A Comparative Study of Tensile Strength of Three Operative Fixation Techniques for Metacarpal Shaft Fractures in Adults: A Cadaver Study

Metacarpal and Phalangeal Nonunions

The majority of phalangeal and metacarpal fractures will proceed to union when appropriately treated. However, when a nonunion does occur, it can lead to significant functional impairment for patients and societal costs. Operative intervention is typically required in these cases, but the technique can vary depending on each individual patient scenario. This article provides an overview of nonunions of the metacarpals and phalanges in the hand, including incidence, risk factors, current treatment options, and postoperative care.

Intramedullary Metacarpal Fracture Fixation: A Biomechanical Study of Screw Diameter and Comparison With Intramedullary Wire Stabilization

PURPOSE

Interest in intramedullary metacarpal fracture fixation (IMFF) with screws is increasing. However, the optimal screw diameter for fracture fixation is not yet established. In theory, larger screws should be more stable, but there is concern about long-term sequelae of larger metacarpal head defects and extensor mechanism injury created during insertion as well as implant cost. Therefore, the purpose of this study was to compare different diameter screws for IMFF to a popular and more cost-effective alternative of intramedullary wiring.

METHODS

Thirty-two cadaveric metacarpals were used in a transverse metacarpal shaft fracture model. Treatment groups consisted of IMFF with 3.0 × 60 mm, 3.5 x 60 mm, and 4.5 x 60 mm screws as well as 4 1.1-mm intramedullary wires. Cyclic cantilever bending was performed with the metacarpals mounted at 45° to simulate physiologic loading. Cyclical loading at 10, 20, and 30 N was performed to determine fracture displacement, stiffness, and ultimate force.

RESULTS

At 10, 20, and 30 N of cyclical loading, all screw diameters tested provided similar stability as measured by fracture displacement and were superior to the wire group. However, ultimate force under load to failure testing was similar between the 3.5- and 4.5-mm screws and superior to 3.0-mm screws and wires.

CONCLUSIONS

For IMFF, 3.0, 3.5, and 4.5-mm diameter screws provide adequate stability for early active motion and are superior to wires. When comparing the different screw diameters, 3.5- and 4.5-mm diameter screws offer similar construct stability and strength superior to the 3.0-mm diameter screw. Therefore, to minimize metacarpal head morbidity, smaller screw diameters may be preferable.

CLINICAL RELEVANCE

This study suggests that IMFF with screws is biomechanically superior to wires in cantilever bending strength in the transverse fracture model. However, smaller screws may be sufficient to permit early active motion while minimizing metacarpal head morbidity.

Ideal Length and Diameter for Intramedullary Screw Fixation of Metacarpal Fractures: A Biomechanical Study

Purpose

This biomechanical study evaluated the effect of intramedullary screw diameter and length relative to 3-point bending force and torsional force when used to stabilize metacarpal shaft fractures.

Methods

Transverse osteotomies were made in the proximal metacarpal shaft in 36 middle finger metacarpal fourth-generation composite Sawbones. To compare screw diameters, antegrade intramedullary screws of 30-mm length were placed in 6 metacarpals, which included 4.7-mm Acutrak 2, Standard Acutrak 2 (4.0 mm), and Mini-Acutrak 2 (3.5 mm) screws. To compare screw lengths, metacarpals were fixated with Standard Acutrak 2 screws of 26, 30, or 34 mm in length, with screw tips bypassing the osteotomy by 6, 10, or 14 mm, respectively. A 6 degrees of freedom robot was used for torsional and 3-point bending testing.

Results

Increasing screw diameter demonstrated significant differences in both 3-point bending and torsional strengths. Maximum torsional loads were 69 Ncm (4.7-mm Acutrak 2), 45 Ncm (Standard Acutrak 2), and 27 Ncm (Mini-Acutrak 2) (P < .05). Loads to failure in the 3-point bending tests were 916 N (4.7-mm Acutrak 2), 713 N (Standard Acutrak 2), and 284 N (Mini-Acutrak 2) (P < .05). Differing screw lengths demonstrated significant differences with maximum torsional loads when comparing the 26-mm screws (22 Ncm) with 30- and 34-mm screws (45 and 55 Ncm, respectively) (P < .05). The 3-point dorsal bending strengths were significantly different between the 26-mm screws (320 N) and 30- and 34-mm screws (713 N and 702 N, respectively) (P < .05).

Conclusions

The results demonstrated significantly higher torsional strength and resistance to 3-point bending with larger intramedullary screw diameters. Further, when selecting the intramedullary screw length, the screw tip should pass at least 10 mm beyond the fracture.

Clinical Relevance

This study provided biomechanical evidence to guide surgeons in selecting intramedullary screw diameter and length for treating metacarpal fractures.

Retrograde Intramedullary Screw Fixation for Metacarpal Fractures: A Systematic Review

Common forms of fixation of metacarpal fractures have historically included percutaneous Kirschner wire fixation, plates and screws, and, more recently, intramedullary screw fixation. Retrograde intramedullary screws (RISs) are a novel modality first described 10 years ago. The purpose of this review is to critically evaluate the published literature assessing outcomes of RIS fixation for metacarpal fractures and create a complication profile for this novel technique. A comprehensive literature search was performed using electronic databases for both clinical and biomechanical studies in relation to RIS fixation published from 2000 to 2020. A total of 19 studies (13 clinical and 6 biomechanical) met the inclusion criteria. The clinical studies examined 603 metacarpal fractures and demonstrated adequate functional outcomes in terms of grip strength, total active motion, and time to return to work. The biomechanical studies examined 80 metacarpal fractures, finding that load to failure in RISs was often equal to or higher than Kirschner wires but less than plate and screws. The complication rate in reviewed studies was 2.8%, with the most prevalent complications being stiffness and extension lag. RIS use in metacarpal fractures appears to provide adequate stability with satisfactory clinical outcomes and minimal complications, although more high-quality studies are needed to fully examine this modality.

Threaded intramedullary headless nail fixation for fractures requiring carpometacarpal stabilization

Carpometacarpal (CMC) fracture-dislocations are uncommon hand injuries, with few studies available regarding their treatment. The current operative treatment options include fixation with K-wires, mini-screws, or plates, though there is no standardized approach because of varying injury patterns and complications associated with each device. The INnate™ threaded intramedullary nail is a relatively novel treatment option that has shown promise in metacarpal fracture fixation by facilitating faster mobilization and recovery with enhanced rotational stability and no compression to prevent fracture displacement and shortening. This study assesses the efficacy of the INnate™ nail for fixation of CMC fracture-dislocations of the second through fifth joints. Nine patients with fourteen CMC fracture-dislocations treated with the INnate™ nail at the University Medical Center between 2019 and 2021 were enrolled in the study. We evaluated postoperative outcomes in terms of pain, total active range of motion (TAM), and return to normal activities. Of the nine patients, seven returned for follow-up. The average time to radiographic union was 11.5 weeks. At final follow-up, no patient reported pain (n = 6). Four patients had 100% TAM, 1 had 95% TAM, and 1 had 25% TAM. The average percentage of normal activity resumed was 84.0% (n = 5). No significant complications were reported. One patient had a dorsal spanning plate; hence, we were unable to record outcomes measures regarding the CMC injury. An additional patient had diminished ROM of the injured hand, but his last follow-up was only 1 month postop. Our pilot data overall suggest that the INnate™ threaded intramedullary nail has the potential to improve treatment algorithms for CMC fracture-dislocations.

Biomechanical comparison of intramedullary screw fixation, dorsal plating and K-wire fixation for stable metacarpal shaft fractures

We compared four methods of metacarpal shaft fixation: 2.2 mm intramedullary headless compression screw; 3.0 mm intramedullary headless compression screw; intramedullary K-wire fixation; and dorsal plate fixation. Transverse mid-diaphyseal fractures were created in 64 metacarpal sawbones and were assigned into four groups. Peak load to failure and stiffness were measured in cantilever bending and torsion. We found that dorsal plating had the highest peak load to failure. However, initial bending stiffness of the 3.0 mm intramedullary headless compression screw was higher than that of the dorsal plates. In torsion testing, dorsal plating had the highest peak torque, but there was no significant difference in torsional stiffness between the plate and intramedullary headless compression screw constructs. We concluded that intramedullary headless compression screw fixation is biomechanically superior to K-wires in cantilever bending and torsion; however, it is less stable than dorsal plating. In our study, the initial stability provided by K-wire fixation was sufficient to cope with expected loads in the early rehabilitation period, whereas dorsal plates and IHCS constructs provided stability far in excess of what is required.

Factors affecting healing following percutaneous intramedullary fixation of metacarpal fractures

Although percutaneous intramedullary nailing of metacarpal fractures is a straightforward and reliable technique, it is not without complications, and patients experience different outcomes. This study analyzed factors affecting fracture healing time and complication rates in patients who underwent percutaneous intramedullary fixation of metacarpal fractures.This study was a retrospective review of the 25 patients who underwent retrograde percutaneous Kirschner wire (K-wire) nailing for fracture of the metacarpal shaft or neck at a military hospital between May 2016 and October 2018. Correlation study and multiple regression analysis were performed to evaluate variables (age, smoking history in pack-years, body-mass index, fracture site, number of K-wires used) that affect time to bone union. Clinical features of patients with metacarpal neck fractures and those with metacarpal shaft fractures were also compared.The metacarpal shaft fractures (as opposed to metacarpal neck fractures) and higher number of K-wire used were associated with longer time to bone union. Mean union time was significantly longer for metacarpal shaft fracture (8.6 weeks) than for metacarpal neck fracture (6.1 weeks) and for patients who received more K-wires than for those who received less (regression coefficient 1.307). One patient suffered fixation failure and required revision operation, and another experienced superficial infection which was treated with intravenous antibiotics.Percutaneous intramedullary nailing is an effective technique for metacarpal fractures, but fracture site and number of K-wire used affect time to achieve bone union.

How to Manage Complications Related to the Use of Intramedullary Screws in Metacarpal Fractures: Case Series

The use of intramedullary screws has been increasing among hand surgeons in cases of metacarpal fractures due to their low morbidity, and because they minimize incisions and dissection, and require less tissue manipulation and deperiostization. However, there are few published articles on the complications that arise from its use. Therefore, the purpose of the current study is to present a series of cases of complications following the use of intramedullary screws in metacarpal fractures that required surgical intervention, and to describe the surgical technique used to solve them .

Methods We performed a retrospective multicenter study in which we reviewed the clinical history, surgical descriptions and radiographs of the patients submitted to fixation of intramedullary compression screws for metacarpal fractures. We defined as complications infection, lesion to the extensor apparatus, bending of the implant, loss of reduction, hardware failure, malrotation, and non-union.

Results Out of a total of 45 patients, we reported 3 cases of complication: 1 patient with loss of reduction, and 2 patients with bending of the implant. In the three cases, the screw was removed without complications, and the focus of the fracture was stabilized.

Conclusion Intramedullary fixation with compression screws is increasingly being used for metacarpal fractures, with reports of low rates of complications. In the series of cases herein reported, the complications were solved without difficulty, and the patients showed a good recovery in hand function in the follow-up. Knowledge of the possible complications and their management enables us to provide more safety to the patient at the time of choosing this technique.

Long-Term Functional Results of Intra- and Extra-Articular Hand Fractures Treatment With Titanium Miniature Plates and Screws With Minimum Follow-Up of 24 Months

Introduction

The purpose of this study was to evaluate the long-term outcome of an extended range of hand fractures treated with titanium, low profile plates, and screws.

Materials and methods

This retrospective study included adult patients with at least one phalangeal and/or metacarpal fracture, treated with mini titanium plates and screws, between 2004-2016, in a single trauma center, that were followed-up for at least 24 months and with complete, intact medical records.

Results

90 patients (79 men and 11 women) with 114 hand (46 phalangeal, 68 metacarpal) fractures fulfilled the inclusion criteria. Thirty-two fractures were open (28.07%), 27 were intra-articular (23.68%), and 12 were both open and intra-articular fractures. The mean age of the patients was 36.02 years (range 17-75). Mean follow-up was 95.3 months (range 24 to 138). Open fractures had a reduced mean grip strength and total active motion. No difference was observed between intra-articular and extra-articular fractures (for grip strength and total active motion). Predictors of the final outcome included the severity of the initial injury (open vs closed) and not the anatomic location (intra- or extra-articular, metacarpal, or phalangeal) of the fracture.

Conclusions

Low-profile plates and screws can successfully be used to establish union and restore the alignment of the fractured bone while achieving a satisfactory clinical outcome, even in cases of open or intra-articular fractures.

Effect of a figure-of-eight cerclage wire with two Kirschner wires on fixation strength for transverse metacarpal shaft fractures: an in vitro study with artificial bone

BACKGROUND

Metacarpal shaft fractures are a common type of hand fracture. Despite providing strong fixation strength, plate fixation has numerous shortcomings. Concerning internal fixation with Kirschner wires (K-wires), although this approach is frequently used to treat metacarpal shaft fractures, the lack of functional stability may result in fixation failure.

OBJECTIVE

To evaluate the effect of figure-of-eight cerclage wire on fixation for transverse metacarpal shaft fractures using two K-wires.

MATERIALS AND METHODS

We used a saw blade to create transverse metacarpal shaft fractures in 14 fourth-generation artificial third metacarpal bones (Sawbones, Vashon, WA, USA), which were assigned to groups undergoing fixation with two K-wires (KP) or with two K-wires and figure-of-eight cerclage wire (KP&F8). All specimens were subjected to material testing, specifically cantilever bending tests. The maximum fracture force and stiffness of the two fixation types were determined on the basis of the force-displacement data. The Mann-Whitney U test was used to compare between-group differences in maximum fracture force and stiffness.

RESULTS

The maximum fracture force of the KP group (median ± interquartile range = 97.30 ± 29.70 N) was significantly lower than that of the KP&F8 group (153.2 ± 69.50 N, p < 0.05; Figure 5a), with the median of the KP&F8 group exceeding that of the KP group by 57.5%. Similarly, stiffness was significantly lower in the KP group (18.14 ± 9.84 N/mm) than in the KP&F8 group (38.25 ± 23.49 N/mm; p < 0.05; Figure 5b), with the median of the KP&F8 group exceeding that of the KP group by 110.9%.

CONCLUSION

The incorporation of a figure-of-eight cerclage wire increased the maximum fracture force and stiffness by 57.5 and 110.9%, respectively, compared with those achieved in standard two K-wire fixation. Therefore, hand surgeons are advised to consider the proposed approach to increase fixation strength.

Metacarpal shaft fixation: a biomechanical comparison of dorsal plating, lag screws, and headless compression screws

Background

Metacarpal shaft fractures are common and can be treated nonoperatively. Shortening, angulation, and rotational deformity are indications for surgical treatment. Various forms of treatment with advantages and disadvantages have been documented. The purpose of the study was to determine the stability of fracture fixation with intramedullary headless compression screws in two types of metacarpal shaft fractures and compare them to other common forms of rigid fixation: dorsal plating and lag screw fixation. It was hypothesized that headless compression screws would demonstrate a biomechanical stronger construct.

Methods

Five matched paired hands (age 60.9 ± 4.6 years), utilizing non-thumb metacarpals, were used for comparative fixation in two fracture types created by an osteotomy. In transverse diaphyseal fractures, fixation by headless compression screws (n = 7) and plating (n = 8) were compared. In long oblique diaphyseal fractures, headless compression screws (n = 8) were compared with plating (n = 8) and lag screws (n = 7). Testing was performed using an MTS frame producing an apex dorsal, three point bending force. Peak load to failure and stiffness were calculated from the load-displacement curve generated.

Results

For transverse fractures, headless compression screws had a significantly higher stiffness and peak load to failure, means 249.4 N/mm and 584.8 N, than plates, means 129.02 N/mm and 303.9 N (both p < 0.001). For long oblique fractures, stiffness and peak load to failure for headless compression screws were means 209 N/mm and 758.4 N, for plates 258.7 N/mm and 518.5 N, and for lag screws 172.18 N/mm and 234.11 N. There was significance in peak load to failure for headless compression screws vs plates (p = 0.023), headless compression screws vs lag screws (p < 0.001), and plates vs lag screws (p = 0.009). There was no significant difference in stiffness between groups.

Conclusion

Intramedullary fixation of diaphyseal metacarpal fractures with a headless compression screw provides excellent biomechanical stability. Coupled with lower risks for adverse effects, headless compression screws may be a preferable option for those requiring rapid return to sport or work.

Level of evidence

Basic Science Study, Biomechanics.

Intramedullary screw fixation for metacarpal shaft fractures: a biomechanical human cadaver study

Intramedullary cannulated compression screws have been introduced for the fixation of unstable metacarpal fractures. In the present study, this technique was compared with dorsal compression plating to evaluate its biomechanical performance in stabilizing metacarpal shaft fractures. In a first set of experiments, the biomechanical characteristics of the screws were analysed in an artificial bone model. In subsequent experiments, midshaft osteotomies were performed in human cadaver metacarpals, followed by plating or intramedullary screw osteosynthesis. The metacarpals were tested to failure in cantilever bending, following a stepwise increasing cyclic loading protocol. We found a significantly lower load at failure and a significantly lower number of cycles to failure in the intramedullary screw group, but both methods offered sufficient stability under these loads. With reference to published loads on the metacarpals during use of the hand, we conclude that intramedullary osteosynthesis yields sufficient strength and stiffness for early active motion. A difference in its fixation stability is noted compared with plate fixation, which may not be clinically relevant.

Cartilage and extensor tendon defects after headless compression screw fixation of phalangeal and metacarpal fractures

Osteosynthesis of metacarpal and phalangeal fractures with headless compression screws leads to a defect in the articular surface and possibly damage to the extensor tendons. This study aimed to quantify the articular surface defect and extensor tendon injuries after implant placement in cadaveric hands. Defect size was assessed with computed tomography. Extensor tendon injuries were assessed by direct visualization and measurement after dissection. In the middle phalanx, the defect size in relation to the joint surface was significantly smaller after anterograde screw placement when compared with retrograde placement. Also, a mini-open approach was found to cause significantly less tendon injury than a percutaneous approach, but there was no difference in tendon damage between retrograde and antegrade screw insertion into the middle phalanx.

Comparison of low-profile locking plate fixation versus antegrade intramedullary nailing for unstable metacarpal shaft fractures--A prospective comparative study

BACKGROUND

The purpose of this study was to compare the effectiveness of mini-open antegrade intramedullary nailing (AIN) and open reduction and internal fixation (ORIF) using the low-profile locking plate for angulated metacarpal shaft fractures, through prospective comparative trial.

METHODS

Group 1 (mini-open AIN; 40 patients) and the other consecutive patients in group 2 (locking plate; 35 patients) who met our inclusion/exclusion criteria were investigated between January 2010 and December 2016. We compared radiological findings (e.g., union and residual angulation or shortening); clinical conditions (e.g., pain, measured on a visual analog scale (VAS), and Disabilities of the Arm, Shoulder, and Hand (DASH) scores); active range of motion (ROM); and grip strength.

RESULTS

Union was achieved in both groups without any major complications. The final angulation measurements were not significantly different (p = 0.402). The final VAS scores were not different (p = 0.868); however, the final DASH score was better in group 1 than in group 2 (p = 0.034). The plates were removed in 14 patients at 9.6 months postoperatively for various reasons. Mean ROM at the time of hardware removal in these 14 patients was significantly lower compared with the final ROM in groups 1 and 2 (non-removal patients). Final grip strengths recovered significantly more in group 1 than in group 2 (p = 0.029). Extension lag was found in four patients in group 2, and the mean amount was 15°; however, it was resolved by tenolysis during hardware removal.

CONCLUSIONS

Both mini-open AIN and low-profile plate fixation are excellent options for metacarpal shaft fractures without significant radiological or clinical problems; however, some clinical outcomes evaluated at least 2 years postoperatively, such as DASH scores and grip strength, were better in the AIN group than in the locking plate group. Plate removal was performed under anesthesia in some patients in the plate group for various reasons, and this may have caused the small differences in the final outcomes evaluated 2 years after surgery.