Combined reconstruction for patellar instability may be more anatomic, less invasive
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Combined reconstruction of the medial patellofemoral ligament and the medial quadriceps tendon-femoral ligament may provide a more anatomical, less invasive alternative technique for patellar instability, according to researchers.
Although MPFL reconstruction in isolation can provide good clinical and radiological results with variable rates of recurrent instability, João Espregueira-Mendes, MD, PhD, noted some risks are associated with this technique. To reduce these risks, Espregueira-Mendes and colleagues developed a technique that reconstructs both the MPFL and medial quadriceps tendon-femoral ligament that has shown to be more anatomic, less invasive and safer.
“With this technique we have four arms that cover a large surface, and the four arms are going from the quadriceps tendon to the adductor tubercle with two arms and another two arms from the patella to the adductor tubercle,” Espregueira-Mendes, of the School of Medicine at the University of Minho, Braga, Portugal, Dom Henrique Research Centre and Clínica Espregueira – FIFA Medical Centre of Excellence Porto, Portugal, told Healio.
In addition to being more anatomic, he noted the combined technique is a soft tissue reconstruction, which eliminates the risk of fracture of the patella. Without bone fixation, Espregueira-Mendes also noted surgeons do not need to use anchors and other devices, making the combined procedure less expensive.
Fixation of the graft around the adductor tendon instead of into the bone allows for this combined technique to be performed in patients with an open physis and provides a more reliable fixation point, according to Espregueira-Mendes.
“We find the Schöttle points on the femur with X-ray and it’s difficult sometimes. You do [make] mistakes on finding the Schöttle point because you need to have a 3D measurement on your X-ray device and it’s not easy, and also you get radiation yourself,” Espregueira-Mendes said. “So for the surgeon, in the regular MPFL reconstruction you need to have radiation. With this technique you don’t need X-ray because you put your graft around the adductor tubercle.”
He added the combined technique provides elasticity that helps avoid over constraint of the fixation, which may lead to osteoarthritis.
“The key point of the surgery is the tension,” Espregueira-Mendes said. “Of course, this is something that you get only with experience, but if you allow the patella to move 1 cm you are in the position to have a good result.”
For postoperative rehabilitation, Espregueira-Mendes noted patients are allowed flexion of the knee up to 90° during the first 6 weeks.
“We protect the flexion of the knee for 90° in 6 weeks and the rehabilitation is a classic rehabilitation for MPFL,” Espregueira-Mendes said.
Perspective
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Most surgical procedures evolve gradually from a surgeon-conceived approach to a more anatomic reconstruction. Such is the case for the medial restraints of the patella when treating lateral patellar instability. The native medial patellofemoral complex has both patellar and quadriceps tendon attachments, so it makes anatomic sense for the reconstruction to incorporate both.
A single sheet, truly anatomic reproduction would be difficult as the “sheet” of the medial patellofemoral complex is complex at the collagen orientation level (understanding that a fascia “sheet approach” has been described). Therefore, prior to future “bioprinting of a true medial patellofemoral complex” to reproduce the separate kinematic behavior of both segments of the medial patellofemoral complex, the use of two separate grafts is logical and is similar to the technique I share. For those with access to allograft, it is an option as it has been shown to be equally effective.
Patella and quadriceps soft tissue attachment sites duplicate anatomy, and soft tissue fixation avoids patellar fracture complications without an increase in future instability as previous authors have reported. The distal extent of the adductor magnus is near the anatomic medial patellofemoral complex femoral attachment, noting the “ribbon” distribution of the attachment that many authors have described. Soft tissue only attachment at the femoral site has been used by other authors in the open physeal patients with good results.
I applaud the authors on their innovative approach. As the authors are masters of the patellofemoral compartment, I know they set the length of the four graft arms appropriately. My words of caution for the less experienced surgeons:
1. Consider not using the term tension as with the patella in the neutral position, there is no tension. Rather, tension develops as the patella is displaced laterally to the 25% excursion the authors cite (one quadrant of displacement). Thus, one might consider the intraoperative technique of placing the knee through full range of motion and setting each graft to achieve a change in length of each graft arm that a) limits lateral patellar displacement to one quadrant and b) allows the graft to become more lax with flexion (anatomometric).
2. The femoral attachment is key in achieving anatomometric behavior of the graft. It is well described as a ribbon within the saddle between the adductor magnus attachment and the medial epicondyle. While this may seem somewhat at odds with the authors’ femoral attachment site, it is not completely. Note that the adductor tendon attachment is not a point, but extends distally as an aponeurosis from the classically shown bony attachment site. Preserving and anchoring to include this distal extension allows a more anatomic behavior of the grafts distal to the adductor magnus “pulley.”
3. The grafts on the proximal side of the pulley may exhibit non-anatomometric length changes and, in some patients, they could become tighter with flexion if fixed near extension. If this graft length change behavior is noted during the intraoperative range of motion assessment, then the proximal graft arm lengths would be set (fixed with suture) in a degree of flexion that avoids “over-tightening.” The four-strand graft approach (MPFL + medial quadriceps tendon-femoral ligament duplication) may be also used with a traditional socket within the anatomic saddle attachment ribbon area that allows anatomometric behavior of all four graft arms.
References:
Bollier M, et al. Arthroscopy. 2011;doi:10.1016/j.arthro.2011.02.014.
Parikh SN, et al. J Bone Joint Surg Am. 2011;doi:10.2106/JBJS.J.01558.
Parikh SN. Tech Knee Surg. 2011;10:171-177.
Shah JN, et al. Am J Sports Med. 2012;doi:10.1177/0363546512442330.
Tanaka MJ, et al. J Bone Joint Surg Am. 2012;doi:10.2106.JBJS.K.01449.
Tanaka MJ, et al. Knee Surg Sports Traumatol Arthrosc. 2019;doi:10.1007/s00167-018-5266-y.
Tanaka MJ, et al. Sports Med Arthrosc Rev. 2019;doi:10.1097/JSA.0000000000000238.
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