Fig. 27.1
Knee Arthrodesis with Kuentscher Nail 1945
In 1960, in Clinical Orthopedics and Related Research, John Charnley reported the results of 171 knee arthrodesis procedures performed by ten surgeons at his clinic, with a consolidation rate of 98.8 % [5]. The principle of compression arthrodesis was introduced, in which 45 kg of pressure was applied with an external fixator. Both operative time and rates of complication were minimal. The most common etiologies were post-tuberculosis joint destruction, primary gonarthrosis, and rheumatoid arthritis.
In the “Arthrodesis” chapter of the 1980 book “Arthritis of the Knee,” Charnley reported that it was already difficult for young orthopedists to comprehend his enthusiasm regarding knee arthrodesis, which he had expressed 20 years previously [6]. In the meantime, knee arthroplasty had become so well developed due to better functional results that joint fusion had been largely replaced as a primary treatment for gonarthrosis. It was only indicated in cases when the joint was so massively rigid that mobilization was no longer possible.
In an article published in the Journal of Bone and Joint Surgery (A) in 2004, Conway et al. summarized the still-current indications, results, and therapeutic alternatives for knee arthrodesis [7]. In industrialized countries, infectious disease has disappeared as a cause of knee destruction, as poliomyelitis is no longer a problem. In the meantime, knee arthroplasty as treatment of arthritis has taken off with an almost unanticipated boom. With the boom, the absolute number of postoperative complications increased, with the peri-prosthetic infection being the most feared. The incidence after primary operations was quoted 1–2 %, and after revision surgery, particularly septic revisions, it was markedly higher. Infection recurrence rates were reported as between 6 and 13 % by Wasielewski et al., and approximately 50 % by Hanssen [8, 9]. To date, these numbers have not markedly changed. Although revision implants and operative techniques have improved since then, the age and comorbidities of patients have continually increased, and the complication risks have risen accordingly. Knee arthrodesis is a withdrawal operation, allowing limb preservation with markedly reduced infection recurrence. Thus, we can thoroughly discuss the renaissance of this procedure with its long history and proven track record.
Our own investigations have shown the superiority of the intramedullary approach over that with an external fixator regarding permanent recovery from infection and good patient acceptance [10]. Currently, one survey recommends knee arthrodesis as the treatment of choice for recurrent infection after the first septic total knee arthroplasty revision [11].
27.2 Indications
Today, the spectrum of indications for knee arthrodesis has changed once again. The classic grounds for treatment including poliomyelitis, tuberculosis, and Charcot knee after tabes dorsalis are no longer present in the general population. The vast majority of cases of primary gonarthrosis as well as secondary joint destruction post-trauma or post-infection are treated with arthroplasty. The rate of postoperative early and late complications has barely changed in the past 10 years; instead it shows an upward trend as a result of the described demographic shift as well as an increase in the indications for surgery. The vast percentage of arthrodesis patients today present with infectious complications after primary or revision total knee replacement. In the authors’ opinion, the following factors should support the implementation of arthrodesis:
Chronic peri-prosthetic infection (present longer than 4 weeks),
Infected soft tissue defect with fistula formation,
Chronic osteitis of the distal femur or proximal tibia,
Infection with multi-resistant pathogens,
Destruction of the extensor mechanism,
Compromised immunity of the patient,
Advanced osteoporosis, in which long-term stable anchoring of a coupled revision total knee arthroplasty is improbable,
Chronic pain syndrome.
Certain patients are so dissatisfied with their primary knee replacement that they refuse revision procedures and request a definitive treatment in the form of fusion at the initial interview.
Knee arthrodesis is also a consideration for the treatment of therapy-refractory chronic knee empyema and involvement of the neighboring bone in the absence of a knee prosthesis. This again should be considered in cases of multiple drug-resistant bacteria, mixed infections, and immunocompromised patients.
The risks of surgery, potential postoperative problems, and limitations in ambulation need to be carefully explained to the patient and his/her family members in multiple, consecutive interviews.
In specialized centers, malignant tumors of the distal femur and the proximal tibia are also added to the list of indications, when these cases cannot be treated with tumor endoprostheses. This chapter will not go any further into these details.
27.3 Contraindications
A knee fusion procedure is always an attempt to preserve the limb, for which revision, re-arthrodesis, and change of approach are also possible. However, knee fusion does not always promise good results. From our point of view, the major contraindications are:
Progressively septic course with impending multi-organ system failure in cases of peri-prosthetic infection or knee joint empyema,
General inoperability,
Previously bedridden patients,
Symptoms of spinal cord injury,
Refractory peripheral arterial disease in stage IV.
Other potential contraindications are contralateral knee disarticulation or arthrodesis as well as severe arthritic deformities of the ipsilateral hip and/or ankle joints. Naturally, the functional results for patients with these comorbidities are massively reduced. In our opinion, in such cases it is particularly important to ascertain whether an arthrodesis might not be the best solution from a selection of suboptimal choices.
27.4 Patient Informed Consent
The patient must always be comprehensively informed of the advantages, disadvantages, and possible complications of a knee arthrodesis procedure, as well as possible treatment alternatives. We always involve the next of kin and caregivers in these conversations, and we never confine the discussions to the preoperative visit one day prior to surgery. Instead, it should be divided over several, sequential interviews. The informational discussions are carried out exclusively by colleagues who have already performed the procedure, or at least acted as an assistant. In addition, it is essential that the informing colleague has personal experience with the postoperative care of patients undergoing knee arthrodesis.
The patient must not be urged toward undergoing the procedure; instead, it is important to introduce treatment alternatives including complication rates and outcomes. The responsible physician must explain in detail his judgment regarding why knee fusion is the most suitable solution for the specific situation of the patient. If the patient is not yet convinced to have the procedure, he/she should be introduced to an external specialist experienced in knee joint revision surgery for a second opinion. If this colleague offers a different treatment option, then the patient can opt for either of the alternatives. For these extremely complex situations, there is still no commonly accepted treatment algorithm; thus, the learning curve is increasing for everyone involved with each additional case.
Once all parties have agreed to have the procedure, the following specifics should be collected, along with the customary clinical examinations:
The type and dimensions of the scar: The patients have all undergone previous surgeries and have compromised soft tissues. Scars and fistulas must be described in the localized findings; preoperative photographic documentation is helpful.
Peripheral pulses: An extensive clinical examination and documentation of the pulses of both legs is indispensable. If there are any abnormalities, Doppler and/or duplex sonography should be performed. If there is evidence of arterial occlusion, fine needle angiography or MR angiography should be added.
Conventional x-rays of the femur and leg in two planes with ruler as gauge and inclusion of the adjacent joints. In cases of preexisting, clinically relevant axial deviation, additional full-length lower extremity x-rays are recommended, also with a ruler. More extensive imaging procedures (CT, MRI) should be reserved for specific situations.
Knee arthrodesis is generally an elective procedure, and thus, significant comorbidities should be clarified and optimized in an interdisciplinary manner. The preparation of blood products is generally unnecessary in cases of external fixator use, and in cases of the intramedullary approach, 2 units of packed red blood cells should be made available.
27.4.1 Advantages of Knee Arthrodesis
Knee arthrodesis offers functionally worse outcomes than a well-fixed, infection-free knee joint endoprosthesis including the distal femur or proximal tibia replacements. There is no doubt of this, which is why it is particularly important to carry out thorough informational interviews as previously discussed. However, knee fusion offers significant advantages compared to an unstable or infected knee endoprosthesis or an amputation. Conway evaluated knee arthrodesis with 70 points on the knee society score, while amputation or failed revision reached less than 50 points. When arthrodesis is performed correctly, the risk of re-infection is significantly lower compared to revision arthroplasty [9, 12, 13]. If a knee arthrodesis leads to bony consolidation, complete hardware removal of external fixator and compression nail is possible. Thus, the risks for revision surgeries or implant-associated infections are eliminated. In our experience, the reinfection rate after the use of a distance arthrodesis (see below) is less than that after a septic prosthetic revision; however, the knee joint arthrodesis module (KAM) remains for the patient’s lifetime.
After knee disarticulation, many patients remain ineligible for new prosthesis and non-ambulatory, and thus, disabled. Pring et al. reported that only 30 % of amputees were ambulatory [14]. In addition, amputees consume some 25 % more energy compared to knee arthrodesis patients [15]. The proportion of patients with persistent pain in the knee is 10 % after the first knee endoprosthesis and increases with each revision. Husted et al. reported on 24 patients suffering peri-prosthetic infections after primary knee endoprosthesis [16]. A two stage prosthetic revision was undergone in 17 cases. The infection was eliminated in 15 cases, but 8 suffered persistent pain. After placement of a knee arthrodesis, however, improvement of pain symptoms can be achieved in over 90 % of patients [10].
Generally, functional outcome is improved in relation to younger age and better mobility and thus better bone quality of the patient at the time of arthrodesis.
27.4.2 Disadvantages of Knee Arthrodesis
Functionally, the principal problem with the permanent joint loss is that of sitting in spaces with decreased legroom (airplanes, theater, cinema). The use of small cars can be problematic, as can climbing ladders. Half of patients will require the permanent use of crutches. Walking distance can remain limited. Limb shortening of approximately 1 cm is the goal of surgery; however the leg length difference can turn out to be longer. Compared to healthy persons, the energy cost of walking is increased by approximately 25 %.
Over the further clinical course, increased load of the ipsilateral hip and ankle joints can be assumed. Thus, pre-existing arthritis can emerge or worsen. The loss of function is permanent. Correction of arthrodesis with endoprosthesis placement after the fact is prone to complications and is rarely performed [17].
27.4.3 Alternate Approaches
Alternative treatment options to arthrodesis yield significantly worse functional outcomes. With knee resection arthroplasty, the joint or the endoprosthesis are removed without replacement, and the limb is stabilized with a supporting orthosis. This spares the patient further operative interventions, but the limb remains unstable and non-weight bearing. Another alternative is the permanent placement of a cement space holder, although in our experience this leads frequently to complications. The joint develops a flexion contracture or the space holder can displace and lead to mechanical irritation. For this reason we no longer offer this procedure.
Knee disarticulation or distal femur amputation remain as radical solutions. However, few patients will be eligible for prosthetics, and thus, will be non-ambulatory [13]. Femoral amputations have a 30 day mortality of up to 22 % and should be performed in older patients only in desperate situations, e.g. in cases of uncontrolled, progressive infections [18]. For active, mobile patients, we see an indication for this only when there is loss of sensation in the leg or when a serious, surgically untreatable circulation problem is present.
Currently, as a result of improved implants and operative techniques, alternative therapies are seldom called for in the treatment of “complicated peri-prosthetic infection of the knee.”
27.5 Operative Method
In this section we introduce the alternative operative methods for knee arthrodesis. The surgeon should be familiar with all of these procedures, and should discuss them, including the corresponding advantages and disadvantages, during the information interviews conducted with the patients and their relatives.
27.5.1 External Fixator
The external fixator is the oldest known arthrodesis procedure and was mentioned in its original form already by Hippocrates in 400 B.C. It remains an installment of septic surgery and is the workhorse in the treatment of complicated knee infections with or without implants. It is a soft-tissue sparing implant, that can be applied in a minimally-invasive manner and allows re-reduction and/or repositioning at any time. Depending on the type and extent of bony defect present, it can be mounted with either a bi- or tri-planar joint bridge. The fixator can be dynamized without anesthesia, and hardware removal can be performed in an ambulatory setting. If the underlying biomechanical principles are respected during implantation, the placement is simple and uncomplicated, and proceeds remote from the infection. This implant is unrivaled in its reasonable price.
27.5.1.1 Indications
In our opinion, the external fixator is indicated for knee arthrodesis when there is relatively little bony loss, the bone quality will allow stable anchoring of a pin for 12 weeks, and the patient is capable of active participation in care. Problems can be expected when these conditions are not fulfilled, for example: If there is high-grade osteoporosis, if the patient is not capable of observing complications arising from a placed fixator, or if direct contact of the resected surfaces of the femur and tibia cannot be established because of extensive bony loss.
27.5.1.2 Outcome
The consolidation rate of knee arthrodesis using an external fixator is high with active, mobile patients with good bone quality. In such cases, the healing rate is up to 90 %. However, it is for these patients that an external fixator is a great imposition, since the fixator impedes the patients in many areas of daily life, requires daily care, and is perceived as unpleasant. In cases of older, less mobile patients with poorer bone quality, the treatment results are unsatisfactory. The consolidation rate is under 50 %, pin infections and/or loosening are more common, and the daily care by external personnel is difficult to organize.
Thus, we use the external fixator for a limited number of arthrodeses, and instead use it as a temporary immobilization in cases of pronounced peri-prosthetic infections prior to a later procedure with an intramedullary device.
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