Proximal Joint Line Research Articles

Gender-specific distribution of knee morphology according to CPAK and functional phenotype classification: analysis of 8739 osteoarthritic knees prior to total knee arthroplasty using artificial intelligence.

Osteoarthritis of the knee is commonly associated with malalignment of the lower limb. Recent classifications, as the Coronal Plane Alignment of the Knee (CPAK) and Functional Phenotype classification, describe the bony knee morphology in addition to the overall limb alignment. Data on distribution of these classifications is not sufficient in large populations. The aim of this study was to analyse the preoperative knee morphology with regard to the aforementioned classifications in long leg radiographs prior to total knee arthroplasty surgery using Artificial Intelligence. The cohort comprised 8739 preoperative long leg radiographs of 7456 patients of all total knee arthroplasty surgeries between 2009 and 2021 from our institutional database. The automated measurements were performed with the validated Artificial Intelligence software LAMA (ImageBiopsy Lab, Vienna) and included standardized axes and angles [hip-knee-ankle angle (HKA), mechanical lateral distal femur angle (mLDFA), mechanical medial proximal tibia angle (mMPTA), mechanical axis deviation (MAD), anatomic mechanic axis deviation (AMA) and joint line convergence angle (JLCA)]. CPAK and functional phenotype classifications were performed and all measurements were analysed for gender, age, and body mass index (BMI) within these subgroups. Varus alignment was more common in men (m: 2008, 68.5%; f: 2953, 50.8%) while neutral (m: 578, 19.7%; f: 1357, 23.4%) and valgus (m: 345, 11.8%; f: 1498, 25.8%) alignment was more common in women. The most common morphotypes according to CPAK classification were CPAK Type I (2454; 28.1%), Type II (2383; 27.3%), and Type III (1830; 20.9%). An apex proximal joint line (CPAK Type VII, VIII and IX) was only found in 1.3% of all cases (n = 121). In men, CPAK Type I (1136; 38.8%) and CPAK Type II (799; 27.3%) were the most common types and women were spread more equally between CPAK Type I (1318; 22.7%), Type II (1584; 27.3%) and Type III (1494; 25.7%) (p < 0.001). The most common combination of femur and tibia types was NEUmLDFA0°,NEUmMPTA0° (m: 514, 17.5%; f: 1004, 17.3%), but men showed femoral varus more often. Patients with a higher BMI showed a significantly lower age at surgery (R2 = 0.09, p < 0.001). There were significant differences between men and women for all radiographic parameters (p < 0.001). Distribution in knee morphology with gender-specific differences highlights the wide range in osteoarthritic knees, characterized by CPAK and phenotype classification and may influence future surgical planning. Level III.

Femur deformity correction planning in sagittal plane using mechanical axis

Recently, deformity correction planning using reference lines and angles is a standard procedure. At the same time, both anatomical and mechanical axes are used for the frontal plane. However, until nowadays, there was no algorithm for planning femoral deformity correction in the sagittal plane based on the mechanical axes of the bone fragments. The aim of this study was to develop a method of femur deformity correction planning in the sagittal plane based on mechanical axes. Materials and Methods: On the basis of computer tomography data of 23 adults with nondeformed femurs, we measured the angular relationships between the anatomical axis of the proximal femur in sagittal plane and mechanical axis (∠maj) and the angular relationships between the femoral neck axis and mechanical axis in sagittal plane (∠laj). Results: It was found that ∠maj was 16.0° ±7.6°, and ∠laj was 10.2° ±2.4°. Based on the data obtained, we developed a method for planning the correction of femoral deformities in the sagittal plane. According to this method, the mechanical axis of the proximal bone fragment can be determined using any of three options: (1) “Joint line based.” In this method, the proximal joint line of the femur is drawn, then from the center of the femur head with the angle 85° (mean value of mPPFA) to this line is drawn a line that is mechanical axis; (2) “Femoral neck based.” The neck axis is drawn first, then from the center of the femur head with the angle 16° (mean value ∠maj) to this line is drawn a line that is mechanical axis; and (3) “Anatomical axis based.” First, the anatomical axis of the proximal femur is drawn, then a line parallel to the anatomical axis from the center of the femoral head is drawn, then a line at an angle of 10° (mean value ∠laj) to it is drawn, that is the mechanical axis. Determination of the mechanical axis of the distal fragment in sagittal plane is made by the following: the distal joint line is drawn and divided into five equal segments. Then, the point located on the border of the front 2/5 and the rear 3/5 of the segment is found. From that point, at an angle of 81° (mean mPDFA), a mechanical axis of the distal femur fragment is drawn. The intersection of the mechanical axes of the proximal and distal fragments defines the apex of the deformity. Conclusion: The proposed method for planning deformity correction based on mechanical axes for the sagittal plane complements the existing planning methods for the frontal plane and improves the quality, namely the accuracy of preoperative planning.

Investigating in vivo knee volumetric bone mineral density and walking gait mechanics in healthy people.

The aim of this study was to investigate if the distribution of subchondral volumetric bone mineral density (vBMD) from peripheral quantitative computed tomography (pQCT) is related to estimates of knee joint loads calculated during walking gait in healthy young people. We recruited 19 young (age 18-40years) healthy people with no self-reported knee pain or pathology. For all participants we collected two forms of data: (1) pQCT data at 2% of tibia length (from the proximal joint line) using a Stratec XCT3000 scanner at 0.2×0.2mm in plane resolution; and (2) indices of joint loading, specifically external joint moment, at the indexed knee during walking gait. Joint moments were calculated from motion capture and ground reaction force data. pQCT scans were performed immediately prior to gait analysis. A sub-group of 9 participants attended a second scanning session to establish the reproducibility of the pQCT workflow. vBMD was extracted for four sub-regions (anteromedial, anterolateral, posteromedial and posterolateral). Reproducibility of the pQCT workflow was good to excellent (ICCs 0.832-0.985) with minimal detectable differences ranging from 2.3-39.5mg HA/cm3. Significant independent correlations were identified between the external rotation moment and the medial-to-lateral (r=0.517), posteromedial-to-posterolateral (r=0.627) and posteromedial-to-anterolateral (r=0.518) vBMD ratios, and between the knee adduction moment and the medial-to-lateral (r=-0.476) and posteromedial-to-posterolateral (r=-0.497) vBMD ratios. There appear to be significant relationships between measures of vBMD from pQCT and indices of joint loading in healthy people. These data are the first to combine imaging at the resolution available with pQCT and indices of joint loading in the same cohort.

Reference values of the femur and tibia mechanical axes and angles in the sagittal plane, determined on the basis of three-dimensional modeling

Background: The reference values of the anatomical, mechanical lines and angles of the femur and tibia in the frontal plane have been sufficiently studied. At the same time, the data concerning the mechanical axis and angles in the sagittal plane are rather contradictory. Aims and objectives. The aim of this study was to determine the 3D reference values of the mechanical axes and angles of the femur and tibia in the sagittal plane. Materials and Methods: The study included data of 23 adult volunteers for whom computer tomography (CT) was done. The inclusion criteria were: absence of the deformity confirmed by long-leg films (using known reference lines and angles (RLA) assessment), absence of torsional deformity confirmed by CT and extended position of the limb. Results: It was found that the mechanical axis of the lower limb in the sagittal plane divides the distal joint line of the femur into two segments: anteriorly - 43.8+7.9%, posteriorly - 56.2+7.9%. The proximal joint line of the tibia, correspondingly, is divided into 23.3+8.8% anteriorly and 76.7+8.8% posteriorly. The found values of mechanical angles were the following: mechanical Posterior Proximal Femoral Angle (mPPFA) - 84.7 + 8.8 °, mechanical Posterior Distal Femoral Angle (mPDFA) - 81.1 + 3.95 °, mechanical Posterior Proximal Tibial Angle (mPPTA) - 81.6 + 2.8 °, mechanical Anterior Distal Tibial Angle (mADTA) - 79.9 + 2.98°. Conclusion: The obtained data on the mechanical axis of the lower limb for the sagittal plane can be used both for deformity assessing, planning and estimating the accuracy of deformity correction.

Is Lower-limb Alignment Associated with Hindfoot Deformity in the Coronal Plane? A Weightbearing CT Analysis.

The goals of lower limb reconstruction are to restore alignment, to improve function, and to reduce pain. However, it remains unclear whether alignment of the lower limb and hindfoot are associated because an accurate assessment of hindfoot deformities has been limited by superposition on plain radiography. Consequently, surgeons often overlook hindfoot deformity when planning orthopaedic procedures of the lower limb. Therefore, we used weight-bearing CT to quantify hindfoot deformity related to lower limb alignment in the coronal plane. (1) Is lower-limb alignment different in varus than in valgus hindfoot deformities for patients with and without tibiotalar joint osteoarthritis? (2) Does a hindfoot deformity correlate with lower-limb alignment in patients with and without tibiotalar joint osteoarthritis? (3) Is joint line orientation different in varus than in valgus hindfoot deformities for patients with tibiotalar joint osteoarthritis? (4) Does a hindfoot deformity correlate with joint line orientation in patients with tibiotalar joint osteoarthritis? Between January 2015 and December 2017, one foot and ankle surgeon obtained weightbearing CT scans as second-line imaging for 184 patients with ankle and hindfoot disorders. In 69% (127 of 184 patients) of this cohort, a combined weightbearing CT and full-leg radiograph was performed when symptomatic hindfoot deformities were present. Of those, 85% (109 of 127 patients) with a median (range) age of 53 years (23 to 75) were confirmed eligible based on the inclusion and exclusion criteria of this retrospective comparative study. The Takakura classification was used to divide the cohort into patients with (n = 74) and without (n = 35) osteoarthritis of the tibiotalar joint. Lower-limb measurements, obtained from the full-leg radiographs, consisted of the mechanical tibiofemoral angle, mechanical tibia angle, and proximal tibial joint line angle. Weightbearing CT images were used to determine the hindfoot's alignment (mechanical hindfoot angle), the tibiotalar joint alignment (distal tibial joint line angle and talar tilt angle) and the subtalar joint alignment (subtalar vertical angle). These values were statistically assessed with an ANOVA and a pairwise comparison was subsequently performed with Tukey's adjustment. A linear regression analysis was performed using the Pearson correlation coefficient (r). A reliability analysis was performed using the intraclass correlation coefficient. Lower limb alignment differed among patients with hindfoot deformity and among patients with or without tibiotalar joint osteoarthritis. In patients with tibiotalar joint osteoarthritis, we found knee valgus in presence of hindfoot varus deformity and knee varus in presence of hindfoot valgus deformity (mechanical tibiofemoral angle 0.3 ± 2.6° versus -1.8 ± 2.1°; p < 0.001; mechanical tibia angle -1.4 ± 2.2° versus -4.3 ± 1.9°; p < 0.001). Patients without tibiotalar joint osteoarthritis demonstrated knee varus in the presence of hindfoot varus deformity compared with knee valgus in presence of hindfoot valgus deformity (mechanical tibiofemoral angle -2.2 ± 2.2° versus 0.9 ± 2.4°; p < 0.001; mechanical tibia angle -1.8 ± 2.1° versus -4.3 ± 1.9°; p < 0.001). Patients with more valgus deformity in the hindfoot tended to have more tibiofemoral varus (r = -0.38) and tibial varus (r = -0.53), when tibiotalar joint osteoarthritis was present (p < 0.001). Conversely, patients with more valgus deformity in the hindfoot tended to have more tibiofemoral valgus (r = 0.4) and tibial valgus (r = 0.46), when tibiotalar joint osteoarthritis was absent (p < 0.001). The proximal joint line of the tibia had greater varus orientation in patients with a hindfoot valgus deformity compared with greater valgus orientation in patients with a hindfoot varus deformity (proximal tibial joint line angle 88.5 ± 2.0° versus 90.6 ± 2.2°; p < 0.05). Patients with more valgus deformity in the hindfoot tended to have more varus angulation of the proximal tibial joint line angle (r = 0.31; p < 0.05). In patients with osteoarthritis of the tibiotalar joint, varus angulation of the knee was associated with hindfoot valgus deformity and valgus angulation of the knee was associated with hindfoot varus deformity. Patients without tibiotalar joint osteoarthritis exhibited the same deviation at the level of the knee and hindfoot. These distinct radiographic findings were most pronounced in the alignment of the tibia relative to the hindfoot deformity. This suggests a detailed examination of hindfoot alignment before knee deformity correction at the level of the proximal tibia, to avoid postoperative increase of pre-existing hindfoot deformity. Other differences detected between the radiographic parameters were less pronounced and varied within the subgroups. Future research could identify prospectively which of these parameters contain clinical relevance by progressing osteoarthritis or deformity and how they can be altered by corrective treatment. Level III, prognostic study.

Radiographic Landmarks for Tunnel Positioning in Posterior Cruciate Ligament Reconstructions

Background: Consistent radiographic guidelines for tunnel placement in single- or double-bundle posterior cruciate ligament (PCL) reconstructions are not well defined. Quantitative guidelines reporting the location of the individual PCL bundle attachments would aid in intraoperative tunnel placement and postoperative assessment of a PCL reconstruction. Hypothesis: Consistent and reproducible measurements in relation to radiographic landmarks for the entire PCL and its individual bundle attachments are achievable. Study Design: Controlled laboratory study. Methods: The femoral and tibial PCL bundle attachment centers of 20 nonpaired fresh-frozen cadaveric knees were labeled using radio-opaque spheres and the attachment areas were labeled using barium sulfate. Anteroposterior (AP) and lateral radiographs of the femur and tibia were obtained, and measurements of the distances between the PCL bundle centers and landmarks were acquired. Results: On the AP femur view, the anterolateral bundle (ALB) and posteromedial bundle (PMB) centers were 34.1 ± 3.0 mm and 29.2 ± 3.0 mm lateral to the most medial border of the medial femoral condyle, respectively. The lateral femur images revealed that the ALB center was 17.4 ± 1.7 mm and the PMB center was 23.9 ± 2.7 mm posteroproximal to a line perpendicular to the Blumensaat line that intersected the anterior margin of the medial femoral condyle cortex. Anteroposterior tibia images revealed that the ALB and PMB centers were located 0.2 ± 2.1 mm proximal and 4.9 ± 2.9 mm distal to the proximal joint line, respectively. The PCL attachment center was 1.6 ± 2.5 mm distal to the proximal joint line. On the lateral tibia view, the ALB center was 8.4 ± 1.8 mm, the PCL attachment center was 5.5 ± 1.7 mm, and the PMB center was 2.5 ± 1.5 mm superior to the champagne glass drop-off of the posterior tibia. Conclusion: Radiographic measurements from several clinically relevant views of the femur and tibia were reproducible with regard to the anatomic locations of the ALB and PMB centers. The measurements from the lateral femur and tibia views provided the most clinically pertinent radiographic measurements intraoperatively. Clinical Relevance: This study established a set of clinically relevant radiographic guidelines for anatomic reconstruction of the PCL. The parameters set forth in this study can be used in both the intraoperative and postoperative settings for both single- and double-bundle PCL reconstructions.

Meniscal bearing uncemented total knee arthroplastyEarly clinical results at a minimum 2-year review

A prospective study of early clinical and radiologic outcome of the Motus (Osteo, Selzach, Switzerland) meniscal bearing total knee arthroplasty was performed. We reviewed the first 75 consecutive prostheses in 62 patients, implanted over a 4-year period. The mean follow-up was 2.5 years. Average preoperative knee score was 97 out of 200 (Knee Society score, 43; functional score, 54) and at 2-year review was 179 out of 200 (Knee Society score, 87; functional score, 92). Average postoperative flexion at 2 years was 113°. No meniscal bearing subluxation, dislocation, or breakages occurred. Radiologically, there was no evidence of subsidence or osteolysis. Our results support the continued use of this meniscal bearing knee prosthesis. It is important to confirm, however, an equal flexion and extension gap without proximal joint line migration. Copyright 2003, Elsevier Science (USA). All rights reserved.