Wiley: Journal of Orthopaedic Research: Table of Contents

Fractures Around Collared and Collarless Hip Stems Initiate in High Strain Regions: A Combined Cadaveric Experiment and Finite Element Analysis

Mon, 17 Aug 2026 23:42:16 -0700

ABSTRACT

Periprosthetic femoral fracture (PFF) is a common early complication after primary total hip arthroplasty. Collared stems reduce but do not eliminate the incidence of PFF, and exhibit variable biomechanical effectiveness, emphasizing our limited understanding of the local bone–implant interaction mechanics. Our goal was to elucidate the relationship between the local strains at the bone–implant interface and the experimental fracture patterns and loads for collared and collarless stems.

Six pairs of women cadaveric femurs implanted with a collarless or collared stem were loaded to failure under simulated stumbling to determine the location of PFF and the load to fracture, which we related to the collar-calcar separation. Corresponding specimen-specific FE models were developed to determine the strain at the bone-implant interface and to predict the fracture onset load and location of fracture, which we related to the experimental location of PFF and the load-to-fracture.

Load to fracture was greater for collared stems and was inversely correlated with the collar-calcar separation at the time of implantation (r = −0.80, p = 0.055). Fractures occurred in areas of high strain. The experimental fracture location coincided with the first yielding cortical element in five cases. The load at which the first cortical element yielded (i.e., onset of fracture was moderately correlated with the experimental fracture load (R ² = 0.43, RMSE = 1231 N).

Our results emphasize the importance of initial calcar contact to realize the benefits of the collar. Localized load transfer was a precursor of macroscopic fracture, which initiated in areas of high tensile strain.

In Vitro Wear Simulation of a Kinematically Aligned Knee Implant Tilted at an Angle of 8°

Mon, 17 Aug 2026 23:34:09 -0700

ABSTRACT

Despite promising results of kinematic alignment (KA), there are still concerns regarding the wear behavior of KA knee implants. In a previous study, mechanically aligned (MA), KA and malaligned (MalA) knee implants were tested in a wear simulation study using Attune knee implant systems. The results showed no increased wear rate for a mild KA (KA4°) and MalA (MalA4°) condition in comparison to MA (MA0°) knee implants. This study analyzes the wear behavior of a KA condition of 8° (KA8°). The test setup was adapted accordingly. In addition, all tests of the previous study (MA0°, MalA4° and KA4°) and the KA8° condition were replicated using PFC implant systems to indicate if the previous results can be transferred to the predecessor model of the Attune knee implant system. The KA8° using the Attune knee implant system did not lead to a higher wear rate (2.4 ± 0.1 mg/10⁶ cycles) in comparison to the wear results of the previous study (3.8 ± 0.5 mg/10⁶ cycles for MA0°; 2.7 ± 0.2 mg/10⁶ cycles for MalA4° and 4.1 ± 0.2 mg/10⁶ cycles for KA4°). The PFC implant system led to higher wear rates than the Attune implant system but showed the same trend for the different alignment methods (5.1 ± 0.4 mg/10⁶ cycles for MA0°; 3.9 ± 0.1 mg/10⁶ cycles for MalA4°, 5.1 ± 0.8 mg/10⁶ cycles for KA4° and 3.5 ± 1.0 mg/10⁶ cycles for KA8°). KA8° did not show wear related problems but further in vitro and in vivo studies are necessary.

Decellularized Extracellular Matrix Mitigates the Senescent Phenotype and Restores Osteogenic Potential in Human Mesenchymal Stromal Cells

Thu, 13 Aug 2026 00:00:00 -0700

ABSTRACT

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.

Glenohumeral Stability During External Rotation in Patients Treated With the Latarjet Procedure: A Two‐Year Dynamic Radiostereometric Study

Sun, 09 Aug 2026 00:00:00 -0700

ABSTRACT

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.

Muscular Pronation in First Metatarsal After Hallux Valgus Osteotomies: A Biomechanical Simulation Study

Sandro Pradetto, Flurina Eck, Stephan Wirth, Arnd Viehöfer — Wed, 05 Aug 2026 00:00:00 -0700

Pronation of the first metatarsal is a relevant factor in hallux valgus recurrence. Muscular torque might affect the derotational effect of transverse osteotomies. Using CT-based three-dimensional foot models, muscular torque acting on the first metatarsal was simulated after transverse osteotomies with varying transverse cutting angles. Transverse correction osteotomy increased net supinating muscular torque compared to the non-osteotomized condition, independent of osteotomy angle. Lateral translation of the first metatarsal modulates muscle-induced pronation and may contribute to derotation after non-rotational osteotomies.

ABSTRACT

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.

Application of Focused Ultrasound for the Treatment of Tendinopathy: An In Vivo Feasibility, Safety, and Efficacy Study

Mon, 03 Aug 2026 00:32:32 -0700

ABSTRACT

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 Allograft Reconstruction of the Femur: A Cadaveric Comparison of Intramedullary and Plate Fixation Techniques

Sun, 02 Aug 2026 00:00:00 -0700

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).

ABSTRACT

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.

Issue Information

Thu, 23 Jul 2026 23:06:40 -0700

Journal of Orthopaedic Research, Volume 44, Issue 8, August 2026.

Monitoring Progressive, Biologically Mediated Tendon Degeneration Using Quantitative Polarized Light Imaging

Leanne E. Iannucci, Spencer P. Lake — Thu, 23 Jul 2026 00:00:00 -0700

ABSTRACT

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.