Today's News

Saturday, February 15, 1997

TKA eases neuropathic arthropathy pain

Total knee arthroplasty (TKA) can provide pain relief and mobility to diabetics and others diagnosed with neuropathic arthropathy, a long-term (average 11.3 years) study shows.

"The severe knee deformity and dysfunction resulting from the neuropathic process often leads to significant disability," said Jonathan M. Archer, MD, attending physician, Regional Medical Center, Madisonville, Ky. who presented his results Friday in scientific paper 268. "Conservative treatment such as bracing and protective weightbearing is more effective in the early stages, and arthrodesis may further reduce a person's activity level."

Dr. Archer reported that all TKA patients were satisfied with their operated knees, which now function much better than before surgery.

Between October 1978 and August 1983, orthopaedic surgeons performed 11 total knee replacements in seven patients who had been diagnosed with neuropathic arthropathy. At the time of surgery, the patients ranged in age from 56 to 80 years (average: 72 years). There were five males and two females.

"All knee prostheses were the modular posterior-stabilized type," Dr. Archer said. "Six custom tibial components-designed with a wedge (half or full) and a stem extension-were used because most patients had severe deformity, especially in varus, and had deep bony depression of medial tibial plateau. During surgery, we always released the distal insertion of medial collateral ligament in severe varus knee to keep ligaments balanced between medial and lateral sides.

Dr. Archer said, "Although four patients died due to other medical problems, we did have the chance to evaluate their operated knees for eight to 12 years."

Three patients (four knees) survived. A 90-year-old patient was excellent at last (10-year) review: his knee score had been 57 before surgery, improved to 89 after surgery and increased to 95 at last follow-up. The two remaining patients (three knees) were followed for 14 and 17 years. Two of the knees were excellent and one, which had undergone two revision surgeries for aseptic loosening, was good.

Dr. Archer noted that many of the patients in this study had varus deformity due to repeated joint abuse because of the loss of normal pain and sensory protection associated with neuropathic arthropathy. "This also could be the reason for aseptic loosening of two knees in this series," he said.

When surgery had to be repeated, the doctors used a posterior-stabilized type prosthesis with stem extensions in both femoral and tibial components. At latest follow-up, no sign of prosthesis loosening on roentgenographic examination was found and all knees were stable.

"The study shows that knee replacement for these patients is feasible provided that correct alignment and stability are achieved," Dr. Archer said. "Posterior-stabilized type knee prosthesis, with its inherent stability in flexion, is ideal for knee reconstruction in these deformed and unstable knees.

"A modular prosthesis can be used in deficient bone stock instead of a custom-augmented prosthesis," he noted. "Modular posterior-stabilized metal-backed components with press fit stem extensions are desirable for this patient population."

The long-term (eight- to 17-year) results of all the operated knees in this series were good-to-excellent. "To achieve this," Dr. Archer said, "careful pre-op evaluation of patient's neurologic status, lower limb muscle strength, the condition of deficient bone and presence of ligament imbalance in the knee are very important. Postoperative care should emphasize rehabilitation, prevention of infection, and regular follow-up."

Co-authors of the study with Dr. Archer are: Liban Chang, MD, attending orthopaedist, Army General Hospital, Taichung, Taiwan, R.O.C; Giles R. Scuderi, MD, director, Insall Scott Kelly Institute for Orthopaedics and Sports Medicine, and attending orthopaedic surgeon, department of orthopaedic surgery, Beth Israel Medical Center, New York, N.Y.; and John N. Insall, MD, chief, adult knee reconstruction, knee arthroplasty, Beth Israel Medical Center and director, Insall Scott Kelly Institute for Orthopaedics and Sports Medicine.