Obtaining a proper position for total hip arthroplasty components is a crucial aspect of implant performance and consequently of patient outcomes. Restoring the original hip center and maintaining the limb length are key factors in reaching the optimal implant positioning. The aim of this study was to assess the accuracy and safety of a computed dynamic analysis system that, through patient-specific guides, tries to improve implant positioning and functional orientation according to patients’ spinopelvic mobility and anatomy. A total of 100 consecutive patients were prospectively enrolled. All patients received an Optimized Positioning System dynamic hip preoperative planning schedule. A CT scan protocol follow-up analysis was performed 6 months after surgery. The mean deviations from the planned acetabular inclination and anteversion were 4.3° and 3.8°, respectively. In total, 98% of cases were within ± 10° of the Lewinnek safe zone, both for inclination and anteversion. The height of osteotomy deviated, on average, 1.6 mm. In total, 100% of cases were included within 4 mm of osteotomy. Patient-specific and laser-guided instrumentation was found to be safe and accurately reproduced dynamic planning in terms of the component orientation, osteotomy level, leg length and offset.

Introduction: Heterotopic ossifications (HO) are common after total hip arthroplasty (THA). The invasiveness of surgical approaches plays a relevant role in HO development. The aims of this study were to assess the development of HO 6 months after THA through direct lateral approach (DLA) or direct anterior approach (DAA) without a dedicated orthopaedic table and to assess the clinical impact of HO. Methods: This is a single-center IRB-approved, quasi-randomized prospective cohort, observational imaging study. Fifty patients underwent primary THA through DLA and 50 through DAA. Age, sex, BMI and side of the affected hip were collected. At the 6 post-operative month the Harris Hip Score (HHS) and the presence of HO (scored through the Brooker classification system) were assessed. Results: There was no significant difference in the demographic data between groups. Operative time was significantly higher in the DAA group (72 ± 10 min vs. 58 ± 8 min: p < 0.03). At 6 post-operative months the incidence of HO was 14% in the DAA group and 32% in the DLA group (p = 0.02). Severe HO (Brooker 3–4) were significantly more common in the DLA group (p = 0.04). There was no significant difference in the HHS of patients with HO between the DAA and DLA groups. There was no association between poorer clinical outcomes and the severity of HO. Conclusion: The DAA without a dedicated orthopaedic table is associated with a significant lower incidence of HO than the DLA 6 months after elective THA. Except for the surgical approach, no other factors correlated with the occurrence of HO. Even though a lower HHS was found with severe HO, the correlation between severity of HO and clinical outcomes did not reach statistical significance.

Obtaining a proper position for THA’s components is a crucial aspect for the implant perfor-mance and consequently patient outcomes. Patient specific kinematic seems to be a key factor to reach the optimal implant positioning. The aim of this study was to assess the accuracy and safety of a computed dynamic analysis system which through patient specific guides tries to improve implant positioning and functional orientation according to patient’s spinopelvic mobility and anatomy.A total of 100 consecutive patients were prospectively enrolled. All patients received an OPS dynamic hip preoperative planning. A TC scan protocol follow up analysis has done at 6 month after surgery.The mean deviation from the planned acetabular inclination and anteversion was 4.3° e 3.8° respectively. The 98% of cases was within +/- 10° of Lewinnek safe zone both for inclination and anterversion. The height of osteotomy deviated on the average of 1.6mm. The 100% cases were included within 4mm of osteotomy. Patient specific and laser guided instru-mentation is safe and accurately reproduce the dynamic planning in terms of components orien-tation, osteotomy level, leg length and offset.