chapter 13: Surgical Treatment of Patellofemoral Chondrosis and Arthrosis
Tibial Tubercle Anteriorization with Bone Graft
Bandi (21) and Maquet (59) proposed improving the effectiveness of the extensor mechanism by transposing the patellar tendon anteriorly. Bandi demonstrated, in his experimental model, up to 33% reduction in patellofemoral loading forces for a 10‑mm anterior displacement (Fig. 13.40). Unit load reduction may be even greater if contact area is increased. It is important to release the lateral retinaculum at the time of anterior transposition. Several authors have reported impressive short‑term results. Unfortunately, longer follow‑up has shown far less desirable long‑term results. Engebretsen et al (60) noted that only 10 of 33 patients showed overall improvement at 3 to 9 years of follow‑up. He found also that patients with low‑grade chondromalacia did least well with the Maquet procedure. Certainly, this is not a procedure for patients with minimal patellar arthrosis! Hehne (61) found that centralization of the tibial tubercle does not reduce overall load on the patella. Hirokawa (62), however, did find 20 to 30% reduction of patellofemoral stress with tibial tubercle elevation, using a mathematical model. We believe the benefits of anteriorization are related to shifting of load as well as load reduction. This load shift involves shift onto the more proximal patellar articular surface, particularly when using a shorter anterior tibial shingle (63).
Sasaki et al (64) noted that anterior displacement of the tibial tubercle in conjunction with high tibial osteotomy may be beneficial in patients with medial and patellofemoral joint arthrosis. Although bone graft may be necessary in some cases, direct anterior displacement of the osteotomized tibia may be preferable.
The anteromedial tibial tubercle osteotomy procedure, as described in this chapter, can give straight anteriorization of the tibial tubercle if a small amount of bone (usually local from the lateral metaphysis) is placed into the osteotomy site (see Fig. 13.38). Another approach has been to do a sagittal or near sagittal plane cut at the level of the medial patellar tendon, cutting in from the lateral tibia to create a shingle of bone that can be mobilized and secured anteriorly with screws placed from lateral to medial (Insert new FIGURE) holding the anteriorized tibial tubercle anteriorly.
Unfortunately, there have been disastrous complications after straight anterior displacement of the tibial tubercle with bone graft(Maquet procedure). Skin sloughs, compartment syndromes, amputation, and mechanical failure (Fig. 13.41) have been reported after straight anteriorization with bone graft. Radin and Labosky (65) have written a helpful article on avoiding such complications. Preoperative use of Silastic skin expanders have been used to help in avoiding skin problems. Also, the surgeon must be careful not to create undue skin tension by placing too much bone graft behind the tubercle. On the whole, the Maquet procedure should be avoided, opting instead for more controlled and less profound anterior tibial tubercle transfer..
Pridie's (66) original concept for the treatment of bone eburnation was to remove all of the dense subchondral bone, thereby exposing cancellous bone. During the 1980’s, surgeons favored arthroscopic abrasion arthroplasty into subchondral bleeding bone (67), thereby bringing new undedifferentiated marrow cells onto the surface in the hope of gaining an improved articular surface with cartilage characteristics
Cellular resurfacing of the patella may be possible as well as resurfacing other articular cartilage defects. Brittberg et al (68) have demonstrated that it is possible to culture autologous articular cartilage cells and transplant the chondrocytes for treatment of knee cartilage defects in rabbits. Research continues on the clinical possibilities of this technique ed: INSERT Figure C. With regard to the patella, it is likely that normalization of stresses on the area of cartilage transplantation would be necessary for long‑term viability of transplanted chondrocytes. Consequently, appropriate realignment and decompression surgery for the patella is often appropriate at the time of resurfacing. OATS (autologous osteochondral transplantation) transplantation to the patella is difficult because of the unusual contours and dense bone of the patella. After bone surfaces are congruous, articular cartilage will typically be prominent and vulnerable (ed: INSERT Figure D).Our experience to date with osteochondral transplant to the patella has been disappointing. Results of OATS or articular cartilage cell transplantation to the patella may be enhanced by the concomitant use of tibial tubercle anteriorization or anteromedialization. (Add other sentence and Minas reference from paper revisions here.
Inside Chapter 13: