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\1USCUlOSKHFTAL SYSTEM

197

Figure 3-15. Umc()mpartmental knee arthroplasty of the Tight medial

compartment.

an increased ROM is obtained because of more normal kinematics of

the knee joint. Revision from a unicompartmental to a tricompartmental knee arthroplasry is ofren warramed ar a larer rime because of continued degeneration; however, newer unicompartmental prosthetic designs may show improved results.4s Associated valgus deformiries may also be correcred by a ribial osreoromy and release of sofr (issue during rhe partial knee replacement.

The tricompartmelltal or total kllee arthroplasty (TKA) is rhe

replacemenr of rhe femoral condyles, rhe ribial articularing surface, and

rhe dorsal surface of rhe parella. This rype of knee arthroplasry involves

replacing rhe medial and lateral comparrmenrs of the joinr, as well as

resurfacing the patellofemoral articulation with prosthetic components

( Figure 3-16A). These componenrs are made of marerials similar ro

rhose of rhe THA. The femoral condyles are replaced wirh a meral

bearing surface rhar articulares wirh a polyerhylene rray implanred on

rhe proximal ribia. The dorsal aspect of rhe parella is ofren resurfaced if

excessive erosion of the cartilage has occurred; however, some surgeons

refrain from rhe parellar implanr if rhe arricular cartilage of the patella

seems reasonably intact, as shown in Figure 3-16B.46

198 ACUTE CARE HANDBOOK FOR PHYSICAL TI IERAPISTS

A

B

Figure 3� 16. A. Anterior view of a right total knee arthroplasty. B. Lateral

view of a right total knee arthroplast),.

The methods of fixation in TKA are similar to those of hip replacemenr. Cementing techniques can be used to fix the components, or the prosthetic design can allow for either porous ingrowth or press-fir. A

press�fit prosthesis has surface modifications or grooves and bioactive

hydroxyapatite to provide macrointerlock with the bone.'o Many sur-

MUSCUlOSKELI;�rAL SYSTEM

199

geons tend to use a hybrid technique by using a cemented tibial component with porous coated femoral and patellar prostheses. Partial weight bearing or weight bearing as tolerated often is allowed after TKA and is

encouraged to promote use of the limb and promote bone remodeling.46

Patients who undergo either type of knee arthroplasty may have

associated preoperative soft tissue contractures. A lateral retinacular

release can be performed to centralize patellar tracking. If performed,

there may be an increased risk of patellar subluxation with flexion.

Special procedures that are performed in either type of knee arthroplasty should be taken into consideration by the physical therapist, because the surgeon may impose restrictions to ROM and weight

bearing. Any additional procedure may prolong healing time secondary to increased edema and pain, which limits the patient's functional mobility and wlerance w exercise.

General medical complications after TKA are similar to those

described with THA. Table 3-7 lists common complications specific

to TKA.

Physical Therapy Intervention after Knee Arthroplasty

Physical therapy intervention after knee arthroplasty is focused on

increasing functional independence. The patients muSt also perform

ROM and strengthening exercises and be educated in positioning

techniques to help reduce swelling. Restrictions on weight bearing

and precautions are also taught to the patient.

Table 3-7. Complications after Total Knee Anhroplasty

Thrombosis and rhromboembolism

Poor wound healing

Infecrion

Joim insrability

Fracrures

Patellar tendon rupture

Parellofemoral instability, component failure, or loosening

Peroneal nerve injury

Component loosening or breakage

Wear and deformation

Source: Adaprcd from JL Guyron. Anhroplasry of Ankle and Knec. In ST Canale ( cd),

Campbell's Oper:ltive Orrhop:lcdics, Vol. I (9th cd). $(. LOllis: Mosby, 1998.

200

AClITE CARE HANDBOOK FOR PHYSICAL THERAPIST'S

• Evaluation and treatment of functional mobility to promote

independence should begin immediately postoperatively. Bed

mobility, transfer training, and gait training on level surfaces and

stairs with appropriate assistive devices should be instructed to the

patient to maximize functional outcomes and safety.

• Strengthening exercises may begin immediately postoperatively,

emphasizing quadriceps exercises. Quadriceps retraining may be

accomplished with overflow from the uninvolved limb or distal

limb. Active-assisted quadriceps exercises should be performed to

increase stability around the operated knee. The patient should be

encouraged to perform exercises independently, within the limits of

comfort.

• Knee immobilizers are often prescribed to protect the knee from

twisting and buckling secondary to decreased quadriceps strength.

With a lateral release, there may be increased pain and edema that

may hinder quadriceps functioning; therefore, a knee immobilizer

or brace may be required for a longer period of time.

•

ROM exercises should begin immediately after TKA. ROM

must be gained early in the rehabilitation of a TKA and is accomplished by passive or active-assisted exercises. If available, a continuous passive motion (CPM) machine may be used immediately postoperatively. The limitations to ROM are often attributed to

pain, swelling, muscle guarding, and apprehension, all of which

can be addressed through physical therapy interventions and

patient education.

• Positioning and edema control should be initiated immediately

to help reduce pain and increase ROM. The patient should be educated to elevate the operated extremity with pillows or towel rolls under the calf to promote edema reduction and promote knee

extension. Ice should be applied after exercise or whenever needed

for patient comfort.

Clinical Tip

•

Educate the patient to elevate the operated limb without putting pillows or towel rolls under the knee. This

type of positioning keeps the knee flexed and will increase

the risk of flexion contractu res and edema.

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201

• The therapist may place a towel roll or blanket along the

lareral aspect of the femur, near the greater trochantet, to maintain the operated extremity in a neutral position. Any external rotation at the hip can result in slight flexion at the knee.

• The therapist should place a pillow or towel roll under

the knee in the degree of available ROM while performing

isometric exercises. This will produce a stronger quadriceps contraction by reducing passive stretch on joint

receptors and pain receptors. This will also provide posterior suppOrt to the knee, providing increased tactile feedback for the patient.

• ROM for the majority of TKA is at least 90 degrees in

rhe operating room. Consult the surgeon for the maximum

amount of flexion obtained. This will provide the therapist

with an idea of how much pain, muscle guarding, and

edema are limiting patient performance.

• When performing active-assistive ROM, the use of hold!

relax techniques to the hamstrings assists to decrease muscle

guarding and increases knee flexion through reciprocal inhibition of the quadriceps muscle. This technique also provides a dorsal glide to the tibia, preparing the posterior capsule for flexion. Gentle massage of the quadriceps mechanism over the muscle belly or throughout the peri patellar region will improve ROM and reduce muscle guarding.