Surgical complication is defined as “any undesirable, unintended and direct result of an operation affecting the patient, which would not have occurred had the operation gone as well as could reasonably be hoped.” (p. 942)
The rate of complications or adverse events after primary total knee arthroplasty (TKA) ranges from 6.1% to 37.1% depending on geography, economic status, and inclusion criteria. The cost of readmissions and rehospitalizations resulting from complications has reached $7.1 billion.
Initially, classifications of surgical adverse events were developed by general surgeons and later applied to the field of orthopedics. A descriptive list of the 22 most pertinent complications after TKA was created by the consensus of experts.
There are numerous postoperative complications. However, deep periprosthetic joint infection, stiffness, in-stability, and mechanical failure of an endoprosthesis top the list and remain the leading causes of failure after TKA.
The etiology of deep joint sepsis is multifactorial and includes numerous nonmodifiable and modifiable conditions. Acute postoperative wound complications, hematoma formation, postoperative blood transfusions, prolonged hospital stays, and hematogenous disseminations from endogenous and exogenous (e.g., indwelling urinary catheters) sources have been related to the development of deep periprosthetic infections.
Severity of wound problems can range from quickly resolved sanguinous drainage and superficial skin eschars to full-thickness capsular necrosis with exposed endoprosthesis and generalized sepsis.
Postoperative wound drainage is a common problem after TKA because of the close proximity of a bulky implant and naturally tenuous soft tissue coverage. Drainage affects 0.33% to 10% of patients undergoing TKA. The drainage is considered substantial when it soaks more than 2 × 2 cm area of gauze, and lasts more than 72 hours after surgery. Tense subcutaneous hematomas and intraarticular fluid escape through capsular defects that can manifest as relatively benign “rose wine” appearing leakage through slightly dehisced edges of the inferior portion of the surgical wound. In many cases the drainage resolves after spontaneous evacuation of a superficial hematoma; however, it can also lead to backflow implant seeding through direct communication with deep joint space.
Onset of drainage varies from immediate soaking through the dressings in a postoperative area to several hours or days after an increase in physical activity. The classic rule of “no patient who has a draining wound should be discharged from the hospital” has become less relevant as contemporary TKA has moved to outpatient settings. In an outpatient setting the surgeon should provide the patient and visiting nursing personnel with explicit wound care instructions. Substantial wound drainage (as described previously) prompts immediate evaluation in the surgeon’s office, where the wound and the joint are inspected for signs of dehiscence, subcutaneous fluctuating hematoma, and tense hemarthrosis. Moderate amounts of serosanguinous drainage, good approximation of skin edges with minimal necrosis, and presumable good integrity of the capsule indicate nonoperative management with sterile, compressive, absorbent dressings; immobilization in extension; rest; and discontinuation of physical therapy. The efficacy of a novel treatment modality, negative pressure wound therapy, remains unproven; furthermore, it can potentially delay time of surgical débridement.
Manual or ultrasound-guided aspiration of substantial intraarticular and subcutaneous fluid collections is possible under strict aseptic conditions in the medical office or in a radiology suite settings.
Considerations are also given for adjustment or even discontinuation of chemical anticoagulation therapy, but mechanical prophylaxis needs to be continued. Reflexive preventive administration of antibiotics is strongly discouraged because of minimal efficacy and potential association with serious complications such as adverse systemic effects, emerging bacterial antibiotic resistance, and beclouding of deep joint infection.
Drainage related to excessive local bleeding and chemical anticoagulation usually stops within 5 to 7 days. Drainage, lasting more than a week is unlikely to stop and requires surgical intervention to prevent backflow contamination. If left untreated, drainage can be associated with as much as a 50% increase in deep periprosthetic infection rates. Surgical The procedure starts with careful wound exploration, débridement and evacuation of subcutaneous fluid collections. Static and dynamic examination of capsular repair is performed to detect fluid egress through the defects. If the capsule is intact and tense hemarthrosis is present, the knee can be aspirated from outside of the wound to decompress the joint and obtain material for microbiological analysis. In that case the skin is closed over a drain without opening the deep space. If the joint capsule is compromised, the surgeon proceeds further with arthrotomy, synovectomy, tibial insert exchange, implant-bone interface débridement, irrigation, and watertight monofilament capsular closure over a closed-suction drain. Multiple cultures must be collected to detect deep joint infection and guide antibiotic therapy.
Periarticular skin and deep soft tissue necrosis represents another complication after TKA. Etiology includes preexisting skin compromises caused by steroid intake, poor surgical technique, forceful wound retraction, tourniquet usage, and excessive anticoagulation, particularly with vitamin K antagonists. Prognosis and management depend on the depth of necrosis. When skin breakdown is superficial and does not involve the capsule, local wound care with delayed staged excisional débridement remains the standard of care. Deep soft tissue necrosis with capsular involvement requires aggressive surgical débridement and advanced soft tissue coverage procedures, such as local and free musculocutaneous flaps with early plastic surgery involvement.
Patients after TKA retain a 1% to 10% life-long risk of deep periprosthetic joint infection. The majority of complications (60% to 70%) happens within the first 2 years after surgery. The mechanism of late infection remains unclear; however, hematogenous seeding from remote sources has been noted in 6% of patients who have documented bacteremia. Microbiological suspects range from a variety of gram-negative and gram-positive species, but Staphylococcus aureus represents 30% to 40% of remote seeding cases. Traditionally, orthopedic surgery and dental governing bodies advocated for a 2-year-long prophylactic administration of antibiotics before invasive dental and surgical procedures. Recommendations were based on anecdotal data, underpowered cohort studies, and clinical analogy with endocarditis. Broad-spectrum antibiotics from the cephalosporin, aminoglycoside, macrolide, and fluoroquinolone families have been used to cover gram-positive and gram-negative species. For example, oral intake of 600 mg of clindamycin, 2 g of amoxicillin, 2 g of cephalexin, or 800 mg of erythromycin was recommended 1 hour before a dental procedure. Genitourinary and gastrointestinal interventions required intravenous administration of 80 mg of gentamycin or 2 g of ampicillin. Recent evidence from rigorous studies was unable to identify increased risk of deep joint infection after oral procedures; furthermore, preprocedural antibiotic prophylaxis failed to prevent the development of subsequent periprosthetic infection. Currently, the American Academy of Orthopedic Surgeons is unable to recommend for or against the use of oral antibiotics and even encourages providers to discontinue routine prophylaxis before dental procedures. Patients are encouraged to maintain good oral hygiene. Routine antimicrobial prophylaxis is also not recommended before genitourinary or lower gastrointestinal endoscopy. The topic of postoperative prophylaxis with antibacterial agents remains highly controversial, suggesting that management needs to be individualized based on each patient’s needs.
Postoperative Radiographic Analyses
Radiography is an essential part of a follow-up process after TKA. It helps to monitor mechanical well-being of the endoprosthesis and to ensure early detection of complications that are still clinically asymptomatic, such as structural wear and breakdown, loosening with progressive malalignment, instability, and disruption of the extensor apparatus. Radiographic findings are used to modify a follow-up schedule and contemplate preemptive treatment to prevent further mechanical damage and preserve long-term knee function.
A systematic approach is required to detect subtle changes. Ideal postoperative radiographs include three standard views of the knee obtained under weight-bearing conditions: anteroposterior, lateral, and skyline views of the patellofemoral joint. It is also advisable to acquire weight-bearing anteroposterior images of the entire lower extremity (bone-length, hip-to-ankle radiographs) once a year. Weight load unmasks the joint’s alignment, ligamentous laxity, and tibial plastic wear.
Each radiograph is analyzed for implant positioning, structural competence, relationships among different components of the endoprosthesis, maintenance of bone-prosthesis interface, and integrity of the adjacent osseous and soft tissue envelope.
The term “implant positioning” assumes relationships between the mechanical axis of the extremity (alignment) and its corresponding bony structures (bone coverage). The mechanical axis of the extremity is drawn on anteroposterior standing radiographs and ideally should be perpendicular to the joint line and pass through the center of the knee. The relationship to the anatomical axis can also be used if only short anteroposterior radiographs are available. Medial distal femoral anatomical and medial proximal tibial angles should be approximately 95 degrees and 90 degrees, respectively. It is important to remember that these measures can be skewed by the presence of abnormal tibial and femoral curves. Coronal malalignment may result in asymmetrical stress redistribution along mechanical interfaces, increased polyethylene wear, and early component loosening.
Sagittal plane alignment assessment includes analysis of posterior tibia slope and the flexion-extension relationship of the femoral component to the distal aspect of the femur on a lateral radiograph. The femoral component should be in a neutral position, demonstrating appropriate posterior offset to ensure proper balance of collateral ligaments. Hyperextension of a femoral component increases the chances of notching the anterior femoral cortex and may result in a periprosthetic fracture and decreased knee flexion. Hyperflexion can lead to internal impingement between the patella and proud anterior flange of the femur, manifesting as stiffness, knee pain, and locking of the patellofemoral articulation.
The amount of anteroposterior slope of a tibial component depends on the design. Most cruciate-retaining baseplates require 3 to 7 degrees of posterior slope to ensure appropriate femoral roll back, whereas posterior-stabilized tibial trays are implanted with a 0 degree slope to prevent instability of the peg in the femoral box during flexion. Excessive anterior or posterior inclination of a baseplate can lead to instability in extension or flexion.
The prosthesis should follow natural anatomy and sit snugly on cortical surfaces. Undersized components tend to subside, whereas oversized components incline to impinge against soft tissues, leading to pain and stiffness. A small lateral projection of a femoral component is acceptable; however, anterior and medial overhang of a femoral component and posterior overhang of a tibial tray should be avoided.
Patellar alignment directly and indirectly reflects the state of an extensor apparatus of the knee, and it is best evaluated on lateral and skyline views. On a good lateral radiograph, the patella aligns against the middle portion of the femoral component with its inferior pole corresponding to the tibiofemoral joint line. Sagittal stance of the patella in relation to the tibiofemoral joint can be described via various formulae, based on ratios between the length of the infrapatellar tendon and the vertical size of the patella (e.g., Insall-Salvati and Caton-Deschamps ratio). An excessively raised tibiofemoral joint line, scarring of an infrapatellar tendon, or a tear of the quadriceps tendon lead to a low-lying patella (patella baja). Patella baja can affect knee kinematics and result in pain and stiffness, whereas high-standing patella (patella alta) can represent acute or chronic tears of the infrapatellar tendon.
Femoral and tibial components should maintain anatomical relationships with congruent matching through the radiolucent shadow of the polyethylene insert. The patellar component should occupy the medial two-thirds of the patellar bone stump and perfectly match the groove of the anterior femoral flange on a skyline view. Lateral position of the patella predisposes it to maltracking and subluxation and can reflect axial malrotation of femoral and tibial pieces.
Parameters, such as bone-component apposition, presence of radiolucent lines, and condition of a cement mantle, are used to describe the quality of prosthetic fixation and assess stability of a prosthesis.
Ideally, press-fit components should maintain intimate contact with corresponding osseous surfaces without interposed radiolucent lines. In cases of cemented fixation uniform 2 to 3 mm cement penetration into distal femoral and proximal tibial metaphyseal cancellous bone is desired.
Radiographic follow-up after TKA requires weight-bearing anteroposterior, lateral, and skyline views. Radiographs are often obtained at 6 weeks, 3 months, 6 months, 1 year, and then every 2 years after surgery. Radiographic goniometry is performed on standing bone-length radiographs as a reference for future follow-up measurements. Particular attention is paid to maintenance of the alignment, condition of the bone-prosthesis interface and cement mantle, and congruence of tibiofemoral and patellofemoral articulations.
Changes in the alignment can be due to subsidence, mechanical wear of the components, alterations in bony anatomy, or changes in limb rotation compared with previous radiographs. Because of force distribution and asymmetrical density of proximal tibial and distal femoral metaphyseal bones, the tibial component typically subsides into varus and extension whereas the femoral component drifts into more flexed position. Instability of the patellar button manifests as lateral subluxation and asymmetrical rotation of the component along the longitudinal axis, observed on a skyline view, or complete dislodgement of the component.
Ideally, the bone-prosthesis interface is characterized by a fluent transition between opposing surfaces; however, the picture is often complicated by the presence of radiolucent lines beneath components of the endoprosthesis. Their importance depends on size, thickness, and progression. Lines can be complete (surrounding the entire component), partial, stable or progressive. Thin (less than 1 mm) stable lucencies, adjacent to the tibial tray and the stem, are acceptable as long as they appear and remain stable within the first 6 months for cemented implants and the first 2 years for cementless implants. Increase in size and development of focal lucencies thicker than 2 mm may signify aseptic or septic loosening of the component. Assessment of the radiolucent lines remains mostly subjective because current scoring systems are unreliable and overly sophisticated for practical usage.
Tibial insert wear can lead to instability, osteolysis, and mechanical damage caused by direct contact between metallic parts of the prosthesis. The plastic piece maintains a uniform, at least 8-mm thick, radiolucent space between femoral and tibial components. Progressive uniform or asymmetrical narrowing of the joint space represents polyethylene wear. In cases of plastic insert dissociation and fragmentation direct contact between femoral and tibial components occurs, and a shadow of the liner can be seen outside of its normal position.
Tibial, femoral, and patellar bone stocks can be affected by fractures and osteolysis. Osteolysis usually manifests as a radiolucent lesion adjacent to the prosthetic components. Typical locations include the posterior femoral condyles, the edge of a tibial tray or stem, areas around the patellar button, or fixation pegs or screws. Osteolysis is typically associated with polyethylene wear.
Any change in the alignment of the extremity and prosthetic components, progression of radiolucent lines, changes in size and shape of a joint space, or focal lesions in supporting osseous structures should raise concern and warrant correlation with clinical symptoms and further investigation into potential underlying conditions, such as infection or aseptic loosening. The patient requires more frequent follow-up visits or even early revision surgery to avoid irreparable damage to the prosthesis and anatomical structures of the knee.
Patients after TKA carry a small, but nonnegligible, risk of adverse events; therefore they need lifelong follow-up to ensure appropriate function of the endoprosthesis and to prevent complications.
Postoperative Follow-Up Visits
Each follow-up visit requires clinical and radiographic assessment of the soft tissue envelope, knee function, and mechanical integrity of the endoprosthesis. A typical follow-up schedule includes appointments at 2 and 6 weeks, 3 and 6 months, 1 and 2 years, and every 2 years thereafter.
The goal of the first visit is to ensure appropriate progress of wound healing, adequacy of pain control, and compliance with physical therapy. Radiographs are usually not required during the first appointment. Pain usually subsides to a moderate level at this point; however, the patient may still require additional support with oral opioid medications in tapering dosages for another 2 to 4 weeks. The patient usually ambulates with an appreciable antalgic limp using assistive walking devices. The wound must be completely clean and dry with well-approximated and viable skin edges. If any drainage is noticed at the 2-week visit, irrigation and débridement to prevent deep infection should be considered. The knee at this point may be moderately swollen and tender to palpation. Range of motion varies at this first visit, but there should be a minimal flexion contracture (5 to 10 degrees) and flexion to 90 degrees. If flexion is <90 degrees, an earlier second visit at 4 or 5 weeks can be scheduled. Then if there is no further improvement, manipulation under anesthesia should be considered.
The main milestone of a 6-week appointment is to demonstrate at least 90 degrees of flexion and full extension; otherwise, manipulation under anesthesia is recommended during the next 2 weeks. The first set of standard radiographs is obtained during this visit. Long-leg standing imaging is also possible during this visit if the patient is comfortable enough to stand with a fully extended knee.
By 3 months, patients approach maximum active range of motion of the knee and transition to independent ambulation. If the knee remains unacceptably stiff, a surgical intervention can be discussed because improvements are typically minimal past the 3-month mark. The topic of functional range of motion remains debatable; however, in Western culture the achievement of full extension and 110 degrees of flexion is considered as a success after TKA.
Pain and swelling usually completely resolve and the patient’s level of physical activity gradually increases 6 to 12 months after surgery. It is important to notice any negative change in objective or subjective symptoms. Spontaneously increased pain, swelling, a feeling of instability, and change in alignment should raise a red flag and trigger further investigations into the cause of the symptoms.
Return to Previous Activities
The majority of previously employed patients return to work after TKA. The length of disability depends on individual progress of recovery and physical requirements of the job. Patients working sedentary jobs are allowed to return whenever they can safely get to work, usually within 6 weeks after surgery. It is important for patients to be able to periodically elevate the operated extremity and walk around during business hours.
Patients can return to light-duty jobs that require more standing and walking whenever they can ambulate without a limp, which is generally around 12 weeks after surgery.
Patients performing heavy-duty work require longer rehabilitation, up to 6 months after surgery. Obviously, individual exceptions are possible.
Return to driving entails discontinuation of opioid pain medications and ability to safely accelerate and decelerate the vehicle. Subjective safe brake response is required after right-sided surgery; as for left TKA, the decision is deferred to the patient.
Postoperative Pain Control
TKA is associated with intense postoperative pain. For the majority of patients, the worst pain period occurs during the first 2 weeks after surgery while the patients are at home. Almost half of the patients describe pain as severe and extreme during that time. Postoperative pain control is affected by economic pressure for early hospital discharge and public scrutiny perceiving opioids as a frequent path to addiction.
Pain management after TKA actually starts before surgery by setting appropriate expectations, educating, and reducing consumption of long-acting opioids in patients who have a history of chronic pain. It is important to establish risk factors for chronic pain after TKA such as poor mental health, presence of multiple medical comorbidities, high-intensity knee pain, pain elsewhere, history of chronic pain, or pain catastrophizing.
Postoperative pain is controlled via pharmacological and nonpharmacological techniques. Pharmacological interventions remain the first line of treatment and include consumption of weak short-acting oral opioids, acetaminophen, nonsteroidal antiinflammatory drugs, COX-2 inhibitors, and gabapentinoids. Opioid medications are reserved for moderate to severe pain; their usage should be gradually tapered off by the 6-week mark after surgery.
Nonpharmacological modalities are heavily supported; they include cryotherapy, compressive dressings, elevation of the extremity, physical therapy with possible inclusion of electrotherapy, and acupuncture.
Pain after TKA usually plateaus 3 to 6 months after surgery; however, 16% to 33% of patients report chronic pain and discomfort lasting past their anticipated recovery time. From a surgeon’s perspective, chronic pain can be classified as surgery-related and surgery-unrelated types. Surgery-related pain originates from complications after TKA and malfunction of the endoprosthesis. Infection, prosthesis loosening, instability, internal impingement because of oversizing and malpositioning of the components, and localized nerve injuries frequently manifest with pain. Surgery-unrelated issues include pain originating from the ipsilateral hip or lumbar spine, vascular obstruction, and other generalized or poorly understood problems such as complex regional pain syndrome, fibromyalgia, and metabolic neuropathy. Management of those conditions is usually deferred to specialists in appropriate fields of medicine. Pain management consultation is occasionally required.
Patients require lifelong follow-up with regular radiographic examination after TKA in order to detect subtle changes and prevent avoidable complications. Standard postoperative antibiotic prophylaxis remains highly controversial, and routine prophylaxis before dental procedures is not currently recommended. Postoperative pain management includes pharmacological and nonpharmacological approaches with judicious use of oral opioid medications.