Biomechanical Comparison of Tibial Plateau Leveling Osteotomy Performed With a Novel Titanium Alloy Locking Plate Construct vs. an Established Stainless-Steel Locking Plate Construct

A novel canine tibial plateau leveling osteotomy (TPLO) fixation device was recently developed with design features such as titanium alloy (TA) material, distal monocortical screw fixation, and a point contact undersurface specifically targeted to reduce surgical site infection rates by ensuring tissue perfusion under the plate. The strength of the novel TPLO construct was compared with that of a predicate stainless steel (SS) locking plate construct with bicortical screws in 16 paired cadaveric canine limbs. The mean loads to failure were 716.71 ± 109.50 N (range 455.69–839.69 N) and 629.50 ± 176.83 N (range 272.58–856.18 N) in the TA and SS groups, respectively. The average ratio of the loads to failure of the paired specimens was 1.18 (p = 0.031). No failure of the TA constructs involved the distal fixation with monocortical screws. Substantial mechanical equivalence of this novel TA monocortical/bicortical fixation construct to an established SS bicortical screw fixation construct is demonstrated. Clinical investigation of potential merits of this novel TA, monocortical/bicortical locking screw/plate system is now warranted.

Surgical Drill Guide for Insertion of an Infra-Acetabular Screw Based on an Anatomically Precontoured Plate System: A Cadaveric Study

Purpose. Due to the anatomic structure of the pelvis, free-hand placement of screws in the acetabular fracture management can be difficult. Infra-acetabular screw fixation increases acetabular stability by distal fixation of the cup. Aim of this cadaveric study is to investigate if a plate-referenced drill guide can provide save placement of an infra-acetabular screw over a precontoured suprapectineal quadrilateral buttress plate (SQBP). Methods. We constructed a drill guide for an infra-acetabular screw based on the surface of an anatomically precontoured SQBP. A total of 12 adult cadaveric acetabular specimens were used for drill guide-assisted placement of the infra-acetabular screw. The drill guide contains a radiopaque spiral to allow longitudinal fine adjustment of the SQBP along the pelvic brim to assure correct position of the plate-drill-guide construct in relation to the Koehler’s teardrop. After screw placement, we conducted a computed tomography (CT) scan of all specimens to assess the actual position of the screw in relation of the infra-acetabular corridor and the acetabular joint surface. Results. The position of the screw was within the infra-acetabular corridor in all cases. We did not see any intra-articular or intrapelvic screw penetration. The mean distance of the centerline of the screw to the medial border of the infra-acetabular corridor was 3.35 mm. The secure distance to the virtual surface of the femoral head to was 7.3 mm. Conclusions. A plate-referenced drill guide can provide safe placement of an infra-acetabular screw for treatment of acetabular fractures. Radiographic fine adjustment is necessary to access the optimal entry point.

Different distal fixation anchors in lumbosacral spinal deformities associated with sacral agenesis: which one is better?

OBJECTIVE Sacral agenesis (SA) is a rare congenital malformation of the spine. There has been a paucity of clinical research to investigate the surgical outcome of spinopelvic fixation in these patients. In this study, the authors aimed to evaluate the outcome of different distal fixation anchors in lumbosacral spinal deformities associated with SA and to determine the optimal distal fixation anchor. METHODS Patients with diagnoses of SA and lumbosacral scoliosis undergoing spinopelvic fixation with S1 screws, iliac screws, or S2-alar-iliac (S2AI) screws were analyzed. The main curve, coronal balance distance, and pelvic obliquity were compared at baseline, postoperatively, and during follow-up in three groups. The complications were also recorded. RESULTS A total of 24 patients were included: 8 patients were stratified into group 1 (S1 screws), 9 into group 2 (iliac screws), and 7 into group 3 (S2AI screws). The main curves were well corrected postoperatively (p < 0.05) in all groups. Coronal balance showed a tendency of deterioration during follow-up in patients with S1 screws (from 18.8 mm to 27.0 mm). Regarding pelvic obliquity, patients with both iliac and S2AI screws showed significant correction (from 3.7° to 2.3° and from 3.3° to 1.6°). Implant-related complications were rod breakage in 3 patients and infection in 1 patient in group 2, and no implant-related complications were observed in group 3. There were 3 cases of unilateral S1 pedicle screw misplacement in group 1. CONCLUSIONS Spinopelvic fixation is a safe and effective procedure that can achieve coronal correction in lumbosacral scoliosis associated with SA. Compared with S1 and iliac screws, S2AI screws as distal fixation anchors can achieve a more satisfactory correction with fewer implant-related complications.

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

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.

Modular tapered conical revision stem in hip revision surgery: mid- term results

Background The aim of this paper is to evaluate the clinical and radiological outcomes of a fluted tapered modular distal-fixation stem at medium to long-term follow-up. The hypothesis of this investigation was to verify if the use of this implant design may have provided potential advantages in femoral revisions and post-traumatic instances where the restoration of the anatomy was the prime concern. Methods We retrospectively reviewed 62 cases of femoral revision surgeries, performed in Paprosky type IIIA and IIIB bone defects between January 2001 and December 2011 with a mean follow-up of 8.5 ± 1.5 years (range 5.1–15.9 years) where a modular fluted stem was used. The clinical assessment was performed with the Harris Hip Score (HHS), and the radiographic evaluation was carried in order to assess the stability of the femoral component. Intra-operative and postoperative complications were recorded, and the rates of complications and revisions for any cause were determined. Results Mean HHS improved 35.4 points from the preoperative assessment. Radiographic evaluation showed a stable stem anchorage in 90.3% of the cases at the last follow-up. Five (8%) implants required additional surgery. Neither breakage of the stem nor loosening of the taper junction were recorded. Kaplan-Meier survivorship was 89.4% (CI: 88.8–90%) for any complication and 92.3% (CI: 91.8–92.7%) according to revision for any causes at 81 months follow-up. Conclusions Our findings suggest that this stem design is a reliable option in cases of complex femoral bone defects, as well as in cases with high functional deficiencies, with promising survivorship.

Sacroiliac Joint Degeneration After Lumbopelvic Fixation

Study Design: Retrospective Study. Objectives: Sacroiliac buttress screws (SBS) and S2 alar iliac screws (SAI) are used as distal screws in cases with long fusion to the pelvis. Distal fixation ends, whether exceeding the sacroiliac joint (SIJ), may affect postoperative degenerative changes in the SIJ. The aim of this study was to investigate SIJ degeneration after lumbosacral and lumbopelvic fixation, using SBS and SAI in degenerative spine diseases, respectively. Methods: This study included 70 patients aged ≥50 years with lumbosacral fusion (>3 levels). They were divided into 2 groups (SBS 20 and SAI 50 cases) based on the type of distal screws. Radiographical and clinical data were reviewed with a minimum 2-year follow-up. Radiographical SIJ degeneration was analyzed using computed tomography; clinical outcomes were evaluated using visual analog scale (VAS) and Japanese Orthopaedic Association Back Pain Questionnaire (JOABPEQ). Results: No significant differences were observed in patients’ preoperative characteristics between the 2 groups. The incidence of SIJ degeneration, including osteophyte formation (30.0% and 8.0%, p = 0.03), intraarticular air (75.0% and 16.0%, p < 0.001), and subchondral cyst (20.0% and 2.0%. p = 0.02) in SBS and SAI groups, respectively, at the follow-up, was significantly higher in the SBS group. Although SIJ degenerative changes were significantly different between the SBS and SAI groups, there was no significant difference in VAS and JOABPEQ scores between the groups at 2 years post-surgery. Conclusions: Lumbosacral fusion can cause SIJ degeneration, which is more frequent when SBS are used in fixation to the sacrum.

Unstable Vancouver B1 Periprosthetic Femoral Fracture Fixation: A Biomechanical Comparison Between Cerclage Wiring and C-Shaped Shape Memory Alloy Implant

Although cerclage wiring is a very useful implant, it has many problems. We manufactured an alphabet C-shaped clip with nitinol (C-clip) that has superelastic property to replace the cerclage wiring.This study aimed to compare the biomechanical stability of cerclage cable and the C-clip. Eighteen synthetic femora were tested. An unstable VB1 fractures model was constructed that oblique fracture line was 8cm below the lesser trochanter with fracture gab. The distal fixation was repaired with a locking plate and four bi-cortical screws. The proximal fixation was repaired two different methods: (1) four-threaded cerclage cables and (2) four new C-clip. In axial compression test, the C-clip was stiffer than the cerclage cable (median stiffness of C-clip = 39.28 N/mm [IQR; 38.84-41.19], cerclage cable = 34.90 N/mm [34.84-35.08], p<0.05). In the torsion test, the C-clip was 0.44 Nm/° [IQR; 0.44-0.45] and cerclage cable = 0.30 Nm/° [0.30-0.33], p<0.05). In the four-point bending test, the C-clip = 39.35 N/mm [IQR; 38.91-40.97] and cerclage cable = 28.38 N/mm, [28.33-30.79], p<0.05) The C-clip may be biomechanically superior to cerclage wiring in terms of stiffness, axial compression, torsion, and four-point bending tests and is a valuable alternative in Vancouver type B1 periprosthetic femoral fracture.

Integrating Finite Element Death Technique and Bone Remodeling Theory to Predict Screw Loosening Affected by Radiation Treatment after Mandibular Reconstruction Surgery

This study developed a numerical simulation to understand bone mechanical behavior and micro-crack propagation around a fixation screw with severe mandibular defects. A mandible finite element (FE) model was constructed in a rabbit with a right unilateral body defect. The reconstruction implant was designed to be fixed using six screws distributed on the distal and mesial sides. The element death technique provided in FE analysis was combined with bone remodeling theory to simulate bone necrosis around the fixation screw in which the strain value reached the overload threshold. A total of 20 iterations were performed to observe the micro-crack propagation pattern for each screw according to the high strain locations occurring in each result from consecutive iterations. A parallel in vivo animal study was performed to validate the FE simulation by placing specific metal 3D printing reconstruction implants in rabbits to compare the differences in bone remodeling caused by radiation treatment after surgery. The results showed that strain values of the surrounding distal bone fixation screws were much larger than those at the mesial side. With the increase in the number of iteration analyses, the micro-crack prorogation trend for the distal fixation screws can be represented by the number and element death locations during the iteration analysis process. The corresponding micro-movement began to increase gradually and induced screw loosening after iteration calculation. The strained bone results showed that relatively high bone loss (damage) existed around the distal fixation screws under radiation treatment. This study concluded that the FE simulation developed in this study can provide a better predictive diagnosis method for understanding fixation screw loosening and advanced implant development before surgery.