Biological Reconstruction of the Osteochondral Unit After Failed Focal Resurfacing of a Chondral Defect in the Knee

Osteochondral tissue engineering: Perspectives for clinical application and preclinical development

The treatment of osteochondral defects (OCD) remains challenging. Among currently available surgical treatments for OCDs, scaffold-based treatments are promising to regenerate the osteochondral unit. However, there is still no consensus regarding the clinical effectiveness of these scaffold-based therapies for OCDs. Previous reviews have described the gradient physiological characteristics of osteochondral tissue and gradient scaffold design for OCD, tissue engineering strategies, biomaterials, and fabrication technologies. However, the discussion on bridging the gap between the clinical need and preclinical research is still limited, on which we focus in the present review, providing an insight into what is currently lacking in tissue engineering methods that failed to yield satisfactory outcomes, and what is needed to further improve these techniques. Currently available surgical treatments for OCDs are firstly summarized, followed by a comprehensive review on experimental animal studies in recent 5 years on osteochondral tissue engineering. The review will then conclude with what is currently lacking in these animal studies and the recommendations that would help enlighten the community in developing more clinically relevant implants.

The translational potential of this article

This review is attempting to summarize the lessons from clinical and preclinical failures, providing an insight into what is currently lacking in TE methods that failed to yield satisfactory outcomes, and what is needed to further improve these implants.

Developmental engineering of living implants for deep osteochondral joint surface defects

INTRODUCTION

The repair of deep osteochondral joint surface defects represents a significant unmet clinical need. Importantly, untreated lesions lead to a high rate of osteoarthritis. The current strategies to repair these defects include osteochondral autograft transplantation or "sandwich" strategies combining bone autografts with autologous chondrocyte implantation, with poorly documented long-term outcomes. In this study, we first investigated the capacity of juvenile osteochondral grafts (OCGs) to repair osteochondral defects in skeletally mature rats. With this regenerative model in view, we produced a new biological, bilayered and scaffold-free Tissue Engineered construct (bTEC) for the repair of a deep osteochondral defect of the rat knee.

METHODS

Cylindrical OCGs were excised from the femoral intercondylar groove of the knee of skeletally immature rats (5 weeks) and transplanted into osteochondral defects created in skeletally mature rats (11 weeks). To create bTECs, micromasses (μMasses) of human periosteum-derived progenitor cells (hPDCs) and human articular chondrocytes (hACs) were produced in vitro using previously optimized chemically defined medium formulations containing growth and differentiation factors including bone morphogenetic proteins. These two μMass types were subsequently implanted as bilayered constructs into osteochondral defects in nude rats. At 4 and 16 weeks after surgery, the knees were collected and processed for subsequent 3D imaging analysis and histological evaluation. Micro-computed tomography (μCT), H&E, and Safranin O staining were used to evaluate the degree and quality of tissue repair.

RESULTS

The osteochondral unit of the knee joint in 5 weeks old rats exhibits an immature phenotype, displaying active subchondral bone formation through endochondral ossification and the absence of a tidemark. When transplanted into skeletally mature animals, the immature OCGs resumed their maturation process, i.e., formed new subchondral bone, established the tidemark, and maintained their Safranin O-positive hyaline cartilage at 16 weeks after transplantation. The bTECs (hPDCs + hACs) could partially recapitulate the biology as seen with the immature OCGs, including the formation of the joint surface architecture with typical zonation, ranging from non-mineralized hyaline cartilage in the superficial layers to a progressively mineralized matrix at the interface with a new subchondral bone plate.

CONCLUSIONS

Cell-based TE constructs mimicking immature OCGs and displaying a hierarchically organized structure comprising of different tissue forming units seem an attractive strategy to treat deep osteochondral defects of the knee.

Ten-Year Average Full Follow-up and Evaluation of a Contoured Focal Resurface Prosthesis (HemiCAP) in Patients in the United Kingdom

A significant number of patients are affected by localized articular damage that is appropriate neither for traditional arthroplasty nor for biological repair. A focal resurfacing system using a matched contoured articular prosthetic (HemiCAP) has been introduced for the treatment of such cases. Independent long-term results of these implants are limited. We retrospectively evaluated the use of this resurfacing system in 14 patients (13 males, 1 female), with a mean age of 40.3 years (range: 28-49), with focal femoral condyle defects. The same consultant orthopaedic surgeon performed all procedures. Our primary outcome measure was revision rate. Secondary outcome measures included radiographic evaluation (prosthesis migration signs, radiolucency), patient-reported functional evaluation (knee injury and osteoarthritis outcome scores), and complications. A total of 10 patients were treated on the medial femoral condyle, 2 were treated on the lateral condyle, and 2 received bicondylar implants (14 in total). Average follow-up was 107 months (range: 59-135). Three patients were lost to follow-up at the time of study. One patient was excluded from the study. Of the 10 left, 2 had to be revised, leading the survival rate to be 80% at 9.4 years. In four contactable patients, average Knee injury and Osteoarthritis Outcomes score at 121 months postsurgery (9.75 years) was 92.9 (as compared with 57.7 preoperatively). There were no complications. This series demonstrates that focal resurfacing is a safe, suitable, and useful temporizing step in knee arthroplasty surgery. The use of the focal resurfacing implant in this way allows the delay in transition to knee arthroplasty. This series shows an excellent functional outcome for remaining implants at average 10 years, with low complication rates.

Focal inlay resurfacing for full-thickness chondral defects of the femoral medial condyle may delay the progression to varus deformity

INTRODUCTION

Full-thickness chondral defects at the knee joint predispose to the beginning of a degenerative process which final consequence is the compartment collapse and finally the deviation to varus, because the cartilage of the medial femoral condyle is the most frequently affected area. Likewise, people with these chondral defects are more likely to develop tricompartmental osteoarthritis, reason why early surgical management should be the treatment of choice. The aim of this study was to compare the pre- and post-operative lower limb alignment (mechanical axis), in cases of full-thickness chondral defects of the femoral medial condyle that have been managed by means of a prosthetic focal inlay resurfacing, at a minimum follow-up of five years.

METHODS

A retrospective study of patients treated for chondral defects in the medial femoral condyle was performed. The inclusion criteria were patients who had undergone a focal inlay resurfacing and minimum follow-up of 5 years. Patients that required a concomitant valguizing tibial osteotomy were finally excluded. The follow-up analysis was performed by means of radiological examinations performed prior to surgery and at the last follow-up visit. The mean limb mechanical axis of the operated knees was calculated both pre- and post-operatively, and comparisons between these two settings were performed.

RESULTS

Ten patients were included: eight men and two women. The mean age at the time of surgery was 55 (40-65) years. The mean follow-up was 9 years (range 5-15). The mean limb mechanical axis was 1.33 ± 4.16 in the pre-operative setting and 2.40 ± 5.50 in the post-operative setting (p = 0.441).

CONCLUSION

In the setting of small to moderate size, unique femoral medial condyle full-thickness chondral lesions, filling the defect with an inlay prosthetic resurfacing may protect against the progression to varus deformity.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

Focal metallic inlay resurfacing prosthesis in articular cartilage defects: short-term results of 118 patients and 2 different implants

BACKGROUND

The goal of this study was to share our experience with two different inlay metallic implants in the treatment of knee cartilage defects and to analyze their effects on functional scores.

METHODS

This retrospective study included 118 patients operated on for focal full-thickness knee cartilage lesions, who were treated with a focal metallic inlay resurfacing prosthesis. A cobalt-chromium (Co-Cr) resurfacing implant was applied to 73 patients with a knee chondral lesion, and a biosynthetic implant was applied to 45. All patients were evaluated preoperatively and postoperatively using the KOOS, VAS, and Tegner activity scores.

RESULTS

The group with the Co-Cr-resurfacing implant showed a significantly greater improvement (p < 0.001) in the Tegner and VAS scores at the 2-year follow-up examination. The KOOS scores were similar in both groups. Median patient age was similar in both groups. All patients had a follow-up of at least 2 years. The preoperative and postoperative scores were compared and significant improvements (p < 0.001) were observed. The biosynthetic implant had a higher revision rate. In the univariate analysis, age and type of implant were significantly associated with revision surgery. In the multivariate Cox-regression analysis model, the type of implant was significantly associated with revision surgery.

CONCLUSION

All the patients operated with the above-mentioned implants showed significant improvements in pain and activity scores. Despite the overall good clinical results, 17% of patients with a biosynthetic implant and > 6% of patients with Co-Cr-resurfacing implant required revision surgery. Age and implant type were the main risk factors associated with revision.

Translational applications of photopolymerizable hydrogels for cartilage repair

BACKGROUND

Articular cartilage lesions generated by trauma or osteoarthritis are the most common causes of pain and disability in patients. The development of photopolymerizable hydrogels has allowed for significant advances in cartilage repair procedures. Such three-dimensional (3D) networks of polymers that carry large amounts of water can be created to resemble the physical characteristics of the articular cartilage and be delivered into ill-defined cartilage defects as a liquid solution prior to polymerization in vivo for perfect fit with the surrounding native tissue. These hydrogels offer an adapted environment to encapsulate and propagate regenerative cells in 3D cultures for cartilage repair. Among them, mesenchymal stem cells and chondrocytes may represent the most adapted sources for implantation. They also represent platforms to deliver therapeutic, biologically active factors that promote 3D cell differentiation and maintenance for in vivo repair.

CONCLUSION

This review presents the benefits of photopolymerization of hydrogels and describes the photoinitiators and materials in current use for enhanced cartilage repair.

Asymptomatic focal calcium pyrophosphate crystal deposition within partially failed repair tissue after matrix-assisted autologous chondrocyte implantation

Possible failures of autologous chondrocyte implantation (ACI), a cell-based technique for articular cartilage repair, are not always clinically apparent and the underlying mechanisms largely remain unknown. This case report presents the first scenario in the literature highlighting an association of a medium-term partial failure of an advanced ACI procedure (matrix-assisted ACI) in the knee with focal asymptomatic calcium pyrophosphate deposition disease, a common inflammatory pyrophosphate arthropathy. The specific presence of CPPDs, resulting from increased biomechanical stresses in the repair tissue-cartilage and repair tissue-subchondral bone integration sites, together with the absence of cartilage regeneration was identified and possibly contributed to the partial failure.Level of evidence V.

Autologous Matrix-Induced Chondrogenesis: A Systematic Review of the Clinical Evidence

BACKGROUND

The addition of a type I/III collagen membrane in cartilage defects treated with microfracture has been advocated for cartilage repair, termed "autologous matrix-induced chondrogenesis" (AMIC).

PURPOSE

To examine the current clinical evidence regarding AMIC for focal chondral defects.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed by searching PubMed, ScienceDirect, and Cochrane Library databases. Inclusion criteria were clinical studies of AMIC for articular cartilage repair, written in English. Relative data were extracted and critically analyzed. PRISMA guidelines were applied, the methodological quality of the included studies was assessed by the modified Coleman Methodology Score (CMS), and aggregate data were generated.

RESULTS

Twenty-eight clinical articles were included: 12 studies (245 patients) of knee cartilage defects, 12 studies (214 patients) of ankle cartilage defects, and 4 studies (308 patients) of hip cartilage defects. The CMS demonstrated a suboptimal study design in the majority of published studies (knee, 57.8; ankle, 55.3; hip, 57.7). For the knee, 1 study reported significant clinical improvements for AMIC compared with microfracture for medium-sized cartilage defects (mean defect size 3.6 cm²) after 5 years (level of evidence, 1). No study compared AMIC with matrix-assisted autologous chondrocyte implantation (ACI) in the knee. For the ankle, no clinical trial was available comparing AMIC versus microfracture or ACI. In the hip, only one analysis (level of evidence, 3) compared AMIC with microfracture for acetabular lesions. For medium-sized acetabular defects, one study (level of evidence, 3) found no significant differences between AMIC and ACI at 5 years. Specific aspects not appropriately discussed in the currently available literature include patient-related factors, membrane fixation, and defect properties. No treatment-related adverse events were reported.

CONCLUSION

This systematic review reveals a paucity of high-quality, randomized controlled studies testing the AMIC technique versus established procedures such as microfracture or ACI. Evidence is insufficient to recommend joint-specific indications for AMIC. Additional nonbiased, high-powered, randomized controlled clinical trials will provide better clinical and structural long-term evidence, thus helping to define possible indications for this technique.

Focal metallic inlay resurfacing prosthesis for the treatment of localized cartilage defects of the femoral condyles: a systematic review of clinical studies

PURPOSE

To systematically review the results of focal metallic inlay resurfacing prosthesis for the treatment of isolated cartilage defects of the femoral condyles.

METHODS

A systematic electronic search of the PubMed database and the Cochrane Library was performed in April 2017 to identify studies that reported clinical or radiographic outcome of focal metallic inlay resurfacing prosthesis for the treatment of isolated cartilage defects of the femoral condyles. Included studies were abstracted regarding study characteristics, patient demographics, prosthetic device and location, indications and contraindications, and outcome measures. Outcome of interest included functional outcome scores, radiographic measures, complications, re-operations, and conversion to arthroplasty. The methodologic quality of the included studies was assessed with the Coleman Methodology Score.

RESULTS

Six studies with a total of 186 patients met the inclusion criteria. Five studies were level IV evidence, and one was level III. The methodologic quality of the included studies was good, with a mean Coleman Methodology Score of 78. Two different implants were used: the HemiCAP^® (five studies; 66% of study group) and UniCAP^® (one study; 34%) implant. The mean age was 46-54 years, and the mean follow-up was 24 months to 7 years. Pre- and post-operative outcome scores were compared in all six studies, and five studies reported significant improvements at the final follow-up for all scores (objective und functional KSS, KOOS, WOMAC, Tegner, HSS Knee and Function score, SF-36 and SF-12 physical component score) except for the SF-36 and SF-12 mental component score. Progression of osteoarthritis was analysed using the Kellgren-Lawrence grading in three studies (30% of study group), with two studies reporting significant progression. The OARSI grading system was analysed in one study with no significant progression. The overall conversion rate to arthroplasty was 22% with considerable differences between the two implants: 9% for HemiCAP^® and 47% for UniCAP^®.

CONCLUSIONS

Focal metallic inlay resurfacing prosthesis seems to be a viable option for a carefully selected group of patients. Significant improvement in knee function and pain was observed in most patients. Uncertainty remains with regard to progression of osteoarthritis because of conflicting results and inconsistent reporting. One out of five patients has to be converted to arthroplasty after an average of 4 years. However, compared to the UniCAP^® implant, considerable lower conversion rates were reported for the smaller HemiCAP^® implant.

LEVEL OF EVIDENCE

Systematic review of level III and IV studies, Level IV.

Focal articular prosthetic resurfacing for the treatment of full-thickness articular cartilage defects in the knee: 12-year follow-up of two cases and review of the literature

INTRODUCTION

The rationale of focal articular prosthetic resurfacing used as a primary arthroplasty procedure in the treatment of articular cartilage defects is still under debate. Conflicting reports raise concern about high rates of re-operations and continued development of osteoarthritis, while others have reported good outcomes. The goal of this paper is to present the long-term results of two patients with a 12-year follow-up and to report the results of a literature review.

MATERIALS AND METHODS

Two patients (male, 70 years; female 63 years) with a follow-up of 12 years were reviewed. Patients were evaluated with standard radiographs to assess the progression of osteoarthritis (OA), a clinical examination including the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity scale. The literature review was performed using the search terms HemiCAP, focal, femoral, condyle, inlay, and resurfacing to identify articles published in the English language up until September 25, 2016.

RESULTS

The clinical and radiographic follow-ups of the patients were 11.9 and 11.8 years, respectively. Both patients were satisfied with their outcome and would have the operation again. Comparing the first postoperative to 12-year follow-up X-rays, the radiographic results demonstrated no signs of periprosthetic loosening, preservation of joint space, and no change in the osteoarthritic stage. KOOS Scores were 86 and 83 for pain, 89 and 93 for symptoms, 88 and 100 for activities of daily living (ADL), 75 and 65 for sports and recreation, and 75 and 81 for quality of life (QOL). The Tegner activity level was 5 and 4. The literature review comprised 6 studies with 169 focal articular prosthetic resurfacing procedures in 169 patients (84 male, 85 female) with a mean age at implantation ranging from 44.7 to 53.7 years and a follow-up range of 20 months to 7 years. Five studies were classified as level 4 and one as level 3. Clinical and radiographic results showed mainly good to excellent outcomes but were different among the studies depending on the indication. Re-operation rates ranged from 0 to 23% depending on the length of follow-up.

CONCLUSIONS

The results suggest that focal articular prosthetic resurfacing is an effective and safe treatment option in selected cases.