A distal femoral fracture medial column buttress anti-rotation intramedullary nail system

Abstract

The present application relates to the technical field of orthopedic medical devices, and particularly relates to a distal femoral fracture medial column support anti-rotation intramedullary nail system, which comprises a main nail configured to be implanted into the femoral medullary cavity from the medial condyle of the femur, extends along its axial direction and has a tail part and a head part; the tail part is provided with an anchoring part for anchoring in the cancellous bone inside the medial condyle of the femur, and the head part is provided with at least one first locking hole; a tension nail configured to be transversely implanted from the medial condyle of the femur to the lateral condyle of the femur and to pass through the tail part of the main nail, for connecting the medial condyle of the femur with the lateral condyle of the femur; and a locking nail configured to pass through the first locking hole of the head part of the main nail, for anchoring the head part of the main nail in the boundary area of the cortical bone and cancellous bone of the lateral condyle of the femur. The intramedullary nail system provides reliable medial column axial support and anti-rotation stability for the distal femoral fracture through minimally invasive implantation from the medial condyle of the femur.

Description

Technical Field

[0001] This invention relates to the field of orthopedic medical device technology, and in particular to an intramedullary nail system for medial column support and anti-rotation of distal femoral fractures. Background Technology

[0002] Comminuted fractures of the supracondylar and intercondylar eminences of the femur (such as AO classifications A3, C2, and C3) are a challenge in clinical treatment. These fractures are often accompanied by severe comminutedness or bone defects of the medial column, leading to loss of medial mechanical support and a very high risk of varus collapse. To achieve stable fixation, current techniques mainly rely on the following three approaches, but all have significant drawbacks: First, the simple distal femoral lateral locking compression plate (LCP): This is the most commonly used approach. However, when the medial column is missing, all the load is borne by the lateral plate, resulting in a huge cantilever moment, which can easily lead to plate fatigue fracture, screw pullout, or varus malunion, resulting in a high failure rate of internal fixation.

[0003] Second, the combination of lateral locking plate and auxiliary medial locking plate (LCP+ALP): To enhance medial support, a small medial plate is placed via a medial approach after the lateral plate is placed. While this approach improves mechanical strength, its inherent drawbacks are extremely prominent: 1. Extremely high risk of vascular and nerve injury: The medial side of the femur is adjacent to the femoral artery, vein, and saphenous nerve. The extensive soft tissue dissection and traction required by the medial approach can easily cause direct damage or compression to these important structures, potentially leading to catastrophic consequences. 2. Significant surgical trauma: A second long incision and extensive dissection are required, disrupting blood supply to the fracture ends, increasing the risk of infection, and violating the principles of minimally invasive surgery. 3. Limited effectiveness in patients with osteoporosis: The medial cortical bone is thinner, resulting in insufficient screw holding force and significantly reduced support.

[0004] Third, lateral locking plate combined with percutaneous medial column screw (LCP+PMCS): This method aims for minimally invasive enhancement. However, the screws only penetrate the bilateral cortex, resulting in weak holding force in osteoporotic bones. It cannot provide sufficient axial support and anti-rotational stability, and still has a high risk of failure.

[0005] Furthermore, existing retrograde intramedullary nail systems (such as those inserted from the lateral femoral condyle) are often insufficient for the stability of complex periarticular fractures as independent fixation devices, and cannot form an effective synergistic enhancement mechanism with lateral plates.

[0006] In summary, there is an urgent clinical need for a new internal fixation solution that can safely and minimally invasively provide strong and reliable medial column support and can work efficiently with the lateral plate system to solve the core problems of poor safety, large trauma, and unreliable mechanical support of existing technologies. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a medial column-supported anti-rotation intramedullary nail system that can be safely and minimally invasively implanted into the medial femoral condyle to provide reliable medial column axial support and anti-rotation stability for distal femoral fractures.

[0008] This invention provides a medial column-supported anti-rotation intramedullary nail system for distal femoral fractures, comprising: The master nail is configured to be inserted into the femoral medullary cavity from the medial condyle of the femur, extending along its axial direction and having a tail and a head; the tail is provided with an anchoring portion for anchoring in the cancellous bone of the medial condyle of the femur, and the head is provided with at least one first locking hole. The tension screw is configured to be inserted transversely from the medial femoral condyle to the lateral femoral condyle and pass through the tail of the main screw to connect the medial femoral condyle and the lateral femoral condyle. The locking pin is configured to pass through a first locking hole in the head of the master pin for anchoring the head of the master pin in the junction of the cortical and cancellous bone of the lateral femoral condyle.

[0009] The intramedullary nail structure is inserted minimally invasively through the medial femoral condyle. The anchoring part of the main nail utilizes the properties of cancellous bone to achieve initial stable fixation, preventing the main nail from loosening or shifting within the medullary cavity. The lag screw transversely penetrates the tail of the main nail and connects to the medial and lateral femoral condyles, not only enhancing the overall connection strength between the main nail and the distal femur but also effectively resisting the separation and displacement of the fracture ends. By applying transverse pressure to the medial and lateral femoral condyles, it promotes close alignment of the fracture site. The locking screw passes through the first locking hole in the head and is anchored at the junction of the cortical and cancellous bone of the lateral femoral condyle. This area has moderate bone density, allowing the locking screw to obtain good holding force, further enhancing the stability of the main nail head. Together with the anchoring part at the tail of the main nail and the lag screw, they jointly construct a multi-dimensional fixation system, significantly enhancing the anti-rotation ability of distal femoral fractures.

[0010] Furthermore, the tail of the main nail is provided with a threaded section to form an anchoring part, while the head of the main nail is a smooth section without threads, and the first locking hole is opened on the smooth section. The smooth section of the head facilitates the smooth insertion of the main nail from this area and conforms to the bone surface, reducing damage to the surrounding soft tissues during insertion, while enhancing the initial stability of the tail of the main nail in the cancellous bone and preventing unnecessary rotation of the main nail in the medullary cavity.

[0011] Furthermore, the tail end face of the master nail is designed as a slope, the gradient of which is adapted to the anatomical surface morphology of the medial femoral condyle. This avoids irritating soft tissues and reduces postoperative pain and discomfort caused by friction between the internal fixation device and surrounding tissues.

[0012] Furthermore, the head of the main nail is provided with multiple first locking holes, the number of locking nails corresponding to the number of first locking holes, and the projections of the axes of the multiple first locking holes onto the cross-section of the main nail are staggered. The staggered arrangement of the multiple first locking holes can fix the head of the main nail from different directions, increasing the anti-torsion effect and preventing the locking nails from loosening.

[0013] Furthermore, the head diameter of the main nail is no larger than the major diameter of its tail threaded section. This allows for a smooth transition during implantation, avoiding increased difficulty in medullary canal reaming and excessive bone damage due to an excessively large head diameter, while ensuring that the tail threaded section can provide sufficient anchoring force.

[0014] Furthermore, the lag screw includes a screw body and an engagement portion located at the front end of the screw body; the tail end of the main screw has a second locking hole through which the screw body can pass; the lag screw is configured to penetrate the medial femoral condyle and the lateral femoral condyle, and is screwed into and locked in the cortical bone of the lateral femoral condyle through the engagement portion at its front end. This effectively prevents the lag screw from coming out postoperatively.

[0015] Furthermore, the engagement part features a self-tapping thread with a triangular thread profile and a pitch of 1.5mm to 2.5mm. The sharp thread profile and moderate pitch enable efficient bone cutting during insertion, ensuring a strong bony bond between the traction screw and the lateral condylar cortex, providing powerful lateral tension.

[0016] Furthermore, the traction screw is a hollow screw, and the screw body diameter is the same as the major diameter of the front engagement portion. This facilitates insertion, does not damage the screw track, and improves stability.

[0017] Furthermore, the axis of the main nail and the axis of the traction screw form an acute angle, creating a triangular support structure for the medial column of the femur. This support structure effectively combines the longitudinal stress borne by the main nail with the lateral tensile force provided by the traction screw, enhancing the support strength for the medial column of the femur.

[0018] Furthermore, the main screw, tension screw, and locking screw are all made of titanium alloy. Titanium alloy has excellent biocompatibility, which can effectively avoid rejection reactions with human tissue and ensure the safety after implantation.

[0019] The beneficial effects of this invention are as follows: This invention provides a medial column-supported anti-rotation intramedullary nail system for distal femoral fractures. The system constructs a multi-dimensional stable fixation system by minimally invasively implanting the main nail from the medial femoral condyle, and using lag screws to laterally connect the medial and lateral femoral condyles, as well as intersecting locking screws to anchor the head of the main nail at the junction of the cortical and cancellous bone of the lateral femoral condyle. First, it solves the cantilever bending moment problem when the traditional lateral steel plate is fixed to the inner column defect. The main nail provides strong and reliable axial support for the inner column through the stable fixation in the cancellous bone by the tail anchoring part and the synergistic effect with the tension nail and locking nail, effectively reducing the risk of inversion and collapse. Secondly, compared to the combination of lateral locking plates and medial plates, this approach only requires a minimally invasive approach through the medial femoral condyle to complete the implantation, avoiding the high risk of vascular and nerve damage and huge surgical trauma associated with the medial approach, and maximizing the protection of blood supply to the fracture ends. Furthermore, the self-tapping threads at the tip of the lag screw and the anchoring of the locking screw in a specific bone area ensure sufficient holding force even in osteoporosis patients, overcoming the shortcomings of insufficient support from percutaneous medial column screws. Finally, the spatially intersecting arrangement of the main screw, traction screw, and locking screw not only provides support for the medial column but also significantly enhances the overall structure's anti-rotation performance through multi-plane mechanical constraints. This effectively prevents rotational displacement of the fracture ends during early postoperative activity, creating a stable mechanical environment for fracture healing. It is particularly suitable for complex distal femoral fractures complicated by medial column bone defects or osteoporosis. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort. Figure 1 This is a schematic diagram of the femoral condyle. Figure 2 This is a schematic diagram of the intramedullary nail system; Figure 3 This is a structural diagram of the master nail; Figure 4 yes Figure 2 A schematic diagram of the implantation status; In the diagram: 1. Main nail, 11. Head, 12. Tail, 13. Anchoring part, 14. First locking hole, 15. Second locking hole, 16. Sloping surface, 2. Tension nail, 21. Engagement part, 3. Locking nail, 4. Distal femur, 41. Lateral femoral condyle, 42. Medial femoral condyle, 43. Cancellous bone, 44. Cortical bone. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] like Figure 1 As shown, the femoral condyle is mainly composed of cancellous bone 43, with a thin layer of cortical bone 44 on its surface. It has a medial femoral condyle 42 and a lateral femoral condyle 41. The medial femoral condyle 42 has a larger radius of curvature and a more regular shape in the sagittal plane; the lateral femoral condyle 41 has a smaller radius of curvature and is more prominent in the sagittal plane. The difference in the morphology of the two condyles matches the corresponding tibial plateau and meniscus, together forming the bony basis for the knee joint to bear weight and achieve flexion, extension, and rotational movements. To address the problems often encountered with traditional intramedullary nails in treating distal femoral fractures, especially those involving medial column instability, such as insufficient medial support, poor anti-rotation ability, and poor postoperative fracture healing or internal fixation failure, a medial column-supported anti-rotation intramedullary nail system for distal femoral fractures is designed, such as... Figure 2 As shown, the system includes a main nail 1, a tension nail 2, and a locking nail 3. The axis of the main nail 1 and the axis of the tension nail 2 form an acute angle, creating a triangular support structure for the medial column of the femur. The main nail 1, tension nail 2, and locking nail 3 are all made of titanium alloy with excellent biocompatibility. The tail 12 of the main nail 1 has a threaded section, which can effectively hold the cancellous bone 43 and provide good axial load. The tension nail 2 at the tail 12 can fix the medial femoral condyle 42 and the lateral femoral condyle 41 into a single unit, further increasing mechanical strength. The head 11 of the main nail 1 is unthreaded, allowing easy access to the junction area of ​​the cortical bone 44 and cancellous bone 43 of the distal femur 4. The locking nail 3 fixes the medial column of the distal femur 4 into a single unit. The stability (axial and rotational) of the medial column of the distal femur 4 is achieved through the intramedullary nail.

[0023] like Figure 3 As shown, the main nail 1 is configured to be inserted into the femoral medullary cavity from the medial femoral condyle 42, extending axially and having a tail 12 and a head 11; the tail 12 has an anchoring portion 13 for anchoring within the cancellous bone 43 of the medial femoral condyle 42, and the head 11 has at least one first locking hole 14. The anchoring portion 13 is specifically an externally threaded structure, the pitch and tooth profile of which are biomechanically optimized to form a strong thread engagement with the cancellous bone 43, providing good support and holding force within the cancellous bone 43, preventing the main nail 1 from loosening or sinking under axial load. The overall length and diameter of the main nail 1 can be designed in various specifications according to the size of the patient's femoral medullary cavity to meet the needs of patients of different body types.

[0024] To avoid irritating the soft tissue, the tail 12 end face of the main nail 1 is set as a ramp 16, the slope of which is configured to adapt to the anatomical surface morphology of the medial femoral condyle 42.

[0025] To avoid increasing the difficulty of medullary canal reaming and causing excessive damage to the bone due to the excessive diameter of the head 11, the diameter of the head 11 of the main nail 1 is no greater than the major diameter of its tail 12 threaded segment, so that the main nail 1 can form a smooth transition during implantation and ensure that the tail 12 threaded segment can provide sufficient anchoring force.

[0026] The tension screw 2 is configured to be inserted laterally from the medial femoral condyle 42 to the lateral femoral condyle 41, and passes through the tail 12 of the main screw 1 to connect the medial femoral condyle 42 and the lateral femoral condyle 41. A second locking hole 15 is provided at the tail 12 of the main screw 1, extending along the width of the distal femur 4. The diameter of this second locking hole 15 matches that of the tension screw 2 to ensure that the tension screw 2 can smoothly pass through and laterally penetrate the bone of the medial femoral condyle 42 and the lateral femoral condyle 41, tightly connecting the two condyles and effectively increasing mechanical strength.

[0027] The traction screw 2 includes a screw body and an engagement portion 21 located at the front end of the screw body. The traction screw 2 is configured to penetrate the medial femoral condyle 42 and the lateral femoral condyle 41, and is screwed into and locked into the cortical bone 44 of the lateral femoral condyle 41 through the engagement portion 21 at its front end. The engagement portion 21 is self-tapping threaded with a triangular thread profile and a pitch of 1.5 mm to 2.5 mm. Its length is selected according to the actual width of the patient's femoral condyle to ensure sufficient bone retention at both ends. The sharp thread profile and moderate pitch enable efficient bone cutting during screwing, ensuring a strong bony bond between the traction screw 2 and the cortical bone 44 of the lateral femoral condyle 41, providing strong lateral traction.

[0028] Specifically, the tension screw 2 is a hollow screw with a through-hole in the center. The diameter of the screw body is consistent with the major diameter of the front occlusal portion 21, facilitating implantation without damaging the screw track and improving stability in the later stages of implantation. During the surgery, the surgeon can pre-implant a guide pin along a pre-designed path (from the medial femoral condyle 42 through the second locking hole 15 at the tail of the main screw 1, pointing towards the lateral femoral condyle 41). The tension screw 2 can then be screwed in along this pre-positioned guide pin, ensuring absolute precision in the implantation path and avoiding potential path deviations that may occur with solid screws during blind or fluoroscopic procedures. This greatly simplifies the surgical procedure and improves the accuracy and efficiency of implantation. The screw body diameter is consistent with the major diameter of the front occlusal portion 21. When implanted along the guide pin, the entire screw body (including the smooth screw body section and the threaded section at the front end) has a very high degree of matching with the diameter of the screw track pre-established by the drill bit or guide pin. The screw body can smoothly follow the guide pin into the screw track without additional track expansion, resulting in low resistance and smooth operation. The entire length of the tension nail 2 forms a tight, gapless fit with the surrounding bone, effectively resisting micromovements in all directions and providing long-term stability for fracture healing.

[0029] The locking pin 3 is configured to pass through the first locking hole 14 of the head 11 of the main nail 1, for anchoring the head 11 of the main nail 1 in the junction area of ​​the cortical bone 44 and cancellous bone 43 of the lateral femoral condyle 41. Preferably, there are 2-3 first locking holes 14 in the head 11 of the main nail 1, and the number of locking pins 3 corresponds to the number of first locking holes 14. The insertion directions of the multiple first locking holes 14 are intersected, forming a multi-planar fixation support. After the locking pin 3 passes through the first locking hole 14 and is screwed into the junction area of ​​the cortical bone 44 and cancellous bone 43 of the lateral femoral condyle 41, it can effectively fix the head 11 of the main nail 1 from different directions, restricting its rotation and displacement within the medullary cavity. The head 11 of the main nail 1 is a smooth, unthreaded segment, which reduces stimulation to surrounding bone tissue during implantation. The first locking hole 14 is located on this smooth segment.

[0030] like Figure 4As shown, during the specific implantation procedure, the patient first lies supine with the affected hip joint flexed at approximately 45° and the knee joint flexed at 90°. The location and morphology of the distal femoral 4th segment fracture are confirmed using C-arm fluoroscopy. The entry point for the main nail is marked on the medial femoral condyle 42. This entry point is typically chosen in the anterior-central region of the medial femoral condyle 42, where the cortical bone 44 is relatively thin, facilitating the implantation of the main nail 1 and effectively avoiding important neurovascular structures. Next, an opening device is used to drill through the cortical bone 44 at the marked point to establish an initial channel. A guide pin is then inserted along this channel, ensuring it passes through the fracture line and reaches the center of the proximal femoral medullary canal. Fluoroscopy is then used again to confirm the guide pin's position. Subsequently, guided by the guide pin, medullary canal reams are used sequentially from small to large. During reaming, the reaming process must be slow and gentle to avoid bone fracture caused by forceful manipulation. The reaming diameter should be 0.5-1 mm larger than the selected main nail 1 diameter to ensure successful implantation and good adhesion to the medullary canal wall. After the medullary canal is reamed, the main nail 1 is slowly screwed into the medullary cavity along the guide pin. During the implantation process, the direction and depth of the main nail 1 are continuously monitored by fluoroscopy to ensure that the head 11 of the main nail 1 reaches the junction area of ​​the cortical bone 44 and cancellous bone 43 of the lateral femoral condyle 41, and the anchoring part 13 of the tail 12 is completely inserted into the cancellous bone 43 of the medial femoral condyle 42, and the slope surface 16 of the tail 12 is in close contact with the anatomical surface morphology of the medial femoral condyle 42. After the main nail is implanted, under C-arm fluoroscopy, a guide pin is drilled through the second locking hole 15 of the main nail tail 12 from the medial femoral condyle 42 to the lateral femoral condyle 41. After confirming that the guide pin has passed through the cortical bone 44 of the lateral femoral condyle 41, the tension screw 2 is screwed in along the guide pin, so that the engaging part 21 of the tension screw 2 is screwed into and locked in the cortical bone 44 of the lateral femoral condyle 41, ensuring that both ends of the tension screw 2 have sufficient bone holding force to tightly connect the medial femoral condyle 42 and the lateral femoral condyle 41. Then, under fluoroscopic guidance, guide pins are drilled into the first locking hole 14 of the head 11 of the main nail 1, ensuring that the guide pin enters the junction area of ​​the cortical bone 44 and cancellous bone 43 of the lateral femoral condyle 41. Then, a corresponding number of locking screws 3 are screwed in along the guide pin, so that the locking screws 3 fix the head 11 of the main nail from different directions. After all locking screws were implanted, anteroposterior and lateral fluoroscopy was performed again using a C-arm X-ray machine to check the fracture reduction, the position and length of the main screw 1 and each locking screw, and to confirm that everything was correct. After that, the surgical incision was rinsed and closed by suturing layer by layer.

[0031] The above description is illustrative only and not restrictive of the present invention. Those skilled in the art will understand that many modifications, variations or equivalents can be made without departing from the spirit and scope defined by the appended claims, and all such modifications, variations or equivalents will fall within the protection scope of the present invention.

Claims

1. A medial column-supported anti-rotation intramedullary nail system for distal femoral fractures, characterized in that: include The main nail (1) is configured to be implanted into the femoral medullary cavity from the medial femoral condyle (42), extending along its axial direction and having a tail (12) and a head (11); the tail (12) is provided with an anchoring portion (13) for anchoring in the cancellous bone (43) of the medial femoral condyle (42), and the head (11) is provided with at least one first locking hole (14). The tension screw (2) is configured to be inserted laterally from the medial femoral condyle (42) to the lateral femoral condyle (41) and pass through the tail (12) of the main screw (1) for connecting the medial femoral condyle (42) and the lateral femoral condyle (41). Locking pin (3) is configured to pass through a first locking hole (14) through the head (11) of the main pin (1) for anchoring the head (11) of the main pin (1) to the junction of the cortical bone (44) and cancellous bone (43) of the lateral femoral condyle (41).

2. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The tail (12) of the main nail (1) is provided with a threaded section to form the anchoring part (13). The head (11) of the main nail (1) is a smooth section without threads, and the first locking hole (14) is opened on the smooth section.

3. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The tail (12) end face of the main nail (1) is set as a ramp (16), the slope of which is configured to adapt to the anatomical surface morphology of the medial femoral condyle (42).

4. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The head (11) of the main nail (1) is provided with a plurality of first locking holes (14), the number of locking nails (3) corresponds to the number of first locking holes (14), and the projections of the axes of the plurality of first locking holes (14) on the cross section of the main nail (1) are staggered.

5. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 2, characterized in that: The diameter of the head (11) of the master nail (1) is not greater than the major diameter of the threaded section at its tail (12).

6. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The tension nail (2) includes a nail body and an engagement portion (21) located at the front end of the nail body; the tail (12) of the main nail (1) has a second locking hole through which the nail body can pass; the tension nail (2) is configured to penetrate the medial femoral condyle (42) and the lateral femoral condyle (41), and is screwed into and locked in the cortical bone (44) of the lateral femoral condyle (41) through the engagement portion (21) at its front end.

7. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 6, characterized in that: The engagement part (21) is a self-tapping thread with a triangular thread profile and a pitch of 1.5 mm to 2.5 mm.

8. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 7, characterized in that: The tension nail (2) is a hollow nail, and the diameter of the nail body of the tension nail (2) is the same as the major diameter of the interlocking part (21).

9. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The axis of the main nail (1) and the axis of the tension nail (2) form an acute angle, forming a triangular support structure for the medial column of the distal femur (4).

10. The medial column-supported anti-rotation intramedullary nail system for distal femoral fractures according to claim 1, characterized in that: The main nail (1), tension nail (2) and locking nail (3) are all made of titanium alloy.

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