Purpose: There has been a resurgence in the use of opening wedge high tibial osteotomy (owHTO). Calcium phosphate cement has been shown to improve strength in compression for augmentation of tibial plateau and owHTO fixation. However, knee kinematics includes a torsional load during ambulation, which is as yet unstudied in this model. The purpose of this paper is to investigate the effect of injectable calcium phosphate cement on the biomechanical stability of standard high tibial osteotomy defect with applied torsional load and ultimate stiffness of the supporting construct.
Methods: Testing was performed on 22 bone mineral density-matched and age-matched cadaver specimens. Intact specimens were treated with 10° opening wedge osteotomies, identical surgical techniques as clinically used and fixation provided by iBalance© PEEK implant (Arthrex, Naples FL). Nine specimens were augmented with calcium phosphate injectable cement, Quickset (Arthrex Inc., Naples Fl). Constructs were for construct stiffness, torsional loads to failure, and mechanisms of failure. As a gold-standard comparison group, four samples were tested with a titanium, fixed angle device alone: Contourlock plate (Arthrex Inc., Naples Fl).
Results: Peak torque to failure was significantly greater in samples augmented with calcium phosphate bone cement (23.0 ± 9.6 Nm) compared with specimens fixed with PEEK implant alone (18.1 ± 7.3). Construct stiffness in torsion was also significantly improved with bone cement application (349.0 ± 126.8 Nm/°) compared with PEEK implant alone (202.2 ± 153.4 Nm/°) and fixed angle implant system (142.9 ± 74.7 Nm/°).
Conclusion: Injectable calcium phosphate cement improves the initial maximal torsional strength and stiffness of high tibial osteotomy construct.
Keywords: Biomechanical; Calcium phosphate; Early weight bearing; High tibial osteotomy; Opening wedge; PEEK.