Mid-term results of all poly total knee replacement versus metal-back total knee replacement

• Author Details:   
• Kaushal R. Patel
• Harshil R. Patel
• Zulfikar M. Patel
• Kalpesh A. Mehta

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Background: Osteoarthritis of knee is one of the most common form of arthritis causing degeneration of articular cartilage and subchondral bone. Joint replacement is the gold standard treatment for patients with advanced osteoarthritis of the knee who despite appropriate medical management, have an unacceptable level of pain or physical function or both. There are mainly two types of implants used for total knee replacement nowadays. One is metal back type and other is all poly type.
Materials and Methods: This is a retrospective multicentric study of 100 total knee replacements performed for comparison of metal back(50) versus all poly(50) total knee replacement on the basis of Clinical(KSS-knee society score, WOMAC-western Ontario & Macmaster university osteoarthritis index score, pain, deformity), radiological(alignment), complications and survival of that joint. All total knee arthroplasty are cruciate sacrificing and done through medial parapatellar approach.

Result:

·         Average age of patients in our study was 58.4 years with a range of 52-80 years. We included 72 females and 28 males in our study.

·       Knee society functional scores were improved from 36.4 to 75.1 for metal back component and 34.90 to 74.20 in all poly total knee replacement

·        Womac score improved from 52.01 to 81 in metal back total knee replacement and improved from 54.07 to 82.39 93 in all poly total knee replacement.

·         97% patients of metal back and 98% of all poly tkr showed improvement in pain.

·         Post operatively 82% patients from the metal back total knee replacement and 92% patients of all poly total knee replacement had alignment between 5 degree valgus to 5 degree varus.

·    The mean fixed flexion deformity in metal back total knee replacement improved from 9 to 3 degrees in metal back total knee replacement and 11 to 1 in all poly total knee replacement.

·    Crude survival rate of implant in our study was 95 % in metal back total knee replacement and 93% in all poly total knee replacement.

Conclusion: Total knee replacement was responsible for pain relief in majority of the patients. Improvement in pain found same in both types.Improvement in ROM[range of movement] was     better in metal back total knee replacement but improvement in FFD[fixed flexion deformity], extensor lag and alignment was better in all poly total knee replacement. Complication rates of infection and periprosthetic fractures were similar in both joints. There was no case of loosening of implant noted in our study.

Keyword: Osteoarthritis knee, Total knee replacement, Metalback, Kss [knee society score], Womac [western Ontario & Macmaster university osteoarthritis index]score