Outcomes and Aseptic Survivorship of Revision Total Knee Arthroplasty

Constrained and semiconstrained implants

In a study of 234 knees (209 patients) with soft-tissue deficiency, Wilke and colleagues²⁰ evaluated the long-term survivorship of revision TKA with use of a semiconstrained modular fixed-bearing implant system. Overall Kaplan-Meier survival rates were 91% (5 years) and 81% (10 years) at a mean follow-up of 9 years. When aseptic revision was evaluated, however, the survival rates increased to 95% (5 years) and 90% (10 years). The authors noted that male sex was the only variable that significantly increased the risk for re-revision (hazard ratio, 2.07; P = .02), which they attributed to potentially higher activity levels. In 2006 and 2011, Lachiewicz and Soileau^21,22 evaluated the survival of first- and second-generation constrained condylar prostheses in primary TKA cases with severe valgus deformities, incompetent collateral ligaments, or severe flexion contractures. Of the 54 knees (44 patients) with first-generation prostheses, 42 (34 patients) had a mean follow-up of 9 years (range, 5-16 years). Ten-year survival with failure, defined as component revision for loosening, was 96%. The 27 TKAs using second-generation prostheses had a mean follow-up of about 5 years (range, 2-12 years). At final follow-up, there were no revisions for loosening or patellar problems, but 6 knees (22%) required lateral retinacular release of the patella (Table 3).

Rotating hinge implants

Neumann and colleagues²³ evaluated the clinical and radiographic outcomes of 24 rotating hinge prostheses used for aseptic loosening with substantial bone loss and collateral ligament instability. At a mean follow-up of 56 months (range, 3-5 years), there was no evidence of loosening of any implants, and nonprogressive radiolucent lines were found in only 2 tibial components. Kowalczewski and colleagues²⁴ evaluated the clinical and radiologic outcomes of 12 primary TKAs using a rotating hinge knee prosthesis at a minimum follow-up of 10 years. By most recent follow-up, no implants had been revised for loosening, and only 3 had nonprogressive radiolucent lines (Table 4).

Endoprostheses (modular segmental implants)

In a systematic review of 9 studies, Korim and colleagues²⁵ evaluated 241 endoprostheses used for limb salvage under nononcologic conditions. Mean follow-up was about 3 years (range, 1-5 years). The devices were used to treat various conditions, including periprosthetic fracture, bone loss with aseptic loosening, and ligament insufficiency. The overall reoperation rate was 17% (41/241 cases). Mechanical failures were less frequent (6%-19%) (Table 5).

2. Functional outcomes

The goal in both primary and revision TKA is to restore the function and mobility of the knee and to alleviate pain. Whereas primary TKAs are realistically predictable and reproducible in their outcomes, revision TKAs are vastly more complicated, which can result in worse postoperative outcomes and function. In addition, revision TKAs may require extensive surgical exposure, which causes more tissue and muscle damage, prolonging rehabilitation. (Appendix 3 is a complete list of studies of functional outcomes of revision TKA.)

This discrepancy in functional outcomes between primary and revision TKA begins as early as the postoperative inpatient rehabilitation period. Using the functional independence measurement (FIM), which estimates performance of activities of daily living, mobility, and cognition, Vincent and colleagues²⁶ evaluated the functional improvement produced by revision versus primary TKA during inpatient rehabilitation. They compared 424 consecutive primary TKAs with 138 revision TKAs. For both groups, FIM scores increased significantly (P = .015) between admission and discharge. On discharge, however, FIM scores were significantly (P = .01) higher for the primary group than the revision group (29 and 27 points, respectively). Furthermore, in the evaluation of mechanisms of failure, patients who had revision TKA for mechanical or pain-related problems did markedly better than those who had revision TKA for infection.

Compared with primary knee implants, revision implants require increasing constraint. We assume increasing constraint affects knee biomechanics, leading to worsening functional outcomes. In a study of 60 revision TKAs (57 patients) using posterior stabilized, condylar constrained, or rotating hinge prostheses, Vasso and colleagues²⁷ examined functional outcomes at a median follow-up of 9 years (range, 4-12 years). At most recent follow-up, mean International Knee Society (IKS) Knee and Function scores were 81 (range, 48-97) and 79 (range, 56-92), mean Hospital for Special Surgery (HSS) score was 84 (range, 62-98), and mean range of motion (ROM) was 121° (range, 98°-132°) (P < .001). Although there were no significant differences in IKS and HSS scores between prosthesis types, ROM was significantly (P < .01) wider in the posterior stabilized group than in the condylar constrained and rotating hinge groups (127° vs 112° and 108°), suggesting increasing constraint resulted in decreased ROM. Several studies have found increasing constraint might lead to reduced function.^28-30