Tibial Tubercle Osteotomy for Anterior Knee Pain: Mid-term Result and Analysis of Prognostic Factors

OBJECTIVES: The aim of this study was to evaluate the mid-term radiological and clinical outcomes of tibial tubercle osteotomy in patients affected by anterior knee pain. In addition, prognostic factors correlated with the outcomes were evaluated. METHODS: The patients treated with tibial tubercle osteotomy (anteromedialization) for anterior knee pain between 2002 and 2014 were included. Exclusion criteria: 1) previous knee surgeries; 2) different procedures to treat anterior knee pain; 3) history of patellar dislocation, 4) Rheumatic conditions. Different variables were collected, as shown in. The patients were prospectively evaluated using the WOMAC short form and Kujala scores. An objective evaluation was performed looking for different potential risk factors and using part of the International Knee Documentation Committee (IKDC) score. Radiological evaluation was performed, including the congruence angle, the grade of osteoarthritis (Kellegren-Lawrence) and the patellar tilt angle. Three main outcomes were identified. The multiple logistic regression was used to analyze the correlation between the variables and a worse outcome. RESULTS: 72 cases were included in the study (9 bilateral). 72.2% of the cases were female, and the average age was 42,2 years (SD15,9). The average BMI was 24.4 kg/m2 (SD5,2). In 70.8% of patients a lateral release was associated to the tibial tubercle osteotomy. 77.8% of patients were evaluated clinically, the remaining, who were unable to come for the visits, were interviewed and the subjective scores were administered by phone. The average follow-up was 68.4 months (SD35.5).In 62.5% of cases a valgus lower limb alignment was detected, with 25% and 39.3% of patients having respectively an increased femoral antiversion and foot pronation. Post-operatively there was a statistical significant improvement in all the scores. No differences in the pre-operative and post-operative congruence angle or patellar tilt were detected (p>0.05). All the osteotomies were healed at the last follow-up. No major complications were detected. In 19 cases a further surgery was necessary, with 17 cases of hardware removal and one case of arthrofibrosis. In one case a major subsequent surgery was necessary (Total Knee Arthroplasty): the cumulative survivorship resulted equal to 92.3% (SD7.4%) at the final follow-up.At the multiple regression analysis, a lower WOMAC score was associated with increased age (> 45 years, OR=141.69), increased femoral antiversion (OR=69.94), poor post-operative muscular trophism (OR=127.61) and persistent post-operative pathologic Q angle (OR=18.84). Similarly, a lower Kujala score was associated with increased age (OR=8.36) and increased foot pronation (OR=5.10). Patients’ poor satisfaction was associated only to post-operative factors, such as presence of a positive Rabot test (OR=4.42) and poor muscolar trophism (OR=5.14). Fig.1 shows the results of regression analysis CONCLUSION: In this study good clinical and radiological outcomes were obtained at mid-term follow-up using tibial tubercle osteotomy to treat anterior knee pain, with a cumulative survivorship of 92.3%. The procedure did not affect radiological angles such as the congruence one or the patellar tilt. Older age, increased femoral antiversion, poor post-operative muscolar trophism, increased foot pronation and persistent pathologic Q angle were significantly correlated with worse subjective outcomes.