A biomechanical comparison of micromotion after ankle fusion using 2 fixation techniques: intramedullary arthrodesis nail or Ilizarov external fixator

BACKGROUND: In difficult ankle arthrodesis situations, intramedullary (IM) arthrodesis nails and external fixation are often considered in lieu of standard fusion techniques. The purpose of this study was to compare the amount of micromotion measured across an ankle fusion site stabilized with either an IM nail or with the Ilizarov external fixator. MATERIALS AND METHODS: The relative bone mineral density of 8 pairs of human cadaveric lower legs was measured by DEXA scanning. One specimen from each pair was randomly assigned to be stabilized with a new generation IM nail and the other with an Ilizarov external fixator. Specimens were tested in compression, rotation, and dorsiflexion. Optical motion capture was used to measure the direct motion occurring at the fusion site. RESULTS: No significant difference was found between the axial displacements (p = 0.94), torsional displacement (p = 0.07), or the dorsiflexion angular displacement (p = 0.28) for the IM rod group and the external fixation group. A weak correlation was found between BMD and displacement. CONCLUSION: Both the new generation IM nail and the Ilizarov external fixator imparted excellent stability to the fusion site despite a wide range of bone mineral densities. Medialization of the talus, the ability to compress the nail, and the addition of a posterior-to-anterior locking screw were thought to improve the performance of the nail. CLINICAL RELEVANCE: Both IM nail and Ilizarov external fixation provided excellent fusion site stability. The decision of which implant to use for complex arthrodesis should be dictated by the clinical needs.     

Arthrodesis of the ankle with cancellous-bone screws and fibular strut graft. Biomechanical analysis

The stability of an arthrodesis with two cancellous-bone screws across the ankle joint was evaluated in eighteen ankles from fresh-frozen cadavera. Tibiotalar motion was recorded in response to the following loading modes: medial-lateral moment, plantar flexion-dorsiflexion moment, and internal-external tibial torque. The series of loading tests was performed with two cancellous-bone screws through the tibia into the talus and a lateral fibular strut graft fixed with a proximal and a distal screw. The tests were repeated after the strut graft was removed, and again after it had been reapplied. The amount of motion at the site of the arthrodesis was greatest with tibial torque and was least with medial-lateral bending; this was true for specimens with or without a fibular strut graft. Removal of the strut graft allowed increased tibiotalar motion for all modes of loading; increases in motion were far greater for specimens of poor bone quality.     

Triple arthrodesis with an external rail fixator: A review of 8 cases

The results of 8 patients who underwent triple arthrodesis with a rail external fixator were reviewed retrospectively. The frame construct allowed immediate axial loading and unrestricted ankle joint mobilization. Assistive ambulatory equipment was not required postoperatively. Periodic adjustment to compression was performed weekly until evidence of radiographic consolidation. The mean duration of frame application was 11.5 weeks. Follow-up averaged 15.9 months. Fusion occurred in all joints. One superficial pin-tract infection developed that resolved with oral antibiotics. The results of this study indicate that the rail frame system provides a viable fixation alternative for triple arthrodesis and warrants further investigation.     

Compression arthrodesis of the ankle by triangular external fixation: biomechanical and clinical evaluation

This article describes a technique of ankle arthrodesis using a triangular external fixation frame and presents the results of biomechanical analysis and clinical experience with the frame. Clinical evaluation of 23 ankle arthrodeses performed using a triangular external fixation frame yielded a 91.3% fusion rate at an average of 11 weeks postfusion. The triangular frame was 79% stiffer than a compression-only external frame in torsion and 39% stiffer in anteroposterior bending. This high rate of fusion is attributed to the elimination of micromotion at the fusion site because of the increased rigidity of the triangular external compression frame.     

A biomechanical analysis of the Ilizarov external fixator

Five configurations of the Ilizarov fixator were analyzed in vitro. The overall stiffness, shear stiffness, and axial motion of the fracture site were determined. The data were compared with the results of eight conventional one-half frame fixators previously tested in the same manner. The Ilizarov fixator allowed significantly more axial motion at the fracture site during axial compression than the other fixators tested. The overall stiffness and shear rigidity of the Ilizarov external fixator were similar to those of the one-half pin fixators in bending and torsion. The stability of the Ilizarov fixator was a function of bone position within the fixator rings and fixation wire tension. The use of olive stop wires increased the shear resistance of the Ilizarov system.     

Revision of ankle arthrodesis with external fixation for non-union.

We evaluated the cases of twenty-six patients (twenty-six ankles) who had had revision of an ankle arthrodesis with external fixation for a nonunion, to determine the reasons for the failure of the previous arthrodesis. Eighteen patients had had supplemental bone-grafting in addition to the external fixation. The failure of the previous arthrodesis was related to inadequate fixation technique in seven patients and to technical problems in two patients; in the other seventeen patients at least one risk factor was identified. We also determined the functional results of the revision operation with external fixation for all patients. The average duration of follow-up was five years (range, two to ten years) in the twenty-two patients who did not have a reoperation for a persistent nonunion. The results were excellent in eleven patients, good in five, fair in four, and poor in six. The over-all rate of union was twenty (77 per cent) of twenty-six, comparable with that after primary arthrodesis; however, supplemental bone-grafting is usually necessary. In the current series, rigid fixation, precise apposition of bone and alignment of the foot, and early treatment of perioperative infection gave satisfactory results.     

Ilizarov支架外固定联合踝关节融合术治疗终末期踝关节炎

目的探讨采用Ilizarov支架外固定联合踝关节融合术治疗终末期踝关节炎的疗效。方法回顾性分析自2013-06—2014-12采用Ilizarov支架外固定联合踝关节融合术治疗的13例终末期踝关节炎。末次随访时摄踝关节正侧位X线片,必要时CT三维重建检查,确定是否达到骨性融合。采用AOFAS评分标准评价踝关节功能。结果本组13例均获得随访10~28个月,平均17个月。术后均骨性融合,骨愈合时间12~18周,平均15周。外固定架拆除时间16~22周,平均20周。3例出现针道并发症,反复使用酒精及百多邦外用后控制;其中1例针道感染流脓,反复换药经久不愈,更换克氏针后愈合。末次随访时踝关节功能按AOFAS评分标准评定:优1例,良9例,可3例。末次随访时AOFAS评分为69~91(79.6±7.2)分,明显高于术前,差异有统计学意义(t=37.450,P0.001)。结论采用Ilizarov支架外固定联合踝关节融合术治疗终末期踝关节炎的骨愈合率高,尤其适用合并感染、软组织条件差、骨质缺损严重及踝关节畸形的患者。     

Functional outcome of knee arthrodesis with a monorail external fixator

Several methods for obtaining knee arthrodesis have been described in the literature and world; over, the commonest cause for arthrodesis is a failed arthroplasty. Less commonly, as in this series, post-infective or traumatic causes may also require a knee fusion wherein arthroplasty may not be indicated. We present salient advantages along with the radiological and functional outcome of twenty four patients treated with a single monorail external fixator. All patients went on develop fusion at an average of 5.4 months with an average limb length discrepancy of 3 cm (1.5–6 cm). Improvements in functional outcome as assessed by the lower extremity functional score (LEFS), and the SF-36 was significant (p = 0.000). Knee arthrodesis with a single monorail external fixator is a reasonable single-staged salvage option in patients wherein arthroplasty may not be the ideal choice. The outcome, though far from ideal, is definitely positive and predictable.     

关节镜下病灶清除并半环槽加压外固定治疗全踝关节结核

目的探讨关节镜下踝关节结核病灶清除并半环槽加压外固定行踝关节融合术治疗全踝关节结核的临床经验。方法6例全踝关节结核患者，男4例，女2例；年龄28-44岁，平均33岁。病程8-23个月，平均13个月；均为单踝关节发病。其中1例伴踝部窦道形成患者曾在外院行切开引流术。术前均行至少3周的抗结核治疗。手术采用踝关节镜前外侧及前内侧入路进行结核病灶清除和胫距关节融合，并用半环槽外固定架固定。结果术后无一例发生皮肤感染及窦道形成等并发症。患者于术后2-7d，平均4d即可下地活动。术后6例均获得随访，随访时间6-42个月，平均21．3个月。6例患者于术后9-17周，平均12．5周达到骨性愈合，其中3例患者术后疼痛消失，其余3例有轻度疼痛及跛行，均无结核复发。结论对没有严重骨破坏的全踝关节结核采用关节镜下病灶清除，具有损伤小、恢复快、病灶清除彻底等优点。半环槽加压外固定，可早期下床活动，有利于融合愈合。     

Ankle arthrodesis using an Ilizarov external fixator in patients wounded by landmines and gunshots

BACKGROUND: We evaluated the results of ankle arthrodesis performed with circular external fixators (CEF) in those patients who had developed tibiotalar arthritis secondary to a landmine or a gunshot injury. MATERIALS AND METHODS: Nineteen ankles in 19 patients were fused using CEF. All patients had approximately 3 (range, 1 to 5) operations for bone and soft tissue reconstruction preceding the arthrodesis. Ankle arthrodesis was performed an average of 2.3 (range, 1 to 7) years after the initial trauma. The mean age at operation was 22 (range, 20 to 31) years old and all patients were male. RESULTS: The average time spent in the CEF was 3.5 (range, 2 to 7) months. The mean followup was 59 (range, 31 to 90) months. Successful arthrodesis was achieved in all patients in an acceptable position. Clinically, 6 patients were assessed as excellent, 9 patients as good, 3 patients as fair, and 1 patient had a poor result. Twelve patients reported no pain postoperatively, 4 patients reported reduced to mild and/or occasional pain, 2 patients reported moderate pain, and 1 patient reported persistent pain. Sixteen patients described their outcome as satisfactory, one was somewhat satisfied, and two were dissatisfied. There were pin track infections in 10 patients and ring sequestration in one patient. CONCLUSION: Patients who have degenerative ankle arthritis due to gunshot wounds and land-mine injuries with poor bone quality and soft tissue conditions at the distal tibia can be successfully managed by using CEF.     

Compression arthrodesis of the ankle by triangular external fixation: an improved technique

In this preliminary report, the authors present a new application of an external tubular fixation system for compression arthrodesis of the ankle. A triangular ankle fusion frame was designed that provides rigid immobilization of the tibiotalar joint, with midfoot control provided by a metatarsal pin. Over the past 3 years, the authors have used this device to achieve solid tibiotalar arthrodesis in 12 of 14 patients. The surgical method, including step-by-step construction and application of the triangular ankle fusion frame, is presented. Early results suggest a nearly 90% union rate, including reoperative cases for failed primary fusion.     

The effects of additional hollow cylinder coated to external fixator screws for treating pilon fracture: A biomechanical perspective

An external fixator is a promising medical device that could provide optimum stability and reduce the rate of complications in treating bone fracture during intervention period. It is noted that the biomechanics behaviour of device can be altered by introducing more features such as material suitability and additional components. Therefore, this study was conducted via finite element method to investigate the effects of additional hollow cylinder coated with external fixator screws in treating Type III pilon fracture. Finite element models which have been validated with experimental data were used to simulate stresses at the pin-bone interface and relative micromovement at interfragmentary fractures during swing (70 N load) and stance phases (350 N load). All bones and external fixators were assigned with isotropic material properties while the cartilages were simulated with hyper-elastic. For the hollow cylinder, polyethylene was assigned due to its properties which are equivalent to the bone. From the results, it is found that stresses at the pin-bone interface for the coated screws were reduced to 54% as compared to the conventional fixator. For the micromovement, there was no difference between both models, whereby the value was 0.03 mm. The results supported previously published literature, in which high stresses are unavoidable at the interface, fortunately, those stresses did not exceed the ultimate strength of bone, which is safe for treating patients. In conclusion, if patients are allowed to bear weight bearing, the external fixator with coated screws is a more favourable option to be fixed into the bone to avoid complications at the interface.     

An in vitro biomechanical study of a hinged external fixator applied to an unstable elbow

Details of the mechanical properties of hinged external fixators are essential to use the fixator properly in the clinical setting. A hinged external fixator (Dynamic Joint Distractor 2) was attached to the lateral side of 7 cadaveric elbows. Cantilever lateral bending tests were performed at 3 flexion angles in varus and valgus directions. Varied states of joint contact and axial loading were studied. Stiffness of the construct was calculated with uniaxial loading. Stiffness decreased with increased elbow flexion. Gap creation made the system less stiff. Axial loading made the system stiffer, especially in valgus testing. Stiffness in varus was approximately 4 times that in valgus. Lateral fixator application with half pins is most effective for protecting against varus-producing forces. When using the external fixator for unstable elbows, attention should be paid to the status of the articular surfaces and the integrity of the ligaments, and this should also be noted for elbow position during rehabilitation.     

Comparative analysis of uniplanar external fixator and retrograde intramedullary nailing for ankle arthrodesis in diabetic Charcot's neuroarthropathy

Background:

Charcot''s neuroarthropathy of ankle leads to instability, destruction of the joint with significant morbidity that may require an amputation. Aim of surgical treatment is to achieve painless stable plantigrade foot through arthrodesis. Achieving surgical arthrodesis in Charcot''s neuroarthropathy has a high failure rate. This is a retrospective nonrandomized comparative study assessing the outcomes of tibio-talar arthrodesis for Charcot''s neuroarthropathy treated by uniplanar external fixation assisted by external immobilization or retrograde intramedullary interlocked nailing.

Materials and Methods:

Records of the authors′ institution were reviewed to identify those patients who had undergone ankle fusion for diabetic neuroarthropathy from January 1998 to December 2008. A total of11 patients (six males and five females) with a mean age of 56 year and diabetes of a mean duration of 15.4 years with ankle tibio-talar arthrodesis using retrograde nailing or external fixator for Charcot''s neuroarthropathy were enrolled for the analysis. Neuropathy was clinically diagnosed, documented and substantiated using the monofilament test. All procedures were performed in Eichenholz stage II/III.Six patients were treated with uniplanar external fixator, while the remaining five underwent retrograde intramedullary interlocking nail. The outcomes were measured for union radiologically, development of complications and clinical follow-up, according to digital archiving systems and old case notes.

Results:

All five (100%) patients treated by intramedullary nailing achieved radiological union on an average follow-up of 16 weeks. The external fixation group had significantly higher rate of complications with one amputation, four non unions (66.7%) and a delayed union which went on to full osseous union.

Conclusion:

The retrograde intramedullary nailing for tibio-talar arthrodesis in Charcot''s neuroarthropathy yielded significantly better outcomes as compared to the use of uniplanar external fixator.     

Three-dimensional stabilization provided by the external spinal fixator compared to two internal fixation devices: a biomechanical in vitro flexibility study

We performed an in vitro study to investigate the stabilization (i.e. motion reduction) provided by the external spinal fixator (ESF), and to compare the three configurations of the ESF with two internal fixation techniques. Six human cadaveric lumbar spine specimens (L3-S1) were subjected to multidirectional flexibility testing in six configurations: (1) intact, (2) ESF in neutral, (3) ESF in distraction, (4) ESF in compression, (5) translaminar facet screw fixation, and (6) internal transpedicular fixation. Both the ESF and the internal fixation systems stabilized the specimens from L4 to S1. In each testing configuration, pure bending moments of flexion-extension, bilateral axial rotation, and bilateral lateral bending were applied to the uppermost vertebra stepwise to a maximum of 10 Nm. The rigid body motion between the vertebrae was measured using an optoelectronic camera system, and custom software was used to calculate the intervertebral rotations. For each applied motion in all testing configurations, the total range of motion (ROM) of L4-S1 is reported. All three ESF configurations stabilized the spine significantly when compared to the intact specimen. The ESF in compression provided significantly more stabilization in flexion-extension than the two other ESF configurations, but no other significant differences were found between the three ESF modes. In flexion-extension the ESF stabilized the spine significantly when compared with the two internal fixation devices. Only in bilateral lateral bending was the ESF inferior to internal transpedicular fixation in providing stabilization. The results of the present study suggest that the ESF provides a high degree of stabilization for preoperative assessment of selected low back pain patients. Whether other non-mechanical factors affect the pain relief experienced by the patients remains unknown.     

可活动外固定支架结合Anchor钉治疗腕关节脱位

目的探讨应用可活动外固定支架结合Anchor钉治疗腕关节脱位的可行性及治疗效果。方法对16例腕关节脱位患者进行腕关节可活动外固定支架固定,同时切开复位,加压空心钉固定骨折,Anchor钉修复腕骨间韧带和桡腕韧带,克氏针临时固定腕骨。结果随访3～6个月,16例患者均基本恢复腕关节功能,未出现再脱位、舟骨月骨坏死等。采用Cooney评价标准:优7例,良7例,可2例。结论可活动外固定支架结合Anchor钉治疗腕关节脱位可有效固定腕关节,韧带修复可靠,利于破损韧带愈合及促进早期逐步功能锻炼,疗效满意。     

Biomechanical comparison of ankle arthrodesis techniques: crossed screws vs. blade plate

Many different techniques for ankle arthrodesis have been described. Experience at our institution with crossed screws internal fixation has not met the 90+% union rate reported in the literature. A compression blade plate is one technique for ankle arthrodesis which has not been evaluated biomechanically. A biomechanical study comparing two groups of sawbone ankle fusion constructs fixed with crossed screws and compression blade plates was performed in order to evaluate the stiffness and rigidity of these two arthrodesis techniques. The crossed screws construct demonstrated superior stiffness during dorsiflexion (p < 0.001) and valgus (p < 0.001) loading. The two constructs were found to have equal strength in resisting plantarflexion, varus and torsional loads although there was a trend for greater resistance by the crossed screws construct. These findings lend biomechanical support to the use of crossed screws for tibiotalar arthrodesis.     

Evaluation of different shape-memory staple configurations against crossed screws for first metatarsophalangeal joint arthrodesis: A biomechanical study

Background

The first metatarsophalangeal joint may be fused in order to treat arthritis or instability. The use of shape-memory staples for fixation is well recognised, but little work has been done into the optimal configuration of staples.

组合式外固定器治疗合并患肢短缩的足踝部畸形

背景：传统的足踝部畸形的矫正需要通过手术来完成,术后需要“静态”的维持。Ilizarov技术遵循的“张力-应力法则”和“牵拉组织再生技术”,在一定程度上打破了传统的矫形模式。目的：探讨Ilizarov技术治疗合并患肢短缩的足踝部畸形的临床疗效。方法：回顾分析2006年8月至2012年10月采用Ilizarov技术治疗的17例下肢及足踝部畸形患者的临床资料。其中男10例,女7例,年龄20~37岁,平均27.5岁。脊髓灰质炎后遗症导致患肢短缩合并足踝负重位外翻畸形患者5例,先天性马蹄内翻足合并患肢短缩7例,高弓足合并患肢短缩3例,跟腱挛缩、仰趾畸形合并患肢短缩2例。所有患者在有限手术重建足踝部软组织平衡或者截骨矫正畸形后安装Ilizarov组合式外固定支架,同时做胫骨的延长。结果：17例患者佩戴Ilizarov支架的时间是16~44周,足踝部矫形支架在3~6个月矫形满意、骨融合确实后单独拆除,骨延长支架根据需要继续佩戴。所有患者都获得随访,随访时间6~48个月,患肢延长2~6 cm,延长段骨矿化满意,足踝部矫形满意。足踝功能参照AOFAS评分：术前（43±5.1）分,术后（76±7.2）分。结论：对于各种原因导致的合并下肢短缩的足踝部畸形的矫治,Ilizarov技术灵活的器械组合可同时完成多方向的畸形矫正,在矫正畸形的同时实施骨延长术。