Poller blocking screw augmentation to treat delayed union of proximal tibial shaft fracture after locked IM nailing.

CASES: We present the cases of two adult male patients with painfully delayed union of proximal tibia diaphyseal fracture after intramedullary nailing. Patients underwent to nail dynamization and Poller blocking screw augmentation at 3 and 5 month, respectively, after the index surgery. Both patients were pain-free after the surgery and bone-union were radiographically evident after 3 months. At 12-month follow-up, patients returned to their previous activities.
CONCLUSIONS: Although nail dynamization is the choice treatment to obtain fracture compression for delayed union of tibial shaft fractures, augmentation with Poller blocking screw could provide additional mechanical stiffness in unstable supra-isthmic shaft fractures of the tibia and favour bone union.

Introduction

Intramedullary nailing (IMN) is considered the treatment of choice for diaphyseal tibia fractures (1). The reported risk of nonunion after nailing in tibial shaft fracture is 0 - 5.5% (2,3). A major risk factor for tibial nonunion is the fracture location, most commonly involving the area proximally or distally to the isthmus (2). In this area the expanding diaphysis going to the metaphysis increases the width of the intramedullary canal and consequently the contact between the nail and the inside cortex decreases(4). The local instability of the construct with residual movement at the fracture site can eventually result into an impaired bone union process.

Nail dynamization, exchange nailing and augmentation plating have been proposed as possible solution for nonunion treatment, particularly for hypertrophic nonunion, aiming to obtain mechanical stability of the fracture and enhance the rigidity of the construct (5).

In case of delayed union less invasive and less time consuming procedures, such as nail dynamization, are more likely indicated(6). The underlying principle of dynamization is based on the enhancement of micromovements at the fracture gap resulting in bone healing stimulation. In fractures of the proximal or distal 1/3 tibial diaphysis, which are typically unstable, nail dynamization did not often provide the desired effect of fracture compression (7). Particularly in more complex fracture patterns such as multi-fragmentary, wedge or oblique fractures, fracture compression could lead to loss of reduction resulting in further sliding, rotation or angulation of the proximal or distal fragment(3).

We speculated that positioning a blocking Poller screw, slightly medial or lateral to the nail, could “augment” the fracture in case of delayed unions of supra- or infra- isthmic fractures, by reducing the width of the medullary cavity, increasing the stiffness of the construct and therefore limiting the movement of the proximal or distal fragment. Here we describe two cases of a delayed union of the proximal third of the tibial diaphysis successfully treated with the insertion of a blocking poller screw. The patients were informed that data concerning their cases would be submitted for publication, and provided consent.

Case report #1

A 49-years old man was admitted to our department on January 2017 for open tibia shaft fracture due to high-energy road accident. Fracture was classified as Gustilo grade III B and an oblique fracture (> 30°) 42A2 of the proximal 1/3 of the tibial diaphysis according to Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) classification (Fig. 1a). Five hours after the injury, the patient received damage control surgery for the open tibia fracture with an external fixator (Fig. 1b). After two months, the external fixator was removed and a temporary splint was applied (Fig. 1c). Skin wound completely healed and no signs of infection were present. White cells count, high erythrocyte sedimentation rate (ESR) and C-reactive protein ( CRP) were normal. After 40 days, the patient was readmitted to our Department and underwent to closed reduction and locked IMN of the tibial shaft fracture (Fig. 2). Both static and dynamic screws were placed and the nail was locked in a static configuration.

Figure 1.

a) Only one x-ray view of the tibia was performed in E.R, showing the open fracture of the proximal 1/3 tibia shaft; b) then an External fixator was placed; c) X-rays after removal of the external fixator and application of a temporary splint.

Figure 2.

(a, b) AP and (c) lateral view of the tibia after locked IM nailing

The day after the surgical procedure, the patient was allowed to walk with two crutches and full-weight bearing. After 60 days from the surgery the patient was able to walk without aids. However, he complained pain at the proximal-mid third of the tibia after walking for more than 60 minutes. Five months after IMN, the anteroposterior (AP) and lateral view radiographs of the lower limb showed a delayed union of the diaphyseal tibia fracture (Fig. 2). Due to this painful delayed-union, we decided to perform the nail dynamization removing the 2 static proximal interlocking screws of the nail and by preserving a screw in a dynamic locking hole (Fig. 3). We then inserted a poller screw slightly medial to the nail from anterior to posterior, in order to provide additional stability of the proximal fragment (Fig. 3c). The patient was allowed to full weight-bearing the day after the surgery. He reported complete pain relief without the need for pain killers since the same day. After one month, AP view radiographs showed callus formation at the lateral cortical bone. The following x-rays at two, three and six months after the surgery, showed the progressive bridging callus and the complete fracture healing at six months (Fig. 3d, 3e). We used the measurement tools of our PACS (Picture archiving and communication system) viewer (Suitestensa RIS PACS, Ebit, Esaote, Italy) to analyze the position of the proximal screw positioned in the dynamic hole of nail, as indirect sign of nail dynamization and fracture compression. However, the screw appeared to be at the same position and no signs of migration were found. At 12 month follow up, the patient still did not complain about pain or discomfort. Passive and active range of motion of the knee is complete and no limb length discrepancy was detected.

Figure 3.

(a, b) AP and lateral view of the tibia showing delayed union. (c) The static screws were removed and a Poller blocking screw was placed slightly medial to the nail; (d, e) AP and lateral view of the tibia showing complete bone union 3 months after dynamization and augmentation with Poller screw. The red circle and the red arrow note indicate that the position of the proximal screw in the dynamic hole did not change

Case report #2

A 38-years old man was admitted to our department on June 2018 for the treatment of a close tibia shaft fracture due to a sport-related injury. Fracture was classified as an AO/OTA intact wedge fracture 42B2 of the proximal 1/3 of the tibial diaphysis (Fig. 4a, 4b). The patient underwent closed reduction and locked intramedullary nailing (IMN) of the tibial shaft fracture (Fig. 4c, 4d, 4e). Both static and dynamic screws were placed. The day after the surgical procedure, the patient was allowed to walk with two crutches and full-weight bearing.

Figure 4.

(a, b) AP and lateral view of the tibia showing a close fracture of the proximal 1/3 of the tibial diaphysis. (c,d) AP and (e) lateral view of the tibia showing IM nailing with 2 proximal and distal locking screw in the static configuration

After three months from the surgery the patient referred persistent pain at the proximal third of the tibia and he still walked with the aid of two canes. At radiographs there was no evidence of callus formation and fracture gap appeared equal to the postoperative images (Fig. 5a, 5b). Moreover, the static proximal locking screw broke. We decided to wait and see if the screw breakage would eventually provide the nail dynamization. After 6 months from the surgery, the patient still complaint pain and there were no signs of fracture healing, nail dynamization and fracture compression.

Figure 5.

a, b) AP lateral view of the tibia at 4 months from the surgery showing sign of hypertrophic delayed union. The red arrow indicates the breakage of one the proximal screws. (c, d) After 5 months from IMN, removal of the broken screw, dynamization of the nail by removing the distal locking screw and fibular osteotomy were performed. In addition a blocking Poller screw was placed slightly medial to the nail. (e, f) 3 months after the dynamization and screw augmentation the fracture was completely healed. The red circle and the red arrow note indicate that the position of the proximal screw in the dynamic hole did not change

In December 2018, we removed the broken screw, performed the nail dynamization by removing the distal locking screws and a fibular osteotomy to favor fracture compression. Moreover, we augmented the fracture stability with a poller blocking screw of the proximal fragment on the medial side of the nail (Fig. 5c, 5d). The day after the surgery the patient was allowed to full-weigh bearing and he reported reduction of pain. Thirty days later he walked without the need for aids and pain-free. Three months later, the facture appeared completely healed, without signs of dynamization of the nail (Fig. 5e, 5f). The patient still did not complain about pain or discomfort. Passive and active range of motion of the knee is complete and no limb length discrepancy was detected. Eventually the patient had returned to his sport activity. Signs of advanced bone remodeling were found at x-rays. As for the first case described, analyzing the position of the proximal screw positioned in the dynamic hole, the were not signs of fracture compression.

Discussion

Non-articular fractures of the proximal and distal tibia account for 5 to 11% of tibia shaft fractures and as the other closed and open tibial shaft fractures, are mainly related to high energy trauma in young adult patients (8). However, according to ageing of the population, increase rates of fragility fractures of the tibial shaft have been reported in elderly patients, often related to complex fracture pattern (8–10). Although IMN represent the best suited option for diaphyseal fractures of long bones, delayed union and nonunion represent frequent complications which are the result of a number of both patient-related and fracture-related factors which could negatively affect the healing process (2,11,12). Impaired blood supply and mechanical instability at the fracture gap are the most important fracture-related factors (13,14).

Surgical approaches such as nail dynamization, exchange nailing and augmentation plating aim to address the mechanical issues supporting delayed union and non-unions (5)(15)(16).

Nail dynamization provides fracture compression trough the removal of interlocking screws of the IM nail, either proximal or distal to the fracture site. The enhancement of micro-movement at the fracture site results in stimulation of osteogenesis. A fracture is considered suitable for dynamization only when sufficient stability at the fracture site is obtained. Moreover, dynamization has to be avoided in case of multi-fragmentary and comminuted fracture at risk for loss of reduction.

Exchange nailing involves removal of the original nail, reaming the tibial canal removing any nonviable tissue and accommodate a new nail at least 1 mm larger than the original(5–7). The procedure theoretically improves healing rates due to increased blood supply and bone autologous grafting induced by reaming, and the additional stability from using a nail of larger radius(5). Augmentation plating consists in placing a plate over a retained nail improving the stiffness of the construct and reducing micromotions (16)(18). Further compression at the nonunion site when needed can be achieved with the use of a dynamic compression plate. Union rates after revision range from 84% to 98% for both femoral and tibia fractures nonunion.

However, exchange nailing and augmentation plating are invasive and technical demanding procedure compared to nail dynamization, therefore, their use should be considered restricted to recalcitrant delayed unions or in those cases not suitable for nail dynamization. On the other hand, nail dynamization should be considered the first choice when radiological signs of impaired bone healing are visible after the first 3 months(19). There is not consensus about the best timing for the procedure but available results suggest that dynamization of delayed union is more promising than dynamization of tibial diaphyseal non-unions(15). Litrenta et al. in a large series of IMN dynamization for tibial shaft fracture, reported a mean 5.2 months from the trauma to the procedure(7). They found out union in 83% of cases and reported worst results in patients with a fracture gap.

In order to provide additional stability after nail dynamization, we used blocking Poller screws to supplement intramedullary nailing for proximal tibial delayed unions. The Poller blocking screw, which was devised by Kretteck et al., have been traditionally applied with the aim to decrease the width of the medullary cavity and guide the nail in the center of the widened meta-diaphyseal flaring area(20). Several authors demonstrated that sagittal-directed blocking screws, placed adjacent to an intramedullary nail with frontally oriented interlocking screws can significantly increase the primary stability in both proximal and distal tibial fractures. (4,21).

The rational for the use of Poller blocking screws in delayed union of proximal or distal shaft fractures is that, decreasing the width of the medullary cavity and enhancing the contact area implant/internal cortex at the center of the widened canal, the mechanical stiffness of the bone-implant construct would result improved (4). In our clinical practice we have applied Poller blocking screws in addition to other traditional surgical techniques for bone healing enhancement of delayed union and nonunion. In the first case, we performed at the same time dynamization by removing the static proximal locking screws and leaving the dynamic screw in order to control rotation(6). The immediate pain relief clinically reported by the patient, should be addressed by the additional stability obtained with the combination of the two procedures. Conversely, we did not found any migration of the nail at digital radiologic analysis, therefore, the role of fracture compression after dynamization has to be considered marginal.

Similarly in the second case we presented, we speculated that the delayed union was related to a combination of wide fracture gap (due to insufficient fracture compression) and fracture instability. The breakage of the static proximal fracture after two months represented the first sign of “need for compression” of this fracture. However, this event did not provide fracture compression and it seemed to make even more instable the fracture gap, with radiological signs of a hypertrophic callus. Therefore, we choose to combine Poller blocking screws augmentation in addition to nail dynamization and fibular osteotomy, to achieve both fracture compression and improved bone-implant construct stiffness. As per the first case, we did not found any migration of the nail at digital radiologic analysis, therefore, we considered marginal the role of fracture compression after dynamization and fibular osteotomy.

To the best of our knowledge, there are no studies in the English literature describing the use of a Poller screw to treat a tibial delayed union or nonunion without changing the nail. In the literature only Eom et a. in 2016 has reported the successful use of a Poller blocking screw to treat a nonunion of femoral shaft fracture(22). They used multiple Poller screw to augment the stability of the distal fragment of a mid-shaft femoral fracture which underwent to nonunion, leading the fracture to healing after 3 months.

Conclusion

Although little information can be brought from a single case report, we conclude that the Poller blocking screw augmentation for delayed union after IMN represented a simple, cost-effective, minimally invasive surgical technique which permitted a quick recovery, full weight-bearing and early pain relief. Blocking screws could increase the overall mechanical stability of distal and proximal tibia fractures, in which a mismatch between nail diameter and canal width exists. In our cases, the main biomechanical effect was determined by the neutralization of the shear forces after the insertion of the Poller screw. Instead, the compression effect - due to nail dynamization was, in our opinion, biomechanically non-significant. We believe that Poller screw augmentation could represent an effective procedure, especially in the hypertrophic delayed union. Biomechanical studies and then large clinical trials are needed in order to provide the evidence about the extensive use of this procedure.