Failure of knee replacement

5.2.3.1 Prosthesis survival

Overall, the prosthesis failure rate is low. The pooled 10-year survival of primary knee replacements is over 90% in clinical studies (Callahan et al. 1994, Forster 2003). Follow-up of consecutive cohorts in arthroplasty register data indicates that the survival rates for aseptic loosening and for any revision have clearly improved since the early 1980s (Robertsson et al. 2001). This improvement is attributable to developments in asepsis, surgical technique and prosthesis designs. In recent register-based studies, survival rates exceeding 95% and 90% at 5 and 10 years have been reported in nationwide scale (Robertsson et al. 2001, Furnes et al. 2002, Gioe et al. 2004, National Agency for Medicines 2008) and even following revision knee replacement (Sheng et al. 2006). By 15 years, the survival of TKR declines to 80%

(Baker et al. 2007, Koskinen et al. 2008).

Male gender and younger age have been associated with higher probability of prosthesis failure in several studies (Heck et al. 1998, Furnes et al. 2002, Rand et al.

2003) but the results concerning the effect of diagnosis and fixation method are more heterogeneous (Heck et al. 1998, Robertsson et al. 2001, Furnes et al. 2002, Gioe et al. 2004). Excellent results for unicondylar knee replacement (UKR) have been reported in certain institutions (Geller et al. 2008), but in larger studies UKR are associated with greater failure rate compared to cemented TKR (Robertsson et al. 2001, Furnes et al. 2007, Koskinen et al. 2008).

5.2.3.2 Reasons for failure *

Despite improvements in the outcome of knee replacement surgery, the most common reasons of failure in the early studies (Ahlberg and Lundén 1981, Bryan and Rand 1982, Cameron and Hunter 1982) – namely infection, aseptic loosening and instability – are still an issue. Altogether these failure mechanisms account for over two thirds of all revision operations (Table 5.2). The most important reasons for the revision of UKR are aseptic loosening and progression of arthritis in non-replaced compartments of the knee (Knutson et al. 1986, Barrett and Scott 1987, Lewold et al. 1998, Robertsson et al. 2001, Gioe et al. 2003 and 2004, Furnes et al.

2007).

In addition to the early reports (Bryan and Rand 1982, Cameron and Hunter 1982), there are few reports dealing with the mechanisms of failure following TKR (Fehring et al. 2001, Sharkey et al. 2002, Gioe et al. 2004, Mulhall et al. 2006).

Besides the three predominant reasons for failure, the reports reviewed list numerous other indications: extensor mechanism-related or patellar complications, dislocation, fracture of components or surrounding bone, osteolysis, polyethylene wear, arthrofibrosis, pain only, progression of arthritis (in unicondylar knee replacements) and other, unspecified reasons (Knutson et al. 1986, Barrett and Scott 1987, Stuart et al. 1993, Lewold et al. 1998, Fehring et al. 2001, Robertsson et al.

2001, Furnes et al. 2002, Sharkey et al. 2002, Gioe et al. 2003 and 2004, Sheng et al.

2004, Sierra et al. 2004, Mulhall et al. 2006, Sheng et al. 2006, Furnes et al. 2007).

As a consequence of using different categorization schemes for failure reasons and differences in case definition and length of follow-up, the distribution of reasons for revision varies considerably between different studies, making any comparisons difficult (Table 5.2).

Approximately a half of prosthesis failures occur relatively early after the index surgery. Of the revisions reported to the Swedish Knee Arthroplasty Register, half were performed within four years of the index arthroplasty (Robertsson et al. 2001).

This figure is comparable to 31–56% at 2 years (Sharkey et al. 2002, Mulhall et al.

2006) and 63% at five years (Fehring et al. 2001) in clinical studies.

Infections, patellar complications and instability emerge as reasons for the early failures occurring within 2–5 years after the primary operation (Fehring et al. 2001, Sharkey et al. 2002, Gioe et al. 2004, Mulhall et al. 2006). In these cases the failure

Table 5.2. Reasons for revision following total knee replacement (TKR) and unicondylar knee replacement (UKR) in previously published studies^*.

Reason for failure TKR,

% of revisions

UKR,

% of revisions

Aseptic loosening 3–55 23–89

Polyethylene wear 3–44 9–23

Patellar / Extensor mechanism -related complications

6–41 1–7

Infection 7–38 2–11

Instability 6–29 2–18

Malalignment 3–12 3

Periprosthetic fracture 1–5 1–5

Progression of arthritis - 17–51

Unspecified reasons 4–31 6–15

*, Knutson et al. 1986, Barrett and Scott 1987, Stuart et al. 1992, Lewold et al. 1998, Fehring et al.

2001, Robertsson et al. 2001, Furnes et al. 2002, Sharkey et al. 2002, Gioe et al. 2003 and 2004, Sheng et al. 2004, Sierra et al. 2004, Mulhall et al. 2006, Sheng et al. 2006, Furnes et al. 2007.

mechanism is closely related to the index arthroplasty. For example, the majority of early infections are caused by perioperative contamination (see section 5.3.4, p. 26).

Similarly, failure to adequately balance soft tissues and component malalignment may lead to instability. In the long haul, prosthesis failure is more often related to implant design and prosthesis fixation. Polyethylene wear and aseptic loosening are frequent reasons for late revision knee replacements (Fehring et al. 2001, Sharkey et al. 2002).

Infections were considered in all studies reviewed and accounted for 7–38% of all reasons for TKR revisions. In UKR, infections were less frequent (Table 5.2). Up to 25–38% of the early revision knee replacements were performed due to infection (Fehring et al. 2001, Sharkey et al. 2002, Mulhall et al. 2006). The proportion of infections from all reasons of revision gradually declines with increase in the length of follow-up (Gioe et al. 2004).

The most common reasons for revision total knee replacement are aseptic loosening of femoral and/or tibial components, polyethylene wear, infection and extensor mechanism -related problems [A]. Among early failures occurring within 2–5 years after the index operation, infections predominate, being the indication for revision in 25–38% of cases [B]. The importance of infections as a reason for revision decreases as the length of follow-up increases [C]. Aseptic loosening and progression of arthritis are the most frequent causes of failure after unicondylar knee replacement [B].