Should Younger Patients Ever Have Knee Replacement Surgery?
Should Younger Patients Ever Have Knee Replacement Surgery?
As Dr Bert outlined in a recent article that he expects may generate some controversy, he not only believes that microfracture is unnecessary during an HTO, but that it should be abandoned completely because "research shows that microfracture has declining efficacy after 2 years and actually destroys bone beneath the surface."
Simply unloading the bone with an HTO allows new knee cartilage to form. "Jung and colleagues showed that if you perform an HTO on a patient with a full-thickness defect in the medial compartment, 94% of the unloaded surface will develop fibrocartilage growth," Dr Bert says.
In a small series of patients who underwent opening-wedge HTO for significant cartilage loss in the medial compartment of the knee, Hinterwimmer and colleagues similarly found that osteotomy increased the thickness or volume of medial cartilage. The study also showed that using HTO to unload the medial compartment did not compromise cartilage in the lateral compartment.
"Studies by Milgrim and colleagues and Johnson and colleagues suggest that aggregates of fibrocartilage sitting beneath the surface are probably responsible for new cartilage formation when the bone is unloaded. Once these aggregates are no longer being loaded, they tend to protrude through the surface and form new cartilage," says Dr Bert.
As with many cartilage repair procedures, the new cartilage that forms is mostly fibrocartilage, which Dr Bert points out "is better than nothing."
Long-term survival of the joint surface depends on regenerating hyaline cartilage, however, and "we are still a long way from figuring out how to convert fibrocartilage to hyaline cartilage." A primary obstacle, according to Dr Bert, is that no one has found a way to prevent chondrocytes from dedifferentiating into fibrocartilage.
Because knee osteoarthritis is progressive and many patients who have undergone a procedure such as UKA or HTO eventually need TKA, it is important to consider the possible effects of treatment on a subsequent TKA.
"Several very good studies show that revision of an HTO to a TKA has the same outcomes as a primary TKA," says Dr Bert. He points out that a retrospective study by Cross and colleagues reported similar knee function scores after 5 years for patients who underwent TKA after a failed HTO and patients who had a primary TKA.
Cross and colleagues also found similar 5-year knee function scores for patients who had TKA after a failed UKA. However, the HTO revision group had a higher risk for complications after TKA than the other cohorts.
A New Zealand database study found similar knee function scores between patients who underwent primary TKA or revision TKA after HTO, whereas patients who underwent revision TKA after UKA had significantly worse function scores than the other groups (P < .001). The study also indicated that compared with patients who underwent a primary TKA, early revision was three times more likely among patients who underwent TKA after HTO (P < .001) and four times more likely among patients who underwent TKA after UKA (P < .001).
Dr Bert says that in his experience, "There are no differences in knee outcome scores, complications, or TKA failure when an HTO is revised to a TKA, as long as the original HTO was done properly using rigid hardware."
A Controversial Contention
As Dr Bert outlined in a recent article that he expects may generate some controversy, he not only believes that microfracture is unnecessary during an HTO, but that it should be abandoned completely because "research shows that microfracture has declining efficacy after 2 years and actually destroys bone beneath the surface."
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Simply unloading the bone with an HTO allows new knee cartilage to form. "Jung and colleagues showed that if you perform an HTO on a patient with a full-thickness defect in the medial compartment, 94% of the unloaded surface will develop fibrocartilage growth," Dr Bert says.
In a small series of patients who underwent opening-wedge HTO for significant cartilage loss in the medial compartment of the knee, Hinterwimmer and colleagues similarly found that osteotomy increased the thickness or volume of medial cartilage. The study also showed that using HTO to unload the medial compartment did not compromise cartilage in the lateral compartment.
"Studies by Milgrim and colleagues and Johnson and colleagues suggest that aggregates of fibrocartilage sitting beneath the surface are probably responsible for new cartilage formation when the bone is unloaded. Once these aggregates are no longer being loaded, they tend to protrude through the surface and form new cartilage," says Dr Bert.
As with many cartilage repair procedures, the new cartilage that forms is mostly fibrocartilage, which Dr Bert points out "is better than nothing."
Long-term survival of the joint surface depends on regenerating hyaline cartilage, however, and "we are still a long way from figuring out how to convert fibrocartilage to hyaline cartilage." A primary obstacle, according to Dr Bert, is that no one has found a way to prevent chondrocytes from dedifferentiating into fibrocartilage.
Because knee osteoarthritis is progressive and many patients who have undergone a procedure such as UKA or HTO eventually need TKA, it is important to consider the possible effects of treatment on a subsequent TKA.
"Several very good studies show that revision of an HTO to a TKA has the same outcomes as a primary TKA," says Dr Bert. He points out that a retrospective study by Cross and colleagues reported similar knee function scores after 5 years for patients who underwent TKA after a failed HTO and patients who had a primary TKA.
Cross and colleagues also found similar 5-year knee function scores for patients who had TKA after a failed UKA. However, the HTO revision group had a higher risk for complications after TKA than the other cohorts.
A New Zealand database study found similar knee function scores between patients who underwent primary TKA or revision TKA after HTO, whereas patients who underwent revision TKA after UKA had significantly worse function scores than the other groups (P < .001). The study also indicated that compared with patients who underwent a primary TKA, early revision was three times more likely among patients who underwent TKA after HTO (P < .001) and four times more likely among patients who underwent TKA after UKA (P < .001).
Dr Bert says that in his experience, "There are no differences in knee outcome scores, complications, or TKA failure when an HTO is revised to a TKA, as long as the original HTO was done properly using rigid hardware."
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