Biomechanical investigation of optimal fixation of isolated talonavicular joint fusion

Despite reports of high nonunion rates for isolated talonavicular fusion, this procedure may be indicated for some patients, including those for whom increased stability of the talonavicular joint in triple arthrodesis is needed. In the biomechanical cadaveric study reported here, we evaluated fixation methods used to provide optimal stability of talonavicular arthrodesis. A physiologic 3-point loading model was used to measure dorsal displacement of the navicular on the talus with 1 or 2 cannulated 4.5-mm screws across the talonavicular joint both with and without one 7.3-mm cannulated screw across the subtalar joint. Statistically significant differences in displacement under cyclic loading to one-half body weight were found. Use of 2 talonavicular screws and no subtalar screw or 1 talonavicular screw plus 1 subtalar screw decreased the motion, as compared with use of 1 talonavicular screw and no subtalar screw.     

Ankle arthrodesis using internal screw fixation

Ankle arthrodesis treated by external fixation frequently results in complications from pin tract infections, loss of position, nonunion, and malunion. A method of ankle arthrodesis using 6.5-mm cancellous screws as the primary fixation hardware was developed. The most important screw is placed from the posterior malleolus into the neck and head of the talus, and medial and lateral malleolar screws are added to secure fixation. Near-normal anatomy is maintained with this technique because little or no bone, only cartilage, is removed. Earlier cases were all done through an anterior approach. Later, special techniques were developed for placing screws and strain-relieving bone grafting was added to promote union. Twenty-three cases that were treated by the earlier technique are reviewed. The overall fusion rate was 74%. Three conditions (avascular talus, pyarthrosis, and spasticity) were identified that placed patients at high risk for failure of fusion. Of the patients who were not in a high-risk group, only one had a delayed union. When the high-risk patients were not included in the statistics, the fusion rate was 93%. The evolved technique shows great promise for accurate and trouble-free ankle arthrodesis.     

Tibiotalocalcaneal arthrodesis: a biomechanical assessment of stability

BACKGROUND: Combined ankle and subtalar (tibiotalocalcaneal) arthrodesis is a procedure that can be used to successfully treat disabling foot and ankle arthropathy and is a reasonable salvage alternative to amputation for the treatment of nonbraceable neuropathic, diabetic, degenerative, or rheumatoid joints. Although many methods of tibiotalocalcaneal (TTC) arthrodesis have been described in the literature, the most popular current methods involve the use of crossed cancellous bone screws, plates, or a locked retrograde intramedullary rod. Fusion in these patients can be difficult, with significant complications including infection, malunion, and nonunion. A persistent nonunion can lead to failure of the hardware and recurrent deformity. METHODS: We biomechanically tested the stability and micromotion in four methods of TTC arthrodesis using liquid metal strain gauges and Instron (Norwood, MA) material testing systems. Anatomically identical synthetic bones with properties very similar to human bone were instrumented and tested. Four instrumentation techniques were tested: 1) three crossed 6.5-mm cancellous screws, 2) two crossed 6.5-mm cancellous screws, 3) locked retrograde intramedullary rod, and 4) locked retrograde intramedullary rod augmented with a single anteromedial bone staple. Six separate specimens for each technique were tested. RESULTS: The three crossed cancellous screw technique provided the greatest stability with respect to micromotion (p < 0.05). The addition of a tibiotalar staple to the locked intramedullary rod conferred stability nearly equal to that of the three crossed cancellous screw fixation (p < 0.05). The locked intramedullary rod group and the two crossed cancellous screw group allowed significant micromotion at the arthrodesis sites, which was a full order of magnitude higher (p < 0.05) than in the three crossed cancellous screw group and the staple augmented intramedullary rod group. CONCLUSIONS: Biomechanically, a staple augmented locked intramedullary rod for TTC arthrodesis confers excellent stability nearly equal to the three crossed cancellous screw technique for TTC arthrodesis.     

Arthroscopic Subtalar Arthrodesis: Does the Type of Fixation Modify Outcomes?

The goal of the present study was to analyze a modified American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale score, time to union, and the incidence of fusion after isolated arthroscopic posterior subtalar arthrodesis using either 1 or 2 screws of different diameters. We reviewed a consecutive series of 65 patients, mean age 50.0?±?15.6 years, including 38 males (58.5%) and 27 females (41.5%), who had undergone arthrodesis from May 2004 to February 2011. The mean follow-up duration was 57.5 (range 24 to 105) months. The patients were divided into 3 groups according to the fixation method used: group 1 (n = 12; 18.5%) underwent fixation with one 6.5-mm screw; group 2 (n = 40; 61.5%) with one 7.3-mm screw; and group 3 (n = 13; 20%) with two 7.3-mm screws. An overall statistically significant (p?<.0001) improvement was seen in the modified AOFAS scale score for all 3 fixation groups; however, the difference was not statistically significant (p?=?.79) among the fixation groups. Fusion was achieved in 62 patients (95.4%) after a mean of 12.1 (range 9 to 16) weeks. The difference in the time to union was not statistically significant (p?=?.781) among the fixation groups. Nine patients (13.8%) experienced complications, and nonunion was significantly (p?=?.005) more prevalent in the single 6.5-mm screw group. In conclusion, all 3 screw configurations led to improved modified AOFAS scale scores, although nonunion was more common among patients fixed with a single 6.5-mm screw.     

Screw fixation of the syndesmosis alters joint contact characteristics in an axially loaded cadaveric model

BackgroundThe purpose of this study was to quantify the effects of rigid syndesmotic fixation on functional talar position and cartilage contact mechanics.MethodsTwelve below-knee cadaveric specimens with an intact distal syndesmosis were mechanically loaded in four flexion positions (20° plantar flexion, 10° plantar flexion, neutral, 10° dorsiflexion) with zero, one, or two 3.5-mm syndesmotic screws. Rigid clusters of reflective markers were used to track bony movement and ankle-specific pressure sensors were used to measure talar dome and medial/lateral gutter contact mechanics.ResultsScrew fixation caused negligible anterior and inferior shifts of the talus within the mortise. Relative to no fixation, mean peak contact pressure decreased by 6%–32% on the talar dome and increased 2.4- to 6.6-fold in the medial and lateral gutters, respectively, depending on ankle position and number of screws.ConclusionsTwo-way ANOVA indicated syndesmotic screw fixation significantly increased contact pressure in the medial/lateral gutters and decreased talar dome contact pressure while minimally altering talar position.     

Comparison of plate and screw fixation and screw fixation alone in a comminuted talar neck fracture model

BACKGROUND: Talar neck fracture fixation has been studied in noncomminuted fracture models, but no large clinical series of comminuted fracture patterns have been published and no biomechanical studies have compared plate fixation with screw fixation in comminuted talar neck fractures. METHODS: Nine matched pairs of fresh frozen talar specimens were stripped of soft tissue and mounted in a cylindrical jig. The talar neck was fractured using a dorsally directed shear force at a rate of 200 mm/min, and dorsal comminution was simulated by removing a 2-mm section of bone from the distal fracture fragment. One specimen from each pair was fixed with either two solid 4.0-mm partially threaded cancellous screws posterior-to-anterior just lateral to the posterior process of the talus or with a four-hole 2.0-mm minifragment plate contoured to the lateral surface of the talar neck and secured with 2.7-mm screws. A 2.7-mm fully threaded cortical screw was placed medially using a lag technique. The specimens were then loaded to failure with a dorsally directed force at a rate of 200 mm/min. Failure was defined as the load producing 2 mm of displacement. A Student's t-test analysis was used with significance set at p < or = 0.05. RESULTS: Posterior-to-anterior screw fixation had a statistically significant higher load to failure than plate fixation (p < 0.05). Mean load to failure for the screw group was 120.7 +/- 68.5 N and 89.7 +/- 46.6 N for the plating group. CONCLUSIONS: Plate fixation may offer substantial advantages in the ability to control the anatomic alignment of comminuted talar neck fractures, but it does not provide any biomechanical advantage compared with axial screw fixation. Further, the fixation strength of both methods was an order of magnitude lower than those found in previous studies of noncomminuted fractures.     

Ankle Arthrodesis: A Retrospective Analysis Comparing Single Column,Locked Anterior Plating to Crossed Lag Screw Technique

Ankle arthrodesis is performed to eliminate pain due to end-stage osteoarthritis, regardless of etiology. This procedure remains the reference standard treatment for end-stage ankle arthritis, despite recent advancements in total ankle replacement. The objective of the present study was to retrospectively evaluate the radiographic and clinical fusion rates and time to bony fusion for patients who underwent ankle arthrodesis using an anterior approach with a single column locked plate construct versus crossed lag screws. We identified 358 patients who had undergone ankle arthrodesis from January 2003 to June 2013. Of the 358 patients, 83 (23.2%) met the inclusion criteria for the present study. Of the 83 included patients, 47 received locked anterior (or anterolateral) plate fixation, and 36 received crossed lag screw constructs. The overall nonunion rate was 6.0% (n = 5), with 1 nonunion in the anterior plate group (2.1%) and 4 nonunions in the crossed lag screw group (11.1%; p = .217). No differences were identified between the 2 groups for normal talocrural angle [χ² (1) = 0.527; p = .468], normal tibial axis/talar ratio [χ² (1) = 0.004; p = .952], and lateral dorsiflexion angle (p = .565). Based on our findings in similar demographic groups, ankle arthrodesis using locked anterior plate fixation is a safe technique with similar complication rates and radiographic outcomes to those of crossed lag screws.     

Ankle arthrodesis for failed total ankle replacement

Between 1999 and 2005, 23 failed total ankle replacements were converted to arthrodeses. Three surgical techniques were used: tibiotalar arthrodesis with screw fixation, tibiotalocalcaneal arthrodesis with screw fixation, and tibiotalocalcaneal arthrodesis with an intramedullary nail. As experience was gained, the benefits and problems became apparent. Successful bony union was seen in 17 of the 23 ankles. The complication rate was higher in ankles where the loosening had caused extensive destruction of the body of the talus, usually in rheumatoid arthritis. In this situation we recommend tibiotalocalcaneal arthrodesis with an intramedullary nail. This technique can also be used when there is severe arthritic change in the subtalar joint. Arthrodesis of the tibiotalar joint alone using compression screws was generally possible in osteoarthritis because the destruction of the body of the talus was less extensive. Tibiotalocalcaneal arthrodesis fusion with compression screws has not been successful in our experience.     

Crossed screws versus dorsomedial locking plate with compression screw for first metatarsocuneiform arthrodesis: a cadaver study

BACKGROUND: We hypothesized that a dorsomedial locking plate with adjunct screw compression would provide superior rigidity compared to crossed screws for first metatarsocuneiform (MTC) arthrodesis. MATERIALS AND METHODS: In ten matched lower extremity pairs, specimens in each pair were randomly assigned to receive screw fixation or plate with screw fixation. Bone mineral density (BMD) was measured. For the crossed-screw construct, two 4.0-mm cannulated screws were used. One screw was inserted dorsal to plantar beginning from the first metatarsal 10 to 15 mm distal to the joint, and the second was inserted from the cuneiform 8 to10 mm proximal to the joint, medial to the first screw, into the first metatarsal. For the plate construct, a 4.0-mm cannulated compression screw was inserted from the dorsal cortex of the first metatarsal to the plantar aspect of the medial cuneiform. A locking plate was inserted dorsomedially across the MTC joint. Specimens were loaded in four-point bend configuration (displacement rate, 5 mm/min) until failure of the fixation or 3-mm deformation. An extensometer was used to measure deformation. RESULTS: There was no difference in load to failure or stiffness between the two groups. BMD was positively correlated with load to failure in the screw (r = 0.893, p = 0.001) and the plate (r = 0.858, p = 0.001) construct. CONCLUSION: The plate construct with compression screw did not show different rigidity as compared with the screw construct with the numbers available. CLINICAL RELEVANCE: Further investigation of a dorsomedial plate with adjunct screw compression may be warranted for first MTC arthrodesis.     

Comparison of Initial Compression Force Across the Subtalar Joint by Two Different Screw Fixation Techniques

The purpose of this study was to compare the magnitude of compressive force across the posterior facet of the subtalar joint between 2 different screw orientations in a simulated subtalar fusion model fixated with cannulated 7.3-mm screws. Eight paired fresh, frozen cadaver feet were used. Before testing, the bone mineral density of the calcanei and tali was measured with dual energy x-ray absorptiometry to ensure comparable bone mineral density. The paired cadaver calcanei and tali were noted to have less than .05 g/cm(2) difference in bone mineral density. The paired specimens were each randomly assigned to 1 of 2 methods of fixation across the subtalar joint: a plantar approach, where the screw was oriented vertically from the plantar aspect of the calcaneus, distal to the tuberosity; and a posterior approach, where the screw was oriented obliquely from the posterior calcaneal tuberosity. A load-sensing washer was placed under the cancellous screw head before insertion of the screw to measure the magnitude of the compression force across the simulated fusion site. The mean compression force for the posterior-to-anterior approach was 581 N, with a standard deviation of 242 N. The mean force for the plantar-to-superior approach was 604 N, with a standard deviation of 276 N. The compression force obtained by the 2 approaches was not significantly different (P = .74). The plantar-to-superior fixation technique represents an alternative subtalar arthrodesis technique to the posterior-to-anterior approach, potentially allowing one to revise a previously failed arthrodesis when the standard fixation techniques cannot be applied.     

Cross-Sectional Area Measurement of the Central Tarsometatarsal Articulation: A Review of Computed Tomography Scans

Currently, disagreement exists regarding the superior method for repairing a ligamentous Lisfranc injury regarding whether to use arthrodesis or open reduction internal fixation. The 2 procedures differ in the amount of articular cartilage destroyed. Arthrodesis removes all the articular cartilage, and open reduction internal fixation places transarticular screws, essentially destroying a portion of cartilage. We performed a review of 30 consecutive computed tomography scans that included both foot length and undamaged first, second, and third tarsometatarsal joints to quantify the amount of articular surface area destroyed by placement of standardized 4-mm diameter screws. Measurements were performed using a freeform tool. The calculated surface area of the screws was subtracted from the measured surface area of the joint to yield the amount of surface area occupied by the screws. Our results demonstrated that the average amount of articular surface area destroyed in the first, second, and third tarsometatarsal joints was 4.87%, 4.79%, and 4.86% respectively, with a standard deviation of <1% for each of the joints. Our results have demonstrated that screw placement accounts for only a small percentage of articular surface destroyed. They also showed that the articular surface damage was comparable among the first 3 tarsometatarsal joints. Additionally, our results were similar to the articular surface area calculated from cadaveric specimens in a previous biomechanical study, demonstrating that computed tomography can allow for reliable and accurate assessments of articular surface areas in the foot.     

In-vitro comparison of biomechanical efficiency of three cannulated screws for arthrodesis of the hindfoot

BACKGROUND: Sufficient inter-fragmentary compression is helpful to achieve successful bony fusion in hindfoot arthrodesis using internal fixation by screws. Beside bone quality, the design of a screw influences inter-fragmentary compression. Compressive force is achievable for any kind of screw system; however, the primary deformation of the bone is different for the different screw systems. The work necessary to achieve compressive force for primary stability was measured for different screw systems and compared to an AO screw with washer. MATERIALS AND METHODS: The compressive force was determined as a function of screw advancement for 3 different cannulated screw types (7.3-mm AO screw with and without washer, the 6.5-mm Herbert screw and the 6.5-mm Ideal Compression Screw (I.CO.S) using different synthetic bone density (0.16, 0.24, 0.48 g/ccm). Compressive force was measured indirectly, via screw tension measurement with strain gauges. RESULTS: We calculated the work to reach a limit of 60 N and the corresponding ratios to the value of the golden standard: I.CO.S (35.2%), Herbert (89.0%), AO screw without washer (116%). CONCLUSION: All screw systems yielded acceptable results but the ICOS did produce greater compression. The essential differences were the primary deformation of the bone before reaching the sufficient compressive force for primary stability.     

Biomechanical Evaluation of Subtalar Fusion: The Influence of Screw Configuration and Placement

Common surgical procedures for subtalar fusion include joint resection, autologous bone grafting, and osteosynthesis with screws in a parallel screw configuration. Although fusion is a routine procedure, the reported rates of nonunion have been high. The present study assessed different screw configurations in terms of their rotational and bending stability in an artificial bone model and cadaver bone. Arthrodesis was always performed with 2 screws. Three different screw configurations were tested: parallel, counter-parallel, and a delta configuration. Two different screw designs were used: a cannulated, partially threaded screw (6.5-mm and 8.0-mm diameter) and a solid screw with a different thread design. Eight experimental groups were investigated as pilot studies in artificial bones and then 3 groups in cadaver bones. The parameters were the primary stiffness and deflection of the construct for loads simulating the internal–external rotation and supination–pronation. Delta positioning of the screws resulted in the greatest biomechanical stiffness and the lowest degrees of deflection of the arthrodesis in the artificial bones and cadaver bones. Increasing the screw diameter from 6.5 to 8.0 mm resulted in no additional stability of the arthrodesis in the artificial bones. The results of the present study have indicated that the delta configuration for arthrodesis results in the greatest construct stiffness and lower relative deflection between the talus and calcaneus in the positions tested.     

Analysis of screw pullout strength: A function of screw orientation in subtalar joint arthrodesis

The purpose of this cadaveric study was to compare the pullout strength and failure load of 2 different screw orientations for subtalar arthrodesis. Twenty-six specimens from 13 cadaver donors (1 left and 1 right each) were used. A 7.3- x 65-mm long-thread profile (32-mm length) cannulated screw inserted into the calcaneus from dorsal to plantar (calcaneal specimens) was compared with a 7.3- x 65-mm short-thread profile (16-mm length) cannulated screw inserted into the talus from plantar to dorsal (talar specimens). A torque screwdriver with a calibrated electronic vernier scale measured the torque of screw insertion. Screw pullout strength and load failure were measured by using a servohydraulic materials testing machine. Distraction was applied along the axis of the screw at a displacement rate of 25 mm/min. The peak torque of insertion in all calcaneal specimens was reached on initial insertion through the dorsal subchondral bone plate of the calcaneus; in talar specimens, it was reached as the screw threads were completely buried into the talus. A significant difference (P = .00647) was found between the mean torque of insertion for the calcaneal (1.50 Nm) and talar specimens (1.30 Nm). A comparison of pullout forces showed a significantly stronger mean failure load for calcaneal specimens (P = .000085). The mean failure load for paired calcaneal specimens was 1782 N compared with a mean 1245 N for talar specimens. Although the pullout force was clearly greater in the dorsal-to-plantar screw application, the pullout force in the plantar-to-dorsal orientation was also considerable.     

Arthrodesis of the ankle in patients who have rheumatoid arthritis.

We reviewed thirty-two arthrodeses of the ankle in twenty-six patients who had rheumatoid arthritis. In seventeen patients (eighteen ankles), a compression arthrodesis was done and external fixation was used. In eight patients (twelve ankles), we used internal fixation with 6.5-millimeter cancellous-bone screws. In the remaining patient, an arthrodesis with external fixation was done in one ankle and internal fixation was used in the other ankle; data for the appropriate ankle are included in each group. The patients were followed for an average of thirty-three months. The two groups were comparable with respect to age, sex, preoperative medications, and severity of disease. The average time to fusion was nineteen weeks in the compression arthrodesis group and seventeen weeks in the internal fixation group. Of the nineteen ankles that had a compression arthrodesis, four failed to fuse; all of the failures were associated with infection. Infection developed in two additional patients, there was malposition of the fusion in three patients, and neurapraxia developed in three patients. Of the thirteen ankles that had internal fixation, three ankles failed to fuse; one of the failures was associated with infection. Infection developed in one additional ankle. In two patients, the ankle fused in excessive valgus. Comparison of the two groups revealed comparable rates of fusion: fusion occurred in fifteen of the nineteen ankles in the group that had compression arthrodesis and in ten of the thirteen ankles in the group that had internal fixation. The method of arthrodesis did not affect the time to fusion or the rate of complications.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reorientierende Arthrodese des oberen Sprunggelenks in der 4-Schrauben-Technik

BACKGROUND: Arthrodesis of the ankle has gained wide acceptance as a first-line treatment option for painful posttraumatic osteoarthritis. The technique using four to five lag screws for internal osteosynthesis is a safe and biomechanically stable method to obtain a sound ankle fusion with good to excellent long-term results in the majority of patients. Malalignment hazards are minimized by preservation of the ankle mortise. METHODS: The meticulous resection of all cartilage and sclerotic bone as well as an atraumatic surgical technique are essential for preventing major complications. The need for revision surgery is minimized by correction of talar malalignment, fusion with the foot in a 90 degrees position and preoperative evaluation of the subtalar joint. In a series of 40 ankle fusions fixed with the lag screw technique, 82.5% good to excellent results were obtained after 5.6 (4.8-7.6) years. No infection, stress fracture or non-union was seen. RESULTS: In cases of osteitis, osteonecrosis, osteoporosis, and poor soft-tissue condition, external fixation techniques are preferred. In the presence of severe loss of bone stock at the distal tibia, stability can be achieved by using a compression nail for tibiotalar fusion without additional subtalar arthrodesis.     

Bending stiffness and pull-out strength of tapered, variable pitch screws, and 6.5-mm cancellous screws in acute Jones fractures

BACKGROUND: Stabilization of fifth metatarsal Jones fractures with intramedullary screws is popular, particularly in athletes, because nonoperative treatment involves prolonged casting and a distinct risk of nonunion or delayed union. Conventional lag screws of various diameters are routinely used for Jones fracture fixation. More recently, tapered, headless, variable pitch screws have become available as an option. These screws have the advantage of not having a protruding screw head, but information regarding their performance in Jones fracture fixation is limited. To determine whether differences exist in the mechanical integrity of fifth metatarsals fixed with each type of screw, this study was designed to compare Jones fracture fixation with 6.5-mm partially-threaded lag screws and headless, tapered, variable pitch compression screws with a 4-mm leading-thread diameter and 5-mm trailing-thread diameter. METHODS: Simulated Jones fractures were created in 20 matched pairs of fresh-frozen fifth metatarsals. One bone from each pair was stabilized with a tapered, variable pitch screw, and the contralateral with a 6.5-mm partially-threaded cancellous lag screw. The stiffness in lateral-to-medial bending of the resulting constructs and the resistance of the screws to pulling out of the distal fragment were quantified. RESULTS: There was no demonstrable difference in bending stiffness between metatarsals fixed with the two types of screws (p = 0.688). The 6.5-mm screw provided significantly higher resistance to pull-out (p = 0.001). CONCLUSIONS: Headless, tapered, variable pitch compression screws of the size tested are not entirely comparable to 6.5-mm lag screws in this application. They are effective in resisting bending but do not offer equivalent resistance to thread pull-out.     

Ankle arthrodesis. A comparison of an arthroscopic and an open method of treatment

An arthroscopic technique and an open technique with malleolar ostectomy for ankle arthrodesis is described and compared. Internal fixation with compression across the tibiotalar joint was utilized for both methods using either 6.5-mm or 7.0-mm cannulated screws. The indications, advantages, results, and complications of these two fusion techniques in 33 patients are reported. Arthroscopic arthrodesis was performed in 17 patients, using open arthrotomy and malleolar ostectomy in 16. The mean time to arthrodesis for patients having the procedure arthroscopically was 8.7 weeks (range, six to 14 weeks), compared to 14.5 weeks in the open arthrotomy group (range, eight to 26 weeks; p less than 0.004). Despite differences in patient selection for each of the two groups, it was concluded that disabling ankle arthritis for certain patients may be more appropriately managed with arthroscopic arthrodesis than by arthrotomy and malleolar ostectomy, utilizing similar methods of internal fixation.     

The effect of bone quality on the stability of ankle arthrodesis. A finite element study

BACKGROUND: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. METHODS: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. RESULTS: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. CONCLUSIONS: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. CLINICAL RELEVANCE. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.