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CURRENT CONCEPTS
An advantage of using the anchor fixation technique is the possibility of using a graft of shorter length, as in the case of the gracilis tendon. Furthermore, the procedure allows for smaller incisions with better aesthetic results. This is because less exposure is required, as looping the graft through the lateral facet of the patella or to expose the bone tunnels is not necessary. Corroborating the opinion of Song et al., another advantage is that it is a relatively simple technique, which results in shorter surgical time and decreased exposure to radiation.
Straight lateral radioscopy was used to identify the femoral insertion site of the graft in all cases, following the parameters described by Schöttle et al. According to studies by Schöttle et al., the use of radioscopy is considered of great importance in determining the ideal anatomical point for graft fixation in the femur. Several authors have shown that non- anatomical positioning of the femoral tunnel interferes with the patellofemoral kinematics. Elias and Cosgarea found that the tunnel positioning error, more proximal in the femur, can overload the medial compartment of the patella, which can lead to degeneration of the medial facet and graft rupture or failure. Similarly, Thaunat and Erasmus suggested that non-proximal anatomical positioning of the graft would lead to hypertensioning of the graft and consequently to knee rigidity. A more distal positioning is not able to tension the graft enough to restrict dislocation of the patella. Amis et al. found that the positioning error in the frontal plane is better tolerated.
Kang et al. suggested that the fixation of the MPFL bands should be performed at different angles, with the ISB at 0° and the SOB at 30°. In this way, the patellar stability can be maintained at higher flexion angles such as at greater than 60°.
Surgical Technique
The patient was placed in the supine position under spinal anesthesia. First arthroscopy was performed to identify associated lesions or to remove intra-articular loose bodies. Lateral retinacular release was not performed in any of the cases.
The gracilis tendon was removed through an incision of about 2 to 3 cm above the pes anserine tendons. The “goose foot” bursa was removed, and the semitendinosus tendon was exposed and resected. The gracilis tendon was considered sufficient due to its resistance, which is compatible with what is expected for MPFL, which is 208 N. However, the semitendinous tendon was used, as it was long enough to permit the preparation of the two bundles, with the passage of the graft through the bone tunnel in the femur.
Then, an incision was made under the medial border of the patella at a distance of 4 to 5 cm between the medial border of the patella and the medial epicondyle of the femur. With the aid of a curette, a sulcus was made on the medial border of the patella, above the transition with the posterior chondral facet, deep enough to accommodate the graft. Two 5-mm metal anchors were inserted into the proximal two-thirds of the patella, 10 to 15 mm from the joint.
The anatomical site on the femur was confirmed with the aid of straight lateral radioscopy, following the parameters described by Schöttle et al. A Kirschner wire was inserted at this point, directed anteriorly and proximally, thus avoiding penetration into the posterior region of the femoral condyle. The femur was drilled to create the bone tunnel, and the central part of the graft was first fixed at this point by using the bioabsorbable interference screw. Next, the two bundles of the graft were passed through the patella by the second layer of the medial retinaculum, with the aid of curved forceps. The two ends of the graft were sutured separately by the anchors. The first bundle, considered as the inferior straight bundle, was set at 30° of flexion; and subsequently, the superior oblique bundle was set at 60° of flexion (Kang et al., 2010, Han et al. 2011 Sadigursky et al. 2012). The required tension was checked by the mobility of the patella, which can reach glide approximately 2 quadrants.
After fixation, the position of the patella was checked by using arthroscopic imaging. Local irrigation was performed with 0.9% physiological saline, the subcutaneous tissue was sutured with Vicryl 2.0, and the skin was sutured with separate stitches of Nylon 3.0.
Postoperative Period
The knee was immobilized in extension with a long brace for 2 weeks. Physical therapy was initiated in the first week with a progressive increase in the arc of motion and should reach 120° of flexion during the sixth week. During the first 3 weeks, partial load with the aid of crutches was allowed. After the third week, the patient was allowed to bear full load without crutches. Isometric exercises to strengthen the quadriceps and elevation of the leg in extension were permitted in the immediate postoperative period. After 6 weeks, the patient should be able to return to normal activity. Contact sports and rotation were allowed at 6 months after surgery.
Conclusion
The double bundle MPFL reconstruction at different angles of flexion, or at the same angle fixing on the patella first, aims to gain stability at higher flexion angles, specially above 45 degrees of knee flexion. Nevertheless more clinical trials should be conducted in the future, especially with the combined medial patellotibial ligament reconstruction, which seems to have similar goals in adult patients. In addition, more precise stratification of the patients should be considered for the elective patients that should undergo the technique.
ISAKOS NEWSLETTER 2015: Volume I 23