Patterns of cartilage degeneration in knees with medial tibiofemoral offset

Changes in coronal tibiofemoral subluxation before and after medial unicompartmental knee arthroplasty: an observation for ten years

INTRODUCTION

Residual coronal tibiofemoral subluxation (CTFS) can cause peripheral contact between the implant components after medial unicompartmental knee arthroplasty (UKA), resulting in premature failure. The aim of this study was to investigate the changes in CTFS before and after surgery.

METHODS

Fifty-nine knees of 51 patients who underwent fixed-bearing medial UKA were retrospectively analyzed. CTFS was measured using anteroposterior knee radiographs in the standing position and under valgus stress before surgery and at two weeks and one, five, and 10 years after surgery. The preoperative and postoperative alignment of the knee and tibial component inclination angle (TCIA) were also evaluated.

RESULTS

Mean preoperative CTFS decreased significantly from 4.6 ± 1.5 mm in the standing position to 3.3 ± 1.1 mm under valgus stress and to 3.5 ± 1.4 mm in the standing position immediately after surgery. No changes in mean CTFS were observed during the 10-year follow-up period. The CTFS at 2 weeks after surgery was strongly correlated positively with the CTFS at the 10-year follow-up and the preoperative CTFS under valgus stress. The postoperative medial proximal tibial angle (MPTA) was strongly correlated negatively with the two-week postoperative CTFS, while TCIA was significantly correlated positively with that.

CONCLUSIONS

Residual CTFS after medial UKA did not change during the mid-term follow-up period, which was predictable to some extent based on the observations noted using the preoperative valgus stress radiographs. Close attention should be paid to patients with severe uncorrectable preoperative CTFS and small MPTA values when considering the indications for medial UKA.

LEVEL OF EVIDENCE

IV.

Region partitioning of articular cartilage with streaming-potential-based parameters and indentation maps

Articular cartilage exhibits site-specific tissue inhomogeneity, for which the tissue properties may continuously vary across the articular surface. To facilitate practical applications such as studying site-specific cartilage degeneration, the inhomogeneity may be approximated with several distinct region-wise variations, with one set of tissue properties for one region. A clustering method was previously developed to partition such regions using cartilage indentation-relaxation and thickness mapping instead of simply using surface geometry. In the present study, a quantitative parameter based on streaming potential measurement was introduced as an additional feature to assess the applicability of the methodology with independent datasets. Experimental data were collected from 24 sets of femoral condyles, extracted from fresh porcine stifle joints, through streaming potential mapping, automated indentation, and needle penetration tests. K-means clustering and Elbow method were used to find optimal region partitions. Consistent with previous findings, three regions were suggested for either lateral or medial condyle regardless of left or right joint. The region shapes were approximately triangular or trapezoidal, which was similar to what was found previously. Streaming potentials were confirmed to be region-dependent, but not significantly different among joints. The cartilage was significantly thicker in the medial than lateral condyles. The region areas were consistent among joints, and comparable to that found in a previous study. The present study demonstrated the capability of region partitioning methods with different variables, which may facilitate new applications whenever site-specific tissue properties must be considered.

Characterizing site-specific mechanical properties of knee cartilage with indentation-relaxation maps and machine learning

Knee cartilage experiences site-specific focal lesion and degeneration, which is likely associated with tissue inhomogeneity and nonuniform mechanical stimuli in the joint, for which a complete picture remains to be depicted. The present study aimed to develop a methodology to quantify knee cartilage inhomogeneity using porcine knee specimens. Automated indentation-relaxation and needle probing were performed on fully intact cartilage to obtain data that essentially represent continuous distributions of cartilage properties in the knee. Machine learning was then introduced to approximate the tissue inhomogeneity with several regions via clusters of indentation locations, and finite element modeling was used to obtain poromechanical properties for each region using indentation-relaxation and thickness data. Significant region dependence was established from the full time-dependent mechanical response. Seventeen regions, or clusters, were found to best approximate the site-specific poromechanical properties of articular cartilage for femoral groove, lateral and medial condyles and tibial plateaus, after up to eight clusters were tested for each of the five cartilage sections. The region partitions recommended, and tissue properties acquired would facilitate implementation of tissue inhomogeneity in future applications, e.g., contact modeling of the knee joint. The results obtained from 14 porcine knees revealed interesting region differences, for example, the two condyles have the same effective stiffness when responding to slowly applied mechanical loadings but substantially lower stiffness in the medial condyle when responding to fast loadings. This mechanical behavior may be associated with the fact that medial femoral cartilage is more prone to focal lesions than the lateral one.

Magnetic Resonance Imaging for Acute Musculoskeletal Injuries of the Knee Joint in Coal Miners: A Retrospective Study

Aim

Coal miners are more prone to musculoskeletal injuries to their knees due to specific repetitive movements while working in the seams. We aimed to identify the kinds of and quantify traumatic musculoskeletal injuries to the knee in the coal miners.

Methods

A retrospective observational analysis of all consecutive emergency admissions of the coal miners with occupational knee injuries between January 2018 and December 2020 was performed. A total of 94 knee trauma events in 79 knees of 76 patients were analyzed in the study. Musculoskeletal injuries of the meniscal and ligamentous/tendinous structures were identified using magnetic resonance imaging of the affected knees.

Results

The medial meniscal and the anterior cruciate ligament injuries were detected in 72.3% and 51.1% of the events, respectively. Grade 2 and 3 medial meniscal injuries were the most common grades (39.7% and 41.2%, respectively). For the anterior cruciate ligament injuries, grade 2 was the most common (56.3%). In 48.9% of the cases, we detected bony bruise/edema in the tibial plateau (52.2%), and the condyles of the femur (45.7%) were almost equally affected. Intraarticular effusions appeared in 59.6% of the cases.

Conclusions

Our findings provide detailed identification of the injuries seen in the coal miners. The medial meniscus and the anterior cruciate ligament are the most frequently injured structures.

Short-term outcomes of Oxford unicompartmental knee arthroplasty with coronal subluxation of the knee: a retrospective case–control study

Background

The goal of this study was to assess short-term outcomes in single compartment osteoarthritis patients associated with the coronal tibiofemoral subluxation (CTFS) of the knee joint after Oxford unicompartmental knee arthroplasty (OUKA), and to establish the potential impact of the degree of CTFS on operative outcomes.

Methods

Data pertaining to 183 patients with medial compartment osteoarthritis that underwent OUKA treatment between February 2016 and June 2019 were retrospectively analyzed. The presence and degree of severity of CTFS were assessed using preoperative weight-bearing anteroposterior X-ray images of the knee. Patients were stratified into three subgroups based upon the observed degree of subluxation: a normal group, a mild subluxation group (CTFS < 0.5 cm), and a severe subluxation group (CTFS ≥ 0.5 cm). Anterior and posterior X-ray examination of the knee was conducted at the time of most recent follow-up for each patient to assess the degree of CTFS correction following OUKA. Clinical function was assessed using Oxford knee score (OKS) and Hospital for Special Surgery score (HSS) values, while pain was rated using visual-analog scale (VAS) scores. The mechanical femoral tibial angle (mFTA), range of motion (ROM), and complication rates in these three groups were additionally compared.

Results

The average follow-up duration for patients in this study was 24.1 months (range: 17–32 months). There were no significant differences in patient age, sex, body mass index (BMI), follow-up duration, mFTA, ROM, OKS, HSS, or VAS scores among these three groups (P > 0.05). After surgery, OKS and HSS scores declined significantly, but no differences in these scores were observed among groups (P > 0.05). Of these patients, 135 (73.8%) were satisfied with the operation, of whom 80 (43.7%) were very satisfied. There were no significant differences in ROM or VAS scores among groups (P > 0.05). The degree of CTFS for patients in the mild and severe subluxation groups was significantly improved following OUKA relative to preoperative values such that the degree of postoperative CTFS did not differ significantly among these groups (P > 0.05). Postoperative mFTA was also significantly improved in these three patient subgroups (P < 0.05). No patients experienced operative complications over the follow-up period.

Conclusions

OUKA can successfully improve clinical symptoms in patients with single compartmental osteoarthritis. Moreover, OUKA can effectively correct CTFS of the knee in these patients, and the degree of preoperative CTFS has no impact on surgical efficacy.

Level of evidence

III.

Current Measurement Strategies of Coronal Tibiofemoral Subluxation: A Systematic Review of Literature

OBJECTIVE. Coronal tibiofemoral (TF) subluxation has generated interest in the last several years due to newfound clinical implications of its presence. However, controversy within the literature concerning how to measure and calculate coronal TF subluxation on radiographic imaging remains. The purpose of this study was to describe how coronal TF subluxation is being measured and calculated in the literature with the goal of describing a reproducible and validated technique for clinical adoption. MATERIALS AND METHODS. A PubMed literature search was performed in March 2020 according to PRISMA guidelines. The terms "tibiofemoral subluxation" and "tibial femoral subluxation" were included in the search. Criteria of interest included radiographic view and evaluation, anatomic landmarks used, and measurement validity. RESULTS. Review of relevant literature resulted in 744 articles, 16 of which met our inclusion criteria. A wide range of measuring techniques, anatomic landmarks, and radiographic views were used with varying validity. Full-limb radiographic views were the most common. Six studies measured the translation of the mechanical axes of the tibia and femur. Eight studies measured the translation of either femoral condyle in reference to the tibial plateau. Coordinate-based software with the iterative closest point algorithm was used in two studies. Whether coronal TF subluxation should be divided by tibial plateau width to account for knee size was controversial. CONCLUSION. A variety of approaches exist for diagnosing and quantifying coronal TF subluxation because of the lack of clear anatomic landmarks within the TF joint that can be used to measure coronal TF subluxation in the horizontal plane. Even when using the same anatomic landmarks, studies varied on how to measure coronal TF subluxation radiographically and whether knee size should be accounted for. Further studies are necessary to standardize (via inter- and intraobserver validation with a control group) an easy, reproducible, and minimally biased approach to measuring coronal TF subluxation on radiographic imaging. We believe our systematic review succinctly provides the necessary information to either develop such a tool or encourage future studies to compare existing techniques to find the most reliable and clinically useful approach for evaluating coronal TF subluxation.

Combined Injury to the ACL and Lateral Meniscus Alters the Geometry of Articular Cartilage and Meniscus Soon After Initial Trauma

Combined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post-traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior-inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage-to-bone height decreased in the region located under the posterior horn of the meniscus, and the thickness of cartilage increased and decreased in the mid and posterior regions of the plateau, respectively). Subjects that suffered an isolated ACL tear did not undergo the same magnitude of change to these articular structures. A majority of the changes in morphometry occurred in the lateral compartment of the knee; however, change in the medial compartment of the knee with a normal appearing meniscus also occurred. Statement of clinical significance: Knee injuries that involve combined trauma to the ACL and meniscus directly affect both compartments of the knee, even if the meniscus and articular cartilage appears normal upon arthroscopic examination. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:759-767, 2020.