| Background:The principle of high tibial osteotomy(HTO)is to transfer the force line from the inflamed and worn medial compartment to the relatively normal lateral compartment through proximal tibial osteotomy,thereby relieving the symptoms of arthritis.The keys to HTO are the correct intraoperative osteotomy position and open angle.The correct osteotomy position can avoid the occurrence of complications such as hinge fractures,and is conducive to the rapid healing of the osteotomy surface,which can promote the early weight bearing of the patient.The correct osteotomy angle can ensure accurate postoperative correction weightbearing line,which is a key factor to ensure the postoperative effect of HTO.In open-wedge high tibial osteotomy(OWHTO),patient specific instruments(PSI)can be designed according to the patient’s individual skeletal characteristics and preoperative plan.Through the fitting of the PSI to the patient’s bone,the osteotomy position and open angle can be accurately marked to achieve the preoperative planned corrective angle and avoid the loss of correct angle.However,PSI application in OWHTO is in the initial and exploratory stage.The difficulties of its application mainly focus on how to balance its minimally invasive nature with precise positioning and how to precisely open the angle.Some scholars have conducted research and development on its use,but its clinical application still has shortcomings.Objective:This study aimed to design a 3D-printed PSI for OWHTO.The PSI was designed with reference to both the proximal anatomic landmarks and the distal landmarks to accurately position the osteotomy,and an open-wedge spacer to achieve the preoperative design of weight-bearing line correction.Verify its validity and accuracy using cadaveric specimens.Method:Lower limb specimens from the foot to 20 cm above the knee joint were obtained from fresh human specimens,and CT thin-layer scans and X-ray examinations were performed.DICOM 3.0 format data from CT scans were imported into Mimics 25.0 software to construct a 3D skeletal model of the lower limb.X-rays were obtained in orthogonal and lateral views,the proximal medial tibial angle(MPTA)and the posterior slope angle(PSA)were measured.The PSI was designed and 3D-printed based on the preoperative plan and the 3D skeletal model of the lower extremities.OWHTO was performed on the specimen using the PSI.Postoperative X-rays were obtained.Two observers who were not involved in the surgery and were unaware of the surgical plan measured MPTA from the orthogonal view and PSA from the lateral view to verify its effectiveness.CT was performed after plate removal,and the DICOM 3.0 format data from the CT scan were imported into Mimics 25.0 software to construct a postoperative 3D skeletal model of the lower extremity,which was compared with the preoperative plan to verify its accuracy.Results:The PSI was adjusted according to the pre-experimental procedure in 1 case.Hinge fracture occurred in 1 case,which may be related to the shallow depth of osteotomy and the large opening angle.According to X-rays of the remaining 8 cadaveric specimens,no statistically significant difference was noted between the preoperative planning and postoperative MPTA(p>0.05).No statistically significant difference was noted between the preoperative and postoperative PSA(p>0.05).According to CT of the 10 cadaveric specimens,no statistically significant difference was noted between the design angle and actual angle(p>0.05).The gap between the designed osteotomy line and the actual osteotomy line was 2.09±0.97 mm in the coronal plane and 1.58±0.80 mm in the sagittal plane.Conclusion:The PSI for OWHTO can precisely achieve the degree of weight-bearing line correction designed preoperatively,osteotomy position and opening angle without increasing the stripping area while avoiding the change of PSA after osteotomy.However,its use still requires a certain degree of proficiency to avoid complications. |
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