(iii) Biomechanics of the knee and TKR

The principal aim of a total knee replacement (TKR) is to restore painless movements of the knee joint. Osteoarthritis, along with other pathologies that damage the articular surface of the knee, results in painful limitation of knee movement and alteration of shape and alignment of the joint. Restoration of the functional anatomy of the knee, including alignment, soft tissue balancing and restoration of the joint line, are integral to improving function. Factors that ensure long-term survival of the replaced knee have to be addressed while performing this procedure. Biomechanics of the knee and its restoration are key to improving both function and survival of a total knee replacement. Screw home movement in terminal extension and femoral roll back in flexion are unique to the knee joint. The patella improves extensor function by increasing its lever arm. Implant designs available include femoral components of fixed or multiple radii, high flexion knee replacements, posterior cruciate retaining or substituting designs and fixed or mobile tibial inserts. Computer navigation has been used to achieve accurate bone alignment and soft tissue balancing. Further research on these advances is essential to define their role in improving the results of TKR.     

Natalizumab and HSV meningitis

Natalizumab (Tysabri, Biogen Idec and Elan Pharmaceuticals) is a monoclonal antibody approved for use in patients with relapsing multiple sclerosis (MS) as well as moderate to severe Crohn’s disease. We report the first case of a patient with a history of MS, on monthly natalizumab, who developed HSV-2 meningitis. We discuss the mechanism of action of natalizumab and review what is known about the reactivation of herpes infection in association with this medication. The question of herpes simplex virus (HSV) and varicella zoster virus (VZV) prophylaxis for patients is raised.     

Microsurgical anatomy of VII and VIII cranial nerves and related arteries in the cerebellopontine angle

Summary The relationships of VII and VIII cranial nerves and related arteries are reviewed in 26 preparations by microdissection techniques. These vessels may be grouped in large (AICA, PICA), medium (LA, SA, CSA, RPI) and small calibre (vasa nervorum, radicullar and medullar branches). The importance of these structures in acoustic neuroma surgery, vestibular neurectomy and cross-compression syndromes is discussed. Vascular loops and elongated arteries are normal structures present at birth.This work was supported by a grant from the AJ Roemmers Foundation     

The seating mechanics of head‐neck modular tapers in vitro: Load‐displacement measurements,moisture, and rate effects

The mechanically assisted crevice corrosion performance of head‐neck modular tapers is a significant concern in orthopedic biomaterials. Fretting crevice corrosion processes in modular tapers are thought to be influenced by a wide array of factors including seating mechanics of the junction, hence there is a need for in vitro test methods that can assess their performance. This study presented a test method to directly measure the load‐displacement seating mechanics of modular tapers and used this method to compare the seating mechanics for different tapers, moisture, seating loads and seating rates. Seating mechanics were explored whereby the instantaneous load‐displacement behavior of the head seating onto the neck is captured and used to define the mechanics of seating. Two distinct taper design/material combinations were assembled wet or dry using axially applied loads (500, 1,000, 2,000, and 4,000 N) at two loading rates of 100 and 10⁴ N/s (n = 5 for each condition) using a servohydraulic test frame. The results showed that pull‐off strength scaled with seating load and ranged between 43% and 68% of seating load depending on sample and wetness. Tapers seated wet had higher pull‐off strengths (2,200 ± 300 N) than those seated dry (1,800 ± 200 N, p < 0.05). Seating mechanics (load‐displacement plots) varied due to sample type and due to wetness with differences in seating energy, seating stiffness, and seating displacement. These results show the detailed mechanics of seating during assembly and provide significant insight into the complex interplay of factors associated with even “ideal” seating (axial, quasistatic) loading. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1164–1172, 2018.

     

Survey of staff attitudes to the smoking ban in a medium secure unit

Aims and methodsThe aim of this survey was to explore staff attitudes to the indoor smoking ban in a medium secure unit and to ascertain if they had experienced any difficulties in imposing the ban in the four months after its introduction. All staff members available on duty who agreed to participate in the survey were interviewed using a semi-structured questionnaire.ResultsThe response rate was 65%. Sixty-four percent of the staff supported the smoking ban. Forty-three percent reported experiencing patient management problems with the majority complaining of increased patient aggression, increased use of staff time in supervising patients smoking. Additionally, supervising staff were still being exposed to passive smoking. Sixty-five percent reported positive effects due to the ban with the majority reporting that patients were sleeping at night due to the smoking area being closed at night.Clinical implicationsA significant proportion of the staff is still opposed to the smoking ban. Changing staff attitudes through educational programmes will be important in ensuring success of a possible future total ban in psychiatric units.     

Management of head and neck trauma in a developing country

Purpose  

To investigate cases of trauma in head and neck region; to elucidate the characteristic problems in a developing country.