chapter 13: Surgical Treatment of Patellofemoral Chondrosis and Arthrosis
Anteromedial Tibial Tubercle Transfer
As the preceding chapters have already shown, lateral subluxation and tilt of the patella frequently lead to arthrosis. The usual patient who enters the physician's office with anterior knee pain has structural malalignment, either traumatic or congenital. Although lateral retinacular release is particularly helpful in relieving tilt, subluxation responds less consistently to lateral release, and patients with progressive arthrosis may not gain any prolonged benefit, particularly if advanced (Outerbridge Grades 3‑4) degeneration has developed. Lateral retinacular release in patients with patellar arthritis but no retinacular tightness is analogous to cutting the medial collateral ligament in a patient with medial knee arthritis.
Bandi (21), Maquet (22), Ferguson (23, 24), Radin (25, 26), and others (27‑34) have studied extensor mechanism anteriorization in the reduction of contact pressure on the patella or in the treatment of patellofemoral pain. Combining realignment of the malaligned extensor mechanism with anterior placement of the tibial tubercle may be extremely helpful in the management of patients with patellar arthrosis related to malalignment (20, 34‑37). Hejgaard and Watt‑Boolsen (33) noted that tibial tubercle anteriorization alone will not correct abnormal patellar tracking. Some very serious complications have been reported with straight tibial tubercle anteriorization using bone graft (38). The less secure fixation of some procedures has led to refinement of the "anteromedialization" concept such that early motion might be possible with better mechanical fixation.
Anteromedial tibial tubercle transfer permits the surgeon to achieve anteriorization of the extensor mechanism while improving patellar balance in the trochlea with medialization. Koshino (39) has shown also that the quadriceps lever arm and strength of knee extension can be improved with this procedure. Because of the frequent association between patellar malalignment and arthrosis, this procedure has been particularly useful in the management of patellofemoral pain patients. It is important, however, to know the correct indications for this procedure and to master the details of surgical technique.
Anteromedial tibial tubercle transfer (20) (Fig. 13.4) might be understood best as a surgical alternative to the Maquet procedure in patients with malalignment and distal or lateral facet arthrosis (Fig. 13.5). Because lateral retinacular release will relieve abnormal tilt of the patella when there is minimal or no arthrosis, it should be the procedure of choice in such patients. At times, however, lateral facet degeneration progresses to a point that simple lateral release will be ineffective, and it is such patients who might be considered for anteromedial tibial tubercle transfer (40‑42). Some patients with distal medial facet patellar arthrosis may benefit from this procedure, because contact stress is relieved, balanced, and moved proximally on the patella, essentially tipping up the "nose" of the patella. It is a particularly good alternative for patients who have patellar arthrosis secondary to malalignment. In most of the patients, the proximal medial facet escapes breakdown. This is the region that receives loading following anteromedialization. As with any surgical procedure, however, it is important to screen out patients who are seeking secondary gain or who have more severe problems, such as reflex sympathetic dystrophy, which will preclude a good result. Also, those patients with a dashboard or crush injury of the proximal patella are less likely to do well because the proximal patella is injured.
FULKERSON'S TECHNIQUE OF ANTEROMEDIAL TIBIAL TUBERCLE TRANSFER (20, 42‑44) (FIGS. 13.6‑13.36)
An anterolateral skin incision extends from the mid‑lateral patella to a point approximately 5 cm distal to the tibial tuberosity. Sharp dissection is used to the lateral retinaculum, which is released completely from the patella only to the level of the vastus lateralis. If further relaease appears to be necessary, it may be extended proximally to release the vastus lateral obliquus of Hallisey (see Chapter 1) only-being sure to preserve the main vastus lateralis tendon. The patella should be everted 90 degrees and examined carefully to determine how much debridement or arthroplasty to perform. Similarly, the surgeon should establish if any resurfacing of the trochlea is necessary, and employ debridement, microfracture arthroplasty, osteochondral core transfer, or articular cartilage cell transplantation as indicated. In general, lesions greater than 1 cm in diameter are treated by microfracture arthroplasy into subchondral bone. Soft but intact articular cartilage is left alone. Loose flaps or fibrillations of articular cartilage are resected. The lesions are measured and described as to extent and location in the operative note. At this point, if there has been clear retinacular pain, a segment of the painful portion of lateral retinaculum may be excised and sent for Gomori's trichrome stain and histologic evaluation.
The proximal anterior compartment musculature (tibialis anterior) is released sharply from the lateral tibia and reflected posteriorly with a periosteal elevator. It is best to avoid traumatizing this muscle and to use careful subperiosteal dissection without cutting muscle. The junction of the lateral and posterior cortices is exposed. The anterior tibial artery and deep peroneal nerve are at this level and must be protected. A Kelly clamp is placed behind the patellar tendon, and the medial and lateral borders of the tendon are identified. After making a linear incision just medial to the anterior tibial crest, a periosteal elevator is used to expose bone from the level of the tibial tuberosity to 5-7 cm distal. The Hoffman drill guide or a suitable alternative (the Mitek Tracker guide, Norwood, MA, works very well))is used to place several long 3.2‑mm drill holes parallel to each other, but in a plane that extends from the anteromedial tibia in a posterolateral direction such that the drill bits enter the tibia just medial to the anterior tibial crest and exit just anterior to the posterolateral corner of the tibia. As the osteotomy plane is designed, it is tapered distally such that only 2 to 3 mm of bone are left on the bone pedicle at the distal hinge, approximately 5 to 7 cm distal to the tibial tuberosity. Great care is taken at all times to preserve the patellar tendon insertion into the tibial tuberosity. Care as also taken to create a perfectly flat osteotomy plane. This is possible if the surgeon spends some time assuring that the guide pins are parallel. Once the osteotomy plane has been demarcated with the long drill bits, the surgeon should assess the alignment of the osteotomy and assure that it will give the obliquity necessary to achieve significant anteriorization of the tibial tubercle (see Fig.13.4). The Tracker guide mentioned above provides a cutting slot for creating the anteromedialization osteotomy and is an excellent alternative system.
At this point, the surgeon may use an oscillating saw or broad flat osteotomes to complete the osteotomy through the defined plane. A cut is also made on the lateral side of the tibia to shorten the osteotomy such that it will not extend proximally (Fig. 13.37). Also, a small, half‑inch osteotome is needed to cut the cortical bone proximal to the patellar tendon insertion. Once the osteotomy is complete, the bone pedicle is hinged distally, as in the Trillat procedure, and the bone pedicle is displaced in an anteromedial direction along the osteotomy plane. The knee may be placed through a range of motion at this point with the osteotomy held in the desired alignment. Twelve to fifteen mm of anteriorization is routine without bone graft, but a small bone graft from the metaphysis may be added to neutralize medialization and add anteriorization in selected cases (Fig. 13.38). The patella is observed to check patellar alignment, load distribution, and tracking. The bone pedicle is generally locked in place with two screws, at least one of which should be placed carefully into the posterior tibial cortex. This fixation prevents rotation, and if the osteotomy is flat, the bone will be quite stable permitting early motion of the knee and prompt healing. A Hemovac may be left in place for 2-24 hours and removed when the drainage diminishes. Assuming stable fixation of the bone pedicle, active and passive motion are started soon after surgery and most patients are discharged the day of surgery or the next morning, non‑weightbearing on crutches with a knee immobilizer, which is removed daily for motion exercises. Patients are encouraged to remove the knee immobilizer at least once a day and bend the knee to 90 degrees. Otherwise, patients keep the knee immobilizer in place for 4 weeks. Crutches are used for at least 6 weeks and until full weightbearing and reasonable quadriceps strength can be achieved. Early full weightbearing predisposes the patient to tibia fracture.
RESULTS OF ANTEROMEDIAL TIBIAL TUBERCLE TRANSFER
O'Hara and Fulkerson (unpublished data) noted that a steep, oblique osteotomy will allow up to 17 mm of tibial tubercle anteriorization without using any bone graft. This procedure provides consistent long‑term relief in appropriate patients. Unlike other extensor mechanism alignment techniques, ninety percent of patients more than 5 years after anteromedialization have had stable results without evidence of deterioration. Complications are less common and less severe than those reported after tibial tubercle advancement using bone graft. Skin slough, compartment syndrome, and avascular necrosis have been avoided using his technique. With early motion, stiffness has not been a problem. Less than two percent of patients have developed a clinically detectable postoperative deep venous thrombosis Six tibial tubercle avulsions or tibia fractures have occurred in over 500 cases (less than two percent). It is now apparent that obese females are at particular risk for this complcation. It is also apparent that early full weight bearing (before the seventh post operative week), predisposes patients to tibia fracture. .Of all patients followed for at least 2 years, 89% have had an objectively good or excellent result. Of those patients with severe patellar arthrosis, 75% have had a good result. Contact pressure studies in cadaver knees have shown substantial reduction of patellar contact pressures consistent with findings in other series of tibial tubercle anteriorization.
Buuck reviewed the long‑term results of our anteromedial tibial tubercle transfer patients (4 to 12 years, mean 8 years). The long‑term satisfaction was consistently good (91%). As anticipated, worker's compensation insurance patients did less well as did those with dashboard and crush‑type injuries. Pidoriano correlated results of our anteromedialization patients with location and severity of articular disease. Those patients with distal, central articular lesions (Ficat's critical zone) and lateral facet lesions did best after anteromedial tibial tubercle transfer, presumably because of preservation of the proximal medial facet, which receives load at the time of anteromedial tibial tubercle transfer. Patients with proximal crush‑type lesions and diffuse articular changes generally did poorly. Consequently, it appears that anteromedial tibial tubercle transfer is best suited to those patients with distal and lateral facet lesions. Also, Pidoriano noted that patients with central trochlea lesions and worker's compensation issues did less well with the anteromedial tibial tubercle procedure.
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