The purpose of this study was to identify 12-month postinjection knee osteoarthritis (KOA) pain trajectories and develop an early prediction model using patient-reported pain scores. Data were derived from a multi-site, single-blind randomized controlled trial of intra-articular injections for KOA. The primary analysis focused on participants assigned to autologous bone marrow aspirate concentrate, umbilical cord tissue-derived mesenchymal stromal cells, or stromal vascular fraction. After data-quality screening, the primary trajectory cohort included 317 participants and the prediction cohort included 295 participants with Screening and Month-3 KOOS-12 Pain scores. Latent class mixed-effects modeling identified a two-class solution selected for clinical interpretability: 66.6% of patients followed an Improved Pain trajectory and 33.4% followed a Persistent Pain trajectory. Although a three-class model had slightly lower BIC, the additional class included only 2.5% of participants and was not retained for the clinical prediction tool. A logistic regression model using KOOS-12 Pain at Screening and 3-month change predicted trajectory membership with AUC = 0.785 in training and AUC = 0.792 in the held-out test set. A training-selected threshold of 0.656 yielded held-out test sensitivity = 0.790, specificity = 0.692, PPV = 0.860, NPV = 0.581, and accuracy = 0.761. The resultant model was implemented as the Symptom Prediction for Outcomes of Treatment (SPOT) web calculator. Clinical Significance: The SPOT web calculator only requires KOOS-12 Pain data from Screening and Month 3 to classify patients as likely to follow an Improved Pain vs. Persistent Pain trajectory after orthobiologic KOA treatment. Trial Registration: ClinicalTrials.gov identifier: NCT03818737.
The anterior cruciate ligament (ACL) has poor intrinsic healing capacity due to exposure to the intra-articular synovial environment of the knee. Therefore, tendon auto- or allograft reconstruction is the mainstay of treatment for a torn ACL. Following reconstruction, there is a high rate of post-traumatic osteoarthritis, likely due to alteration of joint biomechanics, which supports the clinical need to advance primary ACL repair strategies. The ACL is enclosed by a vascularized, synovial-like sheath (ACL-s), which supplies nutrients to the central core (ACL-c). The ACL-s may act as a selective barrier to solute diffusion, protecting the ACL-c from damaging synovial enzymes and/or hyaluronic acid, while allowing nutrient diffusion. Like the synovium, the ACL-s is rich with collagens and resident macrophages, thus may be susceptible to change of function following injury and inflammation. We investigated the healthy and inflammed ACL-s structure, diffusivity, and cellular profile in comparison to the ACL-c and synovium to guide the development and optimization of primary repair technologies. Diffusion and histologic assessments revealed the ACL-s functions as a semi-permeable barrier through lower solute diffusivity and unique collagen organization. RNAseq demonstrated differential expression of extracellular matrix, inflammatory, and immune-related genes across ACL-s, ACL-c, and synovium, with the ACL-s uniquely showing upregulated expression of CX3CR1 and CLDN5 suggestive of an immunologic barrier. This study establishes the potential of the ACL-s to serve an immunologic and functional barrier that protects the underlying ACL-c from the inflammatory milieu following injury, and therefore, should be recapitulated when developing primary ACL repair technologies.
Osteonecrosis is a serious disorder leading to subchondral bone collapse and joint dysfunction. Osteonecrosis has been increasingly diagnosed before bone collapse; however, effective treatments for regenerating necrotic bone remain unavailable. Mesenchymal stem cell (MSC)-based therapies are promising; however, bone marrow-derived MSCs (BMSCs) are limited by donor burden, low yield, and suboptimal regenerative efficacy. Stem cells from human exfoliated deciduous teeth (SHED) exhibit higher proliferative capacity, enhanced growth factor secretion, minimal senescence, and noninvasive harvesting, making them a strong alternative. We evaluated SHED and BMSCs in a refractory rat model of radiation-induced tibial osteonecrosis. In vitro, SHED secreted similar or higher levels of proangiogenic and chemotactic factors-including vascular endothelial growth factor, angiopoietin-2, stem cell factor, monocyte chemoattractant protein-1, and C-C motif chemokine ligand 5-than BMSCs and significantly enhanced macrophage migration. Hydroxyapatite/collagen scaffolds seeded with SHED or BMSCs were transplanted into irradiated tibial bone defects in vivo. Micro-computed tomography revealed significantly accelerated bone regeneration with SHED, but not with BMSCs, compared with cell-free scaffolds. Histology confirmed new bone and marrow formation at SHED-treated sites, accompanied by increased periosteal proliferation and vascularity. Bulk RNA sequencing showed that SHED transplantation upregulated angiogenesis and immune cell recruitment-related pathways, whereas BMSCs upregulated genes associated with endochondral ossification without effective regeneration. Notably, SHED did not differentiate into osteoblasts or chondrocytes in vivo, indicating paracrine mediation of angiogenesis and macrophage recruitment. Given the limited regenerative capacity of necrotic bone, SHED's angiogenic and immunomodulatory activities position it as a promising candidate for cell-based therapy in refractory osteonecrosis.
Autologous cell-based approaches for bone repair using mesenchymal stromal cells (MSCs) in older patients are limited in part by cellular senescence, resulting in impaired MSC self-renewal and differentiation. Currently, the field lacks a standardized method to induce senescence in human MSCs and characterize them for experimental use, as well as effective strategies to mitigate the harmful effects of the senescence-associated secretory phenotype (SASP). We previously demonstrated that MSC-secreted decellularized extracellular matrix (dECM) enhances the osteogenic potential and survival of MSCs. We hypothesized that senescent MSCs would exhibit improved osteogenic potential and reduced SASP activity when maintained on dECM. We first demonstrated that a senescent phenotype can be reliably induced in human MSCs through ionizing irradiation coupled with a 21-day preconditioning phase in culture, evidenced by increased beta-galactosidase staining and enlarged cell area. We then observed that senescent MSCs on dECM exhibit improved osteogenic potential and reduced SASP compared to cells on tissue culture plastic, evidenced by quantifying markers of osteogenic differentiation and ELISAs for known inflammatory cytokines. These data support the promise of dECM as an instructive biomaterial to enhance the regenerative potential of MSCs from older patients for autologous bone repair.
The Latarjet procedure is widely used for anterior shoulder instability with glenoid bone loss, yet its influence on glenohumeral joint (GHJ) kinematics during functional movement remains unclear. This study evaluated GHJ kinematics during active external rotation compared with the contralateral shoulder preoperatively and at 1- and 2-year follow-up using dynamic radiostereometry (RSA) and CT-derived 3D bone models registered to the radiographs. Patient-reported outcomes were assessed using the Western Ontario Shoulder Instability Index (WOSI). Preoperatively, the injured shoulder showed a tendency toward a more anterior (up to 1.5 mm, CI -0.3-3.3) and inferior (up to 1.1 mm, CI -0.3-2.5) humeral head position. At 1 year postoperatively, the humeral head was more posterior (up to 1.8 mm, CI 0.8-2.9) and superior (4.0 mm, CI -4.1-12.1) compared with preoperatively, with an additional posterior shift at 2 years (1.5 mm, CI 0.4-2.6). Postoperative kinematics did not differ from the healthy shoulder. Contact area decreased preoperatively by up to 121.7 mm2 (CI 57.1-186.3) and increased by up to 110.8 mm2 (CI 42.3-179.3) at 2 years. WOSI improved from 55% (CI 49-61) preoperatively to 36% (CI 25-48) at 1 year and 27% (CI 17-36) at 2 years. The Latarjet procedure resulted in GHJ kinematics comparable to the healthy shoulder during external rotation. Postoperatively, kinematics shifted posteriorly and superiorly with improved WOSI scores over 2 years. Clinical Significance: Near-normal GHJ kinematics during external rotation are achieved within 2 years, supporting improved shoulder function in anterior instability following the Latarjet procedure.
Metatarsal pronation has been reported to be a significant recurrence factor for hallux valgus after corrective osteotomies. However, the extent of pronation correction with distal metatarsal I osteotomies varies greatly from patient to patient without the reason being known. The objective of this study was to describe the effect of the metatarsal I osteotomy angle on muscular torque, acting on the first metatarsal. The primary hypothesis was that a varying angle for the transversal cut affects the muscular pronating torque in the first metatarsal. Therefore, three different 3-dimensional foot models have been created, and a distal metatarsal I corrective osteotomy was simulated. The transverse cut of the osteotomy was varied from three different angles (-10°, 0°, 10°). Torque and the pro-/supinating component of eight muscles acting on the first metatarsal have been calculated. No significant difference in pro-/supinating torque acting on the first metatarsal was found between different osteotomy angles. Nevertheless, the lateral shift of the osteotomized metatarsal-I-head in ReveL osteotomy increased supinating torque in almost all analysed muscles, regardless of the angle of the osteotomy. Hence, a tendency (p = 0.082) towards less muscular pronating torque could be shown for all ReveL osteotomies compared to the non-osteotomized status quo. This increased supination was significant especially for the analysed flexors and adductor hallucis caput obliquus.
Mechanical loading-based rehabilitation of tendinopathies improves symptoms and tendon biomechanics, motivating interest in non-invasive treatment options. Focused ultrasound (FUS) is a promising technology that precisely targets tissue regions, inducing desired bioeffects while minimally affecting surrounding tissues. To explore its potential for treating tendinopathies, we sequentially characterized FUS-induced tendon temperature elevations ex vivo, treated uninjured mouse Achilles tendons in vivo, and finally assessed the in vivo effects of FUS treatment of tendinopathic tissues. FUS (1.1 MHz transducer) consisted of thermal-dominant (0.5 MPa peak-peak pressure, continuous pulsing, 100% duty cycle) or mechanical-dominant (2 or 5 MPa, 10 Hz, 1% duty cycle) pulsing for four sessions over 1 week. No adverse events were observed, and mice did not exhibit pain or distress. Relative to untreated tendons, thermal FUS treatment of uninjured tendons did not alter mechanical properties while mechanical (5 MPa) FUS treatment significantly reduced maximum stress and elastic modulus. Tendons from both treatments exhibited mild matrix disorganization and increased cellularity, indicating an adaptive response. When applied to injured tendons, mechanical (5 MPa) FUS treatment reduced cross-sectional area and restored elastic modulus and yield stress to levels of naïve tendons. Although signs of injury persisted, the FUS-treated region exhibited fewer rounded cells and a reduction in sulfated glycosaminoglycan deposits, indicative of injury improvement. These pre-clinical studies demonstrate the safety, feasibility and preliminary efficacy of FUS for tendinopathy treatment. This foundational methodology facilitates further exploration of acoustic treatment parameters and strategies to augment tendon healing.
Intercalary reconstruction following diaphyseal tumor resection is advantageous in that they preserve the joint above and below. Recently, intramedullary devices such as intramedullary nails (IMN), photodynamic bone stabilizing system (PBSS), and intercalary endoprosthetic reconstruction (EPR) have become increasingly used. Understanding the tradeoffs associated with each construct as well as characterizing their mechanical stability is essential for making a patient-specific decision for reconstruction. The mechanical properties of four different constructs used in the reconstruction of segmental defects in a femur model were compared: Double plate (DP) allograft secured by 90-90 plating, allograft secured by IMN and plate fixation, allograft secured by PBSS and plate fixation, as well as an intercalary prosthesis (EPR). Samples were tested in axial, bending and torsional loading, and mechanical properties were compared. The EPR during anterior-posterior bending had 51.63% of the displacement compared to the DP (p = 0.0007), and 55% of the creep over 100 cycles (p = 0.0126) with a rigidity of 201.3% (p = 0.0067). This difference also exists for cyclic torsion where the EPR rotates 52.32% the amount of the DP (p = 0.0044) and has 4.44% of the creep (p < 0.0001). The PBSS and IMN constructs had comparable results across all tests (p > 0.05). Overall, the EPR has comparable or superior mechanical stability to the DP, while the PBSS and IMN have similar mechanical properties. Together, these results can be used as a guide for surgeons to choose different implants depending on individual patient needs.
Degenerative tendon tears are common, but mechanisms behind initiation and progression are not fully understood. There is a clear need to be able to track microstructural changes during progressive biological degradation to better understand degenerative tendon pathophysiology. The aim of this study was to evaluate the sensitivity of a snapshot Stokes polarimetry technique, quantitative polarized light imaging (QPLI), in monitoring the severity and progression of biologically mediated degeneration in tendon. Leveraging a collagenase mediated in vitro tendon digestion model, we assessed the effect of enzyme degradation on polarimetric outcomes from reflectance and transmission modes of QPLI, second harmonic generation (SHG) imaging, histology, and mechanical testing. Changes observed in reflectance mode QPLI (rQPLI) allowed for characterization of progression of degeneration at all digestion severities tested, whereas data acquired from transmission mode QPLI was only able to discern changes at the most severe digestion level. Outcomes from this study establish rQPLI as a powerful tool in the microstructural evaluation of musculoskeletal soft tissues, particularly in the context of monitoring progressive degradation. The findings from this study also highlight the potential multiscale nature of biological degeneration in tendon and emphasize the importance of better understanding these processes to inform regeneration and repair strategies.
This study aims to develop MRI-based 3D statistical shape models for patellar dislocation patients and investigate bone shape features that distinguish between single and recurrent dislocation populations, as well as control and patellar dislocation populations. MRIs from 16 single dislocation patients, 17 recurrent dislocation patients, and 20 control subjects were used to build statistical shape models for femur and patella bones. Bone shape features were extracted and tested for statistical significance (p < 0.05) for distinguishing the single dislocation group from the recurrent dislocation groups, and the control group from the dislocation group. Statistically significant shape features distinguishing the three groups were identified for both bones. A shallower trochlear groove and smaller patellar ridge told the dislocation groups apart from the control group. A prolonged lateral condyle in femur and a laterally shifted ridge and hood shaped lateral facet in patella distinguished the recurrent dislocation group from the single dislocation group. The study's findings from 3D statistical shape modeling of the femur and patella reveal distinct anatomical differences across control, single dislocation, and recurrent patellar dislocation groups. This advanced understanding aids in identifying individuals at higher risk for initial or recurring patellar dislocations, enabling clinicians to tailor treatment and management strategies more effectively to prevent further dislocations and mitigate potential patellofemoral joint damage.
Chondrocytes are mechanosensitive cells whose biosynthetic activity is governed by their local mechanical environment within articular cartilage. This environment is strongly influenced by the pericellular matrix (PCM), a specialized region enriched in collagen VI and a distinct non-fibrillar ground substance. However, the individual mechanical roles of these PCM constituents in regulating chondrocyte mechanotransduction remain poorly understood. In this study, an explicit, concurrent multiscale finite element model of articular cartilage was developed to directly link tissue-level loading to cellular-scale mechanics. The model incorporates anatomically realistic chondrocyte distributions, depth-dependent collagen II fibril architecture, and distinct representations of collagen VI fibrils and the non-fibrillar PCM matrix. Unconfined compression simulations were performed under reference conditions and following targeted alterations (±20%) in collagen VI stiffness, PCM matrix stiffness, or both. Results showed that tissue-level reaction forces were most sensitive to collagen VI stiffness. At the cellular scale, changes in collagen VI and PCM matrix properties significantly modulated chondrocyte circumferential forces and volumetric deformation, particularly in the superficial zone. Stress redistribution analyses revealed a load-sharing mechanism between fibrillar and non-fibrillar PCM components. These findings clarify the distinct mechanical roles of PCM constituents and provide mechanistic insight into how their degradation may disrupt chondrocyte mechanotransduction and contribute to cartilage degeneration.
Rotator cuff tears are among the most common shoulder disorders, and their incidence increases with age. Hyperglycemic conditions are known to enhance oxidative stress and inflammatory signaling in various tissues, potentially contributing to tendon degeneration. Angiotensin II receptor blockers (ARBs) are widely used antihypertensive agents known to possess antioxidant and anti-inflammatory properties. However, their effects on hyperglycemia-induced oxidative stress in tendon tissues remain unclear. This study investigated whether losartan, an ARB, suppresses high glucose-induced oxidative stress in human rotator cuff-derived cells. Tendon-derived cells obtained during arthroscopic rotator cuff repair were cultured and divided into four groups: control (C), control with losartan (CL; 100 μM), high glucose (H; 33 mM), and high glucose with losartan (HL). Cell viability was evaluated using the Cell Counting Kit-8. Expression of RAGE, NOX1, NOX4, IL-6, IL-1β, COL1, and COL3 was analyzed by quantitative real-time PCR. Reactive oxygen species (ROS) were detected by DCFH-DA staining, and apoptosis was assessed by TUNEL staining. High glucose exposure significantly reduced cell viability and increased ROS production and inflammatory gene expression. Losartan treatment under high-glucose conditions mitigated these changes, maintaining cell viability and suppressing the expression of RAGE, NOX1, IL-6, and IL-1β. These findings suggest that losartan modulates oxidative stress pathways under hyperglycemic conditions and may represent a potential therapeutic strategy.
Assessing knee joint pain in experimental osteoarthritis (OA) models remains a significant challenge. Our study demonstrates that the use of an adapted electronic von Frey (aVF) device, featuring a modified tip, surpasses the standard von Frey (sVF) in detecting knee joint pain behavior and evaluating the efficacy of analgesic treatments in an OA model induced by monoiodine acetate (MIA) in male rats. The sVF induced a behavior profile in naïve animals characterized by a hind paw flinching and withdrawal reflex. This behavioral response was affected by intraplantar lidocaine, which increased mechanical thresholds related to sVF and validated it as pain related behavior. In the aVF method, rats displayed no alterations in their mechanical thresholds in absence or presence of lidocaine, suggesting minimal stimulation of hind paw by the modified methodology. In MIA-OA rats, the aVF was able to detect a significant reduction on joint mechanical thresholds. The behavior linked to aVF was significantly affected by systemic delivery of morphine, confirming a nociceptive-like phenotype and suggesting a pain behavior predominantly triggered by joint flexion. The aVF was also able to detect an analgesic profile in MIA-OA rats treated with dexamethasone, LPS-RS, and fucoidan, indicating effectiveness in measuring differential responses triggered by analgesic drugs. Our results suggest aVF as a more appropriate method to evaluate joint pain in rats.
Collapse in osteonecrosis of the femoral head (ONFH) is thought to result from stress concentration at the sclerotic boundary zone, but its precise initiation site has not been identified. We aimed to identify the initiation of collapse using patient-specific finite element models (FEMs) that incorporate the sclerotic boundary zone. Ten hips from 10 patients with type C ONFH who had both pre-collapse (stage 2) and post-collapse (stage 3) computed tomography (CT) images were analyzed. Actual collapse sites were identified on post-collapse CT images or, when inconclusive, determined using micro-CT and subsequent histopathological examination of resected specimens. Patient-specific FEMs were constructed from pre-collapse CT scans with incorporation of the sclerotic boundary zone. For comparison, FEMs were also generated for four femoral heads without sclerotic changes on the articular surface. Equivalent stress on the articular surface and simulated initiation sites of collapse were evaluated and compared with actual collapse sites. In all 10 femoral heads, actual collapse occurred at the interface between the lateral sclerotic boundary and the adjacent necrotic lesion. FEMs demonstrated stress concentration at the sclerotic boundary, and simulated initiation sites corresponded to actual collapse sites. In contrast, femoral heads without sclerotic changes showed no stress concentration at the articular surface, and no simulated collapse was observed on the femoral head surface. In conclusion, collapse in ONFH initiates at the interface between the lateral sclerotic boundary and the adjacent necrotic lesion, highlighting the critical biomechanical role of the sclerotic boundary zone.
Extra-articular bony impingement may contribute to posture-specific groin pain after total hip arthroplasty (THA), but the relative roles of bony morphology and functional pelvic tilt remain unclear. CT reconstructions from 100 cadavers (200 hips) were used to build three-dimensional bone-on-bone collision detection models to quantify impingement-free range of motion (RoM). Femora were rotated in internal/external rotation and abduction/adduction from 30° hyperextension to 120° flexion in 5° flexion increments. Simulations were repeated with pelvic tilt ranging ±30° from neutral as extreme boundaries. The contribution of bony anatomy to early impingement was evaluated using Pearson correlations and two-stage regression, with nested cross-validation used for supplementary internal validation. Mean external rotation to extra-articular bony impingement in extension was 46.6° ± 14.8°, and mean internal rotation to impingement at 90° flexion was 34.4° ± 14.1°. In standing, 30° posterior pelvic tilt reduced external rotation clearance by 13.2° ± 10.2° (p < 0.001); while sitting, 30° anterior pelvic tilt reduced internal rotation clearance by 33.0° ± 12.1° (p < 0.001). Standing impingement was most frequently between the ischial tuberosity and posterior intertrochanteric crest or lesser trochanter, whereas seated impingement predominantly involved the anterior inferior iliac spine (AIIS) and intertrochanteric crest. Multivariable models showed strong in-sample fit and retained good held-out performance on nested cross-validation. High-risk morphologies combined with adverse pelvic tilt produced markedly earlier impingement, with the greatest reduction observed in the seated high-risk subgroup under extreme anterior tilt. These findings quantify posture-dependent extra-articular bony constraints and identify morphology-based phenotypes associated with reduced clearance, providing a biomechanical framework for future patient-specific and implant-based studies after THA.
The aim of this scoping review was to summarize and to synthesize the existing literature on the most performed functional tasks and their associated biomechanical outcomes following total hip arthroplasty (THA). Five databases, including Medline, Embase, CINAHL, Web of Science, and Ergonomics Abstracts were searched based on 3 main concepts: Total hip arthroplasty, functional tasks and biomechanical outcomes. Studies were screened based on titles and abstracts, followed by a full text reading conducted by two authors following inclusion and exclusion criteria. Eighty three studies with a total of 2047 THA and 170 hip resurfacing arthroplasty (HRA) patients were included. Postural balance was the most frequently evaluated functional task, followed by sit-to-stand and stair negotiation. Most participants were older than 60 years, and the surgical approach was infrequently reported. Patient-reported outcome measures were rarely reported alongside motion analysis, with the Harris hip score and the Oxford Hip Score being the most commonly used. Factors such as age, population characteristics, surgical approaches and follow-up durations may influence the biomechanical outcomes of hip replacement. Therefore, caution is warranted when generalizing these findings to all THA population. Further research on young THA and HRA patients in more demanding task such as squat and work-related tasks are required to better understand functional recovery and implant performance under higher mechanical loads.
Femoral shaft fractures cause prolonged disability, and therapies that accelerate bone repair remain limited. Repurposing clinically approved drugs that target biological bottlenecks in healing is a promising strategy. This study investigated whether systemic metformin administration, an anti-diabetic medication with known metabolic regulatory effects, enhances fracture repair in a rat open femoral shaft fracture model. Histological, immunofluorescent, micro-CT, and biomechanical analyses were performed at 6 weeks post-injury comparing metformin-treated and vehicle-treated animals. Metformin markedly accelerated callus maturation, evidenced by earlier hyaline cartilage ossification, increased collagen I deposition and fiber organization, and reduced collagen II and III expression compared with controls. Micro-CT analysis demonstrated increased tissue mineral density, trabecular thickness, and bone volume fraction along with reduced connectivity density, indicating more advanced structural consolidation of the callus. Although biomechanical parameters were not significantly different at intermediate time point, ultimate load and stiffness trended higher in metformin-treated animals, consistent with structural advancement. Mechanistically, metformin increased p-AMPK expression, elevated mitochondrial markers (NDUFB8, TFAM), and reduced extracellular HMGB1 release, suggesting enhanced metabolic capacity and attenuated inflammatory stress during repair. Importantly, metformin's effects were most pronounced during the cartilage-to-bone transition phase, supporting a role for metabolic activation in promoting endochondral ossification. Together, these findings demonstrate that systemic metformin administration promotes earlier structural consolidation of the fracture callus through coordinated metabolic and inflammatory modulation, supporting the potential repurposing of this safe and inexpensive drug as an adjunct strategy to enhance bone repair.
Neglected Achilles tendon rupture is associated with persistent weakness and altered gait; however, the detailed intersegmental foot and ankle biomechanics have not been fully characterized. This study quantitatively evaluated temporospatial, kinematic, and kinetic gait alterations in patients with neglected Achilles tendon rupture using a multi-segment foot model. Thirteen patients were compared with 26 healthy participants selected by propensity score matching based on age, sex, and body mass index. Intersegmental foot and ankle kinematics were calculated using the DuPont foot model, and ankle kinetics, including plantarflexion moment and ankle power, were evaluated along with temporospatial parameters. Patients with neglected Achilles tendon rupture walked more slowly with shorter strides, a wider step width, and a larger stance phase proportion than matched controls. During the terminal stance phase, the hallux dorsiflexion and hindfoot plantarflexion were reduced. Hallux sagittal range of motion decreased, whereas hindfoot sagittal range of motion did not differ significantly. In the coronal plane, the forefoot and hindfoot range of motion were reduced, with a more everted forefoot and a more inverted hindfoot position. The neglected Achilles tendon rupture group demonstrated significantly lower ankle power during the terminal stance phase and reduced ankle plantarflexion moment during the late stance phase compared with the control group. Collectively, these gait-based findings demonstrate measurable functional deficits in patients with neglected Achilles tendon rupture and highlight the clinical importance of recognizing and appropriately treating this condition.
Distraction osteogenesis (DO) for limb lengthening often requires prolonged fixation while the regenerate consolidates. Adjuncts that improve the regenerate quality could reduce morbidity and treatment time. Hyperelastic Bone™ (HEB) is a 3D-printed hydroxyapatite (HA)/polylactic-co-glycolic acid (PLGA) scaffold, but its efficacy as an osteotomy-site adjunct during DO is unclear. After IACUC approval, rabbits underwent left tibial lengthening with a mini-rail external fixator distracted at 0.75 mm/day to 20% tibial length and received no scaffold (control), traditional Hyperelastic Bone™ (10% PLGA/90% HA), or a biphasic formulation (10% PLGA/70% HA/20% β-tricalcium phosphate [β-TCP]) placed subperiosteally at the osteotomy site. The contralateral tibiae served as references. After 8 weeks of consolidation, radiographs, micro-CT (prespecified endpoint: regenerate BMD), and torsional testing (prespecified endpoint: stiffness) were performed. Fourteen rabbits underwent attempted lengthening. Intraoperative fractures (n = 2) and fixation loss (n = 3) reduced complete terminal datasets to nine, all of which completed micro-CT and torsion testing. Radiographs confirmed regenerate formation. Regenerate BMD remained below contralateral values with controls being intermediate to the traditional and biphasic HEB formulations (60.5%, 63.8%, and 54.7% of contralateral, respectively). Despite no mineral density improvement, scaffold-treated regenerate demonstrated higher torsional stiffness and strength metrics, greatest with the biphasic formulation, with lower failure displacement and higher polar moment of inertia. Statement of Clinical Significance: A scaffold that improves functional regenerate performance could enable earlier safer weight bearing and device removal and reduce nonunion/refracture risk in DO.
This study investigated how preoperative bone quality, patient and implant factors can predict the primary stability of a stemless humeral component in total shoulder arthroplasty (TSA). Thirty‑one cadaveric humeri were CT‑scanned with a calibration phantom, and trabecular bone density within the metaphysis was quantified. Specimens were implanted and subjected to cyclic loading at 500 N and 870 N along physiologically representative directions and implant‑to‑bone micromotion was measured using motion capture. Generalized linear models were developed to predict implant micromotion based on patient and implant size factors, including age, height, weight, gender, ethnicity, cancer history, chemotherapy status, apparent peri-implant density, anchor size, head size, resection angle, and load level. Micromotion was significantly larger at 870 N than at 500 N, and males exhibited significantly lower micromotion than females, consistent with the associated higher bone density and larger implant sizes. Peri‑implant density was the strongest individual predictor explaining 34% of micromotion variation. Model predictions went up 49% of micromotion variation if load level was accounted for. Adding anchor and head sizes markedly improved this predictive power to 71%, which outperformed models incorporating patient height and gender (67%). Moderate improvement (73%) was seen when density, load level, height, gender, and anchor size were included after automatic backward selection. These findings demonstrate that bone density only partially predicts primary stability of anatomic stemless shoulder arthroplasty, and that incorporating implant sizing substantially improves predictive accuracy. This preoperative information can provide a more objective and consistent identification of patients with adequate bone quality for stemless fixation.
