TKA beneficial for Paget’s disease patients

At latest follow-up, only two patients with polyostostic Paget's disease had moderate pain, but neither patient had knee instability.

Although performing total knee arthroplasty in patients with Paget’s disease presents some technical challenges, the surgery can yield good clinical results with low revision rates, a retrospective study shows.

Gwo-Chin Lee, MD, and colleagues at the Mayo Clinic in Rochester, Minn., reviewed the results of 21 TKAs performed on 20 Paget’s disease patients. This included 12 men and eight women with a mean age of 71 years.

The disease affected only the femur in 10 knees, only the tibia in six knees, and both the femur and tibia in five knees. Preoperatively, 14 knees had a mean 6º of varus tibiofemoral alignment, three knees had neutral alignment and four knees had a mean 15º of valgus alignment.

Six surgeons had performed all procedures between 1978 and 1999. In all cases, they implanted a cemented total knee prostheses that incorporated a condylar, cruciate-retaining design, according to the study.

The researchers found that surgeons encountered a size mismatch between the femoral and tibial components for 15 of the 21 knees (71%). In these cases, the bone affected by Paget's disease required a larger implant size, according to the study. “Consequently, when performing knee arthroplasty in patients with Paget’s disease, it is important to plan to use a prosthesis which allows matching of different-sized femoral and tibial components,” the authors said in the study.

Surgeons also encountered several technical difficulties during surgery, particularly in exposing the knee joint. The operating surgeon could not evert the patella in four cases and three cases experienced partial patellar tendon detachment at the tibial tubercle.

One patient had a femoral deformity that prevented the use of an intramedullary femoral cutting guide. Surgeons also had difficulty balancing soft tissue in several other cases, according to the study.

Despite these difficulties, range of motion improved from 3º of active extension preoperatively to 94º of flexion postoperatively. Tibiofemoral alignment also improved; 12 knees (58%) had a valgus alignment of 0º to 5º and nine knees (42%) had a valgus alignment of 5º to 10º, according to the study.

An alignment of 0º to 5º is outside the Knee Society’s acceptable valgus range of 5º to 10º, “which demonstrates the difficulty of correcting these complex multilevel, multiplane deformities,” the authors noted. “However, none of these knees had a residual varus tibiofemoral angle and none were associated with early failure,” they said.

Two patients died within two years following surgery and another patient was lost to follow-up. The remaining 17 patients (18 knees) had a mean nine years of clinical follow-up and a mean 6.9 years of radiographic follow-up.

The Mean Knee Society score for pain improved 41 points to average 87 points. Functional scores also improved, from a mean 36 points preoperatively to 67 points postoperatively, according to the study.

At the latest follow-up, 11 patients reported no knee pain, five reported mild pain and two reported moderate pain. Both patients who reported moderate pain had polyostostic Paget’s disease, but neither patient had postop knee instability, the authors noted.

“Subjectively, all patients were satisfied and believed that the procedure had improved their quality of life,” the authors said.

Regarding complications, one patient developed stiffness six weeks postop and required manipulation. No patients developed substantial heterotopic ossification or deep infections, and only one patient required revision due to aseptic loosening at 10 years postop, according to the study.

For more information:
Lee G, Sanchez-Sotelo J, Berry DJ. Total knee arthroplasty in patients with Paget's disease of bone at the knee. J Arthroplasty. 2005;20:689-693.