Arch. orthop. Unf~ll-Chir. 86, 195--209 (1976)

Archiv for orthop~dische und UnfalI-Chirurgie © by J. 17.Bergmann-Verlag 1976

The Fate of the Articular Cartilage in Intracapsular Fracture of the Femoral Neck (Articular Cartilage in Femoral Neck Fracture) Hayato Hirotani and Tetsuo Ito Department of Orthopaedic Surgery, Faculty of Medicine, Kyoto University (Head: Prof. Tetsuo Ito) 54 Kawaharacho, Shogoin, Sakyoku, Kyoto, Japan, 606

Summary. The fate of the articular cartilage of the hip joint with intracapsular neck fracture was studied by histological, histochemical and autoradiographic techniques and by using a polarized microscope and a scanning electron microscope. Cartilage specimens from 93 femoral heads and 7 acetabula were obtained from fractured hips 2 days to 4 ~ years postfracture and from control hips with various disorders. The cartilage degeneration appeared 2 weeks after fracture and advanced steadily with time. The matrix was covered, invaded and ultimately replaced by the fibrous tissue. Chondrocyte viability, though it was lost from the surface, was recognized in the deep matrix even in the oldest fracture examined. It is concluded that the humoral factor directly caused by the injury as well as the biomechanical impairment, i.e. a loss of physical stress, may play an essential role in the pathogenesis of the degeneration. The possibility of regeneration was discussed. Zusammenfassung. Um den Verlauf der Knorpeldegeneration im Hiiftgelenk mit intrakapsul~rer Schenkelhalsfraktur klarzumachen, warden morphologische und autoradiographische Untersuchungen durehgefiihrt. 2 Wochen nach einer Fraktur fanden sich schon Zeichcn yon kartilagener Degeneration, und sie entwickelten sich mit der Zeit. Die Matrix war bedeckt, infiltriert, and sie wurde durch fibrSse Gebilde ersetzt. Die Chondrocyten iiberlebten nicht mehr in der Oberfl~che, jedoch bleiben sie, sogar an i~lteren Frakturen, lebhaft in der Tiefe der Matrix. Wir sind der Ansicht, da6 nicht nur humorale Faktoren, die direkt durch Unfall ausgel6st warden, sondern auch biomechanische L~sionen, d. h. Aus16sen des physikalisehen Strel3, eine gro6e Rolle spielen k6nnen. Die M6glichkeit der Regeneration wurde diskutiert. 13"

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H. Hirotani and T. Ito

The m a j o r i t y of a n a t o m i c a l studies regarding i n t r a e a p s u l a r fracture of the femoral neck have been focused on the osseous changes in the femoral heads (Schmorl, 1924; Santos, 1930; Phemister, 1939; S h e r m a n a n d Phemister, 1947; Coleman a n d Compere, 1961; Catto, 1965a, b ; Banks, 1968; I t o et al., 1975). While these reports provided considerable i n f o r m a t i o n on the healing process a n d its aberration, the literature p e r t a i n i n g to the changes in the articular cartilage is sparse a n d the knowledge of these changes is n o t sufficient (Sherman a n d Phemister, 1947; Langier a n d Forestier, 1973). The purposes of this paper are to present the sequential evidences of the cartilage changes after fracture a n d to discuss the pathogenesis of alterations of the articular cartilage i n heads with fractured neck of the femur.

Materials and Methods Ninety-three femoral heads removed surgically and 7 biopsy specimens taken from the acetabulum at the same time were used for the study (Table 1). Of these, 75 heads were removed as primary treatment from 2 days to 4 years and 4 months after intracapsular neck fracture, 7 being taken following failure of internal fixation. Nine of the remaining heads were obtained from other types of fracture in the proximal end of the femur and served as controls together with two additional heads (Table 1). The cartilage specimens of the aeetabular roof taken from 7 patients with fracture of 2 days to 4 years old. The age range of patients was from 56 to 88 in the cases with intraeapsular neck fracture. The average age of the group was 69.5 years. Seventy-three of the patients (88O/o of all cases) were more than 60 years of age, of whom 47 were 70 years or older, The age scatter of the control group was 38 to 81 years with a mean of 57.7 years. Small specimens of the articular cartilage with underlying bone were taken from the zenithal region and the medial margin of the femoral head cartilage. Specimens were fixed in 10~o buffered formalin and decalcified in 25O/o formic acid-sodium citrate solution. Paraffin sections at six micra were cut vertieMly to the articular surface. Haematoxylin-eosin stain was performed for cellular details and safranin-O fast green stain for acid glyeosaminoglyeans (l%osenberg, 1971). Morphological changes were assessed using the numerieaI scales of the histological and histoehemieal grading system proposed by Mankin et al. (1971).

Table 1. Number of patients Male Intracapsular neck fracture Untreated Failed in internal fixation Controls Intracapsular neck fracture Postradiation of 6°Co Postoperative collapse Extracapsular neck fracture Fracture of the femoral head Hemangioma of the femoral neck Autopsy specimen from a patient with muscular dystrophy Total

Female

Total

8 7 1 6

74 68 6 5

82 75 7 11

0 1 2 1 1

4 1 0 0

0

1

0

14

79

93

Fate of Articular Cartilage in Intracapsular Fracture of Femoral Neck

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Table 2. Number of specimens examined by autoradiography

Thymidine-3H Na~3sS04 Glucosamine-3H Cytidine-~H Proline-SH

Intracapsular neck fracture

Control

20 15 11 30 15

7 4 0 7 5

Small pieces removed from fresh materials under sterile conditions were immediately incubated at 36.6°C for 2½ to 24 h. Incubation medium was Minimum Essential Medium Eagle with Earle's balanced solution containing such radioisotopes as thymidine-SH (100 tzCi/ ml). Na235S0~ (30 y.Ci/ml), glucosamine-SH (100 ~Ci/ml), cytidine3H (10 ~Ci/ml) and proline-Stt (100 ~Ci/ml). Specimens were fixed in 10°/o buffered formalin, decalcified with 10~o EDTA solution and cut at six micra. Autoradiography was carried out with the dipping method. After staining with haematoxylin-eosin, the autoradiograms were examined (Table 2). For the polarized microscopic observation, the sections also stained with 0.01% toluidine blue solution. In 4 of the fresh heads taken from 4 to l0 days, 4 from 16 to 27 days, 1 at 6 months and 1 11 months after fracture, the cartilage was examined with a scanning electron microscope. Small blocks from various areas of these heads were washed with physiologic saline and fixed in 2~o glutaraldehyde (pH 7.4) at 4°C for 2 h. After washing with phosphate buffer and dehydrating in gradual aceton, specimens were dried in air and coated with carbon and palladium alloy in a vacuum evaporator. Observation was made with ttitachi-Akashi Mini SEM Model I I at low magnifications.

Results

Histological and Histochemical Findings. All of t h e 30 femoral heads secured surgically t h e first 2 weeks after f r a c t u r e showed n o r m a l a p p e a r a n c e of t h e a r t i c u l a r cartilage, e x c e p t for 2 cases w i t h p r e v i o u s l y existing o s t e o a r t h r i t i c changes. I n t h e a r t i c u l a r cartilage from t h e 12 heads h a r v e s t e d b e t w e e n 2 t o 4 weeks, t h e r e were w a v y a n d irregular surfaces associated w i t h c h o n d r o c y t e s w i t h p y k n o t i c nuclei a n d e m p t y l a c u n a e in t h e t a n g e n t i a l zone of t h e cartilage (Fig. 1). N o r m a l f e a t u r e s of cartilage, however, were p r e s e r v e d in t h e deeper m a t r i x . I n t h e 25 heads t a k e n d u r i n g t h e s u b s e q u e n t period, safranin-O staining was a b s e n t in t h e m a t r i x of t h e t r a n s i t i o n a l zone. C h o n d r o c y t e s in t h e deeper m a t r i x increased in t h e i r n u m b e r . Cluster f o r m a t i o n s were often o b s e r v e d a n d were a c c o m p a n i e d w i t h halos of intensive safranin-O reaction. A t t h e m a r g i n a l p o r t i o n of t h e cartilage, t h e surface was covered and, in some instances, was i n v a d e d b y fibrous tissue t h a t seemed to proliferate from t h e r e t i n a c u l u m i n v e s t i n g t h e i n t r a c a p s u l a r femoral neck (Fig. 2). The z e n i t h a l portior/ of t h e ~rticular cartilage of t h e 6 specimens o b t a i n e d fl'om 4 to 12 m o n t h s after f r a c t u r e was covered a n d i n v a d e d b y t h e pannus, which p r o b a b l y o r i g i n a t e d from t h e insertion of t h e l i g a m e n t u m teres. The m ~ t r i x u n d e r t h e p a n n u s showed a d i m i n i s h e d staining of c h o n d r o c y t e nuclei ~nd w~s d e p l e t e d of g l y c o s a m i n o g l y c a n s as j u d g e d b y n e g a t i v e safranin-O stain.

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2

Fig. 1. l~egressive changes in the articular surface. Chondrocytes with pyknotic nuclei and empty lacunae are seen in the tangential layer. 68-year-old female, 17 days after fracture. Safranin-O fast green stain, x 200 Fig. 2. The articular surface covered and invaded by the pannus. The matrix underneath the pannus shows negative safranin-O stain. 58-year-old female, 3 months after fracture. Safranin-O fast green stain, × 100

T h e a r t i c u l a r cartilage from t h e 9 u n u n i t e d n e c k fractures left over 1 y e a r u s u a l l y i n d i c a t e d h y p o c e l l u ] a r i t y a n d t h i n n i n g of t h e m a t r i x which was covered b y t h e pannus. I n t h e t e r r i t o r i a l m a t r i x of cell clusters, however, t h e p o s i t i v e safranin-O staining was evident. V a s c u l a r b u d s from t h e s u b c h o n d r a l bone m a r r o w i n t e r r u p t e d t h e c o n t i n u i t y of t h e t i d e m a r k a n d i n v a d e d t h e d e g e n e r a t e d m a t r i x .

Fate of Articular Cartilage in Intracapsular Fracture of Femoral Neck

199

Fig. 3. Degenerated matrix with negative safranin-O stain invaded and replaced by fibrous tissue: pannus and vaseular buds. 62-year-old male, 1 year and 7 months after fracture. Safranin-O fast green stain, x 40

There were many varieties of degeneration in the cartilage at this period. The head removed at 2 years and 7 months presented relatively well the normal structure and stainability. On the other hand, the matrix with negative safranin-O staining was markedly invaded by proliferating fibrous tissue in the head of the 1-year-7-month-old fracture as seen in Figure 3. The 4 heads of fracture of 3 years and older demonstrated the matrix with hypocellularity and pericellular halo of safranin-O stain. Thick covering of the pannus was obvious in the joint surface, particularly in the zenithal region of the cartilage. Connective tissue islands were often observed in the matrix with a total absence of safranin-O stain, the mass consisting of fibrous tissue from either pannus or vascular buds or both. Metaplasia of the connective tissue to form fibroeartilage was frequently evident as judged by positive safranin-O stain (Fig. 4). I n spite of various degrees of matrix degeneration, neither dominant fraying of the cartilage surface nor cleft formation was recognised in all the cartilage observed with the exception of the head with pre-existing osteoarthritis.

200

H. Hirotani and T. Ito

Fig. 4. Most advanced finding in the cartilage degeneration. Degenerated matrix is invaded by fibrous tissue which shows metaplasia to fibrocartilage, positive safranin-O stain recognisable around chondrocytes. 56-year-old female, 3 years and 2 months after fracture. Safranin-O fast green stain, × 40 o Fresh intracapsular neck fracture • Failed to osteosynthesis [] Postradiation subcapifal fracture • Postoperative capital collapse v Fresh exfracapsular neck fracture • Femoral head fracture ~" Acefabular cartilage

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