Biomechanics of common fixation devices for first tarsometatarsal joint fusion-a comparative study with synthetic bones

Early Functional Rehabilitation in Foot and Ankle Surgery

The traditional postoperative management of common foot and ankle procedures has involved a prolonged period of immobilization and nonweight bearing. The concern was loss of correction and fixation failure. However, it has been shown that a prolonged period of nonweight bearing can predispose patients possible deep vein thrombosis, disuse osteopenia, cardiovascular complications, and generalized deconditioning. The authors' institution has published studies reviewing the efficacy of early weight bearing after first metatarsophalangeal joint arthrodesis, modified Lapidus bunionectomy, and open reduction and internal fixation of ankle fractures. This article highlights the literature and rationale supporting the safety of early weight-bearing protocols.

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.

The modified Lapidus fusion: a systematic review of biomechanical studies

Purpose

The biomechanical characteristics of different techniques to perform the modified Lapidus procedure are controversial, discussing the issue of stability, rigidity, and compression forces from a biomechanical point of view. The aim of this systematic review was to investigate the available options to identify whether there is a procedure providing superior biomechanical results.

Methods

A comprehensive literature search was performed by screening PubMed, Embase, and Cochrane databases until September 2021. There was a wide heterogeneity of the available data in the different studies. Load to failure, stiffness, and compression forces were summarized and evaluated.

Results

Seventeen biomechanical studies were retrieved - ten cadaveric and seven polyurethane foam (artificial bone) studies. Fixation methods ranged from the classic crossed screw approach (n = 5) to plates (dorsomedial and plantar) with or without compression screws (n = 11). Newer implants such as intramedullary stabilization screws (n = 1) and memory alloy staples (n = 2) were investigated.

Conclusion

The two crossed screws construct is still a biomechanical option; however, according to this systematic review, there is strong evidence that a plate-screw construct provides superior stability especially in combination with a compression screw. There is also evidence about plate position and low evidence about compression screw position. Plantar plates seem to be advantageous from a biomechanical point of view, whereas compression screws could be better when positioned outside the plate. Overall, this review suggests the biomechanical advantages of using a combination of locking plates with a compression screw.

Plantar Plating in the Modified Lapidus Procedure: Evaluation of Function and Impairment of the Tibialis Anterior Tendon

The modified "Lapidus" procedure (MLP) describes the arthrodesis of the first tarsometatarsal joint. We investigate if there are detectable changes of the tendon or the function of the muscle and clinical outcome after MLP. We reviewed 22 feet. All patients underwent magnetic resonance imaging (MRI) at an average of 27 (range, 12-49) months. Clinical outcome was evaluated using the European Foot and Ankle Society score. Strength was measured and complications were assessed. MRI revealed signs of tendinopathy of the tibialis anterior tendon in 13 feet (59%). The mean total European Foot and Ankle Society score at final follow-up was 17 (range, 6-24) points. The mean postoperative Visual Analog Scale score was 1.4 (range, 0-5). Range of motion and force data were not significantly different to the contralateral side. In conclusion, MRI showed signs of tendinopathy in 59%, which does not seem to affect clinical outcome, but has to be considered when choosing the desired implant and placement. MLP leads to high patient satisfaction rates and significant improvement at midterm follow up.

Identifying Risk Factors for Nonunion of the Modified Lapidus Procedure for the Correction of Hallux Valgus

There is a paucity of literature characterizing risk factors for nonunion associated with the modified Lapidus procedure for correction of hallux valgus. The purpose of this study was to evaluate risk factors associated with nonunion for Lapidus bunionectomies. Patients who underwent modified Lapidus procedure from 2009 to 2018 were retrospectively reviewed. Patient's age, sex, body mass index, prior bunionectomy, history of tobacco use, presence of diabetes mellitus or hypothyroidism, and fixation method were recorded along with pre- and postoperative radiographic parameters. A multiple logistic regression analysis was implemented to estimate the odds of nonunion. Of the 222 patients who met inclusion criteria, nonunion with modified Lapidus procedure was observed in 20 patients (9.01%). Odds of nonunion with modified Lapidus procedure were greater for patients who had undergone previous bunionectomy (odds ratio [OR] = 3.957, 95% confidence interval [CI]: 1.021-15.338), as body mass index increased (OR = 1.091, 95% CI: 1.018-1.170), and as preoperative HV angle increased (OR = 1.108, 95% CI: 1.020-1.203). Odds of nonunion were lower for patients as preoperative intermetatarsal angle increased (OR = 0.739, 95% CI: 0.580-0.941). No significant increased odds of nonunion were found between fixation methods.

Fixation Performance of Bioabsorbable Zn-6Ag Pins for Osteosynthesis

Bioabsorbable implants have become the focus of the latest research for new bone implant materials. With favorable characteristics such as compatible mechanical characteristics, no long-term side effects, and even osteogenesis enhancing properties they seem to be the future of osteosynthesis. Besides these characteristics, they must perform on the same level as traditional implant materials regarding their mechanical support for bone healing. A particular focus in the research for bioabsorbable implants has been on metal alloys, as these have particularly good mechanical properties such as excellent maximum force and high stability. This study focused on the shear strength of new bioabsorbable zinc and magnesium pins in comparison to traditional implants such as K-wires and cancellous bone screws in bone-implant connections. During quasi-static and fatigue loading experiments, magnesium pins (MAGNEZIX, Syntellix AG, Hannover, Germany) and new zinc silver pins (Zn-6Ag) by Limedion (Limedion GmbH., Mannheim, Germany) were compared with conventional osteosynthetic materials. The pins made of the new bioabsorbable alloys withstood the cyclic loads to the same extent as the conventional osteosynthesis materials. In the quasi-static loading, it was shown that the novel Zn-6Ag from Limedion has the same shear strength as the magnesium pin from Syntellix, which is already in clinical use. In addition, the zinc pin showed significantly better shear strength compared to osteosynthesis with K-wires (p < 0.05).

Early Results and Patient-Reported Outcome Measures (PROMS) of an Intraosseous Device for Arthrodesis of the First Tarso-Metatarsal (TMT) Joint

BACKGROUND

We describe a new surgical technique for arthrodesis of the first tarso-metatarsal (TMT) joint using an intraosseous fixation device and the early results including patient-reported outcome measures (PROMS).

MATERIALS AND METHODS

Seventeen consecutive procedures with this method were included. Indication for surgery was hallux valgus. The average age was 42 years (range 26-65). PROMS were collected and the patients were asked to fill out a satisfaction questionnaire. A retrospective review of radiographs and electronic medical notes was conducted.

RESULTS

Overall fusion rate was 94%. Complications included a case of failed fusion, a superficial wound infection and a deep vein thrombosis (DVT). At a mean follow-up of 24 months (range 10-38) radiographic results demonstrated significant improvement in the intermetatarsal angle or IMA (11.7 ± 2.8 degrees to 6.9 ± 2.4 degrees, P < 0.001) and hallux valgus angle or HVA (28.1 ± 7.3 degrees to 12.2 ± 4.3 degrees, P < 0.001). The mean visual analog scale (VAS) score improved significantly from a mean of 7.6 (SD 0.85) preoperatively, to a mean of 2.1 (SD 1.83) post-operatively (P < 0.0001). The Manchester-Oxford Foot Questionnaire (MOXFQ) significantly improved from a mean of 35.8 (SD 10.2), to a mean of 9.2 (SD 17) (P < 0.0001). The final result was satisfactory for 88% of the patients.

CONCLUSIONS

The early results show intraosseous fixation to be a safe and efficient method for the fusion of the first TMT joint providing good patient satisfaction.

Intraosseous device for arthrodesis in foot and ankle surgery: Review of the literature and biomechanical properties

BACKGROUND

Arthrodesis is the surgical fusion of a diseased joint for the purposes of obtaining pain relief and stability. There have been numerous fixation devices described in literature for foot and ankle arthrodesis, each with their own benefits and drawbacks.

AIM

To review the use of intraosseous devices in foot and ankle surgery.

METHODS

There were 9 papers included in the review (6 clinical and 3 experimental studies) all evaluating arthrodesis in the foot and ankle using the IOFIX device (Extremity Medical™, Parsippany, NJ, United States). Outcome scores, union rates, as well as complications were analysed.

RESULTS

IOFIX appears to be safe and effective in achieving arthrodesis of the 1^st metatarsophalangeal, and talonavicular joints with early rehabilitation. In comparison to plate/screw constructs there were fewer soft tissue complications and issues of metalwork prominence. Cadaveric and biomechanical studies on the use of intramedullary fixation for fusion of the tarsometatarsal and ankle joint showed decreased load to failure, cycles to failure and stiffness in comparison to traditional fusion methods using plates and screws, however IOFIX devices produced higher compressive forces at the joint.

CONCLUSION

We describe the reasons for which this biomechanical behavior of the intraosseous fixation may be favorable, until prospective and comparative studies with larger sample size and longer follow-up confirm the effectiveness and limitations of the method.

Anatomical reconstruction of first ray instability hallux valgus with a medial anatomical TMTJ1 plate

BACKGROUND

First tarsometatarsal joint (TMTJ1) arthrodesis is a powerful tool for hallux valgus correction. Past criticism of the TMTJ1 arthrodesis has focused on high non-union rates, and consequent need for delayed weightbearing as prevention. In this study we present a selection and treatment protocol to minimise non-union while allowing early weightbearing.

METHODS

All TMTJ1 arthrodesis procedures for hallux valgus performed by the senior surgeon over the period June, 2016 to July, 2019 were included. An anatomically-designed, medial TMTJ1 plate and screw compression was utilised for TMTJ1 arthrodesis. The construct was augmented with synthetic intermetatarsal stabilisation. All patients were kept non-weightbearing for 2 weeks, followed by progressive weightbearing as tolerated for 4 weeks. Minimum follow-up was 1 year.

RESULTS

300 modified Lapidus procedures were performed for hallux valgus with mean IMA 17° (Range: 14-29). Mean age was 58 years, with 93% female. 284 (94%) had an Akin osteotomy, while 222 cases (74%) were associated with another forefoot procedure. Patients began progressive weight bearing as tolerated from 2 weeks. All were fully weight bearing by 8 weeks post-operatively. There was a 100% union rate in this group. Mean AOFAS Hallux MTP-IP scores rose from 59 pre-operatively to 97 post-operatively. One plate was removed due to tibialis anterior impingement. There were no recurrences at final follow-up.

CONCLUSIONS

We describe a selection and treatment protocol for TMTJ1 arthrodesis for hallux valgus. This yields high union rates while allowing early weight bearing.

LEVEL OF EVIDENCE

4.

Radiographic Outcomes, Union Rates, and Complications Associated With Plantar Implant Positioning for Midfoot Arthrodesis

Background:

Midfoot arthrodesis has long been successfully included in the treatment paradigm for a variety of pathologic foot conditions. A concern with midfoot arthrodesis is the rate of nonunion, which historically has been reported between 5% and 10%. Plantar plating has also been noted to be more biomechanically stable when compared to traditional dorsal plating in previous studies. Practical advantages of plantar plating include less dorsal skin irritation and the ability to correct flatfoot deformity from the same medial incision. The purpose of this study is to report the arthrodesis rate, the success of deformity correction, and the complications associated with plantar-based implant placement for arthrodesis of the medial column.

Methods:

A retrospective review was undertaken of all consecutive patients between 2012 and 2019 that underwent midfoot arthrodesis with plantar-positioned implants. Radiographic outcomes and complications are reported on 62 patients who underwent midfoot arthrodesis as part of a correction for hallux valgus deformity, flatfoot deformity, degenerative arthritis, Lisfranc injury, or Charcot neuroarthropathy correction.

Results:

Statistically significant improvement was seen in the lateral talus–first metatarsal angle (Meary angle) and medial arch sag angle for patients treated for flatfoot deformity correction. In patients treated for hallux valgus deformity, there was a reduction in the intermetatarsal angle from 15.4 to 6.8 degrees. The overall nonunion rate was 6.45% in all patients. The rate of nonunion was higher at the NC joint compared to the TMT joint and with compression claw plates. One symptomatic nonunion required revision surgery (1.7%). There were no nonunions when excluding neuroarthropathy patients and smokers. The odds ratio (OR) for nonunion in patients with neuroarthropathy was 6.05 ( P < .05), and in active smokers the OR was 2.33 ( P < .05).

Conclusion:

Plates placed on the plantar bone surface for midfoot arthrodesis achieved and maintained deformity correction with rare instances of symptomatic hardware for a variety of orthopedic conditions. An overall clinical and radiographic union rate of 94% was achieved. The radiographic union rate improved to 100% when excluding both neuroarthropathy patients and smokers. The incidence of nonunion was higher in smokers, neuroarthropathy patients, naviculocuneiform joint fusions, use of compression claw plates, and when attempting to fuse multiple joints. Incisional healing complications were rarely seen other than in active smokers.

Level of Evidence:

Level IV, case series.

Does the IOFix implant improve union rates?

BACKGROUND

First metatarso-phalangeal joint fusion is the current gold standard for severe hallux rigidus. Data regarding the union rate and the re-operation rate when IOFix (an Intra-osseous fixation device, Extremity medical, New Jersey, USA) is used for hallux rigidus fusion is limited but promising. The aim of this study was to review our outcomes with the IOFix implant.

METHODS

We have conducted a retrospective chart review, following the approval of the hospital IRB committee. Exclusion criteria included bilateral operations on the same patient, multiple surgeries, charcot foot or other structural foot abnormalities (except hallux valgus), rheumatoid arthritis and a recent foot trauma. We collected demographic data, physical examination documentation, functional score evaluations (AOFAS), and Plain radiographic studies.

RESULTS

Thirty patients were included in the study. The mean age was 60.36 ± 9.12 (range 36 to 77) years, 18 (60%) female patients and 12 (40%) male. Fourteen (53.33%) were left side pathologies. The average follow up period was 36.2 ± 12.31 (range 12 to 54) months. Union was obtained in 28 (93.33%) patients, of whom none had requested a hardware removal due to a prominent hardware during a minimum of 2 year follow up period. The mean postoperative AOFAS score was 80.5 ± 10.87 (range 35 to 90). A more stringent inclusion criteria and fusion definitions would have led to an exclusion of two more patients and a dropout of two patients from the "fused" group, which would have led to a fusion rate of 85.71%.

CONCLUSIONS

This is the largest series of hallux rigidus patients that were operated with an IOFix device. The rates of fusion and hardware removal in MTPJ1 arthrodesis performed with an IOFix implant were found to be similar at most when compared to previously described rates that were obtained with other cheaper and more simple fixation devices.

LEVEL OF EVIDENCE

4.

Current Trends in Fixation Techniques

Hallux valgus is an extremely common and often disabling deformity. In addition to valgus deformity of the hallux, varying degrees of varus and supination of the first metatarsal and instability in the metatarsophalangeal and metatarsocuneiform joints are frequently present. Because of the complexity and multiplicity of deformities, surgical techniques and fixation methods continue to be developed to obtain better results. Recent studies have focused on correcting pronation of the first metatarsal as a way of correcting and equalizing the metatarsal sesamoid bones in a more horizontal and stable position, possibly minimizing the chance of recurrence of the deformity.

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.