Knee arthrodesis - ultima ratio for the treatment of the infected knee.

The irretrievable destruction of the knee due to trauma, tumor or infection is the indication for knee arthrodesis. The main reason for knee arthrodesis in terms of infection ist the infected total knee arthroplasty. Central problem is the definition of the term "irretrievable". It is based on the subjective opinion of the attending physician and depends on his expert knowledge of this specific entity. The preservation of a functioning extremity is the main goal. This article shows the typical indications and contraindications for knee arthrodesis following septic knee diseases. In addition it gives insight into the biomechanical and technical considerations to be kept in mind. Finally the postoperative care and outcome of different techniques are analysed.

Introduction

“Although the surgeon may consider an arthrodesis of the knee to be a poor outcome, a limb with a fusion is more efficient and functional than is one with an above-the-knee amputation” [8].

Despite the loss of a functioning joint knee fusion can provide a functional symptom-free extremity [4]. In certain situations it may be the only alternative to amputation [9], [30].

Today manifest irreparable destruction of the knee without any chance of reconstruction or (re)arthroplasty is the indication for knee arthrodesis [8].

These irreversible condition may be caused by:

Trauma

Tumor

Joint infection.

Indications

The indication for knee arthrodesis underwent a constant modification during the decades. In the beginning, based on the lack of sophisticated other options, it was performed in cases of septic arthritis, articular tuberculosis and poliomyelitis as well as in cases of osteoarthritis and rheumatoid arthritis [7], [6], [8], [10], [23].

Based on the developement of new and efficient therapeutical approaches in many of the above mentioned diseases nowadays the main indication for knee arthrodesis is an irreparable knee destruction based on an infected total knee replacement [5], [16], [22], [30]. According to statistical analyses infections of that type appear in 1 to 4% after primary total knee replacement [5]. Due to the rising number of patients who undergo these procedures the problem becomes more and more immanent [1], [25], [27]. After “changing procedures” the infection rate rises up to 20% [14].

Further indications for knee arthrodesis today are [13], [22]:

Methaphyseal bone loss

Ligamentous instability

Multiple failed revisions

Loss of extensor mechanism

Infection with highly virulent organisms

Inadequate soft tissue coverage

A patient unwilling to consider a revision arthroplasty.

According to Vlasak 1995 and Windsor 1993 in 2006 MacDonald pointed out, that knee arthrodesis might be usefull in young patients with unilateral posttraumatic joint destruction in jobs that require heavy manual labour [16], [26], [31]. As early as 1993 Isklar et al. demanded knee arthrodesis to be proceeded as early as possible in order to shorten the course of the disease, calm the infection, lower the use of analgetics and preserve bone and soft tissue [11][. With regard to the patient’s individual “ultima ratio situation” Bierwagen mentioned, that knee arthrodesis in general is the final method in order to preserve the extremity. Failure due to insufficient planning or technique will lead to amputation and subsequently to care dependency [5].

Contraindications

Contraindications for knee arthrodesis include various situations such as [8], [16], [22]:

Infected contralateral knee arthroplasty

Infected ipsilateral hip or ankle arthroplasty

Extended bone defect

Contralateral leg amputation

Contralateral hip or knee arthrodesis

Ipsilateral hip or ankle arthrosis.

Indication and contraindication for knee arthrodesis always have to be individualized to the patient’s specific situation in terms of [16]:

Individual clinical situation

Individual expectations

Individual work area situation

Individual social situation

Individual mental situation.

Biomechanical considerations

Knee arthrodesis leads to significant functional changings in the lower extremity. Thus they also lead to significant biomechanical changings of the lower extremity, the pelvis and even the whole body. According to Conway et al. and Sandrone et al. the following may be detectable [8]:

Increased pelvic inclination

Increased ipsilateral coxal abduction

Increased ipsilateral dorsalflection of the ankle

Increased energy required for walking (plus 25 to 30%) [22]. Thus knee arthrodesis is contraindicated when contralateral above-knee amputation was proceeded earlier (above-knee amputation increases the strain for walking by 25%). In addition the use of oxygen in patients with knee arthrodesis is 0.16 mL/kg/min compared to 0.20 mL/kg/min following above-knee amputation [8], [29].

Depending on the technique and the local situation knee arthrodesis leads to a leg shortening. If the estimated reduction is more than 5 cm (secondary) leg lengthening may be considered [8].

General principles

Depending on the chosen technique, the local situation and the estimated bone loss one has to differentiate between two general principles of knee arthrodeses (Figure 1 (Fig. 1)):

Figure 1

Types of knee arthrodeses

Tibio-femoral contact arthrodesis (“tibio-femoral kissing”)

This concept implicates the direct contact between femur and tibia. Thus bone fusion is possible and the main goal of this procedure.

Tibio-femoral non-contact arthrodesis

This concept is chosen, if the loss of bone stock is this significant, that direct contact between femur and tibia is impossible or does not make sense. In these cases bone fusion is impossible.

Various techniques have been described in the last decades [22]:

Long nail

Modular nail

Non-modular nail

External fixation

Monoplanar fixators

Biplanar fixators

Circular frames

Hybrid systems

Combination of intramedular and external techniques

Compression plating

Vascularized fibular graft.

Strategy

In general

Knee arthrodesis needs a proper preoperative planning. The following considerations should be kept in mind:

Correct tibio – femoral alignment

External rotation tibia vs. femur: 10°

Genuflection: 10°

Tibio-femoral contact arthrodesis: Removal of all cartilage (tibial cancellous bone meets femoral cancellous bone)

Tibio-femoral contact arthrodesis: Fixation under compression in order to increase the bone healing

Slight shortening of the leg in order to ease the "follow-through" of the leg.

Timing of the arthrodesis

According to the literature one may proceed knee arthrodesis in single, two or multi stage strategies [21]. In terms of knee arthrodeses following knee infection the strategy depends on the extent of the infection, it’s course, previous operations, the patient’s general condition and the type and virulence of the infect causative pathogene (Figure 2 (Fig. 2)). This thesis is supported by Waldmann et al. The authors mentioned in 1999 that “following prior surgical procedures resulting in a failed and infected arthroplasty, knee arthrodesis should ideally be attempted as a two stage procedure” [28]. We perform knee arthrodesis mostly in a multy stage regime due to the fact, that the infect situation after one surgical revision mostly is not sufficient calmed. To achieve this more than one operation is needed.

Figure 2

General algorithm for treatment of joint infection

Temorary stabilisation of the knee (infect sedation period)

Analogous to the infect treatment in other sites of the musculo-skeletal system also in infected knees surgical eradication of the infected area and temporary stabilisation are the basic strategy. Thus the way of a temporary knee arthrodesis during the infection treatment has to be defined. The chosen strategy depends on the extent of the infection and the bone stock (Figure 3 (Fig. 3)).

Figure 3

Considerations concerning the temporary knee stabilisation

Choice of the correct method

The choice of the correct method for the definite knee arthrodesis depends on (Figure 4 (Fig. 4)):

Figure 4

Choice of the correct implant

Loss of bone stock

Type and virulence of the pathogene that caused the infection

Patient’s general health.

We perform compression plate tibio-femoral contact arthrodeses as an exception in cases, where internal stabilisation may be particulary promising but the anatomical shape of femur and/or tibia does not allow an intramedullary system. Nevertheless in some cases supplementing the intramedullar stabilisation by plates (and bone grafts) leads to bone fusion even in difficult cases [20], [24].

As a new method in the last years computer assisted navigation for knee arthrodesis is mentioned in the literature. By analogy with computer assisted implantation of total knee replacements the use of this technique should lead to a perfect three dimensional alignement of tibio-femoral contact arthrodeses. Maniar et al. described the method for the first time in a case of septic arthritis in 2011 [17].

Postoperative care

(Modular) internal stabilisation

Mobilisation: First postoperative day

Physiotherapy with full weight-bearing: First postoperative day (intramedular stabilisation).

Tibio-femoral plate arthrodesis: 20 kg for 4 weeks, 1/2 bodyweight till week 8, afterwards gradually rising till full bodyweight (week 12)

Elasto-compressive wrapping until soft tissue is consolidated

Low-dose heparin

Patient visits the outpatient clinic every 2 weeks (month 1–3). Later once a month (month 4–6). Afterwards individual timing.

X-ray every 4 weeks (month 1–3). Afterwards in month 6. Then individual timing. Additional CT in cases of complicated healing of tibio-femoral contact arthrodeses and in order to prove the bony consolidation of the tibio-femoral contact arthrodesis.

External stabilisation

Mobilisation: First postoperative day

Physiotherapy with full weight-bearing: First postoperative day (tibio-femoral contact arthrodesis)

Elasto-compressive wrapping until soft tissue is consolidated

Low-dose heparin

Patient visits the outpatient clinic every 2 weeks (month 1-3). Later once a month (month 4-6). Afterwards individual timing.

X-ray every 4 weeks (month 1-3). Afterwards in month 6. Then individual timing. Additional CT in cases of complicated healing of tibio-femoral contact arthrodeses and in order to prove the bony consolidation of the tibio-femoral contact arthrodesis.

External fixator “specialties”:

Patient

Practice: Cleaning of the fixator wires and Schanz screws

Doc

Tension of the wires (100N): Check once per week

Compression of the arthrodesis: Check every 2 weeks

Fusion rates of tibio-femoral contact arthrodeses

The fusion rates depend on the chosen technique. According to the literature the fusion rates of the intramedullar stabilized arthrodeses are approximately 10 to 15% higher than those achieved by external fixation.

Complications

Due to the fact, that knee arthrodeses are “ultima ratio” procedures, the rate of complications is rather high. According to the literature it ranges between 20 and 84%. Depending on the type of arthrodesis (see below) the following complications may occur [8], [12], [19]:

Tibio-femoral pseudarthroses

Tibio-femoral nonunion

Tibio-femoral malalignment

Insufficient cancellous bone plastic

Persistence or recurrence of the infection

Regardless of the chosen method the rate of recurrent infections is mentioned between 0 and approximately 20%.

Intramedullar arthrodesis: 0 to 22% [3], [9], [18], [15]

External fixation: 0 to 18% [9], [19], [26]

Pain resulting from pseudarthroses or nonunions [2].

Additional fractures

Depending on the method chosen

External fixation:

Neurovascular lesions

Failure of the construction (f.e. breakage of Schanz screws or wires etc.)

Local infection at the entry points of Schanz screws or wires

Fractures

Internal fixation:

Breakage of the osteosynthesis material (intramedular nail, plate)

Dislocation of the osteosynthesis material

Fractures

Résumé

A couple of key-factors may be postulated in order to choose the individual correct technique for knee arthrodesis for each patient:

Key factor I: Profound knowledge of the correct indication for internal or external stabilisation (intramedular nail / plate vs. external fixator).

Key factor II: Profound knowledge of the advantages and disadvantages of the specific methods.

Key factor III: Profound knowledge in trouble-shooting.

Key factor IV: Precise individual planning for every patient.

Additionally one should keep in mind, that:

The risk of recurrent infection is almost similar for internal and fixator based arthrodeses.

The fusion rate for intramedullar contact arthrodeses is significantly higher than the one found when fixator contact arthrodeses are proceeded.

Notes

Competing interests

The author declares that he has no competing interests.