Custom-made implants for massive acetabular bone loss: accuracy with CT assessment.

BACKGROUND: Custom-made implants are a valid option in revision total hip arthroplasty to address massive acetabular bone loss. The aim of this study was to assess the accuracy of custom-made acetabular implants between preoperative planning and postoperative positioning using CT scans. METHODS: In a retrospective analysis, three patients who underwent an acetabular custom-made prosthesis were identified. The custom-made designs were planned through 3D CT analysis considering surgical points of attention. The accuracy of intended implants positioning was assessed by comparing pre- and postoperative CT analyzing the center of rotation (CoR), anteversion, inclination, screws, and implant surface in contact with the bone. RESULTS: The three cases presented satisfactory accuracy in positioning. A malpositioning in the third case was observed due to the posterization of the CoR of the implant of more than 10 mm. The other CoR vectors considered in the third patient and all vectors in the other two cases fall within 10 mm. All the cases were positioned with a difference of less than 10° of anteversion and inclination with respect to the planning. CONCLUSIONS: The current case series revealed promising accuracy in the positioning of custom-made acetabular prosthesis comparing the planned implant in preoperative CT with postoperative CT.

Analysis of the influence of anaesthesia on the clinical and quantitative assessment of the pivot shift: a multicenter international study.

PURPOSE: The main goal of this work was to evaluate the pivot shift test in awake and anesthetized patients by using two different quantitative methodologies and comparing the results with the standard clinical grading, taking advantage of a multicenter international study. METHODS: Patients between 16 and 50 years of age undergoing primary unilateral single-bundle anterior cruciate ligament (ACL) reconstruction were considered eligible. The pivot shift test was performed pre-operatively, with the patient awake and again with the patient under general anaesthesia. The pivot shift test was clinically graded as defined by the International Knee Documentation Committee. The instrumented assessment was performed by using two non-invasive acquisition systems; specifically, a system exploiting an inertial sensor and a video-based application developed on a commercial tablet using skin markers. Lateral compartment translation and the tibial acceleration reached during joint reduction were used as quantitative parameters. RESULTS: A total of 103 patients were enrolled in the study. Statistically significant difference was found between the distributions of clinical grade evaluated in awake patients and those under general anaesthesia (P < 0.01). Comparing awake patients to those under general anaesthesia, lower values were found both for tibial acceleration (3.7 ± 1.5 vs 6.0 ± 4.6 m/s2, P < 0.01) and lateral compartment translation of the involved limb (2.2 ± 1.7 vs 3.0 ± 2.2 mm, P < 0.01). CONCLUSIONS: This study indicated that significant differences in the grading of the pivot shift test exist between awake and anesthetized patients, regardless of the use of quantitative instruments during the evaluation. Actual clinical assessment reported indeed its weakness, presenting subjective variability and dependence on tester's experience. However, several factors might influence the validity of awake examination such as experience level of examiner and cultural factors, as seen in this international multicenter study. LEVEL OF EVIDENCE: Prospective comparative study, Level II.

Assessment of the pivot shift using inertial sensors.

The pivot shift test is an important clinical tool used to assess the stability of the knee following an injury to the anterior cruciate ligament (ACL). Previous studies have shown that significant variability exists in the performance and interpretation of this manoeuvre. Accordingly, a variety of techniques aimed at standardizing and quantifying the pivot shift test have been developed. In recent years, inertial sensors have been used to measure the kinematics of the pivot shift. The goal of this study is to present a review of the literature and discuss the principles of inertial sensors and their use in quantifying the pivot shift test.