Polyethylene-Based Knee Spacer for Infection Control: Design Concept and Pre-Clinical In Vitro Validations

Antibiotic-loaded polymethyl methacrylate (PMMA) has been widely applied in the treatment of knee periprosthetic joint infections. However, problems with antibiotic-loaded PMMA-based spacers, such as structural fracture and implant dislocation, remain unresolved. A novel polyethylene-based spacer, designed with an ultra-congruent articulating surface and multiple fenestrations, was introduced in the current study. Validation tests for biomechanical safety, wear performance, and efficacy of antibiotic cement were reported. During cycle fatigue testing, no tibial spacer failures were observed, and less wear debris generation was reported compared to commercial PMMA-based spacers. The volumetric wear of the novel spacer was within the safety threshold for osteolysis-free volumetric wear. An effective infection control was demonstrated despite the application of lesser antibiotic cement in the 30-day antibiotic elution test. The tube dilution test confirmed adequate inhibitory capabilities against pathogens with the loaded antibiotic option utilized in the current study. The novel polyethylene-based knee spacer may offer sufficient biomechanical safety and serve as an adequate carrier of antibiotic-loaded cement for infection control. Further clinical trials shall be conducted for more comprehensive validation of the novel spacer for practical application.

Use of fresh osteochondral allograft in repair of distal femur after trauma

Preserving the ability to maintain an active lifestyle is a major concern in the reconstruction of the knee in young patients. for the healthy individual who desires to maintain a relatively active lifestyle, fresh osteochondral allografts may serve as an alternative to total joint reconstruction. The use of fresh allografts is primarily indicated in the patient suffering from a traumatic loss of articular seg- ments, who is too young or active for arthroplasty. In addition, fresh osteochon- dral allografts have a number of advantages over arthroplasty such as providing surgeons with a source of large grafts that can be ftted to replace osteochondral defects and cover the majority or entirety of articular surfaces without any donor site morbidity. In this case, a young, active patient lost a 7 x 8 cm portion of their distal femur, including a large portion of the articulating surface. Using a fresh os- teochondral allograft, harvested within 24 hours of donor death, a segment was ftted to match bony apposition, articular congruity, and congruity with the femoral notch and affxed with four partially threaded cancellous screws. Joint function was restored with the allograft in place, allowing the patient to delay the need for a total joint replacement.

Characterizing Trabecular Bone Properties near the Glenohumeral Joint Following Brachial Plexus Birth Injury

Brachial plexus birth injury (BPBI) causes functional arm impairment in 30-40% of those affected due to altered loading on the glenohumeral joint. While gross morphological osseous deformities have been seen in the humerus and scapula, alterations in the underlying trabecular bone microstructure and mineralization are not clear. Using a murine model of BPBI, trabecular bone alterations were explored in the proximal humerus and distal scapula, which surround the articulating surface of the joint. Samples were scanned using micro-CT, reoriented, and analyzed for standard trabecular metrics. The regions of interest closest to the articulating surface showed the greatest detriments. In the scapula, the scapular neck region showed less robust trabecular bone in the neurectomy group with decreased BV/TV (p=0.001), BMD (p=0.001), Conn.D (p=0.006), Tb.N (p<0.0001), and DA (p=0.033), and increased Tb.Sp (p<0.0001) compared to sham. In the humerus, the epiphysis showed less robust trabecular bone in neurectomy group, but to a much lesser extent than the scapular neck. The neurectomy group showed reduced BMD (p=0.007) and Tb.N (p=0.029) compared to sham. Data suggest deformities are worse near the articulating surface, likely due to the greater amount of mechanical loading. The reduction in trabecular microstructure and mineralization may compromise bone strength of the affected limb following BPBI. Further investigation of the underlying trabecular bone deformities following injury are necessary to eventually inform better treatments to limit the development of deformities.

Nanoscale insight into the degradation mechanisms of the cartilage articulating surface preceding OA

Osteoarthritis (OA) is a degenerative disease and leading cause of disability globally. We report the a fundamental study of the mechanisms underlying deterioration of hydrated cartilage in the presence of elevated calcium content preceding OA.

Bilateral Symmetry, Sex Differences, and Primary Shape Factors in Ankle and Hindfoot Bone Morphology

Background: Ankle injuries and joint degeneration may be related to ankle bone morphology. Little data exist to characterize healthy hindfoot bone morphology. The purpose of this study was to characterize side-to-side symmetry and sex differences in ankle and hindfoot bone morphology, and to identify the primary shape factors that differentiate ankle and hindfoot bone morphology among individuals. Methods: Computed tomography was used to create 3D surface models of the distal tibia, talus, and calcaneus for 40 ankle and hindfoot bones from 20 healthy individuals. Morphologic differences between left and right bones of the same individual and between males and females were determined. Statistical shape modeling was performed to identify primary shape variations among individuals. Results: Side-to-side differences in bone morphology averaged 0.79 mm or less. The average distal tibia in males was larger overall than in females. No significant sex difference was noted in the tali. The average female calcaneus was longer and thinner than the average male calcaneus. Variability in ankle and hindfoot bone morphology is primarily associated with articulating surface shape, overall length and width, and tendon/ligament attachment points. Conclusion: In general, the contralateral ankle can serve as an accurate guide for operative restoration of native ankle morphology; however, specific regions demonstrate higher asymmetry. Clinical Relevance: Knowledge of regions of high and low bilateral symmetry can improve hindfoot and ankle reconstruction. Design of ankle prostheses can be improved by accounting for differences in bone morphology associated with sex and shape differences among individuals.

Correction: Nanoscale insight into the degradation mechanisms of the cartilage articulating surface preceding OA

Correction for ‘Nanoscale insight into the degradation mechanisms of the cartilage articulating surface preceding OA’ by Tooba Shoaib, et al., Biomater. Sci., 2020, 8, 3944–3955, DOI: 10.1039/D0BM00496K.

A focused update on preventing ceramic fractures in hip arthroplasty

Ceramic bearings have several desirable properties, such as resistance to wear, hardness, and biocompatibility, that favour it as an articulating surface in hip arthroplasty. However, ceramic fracture remains a concern. We have reviewed the contemporary literature, addressing the factors that can influence the incidence of ceramic bearing surface fracture. Cite this article: Bone Joint J 2019;101-B:897–901.

Polyethylene in total knee arthroplasty: Where are we now?

Polyethylene (PE) remains the gold standard for the articulating surface in hip and knee arthroplasty. To increase arthroplasty longevity and improve wear resistance, newer versions of PE have been designed with resultantly different wear properties. Highly cross-linked polyethylene (HXLPE) is used in total hip arthroplasty with excellent outcomes; however, its use in total knee arthroplasty (TKA) remains conflicting. This review summarizes biomechanical and wear properties, clinical outcomes, and cost of polyethylene inserts in TKA. Simulation studies have convincingly shown decreased wear and oxidation rates with HXLPE when compared to conventional polyethylene (CPE). Registry results have been conflicting, and short- to midterm clinical studies have not demonstrated a significant difference between HXLPE and CPE. The cost of HXLPE inserts is higher than CPE. Long-term clinical data are lacking and further studies are warranted to evaluate the role of HXLPE in TKA.

Dautrey's Procedure Revisited in Management of Recurrent Mandibular Dislocation

ABSTRACT Introduction Mandibular dislocation occurs when the condylar head glides out of the glenoid fossa with the condyle positioned in such a way that its posterior articulating surface lying ahead of the articular eminence. Recurrent mandibular dislocation is relatively uncommon. Patient is extremely distressed and goes through a lot of discomfort. Varied etiologies have been cited in the literature, such as keeping the mouth wide open for long periods of time during dental procedures, yawning, laughing, traumatic injuries to the mandible, psychiatric disturbances, and certain drugs. Acute dislocations are best managed immediately by reduction and intermaxillary fixation. However, dislocations that have remained over a period of a month are considered to be chronic and these cannot be reduced successfully by manual manipulation of the mandible. Such chronic recurrent dislocations are surgically managed with eminectomy, meniscectomy, and condylotomies. A downward and forward osteotomy of the zygomatic arch in front of the articular eminence so as to produce a mechanical obstruction was recommended by Dautrey and Gosserez. This article will highlight the surgical experience of managing six patients with chronic recurrent dislocations of the temporomandibular joints (TMJs) bilaterally employing Dautrey's procedure. How to cite this article Baptist J, Baliga M. Dautrey's Procedure Revisited in Management of Recurrent Mandibular Dislocation. J Contemp Dent Pract 2017;18(1):78-79.