Results of First Study Using Chondrocyte Implantation in Older AdultsFull-thickness cartilage defects (down to the bone) in the knee come with two major problems. First, cartilage doesn't heal well. Second, treatment often results in failure. One of the newer treatment options is autologous chondrocyte implantation (ACI). It works well, but it is limited to younger patients. Older adults (45 years old and older) have been excluded from this approach -- until now.
This report suggests that cartilage implantation is just as successful in older patients as it is in younger ones. In this procedure, chondrocytes (cartilage cells) taken from normal, healthy joint tissue are used to make more chondrocytes. The new cells fill in the hole where the defect exists in the damaged cartilage.
Studies on the use of autologous chondrocyte implantation (ACI) among older adults are very limited. And there's a basic philosophy that by age 45 or older, the patient would do better to have a total knee replacement instead of ACI. Recovery is faster with fewer problems.
Older adults who are healthy and active may not want a total knee replacement just yet. They may find that pain relief and improved joint function available after ACI makes it possible to return to their previous social and recreational activities.
And, in fact, comparing results of ACI in younger versus older patients in this study showed similar results. The success and failure rates were about the same between the two groups. Young or old, the same types of exclusions should remain in effect. These include the presence of inflammatory joint disease, metabolic or crystal disorders, ligament instability, and poor knee joint alignment. ACI is not an option in such cases or if X-rays show 50 per cent (or more) loss of joint space in the knee.
For patients with malalignment, additional reconstructive surgery was done to correct the mechanical axis to neutral. About half the group had some other procedures done at the same time. This included procedures such as osteotomies, ligament repairs, bone grafts, or realignment of the patella (kneecap). The goal was to correct alignment as close to normal as possible in order to prevent degenerative changes that can lead to arthritis.
The ACI procedure was followed by a rehab program designed to prevent overload and damage to the new graft. Exercises for increasing knee joint motion and strength were prescribed and gradually progressed in stages.
The first stage lasted up until six weeks after surgery. A continuous passive motion (CPM) machine was used for six to eight hours each day. With CPM, the leg is strapped into the device, which automatically keeps the lower leg bending and straightening over and over for hours. When not in the unit, the patient could walk putting only partial weight on the foot by touching the toe down. This helped maintain balance without putting load through the healing patch of cartilage.
Stage II consisted of active motion exercises, muscle strengthening, and increased weight-bearing over from week seven to week 12. Full weight-bearing was allowed by the end of 12 weeks. Stage III began 12 weeks (three months) after surgery. By this time, patients felt ready to run but were told to avoid all impact activities for a full year or more. Cutting sports were not allowed for at least 18 months.
Results were assessed before and after treatment using a wide range of rating scales to measure outcomes. For example, patient sense of well-being, sports participation, satisfaction, and symptoms of arthritis were all recorded and compared. The authors took this information into consideration while also looking at the size and type of lesion.
Three subgroups were formed using this type of classification. Some cartilage defects were small and composed of only one damaged spot (first subgroup). Others were large single lesions (second subgroup) or multiple areas of damage on the joint surface (third subgroup).
If more than 20 per cent (or more) of the graft area didn't take or the patient continued to experience disabling pain, it was considered a treatment failure. Another form of failure was delamination. Delamination is the separation of the outer coating of the graft or splitting of the graft into separate layers. Everyone was followed for at least two years. Some patients were in the study for as long as 11 years.
Everyone in all three subgroups improved over time. Failure was reported in 14 per cent of the patients. Failures were more likely to occur in worker's compensation patients than non-worker's compensation patients.
The majority of patients (81 per cent) said they were satisfied with the results and would have the surgery again if they had it to do over again. A small number of patients required additional surgery either to replace part or all of the knee joint or to redo or revise the ACI procedure.
All-in-all, despite being older, potentially having lower metabolic cell activity and larger, more chronic cartilage defects, adults age 45 and older responded well to the ACI treatment approach. Failure rate was the same as for ACI in younger patients (as reported by other researchers).
The authors say that treatment of chronic cartilage defects in this age group doesn't have to be an osteotomy (removal and realignment of bone) or full joint replacement. That's good news for aging adults who are active and who don't want to accept the activity limitations that come with joint replacement. Only a small number of patients felt their knees were worse than before surgery.
Anyone (young or old) who is thinking about having autologous chondrocyte implantation (ACI) for cartilage defects should be told about possible complications. Besides graft failure, one of the most common problems is overgrowth of the implanted cells called hypertrophy.
A second challenging problem is the formation of adhesions (fibrous scar tissue). Both of these complications requires a second surgery to correct the problem. As many as one-third of all ACI patients end up having a second arthroscopic procedure. They call this a second-look arthroscopy. The excess tissue is shaved away or removed, providing long-lasting positive results.
Surgeons in Europe have solved this problem by replacing the periosteal cover used to protect the implant with a new collagen membrane. This new patch is not yet available in the United States. In the meantime, careful patient selection (young or old) remains a key factor in the success of the ACI procedure. Age does not have to be an immediate strike against the patient. Obesity, noncompliance with the rehab program, tobacco use, and loss of joint space are major risk factors for failure. Such patients must be screened for and excluded from this type of surgery.
Ralf E. Rosenberger, MD, et al. Repair of Large Chondral Defects of the Knee with Autologous Chondrocyte Implantation in Patients 45 Years or Older. In The American Journal of Sports Medicine. December 2008. vol. 36. No. 12. Pp. 2336-2344.
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