Alan C. Merchant

Roentgenographic analysis of patellofemoral congruence.

Because previous methods of making roentgenograms of the knee in the axial projection were found to be unsatisfactory, a simple, accurate, and reproducible technique was devised. With the patient supine, the knees are flexed 45 degrees over the end of the table and the legs are supported. The central x-ray beam is inclined downward 30 degrees from the horizontal to strike the film cassette (placed distal to the patellae) at a right angle. The congruence angle , which measures the relationship of the patellar articular ridge to the intercondylar sulcus, was created to measure patellofemoral joint congruence. More than 16 degrees of lateral subluxation of the patella was found to be abnormal at the ninety-fifth percentile in 100 normal subjects.

Classification of patellofemoral disorders

Patellofemoral disorders represent a large portion of the average orthopedists practice. Despite the improvements in patellofemoral radiographs and arthroscopic diagnostic techniques, these disorders are too frequently misunderstood and frustrating to treat. This report proposes a clinical classification for patellofemoral disorders that, it is hoped, will aid our understanding and improve our results of treatment. A major feature of this classification is the recognition that a developmental and familial abnormality, patellofemoral dysplasia, is the etiology for most patellofemoral disorders. Equally important is the assignment of chondromalacia patellae to a secondary position for the most part. Other causes of anterior knee pain and disability are included to complete the classification.

The Female Knee: Anatomic Variations and the Female-specific Total Knee Design

AbstractThe concept and need for a gender-specific or female-specific total knee prosthesis have generated interest and discussion in the orthopaedic community and the general public. This concept relies on the assumption of a need for such a design and the opinion that there are major anatomic differences between male and female knees. Most of the information regarding this subject has been disseminated through print and Internet advertisements, and through direct-to-patient television and magazine promotions. These sources and a recent article in a peer-reviewed journal, which support the need for a female-specific implant design, have proposed three gender-based anatomic differences: (1) an increased Q angle, (2) less prominence of the anterior medial and anterior lateral femoral condyles, and (3) reduced medial-lateral to anterior-posterior femoral condylar aspect ratio. We examined the peer-reviewed literature to determine whether women have had worse results than men after traditional TKAs. We found women have equal or better results than men. In addition, we reviewed the evidence presented to support these three anatomic differences. We conclude the first two proposed differences do not exist, and the third is so small that it likely has no clinical effect. Level of Evidence: Level IV, systematic review. See the Guidelines for Authors for a complete description of levels of evidence.

A modular prosthesis for patellofemoral arthroplasty: design and initial results.

This study was designed to determine if a new and modular prosthesis for patellofemoral arthroplasty would produce results at least as good as those reported for other designs, while simultaneously eliminating the risks of patellar revision should total knee arthroplasty be needed in the future. Another issue was its suitability for the older patient with isolated patellofemoral arthritis in order to avoid destruction of the normal femoro-tibial compartments involved in total knee arthroplasty. Finally, I sought information about the safety and longevity of this prosthesis when used for patellofemoral arthroplasty in severely disabled patients too young to be considered for total knee replacement. From a cohort of 16 patients (8 studied retrospectively and 8 prospectively), aged 26 to 81 years, and followed up for 2.75-6.25 years, 15 (94%) rated their results excellent or good using the Activities of Daily Living Scale. These results are better than previously reported for other prosthetic designs. To date, no patient in this study group has required conversion to a total knee arthroplasty. The design has proven safe for use in both the older and younger patient, but longer followup will be needed to assess greater longevity. Level of Evidence: Therapeutic Study, Level IV-8 (case series-no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

Medial Patellar Instability: A Little Known Cause of Anterior Knee Pain

Anterior knee pain (AKP) is one of the most common patient complaints heard by orthopedic surgeons. A wide variety of causes of AKP have been ascribed to it. Medial patellar instability (MPI) is an objective condition with its own personality provoking incapacitating AKP that should be included in the differential diagnosis of AKP patients, above all in disabling AKP patients after realignment surgery. However, this condition can be difficult to diagnose because it is not well described in the medical literature. Its clinical repercussion was identified at the end of the 1980s. We can now state that it is an objective cause of AKP and that it is more frequent than we had thought, although it might be underdiagnosed because it is still not a well-known entity. The first author has seen many patients with MPI who have seen more than three physicians without a true diagnosis of their condition.

RADIOGRAPHY OF THE PATELLOFEMORAL JOINT

Abstract Radiographs of the knee, and especially the patellofemoral joint, are indeed important, but they must be kept inperspective. There is a tendency for the orthopedist to rely too heavily upon the “x-ray.” Perhaps this is natural because we treat so much trauma, and the diagnostic answers, the fracture classification, and even the preferred treatment are often suggested by the initial radiograph. When it comes to patellofemoral disorders, the history, the physical examination, and the initial radiographs assume nearly equal importance, with the physical examination providing perhaps the best information to explain each patients pathophysiology and to develop a treatment plan. The patellofemoral joint is unique, so its radiographic evaluation will be unique as well. The axial radiograph, which provides the most information, demands that the clinician know exactly what technique was used before an intelligent interpretation can be made. An understanding of the advantages and disadvantages of these different techniques, as well as an appreciation for the various radiographic measurements that separate “normal” from “abnormal,” will make the clinicians task much easier.

Is It Lateral Retinacular Lengthening Versus Lateral Retinacular Release or Over-Release?

To the Editor: As the first author to publish about the lateral release, in 1974, I feel an obligation to comment on the article “Open Lateral Patellar Retinacular Lengthening Versus Open Retinacular Release in Lateral Patellar Hypercompression Syndrome: A Prospective Double-Blinded Comparative Study on Complications and Outcome” by Pagenstert et al. in the June 2012 issue of Arthroscopy. The abstract describes a well-designed prospective study with the results clearly favoring lengthening compared with release. However, the abstract fails to show a design flaw that made these poor results for the release-only group a foregone conclusion. In the body of the work, we learn that all the patients had nearly identical releases to the same endpoint. Then, half of the patients had a pants-over-vest closure of the lateral capsuloligamentous structures to achieve the lengthening, and the remaining half had neither closure nor repair as the release-only cohort. In the description of the surgical procedure, the authors described the 2 techniques in detail. In both groups the release was extended in a stepwise manner until a “turn-up” sign of 90 patellar rotation (rotational elevation of the lateral patella up to 90 in relation to the epicondylar axis) ensured a complete decompression. This technique of using the 90 turn-up sign as an endpoint for a lateral release was taken from a study published in 1986. Soon after its publication, the 90 turn-up test for an adequate release was either quickly discarded or never adopted by careful and knowledgeable surgeons for the very reasons found in this study: an unacceptably high incidence of quadriceps atrophy, iatrogenic medial patellar subluxation, and worse clinical outcomes, all the result of over-release of the lateral retinaculum. Unfortunately, many surgeons attributed these severe adverse complications caused by overrelease to all lateral release procedures. It appears to be more than a coincidence that the 2 studies referenced by the authors that showed a very high incidence of medial patellar subluxation and poor results were published 2 years and 4 years after the 90 turn-up test was published. Such excessive overrelease of the lateral soft tissues plus improper patient selection, such as releasing a lateral retinaculum that is not tight, are the major reasons for poor results after lateral release surgery. Because the purpose of a lateral release is to normalize the tight soft-tissue restraints, there is no reason to release the retinaculum beyond the goal of 1 to 2 patellar quadrants of medial patellar glide or a lateral tilt-up of approximately 60 as advocated by Ewing in 1991. To my knowledge and in my experience, an isolated lateral retinacular release performed properly in this manner has never caused an iatrogenic medial subluxation with severe quadriceps atrophy. This study raises ethical concerns about the selection of a technique that is known to produce such an extensive lateral release that it can cause an overrelease, which in a high proportion of patients leads to the severe complication of iatrogenic medial subluxation, and then leaving half the patients unrepaired. In the introduction, the authors seem to understand that such an extensive decompression can lead to an overrelease, which can then be repaired by the Z-plasty lengthening. If the selection of the 90 turn-up test as an endpoint was made without knowledge of its severe and adverse consequences, perhaps the publication of this letter will help correct this deficiency. Finally, I would challenge the authors to repeat the study but instead use the standard lateral release technique to compare with the lengthening technique. Such a study would be a more realistic comparison, provide information that is new, and avoid the risk of serious injury for the release-only patients.

A Philosophy of the Patellofemoral Joint: A Logical Clinical Approach

A philosophy or pathomechanical and pathophysiological theory of the patellofemoral joint is described which leads to a logical etiology-based clinical classification, provides a framework for measurement and analysis of the six anatomic abnormalities that affect the normal function of the patellofemoral joint, and presents a simple and logical approach to treatment, both operative and non-operative. This theory, based on the careful clinical measurement of these six potential abnormalities, is also able to explain the two major symptoms of patellofemoral disorders, anterior knee pain and patellar instability, using available scientific data.

Comparison of the vastus-splitting and median parapatellar approaches for primary total knee arthroplasty: a prospective, randomized study. Surgical technique.

To The Editor: The otherwise excellent article, “Comparison of the Vastus-Splitting and Median Parapatellar Approaches for Primary Total Knee Arthroplasty: A Prospective, Randomized Study. Surgical Technique” (2007;89 Suppl 2 Part 1:80-92), by Kelly et al., was marred by an error in the legend to Figure 1. The axial radiograph of the knee was mislabeled as “a Merchant radiograph of the …