chapter 5: Arthroscopy of the patellofemoral joint
ARTHROSCOPIC MEDIAL IMBRICATION
Availability of arthroscopic tools that facilitate suture passage inside a joint have made arthroscopic medial imbrication quite feasible. Radiofrequency thermal shrinkage has been tried by some surgeons following lateral release, but it is unlikely that medial capsule will “pull” a patella medially as a result of tissue shrinkage. In fact, thermal techniques inevitably damage tissue in the short run and could lead to weakening of the medial capsule or medial patellofemoral ligment inadvertently.
When there is lateral patella subluxation, medial capsule imbrication may be necessary to reduce a patella into the trochlea and restore normal tracking mechanics. Using an 18 gauge needle and a penetrating (bird-beak) grasper several sutures (preferably #2 nonabsorbable) mayplaced into the deficient medial capsule/patellofemoral ligament such that the tissue is gathered and tightened upon tying the suture ends. This may be accomplished in an inside-out or ouside-in fashion. We have used two methods for shortening the tissue-either incision of the tissue between the sutures or careful radiofrequency shsrinkage in an antero-posterior corn row fashion after tying the sutures to gather tissue and take strain out of the medial capsule. In either case, the surgeon must be certain that there is adequate tissue gathering to assure a true realignment. We feel these patients must be protected for 5-6 weeks, but limited, single cycle flexion of the knee daily after the first 2-3 weeks, depending on the quality of the imbrication and tissue.
When there is a larger articular lesion which requires resurfacing in the patellofemoral joint, there are several options. The surgeon may harvest articular cartilage for culture and plan a later articular cartilage implantation (ACI). Another option is to perform an osteochondral autograft. At the time of arthrocopy, however, the surgeon may also abrade or penetrate the subchondral bone in the defect to accomplish resurfacing by bone marrow stimulation. In general, we favor this last option, whenever possible, as described by Steadman(personal communication).
Particularly for smaller(<1.5cm.) lesions, arthroscopic microfracture arthroplasty (Steadman) has been effective in our experience. Under arthroscopic control, the Steadman arthroscopic microfracture picks are used in a circumferential fashion to penetrate into the subchondral bone of the articular defect with 3-4 mm between the penetrations. Of course this can be done with a drill or wire, but we find the picks extremely easy to use and effective. Following this procedure, motion is desireable but loading of the treated area should be very limited for about 6 weeks.
In our experience to date, osteochondral transfer arthroplasty and articular cartilage cell implantation are best performed as open procedures.
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