Post-operative Virtual Range of Motion in Robotic-assisted THA Patients to determine Pre-operative Simulation Needs

For preoperative simulations of hip range of motion to be useful in predicting complications after total hip arthroplasty (THA), the factors that could affect post-operative function must be considered including, but not limited to, bony impingement, pelvic position, and implanted vs. planned differences. This study retrospectively simulates ranges of motion to prosthetic and bony impingement of THA patients with known planned and implanted component positions and pelvic tilt to determine the factors and needs to accurately simulate range of motion preoperatively.Twenty-two (22) anterolateral, cementless total hip arthroplasties were performed using robotic-arm assisted technology which allowed capture of the implanted stem version and position in addition to robotic-assisted cup placement to plan. With the known implanted positions and preoperative 3-dimentional (3D) bone models, six (6) hip maneuvers were virtually simulated in custom software. Correlations were evaluated between planned and implanted component positions, pelvic tilt, ranges of motion, and patient-reported outcomes.Average ranges of motion to impingement were similar to those of previous simulation and navigation studies. Supine tilt varied from -10 ̊ (posterior) to 15 ̊ (anterior) with an average of 3.4±6.6 ̊. Very little correlation was seen between native or planned stem version and implanted stem version. Correlations were seen between some maneuvers such as internal rotation (IR) at 90 degrees flexion (F) (IR@90F) and combined component version and pelvic tilt. Bony impingement occurred during IR@90F in 9 of the 22cases. Pelvic tilt assessment, bony impingement detection, better prediction of implanted component position or the ability to execute a plan, such as robotically, would all provide a more accurate pre-operative simulation of the post-operative patient’s function.

Trans-lateral Decubitus Radiograph of the Hip: A New View to Measure the Version of the Femoral Stem

Background We developed a radiological method, trans-lateral decubitus view, to measure stem version and assessed its reliability as well as the validity.Methods Trans-lateral decubitus view of the hip was a lateral radiograph, which was taken with the patient in lateral decubitus position, hip extension, 90° knee flexion and patella facing forward. In 40 patients, who underwent total hip replacement (THR), a trans-lateral decubitus view and CT scan of the hip were taken. Three observers measured stem neck-shaft angle (α) on hip AP view, and the stem anteversion (β), which was the angle between the axis of stem neck and axis of the femur, on the trans-lateral decubitus view. The stem version (θ) was calculated using the formula; θ = arc ((tan (180°-β) /tan (180°-α)). The intra and inter-observer reliabilities of each measurement were examined. The radiological measurements were compared with those on the CT scan to evaluate their validity.Results The mean stem anteversion on radiological measurement was 23.72° (SD 8.17) and the mean CT measurement was 23.91° (SD 10.25) (p = 0.929). The intra- and interobserver reliabilities of the radiological measurements were 0.934 and 0.931, respectively. Those of CT measurements were 0.941 and 0.942, respectively. When the radiological anteversion was between -30° and 30°, the correlation coefficient between radiological measurements and CT measurements was 0.729 (p = 0.001).Conclusion The trans-lateral decubitus method appears reliable and valid for the measurement of femoral stem version. Trial Registration: NCT02554149 (29 March 2016).

A technique for humeral prosthesis placement in reverse total shoulder arthroplasty for fracture

Recent trends have illustrated the benefits of treating displaced fractures of the proximal humerus with reverse total shoulder arthroplasty. Clinical results have demonstrated reliable restoration of function in situations where results following hemiarthroplasty have been variable and difficult to predict. Data have demonstrated landmarks to assist with humeral stem height in hemiarthroplasty. However, intraoperative landmarks to guide placement of the humeral component in reverse shoulder arthroplasty have not been described. In this technique, the superior border of the pectoralis tendon is utilized. A distance of 5.0 cm is used to assist in placement of the most superior aspect of the metallic humeral component and with humeral stem version. This technique can be used as a guide to assist a treating physician in situations where bony fracture and comminution make humeral stem height placement difficult to judge.