The performance of resurfacing implants for focal cartilage defects depends on the degenerative condition of the opposing cartilage

A hybrid repair strategy for full-thickness cartilage defects: Long-term experimental study in eight horses

The objective of this study was to evaluate a non-resorbable implant for the focal repair of chondral defects in eight adult horses with 12-month follow-up. The bi-layered construct composed of a polycarbonate-urethane-urea biomaterial which was printed in 3D fashion onto a bone anchor was implanted into surgically created osteochondral defects into the femoropatellar joints of eight horses. The analysis of post-mortem outcomes were compared to defects treated with microfracture in the same animal on the contralateral femoropatellar jointfemoropatellar joint. The overall macroscopic scoring after 12 months yielded higher scores in the OCI-treated stifles compared to MF treatment (p = 0.09) with better quality and filling of the defect. Histology revealed good anchorage of repair tissue growing into the 3D structure of the implant and histopathology scoring for adjacent native cartilage showed no difference between groups. MRI and micro-CT showed overall less sclerotic reactions in the surrounding bone in the implant group and no foreign body reaction was detected. Biomechanical analysis of the repair tissue revealed a significantly higher peak modulus (p < 0.05) in the implant group (0.74 ± 0.45) compared to the microfracture control group (0.15 ± 0.11). Dynamic loading yielded higher values for the repair tissue overgrowing the implant group (0.23 ± 0.17) compared to the microfracture control (0.06 ± 0.06) (p < 0.05). The bi-layered osteochondral implant provided a safe implant for focal repair of full-thickness osteochondral defects, as no adverse reaction was seen within the joints and the level of degeneration of adjacent cartilage to the repair site was not different compared to that seen in defects treated with microfracture after 12 months.

Focal resurfacing of the knee - A systematic review and meta-analysis

PURPOSE

In order to assess the published validity of focal resurfacing of the knee, a systematic review and meta-analysis were conducted to (i) evaluate revision rates and implant survival of focal resurfacing of the knee; (ii) explore surgical complications; and (iii) evaluate patient reported clinical outcome measures.

METHODS

PubMED, Cochrane Library and Medline databases were searched by 2 independent reviewers in February 2022 for prospective and retrospective cohort studies evaluating any of the following implant types: HemiCAP®, UniCAP®, Episealer® or BioBoly®. Data on incidence of revision, complications and various patient reported outcome measures, such as Knee Society Score (KSS) or Knee Injury and Osteoarthritis Outcome Score (KOOS) was sourced.

RESULTS

A total of 24 published studies were identified with a total of 1465 enrolled patients. A revision rate of 12.97% over a 5.9 year weighted mean follow-up period was observed across all implant types. However, in one series a Kaplan-Meir survival as high as 92.6% at a 10-year follow-up period was noted. A statistically significant improvement was documented across multiple subjective clinical outcomes scores, for example a mean 4.56 point improvement of the VAS (0-10) pain score. The Kellgren-Lawrence score was used to evaluate the radiological progression of osteoarthritis and showed a small significant reduction in all anatomical locations, hence not supporting the hypothesis that focal femoral implants can lead to the progression of osteoarthritis in the affected compartment. There was a low reported incidence of post-operative complications such as aseptic loosening or deep wound infection.

CONCLUSIONS

Focal femoral resurfacing appears to be a viable treatment option for focal symptomatic chondral lesions in patients beyond biological reconstruction, with low revision rates and high patient satisfaction especially at short and medium length follow-up.

The effect of HydroSpacer implant placement on the wear of opposing and adjacent cartilage

A HydroSpacer implant, that is, a swelling hydrogel confined by a spacer fabric, was developed to repair focal cartilage defects and to prevent progression into osteoarthritis. The present study evaluated the effect of implant placement height in an osteochondral (OC) plug on wear of the opposing and adjacent cartilage. Three-dimensional warp-knitted spacer fabrics, polycaprolactone with poly(4-hydroxybutyrate) pile yarns, were filled with a hyaluronic acid methacrylate and chondroitin sulfate methacrylate hydrogel. After polymerization of the hydrogel, these HydroSpacers were implanted in OC defects (ø 6 mm) created in bovine OC plugs (ø 10 mm) and allowed to swell to equilibrium. A custom-made pin-on-plate wear apparatus was used to apply simultaneous compression and sliding against bovine cartilage. Cartilage damage, visualized with Indian ink, was only seen for the group in which the HydroSpacer was placed flush with the surrounding cartilage. A significant increase on average surface roughness of the sliding path compared to the adjacent cartilage confirmed surface damage for this group. When the implants were recessed (with and without extra hydrogel layer on top of the implant), this damage was not observed, but the cartilage surrounding the implants was compressed (without damage) indicating substantial load sharing with the implant. Furthermore, it was shown that all defects treated with a HydroSpacer implant resulted in shear forces comparable to intact cartilage. Clinical significance: The present study suggests that placing a HydroSpacer implant recessed into the surrounding cartilage would decrease wear of the opposing cartilage. Altogether, this study supports the development of textile-constraining hydrogels for cartilage replacement.

Surface texture analysis of different focal knee resurfacing implants after 6 and 12 months in vivo in a goat model

The clinical success of osteochondral implants depends significantly on their surface properties. In vivo, an implant may roughen over time which can decrease its performance. The present study investigates whether changes in the surface texture of metal and two types of polycarbonate urethane (PCU) focal knee resurfacing implants (FKRIs) occurred after 6 and 12 months of in vivo articulation with native goat cartilage. PCU implants which differed in stem stiffness were compared to investigate whether the stem fixating the implant in the bone influences surface topography. Using optical profilometry, 19 surface texture parameters were evaluated, including spatial distribution and functional parameters obtained from the material ratio curve. For metal implants, wear during in vivo articulation occurred mainly via material removal, as shown by the significant decrease of the core-valley transition from 91.5% in unused implants to 90% and 89.6% after 6 and 12 months, respectively. Conversely, for PCU implants, the wear mechanism consisted in either filling of the valleys or flattening of the surface by dulling of sharp peaks. This was illustrated in the change in roughness skewness from negative to positive values over 12 months of in vivo articulation. Implants with a softer stem experienced the most deformation, shown by the largest change in material ratio curve parameters. We therefore showed, using a detailed surface profilometry analysis, that the surface texture of metal and two different PCU FKRIs changes in a different way after articulation against cartilage, revealing distinct wear mechanisms of different implant materials.