Rock back phenomenon in 32 dogs that underwent tibial plateau levelling osteotomy

Abstract

The aim of this study was to evaluate the postoperative temporal changes in the tibial plateau angle (TPA) after a tibial plateau levelling osteotomy (TPLO) in dogs. The TPA of thirty-two dogs were measured before surgery (TPA<sub>1</sub>), immediately after the TPLO (TPA<sub>2</sub>), and later at the healing of the osteotomy site (TPA<sub>3</sub>). Three observers carried out three TPA measurements for each patient at the time of the evaluation. TPA changes were observed over the bone healing (2.05 ± 3.05°); however, no statistical significance was noted when comparing TPA<sub>3</sub> and TPA<sub>1</sub>. There were no statistical differences in the inter-observer measurements among TPA<sub>1</sub>, TPA<sub>2</sub>, and TPA<sub>3</sub> (P > 0.05). The comparison between the preoperative TPA<sub>1</sub> and the rock back showed a low positive correlation (S = 4 735.9, P = 0.471 5, r = 0.131 976 9). There was also a low positive correlation between the body weight (kg) and the change in the TPA during the bone healing (S = 4 581.8, P = 0.381, r = 0.160 234 7). Although changes in the TPA have been observed over the time of the bone healing, they were not influenced by the preoperative and postoperative TPA, or by the body weight. The magnitude of the variation in the TPA is not determined by the previous inclination or by the degree of rotation in the plateau.

Effect of Plate Inclination and Osteotomy Positioning on Rock-back following Tibial Plateau Levelling Osteotomy in Dogs

“…27 The present study did not demonstrate a relationship between preoperative TPA and rock-back, which differs from previous research. 16 However, the range of TPA for our clinical cohort was not reflective of the clinical extremes, especially for dogs with excessively steep TPA. Based on these results, a relationship between excessive preoperative TPA and rock-back cannot be ruled out.…”

“…While rock-back has been previously described and investigated, no risk factors have been definitively identified in clinical patients. 1,[16][17][18]22 The degree of change in TPA that constitutes rock-back has been poorly established in the literature. 14,16,20,22 An increase in TPA of !2 degrees was used as the cutoff in the present study to reflect the previously published ideal narrow range of TPA that resulted in the neutralization of tibial thrust, the previously published average change in TPA throughout osteotomy healing, and the TPA change in a biomechanical model of appropriately positioned TPLO implants.…”

“…1,2,[7][8][9][10][11] Several complications have been reported following TPLO, including implant failure, infection, patellar fracture, tibial tuberosity fracture, patellar desmitis, tibial fracture, meniscal tear, and rockback. [12][13][14][15][16] Rock-back is a reported complication following TPLO, whereby TPA increases between the index surgery and osteotomy union. 1,[16][17][18] Some studies have identified overt fragment instability, fibular fracture, and loss of osteotomy reduction associated with a dramatic change in TPA and have applied the term rock-back; however, these observations tend to be associated with overt construct failure.…”

“…[12][13][14][15][16] Rock-back is a reported complication following TPLO, whereby TPA increases between the index surgery and osteotomy union. 1,[16][17][18] Some studies have identified overt fragment instability, fibular fracture, and loss of osteotomy reduction associated with a dramatic change in TPA and have applied the term rock-back; however, these observations tend to be associated with overt construct failure. 18,19 Other studies have identified a more subtle change in TPA without corresponding construct failure or loss of osteotomy reduction.…”

“…18,19 Other studies have identified a more subtle change in TPA without corresponding construct failure or loss of osteotomy reduction. 14,[16][17][18]20,21 Both of these described complications have been termed rock-back in the literature. It is unclear whether these are two distinct complications or a spectrum of the same complication.…”