Abstract
Purpose
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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
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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
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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
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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.
Introduction
Multiple treatment strategies exist for metatarsus primus varus and hallux valgus deformities. The Lapidus arthrodesis of the first metatarsocuneiform (MTC) joint is one of the most common surgical procedures, including the fusion of the second metatarsus and/or the second cuneiform bone. After being mentioned by Truslow (1) and Kleinberg (2), it was Lapidus who named this procedure in 1934 (3, 4). Since then, it has been widely used to treat arthritis, instability, and deformity of the fore- and midfoot. Various modifications have been described afterward by several authors, such as Butson or Giannestras (5, 6), aiming at achieving stability of the first MTC joint. Today, the modified Lapidus procedure is considered the arthrodesis of the MTC joint alone.
The most established method for the modified Lapidus procedure comprises a fusion of the first MTC joint using two crossed screws (Fig. 1). However, this procedure is known for its high non-union rate, up to 20% (7). Accordingly, in the past two decades, several implants and surgical techniques have been introduced (8), as shown in Figs. 2, 3, and 4. These include locking plates in a medial, plantar, and dorsal position (Figs. 2A, B, and C), interosseous or intramedullary stabilizers (Fig. 3), as well as the so-called memory staples (Fig. 4). All of them have been tested biomechanically to detect one another's superiority in improving patient safety by allowing early weight-bearing. Yet, it remains unknown which method is better or which material has the best outcomes. Rapid mobilization and return to everyday life after surgery are crucial for the patient to avoid complications such as secondary dislocation, deep-venous thrombosis, or non-union. In this light, evidence-based data could guide surgeons in understanding the biomechanical properties of the different options to choose the most suitable implant and provide the best fixation strategy.
The aim of this systematic review was to investigate the biomechanical characteristics of the different options proposed for the MTC joint arthrodesis. It represents an analysis of what has been tested in the literature in vitro on cadaveric models or artificial bone material. It gives evidence as to what implant is preferable from a biomechanical point of view. It focuses on the controversial debate of which implant provides more stability and safety to the patient during the healing process. Secondarily, it sheds light on what has been developed for this kind of surgery, overviewing and analyzing the results of the different studies.
Methods
This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA), a guideline that describes the items required for reporting in systematic reviews and meta-analyses (9, 10). Furthermore, specific suggestions for systematic reviews of diagnostic imaging studies were followed (11). A meta-analysis was not performed due to heterogeneity among the studies, a large number of different implants, and different study settings. A homogeneous testing protocol for the in vitro models in the different studies was unavailable.
Search strategy
Two co-authors (MR and MG) performed independently a comprehensive literature search of PubMed/Medline, Embase, Google Scholar, and the Cochrane library databases to find relevant published articles related to the review focus: biomechanical studies on the MTC joint fusion in the modified Lapidus technique. This search string based on a combination of keywords, Boolean operators, and truncations (*) was created and used: (A) ‘arthrodesis’ OR ‘fusion’ AND (B) ‘first metatarsocuneiform joint’ OR ‘first tarsometatarsal joint’ AND (C) ‘biomechanical cadaver study’ OR ‘biomechanical Sawbone study’ AND (D) ‘compression plates’ OR ‘crossed screws’ OR ‘locking plate’ OR ‘compression screw’. No beginning date limit nor language restrictions were used. The literature search was updated until September 2021. To expand the literature search, the references of the retrieved articles were also screened for possible additional records.
Sudy selection
All biomechanical studies comparing different types of MTC joint arthrodesis were included in this study. We selected both cadaveric studies and Sawbone® studies (polyurethane foam).
The exclusion criteria for the systematic review were: (a) articles not within the field of interest; (b) reviews, editorials, letters, comments, and conference proceedings; (c) all clinical studies; (d) biomechanical studies different from cadaver studies or Sawbone® studies; as well as (e) biomechanical studies comparing the modified Lapidus procedure with the classic Lapidus operation and trans cuneiform stabilization.
Two co-authors (MR and MG) independently screened the abstracts of the retrieved articles, applying the predefined inclusion and exclusion criteria. Subsequently, the researchers independently reviewed the selected articles' full text to assess their inclusion eligibility in the systematic review. Any disagreement was solved through a consensus among the researchers performed at the Department of Foot and Ankle Surgery at the Ospedale Civico di Lugano in September 2021 via ‘zoom©’ virtual communication platform.
Data extraction
For each selected article, information was collected on the basic study characteristics (authors, year of publication, country, and study design). Missing data were labeled as not reported (NR).
Quality assessment
The quality assessment of the studies included in this systematic review was critically appraised using the QUality Appraisal for Cadaveric Studies scale (QUACS scale). The scale consists of a checklist encompassing 13 items. Each is to be scored with either 0 (no/not stated) or 1 (yes/present) point. Points are only assigned if a criterion is met without any doubt. As one item (‘Applied statistics are appropriate’) is not always applicable, the maximum score is 12 or 13 depending on the study content. To enhance comparability of results, quality rating is expressed as a percentage value (reached score/maximum score (%)) (12).
Results
Literature search
Overall, 97 records were identified through the comprehensive literature search of the PubMed/Medline, Embase, Google Scholar, and Cochrane library databases. After screening 92 abstracts, 72 records were excluded because they were not in the field of interest, 48 being patient studies and not biomechanical studies, 20 being reviews/editorials/letters, and 4 being case reports or small case series to the modified Lapidus fusion. Twenty articles were selected, and their full text was retrieved. No additional records were found screening the references of these articles, whereas further three articles were excluded after the analysis of the full text. Despite being biomechanical cadaveric investigations, the studies of Ray et al. and Ehredt et al. were excluded because the classic Lapidus procedure was compared with the modified Lapidus operation (7, 13). Li & Myerson wrote a narrative review focusing on the evolution of the Lapidus procedure. The study did not focus on biomechanical analyses and was excluded (14). Therefore, 17 articles were included in the qualitative analysis (systematic review) (8, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29). The characteristics of the 17 studies included in the systematic review are presented in Tables 1 and 2.
The flowchart of the literature search is described in Fig. 5.
Basic study details and technical aspects.
Reference | Year | Country | DEXA | Operation technique | Material tested | Testing method | n | Plate position |
---|---|---|---|---|---|---|---|---|
Biomechanical cadaver study | ||||||||
Cohen et al. (15) | 2005 | USA | Yes | Four-point bending | 20 | Dorsal | ||
Crossed screws | 4.0 mm cannulated screws (DePuy) | |||||||
Locking plate, no compression screw | H-locking plate (Normed Medizin Technik) | |||||||
Gruber et al. (16) | 2008 | USA | Yes | Four-point bending | 20 | Dorsal | ||
Crossed screws | 4.0 mm cannulated screws (DePuy) | |||||||
Locking plate with compression screw | Lapidus plate and dorsal compression screw (Darco International) | |||||||
Scranton et al. (17) | 2009 | USA | No | Cantilever bending | 20 | Medial | ||
Crossed screws | 4.0 mm cannulated screws (Synthes) | |||||||
Locking plate with compression screw | Lapidus plate and plantar compression screw (Arthrex) | |||||||
Klos et al. (18) | 2010 | Switzerland | Yes | Four-point bending | 16 | Medial | ||
Crossed screws | 4.0 mm cannulated screws (Synthes) | |||||||
Locking plate with compression screw | X-plate and partially threaded compression screw (Synthes) | |||||||
Klos et al. (19) | 2011 | Switzerland | Yes | Cantilever bending | 12 | Dorsomedial vs plantar | ||
Locking plate medial with compression screw | H-shaped DARCO LPS locked plate (Wright Medical) + 4.0 mm compression screw | |||||||
Locking plate plantar with compression screw | DARCO plantar plate (Wright Medical) +4.0 mm compression screw | |||||||
Cottom et al. (20) | 2013 | USA | No | Cantilever bending | 20 | Medial | ||
Plate with plantar compression screw | Lapidus plate LPS (Arthrex) + compression screw from plantar | |||||||
Plate with interplate compression screw | Lapidus plate LPS (Arthrex) + compression screw in the plate | |||||||
Roth et al. (21) | 2014 | Germany | Yes | Four-point bending | 14 | Plantar | ||
Interosseous fixation | IO FIX® (Extr. Medical) + compression screw | |||||||
Plantar plate with compression screw | Plantar locking plate (Wright Medical) + compression screw (Königssee Implant) | |||||||
Baxter et al. (22) | 2014 | USA | Yes | Four-point bending | 20 | Dorsomedial | ||
Crossed screws | 4.0 mm cannulated screws (Synthes) | |||||||
Compression plate, no compression screw | Claw II® Polyaxial Compression Plating System (Wright Medical) | |||||||
Graham et al. (25) | 2016 | USA | No | Cantilever bending | 14 | Dorso- medial | ||
Open wedge plates | Osteo-WEDGE™ (GraMedica) | |||||||
Intact bone | Intact cadaver bone | |||||||
Cottom et al. (27) | 2017 | USA | NR | Cantilever bending | 16 | Medial vs plantar | ||
Plate with plantar compression screw | Lapidus plate LPS (Arthrex) + compression screw from plantar | |||||||
Plate with interplate compression screw | Lapidus plate plantar (Arthrex) + compression screw in the plate | |||||||
Biomechanical Sawbone® Study | ||||||||
Aiyer et al. (23) | 2015 | Australia | NR | Four-point bending | 10 | Dorsal | ||
Plate no compression screw | Claw II® (two hole) compression plate (Wright Medical) | |||||||
Crossed screws | 4.0 mm cannulated screws (Synthes) | |||||||
Single staple | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Two staples | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Russell et al. (24) | 2015 | Australia | NR | 3p-/4p-/cantilever | 10 | NR* | ||
Single staple | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Two staples | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Hoon et al. (30) | 2016 | Australia | NR | Four-point bending | 18 | NR** | ||
Plate no compression screw | Eight-hole quarter tubular plate (Synthes) | |||||||
Single staple | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Double staples | BME Speed™ Staple (Biomedical Enterprises) | |||||||
Knutsen et al. (26) | 2016 | USA | NR | Four-point and cantilever bending |
16 | Dorsal | ||
Crossed screws | 3.5 mm crossed lag screws (Synthes) | |||||||
Dorsal locking plate no compression screw | 2.7 mm 5-hole locking plate (Synthes) no compression screw | |||||||
Intraosseous fixation | IO FIX® (Extr. Medical) + plantar dorsal | |||||||
Intraosseous fixation | IO FIX® (Extr. Medical) + dorsal plantar | |||||||
Burchard et al. (28) | 2018 | Germany | NR | Cantilever bending | 9 | Plantar vs medial | ||
Plantar plate fixation | PEDUS L Plantar Plate® (Axomed) | |||||||
Medial plate fixation | Double Bridge Plate® (Königsee) | |||||||
Intraosseous fixation | IO FIX® (Extr. Medical) + dorsal plantar | |||||||
Dayton et al. (29) | 2018 | USA | NR | Cantilever bending | 20 | Dorsomedial vs plantar |
||
Plate dorsal-medial | PLANTAR-PYTHON Plate® (Treace Medical Concepts, Inc.) | |||||||
Plate medio-plantar | PLANTAR-PYTHON Plate® (Treace Medical Concepts, Inc.) | |||||||
Drummond et al. (8) | 2018 | USA | NR | Cantilever bending | 27 | Medial vs dorsal vs plantar | ||
Crossed screws with: | 4.0 mm cross. screws (Zimmer Biomet) | |||||||
Medial plate | Minifragment plates (Zimmer Biomet) | |||||||
Dorsal plate | Minifragment plates (Zimmer Biomet) | |||||||
Plantar plate | Minifragment Plates (Zimmer Biomet) |
*No plate has been tested; **No anatomic model: only synthetic bone block in testing protocol.
DEXA, dual energy X-ray absorptiometry (for meauring bone density); NR, not relevant.
Location of the companies mentioned are as follows - Arthrex: FL, USA; Wright Medical: MI, USA; Extremity Medical: NJ, USA; Königsee Implantate : Thuringen, Germany; GraMedica: MI, USA; Biomedical Enterprises Treace Medical Concepts: FL, USA; Zimmer: IN, USA; Axomed: Freiburg im Breisgau, Germany
Diagnostic accuracy data (presented as mean n/mm) of tested materials in the included studies. The order of the included studies is chronological.
Reference/ operation technique | Maximum load to failure | Initial stiffness of construct | Final stiffness of construct | Bending moment | Cycles to failure | Plantar gapping |
---|---|---|---|---|---|---|
Cohen et al. (15) | ||||||
Crossed screws | 140.1 | 83.1 | NR | NR | NR | NR |
Locking plate, no compression screw | 58.1 | 20 | NR | NR | NR | NR |
Gruber et al. (16) | ||||||
Crossed screws | 120.4 | 47.9 | NR | NR | NR | NR |
Locking plate with compression screw | 110.8 | 60 | NR | NR | NR | NR |
Scranton et al. (17) | ||||||
Crossed screws | 78.0 | NR | NR | 4.4 | NR | NR |
Locking plate with compression screw | 108.0 | NR | NR | 6.0 | NR | NR |
Klos et al. (18) | ||||||
Crossed screws | NR | 1.35† | NR | NR | 2512.5 | NR |
Locking plate with screws | NR | 1.45† | NR | NR | 3056.2 | NR |
Klos et al. (19) | ||||||
Locking plate medial plus compression screw | 110.0 | 30.70 | 7.0 | 5.3 | NR | NR |
Locking plate plantar plus compression screw | 192.6 | 33.9 | 24.8 | 9.1 | NR | NR |
Cottom et al. (20) | ||||||
Medial plate plus dorsal compression screw | 205.5 | NR | NR | 8.2 | NR | NR |
Plantar plate plus interplate compression screw | 383.2 | NR | NR | 15.3 | NR | NR |
Roth et al. (21) | ||||||
Plantar plate with compression screw | 167.1 | 131.0 | 188.1 | NR | 7517 | NR |
Interosseous fixation | 68.6 | 43.3 | 63.4 | NR | 2996 | NR |
Baxter et al. (22) | ||||||
Crossed screws | NR | NR | NR | NR | NR | 1.1 |
Plate, no compression screw | NR | NR | NR | NR | NR | 3.2 |
Aiyer et al. (23) | ||||||
Plate, no compression screw | 531.8 | 233.1 | NR | NR | NR | 7.0 |
Crossed screws | 1030.4 | 439.7 | NR | NR | NR | 1.71 |
Single staple | 501.8 | 214.2 | NR | NR | NR | 3.29 |
Two staples | 610.6 | 263 | NR | NR | NR | 4.62 |
Russell et al. (24) | ||||||
Single staple | NR | 217.1* | NR | NR | NR | 4.71** |
Two staples | NR | 250.7* | NR | NR | NR | 2.79** |
Graham et al. (25) | ||||||
Open wedge plates | 120 | 4.1 | NR | 5.6 | NR | NR |
Intact bone | 108 | 14.2 | NR | 6.1 | NR | NR |
Hoon et al. (30) | ||||||
Plate, no compression screw | 19.50 | 10.8 | NR | NR | NR | NR |
Single staple | 51.1 | 9.3 | NR | NR | NR | NR |
Double staples | 108.4 | 29.0 | NR | NR | NR | NR |
Knutsen et al. (26) | ||||||
Crossed screws | NR | NR | NR | NR | NR | NR |
Dorsal plate, no compression screw | NR | NR | NR | NR | NR | NR |
Intraosseous fixation | NR | NR | NR | NR | NR | NR |
Intraosseous fixation | NR | NR | NR | NR | NR | NR |
Cottom et al. (27) | ||||||
Medial plate with planto-dorsal compression screw | 255.4 | 25.7 | NR | 10.2 | NR | NR |
Plantar plate with interplate compression screw | 197.5 | 17.3 | NR | 7.9 | NR | NR |
Burchard et al. (28) | ||||||
Plantar plate fixation | 324 | NR | NR | NR | NR | 0.03 |
Medial plate | 377 | NR | NR | NR | NR | 0.06 |
Intraosseous fixation | 173 | NR | NR | NR | NR | 0.08 |
Dayton et al. (29) | ||||||
Plate dorsal-medial | 210.9 | NR | NR | NR | 102 | MR |
Plate medio-plantar | 247.3 | NR | NR | NR | 207 | NR |
Drummond et al. (8) | ||||||
Screws with medial plate | 260.4 | NR | NR | NR | NR | NR |
Screws with dorsal plate | 285 | NR | NR | NR | NR | NR |
Screws with plantar plate | 351.9 | 55.7 | NR | NR | NR | NR |
*Stiffness at 4pt dorsal bending; **Plantar gapping at a bending of 3 mm; †indicates n/degrees.
NR, not reported
Qualitative analysis (systematic review)
Basic study and patient characteristics
After screening the selected databases, 17 articles evaluating different types of the modified Lapidus arthrodesis of the first MTC joint in a biomechanical study model were included in the qualitative analysis (Table 1) (8, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29). Out of these, ten articles were cadaver studies (56.3%) and seven articles were polyurethane foam type IV Sawbone® studies (43.7%). All selected articles were published in the last 15 years (from 2005 to 2021) by research groups from different continents (America, Europe, and Australia), with studies from America being the most represented (56.3%). Three articles were from Australian research groups (18.7%), 2 from both Switzerland and Germany (12.5% each). All studies compared different types of MTC joint arthrodesis. Twelve articles investigated two different operation methods for MTC fusion (68.8%), four articles compared three different types of MTC joint fusion (25%), and one article compared four different materials for MTC joint arthrodesis (6.2%). In the 17 included studies, 13 different types of plates were investigated.
Biomechanical testing
Ten of the 17 studies were on cadaver bones, while the remaining seven studies were on artificial full bone models (Sawbone®). The artificial bone models consisted of full bone models without joints or ligaments, and the cadaveric bones were fresh-frozen specimens with full feet and exarticulated at the level of the ankle joint.
Crossed screws vs plate
Several studies presented a similar setting using a four-point bending test model (15, 16, 18, 22, 23), Scranton et al. (17) used a cantilever model, while Knutsen et al. (26) described both a four-point bending and a cantilever loading scenario.
Five of them tested the two crossed screws vs different kinds of plate fixation in a cadaver study setting (15, 16, 18, 22), while Aiyer et al. added alloy staples to the comparison and performed the study on artificial bone models (23).
Cohen et al. tested catastrophic failure and stiffness of construct. They found significantly higher load to failure and higher stiffness of construct in 4.0 mm cannulated crossed screws (DePuy) vs an angle stable H-locking plate (Normed Medizin Technik) (15).
Gruber et al. used the same test setting using 4.0 mm cannulated crossed screws (DePuy) vs a Lapidus plate (Darco International), adding a compression screw dorsally. This study's findings showed no significant difference between the two groups in terms of stiffness and catastrophic load to failure (16). They concluded that biomechanically a compression screw would improve stability.
Klos et al. tested 4.0 mm crossed screws (Synthes) and an X-shaped plate (Synthes). To simulate weight-bearing while walking, the testing protocol was modified to a cyclic loading model. Failure was defined as a gapping of the construct on the plantar side of 3 mm. The result showed a significantly higher number of cycles to failure in the plate with the dorsal compression screw group vs the two crossed screw group (18).
Baxter et al. compared the Claw II polyaxial compression plating system (Wright Medical) with two crossed cannulated screws finding the construct of two crossed lag screws to provide significantly greater stability than the plating construct (22).
Aiyer et al. compared the application of either one or two shape memory alloy staples BME Speed™ Staple (Biomedical Enterprises) with Claw II plate (Wright Medical) fixation and with two crossed screws (Synthes). They concluded that crossed screws have the greatest load to failure and less plantar gapping than the other constructs (23).
Concerning the cantilever model, Scranton et al. tested the Lapidus locking plate (Arthrex) with a plantar compression screw vs 4.0 mm crossed screws (Synthes), finding a higher load to failure and bending moment in the plate construct with compression screws (17).
Knutsen et al. compared four groups with three implants: 3.5 mm crossed lag screws (Synthes), 2.7 mm five-hole locking plate (Synthes), no compression screw, IO FIX® (Extremity Medical) + plantar–dorsal, and dorsal-plantar. Results showed significantly higher loading and less gapping at failure with crossed screws and intramedullary fixation when compared to plating without compression screw construct. The plantar position of the IO FIX® had biomechanical advantages (26).
Plate vs plate
Six studies compared different types of plate constructs. Half of the studies are cadaveric studies (20, 21, 28), while the other half was performed on artificial bone models (29, 30).
Klos et al. compared MTC arthrodesis medial plating vs plantar plating and found a significant benefit for medial plating in maximum load to failure, in the initial and final stiffness of construct, and in the bending moment (19).
In 2013, Cottom et al. compared the different possibilities of inserting the compression screw either medially through the plate or from the plantar side outside of the plate. The result was a significantly higher maximum load to failure with a plantar compression screw, with a greater bending moment. The positioning of the interfragmentary compression screw had an impact on the stability of the construct (20). In 2017, they demonstrated that even though there was no statistical difference between the two groups, they confirmed that the medial plate with a plantar compression screw had a higher stiffness, a higher load to failure, and a greater bending moment. In conclusion, the plate with an extra-plate compression screw was advantageous (27).
Burchard et al. compared a medial locking plate (Double Bridge Plate®) in combination with crossed screw, a plantar locking plate (PEDUS L Plantar Plate®) also in combination with crossed screw, and an intramedullary fixation device (IO FIX®). Results showed the greatest stiffness in plantar plating, whereas intramedullary fixation provided a higher compression force (28).
Dayton et al. compared the positioning of the Plantar-Python Plate® (Treace Medical Concepts, Inc.) in a dorsomedial position and in a dorsomedial-plantar position. The results showed a significantly greater number of cycles to failure and a significantly higher load to failure in the tension side dorsomedial-plantar model (29).
Drummond et al. focused their research in a cantilever setting with two crossed screws applicating minifragment plates (Zimmer Biomet) in different positions: dorsal, medial or plantar. They found superior results in plantar and medial plate positions (8).
Staples
Besides the study by Aiyer et al. in 2015 (23) mentioned above, two more studies comparing single to double stables were performed. Both were conducted on Sawbone®.
According to the biomechanical study of Russell et al., who compared the use of one vs two BME Speed™ Staples (Biomedical Enterprises), there was a significantly higher contact force with less plantar gapping in the group with two staples (24).
Hoon et al. found significantly higher mean compression loads and contact areas using two memory BME Speed™ Staples (Biomedical Enterprises) compared to one staple or a quarter tubular plate. They also add that the plate provided significantly higher stability (30).
Intramedullary implants
Compared to the abovementioned studies by Knutsen et al. (26) and Burchard et al. (28) , Roth et al. tested in a cadaveric study with a four-point bending setting the intramedullary implant IO Fix (Extremity Medical™) v a plantar plate (Wright Medical™) both with a compression screw (Königsee) and found the plate construct to be significantly stronger and stiffer (21).
Osteo-WEDGE(™) bone plate locking system
Graham et al. compared in a cadaveric study on full foot models the inherent strength of the first MTC joint and surrounding bones fixated with the osteo-WEDGE(™) bone plate locking system (OW) with that of intact specimens. The results were similar in strength, stiffness, and bending moment, and so they concluded that the mechanical strength of the OW is comparable to that of intact specimens (25).
To summarize, 17 studies were reported with a wide heterogeneity in their measures, without a homogeneous testing protocol. Testing methods ranged from cantilever, three-point bending to four-point bending model. Plates with compression screws were advantageous to the other surgical implants. Crossed screws are inferior to plates when a compression screw is used. Interosseous stabilators and memory alloy staples did not show advantages even though less studies are available. No meta-analysis was performed due to the wide heterogeneity of 13 different plates tested, different testing protocols, as well as different testing models.
Quality assessment (QUACS scale)
The quality appraisal of studies included in the systematic review is reported in Table 3 and briefly described below.
QUality appraisal for Cadaveric Studies scale (QUACS scale).
Reference | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | Total score | Reached / maximum score % |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Cohen et al. (15) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 10 | 76.9 |
Gruber et al. (16) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 9 | 69.2 |
Scranton et al. (17) | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 | 92.3 |
Klos et al. (18) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 84.6 |
Klos et al. (19) | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 | 92.3 |
Cottom et al. (20) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 84.6 |
Roth et al. (21) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 84.6 |
Baxter et al. (22) | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 | 92.3 |
Aiyer et al. (23) | 1 | 1 | 1 | * | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10 | 83.3* |
Russell et al. (24) | 1 | 1 | 1 | * | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10 | 83.3* |
Graham et al. (25) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 84.6 |
Hoon et al. (30) | 1 | 1 | 1 | * | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10 | 83.3* |
Knutsen et al. (26) | 1 | 1 | 1 | * | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 9 | 75* |
Cottom et al. (27) | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 84.6 |
Burchard et al. (28) | 1 | 1 | 1 | * | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 9 | 75* |
Dayton et al. (29) | 1 | 1 | 1 | * | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10 | 83.3* |
Drummond et al. (8) | 1 | 1 | 1 | * | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11 | 91.7* |
Overall percentage | 83.6 |
Items of QUACS scale: 1. Objective stated; 2. Basic information about sample is included; 3. Applied methods are described comprehensibly; 4. Study reports condition of the examined specimens; 5. Education of dissecting researchers is stated; 6. Findings are observed by more than one researcher; 7. Results presented thoroughly and precise; 8. Statistical methods appropriate; 9. Details about consistency of findings are given; 10. Photographs of the observations are included; 11. Study is discussed within the context of the current evidence; 12. Clinical implications of the results are discussed; 13. Limitations of the study are addressed. *Sawbone® Study. This question remains unanswered and uncounted. Percentage only on 12 items.
In the seven studies that used polyurethane foam specimen, the scale item 4 (’Study reports condition of the examined specimens’) remained unanswered and uncounted for the percentage as described in literature (12). Concerns in almost all studies except for one were in scale item 6 (’Findings are observed by more than one researcher’). Only Scranton et al. reported about more than one researcher observing the findings (17). In only three studies, the experience of the operating surgeon was stated (scale item 5) (8, 19, 22). The rest of the scale items were generally assessed with good quality. The overall percentage of the quality appraisal of the included studies was 83.6%.
Discussion
This systematic review investigated the different implants and techniques utilized for the arthrodesis of the first MTC joint.
The literature addressed this important topic through clinical trials, and a narrative review previously published but with a different focus. Li & Myerson reviewed the evolution of the Lapidus procedure. They gave an overview of the implants utilized but mainly discussed the indications and the techniques of the classic and the modified Lapidus fusion in general (14). Nowadays, evidence-based data are decisive in establishing a treatment protocol aimed at the patient’s safety and well-being. Thus, this study explored this topic with a systematic approach to highlight the evidence by summarizing the biomechanical studies for the MTC joint fusion with the modified Lapidus approach.
The Lapidus procedure has evolved through numerous iterations and advances in both techniques and implants, leading to improved outcomes and accelerated postoperative protocols (8). Yet, there is no agreement on the most suitable material and method of choice neither from a biomechanical nor from a clinical point of view. Gruber et al. found bone marrow density positively correlated with load to failure (16). In patients with good bone quality, screw-only constructs can still be considered the standard of care (8, 17). However, a non-union rate of up to 20% made it necessary to find new fixation methods (7).
A total of 17 studies were included in this systematic review with the aim of comparing the different fixation methods (8, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 15). This study aimed to summarize what has been tested in the literature from a biomechanical point of view.
Biomechanical testing method
From 2000 up to 2014, specimens were used in the retrieved articles. However, only six of the ten cadaveric bone studies did a DEXA testing. The lack of DEXA testing is considered as risk of bias. After 2014, mainly polyurethane type IV artificial models (Sawbone®) were used. Some publications validate polyurethane foam type IV models as comparable to cadaveric bone models (31, 32, 33, 34, 35). However, all validations were made on the tibia and femur. The small articulations of the foot, especially of the Lisfranc joint line, equilibrating mobility and stability, are complex. The use of artificial bone (Sawbone®) should be considered a risk of bias. Within the last two decades, testing methods and protocols were modified in the studies. The initial testing method measured the maximum load to failure and the mean stiffness of the construct. Failure was mainly defined as a gapping of more than 3 mm on the opposite side of where the bending force was applied. Also, catastrophic failure of the construct (e.g. material failure and bone fracture) was documented. Cohen et al., Gruber et al., Scranton et al., and Klos et al. (2010) tested their models with a static loading approach (15, 16, 17, 18). The following studies tested their models with a cyclic loading approach imitating real weight-bearing forces (8, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30).
Crossed screw fixation vs plating and different plate positions (Figs. 1 and 2)
Screw fixation has been the first and most commonly used technique of the modified Lapidus arthrodesis (18). There is a consensus that osteotomies, fractures, and arthrodeses heal with stability and compression forces. Cohen et al. tested two crossed screws vs plate fixation without using a compression screw and found a significantly higher load to failure in the crossed screw group (15). Gruber et al. found a higher initial stiffness utilizing a locking plate with a compression screw with a similar load to failure in both groups: crossed screws and plate with compression screw (16). Scranton et al. and Klos et al. found the locking plate with compression screw to be superior to the crossed screws technique (17, 18). Klos et al. tested, therefore, in a second biomechanical study, two different kinds of plate application (dorsomedial and plantar). Results showed superior stability in the plantar plate group (19). This result was confirmed by the studies of Dayton et al. and Drummond et al. (8, 29). Plantar application of plates or compression screws showed biomechanical advantages in the studies of Cottom et al. and Roth et al. (20, 21). Their works showed in different study settings superior load to failure in plantar applicated fixation methods in either screws or plates (20, 21).
This systematic review shows an advantage in plating vs crossed screws as a fixation method when a compression screw is used. Plantar application of the plate leads to a higher load to failure, a higher bending moment, and more cycles to failure. In actual surgical procedures, the anatomy of the insertion of the tibialis posterior tendon should be considered to guarantee the correct positioning of the plate, as described by Plaass et al. (36). Therefore, a safe and reliable method could be the dorsomedial application of the plate in combination with a compression screw (8, 15, 16, 17, 18, 19, 20, 21, 29). Evidence to this issue is lacking, and the literature shows clinical studies where plantar and dorsomedial application of the plates are feasible methods with union rates up to 98% and equal patients’ satisfaction (37, 38).
Cottom et al. tested a compression screw inside the plate vs a compression screw outside the plate in one study from the medial side and in a second study from the plantar side. The result was a higher load to failure, higher compression forces, and superior stiffness when the compression screw is positioned outside of the plate (20, 27).
Plate designs, varied from angle stable implants to non-angle stable implants, variable angle implants, 2.0 mm implants to 3.5 mm implants, and two-hole plates up to eight-hole plates. These aspects made it difficult to compare and summarize the plating group or to find differences.
Memory alloy staples vs crossed screws vs plating
Russell et al. found two staples superior to one staple (24). It seems to be clear that two implants give more stability than one implant. Also Aiyer et al. found two staples superior to one staple but inferior to a crossed screws construct and equal to the Claw II® (two-hole) compression plate (23). No compression screw was used with the plate, which seems to be an essential aspect for stability and compression forces. The Claw II® plate is a two-hole plate which appears to be weak when confronted to other implants. Hoon et al. compared a non-foot but bone block model of Sawbone®. They found the application of two staples superior to one staple and superior to an eight-hole quarter tubular plate (24). However, compression screw had not been used with the plate.
According to the investigations of Aiyer et al., Russel et al., and Hoon et al., using two shape-memory alloy staples gives superior stability to one staple. However, an advantage to plating constructs could not be found (23, 24, 30). Of the 17 included studies, only three investigated the use of shape-memory alloy staples (18.8%). Further investigations with standardized protocols are necessary to evaluate the actual benefit of these implants. In fact, the plate construct failure could be due to the design within these studies (e.g. no compression screw and weak implant).
Interosseous fixation vs plates vs crossed screws
Roth et al. tested the interosseous implant IO FIX® vs a locking compression plate with a compression screw and found the IO FIX® significantly inferior to the plate. All measured variables were in favor of the plate construct (21). Knutsen et al. tested the IO FIX® vs crossed screws and a locking plate without a compression screw. Interestingly, the interosseous fixation method turned out to be superior to the plate construct, and a plantar positioning of the IO FIX® had advantages compared to the dorsal application (26). However, the lack of a compression screw in or outside the plate construct could have influenced this outcome. Plantar positioning of the implants, either plates or IO FIX®, seemed to have biomechanical advantages. In the study of Burchard et al., the interosseous fixation method was confronted with two different plates (plantar and mediodorsal). The interosseous implant was inferior to both plate constructs (28). The interosseous fixation IO FIX® was tested by Roth et al., Knutsen et al., and Burchard et al. with an inferior result compared to other implants such as plates or crossed screws (21, 26, 28). Three of the 17 retrieved studies investigated the interosseous fixation method (18.8%).
This systematic review of the literature gives a complete overview of the materials tested in biomechanical studies for MTC joint arthrodesis. Despite the strengths of being a systematic review, some limitations and biases should be considered. This study was not registered in any registry. One limitation of all biomechanical studies is that in vivo bone differs from cadaveric and polyurethane type IV foam models. In several studies of the systematic review, Sawbone® models were used. This might have an impact on strength, stiffness, and stability when compared to real bone. A meta-analysis was not possible. There are no studies comparing the different types of plates, which are all considered and summarized as plate constructs. We found a great variety of plates among the different studies, yet none of these studies compared the 13 different plates. The choice of implant is an important risk of bias to the outcome of the different variables, especially compared to other materials and operation techniques.
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. If a plate is used, a compression screw gives additional stability and compression forces. 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.
Further studies with standardized protocols are needed for the evaluation of other implants, such as staples and interosseous/intramedullary implants.
Overall, this review suggests the biomechanical advantages of using a combination of locking plates with a compression screw.
ICMJE conflict of interest statement
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding
This study received no financial funding.
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