Biomechanical Principles of Intramedullary Nails in Veterinary and Human Medicine.

Intramedullary nails are specialized metal rods inserted into the medullary cavity of a fractured bone and secured to reduce load on the fracture site, provide stability, and permit healing. The purpose of this review is to highlight the biomechanics of orthopaedic intramedullary nailing, as well as discuss the biomechanical considerations that have shaped implant design and fixation technique in veterinary and human medicine. Relevant studies were included from the PubMed database and Google Scholar for discussion on the basic science and nail design of intramedullary nails. Implant design and implementation continues to progress, with new innovative designs currently under investigation. A lack of consensus remains on the superior implant material. Recent studies, particularly in human populations, have supported the use of reaming based on reoperation rates, nonunion rates, and dynamization. Design modifications, such as the expandable intramedullary nails and angle-stable interlocking designs, have been investigated as methods of improving cortical contact and resisting torsional stress. Intramedullary nailing is a valuable stabilization technique for long bone fractures across a variety of species. The technology continues to undergo design improvements in both veterinary and human medicine.

Eccentric Hamstring Strength Imbalance among Football and Soccer Athletes.

OBJECTIVES: Hamstring strain injuries (HSI) are common among football and soccer athletes. Eccentric strength imbalance is considered a contributing factor for HSI. There is, however, a paucity of data on hamstring imbalances of soccer and American football athletes as they age and advance in skill level. High school athletes will display greater interlimb discrepancies compared with collegiate and professional athletes. In addition, soccer athletes will exhibit greater hamstring asymmetry than American football athletes. METHODS: Hamstring testing was performed on soccer and American football athletes using the NordBord Hamstring Testing System (Vald Performance, Albion, Australia). Age, sex, weight, sport specialization, and sport level were recorded. Maximum hamstring forces (N), torque (N · m), and work (N · s) were measured. Hamstring imbalance (%) was calculated by dividing the absolute value of the difference in leg forces divided by their sum. One-way analysis of variance and independent sample t tests compared measurements between athlete groups. RESULTS: A total of 631 athletes completed measurements, including 88 high school male soccer, 25 college male soccer, 23 professional male soccer, 83 high school female soccer, 28 college female soccer, 288 high school football, and 96 college football athletes. High school soccer players displayed significantly greater imbalances for torque (P = 0.03) and work (P < 0.01) than football athletes. Imbalances for maximum force (P = 0.035), torque (P = 0.018), and work (P = 0.033) were significantly higher for male soccer athletes in high school compared with college- and professional-level athletes. Female high school soccer players had significantly higher imbalance in torque (P = 0.045) and work (P = 0.001) compared with female collegiate soccer players. Football athletes did not experience significant changes in force imbalances between skill levels. CONCLUSIONS: High school soccer athletes exhibit greater hamstring imbalances than football athletes. Higher levels of play in soccer, for both male and female athletes, correlate with less hamstring asymmetry.

Suspensory fixation for bone transfer procedures in shoulder instability is superior to screws in an angled construct: a biomechanical analysis.

Background: The Latarjet procedure is a common bony augmentation procedure for anterior shoulder instability. Historically, screw fixation is used to secure the coracoid graft to the anterior glenoid surface; however, malpositioning of the graft leads to oblique screw insertion that contributes to complications. Suture buttons (SBs) are a more recent fixation technique that have not been studied alongside standard screw fixation in the context of biomechanical models of angulated fixation. This study aims to compare the biomechanical strength of single and double, screw and SB fixation at various levels of angulation. Methods: Testing was performed using polyurethane models from Sawbones. The graft piece was secured with screw fixation (Arthrex, Naples, FL, USA) or suspensory button (ABS Tightrope, Arthrex, Naples, FL, USA). Single or double constructs of screws and SBs were affixed at 0°, 15°, and 30° angles to the face of the glenoid component. An aluminum testing jig held the samples securely while a materials testing system applied loads. Five constructs were used for each condition and assessed load to failure testing. Results: For single fixation constructs, suspensory buttons were 60% stronger than screws at 0° (P < .001), and 52% stronger at 15° (P = .004); however, at 30°, both were comparable (P = .180). Interestingly, single suspensory button at 15° was equivalent to a single screw at 0° (P = .310). For double fixation, suspensory buttons (DT) were 32% stronger than screws at 0° (P < .001) and 35% stronger than screws at 15° (P < .001). Both double fixation methods were comparable at 30° (P = .061). Suspensory buttons at 15° and 30° were equivalent to double screws at 0 (P = .280) and 15° (P = .772), respectively. Conclusion: These measurements indicate that the suspensory button has a significantly higher load to failure capacity over the screw fixation technique, perpendicularly and with up to 15° of angulation. These analyses also indicate that the suspensory button fixation offers superior strength even when positioned more obliquely than the screw fixation. Therefore, suspensory button fixation may confer more strength while offering greater margin for error when positioning the graft.

Impact of Sling Use on Functional Mobility in a Geriatric Population.

OBJECTIVES: Sling immobilization is commonly used following rotator cuff repair. The purpose of this study was to determine the detrimental impact of sling usage on mobility and balance in an older adult population through validated gait and balance testing. The authors hypothesize that sling use will negatively affect balance and stability. METHODS: This institutional review board-approved and registered randomized prospective clinical trial enrolled patients from 2019 to 2021. Following informed consent, patients were randomized into two groups: a sling worn (group 1) and no sling worn (group 2). Participants were assessed via the Edmonton Frail Scale as well as Tinetti gait and balance scoring. RESULTS: Fifty patients were included in the study, 23 (46%) men and 27 (54%) women, with a mean age of 72.2 years. The balance score median was 16.00 for participants not wearing a sling and 15.00 for participants wearing a sling. The gait score median was 12.00 for participants not wearing a sling and 11.50 for participants wearing a sling. The balance and gait scores were significantly greater when patients were not wearing a shoulder sling with P values of 0.006 and 0.011, respectively. The overall combined gait and balance score was significantly greater, with median values of 27.00 for participants not wearing a sling and 26.00 for participants wearing a sling (P = 0.001). Patients reported little to no anxiety about falling while wearing the sling, with a score of 0.16. CONCLUSIONS: Postoperative sling immobilization negatively affects balance and gait in the geriatric population, potentially increasing the risk of postoperative falls in an already at-risk population.