Can We Predict Amount of Correction Using Guided Growth around the Knee? - The 37th Annual Meeting of the Israel Orthopaedic Association, December 13-14, 2017, Tel Aviv, Israel

Barry Danino ¹ Robert Rödl ² John E. Herzenberg ⁴ Lior Shabtai ⁴ Franz Grill ³ Unni Narayanan ⁵ Eitan Segev ¹ Shlomo Wientroub ¹

¹Department of Pediatric Orthopaedics, Dana Children's Hospital, Tel-Aviv Sourasky Medical Center, The Sackler Faculty of Medicine, Tel Aviv University., Tel Aviv
²Klinik und Poliklinik für Allgemeine Orthopädie und Tumororthopädie, Universitätsklinikum, Münster
³Orthopedic Hospital Speising, Orthopedic Hospital Speising, Vienna
⁴International Center for Limb Lengthening, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, Baltimore
⁵Pediatric Orthopaedics, Sickkids Hospital, Toronto

Purpose: To define and validate a constant predicting amount of correction using temporary hemiepiphysiodesis around the knee in patients with idiopathic etiology.

Methods: Retrospective multicenter study conducted at 5 centers including data on 372 physes in 206 patients (110 males 96 females), with an average follow up of 16 months after plate insertion. Alignment analysis was compared preoperatively and in at least 2 measurements postoperatively; after calculating average rate of correction (degrees/month) the result was used as a constant - predicting amount of correction in several points along the follow up period. Correlation between actual and calculated amount of correction was evaluated by Pearson correlation coefficient.

Results: Statistically significant correlation was found between calculated and actual mechanical lateral distal femoral angle (mLDFA) in valgus deformity during the first year of correction (r=0.73-0.87, p<0.01). Calculating the mLDFA later is not predictable. Calculated mLDFA of varus deformity didn`t correlate the actual mLDFA.

Similar correlation was found also between calculated and actual mechanical medial proximal tibial angle (mMPTA) in valgus deformity during the first 8 months of correction (r=0.74-0.94, p<0.01). Calculating the mMPTA later is not predictable. Statistically significant correlation was also found between calculated and actual mMPTA in varus deformity correction during all follow up period (r=0.74-0.92, p<0.01).

Conclusion: Valgus correction by guided growth in the distal femur / proximal tibia in idiopathic patients is highly predictable during the first 12/8 months of correction respectively. Varus correction in the femur is less predictable.

Valgus correction in the tibia is predictable during the first 8 months after initial surgery, Varus correction in the tibia was found to be highly predictable during all follow up period.

Significance: This study presents a validate tool to predict the amount of correction in guided growth of idiopathic coronal plane deformities around the knee. This constant can be used when evaluating patients before surgical intervention to determine timing of surgery.