A safe technical modification and mid-term results in the removal of locking screws with damaged heads

Abstract

Objectives

This study aims to describe a safe method, which does not require additional instruments, for the removal of titanium locking screws with stripped or cold welded heads. Additionally, it evaluates the outcomes of patients in whom this method was applied.

Methods

The proposed method involves using a 3.0 ball-type abrader attached to a standard orthopedic machine to abrade the screw head until it completely separates from the plate hole. This technique was compared to the conventional high-speed burr method, focusing on the maximum temperature generated during the process, as measured with a thermal camera on an artificial bone model. Additionally, the outcomes of 22 patients treated with this technique and followed for at least 12 months were evaluated.

Results

The surface temperature of the plate reached 101.4 °C during the high-speed burr technique. In contrast, when the same technique was performed using the orthopedic machine, the plate surface temperature increased to 62.4 °C. This technique was applied to 22 patients, with an average age of 37 years, and a mean follow-up period of 18.5 months. No complications were reported in any of the patients. Among the removed screws, 14 (63.7%) were 3.5 mm, 4 (18.2%) were 2.7 mm, 3 (13.6%) were 2.4 mm, and 1 (4.5%) was 4.5 mm. Cold welded was observed in only one 4.5 mm screw, while head stripping was observed in all other cases.

Conclusion

This modified technique, using a standard orthopedic machine and burr tip, provides a safe and effective method for removing damaged screws that does not require complex or additional instruments.

Introduction

The introduction of locking plates has significantly broadened their applications, particularly in the field of fracture fixation. Initially designed for bridging plating in multifragmentary fractures [1], their use has now become standard in the treatment of periarticular fractures and osteoporotic fractures, largely due to their numerous advantages [2]. However, the increased utilization of locking screws has led to a rise in complications associated with implant removal. The most prevalent issues encountered during the removal of locked plates include cold welded and screw head stripping [3,4,5]. Notably, these complications are often only identifiable during the surgical procedure, which complicates the situation further. The challenges associated with hardware removal and the resulting prolonged surgical times have heightened the risk of complications, including iatrogenic fractures, soft tissue problems, and infections.

The literature presents various techniques for the removal of damaged or cold welded locking screws. These methods include the use of cone extraction screws, the destruction of the screw head with a tungsten drill bit, diamond-tipped high-speed burrs, and cutting plates with discs [6,7,8]. Many of these techniques necessitate sophisticated tools and require advanced preparation. Currently, there is no definitive technique documented in the literature that is safe for all situations without the use of specialized equipment.

In this study, we introduce a technical modification that we believe allows for the safe removal of all stripped locking screws. Our hypothesis is that locking screws with damaged heads can be removed without complications using easily accessible equipment such as a standard orthopedic motor and burr tip. Additionally, we compared this technique by measuring the temperatures generated during the high-speed burr method. We also analyzed the outcomes of 22 patients who underwent surgery using this technique, all of whom had a follow-up period of at least 12 months. The aim of this study is to define a modified technique that can be employed in various situations using safe and easily accessible equipment.

Patients and methods

Between August 2020 and August 2023, the technical modification described in this study was applied to 22 cases. Notably, all instances of challenging implant removal involved a titanium plate. This study retrospectively reviewed the 22 patients who underwent the described technical modification. Data were collected by examining computerized records and radiological rates and focused on the following effects: age at presentation, gender, reason for implant removal, location of the screw, plate type, technical application features, soft tissue problems, presence of iatrogenic fracture, presence of metal debris, union status and follow-up period. Before the study, approval was obtained from Eskisehir Osmangazi University, Faculty of Medicine ethics committee (03.10.2024/36).

Operative technique (Fig. 1)

Fig. 1

(1) During the destroying all the surfaces of the locking screw head that hold the plate protecting the soft tissue with moist pads from metal debris. (2) Complete destruction of the stripped screw head (3) The plate is removed by maneuvering with an osteotome (4) The remaining screw tip is long enough for use a locking pliers or T-Handle

Step 1: An incision is made over the previous scar to expose the bone, and all fibrotic tissues are carefully debrided.

Step 2: Moist pads are placed around the stripped locking screw to protect the surrounding soft tissues from metal debris generated during the destruction of the screw head.

Step 3: A 3.0 ball burr (Midas Rex Legend^® Ball-Fluted Carbide-MedNext^®) is attached to a standard orthopedic machine. The burr is used to completely destroy all surfaces of the locking screw head that are in contact with the plate. Throughout this procedure, continuous irrigation and aspiration with saline at room temperature are performed to prevent thermal necrosis.

Step 4: By destroying the locked screw head, the plate is released. The plate is then removed by maneuvering it with an osteotome from the bone-plate interface.

Step 5: If the remaining screw tip is sufficiently long, it can be removed by grasping it with locking pliers or a T-handle and turning it. If there is not enough screw tip exposed to grasp, the screw is removed by freeing the area around it using a trifine.

Comparison of the surgical technique with the high-speed burr technique (Fig. 2)

Fig. 2

(1) A 3.5 titanium LCP plate was applied to an artificial bone model. (2) Destruction of screw head with high speed burr (3) Destruction of screw head with standard orthopedic motor (4) The remaining screw tip is long enough for use a locking pliers or T-Handle

A 3.5 LCP titanium plate (Acumed^®) was applied to an artificial bone model (Synbone^®). A high-sensitivity thermal imager (Testo 875-1i, Testo SE & Co. KGaA) was properly positioned and secured for the experiment. Initially, the screw head was abraded using a high-speed burr with a 3.0 ball tip (Midas Rex Legend^® from Medtronic, Fort Worth, TX, USA) until the plate was released. During this procedure, the temperatures recorded on both the bone surface and the plate surface were monitored.

Subsequently, the same procedure was performed by the same surgeon using a new burr tip and a new implant of the same type, this time connected to a standard orthopedic machine. By using a new burr tip and implant, the wear and heat that may have occurred in the previous application were prevented from affecting the results of the next application. The temperatures on the bone surface and the plate surface were recorded again throughout the process. Both procedures were performed by the same surgeon without interruption and without irrigation.

Results

It was observed that the temperature on the plate surface increased to 101.4 °C during the high-speed burr procedure (Fig. 3). In contrast, during the procedure performed with the orthopedic machine, the temperature on the plate surface reached a maximum of 62.4 °C (Fig. 4).

Fig. 3

Temperature measurement during high speed burr application

Fig. 4

Temperature measurement during burr application with standard motor

The study included 12 female (54.5%) and 10 male (45.5%) patients, with a mean age of 37 years. The average follow-up period was 18.5 months, ranging from 12 to 35 months. The reasons for implant removal were as follows: soft tissue irritation in 8 patients (36.4%), non-union in 4 patients (18.2%), discomfort due to the implant in 4 patients (18.2%), pain in 3 patients (13.6%), impaired mobility in 2 patients (9.1%), and young age in 1 patient (4.5%). The anatomical distribution of the removed implants included: 1 femur shaft (4.5%), 4 distal tibia (18.2%), 3 clavicles (13.8%), 3 lateral malleoli (13.8%), 1 distal radius (4.5%), 2 ulna shafts (9.2%), 1 radius head (4.5%), 1 distal femur (4.5%), 1 radius shaft (4.5%), 1 distal humerus (4.5%), 1 olecranon (4.5%), 1 metacarpal shaft (4.5%), 1 proximal humerus (4.5%), and 1 humerus shaft (4.5%).

Regarding the removed screws, 14 (63.7%) were 3.5 mm, 4 were 2.7 mm (18.2%), 3 were 2.4 mm (13.6%), and 1 was 4.5 mm (4.5%). All screw heads were in a hexa head configuration. Cold-welded was observed in only one 4.5 mm screw, while head stripping occurred in all other screws. No complications were reported in any patient. Patient outcomes are summarized in Table 1.

Table 1 Summary of the patient data

Discussion

In this study, we tried to define a safe technical modification that can be applied with easily accessible equipment for the removal of locked screws with damaged heads, which are a problem in our daily practice. In this technical modification, only the standard orthopedic machine and burr tip that are readily available in every operating room are used. Since the screw head problems cannot be detected preoperatively, preoperative preparation is required in all surgeries requiring implant removal. We believe that the use of standard equipment that can be accessed at any time in the modification described in this study is advantageous as it does not require additional preoperative preparation. In addition, the most important concern in the high-speed burr technique that we modified was the formation of thermal necrosis. Studies have shown that bone temperatures above 50 °C for one minute or longer or above 70 °C, cause necrosis of bone cells [9]. Therefore, we wanted to compare the modified technique with the high-speed burr technique in terms of the heat they produce. When applied without any interruption and irrigation, the temperature increased to a maximum of 62.4 °C with this technique. Therefore, in the light of current literature information, we can say that it is safe in terms of bone necrosis when not applied without an interruption longer than 1 min. We also evaluated the mid-term results of the patients who used the technique and showed that the technique can be used safely.

The advancement of locking screw technology has introduced challenges such as the cold welding of screws to plates and the stripping of screw heads, particularly in softer titanium implants [6, 8]. The most effective strategy for preventing stripped screw heads is to take preventive measures during the initial placement. This includes adhering to technical guidelines, using a torque-limited screwdriver, and ensuring the screw is placed perpendicular to the plate’s axis. Despite these precautions, screw removal issues are frequently encountered in daily practice. Various techniques have been described in the literature for removing screws with damaged heads, often caused by stripping the screwdriver inside the locked screw head. One such technique involves wrapping a gauze pad over the screwdriver tip to increase grip and provide additional torque. Another suggestion is to place a small layer of foil inside the screw head [10, 11]. However, these methods are only effective in cases of minimal screw head damage and are often insufficient for more severe cases.

Another approach involves using tapered reverse thread removal devices, which are available for screws ranging from 1.5 to 7.3 mm in size from several manufacturers. The appropriate-sized cone removal device is placed on the damaged screw head and turned counterclockwise while applying pressure along the screw axis. Once a tight grip is achieved, the screw is removed by turning it with the removal device. However, this technique is not effective in cases of cold welding or cross-threading, and there have been frequent reports of conical extraction device fractures [6,7,8]. Additionally, this method requires the availability of special devices prior to surgery, which may not always be feasible.

Some studies have explored the technique of cutting the plate around a stripped screw using a high-speed carbide-tipped burr [6, 12, 13]. While this method can be effective, it has notable disadvantages, such as the formation of metal debris and the risk of thermal necrosis. Additionally, it requires access to a high-speed burr device. As demonstrated in this study, using a high-speed burr generates significantly more heat compared to using a standard orthopedic motor, which produces approximately 40 °C less heat. Another technique described by Ji-Hoon Bae et al. involves bending the plate and rotating it around the stripped screw to remove the screw along with the plate [14]. However, this method carries a high risk of iatrogenic fracture due to the lack of load support on the bone during the bending process. Furthermore, this technique is only feasible if there is a single screw left on the plate, as multiple screws would prevent the necessary bending of the plate.

In a technique described by Seok-Jung Kim et al., a new hole is drilled adjacent to the stripped screw using a large drill bit. Following this, an osteotome is used to push the plate, allowing the locked screw to slide into the area without a lock. Once the screw is in this position, it can be removed by applying a lifting force to the plate with the aid of an elevator and osteotome [15]. This technique is advantageous as it does not require any additional specialized tools, making it accessible in various surgical settings. However, it is important to note that this method is only applicable to stripped screws located in combi holes, limiting its use in other scenarios.

In the study by Ehlinger et al., a technique involving the complete destruction of the screw head using a tungsten drill was described. Once the screw head is destroyed, the plate can be removed, and the remaining part of the screw embedded in the bone is extracted with the help of a trephine [4]. Similarly, Park et al. [16] described a method where the screw is separated from the plate by destroying the screw head with a 6 mm non-medical drill. While these techniques are effective, they involve a more uncontrolled application of force, leading to the complete destruction of the screw section up to the bone. In contrast, the technical modification described in this study allows for more controlled progression. This method may enable the removal of the screw using locking pliers while preserving a portion of the screw that remains outside the bone. By doing so, the risk of bone damage and iatrogenic fracture is reduced, offering a safer alternative to the more destructive methods.

Another technique described by Kumar et al. [17] involves capturing the screw by entering the bone with a specialized grooved trephine-like device from the tip of the screw rather than from the head. This method eliminates the risks associated with high-speed burrs, such as metal debris and thermal damage. However, it does require an additional approach from the side where the screw exits, which can be challenging since locking screws are often designed to pass through only a single cortex and may not exit from the opposite cortex. This limitation can complicate the identification and access to the screw. Furthermore, this technique is not effective in cases of cold welded, where the screw is tightly bonded to the plate, making removal difficult. Overall, while this method offers certain advantages, its applicability is limited by the specific circumstances of the screw’s placement and condition.

In a multicenter study by Schwarz et al. [18], it was found that 41 out of 205 patients (20.1%) who underwent implant removal encountered technical difficulties due to head stripping. Similarly, Fujita et al. [19] reported a difficulty rate of 9.1%, noting that for 3.5 mm locking screws, the risk of complications increased to approximately 50% if more than a year had passed since their application. Despite these challenges, surgeons were able to remove the implants using various described techniques, with only one patient experiencing a complication, specifically an intraoperative refracture. This highlights the importance of employing effective removal techniques to minimize complications. In the study, it was observed that 19.5% of patients who had implants removed faced technical difficulties, underscoring the need for continued refinement and adaptation of removal strategies to improve outcomes. All implants in the study were successfully removed using the described technique, and no complications were observed. The risk of iatrogenic fracture is often associated with the excessive force applied during the drilling of the screw head. However, the technical modification presented allows for a more controlled approach, utilizing a step-by-step method with a controlled burr down technique. This approach minimizes the need for excessive force, thereby reducing the risk of complications and ensuring a safer removal process. By carefully managing the drilling process, surgeons can effectively mitigate the potential for bone damage and improve overall patient outcomes.

In this study, it was found that only one 4.5 mm screw caused technical difficulties, attributed to cold welded, likely due to being locked by a motor without a torque-limited screwdriver. All other screws that presented challenges were 3.5 mm or smaller in diameter. The increased risk of head stripping with smaller screw diameters is believed to be due to the reduced contact area between the screw head and the screwdriver, as both the circumference and depth of the head decrease with smaller diameters. Fujita et al. [19] concluded that the highest risk was associated with 3.5 mm diameter locking screws, while the risk was lower for 2.4/2.7 mm diameter screws, possibly due to the quality of the bone they were fixed to and their shorter length. While this conclusion may hold true, it’s important to remember that locking screws are crucial for the strength of the plate attachment. Therefore, careful consideration of screw size, bone quality, and the specific surgical context is essential to minimize complications during implant removal.

This study has many limitations. The retrospective nature of the study and the short follow-up period are natural limitations. In addition, the fact that it only covers the mid-term results of the patient group in which the technical modification was applied and that comparisons cannot be made with case series in which other techniques were used (especially the high-speed burr technique) are important limitations. In addition, although the temperature measurements were performed by a single surgeon, this does not provide an objective standard and creates a risk of bias.

Conclusions

In this study, a technical modification was reported that can be used safely for implant removal without the need for additional sophisticated devices.