Anatomic Double Bundle single tunnel Foreign Material Free ACL-Reconstruction - a technical note

Abstract

The anterior cruciate ligament (ACL) consists of two bundles, the anteromedial (AM) and posterolateral bundle (PM). Double bundle reconstructions appear to give better rotational stability. The usual technique is to make two tunnels in the femur and two in the tibia. This is difficult and in small knees may not even be possible. We have developed a foreign material free press fit fixation for double bundle ACL reconstruction using a single femoral tunnel ((R)). This is based on the ALL PRESS FIT ACL reconstruction. It is suitable for the most common medium and, otherwise difficult, small sizes of knees.

Method: Using diamond edged wet grinding hollow reamers, bone cylinders in different diameters are harvested from the implantation tunnels of the tibia and femur and used for the press fit fixation. Using the press fit technique the graft is first fixed in tibia. It is then similarly fixed under tension in the femoral side with the knee in 120 degree flexion. This is called Bottom To Top Fixation (BTT). On extending the knee the graft tension is self adapting. Depending on the size of the individual knee, the diameter of the femoral bone plug is varied from 8 to 13 mm to achieve an anatomic spread with a double bundle-like insertion. The tibia tunnel can be applied with two 7 or 8 mm diameter tunnels overlapping to a semi oval tunnel between 10 to 13 mm.

Results: Since May 2003 we have carried out ACL-reconstructions with Hamstring grafts without foreign material using the ALL PRESS FIT technique. Initially, an 8 mm press fit fixation was used proximally with good results. Since April 2008, the range of diameters was increased up to 13 mm. The results of the Lachman tests have been good to excellent. Results of the Pivot shift test suggested more stability with femoral broader diameters of 9,5 to 13 mm.

Conclusions: The foreign material free fixation of ham-string in the ALL PRESS FIT Bottom To Top Fixation is a successful method for ACL Reconstruction. The Diamond Instruments and tubed guiding devices are precise, reliable and easy to manage. On this basis a double bundle reconstruction is achieved using a single tunnel. A broad anatomic femoral insertion with autogenous bone plugs inserted near the cortex seems to improve rotational stability.

Keywords: ACL; bottom to top; double bundle; foreign material free; press fit; single tunnel.

Figure 1

Semitendinosus- and Gracilis tendon are prepared in two bundles. A suture indicates the minimum length in the femoral tunnel. In the tibia side sutures keep the 11 mm bone cylinder from the tibia head. The bone-window is necessary for bone-bone-contact healing.

Figure 2 a,b,c,d.

The graft is implanted bottom to top (BTT). The distal bone cylinder is impacted press fit under the tibia plateau (a). The proximal graft is tensioned and fixed press fit in 120 degree knee flexion (b). The tension of the graft is self adapting in extension (c,d).

Figure 3

The width of a 11 mm diamond instrument overlaps the insertion of AM and PL bundle. The bone cylinder harvested from this tunnel is given back press fit and forms the two bundles.

Figure 4

In extension the bundles self adapt the graft tension. After a year the bundles show regular signal and anatomic position.

Figure 5

40 y, M, femoral single tunnel with 13 mm diameter and original ridge (left). ACL rerupture with adequate trauma after 7 months. The broad insertion of the AM and PL bundle of the graft with a reorganized bifurcate ridge can be observed as evidence of a two bundle engrafting on the bonecylinder and reorganization of the origin insertion (central, right).