Physical Examination

A complete review of the physical examination of the patellofemoral joint is beyond the scope of this chapter, but we will review the pertinent examination points. The exam should begin with a gait evaluation and hip range of motion to assess for increased femoral anteversion, in-toeing, or pes planus that can all predispose the patient to a relative genu valgum of the lower extremity and lead to patellar tilt or subluxation. Increased mobility of the joints is also assessed (elbow, thumb, etc.) because it may predispose the patient to early failure if a soft-tissue only technique is used for patellar stabilization. The skin should also be evaluated for changes associated with complex regional pain syndrome or previous incisions that would alter the standard approach to the tibial tubercle osteotomy. Muscle atrophy should also be assessed as a sign of nerve damage or the need for preoperative physical therapy for strengthening.

Specific tests for the evaluation of the patellofemoral joint include noting patellofemoral crepitance, joint effusion, lower extremity Q-angle, patellar J-sign, lateral retinacular tightness, patellar quadrant mobility, patellar apprehension test, patellar grind test, and stability/pain relief with a lateral to medial force on the patella (i.e., you are simulating holding the patella in an unloaded/reduced position).

Imaging Studies

Imaging studies should start with a complete set of knee x-rays consisting of bilateral anterior-posterior (AP) standing views, bilateral posterior-anterior (PA) 45 degrees; flexed views, a lateral view with the knee in 30 degrees; of knee flexion, and a Merchant view.⁹

The Merchant view is needed rather than the skyline view because as the knee is hyperflexed in the skyline view, the patella is captured by the bony anatomy of the trochlea, and subtle variations of patellar tilt or subluxation are lost at knee angles greater than 30 degrees;.¹

The Merchant view allows the evaluation of patellar tilt (patellofemoral angle of Laurin),¹⁰ trochlear dysplasia, and patellar subluxation (congruence angle)⁹ (Fig. 13-1, A–C). The lateral view allows the evaluation of patellar joint space, trochlear dysplasia, patellar alta/baja, and patellar tilt (Fig. 13-2, A–B). One can also use MRI or CT scans to measure similar angles of patellar subluxation and tilt.^3,11–16

FIGURE 13-1 Measuring tilt and subluxation. A, Normal patellofemoral angle of Laurin. Used to measure patellar tilt. The solid line along the lateral patellar facet should open laterally when referenced to the dotted line along the medial and lateral trochlear ridges. B, Abnormal patellofemoral angle of Laurin. Both of the lines are parallel to each other and thus are consistent with lateral patellar tilt. C, Abnormal congruence angle. Used to measure patellar subluxation. Line AB is along the lateral trochlea, and line CB is along the medial trochlea. Line BD is drawn as the bisector of the trochlear groove angle. Finally, line BD’ is drawn from the central trochlea to the central ridge of the patella. Line BD’ should be equal or medial to the bisector line BD. If it is lateral (as in this case), patellar subluxation can be confirmed.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17. issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 225. Copyright 2007, with permission from Elsevier.)

FIGURE 13-2 Lateral x-ray images showing a normal knee (A) and a knee with lateral tilt (B). A, Arrowhead showing the central patellar ridge, which should not overlap with the medial and lateral patellar facets (arrow line), in a normal knee without patellar tilt. B, Arrowhead showing near superimposition of the central patellar ridge on the lateral patellar facet, in a knee with patellar tilt. Note that the posterior femoral condyles should be superimposed for proper measurements of patellar tilt on the lateral x-ray view.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 224. Copyright 2007, with permission from Elsevier.)

Another important measurement for malalignment of the extensor mechanism is the tibial tubercle-trochlear groove (TT-TG) measurement (Fig. 13-3). This relates how far lateral the tibial tubercle is in relation to the central portion of the trochlea.¹⁷ Normal TT-TG values are less than 10 mm, and grossly abnormal values are between 18 to 20 mm. The TT-TG can be easily measured on CT or MRI scans and should be thought of as a guide as to how far to move the tubercle during the osteotomy procedure. The final amount of anteromedialization is based on the intraoperative assessment of patellar stability.

FIGURE 13-3 Tibial tubercle-trochlear groove measurement (TT-TG). A CT scan was obtained and an image through the tibial tubercle was superimposed on an image through the femur. Line 1 is parallel to the posterior femoral condyles. Line 2 is through the highest point of the tibial tubercle and perpendicular to line 1. Line 3 is through the nadir of the trochlear groove and also perpendicular to line 1. The distance between lines 2 and 3 is the TT-TG (labeled as line 4). It equals 1.68 cm, which is on the limits of being abnormal.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 226. Copyright 2007, with permission from Elsevier.)

Holding Area

The patient is identified in the surgical holding area and the correct knee is identified according to the “Sign Your Site” protocol. The patient is given preoperative antibiotics and an exam is carried out showing the patient again the stability of the patella once the realignment is completed.

Any pain blocks can be done at this time by the anesthesia service, although in order to monitor for postoperative function and the possibility of a postoperative compartment syndrome, we do not routinely use nerve blocks for this operation.

Patient Positioning

The patient is brought back to the operating room and placed supine on the operating room table.

After the anesthesia service has secured an airway, a Foley catheter is placed in the standard fashion. The patient is kept supine during the procedure, and a small bump is placed under the ipsilateral hip to avoid the obligate external rotation that occurs in the lower extremity when the patient falls asleep. An exam under anesthesia is documented, looking specifically for knee effusion, passive range of motion, patellar tracking, patellar tilt, and the amount of lateral or medial patellar subluxation.

For the arthroscopy portion of the procedure, we use a lateral post.

A tourniquet is placed at the upper thigh area, and the lower extremity is prepped and draped in the standard fashion. To avoid capturing the quadriceps with tourniquet inflation and thus altering the normal patellar tracking, the knee is hyperflexed for tourniquet inflation.

Arthroscopy

A thorough arthroscopy is performed documenting any cartilaginous defects of the patella or trochlea. One should be acutely aware of defects of the medial or proximal patellar facet or medial trochlea, because this would be a contraindication for the anteromedialization procedure.

Patellar tilt and subluxation should be documented early in knee flexion (i.e., <15–20 degrees) because at greater knee flexion angles the patella is constrained by the trochlear bony anatomy, thus obscuring the patellar tilt and subluxation (Fig. 13-4, A). The other knee compartments are visualized, and any other concomitant arthroscopic surgery is performed at this time (Fig. 13-4, B).

FIGURE 13-4 A, View of patellofemoral joint arthroscopically before tibial tubercle transfer. Note the severe lateral patellar tilt and subluxation. B, View of patellofemoral joint after tibial tubercle transfer with anatomic alignment of the patella on the trochlea.

(Reprinted from Operative Techniques in Orthopaedics, vol. 17, issue 4, James Bicos and John P. Fulkerson, Indications and Technique of Distal Tibial Tubercle Anteromedialization, p. 226. Copyright 2007, with permission from Elsevier.)

Incision/Superficial Dissection

The arthroscope is removed but still kept sterile on the field in order to assess the postanteromedialization tibial tracking.

An 8 to 10 cm incision is made incorporating the inferolateral arthroscopy portal proximally and distally extending toward the tibial tubercle. The incision is kept just lateral to the anterior tibial crest to avoid having the incision over the subcutaneous bony skin. In addition, the line of the incision avoids placement of the hardware (tibial fixation screws) directly underneath the skin incision itself (Fig. 13-5). The incision is deepened down to the level of the patellar paratenon and just above the periosteum of the anteromedial tibia.