Knee arthroplasty after fracture about the knee has been shown to carry a higher risk of infection [3–5, 25–27]. This may be due to a damaged soft tissue envelope resulting from the original injury and/or open reduction and internal fixation exposure or to colonization of hardware, especially in the case of external fixators. Knee arthroplasty patients who have had prior infections following tibial plateau fixation are four times more likely to require additional procedures compared to patients who did not have a prior infection [27].

The preoperative work-up should include laboratory tests for markers of infection (complete blood count, C-reactive protein, and erythrocyte sedimentation rate) [1]. An aspiration of the knee should be obtained and the specimen sent for Gram stain, culture, and sensitivities [28]. During the total knee replacement operation itself, intraoperative Gram stain, intraoperative frozen section, and culture may also be useful. If there is a high index of suspicion for infection at the time of surgery, it may be appropriate to perform a staged primary total knee replacement with the first stage consisting of a thorough debridement of the knee, including making the definitive bone resections for the arthroplasty. The implantation of the prosthesis is delayed until the presence of infection in the knee tissue is resolved. During the first stage, the initial distal, anterior, and posterior femoral bone resections are performed. The proximal tibial resection and posterior patellar resection are also done, and an antibiotic-impregnated acrylic spacer block is inserted . This procedure serves as an aggressive debridement since the articular surfaces are resected at this stage. Finishing resections such as femoral chamfers and tibial stem preparation are completed during the second stage when the prostheses themselves are implanted with antibiotic-impregnated cement. In the authors’ experience, considerable success has been achieved in treating patients at high risk in this way. Implantation of the knee prostheses may be done as early as 1 week after this first stage if the intraoperative culture results are negative. However, if they are positive, implantation is delayed for 6 weeks or more, while the infection is treated with an organism-specific course of parenteral antibiotics. This scenario is similar to the two-stage treatment of an infected total knee replacement. Antibiotic impregnated cement is advised for the second stage, even if there was no evidence found of an active infection .

In addition to a routine series of radiographs of the knee, it may be necessary to obtain additional imaging such as a full-length standing anteroposterior radiograph or CT scan to clearly define any deformity resulting from the fracture [7]. A technetium diphosphonate bone scan, gallium scan, or magnetic resonance imaging (MRI) may be useful for localizing infection if there is a high suspicion for its presence. These scans are particularly suggested in cases in which numerous operative procedures were performed or cases in which the patient had a prolonged, complicated course of treatment. The value of preoperative MRI is controversial. However, metal artifact reduction sequences can minimize the effects of retained hardware on image quality. MRI scans can evaluate the extent of intra-articular injury for acute fractures, and they can assess both acute and chronic injuries to periarticular ligaments [1, 29]. CT scans are useful in the setting of acute fracture to define the degree of intra-articular comminution and to assist making the decision between internal fixation and immediate arthroplasty.

Full-length standing radiographs are important for preoperative planning to determine the possible need for corrective osteotomy [7]. This is particularly important if there is a significant malunion present that may affect the overall alignment of the knee, and the deformity can be multiplanar (Fig. 23.1). Cross-sectional imaging may best define the deformity in all three planes and identify nonunions. Biplanar slot radiography is a new imaging modality that produces simultaneous orthogonal radiographs. Compared to CT, the images are acquired with the patient standing, the radiation dose is significantly reduced, and three-dimensional surface models (versus volumetric rendering) of bony anatomy can be created [30, 31].

The soft tissue envelope may be compromised either as a result of the initial injury or as a result of subsequent surgeries. An effort should be made to incorporate old incisions and to avoid large subcutaneous tissue flaps, if possible. If tissue flaps must be created, they should be thick and deep to the fascial plane. In the case of multiple incisions, the most lateral incision that is practical should be used [3], since the vascular supply to the skin anterior to the knee is primarily derived from the medial side [1]. If there are old incisions that cannot be used practically, then it may be necessary to adjust the incision medially or laterally to increase the width of the skin bridge; the minimum recommended skin bridge is 6 cm. Hockey stick incisions and transverse incisions may present a particular concern. In general, an incision can be crossed at right angles but should not be crossed acutely (≤60°). Incisions older than 10 years probably can be ignored.

If there are particular concerns about the soft tissue envelope, the surgeon may perform a delay procedure, in which only the skin incision and soft tissue dissection is performed, and the wound is closed. The healing of this incision is then monitored for 2 weeks to determine the presence of eschar formation and to permit neovascularization of the soft tissue flaps . If skin necrosis develops, then separate vascularized soft tissue coverage grafts would be needed prior to or at the time of the knee replacement stage [3, 32]. Similarly, if the soft tissue envelope over the tibial tubercle or patellar tendon appears tenuous, preemptive flap coverage may be considered, and total knee arthroplasty can be performed after flap maturation and recovery of knee range of motion [1]. A gastrocnemius muscle flap or vascularized free myocutaneous flap may be used in this situation to obtain healthy soft tissue coverage [4]. If a patient has received prior soft tissue coverage procedures (e.g., skin grafting or muscle flap transfer) or vascular repair, respective consultations with a plastic surgeon or vascular surgeon may be prudent [1]. Intraoperative angiography can be used to plan the surgical incision and to assess wound closure, which may help mitigate the risk of wound necrosis and other wound-related complication [33].

In situations in which the skin is adherent to the underlying extensor mechanism, tissue expanders may be inserted to stretch the skin and create neovascularized environment before the primary total knee replacement [34]. As in revision situations, it may be necessary to extend the original incision proximally and distally to more clearly define the subcutaneous tissue planes. This enables the surgeon to find the proper depth of the plane between the extensor mechanism and subcutaneous adipose tissue or scar.

Scar tissue and bone deformity or overgrowth may make exposure of the knee quite difficult. In general, the surgical approach should protect the patellar tendon and collateral ligaments. Adhesions in the suprapatellar pouch, medial and lateral gutters, and around the extensor mechanism are excised first. A standard medial soft tissue peel is performed off the proximal medial tibia, extending posteriorly past the mid-coronal plane. The patella does not need to be everted but can be retracted laterally. Knee flexion, cruciate ligament release, release of the anterior horns of both menisci, and external rotation of the tibia should be attempted next. If these steps do not provide adequate exposure, the surgeon may need to consider techniques such as a quadriceps snip, lateral retinacular release, V-Y quadriceps turndown, or tibial tubercle osteotomy to facilitate exposure [1, 25, 35]. The quadriceps snip is generally the preferred choice due to its relative simplicity and ability to be extended. Furthermore, it does not alter postoperative rehabilitation. It is performed by extending proximally and laterally at a 45-degree angle from the standard medial arthrotomy that is performed during most primary replacement surgeries. Early lateral retinacular release is performed when there is difficulty with lateral exposure or in cases in which there is considerable scarring from a previous lateral incision or adherent scar along the lateral femoral gutter. A V-Y turndown can be created by extending the lateral retinacular release proximally into the medial parapatellar arthrotomy. A turndown risks patella and patellar tendon devascularization and a postoperative extensor lag. Thus, it should be employed judiciously, if ever, and tibial tubercle osteotomy is typically preferred over a V-Y turndown [36]. This technique is particularly recommended if a previous tibial tubercle osteotomy was used during the initial approach for open reduction and internal fixation of a tibial plateau fracture. The osteotomy should include the entire patellar tendon insertion, and the fragment is typically 8–9 cm long, 2 cm wide, and 5–10 mm deep. A lateral soft tissue “hinge” should be preserved to protect the blood supply to the fragment, and fixation can be performed with screws or wires [1].

In rare situations, skeletonization of the distal femur may be required if there is substantial preoperative ankylosis. In these latter situations, the surgeon should be prepared to use prostheses with further built-in constraint, such as a constrained condylar knee, or total condylar III implant. In extraordinary cases of severe distal femoral malunion or severe proximal tibial condyle disruption and bone loss, constrained rotating hinge designs may be required .

Intraoperatively, careful attention should be paid to implant sizing, since oversized implants can lead to pressure necrosis of the overlying skin. If soft tissue coverage seems marginal during surgery, postoperative range of motion should be delayed several days in order to monitor the wound. At-risk wounds with persistent drainage or marginal necrosis may require early operative debridement and possible myocutaneous flap coverage [1].

Fixed flexion and valgus deformities place the peroneal nerve at risk for neuropraxia postoperatively, and at least one large study has confirmed that posttraumatic arthritis patients are at increased risk for peroneal nerve palsy after knee arthroplasty [37]. Maintaining the knee in slight flexion postoperatively may mitigate the risk for peroneal palsy in these cases. For severe, chronic deformities, primary peroneal neurolysis may be considered [1].