We evaluated the outcome in a series of patients with recurrent patellar dislocation who had either medial transfer of the tibial tuberosity and lateral release or an isolated lateral release as the primary treatment. The decision to use one or other procedure was based on a pre-operative distance between the tibial tuberosity to the trochlear groove (TTTG) of less than 10 mm to include the tibial tuberosity transfer in addition to the lateral release.

Between April 2002 and December 2006, 49 patients (63 knees) underwent one of these procedures. A total of 35 patients (46 knees) was evaluated at a mean of 38 months (13 to 71) post-operatively. Medial transfer of the tibial tuberosity was performed in 33 knees and isolated lateral release in the remaining 13. Evaluation included the International Knee Documentation Committee (IKDC), the Kujala and the Short-form 36 scores. From the tibial tuberosity group 23 knees also underwent radiological examination at follow-up.

There were further episodes of patellar dislocation in six of the 46 knees available for review. Further dislocation was noted in five of 33 knees (15.2%) in the tibial tuberosity transfer group and in one of 13 knees (7.7%) in the lateral release group. The mean subjective IKDC score was 80.4 (sd 11.6), the mean Kujala score 88 (sd 8.2) and the mean objective IKDC score was 79% normal and 21% nearly normal. The mean post-operative TTTG distance in the tibial tuberosity transfer group was 8.9 mm (3.2 to 15.7) compared with the mean pre-operative value of 16.8 mm (12.2 to 24.4).

There are many procedures described to address recurrent patellar instability. This study evaluated the clinical and radiological outcome of a cohort of patients who had been treated using an algorithm based on plain radiography and CT findings to select the appropriate surgical procedure.

64 knees in 49 consecutive skeletally mature patients were treated by one surgeon over 4.8 years. They underwent either tibial tuberosity transfer and lateral release (TTT/LR) or lateral release alone (LR) based on their patellar height and tibial tuberosity trochlear groove (TTTG) distance. Of the knees that were reviewed, 33 underwent TTT/LR and 13 LR. 46 knees in 35 patients were evaluated clinically (42 in 32) or by phone (4 in 3) at a minimum of 1 year. Evaluation included the Kujala and IKDC (subjective and objective) scores and 31 knees underwent repeat radiological examination.

There had been one or more further episodes of instability in 6/46 knees (13%). Only one knee had more than one further episode of instability. The rate of further instability was 8% in the LR group and 15% in the TTT/LR group. The mean overall subjective IKDC score was 80 (LR: 85, TTT/LR: 79). The mean overall objective IKDC scores were 79% A and 21% B (LR: 67% A, 33% B; TTT/LR: 83% A, 17% B). The mean overall Kujala score was 88 (LR:86, TTT/LR: 88). Three patients developed a clinically significant haemarthrosis (LR: 2, TTT/LR: 1), one of whom required an arthroscopic washout. The mean postoperative TTTG distance in the TTT/LR group was 8.5mm compared to the mean preoperative value of 16.2mm (p < 0001). However, there was also a mean reduction in the TTTG distance in the non operated knees of 2.6mm, suggesting a clinically relevant measurement error for this variable.

The algorithm resulted in satisfactory outcomes for most patients. However, changes have subsequently been made in an attempt to further improve outcomes. These include using medial patellar glide to assess the requirement for a lateral release, measuring the TTTG distance with the knee extended, lowering the threshold for distal TTT, raising the threshold for medial TTT, and adding medial patellofemoral ligament reconstruction to the surgical options.