Continuous Passive Motion Promotes and Maintains Chondrogenesis in Autologous Endothelial Progenitor Cell-Loaded Porous PLGA Scaffolds during Osteochondral Defect Repair in a Rabbit Model

Outcomes of ankle joint distraction in a paediatric and young adult cohort presenting with symptomatic ankle arthritis

Ankle arthritis in paediatric and young adult patients causes significant morbidity; therefore, joint-preserving procedures are preferable. Ankle joint distraction (AJD) is a technique that preserves the native joint. However, only short-term outcomes are reported in paediatric patients. Therefore, this study reports on intermediate-term outcomes in a paediatric cohort. Demographics for all patients who underwent AJD at two centres were prospectively collected. Case records were reviewed retrospectively for complications and further intervention. Mean joint space at baseline and follow-up radiographs were evaluated by two independent observers. All patients were contacted for completion of a Foot and Ankle Outcome Score (FAOS). Seven patients received AJD between February 2016 and June 2019. Median age at surgery was 15 years (9.0-24.6 years). Complications included one superficial pin-site infection and one patient death due to complications from juvenile idiopathic arthritis 6.2 years post-operatively. Two patients were converted to fusion, at 12.6 months and 26.2 months following frame removal; one patient underwent spontaneous fusion at 9 months following frame removal. The four patients who continued without further intervention achieved 2.59 mm mean joint space at last follow-up (0.65-5.08 mm) and FAOS of 35-79%. Mean follow-up length was 4.3 years (2.9-6.3 years) with final radiographs at mean 2.6 years. While recognising the limitations of this retrospective review, several patients had significant, sustained improvements in joint space with good clinical outcome. Complications for this procedure are minimal, and it is a potential joint-preserving option for managing end-stage ankle arthritis in young patients.

Hyalofast Cartilage Repair Surgery with a Full Load-Bearing Rehabilitation Program One Day after Operation Reduces the Time for Professional Athletes to Return to Play

Background and Objectives: This study evaluated the effectiveness of Hyalofast cartilage repair surgery with an early, full load-bearing rehabilitation program one day after the operation for reducing the time needed for professional athletes to return to play. Materials and Methods: This prospective study included 49 patients aged between 19 and 38 years who had undergone surgical reconstruction of cartilage using the microfracture technique combined with a Hyalofast scaffold. All patients were active professional athletes. Early rehabilitation was implemented from the first postoperative day, fully loading the operated limb. A clinical evaluation was based on the KOOS and SF-36 questionnaires used during subsequent follow-up visits. All patients underwent magnetic resonance imaging (MRI) to evaluate the effect of the surgery after one year. Results: The clinical results demonstrated a statistically significant improvement in the number of complaints about pain and in the quality of life of the patients, measured in all of the applied scales, with comparisons made between six months or one year post-surgery and pre-surgery. Importantly for athletes, the parameter related to sports and recreation improved from 14 ± 11.1 to 95 ± 7.7 6 months after surgery and to 99.8 ± 1.8 one year after surgery. The overall quality of life score improved from 30 ± 18 to 88 ± 8.8 one year after surgery. Conclusions: These results show that this approach significantly shortened the time needed for the athletes to return to sports at the same level as before the surgery (athletes returned to sports in approximately 2.5-3 months). The mean follow-up time was 19.75 months. This technique can be considered a viable option for the treatment of cartilage injuries in professional athletes, allowing them to return to play more quickly in a safe and healthy way.

MECHANOBIOLOGICAL APPROACHES FOR STIMULATING CHONDROGENESIS OF STEM CELLS

Chondrogenesis is the process of differentiation of stem cells into mature chondrocytes. Such a process consists of chemical, functional, and structural changes which are initiated and mediated by the host environment of the cells. To date, the mechanobiology of chondrogenesis has not been fully elucidated. Hence, experimental activity is focused on recreating specific environmental conditions for stimulating chondrogenesis, and to look for a mechanistic interpretation of the mechanobiological response of cells in the cartilaginous tissues. There are a large number of studies on the topic that vary considerably in their experimental protocols used for providing environmental cues to cells for differentiation, making generalizable conclusions difficult to ascertain. The main objective of this contribution is to review the mechanobiological stimulation of stem cell chondrogenesis and methodological approaches utilized to date to promote chondrogenesis of stem cells in-vitro. In-vivo models will also be explored, but this area is currently limited. An overview of the experimental approaches used by different research groups may help the development of unified testing methods that could be used to overcome existing knowledge gaps, leading to an accelerated translation of experimental findings to clinical practice.

Material-Assisted Strategies for Osteochondral Defect Repair

The osteochondral (OC) unit plays a pivotal role in joint lubrication and in the transmission of constraints to bones during movement. The OC unit does not spontaneously heal; therefore, OC defects are considered to be one of the major risk factors for developing long-term degenerative joint diseases such as osteoarthritis. Yet, there is currently no curative treatment for OC defects, and OC regeneration remains an unmet medical challenge. In this context, a plethora of tissue engineering strategies have been envisioned over the last two decades, such as combining cells, biological molecules, and/or biomaterials, yet with little evidence of successful clinical transfer to date. This striking observation must be put into perspective with the difficulty in comparing studies to identify overall key elements for success. This systematic review aims to provide a deeper insight into the field of material-assisted strategies for OC regeneration, with particular considerations for the therapeutic potential of the different approaches (with or without cells or biological molecules), and current OC regeneration evaluation methods. After a brief description of the biological complexity of the OC unit, the recent literature is thoroughly analyzed, and the major pitfalls, emerging key elements, and new paths to success are identified and discussed.

Restoring Osteochondral Defects through the Differentiation Potential of Cartilage Stem/Progenitor Cells Cultivated on Porous Scaffolds

Cartilage stem/progenitor cells (CSPCs) are cartilage-specific, multipotent progenitor cells residing in articular cartilage. In this study, we investigated the characteristics and potential of human CSPCs combined with poly(lactic-co-glycolic acid) (PLGA) scaffolds to induce osteochondral regeneration in rabbit knees. We isolated CSPCs from human adult articular cartilage undergoing total knee replacement (TKR) surgery. We characterized CSPCs and compared them with infrapatellar fat pad-derived stem cells (IFPs) in a colony formation assay and by multilineage differentiation analysis in vitro. We further evaluated the osteochondral regeneration of the CSPC-loaded PLGA scaffold during osteochondral defect repair in rabbits. The characteristics of CSPCs were similar to those of mesenchymal stem cells (MSCs) and exhibited chondrogenic and osteogenic phenotypes without chemical induction. For in vivo analysis, CSPC-loaded PLGA scaffolds produced a hyaline-like cartilaginous tissue, which showed good integration with the host tissue and subchondral bone. Furthermore, CSPCs migrated in response to injury to promote subchondral bone regeneration. Overall, we demonstrated that CSPCs can promote osteochondral regeneration. A monophasic approach of using diseased CSPCs combined with a PLGA scaffold may be beneficial for repairing complex tissues, such as osteochondral tissue.

Return-to-Play and Rehabilitation Protocols following Cartilage Restoration Procedures of the Knee: A Systematic Review

OBJECTIVE

The purpose of this study is to systematically review the literature and to evaluate the reported rehabilitation protocols, return-to-play guidelines, and subsequent rates of return to play following cartilage restoration procedures in the knee.

DESIGN

MEDLINE, EMBASE, and the Cochrane Library were searched according to the PRISMA guidelines to find studies on cartilage restoration procedures in the knee, including (1) microfracture (Mfx), (2) osteochondral autograft transfer (AOT), (3) osteochondral allograft implantation (OCA), and (4) autologous chondrocyte implantation (ACI). Studies were included if they reported return-to-play data or rehabilitation protocols.

RESULTS

Overall, 179 studies fit our inclusion criteria, with 48 on Mfx, 34 on AOT, 54 on OCA, and 51 on ACI. The rate of return to play was reported as high as 88.2% with AOT, and as low as 77.2% following OCA, with rates of return to play at the same/higher level as high as 79.3% with AOT, and as low as 57.3% following ACI. The average reported time of return to play was as low as 4.9 months with AOT, and as high as 11.6 months following ACI.

CONCLUSIONS

The majority of patients are able to return to play following cartilage restoration procedures in the knee, regardless of surgical procedure utilized. However, while the rate of return to play at the same level was similar to the overall rate of return following AOT, there was a large number of patients unable to return to the same level following Mfx, OCA, and ACI. Additionally, there is wide variety in the rehabilitation protocols, and scant literature on return-to-play protocols.

Rehabilitation and Return-to-Play Criteria After Fresh Osteochondral Allograft Transplantation: A Systematic Review

Background:

Fresh osteochondral allograft (OCA) is a treatment option that allows for the transfer of size-matched allograft cartilage and subchondral bone into articular defects of the knee. Although long-term studies show good functional improvement with OCA, there continues to be wide variability and a lack of consensus in terms of postoperative rehabilitation protocols and return to sport.

Purpose:

To systematically review the literature and evaluate the reported rehabilitation protocols after OCA of the knee, including weightbearing and range of motion (ROM) restrictions as well as return-to-play criteria.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

PubMed, EMBASE, Cumulative Index of Nursing Allied Health Literature, SPORTDiscus, and Cochrane databases were searched according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for studies on knee OCA. Studies were included if they reported return-to-play data or postsurgical rehabilitation protocols.

Results:

A total of 62 studies met the inclusion criteria, with a total of 3451 knees in 3355 patients. Concomitant procedures were included in 30 of these studies (48.4%). The most commonly cited rehabilitation protocols included weightbearing restrictions and ROM guidelines in 100% and 90% of studies, respectively. ROM was most commonly initiated within the first postoperative week, with approximately half of studies utilizing continuous passive motion. Progression to weightbearing as tolerated was reported in 60 studies, most commonly at 6 weeks (range, immediately postoperatively to up to 1 year). Of the 62 studies, 37 (59.7%) included an expected timeline for either return to play or return to full activity, most commonly at 6 months (range, 4 months to 1 year). Overall, 13 studies (21.0%) included either objective or subjective criteria to determine return to activity within their rehabilitation protocol.

Conclusion:

There is significant heterogeneity for postoperative rehabilitation guidelines and the return-to-play protocol after OCA of the knee in the literature, as nearly half of the included studies reported use of concomitant procedures. However, current protocols appear to be predominantly time-based without objective criteria or functional assessment. Therefore, the authors recommend the development of objective criteria for patient rehabilitation and return-to-play protocols after OCA of the knee.

Beneficial Therapeutic Approach of Acellular PLGA Implants Coupled With Rehabilitation Exercise for Osteochondral Repair: A Proof of Concept Study in a Minipig Model

BACKGROUND

Osteochondral (OC) repair presents a significant challenge to clinicians. However, whether the use of acellular spongy poly(lactic-co-glycolic acid) (PLGA) scaffolding plus treadmill exercise as a rehabilitation program regenerates OC defects in a large-animal model has yet to be determined.

HYPOTHESIS

PLGA scaffolding plus treadmill exercise may offer improved OC repair for both high and low weightbearing regions in a minipig model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 9 mature minipigs (18 knees) were randomly divided into the treadmill exercise (TRE) group or sedentary (SED) group. All pigs received critically sized OC defects in a higher weightbearing region of the medial condyle and a lower weightbearing region of the trochlear groove. In each minipig, a PLGA scaffold was placed in the defect of the right knee (PLGA subgroup), and the defect of the left knee was untreated (empty defect [ED] subgroup). The TRE group performed exercises in 3 phases: warm-up, 3 km/h for 5 minutes; main exercise, 4 km/h for 20 minutes; and cool-down, 3 km/h for 5 minutes. The total duration was about 30 minutes whenever possible. The SED group was allowed free cage activity.

RESULTS

At 6 months, the TRE-PLGA group showed the highest gross morphology scores and regenerated a smooth articular surface covered with new hyaline-like tissue, while the defects of the other groups remained and contained nontransparent tissue. Histologically, the TRE-PLGA group also revealed sound OC integration, chondrocyte-like cells embedded in lacunae, abundant glycosaminoglycans, a sound collagen structure, and modest inflammatory cells with an inflammatory response (ie, tumor necrosis factor-α, interleukin-6). In addition, in the medial condyle region, the TRE-PLGA group (31.80 ± 3.03) had the highest total histological scores (TRE-ED: 20.20 ± 5.76; SED-PLGA: 10.25 ± 6.24; SED-ED: 11.75 ± 6.50; P = .004). In the trochlear groove region, the TRE-PLGA group (30.20 ± 6.42) displayed significantly higher total histological scores (TRE-ED: 19.60 ± 7.00; SED-PLGA: 10.00 ± 5.42; SED-ED: 11.25 ± 5.25; P = .006). In contrast, the SED-PLGA and SED-ED groups revealed an irregular surface with abrasion, fibrotic tissue with an empty void and inflammatory cells, disorganized collagen fibers, and less glycosaminoglycan deposition. Micro-computed tomography analysis revealed that the TRE-PLGA group had integrated OC interfaces with continued remodeling in the subchondral bone. Furthermore, comparing the 2 defect regions, no statistically significant differences in cartilage regeneration were detected, indicating the suitability of this regenerative approach for both high and low weightbearing regions.

CONCLUSION

Implanting an acellular PLGA scaffold plus treadmill exercise promoted articular cartilage regeneration for both high and low weightbearing regions in minipigs.

CLINICAL RELEVANCE

This study suggests the use of a cell-free porous PLGA scaffold and treadmill exercise rehabilitation as an alternative therapeutic strategy for OC repair in a large-animal knee joint model. This combined effect may pave the way for biomaterials and exercise regimens in the application of OC repair.