Correction outcomes of the postoperative malalignment salvaged by the temporary application of the hexapod external fixator in tibial diaphyseal fractures treated by monolateral external fixation

BackgroundPostoperative malalignment in fractures treated by monolateral external fixation is not uncommon in clinical practice. Accurate reduction without excessive tissue disruption caused by surgical intervention and sequentially manage the fractures using monolateral external fixation for definitive treatment is still a challenge for surgeons. The purpose of our study was to evaluate the feasibility and effectiveness of the temporary application of the hexapod external fixator (HEF) for the postoperative malalignment correction in tibial diaphyseal fractures treated by monolateral external fixation.MethodsWe carried out a retrospective analysis of 23 trauma patients with tibial diaphyseal fracture treated by the monolateral external fixation at our institution from January 2016 to May 2019. There were 21 males and 2 females with a mean age of 38 years (range 18-60 years). The hexapod external fixator was temporarily applied due to postoperative malalignment within two weeks and who unwilling to undergo a secondary surgical intervention. For patients with postoperative malalignment requiring correction, the HEF components were installed on the original existing half pins of the monolateral external fixator after removing the connecting rod. The standard anteroposterior and lateral X-rays of the injured limb combined with the temporary HEF were conducted to measure the hexapod external fixator parameters. Any residual deformities were corrected by gradual struts adjustment with the aid of computer-based software. When satisfactory alignment was achieved, the HEF was removed, and the monolateral external fixator was sequentially used as the definitive structure.ResultsAll patients acquired functional reduction, which was evaluated by radiographs. The mean correction time was 4 days (range 2 to 8 days). The mean coronal plane translation (1.3±1.0 mm), coronal plane angulation (0.9±0.7°), sagittal plane translation (1.4±1.1 mm), and sagittal plane angulation (0.7±0.7°) after correction were all less than those (7.0±4.9 mm, 4.7±2.3°, 5.6±3.6 mm, 3.2±2.5°) before correction.ConclusionsThe temporary application of the hexapod external fixator is an alternative and feasible method for the postoperative malalignment correction in tibial diaphyseal fractures treated by monolateral external fixation.     

轴向载荷分担比指导外固定器动力化的临床应用

目的:探讨轴向载荷分担比用于胫腓骨骨干骨折术后指导外固定器轴向动力化促进骨折愈合的有效性。方法:选取外固定器治疗的胫腓骨骨干骨折患者100例,随机分为观察组50例,对照组50例。观察组在轴向载荷分担比指导下行外固定器轴向动力化治疗,对照组未行动力化,随访比较两组的治疗效果。结果:所有患者均获随访,随访时间4～12个月,平均6.5个月,治疗期间所有患者均未出现外固定针断裂、松动及再骨折等并发症,观察组1例骨搬移患者轴向载荷分担比5%,X线片显示骨折断端有连续性骨痂通过,拆除外固定器连接杆后发生移位,恢复原数值行轴向加压再动力化,现已愈合。观察组除外1例骨搬移患者,其余49例患者外固定器固定时间为[(24.4±4.7)周],骨折临床愈合时间为[(22.4±4.7)周],与对照组50例患者外固定器固定时间[(29.3±5.6)周],骨折临床愈合时间[(27.3±5.6)周]比较,显著减少(P0.05)。结论:外固定器轴向载荷分担比指导胫腓骨骨干骨折外固定术后轴向动力化可以加速骨折愈合,但不适合骨搬移截骨端已硬化患者。     

单边和环形外架在感染性胫骨骨不连治疗中的对比研究

目的:对比单边和环形外架在感染性胫骨骨不连中的治疗效果,探索成骨能力更好和并发症更少的外固定架构型。方法:回顾性纳入2010年1月至2014年12月治疗的150例感染性胫骨骨不连患者,符合纳入和排除标准的患者根据外固定类型分为单边组和环形组,收集两组患者的一般资料和围手术信息,通过像素比评价新生骨质量,通过并发症评估治疗效果,并根据并发症情况分析治疗注意事项。结果:共64例胫骨中段感染性骨不连患者纳入研究,单边组26例,环形组38例。两组患者一般资料比较差异无统计学意义(P>0.05)。两组患者新生骨像素比分别为0.91~0.97(0.94±0.03)和0.93~0.97(0.95±0.02),差异无统计学意义(P>0.05)。单边组外固定指数为34.1~50.6(42.3±8.3) d/cm,环形组为44.5~56.1(45.8±10.3) d/cm,差异无统计学意义(P>0.05)。单边组7例(26.9%)存在并发症,环形组5例(13.2%),组间比较差异无统计学意义(P>0.05),但单边组5例发生足下垂,通过后续治疗后缓解,环形组无此情况。单边组的下地时间比环形组晚(P<0.05)。结论:在治疗感染性骨不连时,单边和环形外架都能取得满意的骨愈合结果,且效果相当。对于骨质疏松严重,并发症多,需要早期下地的患者建议采用环形外架固定。如果选择单边外架,预期延长长度长、固定时间久的建议采用羟基磷灰石涂层螺钉固定,严密监测踝关节活动,防止足下垂畸形。     

Auto Strut: a novel smart robotic system for external fixation device for bone deformity correction,a preliminary experience

PurposeSeveral hexapod external fixators are used in the treatment of bone fracture and deformity corrections. One characteristic of all of them is the requirement for manual adjustment of the fixator struts. The purpose of this study was to introduce a novel robotic system that executes automatic adjustment of the struts.MethodsTen patients were treated for various bone deformities using a hexapod external fixator with the Auto Strut system. This new system automatically adjusts the fixator struts according to a hexapod computer-assisted correction plan. During each visit, the progress of the correction was assessed (clinically and radiographically) and reading of the strut scale numbers was performed and compared with the original treatment plan.ResultsAll patients completed treatment during the follow-up period, achieving all planned correction goals, except from one patient who switched to manual struts due to personal preference. The device alarm system was activated once with no device-related adverse events. Duration of distraction ranged between ten and 90 days with a distraction index ranging between eight and 15 days/cm. Regenerate consolidation time between one and seven months. In total, 48 struts of eight patients were recorded and analyzed. In all, 94% of the final strut number readings presented a discrepancy of 0 mm to 1 mm between planned and actual readings, indicating high precision of the automatic adjustment.ConclusionThis study presents preliminary results, showing that Auto Strut can successfully replace the manual strut adjustment providing important advantages that benefit the patient, the caregiver and the surgeon.Level of EvidenceLevel II     

Stabilization of a short juxta-articular bone segment with a circular external fixator

The objective of the current study was to evaluate the stabilization of a simulated juxta-articular bone segment with a circular external fixator, and to determine which method of fixation improved bending stabilization while preserving the axial dynamization of a three-wire configuration. Frames were divided into three groups: wire, half-pin and hybrid and tested in axial compression, torsion, anteroposterior bending and mediolateral bending. Hybrid frames using 4 mm half-pins improved the anteroposterior stabilization of the short bone segment while maintaining axial characteristics similar to a three-wire frame. Increasing the bending stabilization will improve bone segment alignment while permitting axial micromotion beneficial to bone healing.     

Taylor spatial frame-software-controlled fixator for deformity correction-the early Indian experience

Background:

Complex deformity correction and fracture treatment with the Ilizarov method needs extensive preoperative analysis and laborious postoperative fixator alterations, which are error-prone. We report our initial experience in treating the first 22 patients having fractures and complex deformities and shortening with software-controlled Taylor spatial frame (TSF) external fixator, for its ease of use and accuracy in achieving fracture reduction and complex deformity correction.

Settings and Design:

The struts of the TSF fixator have multiplane hinges at both ends and the six struts allow correction in all six axes. Hence the same struts act to correct either angulation or translation or rotation. With a single construct assembled during surgery all the desired axis corrections can be performed without a change of the montage as is needed with the Ilizarov fixator.

Materials and Methods:

Twenty-seven limb segments were operated with the TSF fixator. There were 23 tibiae, two femora, one knee joint and one ankle joint. Seven patients had comminuted fractures. Ten patients who had 13 deformed segments achieved full correction. Eight patients had lengthening in 10 tibiae. (Five of these also had simultaneous correction of deformities). One patient each had correction of knee and ankle deformities. Accurate reduction of fractures and correction of deformities and length could be achieved in all of our patients with minimum postoperative fixator alterations as compared to the Ilizarov system. The X-ray visualization of the osteotomy or lengthening site due to the six crossing struts and added bulk of the fixator rings which made positioning in bed and walking slightly more difficult as compared to the Ilizarov fixator.

Conclusions:

The TSF external fixator allows accurate fracture reduction and deformity correction without tedious analysis and postoperative frame alterations. The high cost of the fixator is a deterrent. The need for an internet connection and special X-rays to operate the fixator add to its complexity.     

Do axial dynamic fixators really produce axial dynamization?

The use of dynamic external fixators for the treatment of long bone fracture is widespread and well accepted. It is claimed that dynamization, i.e. small micromovements of compression/distraction at the fracture site, can be produced by allowing sliding of an inner rod within an outer housing. However, as the forces on the fixator are not direct but transferred from the bone via bone pins, there is a bending moment on the fixator. This produces "self-locking" and effectively prevents axial movements. We have studied the effect of this moment on the binding properties of the Orthofix system. The amount of movement at a simulated fracture site allowed before this locking occurs was measured and its implications discussed. It would appear that true axial dynamization does not take place using this system.     

Mechanical rigidity of the Ortho-SUV frame compared to the Ilizarov frame in the correction of femoral deformity

The Ortho-SUV frame (OSF) is a novel hexapod circular external fixator which draws upon the innovation of the Ilizarov method and the advantages of hexapod construction in the three-dimensional control of bone segments. Stability of fixation is critical to the success or failure of an external circular fixator for fracture or osteotomy healing. In vitro biomechanical modelling study was performed comparing the stability of the OSF under load in both original form and after dynamisation to the Ilizarov fixator in all zones of the femur utilising optimal frame configuration. A superior performance of the OSF in terms of resistance to deforming forces in both original and dynamised forms over that of the original Ilizarov fixator was found. The OSF shows higher rigidity than the Ilizarov in the control of forces acting upon the femur. This suggests better stabilisation of femoral fractures and osteotomies and thus improved healing with a reduced incidence of instability-related bone segment deformity, non-union and delayed union.     

Unicortical self-drilling external fixator pins reduce thermal effects during pin insertion

Introduction

External fixation is associated with the risk of pin loosening and pin infection potentially associated to thermal bone necrosis during pin insertion.

Objective

This study aims to investigate if the use of external fixator systems with unicortical pins reduces the heat production during pin insertion compared to fixators with bicortical pins.

Methods

Porcine bone specimens were employed to determine bone temperatures during insertion of fixator pins. Two thermographic cameras were used for a simultaneous temperature measurement on the bone surface (top view) and a bone cross-section (front view). Self-drilling unicortical and bicortical pins were inserted at different rotational speeds: (30–600) rpm. Maximum and mean temperatures of the emerging bone debris, bone surface and bone cross-section were analyzed.

Results

Maximum temperatures of up to 77?±?26 °C were measured during pin insertion in the emerging debris and up to 42?±?2 °C on the bone surface. Temperatures of the emerging debris increased with increasing rotational speeds. Bicortical pin insertion generated significantly higher temperatures at low insertion speed (30 rpm)

Conclusion

The insertion of external fixator pins can generate a considerable amount of heat around the pins, primarily emerging from bone debris and at higher insertion speeds. Our findings suggest that unicortical, self-drilling fixator pins have a decreased risk for thermal damage, both to the surrounding tissue and to the bone itself.

     

Comparative clinical study on deformity correction accuracy of different external fixators

Purpose

In this study, the correction accuracy of Smart Correction spatial fixators and of Ilizarov-type external fixators are compared in terms of deformity complexity.

Methods

Seventy-seven (40 male, 37 female) bone segments of 57 patients treated with a Smart Correction device were compared with 94 (51 male, 43 female) segments of 68 patients treated with an Ilizarov fixator. Mean age of the Smart Correction group was 20.69?±?12.94 years, and or the Ilizarov group 22.45?±?12.18 years. Patients were categorised according to limb lengthening and the number of deformity planes.

Results

A longer correction period was found with Ilizarov (66.53?±?47.7 days) compared with Smart Correction (49.05?±?35.6 days) devices. The bone healing index of the Ilizarov group was significantly better compared with the spatial group. Residual deformity after treatment was significantly lower with the Smart Correction device; however, this relationship could not be shown between subgroups. Although there was no significant difference between subgroups, mean residual deformity was higher with the increasing number of planes of the deformity.

Conclusions

The Smart Correction fixator is an accurate device that allows ease of application and planning. It demonstrates higher accuracy for correcting deformities compared with an Ilizarov external fixator. With an increasing number of planes, the difference between the two devices becomes even more pronounced. The relationship between the complexity of the deformity and residual deformity may possibly be significantly greater in favour of the Smart Correction fixator in a study with a larger sample size.     

The effects of dynamization and destabilization of the external fixator on fracture healing: a comparative biomechanical study in dogs

This study compared the effects of axial dynamization and staged destabilization on fracture healing. Bilateral midshafts of canine tibiae were osteotomized and fixed with an external fixator. The hind limbs were divided into two groups: the destabilized group in which the fixator's stiffness was progressively reduced over time and the axially dynamized group in which the fixator was axially dynamized. The healed tibiae were tested for 3-point bending in the anteroposterior plane. The biomechanical tests performed 2 months postoperatively revealed that the side with the destabilized fixator was more rigid than the side with the axially dynamized fixator, but the differences were insignificant (P=.20). This study showed staged destabilization of the fixator's stiffness was as effective on the enhancement of fracture healing as axial dynamization.     

Evaluation of a novel semicircular locking external fixator for treating fractures of long bones: Biomechanical comparison with a circular external fixator

PurposeThis study aimed to investigate the biomechanical properties of a novel semicircular locking external fixator with locking screw mechanism, shape of trapezoidal corrugations, half- ring designed for greater stability.Materials and methodsThe novel external fixator had a half-ring with the shape of trapezoidal corrugations and locking screws fixing the bone at different angles in all three planes (sagittal, axial, and coronal). The biomechanical properties of the semicircular locking external fixator (group 1) were compared with those of a standard Ilizarov-type circular external fixator (group 2) (TST, ?stanbul, Turkey) in an experimental study design. Five frames were used in each group. Standard PE 1000 (polyethylene) rod models (n = 10) simulating the tibia bone model were used. Both systems were compared biomechanically by applying axial and torsional loads simultaneously.ResultTwo samples in group 2 were damaged before the test ended during axial loading. All of the samples in group 1 completed the tests without damage after 150,000 cycles. The axial stiffness of the semicircular locking external fixator was found to be significantly higher than that of the Ilizarov-type circular external fixator (p < 0.05). No statistically significant difference was found between the two fixators in torsional loading. The application time of semicircular locking external fixator was significantly shorter than Ilizarov-type circular external fixator (p < 0.05).ConclusionThe novel semicircular locking external fixator was biomechanically stronger than the Ilizarov-type external fixator for treating fractures of long bones. It can be used as a permanent external fixator for the definitive treatment of long bone fractures with soft tissue damage in terms of stability and application time.     

Effect of early axial dynamization on tibial bone healing: a study in dogs.

Early axial dynamization and its effect on experimental tibial bone healing was compared with healing under rigid fixation in a time-sequenced manner using dogs. An external fixator that could be rigidly locked or set to allow free axial movement while preventing bending and shear was used. Both tibias were osteotomized and externally fixed, leaving a gap between bone ends of 2 mm. At 1 week, one side was dynamized, whereas the other side was kept rigidly locked as a control. Dogs were euthanized at 1 day and 1, 3, 5, 8, and 11 weeks after dynamization. The outcome measures were static and dynamic load-bearing, periosteal callus development, new bone formation, callus tissue composition, and mechanical strength. Load bearing was higher on the dynamized limbs during standing for the first 5 weeks and during gait for the first 3 weeks after dynamization compared with the controls. Maximum periosteal callus size was reached faster and was distributed more symmetrically on the dynamized side. The periosteal callus area decreased at 12 weeks on the dynamized sides, but there was no significant change in the area on the control sides. Endosteal new bone formation and bone density decreased between 9 and 12 weeks only on the dynamized sides. The dynamized side showed a significantly higher torsional stiffness at 6 weeks than did the controls. There were no significant differences between dynamized and control tibias at other times. Maximum torque also tended to be higher on the dynamized sides at the same time. Early axial dynamization appeared to accelerate callus formation and remodeling and to provide higher mechanical stiffness during early stages of bone healing.     

A novel way to dynamize a spatial frame and optimize fracture healing

BackgroundFracture site motion creates mechanical strains on the healing tissues which influences bone formation. Axial micro-motion maximizes dilatational strains, whereas shearing motions maximize deviatoric strains on the healing tissues. Dilatational strains optimize bone healing, deviatoric strains retard bone healing. Dynamization of external fixation using either an Ilizarov or Spatial Frame platform is used to increase loading on the limb which increases the mechanical stress and strain on the tissues to improve healing. The scientific literature does not address how dynamization of the spatial frame effects fracture site motion. The purpose of this study is to assess the effect of modified shoulder bolts incorporated into a spatial frame during dynamic loading.MethodsFive identical two-ring spatial frame constructed were mounted on Sawbones tibias with an osteotomy performed distal to the tibial tubercle. Sinusoidal load was applied at a rate of 0.25 Hz. Axial force and displacement, in addition to motion of the proximal and distal tibia segments were recorded. Eight constructs were tested: 1) All struts of the Spatial Frame rigid, 2) Strut #1 loose, 3) Struts #1 and #3 loose, 4) Struts #1, #3 and #5 loose, 5) All struts loose, 6) All struts rigid with dynamization bolts on the proximal end, 7) All struts rigid with dynamization bolts on alternating sides, 8) Threaded rods between the rings with two millimeters of dynamization.ResultsNo difference in vertical displacement was observed between the Ilizarov and all struts locked. No significant difference in shear values between all struts locked and modified shoulder bolt struts was observed. Increase in vertical movement with the modified shoulder bolts was an average of 1.83 mm. Significant shear forces at the fracture site were observed with unlocking single or multiple struts of the spatial frame.ConclusionModified shoulder bolts can be used for spatial frame dynamization without increasing shear motion.     

Femoral bone transport by a monolateral external fixator with or without the use of intramedullary nail: a single-department retrospective study

Backgrounds

Treatment for bone defect remains a challenge for orthopedists. Bone transport gives an effective alternative, which can be performed with an external fixator alone or combined with an intramedullary nail. Each has its advantages and disadvantages. We present a retrospective study to find out the optimal choice by evaluating the outcomes of treatment for femoral bone defect with two methods.

Methods

Two groups of patients, the monolateral external fixator alone (group A, n = 13) and the monolateral external fixator combined with intramedullary nail (group B, n = 15), were compared. Duration of the external fixator, external fixator index, radiographic consolidation index, complication, and total cost for treatment was also recorded. A modified classification of the Association for the Study and Application of the Method of Ilizarov (ASAMI) was used to assess results in two groups of patients; another SF-36 health survey questionnaire was used to assess the life qualities patients of two groups.

Results

Healing was achieved in 13/13 and 13/15 of the two groups, respectively. The rates of complications were significantly higher in the group A. Two patients performed amputations because of persistent deep infections in group B. Statistically significant difference was found when comparing ASAMI scores and categories of the SF-36 health survey.

Conclusions

Bone transport by monolateral external fixator with the use of intramedullary nail reduces the incidence of complication and the duration of external fixator time that give patients a better life quality in both physical and emotional. However, if chronic osteitis exists, bone transport should be treated with monolateral external fixator alone due to a lower rate of amputations.     

Dynamic vs static external fixation of distal radial fractures: A randomized study

Objectives:

The present randomized study is conducted to compare the functional and anatomical outcomes of dynamic multiplanar external fixation against that of static external fixation in the management of displaced unstable comminuted fractures of the distal radius.

Materials and Methods:

Sixty adult patients with displaced unstable comminuted fractures of the distal radius were randomly allocated either to the dynamic (n=30) or static (n=30) fixator groups. Patients in the dynamic fixator group were managed with closed reduction and application of Penning-type articulated fixator (Orthofix, Srl, Italy); the injured wrist was partially dynamized at 3 weeks. Patients in the static group were managed with monoplanar static external fixator of Joshi''s external stabilizing system (JESS) type fixator. In both groups, the fixator was maintained for 6–8 weeks. The patients were followed-up over 2 years. The primary outcome measures were the functional outcome as measured using the Gartland and Werley and DASH scores and anatomical outcome as measured using the Lindstrom score. The secondary objective was to correlate anatomical and functional outcomes and to look at overall local complications.

Results:

Palmar tilt was better restored in the Penning fixator group (P<0.0001). There was reduced loss of ulnar tilt (P=0.05) and radial height (P=0.04) in the Penning fixator group. Gartland and Werley score was better in the Penning fixator group at each time point of the follow-up. The DASH score was similar in the two groups at 2 years (P=0.14). There was poor correlation (0.19) between functional outcome and anatomical restoration at 2 years.

Conclusions:

In the management of displaced unstable comminuted fracture of the distal radius, use of an articulated multiplanar external fixator, allowing partial dynamization of the injured wrist at 3 weeks, resulted in improved early functional and anatomical outcome as compared to static external fixation. However, there was no significant difference in functional outcome at 2 years.     

In vivo assessment of regenerate axial stiffness in distraction osteogenesis.

This paper presents an in vivo test for assessment of regenerate axial stiffness after the distraction phase of lengthening therapy. The test result supplements radiography in evaluating bone healing and assists in determining when the regenerate stiffness is sufficient for removal of the external fixator. The test is non-invasive and does not require fixator removal. The theoretical basis for the method is that an externally applied load is shared between the fixator and the regenerating bone. The amount of load carried by the regenerate depends on its axial stiffness, which increases with advanced mineralization. By measuring the force in the fixator while applying a known external load to the limb, the load-share ratio between fixator and limb can be assessed. A load-share ratio of 100% indicates that the entire load is carried by the fixator. The ratio decreases as the regenerate structure gradually stiffens. In a clinical trial of 22 individuals with tibial lengthening, the fixator was removed when the load-share ratio dropped below 10%. None of the patients experienced fracture after removal of the fixator.     

Intelligenter Fixateur externe für Frakturbehandlung und Korrekturen

Intelligent implants are characterized by measurement sensors and a corresponding evaluation unit. External systems offer the additional possibility to implement actuators, which are controlled by the sensors via a knowledge-based control software. An external fixator has been developed that can perform adjustments of the fixator autonomously by a permanently mounted microcontroller system. Additionally, it will inform the surgeon and the patient about the fracture healing progress, e.g. indicate possible weight bearing of the extremity. The intelligent system is based on a 6 degrees of freedom controllable hexapod robot kinematic. By implementation of motors, gears and position sensors a motorized external fixator and by insertion of force sensors, a 6 degrees of freedom measuring fixator system was accomplished. Currently, a motor control and measuring electronic is realized on a 2×3 cm circuit board. A software was developed, performing motor controlled bone movements which are input by a 3-dimensional input device (?3D mouse“). Bone movements can be simulated or observed online on the computer screen. Intelligent external fixator systems will not only optimize bone healing and increase patient safety but also enable cost reductions.     

Femoral locking plate failure salvaged with hexapod circular external fixation: a report of two cases

Femoral non-unions are difficult to treat even for the experienced orthopaedic trauma surgeon. If the non-union follows failure of modern stable internal fixation, the complexity of the management is further increased. We report two cases of stiff hypertrophic femoral non-unions after failed locking plate fixation that were successfully treated with a new hexapod circular external fixator. In addition to providing the necessary stability for functional rehabilitation and union, the hexapod circular fixator software allows gradual correction of deformities in order to restore the normal mechanical alignment of the limb.     

Salvage of infected total knee arthroplasty with Ilizarov external fixator

Background:

Knee arthrodesis may be the only option of treatment in cases of chronic infected total knee arthroplasty (TKA) with concomitant irreparable extensor mechanism disruption, extensive bone loss or severe systemic morbidities. Circular external fixation offers possible progressive adjustment to stimulate the bony fusion and to make corrections in alignment. We evaluated the results of knee arthrodesis with one or two stage circular external fixator for infected TKA.

Materials and Methods:

16 cases of femoro-tibial fusion were retrospectively evaluated. Male-to-female ratio was 10:6. Mean age of the patients was 62.2 years. Cierney-Mader classification was used for anatomical and physiological evaluation while the bone stock deficiency was classified into mild, moderate and severe. Surgical technique involved either single or two stage arthrodesis using circular external fixator.

Results:

Union was achieved in 15 patients (93.75%). The mean duration for union (frame application time) in these patients was 28.33 weeks (range 22 to 36 weeks). Analysis showed that in the group with frame application time of less than 28 weeks, the incidence of mild to moderate bone deficiency was 83.33%, while in the frame application time more than 28 weeks group the incidence was 20% (P-value 0.034). Similarly the incidence of Cierney-Mader 4B (Bl, Bs, Bls) was found to be 33.33% in the group of frame application time of less than 28 weeks, while it was 90% in the group with frame application time more than 28 weeks (P-value 0.035).

Conclusion:

Circular external fixator is a safe and reliable method to achieve knee arthrodesis in cases of deep infection following TKA. Severe bone stock deficiency and Cierney- Mader type B host are likely risk factors for prolonged frame application time. We recommend a two-stage procedure especially when there is compromised host or severe bone loss.