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onarthrosis in a patient who has had a fracture about the knee may result from direct injury to the articu- lar surface at the time of fracture or it may result sec- ondarily from altered mechanics across the knee with associated ligament injuries and bony deformities. It may be incidental to the fracture that has occurred in the metaphyseal or diaphyseal region of the knee. Also, sec- ondary arthritic deterioration may develop from hard- ware penetrating into the joint.Total knee arthroplasty in these patients presents an array of technical challenges to the surgeon. Damage to the soft tissue envelope of the knee makes exposure more difficult and may lead to healing problems and stiffness due to the associated scarring that may develop from the fracture itself or from the extent of surgery required to initially fix the fracture.1There is a greater risk of infec- tion due to soft tissue envelope compromise and possible bacterial colonization of bone or hardware.1,2Bone loss, bone deformity, and fracture nonunion can present prob- lems that may require augments, long-stemmed implants, or even an osteotomy to solve.3Furthermore, issues relat- ing to the patella present their own challenges.1Finally, soft tissue balancing of the knee can be difficult particu- larly if the collateral ligaments have been damaged.
Although primary total knee replacement is not infrequently performed for post-traumatic osteoarthritis secondary to fracture, the technical challenges these clin- ical cases offer demand techniques that are more fre- quently seen during revision total knee replacement. The only significant difference between primary total knee replacement for arthritis involving an intra-articular or extra-articular fracture and revision surgery is that the surgeon may have more bone stock at his or her disposal when performing the reconstruction. Only in severe intra-articular tibial plateau or femoral condylar fractures could there be extenuating circumstances in which there
is extraordinary bone loss secondary to the severity of the fracture (Figure 21-1).
PREOPERATIVE CONSIDERATIONS
Infection Risk
Knee arthroplasty after fracture about the knee has been shown to carry a higher risk of infection.1,2,4This may be due to a damaged soft tissue envelope resulting from the original injury and/or open reduction and internal fixa- tion exposure or to colonization of hardware, especially in the case of external fixators. The preoperative workup should include laboratory tests for markers of infection (complete blood count, C-reactive protein, and erythro- cyte sedimentation rate). An aspiration of the knee should be obtained and the specimen sent for Gram’s stain, culture, and sensitivities.5During the total knee replace- ment operation itself, intraoperative Gram’s stain and culture may also be useful. If there is a high index of sus- picion of infection at the time of surgery it may be appro- priate 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 cuts 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 is also done and an antibiotic-impreg- nated acrylic spacer block is inserted. This procedure basi- cally serves as a very aggressive debridement since the articular surfaces are resected at this stage. Finishing resections such as femoral chamfers and tibial stem preparation are done during the second stage when the prostheses themselves are implanted with antibiotic 237
Total Knee Arthroplasty After Fractures About the Knee
Russell E. Windsor and William L. Walter
impregnated cement. 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, implan- tation is delayed for 6 weeks or more while the infection is treated with an appropriate course of parenteral or oral antibiotics. This scenario is similar to the two-stage treat- ment of an infected total knee replacement. Antibiotic impregnated cement should be used during the second stage even if there was no evidence found of an active infection.
Imaging
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.3 A Technetium-diphosphonate bone scan or gallium scan may be useful for localizing infection if there is a high suspicion for its presence. These scans are par- ticularly suggested in cases in which numerous operative procedures were performed or cases in which the patient had a prolonged, complicated course of treatment.
The full-length standing radiographs are important for preoperative planning to determine the possible need for corrective osteotomy.3This is particularly important if there is a significant malunion present that may affect the overall alignment of the knee. Malunion may make it difficult or impossible to use intramedullary instrumen- tation to gain appropriate alignment of the distal femoral or proximal tibial resection. Hence, extramedullary align- ment guides should be used to obtain a correctly aligned resection.
A good rule for handling malunion situations is to mark out a line on the standing radiograph of the planned resection that would provide the correct mechanical axis.
If there is the risk of violating the collateral ligament insertions on the femur, then a corrective osteotomy should be contemplated. If osteotomy is required, it is usually performed at the site of the original malunion.
Otherwise, a swan-neck or curved bow deformity would be obtained because of the malunion site and the osteotomy site working together to create this anatomic relationship.
EXPOSURE
Soft Tissue Envelope
The soft tissue envelope may be compromised either as a result of the initial injury or as a result of subsequent sur- geries. An effort should be made to incorporate old inci- sions if possible. In the case of multiple incisions, the most lateral incision that is practical should be used.1If there are old incisions that cannot practically be used, then it may be necessary to adjust the incision medially or laterally to increase the width of the skin bridge.
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 obliquely. Incisions older than 10 years can probably be ignored. If there are particular concerns about the soft tissue envelope, the surgeon may perform the skin inci- sion only and delay the definitive procedure. The healing of this incision can be monitored and if necessary the definitive procedure may be performed with the cover of a vascularized flap.1,6
A delay procedure only may be performed to determine the healing potential of the wound. During this procedure, the incision and underlying soft tissue dissec- tion is performed and the wound is closed. Healing is observed for a 2-week period to determine the presence of eschar formation and to permit neovascularization of the soft tissue flaps. If skin necrosis develops, then sepa- rate soft tissue coverage grafts would be needed prior to the knee replacement implantation stage. A gastrocne- FIGURE 21-1. Anteroposterior radiograph showing a medial
tibial plateau fracture with severe depression of the medial tibial condyle.
mius muscle flap or vascularized free myocutaneous flap may be used in this situation to obtain healthy soft tissue coverage.2
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.
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. The surgeon may need to consider techniques such as a rectus snip, lateral retinacular release, or tibial tubercle osteotomy to facilitate exposure.4,7The rectus snip is generally the pre- ferred choice due to its relative simplicity and ability to be extended. It is performed by extending proximally and laterally the standard medial arthrotomy that is per- formed during most primary replacement surgeries. Early lateral retinacular release is performed when there is dif- ficulty with exposure and eversion of the patella or in cases in which there is considerable scarring from a pre- vious lateral incision or adherent scar along the lateral femoral gutter. Tibial tubercle osteotomy is used when patellar eversion is still not possible even with the use of the quadriceps snip. This technique is particularly rec- ommended if a previous tibial tubercle osteotomy was used during the initial approach for open reduction and internal fixation of a tibial plateau fracture.
Since there is frequently scar tissue present from pre- vious open reduction procedures, it may be necessary to recreate the medial and lateral gutters. With this tech- nique, the scar tissue adhesions that have formed between the quadriceps mechanism and femur may be fully excised. 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 con- straint, 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.
REMOVING HARDWARE
Removal of hardware is not mandatory unless the pres- ence of the hardware interferes with instrumentation, placement, or function of the arthroplasty. A longer inci-
sion and greater exposure are usually required to remove hardware. It is only necessary to use the original medial or lateral incision if it is clear that the implant is not reachable by the standard midline incision that will be used during the replacement. Often, buttress plates affixed to the lateral tibial plateau may be simply removed by entering the anterolateral muscle compartment through and extended midline incision. The soft tissue envelope should be assessed preoperatively to determine the likeli- hood of success. Obese patients may have enough adipose tissue coverage to permit easy access to the lateral side of the joint by further lateral dissection through the midline incision. A separate incision may be necessary if instru- mentation can not be easily applied to the implants through the midline incision. Use of a single midline inci- sion simplifies the exposure and decreases the risk of skin flap necrosis that may arise as a result of the presence of two freshly made incisions (Figure 21-2).
FIGURE 21-2. Medial and lateral plates may be removed from the midline incision used during the total knee replacement. Also, these plates may be removed as a separate procedure.
Nevertheless, as a general rule, all hardware should be removed unless this procedure unnecessarily places the operative environment in danger of necrosis or additional bone loss by difficult extraction techniques. If there is a suspicion of infection, the hardware may be removed during a separate stage and a sample of deep tissue can be obtained and sent for frozen section, routine pathol- ogy, culture, and sensitivity. A separate removal stage is generally reserved for large implants that may extend far away from the knee joint itself.
Proximal intramedullary femoral nails that extend to the distal metaphysis would interfere with the use of intramedullary alignment instrumentation. In this case, extramedullary alignment instruments should be consid- ered. The nail should only be removed if there is little risk of disrupting the proximal aspect of the femur.
BONE LOSS
Contained defects of the tibial plateau or femoral condyles can be filled with morsellized bone graft that can usually be obtained from the resected bone.1However, it may be necessary to add a stem to the component to add stability to the construct if there is still proximal discon- tinuity that mandates additional fixation.8If there is an uncontained tibial or femoral defect, then augments and a stems should be added to the component. Frequently, it may be necessary to combine grafting with the use of metal augmentation.
Larger defects may require the use of a distal femoral or proximal tibial replacement that is used for the treat- ment of tumor excisions in this area. Bulk allografts may be also used in these situations and the surgeon must weigh the risk and benefits of allograft incorporation, sta- bility, and long-term survivorship. This decision-making process is somewhat age-dependent, as allograft usage would be considered in the younger patient with better bone stock and large constrained, distal femoral or prox- imal tibial replacements are better suited for the older patient with more compromised bone stock.
BONE DEFORMITY
Malunion or nonunion may result in deformity of either the tibia or the femur. This may be in the coronal plane (varus/valgus), sagittal plane (flexion/extension), the axial plane (rotation), or any combination of these. If the deformity is not corrected, the altered mechanics that may have caused the arthritis could lead to early failure of the device.9,10
Intra-articular deformity (deformity within the col- lateral ligaments) may be corrected with the bone cuts or may require augments; however, extra-articular defor- mity (deformity proximal to the femoral origin of the col- lateral ligaments or distal to the tibial insertion) may need to be corrected by osteotomy3,10(Figure 21-3).
NONUNION
Open reduction and internal fixation of nonunited frag- ments with screws or plate and screws may be possible at the time of arthroplasty.1If implant stability is compro- mised, a stem may be added to a femoral or tibial com- ponent. Long stemmed prosthesis may be appropriate to span a transverse nonunion. Bone graft, bone graft sub- stitutes, and adjuvants can also be considered.
For proximal tibial nonunions or femoral condylar nonunions, the initial resection of bone may be signifi- cant enough that the nonunited segment is almost com- pletely excised. In these cases, simple metal augments may be used. The resected bone, however, serves as an excel- lent source for autogenous graft material and is packed around a persistent non-union site. The combination of stem extensions, fixation of the nonunited fracture frag-
A B
FIGURE 21-3. (A and B) Anteroposterior and lateral x-ray of a midshaft femoral malunion. This patient underwent corrective osteotomy as a separate procedure, prior to the performance of a total knee replacement.
ments with a cemented or porous implant and autologous bone graft is quite successful in bringing about union of the fracture site and handling of the arthritic condition (Figure 21-4).
Protected weightbearing may be necessary based on the overall stability of the reconstruction. However, in most cases, the postoperative rehabilitation course pro- gresses uneventfully.
ACUTE FRACTURE
In the majority of cases a fracture about the knee should be treated by open reduction and internal fixation as appropriate. Arthroplasty is then performed later if and when arthritis has developed. However, if there is poor prospect for normal joint function (in the case of preex- isting arthritis or significant chondral injury), particularly in an elderly or frail patient, arthroplasty may be appro- priate at the time of the acute fracture.11,12
Certainly, open reduction and internal fixation should be considered first, as every attempt should be made to preserve bone stock. If post-traumatic arthritis occurs after the fracture has healed, total knee replacement can
be performed in the area where the fracture has united.
Nevertheless, in the elderly, fracture treatment may dictate partial or nonweightbearing, or prolonged bed rest that may pose the threat of venous thromboembolic disease or pulmonary embolism. In this case, it may be more prudent to consider primary knee replacement, especially when treating intra-articular fractures. The benefits include quick rehabilitation and early mobiliza- tion without the need for prolonged protected weight bearing. In general, all attempts should be made to pre- serve the natural knee anatomy. However, there may be extenuating circumstances when total knee replacement is the more prudent option.
PATELLA CONSIDERATIONS
Care should be taken to avoid rupture of patella tendon at the time of surgery by using techniques previously mentioned to facilitate the exposure without putting undue tension on the patella tendon.1If the exposure is difficult, it may be necessary to secure the patella tendon to the tibial tubercle with a bone pin. There is a higher risk of delayed rupture of the extensor mechanism in this
A B
FIGURE 21-4. (A and B) Preoperative and postoperative x-ray of a supracondylar femur fracture.
The resected one was used as autograft. An intramedullary stem extension was utilized to obtain control of the fracture.
patient group that may occur during extensor mechanism eversion and flexion of the knee, particularly in patients who have diabetes or are taking oral steroids.1,2
Fractures of the proximal tibia can result in scarring of the patella tendon and patella baja. Mild cases may require fashioning of a recess in the anterior portion of the tibial polyethylene but more severe cases may require tibial tubercle osteotomy or even an extensor mechanism allograft.
In cases in which a tibial tubercle osteotomy was per- formed to expose a tibial fracture for reduction and inter- nal fixation, the tibial tubercle may progress to nonunion (Figure 21-5). In addition to fixation with screws, this may require bone grafting and bone graft adjuvants and perhaps also reinforcement with a cable or wires. It may be necessary to splint the limb in extension postopera- tively and may compromise overall rehabilitation of the arthroplasty.
Patella fracture if unhealed and not amenable to fix- ation may be treated by simple debridement of prominent bone or by complete patellectomy keeping in mind that extensor strength will be compromised.
SOFT TISSUE BALANCING
Stiffness
Preoperative range of motion may be less than normal in which case the surgeon should expect poorer postopera- tive range of motion, particularly in the case of distal femoral fracture. Some cases require manipulation of the knee in the first 6 to 12 weeks postoperatively.1Extensor mechanism scarring is difficult to release. Extensor mech- anism lengthening is not recommended as secondary quadriceps mechanism weakness may develop despite the possibility of improved flexion. Scar tissue may be excised in the medial and lateral gutters. But, flexion may only be marginally increased if interstitial scarring of the quadri- ceps muscle is present. The vastus intermedius may be lifted off and dissected free from the anterior aspect of the femur.
Stiffness is less of a secondary problem after tibial plateau or shaft fractures. The stiffness that is created is generally intra-articular rather than extra-articular, which is the case in supracondylar femur or femoral shaft fractures.
A B
FIGURE 21-5. (A and B) Preoperative and postoperative radiograph of a knee with a complex femoral fracture that was initially exposed using a tibial tubercle osteotomy. A non-union developed and two attempts at bone grafting and fixation of the tibial tubercle were required before healing occurred. Bone graft adjuvants were required. The large size of the tibial tubercle osteotomy per- mitted ultimate fixation and healing to occur.
Ligament Balancing
If extra-articular deformity is corrected by intra-articular compensatory angular resection, balancing may not be possible. These particular deformities may be more appropriately treated by an osteotomy. Extensive soft tissue release may be necessary at the time of surgery either to correct deformity or for stiffness. Substantial soft tissue release may compromise stability of the knee. Also, ligament injuries, which may result from the original trauma or are secondary to the subsequent abnormal mechanics, may also compromise knee stability. A more constrained device, in conjunction with stems to strengthen fixation may be required. In the most significant cases of severe bone loss and soft tissue scarring, rotating hinged prostheses may be required (Figure 21-6).
REFERENCES
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969–975.
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7. Whiteside LA. Surgical exposure in revision total knee arthroplasty. Instr Course Lect. 1997;46:221–225.
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85-A(6):1062–1065.
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FIGURE 21-6. Radiographs of a patient with a severely com- minuted distal femur fracture and non-union. The distal femoral fragment is underneath the posterior aspect of the proximal frag- ment and it is flexed. The supracondylar screw pulled through the distal fragment as well. A rotating hinge was required due to severe bone loss, deformity and lack of knee ligament stability.
