Total knee Arthroplasty

    Last updated date: 18-May-2023

    Originally Written in English

    Total knee Arthroplasty

    Total knee Arthroplasty

    Overview

    Knee replacement arthroplasty is a popular procedure that replaces a damaged, worn, or diseased knee with an artificial joint. It is more often known as a complete knee replacement, and it is a relatively dependable operation with predictable outcomes.

    While osteoarthritis (OA) affects millions of Americans, the knee is the most usually afflicted joint. OA is characterized by a slow deterioration and loss of articular cartilage. The yearly incidence of symptomatic knee OA is estimated to be 240 per 100,000 patients per year, with about 400,000 primary TKA operations performed in the United States each year.

     

    What is total knee arthroplasty?

    Total Knee arthroplasty definition

    Individuals with symptomatic osteoarthritis in at least two of the three compartments of the knee who have failed conservative therapy should consider total knee arthroplasty (TKA). Furthermore, partial knee arthroplasty (PKA) is a good therapy choice for those who have symptomatic osteoarthritis in one compartment of their knee and have failed conservative treatment. The major objective of either operation is to provide long-term pain relief while also improving functional status.

    TKA dates back to the mid to late 1800s, when the earliest implants were manufactured from ivory and attached to the bone using colophony and plaster of Paris. This design was not successful, and it was subsequently replaced by metal implants in the 1930s. A hinged prosthesis was developed in the 1950s to replace the femur and tibia, as well as the supporting ligaments encircling the knee.

    While the outcomes were good, there was a significant failure rate and a poor long-term prognosis due to the failure to reproduce the normal kinematics of the knee joint. This was eventually replaced with a prosthesis that reproduced the geometry of the distal femur, retained the collateral and cruciate ligaments, and comprised of a tibial plastic bearing.

    Since the 1970s, when this breakthrough in prosthesis was made, the design has evolved to focus on imitating the anatomy and natural function of the knee joint. Furthermore, advancements in fixation techniques and the wear qualities of the bearing surface have been established, which has a favorable impact on the knee replacement's lifetime.

     

    Anatomy and Physiology

    The knee is a synovial hinge joint that has very little rotational mobility. It is made up of three bones: the distal femur, the proximal tibia, and the patella. There are three distinct articulations and compartments: the medial femorotibial, the lateral femorotibial, and the patellofemoral. The congruity of the joint, as well as the collateral ligaments, offer stability to the knee joint.

    The capsule completely encircles the joint and extends proximally into the suprapatellar pouch. The femoral condyles, tibial plateaus, trochlear groove, and patellar facets are all covered with articular cartilage. Menisci are placed between the femur and tibia in the medial and lateral compartments, acting to preserve the articular cartilage and support the knee.

    The mechanical axis of the femur is 3 degrees valgus to the vertical axis, as defined by a line drawn from the center of the femoral head to the center of the knee. The anatomic axis of the femur is 6 degrees valgus to the mechanical axis and 9 degrees valgus to the vertical axis, as defined by a line bisecting the femoral shaft.

    The proximal tibia is turned 3 degrees varus. The proximal tibia's varus position, along with the offset of the hip center of rotation, results in the tibia's weight-bearing surface being parallel to the ground. The proximal tibia's sagittal alignment slopes posteriorly by 5 to 7 degrees. The asymmetry of normal bone architecture preserves joint alignment and ligamentous tension.

     

    Patellofemoral Joint

    The patellofemoral joint (PFJ) increases the lever arm of the extensor mechanism. The patellar tendon receives the tensile forces generated by the quadriceps tendon via the patella. The maximal contact force between the patella and femoral trochlea occurs at 45 degrees of knee flexion, while joint response forces in deep squatting approach 7-times body weight.

    The quadriceps muscles stabilize the PFJ dynamically, and passive anatomic constraints include the following:

    • Medial patellofemoral ligament: Primary passive restraint against lateral translation at 20 degrees of flexion
    • Medial patellomeniscal ligament: Contributes 10% to 15% of the total restraining force
    • Lateral retinaculum: Provides 10% of the total restraining force

     

    Tibiofemoral Articulation

    During walking and climbing, the tibiofemoral articulation distributes body weight from the femur to the tibia and creates joint response forces of 3 and 4 times body weight, respectively. From 10 degrees of hyperextension to 140 to 150 degrees of hyperflexion, motion occurs in the sagittal plane. 

    Extremes of flexion are frequently reduced as a result of direct contact between the posterior thigh and the calf. In order to maximize knee flexion prior to impingement, the tibiofemoral contact point and femoral center of rotation migrate posteriorly with increasing degrees of flexion. A range of motion (ROM) of 0 to 75 degrees is all that is required for normal gait.

    The lateral collateral ligament (LCL), which resists varus stresses, and the medial collateral ligament (MCL), which resists valgus stress pressures, give knee stability in the coronal plane. Furthermore, the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) of the knee give resistance to anteriorly and posteriorly directed stresses, respectively. The posterolateral corner structures give resistance to external rotatory pressures (PLC).

     

    Indications

    Total knee Arthroplasty Indications

    TKA is a well-described therapy option for individuals with osteoarthritic knee discomfort who have failed conservative treatment approaches. It is a dependable technique that relieves pain while also improving the patient's functional condition. Furthermore, the requirement for correction of a substantial or growing knee deformity with signs of osteoarthritis might be a reason for TKA. A patient with persistent knee pain who does not have radiographic evidence of knee osteoarthritis should be evaluated further to rule out other possible causes of their discomfort.

    Clinical symptoms of osteoarthritis include:

    • Knee pain
    • Pain with activity and improving with rest
    • Pain gradually worsens over time
    • Decreased ambulatory capacity

     

    Clinical evaluation includes:

    • Full knee exam including range of motion and ligamentous testing
    • Knee radiographs include standing anteroposterior, lateral, 45-degree posteroanterior, and skyline view of the patella

     

    Radiographic evidence of osteoarthritis includes:

    • Joint space narrowing
    • Subchondral sclerosis
    • Subchondral cysts
    • Osteophyte formation

     

    Conservative treatment includes:

    • Non-steroidal anti-inflammatory medication
    • Weight loss
    • Activity modification
    • Bracing
    • Physical therapy
    • Viscosupplementation
    • Intra-articular steroid injection



    Other indications include:

    Absolute

    • Active or latent (less than 1 year) knee sepsis
    • Presence of active infection elsewhere in body
    • Extensor mechanism dysfunction
    • Medically unstable patient

    Relative

    • Neuropathic joint
    • Poor overlying skin condition
    • Morbid obesity
    • Noncompliance due to major psychiatric disorder, alcohol, or drug abuse
    • Insufficient bone stock for reconstruction
    • Poor patient motivation or unrealistic expectation
    • Severe peripheral vascular disease

     

    Preparation

    Total knee Arthroplasty Preparation

    Nonoperative Treatment Modalities

    Weight loss, physical exercise, physical therapy programs, and NSAIDs and/or tramadol are among the nonoperative therapeutic methods recommended in the Evidence-Based Clinical Guidelines for the treatment of symptomatic hip or knee osteoarthritis. Acupuncture, chondroitin supplements, hyaluronic acid injections, corticosteroid injections, lateral wedge insoles, and offloading braces are some of the other techniques that were not supported by moderate or strong evidence but are commonly regarded viable alternative therapeutic alternatives.

     

    Preoperative Evaluation: Clinical Examination

    Before performing a TKA on any patient, a comprehensive history and physical examination are necessary. Patients should be questioned about any past procedures or treatments. Prior joint replacements, arthroscopic treatments, or other knee surgeries should be taken into account. Old surgical scars might have an impact on the surgical approach. Patients with a history of previous injuries or surgeries may also present with mechanical axis abnormalities, retained hardware, or knee instability in any plane. A variety of factors might influence the TKA prosthesis that is most suited to the patient.

    Before undergoing elective TKA surgery, we recommend that each patient obtain a full medical examination, as well as any relevant medical optimization testing. On a case-by-case basis, a surgeon must examine the associated risks and possible advantages of doing TKA.

    The total mechanical axis of the limb is evaluated during the physical examination. Before doing any surgery around the knee, it is necessary to rule out or at least evaluate hip pathology. The vascular state of the limb should also be evaluated by looking for any chronic venous stasis alterations, cellulitis, or wounds/ulcerations on the extremities. The pulses should be symmetric and noticeable from a distance. 

    Preoperative range of motion of the knee and surrounding joints should be recorded (hip, ankle). The soft tissues of the knee joint should be evaluated for indications of gross atrophy, general symmetry, and ligamentous stability in all planes. It is critical to document the presence of any varus/valgus plane laxity as well as the capacity to repair the deformity. These factors assist the surgeon in preparing for soft tissue releases that may be necessary to aid mechanical axis correction, as well as planning for further bone resection that may be required in the presence of substantial contractures.

     

    Preoperative Evaluation: Radiographs

    Preoperative radiographs are examined for general mechanical alignment, the presence of deformity, and bone loss, including a weight-bearing anteroposterior (AP) view. The tibiofemoral angle can be used to determine the severity of coronal deformity. The discrepancy between the mechanical and anatomic axes of the femur is used to compute the femoral resection angle. The lateral view of the knee is critical for determining the natural posterior slope of the proximal tibia and the presence of posterior osteophytes on the femoral condyles.

    Although the patellofemoral radiographic image is not required for TKA templating, it does assist the surgeon to assess the extent of patellofemoral arthritis and deformity. In severe cases of patellofemoral deformity, osteophyte excision may be required before attempting to evert the patella during the surgery. A surgeon might also prepare for a lateral release to optimize patellar tracking.

     

    Total knee arthroplasty procedure

    Total knee arthroplasty procedure

    The medial parapatellar, midvastus, and subvastus routes are the most often used for the typical main TKA technique. The medial parapatellar method, which involves proximal dissection into a medial cuff of the quadriceps tendon to promote superior tissue quality closure at the end of the treatment, is the most usually used.

    A thorough, continuous medial subperiosteal dissection sleeve is conducted proximally, while preserving intimate contact with the proximal tibial bone. The extent of dissection is frequently determined by the amount of deformity to be addressed. This medial release is often vigorous in situations of severe varus deformity and modest in cases of moderate to advanced valgus knee deformity. This soft tissue sleeve is also used to resect the medial meniscus.

    The midvastus and subvastus techniques are alternatives to the usual medial parapatellar arthrotomy. The quadriceps tendon is saved by using the midvastus technique. Instead, the vastus medialis obliquus (VMO) muscle belly is dissected along a trajectory oriented toward the superomedial part of the patella's proximal pole.

    The subvastus technique additionally protects the quadriceps tendon by lifting the VMO muscle belly away from the intermuscular septum. The subvastus technique protects the patella's vascularity but should be used with caution since it can restrict exposure in very difficult instances or in extremely obese people.

     

    Wound Closure

    Wound Closure

    The most current literature remains contentious in terms of the optimal knee position and suture material used during TKA closure. Attention to detail is necessary, and a systematic conclusion is universally recommended. Closure using uni- or bi-directional barbed suture for the arthrotomy, deep fascial, and deep dermal/subcutaneous layers is a favored approach.

    For the skin, staples or monocryl might be used. A sterile dressing is then placed and remained in place for the first 7 days without being changed. Furthermore, a minimum webril/ace soft wrap dressing is given to the knee for a maximum of 24 hours to promote the optimal balance of wound healing and postoperative knee mobility.

     

    Other Considerations

    While waiting for the cement to harden completely and before removing the tourniquet, topical tranexamic acid (TXA) is the preferable treatment. Other contentious technical modalities in TKA include the use of a tourniquet, cementing the patella, femoral, and/or tibial components, and introducing a betadine soak to the wound as part of the profuse saline irrigation that is performed before to closing the arthrotomy and surgical incision. Prior to arthrotomy closure, preferred approaches include the application of a tourniquet, cementing all components, and saline-only copious pulsatile irrigation.

     

    Complications

    Complications from TKA have a negative impact on results and patient satisfaction. Despite the fact that TKA remains a dependable and reproducibly effective procedure in patients suffering from severe advanced degenerative arthritic knees, data indicate that up to one in every five patients who have received primary TKA are unsatisfied with the outcome.

    Periprosthetic Fracture

    TKA periprosthetic fractures (PPFs) are further distinguished by implant placement and residual stability. PPFs in the distal femur occur at a 1% to 2% incidence, with risk factors including reduced patient bone quality, greater confined TKA components, and, while contentious, anterior femoral notching as a possible risk factor for postoperative fracture.

    Tibial PPFs develop at an incidence of 0.5 to 1%, and risk factors include previous tibial tubercle osteotomy, component malposition and/or loosening, and use of long-stemmed components. Patellar PPFs are less common in unresurfaced TKA patients, with incidence rates ranging from 0.2 percent to as high as 15% to 20%. Osteonecrosis, technical mistakes in asymmetry or over-resection, and implant-related relationships such as the following are all risk factors for fracture.

    • Central, single peg implants
    • Uncemented fixation
    • Metal-backed components

     

    Aseptic Loosening

    TKA aseptic loosening occurs as a result of a macrophage-induced inflammatory response, which results in bone loss and TKA component loosening. Patients frequently appear with discomfort that worsens with weight-bearing activities and/or recurring effusions. At rest or with range of motion, patients may experience only little discomfort. 

    Serial imaging and infection tests are necessary to properly work up these problems, which are finally addressed with revision surgery if symptoms continue and the patient is deemed a viable surgical candidate. Particulate debris generation, macrophage-induced osteolysis, component micromotion, and particulate debris dispersion are all processes in aseptic loosening.

     

    Wound Complications

    TKA postoperative wound complications range from superficial surgical infections (SSIs) such as cellulitis, superficial dehiscence, and/or delayed wound healing to deep infections resulting in full-thickness necrosis, which necessitates returns to the operating room for irrigation, debridement (incision and drainage), and rotational flap coverage.

     

    Periprosthetic Joint Infection

    According to the research, the incidence of prosthetic total knee infection (TKA PJI) after initial TKA is around 1% to 2%. Patient-specific risk factors include morbid obesity, smoking, intravenous [IV] drug use and misuse, alcohol abuse, and poor dental hygiene, as well as individuals with a history of uncontrolled diabetes, chronic renal and/or liver disease, malnutrition, and HIV (CD4 counts less than 400).

    Staphylococcus aureus, Staphylococcus epidermidis, and coagulase-negative staphylococcus bacteria are the most prevalent offending bacterial species in the acute situation. In the acute context (less than 3 weeks after initial surgery), treatment can be limited to incision and drainage, polyethylene exchange, and component retention. Furthermore, IV antibiotics are used for up to 4 to 6 weeks. Outcomes vary and are frequently impacted by many intraoperative, patient-related variables, and the offending bacterial organism, although studies indicate a 55% success rate.

    More severe therapies, particularly when the presentation is beyond the acute period (3 to 4 weeks), involve a 1 or 2-stage revision TKA operation with interval antibiotic spacer implantation. The surgeon is responsible for ensuring and documenting proof of infection elimination.

     

    Other Complications and Considerations

    Other potential complications after TKA are beyond the scope of this review but include:

    • TKA instability: This can happen in the coronal or sagittal plane (s). In addition, when patients complain of prolonged anterior knee discomfort, consideration is given to patellar maltracking or other PFJ concerns (for example, overstuffing the joint) in the postoperative context.
    • Stiffness
    • Vascular injury and bleeding
    • Peroneal nerve palsy
      • One of the most common complication after TKA to correct valgus deformity. During soft tissue balancing of a valgus knee, the iliotibial band preferentially affects the extension space more than flexion space and inserts on Gerdy's tubercle. The popliteus is preferentially affects flexion space more than extension space.
    • Metal hypersensitivity 
    • Heterotopic ossification

     

    Conclusion

    Total knee Arthroplasty

    The number of individuals suffering from knee discomfort caused by osteoarthritis will continue to climb, particularly as life expectancy and obesity rates rise. These two mechanisms lead to articular cartilage wear and tear in the major weight-bearing joints found in primary osteoarthritis.

    Secondary osteoarthritis, or osteoarthritis induced by an abnormal concentration of force across the joint, such as in rheumatoid or post-traumatic situations, can also occur in patients. In either scenario, a comprehensive history, physical examination, and suitable radiographs are required for an accurate diagnosis. The first therapy is conservative and involves any and all of the above-mentioned combinations.

    When conservative therapy no longer works, surgical intervention may be considered. In the right patient, TKA is a dependable surgical technique with a predictable outcome. With 10 to 25 years of follow-up, reported survival rates are as high as 85 percent. Improvements in pain and functional scores are also typically observed after the therapy.