Radiological outcome following proximal realignment procedure for habitual dislocation of patella

Introduction: Instability of the patellofemoral joint may manifest as acute patellar dislocation, recurrent patellar dislocation or subluxation, habitual patellar dislocation or chronic patellar dislocation. Habitual dislocation of patella is a condition where the patella dislocates whenever the knee is flexed and spontaneously relocates with extension of the knee. We conducted this study to know the radiological outcome following proximal realignment procedure (Campbell procedure) for habitual dislocation of patella. Materials and Methods: The study was conducted from June 2017 to January 2019 with a minimum follow up of 6 months and a maximum follow up of 2 years. Inclusion Criteria: All patients with habitual patellar dislocation, age between 5 to 40 years. Exclusion Criteria: Patient age less than 5 years and aged above > 40 years, past history of knee surgery, acute patellar dislocation and knee effusions. Radiological assessment was done by measuring sulcus angle and congruence angle. Conclusion: we conclude that following proximal realignment procedure (Campbell procedure) for habitual dislocation of patella radiological parameters were brought back to normal. There were no significant changes in sulcus angle. Congruence angle was brought back to normal, which was statistically significant (p<0.001). © 2019 Published by Innovative Publication. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by/4.0/)


Introduction
The incidence of patella dislocation ranges from 6 per 100,000 in the adult population to 43 per 100,000 in the pediatric population. Habitual dislocation of patella is a condition w here the patella dislocates whenever the knee is flexed and spontaneously relocates with extension of the knee. The causes of habitual patellar dislocation include contracture and fibrosis of the quadrice ps femoris, vastus lateralis, and lateral retinaculum, abnormal iliotibial band attach ment, repeated intramuscular injections into the thigh, genu valgum, patella alta due to the abnormal position of an elongated patellar tendon, systemic ligament laxity and dysplastic lateral femoral condyle. 4 Campbell developed the Campbell's procedure as a method of

Exclusion Criteria
Patient age less than 5 years and aged above > 40 years, past history of knee surgery, acute patellar dislocation and knee effusions. All patients were clinically evaluated for medial joint line tenderness, ROM at knee, Q angle, apprehension test, Positive J sign (lateral Subluxation) and ligamentous laxity. Radiological assessment was done by measuring S ulcus angle, Congruence angle. Following radiographs are taken for all the patients -Knee-anteroposterior view with full weight bearing, Knee-lateral view with full weight bearing in 30 degree flexion, Merchant view (45 degree skyline view), Laurin view (30 degree skyline view). Postoperative radiographic evaluation was done periodically at 6 weeks, 3months, 6 months and yearly.
Sulcus Angle: Sulcus angle defined as the angle formed between lines joining the highest points of the bony medial (B) and lateral condyles (C) and the lowest bony point of the intercondylar sulcus (A). The mean sulcus angle (138* +/-6*).

Congruence Angle
Identify the highest point of the medial (B) and lateral (C) condyles and the lowest point of the intercondylar sulcus (A). Bisect the sulcus angle (BAC) to establish the zero reference line (AX). Identify the lowest point on the articular ridge of the patella (D) and draw a line from A to D. The angle DAX is the congruence angle. All values medial to the zero reference line AX are designated as negative and those lateral as positive. All values medial to the zero reference line AX are designated as minus and those lateral as plus. Normal angle is defined as < -16 degrees.

Surgical technique
A midline skin incision was made from the quadriceps tendon to the tibial tubercle. Deep tissue dissection was extended from quadriceps tendon to tibial tubercle. A lateral retinacular release was then performed. The exposure was deepened to the level of the medial capsule and the retinaculum. A proximally based strip of medial capsule, 10x2cm wide, was then developed. This is followed by closure of the medial arthrotomy. The proximally based strip of medial capsule is then passed over the quadriceps tendon at the superior pole of the patella from a medial to lateral direction. The flap then passed medially under the quadriceps tendon and sutured to the fascia in the region of the adductor magnus tendon. The wound was then closed in a routine fashion over hemovac drain. Postoperatively, the knee is immobilized for four weeks in the cast with knee in 30 degree flexion and then rehabilitated.

Post op protocol
Cast is opened on 12 day and suture removal will be done, and cast is reapplied with knee in 30 flexion, with well padding at pressure points. 48 They were asked to review after 1 month. Patients were evaluated clinically for wound status, range of motion, patellar tracking, deformity correction, ligament laxity and neurological status. Radiological assessment is done by measuring sulcus angle and congruence angle. Subjective evaluation was done by Kujala index scoring.

Conclusion
Our prospective study consisted of 15 cases, (9 male, 6 female). No patient missed the follow up during  this study series. The average follow up period was 6 months. All cases were treated with Campbell's procedure for habitual dislocation of patella. Of all the 15 knees operated with lateral release and medial plication, 12 knees had significant improvement in functional scores and congruence angle on radiographs. There were no stati stically significant changes in sulcus angle as trochleoplasty procedure was not done and there was inadequate study time to notice bony changes in growing patients. In our study preoperative and postoperative range of motion was unchanged. Radiological assessment showed statistically significant changes in congruence angle. No improvement of sulcus angle on X-rays doesn't always correlate with poor functional outcome. Of three cases that had recurrence, one was revised with modified Galeazzi's technique 38 and one patient underwent modified Roux Goldthwait procedure 31 and last one was revised with trochleoplasty and modified Roux Goldthwait procedure. Thus we conclude that Campbell procedure is a safe and effective procedure for treating habitual patellar dislocation. Future study to quantify a medial laxity (amount of medial soft tissue to be imbricated and/or additional dynamic stabilization procedure) is desirable. Further no single procedure is fully effective in the surgical treatment of all cases of lateral patella dislocation. Long term follow-up is desirable to evaluate distal femur remodeling.

Source of Funding
None.

Conflict of Interest
None.