Biomechanical evaluation of mini-fragment hardware for supination external rotation fractures of the distal fibula

Comparison of elective implant removal and complication rates between mini and small fragment implants for lateral malleolar fixation

INTRODUCTION

Implant removal after open reduction and internal fixation (ORIF) of ankle fractures is common. Mini-fragment implants have gained popularity for their smaller size, with studies showing similar load to failure to small-fragment implants. We hypothesized mini-fragment implant use for ORIF of the distal fibula is associated with a lower implant removal rate and without an increase in implant failure.

METHODS

In this retrospective review study at two level-one trauma centers, adult patients (>18 years) with a lateral malleolar or bimalleolar fracture were included. Chart review was performed to determine if patients received ORIF of the distal fibula with mini-fragment implants or small-fragment implants. The primary outcome was elective implant removal of the fibular plate. Secondary outcomes included complications requiring reoperation.

RESULTS

Five-hundred and five patients were included with a mean age of 50.6 ± 17.8 years old with a mean follow-up of was 75.7 ± 61.0 weeks. Sixty patients (11.9 %) received mini-fragment fixation. The rate of elective distal fibula implant removal for the mini-fragment group was 8.3 % (5 of 60) compared to 10.8 % (48 of 445) in the small-fragment group (p = .66). The complication rate was 6.7 % (4 of 60) for the mini fragment group versus 6.5 % (29 of 445) for the small fragment group (p = 1.00). Logistic regression demonstrated that each additional week of follow-up increased the implant removal rate with the observed odd ratio (OR) of 1.007 (95 % CI 1.002-1.012).

CONCLUSION

Elective implant removal rates and complications requiring reoperation were similar between mini-fragment and small-fragment fixation of distal fibula fractures. The hypothetical benefit of low-profile mini-fragment implants should be balanced with the higher implant cost.

Minifragment plating of the fibula in unstable ankle fractures

INTRODUCTION

Only 6.4-17% of the load is transmitted through the fibula when weight-bearing. Plate fixation of distal fibular fractures using minifragments (≤ 2.8 mm) could lead to similar reduction with less implant removal (IR) rates, compared to small-fragment plates (3.5 mm). We hypothesized that the use of minifragment plates is at least similar in unscheduled secondary surgery.

MATERIALS AND METHODS

In this retrospective cohort study, all patients with surgically treated distal fibular fractures between October 2015 and March 2021 were included. Patients treated with plate fixation using minifragments and patients treated with small-fragment plates were compared regarding the following outcomes: secondary dislocation, malreduction, implant malposition, nonunion, surgical site infections (SSI) and IR.

RESULTS

Sixty-five patients (54.2%) received a minifragment implant (≤ 2.8 mm) and 55 patients (45.8%) received a small-fragment implant (3.5 mm). There were no patients needing secondary surgery in the minifragment group compared to 9 patients following fixation using small-fragment implants (3 with secondary dislocation, 5 with malreduction and 1 with malposition, p = 0.001). SSI rates were 3.1% for minifragment and 9.1% for small-fragment implants (p = 0.161). Implant removal was performed significantly less often following use of minifragment implants (17.8% and 53.2%, p < 0.001).

CONCLUSIONS

In this cohort, minifragment plate fixation for distal fibular fractures is an adequate fixation method offering stable fixation with significant lower need for implant removal and comparable complications to small-fragment plates, although an adequately powered randomized controlled study is needed for implementation in a clinical setting.

LEVEL OF EVIDENCE

Therapeutic, III.

Screw-only fibular construct for Weber B ankle fractures: A retrospective clinical and cost comparison to assess feasibility for resource-limited settings

INTRODUCTION

Ankle fractures are one of the most common injuries sustained worldwide, with the majority being isolated lateral malleolus fractures. The majority of the world's population live in Low and Middle Income Countries (LMIC), where implant cost may limit surgical treatment of ankle fractures. We investigate if Weber B ankle fractures could be effectively treated with a lower-cost technique using two screws between the fibula and the tibia to neutralize an interfragmentary lag screw.

METHODS

After IRB approval, consecutive patients from January 1, 2020 to December 31, 2020 with Weber-B ankle fractures were treated using AO technique (AOT) with plate osteosynthesis neutralizing an interfragmentary screw. Syndesmotic injuries, as well as injuries to the medial malleolus or foot were treated according to the surgeon's preferences. From January 1, 2021 to December 31, 2021 these injuries were treated with a screw-only technique (SOT) with two fibula pro tibia screws to neutralize an interfragmentary screw. Patient demographics including age, sex, BMI, smoking status, associated rheumatoid arthritis, and associated diabetes mellitus were recorded. The primary outcome variable was a stable radiographic mortise at six weeks post-surgery, secondary outcome variables included clinical union, infection, hardware removal, and implant cost for lateral malleolar fixation charged to the hospital.

RESULTS

Seventeen AOT and 10 SOT constructs were included. Demographic characteristics were similar between groups. All fractures maintained a stable mortise with clinical union at 6 weeks without infection. There was a statistically significant difference in hardware removal (17.6% AOT, 50% SOT, p = 0.012). The average implant cost to the hospital of the lateral malleolar fixation was significantly less in the SOT group ($592 (SD $229)), compared to the AOT group ($1,949.97 (SD $562)), (p < 0.0001).

CONCLUSION

We introduce proof of concept of a novel lower-cost fixation strategy for Weber B ankle fractures that maintained a stable mortise with clinical union at six weeks post-surgery. However, there was a significantly higher rate of hardware removal following fixation with a screw-only construct.

The influence of mini-fragment plates on the mechanical properties of long-bone plate fixation

Objective:

Mini-fragment plates (MFPs) are increasingly used in fracture surgery to provide provisional fixation. After definitive fixation, the surgeon decides whether to remove the plates or leave them in place as additional fixation, based on the perceived biomechanical influence of the MFP. However, there are no current biomechanical studies to guide this decision. Therefore, the purpose of this study was to evaluate the influence of MFPs on the four-point bending and torsional stiffness of long bone transverse and simple wedge fracture fixation constructs.

Methods:

Fourth-generation composite bone cylinders were cut to produce transverse (AO-OTA classification 12-A3) and simple wedge (AO-OTA classification 12-B2) fracture models. The specimens were fixed using a low-contact dynamic compression plate (LC-DCP) and MFPs. Specimens were tested in four-point bending and torsion utilizing 3 different MFP orientations.

Results:

No statistically significant differences in bending stiffness were found between control and MFP groups for transverse fracture constructs. MFPs significantly increased the bending stiffness for wedge fracture constructs under certain loading conditions. This increase was observed when MFPs were positioned both orthogonal (85.1% increase, P = .034) and opposite (848.2% increase, P < .001) to the LC-DCP. MFPs significantly increased the torsional stiffness for both transverse and wedge fracture constructs when MFPs were positioned both orthogonal (transverse: 27.7% increase, wedge: 16.7% increase) and opposite (transverse: 28.4%, wedge: 24.2% increase) to the LC-DCP.

Conclusions:

Our results indicate that including MFPs in definitive fixation can increase the bending and torsional stiffness of a long-bone fracture fixation construct. This suggests that the biomechanical influence of MFPs should be considered. However, clinical studies will be required to test the applicability of these findings to the clinical setting.

Management of Isolated Lateral Malleolus Fractures

Isolated lateral malleolus fractures represent one of the most common injuries encountered by orthopaedic surgeons. Nevertheless, appropriate diagnosis and management of these injuries are not clearly understood. Ankle stability is maintained by ligamentous and bony anatomy. The deep deltoid ligament is considered the primary stabilizer of the ankle. In the setting of an isolated lateral malleolus fracture, identifying injury to this ligament and associated ankle instability influences management. The most effective methods for assessing tibiotalar instability include stress and weight-bearing radiographs. Clinical examination findings are important but less reliable. Advanced imaging may not be accurate for guiding management. If the ankle is stable, nonsurgical management produces excellent outcomes. In the case that clinical/radiographic findings are indicative of ankle instability, surgical fixation options include lateral or posterolateral plating or intramedullary fixation. Locking plates and small or minifragment fixation are important adjuncts for the surgeon to consider based on individual patient needs.

Implant Failure Rates and Cost Analysis of Contoured Locking Versus Conventional Plate Fixation of Distal Fibula Fractures

The authors analyzed 330 consecutive Weber B distal fibula fractures that occurred during a 3-year period and were treated with either a contoured locking plate or a conventional one-third tubular plate to compare the cost and failure rates of the 2 constructs. The primary outcomes were failure of the distal fibular implant and loss of reduction. Secondary outcomes were surgical wound infection requiring surgical debridement and/or removal of the fibular implant, and removal of the fibular plate for persistent implant-related symptoms. No failure of the fibular plates or distal fibular fixation occurred in either group. A total of 5 patients required surgical revision of syndesmotic fixation within 4 weeks of the index surgery. Of these patients, 1 was in the contoured locking plate group and 4 were in the one-third tubular plate group (P=.610). The rate of deep infection requiring surgical debridement and/or implant removal was 6.2% in the contoured locking plate group and 1.4% in the one-third tubular plate group (P=.017). The rate of lateral implant removal for either infection or symptomatic implant was 9.3% in the contoured locking plate group and 2.3% in the one-third tubular plate group (P=.005). A typical contoured locking plate construct costs $800 more than a comparable one-third tubular plate construct. Based on a calculated estimate of 60,000 locking plates used annually in the United States, this difference translates to a potential avoided annual cost of $50 million nationally. This study demonstrates that it is possible to treat Weber B distal fibula fractures with one-third tubular plates at a substantially lower cost than that of contoured locking plates without increasing complications. [Orthopedics. 2017; 40(6):e1024-e1029.].

Reducing Fracture Risk Adjacent to a Plate With an Angulated Locked End Screw

OBJECTIVES

Locking screws often are used in the treatment of osteoporotic fractures. Studies show that locking screws can increase bone stresses at the plate end, which increases the possibility of peri-implant fracture. This study evaluates whether the technique used to insert the end screw is related to the fracture tolerance adjacent to the plate.

METHODS

Twelve groups of plate constructs were evaluated using a fibular diaphyseal surrogate with mechanical properties similar to osteoporotic bone. All inboard screws were nonlocked with only the end screw fixation differing among groups. The end screws were inserted either perpendicularly to the plate or at an angle of 30 degrees for 6- and 12-hole plates. For both orientations, the end screws were inserted nonlocked, locked, or by a locked overdrilling technique, resulting in 6 groups per plate length. The perpendicular nonlocked screws represented a control group. The constructs were tested to failure in 4-point bending to determine peak load, failure energy, and stiffness.

RESULTS

All constructs failed by peri-implant fracture along a plane through the 2 cortical holes of the end screw. Compared with the control group, an angulated locked screw at the plate end significantly increased the peak bending moment and energy required to produce a fracture for both plate lengths (6-hole, P = 0.008, P < 0.001; 12-hole, P = 0.006, P < 0.001).

CONCLUSIONS

The use of an angulated locked end screw may enhance the resistance of osteoporotic bone to peri-implant fractures caused by bending forces.

Clinical Comparison of Minifragment Plates Versus Conventional Semitubular Plates for Fixation of Distal Fibula Fractures

BACKGROUND

Although operative stabilization of unstable distal fibula fractures is frequently performed and discussed, the ideal implant and technique for these injuries is still debated.

QUESTIONS/PURPOSES

The purpose of this study was to determine if minifragment plating of distal fibula fractures would clinically provide equivalent fixation and cost and minimize hardware prominence when compared with standard one-third tubular plating.

PATIENTS AND METHODS

A retrospective review was conducted on 44 patients who had undergone operative stabilization of a displaced fibula fracture. Inclusion required fibula fixation with either a traditional one-third semitubular plate or a 2.7-mm minifragment plate. Retrospective review of the patient demographics, injury and surgical variables, and radiographs was completed by two surgeons not involved with the patients' original care.

RESULTS

The minifragment group demonstrated equivalency in maintenance of fracture reduction relative to standard tubular plating. Both groups were able to maintain the talocrural angle with less than 1° of change from initial postoperative to final postoperative radiographs. No significant differences were seen in postoperative hardware irritation between groups.

CONCLUSIONS

Use of a minifragment plating system for displaced fibula fractures appears to be safe but comes with the significant potential added cost of the technology. Interestingly, no significant differences were seen in implant-related irritation or implant removal, but further investigation with a larger study population would help better determine these outcomes.

A biomechanical evaluation of locked plating for distal fibula fractures in an osteoporotic sawbone model

BACKGROUND

Supination external rotation (SER) injuries are commonly fixed with a one third tubular neutralization plate. This study investigated if a combination locked plate with additional fixation options was biomechanically superior in osteoporotic bone and comminuted fracture models.

METHODS

Using an osteoporotic and a comminuted Sawbones model, SER injuries were fixed with a lag screw for simple oblique fibula fractures, and either a one third tubular neutralization plate or a locking plate. Samples were tested in stiffness, peak torque, displacement at failure, and torsion fatigue.

RESULTS

There was no statistically significant difference in biomechanical testing for fractures treated with a lag screw and plate. For comminuted fractures, locked plating demonstrated statistically significant stiffer fixation.

CONCLUSION

A combination locked plate is biomechanically superior to a standard one third tubular plate in comminuted SER ankle fractures. There was no biomechanical superiority between locked and one third tubular plates when the fracture was amenable to a lag screw.