Investigation of adaptive muscle synergy modulated motor responses to grasping perturbations.

This study investigated how muscle synergies adapt in response to unexpected changes in object weight during lifting tasks. The aim was to discover which motor control strategies individuals use to maintain their grasping performance. Muscle synergies were extracted from the muscle activity of fifteen healthy participants who lifted objects of identical appearance but varying weights in a randomized order, which introduced artificial perturbations. Reaching and manipulation phases of object lifting were analyzed using constrained non-negative matrix factorization and k-means clustering. Participants exhibited a perturbation-independent and thus consistent recruitment of spatial synergy components, while significant adaptations in muscle synergy activation occurred in response to unexpected perturbations. Perturbations caused by unexpectedly heavy objects led to delayed and gradual increases in muscle synergy activation until the force required to lift the object was reached. In contrast, perturbations caused by lighter objects led to reductions in excess muscle synergy activation occurring later. Sensorimotor control maintains the modularity of muscle synergies. Even when external mechanical perturbations occur, the grasping performance is preserved, and control is adapted solely through muscle synergy activation. These results suggest that using pure spatial synergy components as control signals for myoelectric arm prostheses may prevent them from malfunctioning due to external perturbations.

Treatment of osteoarthritis by implantation of Mg- and WE43-cylinders - A preclinical study on bone and cartilage changes and their influence on pain sensation in rabbits.

With its main features of cartilage degeneration, subchondral bone sclerosis and osteophyte formation, osteoarthritis represents a multifactorial disease with no effective treatment options. As biomechanical shift in the trabecular network may be a driver for further cartilage degeneration, bone enhancement could possibly delay OA progression. Magnesium is known to be osteoconductive and already showed positive effects in OA models. We aimed to use magnesium cylinders to enhance subchondral bone quality, condition of cartilage and pain sensation compared to sole drilling in vivo. After eight weeks of implantation in rabbits, significant increase in subchondral bone volume and trabecular thickness with constant bone mineral density was found indicating favored biomechanics. As representative for pain, a higher number of CD271+ vessels were present in control samples without magnesium. However, this result could not be confirmed by sensitive, objective lameness evaluation using a pressure sensing mat and no positive effect could be shown on either cartilage degeneration evaluated by OARSI score nor the presence of regenerative cells in CD271-stained samples. The presented results show a relevant impact of implanted magnesium on key structures in OA pain with missing clinical relevance regarding pain. Further studies with shifted focus should examine additional structures as joint capsule or osteophytes.

The Impact of Epidural Analgesia on Immobility and extended Hospital Stay After Periacetabular Osteotomy.

AIMS: Early mobilisation after periacetabular osteotomy (PAO) represents an important goal after surgery. The purpose of this study was to determine whether the use of epidural aznalgesia (EA) is associated with prolonged immobility and an increased length of stay (LOS) after PAO surgery. METHODS: From January 2022 to July 2023, the study included a cohort of 150 PAO procedures all performed by the same surgeon (SSA). Patients were categorized into two distinct groups: those who received epidural analgesia (EA) (79 PAOs) and those who did not receive EA (71 PAOs). "Ready for discharge" was defined as the ability to ascend and descend a standardized flight of stairs independently. Multivariable linear regression was used to identify additional factors influencing LOS after PAO. RESULTS: Patients in the EA group were ready for discharge 5.95 ± 2.09 days after surgery which was significantly longer than in the No EA group´s average of 4.18 days ± 2.5, (p < 0.001). While the reduction in the number of patients experiencing pulmonary embolism in the No EA group did not reach statistical significance, it still demonstrated a relevant decrease from two patients within the EA group (2.53%) to 0 (0%) in the No EA group. The active engagement of the surgeon in mobilising patients led to a substantial reduction in LOS, decreasing it from 5.81 ± 2.18 days to 2.2 ± 0.77 days (p < 0.001). Multivariable analysis revealed five independent factors influencing the LOS following PAO which included absence of EA, surgeon-led mobilisation within 24 h after surgery, postoperative hemoglobin levels, BMI, and prior experience with PAO surgery on the contralateral side. CONCLUSIONS: Opting against the use of EA in patients undergoing PAO is advisable, as it will result in extended postoperative immobility and the associated risks. Additionally, the active participation of the surgeon in the mobilisation process is strongly recommended.

Unveiling the learning curve of periacetabular osteotomy.

Aims: Periacetabular osteotomy (PAO) is widely recognized as a demanding surgical procedure for acetabular reorientation. Reports about the learning curve have primarily focused on complication rates during the initial learning phase. Therefore, our aim was to assess the PAO learning curve from an analytical perspective by determining the number of PAOs required for the duration of surgery to plateau and the accuracy to improve. Methods: The study included 118 consecutive PAOs in 106 patients. Of these, 28 were male (23.7%) and 90 were female (76.3%). The primary endpoint was surgical time. Secondary outcome measures included radiological parameters. Cumulative summation analysis was used to determine changes in surgical duration. A multivariate linear regression model was used to identify independent factors influencing surgical time. Results: The learning curve in this series was 26 PAOs in a period of six months. After 26 PAO procedures, a significant drop in surgical time was observed and a plateau was also achieved. The mean duration of surgery during the learning curve was 103.8 minutes (SD 33.2), and 69.7 minutes (SD 18.6) thereafter (p < 0.001). Radiological correction of acetabular retroversion showed a significant improvement after having performed a total of 93 PAOs, including anteverting PAOs on 35 hips with a retroverted acetabular morphology (p = 0.005). Several factors were identified as independent variables influencing duration of surgery, including patient weight (ß = 0.5 (95% confidence interval (CI) 0.2 to 0.7); p < 0.001), learning curve procedure phase of 26 procedures (ß = 34.0 (95% CI 24.3 to 43.8); p < 0.001), and the degree of lateral correction expressed as the change in the lateral centre-edge angle (ß = 0.7 (95% CI 0.001 to 1.3); p = 0.048). Conclusion: The learning curve for PAO surgery requires extensive surgical training at a high-volume centre, with a minimum of 50 PAOs per surgeon per year. This study defined a cut-off value of 26 PAO procedures, after which a significant drop in surgical duration occurred. Furthermore, it was observed that a retroverted morphology of the acetabulum required a greater number of procedures to acquire proficiency in consistently eliminating the crossover sign. These findings are relevant for fellows and fellowship programme directors in establishing the extent of training required to impart competence in PAO.

Higher satisfaction and function scores in restricted kinematic alignment versus mechanical alignment with medial pivot design total knee arthroplasty: A prospective randomised controlled trial.

PURPOSE: Restricted kinematic alignment (rKA) in total knee arthroplasty (TKA) and medial pivot (MP) knee designs already showed superior outcomes in independent comparative studies. The objective of this study was to assess whether rKA with MP TKA provides better clinical and functional outcomes compared to mechanical alignment (MA) with MP TKA. METHODS: This is a randomised, parallel two group study involving a total of 98 patients with end-stage knee osteoarthritis. Patients were randomly allocated to either rKA or MA TKA procedures conducted with a MP prothesis using patient-specific instruments between 2017 and 2020. Final follow-up was at 2 years postoperatively. Demographic data and clinical and functional scores (Oxford knee score, knee society score [KSS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], forgotten joint score [FJS]) were collected and compared preoperative, 1 year postoperative and 2 years postoperative. Coronal plane alignment of the knee and functional knee phenotype classification were recorded. RESULTS: A total of 47 patients (rKA) and 51 patients (MA) were included in final analysis. Superior joint awareness scores (FJS) were found at 1 year postoperative for rKA (62.2 vs. 52.4, p = 0.04). KSS subscores (expectation score, satisfaction score) improved with rKA with significant differences at both 1 and 2 years postoperatively. Major differences between rKA and MA were found in subgroup analysis of varus and neutral CPAK phenotypes. Both 1 year and 2 years postoperatively, FJS was significantly better in KA compared with MA in varus CPAK phenotypes (63.1 vs. 44.9, p = 0.03; 71.1 vs. 46.0, p = 0.005). Further clinical and functional scores showed improvement in the varus CPAK phenotypes with predominantly significant improvement in the expectation and satisfaction KSS subscores. No significant differences were found in the comparison of rKA and MA in neutral CPAK phenotypes. CONCLUSION: The rKA of MP TKA design shows superior patient satisfaction and self-reported function when compared to MA MP TKA. Furthermore, rKA MP TKA shows superior joint awareness at early postoperative stage. The most important clinical relevance of this study is the clear superiority of rKA in varus phenotypes. LEVEL OF EVIDENCE: Level II.

Very early migration of a calcar-guided short stem: a randomized study of early mobilization and the influence of a calcium phosphate coating with 60 patients.

This study analyzed the migration of a calcar-guided short stem to determine the course of very early migration, as well as evaluated the effect of an additional calcium phosphate (CP) coating on a titanium plasma spray (TPS) coating, which has not been analyzed previously. Sixty patients were enrolled in this study and were treated with the A2 calcar-guided short stem. The implant coating was randomized with either the TPS or an additional CP coating, and radiostereometric analysis was performed with the baseline measurement before initial weight-bearing, along with follow-up examinations at 1 week, 6 weeks, 3 months, and 6 months. Implant migrations were 0.27 mm (standard deviation [SD], 0.13 mm) and 0.74 mm (SD, 1.11 mm) at 1 week and 6 months post-surgery, respectively, and 65% and 87% of the implants reached their final position 1 week and 6 weeks after surgery, respectively. After 6 weeks, 3 months, and 6 months, a significant increase was noted in the migration of the CP coating group vs. that of the TPS coating group. Upon the final observation at 6 months, the groups displayed on average a 0.74-mm migration. Most of the analyzed implants ceased migration within the first week post-surgery, but the CP coating demonstrated a higher and more prolonged migration compared to the TPS coating.

Contribution of various forefoot areas to push-off peak at different speeds and slopes during walking.

BACKGROUND: Push-off during the terminal stance phase has a major impact on forward progression during walking. During this phase, the ground reaction force is applied to a small area under the forefoot. A better understanding of how single forefoot areas contribute to push-off peak in healthy subjects is needed to develop biomimetic orthopedic devices for forefoot amputees. RESEARCH QUESTION: What is the contribution of different forefoot sole areas to push-off peak as a function of speed and slope? METHODS: In this analytical study, 15 healthy subjects walked on a treadmill at different speeds (0.8 m/s; 1.2 m/s; 1.6 m/s; max. gait speed) without de-/inclination and on different slopes (-10°; -5°; 0°; 5°; 10°) with normal walking speed. The Novel Pedar-X System was used to measure vertical sole force. Push-off peak of the entire sole was determined and relative contributions of the areas under the hallux, first ray, and toes (I-V) were calculated and analyzed using separate repeated-measures ANOVA (α = 0.05). RESULTS: Push-off peak increases with faster walking speeds as well as with 10° inclination. Downhill walking is associated with a reduced push-off peak. The contribution of all forefoot areas increases with faster walking speeds and at a declination of -10°. Push-off contribution of the area under the hallux increases by about 64.6% at fast walking compared to slow walking and this increase is higher than that of the area under the first ray and toes (p < 0.05). SIGNIFICANCE: These findings indicate the major role of the hallux in speed generation and the importance of the forefoot during downhill walking. The results show the need for an adequate assistive device even in hallux amputation cases to compensate for deficits in the push-off phase.

What do users and their aiding professionals want from future devices in upper limb prosthetics? A focus group study.

BACKGROUND: High rejection rates of upper limb prosthetics indicate that current prosthetic devices only partially meet user demands. This study therefore investigated the benefits and challenges with current prostheses, associated services and potential areas for improvement from the perspective of upper limb prosthesis users and various professionals working in the field of upper limb and hand prosthetics. METHODS AND FINDINGS: Seven different focus group discussions were conducted with 32 participants. Participants were grouped by prosthesis type, if they were prosthesis users, or professionals. All focus group discussions were transcribed verbatim, and a summarizing content analysis was performed. Three main topic areas to be addressed emerged from the interviews: 1. a properly functioning prosthesis, 2. the infrastructure, and 3. users' psychological and physical prerequisites. The interaction between a well-functioning prosthesis and a well-developed infrastructure was shown to be important for successful use. CONCLUSIONS: Our study raises many of the same issues that have been reported in previous qualitative studies, dating back over several decades. This study underlines the need to include users and professionals in the future development of prosthetic devices.