Remodelling of human hamstring autografts after anterior cruciate ligament reconstruction.

PURPOSE: Histological analysis of the remodelling process of human hamstring tendon (HT) grafts after standardized anterior cruciate ligament reconstruction (ACLR) with an accelerated rehabilitation protocol. METHODS: Sixty-seven patients underwent retrieval of mid-substance biopsies after clinically successful hamstring autograft ACLR. Samples were allocated to one of three groups depending on the time point of retrieval: group 1 (6-12 months; n = 15), group 2 (13-24 months; n = 16) and group 3 (>24 months; n = 11). Biopsies from native HT (n = 17) and ACL (n = 8) served as controls. Cellular density, vascular density and myofibroblast density and collagen fibril alignment were analysed by haematoxylin-eosin, Masson-Goldner-Trichrom and immunohistochemical staining protocols. RESULTS: Compared with native HT (330.4/mm²), total cell number was increased in groups 1-3 (Group 1 = 482.0/mm² (P = 0.036); group 2 = 850.9/mm² (P = 0.005); and group 3 = 595.6/mm² (P = 0.043). There were no significant differences between the groups for vessel density. Myofibroblast density was higher in group 2 (199.6/mm²) compared with native HT (1.9/mm², P = 0.014). Collagen orientation was irregular up to 12 months. Thereafter, collagen orientation became more regular, adapting to, but not fully restoring, the appearance of the intact ACL. For the first 12 months, cells were predominantly ovoid. Ensuing cell morphology changed to spindle shaped in group 2 and predominantly narrow long cells over 24 months. CONCLUSION: Human hamstring grafts showed typical stages of graft remodelling, which was not complete up to 2 years after ACLR. The remodelling process in humans was prolonged compared with the results obtained in several animal studies. LEVEL OF EVIDENCE: Case-control study, Level III.

Three-dimensional stereology as a tool for evaluating bladder outlet obstruction.

OBJECTIVE: In a pilot study we evaluated whether implementation of a novel 3D stereologic technique can prove that bladder outlet obstruction (BOO) is associated with morphologic changes in the bladder wall. MATERIAL AND METHODS: Ten males (mean age 69.7 years; range 58-84 years) with lower urinary tract symptoms (LUTS) suggestive of BOO and five controls (mean age 48.6 years; range 43-53 years) without LUTS were studied. All participants underwent a full examination, including determination of the International Prostate Symptom Score, laboratory analysis and a urodynamic evaluation. A cold-cup biopsy, taken during cystoscopy, was stereologically evaluated to determine the smooth muscle cell volume and the fractions of collagen and smooth muscle using light and electron microscopy. RESULTS: The collagen fraction was higher in patients than in controls (probably because the patients were older). There was no relation between the Abrams-Griffiths number and either the interstitial fraction or the collagen fraction. Furthermore, the results suggest an age-associated effect of morphological changes in the bladder wall. The smooth muscle volume also showed no relationship with the severity of obstruction. CONCLUSIONS: This pilot study shows that, even with the implementation of subtle morphometric techniques, there seems to be no relationship between the severity of BOO and bladder wall morphology. It is possible that interstitial collagen in the bladder wall increases with age. It seems that bladder wall morphology is heterogeneous within small areas.