Mini-Open Lateral Approach Trochleoplasty for Patellar Dislocation

Abstract

Background:

Patellar dislocation is a common knee complaint, and anatomical patellofemoral abnormalities, especially trochlear dysplasia, increase the risk for recurrent dislocations. To stabilize the dislocating patella, trochleaplasty to correct trochlea dysplasia has become an accepted surgical management strategy. A surgical technique for a mini-open lateral approach thin-flap trochleoplasty is presented.

Indications:

Trochleoplasty is the preferred surgical option for patients with severe trochlea dysplasia, characterized by a bump height >5 mm, a lateral trochlea inclination (LTI) angle of <10°, and a positive J-sign.

Technique Description:

A mini-open lateral approach trochleoplasty is a less-invasive surgical modification of a thin-flap deepening trochleoplasty. In this technique, the trochlear cartilage remains intact, and the subchondral bone is removed from proximal to distal, under the cartilaginous flap, to an extent that allows the new trochlear shape to be formed and the sulcus groove to be located more anatomically. Importantly, the lateral condyle trochlear bone-cartilage junction remains intact, preventing loss of lateral condyle height, improving LTI angle, and optimizing trochlea flap healing.

Results:

Postoperatively, immediate free range of motion and full weightbearing allow for a fast recovery, preventing stiffness, and return to sports follows the general timeline after isolated medial patellofemoral ligament reconstruction. Cartilage healing has been reported to be good, with no significant lesions, in >5-year magnetic resonance imaging (MRI) follow-up.

Conclusion:

Mini-open lateral approach trochleoplasty is a safe and effective procedure. Trochlea dysplasia can be corrected to a normal or nearly normal trochlea with mini-open lateral approach trochleaplasty, based on postoperative MRI analysis. A satisfying subjective long-term outcome can be expected for this surgical technique in trochleoplasty.

Patient Consent Disclosure Statement:

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

Background

Patellar dislocation is a common knee complaint, and anatomical patellofemoral abnormalities, especially trochlear dysplasia, increase the risk for recurrent dislocations. To stabilize the dislocating patella, trochleaplasty to correct trochlea dysplasia has become an accepted surgical management strategy.^2-5,10 A surgical technique for a mini-open lateral approach thin-flap trochleoplasty is presented.

Indications

Trochleoplasty is the preferred surgical option for patients with severe trochlea dysplasia, characterized by a bump height >5 mm, a lateral trochlea inclination angle of <10°, and a positive J-sign.

Technique Description

For a mini-open thin flap deepening trochleoplasty, the skin incision is located in the midline, measuring 4 to 8 cm in length, depending on the knee size and the thickness of the subcutaneous tissue. A lateral subvastus mini-arthrotomy is performed, and the lateral capsule is opened in 2 layers for the lateral retinacular lengthening procedure during the closure.

The same skin incision can be used for medial patellofemoral ligament (MPFL) reconstruction and concomitant procedures, such as cartilage repair. In the lateral subvastus approach, the patella is subluxated medially, and Steinman pins hold soft tissues laterally and proximally to maintain a superolateral view of the trochlea. In this case of flat trochlea with a 5° lateral trochlear inclination angle and a bump height of 8 mm, trochleaplasty starts by dissecting the distal femoral periosteal flap with a scalpel and elevating it up to the margin of the trochlear cartilage.^1,2,7

Under the periosteum, proximal to the trochlear cartilage, a supratrochlear spur can be removed with an osteotome, and access to the subchondral bone, located under the trochlear cartilage, is made from the proximal direction. Working on the level of the anterior distal femoral cortex, in the sagittal plane, the excess amount of bone to be removed in this case requires about 8 mm deepening to establish a new trochlear groove. The new anatomical trochlear groove should be located more laterally than the dysplastic original, which must be kept in mind when planning bone removal under the cartilage. The trochlear osteochondral flap is carefully thinned with a reamer as extra subchondral bone is removed. Please note that the lateral margin of the trochlea remains intact; it does not have to be cut or mobilized to create a deepening trochleoplasty. The intact lateral margin of the trochlea may facilitate healing, as the inclination angle is easier to correct. ⁶

This thin flap deepening trochleaplasty requires subchondral bone removal only in the mid part (new sulcus groove) and medial side of the dysplastic trochlea. After reaming, only 2 to 3 mm of subchondral bone is left under the cartilage flap. With careful thinning, especially in the midline under the new sulcus groove, the osteochondral flap starts to become mouldable and elastic in a new form to create the trochlear groove. Please control the elasticity of the flap very carefully, not to break the cartilage, but make it thin enough to be able to reshape toward the normal trochlear groove. While the lateral edge of the trochlea remains intact, with some thumb pressure, you can feel how the osteochondral flap starts to become mouldable as desired to create a close to normal lateral inclination angle, around 15° to 20°, correcting the J-tracking. In addition to reshaping the trochlear groove, some bone grafting under the proximal lateral corner under the periosteal flap will lengthen the lateral trochlea inclination proximally. This lateral lengthening improves patella engagement to the new trochlea. Osteochondral flap fixation is performed by using a single small 2.7-mm bioabsorbable screw (Compress-On; Inion). The screw should be positioned at the deepest part of the new trochlea groove, flush with the cartilage, and any interference with the patella cartilage should be eliminated. Please note that, as the lateral margin of the trochlea remains intact in this trochleaplasty technique, a certain tension remains in the flap, which makes fixation manageable from a single point only. If the osteochondral flap were more aggressively mobilized, the mediolateral tension of the flap would be lower, and an additional screw should be introduced.

Results

As a result of this technique, the bump has been removed, and the trochlea inclination is corrected to near normal, stabilizing the lateral support of the trochlea and eliminating J-tracking. Trochleaplasty is finalized by closing the periosteal flap proximally with absorbable sutures. Finally, MPFL reconstruction is performed concomitantly through the same skin incision and lateral retinacular lengthening by suturing the superficial capsular layer to the posterior lateral layer in a lengthened position. Postoperatively, immediate free range of motion and full weightbearing allow for a fast recovery, preventing stiffness, and return to sports follows the general timeline after isolated MPFL reconstruction. Complications reported for the thin flap trochleoplasty technique are similar as any patellofemoral stabilizing surgery, including recurrent dislocation and subjective instability.^4,7-9,12 With the presented surgical technique and immediate mobilization, knee stiffness is rare (<1%). Cartilage healing has been reported to be good, with no significant lesions, in >5-year magnetic resonance imaging (MRI) follow-up. ¹¹

Conclusion

Mini-open lateral approach trochleoplasty is a safe and effective procedure. Trochlea dysplasia can be corrected to a normal or nearly normal trochlea with mini-open lateral approach trochleaplasty, based on postoperative MRI analysis. A satisfying subjective long-term outcome can be expected for this surgical technique in trochleoplasty.