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Introduction: Congenital dislocation of the patella and recurrent symptomatic dislocation in adolescents are difficult pathologies to treat. Stanisavljevic described an extensive release procedure essentially involving medializing the entire lateral quadriceps and medial soft tissue stabilization. There are no significant series reporting the success of this method. This procedure has been performed in our institution over several years and we report our results. Method: Retrospective case series. Between 1990 and 2007, 20 knees in 13 children and adolescents (mean age 12.8 years; 4-17, 7 female) with recurrent or congenital dislocation of the patella (8 knees) underwent this procedure after failed conservative treatment (mean follow-up 7.5 years; 4-16). All were immobilized in a long leg cast for 6 weeks. Results: Five knees in five patients (20 %, 1 congenital dislocation) reported their knees as improved without further dislocations. Out of the 15 knees with failures (80 %) 12 in six patients (60 %) were revised due to redislocation. Three knees in two patients (15 %) still had dislocations or subluxations, but any revision was refused. Three knees in three patients caused pain and discomfort during daily activity. Redislocation first developed after a mean of 21.3 months (4-72) postoperatively. Only one patient had returned to sport at the 12-month follow-up. Discussion: The Stanisavljevic procedure produces a mediocre success rate with our long-term follow-up series showing a failure rate up to 80 %. We therefore recommend more specific procedures dealing with the anatomical deformity such as trochleaplasty to produce superior success rates. [ABSTRACT FROM AUTHOR]

Objective: Tibial tubercle trochlear groove distance (TTD) is a significant factor in patello-femoral instability. Initially described on CT scans with the knee in full extension, the measurement has been validated on MR scans. Dedicated knee MRI coils have subsequently superseded both CT and MRI body coils for knee imaging. However, the knee rests in partial flexion within the dedicated knee coil. The objective of this study is to investigate whether images from dedicated knee MRI coils produce different TTD measurements from MR body coils. Materials and methods: Thirty-two symptomatic knees (27 patients) had simultaneous knee MR scans performed in both a dedicated knee coil and a body coil. TTD measurements were independently compared to assess whether the coil type used affected TTD. Results: Patients' ages ranged from 10 to 27 years (mean 15 years). Mean TTD in the dedicated knee coil (partially flexed knee) was 11.3 mm compared with 19.9 mm in the body coil (that permits full knee extension). The mean difference was 8.6 mm, which was highly significant ( p < 0.0001, unpaired t test). Inter-rater correlation co-efficient was 96 %. Of the knees that recorded a 'normal' TTD on the dedicated knee coil, 60-100 % recorded a 'pathological' TTD on body coil images, depending on which diagnostic value for 'normal' cut-off was used. Conclusion: This study has identified a highly significant difference in TTD measurement when knees are scanned in a dedicated knee coil with the knee partially flexed, compared with an MR body coil. It is critical for surgeons and radiologists managing patello-femoral instability to appreciate this profound difference. TTD measurement taken from knees scanned in dedicated knee coils may lead to patients being falsely re-assured or erroneously denied surgery. [ABSTRACT FROM AUTHOR]