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Percutaneous iliosacral screw fixation and transsacral fixation are challenging procedures requiring extensive knowledge of sacral anatomy to avoid damaging nearby neurovascular structures. Greater knowledge of anatomical screw trajectory and size allowances would be helpful to guide surgical placement. An anatomical study of 40 cadaveric sacra in specimens ages 18-65 was performed. Three-dimensional surface scans were obtained, and computer modeling software was used to simulate a 7.3 mm diameter screw with 1 mm buffer inserted orthogonal to the sacroiliac joint in the pelvic inlet and outlet views. Transsacral screws were also inserted into S1 and S2 vertebrae. For screws orthogonal to the sacroiliac joint, the overall mean screw insertion angle was 4.1° ± 7.5° (range, -18.3° to 22.0°) in the inlet view in the posterior to anterior direction, and 21.7° ± 5.1° (range, 8.2°-36.3°) in the outlet view in the caudal to cranial direction. Before breaching the sacrum, the range of sacral tunnel lengths was between 31.1 and 70.1 mm with a range of diameters between 9.3 and 13.3 mm. Transsacral screws inserted into either the S1 or S2 vertebrae did not breach the sacrum in 40% (16/40) at each level. 30% (12/40) of sacra could not safely accommodate both S1 and S2 transsacral screws. There is an initial screw insertion angle range of -4° to 12° in the inlet view and 16°-27° in the outlet view. There was always adequate size to accept a 7.3 mm or larger screw.

Background The anatomy of the undulating distal femoral physis may be relevant to growth disturbance after physeal fractures and screw fixation about the physis. The surface anatomy of this physis has not been well described. Methods We performed an anatomic study on 26 cadaveric distal femoral epiphyses in specimens 3 to 18 years of age. High-resolution 3-dimensional surface scans were obtained and analyzed to determine the heights, approximate surface areas, and locations of the major undulations. Results Gross examination revealed lateral and anteromedial peripheral notches at the metaphyseal-epiphyseal junction, which deepen with advancing skeletal maturity. Within the epiphysis, there are 3 major undulations: a central ridge, lateral ridge, and medial peak, with mean heights of 5.5 mm (range, 2.9 to 9.8 mm), 2.5 mm (1.0 to 5.7 mm), and 2.9 mm (0.9 to 4.7 mm), respectively. The normalized height and surface area of each undulation decreased with increasing age, most dramatically in the central ridge. With respect to a line connecting the medial and lateral aspects of the physis, we found that the central peak passes more superior with younger age, and tends to be more posteriorly located. The lowest point of the physis is located either anteromedial or posterolateral. Conclusions The central ridge, lateral ridge, and medial peak are the 3 major undulations in the distal femoral physis. The central ridge has the greatest height and most dramatic decrease in relative size with increasing age, suggesting structural importance. This anatomic data can guide metaphyseal and epiphyseal screw fixation. Clinical relevance This study provides quantitative data on the topographic anatomy of the distal femoral physis, which can guide screw placement about the physis. These data may help identify fractures patterns with a greater risk of growth disturbance and key radiographic landmarks for guiding fracture reduction.

Femoroacetabular impingement has been proposed as a cause of early osteoarthritis, but it is not known how this develops over time or whether the shape of the proximal femur influences this risk.(1) Which areas of the acetabulum are worn more frequently by individuals with a cam deformity of the proximal femur? (2) Do observed acetabular wear patterns differ based on the etiology of the cam deformity? (3) Do wear patterns of individuals with a cam deformity differ based on an individual's age?We examined 645 corresponding femora and acetabuli from the Hamann-Todd Osteological Collection and determined the offset and alpha angle using photographs; 370 specimens met inclusion criteria and were examined for signs of wear and the locations of wear were recorded. Specimens were separated into eight subgroups based on age either younger than 40 years or older than 60 years, alpha angle greater or less than 55°, and degree of anterior head-neck offset. We compared the prevalence of wear between groups in each location.Individuals with abnormal geometry of the proximal femur demonstrated different wear patterns from individuals with normal geometry. There were few differences in wear patterns identified based on the etiology of the femoral deformity. Abnormal femoral geometry was associated with more frequent wear primarily at the anterosuperior acetabulum for individuals younger than 40 years of age and globally for individuals older than 60 years of age.Femoral geometry appears to influence the pattern of acetabular wear occurring over time.

Background: It has been proposed that the epiphyseal tubercle on the inferior surface of the capital femoral epiphysis may be responsible for the clinical distinction between a stable and an unstable slipped capital femoral epiphysis (SCFE). The anatomy of the tubercle and its relationship to the lateral epiphyseal vessels have not previously been rigorously defined. Methods: Twenty-two cadaveric capital femoral epiphyses from donors who had been three to seventeen years of age were analyzed and then digitized with use of a high-resolution laser scanner. The height, location, and approximate surface area of the epiphyseal tubercle were measured and were normalized to the size of the entire capital femoral epiphysis. Results: In all specimens except that from the youngest donor, the foramina for the lateral epiphyseal vessels were visible and were located directly superior to the epiphyseal tubercle. The height of the epiphyseal tubercle was 4.4 ± 1.1 mm. When normalized to the overall size of the capital femoral epiphysis, the relative height (r = 0.71) and relative area (r = 0.56) of the epiphyseal tubercle decreased with increasing age. The epiphyseal tubercle was consistently located in the posterosuperior quadrant, with its position being more posterior and less superior in specimens from younger donors. Conclusions: The epiphyseal tubercle appears to be a major stabilizer, or keystone, of the capital femoral epiphysis and the lateral epiphyseal vessels. Its relative decrease in height and surface area with increasing age may help explain the susceptibility of individuals to SCFE in adolescence: in a stable SCFE, the physis rotates on the tubercle; however, in an unstable SCFE, the tubercle dislodges, leading to more substantial displacement of the capital femoral epiphysis and the lateral epiphyseal vessels, risking osteonecrosis. Clinical Relevance: These anatomic data offer a possible insight into the pathogenesis of SCFE and the potential complication of osteonecrosis. When fixation of an SCFE is performed with a single screw, the posterosuperior quadrant should be avoided to maximize any possible derotational effect of the epiphyseal tubercle.