Cyst formation in the subchondral bone following cartilage repair

Progressive subchondral bone cyst formation following autologous chondrocyte implantation with all-suture anchors: a Case Report with histological evaluation

BACKGROUND

Subchondral bone cysts (SBCs) can significantly impact the outcomes of cartilage repair procedures such as autologous chondrocyte implantation (ACI). However, the etiology and progression of SBCs following ACI remain poorly understood. This case report highlights a progressively enlarging SBC following ACI using all-suture anchors, treated with autologous osteochondral transplantation (AOT).

CASE PRESENTATION

A 58-year-old female with progressive right knee pain, varus alignment, and Kellgren-Lawrence grade 3 osteoarthritis underwent atelocollagen-associated ACI combined with medial opening wedge high tibial osteotomy. Longitudinal radiological assessment revealed bone hole enlargement corresponding to all-suture anchor sites, with one hole continuing to expand up to 15 months postoperatively, reaching a size of 11 × 13 × 13 mm. This expanding SBC exhibited a connection to the joint cavity via a tiny fissure, scant osteosclerotic rim on CT, and fluid intensity on MRI. Histological analysis of tissue obtained during subsequent AOT revealed several findings. The SBC was located at the anterior portion of the medial femoral condyle, just beneath the all-suture anchor. Osteochondral necrosis was observed surrounding the anchor site, with no evidence of foreign body reaction. The cyst was filled with a mucoid substance and featured an aggregation of foamy macrophages. A sclerotic wall indicative of a strain response was observed. Notably, the presence of osteoclasts along the adjacent bone surface indicated ongoing bone resorption. The patient underwent AOT, which resulted in confirmed bone union. Postoperative follow-up demonstrated successful integration of the osteochondral graft and improved knee function scores over three years.

CONCLUSION

This case report documents SBC formation following knee surgery with all-suture anchors and provides histological evaluation of such a cyst. The observed histological findings may contribute to our understanding of SBC pathophysiology in the context of cartilage repair procedures. This case underscores the importance of secure suturing techniques in high-stress areas and suggests the potential benefit of extended post-operative monitoring of SBC progression beyond one year. These observations may inform future strategies for the early detection of SBC formation and its progression, as well as timely intervention to prevent further joint damage in similar cases, though further research is needed to establish broader clinical implications.

Medial Cystic Osteochondral Lesions of the Talus Exhibited Lower Sports Levels, Higher Cyst Presence Rate, and Inferior Radiological Outcomes Compared With Lateral Lesions Following Arthroscopic Bone Marrow Stimulation

PURPOSE

To compare the patient-reported outcomes and radiologic outcomes of the patients with medial and lateral cystic osteochondral lesions of the talus (OLTs) following bone marrow stimulation (BMS).

METHODS

Patients with cystic OLTs who underwent BMS between January 2016 and February 2021 were retrospectively analyzed, and the minimum follow-up time was more than 24 months. Patients were paired in a 1:1 ratio (medial cystic OLT [MC-OLT]/lateral cystic OLT [LC-OLT]) based on the OLT area within 30 mm2, follow-up within 1 year, age within 5 years, and ligament surgery (yes/no). The visual analog scale and Foot and Ankle Ability Measure (FAAM)-Activities of Daily Life and Sports scores were assessed preoperatively and postoperatively. The magnetic resonance observation of cartilage repair tissue scores and presence of cysts after BMS were also evaluated. Additionally, the receiver operating characteristic curve was performed.

RESULTS

The matched patients were divided into the MC-OLT (n = 31, 43.35 ± 12.32 months) and LC-OLT groups (n = 31, 43.32 ± 14.88 months, P = .986). Thirty patients of each group achieved a power of 80% and an α = 0.05 in this study. The MC-OLT group showed significantly less improvement in FAAM-Activities of Daily Life and sports scores (P = .034, P < .001, respectively), lower magnetic resonance observation of cartilage repair tissue scores (80.80 ± 11.91 vs 86.00 ± 8.50, P = .010), and higher presence rate of cysts after BMS (45.16% vs 16.12%, P = .013). Regarding FAAM sports scores, the LC-OLT group had significantly more patients exceeding the minimal clinically important difference (80.64% vs 51.61%, P = .031). Furthermore, an OLT depth of 7.23 mm (sensitivity: 78.6%; specificity: 70.6%) might serve as a cutoff value for predicting the presence of cysts in medial cystic OLTs following BMS.

CONCLUSIONS

Medial cystic OLTs exhibited markedly lower sports levels, higher cyst presence rate, and inferior radiologic outcomes following BMS than lateral counterparts. Additionally, an OLT depth of 7.23 mm could be the cutoff value for predicting the presence of cysts regarding medial cystic OLTs after BMS.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

NGF-BMSC-SF/CS composites for repairing knee joint osteochondral defects in rabbits: evaluation of the repair effect and potential underlying mechanisms

BACKGROUND

With the rapid growth of the ageing population, chronic diseases such as osteoarthritis have become one of the major diseases affecting the quality of life of elderly people. The main pathological manifestation of osteoarthritis is articular cartilage damage. Alleviating and repairing damaged cartilage has always been a challenge. The application of cartilage tissue engineering methods has shown promise for articular cartilage repair. Many studies have used cartilage tissue engineering methods to repair damaged cartilage and obtained good results, but these methods still cannot be used clinically. Therefore, this study aimed to investigate the effect of incorporating nerve growth factor (NGF) into a silk fibroin (SF)/chitosan (CS) scaffold containing bone marrow-derived mesenchymal stem cells (BMSCs) on the repair of articular cartilage defects in the knees of rabbits and to explore the possible underlying mechanism involved.

MATERIALS AND METHODS

Nerve growth factor-loaded sustained-release microspheres were prepared by a double emulsion solvent evaporation method. SF/CS scaffolds were prepared by vacuum drying and chemical crosslinking. BMSCs were isolated and cultured by density gradient centrifugation and adherent culture. NGF-SF/CS-BMSC composites were prepared and implanted into articular cartilage defects in the knees of rabbits. The repair of articular cartilage was assessed by gross observation, imaging and histological staining at different time points after surgery. The repair effect was evaluated by the International Cartilage Repair Society (ICRS) score and a modified Wakitani score. In vitro experiments were also performed to observe the effect of different concentrations of NGF on the proliferation and directional differentiation of BMSCs on the SF/CS scaffold.

RESULTS

In the repair of cartilage defects in rabbit knees, NGF-SF/CS-BMSCs resulted in higher ICRS scores and lower modified Wakitani scores. The in vitro results showed that there was no significant correlation between the proliferation of BMSCs and the addition of different concentrations of NGF. Additionally, there was no significant difference in the protein and mRNA expression of COL2a1 and ACAN between the groups after the addition of different concentrations of NGF.

CONCLUSION

NGF-SF/CS-BMSCs improved the repair of articular cartilage defects in the knees of rabbits. This repair effect may be related to the early promotion of subchondral bone repair.

3D Printing of Cobalt-Incorporated Chloroapatite Bioceramic Composite Scaffolds with Antioxidative Activity for Enhanced Osteochondral Regeneration

Osteochondral defects are often accompanied by excessive reactive oxygen species (ROS) caused by osteoarthritis or acute surgical inflammation. An inflammatory environment containing excess ROS will not only hinder tissue regeneration but also impact the quality of newly formed tissues. Therefore, there is an urgent need to develop scaffolds with both ROS scavenging and osteochondral repair functions to promote and protect osteochondral tissue regeneration. In this work, by using 3D printing technology, a composite scaffold based on cobalt-incorporated chloroapatite (Co-ClAP) bioceramics, which possesses ROS-scavenging activity and can support cell proliferation, adhesion, and differentiation, is developed. Benefiting from the catalytic activity of Co-ClAP bioceramics, the composite scaffold can protect cells from oxidative damage under ROS-excessive conditions, support their directional differentiation, and simultaneously mediate an anti-inflammatory microenvironment. In addition, it is also confirmed by using rabbit osteochondral defect model that the Co-ClAP/poly(lactic-co-glycolic acid) scaffold can effectively promote the integrated regeneration of cartilage and subchondral bone, exhibiting an ideal repair effect in vivo. This study provides a promising strategy for the treatment of defects with excess ROS and inflammatory microenvironments.

Concomitant Subchondral Bone Cysts Negatively Affect Clinical Outcomes Following Arthroscopic Bone Marrow Stimulation for Osteochondral Lesions of the Talus

PURPOSE

To study the effects of concomitant subchondral bone cysts (SBCs) on prognosis after arthroscopic bone marrow stimulation (BMS) for osteochondral lesions of the talus (OLTs) less than 100 mm2 and to further assess the correlation between cystic OLT area, depth, or volume and postoperative outcomes.

METHODS

We retrospectively analyzed consecutive patients with OLTs (<100 mm2) who received BMS between April 2017 and May 2020 with a minimum follow-up of 24 months. Lesion area, depth, and volume were collected on preoperative magnetic resonance imaging. Visual analog scale (VAS), American Orthopedic Foot and Ankle Society, Karlsson-Peterson, Tegner, Foot and Ankle Ability Measure (FAAM)-Activities of Daily Life and Sports scores were assessed before surgery and at the latest follow-up. Additionally, a general linear model (GLM) and a Pearson correlation analysis (PCA) were performed to investigate the effects of concomitant cysts on postoperative results.

RESULTS

Eighty-two patients with a mean follow-up of 39.22 ± 12.53 months were divided into non-cyst (n = 45; 39.91 ± 13.03 months) and cyst (n = 37; 38.37 ± 12.02 months) groups. There was no significant difference in the OLT area between the non-cyst and cyst groups (46.98 ± 19.95 mm2 vs 56.08 ± 22.92 mm2; P = .093), but the cyst group showed significantly greater depth (6.06 ± 1.99 mm vs 3.96 ± 1.44 mm; P = .000) and volume (248.26 ± 156.81 mm3 vs 134.58 ± 89.68 mm3; P = .002). The non-cyst group showed significantly more improvement in VAS pain, Karlsson-Peterson, Tegner, and FAAM scores than the cyst group (P < .05). The GLM indicated that SBCs negatively affected VAS pain and Tegner scores (P < .05). For OLTs with cysts, the PCA showed that an area of 90.91 mm2, depth of 7.56 mm, and volume of 428.13 mm3 were potential cutoff values associated with poor outcomes.

CONCLUSIONS

The concomitant SBCs negatively affected the prognosis of OLTs after BMS. For OLTs with cysts, an area of 90.91 mm2, depth of 7.56 mm, and volume of 428.13 mm3 were the potential cutoff values associated with poor outcomes after BMS.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

A guide to preclinical evaluation of hydrogel-based devices for treatment of cartilage lesions

The drive to develop cartilage implants for the treatment of major defects in the musculoskeletal system has resulted in a major research thrust towards developing biomaterial devices for cartilage repair. Investigational devices for the restoration of articular cartilage are considered as significant risk materials by regulatory bodies and therefore proof of efficacy and safety prior to clinical testing represents a critical phase of the multidisciplinary effort to bridge the gap between bench and bedside. To date, review articles have thoroughly covered different scientific facets of cartilage engineering paradigm, but surprisingly, little attention has been given to the preclinical considerations revolving around the validation of a biomaterial implant. Considering hydrogel-based cartilage products as an example, the present review endeavors to provide a summary of the critical prerequisites that such devices should meet for cartilage repair, for successful implantation and subsequent preclinical validation prior to clinical trials. Considerations pertaining to the choice of appropriate animal model, characterization techniques for the quantitative and qualitative outcome measures, as well as concerns with respect to GLP practices are also extensively discussed. This article is not meant to provide a systematic review, but rather to introduce a device validation-based roadmap to the academic investigator, in anticipation of future healthcare commercialization. STATEMENT OF SIGNIFICANCE: There are significant challenges around translation of in vitro cartilage repair strategies to approved therapies. New biomaterial-based devices must undergo exhaustive investigations to ensure their safety and efficacy prior to clinical trials. These considerations are required to be applied from early developmental stages. Although there are numerous research works on cartilage devices and their in vivo evaluations, little attention has been given into the preclinical pathway and the corresponding approval processes. With a focus on hydrogel devices to concretely illustrate the preclinical path, this review paper intends to highlight the various considerations regarding the preclinical validation of hydrogel devices for cartilage repair, from regulatory considerations, to implantation strategies, device performance aspects and characterizations.

Seamless and early gap healing of osteochondral defects by autologous mosaicplasty combined with bioactive supramolecular nanofiber-enabled gelatin methacryloyl (BSN-GelMA) hydrogel

Autologous mosaicplasty is a common approach used to treat osteochondral defects in clinical practice. Gap integration between host and transplanted plugs requires bone tissue reservation and hyaline cartilage regeneration without uneven surface, graft necrosis and sclerosis. However, poor gap integration is a serious concern, which eventually leads to deterioration of joint function. To deal with such complications, this study has developed a strategy to effectively enhance integration of the gap region following mosaicplasty by applying injectable bioactive supramolecular nanofiber-enabled gelatin methacryloyl (GelMA) hydrogel (BSN-GelMA). A rabbit osteochondral defect model demonstrated that BSN-GelMA achieved seamless osteochondral healing in the gap region between plugs of osteochondral defects following mosaicplasty, as early as six weeks. Moreover, the International Cartilage Repair Society score, histology score, glycosaminoglycan content, subchondral bone volume, and collagen II expression were observed to be the highest in the gap region of BSN-GelMA treated group. This improved outcome was due to bio-interactive materials, which acted as tissue fillers to bridge the gap, prevent cartilage degeneration, and promote graft survival and migration of bone marrow mesenchymal stem cells by releasing bioactive supramolecular nanofibers from the GelMA hydrogel. This study provides a powerful and applicable approach to improve gap integration after autologous mosaicplasty. It is also a promising off-the-shelf bioactive material for cell-free in situ tissue regeneration.

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A novel strategy that can effectively enhance post-mosaicplasty interstitial integration was developed.

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The bioactive supramolecular nanofibers (BSN) exhibited comparable bioactivity to insulin-like growth factor-1 (IGF-1).

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The BSN-GelMA hydrogel is a promising off-the-shelf bioactive material for cell-free in situ tissue regeneration.

Outcomes of bone marrow aspirate concentrate and matrix-induced chondrogenesis (BMIC) for treatment of osteochondral lesions of the talus

BACKGROUND

To analyze the outcomes of Bone marrow aspirate concentrate and Matrix-Induced Chondrogenesis (BMIC) in Osteochondral Lesions of the Talus (OLTs).

METHODS

Patients with OLTs treated with BMIC from June 2013 to July 2020 were included. Visual Analogue Scale (VAS), Foot Function Index (FFI), and Foot Ankle Outcome Score (FAOS) before treatment and at last follow-up were subjected to analysis.

RESULTS

Forty-five patients were included and mean follow-up was 39.1 months (range, 13-97 months). Mean lesion size and depth were 180.7 ± 110.4 mm² and 9.6 ± 3.7 mm, respectively. BMIC was performed without malleolar osteotomy in 36 patients (80%) and bone graft was performed in 42 (93.3%). VAS, FFI, and FAOS improved significantly. No complication occurred and no revision was required.

CONCLUSIONS

The BMIC procedure is feasible and should be considered a viable treatment option for OLTs associated with large subchondral bone defects.

Structural features of subchondral bone cysts and adjacent tissues in hip osteoarthritis

OBJECTIVE

Focal lesions within the subchondral bone, termed subchondral bone cysts (SBCs), are clinically accepted radiographic markers of advanced osteoarthritis (OA), but their etiology in the hip is not well understood.

DESIGN

This study used micro-computed tomography (μCT), and histological and immunocytological analysis to examine the prevalence, size, location, and morphological and cellular features of SBCs found within 34 femoral heads (14 male, 20 female; age range = 43-80 years) obtained from total hip arthroplasty procedures.

RESULTS

SBCs were common-present in 91% of the femoral heads examined-and frequently commuted with the surface of the femoral head, but otherwise showed no preferred anatomical location. Few associations were found between SBC features and patient characteristics such as BMI, age and sex. SBCs were also heterogenous in composition, ranging from fibrous (most common) to predominantly fatty (least common) and often containing vasculature, nerve fibers, cartilage islands, and bony spicules. Despite this heterogeneity, focal abnormalities in bone density and cartilage thickness were consistently observed. Bone adjacent to SBCs was denser than that in the primary compressive group, and cartilage thickness in regions overlying SBCs was lower than in non-overlying regions. In contrast to these local bony changes, μCT-based finite element analyses indicated that the stiffness of the primary compressive group was only mildly affected by SBCs.

CONCLUSIONS

These findings indicate that SBCs in the femoral head involve extensive perturbations in cellular activity, culminating in myriad skeletal tissue types and spatially heterogenous changes in bone and cartilage morphology that are likely to affect OA progression.

Association of Subchondral Changes With Age and Clinical Outcome in Patients With Osteochondral Fractures in the Knee: MRI Analysis at 1 to 10 Years Postoperatively

Background:

Predictive factors influencing outcomes after surgical fixation of osteochondral fractures (OCFs) in the knee, particularly time between injury and surgery, have not been determined.

Purpose:

To report imaging and clinical outcomes after OCF fixation and to assess the association between clinical scores and patient characteristics, lesion morphology, and appearance on magnetic resonance imaging (MRI) scans.

Study Design:

Case series; Level of evidence, 4.

Methods:

We assessed the clinical and imaging outcomes of 19 patients after screw fixation for OCFs in the knee at a minimum follow-up of 1 year. Patient characteristics, lesion morphology, and time from trauma to surgery were reviewed for each patient. At final follow-up, patients completed a 100-point visual analog scale (VAS) for pain, Tegner activity scale, Knee injury and Osteoarthritis Outcome Score (KOOS), and patient satisfaction survey. Postoperative MRI scans were assessed using the MOCART (magnetic resonance observation of cartilage repair tissue), Osteochondral Allograft MRI Scoring System, and bone marrow edema (BME) size.

Results:

The mean patient age at surgery was 21.3 ± 11.4 years, and the median time from trauma to surgery was 10 days (range, 0-143 days). The refixed OCF fragment failed in 1 (5.3%) patient on the lateral condyle at 15 months postoperatively. The mean follow-up for the remaining 18 patients was 4.7 ± 3.2 years, and postoperative outcomes were as follows: VAS pain score, 9.5 ± 17.9; Tegner score, 4.8 ± 2.3; KOOS–Pain, 85.9 ± 17.6, KOOS-Symptoms, 76.4 ± 16.1; KOOS–Activities of Daily Living, 90.3 ± 19.0; KOOS–Sport, 74.4 ± 25.4; and KOOS–Quality of Life, 55.9 ± 24.7. Overall, 84.2% were satisfied or very satisfied with outcomes. Patient age was significantly associated with KOOS subscale scores and subchondral imaging parameters including BME and presence of subchondral cysts, which in turn were the only imaging variables linked to clinical outcomes (P < .05). Time from injury to surgery was not correlated with clinical or imaging outcomes.

Conclusion:

Fixation of OCFs yielded acceptable clinical and imaging outcomes at a mean 5-year follow-up with seemingly little influence of delayed surgical treatment. Postoperative subchondral changes were significantly associated with clinical outcomes and were linked to patient age at surgery.

Virtual monoenergetic images from photon-counting spectral computed tomography to assess knee osteoarthritis

Background

Dual-energy computed tomography has shown a great interest for musculoskeletal pathologies. Photon-counting spectral computed tomography (PCSCT) can acquire data in multiple energy bins with the potential to increase contrast, especially for soft tissues. Our objectives were to assess the value of PCSST to characterise cartilage and to extract quantitative measures of subchondral bone integrity.

Methods

Seven excised human knees (3 males and 4 females; 4 normal and 3 with osteoarthritis; age 80.6 ± 14 years, mean ± standard deviation) were scanned using a clinical PCSCT prototype scanner. Tomographic image reconstruction was performed after Compton/photoelectric decomposition. Virtual monoenergetic images were generated from 40 keV to 110 keV every 10 keV (cubic voxel size 250 × 250 × 250 μm³). After selecting an optimal virtual monoenergetic image, we analysed the grey level histograms of different tissues and extracted quantitative measurements on bone cysts.

Results

The optimal monoenergetic images were obtained for 60 keV and 70 keV. Visual inspection revealed that these images provide sufficient spatial resolution and soft-tissue contrast to characterise surfaces, disruption, calcification of cartilage, bone osteophytes, and bone cysts. Analysis of attenuation versus energy revealed different energy fingerprint according to tissues. The volumes and numbers of bone cyst were quantified.

Conclusions

Virtual monoenergetic images may provide direct visualisation of both cartilage and bone details. Thus, unenhanced PCSCT appears to be a new modality for characterising the knee joint with the potential to increase the diagnostic capability of computed tomography for joint diseases and osteoarthritis.

The Effect of Bone Marrow Stimulation for Cartilage Repair on the Subchondral Bone Plate

PURPOSE

To investigate the effect of bone-marrow stimulation (BMS) on subchondral bone plate morphology and remodeling compared to untreated subchondral bone in a validated minipig model.

METHODS

Three Göttingen minipigs received BMS with drilling as treatment for two chondral defects in each knee. The animals were euthanized after six months. Follow-up consisted of a histological semiquantitative evaluation using a novel subchondral bone scoring system and micro computed tomography (µCT) of the BMS subchondral bone. The histological and microstructural properties of the BMS-treated subchondral bone were compared to that of the adjacent healthy subchondral bone.

RESULTS

The µCT analysis showed that subchondral bone treated with BMS had significantly higher connectivity density compared to adjacent untreated subchondral bone (26 1/mm³ vs. 21 1/mm³, P = 0.048). This was the only microstructural parameter showing a significant difference. The histological semiquantitative score differed significantly between the subchondral bone treated with BMS and the adjacent untreated subchondral (8.0 vs. 10 P = < 0.001). Surface irregularities were seen in 43% and bone overgrowth in 27% of the histological sections. Only sparse formation of bone cysts was detected (1%).

CONCLUSIONS

BMS with drilling does not cause extensive changes to the subchondral bone microarchitecture. Furthermore, the morphology of BMS subchondral bone resembled that of untreated subchondral bone with almost no formation of bone cyst, but some surface irregularities and bone overgrowth.