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

Histological and Radiological Assessment of Endogenously Generated Repair Tissue In Vivo Following a Chondral Harvest

OBJECTIVE

To examine repair tissue formed approximately 15 months after a chondral harvest in the human knee.

DESIGN

Sixteen individuals (12 males, 4 females, mean age 36 ± 9 years) underwent a chondral harvest in the trochlea as a pre-requisite for autologous chondrocyte implantation (ACI) treatment. The harvest site was assessed via MRI at 14.3 ± 3.2 months and arthroscopy at 15 ± 3.5 months (using the Oswestry Arthroscopy Score [O-AS] and the International Cartilage Repair Society Arthroscopy Score [ICRS-AS]). Core biopsies (1.8 mm diameter, n = 16) of repair tissue obtained at arthroscopy were assessed histologically (using the ICRS II and OsScore histology scores) and examined via immunohistochemistry for the presence of collagen types I and II.

RESULTS

The mean O-AS and ICRS-AS of the repaired harvest sites were 7.2 ± 3.2 and 10.1 ± 3.5, respectively, with 80.3% ± 26% repair fill depth on MRI. The histological quality of the repair tissue formed was variable, with some hyaline cartilage present in 50% of the biopsies; where this occurred, it was associated with a significantly higher ICRS-AS than those with no hyaline cartilage present (median 11 vs. 7.5, P = 0.049). Collagen types I and II were detected in 12/14 and 10/13 biopsies, respectively.

CONCLUSIONS

We demonstrate good-quality structural repair tissue formed following cartilage harvest in ACI, suggesting this site can be useful to study endogenous cartilage repair in humans. The trochlea is less commonly affected by osteoarthritis; therefore, location may be critical for spontaneous repair. Understanding the mechanisms and factors influencing this could improve future treatments for cartilage defects.

Systematic Comparison of Biomaterials-Based Strategies for Osteochondral and Chondral Repair in Large Animal Models

Joint repair remains a major challenge in orthopaedics. Recent progress in biomaterial design has led to the fabrication of a plethora of promising devices. Pre-clinical testing of any joint repair strategy typically requires the use of large animal models (e.g., sheep, goat, pig or horse). Despite the key role of such models in clinical translation, there is still a lack of consensus regarding optimal experimental design, making it difficult to draw conclusions on their efficacy. In this context, the authors performed a systematic literature review and a risk of bias assessment on large animal models published between 2010 and 2020, to identify key experimental parameters that significantly affect the biomaterial therapeutic outcome and clinical translation potential (including defect localization, animal age/maturity, selection of controls, cell-free versus cell-laden). They determined that mechanically strong biomaterials perform better at the femoral condyles; while highlighted the importance of including native tissue controls to better evaluate the quality of the newly formed tissue. Finally, in cell-laded biomaterials, the pre-culture conditions played a more important role in defect repair than the cell type. In summary, here they present a systematic evaluation on how the experimental design of preclinical models influences biomaterial-based therapeutic outcomes in joint repair.

Systematic Postoperative Assessment of a Minimally-Invasive Sheep Model for the Treatment of Osteochondral Defects

To assess the clinical course of a sheep stifle joint model for osteochondral (OC) defects, medial femoral condyles (MFC) were exposed without patella luxation using medial parapatellar skin (3–4 cm) and deep incisions (2–3 cm). Two defects (7 mm diameter; 10 mm depth; OC punch) were left empty or refilled with osteochondral autologous transplantation cylinders (OATS) and explanted after six weeks. Incision-to-suture time, anesthesia time, and postoperative wound or impairment scores were compared to those in sham-operated animals. Implant performance was assessed by X-ray, micro-computed tomography, histology, and immunohistology (collagens 1, 2; aggrecan). There were no surgery-related infections or patellar luxations. Operation, anesthesia, and time to complete stand were short (0.5, 1.4, and 1.5 h, respectively). The wound trauma score was low (0.4 of maximally 4; day 7). Empty-defect and OATS animals reached an impairment score of 0 significantly later than sham animals (7.4 and 4.0 days, respectively, versus 1.5 days). Empty defects showed incomplete healing and dedifferentiation/heterotopic differentiation; OATS-filled defects displayed advanced bone healing with remaining cartilage gaps and orthotopic expression of bone and cartilage markers. Minimally-invasive, medial parapatellar surgery of OC defects on the sheep MFC allows rapid and low-trauma recovery and appears well-suited for implant testing.

Treatment of osteochondral defects: chondrointegration of metal implants improves after hydroxyapatite coating

PURPOSE

The treatment of osteochondral defects in joint cartilage remains challenging due to its limited repair capacity. This study presents a metallic osteochondral plug with hydroxyapatite (HA)-coated cap edges for improved implant-tissue contact. The hypothesis was that improved attachment prevents from synovial fluid-influx and thereby avoids osteolysis and resulting implant instability.

METHODS

In total, 24 female, adult sheep were randomized into three groups. All animals received an Episealer^®-implant in the medial condyle of the right knee. The implants were coated with two different HA versions or uncoated (control group). After 12 weeks, the implant-tissue connections were analysed radiologically and histologically.

RESULTS

In general, the groups with the coated cap edges showed a better quality of tissue connection to the implant. The occurrence of gaps between tissue and implant was more seldom, the binding of calcified and hyaline cartilage to the cap was significantly better than in the uncoated group. A histomorphometrically measured lower amount of void space in these groups compared to the group with the uncoated edges confirmed that.

CONCLUSIONS

The hypothesis of a tighter cartilage bone contact was confirmed. The HA coating of the implant's cap edges resulted in better adherence of cartilage to the implant, which was not previously reported. In conclusion, this led to a better contact between implant and cartilage as well as neighbouring bone. In clinical routine, joint fluid is aggressive, penetrates through cartilage rifts, and promotes osteolysis and loosening of implants. The observed sealing effect will act to prevent joint fluid to get access to the implant-tissue interfaces. Joint fluid is aggressive, can cause osteolysis, and can, clinically cause pain. These effects are liable to decrease with these findings and will further the longevity of these osteochondral implants.

Analysis of Defect Size and Ratio to Condylar Size With Respect to Outcomes After Isolated Osteochondral Allograft Transplantation

BACKGROUND

Osteochondral allograft transplantation (OCA) is a successful knee joint preservation technique; however, the effects of defect size and defect size:condyle ratio (DSCR) are poorly understood.

PURPOSE

To quantify clinical outcomes of isolated OCA of the knee based on defect size and DSCR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Data from patients who underwent OCA of the knee without major concomitant procedures by a single surgeon were analyzed at a minimum follow-up of 2 years. Osteochondral defect size was measured intraoperatively, and femoral condyle size was measured with preoperative imaging. Patient-reported outcomes, reoperations, and survival rates were analyzed per defect size and DSCR, comparing males and females and patients <40 and ≥40 years old.

RESULTS

Sixty-eight patients were included, of whom 57% were male (mean ± SD: age, 34.5 ± 10.3 years; follow-up, 5.2 ± 2.6 years). Mean osteochondral defect size and DSCR were 3.48 ± 1.72 cm² and 0.2 ± 0.1, respectively. Defect size was larger among males as compared with females (3.97 ± 1.71 cm² vs 2.81 ± 1.16 cm², P = .005), while DSCRs were not significantly different between sexes ( P = .609). The cohort as a whole demonstrated improvements in the following scores: Lysholm, International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and 12-Item Short Form Health Survey Physical ( P < .05). There were 27 reoperations (39.7%) at a mean of 2.5 ± 1.92 years and 8 failures (11.8%) at a mean of 2.62 ± 1.3 years. Mean DCSR was higher among patients with graft failure (0.26 ± 0.20 vs 0.19 ± 0.07, P = .049). After stratification by age, failures among patients ≥40 years old were associated with a larger defect size (mean 5.37 ± 3.50 cm² vs 3.22 ± 1.32 cm², P = .03) and higher DSCR (mean 0.30 ± 0.25 vs 0.19 ± 0.06, P = .05) when compared with nonfailures. Failures among patients <40 years old were not significantly associated with defect size or DSCR ( P > .05) as compared with nonfailures.

CONCLUSION

Patients undergoing isolated OCA transplantation demonstrated significant clinical improvements and a graft survival of 88.2% at 5.2 years. Failures overall were associated with a larger DSCR, and failures among patients ≥40 years old with a larger DSCR and larger defect size. Increasing defect size among males was positively correlated with some improved outcomes, although this was not maintained in analysis of the DSCR, suggesting similar prognosis after OCA regardless of sex.

CLINICAL RELEVANCE

Failed osteochondral allografts are associated with larger defect sizes and defect:condyle ratios in this study, providing additional information to surgeons for appropriate patient consultation.

Healing of Osteochondral Defects via Endochondral Ossification in an Ovine Model

OBJECTIVE

The objective of this study was to describe the mechanism of healing of osteochondral defects of the distal femur in the sheep, a commonly used translational model. Information on the healing mechanism be useful to inform the design of tissue engineering devices for joint surface defect repair.

DESIGN

A retrospective study was conducted examining 7-mm diameter osteochondral defects made in the distal medial femoral condyle of 40 adult female sheep, comprising control animals from 3 separate structures. The healing of the defects was studied at post mortem at up to 26 weeks.

RESULTS

Osteochondral defects of the distal femur of the sheep heal through endochondral ossification as evidenced by chondrocyte hypertrophy and type X collagen expression. Neocartilage is first formed adjacent to damaged cartilage and then streams over the damaged underlying bone before filling the defect from the base upward. No intramembranous ossification or isolated mesenchymal stem cell aggregates were detected in the healing tissue. No osseous hypertrophy was detected in the defects.

CONCLUSIONS

Osteochondral defects of the medial femoral condyle of the sheep heal via endochondral ossification, with neocartilage first appearing adjacent to damaged cartilage. Unlike the mechanism of healing in fracture repair, neocartilage is eventually formed directly onto damaged bone. There was most variability between animals between 8 and 12 weeks postsurgery. These results should be considered when designing devices to promote defect healing.

Definition of a Critical Size Osteochondral Knee Defect and its Negative Effect on the Surrounding Articular Cartilage in the Rat

BACKGROUND

Joint trauma is predisposing to the incidence of osteoarthritis (OA) of the knee. There is a limited knowledge on the impact of posttraumatic osteochondral defects on the whole joint. This study was designed to define a critical size osteochondral defect in the knee of rats and to investigate a possible association between osteochondral defects and degeneration of the surrounding joint surface.

METHODS

Cylindrical osteochondral defects of different sizes were created in the knee joint of rats. The natural course of these lesions was studied by macroscopic observation, histology, and immunohistochemistry. Gene expression of the articular cartilage surrounding the defects in vivo and of articular chondrocytes cultured in vitro in IL1β and fibroblast growth factor 2 (FGF2) supplemented media was evaluated by quantitative polymerase chain reaction (qPCR).

RESULTS

In defects of 0.9 mm diameter, spontaneous joint surface healing was observed but also upward advancing of the subchondral bone plate at 16 weeks. Larger 1.4 mm diameter defects were critical size, not resulting in successful healing at any time point. Importantly, the articular cartilage surrounding the defects expressed FGF2 and IL1β, but not ACAN and Col2. Chondrocytes cultured in IL1β and FGF2 supplemented media lost the natural fibroblast growth factor receptors - FGFr1/FGFr3 balance and showed decreased viability.

CONCLUSIONS

A critical size osteochondral defect was defined as 1.4 mm in diameter in rat. Subchondral bone plate advancement occured rapidly. The articular cartilage surrounding osteochondral defects showed catabolic activity with expression of IL1β, FGF2 and a disturbed FGFr1/FGFr3 balance, potentially initiating a process of early osteoarthritic disease.

Suspended Manufacture of Biological Structures

A method for the production of complex cell-laden structures is reported, which allows high-levels of spatial control over mechanical and chemical properties. The potential of this method for producing complicated tissues is demonstrated by manufacturing a complex hard/soft tissue interface and demonstrating that cell phenotype can be maintained over four weeks of culture.

Osteochondral Allograft Transplantation of the Knee: Analysis of Failures at 5 Years

BACKGROUND

Osteochondral allograft transplantation (OAT) is being performed with increasing frequency, and the need for reoperations is not uncommon.

PURPOSE

To quantify survival for OAT and report findings at reoperations.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A review of prospectively collected data of 224 consecutive patients who underwent OAT by a single surgeon with a minimum follow-up of 2 years was conducted. The reoperation rate, timing of reoperation, procedure performed, and findings at surgery were reviewed. Failure was defined by revision OAT, conversion to knee arthroplasty, or gross appearance of graft failure at second-look arthroscopic surgery.

RESULTS

A total of 180 patients (mean [±SD] age, 32.7 ± 10.4 years; 52% male) who underwent OAT with a mean follow-up of 5.0 ± 2.7 years met the inclusion criteria (80% follow-up). Of these, 172 patients (96%) underwent a mean of 2.5 ± 1.7 prior surgical procedures on the ipsilateral knee before OAT. Forty-eight percent of OAT procedures were isolated, while 52% were performed with concomitant procedures including meniscus allograft transplantation (MAT) in 65 (36%). Sixty-six patients (37%) underwent a reoperation at a mean of 2.5 ± 2.5 years, with 32% (21/66) undergoing additional reoperations (range, 1-3). Arthroscopic debridement was performed in 91% of patients with initial reoperations, with 83% showing evidence of an intact graft; of these, 9 ultimately progressed to failure at a mean of 4.1 ± 1.9 years. A total of 24 patients (13%) were considered failures at a mean of 3.6 ± 2.6 years after the index OAT procedure because of revision OAT (n = 7), conversion to arthroplasty (n= 12), or appearance of a poorly incorporated allograft at arthroscopic surgery (n = 5). The number of previous surgical procedures was independently predictive of reoperations and failure; body mass index was independently predictive of failure. Excluding the failed patients, statistically and clinically significant improvements were found in the Lysholm score, International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and Short Form-12 physical component summary at final follow-up ( P < .001 for all), with inferior outcomes (albeit overall improved) in patients who underwent a reoperation.

CONCLUSION

In this series, there was a 37% reoperation rate and an 87% allograft survival rate at a mean of 5 years after OAT. The number of previous ipsilateral knee surgical procedures was predictive of reoperations and failure. Of the patients who underwent arthroscopic debridement with an intact graft at the time of arthroscopic surgery, 82% experienced significantly improved outcomes, while 18% ultimately progressed to failure. This information can be used to counsel patients on the implications of a reoperation after OAT.

Platelet-Rich Plasma May Improve Osteochondral Donor Site Healing in a Rabbit Model

PURPOSE

The purpose of this study was to assess the effect(s) of platelet-rich plasma (PRP) on osteochondral donor site healing in a rabbit model.

METHODS

Osteochondral donor sites 3 mm in diameter and 5 mm in depth were created bilaterally on the femoral condyles of 12 New Zealand White rabbits. Knees were randomized such that one knee in each rabbit received an intra-articular injection of PRP and the other received saline (placebo). Rabbits were euthanized at 3, 6, and 12 weeks following surgery. Repair tissue was evaluated using the International Cartilage Repair Society (ICRS) macroscopic and histological scores.

RESULTS

No complications occurred as a result of the interventions. There was no significant difference in macroscopic scores between the 2 groups (5.5 ± 3.8 vs. 3.8 ± 3.5; P = 0.13). Subjective macroscopic assessment determined greater tissue infill with fewer fissures and a more cartilage-like appearance in PRP-treated knees. Overall ICRS histological scores were better in the PRP group compared with the placebo (9.8 ± 2.0 vs. 7.8 ± 1.8; P = 0.04). Histological scores were also higher in the PRP group compared with the placebo group at each time point. Greater glycosaminoglycan and type II collagen content were noted in the repair tissue of the PRP group compared with the placebo group.

CONCLUSION

The results of this study indicate that PRP used as an intra-articular injection may improve osteochondral healing in a rabbit model.

Bone substitutes and implantation depths for subchondral bone repair in osteochondral defects of porcine knee joints

PURPOSE

The purpose of this study was to identify the optimal material and implantation method for subchondral bone repair.

METHODS

Four osteochondral defects in a femoral groove were created in both knees of 12 pigs, and the total number of defects was 96. Eight defects were left empty (empty group). Beta-tricalcium phosphate (β-TCP) bone substitutes with 75 and 67 % porosity were implanted in 30 and 29 defects, respectively (β-TCP75 and β-TCP67 groups). Hydroxyapatite (HA) bone substitutes with 75 % porosity were filled in 29 defects (HA group). Bone substitutes were implanted at 0, 2, or 4 mm below the subchondral bone plate (SBP). The reparative tissue was assessed using microfocus computed tomography and histology 3 months after implantation.

RESULTS

Regardless of the kind of bone substitutes, the defects were filled almost completely after implanting them at the level of the SBP, while the defects remained after implanting them at 2 or 4 mm below the SBP. Reparative tissue of the β-TCP75 group was similar to the normal cancellous bone, while that of the β-TCP67 or HA group was not.

CONCLUSIONS

Subchondral bone defects were filled almost completely only when bone substitutes were implanted at the level of the SBP. The reparative tissue after implanting the β-TCP bone substitutes with 75 % porosity was the most similar to the normal cancellous bone. Therefore, implanting the β-TCP bone substitutes with 75 % porosity at the level of the SBP could be recommended as a treatment method for subchondral bone repair in osteochondral defects.

LEVEL OF EVIDENCE

I.

Does an injection of a stromal vascular fraction containing adipose-derived mesenchymal stem cells influence the outcomes of marrow stimulation in osteochondral lesions of the talus? A clinical and magnetic resonance imaging study

BACKGROUND

Marrow stimulation for the treatment of osteochondral lesions of the talus (OLTs) is controversial in patients with poor prognostic factors of OLTs. Currently, mesenchymal stem cells (MSCs) are expected to biologically augment the treatment of OLTs.

PURPOSE

To compare the clinical and magnetic resonance imaging (MRI) outcomes between an injection of MSCs with marrow stimulation and marrow stimulation alone in patients with OLTs.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 49 patients (50 ankles) with OLTs underwent follow-up MRI after arthroscopic treatment. Among these 50 ankles, 26 underwent marrow stimulation alone (conventional group), and 24 underwent marrow stimulation with an injection of a stromal vascular fraction (SVF) containing MSCs (MSC group). Clinical outcomes were evaluated according to the visual analog scale (VAS) for pain, American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale, and Tegner activity scale. The magnetic resonance observation of cartilage repair tissue (MOCART) score was used for the MRI evaluation of repaired lesions.

RESULTS

The mean VAS score, AOFAS score, and Tegner score improved from 7.1 ± 1.2, 68.5 ± 5.6, and 3.4 ± 0.6 to 3.9 ± 0.8, 78.3 ± 4.9, and 3.5 ± 0.8, respectively, in the conventional group and from 7.1 ± 0.8, 67.7 ± 4.7, and 3.4 ± 0.5 to 3.2 ± 0.8, 83.3 ± 7.0, and 3.9 ± 0.7, respectively, in the MSC group. All clinical outcomes, including the VAS, AOFAS, and Tegner scores, improved significantly in the MSC group compared with the conventional group (P = .003, .009, and .041, respectively). There was a significant difference (P = .037) in the mean MOCART score between the conventional and MSC groups (49.4 ± 16.6 vs 62.1 ± 21.8, respectively), and significant correlations of the MOCART score with clinical outcomes were found in both groups (P < .05). Patient age (≥46.1 years), large lesion size (≥151.2 mm(2)), and the presence of subchondral cysts were associated with a worse MOCART score in the conventional group (P = .015, .004, and .013, respectively) but not in the MSC group.

CONCLUSION

Clinical and MRI outcomes of an injection of an SVF containing MSCs with marrow stimulation were encouraging, compared with marrow stimulation alone, for the treatment of OLTs. Therefore, an injection of an SVF containing MSCs with marrow stimulation should be considered as a treatment for OLTs, even when poor prognostic factors, including older age, large-sized lesion, or the presence of subchondral cysts, exist.

Influence of basal support and early loading on bone cartilage healing in press-fitted osteochondral autografts

PURPOSE

The influence of basal graft support combined to early loading following an osteochondral autograft procedure is unclear. It was hypothesized that bottomed grafts may allow for early mobilization by preventing graft subsidence and leading to better healing.

METHODS

Osteochondral autografts were press fitted in the femoral condyles of 24 sheep (one graft per animal). In the unbottomed group (n = 12), a gap of 2 mm was created between graft and recipient bone base. In the bottomed group (n = 12), the graft firmly rested on recipient bone. Animals were allowed immediate postoperative weightbearing. Healing times were 3 and 6 months per group (n = 6 per subgroup). After killing, histological and histomorphometric analyses were performed.

RESULTS

Unbottomed grafts at 3 months showed significantly more graft subsidence (P = 0.024), significantly less mineralized bone (P = 0.028) and significantly worse cartilage and subchondral bone plate healing (P = 0.034) when compared to bottomed grafts. At 6 months, no differences were seen. Compared to the native situation, unbottomed grafts showed significantly more graft subsidence (P = 0.024), whereas bottomed grafts did not. Cystic lesions were seen in both groups. Osteoclasts were closely related to the degree of bone remodelling.

CONCLUSION

In the animal model, in the case of early loading, bottomed osteochondral autografts have less chance of graft subsidence. Evident subsidence negatively influences the histological healing process. In the osteochondral autograft procedure, full graft support should be aimed for. This may allow for early mobilization, diminish graft subsidence and improve long-term integration.