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

First Tarsometatarsal Joint Fusion in Foot-A Biomechanical Human Anatomical Specimen Analysis with Use of Low-Profile Nitinol Staples Acting as Continuous Compression Implants

Background and Objectives: The aim of this study was to investigate under dynamic loading the potential biomechanical benefit of simulated first tarsometatarsal (TMT-1) fusion with low-profile superelastic nitinol staples used as continuous compression implants (CCIs) in two different configurations in comparison to crossed screws and locked plating in a human anatomical model. Materials and Methods: Thirty-two paired human anatomical lower legs were randomized to four groups for TMT-1 treatment via: (1) crossed-screws fixation with two 4.0 mm fully threaded lag screws; (2) plate-and-screw fixation with a 4.0 mm standard fully threaded cortex screw, inserted axially in lag fashion, and a 6-hole TMT-1 Variable-Angle (VA) Fusion Plate 2.4/2.7; (3) CCI fixation with two two-leg staples placed orthogonally to each other; (4) CCI fixation with one two-leg staple and one four-leg staple placed orthogonally to each other. Each specimen was biomechanically tested simulating forefoot weightbearing on the toes and metatarsals. The testing was performed at 35-37 °C under progressively increasing cyclic axial loading until construct failure, accompanied by motion tracking capturing movements in the joints. Results: Combined adduction and dorsiflexion movement of the TMT-1 joint in unloaded foot condition was associated with no significant differences among all pairs of groups (p ≥ 0.128). In contrast, the amplitude of this movement between unloaded and loaded foot conditions within each cycle was significantly bigger for the two CCI fixation techniques compared to both crossed-screws and plate-and-screw techniques (p ≤ 0.041). No significant differences were detected between the two CCI fixation techniques, as well as between the crossed-screws and plate-and-screw techniques (p ≥ 0.493) for this parameter of interest. Furthermore, displacements at the dorsal and plantar aspects of the TMT-1 joint in unloaded foot condition, together with their amplitudes, did not differ significantly among all pairs of groups (p ≥ 0.224). Conclusions: The low-profile superelastic nitinol staples demonstrate comparable biomechanical performance to established crossed-screws and plate-and-screw techniques applied for fusion of the first tarsometatarsal joint.

Biomechanical Comparison of Medio-Plantar and Plantar Plate Fixation for First Tarsometatarsal Joint Arthrodesis

Plantar plate positioning has been demonstrated as biomechanically superior. However, some operators remain resentful about the morbidity of the surgical approach. To provide improved plate fixation for first tarsometatarsal joint arthrodesis with respect to the tibialis anterior tendon, a medio-plantar plate was developed. The purpose of this biomechanical study was to compare its construct stability to that of a plantar plate construct. Twelve pairs of fresh frozen human specimens were used in a matched pair test. Each pair was fixed with a 4 mm compression screw and either a plantar locking plate or a medio-plantar locking plate. A cantilever beam test was performed in dorsiflexion. Before and after cyclic loading (5000 cycles; 40 N), bending stiffness and relative movements at the joint space were monitored in a quasi-static test including optical motion tracking. Maximum load and bending moment to failure were investigated in a load-to-failure ramp test. The bending stiffness of both groups did not significantly differ before (plantar 49.9 N/mm ± 19.2; medio-plantar 53.9 N/mm ± 25.4, p = 0.43) or after (plantar 24.4 N/mm ± 9.7; medio-plantar 35.3 N/mm ± 22.0, p = 0.08) cyclic loading but decreased significantly in both groups (p < 0.01) after cyclic loading. Relative movement increased significantly during cyclic testing in both groups (p < 0.01) but did not differ significantly between the groups before (p = 0.29) or after (p = 0.16) cyclic loading. Neither load nor bending moment to failure were significantly different (plantar 225 N ± 78, 10.8 Nm; medio-plantar 210 N ± 86, 10.1 Nm, p = 0.61). Both plate constructs provided equivalent construct stability, both being well suited for Lapidus arthrodesis.

Radiographic Evaluation of First Tarsometatarsal Joint Arthrodesis for Hallux Valgus Deformity: Does the Fusion of the First to the Second Metatarsal Base Reduce the Radiological Recurrence Rate?

BACKGROUND

Modified Lapidus arthrodesis (MLA) is a well-established treatment option for symptomatic hallux valgus deformity (HVD). However, recurrence of the deformity remains a concern. The goal of this study was to evaluate the effect of an additional intermetatarsal fusion on the radiographic recurrence rate after first tarsometatarsal (TMT-I) arthrodesis.

METHODS

This is a retrospective evaluation of 56 feet that underwent TMT-I arthrodesis for moderate to severe HVD. Twenty-three feet received an isolated arthrodesis of the TMT-I joint (TMT-I), whereas 33 feet received an additional fusion between the base of the first and the second metatarsal bone (TMT-I/II). Various radiological parameters were determined preoperatively, 6 weeks and at a mean of 2 years postoperatively.

RESULTS

The intermetatarsal angle (IMA) and the hallux valgus angle (HVA) were significantly lowered at both follow-up evaluations in both groups. In the TMT-I/II group, the initial reduction of HVA was significantly higher (29.3° vs 21.1°). This difference disappeared by the second follow-up, leaving no significant differences between both techniques at final follow-up. Radiological recurrence rates of HVD were comparable in both groups.

CONCLUSIONS

Isolated TMT-I arthrodesis provides reliable radiological results in the correction of HVD. Whether additional fusion of the first and second metatarsal base should be routinely performed remains unclear.

LEVELS OF EVIDENCE

Level 3.

First Tarsometatarsal Joint Fusion for Hallux Valgus Deformity: A Retrospective Comparison of Two Fixation Constructs Regarding Initial Maintenance of Correction and Complications: Traditional Crossing Screw Fixation Versus Dorsomedial Locking Plate and Intercuneiform Compression Screw

Various fixation constructs exist to address hallux valgus when performing a first tarsometatarsal joint arthrodesis. The goal of this present study is to compare complication rates, and degree and maintenance of angular correction between a dorsomedial locking plate with intercuneiform compression screw construct versus traditional crossing solid screw fixation construct. The plate plus intercuneiform compression screw construct fixation utilized a combined sagittal saw and curette method of joint preparation while the crossed screw fixation group utilized a curette and bur technique. A retrospective review was conducted of consecutive patients who underwent a midfoot fusion using either constructs. Sixty four total feet in 56 patients were enrolled in the study. Twenty four consecutive patients (32 feet) who underwent a midfoot arthrodesis using the locking plate and intercuneiform fixation were fully fused (100%) by 10 weeks postoperatively, with no incidents of nonunion and one deep vein thrombosis event. Thirty two consecutive patients (32 feet) who underwent midfoot arthrodesis with crossing screw fixation had 2 nonunion events, one that was asymptomatic and the other that required a revision midfoot fusion. There was a statistically significant improvement from the pre-operative intermetatarsal angle, hallux abductus angle compared to the 10 week and 1 year radiographs (p < .05) for the entire cohort for both fixation constructs. There was a statistically significant increase in American College of Foot and Ankle Surgery first ray scores from pre-op to 1 year follow-up for both fixation constructs. Overall, the dorsomedial locking plate plus intercuneiform compression screw fixation construct better maintains Intermetatarsal angle (IMA) correction at midterm follow-up compared to the traditional crossing screw construct. Both cohorts overall demonstrate similar fusion rates at 10 weeks, nonunion events, incidences of broken hardware, hardware removal, deep vein thrombosis, neuritis at 1 year postoperatively, and hallux varus.

Union Rates With the Use of Structural Allograft in Lapidus Arthrodesis: A Comparison Between Two Fixation Constructs

Although structural allograft has been previously described as acceptable practice for reconstructive foot and ankle surgery, results for an allograft bone wedge in Lapidus arthrodesis are unknown. Additionally, there is no consensus on the superiority of a single fixation construct in Lapidus cases. Our objective was (1) to report union rates for Lapidus arthrodesis with and without the use of an allograft bone wedge and (2) to determine if fixation construct impacts rates of union when using structural allograft. A review was performed for Lapidus cases with fixation constructs of 2 crossed compression screws (CS) and a medial locking plate with single transarticular screw (MPS), both with and without use of an allograft bone wedge. Inclusion required a CT scan to evaluate bony union. There was no significant difference in union rates (p = .41) between the use (90%) and the nonuse (97%) of an allograft bone wedge. Union rates were significantly different (p = .04) when comparing CS fixation (85%) and MPS fixation (98%). The comparative results between the fixation constructs highlight the importance of compression across the arthrodesis site as part of a robust fixation construct. Our findings demonstrate that the use of an allograft bone wedge in Lapidus arthrodesis may mitigate complications due to metatarsal shortening while providing satisfactory rates of union.

Two Orthogonal Nitinol Staples and Combined Nitinol Staple-Screw Constructs for a First Metatarsophalangeal Joint Arthrodesis: A Biomechanical Cadaver Study

BACKGROUND

End-stage hallux metatarsophalangeal (MTP) joint arthritis is commonly treated with arthrodesis using stainless steel or titanium implants. These implants provide static compression that is maximal at the time of implant insertion. Alternatively, nitinol staples are capable of dynamic compression. They have most frequently been used for midfoot arthrodesis procedures. However, their biomechanical performance during hallux MTP arthrodesis has not been described.

METHODS

8 matched pairs of cadaveric feet (4 female, 4 male) were prepared for hallux MTP arthrodesis using cup and cone reamers. Cadaveric pairs were then instrumented with either (1) a transarticular lag screw and dorsal nitinol staple or (2) orthogonal nitinol staples placed dorsally and medially. Walking in a short leg cast for 6 weeks was simulated by applying 90-N forces at 3 Hz to the plantar proximal phalanx for up to 250 000 cycles. Failure was defined as catastrophic implant failure or plantar gapping beyond 7 mm.

RESULTS

15 of 16 specimens failed cyclic loading. All 8 specimens fixed with orthogonal staples failed at an average of 37 ± 81 cycles. 7 of 8 specimens fixed with a dorsal staple and crossed screw failed at 14 900 ± 39 000 cycles. Collectively, 5 specimens failed because of bone fracture (1 in orthogonal staples, 4 in staple-screw group) and 10 failed because of excessive gap formation (7 in orthogonal staples, 3 in staple-screw group). The number of cycles to failure was significantly lower (P = .0469) in the orthogonal staple constructs compared with the dorsal staple and crossed screw constructs.

CONCLUSION

The tested constructs permit significant motion at the first MTP fusion surface during simulated protected weightbearing. Although multiple in vivo factors should be considered when extrapolating results from this cadaveric study, this motion may result in clinical failure with early postoperative weightbearing protocols.

CLINICAL RELEVANCE

We report the first biomechanical evaluation of hallux MTP arthrodesis using modern nitinol staples in 2 separate constructs.

Salvage of Failed Lisfranc/Midfoot Injuries

Salvage of Lisfranc, or tarsometatarsal injuries, may be necessary because of a variety of clinical scenarios. Although rare, these injuries represent a broad spectrum of injury to the midfoot ranging from low-energy ligamentous injuries to high-energy injuries with significant displacement and associated fractures. Poor outcomes and complications may occur including posttraumatic arthritis, instability, pain, infection, and loss of function. Strategies and technical considerations for salvage of these complex injuries are provided.

The Lapidus Arthrodesis: Examining the Effect of the Metatarsal Base Transfixion Screw

The modified Lapidus bunionectomy is a useful and highly powerful procedure for correcting hallux abducto valgus. Traditionally reserved for "severe" deformities, this procedure has seen a recent resurgence in the podiatric community for its unique ability to achieve tri-planar correction of this challenging deformity. Although this procedure has been extensively studied in both biomechanical labs and the clinical arenas, no clear consensus has been achieved regarding optimal fixation for this thought-provoking procedure. The current study examined the differences in strength between commercially available 5-hole locking plates with interfragmentary compression vs a crossed-screw with a third "transfixation" screw construct in a controlled setting. Ten fresh-frozen cadaveric match pair limbs (20 total limbs) were used to complete this study. Ten limbs were randomly assigned to a 3-screw construct. The other 10 contralateral limbs were assigned to a commercially available 5-hole locking plate (5 stainless steel and 5 titanium alloy) with an interfragmentary lag screw construct. The first rays were then isolated and potted into a 4-point bending device. The specimens were loaded to failure in a servohydraulic load frame at a controlled rate. Failure was defined as catastrophic or 3 mm of plantar gapping at the arthrodesis site. The mean maximal load to failure was 310.9 ± 109.4 N for the 3-screw construct. The mean maximal load to failure for the locking plate constructs was 264.1 ± 100.9 N. This difference was not statistically significant (p = .328). These results suggest that a 3-screw construct for Lapidus arthrodesis is as strong as commercially available locking plate constructs.

Lapidus arthrodesis in combination with arthrodesis of the first metatarsophalangeal joint-biomechanical cadaver study comparing two methods of fixation

AIMS

To assess the results of a biomechanical test of cadaveric specimens, comparing 2 methods of fixation of modified Lapidus arthrodesis in combination with arthrodesis of the first metatarsophalangeal joint.

METHODS

A total of 12 cadaveric specimens were used in the test. Arthrodesis of the first MTP joint was in all patients fixed with a Variable Angle LCP 1st MTP Fusion Plate 2.4/2.7. Two methods of fixation of the Lapidus arthrodesis were compared, i.e. fixation with two screws in the PS (plate-screw) version versus fixation with X-Locking Plate 2.4/2.7 in the PP (plate-plate) version. Measurements were obtained with the use of a testing machine ZWICK Z 020-TND with an optical device Mercury RT for measuring deformities. Each specimen was subjected to 3 loading options, a. displacement 5 mm, the support is placed under the proximal phalanx, b. displacement 5 mm, the support is placed under the first metatarsal head and c. load to failure, the support is placed under the first metatarsal head.

RESULTS

In all specimens the PS construct showed a statistically considerably higher stiffness than the PP construct. In all specimens treated with the PP construct the load to failure was lower than in the PS construct. For loading mode a., at a significance level of 0.05 (P<0.05), the P-value was 0.036, for mode b. the P-value was 0.007 and for loading mode c. the P-value was 0.006. In addition, age-related decrease in stiffness of the specimen was proved at a significance level of 5% (P=0.004).

CONCLUSION

In all the three loading modes, the PS (plate-screw) construct showed a statistically higher stiffness than the PP (plate-plate) construct.

Biomechanical Comparison of First Tarsometatarsal Arthrodesis Constructs Over Prolonged Cyclic Testing

Background:

Traditionally, a lengthy period of nonweightbearing is required following arthrodesis of the first tarsometatarsal (TMT) joint in order to provide a stable healing environment for the bones. The goal of this research was to determine the resistance to plantar gapping of 2 locked intramedullary devices and a medial plate with crossing screw, all specifically designed for hallux valgus correction, and compare them to traditional 2–crossing screw fixation under a cyclic testing protocol. We hypothesized the locked intramedullary devices and the medial plate with crossing screw would better resist plantar gapping.

Methods:

Forty cadaver specimens received 1 of 4 operative treatments: a locked intramedullary device with 2 points of fixation in the cuneiform, a locked intramedullary device with 1 point of fixation in the cuneiform, a medial plate with crossing screw, or 2 crossing screws. We applied dorsiflexion bending forces to the first TMT joint using a cadaveric fatigue model for 20 000 cycles. The plantar gap between the metatarsal and cuneiform was measured at the beginning and end of cyclic testing. Thirty-six specimens were included in the final data set.

Results:

Both locked intramedullary device groups and the medial plate with crossing screw group exhibited significantly less gap widening compared to the 2–crossing screw group (vs 3-hole intramedullary device, P = .014; vs 4-hole intramedullary device, P = .010; and vs medial plate with crossing screw, P = .044). The intramedullary device groups were the most stable during the cyclic fatigue test, exhibiting the smallest gap widening. The medial plate with crossing screw fixation was also more stable than crossing screws in the cyclic fatigue model.

Conclusions:

The locked intramedullary devices and medial plate with crossing screw resisted plantar gapping better than 2 crossing screws when used for first TMT arthrodesis.

Clinical Relevance:

These results indicate that locked intramedullary devices and medial plates with crossing screws may promote superior bone healing and may better tolerate early weightbearing compared with 2 crossing screws.

Neurovascular structures at risk with percutaneous fixation in tarsometatarsal fusion: A cadaveric study

INTRODUCTION

First tarsometatarsal (TMT) joint fusion is routinely used for arthritis and deformities. Common fixation methods include a locking plate construct, cross-screws, or combinations of the two. Cross screws have proven effective for union and stability; however, there is a potential for harm to nearby neurovascular structures due to the nature of percutaneous insertion technique. This study assessed risk of damage to the superficial peroneal nerve with percutaneous TMT fusion.

METHODS

Nine fresh-frozen cadaver specimens were included. A medial incision in the internervous plane was made for TMT joint preparation. Two crossed percutaneous wires followed by 4.0 cc screws were placed in the dorsal aspect of the proximal aspect of first metatarsal and in the medial cuneiform. Both were 10-15 mm from the TMT joint line. The dorsal aspect of the foot was dissected and examined for neurovascular interruptions, particularly branches of the superficial peroneal nerve.

RESULTS

Results showed a mean distance of 4.33 mm from the proximal pin to the medial branch of the superficial peroneal nerve. The distal pin had a mean distance of 6.44 mm from the medial branch, with one pin 9 mm from the lateral branch. One incident of direct injury to the neurovascular bundle was observed.

CONCLUSION

Preparing the joint from the medial side using a percutaneous approach is less invasive, but presents a relative risk for neuritis. Care should be taken during insertion of the percutaneous screw after TMT joint preparation for fusion.

LEVEL OF EVIDENCE

Level V, cadaver study.

Plate Alone Versus Plate and Lag Screw for Lapidus Arthrodesis: A Biomechanical Comparison of Compression

Background. Arthrodesis of the first tarsal metatarsal joint can be accomplished in many ways. The compressive force attained between various constructs remains unclear. This study compares compression achieved through a locking/compression Lapidus plate both with and without the addition of a lag screw. Methods: A dorsal medial Lapidus/locking compression plate (Total Compression Plate System, OrthoPro, Salt Lake City, UT, now Wright Medical) was applied to one cadaveric limb, while the same plate with the addition of a 4.0-mm cannulated lag screw was applied to the contralateral limb for a total of 5 matched pairs of cadaveric specimens. Compressive force was recorded over time and compared between the constructs using a compression sensor (8" FlexiForce Resistive Force Sensor, Phidgets Inc, Calgary, Alberta, Canada). Results: Compression was maintained for 45.4 minutes in the plate only construct, and 317 minutes with the addition of the lag screw (P = .010). The mean time to 50% peak compression for the plate only construct was 4.90 minutes compared with 15.11 minutes for plate with lag screw construct (P = .012). Conclusion: The addition of a lag screw is recommended for extending the length of compression and possibly reducing nonweightbearing time and the risk of nonunion. Levels of Evidence: Level V.

Effect of Fixation Type and Bone Graft on Tarsometatarsal Fusion

BACKGROUND:

End-stage tarsometatarsal (TMT) arthritis is commonly treated with arthrodesis of involved joints. Fixation hardware can consist of varying combinations of screws, plates, and staples with or without supplemental bone graft. There are limited data to demonstrate either superiority of a given fixation method or the impact of bone graft on fusion rates. The purpose of this study, therefore, was to determine whether nonunion rates after TMT arthrodesis were influenced by either the use of screw vs plate fixation or the addition of bone graft vs no bone graft.

METHODS:

All patients older than 18 years undergoing arthrodesis for TMT arthritis between July 1991 and July 2016 were identified retrospectively. Exclusion criteria included less than 12 months follow-up, prior midfoot surgery, any added procedure beyond TMT arthrodesis using plates or screws, and acute foot trauma. All patients with radiographic or clinical nonunion, including those requiring revision surgery, were identified. Demographic data and associated risk factors were recorded via chart and radiographic image review. Eighty-eight patients (88 feet, mean follow-up: 75.1 ± 51.4; range, 12-179), with a total of 189 joints and who met enrollment criteria were treated by 9 different surgeons with arthrodesis.

RESULTS:

The overall nonunion rate was 11.4%. Significant independent risk factors associated with nonunion were (1) arthrodesis using plate fixation with all screws through the plate (odds ratio [OR], 6.2; 95% confidence interval [CI], 1.8-21.3; P = .004), (2) smoking during the perioperative period (OR, 7.9; 95% CI, 2.1-30.2; P = .002), and (3) postoperative nonanatomic alignment (OR, 11.2; 95% CI, 2.1-60.8; P = .005). Bone graft utilization was found to significantly lower the rate of nonunion (OR, 0.2; 95% CI, 0.1-0.6; P = .006).

CONCLUSION:

Isolated plate fixation, smoking, and postoperative nonanatomic alignment appear to significantly increase the rate of nonunion among patients undergoing TMT arthrodesis for midfoot arthritis. Concomitant use of autogenous bone graft significantly decreased this risk.

LEVEL OF EVIDENCE:

Level III, retrospective comparative study.

Biomechanical Comparison of Fixation Devices for First Metatarsocuneiform Joint Arthrodesis

Common surgical treatment of first tarsal-metatarsal arthritis is by first metatarsocuneiform joint arthrodesis. While crossed-screw and locking plate fixation are the most widely used methods, a novel construct was designed to alleviate soft tissue irritation while still providing stable fixation. Using anatomic first metatarsal and medial cuneiform composites, we compared 3 arthrodesis implants (crossed-screw, dorsal locking plate, and IO Fix) under 2 cyclic bending loading scenarios (cantilever and 4-point bending). Additionally, the optimal orientation (plantar-dorsal or dorsal-plantar) of the IO Fix construct was determined. Failure load, diastasis, joint space angle, and axial and angular stiffness were determined. Both crossed-screw fixation and the IO Fix constructs experienced significantly higher failure loads than the dorsal locking plate during both loading scenarios. Additionally, they had lower plantar diastasis and joint space angle at failure than the plate. Moreover, the plantar-dorsal IO Fix construct was significantly stiffer than the crossed-screw during cantilever bending. Finally, the plantar-dorsal orientation of the IO Fix device had higher failure load and lower diastasis and angle at failure than in the dorsal-plantar orientation. The results suggest that the IO Fix system can reduce motion at the interfragmentary site and ensure compression for healing comparable to that of the crossed-screw fixation.

LEVELS OF EVIDENCE

Level V: Bench testing.

Biomechanical investigation of two plating systems for medial column fusion in foot

Background

Arthrodesis of the medial column (navicular, cuneiform I and metatarsal I) is performed for reasons such as Charcot arthropathy, arthritis, posttraumatic reconstruction or severe pes planus. However, the complication rate is still high and mainly resulting from inadequate fixation. Special plates, designed for medial column arthrodesis, seem to offer potential to reduce the complication rate. The aim of this study was to investigate biomechanically plantar and dorsomedial fusion of the medial column using two new plating systems.

Methods

Eight matched pairs of human cadaveric lower legs were randomized in two groups and medial column fusion was performed using either plantar or dorsomedial variable-angle locking compression plates. The specimens were biomechanically tested under cyclic progressively increasing axial loading with physiological profile of each cycle. In addition to the machine data, mediolateral x-rays were taken every 250 cycles and motion tracking was performed to determine movements at the arthrodesis site. Statistical analysis of the parameters of interest was performed at a level of significance p = 0.05.

Results

Displacement of the talo-navicular joint after 1000, 2000 and 4000 cycles was significantly lower for plantar plating (p≤0.039) while there was significantly less movement in the naviculo-cuneiform I joint for dorsal plating post these cycle numbers (p<0.001). Displacements in all three joints of the medial column, as well as angular and torsional deformations between the navicular and metatarsal I increased significantly for each plating technique between 1000, 2000 and 4000 cycles (p≤0.021). The two plating systems did not differ significantly with regard to stiffness and cycles to failure (p≥0.171).

Conclusion

From biomechanical point of view, although dorsomedial plating showed less movement than plantar plating in the current setup under dynamic loading, there was no significant difference between the two plating systems with regard to stiffness and cycles to failure. Both tested techniques for dorsomedial and plantar plating appear to be applicable for arthrodesis of the medial column of the foot and other considerations, such as access morbidity, associated deformities or surgeon's preference, may also guide the choice of plating pattern. Further clinical studies are necessary before definitive recommendations can be given.

The Impact of Nitinol Staples on the Compressive Forces, Contact Area, and Mechanical Properties in Comparison to a Claw Plate and Crossed Screws for the First Tarsometatarsal Arthrodesis

Background The optimal fixation method for the first tarsometatarsal arthrodesis remains controversial. This study aimed to develop a reproducible first tarsometatarsal testing model to evaluate the biomechanical performance of different reconstruction techniques. Methods Crossed screws or a claw plate were compared with a single or double shape memory alloy staple configuration in 20 Sawbones models. Constructs were mechanically tested in 4-point bending to 1, 2, and 3 mm of plantar displacement. The joint contact force and area were measured at time zero, and following 1 and 2 mm of bending. Peak load, stiffness, and plantar gapping were determined. Results Both staple configurations induced a significantly greater contact force and area across the arthrodesis than the crossed screw and claw plate constructs at all measurements. The staple constructs completely recovered their plantar gapping following each test. The claw plate generated the least contact force and area at the joint interface and had significantly greater plantar gapping than all other constructs. The crossed screw constructs were significantly stiffer and had significantly less plantar gapping than the other constructs, but this gapping was not recoverable. Conclusions Crossed screw fixation provides a rigid arthrodesis with limited compression and contact footprint across the joint. Shape memory alloy staples afford dynamic fixation with sustained compression across the arthrodesis. A rigid polyurethane foam model provides an anatomically relevant comparison for evaluating the interface between different fixation techniques. Clinical Relevance The dynamic nature of shape memory alloy staples offers the potential to permit early weight bearing and could be a useful adjunctive device to impart compression across an arthrodesis of the first tarsometatarsal joint.

LEVELS OF EVIDENCE

Therapeutic, Level V: Bench testing.

Evaluation of Nitinol Staples for the Lapidus Arthrodesis in a Reproducible Biomechanical Model

While the Lapidus procedure is a widely accepted technique for treatment of hallux valgus, the optimal fixation method to maintain joint stability remains controversial. The purpose of this study is to evaluate the biomechanical properties of new shape memory alloy (SMA) staples arranged in different configurations in a repeatable first tarsometatarsal arthrodesis model. Ten sawbones models of the whole foot (n = 5 per group) were reconstructed using a single dorsal staple or two staples in a delta configuration. Each construct was mechanically tested non-destructively in dorsal four-point bending, medial four-point bending, dorsal three-point bending, and plantar cantilever bending with the staples activated at 37°C. The peak load (newton), stiffness (newton per millimeter), and plantar gapping (millimeter) were determined for each test. Pressure sensors were used to measure the contact force and area of the joint footprint in each group. There was a statistically significant increase in peak load in the two staple constructs compared to the single staple constructs for all testing modalities with P values range from 0.016 to 0.000. Stiffness also increased significantly in all tests except dorsal four-point bending. Pressure sensor readings showed a significantly higher contact force at time zero (P = 0.037) and contact area following loading in the two staple constructs (P = 0.045). Both groups completely recovered any plantar gapping following unloading and restored their initial contact footprint. The biomechanical integrity and repeatability of the models was demonstrated with no construct failures due to hardware or model breakdown. SMA staples provide fixation with the ability to dynamically apply and maintain compression across a simulated arthrodesis following a range of loading conditions.

Biomechanical Comparison of External Fixation and Compression Screws for Transverse Tarsal Joint Arthrodesis

BACKGROUND

Transverse tarsal joint arthrodesis is commonly performed in the operative treatment of hindfoot arthritis and acquired flatfoot deformity. While fixation is typically achieved using screws, failure to obtain and maintain joint compression sometimes occurs, potentially leading to nonunion. External fixation is an alternate method of achieving arthrodesis site compression and has the advantage of allowing postoperative compression adjustment when necessary. However, its performance relative to standard screw fixation has not been quantified in this application. We hypothesized that external fixation could provide transverse tarsal joint compression exceeding that possible with screw fixation.

METHODS

Transverse tarsal joint fixation was performed sequentially, first with a circular external fixator and then with compression screws, on 9 fresh-frozen cadaveric legs. The external fixator was attached in abutting rings fixed to the tibia and the hindfoot and a third anterior ring parallel to the hindfoot ring using transverse wires and half-pins in the tibial diaphysis, calcaneus, and metatarsals. Screw fixation comprised two 4.3 mm headless compression screws traversing the talonavicular joint and 1 across the calcaneocuboid joint. Compressive forces generated during incremental fixator foot ring displacement to 20 mm and incremental screw tightening were measured using a custom-fabricated instrumented miniature external fixator spanning the transverse tarsal joint.

RESULTS

The maximum compressive force generated by the external fixator averaged 186% of that produced by the screws (range, 104%-391%). Fixator compression surpassed that obtainable with screws at 12 mm of ring displacement and decreased when the tibial ring was detached. No correlation was found between bone density and the compressive force achievable by either fusion method.

CONCLUSION

The compression across the transverse tarsal joint that can be obtained with a circular external fixator including a tibial ring exceeds that which can be obtained with 3 headless compression screws. Screw and external fixator performance did not correlate with bone mineral density. This study supports the use of external fixation as an alternative method of generating compression to help stimulate fusion across the transverse tarsal joints.

CLINICAL RELEVANCE

The findings provide biomechanical evidence to support the use of external fixation as a viable option in transverse tarsal joint fusion cases in which screw fixation has failed or is anticipated to be inadequate due to suboptimal bone quality.

Metatarsus Primus Varus Correction

We present a discussion on the use of proximal first-ray osteotomies in the surgical treatment for hallux valgus as a valid option compared with first-tarsometatarsal arthrodesis. Recent and historical literature tells us that stability of the first ray is a function of the alignment and reestablishment of retrograde stabilizing forces at the first tarsometatarsal joint. This realignment and stabilization may be accomplished with the use of distal soft tissue and proximal osteotomy procedures.

Crossed-screws provide greater tarsometatarsal fusion stability compared to compression plates

BACKGROUND

Hallux valgus is a common deformity that is often treated with a fusion of the first tarsometatarsal (TMT) joint. Crossed-screws are currently the accepted standard but advances in plate systems present opportunities for improved clinical outcomes; however, in vitro testing should be performed prior to clinical implementation. The purpose of this study was to determine whether a locking plate with surgeon-mediated compression provides similar fusion stability compared to crossed-screws and if bone density or joint size are related to construct success.

METHODS

Ten matched-pair cadaveric specimens received first TMT fusions with either crossed-screws or a compression plate and were loaded for 1000 cycles to assess the amount of joint motion measured as plantar gapping. Bone density was quantified using computed tomography images of each specimen, and joint height was measured with calipers.

RESULTS

Crossed-screws provided 3 times greater resistance to plantar gapping compared to compression plates after 1000 cycles. Bone density and joint size did not affect resistance to plantar gapping for either construct.

CONCLUSION

Lag screws or a plantarly applied plate are needed to maximize TMT fusion stability prior to osseous union. Dorsomedially applied plates are also effective when paired with a lag screw placed across the TMT joint. These constructs do not appear to depend on bone density or joint size, suggesting that patients with osteoporosis are viable candidates.

CLINICAL RELEVANCE

The results of this study suggest that traditional, lagged cross-screws provide greater stability to that of a dorsally place compression plate and may lead to better rates of union.

LEVELS OF EVIDENCE

Therapeutic, Level V: Cadaveric Study.

First Tarsometatarsal Arthrodesis: An Anatomic Evaluation of Dorsomedial Versus Plantar Plating

Fusion of the first tarsometatarsal joint is a widely used procedure for the correction of hallux valgus deformity. Although dorsomedial H-shaped plating systems are being increasingly used, fusion can also be achieved by plantar plating. The goal of the present study was to compare these 2 operative techniques based on the anatomic considerations and show the potential pitfalls of both procedures. Six pairs of deep-frozen human lower legs were used in the present cadaveric study. In a randomized manner, either dorsomedial arthrodesis or plantar plating through a medial incision was performed. With regard to arterial injury, the plantar technique resulted in fewer lesions (plantar, 4 injuries [66.7%] to the terminal branches of the first digital branch of the medial plantar artery; dorsomedial, 3 injuries [50%] to the main trunks of the plantar metatarsal arteries and the first dorsal metatarsal artery). With respect to injury to the veins, the plantar procedure affected significantly fewer high-caliber subcutaneous trunk veins. The nerves coursing through the operative field, such as the saphenous and superficial fibular nerves, were compromised more often by the dorsal approach. Neither the plantar plating nor the dorsomedial plating technique was associated with injury to the insertion of the tibialis anterior muscle. Both studied techniques are safe, well-established procedures. Arthrodesis with plantar plating, however, offers additional advantages and is a reliable tool in the foot and ankle surgeon's repertoire.

Screw fixation diameter for fifth metatarsal jones fracture: a cadaveric study

The fifth metatarsal Jones fracture is a well-documented injury occurring at the proximal diaphyseal-metaphyseal junction. Conservative versus surgical intervention has been discussed in published studies for the management of Jones fractures. Solid intramedullary fixation relies on accurate matching of the screw diameter to the intraosseous diameter. The purpose of the present cadaveric study was to determine the average intraosseous diameter of the proximal fifth metatarsal as it relates to screw size selection for Jones fracture stabilization. Twenty fresh-frozen cadaver legs were used for examination. The fifth metatarsal was completely dissected. A transverse osteotomy was performed from laterally to medially along the midline of the metatarsal. A digital caliper was used to measure the diameter of the medullary canal of the fifth metatarsal. The measurement was taken at the narrowest portion of the medullary canal just distal to the proximal metaphysis. The mean dorsal to plantar diameter of the fifth metatarsal was 6.475 ± 1.54 (range 4 to 12) mm and the mean medial to lateral diameter was 4.6 ± 0.85 (range 3 to 6) mm. Intramedullary screw fixation has shown beneficial results in the treatment protocol of fifth metatarsal Jones fractures. Our study has demonstrated that a 4.5-mm cannulated screw is the narrowest diameter screw that can be used in the average fifth metatarsal and still obtain adequate intraosseous purchase. When selecting the appropriate screw, the surgeon must be comfortable selecting the largest screw that will achieve the maximal interface with the dense cortical bone in both the medial to lateral and dorsal to plantar plane.

Intraosseous fixation compared to plantar plate fixation for first metatarsocuneiform arthrodesis: a cadaveric biomechanical analysis

BACKGROUND

Metatarsocuneiform (MTC) fusion is a treatment option for management of hallux valgus. We compared the biomechanical characteristics of an internal fixation device with plantar plate fixation.

METHODS

Seven matched pairs of feet from human cadavers were used to compare the intramedullary (IM) device plus compression screw to plantar plate combined with a compression screw. Specimen constructs were loaded in a cyclic 4-point bending test. We obtained initial/final stiffness, maximum load, and number of cycles to failure. Bone mineral density was measured with peripheral quantitative computed tomography. Performance was compared using time to event analysis with number of cycles as time variable, and a proportional hazard model including shared frailty model fitted with treatment and bone mineral density as covariates.

RESULTS

On average the plates failed after 7517 cycles and a maximum load of 167 N, while the IM-implants failed on average after 2946 cycles and a maximum load of 69 N. In all pairs the 1 treated with IM-implant failed earlier than the 1 treated with a plate (hazard ratio for IM-implant versus plate was 79.9 (95% confidence interval [6.1, 1052.2], P = .0009). The initial stiffness was 131 N/mm for the plantar plate and 43.3 N/mm for the IM implant. Initial stiffness (r = .955) and final stiffness (r = .952) were strongly related to the number of cycles to failure. Bone mineral density had no effect on the number of cycles to failure.

CONCLUSION

Plantar plate fixation created a stronger and stiffer construct than IM fixation.

CLINICAL RELEVANCE

A stiffer construct can reduce the risk of nonunion and shorten the period of non-weight-bearing.

Immediate weightbearing after Lapidus arthrodesis with external fixation

A common surgical treatment of severe hallux abductovalgus deformity with coincident first ray hypermobility is metatarsal-cuneiform fusion or Lapidus procedure. The aim of the present study was to illustrate a reliable and novel method of fixation for Lapidus fusion using an external fixation device through a retrospective cohort investigation of consecutive patients. Twenty Lapidus fusions were performed in 19 patients, including 17 females (89.47%) and 2 males (10.53%). The mean age at surgery was 41 (range 20 to 64) years. The patients were evaluated clinically and radiographically pre- and postoperatively. The mean duration in the fixator was 12 (range 3 to 34) weeks. The mean interval to radiographic union was 9.2 (range 4.7 to 30.7) weeks in 18 of 20 feet (90%) and 2 (10%) were designated as nonunion. The mean follow-up period was 37 (range 5.6 to 211.1) weeks. The most common complication was pin tract infection in 5 patients (6 feet) and was treated with oral antibiotics; only 1 foot required early hardware removal. According to the visual analog scale, the mean patient pain score decreased significantly from 8.2 ± 2.7 to 0.83 ± 0.98 postoperatively (p < .001). Our results highlight that immediate weightbearing after Lapidus fusion with external fixation is a viable treatment option for the correction of severe hallux abductovalgus with associated hypermobility.

Topical review: locking plate technology in foot and ankle surgery

The use of locking plate technology in foot and ankle surgery has increased over the last decade. Reported applications include fracture repair, deformity correction, and arthrodesis. There is limited evidence, however, to guide clinicians with regard to the appropriate and optimal use of this technology. This work aims to examine the current biomechanical and clinical evidence comparing locking construct technology to other forms of fixation in the field of foot and ankle surgery.

Modified Lapidus arthrodesis with plantar plate and compression screw for treatment of hallux valgus with hypermobility of the first ray: a preliminary report

BACKGROUND

TMT-1 arthrodesis is an established method in hallux valgus surgery, but it is technically demanding and typically calls for a period of postoperative immobilization.

METHODS

In this cohort study, initial experience with a plantar plate is described. 58 patients (59 arthrodesis) were included.

RESULTS

The mean duration of protected full weight bearing was 7 weeks. 94.12% patients were satisfied with the results, bony union was achieved in 98.31%. The Foot Function Index improved by 33 to a mean of 8 (p<.001). The postoperative Mayo Clinic Forefoot Score was excellent in 47.04 and good in 47.04%. The mean hallux valgus angle improved by 24.4-13.2° (p<.001). The mean first intermetatarsal angle improved by 11.2-5.2° (p<.001).

CONCLUSION

Initial experience with this form of fixation appears to provide suitable stability, allow early-protected weight bearing, with an acceptable level of complications.

New techniques and alternative fixation for the lapidus arthrodesis

Arthrodesis of the first metatarsocuneiform joint is a powerful and durable procedure to help correct moderate to severe hallux valgus and/or first ray hypermobility. However, painful nonunion remains a notoriously high potential outcome. Research regarding locking plates seems promising, and data show lower rates of nonunion. Innovative fixation techniques are new and should be considered in the future as further literature is available on their long-term use. Regardless of the fixation, proper joint preparation and good compression is fundamentally the most important. A case of Lapidus fusion with locking plates after a failed arthrodesis with screws alone is presented.

Biomechanical comparison of a locking plate with intraplate compression screw versus locking plate with plantar interfragmentary screw for Lapidus arthrodesis: a cadaveric study

Lapidus arthrodesis (first metatarsal cuneiform arthrodesis) has become an accepted procedure for hallux abducto valgus. Several variations of fixation have been described. Earlier weightbearing postoperatively has been one reported benefit of using locking plates for fixation. Additionally, studies have demonstrated that fixation placed on the plantar or tension side of the arthrodesis increases the biomechanical advantage. We performed a biomechanical cadaveric study of the Lapidus procedure, comparing a previously reported technique using a low profile locking plate with an intraplate compression screw versus the same locking plate with a plantar interfragmentary screw (PIFS) placed on the tension side of the arthrodesis in 10 fresh, paired, cadaver limbs. The mean ultimate load of the plate with a PIFS was 383.2 ± 211.5 N, and the mean ultimate load of the plate with an intraplate compression screw was 205.5 ± 97.2 N. The mean ultimate load of the LPS Lapidus plate with a PIFS was statistically greater (p = .027) than that with the plate intraplate compression screw. Our results indicated that changing the orientation of the compression screw to a PIFS significantly increased the stability of the Lapidus arthrodesis fixation construct. The modified construct with the PIFS might decrease the incidence of nonunion and, ultimately, allow patients to bear weight faster postoperatively.

Fixation of lapidus arthrodesis with a plantar interfragmentary screw and medial locking plate: a report of 88 cases

Lapidus arthrodesis is a powerful procedure that can be used to correct pathologic features within the forefoot or midfoot. Many different methods of fixation for this procedure have been reported. The use of plating constructs has been shown to provide increased stability compared with screw-only constructs. The technique we have described consists of a plantar to dorsal retrograde lag screw across the arthrodesis site, coupled with a low-profile medial locking plate. A total of 88 consecutive patients were treated with this modification of the Lapidus procedure by 2 surgeons and were retrospectively evaluated. All patients followed an early postoperative weightbearing protocol. Patient age, gender, follow-up duration, interval to weightbearing and radiographic fusion, preoperative and postoperative intermetatarsal angle, hardware removal, preoperative and postoperative American Orthopaedic Foot and Ankle Society midfoot scores, and adjunct procedures were analyzed. The mean follow-up period was 16.76 ± 5.9 (range 12 to 36) months, and all healed fusions demonstrated radiographic union at a mean of 51 ± 19.1 (range 40 to 89) days. The patients were treated with weightbearing starting a mean of 10.90 ± 4.1 (range 5 to 28) days postoperatively. Complications included 15 patients (17%) requiring hardware removal, 2 cases (2%) of hallux varus, 6 cases (7%) of radiographic recurrent hallux valgus, and 2 patients (2%) with first metatarsocuneiform nonunion. The results of the present study have demonstrated that plantar lag screw fixation with medial locking plate augmentation for Lapidus arthrodesis allows for early weightbearing with satisfactory outcomes, improved clinical and radiographic alignment, and improved American Orthopaedic Foot and Ankle Society scores.

Medial column procedures in the correction of adult acquired flatfoot deformity

AAFD is a complex problem with a wide variety of treatment options. No single procedure or group of procedures can be applied to all patients with AAFD because of the variety of underlying etiology and grades of deformity. As the posture of the foot progresses into hindfoot valgus and forefoot abduction through attenuation of the medial structures of the foot, the medial column begins to change shape. The first ray elevates and the joints of the medial column may begin to collapse. Careful physical examination and review of weight-bearing radiographs determines which patients have an associated forefoot varus deformity that may require correction at the time of flatfoot reconstruction. Correction of an AAFD requires a combination of soft-tissue procedures to restore dynamic inversion power and bony procedures to correct the hindfoot and midfoot malalignments. If after these corrections forefoot varus deformity remains, the surgeon should consider use of a medial column procedure to recreate the “triangle of support” of the foot that Cotton described.5 If the elevation of the medial column is identified to be at the first NC or the first TMT joint, then the joint should be carefully examined for evidence of instability, hypermobility, or arthritic change. If none of these problems exist, then the surgeon can consider use of the joint-sparing Cotton medial cuneiform osteotomy to correct residual forefoot varus. However, if instability, hypermobility, or arthritic change is present, then the surgeon should consider use of an arthrodesis of the involved joint to correct residual forefoot varus. Either procedure provides a safe and predictable correction to the medial column as part of a comprehensive surgical correction of AAFD.

Fixation of the Lapidus arthrodesis with a plantar interfragmentary screw and medial low profile locking plate

The Lapidus arthrodesis can be used to correct pathology within the forefoot or midfoot, and severe hallux valgus deformities as well as hypermobility of the medial column may be amenable to correction with this procedure. Many different skeletal fixation methods have been described for this procedure, and one form that appears to provide enough construct stability to allow patients to bear weight early in the postoperative period is described herein. This construct consists of an interfragmental compression screw oriented from the plantar aspect of the first metatarsal to the superior aspect of the medial cuneiform, with medial locking plate augmentation.

Plantar versus dorsomedial locked plating for Lapidus arthrodesis: a biomechanical comparison

BACKGROUND

Lapidus arthrodesis with a plate and a compression screw is an established procedure in hallux valgus surgery. The present study was performed to investigate the potential benefit of a compression screw combined with a plantarly applied angle-stable, anatomically precontoured plate or a dorsomedially applied angle-stable plate.

METHODS

In six pairs of human cadaver specimens, one specimen each was randomized to receive a dorsomedial H-shaped plate, while the other received a plantar plate. Bone mineral density was measured with peripheral quantitative computed tomography. The specimens were loaded quasi-statically, followed by cyclic loading. Finally, they were loaded to failure. In the static tests, stiffness and range of motion (ROM) data were obtained. In the cyclic tests, the constructs' displacement was studied. In the load-to-failure test, stiffness and maximum load to failure were measured.

RESULTS

The two groups did not differ significantly with regard to BMD (p = 0.25). Any significant differences observed were in favor of the plantar constructs, which had greater initial stiffness (p = 0.028) and final stiffness (p = 0.042), a smaller ROM (p = 0.028), and a greater load to failure (p = 0.043). There was no significant difference regarding displacement (p = 0.14).

CONCLUSION

In the static tests, the plantar angle-stable plate construct was superior to the dorsomedial angle-stable plate construct.

CLINICAL RELEVANCE

Plantar plating appears to offer biomechanical benefit. Clinical studies will be required to show whether this translates into earlier resumption of weightbearing and into lower rates of nonunion.

Modern techniques in hallux abducto valgus surgery

Hallux abducto valgus surgery is in a constant state of evolution. Innovation is driven by surgeons pursuing the perfect procedure for any clinical scenario. The end point is to eliminate complications and produce satisfied patients. Medical device technology has helped pave the way for some recent advances in bunion surgery. The use of opening base wedge plates, locking plates for the Lapidus fusion, suture endobuttons, and staples for the Akin procedure are the focus in this review of modern techniques.

Fixation of first tarsometatarsal arthrodesis: a retrospective comparative cohort of two techniques

BACKGROUND

Presently, indications for the Lapidus procedure include patients with many pathologies of the first metatarsocuneiform joint. Currently the standard in many areas is that of two or three crossed screws through the first tarsometatarsal region. This type of fixation requires an extended period of nonweightbearing and may be difficult for patient compliance.

MATERIALS AND METHODS

The present study is a retrospective comparison of crossed screw fixation to locking plate fixation without a lag screw on union rates, time to weightbearing, and complications.

RESULTS

One hundred forty-three first TMT fusions met the inclusion criteria. There were 96 fused by crossed screw construct (CS) and 47 by the locked plate with or without compression screw (LP). There was a significant difference in time to full weightbearing and union rate. Time to full weightbearing was 8.8 (range, 3 to 16) weeks and 7.8 (range, 1.5 to 34) weeks in the CS and LP groups, respectively (p < 0.001). Union rate was 89.4% (88 of 96 joints) and 98.5% (46 of 47 joints) in the CS and LP groups, respectively (p < 0.001).

CONCLUSIONS

We found that when using a dorsal-medial locked plate with or without lag screw lead to a superior rate of union compared to standard crossed screw constructs even while allowing earlier return to full weightbearing.

Biomechanical comparison of hallux valgus correction using the proximal chevron osteotomy fixed with a medial locking plate and the Ludloff osteotomy fixed with two screws

BACKGROUND

For moderate-to-severe hallux valgus deformities with a 1-2 intermetatarsal angle in excess of 15 degrees , a proximal first metatarsal osteotomy is indicated. The ideal osteotomy has yet to be defined, but should inherently limit the incidence of dorsal malunion and allow for early ambulation. The present study evaluates the mechanical integrity of two popular first metatarsal osteotomies.

METHODS

Ten matched pairs of fresh-frozen cadaveric first metatarsals were harvested. In one metatarsal from each pair, a Ludloff osteotomy was created and fixed with two cannulated 3.5mm screws. In the contralateral first metatarsal, a proximal chevron osteotomy was performed and subsequently fixed with a medially applied locking plate. All specimens were mounted within an Instron 1321 servohydraulic materials testing machine and subjected to a plantar-to-dorsal cantilever bending protocol for 1000 cycles.

FINDINGS

Two of ten Ludloff osteotomies failed prior to completion of 1000 loading cycles by fracture at the distal screw site, whereas six of ten proximal chevrons failed prior to the 1000th cycle. The mode of failure in this group was by cut-out of the plantar-proximal screw. The bending stiffness of the Ludloff osteotomy exceeded that of the proximal chevron at all measurement points between the 1st and 200th load cycles (P<0.05). After 200 cycles, an inadequate number of plate constructs survived to allow statistical comparison.

INTERPRETATION

The results of the present study indicate that the proximal chevron osteotomy fixed with a medially based locking plate exhibits mechanical properties inferior to those of the Ludloff osteotomy under the tested conditions.