Reconstruction of the Medial Patellofemoral Ligament With Arthroscopic Control of Patellofemoral Congruence Using Electrical Stimulation of the Quadriceps

Abstract

Reconstruction of the medial patellofemoral ligament (MPFL) for recurrent patellar dislocation provides significant improvements in knee function. However, various complications have been reported, with most attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and inappropriate graft tension. Patellofemoral congruence at 30° of flexion on arthroscopy was therefore controlled using devices able to modify the length of the reconstructed MPFL. This was done under circumstances of external rotation of the knee joint and electrical stimulation of the quadriceps with the purpose of maintaining the patella in a lateral shift. Advantages of this technique include completely controllable correction on arthroscopy under the worst patellofemoral congruence induced by external rotation of the knee joint and electrical stimulation of the quadriceps at 30° of flexion of the knee joint; in other words, voluntary determination of lateral shift during arthroscopy.

Figures

Fig 1

Photographs showing specially made devices used for reconstruction of the medial patellofemoral ligament. (A) From left to right: graft gripper (GG), graft tensioner (GT), tensioner guide (TG), staple guide (SG), graft pusher (GP), and staple tamper (ST). The wing nut of the GG is used to fix the graft to the GG. The wing nut at the tail of the GT is used to fix the TG or SG to the GT. (B) The GT, with bifurcated tip, is fixed to the femur using 2 Kirschner wires (K-wire) with diameters of 2.0 mm. The GG is mounted to the GT to grasp and pull the graft. The 1.2-mm K-wire is introduced into the guide tunnel of the TG. The GP is introduced into the slit of the SG and fixed to the SG using the screw at the end of the GP. The ST is used to tamp a spike staple. The GP and GT have rules on the end to allow accurate operative procedures.

Fig 2

Photographs showing how devices are used on the medial side of the left knee joint. (A) The graft tensioner attached to the tensioner guide is introduced through the posteromedial incision, with a Kirschner wire (K-wire) with a diameter of 1.2 mm inserted into the guide tunnel of the tensioner guide and fixed to the femoral insertion site of the medial patellofemoral ligament with 2 K-wires with diameters of 2.0 mm. (B) The Poly-Tape is passed between the second and third layers on the medial side of the knee, between the bifurcated tips of the graft tensioner, and secured to the graft gripper, which is mounted on the graft tensioner. (C) After the patella is reduced to the planned position by sliding the graft gripper on the graft tensioner, the staple guide is mounted on the graft tensioner, and the graft pusher is introduced through the slit of the staple guide so that the graft pusher presses the Poly-Tape to the femur, simulating final fixation of the Poly-Tape with staples.

Fig 3

Drawing showing how to reduce the patella to the planned position in a left knee joint viewed from the proximal direction. The patella is reduced to the planned position (upper closed arrow), which can be expressed as the position of the patellar central ridge (PPCR), by sliding the graft gripper on the graft tensioner (lower closed arrow), while the patella is shifted laterally (open arrow) by external rotation of the knee joint (ER) and electrical stimulation of the quadriceps (ESQ). The tangent touching the medial (M) and lateral (L) articular surfaces of both sides of the trochlear groove is assumed to be the x-axis. The point on the trochlear groove that is the furthest from the x-axis is considered to be the deepest point (D). The intersection of the x-axis and the line that meets the x-axis at a right angle and passes through D is assumed to be 0 on the x-coordinate, and the lateral point of tangency (L) is assumed to be 100. The intersection between the x-axis and the line that is perpendicular to the x-axis and passes the patellar central ridge (C) is designated as P. The position of P is measured as PPCR (%) on the x-coordinate.

Fig 4

Treatment algorithm showing the medial patellofemoral ligament (MPFL) reconstruction technique from step 14 to step 17. If the maximum lateral shift is not as expected with the second attempt at step 16, the procedure advances to step 17, because obtaining the planned maximum lateral shift without complications seems infeasible.