Intramedullary nailing is regarded as one of the most convenient biological options among the alternative methods for treating distal femoral diaphyseal and metaphyseal fractures.1–3 However, inadequate reduction and malunion is frequently encountered in relation to fracture morphology because the distal medulla of the femur is wider than the middle diaphysis and the intramedullary nail cannot completely fill the intramedullary canal.4–7 Ideal reduction can be ensured using methods such as open reduction and anatomic plate application or wire cerclage, but these methods increase soft tissue and periosteal circulation damage and infection risk.8 If these problems with reduction can be efficiently resolved, intramedullary nailing will be the more commonly preferred treatment for distal femoral fractures. This article describes how blocking screws can offer a solution for reducing these fractures. Successful results were obtained from studies conducted on the use of blocking screws.4,6,7,9–13 The requirement of blocking screws mostly emerges intraoperatively. Therefore, a surgeon must have detailed information about deformity types and their blocking screw correction methods. The purpose of this study was to use pictorial descriptions and clinical examples to demonstrate fracture deformities that are common in the distal femur and how to create solutions for them by using blocking screws.
Materials and Methods
Thirty-four patients with distal femoral fractures underwent intramedullary nailing at the authors’ institution between January 2005 and June 2011. Seven of 18 patients treated with antegrade nailing and 8 of 16 patients treated with retrograde nailing needed 1 or 2 blocking screws.
While performing antegrade or retrograde intramedullary nailing in distal diaphyseal or metaphyseal fracture of femur, if reduction is not achieved, the nail is removed and the guidewire is left inside. The nail is reinserted after a blocking screw is placed at a suitable location under fluoroscopy. The blocking screw guides the intramedullary nail toward the desired direction inside the large intramedullary canal while ensuring the reduction of the displaced fragment. Blocking screws are more often applied to shorter and larger fragments from wide-angle corners formed by fracture lines with bone cortexes on the concave sides of the deformities. Sometimes, a second blocking screw may be applied to a long fragment from a wide-angle corner formed by the fracture line with the bone cortex on the concave side of the deformity. If the screw is placed this close to the fracture, the fracture may become more complex. To prevent fracture propagation, it is necessary to insert the screw 1 to 3 cm away from the fracture line. This distance may differ according to fracture type and bone quality. Fluoroscopically controlling the insertion point after drilling is useful before inserting the blocking screw because the localization can be changed if concerns exist regarding the localization.
When inserting the blocking screws from the lateral to medial direction, surgeons must be aware of the saphenous nerve lying medially and the sural nerve lying laterally around the knee. For blocking screws inserted from the anterior to posterior direction, avoiding injury to the patellofemoral joint is essential. The authors inserted anteroposterior screws from the point localized at 3 cm away from the superior pole of the patella. To prevent damage to the medial and lateral superior geniculate arteries and their branches localized anteriorly just above the articular level, the authors also made a blunt dissection after skin incision for the subcutaneous tissue and muscles.
Of the 15 patients, 10 were men and 5 were women. Mean patient age was 38.8 years (range, 22–58 years). Six patients had distal diaphyseal fractures and 9 had distal diaphyseo-metaphyseal fractures. All fractures were extra-articular. Other than in 3 patients, all fractures resulted from high-energy trauma, and 4 patients had polytrauma. Of these fractures, 5 were open. Most commonly, blocking screw application from the anterior side on the distal femoral fragment due to recurvatum on the sagittal plane (n=7) was performed. Blocking screws were placed on required locations due to varus on the coronal plane in 2 patients, valgus on the coronal plane in 2 patients, and translation on the coronal plane in 2 patients, in association with or without the above-mentioned deformity. Mean follow-up was 26.6 months (range, 12–48 months). Mean time to union was 12.6 weeks (range, 8–32 weeks). Delay to union was observed in a 31-year-old polytrauma patient who was a smoker. In this patient, union was achieved at week 32, and no additional surgical intervention was required. In 2 patients, implants were removed due to implant discomfort after union was achieved. No additional complication was related to the added blocking screw. Screw applications were replaced due to inconvenience of their locations, but no fragmentation increased in any patient due to the blocking screws. No infection was observed.
Patient demographics are shown in the Table. Based on the anatomic soft tissue features of the region and morphology of the fracture, recurvatum, varus and valgus deformities, or translation are often encountered in the distal femur. A pictorial description of reduction and blocking screw application for deformities on the sagittal and coronal planes are shown in Figures 1 and 2. Sample radiographs for both deformities are shown in Figures 3 and 4. When sagittal and coronal plane deformities are concurrently found, blocking screw application on 2 different planes is combined at locations required by the deformity.
Table: Patient Demographic Data
Figure 1: Illustrations showing the use of blocking screws to correct recurvatum deformity on the sagittal plane. Because the gastrocnemius muscle pulls the distal fragments backward and downward, recurvatum deformities on the sagittal plane often occur in distal femur fractures (A). If the deformity cannot be satisfactorily corrected by a retrograde intramedullary nail, the nail is removed and the procedure is switched to blocking screw (B). A blocking screw is placed on the large distal fragment anterior to the guidewire from the wide-angle corner (formed by fracture line with bone cortex) in a lateral to medial direction (C). When the nail is reapplied, reduction is mostly achieved (D). If reduction is still not satisfactory, the nail is removed and a second blocking screw is placed proximal to the fragment posterior to the guidewire (E). The nail is readvanced, and reduction is achieved (F).
Figure 2: Illustrations showing the use of blocking screws to correct a deformity on the coronal plane. Valgus or varus deformity or translation may occur depending on the fracture morphology on coronal plane in distal femur fractures (A). If satisfactory deformity correction cannot be obtained when the nail is applied, the nail is removed and the guidewire is left inside (B). If valgus deformity or translation to the medial side is present, a blocking screw is placed on the large distal fragment from the lateral side of the guidewire in anteroposterior direction (C). The nail is reapplied, and reduction is achieved (D). If desired reduction is still not achieved, the nail is removed and a second blocking screw is applied to the proximal fragment from the medial side in valgus deformity (E). The nail is readvanced, and reduction is achieved (F).
Figure 3: Preoperative anteroposterior (A) and lateral (B) radiographs showing a distal femoral shaft fracture with a sagittal plane deformity. Postoperative 1-month anteroposterior (C) and lateral (D) radiographs showing intramedullary nailing and the blocking screw (red arrows). Postoperative 48-month follow-up anteroposterior (E) and lateral (F) radiographs showing union without deformity (red arrows).
Figure 4: Preoperative anteroposterior (A) and lateral (B) radiographs showing a distal femoral shaft fracture with a coronal plane deformity. Postoperative anteroposterior (C) and lateral (D) radiographs showing intramedullary nailing and blocking screws (black arrows).
Closed antegrade or retrograde nailing is a recognized treatment for distal femur fractures. However, malunion or non-union are not rare because the medulla of the distal femur is wider than the middle diaphysis and the nail may not completely fill the intramedullary canal. The risk of malunion proportionally increases as the distal fracture segment becomes shorter.4,5,14,15 Recurvatum on the sagittal plane due to stretching the gastrocnemius, translation, and varus or valgus on the coronal plane based on morphology of the fracture are often encountered deformities in distal femur fractures. It may not be always possible to completely correct those deformities with standard closed intramedullary nailing.6
Blocking screws are often applied to remove the problem of reduction in intramedullary nailing of fractures close to enlarged ends of long bones. Blocking screws were first reported for use in the tibia by Krettek et al.9,10 Stedtfeld et al7 reported the applications of blocking screws at the distal region of other long bones. Ostrum and Maurer6 reported treating distal femur fractures with retrograde intramedullary nailing and blocking screws. Blocking screws are aimed to guide the intramedullary nail to the desired direction by narrowing the intramedullary canal and obtaining better reduction. Blocking screws also increase stabilization.7,9–11
In the current study, patients with blocking screws most commonly sustained high-energy traumas, and many patients had polytrauma and open fractures. Blocking screws were mostly required for unstable fractures with higher displacements. In such patients with higher complication risks, treatments were successfully completed with no significant complications.
Because the medullary canal of the distal femur has a larger diameter than the intramedullary nail, the nail cannot fully fill the canal; therefore, distal locking of the nail should be performed. Locking should be performed with at least 2, or preferably 3, locking screws on more than 1 plane if possible.7,16,17 Strong distal locking retrograde nails in the shape of spiral wedges are preferred. Ostrum and Maurer6 reported the combined use of blocking screws with retrograde intramedullary nailing. Retrograde nailing is more convenient in distal femur metaphyseal fractures. However, antegrade nailing is also often used in distal diaphyseal fractures. Therefore, the authors preferred to address both retrograde and antegrade nailing cases.
Before making a decision on whether to use blocking screws, the authors focused on achieving closed reduction. If achieving closed reduction was not possible, they applied or inserted supplemental surgical equipment, such as ball-spike pushers, Schanz screws, Steinmann pins, bone hooks, or Weber reduction clamps, percutaneously. If these equipment did not help gain and maintain reduction, blocking screws were used as a final solution. The main purpose of using blocking screws was to achieve reduction, but they were also useful for maintaining permanent reduction. Loss of adequate reduction can be seen after removing supplemental equipment that keeps the fracture reduced. In some patients, blocking screws were also used for this purpose.
An important potential risk in blocking screw applications is that a new fracture lying from the blocking screw to the fracture line occurs when the intramedullary nail is advanced through the narrow intramedullary canal after the blocking screw is placed. This can be prevented by accurately selecting the point where the blocking screw will be placed. Both screws should be close to the mid-line to efficiently direct the intramedullary nail to the contralateral side, and the intramedullary nail should fit the remaining canal. However, an adequate distance should be left between the screw and the fracture line. If the location of the screw is not appropriate during application or if the intramedullary nail does not advance next to the blocking screw, the location of the screw should be changed. If desired reduction cannot be ensured despite all attempts, it should be replaced with another technique, such as wire cerclage.
An important disadvantage of this method is that it is necessary to perform it under fluoroscopy throughout the whole procedure and that the patient is exposed to more radiation. A limitation of this study was that intraoperative radiation exposure time was not reported.
The aim of this study was to clarify how blocking screws should be placed in different types of fractures. With better understanding of blocking screw functions, surgeons will observe better reduction than that obtained by standard nailing. Unless a more complex fracture is created due to placing a screw in an inadequate location, it does not seem possible that a blocking screw will not positively contribute to the treatment. The contribution to the maintenance of reduction and to the stabilization should be noted.
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- Janzing HM, Stockman B, Van Damme G, Rommens P, Broos PL. The retrograde intramedullary supracondylar nail: an alternative in the treatment of distal femoral fractures in the elderly?Arch Orthop Trauma Surg. 1998; 118(1–2):92–95 doi:10.1007/s004020050320 [CrossRef].
- Zlowodzki M, Williamson S, Cole PA, Zardiackas LD, Kregor PJ. Biomechanical evaluation of the less invasive stabilization system, angled blade plate, and retrograde intramedullary nail for the internal fixation of distal femur fractures. J Orthop Trauma. 2004; 18(8):494–502 doi:10.1097/00005131-200409000-00004 [CrossRef].
- Ricci WM, Bellabarba C, Evanoff B, Herscovici D, DiPasquale T, Sanders R. Retrograde versus antegrade nailing of femoral shaft fractures. J Orthop Trauma. 2001; 15(3):161–169 doi:10.1097/00005131-200103000-00003 [CrossRef].
- Sanders R, Koval KJ, DiPasquale T, Helfet DL, Frankle M. Retrograde reamed femoral nailing. J Orthop Trauma. 1993; 7(4):293–302 doi:10.1097/00005131-199308000-00001 [CrossRef].
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- Stedtfeld HW, Mittlmeier T, Landgraf P, Ewert A. The logic and clinical applications of blocking screws. J Bone Joint Surg Am. 2004; 86:17–25.
- Zlowodzki M, Bhandari M, Marek DJ, Cole PA, Kregor PJ. Operative treatment of acute distal femur fractures: systematic review of 2 comparative studies and 45 case series (1989 to 2005). J Orthop Trauma. 2006; 20(5):366–371 doi:10.1097/00005131-200605000-00013 [CrossRef].
- Krettek C, Miclau T, Schandelmaier P, Stephan C, Möhlmann U, Tscherne H. The mechanical effect of blocking screws (“Poller screws”) in stabilizing tibia fractures with short proximal or distal fragments after insertion of small-diameter intramedullary nails. J Orthop Trauma. 1999; 13(8):550–553 doi:10.1097/00005131-199911000-00006 [CrossRef].
- Krettek C, Stephan C, Schandelmaier P, Richter M, Pape HC, Miclau T. The use of Poller screws as blocking screws in stabilising tibial fractures treated with small diameter intramedullary nails. J Bone Joint Surg Br. 1999; 81(6):963–968 doi:10.1302/0301-620X.81B6.10000 [CrossRef].
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Patient Demographic Data
|Patient No./Sex/Age, y||Etiology||OTA AO Fracture Type||Open/Closed||Deformity During IM Nailing||Technique||Blocking Screw||FU, mo||Fracture Union Time, wk|
|1/M/28||Traffic accident, polytrauma||32 B2||Closed||Varus at coronal plane||Antegrade||1 to distal from medial side||24||12|
|2/M/49||Traffic accident, polytrauma||32 A3||Closed||Recurvatum at sagittal plane||Antegrade||1 to distal from anterior side; 1 to proximal from posterior side||18||12|
|3/M/31||Traffic accident, polytrauma||32 C3||Open; type 2||Recurvatum at sagittal plane||Antegrade||1 to distal from anterior side||12||32|
|4/M/53||Fall from height||32 A2||Closed||Recurvatum at sagittal plane||Antegrade||1 to distal from anterior side||25||8|
|5/M/38||Gunshot||33 A3||Open; type 3C||Recurvatum at sagittal plane||Retrograde||1 to distal from anterior side||12||16|
|6/F/30||Traffic accident, polytrauma||33 A3||Open; type 3A||Medial translation at coronal plane||Retrograde||1 to distal from lateral side||48||8|
|7/F/37||Falling down||32 A3||Closed||Recurvatum at sagittal plane||Retrograde||1 to distal from lateral side||20||10|
|8/M/35||Gunshot||33 A3||Open; type 3C||Recurvatum at sagittal plane||Retrograde||1 to distal from lateral side||48||8|
|9/M/58||Falling down||33 A1||Closed||Valgus at coronal plane||Retrograde||1 to distal from lateral side||15||12|
|10/M/22||Motorcycle accident||33 A2||Open; type 3A||Recurvatum at sagittal plane||Retrograde||1 to distal from lateral side; 1 to distal from anterior side||48||13|
|11/F/27||Traffic accident||33 A3||Closed||Recurvatum at sagittal plane||Retrograde||1 to distal from anterior side||24||11|
|12/M/37||Motorcycle accident||32 A3||Closed||Varus at coronal plane||Antegrade||1 to distal from medial side||36||14|
|13/M/55||Falling down||33 A2||Closed||Recurvatum at sagittal plane||Antegrade||1 to distal from anterior side||14||10|
|14/F/44||Traffic accident||33 A3||Closed||Recurvatum at sagittal plane||Antegrade||1 to distal from anterior side||32||15|
|15/F/38||Traffic accident||33 A2||Open; type 2||Valgus at coronal plane||Retrograde||1 to distal from lateral side||18||8|