The Effect of Femoral Cutting Guide Design Improvements for Patient-Specific Instruments

Enhancing Surgical Efficiency and Radiological Outcomes Through Advances in Patient-Specific Instrument Design

Background/Objectives: Patient-specific instrumentation (PSI) in total knee arthroplasty (TKA) uses preoperative three-dimensional imaging to create cutting blocks tailored to patient anatomy. However, there is debate regarding the additional benefits of PSI in terms of improved alignment or functional outcomes compared to using conventional instruments. Although PSI design has undergone continuous development, the improvements have not been incorporated. Therefore, the aim of this study was to compare the surgical time and radiological outcomes between advanced-design PSI and conventional instruments. Methods: We conducted a retrospective review of 328 patients who underwent primary TKAs using PSI for osteoarthritis and compared them with 328 matched patients who underwent TKA performed with conventional instruments during the same period (March 2023 to August 2024). We compared the surgical time and component alignment between the advanced-design PSI group and the conventional instrument group. Results: The average surgical time was significantly shorter in the advanced-design PSI group (47.6 ± 12.4 min) compared to the conventional instrument group (59.2 ± 14.2 min, p < 0.05). The advanced PSI design group had a significantly lower occurrence of outliers in hip-knee-ankle alignment (7%) compared to the conventional instrument group (36.3%). This trend was also observed in femoral coronal alignment, tibial coronal alignment, and femoral sagittal alignment. Conclusions: The use of advanced-design PSI demonstrated significantly reduced surgical time and improved alignment compared to conventional instruments. This highlights that proper design is a key factor for PSI to achieve superior biomechanical effects. Our study shows that advanced-design PSI technology has the potential to replace conventional instruments in TKA, though further research is required to determine its clinical outcomes and economic benefits.

Whole-genome sequencing unravels novel genetic determinants and regulatory pathways associated with triamcinolone acetonide-induced ocular hypertension

Glucocorticosteroids commonly used to treat certain ocular inflammatory conditions cause an unwarranted elevation in intraocular pressure (IOP) leading to steroid-induced ocular hypertension (OHT). This study aims to identify novel genetic variants in the Indian population associated with steroid responsiveness, specifically to that of intravitreal Triamcinolone acetonide (TA) injections, which leads to OHT in 27% of the TA-treated Indian subjects. Genetic determinants and pathways regulating TA-OHT progression were investigated by applying whole-genome sequencing (WGS) on DNA extracted from 53 blood samples that included TA responders and non-responders. Sequencing analysis yielded 45 intronic and 49 exonic variants to be associated with TA-OHT, which are known to play a vital role in eye, heart, brain, and bone deformities. Of these, the most significant genetic variant associated with TA-OHT was further considered for molecular dynamics (MD) simulation studies. Variants in the CRPPA, PLOD1, ARHGAP1, TIMELESS and TNFSF4 genes were found to be directly implicating TA-OHT. Furthermore, these genes were enriched in pathways associated with cardiomyopathy, focal adhesion, extracellular matrix, and actin cytoskeleton reorganization. MD simulation studies revealed that the top significant variant (rs141625803) in the CRPPA gene possesses a high pathogenic and structurally destabilizing effect. Thus, novel genetic variants that could be significantly associated with the TA-OHT progression were identified in this study. Validation of these targets in a larger cohort of patients along with their functional analysis would inform on the disease, thereby adding to the existing knowledge on the pathophysiology of TA-OHT.

Evidence of the moderating role of hair cortisol and hair cortisone in the relationship between work stress and depression symptoms among Chinese fishermen

BACKGROUND

Stress plays an important role in the pathogenesis of depression through functional changes to the hypothalamic-pituitary-adrenal (HPA) axis, a key output of which is the stress hormone cortisol. But the precise relationship between HPA axis activity and depression remains unclear, in part because mostly cortisol measurement only provides reflect acute or short-term fluctuations. In this study, hair cortisol and its metabolite cortisone were measured in a prospective, pre and post follow-up study of working stress and depressive symptoms in Chinese fishermen. We evaluated HPA activity, work stress, and depression symptoms before and after fishing to determine whether cortisol and cortisone in hair can moderate the work stress and depression symptoms of Chinese fishermen.

METHODS

Hair cortisol, hair cortisone, work stress, and depression were measured in Chinese fishermen (n=229; age 16-65) before and after 1-3 months at sea. A week after the fishermen returned, they provided 2-4 cm hair segments closest to the scalp. We measured hair cortisol and hair cortisone using high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

The work stress and hair cortisol of fishermen before fishing were significantly higher than those after fishing, while hair cortisone was lower. There was no significant difference in depressive symptoms. Fishermen with low hair cortisol or high hair cortisone were more likely to show depressive symptoms after experiencing stress, and were less likely to show depressive symptoms when faced with lower levels of work stress, consistent with the differential susceptibility model.

LIMITATIONS

The assumption of an average hair growth of 1 cm/month may cause time overlap between pre- and post-fishing, and time error between the hormone data and questionnaire collection. The present study evaluated only two observation points. The use of self-report scales may affect interpretability of the results. Finally, the study used a limited sample of marine fishermen working out of a single location in Hainan province, China.

CONCLUSIONS

Hair cortisol and hair cortisone appear to have a moderating role in the relationship between work stress and depressive symptoms among fishermen, which fits with the differential susceptibility model of depression. However, their mechanisms of moderation are not the same, which may reflect the complexity of physiological indicators.

3D-printed saw guides for lower arm osteotomy, a comparison between a synthetic CT and CT-based workflow

BACKGROUND

Three-dimensional (3D)-printed saw guides are frequently used to optimize osteotomy results and are usually designed based on computed tomography (CT), despite the radiation burden, as radiation-less alternatives like magnetic resonance imaging (MRI) have inferior bone visualization capabilities. This study investigated the usability of MR-based synthetic-CT (sCT), a novel radiation-less bone visualization technique for 3D planning and design of patient-specific saw guides.

METHODS

Eight human cadaveric lower arms (mean age: 78y) received MRI and CT scans as well as high-resolution micro-CT. From the MRI scans, sCT were generated using a conditional generative adversarial network. Digital 3D bone surface models based on the sCT and general CT were compared to the surface model from the micro-CT that was used as ground truth for image resolution. From both the sCT and CT digital bone models saw guides were designed and 3D-printed in nylon for one proximal and one distal bone position for each radius and ulna. Six blinded observers placed these saw guides as accurately as possible on dissected bones. The position of each guide was assessed by optical 3D-scanning of each bone with positioned saw guide and compared to the preplanning. Eight placement errors were evaluated: three translational errors (along each axis), three rotational errors (around each axis), a total translation (∆T) and a total rotation error (∆R).

RESULTS

Surface models derived from micro-CT were on average smaller than sCT and CT-based models with average differences of 0.27 ± 0.30 mm for sCT and 0.24 ± 0.12 mm for CT. No statistically significant positioning differences on the bones were found between sCT- and CT-based saw guides for any axis specific translational or rotational errors nor between the ∆T (p = .284) and ∆R (p = .216). On Bland-Altman plots, the ∆T and ∆R limits of agreement (LoA) were within the inter-observer variability LoA.

CONCLUSIONS

This research showed a similar error for sCT and CT digital surface models when comparing to ground truth micro-CT models. Additionally, the saw guide study showed equivalent CT- and sCT-based saw guide placement errors. Therefore, MRI-based synthetic CT is a promising radiation-less alternative to CT for the creation of patient-specific osteotomy surgical saw guides.

Regional Lymph Node Metastasis of Scalp Angiosarcoma: A Detailed Clinical Observation Study of 40 Cases

BACKGROUND

The incidence of lymph node metastasis (LNM) of angiosarcomas is reported to be less than 15%, and elective neck management has not been indicated. This study evaluated the incidence and pattern of regional LNM in patients with scalp angiosarcomas using the clinical data of its full course to understand time-event sequences of scalp angiosarcomas.

METHODS

This retrospective study included all consecutive cases of pathology-confirmed angiosarcomas and analyzed 40 cases of scalp angiosarcomas. The survival plots were estimated using the Kaplan-Meier method, and the results are presented mainly in a descriptive manner.

RESULTS

The overall survival rate for the patients was 35.8% at 2 years. In contrast to previous reports, regional LNM was observed in more than half of the patients (52.5%) with scalp angiosarcoma. Meanwhile, a direct spread to distant organs occurred in only 27.5% of the patients. Regional LNM could predict clinical manifestation of systemic disease within 3 to 6 months. No differences in survival rates between patients with and without LNM were observed in this series. Occurrence of LNM seemed to be correlated with a high mitotic rate of primary tumors, but not with tumor grade or tumor dimension. The first-echelon lymph nodes from scalp angiosarcoma were peri-parotid, post-auricular, and level 2 lymph nodes.

CONCLUSIONS

For a localized scalp angiosarcoma, it seems reasonable for initial curative surgery to include prophylactic evaluation of regional lymph nodes for pathologic nodal staging, prognosis estimation, and the decision for systemic treatments.

Exploring Associations Between a Biological Marker of Chronic Stress and Reported Depression and Anxiety in People With Aphasia

Purpose Living with the communication impairment of aphasia can be stressful. Chronic stress, depression, and anxiety are intimately linked, may be more pervasive in people with poststroke aphasia than the general population, and may influence cognitive function and treatment outcomes. In this project, we explored the psychological constructs of depression and anxiety and their associations with a biomarker measure of chronic stress in people with aphasia. Method Fifty-seven participants with aphasia completed measures of depression and anxiety and provided a hair sample from which to extract the stress hormone cortisol. Pearson product-moment correlational analyses were used to identify associations between depression, anxiety, and long-term level of cortisol via hair sample. Results While cortisol level was not associated with depression and anxiety across this sample of people with aphasia, a post hoc analysis showed a significant, positive correlation between a subset of participants with moderate and higher levels of depression and elevated cortisol level. Conclusions Chronic stress, depression, and anxiety have been little explored in people with aphasia to date, yet they are associated with future health consequences and impaired cognitive function, motivating further research as well as consideration of these factors in aphasia rehabilitation.

Diurnal Cortisol Dynamics, Perceived Stress, and Language Production in Aphasia

Purpose The current study investigated diurnal cortisol dynamics in adults with and without aphasia, along with subjective reports of stress and measures of language production. Dysregulation of cortisol, a common biomarker of stress, is associated with cognitive dysfunction in different clinical populations. However, little is known about the consequences of stress-induced cortisol disturbances for stroke survivors, including those with aphasia. Method Nineteen participants with aphasia and 14 age-matched neurotypical adults were tested. Saliva samples were collected from participants to assess the cortisol awakening response, a marker of the integrity of the hypothalamic-pituitary-adrenal (HPA) axis. Participants also completed 2 subjective stress questionnaires. Language was evaluated using 3 short, picture description narratives, analyzed for discourse (dys)fluency and productivity markers. Results In contrast to neurotypical participants, adults with aphasia did not show the predictable cortisol awakening response. Participants with aphasia also showed an unusual heightened level of cortisol upon awakening. Additionally, neurotypical participants demonstrated an association between intact language performance and the cortisol awakening response, whereas the participants with aphasia did not, although they did perceive the language tasks as stressful. Conclusion This study indicates that the functionality of the HPA axis, as indexed by cortisol, contributes to optimal language performance in healthy adults. The absence of an awakening response among participants with aphasia suggests that stroke leads to dysregulation of the HPA axis, although the degree to which this impairment affects language deficits in this population requires further investigation.

Effect of Post-Cam Design for Normal Knee Joint Kinematic, Ligament, and Quadriceps Force in Patient-Specific Posterior-Stabilized Total Knee Arthroplasty by Using Finite Element Analysis

The purpose of this study is to investigate post-cam design via finite element analysis to evaluate the most normal-like knee mechanics. We developed five different three-dimensional computational models of customized posterior-stabilized (PS) total knee arthroplasty (TKA) involving identical surfaces with the exception of the post-cam geometry. They include flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs. We compared the kinematics, collateral ligament force, and quadriceps force in the customized PS-TKA with five different post-cam designs and conventional PS-TKA to those of a normal knee under deep-knee-bend conditions. The results indicated that femoral rollback in curve-and-curve (concave) post-cam design exhibited the most normal-like knee kinematics, although the internal rotation was the closest to that of a normal knee in the helical post-cam design. The curve-and-curve (concave) post-cam design showed a femoral rollback of 4.4 mm less than the normal knee, and the helical post-cam design showed an internal rotation of 5.6° less than the normal knee. Lateral collateral ligament and quadriceps forces in curve-and-curve (concave) post-cam design, and medial collateral ligament forces in helical post-cam design were the closest to that of a normal knee. The curve-and-curve (concave) post-cam design showed 20% greater lateral collateral ligament force than normal knee, and helical post-cam design showed medial collateral ligament force 14% greater than normal knee. The results revealed the variation in each design that provided the most normal-like biomechanical effect. The present biomechanical data are expected to provide useful information to improve post-cam design to restore normal-like knee mechanics in customized PS-TKA.

Human-like Cmah inactivation in mice increases running endurance and decreases muscle fatigability: implications for human evolution

Compared to other primates, humans are exceptional long-distance runners, a feature that emerged in genus Homo approximately 2 Ma and is classically attributed to anatomical and physiological adaptations such as an enlarged gluteus maximus and improved heat dissipation. However, no underlying genetic changes have currently been defined. Two to three million years ago, an exon deletion in the CMP-Neu5Ac hydroxylase (CMAH) gene also became fixed in our ancestral lineage. Cmah loss in mice exacerbates disease severity in multiple mouse models for muscular dystrophy, a finding only partially attributed to differences in immune reactivity. We evaluated the exercise capacity of Cmah^-/- mice and observed an increased performance during forced treadmill testing and after 15 days of voluntary wheel running. Cmah^-/- hindlimb muscle exhibited more capillaries and a greater fatigue resistance in situ Maximal coupled respiration was also higher in Cmah null mice ex vivo and relevant differences in metabolic pathways were also noted. Taken together, these data suggest that CMAH loss contributes to an improved skeletal muscle capacity for oxygen use. If translatable to humans, CMAH loss could have provided a selective advantage for ancestral Homo during the transition from forest dwelling to increased resource exploration and hunter/gatherer behaviour in the open savannah.

The Effect of Patient-Specific Instrumentation Incorporating an Extramedullary Tibial Guide on Operative Efficiency for Total Knee Arthroplasty

This retrospective study was to determine if patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) leads to shortened surgical time through increased operating room efficiency according to different tibial PSI designs. 166 patients underwent primary TKA and were categorized into three groups as follows: PSI without extramedullary (EM) tibial guide (group 1, n = 48), PSI with EM tibial guide (group 2, n = 68), and conventional instrumentation (CI) group (group 3, n = 50). Four factors were compared between groups, namely, operative room time, thickness of bone resection, tibial slope, and rotation of the component. The mean surgical time was significantly shorter in the PSI with EM tibial guide group (group 2, 63.9 ± 13.6 min) compared to the CI group (group 3, 82.8 ± 24.9 min) (P < 0.001). However, there was no significant difference in the PSI without EM tibial guide group (group 1, 75.3 ± 18.8 min). This study suggests that PSI incorporating an EM tibial guide may lead to high operative efficiency in TKA compared to CI. This trial is registered with KCT0002384.

CT- versus MRI-based patient-specific instrumentation for total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

To determine whether computed tomography (CT) or magnetic resonance imaging (MRI) is more suitable for the patient-specific instrumentation (PSI) systems for total knee arthroplasty (TKA).

METHODS

PubMed, Embase, and the Cochrane Library were searched from inception to June 2016 for prospective comparative trials that compared CT- versus MRI-based PSI systems for TKA. Our predefined primary outcome was the outliers incidence of coronal overall limb alignment.

RESULTS

Six studies with a total of 336 knees meeting the eligibility criteria, and four trials were included in the meta-analysis. Compared with MRI-based PSI systems, CT-based PSI systems were associated with a higher outliers incidence of coronal overall limb alignment (risk ratio: 1.67; 95% confidence interval (CI): 1.03-2.72; P = 0.04), more angular errors of coronal overall limb alignment (mean difference (MD): 1.01°; 95% CI: 0.47-1.56; P = 0.0003), and longer operation time (MD: 5.02 min; 95% CI: 1.26-8.79; P = 0.009). While no significant differences in the coronal/sagittal alignment of the femoral/tibial component outliers, the angular errors of coronal overall limb alignment, the angular errors of the femoral/tibial component in coronal plane, or incidence of change of implant size of the femoral/tibial component were observed.

CONCLUSIONS

The current limited evidence suggests that MRI-based PSI systems exhibit higher accuracy for TKA regarding the coronal limb axis than CT-based PSI systems. However, well-designed studies comparing CT-versus MRI-based PSI systems for TKA are warrant to confirm these results before widespread use of this technique can be recommended.