Realignment for Patellofemoral Arthritis

Albert Lin, MD

Robin West, MD

Dr. West or an immediate family member serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons and the American Orthopaedic Society for Sports Medicine. Neither Dr. Lin nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

PATIENT SELECTION

Patellofemoral arthritis is a common and often debilitating cause of anterior knee pain. Causes of patellofemoral arthritis may be related to limb alignment, the bony architecture of the trochlea and the patella, and the integrity of the surrounding soft tissues.¹^,²^,³ Because of these multifactorial causes, treatment options may be particularly challenging. Surgical treatment may be indicated for patients in whom nonsurgical management—consisting of activity modification, bracing treatment, physical therapy, medications, and injections—fails. The surgical treatment is variable, depending on the patient’s age and activity level, the degree and location of chondral damage, and the association with tibiofemoral arthritis.⁴^,⁵^,⁶ Current procedures include lateral release, cartilage restoration, patellofemoral arthroplasty, total knee arthroplasty, and patellar realignment. Patellar realignment consisting of anteromedialization of the tibial tubercle with osteotomy, as first described by Fulkerson for patellar instability, is an excellent option for patients with isolated lateral facet arthritis.¹^,⁵

The indications for anteromedialization of the tibial tubercle for patellofemoral arthritis and pain include isolated distal/lateral patella facet or lateral trochlear chondrosis with no chondrosis of the proximal/medial patellofemoral joint.⁵ Other indications may include more central patellar wear in patients with patellar subluxation seen on radiographs, where the central patella is articulating with the lateral trochlear ridge throughout the early flexion zones. These patients may or may not have associated symptoms of patellar instability or an increased tibial tuberosity-to-trochlear groove (TT-TG) distance.²

Contraindications to tibial tubercle anteromedialization include severe medial and/or proximal patellar chondrosis that would be subject to increased loading after transfer. Standard contraindications to osteotomy around the knee include osteoporosis, nicotine use, nonspecific pain, complex regional pain syndrome, infection, inflammatory arthropathies, patella baja, or arthrofibrosis. A relative contraindication is the presence of a varus knee, medial compartment arthritis, or the post-medial meniscectomy knee because the peak pressure will increase in the medial tibiofemoral joint space after medialization of the tibial tubercle.⁷ Another relative contraindication is the presence of severe medial and/or lateral compartment arthritis of the knee, which would require a more global procedure, such as a total knee arthroplasty, to address all pathologies.¹

PREOPERATIVE IMAGING

Radiographs

We take standard 45° flexion weight-bearing PA, lateral, and Merchant views of both knees (Figure 1). The weight-bearing flexion radiographs show the degree of tibiofemoral joint space narrowing. The Merchant view is used to assess patellar tilt, subluxation, and trochlear dysplasia. The lateral view is used to evaluate the patellar height and trochlear dysplasia.

Magnetic Resonance Imaging

MRI is useful in evaluating injury to the medial patellofemoral ligament and the degree and location of articular cartilage loss. Bone bruise patterns and other associated ligamentous or meniscal injuries can also be identified. MRI can also be used to assess the lateral offset of the tibial tuberosity from the deepest point in the trochlear groove (TT-TG distance). A distance greater than 20 mm is nearly always associated with patellar instability and can be addressed with a tibial tubercle realignment as well.²

Computed Tomography

Cross-sectional imaging with CT slices at different positions along the lower limb can provide a three-dimensional view of the patellofemoral joint. These CT cuts can be used to assess the TT-TG distance, femoral anteversion, and patellar tracking at different flexion angles. We rarely order a CT scan in the treatment of patellofemoral arthritis and occasionally order a CT scan in the treatment of patellofemoral instability in patients with correlating femoral anteversion, increased tibial torsion, and patellar maltracking. MRI is equally as reliable as CT in assessing the TT-TG distance.⁸

FIGURE 1 Preoperative radiographs obtained before realignment for patellofemoral arthritis include 45° flexion weight-bearing PA (A), 30° lateral (B), and Merchant (C) views.

PROCEDURE

Room Setup/Patient Positioning

The affected extremity is identified and signed in the preoperative holding area. The patient is placed supine on the operating room table. All bony prominences are well padded. A tourniquet is applied, and the leg is prepped and draped. A surgical time-out is called at this time prior to the skin incision.

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