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Custom Patellofemoral Arthroplasty of the Knee
Domenick J. Sisto, MD1; Vineet K. Sarin, PhD1
1 Los Angeles Orthopaedic Institute, 4955 Van Nuys Boulevard, Suite 615, Sherman Oaks, CA 91403. E-mail address for D.J. Sisto: laortho1@yahoo.com
View Disclosures and Other Information
A video supplement to this article will be available from theVideo Journal of Orthopaedics.A video clip will be available at the JBJS web site, www.jbjs.org. TheVideo Journal of Orthopaedicscan be contacted at (805) 962-3410, web site: www.vjortho.com.
The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. One or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (V.K. Sarin is an employee of [receives salary from] Kinamed, Inc.). No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at Los Angeles Orthopaedic Institute, Sherman Oaks, California

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2006 Jul 01;88(7):1475-1480. doi: 10.2106/JBJS.E.00382
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Abstract

Background: The treatment of isolated patellofemoral arthritis is controversial. Several surgical procedures have been used to treat the severely degenerated patellofemoral joint, with varying degrees of success. The purpose of this study was to determine the clinical results of a custom patellofemoral arthroplasty for the treatment of isolated patellofemoral degenerative arthritis of the knee.

Methods: From 1995 through 2002, twenty-five patellofemoral replacements, three of which were bilateral, were performed in twenty-two patients for the treatment of isolated patellofemoral arthritis of the knee. According to the Ahlback radiographic evaluation scale, the mean preoperative score for the severity of the arthritis was 4.65 points in the patellofemoral compartment and 0.5 point in both the medial and the lateral compartment. The patients included sixteen women (two of whom had a bilateral replacement) and six men (one of whom had a bilateral replacement) with a mean age of forty-five years at the time of the index arthroplasty. Seventeen patients (nineteen knees) had had a prior procedure on the knee. The mean preoperative Knee Society functional score was 49 points, and the mean preoperative Knee Society objective score was 52 points.

Results: At a mean of seventy-three months (range, thirty-two to 119 months) postoperatively, all twenty-five implants were in place and functioning well. There were eighteen excellent and seven good results. The mean Knee Society functional score was 89 points, and the mean Knee Society objective score was 91 points. No patient had required additional surgery or had component loosening.

Conclusions: On the basis of our relatively short-term follow-up study, custom patellofemoral arthroplasty appears to be a safe and effective treatment for isolated patellofemoral arthritis of the knee. We believe that the results presented in this paper justify the additional cost associated with the custom device.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Domenick J Sisto, M.D.
    Posted on August 08, 2006
    Drs. Sisto and Sarin respond to Dr. Grelsamer
    Los Angeles Orthopaedic Institute

    We thank Dr. Grelsamer for his interest in our study and for the opportunity to discuss the custom approach to patellofemoral arthroplasty in more detail. Dr. Grelsamer correctly observes that our published series does not include patients with a flat or convex femoral trochlea. While we agree that treatment of patients with isolated patellofemoral arthritis and concomitant severe trochlear dysplasia can be a challenge, we believe that a custom approach to patellofemoral arthroplasty is a reasonable treatment option for this indication.

    The posterior (articulating) surface of the custom patellar implant is designed to replicate the native surface and is defined by a pre-operative computed tomography scan. In contrast, the prosthetic femoral trochlea is designed to conform to the articular radius of the mating patella implant and is thickened laterally and medially along its borders to compensate for any lack of native medial-lateral stability. The thickness of the custom implant along the patellar tracking arc is designed to reestablish the anterior position of the femur.

    Stability of the implant construct and extensor mechanism is fundamental to the successful outcome of any patellofemoral arthroplasty, including the custom approach. The presence of trochlear dysplasia, as Dr. Grelsamer points out, further underscores the importance of achieving a stable and balanced extensor mechanism intra-operatively. A convex trochlea may increase the tendency to overstuff the patellofemoral joint and this possibility must be addressed during design of the custom implant and during the implantation procedure.

    Finally, we agree with Dr. Grelsamer that patellofemoral arthroplasty is indicated in the elderly patient with isolated patellofemoral arthritis whose medial/lateral compartments would not be expected to become symptomatic during their lifetime. The purpose of our study, though, was to report on the use of custom patellofemoral arthroplasty in a younger population.

    Ronald P. Grelsamer
    Posted on August 02, 2006
    Custom Patellofemoral Replacement in thePresence Of Trochlear Dysplasia
    Mount Sinai Medical School, New York, NY

    To The Editor:

    Young patients with isolated patellofemoral arthritis not uncommonly have a dysplastic trochlea. Instead of being concave, the trochlea is flat or even convex. In such a setting I have always worried that a custom implant that duplicates the articulating anatomy of the patient's patella (convex) will lead to an unstable construct. The authors do not appear to have encountered this problem. Could they comment on this?

    As an aside, I would think that their patellofemoral replacement (or any other) would be equally indicated in the frail and elderly population where deterioration of the other compartments is not likely to take place in their lifetime.

    The author(s) of this letter to the editor did not receive payment or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author(s) are affiliated or associated.

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