chapter 13: Surgical Treatment of Patellofemoral Chondrosis and Arthrosis

Infrapatellar Contracture Syndrome

Paulos reviewed the infrapatellar contracture syndrome (69), a condition that can occur following cruciate ligament reconstruction, trauma, or other surgery around the anterior knee. Since Shelbourne and Nitz (70) introduced accelerated rehabilitation after cruciate ligament reconstruction, this complication has been far less common as a complication of cruciate ligament surgery. Nonetheless, there are many patients who are left with chronic scar behind the patellar tendon after trauma or surgery to the knee, and they will ultimately develop anterior knee pain as well as stiffness.

As a consequence of infrapatellar contracture, anterior knee pain may become intractable, and abnormally increased contact stress on patellofemoral articular surfaces is common. It is important to release this contracture, using an open technique to assure complete release of all tight, tethering bands. Early motion following this type of release is imperative.

Although most patients respond very favorably to complete release of an infrapatellar contracture, I have noted that some problems with anterior knee pain continue in many of these patients. The patient frequently may be happy with improved motion after the contracture release and experience reduction of pain but be left with some functional loss, and may return to the office requesting additional treatment for residual pain. Depending on the amount of actual articular damage, anteriorization of the tibial tubercle may be appropriate in some of these patients, provided there is good proximal articular cartilage on the patella. McMahon et al (71) have noted that resection of the retropatellar tendon fat pad will not compromise vascularity of the patella, so pain must be attributed to other factors. It is likely that some irreversible damage occurs to articular cartilage of the patella with infrapatellar contracture.

Patellofemoral  Replacement

Many materials have been tried in the past, both artificial and natural. Arthroplasties with skin, fascia, fat pad, and bursa have been tried (72‑76). Polyethylene replacement of the patella alone has been less successful than metal on articular cartilage (Fig. 13.42). McKeever (77) introduced a metal resurfacing prosthesis that has been reported to give reasonable results (77‑79). In 1992, Harrington (80) reviewed the long‑term (5‑8 years) results of McKeever patella resurfacing in 28 patients (mean age, 36 years). Nineteen of the patients had normal trochlear cartilage. Seventeen of the twenty‑eight patients had a good or excellent result. There were three patients with poor results, which were attributed to tricompartmental arthritis. Harrington (80) noted a need for prolonged physical therapy after patella resurfacing, but had no problems of instability or prosthetic loosening.

Worrell (81) reported a redesigned version of the McKeever prosthesis in 1975 and published his results in young patients in 1986. Pickett and Stoll and Pickett (82) reported better results with patellar replacement than with patellectomy. Blazina et al (83) recommended patellofemoral replacement particularly for patients with severe femoral groove degeneration. Worrell (81) suggested that prosthetic resurfacing of the patella is most appropriate for patients with Grades 3 or 4 chondromalacia of the patella and poor quadriceps function. Scott (84) has cautioned that there are numerous potential serious complications of prosthetic patellar replacement surgery including patella fracture and prosthesis loosening.

There has been a recent resurgence of interest in patellofemoral replacement, but no one prosthesis has emerged as definitive. There are many questions remaining to be answered about the use of patellofemoral replacement. What seems clear is that this is one alternative when articular preservation alternatives are exhausted or inappropriate. I have done ten patellofemoral replacements and have had better results when there are no compensation issues involved.  Currently, I do not recommend patellofemoral replacement in worker’s compensation patients.

If isolated patellofemoral replacement is chosen, the surgeon must be sure that the extensor mechanism is cenralized, there is no patella alta, the patient is fit enough to recover, the remainder of the knee is satisfactory, and the patient is motivated.
There are several unicompartmental patellofemoral prostheses available and these are still evolving.  Criteria for selecting the prosthesis should include a smooth transition from the trochlea component to the intercondylar notch area, adequate but not excessive trochlear depth, accurate and easy to use instrumentation, minimize bone resection, and minimal polyethylene-articular cartilage contact upon knee flexion.






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