MPFL Reconstruction With a Double-Loop Gracilis: The Concept of “Favorable Anisometry”

Abstract

Background:

Medial patellofemoral ligament (MPFL) reconstruction has shown very good results in patella dislocation and patient satisfaction. However, correct positioning and tensioning of the graft can be difficult to achieve and can lead to complications.

Indications:

Medial patellofemoral ligament reconstruction is always indicated for recurrent patellar instability with dislocation in extension, with or without other procedures that aim to correct predisposing factors of instability.

Technique Description:

An arthroscopic examination is first done to assess chondral lesions. The gracilis tendon is detached from the tibia and prepared to pass through 3-mm drill holes. The medial edge of the patella is exposed, and two 3-mm drill holes are made. Dissection is performed with a scissors between the second and third layers toward the medial epicondyle, where a small skin incision is made. A guidewire is placed just anterior and distal to the adductor tubercle. A suture is used to test the isometry of the femoral drill hole. If correct tension or “favorable anisometry” is achieved, a 5-mm bone anchor is placed. The graft is looped and pulled into the femoral hole with sliding sutures. The 2 free ends of the graft are pulled through the patellar drill holes and looped back onto themselves. The graft is tensioned with the knee in maximum extension while pulling the patella proximally with a bone hook as hard as possible in the direction of the femoral shaft. The principle is that with maximum quads contraction, the tension in the patella tendon should be more than in the reconstructed MPFL.

Results:

Immediate full range of motion, intensive isomeric quads contraction exercises, and full weight-bearing with crutches for 2 to 4 weeks are recommended. Sport can be resumed after 3 months, but it usually takes 6 months to play at the same level as before.

Discussion/Conclusion:

The technique of “favorable anisometry” of the MPFL has shown a very low rate of recurrence of patella dislocation. Complications are rare and extensor lag is very uncommon, thanks to the specificity of tensioning the graft.

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

In this video, we present the surgical technique for an anatomical reconstruction of the medial patellofemoral ligament with a double-loop gracilis tendon and describe the principle of “favorable anisometry” of the graft. None of the authors have a conflict of interest. The goal of this video is to describe the surgical technique for a medial patellofemoral ligament (MPFL) reconstruction using a double-loop gracilis tendon. It includes tips to avoid pitfalls, our rehabilitation protocol, and the results of this technique. In most patella dislocations, there is a predisposing factor that leads to dislocation, such as patella alta, ligament hyperlaxity, trochlear dysplasia, or lower limb malalignment. We believe that form follows function and that the articular surface of the patella reflects the corresponding trochlea. If this is true, the relation between the patella and the trochlea should not be disturbed, and an unstable patella should be restored to its original natural position. This should prevent a misfit between the patella and its trochlea, allowing for maximum contact area in the patellofemoral (P-F) joint, decreasing the possibility of progressive P-F degeneration. The aim of our MPFL reconstruction is not to disturb the natural articulation between the trochlea and its corresponding patella but to reconstruct the deficient MPFL with a stronger ligament than the original to compensate for the underlying predisposing factors to patella dislocation. This clinical case illustrates our indications and technique. This case is of a left knee in a 22-year-old woman with recurrent patella dislocation. On clinical examination, she was hyperlax, with slight valgus morphotype and 10° bilateral recurvatum, a J-sign, and a positive apprehension test. There was a tender area on the lateral side of the femoral condyle. On radiographs, there was a crossing sign showing a trochlear dysplasia type A in Dejour classification, a loose body in the para-patellar gutter, and normal patellar height. Under anesthetic, it was easy to dislocate the patella; there are also more than 2 quadrants of lateral movement. We always first do an arthroscopic examination with special attention to chondral lesions on the medial patella facet and the lateral femoral condyle. The chondral fragment in the lateral gutter was removed. The gracilis tendon is exposed through an oblique medial incision and a cut through the sartorius fascia. The tendon is kept attached distally on the tibia and stripped from the muscle; the proximally freed tendon is now dissected off the tibia with a periosteal strip to gain maximum length. The graft is prepared, and excessive tendon tissue is removed to allow for passing through a 3-mm drill hole. Krackow-type sutures are attached at both ends for later pulling through the drill holes in the patella. The graft is soaked in swab wet with a gentamicin solution. We now expose the medial edge of the patella through a short longitudinal incision. The superficial fascia is split, and a dissecting scissors is used to dissect between the second and third layers toward the medial epicondyle. A small skin incision is made, and the fascia is split over the tip of the scissors. The dissecting scissors is used to pull a double-looped suture, with a knot, from the medial epicondyle to the medial edge of the patella. This suture will be used to test the isometry of the femoral drill hole. On the medial edge of the patella, two 3-mm drill holes are made, the first hole on the central medial patella edge and the second about 10 to 15 mm proximal depending on the size of the patella. The 3-mm drill holes are cleaned with a tape allowing for easy passage of the graft. The adductor tubercle is usually easy to palpate; a guidewire is placed just anterior and distal to the tubercle. The loop, in the double suture, is placed around the guidewire and from there pulled anterior between the fascial layers to the 2 drill holes on the medial edge of the patella. The normal patella is tight in the first 30° of flexion and then becomes lax with further flexion. The free end of the suture is pulled through the 2 holes on the medial edge of the patella. With the knee in 30° of flexion, the suture ends are clamped with 2 separate needle holders and the isometry tested. Moving the femoral guidewire proximally will decrease the tension in extension and increase it in flexion; moving it distally has the opposite effect. If the correct tension or so-called “favorable anisometry” is achieved, a 4.5-mm drill hole is made over the guidewire. The drill hole is expanded with the arthroscopy obturator. A 5-mm bone anchor is placed into the 4.5-mm hole in the medial femur. The graft is looped and the loop pulled into the 4.5-mm hole with sliding sutures. The graft and a “pulled-back suture” are now retrieved at the medial edge of the patella. The 2 free ends of the graft are pulled through the drill holes and looped back onto themselves using the “pull-back suture.” The graft is tensioned with the knee in maximum extension while pulling the patella proximally with a bone hook as hard as possible in the direction of the femoral shaft. The principle is that with maximum quads contraction, the tension in the patella tendon should be more than in the reconstructed MPFL. The bone hook is removed, and the graft is sutured to the soft tissue on the patella and then onto itself in a double-looped fashion. Testing at the end of the operation shows a stable patella with a good range of medial and lateral translation. The pre-patellar fascia is closed as well as the subcutaneous and cutaneous layers.

Postoperatively, we recommend immediate full range of motion, intensive isomeric quads contraction exercises, and full weight-bearing with crutches for support. As soon as proper quads control is achieved, the crutches can be discarded, usually between 2 and 4 weeks. We do not recommend a knee brace. Physiotherapy aims to recover early active and passive range of movement, and focus on intensive quads and general muscle rehabilitation. Depending on the quads strength, sport can be resumed as early as 3 months, but it usually takes 6 months to be fully confident and play at the same level as before. What are the possible complications, and how to avoid? The MPFL is a nonisometric ligament, tight in the first 30° of flexion and then becomes lax as the patella enters the intercondylar groove. If the ligament is too tight in flexion and loose in extension, the patient will lose full flexion and might have unstable patella in full extension. Our technique of ensuring the ligament is in a favorable nonisometric position prevents a ligament too tight in flexion and loose in extension. If the reconstructed MPFL is too tight in extension, the patient will have an extensor lag as the tension with knee extension is less in the patellar tendon than in the reconstructed MPFL. Pulling on the patella with the knee in full extension simulates quadriceps contraction and avoids a ligament too tight in extension. The tension in the patellar tendon should be more than in the reconstructed MPFL as this prevents the complication of an extensor lag. We published a series of 23 consecutive MPFL reconstructions using this technique in recurrent patella dislocations. There was no recurrence of dislocation, and the Kujala score was 93 points after a mean 2.3-year follow-up. Only one patient had an extensor lag at last follow-up, and preoperative chondral lesions were associated with lower knee function scores. We reported on the outcomes of 26 knees with 13 to 20 years of follow-up treated with isolated MPFL reconstruction at the biannual ISAKOS (International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine) meeting in 2015. There was only one recurrent dislocation in a professional rugby player, occurring 12 years after surgery. Scores were still good at last follow-up, primary chondral damage was associated with lower Lysholm score, whereas patella alta was associated with lower Kujala score. Patella height increases the anisometry of the graft, and we now recommend performing an associated distalization of the tibial tubercle in cases of severe patella alta. According to Victor, the tension in the proximal and distal fibers of the MPFL is different. In contrast to other techniques, we tension the proximal and distal limbs of the reconstructed ligament separately, probably creating a more normal MPFL ligament. We do not recommend doing a lateral release in combination with an MPFL reconstruction. The lateral retinaculum is lax in extension and tight in flexion. It has been shown that a lateral release can increase patella instability. The position of the femoral tunnel is important because it has a large effect on the isometry of the ligament. Combining the different descriptions published, the insertion should be seen as an area rather than a point. It must be individualized by an intraoperative graft tension assessment. If the femoral attachment is too proximal, the graft will be loose in extension and ineffective, and tight in flexion, which can lead to loss of flexion, patellofemoral pain, and degeneration. On the opposite, an attachment that is too distal can lead to an overtight graft in extension, resulting in an extensor lag. In conclusion, isolated MPFL reconstruction is effective in stabilizing the patella over a long period. It allows patients to play at the highest level. The favorable anisometry of the graft must be checked carefully, and our technique prevents an overtight reconstructed MPFL. Results are stable over 16 years, and it might decrease the possibility of late patellofemoral degeneration.