Medial Patellofemoral Ligament Reconstruction Using Adductor Magnus Tendon

INTRODUCTION

Pathogenesis

Acute lateral patellar dislocations are associated with injury to the medial patellofemoral ligament (MPFL); a traumatic first-time patellar dislocation results in MPFL injury approaching 100%.¹
Surgical stabilization has been recommended after failure of appropriate nonoperative management.
The goal of MPFL reconstruction is to restore the loss of medial soft-tissue patellar stabilizer, which has been injured and/or chronically lax because of lateral patellar dislocation(s).
MPFL reconstruction using the adductor magnus tendon (AMT) is a preferred surgical technique, especially in the skeletally immature knee, because it does not involve drilling near the distal femoral physis.²,³ It is important in skeletally immature knee that femoral fixation technique is not disruptive to the region of the growth plate.
Though most MPFL reconstruction techniques in skeletally mature patients utilize an alternative graft and femoral fixation method, MPFL reconstruction using AMT is not restricted to skeletally immature population.
MPFL reconstruction using AMT is an anatomic approach with a flat graft similar to native MPFL⁴,⁵ (Figure 9.1).
Table 9.1 lists indications and contraindications of MPFL reconstruction using adductor magnus tendon.

EVALUATION

Patient History

The indication of MPFL reconstruction is typically in patients with a history of multiple lateral patellar dislocation episodes.
Patellar subluxation, defined as lateral patella translation without complete movement out of the groove, can sometimes be an indication in the skeletally immature population, owing to an atraumatic etiology of pediatric onset of patellar instability.

Physical Examination and Imaging

An isolated MPFL reconstruction is not indicated if high degree of trochlea dysplasia or excessive patellar
height (patella alta) is present on physical examination or imaging.

Figure 9.1 Schematic diagram illustrating the medial side of the right knee. The adductor magnus tendon is cut and transferred toward patella (arrows) to reconstruct the medial patellofemoral ligament.

TABLE 9.1 Indications and Contraindications for MPFL Reconstruction Using Adductor Magnus Tendon

Indications	Contraindications
Recurrent lateral patellar dislocations Symptomatic recurrent patellar subluxation Skeletally immature patients	Patellofemoral pain without instability Presence of high-degree trochlear dysplasia or significant patella alta Severe rotational and coronal plane deformities Permanently dislocated or habitual dislocation in flexion

Rotational and coronal plane deformities of the femur and tibia should be evaluated and may need to be addressed prior to or in addition to MPFL reconstruction. MPFL reconstruction alone cannot compensate for extreme physical alterations of the extensor mechanism.
An isolated MPFL reconstruction is not indicated in permanently dislocated or habitually dislocating patella, or patellar dislocation in flexion, because of major anatomic factors including bony and lower limb alignment deformities. An isolated MPFL reconstruction is unlikely to eliminate such abnormal patellar tracking.

SURGICAL MANAGEMENT

Surgical Anatomy

The MPFL has been described as the most important medial restraint against lateral patellar displacement.⁶,⁷
It acts as a checkrein between the medial femoral condyle and the patella.⁷
It is a vertically oriented ligament found in the same layer as the medial collateral ligament. It is an extracapsular structure found in layer 2 of the three-layer description by Warren and Marshall.⁸
It attaches to the femur 10 mm proximal and 2 mm posterior to the medial epicondyle, in the saddle between the medial epicondyle and the adductor tubercle (Figure 9.2).
The adductor tubercle is a readily palpable bony prominence and a more discrete anatomic point and may be a preferred landmark for locating the femoral insertion of the MPFL during surgery. The MPFL attaches approximately 2 mm anterior and 4 mm distal to the adductor tubercle.⁹
The width of the MPFL at the femoral insertion is approximately 10 mm.⁹
The patella attachment of the MPFL is approximated at the junction of the proximal and middle thirds of the patella, typically at the location where the perimeter of the patella becomes more vertical.
The MPFL patellar attachment has a mean width of 28 mm and is wider than the femoral attachment.⁹

Preoperative Planning

Multiple factors that predispose to patellar instability, including ligamentous laxity, muscular weakness, shallow trochlea, patella alta, and/or poor body mechanics, should be carefully analyzed and documented, prior to performing MPFL reconstruction. Some of these factors could be addressed with a good rehabilitation program, and some may warrant surgical correction combined with MPFL reconstruction.¹⁰

Surgical Technique

Positioning

The patient lies in a supine position with both limbs exposed; access to the contralateral knee is recommended to give an opportunity to examine lateral patellar translation of the unaffected knee during the operation.

Examination Under Anesthesia

An examination under anesthesia can be used to document excessive lateral patella translation.
The degree of lateral patellar translation is verified under anesthesia using the lateral glide test that measures translation of a patella using quadrants (one-fourth the width of the patella) as the unit of measurement.¹¹

Arthroscopy

Arthroscopy is used to stage articular cartilage lesions and for debridement/repair of cartilage injuries, osteochondral fractures, and/or address loose bodies.

Figure 9.2 The adductor magnus (AM) tendon on the medial aspect of a right knee cadaveric specimen. The foot is toward the left and the hip to the right side. The medial patellofemoral ligament (MPFL) femoral attachment is located distal to the AM tendon and between the adductor tubercle and the medial epicondyle (marked with ink). The AM tendon is located posterior and medial to the vastus medialis obliquus (VMO) muscle. The VMO muscle is overlying the MPFL.

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