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ACI shows promise for patellofemoral defects
Autografting boosts results over surgery alone.
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At a recent meeting of the International Cartilage Repair Society, one of the nation’s leaders in cartilage repair gave his parameters for using autologous chondrocyte implantation for patellofemoral disease.
“Patellofemoral chondromalacia is a really catchword that is used out of context,” said Tom Minas, MD, director of the Cartilage Repair center, at Brigham and Women’s Hospital in Boston. “What we are talking about is major knee pain. And frequently the cause of damage to the patella is underlying maltracking, dysplasia of the trochlea. This accounts for why females are commonly more affected than males, and often why the first presentation by someone in trouble with instability and subsequent pain is a traumatic dislocation.”
Detection
Minas said that he uses a simple patella reduction test to tell if the joint is maltracking. “You reduce the patella in the extended knee position, and have the patient retract their quadriceps,” he said. “What you find is that you get a laterally based tracking, which is to conclude that there is maltracking of the patella. One problem is that these patients’ body habits tend for them to be obese and that is not so easy.”
Having the proper evaluation tools can be helpful. Minas said that standard x-rays can determine joint space, but will not tell you about the tracking. “My preferred test to assess the tracking of the patellofemoral joint is a CT scan with gadolinium. Assess with the quadriceps in extension with the quadriceps both flat and contracted to demonstrate patellar tilt, subluxation or both. It will also tell you about dysplasia of the trochlea and the gadolinium will isolate the areas with cartilage damage. The things that I am looking for are tilt, subluxation and cartilage loss are assessed with one test,” he said.
MRI arthrograms with interactive intravenous gadolinium are also useful in assessing articular cartilage localization as well as the “Gold Standard” arthroscopic examination.
Personal experience
Minas said there are three factors that he uses to determine the most appropriate treatment for patellofemoral disease; patellar tilt, patellar subluxation and localization of chondrosis on the patella, the trochlea or both.
He related his center’s experience with 130 patients with 2- to 9-year follow-up, who were treated for lesions of the patella or trochlea, or multiple lesions involving the patella and/or the trochlea. Overall, there were 53 patellar defects with the average lesion being 5cm², and 98 trochleas with an average 5.8 cm². “The average amount of transplant per knee was 11 cm²,” he said.
In the 130 patients there were subgroups based on the location and involvement of the defects, such as patella, trochlea, patella plus trochlea, weight bearing condyle plus patella, weight bearing condyle plus trochlea — which was the most common wear pattern — and weight bearing condyle plus patella and trochlea.
“In this group of patients, 90% of the patellar injuries were Type III and Type IV injuries,” Minas said. “These are the most difficult injuries to treat.”
In the trochlea group, the average size of the transplant was 6 cm². He said that 48% of these patients required realignment osteotomies of the tibiafemoral joint, the patellofemroal joint or both.
The results
Minas and colleagues used prospective outcomes scores included the WOMAC, Knee Society and SF-36 for patient assessment. “We had significant improvement in pain and stiffness,” he said. “The Knee Society Scores noted that these preop and postop scores were comparable to total knee replacement scores where we had good clinical improvement in pain and functionality. The SF-36, the physical component, showed excellent clinical improvement as well.”
He said that many of the population were disabled and unable to perform competitive sports preoperative. The majority was able to perform sports postoperatively.
“The patients were assessed for their quality of life with a patient satisfaction survey,” he said. “They graded their knees as excellent in 80% of the cases. Fair-improved in 18% and poor in three patients. Eighty-eight percent said they would choose the surgery again, 82% said they were satisfied with their surgical outcomes and 86% said they were better than they were before the surgery.”
Minas said that 12 patients went on to joint replacement surgery, receiving either compartmental replacement of the patellofemoral joint, the tibiafemoral joint, or total knee replacements. “Revision ACI (autologous chondrocyte implantation) was performed in eight patients, and we had some patients who had a progressive disease in other nontransplanted surfaces with symptoms that required surgery. Some of the grafts in patients had catching with partial laminations of the edges that were debrided and did well.”
Surgical algorithm
He said that he reserves the option of a patellofemoral prosthesis when the joint space is completely obliterated and lost. “When the patient is someone who had a dyplastic patellofemoral joint, presenting in their early 40s, my preference is to preserve the tibiafemoral joint with a patellofemoral prosthesis, which is minimally involved with bone and cartilage removal on the trochlear side, and a standard patellar prosthesis,” he said. “When the tibiafemoral joint finally fails, the prosthesis can be converted to a primary total knee, retaining the patella on the prosthesis.”
Minas concluded his presentation with a brief description of his algorithm for surgery in these cases.
Patellar tilt in isolation: This is a rare disease, he said. “In my practice, I do about 250 arthroscopies a year and I only perform two or three lateral releases because there is usually something causing that subluxation. That will continue to be present after a lateral release and the patient will not improve.
Patellar tilt with subluxation: “The question of what to do is dependent on the area of cartilage loss. If there is no articular cartilage injury we recommend an with a tibial tubercle osteotomy and a lateral release to centralize the patella.”
Cartilage damage limited to the Type I or Type II patella: “In other words, the inferior pole or lateral facet maltracking. An osteotomy alone without cartilage repair is effective. In the situation where you have pan patellar cartilage loss of the patella, or trochlear involvement, or medial patellar facet trochlea, which is a very common pattern, this is where we suggest ACI grafting to get a good clinical result, instead of a poor clinical outcome with surgery alone.”
“And of course, when there is a complete loss of joint space the only option is prosthesis.”
For more information:
- Minas T. ACI in the Patellofemoral joint, 2- to 9-year follow-up of the first 130 patients. Paper 4a-B. Presented at the 6th Symposium of the International Cartilage Repair Society. Jan. 8-11, 2006. San Diego.