High Accuracy of Intraoperative Planning for Tibial Tubercle Distalization: A Retrospective Comparison of Intraoperative Measurements and Postoperative Radiographic Outcomes.

PURPOSE: To evaluate the relation between intended intraoperative distalization and actual postoperative change in patellar height, as measured by the Caton-Deschamps Index (CDI). METHODS: A retrospective cohort undergoing medial patellofemoral ligament reconstruction with distalization tibial tubercle osteotomy was analyzed. Inclusion criteria consisted of subjects between the ages of 14 and 60 years who underwent medial patellofemoral ligament reconstruction with distalization tibial tubercle osteotomy, had been diagnosed with patellofemoral instability, and had perfect lateral radiographs. CDI was calculated pre- and postoperatively using standardized digital software. Two distalization techniques were used: (1) a distal oblique osteotomy using an anterior cruciate ligament saw blade with the autograft translated proximally and (2) a standard anteromedialization osteotomy with distalization achieved by inserting adjacent autograft bone proximally. Planned CDI change based on intraoperative measurements was compared with actual CDI change using Pearson correlation, linear regression, paired t-tests, and Bland-Altman analysis. RESULTS: The final cohort consisted of 22 knees in 18 patients (mean age 22.2 ± 8.1 years). Preoperative CDI averaged 1.42 ± 0.15 and postoperative CDI 1.07 ± 0.11. The planned CDI reduction was 0.35 ± 0.11, and the achieved change was 0.34 ± 0.13. Pearson correlation revealed r = 0.892. Linear regression showed R2 = 0.795 with a slope of 0.981. Paired t-test showed no significant difference between planned and actual CDI change (P = .60). Bland-Altman analysis indicated mean bias of -0.006 with 95% limits of agreement from -0.118 to +0.105. CONCLUSIONS: Intraoperative planning for distalization tibial tubercle osteotomy translates into accurate postoperative correction of patellar height with minimal bias. These findings support the reliability of intraoperative measurement in achieving radiographic goals and reinforce the use of CDI as a practical metric for surgical planning in patellfemoral instability. LEVEL OF EVIDENCE: Level IV, retrospective case series.