(a–e) Intraoperative views obtained during the first surgical stage in the patient before removing the implant (a) and after implant removal (b). (c) Extracted components. (d) Trial articulating spacer. (e) Final articulating spacer implanted with gentamicin-loaded cement
The presence of previous incisions may influence the approach. Whenever possible, the previous incision should be incorporated to the new incision. In the presence of several prior incisions, the most lateral one should be used as most of the blood supply to the skin comes from the medial side [1, 2]. Parallel longitudinal incisions should be avoided as they could result in skin necrosis if the distance between them is less than 7 cm. If only part of the previous incision can be used, the angle between the two incisions must be of at least 60° so as to prevent skin damage in the area of the posterolateral corner. Previous transverse incisions do not entail a risk for skin devascularization, which means that they can be crossed by the new incision or they may be ignored during revision surgery.
Exposure of the knee joint and of the primary prosthetic components during rTKA is often complicated by a stiff, thickened, and fibrotic capsule and by the synovitis observed in the majority of cases. Painless flexion contractures and the infection itself, as well as wear particles and repeated trauma in cases of unstable prostheses, tend to result in stiffness and loss of elasticity of the periarticular structures and often make knee exposure more difficult. For this reason, the surgeon must conduct a thorough and systematic resection of the structures that constrain the joint, which include the fibrosis, the synovial tissue, the suprapatellar bursa, and both the lateral and medial recesses. The surgeon must possess an in-depth knowledge of the knee’s anatomy in order not to damage key structures for knee stability (collateral ligaments and stabilizers of the extensor mechanism).
Several extended approaches have been described for revision of TKA in the setting of a stiff knee. Although in most cases a thorough resection of fibrotic tissue is enough to afford appropriate exposure of the prosthetic components, the surgeon should be familiar with such approaches as they facilitate extraction of prosthetic components, soft tissue balancing, bone defect reconstruction, and long stem implantation in complex cases involving stiff knees, reducing surgical time and associated complications .
18.104.22.168 Anteromedial Approach
This is the surgical approach used in over 90% of revision TKA procedures. The incision is performed en bloc, without dissecting the subcutaneous tissues to minimize the risk of necrosis, and must be continued proximally to allow adequate exposure of the prosthesis. Distally, the incision should extend to about 7 cm below the inferior pole of the patella. All intra-articular tissues (synovial membrane, fibrotic tissue, and joint capsule) are thoroughly resected until healthy tissue is encountered. The knee must be progressively flexed until 100° of flexion are obtained, which in most cases requires meticulous soft tissue release. Knee flexion accompanied by external rotation of the tibia relaxes tension from the extensor mechanism and reduces the risk of patellar tendon avulsion, which is one of the most dreaded complications at this stage of the procedure. Medial release should continue posteriorly to the posteromedial corner of the tibia. In the event of persistent stiffness, the lateral retinaculum must be released to allow lateral eversion or displacement of the patella. Removal of the polyethylene insert facilitates exposure of the components and should be performed routinely at this point prior to deciding whether additional soft tissue releases are necessary.
22.214.171.124 Anterolateral Approach
This approach must be selected when there is a previous lateral incision and in cases with valgus deformities, flexion contracture, or external tibial torsion. The approach is performed from the vastus lateralis, lateral to the quadriceps tendon, and continues along the lateral border of the patella down to the tibial tuberosity.
126.96.36.199 Extended Approaches
In cases where, in spite of a careful soft tissue release, 100° of knee flexion or an eversion or lateral displacement of the patella cannot be obtained without excessive tension, the surgeon may extend the approach proximally to the quadriceps tendon or perform a tibial tuberosity osteotomy. Proximal techniques appear to be the preferred option for the majority of authors .
The arthrotomy is extended proximally and distally at an angle of 45° up to the border of the vastus lateralis . This technique does not require any changes to the rehabilitation protocol following the revision procedure and allows immediate active mobilization.
V-Y Quadriceps Turndown
This extended approach may be considered when a quadriceps snip is not sufficient. It consists in continuing the quadriceps snip arthrotomy through the vastus lateralis tendon and the lateral retinaculum up to the superior portion of the iliotibial band, thus preserving the vascularization of the lateral geniculate artery. This approach entails a postoperative restriction of knee flexion for 4–6 weeks and may induce a knee extension lag. For that reason, it is only used in very specific cases where lengthening of the extensor mechanism is required.
Tibial Tuberosity Osteotomy
An 8–10 cm-long osteotomy is performed on the medial side, leaving a bone bridge on the lateral cortex and fixing the osteotomy posteriorly with K-wires and a screw. To carry out this osteotomy, the anteromedial incision must be lengthened exposing 10–15 cm of the proximal tibia. A saw must be used from medial to lateral, creating a 10-cm-long, 2-cm-wide, and 1-cm-thick bone fragment. The lateral part of the osteotomy is completed with a chisel. The fragment is elevated subperiostically, taking care to spare the periosteum and leaving the muscle attached to the fragment. Flexion, extension, and weight bearing are allowed from the second week post-op. This technique has been associated with a large number of complications, including fractures of the bone fragment, delayed healing, and loosening of the fixation devices. In contrast to the V-Y quadriceps turndown, tibial tuberosity osteotomy results in low postoperative patient satisfaction and a lower postoperative range of motion. However, the V-Y quadriceps turndown tends to give rise to a significant knee extension lag .
19.2.2 Prosthetic Component Removal
Removal of the prosthetic components may be challenging. Care must be taken to preserve as much bone as possible and avoid a fracture, which could compromise reconstruction of the knee during the revision procedure. Multiple instruments can be used to successfully remove a prosthetic component such as osteotomes, a Gigli saw, chisels, powered instruments (saws, reamers, etc.), and ultrasound devices, which are particularly useful for cement removal .
The majority of present-day prostheses come with specific removal instruments that contribute to minimizing bone destruction when the prosthesis is extracted. Prosthetic components must be removed in a predetermined sequence: the first component to be extracted is the polyethylene insert, followed by the femoral component. The last component to be removed is the tibial component. There is no consensus on the advisability of revising the patellar component if the latter is not loose or if there are no clear signs of abnormal wear. In these cases, the short- and medium-term results of patellar component retention are similar to those of patellar component retention .
In prosthetic systems with an all-poly tibial component (with no metal tray), the all-poly tibia must be the first component to be removed. The prosthesis-cement interface should be approached with an oscillating saw and chisels.
In cemented components, the cement-prosthesis interface should be approached first, thereby preserving as much bone stock as possible for the subsequent reconstruction.
With stemmed components, ease of removal usually depends on the type of stem used and the firmness of the fixation achieved. At times, it is possible to remove the main body or the tibial or the femoral component first and leave the removal of the stem for later. In general, extraction of well-fixed cemented stems and some rough and porous-surfaced cementless stems may prove extremely challenging for the surgeon, making it necessary to resort to instruments specifically designed to remove hip prosthetic stems and to techniques such as a Wagner-type osteotomy.
19.2.3 Articulating Spacers and Antibiotic-Loaded Cement
Once the components and the cement have been removed, and the joint has been prepared by meticulous debridement of nonviable soft tissues, aggressive synovectomy, and careful reaming of the canal, an articulating spacer with antibiotic-loaded cement is placed in the surgical site, and the skin is closed until the infection has resolved and the second surgical stage can be performed (Figs. 19.2 and 19.3).
(a–b) Anteroposterior (a) and lateral (b) knee radiographs of the patient of Fig. 19.1 following the first surgical stage. The image shows the articulating spacer implanted during the first surgical stage
(a–b) Intraoperative view of the same patient of Fig. 19.1 obtained during the second surgical stage and before (a) and after implantation of the new prosthesis (b). A rotational hinge prosthesis was implanted
The cement used to fix the spacer must be loaded with antibiotics. The antibiotics may be added either during the manufacturing process or by the surgeon in the operating room. Although antibiotic-loaded cement is useful in preventing infection, the amount of antibiotic it contains is usually insufficient to treat an established infection. The antibiotic should ideally be water soluble and thermally stable to withstand the exothermic reaction generated during cement polymerization, be active against bacterial pathogens, possess an extended release profile, and show little local toxicity. Additionally, it should be selected on the basis of the results of preoperative cultures and should cover the most common nosocomial pathogens (empirical treatment).
The most frequently used antibiotics are aminoglycoside antibiotics (gentamicin and tobramycin) although the use of vancomycin is becoming increasingly widespread as it covers gram-positive bacteria as well as methicillin-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). Although there is no consensus on the amount of antibiotic needed for a 40 g bag of cement, some series suggest that the required dose ranges between 2 and 5 g of gentamicin, 2.5–9.5 g of tobramycin, and 3–9 g of vancomycin . Ceftazidime is also a useful antibiotic as it covers both gram-positive and gram-negative bacteria, as well as Pseudomona.
Spacers can be classified into static or dynamic, depending on whether they allow joint motion between the first and second surgical stages. Both contribute to preventing instability, pain, and soft tissue contractures and maintaining the joint space until implantation of the new prosthesis. Static spacers are only indicated in cases of soft tissue involvement or severe bone defects. In these cases mobility is restricted as a result of severe joint instability, which means that the use of articulating spacers is contraindicated .
Dynamic (articulating) spacers allow greater knee range of motion during the first and second surgical stages, are associated with the same infection control rate as static spacers , and, according to some studies , allow a greater arc of knee motion following the second surgical stage. Three types of dynamic spacers have been described.
188.8.131.52 Cement-on-Cement Spacer
These spacers may be produced by a manufacturer or be custom-made by the surgeon intraoperatively using molds of variable sizes or shaping them using the explanted components as a model. These spacers have demonstrated infection resolution rates of 80–100% in different series. Complications such as spacer subluxation or breakage are uncommon. Although placement of these spacers tends to be straightforward, care must be exercised to ensure correct orientation of the femoral component so as to minimize the incidence of spacer breakage.
184.108.40.206 Cement-on-Polyethylene Spacer
This kind of spacer consists of a handmade cement femoral component and a stemmed all-poly tibial component. The infection control rate for this type of spacer has been reported to be in excess of 90% .
220.127.116.11 Metal-on-Polyethylene Spacer
This category includes a wide range of options that go from using the re-sterilized retrieved femoral component with a new polyethylene insert , both fixed with antibiotic-loaded cement, to using the PROSTALAC system , which consists of a femoral component with a stainless steel articulating surface and a posterior-stabilized all-poly tibial component. The PROSTALAC system exhibits infection control rates, ranging between 88% and 95% in the different series. Disadvantages of this kind of spacer include its relatively poorer infection control potential and its higher cost.
Few studies exist that compare the different kinds of dynamic spacers. In a comparison of cement-on-cement vs. metal-on-polyethylene spacers, Jämsen et al.  obtained a higher Knee Society Score (KSS) and a shorter first-stage operative time in patients with a metal-on-polyethylene spacer. Nonetheless, no significant differences were observed following the second surgical stage between the groups as regards knee range of motion.
19.3 Patient Management Until the Second Surgical Stage
19.3.1 Intravenous Antibiotic Treatment
Insall  reported that a period of approximately 6 weeks of intravenous (IV) antibiotic treatment must precede the second surgical stage. However, the length of this treatment period has been called into question as it may increase the cost of hospitalization, exacerbate the toxic effect of antibiotics, and aggravate bacterial resistance to commonly used antibiotics. As periarticular tissue receives little vascular supply in the presence of periprosthetic infection, delivery of systemic IV antibiotics to the joint may prove challenging. The use of spacers fixed with antibiotic-loaded cement tends to be effective as the antibiotic is released at the infection site and bactericidal activity lasts several months. Several studies on the effect of short-course (2–3 weeks) intravenous antibiotic therapy [15, 16] have shown infection resolution rates similar (>90%) to protocols based on long-term IV antibiotic therapy. Few studies compare both regimens (short vs. long) of systemic antibiotic treatment in revision TKA. Hsieh et al.  compared a 1-week vs. a 6-week regimen IV treatment in hip revision surgery and found no significant differences regarding infection control in both groups. However, length of hospital stay, cost, and nephrotoxicity were higher in the longer regimen.
A short (usually 2-week) course of broad-spectrum IV antibiotics can be used. Once the causative pathogen has been identified through intraoperative cultures, oral therapy is instituted on the basis of an antibiogram following consultation with the multidisciplinary team, including microbiologists and infectious disease physicians. Antibiotic treatment is completed after hospital discharge until C-reactive protein (CRP) and ESR (erythrocyte sedimentation rate) levels have decreased and clinical signs of infection have disappeared, which normally occurs after 4–6 weeks. When that happens, antibiotic treatment must be discontinued, and a 2-week clearance period must be observed before the second surgical stage. These indications may vary according to the patient’s immune status, the condition of the soft tissues, and the type of causative organism. For example, in immunocompromised patients, or those with large fistulas or virulent microorganisms such as methicillin-resistant Staph aureus, the duration of systemic antibiotic treatment must be extended, and the second surgical stage deferred until resolution of the infection can be ascertained or a first stage repeated.