Surgeon cites advantages of biologic unicompartmental knee replacement

Researchers are now studying individual patients’ genetic propensity for cartilage regeneration.

March 2008

In light of recent advances in cartilage restoration techniques, some researchers are highlighting the potential of biologic unicompartmental knee arthroplasty for patients with bipolar lesions.

At the World Congress of the International Cartilage Repair Society, Jack Farr II, MD, provided an overview of the current state of biologic unicompartmental knee arthroplasty (UKA).

“In certain circumstances, it is now possible to restore the damage in the compartment biologically,” Farr told Orthopaedics Today International. “Through incremental improvements in current cartilage restoration applications, there is mounting evidence that this biologic approach has increasing merit.”

Anteromedialization

Studies on bipolar cartilage restoration report early success rates between 50% and 80%, Farr said. In his unpublished research, Farr and colleagues found a 50% failure rate using patellofemoral osteochondral fresh allografts for bipolar cases. The group also saw a trend toward better outcomes in patients who underwent concomitant anteromedialization (AMZ) of the tibial tuberosity compared to those who did not.

In a patellofemoral autologus chondrocyte implantation (ACI) study that included 24 bipolar cases, Tom Minas, MD, reported 71% overall good and excellent outcomes. Nearly 80% of the group also underwent AMZ, Farr noted.

He also cited research by Ian Henderson, FRACS, who reported 54.5% good and excellent results in patellofemoral patients who underwent ACI only and 86% good and excellent outcomes in those who received ACI with AMZ.

Farr and his colleagues also conducted a study on 39 patients treated with patellofemoral ACI. Of the six patients with bipolar lesions (seven knees), five knees had an extremely lateral patella and two had congruent and stable patellofemoral compartments preoperatively. Surgeons performed concomitant AMZ on six knees, and the remaining knee had a prior AMZ. A minimum 2-year follow-up revealed that six knees had good or excellent results, Farr noted.

Farr said there are few published studies regarding bipolar tibiofemoral articular cartilage restoration: Allan E. Gross, MD, FRCS, had limited success with bipolar allografts and stopped performing the technique; and William D. Bugbee, MD, still uses them in select bipolar salvage cases.

In two studies investigating patients undergoing concomitant ACI and meniscal allograft transplantation, Farr and his colleagues found that 50% of the bipolar salvage patients had good or excellent results. Other ACI studies that included bipolar tibiofemoral salvage cases showed between 67% and 90% good and excellent results.

Outlook for the future

“Patients under the age of 40 years present a great challenge for a standard UKA/PFA (patellofemoral arthroplasty), as the implants would be expected to fail when the patient was still quite young. There would be a high probability that the revision of the UKA/PFA to a primary total knee would be followed by a revision total knee in their lifetime,” Farr said.

“The goal then is to provide a durable biologic restoration that can at least last long enough that the patient delays the path to arthroplasty and becomes more age-appropriate for definitive replacement.”

Future research includes developing standardized outcome tools to compare bipolar cartilage restoration studies and finding causes of failure.

He highlighted work by Dan Saris, MD, which analyzed the genetic propensity of individual patients’ chondrocytes to form hyaline cartilage.

“Understanding the strengths and weaknesses of the patient’s biologic ability to repair and restore is the first step, optimizing and testing the quality of the implants (whether autograft, allograft, scaffold or growth factors) is the second,” Farr said.

For more information:

• Jack Farr II, MD, is the medical director of the Cartilage Restoration Center of Indiana. He can be reached at Indiana Orthopaedic Surgery Center, 5255 E. Stop 11 Road, Suite 300, Indianapolis, IN 46237, U.S.A.; +1-317-884-5200; e-mail: indyknee@hotmail.com. He receives institutional or research funding from Genzyme Biosurgery; funding and stock options from Regeneration Technologies; funding royalties and is a consultant for Stryker Orthopaedics and Johnson & Johnson; funding and is a consultant for OrthoFix; miscellaneous funding from Pfizer; royalties or stock options from Osteobiologics; and is a consultant for and receives royalties from Bionicare.

References:

• Bugbee WD, Convery FR. Osteochondral allograft transplantation. Clin Sports Med. 1999;18(1):67-75.
• Farr J. Autologous chondrocyte implantation improves patellofemoral cartilage treatment outcomes. Clin Orthop Relat Res. 2007; 463:187-194.
• Farr J. Biologic unicompartmental knee replacement. #11.1. Presented at the 7th World Congress of the International Cartilage Repair Society. Sept. 29-Oct. 2, 2007. Warsaw.
• Farr J, Rawal A, Marberry KM. Concomitant meniscal allograft transplantation and autologous chondrocyte implantation: minimum 2-year follow-up. Am J Sports Med. 2007;35(9):1459-1466.
• Henderson I, Lavigne P. Periosteal autologus chondrocyte implantation for patellar chondral defect in patients with normal and abnormal patellar tracking. Knee. 2006;13;274-279.
• Saris DB, Vanlauwe J, Victor J, et al. Characterized chondrocyte implantation results in better structural repair when treating symptomatic cartilage defects of the knee in a randomized controlled trial versus microfracture. Am J Sports Med. 2008;36(2):235-246.