Search results

The analysis of the dataset pertaining to helical and twisted plating yielded a range of studies conducted over a period extending from 1992 to 2023. Of the 32 studies that came up in the first search, 23 were included into this narrative review after full-text screening. A total of seven studies focused on the femur making it the most frequently investigated bone. The humerus was subject of six studies. Other anatomical regions of interest included the clavicle, tibia, and ulna, each being represented in a single study, while one study specifically examined sheep tibia.

In terms of study types, clinical case series were the most common investigations, with a total of six studies conducted. Biomechanical investigations were identified in seven studies, where two of the seven were conducted using artificial bones. Clinical retrospective comparative studies were noted in four instances. Finite element simulations were explored in three studies, anatomical analyses were performed in five studies, and a single study provided an overview of the topic.

Geographically, the distribution of studies was concentrated in Europe and Asia. European institutions, specifically from Switzerland, Austria, Germany, Spain, Italy, and Turkey, contributed to a total of thirteen studies. In contrast, Asian research, emanating from countries such as South Korea, India, China, and Singapore, was represented in five studies. Additionally, there was one study from South America.

No randomized controlled trials were detected, indicating a potential area for future research. This gap in the literature underscores the need for future research, particularly high-quality empirical studies, to determine the efficacy and application scope of helical plating more conclusively in orthopaedic trauma surgery.

Simulation studies

Finite element analysis (FEA) has provided new perspectives on the biomechanical efficiency of helical plating systems in the field of fracture therapy. A study comparing the deformation and stability of straight versus helical compression plates in transverse and oblique fractures on sheep tibiae concluded that helical plates demonstrated superior fracture gap closures and torsional resistance under axial compression loads compared to straight plates [17]. Here it is vital to take into account that helical plates cause more shear and rotational movement under axial stress in horizontal fracture gaps compared to straight plates [18]. The merging of computational and experimental approaches in this work demonstrated that helical designs excel in stabilizing transverse fractures.

Zhang et al. [19] looked at the biomechanical features of Herbert screws and helical plate fixations in midshaft displaced clavicle fractures. While Herbert screw fixation mirrored the stress distribution of an unbroken clavicle and was appropriate for minor fractures, helical plate fixation achieved more stability. The former was related to stress shielding, indicating a preference for helical plate fixation in patients requiring early return to activity with restrictions on postoperative shoulder mobility and weight-bearing.

Further investigation into the hemi-helical plate (HHP) demonstrated its improved ability for oblique fracture repair, which is particularly effective in helical cracks caused by torsional stresses and comminuted fractures [20]. The circumferential HHP design provides compressive strength at fracture sites and exceeds straight plates in terms of fracture-holding capability and flexibility under varying loading situations, so it enhances both axial and torsional stiffness in synthetic bone constructs, offering effective load distribution [16]. Both experimental data and FEA supported this. Furthermore, Krishna et al. [20] found higher resistance to screw pullout as compared to straight plates and reasoned this due to the different screw angulation in helical plate constructs.

A recent FEA study [21] reveals that helical plating leads to slightly deferred bone healing due to larger shear movements, offers clinical benefits like reduced stiffness, lower neurovascular risks, and improved load distribution.

These findings add considerably to the orthopaedic knowledge by showing the enhanced stability provided by helical plating systems in certain fracture configurations. They open the path for future fracture fixation technology advances and possible better results for complicated fractures. However, higher torsional and shear movements at the fracture gap were detected in FEA studies, possibly influencing the fracture gap healing [21].

Clinical studies and comparative analysesCase series on twisted plates

Three clinical case series on helical plating have been published so far, one of them dealing with humeral fractures, one—with femoral fractures, and one—with both and additional proximal tibial fractures.

In their case series, Kumar et al. [12] introduced a 90° twisted plate for orthopaedic fixation, applying it to 24 humeral, 6 tibial, and 2 radial fractures with varying hole counts: 8 for humerus, 6 for tibia, and 4 for radius. The novel plate’s strength was compared to that of a standard flat plate. The twisted plate was found to be 49% stronger against bending and 132% stronger against twisting (Fig. 1).

Bülhoff and colleagues explored a 95° twisted plate to enhance the stability of subtrochanteric fracture fixation in combination with intramedullary nailing, although the number of cases in this study was not specified [22]. More recently, Nicolacai et al. [23] reported on 24 cases using Zimmer Biomet’s anatomic locking plate system (ALPS)—a 45° twisted plate with an additional anterior kink to avoid the deltoid insertion during humeral fracture fixation—, achieving a 100% union rate with only a single instance of iatrogenic temporary radial palsy.

Case series on helical plates

Four clinical case series on helical plating have been published so far, all of them dealing with humeral fractures.

Along with describing his technique on helical plating, Fernández presented 20 cases involving multifragmentary proximal humeral fractures, fixated with manually pre-contured helical plates [24]. The patients were treated using periosteal implants positioned laterally at the proximal humerus and anteriorly at the distal humerus. The cases included nonunion fractures extending to the proximal part of the bone and comminuted humeral shaft fractures categorized as 3- and 4-part proximal humeral fractures. However, the clinical outcome of this patients has not been reported.

Yang [25] described 9 cases of comminuted humeral fractures treated with manually pre-contoured helical plates angled at 90° to spare the deltoid insertion and additional bone grafting in two cases, finding that all fractures healed within 14 to 28 weeks without significant complications, though there were instances of hardware removal and two unsatisfactory outcomes. Moon et al. [26] analyzed the treatment of 12 humeral fractures using manually pre-contoured plates based on a cadaveric humerus model, utilizing a 90° helical angle. Their approach included 5 limited-contact dynamic compression plates (LC-DCP) with 12 holes and 7 long PHILOS plates with 10 holes, noting one case of delayed fracture union. Garcia-Virto et al. [27] reported on 15 AO/OTA 12 C humeral fractures treated with a 90° contoured helical plate, featuring at least 4 distal locking screws, with a mean Constant Score of 72 ± 13 points after 6 months.

A primary issue identified in case reports is the lack of consensus on the optimal design of the osteosynthesis plates, compounded by the challenge of standardizing intraoperative contouring across various surgeons. Nevertheless, it is evident that for Minimally Invasive Plate Osteosynthesis (MIPO) of the humerus, a 45° helical configuration is most suitable as it is pushed through the weaker middle part of the deltoid insertion, which is not possible with 90° helical plates and the ALPS [28, 29]. In ORIF procedures, a higher degree of angulation, up to 90° or 45° with an additional anterior kink like in the ALPS plate, may be beneficial for better positioning of the plate anterior to the deltoid muscle attachment. Nevertheless, this approach is not feasible with MIPO techniques as it could potentially cause more harm and long-term weakening of the strong anterior portion of the deltoid muscle [28].

Comparative studies

Comparative studies have exclusively investigated the outcomes of humeral fractures, providing focused insights into the effectiveness of different treatment approaches.

A retrospective study comparing helical plating to straight PHILOS plating for shoulder function after one year revealed comparable outcomes in 30 patients. Both treatments yielded good shoulder function and there were no significant differences in normalized Constant Scores or surgical complications between the two groups [30].

A decade-long study compared straight versus helical PHILOS plates in treating humeral shaft fractures in 62 patients [9]. No iatrogenic radial nerve damage was reported in the helical plate group, while two cases of nerve damage occurred in the straight plate group, though being not statistically significant. The findings suggest that helical plating might safely prevent radial nerve damage.

Comparing the efficacy of pre-contoured plates shaped on artificial bones (Synbone, Zizers, Switzerland) versus 3D-printed models for proximal third humeral shaft fractures, a study by Wang et al. [31] found that 3D printing significantly reduced both the surgery duration and blood loss. The two groups had similar outcomes regarding fracture healing and functional scores, indicating 3D printing’s value in simplifying the surgical procedure.

Comparing the lateral approach with the use of straight plates versus MIPO approach with 45° and 90° helical plates for treatment of humeral shaft fractures [32], the study found that while the operation time was shorter for the lateral approach, the overall complication rate was significantly lower for MIPO with helical plates. Both methods achieved satisfactory results, but the helical plates demonstrated advantages in complication rates [33].

The comparative studies on humeral fractures reveal that helical plating is as effective as traditional straight plating in terms of functional recovery and safety, with additional benefits such as possible lower radial nerve damage and fewer complications, while 3D printing technology in plate contouring significantly reduces surgery time and blood loss, arguing for a wider application of these techniques.

Biomechanical characteristics of helical plating

Five biomechanical investigations have been reported in the literature so far, two in the humeral shaft region and three in the femoral shaft region, all dealing with custom-bent helical implants and none with the ALPS.

In the humeral region, straight plates, intramedullary nails, 45° helical plates and 90° helical plates have been compared in an artificial bone model using a non-destructive quasistatic test setup [29]. It was concluded that 90° helical plates were associated with higher fracture gap movements in the sagittal plane (flexion / extension) Nevertheless, they demonstrated improved resistance against displacements in the coronal plane (varus / valgus) compared to straight plates during pure bending. In contrast, 45° helical plates demonstrated equitable biomechanical competence as straight plates. The authors considered 45° helical plates as valid alternative to straight plates from a biomechanical perspective. However, no cyclic tests were performed, and only artificial bones were used. Furthermore, all investigated plate designs revealed less resistance to axial deformation under axial loading as compared to intramedullary nails. Nevertheless, all plates demonstrated higher resistance to torsional loading which was due to nail toggling [29]. The second biomechanical study compared 90° helical plates with straight plates in a human cadaveric bone model under torsional cyclic loading [18]. The authors concluded that 90° helical plating is associated with lower resistance to flexion/extension and internal rotation with bigger shear interfragmentary displacements as compared to straight plating and therefore cannot be considered as its real alternative [18].

Given the upper extremity’s major exposure to torsional stress and the prevalent method of contouring plates by torsion, such contoured plates may perform suboptimal [34]. This might be the reason why 90° helical plates performed inferiorly compared to straight plates when loaded under cyclic torsion. On the other hand, 45° helical plates seem to be a true alternative to straight plates in the upper extremity from a biomechanical perspective, however, biomechanical research under cyclic loading in a human cadaveric bone model is still pending to confirm these results.

Double plating in orthopaedic surgery stabilizes fractures using two bone plates, optimizing load distribution, reducing stiffness-related complications, and enhancing stability compared to single-plate systems [35]. In the femoral region one study compared 180° helical plating to conventional straight lateral plating in an artificial bone model simulating a distal femoral fracture in young patients [35]. The authors concluded that helical plating showed higher shear and flexion movements. Yet, it demonstrated improved initial axial stability and resistance against varus/valgus deformation compared to straight lateral plating. Besides that, the helical plating was associated with significantly higher endurance to failure and may be considered as valid alternative to lateral straight plating [35].

Double plating definition

The second study evaluated double plate constructs in geriatric distal femoral fractures using a paired cadaveric bone model under cyclic axial loading [36]. One group was instrumented with two straight plates while the other group was instrumented with a medial 90° helical plate. The authors concluded that for geriatric patients, helical double plating with an additional 90° medial helical plate presents a biomechanical advantage over straight double plating by offering better damping during axial loading and avoiding the medial neurovascular structures, addressing the issue of excessive stiffness associated with straight plates [36].

The third study evaluated a similar double plate construct with an additional medial 90° helical plate and found an increased axial and torsional construct stiffness. The authors recommended that its use should be considered in very demanding situations for gap fractures, where single plate osteosynthesis provides inadequate stiffness for fracture healing and induces nonunion [16], as it has been shown that double-plate osteosynthesis or use of one intramedullary and one extramedullary implant improves stability [37, 38].

These five studies reveal an insight into the biomechanical behavior of the different helical plate designs under various loading conditions. The 180° helical plate behaves like a spring when axially loaded—like in the lower extremity—which leads to better resistance to failure, however, it comes with greater shear and torsional stresses at the fracture gap. The 90° helical implant in a double plate construct reveals similar improved damping capabilities under axial load, however, the additional lateral straight plate compensated for the torsional and shear forces at the fracture gap.