The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

This is the 12th edition of the textbook of rheumatology first published in 1940. Like its predecessors, it presents voluminous and authoritative material on all facets of rheumatic diseases, from paleopathology to molecular biology to clinical features and treatment. The 143 contributors represent many of the top academic rheumatology divisions and related fields in the United States and abroad. It is impractical to read tomes like this from cover to cover. Instead, I tried to put the textbook through its paces by reading the sections that were pertinent to my clinical practice over a four-week period. Thus, while I did not see every condition described in the book, I found that I covered a surprising amount of it, either directly in my own patients, or during teaching sessions with fellows, house staff, and students, and in discussions with colleagues. My bias is that a subspecialty textbook should have two purposes:

Arthritis and Allied Conditions: A Textbook of Rheumatology

It is recommended in the TKA operation to balance the tension of soft tissues to make the rectangular gap in both flexion and extension because significant imbalance may result in eccentric stress on the polyethylene insert. However, no intensive research has been done on the medial and lateral laxity of the normal knee X-ray of 50 normal knees were taken under the varus or valgus stress in both extension and flexion at 80 degrees. The angle of lines on the femoral condyles and tibia plateau was measured. The same methods were also done for the 20 osteoarthritis knees. In extension of the normal knees, the mean angle was 5.06 degrees in varus stress and was 2.46 degrees in valgus stress. In flexion of the normal knees, the mean angle was 5.04 degrees in varus stress and was 1.82 degrees in valgus stress. Therefore, the lateral laxity was significantly larger than the medial laxity in both extension and flexion (p There are some arguments about the priority to make the perfect rectangular gaps. The methods to measure the tension of soft tissues during the operation are not accurate and does not always reflect the post-operative tensions. Furthermore, the tension during the operation may be different from dynamic phase such as walking and standing. The present study showed that the mediolateral laxity was asymmetrical in the normal knees. This imbalance may be necessary for the medial pivot movement of the normal knee. These results suggest that a slight lateral laxity is acceptable during TKA operation and may be beneficial to achieve the normal kinematics especially for the cruciate retaining prosthesis.

Asymmetry of medio-lateral laxity in the normal knee

A method for designing a two-part joint prosthesis (830) comprises: providing kinematic data of a subject's joint under load; and designing the joint prosthesis using the kinematic data, wherein the working surfaces of the two-part prosthesis comprise, consist essentially of or consist of cellular material. Advantageously, the method may not require any intra-operative adjustments to replace one or more of the components (831, 832), e.g. with a component of a different size. In particular, if components are made of biological tissues, such as a patient's own cells, it is advantageous to design and produce an implant that requires no adjustments intra-operatively as each implant may be manufactured specifically for each patient, and the time and costs of producing a range of sizes, most of which would not be required, would otherwise be prohibitive.

Method for designing a joint prosthesis

In image-free total knee arthroplasty (TKA) navigation, infra-red markers are attached to bony landmarks to provide kinematic data intra-operatively, with the aim of improving the precision of implant placement. In non-invasive navigation, infra-red markers are attached to the skin surface, with recent evidence suggesting that this can give repeatable measurements of lower limb mechanical alignment. The aim of our study was to evaluate the use of a non-invasive navigation system in the assessment of mechanical alignment with applied coronal force through the range of flexion. A previously validated non-invasive system (Physiopilot™) was tested on 23 volunteers with healthy knees. Two users performed two registrations of the software workflow on each participant's right and left knees. A force was manually applied to the end-point of varus and valgus knee laxity and the measured change in mechanical alignment was recorded. Force was applied with the knee positioned in increments of flexion from 0 to 90°. In keeping with previous studies, satisfactory values of coefficient of repeatability (CR) of 1.55 and 1.33 were found for intra-observer repeatability in measurement of supine mechanical femoro-tibial angle (MFTA) in extension, with a good inter-observer correlation of intraclass correlation coefficient (ICC) .72. However, when flexion was introduced, intra-observer and inter-observer reliability fell out with acceptable limits. Therefore, the trial did not support use of the Physiopilot™ system as a measure of MFTA when flexion is introduced. It was felt that learning-curve, soft tissue artefacts and lack of force standardisation equipment may have accounted for significant levels of error, with further studies required to address these issues.

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F. Henderson

Papers

Assessment of knee alignment with varus and valgus force through the range of flexion with non-invasive navigation