Characteristics of repair tissue in second-look and third-look biopsies from patients treated with engineered cartilage: relationship to symptomatology and time after implantation

Abstract

Introduction: The present study established characteristics of tissue regrowth in patients suffering knee lesions treated with grafts of autologous chondrocytes grown on three-dimensional hyaluronic acid biomaterials.

Methods: This multicentred study involved a second-look arthroscopy/biopsy, 5 to 33 months post implant (n = 63). Seven patients allowed a third-look biopsy, three of which were performed 18 months post implant. Characteristics of tissues were histologically and histochemically evaluated. The remaining bone stubs were evaluated for cartilage/bone integration. For data analysis, biopsies were further divided into those obtained from postoperative symptomatic patients (n = 41) or from asymptomatic patients (n = 22).

Results: The percentage of hyaline regenerated tissues was significantly greater in biopsies obtained after, versus within, 18 months of implantation. Differences were also observed between symptomatic and asymptomatic patients: reparative tissues taken from symptomatic patients 18 months after grafting were mainly fibrocartilage or mixed (hyaline-fibrocartilage) tissue, while tissues taken from asymptomatic patients were hyaline cartilage in 83% of biopsies. In a small group of asymptomatic patients (n = 3), second-look and third-look biopsies taken 18 months after surgery confirmed maturation of the newly formed tissue over time. Cartilage maturation occurred from the inner regions of the graft, in contact with subchondral bone, towards the periphery of the implant.

Conclusions: The study indicates that, in asymptomatic patients after chondrocyte implantation, regenerated tissue undergoes a process of maturation that in the majority of cases takes longer than 18 months for completion and leads to hyaline tissue and not fibrous cartilage. Persistence of symptoms might reflect the presence of a nonhyaline cartilage repair tissue.

Figure 1

Histological and immunohistochemical analysis of a second-look cartilage biopsy with hyaline characteristics. Analysis of a second-look cartilage biopsy with hyaline characteristics taken 14 months after Hyalograft^® C Autograft implantation. (a) H & E and eosin staining. (b) Glycosaminoglycan (safranin-O) staining. (c) Collagen type I (immunohistochemistry). (d) Collagen type II (immunohistochemistry). (e) Polarized light microscopy.

Figure 2

Histological and immunohistochemical analysis of a second-look cartilage biopsy with fibrocartilage characteristics. Analysis of a second-look cartilage biopsy with fibrocartilage characteristics taken 10 months after Hyalograft^® C Autograft implantation. (a) H & E staining. (b) Glycosaminoglycan (safranin-O) staining. (c) Collagen type I (immunohistochemistry). (d) Collagen type II (immunohistochemistry). (e) Polarized light microscopy.

Figure 3

Histological and immunohistochemical analysis of a second-look cartilage biopsy with mixed (hyaline and fibrocartilage) characteristics. Analysis of a second-look cartilage biopsy with mixed characteristics taken 10 months after Hyalograft^® C Autograft implantation. (a) H & E staining. (b) Glycosaminoglycan (safranin-O staining). (c) Collagen type I (immunohistochemistry). (d) Collagen type II (immunohistochemistry). (e) Polarized light microscopy.

Figure 4

Tide mark evidence for repair tissue. Tidemark evidence from a patient with hyaline repair tissue 12 months after implantation of the Hyalograft^® C Autograft. Blue arrow, surface direction.

Figure 5

Histological and immunohistochemical analysis data for biopsies obtained before or after 18 months post implantation. Data obtained from histological and immunohistochemical analyses of the biopsies were divided into two groups: biopsies taken before (n = 59) or after (n = 11) the cutoff point of 18 months post Hyalograft^® C Autograft implantation. Only 23.7% of specimens (n = 59) obtained from patients before 18 months showed characteristics of hyaline cartilage, whereas 45.4% of specimens (n = 11) taken after more than 18 months were of hyaline cartilage. Fibrocartilage was present in 55.9% of biopsies taken before 18 months and in 27.3% of those taken after more than 18 months. Similarly, mixed tissue was present in 20.3% of biopsies taken before 18 months and in 27.3% of those taken after more than 18 months.

Figure 6

Histological and immunohistochemical analysis data for biopsies obtained from asymptomatic patients only (n = 47). The biopsies were divided into those taken before (n = 41) or after (n = 6) the cutoff point of 18 months post Hyalograft^® C Autograft implantation. Six biopsies were taken from asymptomatic patients longer than 18 months after surgery. Results showed that five out of six consisted primarily of hyaline cartilage (83.3%); only one biopsy contained mixed tissue (17.7%).

Figure 7

Direction of tissue maturation in a biopsy classified as mixed. Glycosaminoglycan (safranin-O) staining from a patient with mixed tissue 18 months after implantation with Hyalograft^® C Autograft.