No reduced patellar loading with latest-generation cruciate-retaining total knee arthroplasty-a comparative study of Attune and Press-Fit Condylar®.

PURPOSE: To investigate if the latest-generation cruciate-retaining total knee arthroplasty (CR-TKA) systems through more patella-friendly femoral trochlea reduce the patellar bone loading. METHODS: Twenty patients who underwent Attune CR-TKA were matched with twenty-one patients who underwent Press-Fit Condylar® (PFC) CR-TKA. The patella was always preserved. The in vivo patellar loading was measured twice by two blinded observers and localised on an 8-quadrant grid on 1-year post-operatively SPECT/CT images. The position of the TKA components, patella height, thickness, tilt, and tibial tuberosity-trochlear groove index were measured in 3D CT. Knee function was assessed pre-operatively, at 12 and 24 months post-operatively with the knee society score (KSS). All data were compared between groups with the Mann-Whitney U test and within groups with Spearman's correlation. RESULTS: A significantly higher bone tracer uptake (BTU) was seen in the Attune group in the lateral non-articular patellar quadrants. No other significant differences of the BTU were seen. The post-operative KSS did not differ significantly. Spearman's correlation showed no correlations between the significantly higher BTU of the lateral non-articular patellar quadrants and the position of the TKA and patellar measurements. All patellar measurements did not correlate with bone stress in SPECT/CT. CONCLUSION: No significant improvement in terms of in vivo patellar bone stress was seen with the latest-generation CR-TKA system. The increased bone stress at the non-articular lateral patellar quadrants of the Attune could be due to higher stabilising quadriceps forces.

Good correlation between bone tracer uptake in SPECT/CT and intraoperative findings of chondral lesions graded with the ICRS scoring.

The question if bone tracer uptake in SPECT/CT reflects the intraoperative cartilage status of the knee is still unanswered. In this study, thirty-three consecutive patients (male:female = 11:22; mean age ± standard deviation 61 ± 15) with bi- or tri-compartmental knee osteoarthritis who underwent SPECT/CT before total knee arthroplasty (TKA) were collected. The knee was graded in eleven different anatomical regions. In each region, the maximal relative bone tracer uptake (mrBTU) was measured twice by two observers with a six weeks interval. The intraclass correlation coefficients (ICC) showed excellent correlations and mean values were used. Intraoperatively every region was assessed with the macroscopic International Cartilage Repair Society (ICRS) scoring. A factorial analysis and a non-parametrical Spearman's correlation were calculated among the 11 knee regions on both mrBTU and ICRS scores and significant correlations were seen between regions belonging to the same knee compartment (p < 0.05). A non-parametrical Spearman's correlation was also performed to investigate the correlation between rmBTU in SPECT/CT and intraoperative ICRS cartilage grading. Significant correlations were seen on the medial compartment, on the proximal femoral trochlea and on the medial patellar facet (p < 0.05). A significant correlation between SPECT/CT and intraoperative findings was so demonstrated in several regions. The low accuracy of the macroscopic ICRS scoring system on grade I-II lesions could have affected the missing correlations on the lateral compartment since the selected presented mainly a varus gonarthrosis. The use of an objective measure as the rmBTU could overcome the limit of the subjectivity of MRI findings in early osteoarthritis. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:522-528, 2019.

The type of approach does not influence TKA component position in revision total knee arthroplasty - A clinical study using 3D-CT.

BACKGROUND: The influence of the surgical approach on the position of the prosthetic components in revision of total knee arthroplasties (rTKA) is still not clear. This study compared the medial parapatellar approach (MPA) and lateral parapatellar subvastus approach with tibial tubercle osteotomy (LPA). METHODS: Forty-two consecutive patients underwent rTKA from 2006 to 2016 with either MPA (n=21) or LPA (n=21) because of aseptic loosening, infection, malposition or instability (mean follow-up: 41.5months). Revision TKA component position and leg alignment were assessed on three-dimensional CT (3D-CT) images and compared between groups using a t-test (p<0.05). Rotation of rTKA components graded into internal, neutral or external rotation and rates of postoperative complications and revisions were compared between groups with a chi2-test (p<0.05). RESULTS: Group MPA and LPA showed no significant differences with respect to the femoral component (coronal: 0.6° vs 0.9°; sagittal: 7.5° vs 7.7°; transversal: 0.4° vs -0.2°), tibial component (coronal: 0.1° vs 0.3°; sagittal: 3.1° vs 1.6°; transversal: 6.9° vs 9.3°) and leg alignment (varus: 0.2° vs 1.1°) (p<0.05). Group LPA showed a non-significant (p=0.25) higher incidence of neutrally (28.6% vs 9.5%) and less internally (23.8% vs 38.1%) rotated tibial components. Rates of complication and revisions did not differ significantly. CONCLUSIONS: In contrast with primary TKA, the two approaches did not influence postoperative rTKA position. This can be explained with the more extensive approach at rTKA and means that no corrections of the orientation of the components are needed performing either MPA or LPA.

Patterns of bone tracer uptake on SPECT-CT in symptomatic and asymptomatic patients with primary total hip arthroplasty.

PURPOSE: The primary purpose of this study was to compare bone tracer uptake (BTU) on SPECT/CT in symptomatic and asymptomatic total hip arthroplasty (THA) and identify a possible relationship between BTU patterns and patient's symptoms. The secondary purpose was to investigate if the fixation methods (cemented versus uncemented) lead to different BTU patterns. METHODS: A total of 58 THAs, 31 symptomatic (group S) and 27 asymptomatic (group AS), were prospectively collected and retrospectively analyzed. All symptomatic patients underwent standardized detailed history, clinical examination, radiographs and 99mTc-HDP SPECT/CT. BTU in SPECT/CT was quantified in three dimensions and anatomically localized in a scheme of quadrants and levels using a customized previously validated software. T tests were used on both quadrants and levels inside and between groups. A Pearson correlation was performed for BTU within the quadrants. An area under receiver operating characteristic curves was drawn in order to find a BTU value that could differentiate the two groups. Within the groups, patients with cemented and uncemented stems were compared for influences on BTU intensity. RESULTS: The causes of pain were identified in 61% of the patients. The most common problem was aseptic loosening (n = 12). In group AS, levels 1, 2 and 5 had similar BTUs. BTUs in these levels were significantly higher than in level 3, 4 and 6. In group S, no significant differences were seen in terms of BTU in level 1-5. However, BTU here was significantly higher than at level 6 (p < 0.001). In both groups, level 1, the superior, had a significantly higher BTU than level 2 (group AS p < 0.01, group S p < 0.05). Comparing the BTU of the two groups among levels, significant differences were found for level 4, level 5 and the entire stem areas (p < 0.05). The ROC curve calculated on the whole stem allowed identification of a BTU ratio of 3.1 that separated the 92.6% patients of group AS with BTU < 3.1 from the 54.8% of patients of group S with a BTU ≥ 3.1. With regards to the fixation technique, only the BTU at the level 6 in group S presented a significant difference between cemented and uncemented stems (p < 0.05). CONCLUSIONS: Higher BTU levels significantly correlated with symptoms, but a normal BTU could not exclude a specific pathology after THA. A threshold of BTU in SPECT/CT was identified to distinguish between symptomatic and asymptomatic patients after THA.

Medial parapatellar approach leads to internal rotation of tibial component in total knee arthroplasty.

PURPOSE: The purpose of this study was to investigate if the type of approach [medial parapatellar approach (MPA) versus lateral parapatellar approach with tibial tubercle osteotomy (LPA)] influences rotation of femoral and/or tibial component and leg axis in total knee arthroplasty (TKA). It was the hypothesis that MPA leads to an internally rotated tibial TKA component. METHODS: This study included 200 consecutive patients in whom TKA was performed using either a parapatellar medial (n = 162, MPA) or parapatellar lateral approach with tibial tubercle osteotomy (n = 38, LPA). All patients underwent clinical follow-up, standardized radiographs and computed radiography (CT). TKA components' position and the whole leg axis were assessed on 3D reconstructed CT scans (sagittal, coronal and rotational). Mean values of TKA component position and the whole leg alignment of both groups were compared using a t test. The tibial component was graded as internally rotated (<3° of external rotation (ER)), neutral rotation (equal or between 3° and 6° of ER) and externally rotated (>6° ER). The femoral component was graded as internally rotated [>3° of internal rotation (IR)], neutral rotation (equal or between -3° IR and 3° of ER) and externally rotated (>3° ER). RESULTS: There was no significant difference in terms of whole leg axis after TKA between both groups (MPA: 0.2° valgus ± 3.4; LPA: 0.0° valgus ± 3.5). Means of tibial component rotation were 2.7° ER ± 6.1 (MPA) and 7.6° ER ± 5.4 (LPA). Patients of group LPA presented a significantly less internally rotated (LPA: 18.4%; MPA: 48.8%) and more externally rotated (LPA: 52.6%; MPA: 22.8%) tibial component (p < 0.001). No significant differences were seen for the femoral component position, tibial valgus/varus and tibial slope. CONCLUSION: The type of approach (medial versus lateral) significantly influenced tibial TKA component rotation. It appears that a MPA tends to internally rotate the tibial TKA component and a LPA tends to externally rotate the tibial TKA. The anterior cortex should not be used as landmark for tibial TKA component placement when using the lateral approach with tibial tubercle osteotomy. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

Coronal femoral TKA position significantly influences in vivo patellar loading in unresurfaced patellae after primary total knee arthroplasty.

PURPOSE: As patellar tracking and loading is influenced by tibial tuberosity and trochlear groove (TT-TG) distance, patellar height, thickness and tilt as well as TKA component position, it was our hypothesis that these parameters significantly correlate with patellar BTU intensity and localization in SPECT/CT. The purpose of the study was to investigate whether TKA component position as well as the height, thickness and tilt of the unresurfaced patella influences the intensity and the distribution pattern of BTU in SPECT/CT. METHODS: A total of 62 consecutive patients who underwent primary TKA without patellar resurfacing were prospectively included. Demographic data such as age, gender, side and type of primary TKA were noted. All patients underwent clinical and radiological examination in a specialized knee clinic, including standardized radiographs (anterior-posterior and lateral weight bearing, patellar skyline view) and Tc-99m-HDP-SPECT/CT before, 12 and 24 months after TKA. SPECT/CT images were analysed on 3D reconstructed images. Rotational, sagittal and coronal position of the tibial and femoral TKA components was assessed using a previously validated analysis software. Measurements of BTU including intensity and anatomical distribution pattern were also performed from 3D data. The patellar height, thickness and tilt were measured, and the distance between TT and TG was measured using axial CT images. Univariate analysis was performed to identify any correlations between BTU and TKA component position and patellar measurements (p < 0.05). RESULTS: The highest median BTU was measured in the superior posterior parts of the patella. A statistically significant correlation was found between valgus alignment of the femoral TKA and increased BTU at the lateral patellar regions (p < 0.05). External rotation of the tibial TKA correlated with increased BTU at the lateral superior joint adjacent part (p < 0.05). No correlation was found between the tibial TKA position (varus-valgus, anterior and posterior slope), TT-TG distance, patellar height and patellar BTU values. CONCLUSIONS: A significant correlation of increased patellar BTU was found with femoral valgus TKA alignment. These findings highlight the importance of femoral TKA position in coronal plane with regard to post-operative patellar tracking. Moreover, these facts might explain anterior knee pain in unhappy TKA with femoral valgus alignment. LEVEL OF EVIDENCE: Diagnostic study, Level II.

Influence of surgical approach on heterotopic ossification after total hip arthroplasty - is minimal invasive better? A case control study.

BACKGROUND: Heterotopic ossification (HO) is a well-known complication after total hip arthroplasty (THA). Recently, the trend is to operate THA minimally invasive being less traumatic than standard approaches and promising a faster return to activity. The purpose of the study was to investigate if minimal invasive surgery (MIS), leads also to less HO after THA. METHODS: This retrospective study included 134 consecutive patients undergoing THA. In 42 (31.3%) patients a standard modified anterolateral (STD-Watson-Jones), in 28 (20.9%) patients a standard transgluteal Bauer approach (STD-Bauer), in 39 (29.1%) a MIS direct anterior approach (AMIS) and in 25 (18.7%) patients a MIS anterolateral (MIS-AL) approach was used. Standard preoperative anterior-posterior and lateral radiographs were assessed for occurrence of HO. HO was classified according to Brooker. In addition, short- and long-term adverse events were noted. Data was statistically analyzed using Chi-square tests, analysis of variance, multivariate data analysis and Pearson's correlation (p < 0.05). RESULTS: Overall, HO was found in 38 caucasian patients (28.4%) after THA. The STD-Watson-Jones group showed the highest HO rate (45.2% n = 19) with a significant difference to the AMIS (23.1% n = 9) and STD-Bauer approach (14.3% n = 4). No statistical difference was found to the MIS-AL approach (24.0% n = 6). Postoperative complications did not differ significantly except for a higher incidence of Trendelenburg`s sign in STD-Bauer. CONCLUSIONS: The rate and degree of HO after THA were significantly different with regards to the surgical approach. The standard modified anterolateral approach resulted in the highest HO rate, however, MIS approaches showed higher HO rates than the STD-Bauer.