drilled subarticular spongiosa was better restored after 1.0-mm drilling, indicated by significantly higher bone volume and more and thinner trabeculae. Moreover, the bone mineral density of the subchondral bone in 1.0-mm drill holes was similar to the adjacent subchondral bone, whereas it was significantly reduced in 1.8-mm drill holes. No significant correlations existed between cartilage and subchondral bone repair.

CONCLUSION

Small subchondral drill holes that reflect the physiological trabecular distance improve osteochondral repair in a translational model more effectively than larger drill holes.

CLINICAL RELEVANCE

These results have important implications for the use of subchondral drilling for marrow stimulation, as they support the use of small-diameter bone-cutting devices.

Advanced Therapy Medicinal Products and Exemptions to the Regulation 1394/2007: How Confident Can We be? An Exploratory Analysis

The market authorization procedure for medicinal products for human use is relying on their demonstrated efficacy, safety, and pharmaceutical quality. This applies to all medicinal products whether of chemical or biological origin. Since October 2009, the first advanced therapy medicinal product (ATMP) has been authorized through the centralized procedure. ATMPs are gene therapy medicinal products, somatic cell therapy medicinal products or tissue-engineered products. An appropriate ATMP – Regulation is dealing with ATMP requirements. Two exemptions are foreseen to the ATMP Regulation: (a) Products, which were legally on the Community market when the Regulation became applicable, should comply to the Regulation by December 30, 2012. (b) The hospital exemption rule for non-routine products for an individual patient. In this work we explored whether the actual application of the Regulation on ATMPs is in line with the aim of the Regulation in terms of guaranteeing the highest level of health protection for patients. Based on the analysis of the relative efficacy of the only EC authorized ATMP and its exempted alternatives, there is evidence against this Regulation 1394/2007 assumption.

Cartilage from the edge of a debrided articular defect is inferior to that from a standard donor site when used for autologous chondrocyte cultivation

The aim of this study was to evaluate the cultivation potential of cartilage taken from the debrided edge of a chronic lesion of the articular surface. A total of 14 patients underwent arthroscopy of the knee for a chronic lesion on the femoral condyles or trochlea. In addition to the routine cartilage biopsy, a second biopsy of cartilage was taken from the edge of the lesion. The cells isolated from both sources underwent parallel cultivation as monolayer and three-dimensional (3D) alginate culture. The cell yield, viability, capacity for proliferation, morphology and the expressions of typical cartilage genes (collagen I, COL1; collagen II, COL2; aggrecan, AGR; and versican, VER) were assessed. The cartilage differentiation indices (COL2/COL1, AGR/VER) were calculated. The control biopsies revealed a higher mean cell yield (1346 cells/mg vs 341 cells/mg), but similar cell proliferation, viability and morphology compared with the cells from the edge of the lesion. The cartilage differentiation indices were superior in control cells: COL2/COL1 (threefold in biopsies (non-significant)); sixfold in monolayer cultures (p = 0.012), and 7.5-fold in hydrogels (non-significant), AGR/VER (sevenfold in biopsies (p = 0.04), threefold (p = 0.003) in primary cultures and 3.5-fold in hydrogels (non-significant)). Our results suggest that the cultivation of chondrocytes solely from the edges of the lesion cannot be recommended for use in autologous chondrocyte implantation.

Surgical preparation for articular cartilage regeneration without penetration of the subchondral bone plate: in vitro and in vivo studies in humans and sheep

BACKGROUND

To prevent hemorrhage, fibrin clot formation, and subsequent activation of the inflammatory response, surgical preparation for articular cartilage regeneration should avoid penetration of the subchondral bone plate.

HYPOTHESIS

Current surgical procedures with ring curettes do not violate the subchondral bone plate.

STUDY DESIGN

Controlled laboratory study.

METHODS

The subchondral bone plates of normal human (n = 5) or sheep (n = 12) cadaver femoral condyles were prepared in vitro using either traditional debridement for autologous chondrocyte implantation/transplantation (ACI/ACT) or a modified approach aimed at deliberately violating the subchondral bone plate (ie, brute force). Effects were analyzed by light microscopy. In addition, subchondral bone plates of osteoarthritic (OA) human knees undergoing total knee arthroplasty (n = 5) or normal sheep knees (n = 5) were prepared in vivo. To approximate normal/regular wear, in humans, only OA samples with maximally grade 3A (International Cartilage Repair Society score) were used.

RESULTS

In both human and sheep (in vitro), no penetration of the subchondral bone plate was observed by either standard preparation or brute force. In vivo, standard preparation of human or sheep knees also did not violate the tidemark line. Human and sheep specimens prepared by brute force, however, occasionally showed areas with an open bone marrow space.

CONCLUSION

Traditional debridement techniques for ACI/ACT using a ring curette do not violate the normal subchondral bone plate in vitro or in vivo. Even in OA knee joints, the bone plate is only violated by brute force. Therefore, the standard technique appears suitable for studies on cartilage regeneration in cases of traumatic and possibly even osteoarthritic defects.

CLINICAL RELEVANCE

The described surgical preparation technique is the traditional debridement technique for the ACI/ACT. The classic indication for the ACI/ACT is an articular cartilage injury, common in athletes.