Lateral trochlear lengthening osteotomy

Abstract

Introduction: The purpose of this study was to describe the indications and technical aspects as well as evaluate the clinical and functional outcome of lengthening osteotomy of the lateral trochlear ridge in patients with patellofemoral pain and/or patella instability and presence of trochlear dysplasia Dejour type A or lack of Dejour type dysplasia and short lateral articular trochlea.

Materials and methods: Six consecutive adult patients were treated with a lateral trochlear lengthening osteotomy. Five patients received a concomitant medial patellofemoral ligament reconstruction. Three patients had prior patella stabilization surgeries. Trochlea dysplasia (Dejour classification), Caton-Dechamps index, tibial tubercle trochlear groove (TT-TG) distance, patellar tilt and lateral condylar index were measured in preoperative MRIs. Clinical and functional evaluation included the Kujala Anterior Knee Pain Scale, the Lysholm Knee Score, the Tegner Activity Score, a subjective evaluation form and isokinetic muscle strength.

Results: Four patients had a Dejour type A dysplasia, two patients had no dysplasia. The mean (range) Caton-Dechamps index was 1.09 (0.95-1.16), TT-TG distance 10.9 mm (9.2-15.6 mm), patellar tilt 15° (4-32°) and lateral condylar index 82.0% (74-90%). One patient was lost to follow up, all others were followed for 2-5 years. All patients were satisfied with the clinical outcome. The Lysholm score increased from 55 (37-79) to 89 (76-100), the Tegner activity score from 3.6 (2-6) to 5.6 (5-7). The Kujala score postoperative was 90 (75-96). Some but not all patients had full strength recovery compared to the contralateral leg.

Conclusion: We recommend measuring the lateral condylar index and considering the indication of a lateral trochlear lengthening osteotomy as an additional or isolated procedure in selected patients with trochlear dysplasia Dejour type A or lack of dysplasia and short lateral articular trochlea depending on the extent of the patellar instability.

Level of evidence: Level IV, Case Series.

Trial registration number: NCT04378491, clinicaltrials.gov, May 7, 2020.

Keywords: Patella instability; Patellofemoral pain; Trochlear lengthening; Trochlear osteotomy.

Conflict of interest statement

The authors declare that they have no conflict of interest.

© 2021. The Author(s).

Figures

Fig. 1

Indication for a lateral lengthening osteotomy in a patient with short lateral trochlea (lateral condylar index i/ii = 84%, a) and lack of trochlear dysplasia Dejour type (sulcus angle 133°, b), normal patellar height quantified by a normal Caton–Deschamps index of 0.95 (i/ii, c), TT-TG distance of 9.2 mm (d), and normal patellar tilt of 13° (e)

Fig. 2

The lateral condylar index: two circles are drawn in a sagittal MRI image at the level where the anterior cruciate ligament is present at its entire length. The line connecting the centers of the two circles defines the femoral axis. A line vertical to the femoral axis tangential to the distal femoral cartilage serves as baseline to measure the length of the anterior (a) and posterior (p) cartilage length. The value (a/p × 100%) is the lateral condylar index. In this patient a pathologic lateral condylar index of 80% was calculated

Fig. 3

Intraoperative images of a lateral lengthening osteotomy. Note the short lateral articular trochlea before the intervention (arrow, a) and the lengthening of the lateral trochlea after the intervention (arrow, b)

Fig. 4

Intraoperative images of a lateral lengthening osteotomy. Note the short incision (a), the opening of the osteotomy and the filling with cancellous bone (b) as well as the suturing of the periosteum (c)

Fig. 5

Preoperative (a) and postoperative (b) MRI images of a patient with a lateral trochlear lengthening osteotomy. Note the difference between the anterior condyle length before the operation (blue arrow, a) and after the operation (red arrow, b). The lateral condylar index was 84% preoperatively and 120% postoperatively. The yellow arrow represents the posterior condyle length and the green line the femoral axis (a, b)

Fig. 6

Preoperative (a) and postoperative (b) MRI images of a lateral trochlear lengthening osteotomy in a patient with short lateral trochlea and presence of a lateral bump (red arrow, a). Note the lengthening of the trochlea and the leveling of the bump postoperatively (red arrow, b)

Fig. 7

a An osteotomy was performed with a chisel 5 mm posterior to the lateral cartilage of the trochlea along the anteroposterior axis (red dashed line), beginning at the level of trochlear cartilage to periosteum transition (green arrow) in craniocaudal direction. b The cartilage and periosteum were elevated proximally providing a lengthening of the lateral trochlea (blue arrow). Cancellous bone was harvested from the lateral femoral condyles and inserted in the osteotomy gap in a press fit technique (red arrow)