Monocortical fixation for locking plate distal screws does not impair mechanical properties in open-wedge high tibial osteotomy

Abstract

Background The neurovascular bundle containing the deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy (OWHTO), particularly due to drilling for bicortical fixation at distal screw holes. Therefore, monocortical fixation is recommended for distal fixation of a long locking plate as long as good stability is ensured. The purpose of this study was to analyse the biomechanical properties of monocortical fixation of distal locking screws for OWHTO. Methods Three-dimensional models of bone and fixation materials simulating OWHTO were created using computed tomographic data of patients and material data of a T-shaped long locking plate and screws. Three of the four distal screws of the locking plate were chosen for a bicortical fixation or monocortical fixation procedure. In addition, loss of correction was assessed by measuring the medial proximal tibial angle (MPTA) in patients who underwent OWHTO with two bicortical and two monocortical distal fixation screws at 1 month and 1 year after surgery. Results No significant differences in stress were observed in either the normal or osteoporotic bone model between the monocortical and bicortical fixation models, including in the area of the lateral hinge at the osteotomy site. Furthermore, there were no significant differences in MPTA between the early post-operative period and 1-year follow-up. Conclusions The monocortical fixation method for three distal screws of the locking plate did not worsen the mechanical properties of fixation for OWHTO using a long locking plate with four proximal and four distal screws. In actual surgery, the number of distal bicortical screws should be reduced based on the patient’s condition, taking into account the risk of lateral hinge fracture and unexpected surgical complications. Using at least two bicortical screws would be practical considering the various factors related to reduced fixing ability.

Tibial shaft fracture after medial open‐wedge distal tibial tuberosity osteotomy: A case report

“…To avoid this risk, mono‐cortical fixation of several of the distal screws is recommended. Finite element analysis of mono‐cortical fixation for three distal screws (2, 3, and 4) of the locking plate showed no impairment of biomechanical stability as compared with bi‐cortical fixation for all four distal screws in OWHTO 14 . However, the mechanical properties of the tibia after OWDTO are different from those after OWHTO, particularly the anterior osteotomy line that is located on the diaphysis in OWDTO, while it is located on the metaphysis in OWHTO.…”

“…Finite element analysis of mono‐cortical fixation for three distal screws (2, 3, and 4) of the locking plate showed no impairment of biomechanical stability as compared with bi‐cortical fixation for all four distal screws in OWHTO. 14 However, the mechanical properties of the tibia after OWDTO are different from those after OWHTO, particularly the anterior osteotomy line that is located on the diaphysis in OWDTO, while it is located on the metaphysis in OWHTO. To the best of our knowledge, no study has presented any investigation of the stability of mono‐cortical fixation of distal screws in OWDTO.…”

Mechanical Properties and Failure Mode of Proximal Screw Fixation Technique Using Locking Compression Plate for Proximal Interphalangeal Arthrodesis in Horses: An Ex Vivo Study

“…10,11 For locking screws, cross-threading between the screw head and plate hole threads provides enough angular stability for unicortical application, 10 but the construct resistance may not be the same when the locking screw is applied bicortically. [12][13][14] The use of only locking screws has also been suggested for PIP arthrodesis, 4 with retrospective studies reporting the use of bicortical screws in the proximal plate hole without describing potential risks of peri-implant fractures. 15,16 In a meta-analysis, de Souza and colleagues found that 65% of horses undergoing PIP arthrodesis (using different implants) returned to their activities.…”