Total Knee Arthroplasty

Total knee arthroplasty (TKA) has been shown to be an effective long-term intervention for the elderly population to relieve knee pain, improve function, increase social mobility and interaction, and contribute to psychological well-being.

 

Indications

Although pain and loss of function are the primary reasons for a TKA, the procedure can also be used to correct knee instability and lower extremity alignment and for the treatment of isolated but severe patellofemoral disease. Because TKA is generally contraindicated in younger and more active patients, those with unicompartmental osteoarthritis of the knee may be considered candidates for a high tibial osteotomy or a distal femoral osteotomy. The high tibial osteotomy is used with isolated medial compartment arthritis. The distal femoral osteotomy is used in lateral compartment arthritis. The short-term results for these procedures have been very successful, even to the point where the need for TKA is eliminated. However, permanent pain relief with high tibial osteotomy is as yet unlikely.

Absolute and relative contraindications for a TKA include but are not limited to

• active infection of the knee
• significant genu recurvatum
• severe obesity
• return to high-impact sports or occupations
• arterial insufficiency
• neuropathic joint
• mental illness

Procedure

Several techniques are at the surgeon's disposal. The choice of approach is determined by surgeon's knowledge and comfort. Three approaches are commonly described: anterior, subvastus, and lateral.

• Anterior approach. The anterior approach is generally through an anterior midline longitudinal skin incision and median parapatellar arthrotomy. The advantages of this approach include its extensile potential and its wide exposure medially and laterally. The disadvantages include its violation of the quadriceps mechanism, and the potential for patellar devascularization.

• Subvastus approach. The subvastus approach uses the same midline anterior skin incision as the anterior approach. The advantages of this approach include maintenance of the quadriceps mechanism with decreased postoperative pain and earlier functional recovery.⁸³ The disadvantages include its somewhat limited exposure.

• Lateral approach. The lateral approach occurs lateral to the patella and through the medial edge of Gerdy's tubercle. Proponents of this technique feel that it is a superior method in the correction of valgus deformity.

Most primary arthroplasties rely upon the patient's anatomy to offer stability to the articulation. Anatomic structures that can offer  stability include the posterior cruciate ligament (PCL) and a balancing of the soft tissues around the knee. The fate of the PCL in primary TKA is controversial. If the PCL is sacrificed, a posterior stabilizer (see below) is used. However, the long-term results of PCL-retaining and posterior-stabilized TKAs are similar. PCL substitution may be indicated in patients requiring TKA who present with end-stage degenerative joint disease with varus or valgus malalignment and associated flexion contracture, with a combined deformity greater than 15 degrees.

Many early designs of TKA replaced only the tibiofemoral joint and did not address the patellofemoral articulation. The posterior stabilizer was developed to increase the arc of motion of these earlier models and thereby improve the functional results of TKA. Although the ROM improved substantially with these components, patellofemoral complications emerged as a major problem after knee replacement. Errors in sizing, alignment, and rotation of the tibial and femoral component were eventually appreciated as contributing factors to many of these patellofemoral problems. In addition, many of these complications appear to be secondary to patellar resurfacing which may be a part of the procedure. Whether to resurface the patella remains among the most controversial topics in TKA.

Surprisingly high loads are transmitted across the patellofemoral articulation. Following a knee replacement, there is a decrease in the contact area and consequent increase in the contract stress. A study by Matsuda and colleagues showed that resurfacing the patella decreased the contact area to a greater degree compared with not resurfacing the patella. In addition, kinematic studies of motion of the patellofemoral joint after knee replacement have consistently shown some degree of altered kinematics.

Postsurgical Rehabilitation

Preoperative instruction is believed to be invaluable in the early postoperative setting. Preoperative instruction should include education regarding the ice-compression-elevation program, ROM exercises, isometric quadriceps strengthening, patellofemoral mobilization, and gait training with the appropriate postoperative assistive devices.

Complications associated with TKA include the following :

• Thromboembolic disease.
• Fat embolism.
• Poor wound healing.
• Infection.
• Periprosthetic fractures.
• Neurologic problems. Peroneal nerve palsy is the most common neurologic complication of TKA.
• Vascular problems. Injuries to the superficial femoral, popliteal, and genicular vessels have all been reported following TKA.
• Arthrofibrosis.
• Disruption of the extensor mechanism.

Postoperative rehabilitation for primary TKA continues to be studied in an effort to decrease the cost while still providing the quality of clinical results expected by the surgeon and the patient.

A review of the literature reveals inconsistent practice patterns in the physical therapy management of TKA patients.The postsurgical rehabilitation program that follows is based on the consensus found. The program is divided into two components: the inpatient stay and the outpatient course.

The success of the rehabilitation program for this patient population is dependent on knowledge of the surgical procedure, communication with the surgeon and the patient, and above all, the ability of the rehabilitation team to educate the patient to participate actively in the treatment program.

Phase 1: Inpatient Phase (1 Dayuntil Discharge)

This phase typically involves 4–10 physical therapy sessions.

The subject of continuous passive motion (CPM) device use following a TKA has been debated for years, with some surgeons advocating and others opposing its use. The use of a CPM device has been promoted as a means to facilitate a more rapid recovery by improving flexion range, decreasing length of hospital stay, and lowering the amount of narcotic use. However, studies have shown that the effect of CPM devices on analgesia consumption, ROM, hospital stay, and complications has been variable:

• Data support the use of CPM to decrease the rate of manipulation for poor ROM after TKA.
• The long-term ROM probably is not increased by the use of CPM after TKA.
• Although it appears that the use of a CPM device does help regain knee flexion quicker, it is not as effective in the enhancement of knee extension.
• Knee impairments or disability are not reduced with the use of a CPM at discharge from hospital.
• Because of standardized inpatient hospital clinical pathways, the length of hospital stay is not decreased by the use of a CPM device and, depending on the hospital involved, the overall cost is not increased.
• Wound complications probably are not increased with the use of CPM, provided good technique is used in wound closure, and gradual increase in ROM occurs during the first 4 days postoperatively.

It is still not clear whether ROM is achieved faster and whether the prevalence of deep vein thrombosis (DVT) and analgesics use are decreased with CPM.

If ligament instability is present in the days immediately following the surgery, a postoperative knee brace is used which is initially adjusted to a 0- to 90-degree position. The brace functions to allow free movement in the 0- to 90-degree range, while preventing varus and valgus forces to the knee, and thus assists in maintaining the corrective alignment obtained in surgery.

Goals

• Prevent postoperative complications including DVT, infection, and pulmonary embolus.
• Reports of pain to be 5/10 or less.
• Minimize detrimental effects of immobilization.
• Patient to achieve an independent or supervised functional level for the following:
  • Transfers in and out of bed, on and off a commode, up and down from an appropriate chair (high or elevated).
  • Ambulation at a household level with an appropriate assistive device.
  • Stair negotiation of one or more steps, as dictated by home environment, with appropriate assistive device and with or without handrail.
  • Adherence to weight-bearing status.
• Active assistive ROM to be at 5–90 degrees of involved knee motion or better.
• Patient to achieve functional straight leg raise without extensor lag.
• Motor performance to be at 3/5 on manual muscle test.

Electrotherapeutic and Physical Modalities

Modalities to reduce pain and swelling (ice and elevation) are initiated as early as possible. With the physician's permission, electrical stimulation can be used for edema reduction, muscle reeducation, and pain control. The use of neuromuscular electrical stimulation (NMES) has been shown to reduce extensor lag and the length of stay in the acute care setting when used in conjunction with a CPM machine.

Hecht and colleagues compared the effectiveness of local applications of cold and heat in conjunction with exercise versus exercise alone on postsurgical pain of the knee. The application of cold with exercise was rated as providing significantly greater relief than the application of heat plus exercise or exercise alone, and swelling was also significantly decreased in the group that received the cold therapy. No other significant differences between groups were found.

Therapeutic Exercise and Home Program

Exercise encourages early enforcement of quadriceps activity and passive ROM, as well as reduction of joint effusion. The patient is instructed to perform sets of 10 repetitions of isometric contractions during every waking hour, focusing on breathing normally during these exercises. These exercises are usually initiated on the first or second postoperative day and include the following:

• Resistive exercises to the uninvolved extremities.
• Deep breathing exercises.
• Proper elevation and positioning of the involved lower extremity.
• Active assistive knee flexion and extension to the involved knee. If CPM is ordered, it is typically applied immediately after surgery in the recovery room to patient's tolerance, so as not to irritate the soft tissue response to the surgery. The patient is encouraged to remain on the unit for 10–12 hours each day, with gradual increases in both extension and flexion ranges as tolerated.
• Ankle pumps, quadriceps sets, gluteal sets, hamstring sets, heel slides.
• Straight leg raising.During the early days postoperatively, leg raises are limited to the supine and prone positions to prevent the varus and valgus forces associated with hip abduction and adduction in the initial healing phase. Cemented fixation allows for these movements at 2 weeks postsurgery. However, in uncemented knee replacements, hip abduction and adduction are not permitted until 4–6 weeks, pending sufficient bony ingrowth on radiographic examination.
• Seated knee extension.
• Standing knee flexion of the involved leg.

Functional Training

Functional training includes the following:

• Transfer training in and out of bed, from bed to and from chair, and to and from commode or elevated toilet seat.
• Gait training, including instruction on weight-bearing status, use of an assistive device, and stair negotiation. Ambulation on different levels can occur by the second or third day, if appropriate. The correct progression of weight bearing is crucial to the overall success of the joint replacement, and depends on the type of fixation and alignment. In patients with porous-coated prostheses, limited weight bearing is essential to allow for sufficient bony ingrowth into the prosthesis, and to prevent loosening of the appliance and premature failure of the surgical alignment. Full weight bearing is generally allowed at 6 weeks, based on a radiographic examination and the patient's body weight.

Manual Therapy

Manual therapy techniques include patellar mobilization and soft tissue techniques. Because unrestricted patellofemoral mobility is essential for normal knee motion, mediolateral and superior patellofemoral mobilizations are initiated as early as the second postoperative day.

The patient is discharged from the hospital to home or an extended care facility when medically stable. To be discharged to home, the patient should be able to demonstrate 80–90 degrees of active or active assisted knee motion, transfer supine to sit and sit to stand, ambulate 100 feet, and ascend and descend three steps or more, as the home environment dictates.

If functional independence is required before a patient returns home, the patient is typically transferred to an acute or subacute care setting. If adequate home care and safe transport are available, the patient is allowed to return home.

Home Care Phase (1–2 Weeks)

This phase typically involves a visit from a physical therapist for 3 days a week. A physical home care assessment usually occurs within 24 hours after hospital discharge.

During this phase, the role of the physical therapist is to address any safety concerns including moving or adjusting the height of furniture, removal of any throw rugs, review of sitting and sleeping positions, and progression of the home exercise program. Weight-bearing exercises are typically introduced at this time. These include seated heel raises , sit-to-stand exercises, mini-lunges (weight shifting), and mini-squats.

Specific transfers in the home and car are practiced. Gait training is advanced to crutches or cane, depending on the patient's balance. Once patients are no longer homebound, they begin outpatient physical therapy.

Phase 2: Outpatient (Weeks 3–6)

This phase typically involves three to eight physical therapy sessions.

Goals

• Patient to demonstrate functional independence with gait and an assistive device on level surfaces and stairs.
• Patient to normalize gait pattern as necessary.
• Patient to achieve independence with basic activities of daily living (ADLs). ADLs may cause pain at this time. The patient should be advised against overactivity.
• Active range of motion (AROM) of involved knee flexion to be at 110–125 degrees. This degree of knee flexion is necessary for successful stair negotiation and for sitting on a regular toilet seat.
• AROM of knee extension to be at 0 degrees to normalize gait.
• Motor performance to be at 4/5 for the involved extremity, demonstrated by single-leg half squat at 65% of body weight.
• Reports of pain to be 3/10 or less.

Electrotherapeutic and Physical Modalities

Electrical muscle stimulation is used in this phase of rehabilitation, with particular attention to the vastus medialis obliquus. Once full extension is achieved, NMES is applied throughout ROM and during multiple-angle isometrics including those angles at which the quadriceps appears to function less efficiently.In the more advanced stages of weight bearing, NMES is applied in the standing position to enforce strengthening of the quadriceps in the end range of extension, while incorporating proprioceptive training through the closed kinetic chain.

Therapeutic Exercise and Home Program

The exercise program during this phase can include the following:

• Aerobic conditioning (stationary cycling, upper body ergonometer). Through seat adjustment on the stationary bicycle, emphasis can be placed on either flexion or extension, maintaining a comfortable, slow cadence so as not to traumatize the joint at its end range while gaining the benefit of prolonged stretch and high repetition. The reciprocal pattern of bicycling incorporates multiple joint motions and strengthening through a functional pattern of movement. Because most of this patient population has had a limited activity level since prior to surgery, it is not long before this cycling program becomes an aerobic activity, and therefore affects cardiovascular endurance as well.
• Aquatic therapy (deep-water jog, squats, straight leg raises, step-up exercises), if available.
• Isotonic exercises with ankle weights or surgical tubing. These exercises include knee extension, knee flexion, straight leg raising in all four planes (flexion, extension, adduction, abduction), and bridging.
• Side-lying hip external rotation . The patient lies on the uninvolved side with the shoulders and hips perpendicular to the table and the knees flexed to about 45 degrees. The patient lifts the top knee toward the ceiling, maintaining the pelvic position and contact of the feet.
• Flexibility exercises. A basic flexibility program is introduced, which includes stretches of those two-joint muscle groups that cross the knee joint, in particular, the hamstrings, gastrocnemius, and quadriceps.
• Weight-bearing exercises including partial lunges, leg press, bilateral heel raises, wall slides, and partial squats.

Neuromuscular Training

The following exercises may be performed based on the goals of the intervention:

• Balance-and-reach exercises.
• Backward walking.
• BAPS (biomechanical ankles platform system).
• Toe-heel walking.
• Side-stepping.
• Mini-trampoline exercises.
• Single limb balancing on the involved leg.

Manual Therapy

Manual therapy during this phase includes joint mobilizations to the patella, as appropriate, and soft tissue techniques to stretch the surrounding musculature.

Phase 3 (Weeks 7–12)

This phase typically involves 3–12 physical therapy sessions.

Goals

• Patient to achieve independence and pain-free motion with all ADLs.
• Patient to have independent, normal gait pattern with single-point cane over all surfaces.
• Patient to achieve return to employment or previous hobbies as indicated.
• AROM to be at 0–115 degrees.
• Motor performance to be at 5–/5 on manual muscle testing or equal to the uninvolved leg.
• Reports of pain to be at 2/10 or less.

Therapeutic Exercise

• Emphasis is placed on remaining muscle performance and ROM deficits.
• Self-stretching exercises are performed.
• Gait training is advanced to use of a single-point cane on stairs and all surfaces.
• Endurance activities in this phase shift to a progressive walking program. The program begins with 8- to 10-minute walking sessions, progressing to 60-minute walk as tolerated. The level of activity achieved after a TKA is dependent on a number of factors. The most significant consideration for patients and orthopaedic surgeons in considering athletic activity after knee replacement is wear at the weight-bearing surface.

Neuromuscular Retraining

Various techniques and changes in direction can be applied to lateral step-ups to make the exercise more difficult and challenging to the proprioceptive system.

Higher levels of balance board activities are introduced. Walking activities may be progressed to include side-stepping and quick changes in direction.

Manual Therapy

Manual therapy techniques include

• joint mobilization to the patella as indicated
• passive stretching of the two joint muscles of the knee and hip (gastrocnemius, hamstrings, rectus femoris)

Outcomes

Traditionally, clinical rating scores have been used to assess results following TKA. These rating systems typically aggregate weighted scores for pain, ROM, stability, alignment, and functional ability.

The use of patient-reported outcome measures for assessing the outcomes of TKA has been emphasized in the orthopaedic literature over the past 10 years. Patient self-reported measures of outcome, such as the WOMAC and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), have now been accepted by the orthopaedic community.

Both the condition-specific WOMAC and the generic SF-36 capture the improvement in pain in patients undergoing comprehensive inpatient rehabilitation intervention sufficiently well.

Mark Dutton, PT,Orthopaedic Examination, Evaluation, and Intervention 2nd edition McGraw-Hill 2008  ISBN: 0071474013 

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