Patellar medial closing-wedge osteotomy in patello-femoral instability: Indications and outcomes

Abstract

Background: Patellofemoral (PF) instability is a syndrome involving several factors and conditions. Trochlear dysplasia (TD) has been shown to be the feature most frequently diagnosed in patients with OPI (Objective Patellar Instability). Even the patella might have an altered shape. Articulating during growth with an abnormal trochlea might lead the patellar posterior surface to modify accordingly, becoming congruent with the trochlear shape. A mismatch between the two articulating surfaces has a role in patellofemoral dislocations.Rarely and in case of a highly dysplastic patella, reshaping only the trochlear groove might lead subsequently to an incongruence between the two bones.When isolated sulcus-deepening trochleoplasty does not restore a congruent patellofemoral tracking tested perioperatively, further surgical procedures might be required.

Methods: A medial closing wedge patellar osteotomy (MCWPO) added to sulcus deepening trochleoplasty should be performed to create a congruent patellofemoral joint.Indications for this procedure are Wiberg type III or IV patella with an intraoperative abnormal patellar tracking after the sulcus deepening trochleoplasty procedure has been concluded.

Results: From January 2012 to August 2020, 21 (6 right and 15 left knees) sulcus deepening trochleoplasties with a concomitant medial closing wedge patellar osteotomy have been performed. The mean follow up was 35,25 months (ranging from 10 to 60 months). The average Kujala, IKDC and Lysholm score were respectively 70,14 ± 15,51; 55,75 ± 7,12 and 77,12 ± 14,80. No further patellar dislocation has been assessed in those patients during follow up.

Conclusion: This technique has shown good and promising clinical outcomes and should be considered when treating patients with a still unsatistactory patellofemoral tracking after the sulcus deepening trochleoplasty has been performed due to a patella-trochlea shape mismatch.

Keywords: Patella; Patellar closing wedge; Patellar osteotomy; Patollofemoral instability; Trochlea dysplasia.

Fig. 1

The Classification of patellar shape. Type 1: the medial facet is concave and has almost the same area of the lateral facet. Type 2: the medial facet is still concave, but is smaller than the lateral face. Type 3: the medial facet is convex and is almost vertical. Type 4: the medial facet is absent.

Fig. 2

A. Osteotomy in the coronal plane. B. The patella thinning osteotomy. C. Opening wedge sagittal osteotomy. D. Closing sagittal wedge osteotomy.

Fig. 3

(A–D). Intraoperative images showing the patellar osteotomy technique in a right knee (Patient n°4). The knee is view from the front, with its proximal part at the top of the pictures. The patella is everted and its medial side exposed. A. The thickness of the wedge is drawn with a pencil. B. The bone wedge is cut with an oscillating saw; the tip of the wedge should end at the midline of the patella. C. Two transfixiant holes are drilled in the medial facet of the patella, passing both sides of the osteotomy. D. The osteotomy is closed and fixed with absorbable sutures.

Fig. 4

The rationale of the technique is to reshape the patella in order to obtain congruence between it and the newly formed trochlea after sulcus deepening trochleoplasty.