Purpose: A summary is provided on the existing knowledge about the specific healing phases of the intra‐articular hamstring tendon graft used for ACL reconstruction. Differences between human and animal in vivo studies are explained, and implications for the postoperative time period are laid out.Methods: A systematic review of the existing literature was performed on the topic of tendon remodelling of hamstring grafts in ACL reconstruction using Medline database. Publications between 1982 and 2012 were included. Special focus was directed on in vivo human and animal studies analysing intra‐articular free tendon graft remodelling.Results: Animal and human in vitro and vivo researches have demonstrated three characteristic stages of graft healing after ACL reconstruction: an early graft healing phase with central graft necrosis and hypocellularity and no detectable revascularization of the graft tissue, followed by a phase of proliferation, the time of most intensive remodelling and revascularization and finally, a ligamentization phase with characteristic restructuring of the graft towards the properties of the intact ACL. However, a full restoration of either the biological or biomechanical properties of the intact ACL is not achieved.Conclusion: Significant knowledge on human cruciate ligament remodelling has been added in the understanding of the processes during the course of graft healing. Most importantly, the remodelling process in humans is prolonged compared to animal studies. While today´s rehabilitation protocols are often extrapolated from findings of animal in vivo healing studies, current findings of human in vivo healing studies might require new post‐operative regimens following hamstring ACL 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.

We reviewed 21 patients with Mason type-III fractures of the radial head treated by resection, evaluating the results at 16 to 30 years by a standard questionnaire and clinical and radiological examination of the elbow and wrist. Seventeen patients had an excellent result, three were good and one fair. Resection of the radial head is a satisfactory method of treatment of such fractures. Prosthetic replacement seems to be indicated only when there is valgus instability of the elbow.

Purpose: The purpose of this investigation was to evaluate systematically the literature concerning biopsy, MRI signal to noise quotient (SNQ) and clinical outcomes in graft‐maturity assessment after autograft anterior cruciate ligament reconstruction (ACLR) and their possible relationships. Methods: The systematic review was reported and conducted according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta‐Analyses) guidelines. Studies through May 2019 evaluating methods of intra‐articular ACL autograft maturity assessment were considered for inclusion. Eligible methods were histologic studies of biopsy specimens and conventional MRI studies reporting serial SNQ and/or correlation with clinical parameters. Results: Ten biopsy studies and 13 imaging studies, with a total of 706 patients, met the inclusion criteria. Biopsy studies show that graft remodeling undergoes an early healing phase, a phase of remodeling or proliferation and a ligamentization phase as an ongoing process even 1 year after surgery. Imaging studies showed an initial increase in SNQ, peaking at approximately 6 months, followed by a gradual decrease over time. There is no evident correlation between graft SNQ and knee stability outcome scores at the short‐ and long‐term follow‐up after ACLR. Conclusions: The remodeling of the graft is an ongoing process even 1 year after ACLR, based on human biopsy studies. MRI SNQ peaked at approximately 6 months, followed by a gradual decrease over time. Heterogeneity of the MRI methods and technical restrictions used in the current literature limit prediction of graft maturity and clinical and functional outcome measures by means of MRI graft SNQ after ACLR. Level of evidence: Level IV, systematic review, including level III and IV studies.

Purpose: Primary aim of the study was analysis of hamstring tendon regeneration after anterior cruciate ligament reconstruction (ACLR). Secondary aim was analysis of isokinetic muscle strength in relation to hamstring regeneration. The hypothesis was that regeneration of hamstring tendons after ACLR occurs and that regenerated hamstring tendons contribute to isokinetic hamstring strength with regeneration distal to the knee joint line.Methods: Twenty‐two patients scheduled for ACLR underwent prospective MRI analysis of both legs. MRI parameters were tendon regeneration and morphology, muscle retraction and muscle cross‐sectional area. A double‐blind, prospective analysis of isokinetic quadriceps and hamstrings strength was performed.Results: Regeneration of the gracilis tendon after ACLR occurred in all patients. Regeneration of the semitendinosus tendon occurred in 14 patients. At 1 year, the surface area of the semitendinosus and gracilis muscle decreased compared to both preoperatively (P < 0.01) and the contralateral leg (P < 0.01). The cross‐sectional area of the semitendinosus muscle decreased in the absence of tendon regeneration (P = 0.05). The cross‐sectional area of the gracilis muscle was greater in case of regeneration distal to the joint line (P = 0.01). Muscle retraction of the semitendinosus muscle was increased in case of nonregeneration (P = 0.02). There was no significant relationship between isokinetic flexion strength and tendon regeneration.Conclusion: Hamstring tendons regenerated after harvest of both semitendinosus and gracilis tendons for ACLR. There was no relation between isokinetic flexion strength and tendon regeneration.Level of evidence: Prognostic study, Level II.