Patellofemoral joint arthroplasty: patient selection,surgical technique and outcomes

Isolated patellofemoral arthritis is an increasingly recognized entity, and is usually associated with previous patellofemoral dysplasia or instability. Patellofemoral arthroplasty (PFA) has evolved significantly in recent years, both in terms of implant design and importantly in the understanding of appropriate patient selection. This review outlines the indications and investigations for PFA, provides a brief history of the development of contemporary implants, and presents the clinical outcomes for the prostheses most commonly used in the UK. In addition, it provides a detailed surgical technique for implantation of an onlay implant, with tips on how to optimize patellofemoral biomechanics and thus achieve a consistently good outcome.     

Combining two-point genetic linkage analyses using mapping functions

A likelihood ratio statistic is proposed for combining two-point genetic linkage analyses when the two-point analyses are between a trait and a well-defined map of markers. It is assumed that the two-point analyses are independent, as in the case of choosing only the most informative marker per family. The asymptotic distribution of the likelihood ratio statistic is derived under the null hypothesis of no linkage of the trait with a map of 2 markers, with intermarker genetic distance δ. This distribution is shown to be a chi-square mixture distribution with mixing probability depending on δ and the assumed mapping function. We use this asymptotic result to approximate the distribution of the likelihood ratio statistic for the more general case of more than 2 markers. Simulation results indicate that this may be reasonable. Power is evaluated by simulations and results indicate that this approach, which constrains the intermarker distances to their known values, tends to be more powerful than other methods proposed in the literature. © 1994 Wiley-Liss, Inc.     

Peribursal fat plane of the shoulder: anatomic study and clinical experience

A comprehensive anatomic and radiographic analysis of the peribursal fat plane in 12 cadavers confirmed that the fat plane seen on radiographs represents extrasynovial fat lining the subacromial bursa and documented the anatomic relations of the bursa. A three-part retrospective clinical evaluation of rotator cuff tears, calcific tendinitis, and rheumatoid arthritis was performed. Two osteoradiologists blindly graded the appearance of the peribursal fat plane with the shoulder in external versus internal rotation in 21 patients with arthrographically intact rotator cuffs and 21 patients with disrupted rotator cuffs. The peribursal fat plane was seen better with disrupted rotator cuffs. The peribursal fat plane was seen better with the shoulder in internal rotation and was seen in 60% of control subjects but only 21% of patients with rotator cuff tears. Partial or complete obliteration of this fat plane is a sensitive (79%) but less specific (60%) indicator of rotator cuff tears. Obliteration of the peribursal fat plane by inflammatory processes in adjacent tissues, including calcific tendinitis and rheumatoid arthritis, occurred with a high frequency.