Impact of acetabular roof's angle on precision of cup center of rotation reproduction and placement in total hip arthroplasty.

Introduction: Total hip arthroplasty (THA) is nowadays considered as the most effective treatment option for end-stage hip osteoarthritis (OA) and one of the most successful orthopedic procedures. Precise reproduction of the center of rotation (COR) is among the most important aspects of recreating native hip biomechanics after THA as it is strictly related to muscle tension and force distribution within the hip joint. Both vertical and horizontal shift in cup positioning and COR restoration are commonly observed radiological signs corresponding with lesser functional outcome. The aim of this study was to assess whether the superior border of the native acetabulum morphology has an impact on cup positioning and COR restoration in patients undergoing THA as treatment of primary OA of the hip. Material and methods: A cohort of 150 consecutive patients with diagnosis of end-stage primary hip OA who underwent THA via an anterolateral approach with the same implant in 2021 was analyzed retrospectively. Standard standing pelvic X-rays were performed pre- and postoperatively and appropriate measurements were taken. Several radiological parameters on obtained X-rays were assessed. Statistical analysis of all the measurements was performed. Results: There was a statistically significant positive weak correlation between cup offset and acetabular roof angle (rs = 0.25, p = 0.002). There were statistically insignificant positive correlations between acetabular roof angle and COR restoration (rs = 0.14, p = 0.097), acetabular roof angle and total offset (rs = 0.087, p = 0.29) and a negative correlation between acetabular roof angle and femoral offset (rs = 0.071, p = 0.39). Conclusions: The present study revealed that preoperative acetabular roof angle influences the positioning of the prosthetic cup in the transverse axis. There also seems to be a correlation between the acetabular roof angle and COR restoration, but its significance needs further evaluation. Surgeons could use this knowledge to preoperatively assess the risk of cup malposition and adjust their technique during the THA procedure with probable improvement of hip function.

Differences in joint line level and posterior condylar offset during total knee replacement with use of gap-balancing and measured resection techniques-matched cohort study.

BACKGROUND: Total knee replacement (TKR) is considered one of the most common elective orthopaedic procedures. The main focus of TKR is to offer patient's symptomatic relief from persistent knee pain. To achieve this it is crucial to restore joint biomechanics by performing proper bone cuts. Some surgeons favor the measured resection technique, others prefer gap balancing technique. The researchers of the presented study performed TKR using these two techniques. The aim of this study was to compare the postoperative change in joint line and posterior condylar offset after TKR with use of anatomic knee design implants between gap balancing and measured resection techniques. METHODS: Two hundred twenty-five X-rays of patients who underwent TKR performed by a single surgeon between 2020 and 2021 were analyzed. The first group of patients (101) was operated with the use of gap balancing technique and the second group (124) was operated with the use of measured resection technique. Patients included in the study were > 50 years of age, had confirmed primary knee osteoarthritis, underwent primary TKR with a PS (posterior stabilized) knee implants without patella resurfacing and had at least 15 degree flexion contracture. T-student test and U Mann-Whitney test were used in statistical analysis of results, according to the normality of distribution examined with the Shapiro-Wilk test. Post-hoc analysis was performed using the Dwass-Steel-Crichtlow-Fligner test (DSCF). RESULTS: The postoperative analysis showed a significantly elevated joint line level in the gap balancing group (-2.6 ± 4.1 vs -0.7 ± 4.8, p < 0.0005). In the gap balancing group significantly more patients had joint lines elevated > 2 mm comparing to measured resection technique. The difference between pre- and postoperative PCO (posterior condylar offset) and PCOR (posterior condylar offset ratio) results had no significant differences (100.8 ± 11.8 vs 101 ± 12.5, p > 0.05) between the groups. CONCLUSIONS: The results of the study suggest that when it comes to restoring joint line level measured resection technique seems to be superior in comparison to the gap balancing technique. What is more, results indicate measured resection is equal in terms of restoring posterior condylar offset to the gap balancing technique. TRIAL REGISTRATION: NCT04164147, date of registration: November 14, 2019.

Comparison of Femoral Component Rotation between Robotic-Assisted vs. Soft-Tissue Tensor Total Knee Arthroplasty with Anatomic Implants.

Background and Objectives: Total knee arthroplasty (TKA) is the most effective treatment method for end-stage osteoarthritis. One of the most important aspects of this surgery is adequate implant positioning, as it guarantees the desired outcome of restoring limb biomechanics. Surgical technique is being continuously improved along with hardware development. There are two novel devices designed to help establish proper femoral component rotation: soft-tissue tensor and robotic-assisted TKA (RATKA). This study compared the femoral component rotation achieved with the use of three methods: RATKA, soft tissue tensioner and the conventional measured-resection technique, all of them utilizing anatomical design prosthesis components. Materials and Methods: A total of 139 patients diagnosed with end-stage osteoarthritis underwent total knee arthroplasty between December 2020 and June 2021. After the surgery, they were divided into three groups depending on procedure technique and implant type: Persona (Zimmer Biomet) + Fuzion Balancer, RATKA + Journey II BCS or conventional TKA + Persona/Journey. Postoperatively, a computed tomography examination was performed in order to measure femoral component rotation. All three groups were compared independently during statistical analysis. Fisher's exact, Kruskal-Wallis and Dwass-Steel-Crichtlow-Fligner tests were used for particular calculations. Results: Statistically significant differences in femoral component rotation between groups were noticed. However, in terms of values other than 0° in external rotation, no significant variance was revealed. Conclusions: Additional total knee arthroplasty instruments seem to improve the outcomes of the surgery, providing better component positioning than in the conventional measured-resection technique based only on bone landmarks.

Curve-on-curve technique does not improve tibial coverage in total knee arthroplasty in comparison to tibial tuberosity technique with use of anatomical implants: randomized controlled trial.

INTRODUCTION: During the last years, main attention while performing total knee replacement was paid to femoral component alignment; however, there is still lack of studies concerning tibial baseplate rotational alignment, especially in terms of anatomical designs of knee prosthesis. Some recent studies proved that tibial baseplate malrotation might be a cause of knee pain and patients' dissatisfaction. The aim of this study was to compare tibial component rotation and its coverage on the tibial plateau achieved with curve-on-curve and tibial tuberosity techniques (t-t technique) with use of anatomic knee designs with asymmetric tibial baseplate. MATERIALS AND METHODS: A total of 88 patients were randomly assigned in a 1:1 ratio to undergo total knee arthroplasty with use of the PERSONA PS (Zimmer Biomet) knee design with an asymmetric baseplate. The rotation of the tibial component was assessed and performed with two different techniques: curve-on-curve technique and tibial tuberosity technique. Tibial component rotation was measured on computed tomography (CT) scans using the method suggested by Benazzo et al. and designed for asymmetrical implants. For the measurement of the tibial bone coverage, the component surface area was outlined and measured on a proper CT section, then the tibial cut surface area was outlined and measured on a section just below the cement level. Pre- and post-operative range of motion was measured by another independent researcher 12 months post-operatively during follow-up visit. RESULTS: There was a statistically significant difference between both groups in median value of tibial rotation angle: 7° (interquartile range (IQR) = 0-12) in curve-on-curve technique group vs 2° (IQR-1-7) in tibial tuberosity technique group, probability value (p) = 0.0041, with values above 0 meaning external rotation of the component. There was no statistically significant difference between both groups in terms of range of motion (ROM) with average values of 124.3° ± 13.0° for curve-on-curve technique and 125.6° ± 12.8° for t-t technique with p = 0.45. There was a statistically insignificant difference between both groups in terms of coverage percentage in slight favor for curve-on-curve technique (85.9 ± 4.2 vs 84.5 ± 4.8, p = 0.17). CONCLUSION: In this study, no difference between the groups in terms of tibial bone coverage and range of motion was proved, even though both techniques differed significantly with values of tibial rotation. Future studies should be focused on influence of specific values of tibial rotation on patient-reported outcomes and survivorship of anatomic knee implants.

How to analyze postoperative radiographs after total hip replacement.

Total hip replacement is one of the most widely performed surgeries. It is stated as the most efficient method of treating end-stage osteoarthritis of the hip joint. What is more, it significantly improves the quality of patients' lives, relieves them from pain and restores decreased range of motion, provided that is conducted properly. Aim of this article is to indicate which constituents of prosthetic placement can be easily measured on postoperative radiographs and point out how to interpret obtained results. Multiple mechanical factors, such as center of rotation, femoral offset, acetabular offset, acetabular inclination, acetabular anteversion and leg length discrepancy can be measured on postoperative radiographs. To provide a successful surgery and to acquire both radiological and clinical satisfying results, proper prosthetic placement is crucial. Malpositioning of each element, in varying degrees may lead to dislocation or reoperation.