Table 2 Comparison of surgical anatomical parameters for HTO in sheep and humans (adapted from (Pape & Madry 2013) with permission)
From: Large animal models in experimental knee sports surgery: focus on clinical translation
Congenital anatomical differences | Sheep stifle joint | Human knee | Surgical consequence for the sheep HTO model |
|---|---|---|---|
Tibial plateau width [mm] | 46-56 | 60-70 | Match screw length |
| Â | Â | Â | Narrow and strait plate design necessary |
Tibia valga [°] | 3.5 | 0 | Valgus overcorrection more likely |
Normal knee range of motion (transverse axis) [°] | 0-35-72 | 0-0-140 | Dorsal plate positioning after open wedge HTO is recommended due to increased loading of the posterior tibial plateau |
tibial tuberosity dimension adding to the AP diameter of the tibial head [%] | 30-35 | 10-15 | Anterior plate misplacement more likely |
Tibial tuberosity height distance in relation to joint line [mm] | 10-15Â mm | 25-30Â mm | Anterior plate misplacement more likely |
Posterior slope of the posterior articular surface [°] | 20 ± 3 | 0-10 | Narrow and straight plate design necessary for posterior placement |
Biomechanical properties of tibial head | Brittle cortical bone, together with little spongious bone | Elastic cortical bone with an exuberant amount of spongious bone | Bicortical proximal screw placement mandatory to avoid fracture/dislocation |
Biplanar osteotomy mandatory regardless of the desired direction of correction | |||
Musculature of the hind limb | Voluminous on medial and lateral side of the femur | Remote from bony knee structures | Distal femoral and proximal lateral tibial osteotomy almost impossible to conduct, stay on the medial side of the proximal tibia for any desired correction angle |
Trochlea ridge | Medial ridge extending further cranially and dorsally than lateral ridge | Lateral ridge extending further laterally and anteriorly | Higher propensity of patella instability after valgus correction |