The stability of three commercially available implants used in medial opening wedge high tibial osteotomy

This biomechanical study tested three commercially available fixation devices for medial opening wedge high tibial osteotomy (HTO). A medial opening wedge HTO model was created on replicate tibias. Fixation was achieved with one of three fixation devices: VS Osteotomy plate (EBI, Parsippany, NJ), Arthrex Osteotomy plate (Arthrex, Naples, Fla), and OsteoTrac plate (DJ Orthopedics Inc, Vista, Calif). For each fixation system, seven specimens were cyclically loaded in compression and torsion under physiologic loads on a servohydraulic machine. Mean axial stiffness was 2425 N/mm, 2358 N/mm and 2258 N/mm, respectively, for the EBI, Arthrex, and Alaron surgical plates. Mean torsional stiffness was 4.5 Nm/degree, 4.1 Nm/degree and 4.0 Nm/degree, respectively, for the EBI, Arthrex, and DJ Orthopedics surgical plates. Though the differences are not statistically significant between the three fixation devices (P=.74 for mean axial stiffness and P=.10 for mean torsional stiffness), there is insufficient statistical power to rule out a true difference. Using this replicate tibia model, all three fixation devices tested appear to successfully stabilize the osteotomy site with regards to physiologic axial and torsional loads.     

Finite element analysis of Puddu and Tomofix plate fixation for open wedge high tibial osteotomy

The use of open wedge high tibial osteotomy (HTO) to correct varus deformity of the knee is well established. However, the stability of the various implants used in this procedure has not been previously demonstrated. In this study, the two most common types of plates were analysed (1) the Puddu plates that use the dynamic compression plate (DCP) concept, and (2) the Tomofix plate that uses the locking compression plate (LCP) concept. Three dimensional model of the tibia was reconstructed from computed tomography images obtained from the Medical Implant Technology Group datasets. Osteotomy and fixation models were simulated through computational processing. Simulated loading was applied at 60:40 ratios on the medial:lateral aspect during single limb stance. The model was fixed distally in all degrees of freedom. Simulated data generated from the micromotions, displacement and, implant stress were captured. At the prescribed loads, a higher displacement of 3.25 mm was observed for the Puddu plate model (p<0.001). Coincidentally the amount of stresses subjected to this plate, 24.7 MPa, was also significantly lower (p<0.001). There was significant negative correlation (p<0.001) between implant stresses to that of the amount of fracture displacement which signifies a less stable fixation using Puddu plates. In conclusion, this study demonstrates that the Tomofix plate produces superior stability for bony fixation in HTO procedures.     

Comparative analysis of fixation configurations and their effect on outcome after medial open-wedge high tibial osteotomy

PurposeThe purposes of this study were to analyze and compare 1) the postoperative fixation configurations, and 2) radiological and clinical outcomes between the new conceptual fixation device (LCfit) and the conventional locking plates.MethodsRetrospective comparative analysis of 304 cases who underwent open-wedge high tibial osteotomy with four different locking plate systems including the LCfit system was conducted. In analyzing the fixation configuration of each locking plate system, the plate position, the gap between plate and bone, screw angle, and screw length were evaluated from postoperative CT scans. The clinical outcomes and radiological parameters of four patient groups corresponding to the four locking plate systems were also compared.ResultsIn the analysis of the fixation configurations, the LCfit system showed more posteromedial plate position, decreased gap between plate and bone, reduced screw angle, and longer screw length compared to the other three locking plates. However, there were no significant differences in clinical outcomes and radiological parameters such as hip-knee-ankle angle, weight-bearing line position, medial proximal tibial angle, and posterior slope between the four groups.ConclusionThe newly designed fixation system (LCfit) for open-wedge high tibial osteotomy showed fixation configurations that have theoretical mechanical advantages over conventional anatomical locking plates. However, there were no significant differences in clinical outcomes and radiological parameters between LCfit and the other locking plate systems.Level of evidenceLevel III, retrospective cohort study.     

骨质疏松性肱骨近端骨折PMMA骨水泥强化螺钉钢板固定的有限元分析

目的：借助有限元分析的方法探讨肱骨近端聚甲基丙烯酸甲酯（polymethyl methacrylate,PMMA）骨水泥强化螺钉钢板固定对骨质疏松性肱骨近端骨折内固定稳定性的影响。方法：制作肱骨近端2部分骨折伴干骺端骨缺损的不稳定肱骨近端骨折数字化模型,分别建立肱骨近端骨水泥强化螺钉钢板固定及普通螺钉钢板固定的有限元模型,分析螺钉周围松质骨应力、整体刚度、钢板最大应力及螺钉最大应力。结果：肱骨近端骨水泥强化螺钉钢板固定的头端6枚螺钉周围松质骨最大应力分别为：1号钉1.07 MPa,2号钉0.43 MPa,3号钉1.16 MPa,4号钉0.34 MPa,5号钉1.99 MPa,6号钉1.57 MPa,普通螺钉钢板固定为：1号钉2.68 MPa,2号钉0.67 MPa,3号钉4.37 MPa,4号钉0.75 MPa,5号钉3.30 MPa、6号钉2.47 MPa。两组模型的整体刚度分别为：骨水泥结构448 N/mm、普通结构434 N/mm。钢板的最大应力均出现在结合孔：骨水泥结构701 MPa、普通结构420 MPa。螺钉的最大应力均出现在4号钉的尾端：骨水泥结构284 MPa、普通结构...     

Central placement of the screw in simulated fractures of the scaphoid waist: a biomechanical study

BACKGROUND: Recent reports on internal fixation of acute fractures of the scaphoid waist have demonstrated higher rates of central placement of the screw when cannulated screws were used than when noncannulated screws were used. This cadaveric study was designed to determine whether central placement in the proximal fragment of the scaphoid offers a biomechanical advantage. METHODS: Eleven matched pairs of scaphoids were removed from fresh cadaveric wrists. Each scaphoid was placed in a custom manufactured jig that was used to create reproducible central and eccentric positioning of the guidewire. Then a linear osteotomy was made followed by placement of a Herbert-Whipple cannulated screw to fix the osteotomy. The specimen was then potted in a holder with use of polymethylmethacrylate with a Kirschner wire passed through the proximal end of the scaphoid and placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. The load acting through the plunger was measured with use of a load-cell, and its excursion was measured with use of a linear variable differential transformer. Stiffness, load at 2 mm of displacement, load at failure, and mechanism of failure were measured, and the two groups were compared with regard to stiffness and strength. RESULTS: Central placement of the screw in the proximal fragment of the scaphoid had superior results compared with those after eccentric positioning of the screw. Fixation with central placement of the screw demonstrated 43% greater stiffness (12.7 N per mm compared with 8.9 N per mm; p < 0.01), 113% greater load at 2 mm of displacement (126 N compared with 59.1 N; p < 0.01), and 39% greater load at failure (712 N compared with 513 N; p > 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Central placement of the screw in the proximal fragment of the scaphoid offers a biomechanical advantage in the internal fixation of an osteotomy of the scaphoid waist. Clinical efforts and techniques that facilitate central placement of the screw in the fixation of fractures of the scaphoid waist should be encouraged.     

Anteromedial plating without filling the gap in open wedge high tibial osteotomy may increase the risk of screw breakage,which can be reduced by medial plating and bone-substitute insertion

BackgroundOpen wedge high tibial osteotomy (OWHTO) brings new complications such as screw breakages with or without correction loss and time-dependent increased posterior tibial slopes (PTS) due to the opening gap. For preventive purposes, we changed our OWHTO procedure from anteromedial plating without filling the gap (non-grafted group, n = 40, 2009–2012) to medial plating with bone-substitute insertion (grafted group, n = 45, 2012–2015). The objectives of this study were to evaluate the complication patterns and the effects of the modifications.MethodsPatients undergoing OWHTO with TomoFix plates were included in this retrospective study. Demographics, clinical outcomes (flexion range and Japanese Orthopaedic Association score) and radiological outcomes (femorotibial angle) were assessed in both groups pre-operatively and 2-years postoperatively. The plate installation angle [PIA] and screw insertion depth [SID] were measured on computed tomographic slices at 6 months. PIA/SID was defined as the angle between the tibial anteroposterior axis and plate–width axis/the distance between the proximal screw tip and the proximal tibiofibular joint. The non-grafted group was further divided into complication and non-complication subgroups. Screw breakages were assessed during plate removal (1.5–2.5 years postoperatively).ResultsThere were no differences in baseline characteristics or radiological/clinical outcomes between the non-grafted and grafted groups. There were 0 and 11 complications in the grafted and non-grafted groups, respectively. Complications included 7 screw breakages, 4 correction losses, and 5 time-dependent increased PTS with some overlaps. PIA and SID were significantly lower (p < 0.001) and higher (p < 0.001), respectively, in the grafted group and significantly lower (p = 0.018) and higher (p = 0.040), respectively, in the non-complication subgroup within the non-grafted group. The cutoff value of PIA for complications was calculated at 48.0°.ConclusionsMedial plating OWHTO (PIA<48°) using bone-substitute with deeper screw insertion reinforces the opening gap for better angular stability compared with anteromedial plating without bone-substitute.     

Longer Term Outcomes Following High Tibial Osteotomy for Osteoarthritis: A Prospective,Multi-Centre Observational Study Comparing Tomofix and OPTY-LINE Devices

PurposeAssessing surgical accuracy and patient-recorded outcome measures for patients fitted with either the OPTY-LINE intramedullary realignment system or the Tomofix plate for medial opening wedge high tibial osteotomy (HTO).Patients and methodsTwo matched case series of patients with symptomatic medial compartment osteoarthritis without other significant knee pathology. One group comprised of 19 patients receiving the Tomofix plate, whereas another comprised of 12 patients receiving the OPTY-LINE intramedullary nail. Patella-centred long leg alignment radiographs were assessed to calculate surgical accuracy in all cases. Patients completed knee injury osteoarthritis outcome scores (KOOS) and osteotomy surgery patient satisfaction questionnaires pre-operatively and at 24 months post-surgery.ResultsAbsolute surgical accuracy at 2 years post-surgery was a mean 4.2 [standard deviation 3.7] for OPTY-LINE versus 9.2 [SD 7.8] for Tomofix (p = 0.11, Mann–Whitney U test). On average, patients in either the OPTY-LINE or Tomofix cohort reported at least a minimal perceptible clinical improvement—minimum average improvement of 15—for all five KOOS themes. No significant difference in change of KOOS scores over time or patient satisfaction levels were observed between the two cohorts.ConclusionThe OPTY-LINE device for HTO performs to a similar level as the Tomofix device. Surgical accuracy data are promising for OPTY-LINE, but does not seem to readily translate into difference in patient-reported outcomes compared to Tomofix. Even longer follow-up periods, to measure survival rates, and true randomised trials on larger samples can elucidate if there is a benefit for using one device over the other.     

Biomechanical Comparison of Two Pediatric Blade Plate Designs in Proximal Femoral Osteotomies

Background

Blade plates are frequently used for internal fixation following proximal femoral varus rotational osteotomy to treat hip dysplasia in children with cerebral palsy. Recently, cannulated blade plates with the option for a proximal locking screw have demonstrated ease of insertion and low complication rates. Although there are two commonly used blade plates with a proximal screw option, no comparison of their biomechanical profiles has been undertaken.

Questions/Purposes

Our study sought to compare the structural properties under axial loading, as well as the biomechanical contribution of a proximal screw, of two different 90° cannulated blade plates designed for pediatric proximal femurs. Plate A has a hole distal to the blade designed to attach a plate inserter, through which a 3.5-mm non-locking cortical screw could be placed. Plate B has a threaded hole distal to the blade designed to accept a 3.5-mm locking screw.

Methods

Plate A and plate B were inserted into 33 left pediatric synthetic proximal femurs. Axial loading to failure of plate A with and without a proximal screw was compared to that of plate B with and without a proximal screw. An additional 10 samples using plate B, with and without a proximal locking screw, were tested in tension to quantify the effect of the proximal screw on pullout strength.

Results

Plate B failed at a higher axial load than plate A. The addition of a proximal screw did not affect the axial load to failure for either plate. Pullout testing revealed that blade plates fixed with the proximal screw failed in tension at a significantly higher load (856.3?±?120.9 N) than those without proximal fixation (68.1?±?9.3 N, p?<?0.001).

Conclusions

Plate B failed at a higher axial load in biomechanical testing, likely related to differences in its design. The addition of a proximal screw did not increase the axial loading properties of the blade plate construct but did increase the pullout strength by a factor of 12. These results may be used to influence implant selection and post-operative rehabilitation following proximal femoral osteotomies in children.

     

Editorial Commentary: Tibial Slope Should Be Naturally Maintained by Proper Posterior Cortical Osteotomy and Gap Distraction in Open-Wedge High Tibial Osteotomy

The tibial slope usually increases after open-wedge high tibial osteotomy (OWHTO) because of several factors. The anteromedial cortex of the proximal tibia is angulated 45° relative to the posterior cortex, whereas the lateral cortex is nearly perpendicular. Therefore, an OWHTO with equal anterior and posterior gaps will increase the tibial slope. In addition, an anteromedial approach to the proximal tibia because of concern about neurovascular injury results in the failure to perform a proper osteotomy of the posterolateral cortex. Slope-optimization methods include a sagittally oriented hinge, posterior bone grafting, posterior plating, and forcefully extending the knee to compress the anterior gap sagittally oriented hinge, posterior positioning of the wedged plate, and knee extension during fixation. However, if the tibial slope is easily controlled using knee extension, this may indicate fracture of the lateral hinge, whereas a preserved lateral hinge is a prerequisite for a successful OWHTO. Most of all, a proper posterior cortical osteotomy is the key step to preventing increased tibial slope in OWHTO. Again, if an incomplete osteotomy is performed posterolaterally, the opening gap is increased anteriorly, leading to an unnecessary increase in posterior tibial slope; for biplanar osteotomy, retrotubercular osteotomy should be performed close to the patellar tendon and not be advanced to the posterolateral side of the hinge.     

Hybrid Lateral Closed-Wedge High Tibial Osteotomy Showed Similar Accuracy in Angular Correction and Reduction of Posterior Tibial Slope Compared to Opening-Wedge High Tibial Osteotomy: A Correction Angle Matched Cohort Study

BackgroundWe aimed to compare the accuracy of applied correction angle between hybrid lateral closed wedge high tibial osteotomy (hybrid HTO) and medial open wedge high tibial osteotomy (OWHTO), and verify previous reports on hybrid HTO by matching correction angle between groups. Change in various radiological parameters including union rate were also compared.MethodsA total of 50 OWHTO patients were selected for 2:1 propensity matching with 25 hybrid HTO patients. Rate of correction error was calculated by dividing the difference between the change in medial proximal tibial angle and preoperatively planned correction angle (PRD) by planned correction angle. Accuracy of angular correction was assessed using PRD and correction error rates. Hip-knee-ankle axis, mechanical lateral distal femoral angle, medial proximal tibial angle, joint line convergence angle, and length of the entire lower limb and tibia were measured. The Caton-Deschamps index (CDI) was used to assess change in patellar height. Serial postoperative radiographic analysis was performed to assess the union rate.ResultsThe discrepancy between planned correction angle and real correction angle was 0.8 ± 2.3° in hybrid HTO and 1.1 ± 3.4° in OWHTO (P > .05), and the rate of error in osteotomy was similar between the groups approximately 6%. Postoperatively, posterior tibial slope (PTS) (P < .001), tibia length, and CDI (P < .001) were significantly different between groups. The amount of change in PTS (P < .001), tibia length in hybrid HTO (P < .001), and CDI (P < .001) were significantly different between groups. Union rate of osteotomy site was significantly faster in hybrid HTO than in OWHTO (P < .001).ConclusionHybrid HTO showed similar accuracy in angular correction compared to correction angle-matched OWHTO. Reduction in PTS, tibial shortening, maintained patellar height relative to the proximal tibia, and faster osteotomy site union were also confirmed in hybrid HTO.     

Biomechanical superiority of plate fixation for proximal tibial osteotomy

Proximal tibial osteotomies require secure and durable fixation to allow early range of motion; however, biomechanical data comparing commonly used fixation methods are lacking. The current study was done to quantify the dynamic biomechanical performance of blade staple fixation and plate fixation of simulated proximal tibial osteotomies. A 15 degrees proximal tibial osteotomy was done on each of 18 synthetic adult composite tibias. Blade staples were used as the means of fixation in nine tibias; plate fixation was used in the remaining nine tibias. The specimens were stressed cyclically in sinusoidal loading whose peak compression and tension loads imitate those measured during normal gait. Device performance was quantified by measuring displacement at the osteotomy site and the number of cycles to failure. Plate fixation had a greater fatigue life than staples (eight plates surviving past 200,000 cycles versus one blade staple) and showed a trend toward less displacement (0.69 mm versus 0.97 mm). Plate fixation of proximal tibial osteotomies offers better fixation and dynamic mechanical performance than blade staples.     

Locking plate fixation of humeral head fractures with a telescoping screw. A comparative biomechanical study versus a standard plate

ObjectivesLocking plate fixation of humeral head fractures bares the risk of glenohumeral screw penetration. In order to circumvent this problem it is recommended to insert shorter locking screws having at least a 6 mm distance to the humeral head cortex. This in turn may reduce fixation stability and may lead to early varus displacement. One second frequent failure mechanism is cranial displacement of the greater tubercle. The study evaluates the biomechanical properties of a locking plate employing an additional telescoping screw that may enhance resistance to varus displacement. Screw in screw fixation of the greater tubercle may reduce the rate of cranial displacement.MethodsIn four paired fresh-frozen human cadaver humeri (age > 70 years) a Neer IV/3 fracture was created with a 5 mm osteotomy gap simulating metaphyseal comminution. Limbs were randomly assigned to receive plate fixation with an additional telescoping screw (Humerus Tele Screw: HTS) and on the contralateral limb Philos plate fixation before biomechanical evaluation (MTS-Bionix 858.2). Standard locking screws were placed in both groups 6 mm below the radiological head circumference; the telescoping screw was placed in the subchondral layer. The greater tubercle was fixed with an additional screw in both techniques, in the HTS group the screw was anchored in the sleeve of the telescrew (screw in screw fixation).FindingsFixation stability with a mean stiffness of 300.9 ± 28.8 N/mm in the HTS plate group proved to be significantly higher than in the Philos plate group (184.2 ± 23.4 N/mm; p = 0.006). The HTS plate also resisted higher loads in terms of fixation failure with loss of reduction at 290 ± 58.6 N in comparison to 205 ± 8.6 N for the Philos plate (p = 0.2). Displacement of the greater tubercle occurred in no case of the HTS plate group and in two out of four cases in the Philos plate group.InterpretationThe HTS plate provides high fixation stability in an in vitro humeral head fracture model and securely prevents displacement of the greater tubercle.     

Biomechanical Comparison of Internal Fixation Techniques for the Akin Osteotomy of the Proximal Phalanx

The Akin osteotomy is performed at the proximal phalanx for correction of an abducted great toe in a hallux abducto valgus deformity. Several internal fixation techniques have been widely advocated; however, their respective stabilities have not been compared. A biomechanical analysis was performed comparing 5 commonly used fixation techniques for the Akin osteotomy to determine the strongest method in simulated weightbearing in sawbone models. An Akin osteotomy was uniformly performed on 25 sawbones and fixated with 5 different internal fixation types, including a 2-hole locking plate and locking screws, a heat-sensitive memory staple (8 mm × 8 mm), a 28-gauge monofilament wire, 2.7-mm bicortical screws, and crossed 0.062-in. Kirschner wires. The results of simulated weightbearing load to failure rates with an Instron compression device demonstrated the following mean load to failures: crossed Kirschner wire, 57.05 N; 2-hole locking plate, 36.49 N; monofilament wire, 35.69 N; heat-sensitive memory staple, 34.32 N; and 2.7-mm bicortical screw, 13.66 N. Statistical analysis demonstrated the crossed Kirschner wire technique performed significantly better than the other fixation techniques (p < .007); the 4 other techniques were found not to be significantly different statistically (p = .041) from each another. Our study results suggest a crossing Kirschner wire construct significantly increases the stability of the Akin osteotomy in a sawbone model. This might be clinically extrapolated in an effort to improve patient outcomes because these osteotomies can undergo nonunion and malunion, resulting in postoperative pain and swelling.     

Opening wedge high tibial osteotomy for medial compartment knee osteoarthritis: Planning and improving outcomes: Case series and literature review

BackgroundOpening wedge high tibial osteotomy (OWHTO) is a safe surgical procedure to treat medial compartmental osteoarthritis caused by a varus deformity. Over-correction of this varus deformity can lead to lateral compartment over-loading. In our study, we planned our correction by using the mechanical axis deviation (MAD).PurposeThe purpose of this study is to evaluate the clinical and radiological results of OWHTO based on planning using the MAD measurements.Study DesignRetrospective Case Series.Methods14 patients with Kellgren- Lawrence classification (KL) grade 3 or above underwent OWHTO, with plans to have the mechanical axis pass through 5–15 mm lateral to the center of the tibial plateau. Pre-operative and post-operative radiographic measurements were made and compared using the student t-test. SF-36 scores were obtained for clinical performance.ResultsOur patients experienced MAD from 25.9 mm medial to the center of the tibial plateau pre-operatively to 12.7 mm lateral to the center of the plateau post-operatively. The mean change in MAD was 38.7 mm (p < 0.0001). The accuracy of our correction compared to the planned MAD was 98.3%. The mechanical axis angle shifted from 7.35° of varus to 3.5° of valgus (p < 0.0001). All patients had post-operative alignments of 1–6° of valgus, with 11 of out the 14 patients with alignments less than 5° of valgus, preventing over-loading of the lateral compartment.ConclusionUsing MAD measurements is an accurate planning method for OWHTO that corrects varus deformity without over-loading the lateral compartment, and leads to improved clinical outcomes.     

Modified Ni-Nail and C-Nail systems for intra-articular fractures of the calcaneus: A biomechancial study

ObjectivesWe have proposed a novel intramedullary nail (Ni-Nail) by incorporating a sustentaculum tali screw to improve the fixation stability of minimally invasive treatment for calcaneal fractures. This study aimed to evaluate the biomechanical characters of the Ni-Nail system and compare it with traditional C-Nail system.MethodsA finite element model of a Sanders type-IIIAB calcaneal fracture was reconstructed and fixed using two intramedullary nail systems, which was validated by a cadaver study. A vertical loading of 700 N was applied to the subtalar joint surfaces, and 525 N Achilles tendon tension was applied to the superior border of the Achilles tuberosity. The von Mises stresses and fracture displacements of both fixation models were evaluated.ResultsThe maximum von Mises stress of the screws of Ni-Nail and C-Nail were 27.92 MPa and 57.42 MPa, respectively, while that of the main nail were 67.44 MPa and 53.01 MPa. In addition, the maximum fracture displacement of the Ni-Nail was larger than that of C-Nail by 15.6% (0.37 mm vs.0.32 mm).ConclusionsOur static simulation analysis showed that both Ni-Nail and C-Nail demonstrated similar biomechanical stability for calcaneal fixation. The Ni-Nail features a simple structure that is easier to operate and less traumatizing. Future studies may consider to further evaluate the clinical effectiveness by clinical trials and follow-ups.     

Kombination von VKB-Ersatzplastik und hoher tibialer Umstellungsosteotomie

Objective

Replacement of the anterior cruciate ligament (ACL) with an autologous tendon together with a high tibial osteotomy (HTO) in one operation.

Indication

Simultaneous symptomatic ACL insufficiency and symptomatic varus osteoarthritis.

Contraindications

Risk of a higher complication rate for a one-stage procedure, e.g., in loss of motion due to soft tissue contracture, loss of motion due to insufficiency of a existent ACL replacement with tunnel malplacement, tunnel widening of an existent ACL replacement with the risk of tunnel confluence, infection in a former operation. Varus osteoarthritis with a hollow posteromedial tibial plateau (knee abuser). Exclusion criteria include PLC insufficiency, lateral or posterolateral instability, lateral arthritis.

Surgical technique

Osteotomy: placement of the two K-wires from the medial tibia about 4–5 cm below the medial tibial plateau towards the lateral hinge about 2 cm below the lateral tibial plateau. Mobilization of the long fibers of the medial collateral ligament distal of the osteotomy, mobilization of the pes anserinus tendons. Frontal and axial osteotomy with an oscillating saw. Completion and opening of the osteotomy with chisels. Opening of the osteotomy with a spreader according to the new leg axis of the preoperative planning. Fixation of the osteotomy with an angle stable plate (PPP Arthrex, Tomofix Synthes). In case of a distal osteotomy of the hiberosity fixation with 2 screws. Arthroscopy: positioning of a 2.4 mm K-wire in the center of the remnant femoral ACL insertion, cannulated drilling according to the graft diameter. Positioning of a 2.4 mm K-wire in the center of the remnant tibial ACL insertion, cannulated drilling. In the case of interference of the tibial tunnel with one of the osteotomy screws, removal of the screw and finishing of the tunnel preparation. Measurement of the length and insertion of the respective osteotomy screw. Insertion of the graft and fixation with a button-wire construct at the femur and with a bioabsorbable interference screw and a lag screw at the tibia.

Postoperative management

Postoperative management relating to weight bearing rehabilitation follows osteotomy rules, while range of motion rehabilitation follows the ACL protocol.     

股骨颈动力交叉钉系统内固定植入物安放位置的力学差异分析与临床应用

目的:利用三维重建方法建立股骨颈动力交叉钉系统内固定有限元模型,比较植入物不同置入位置对内固定效果差异的影响。方法:分别建立植入物处于股骨中上三分之一处,股骨中心以及股骨中下三分之一处,股骨中心沿矢状面前三分之一处,股骨中心沿矢状面后三分之一处,5种股骨颈动力交叉钉系统内固定有限元模型,比较在这5种位置下,股骨颈动力交...     

Biomechanical comparison of four different posterior malleolus fixation techniques: A finite element analysis

PurposeThe objective of this study was to compare the biomechanical behavior of four fixation methods for posterior malleolar fracture (PMF) by finite element analysis (FEM).MethodsFour internal fixation techniques used for fixation of PMF were assessed by FEM - a computational study: posterior one-third tubular 3.5 mm buttress plate (PP) with one screw (PP 1 screw), PP with two screws (PP 2 screws), two cannulated 3.5 mm lag screws in the antero-posterior (AP) direction (AP lag screws), and two postero-anterior (PA) cannulated 3.5 mm lag screws (PA lag screws). PMF with 30% and 50% fragment sizes were simulated through computational processing reconstructed from computed tomography (CT). The simulated loads of 700 N and 1500 N were applied to the proximal tibial end. The FEM evaluated the total and localized displacements of the PMF. For the analysis of stresses, the variables maximum principal (traction) and minimum principal (compression) were used. For the metallic implants, the equivalent von Mises stress (VMS) was used.ResultsPA lag screw showed the lowest values for total and localized displacement, minimum and maximum total stress, and VMS in both physiological conditions and sizes of posterior malleolus involvement. The localized displacement was statistically lower for lag screws compared to PP techniques at 700 N (p < 0.05) and 1200 N (p < 0.05). The maximum total stress was statistically lower for PA lag screws compared to PP 1 fixation with 700 N (p = 0.03) and 1200 N (p = 0.039).ConclusionPA lag screws yield better results in terms of total and localized displacement, minimum and maximum total stress, and VMS in both physiological conditions and sizes of posterior malleolus involvement. These results demonstrate that PA lag screws are biomechanically the most efficient technique for the fixation of PMF.     

Biomechanical comparison of two different locking plates for open wedge high tibial osteotomy

Background

The purpose of this study was to compare the mechanical stability of a relatively thin locking plate (FlexitSystem implant) with a relatively firm locking plate (TomoFix implant), both used for opening wedge high tibial osteotomy.

Assessment of unloading effects after open wedge high tibial osteotomy using quantitative bone scintigraphy

IntroductionWe evaluated changes in bone tracer uptake (BTU) in open wedge high tibial osteotomy (OWHTO) and determined if BTU correlates with clinical symptoms, postoperative alignment, or cartilage regeneration after OWHTO.Materials and methodsSeventy-five knees in 64 patients who underwent OWHTO for medial compartment osteoarthritis were enrolled in this retrospective study. All cases were assessed preoperatively and at plate removal using bone scintigraphy. Visual analog scale (VAS), Japanese Orthopedic Association (JOA) score, Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS), and the weight-bearing line ratio (WBLR) were assessed preoperatively and at plate removal. In addition, cartilage regeneration was evaluated at plate removal. We assessed changes in BTU for the medial and lateral compartment after OWHTO and the correlations between BTU of the medial compartment and all other parameters were analyzed.ResultsPostoperatively, all outcome measures significantly improved: mean VAS 61.4 ± 18.3 to 9.5 ± 8.2, mean JOA score 65.1 ± 11.5 to 94.7 ± 6.0, mean OKS 29.4 ± 8.1 to 42.3 ± 4.1, mean KOOS 57.0 ± 14.3 to 83.7 ± 9.6, mean WBLR 22.8 ± 10.9 to 70.0 ± 9.4. Cartilage regeneration was observed in 53 knees (70.7%). BTU of the medial compartment significantly decreased after OWTHO, whereas no increased postoperative BTU was found in the lateral compartment. Postoperative BTU of the medial compartment significantly correlated with VAS, KOOS, and WBLR. No statistically significant associations were found between BTU and cartilage regeneration.ConclusionsOWHTO significantly decreased BTU of the medial compartment, which correlated with knee pain and postoperative mechanical alignment. Unloading effects of OWHTO led to pain relief after surgery, regardless of cartilage regeneration.