Summary
Introduction Patellar dislocation is one of the commonest knee injuries in adolescents. Although treatment usually leads to good results, the influence of anatomical and functional factors on therapeutic strategy has been underestimated, especially in cases of recurrence.
Patients and Methods The course of treatment has been analysed in 88 patients with 136 patellar dislocations. The importance of anatomical conditions was studied using X-ray and MRI findings. The treatment results were critically evaluated in comparison with current recommendations.
Results From 2000 to 2015, 109 patellar dislocations occurred in 88 patients; a further 27 previous dislocations were reported by the patients (mean age 14 years, 47 boys and 41 girls). About one-third of patients (35.2 %) suffered one or more recurrences. Almost half (48.6 %) of the dislocations occurred during physical exercise, particularly ball sports. Osteochondral flake fracture was found in 9 % of the patients, and a lesion of the medial patellofemoral ligament in 96 %. There was an anatomical predisposition to patellar dislocation in almost all cases. The sulcus angle, patellar and trochlear dysplasia, and patellar height were highly significantly different between the patient group and controls. The TT-TG distance was subsequently calculated, but had no impact on therapy. Seventy-seven patients were treated conservatively and 32 patients surgically. The conservative procedure included partial immobilisation for six weeks. Surgical reconstruction or tightening was performed in 27 cases; in five, in combination with other surgical procedures. Plasty of the medial patellofemoral ligament with a tendon graft was performed in five patients, and osteochondral or meniscal lesions were repaired in 10 patients. Recurrences occurred in 41.7 % of conservatively treated knees and in 29.6 % of surgically treated knees (without reconstruction with a tendon graft). No recurrence was seen after reconstruction of the medial patellofemoral ligament with a tendon graft. Fifty-four patients underwent a follow-up examination. Fourteen of these (25.9 %) had suffered a recurrence. The outcome 16 months after the end of treatment was mostly good, as were the results of self-assessment (Larson-Lauridsen Score).
Conclusion An anatomical predisposition is detectable in almost all cases of patellar dislocation, but frequently occurs with an accident event, e.g. in ball sports. Primary patellar dislocations without serious concomitant injuries may be treated conservatively. In the event of recurrence, the indication for surgery is given, even in young patients and in any patient with an osteochondral flake fracture. Tightening reconstruction of the MPFL used to be frequently performed, but is associated with a high rate of recurrence.
Key words
patellar dislocation - children - adolescents - MPFL - trochlear dysplasia
