Effects of Increased Retroversion Angle on Glenoid Baseplate Fixation in Reverse Total Shoulder Arthroplasty: A Finite Element Analysis.

BACKGROUND: Increased glenoid retroversion occurs in patients with severe arthritis but its effect on baseplate fixation of a reverse total shoulder arthroplasty (rTSA) is not clear. The purpose of this study is to determine the effects of increasing glenoid retroversion on baseplate fixation in rTSA using finite element analysis (FEA) modelling. METHODS: Five sets of computerized tomographic (CT) images of healthy normal shoulders were selected and segmented with Amira (Thermo Fisher Scientific) to obtain the solid geometries. Scapula FEA models with 5°, 10°, 15°, 20° and 25° retroversion angles were generated for each healthy scapula geometry and a rTSA glenoid baseplate was implanted on each model. Maximum stress at the anterior and posterior portions of the glenoid and the micromotion between the bone and baseplate were recorded. After simulation with normal scapular bone material properties (Young's modulus 4GPa and Poisson's ratio 0.3), another set of simulations was run on each subject with a 25° retroversion angle and poor bone quality (Young's modulus 500 MPa and Poisson's ratio 0.3) to study a worst-case scenario. Micromotions in each model were also recorded. All statistical analysis was done with SPSS. RESULTS: Simulation results of models generated from the same subject but with different retroversion angles showed a clear pattern: as retroversion angle increased, the stresses increased posteriorly and decreased anteriorly. Also, micromotion between the bone and the baseplate increased with the increase of retroversion angle. With analysis of variance (ANOVA), we found that all three values change significantly as the retroversion angle increases (p < 0.001). The simulation results also showed that micromotion was large in shoulders with small glenoid size and poor bone quality. However, even in the model with the worst-case scenario (smallest glenoid size, poorest bone quality and 25° retroversion angle), the maximum micromotion and the maximum stresses are still within the safe range. DISCUSSION: In all cases with both normal and poor bone quality, the stresses and micromotion stayed below the threshold to allow for bone ingrowth of the glenoid baseplate to occur. Based on these results, for glenoid baseplates with a central peg/post and 4 screws for fixation, rTSA baseplate retroversion does not need to be corrected to less than 10° to provide good initial fixation as has been recommended for a cemented glenoid component and can withstand the initial stresses and micromotion up to 25° of retroversion. LEVEL OF EVIDENCE: Basic Science Study; Computer Modeling.

Three-dimensional analyses to predict surgical outcomes in non-displaced or valgus impaction fractures of the femoral neck: A multicenter retrospective study.

INTRODUCTION: The aim of our study was to (1) report our surgical outcomes of internal fixation in patients with non-displaced or valgus impaction fractures of the femoral neck, (2) introduce our new three-dimensional assessment method using a combination of X-ray and CT imaging, and (3) determine which radiologic measurements significantly predicted fixation failure. HYPOTHESIS: We hypothesized that high posterior tilt angle and retroversion angle are related to high incidence of non-union and osteonecrosis. MATERIALS AND METHODS: From January 2009 to December 2016, 64 elderly patients in two institutions with non-displaced or valgus impaction fractures of the femoral neck who had internal fixation using multiple parallel cannulated screws were enrolled. To determine the independent predictors of non-union, osteonecrosis, and re-operation, various clinical variables and radiologic variables, including the valgus angle on coronal CT images, the posterior tilt angle on Lorenz images, and the retroversion angle on axial CT images, were analyzed. RESULTS: Non-union was identified in nine of the 64 patients (14.1%) and nine of the 55 patients (16.4%) who achieved bony union had femoral head osteonecrosis with subsequent segmental collapse. The multiple logistic regression model showed that a low bone mineral density of the femur, a higher posterior tilt angle on Lorenz image, and a higher retroversion angle on axial CT images were independent predictors of non-union and re-operation. DISCUSSION: Primary hip arthroplasty should be considered when a posterior tilt angle of more than 9 degrees on Lorenz images or a retroversion angle of more than 13 degrees on axial CT images is identified in patients with osteoporotic valgus impaction fractures. TYPE OF STUDY AND LEVEL OF PROOF: III, Retrospective comparative study.

Glenoid morphology in light of anatomical and reverse total shoulder arthroplasty: a dissection- and 3D-CT-based study in male and female body donors.

BACKGROUND: Placement of the glenoid baseplate is of paramount importance for the outcome of anatomical and reverse total shoulder arthroplasty. However, the database around glenoid size is poor, particularly regarding small scapulae, for example, in women and smaller individuals, and is derived from different methodological approaches. In this multimodality cadaver study, we systematically examined the glenoid using morphological and 3D-CT measurements. METHODS: Measurements of the glenoid and drill hole tunnel length for superior baseplate screw placement were recorded to define size of the glenoid and the distance to the scapular notch on cadaveric specimens. Glenoid angles were determined on both, 3D-CT-scans of the thoraxes using the Friedman method and on subsequently isolated scapulae from 18 male and female donors (average 84 years, range 60-98 years). RESULTS: Mean glenoid height was 36.6 mm ± 3.6, and width 27.8 mm ± 3.1 with a significant sex dimorphism (p ≤ 0.001): in males, glenoid height 39.5 mm ± 3.5, and width 30.3 mm ± 3.3, and in females, glenoid height 34.8 mm ± 2.2, and width 26.2 mm ± 1.6. The average distance from the superior screw entry to its exit in the scapular notch measured by calliper was 27.2 mm ± 6.0 with a sex difference: in males, 29.4 mm ± 5.7, and in females, 25.8 mm ± 5.9 mm with a minimum recorded distance of 15 mm. Measured by CT, the mean inclination angle for male and female donors combined was 13.0° ± 7.0, and the ante-/retroversion angle -1.0° ± 4.0°. CONCLUSION: This study is one of the first to combine dissection, including drill holes, with anatomical measurements and radiological data. In some women and smaller individuals, smaller baseplates should be selected. The published safe zone of 20 mm is generally feasible for superior screw placement, however, in small patients this distance may be substantially shorter than expected and start as of 13 and 15 mm, respectively. No correlation between glenoid height or width with the length of our drilling canal towards the scapular notch was found. Preoperative CT-based treatment planning to determine version and inclination angles is recommended.

Correlation between anatomical parameters of intertubercular sulcus and retroversion angle of humeral head.

OBJECTIVE: To obtain anatomical data on intertubercular sulcus of humerus, evaluate the correlation between intertubercular sulcus and retroversion angle of humeral head, to guide the positioning of torsion angle of prosthesis during total shoulder arthroplasty and provide references for shoulder prosthesis design. METHODS: Using a Siemens Ultrahigh speed 64- rows multi-slices spiral CT scanner and 20 dried adult humeral specimens (intact specimen, no fractures or pathological damage), of these, left lateral in 10 cases, right lateral in 10 cases, male or female all inclusive, specimens are all provided by Anatomy Department of Weifang Medical College, scan ranged from the highest point of humeral head to the distal ends of trochlea. And scanned data were subjected to statistical analysis. RESULTS: There is a linear correlation between the distance from intertubercular sulcus to central axis line of humeral head, position angle of intertubercular sulcus and retroversion angle of humeral head at the beginning slice of intertubercular sulcus. There is a linear correlation between position angle of intertubercular sulcus and retroversion angle of humeral head at the slice of surgical neck. CONCLUSION: There is a linear correlation between position of intertubercular sulcus and retroversion angle of humeral head, in total shoulder arthroplasty, using intertubercular sulcus as anatomical landmark will help to accurately position torsion angle of individualized prosthesis. Position angle of intertubercular sulcus is an objective, flexible positioning indicator.

Effect of transepicondylar axis of different position on volume rendering technique measuring the humeral head retroversion angle with multi-slice spiral CT / 中国矫形外科杂志

[Objective]To evaluate the effect of transepicondylar axis of different position on volume rendering technique measuring the humeral head retroversion angle with multi slice spiral CT.[Method]Fifty-one dry humerus specimens were scanned with 16 slice spiral CT scanner,At top view the three-group humeral head retroversion angle decided by the transepicondylar axis of different position were measured by volume rendering technique,As to two-dimension CT method,the distal reference axis of the humeral head retroversion angle was defined by three sections of different levels,the total six-group data on humeral head retroversion angle were analyzed by Statistics.[Result]The humeral head retroversion angle ranged from 4? to 59.8?,the humeral head retroversion angle of six groups were(25.5?10.2)?,(25.0?10.8)?,(25.7?10.8)?,(27.3?10.3)?,(26.3?10.2)?,(25.8?10.4)? respectively.The Statistics showed that the results have no significant difference among them.The more distal the humerus was,the smaller humeral head retroversion angle defined by a line between the epicondyles on two-dimension CT method was.[Conclusion]The humeral head retroversion angle is markedly variable,the humeral head retroversion angle of shoulder joint prosthetic design should be individual.The transepicondylar axis of different position has no effect on volume rendering technique measuring the humeral head retroversion angle with multi slice spiral CT.The top view at which lateral epicondyle of the humerus showing mini-triangulum and the anterior surface of the distal humerus articulation with the forearm being shaded is more simple,faster and precise for the volume rendering technique measuring the humeral head retroversion angle with multi slice spiral CT.

Normal Humeral Head Retroversion Angle in Korean Measured with Semil - axial View / 대한정형외과학회잡지

A reduced retroversion angle of humeral head may predispose to recurrent anterior shoulder dislocation and may also be a factor in persistent instability after soft tissue procedures. Rotation osteotomy of proximal humerus is one of many surgical modalities proposed for recurrent anterior shoulder dislocation. To support such an operation, fundamental knowledge of shoulder anatomy is essential. The semi-axial view by Soderlund have been regarded as simple and reliable method for measuring humeral head retroversion angle. The purpose of this study was to evaluate validity of the semi-axial view and to assess reference values for humeral head retroversion angle in Korean. Humeral head retroversion angle was determined from 80 healthy subjects, 48 men and 32 women. Radiographs which shown less than 10degrees between humeral shaft axis and epicondylar axis were defined as acceptable radiographs by Soderlund. Acceptable radiographs were selected and two orthopedic surgeons measured retroversion angle, separately. Acceptable radiographs were obtained in only 70 shoulders (43.8%). The mean angle was 35.2+/-8.24degrees for dominant hand and 32+/-6.27degrees for nondominant in Korean. The mean angle was 35.3+/- 7.78degrees for right side and 31.9+/-6.8degrees for left. The interobserver difference was 2.9degrees. The semi-axial view by Soderlund was not reproducible solely. But if correct arm position is considered, the method presented is easy to use daily.