Distal Interlocking Screws Research Articles

Interlocking nailing without imaging: the challenges of locating distal slots and how to overcome them in SIGN intramedullary nailing

Placement of the distal interlocking screw is the most difficult part in all intramedullary nail interlocking screw systems and the Surgical Implant Generation Network (SIGN) interlocking system is not an exception. SIGN nails are interlocking implants designed with a precision instrumentation set for use in treatment of long bone fractures without an image intensifier. Locating the distal slots of SIGN nails could be challenging for young SIGN surgeons when treating very complex comminuted fractures and in obese patients. This study was stimulated by a patient who presented one year after surgery with knee pain due to a migrating nail because of missed distal screws. A total of 48 patients divided into two groups of 24 were studied retrospectively and prospectively. The retrospective studies revealed that failure to locate distal locking slots in ten antegrade nailing procedures was due to wrong entry point and comminution of the fracture. The challenges encountered led us to innovating methods to overcome the difficulties of placement of distal screws in a prospective study. Application of methods A and B made location of the distal slots easier in the prospective study even though there were more complex comminuted fractures. The methods also reduced the antegrade operation time by 1 hour 11 minutes. We concluded that SIGN nailing could be challenging and frustrating at the early learning stage. Application of the two innovative methods will make distal slot location easier. They will also make SIGN interlocking nailing less difficult for young SIGN surgeons as they journey through the learning curves.

Distal Interlocking Screws With a Modular Revision Stem for Revision Total Hip Arthroplasty in Severe Bone Defects

A prospective study of 15 patients was designed to examine whether the modular cementless revision stem (Revitan curved; Zimmer GmbH, Winterthur, Switzerland) is suitable for stem revisions with a defective isthmus when distal interlocking screws are also used for fixation. During a follow-up period of 35.4 ± 11.4 months (24-70 months), there was one stem loosening with screw breakage in a case of a stem that was too thin. According to Engh et al, bony ingrowth fixation of the stem occurred in 12 cases and stable fibrous fixation in 2 cases. The Harris Hip Score rose continuously from 44.7 ± 12.9 points preoperatively to 75 ± 10 points at 24 months. This concept of additional stem fixation with distal interlocking screws represents a useful treatment option for revision arthroplasty in rare cases of a defective isthmus.

Reducing radiation exposure in intra-medullary nailing procedures: Intra-medullary endo-transilluminating (iMET)

The purpose of the study was to reduce the level of radiation exposure during intra-medullary nailing procedures. A visible light source was inserted into the medullary bone cavity in order to detect the distal interlocking screw holes. The light penetrates out of the bone surface, revealing the position of the screw hole, and this allows the subsequent drilling and placing of the interlocking screw to be free of fluoroscopy. Among the 19 consecutive tibia-fracture patients recruited for this study, no repetition of the drilling procedure or insertion of a transverse interlocking screw was needed. The average time to finish the insertion of one distal interlocking screw was 4.1 ± 1.8 min. It was extrapolated that 13–41% of previous radiation exposure levels could be saved. The non-fluoroscopic approach thus decreases the health hazards that the patients are experiencing as well as those of the surgical team who need to perform such intra-medullary nailing operations on a routine basis.

Introduction: Biology and New Technical Trends in Intramedullary Nailing of the Femur

In the early part of the new millennium, technique and implant improvements in orthopaedic traumatology have focused on minimally invasive surgical techniques and fixedangle or locked plating. Meanwhile, during this period, improvements in both implants and surgical techniques for intramedullary nailing have also been recognized. The focus of this Journal of Orthopaedic Trauma supplement is to highlight the advances in implants, surgical techniques, and basic science research for intramedullary nailing of the femur. The slotted cloverleaf nails of Kuntscher (Fig. 1) and the intramedullary implants of today share little more than outward appearance. Certainly, the development of interlocking screws has been a major step. Changes in implant design and instrumentation allow for easier insertion. New alternatives for proximal and distal interlocking screws provide additional stability for juxtaarticular fractures. Interlocking screws that are angle stable or attach to the nail optimize stability in unstable and/or osteoporotic fractures. Internal nail compression instrumentation and techniques allow for better adaptation of displaced fractures. Moreover, a more thorough understanding of the posttraumatic, hypoxemic, and immunologic changes has provided the ability to better plan the best timing for intramedullary fracture fixation. Also, an increasing body of research on the technical aspects of intramedullary nailing has provided new animal models for the study of fracture healing. Additionally, research directed toward maximizing functional recovery in terms of rehabilitation has improved patient outcomes. It is hoped that the advancements addressed in this supplement will contribute positively to the art and science of intramedullary nailing of femoral shaft fractures. The authors would like to thank the Editor of the Journal of Orthopaedic Trauma for the opportunity to summarize the recent developments. FIGURE 1. Gerhard Kuntscher, 1900–1972.

An intramedullary nail with multifunctional interlocking for all types of fracture in both femurs

A femoral compound interlocking intramedullary nail (FCIIN) was designed to treat all types of fractures between the trochanter and epicondyle of both femurs. It could substitute for femoral interlocking intramedullary nails (FIIN) at five points. According to the morphological characteristics of the femoral medullary canal, the nail is designed to accommodate a 1250 mm radius of radian and a 135° neck-shaft angle. Three interlocking holes of 6.5 mm diameter are located at the proximal end of the FCIIN, making crossing of the screws possible. The hole is designed to be vertical (90°) or oblique (45° upper or lower). At the tip of the proximal interlocking screws, whose root diameter gradually increases from 3.5 mm to 6.5 mm, a self-tapping cancellous screw is placed. There are two types of distal interlocking screws. One is a fine thread and the other a bolt screw. Two interlocking holes and a recess 4.5 mm in diameter are located at the distal end of the FCIIN. Under biomechanical destructive testing, the proximal interlocking screw device has satisfactory strength and reasonable structure. A total of 47 patients (31 males and 16 females, with an average age of 39.83 years) with femoral fractures were assessed in this study. Fourteen cases were diagnosed as intertrochanteric, 7 as subtrochanteric, 18 as femoral shaft, and 8 as supracondylar fractures. All 47 patients were treated with the FCIIN. Of the 47 patients, anatomic reduction was achieved in 34, good reduction in 11, and forced line reduction in 2 cases. Reduction was excellent or good in 95.87% of the fractures. The removal time of the FCIIN was 12 to 21 months (average, 16.9 months). One patient with an intertrochanteric fracture who had a fixation failure combined with non-union achieved healing with an external fixator at 18 months. Failure to insert the distal interlocking screws occurred in 5 patients but did not affect bone healing. The FCIIN is a useful device in the treatment of a variety of femoral fractures.

Unreamed Intramedullary Nailing with Oblique Proximal and Biplanar Distal Interlocking Screws for Proximal Third Tibial Fractures

To assess the outcome of unreamed intramedullary nailing through the lateralised entry point using oblique proximal and biplanar distal interlocking screws. 15 men and 3 women aged 25 to 58 (mean, 37) years underwent unreamed intramedullary nailing with oblique proximal and biplanar distal interlocking screws for proximal third metaphyseal tibial fractures. The entry point was kept proximal to the tibial tuberosity and slightly lateral to midline. Proximal locking was at 45 degrees to the coronal and sagittal planes. Biplanar distal locking was in the coronal and sagittal planes. 16 patients had bone union within 20 (mean, 17; range, 14-27) weeks; 2 underwent dynamisation for delayed union. Three patients had valgus angulation of less than 5 degrees; 2 had a loss of terminal knee flexion; 3 had a loss of ankle dorsiflexion; and 3 had shortening of more than 0.5 cm. Functional outcomes were excellent in 13, good in 4, and fair in one patient. No patient endured neurovascular injury, compartment syndrome or implant failure. Unreamed intramedullary nailing with oblique proximal and biplanar distal interlocking screws for proximal third tibial fractures was effective in preventing malalignment.

Factors influencing interlocking screw failure in unreamed small diameter nails – A biomechanical study using a distal tibia fracture model

Background Unreamed tibia nails with small diameters are increasingly used for fracture fixation. However, little is known about the fatigue strength of proximal and distal interlocking screws in those nails. To date, no data are available reporting on mechanical differences of solid compared to cannulated tibial nails. The aim of this study was to assess the fatigue strength of proximal and distal interlocking screws of solid and cannulated small diameter tibia nails. Methods We created a distal tibia fracture model (AO/OTA 43 A3) using 16 Sawbones. After fracture stabilization with one of four different nail types (Expert Tibial Nail™, VersaNail™, T2 Tibial Nailing System™, Connex™), mechanical testing was performed in three loading series (40,000 cycles each) with incremental loads. Timing and type of interlocking screw failure were assessed. Findings Interlocking screw failure was observed significantly earlier (after a mean interval of 57,042 cycles) in cannulated tibial nails (VersaNail™, T2™) compared to solid nails (after a mean interval of 88,415 cycles; P < 0.001). Proximal interlocking screw failure was recorded if oblique screws were used proximally (VersaNail™, T2™, Connex™). No distal interlocking screw failure was recorded in the Connex™ nail. Two- and three-part fractures of proximal or distal interlocking screws were observed in all specimen. Interpretation Proximal and distal interlocking screw failure has to be considered in small diameter nails in case of delayed fracture healing. To support our results, further experimental studies and clinical series are necessary.

Pseudoaneurysm of the lateral geniculate artery at the distal interlocking screw site

Arterial complications at the site of distal interlocking screws of interlocked intramedullary nails are uncommon. This case report illustrates a 45-year-old male who was diagnosed with a pseudoaneurysm of the lateral geniculate artery when he was worked-up for persistent pain and swelling over the distal lateral thigh. He underwent obliteration of the pseudoaneurysm with thrombin injection and had excellent relief of pain and subsequent decrease in swelling. We are not aware of any case reports of pseudoaneurysm of the lateral geniculate artery at the distal screw insertion site of interlocked intramedullary nails.

Efficacy of an aiming device for the placement of distal interlocking screws in trochanteric fixation nailing

Locked intramedullary nailing continues to be the surgical treatment of choice for most long bone fractures. Performing distal interlocks can be a technical challenge. Free hand (FH) technique remains to be most popular. Radiation exposure, particularly to the surgeon still remains a concern with this technique. A prospective randomized analysis of 20 patients undergoing operative fixation with long trochanteric fixation nailing for intertrochanteric or subtrochanteric fractures was performed. The groups were randomized into (1) aiming arm group (AA) and (2) FH group by computer generated randomization technique. Two distal interlocking screws were placed in every case. Various parameters were analyzed including total operating time, distal interlocking time, total fluoroscopy time, distal fluoroscopy time and nail dimensions. The variables in two groups were compared to each other using Fischer's exact test. The mean distal interlock time was 7.1 +/- 2.4 and 12.1 +/- 3.2 min for AA and FH techniques respectively. There was a 41.3% decrease in the distal interlock time with the device, which was statistically significant (P < 0.001). The distal interlock fluoroscopy time was 9.2 +/- 4.9 and 28.9 +/- 16.4 s with AA technique and the FH technique respectively. This 68.2% reduction in time taken for distal fluoroscopy was statistically significant (P < 0.001). However, the reduction in the total fluoroscopy time was statistically not significant. The AA is very efficient and user friendly and also reduces the radiation exposure.

Correction of Anteversion in Skeletally Immature Patients

There has been reluctance by some surgeons to accept antegrade femoral nailing in children and adolescents due to concerns about producing iatrogenic osteonecrosis or growth disturbance of the femoral neck. Others believe that with the recent advent of pediatric transtrochanteric intramedullary nails, femoral fracture and osteotomy fixation may now safely be accomplished using these devices. Extrapolating from experience treating mature patients, the senior author (P.S.) has adopted the technique of percutaneous femoral osteotomy and transtrochanteric intramedullary fixation in skeletally immature patients as a standard approach for the correction of anteversion, combining this with concomitant surgery as indicated. With the institutional review board approval, we reviewed our experience using the Phillips intramedullary rod (EBI/Biomet, Inc, Warsaw, Ind), to secure femoral osteotomies in a series of 30 patients with 40 femoral osteotomies (10 bilateral). The etiologies of anteversion included idiopathic and neuromuscular. There were 10 boys and 20 girls, ranging in age from 8 to 16 years and in weight from 32 to 60 kg. Additional surgical bony and soft tissue procedures were combined as indicated. These included supramalleolar osteotomy, hindfoot stabilization, tendon lengthening or transfers, and hemiepiphysiodesis in select patients. Two of the femoral rotational corrections were combined with shortening. Despite early mobilization without casts, each osteotomy healed primarily in an average of 3 months, and the complication rate was exceedingly low. One patient had removal of a loose distal interlocking screw at 6 weeks postinsertion. By that time, he had formed good callus and had rotational stability; thus, the outcome was not compromised. Importantly, we have not observed osteonecrosis, growth disturbance of the femoral neck, or limb length discrepancy resulting from this treatment method. In the skeletally immature patient, femoral anteversion can safely be corrected using the Phillips/Biomet antegrade locked intramedullary rod, placed through a transtrochanteric approach; growth disturbance has not been encountered. This device is well tolerated, with a low complication rate. Compared with alternative techniques, recuperation is rapid and fixation problems seen with plates or crossed pins/spica are largely circumvented. The advantages include quadriceps sparing, minimal blood loss, and the use of a load-sharing, low-profile implant. IV (retrospective, clinical).

Nailing Before Vascular Repair in Tibial Fracture With Associated Arterial Injury

The incidence of arterial injuries in extremity fractures is approximately 1% to 2%. In patients with combined vascular and orthopedic injury but without a mangled extremity, the decision whether to give priority to the fracture fixation or to the vascular repair is still somewhat controversial. We successfully used the unreamed tibial nail before the arterial repair when treating an open tibial shaft fracture associated with a torn anterior tibial artery and present it as an illustrative case for the method. Fracture alignment was achieved manually and an unreamed tibial nail was introduced. The nail was secured only proximally by two interlocking screws inserted through jig. The procedure provided good alignment and length for end-to-end reconstruction of the anterior tibial artery. The distal interlocking screws were inserted at the end of vascular reconstruction.

A new fluoroscopy-free navigation device for distal interlocking screw placement

During the treatment of tibia fracture with interlocking nails, the most uncomfortable procedure is for an orthopaedic surgeon to find the location for the distal locking screws. In this study, a fluoroscopy-free non-contact navigation device was developed for the placement of distal locking screws in the tibia intramedullary nailing. This device utilizes a 3D digitization arm integrated with spatial coordinate registration module, graphical user interface module and sound-guided navigation module. The 3D digitization arm, a five-DOF passive robotic arm, was used to register the spatial coordinates of proximal and distal landmarks just before placement of the nail. The registered coordinates were then incorporated with the coordinates of the proximal landmarks after nail placement to calculate the coordinate transformation matrix. The transformed spatial coordinates of the distal screw holes were then computed in real time for interlocking nail navigation. A sound-guided navigation module was designed in which a sound with different tones and intermittence frequencies was produced, as the probe of the digitization arm navigates toward the location of distal screw holes. No intra-operative fluoroscopy was required. In vitro assessment was performed successfully with a donor bone, and a clinical case of a young male with tibia fracture was also carried out in the operating theatre. Operation time, distal screw insertion, total radiation time and accuracy of the distal interlocking screw placement were measured. The surgery was conducted under sterile conditions without complication, and the clinical course was smooth with prompt bone healing.

Der Einsatz einer modularen Hüftprothese (MHP) mit distaler Verriegelungsmöglichkeit bei Knochendefektsituationen des Femurs

Patients with bony defects of the proximal femur after trochanteric fracture, implant failure (cut-out), periprosthetic fracture or aseptic loosening of prosthesis are difficult to treat with primary or revision endoprosthesis. Modular femoral hip prosthesis (MHP) with stems of different length and the possibility of distal interlocking screws are an operative solution for those patients. In a prospective study from January 1996 to January 2002 all patients treated with a MHP because of proximal and / or distal femoral bony defect or fracture were included. Follow-up after 6 to 30 months was evaluated clinically and radiologically in hospital. Change of modified Harris Hip Score and radiological signs of loosening (radiolucent line, migration of MHP, breaking interlocking screw) were documented. 106 patients with a follow-up of 58.5 % were included in the study. At time of follow-up clinical and radiological outcome after trochanteric fracture was good. Harris Hip Score was comparable to the situation of patients before fracture, only one MHP was loose. However in patients after revision arthroplasty 25 % of MHP were loose and in many patients the interlocking screw was broken. Distal interlocking screw in MHP prevents stability after trochanteric fracture to achieve osseointegration. However in case of periprosthetic fracture or revision arthroplasty MHP shows insufficient stability in many cases.

The effectiveness of the external distal aiming device in intramedullary fixation of tibial shaft fractures

Intramedullary nailing has become a popular and effective procedure for the treatment of most fractures of the tibial diaphysis. However, distal interlocking screw placement under fluoroscopic control is responsible for the majority of the radiation exposure and a significant loss of surgical time in the entire nailing procedure. To limit fluoroscopy use, during distal interlocking screw placement, Orthofix has developed a distal targeting device which compensates for the inevitable deformation of the nail in the sagittal plane during its insertion. This prospective clinical study evaluates the efficacy of this distal targeting device for distal locking. One hundred and fifteen fresh tibial fractures in the same number of patients with a mean age of 37.5 years (17-85 years) were treated with operative stabilization using the Orthofix tibial nailing system. The mean duration of the operation was 38 min (20-55 min). A mean of four intra-operative plain X-rays (2-6 X-rays) were used in 103 cases to confirm guide wire placement, final nail insertion and accuracy of screws placement. The mean duration of the use of the image intensifier utilized in the remaining 12 fractures was 5 s (3-8 s). The distal targeting device failed in 12 (5.2%) distal locking screws. This study demonstrates that distal locking can be performed easily and successfully with minimal exposure to radiation, once the surgeon develops a reasonable experience with the use of this distal targeting device.

The risk of injury to neurovascular structures from distal locking screws of the Unreamed Humeral Nail (UHN): A cadaveric study

When performing distal interlocking of an intramedullary humeral nail, there is risk of iatrogenic injuring to the neurovascular structures. Our cadaveric study with frozen sections through the distal humerus presents the anatomic relationship of the different neurovascular bundles and the trajectories used for the implantation of the three distal interlocking screws of the AO-UHN. The middle lateromedial pin was in direct contact with the radial nerve in 3 out of 10 cases, with the ulnar nerve in 3 out of 10 cases and with the brachial artery in 1 out of 10 cases. We recommend using only the two anteroposterior screws for distal interlocking, avoiding the lateromedial locking option. If this lateromedial locking screw is needed to gain adequate stability, it should be introduced under visual control.

Accurate and reliable pose recovery of distal locking holes in computer-assisted intra-medullary nailing of femoral shaft fractures: A preliminary study

Objective: One of the difficult steps in intra-medullary nailing of femoral shaft fractures is distal locking – the insertion of distal interlocking screws. Conventionally, this is performed using repeated image acquisitions, which leads to considerable irradiation of the patient and surgical team. Virtual fluoroscopy has been used to reduce radiation exposure, but can only provide multi-planar two-dimensional projection views. In this study, two calibrated fluoroscopic images were used to automatically recover the positions and orientations of the distal locking holes (DLHs). The ultimate goal is to provide precise three-dimensional guidance during distal locking.Methods: A model-based optimal fitting process was used to reconstruct the positions and orientations of the DLHs from two calibrated fluoroscopic images. No human intervention is required. A preliminary in vitro validation study was conducted to analyze the accuracy and reliability of the technique using images acquired from different viewpoints. The ground truths of the DLH were obtained by inserting a custom-made steel rod through the hole and then digitizing both the top and bottom centers of the rod using a sharp pointer. The recovery errors were computed by comparing the computed results to the ground truths.Results: In all experiments, the poses of the DLHs could be recovered fully automatically. When the recovered positions and orientations of the DLHs were compared to their associated ground truths, a mean angular error of 0.5° (STD = 0.2°), and a mean translational error of 0.1 mm (STD = 0.0 mm) were found.Conclusions: Accurate and reliable pose recovery of distal locking holes from two calibrated fluoroscopic images is achievable. Our preliminary in vitro experimental results demonstrate that the recovered poses of the distal locking holes are sufficiently accurate for intra-operative use.

Accurate and reliable pose recovery of distal locking holes in computer-assisted intra-medullary nailing of femoral shaft fractures: A preliminary study

Objective: One of the difficult steps in intra-medullary nailing of femoral shaft fractures is distal locking – the insertion of distal interlocking screws. Conventionally, this is performed using repeated image acquisitions, which leads to considerable irradiation of the patient and surgical team. Virtual fluoroscopy has been used to reduce radiation exposure, but can only provide multi-planar two-dimensional projection views. In this study, two calibrated fluoroscopic images were used to automatically recover the positions and orientations of the distal locking holes (DLHs). The ultimate goal is to provide precise three-dimensional guidance during distal locking.Methods: A model-based optimal fitting process was used to reconstruct the positions and orientations of the DLHs from two calibrated fluoroscopic images. No human intervention is required. A preliminary in vitro validation study was conducted to analyze the accuracy and reliability of the technique using images acquired from different viewpoints. The ground truths of the DLH were obtained by inserting a custom-made steel rod through the hole and then digitizing both the top and bottom centers of the rod using a sharp pointer. The recovery errors were computed by comparing the computed results to the ground truths.Results: In all experiments, the poses of the DLHs could be recovered fully automatically. When the recovered positions and orientations of the DLHs were compared to their associated ground truths, a mean angular error of 0.5° (STD = 0.2°), and a mean translational error of 0.1 mm (STD = 0.0 mm) were found.Conclusions: Accurate and reliable pose recovery of distal locking holes from two calibrated fluoroscopic images is achievable. Our preliminary in vitro experimental results demonstrate that the recovered poses of the distal locking holes are sufficiently accurate for intra-operative use.

Tibiotalocalcaneal Arthrodesis Using a Dynamically Locked Retrograde Intramedullary Nail

Tibiotalocalcaneal arthrodesis is an important salvage method for patients with complex hindfoot problems, including Charcot arthropathy, osteonecrosis of the talus, combined arthritis of the ankle and subtalar joint, and failed total ankle arthroplasty. This study evaluated the results of a dynamic retrograde intramedullary nail for fixation with posterior to anterior distal interlocking screws placed through the calcaneus for tibiotalocalcaneal fusion. Thirty-three consecutive tibiotalocalcaneal fusions were done by a single surgeon (DBT) and were stabilized with a dynamic retrograde intramedullary nail. Time to fusion, impaction of the nail relative to the intramedullary canal, nail-tibial angle, and complications were noted. Average followup was 14 months. Twenty-nine of 33 feet (88%) fused at an average of 3.7 months after surgery. Average impaction of the nail was 2.3 (0.5 to 5.0) mm. Cortical hypertrophy at the tip of the rod or at the proximal interlocking screw was noted in 13 of 27 patients. A trend toward a higher nonunion rate was noted in patients with an increased nail-tibial angle. Dynamic retrograde intramedullary nailing for fixation of the tibiotalocalcaneal fusions is a good method of stabilizing this complex fusion construct.

Pseudoaneurysm of Superficial Femoral Artery Following Proximal Femoral Nail Fixation

Pseudoaneurysm of the femoral artery is a rare complication following the fixation of the fracture of proximal femur or protruded bony fragment and reports injuring on superficial femoral artery is very rare compared to deep femoral artery complicated by the insertion of distal interlocking screw. The chance of injuring superficial femoral artery may increase by deep insertion of drill bit or the repetitive arterial pulsation on prominent distal interlocking screw tip during the perioperative period. Authors experienced one case of injury on the superficial femoral artery postoperative 42 hours followed by the use of proximal femoral nail advocated by the AO group recently and would like to call attention upon the possibilities of vessel injury complicated with the use of the distal interlocking screw.

Experiences with the BiCONTACT revision stems with distal interlocking

The first consecutive 68 revision total hip arthroplasties of a cementless distal interlocking femoral stem (BiCONTACT; Aesculap AG, Tuttlingen, Germany) are included in this study. Average follow-up time was 40 months (range, 36–49 months). At follow-up evaluation, one patient had died, and one could not be located. The average Harris hip score improved from 60 points to 88 points. All cases showed radiographic evidence of a bone ingrown prosthesis, and no subsidence was seen. No osteolysis and no radiologic loosening were noted. No repeat revision was needed during the follow-up period. The results of the distal interlocking femoral stems (BiCONTACT) in cementless revision total hip arthroplasty were satisfactory. These findings suggest that a diaphyseal fixation of the revision femoral stem with distal interlocking screws can provide primary axial and rotational stability of the prosthesis in revision surgery.