As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells. Cite this article: Bone Joint Res 2020;9(12):857–869

The childhood hip conditions of Developmental Dysplasia, Legg-Calve-Perthes Disease and Slipped Capital Femoral Epiphysis have a wide spectrum of anatomical outcomes following childhood treatment; ranging from morphologies, which result in normal hip function throughout life, to severely deranged morphologies, which result in pain and disability during childhood and adolescence. Some of these outcomes are as a result of well-intentioned interventions that result in catastrophic complications. In 2003, after years of working with impingement complicating periacetabular osteotomies and building on the work of William Harris, Reinhold Ganz published his concepts of ‘cam’ and ‘pincer’ hip impingement, and how these anatomical morphologies resulted in hip arthritis in adulthood. These concepts of impingement were added to his previous published work on hip instability to provide a comprehensive theory describing how hip arthritis develops on the basis of anatomical abnormalities. Surgical techniques have been developed to address each of these morphological pathologies. Ganz's concepts of hip impingement and instability may be applied to severe paediatric hip deformities to direct reconstructive joint preserving surgery to both the femur and the acetabulum. Ganz's surgical approaches have also been refined for use in paediatric hip surgery to allow radical reshaping salvage osteotomies to be performed on the developing femoral head with minimal risk of the devastating consequence of vascular Necrosis

The authors present their experience of acetabular fractures, as examined according to Harris’ recent (2004) CT based classification into four separate groups and relative sub-groups. Each group is here represented as a completely documented clinical case, with pre and post-op roent-grams as well as axial and volume rendering CT imagery. The Harris classification differs from the classic and 40 year old Letournel classification, basically ignoring the fracture complexity and focusing on the pattern of the fracture itself, with respect to column walls and extension beyond the acetabulum. It’s also possible to include some commonly seen fractures otherwise not classified by Letournel. Fracture comminution therefore is not a defining characteristic. This topographic approach is easier for the surgeon to comprehend and memorize, thus facilitating pre-operative planning and the possibility of interdepartmental assessment of the fracture types. Obviously, computerized tomography is the defining technique of this classification. The axial CT display of acetabular fracture patterns within the pelvis is furthermore confirmed by the 3D reformatted images. This classification is loosely based on that of Tile and Helfet ; with the advantage of further simplifying the sub-groups from 27 to 16. The Harris classification is simple and unambiguous, providing clear indications for both diagnosis and surgical treatment planning of this most complex chapter of Traumatology