Journal of Orthopaedic Research®最新文献

In revision hip arthroplasty, modular stems enable intraoperative adjustment of the biomechanics of the hip to ensure a stable joint function even in complex anatomical cases. Modular stem junctions, however, carry the risk of junction degradation due to corrosive processes or even junction breakage. Fretting-corrosion has been mentioned as precursor of junction breakage but has hardly been systematically assessed. To investigate relations between corrosion and fretting, and implant and patient specific parameters and connection strength, respectively, a collection of 53 retrieved modular hip stems of different implant systems was investigated. Corrosion and fretting at the stem-neck taper connection were rated with a modified Goldberg score. Taper contamination was assessed with a similar scoring system. If the hip stems were still joint to the neck piece, the push-out force to detach the parts was recorded as a measure for taper junction strength. A multivariate regression analysis revealed that corrosion and fretting were significantly affected by implantation time, taper contamination, body weight and implant system. Taper junction strength was not altered by corrosion or fretting but by taper contamination. The results indicate that implant geometry parameters are not related to the extent of corrosive degradation at the junction, but taper contamination significantly increased corrosion at taper surfaces. This underlines the importance of the cleanliness of the taper surfaces during hip stem assembly for a long-term stability of the modular implant.

Cementless total knee arthroplasty implants offer advantages over cemented implants, such as bone preservation and easier revision procedures. However, the optimal interference fit required to achieve a good press-fit fixation, essential for both primary and long-term stability, remains uncertain. This study uses finite element analysis to investigate the effects of two interference fits (350 µm and 700 µm) on micromotions, gap behavior, and plastic deformation at the bone-implant interface of a cementless femoral component under various loading conditions. Finite element models were developed using paired cadaveric femurs, incorporating microCT and optical scans. Micromotions were quantified as shear displacement, while gaps were quantified as normal displacement. Bone response was assessed by quantifying the volume of bone experiencing total equivalent plastic strain. The models showed moderate correlation with experimental results, predicting 35% of displacement variability. Although high interference fit implants slightly reduced micromotions and gaps, these differences were not statistically significant (p = 0.252 and p = 0.759, respectively). The high interference fit implants exhibited significantly greater plastic deformation (+15.7%, p = 0.031), particularly at the posterior femoral condyles. These findings suggest that while an increased interference fit does not enhance primary stability, it may lead to more plasticity in the bone, potentially leading to more damage. Thus, optimizing the interference fit is crucial to balance implant fixation and minimize bone damage.

Adequate bone quality is necessary for reliable cementless fixation during total knee arthroplasty (TKA). Hounsfield Units (HUs) can be a useful surrogate of bone density, and therefore a proxy of bone quality. We sought to determine whether HU would correlate with subjective intraoperative assessment of bone quality and hence use of cementless fixation. A retrospective review of patients who underwent a robotic-assisted TKA between June 2022 and June 2024 by a single surgeon was conducted. HU measurements were obtained at three regions of interest (ROI) within the tibial plateau on preoperative axial-CT scans. Patients were divided into cementless or cemented tibial implant fixation groups based upon subjective intraoperative bone quality assessment. Demographic data such as age, sex, and BMI were collected. The final cohort included 630 patients. Cementless fixation was used in 58.3% of cases. Cementless patients had a higher combined overall average HU measurement (152.7 vs. 105.6, p < 0.001). Point-biserial correlation showed moderate inverse correlations between implant fixation type and HU measurements (all p < 0.001). ROC analysis and predictive modeling found that the best performance was derived from the combined model followed by combined demographics alone, and then HU measurements alone (AUC: 0.853 vs. 0.808 vs. 0.757). Standalone demographic resulted in the poorer predictive modeling. Ultimately, cementless fixation was associated with higher HU measurements compared to cemented fixation in all 3 ROI. HU in conjunction with combined demographic data offered the greatest confidence in predicting fixation type and therefore may be utilized to aid in decision-making and surgical planning for TKA.

Overuse-induced muscle disorders (OIMD) frequently occur in athletes due to excessive and improper use under high physical demand, often leading to muscle pain and weakness. Limited studies have shown intramuscular fibrosis in OIMD, with fibro-adipogenic progenitors (FAPs), also known as mesenchymal stromal cells (MSCs), playing a crucial role in this fibrosis. This study aimed to develop a rat OIMD model using neuromuscular electrical stimulation-induced isometric exercise (NMES-ISO) and to investigate mechanisms by which excessive exercise without adequate rest leads to OIMD. We hypothesize that daily NMES-ISO would cause muscle weakness and fibrogenesis mediated by FAP activation triggered by muscle fiber damage. Male Wistar rats received daily NMES-ISO loading on the plantar flexor muscles at a lengthened position. Two weeks of NMES-ISO led to decreased muscle torque without muscle mass reduction. Masson-Trichrome stain revealed collagen-rich fibrogenic lesions in the gastrocnemius muscles, while Evans blue stain detected no muscle fiber damage during the first 5 days. MRI showed increased T2*wi signals correlating with fibrogenic areas. Excessive NMES-ISO stimulated FAP proliferation. This study established a rat model of OIMD using NMES-ISO, characterized by muscle weakness and intramuscular fibrogenesis. Contrary to our hypothesis, FAP activation occurred without overt muscle injury, suggesting excessive mechanical loading may directly trigger FAP proliferation and fibrogenesis. It was cautioned that even relatively safe isometric contraction training could lead to FAP activation and intramuscular fibrosis without proper methods and recovery periods.

Internal rotation (IR) is not reliably improved after reverse shoulder arthroplasty (RSA). This study aimed to identify surgical parameters that predict kinematics of the hand-to-back motion (H2B) after RSA and to identify associations between kinematics and clinical outcomes after RSA. We hypothesized that less humeral retroversion, more lateralization and a larger glenosphere would predict kinematics associated with favorable outcomes post-RSA. Thirty-five patients performed H2B while synchronized biplane radiographs were collected. Digitally reconstructed radiographs, constructed from patient-specific bone plus implant models, were matched to the biplane radiographs to determine kinematics. The total contribution to motion, the end position, peak angles, and range of motion (ROM) were found for all glenohumeral and scapular rotations. The path of the center of the humeral insert on the glenosphere was calculated. Patient-reported outcomes, clinical ROM, and strength were measured. Associations were determined between intraoperative variables and kinematics as well as between kinematics and outcomes. The results demonstrated that glenosphere tilt predicted glenohumeral and scapular kinematics; these kinematics were associated with IR ROM, strength, and more favorable patient-reported outcomes. A larger glenosphere predicted a center of contact that was associated with more strength in IR. All components of scapular rotation were associated with favorable outcomes, suggesting rehabilitation focusing on scapular motion may improve outcomes post-RSA. Glenosphere tilt and size predicted kinematics that were associated with range of motion, strength, and patient-reported outcomes.