chapter 10: Patellar Dislocation
Treatment of this condition is similar to that in the patient with recurrent subluxation; also, the surgeon should be certain to replace major osteochondral fragments whenever possible as would be done in the acute patellar dislocation patient. Results of surgical treatment are not always good at long‑term follow‑up, however (49).
In general, if the patient has had recurrent dislocations rather than subluxations, the degree of malalignment will be greater, and there may be considerable damage to the medial patella and lateral trochlea such that more definitive surgical realignment may be necessary. Additionally, Cerullo et al (50) have noted that the best results of extensor mechanism realignment were in patients with greater preoperative instability.
In some cases, when there are symptoms related primarily to medial facet articular damage (Fig. 10.7), the loose articular fragments may be resected, and drilling, cautious abrasion, or microfracture can be used to induce bleeding from subchondral bone. One must assure patellar stability, however, to avoid further injury to the already compromised medial facet.
In our opinion, the Trillat procedure as described by Cox (51) and reviewed in Chapter 7 forms the basis of realigning a chronically dislocating extensor mechanism that is malaligned (Q angle over 20 dgrees, and TT-TG relationship over 20), particularly when the lateral trochlea is deficient. Riegler (52) also reported good results with the Trillat procedure, although other formal realignment procedures are available, and may be preferred by some surgeons (53). Vastus medialis obliquus advancement may be necessary but carries the risk of overloading an already damaged medial facet. Placing "anchor" sutures in the distal aspect of the central quadriceps tendon avoids tethering the medial facet at the time of vastus medialis obliquus advancement. Lateral retinacular release alone is probably appropriate in treating the first dislocation acutely at the time of arthroscopy and osteochondral fragment fixation to treat patients with documented patellar tilt. Miller and Bartlett have reported satisfactory short‑term results with lateral release for recurrent patellar dislocation (54). Aglietti et al (55), however, noted that results of surgical treatment for recurrent patellar dislocation were worse using lateral release alone. He recommended combining lateral release with proximal or distal realignment as necessary. In our opinion, lateral release is not adequate for all patients with patellar dislocation, and the surgeon should keep an open mind to medial imbrication or tibial tubercle transfer when necessary to fully correct patellar alignment. Also, as Gomes (56) noted, the surgeon must decide whether to do a medial patellofemoral ligament reconstruction following patellar dislocation. Another option is tenodesis of the distal adductor magnus tendon to the medial patella for recurrent dislocation (57), but we have no experience with this.
Some patients who have recurrent dislocation with Outerbridge Grades 3 to 4 arthrosis and lateral tracking may benefit from anteromedial tibial tubercle transfer to unload a deficient patellar articular surface at the time of realignment. In some cases, articular resurfacing may be appropriate at this time if a damaged surface cannot be adequately unloaded by AMZ
When arthroscopic realignment can reconstitute the medial patellofemoral ligament without adding stress to deficient medial patella articular cartilage, this is a reasonable alternative. In general, as the degree of patella malalignment, dysplasia, and instability increases, medial tibial tubercle transfer becomes increasingly attractive, as there is increasing risk of medial repair disruption or adding excessive load to a damaged medial patella with imbrication. The option of viewing the imbrication arthroscopically has appeal and should add a measure of safety to an imbrication procedure. The final decision should be made to serve the patient’s best long term interest and avoid causing any added problem. As usual, surgical precision is, both in decision making and execution, is most important.
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