Combined Effects of External Moments and Muscle Activations on ACL Loading during Numerical Simulations of a Female Model in OpenSim

Background: Anterior cruciate ligament (ACL) injuries have been studied using a variety of methods and tools. However, each is hindered by specific limitations with respect to its application. Aim: To assess the combined effects of external moments and muscle activations on ACL loading using serial, forward dynamics (FD) simulations of single leg, hyperextension landings in OpenSim. Methods: The FD tool of OpenSim was iteratively run using different combinations of knee-spanning muscle activation levels, internal rotation and valgus knee moment magnitudes. A regression was conducted on the data in order to predict ACL loading under different conditions. Results: A purely abduction moment leads to greater mean ACL loading than a purely internal rotation moment or any combination of the two. Additionally, the generalized boosted regression model using both external moments and certain knee muscles identified the internal rotation moment as the most important variable in predicting the ACL load (R2 = 0.9; p < 0.0001). Conclusion: This study demonstrated a novel and practical application of an OpenSim musculoskeletal model that supports the ACL injury mechanism of landing with low knee flexion angles, high muscle forces of the Quadriceps muscles and an external knee valgus moment, though further investigation is needed.

The use of the constrained prosthesis in the difficult primary knee arthroplasty

Background: The constrained knee prosthesis has the basic indication in revision arthroplasty, but the latest literature reveals that it takes place also in primary total knee arthroplasty in cases of knee osteoarthritis associated with major deformities. Material and methods: Present study is based on the surgical treatment, using the constrained knee prosthesis in the primary total knee arthroplasty, during 2019-2021, of 28 patients with knee osteoarthritis associated with severe deformities in varus or valgus, in the Big Joint Replacement Department, Clinical Hospital of Traumatology and Orthopedics, Chisinau. Results: In this study, the following criteria were evaluated: the type of deformity – valgus (10 cases) and varus (18 cases); the degree of deformation – for varus knees was on average 300 , and for valgus knee – 250 ; bone attrition – 11 cases with bone defects where it was necessary to use augmentations; affected side – in 19 cases the right knee was affected and 9 cases the left one; the women/men ratio was 4/1; the mean age of the patients was 67.5 years; average duration of the intervention – 140 minutes; in 5 cases a lateral para-patellar approach was performed, of which 2 cases with tibial tuberosity osteotomy; complications – 1 case with intra-operative periprosthetic fracture and 2 cases with superficial infections of the operated joints. Conclusions: Osteoarthritis of the knee progresses rapidly, leading to severe deformities, significant bone defects and joint instability, which are indications to use the constrained prosthesis in the primary total knee arthroplasty, long-term follow-up is necessary to obtain the last conclusion, but from this study the constrained knee prosthesis like primary implant for special indication had promising results.

Frontal knee alignment influences the vertical orientation of the femoral neck in standing position

Aims The aim of this study was to determine the association between knee alignment and the vertical orientation of the femoral neck in relation to the floor. This could be clinically important because changes of femoral neck orientation might alter chondral joint contact zones and joint reaction forces, potentially inducing problems like pain in pre-existing chondral degeneration. Further, the femoral neck orientation influences the ischiofemoral space and a small ischiofemoral distance can lead to impingement. We hypothesized that a valgus knee alignment is associated with a more vertical orientation of the femoral neck in standing position, compared to a varus knee. We further hypothesized that realignment surgery around the knee alters the vertical orientation of the femoral neck. Methods Long-leg standing radiographs of patients undergoing realignment surgery around the knee were used. The hip-knee-ankle angle (HKA) and the vertical orientation of the femoral neck in relation to the floor were measured, prior to surgery and after osteotomy-site-union. Linear regression was performed to determine the influence of knee alignment on the vertical orientation of the femoral neck. Results The cohort included 147 patients who underwent knee realignment-surgery. The mean age was 51.5 years (SD 11). Overall, 106 patients underwent a valgisation-osteotomy, while 41 underwent varisation osteotomy. There was a significant association between the orientation of the knee and the coronal neck-orientation. In the varus group, the median orientation of the femoral neck was 46.5° (interquartile range (IQR) 49.7° to 50.0°), while in the valgus group, the orientation was 52.0° (IQR 46.5° to 56.7°; p < 0.001). Linear regression analysis revealed that HKA demonstrated a direct influence on the coronal neck-orientation ( β = 0.5 (95% confidence interval (CI) 0.2 to 0.7); p = 0.002). Linear regression also showed that realignment surgery was associated with a significant influence on the change in the coronal femoral neck orientation ( β = 5.6 (95% CI 1.5 to 9.8); p = 0.008). Conclusion Varus or valgus knee alignment is associated with either a more horizontal or a more vertical femoral neck orientation in standing position, respectively. Subsequently, osteotomies around the knee alter the vertical orientation of the femoral neck. These aspects are of importance when planning osteotomies around the knee in order to appreciate the effects on the adjacent hip joint. The concept may be of even more relevance in dysplastic hips. Cite this article: Bone Jt Open 2021;2(12):1057–1061.

Bilateral Symptomatic Mucoid Degeneration of the Anterior Cruciate Ligament with Anterior Knee Pain but No Limited Knee Flexion

Mucoid degeneration of the anterior cruciate ligament (ACL) is a rare cause of anterior knee pain (AKP). Some case reports have been published; however, it is difficult to diagnose and is often underdiagnosed or misdiagnosed because of its pathophysiological ambiguity. We report a rare case of a patient diagnosed with bilateral mucoid degeneration of the ACL with AKP and no limited joint range of motion (ROM). A 59-year-old man with spontaneous right AKP was admitted to our hospital. He first underwent arthroscopic resection of the thickened medial plica protruding far into the medial patellofemoral joint (PFJ) but felt little effectiveness thereafter. He then had an arthroscopic release of the lateral patellar retinaculum because of valgus knee and patellar instability, which resulted in only temporary improvement. Then, the AKP relapsed, this time with limitations in the ROM. Magnetic resonance imaging (MRI0 showed a diffuse, thickened ACL with a high inhomogeneous intensity in the T2-weighted and proton density weighted images and which looked similar to a celery stalk. Based on the patient’s history and MRI findings, we suspected mucoid degeneration of the ACL and subsequently performed arthroscopic excision. At the same time, AKP appeared on the other side. Since the MRI demonstrated a similar celery stalk image as before, the same operation was performed on this side, as well. Finally, AKP and the limitation of the ROM were relieved approximately one month after surgery. Due to the patient only suffering from AKP with a preserved ROM, it took about 14 months to diagnose this disease. It should, therefore, always be considered in cases of AKP alone.

Medial closure supracondylar femoral osteotomy: an effective solution for long-term treatment of arthritic valgus knee?

Purpose The aim of this work was to retrospectively analyze the clinical, subjective, and radiological results of medial closing-wedge distal femur osteotomy (MCW-DFO) for the treatment of osteoarthritis (OA) in valgus knee at medium- to long-term follow-up. Materials and methods A total of 57 patients (62 knees) treated with MCW-DFO between 1984 and 2018 were included in the study. Patient age at the time of the surgery ranged between 28 and 61 years (average: 48 years). All patients with a minimum follow-up of 4 years were contacted to request for them to undergo clinical, subjective, and radiological evaluation. Preoperative hip–knee–ankle (HKA) angle (i.e., preoperative valgus malalignment) was 8.6° ± 2°. Patients were evaluated using the following scales: the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Knee Society Score (KSS), the International Knee Documentation Committee (IKDC), the Visual Analog Scale (VAS), and the Numeric Rating Scale 11 (NRS-11). Results Mean follow-up was 11.6 ± 4.9 years, and a total of 17 patients (20 knees) were available for the last examination. At maximum follow-up, 4 patients underwent conversion to a total knee replacement (20%); their survival rate was 100% at 10 years and 66.7% at 15 years, as estimated using the Kaplan–Meier curve. The subjective Knee Society Score improved on average from 37.7 ± 10 to 63.9 ± 15.4. The objective Knee Society Score improved on average from 42.2 ± 11.7 to 75 ± 22.5. The pain detected through the VAS and NRS-11 scales improved from 56.7 ± 12.9 to 42 ± 17.1 and from 5.8 ± 1.1 to 4.4 ± 1.7, respectively. Thirteen patients (70%) required hardware removal at an average time of 19 ± 4 months due to a local nuisance. Conclusions MCW-DFO can improve symptoms in patients with osteoarthritis in a valgus knee at medium- to long-term follow-up, reducing the progression of osteoarthritis in properly selected patients.

Analysis of Gender Differences in the Rotational Alignment of the Distal Femur in Kinematically Aligned and Mechanically Aligned Total Knee Arthroplasty

To compare the angle between the external rotation references of the femoral components in the axial plane by gender and lower limb alignment in Korean patients with osteoarthritis (OA). Magnetic resonance (MR) images of 1273 patients were imported into a modeling software and segmented to develop three-dimensional femoral bony and cartilaginous models. The surgical transepicondylar axis (sTEA), posterior condylar axis (PCA), the kinematically aligned axis (KAA), and anteroposterior axis were used as rotational references in the axial plane for mechanically aligned (MA) TKA. The relationship among axes were investigated. Among 1273 patients, 942 were female and 331 were male. According to lower limb alignment, the varus and valgus knee groups comprised 848 and 425 patients, respectively. All measurements, except PCA-sTEA, differed significantly between men and women; all measurements, except PCA-sTEA, did not differ significantly between the varus and valgus knee groups. In elderly Korean patients with OA, rotational alignment of the distal femur showed gender differences, but no differences were seen according to lower limb alignment. The concern for malrotation of femoral components during kinematically aligned TKA is less in Koreans than in Caucasians and relatively less in women than in men. In MA TKA, malrotation of the femoral components can be avoided by setting different rotational alignments for the genders.