A New Technique for Distalization of the Tibial Tubercle That Allows Preservation of the Proximal Buttress

Abstract

Background: Tibial tubercle osteotomy (TTO) is a treatment option for patients with patellofemoral instability and chondrosis. Occasionally, these patients also present with patella alta, and distalization of the tibial tubercle is desirable. Free distal transfer of the tubercle, however, can compromise mechanical stability of the osteotomy construct, leading to loss of fixation.

Purpose: To evaluate alternative TTO proximal cut geometries to investigate whether these can result in tubercle distalization while preserving the proximal buttress.

Study design: Descriptive laboratory study.

Methods: Three variants of TTO cut geometry were evaluated on Sawbones as well as cadaveric knees. The proximal cut of the osteotomy was modified in 2 axes: anterior-posterior (AP) and medial-lateral (ML). Three variations were used: ML neutral/AP neutral, ML 30° proximal/AP neutral, and ML neutral/AP 30° proximal. The medial cut plane was 45° for all specimens. Tibial tubercle position was evaluated before and after osteotomy to calculate anteriorization, medialization, and distalization.

Results: Distalization was achieved with all variants. Increasing the inclination angle of the proximal cut in the AP and ML axes resulted in maximum distalization. A proximally directed cut yielded significantly more distalization when performed in the AP axis than in the ML axis (P < .05). Even the standard, neutral cut resulted in 5 mm of distalization.

Conclusion: Fulkerson osteotomy allows 3-dimensional repositioning of the tibial tubercle and has historically been utilized to achieve anteriorization and medialization. Even the neutral cut of a standard TTO resulted in distalization, which is relevant for patients with preexisting patella baja. Modification of the proximal cut increased distalization of the tubercle while preserving the proximal buttress, a potential benefit for construct stability.

Clinical relevance: These results provide a guideline for adjusting the proximal cut geometry in Fulkerson TTO to meet specific patient needs.

Keywords: knee injury; osteotomy; patellofemoral joint; patellofemoral syndrome.

Figure 1.

(A) The starting points are represented by dashed lines: AB, proximal cut (3 cm); BC, medial cut (7 cm). The double-arrow line (h) defines the distance of the proximal cut from the tibial plateau (2.5 cm). The most prominent point of the tibial tubercle (P) was used as a reference point to determine changes in position. (B) The most posterior lateral exit point (E) is where the lateral countercut starts; it is halfway between the anterior and posterior aspects of the lateral tibial wall.

Figure 2.

Proximal cut planes. (A) The dashed lines show the 2 variations for the medial-to-lateral proximal cut: the black line shows a neutral position; the red line, a distally directed cut; and the blue line, a proximally directed cut. (B) The dashed lines demonstrate the planes used for the anterior-to-posterior proximal cut: the black line shows a neutral position and the blue line, a proximally directed cut.

Figure 3.

Contact point between the posterolateral aspect of the tubercle fragment and the medial proximal shelf/buttress (red circle), providing resistance to proximal migration.

Figure 4.

Anterior views of a right tibia Sawbones specimen after tibial tubercle osteotomy: proximal cut medial-lateral neutral/anterior-posterior neutral. The image compares tibial tubercle position (P) before and (P′) after transfer. The double-arrow line represents the amount of distalization.