[Overview].
Subtrochanteric fracture of the femur, most authors define this fracture as a fracture occurring between the superior border of the lesser trochanter and the femoral stenosis. The fracture line sometimes continues proximally to the greater trochanter and distally to below the stenosis in the upper third of the femur; some literature reports the incidence to be 10%-30% of hip fractures. The complications of nonoperative treatment are high, and surgical treatment is mostly recommended.
[Anatomy and anatomy and physiology].
Subtrochanteric femur is an area of high mechanical stress concentration with high pressure in the medial cortex and high tension in the lateral cortex, and this area is composed of cortical bone, which is mostly comminuted when fractured, so fracture healing is slow and easy to cause non-union. After fracture, the proximal end of the fracture produces typical abduction, flexion and external rotation deformity, while the medial end of the femur is pulled medially by the strong adductor muscle due to the attachment of the adductor muscle. The stress on the internal fixation is concentrated, which makes it prone to fracture and failure.
[Etiology and pathogenesis
In the elderly, most of the fractures are typical low-energy injuries, accounting for only 25% of the fractures, while in the young, they are often caused by high-energy injuries such as car accidents, falls, and falls, which are prone to combined femoral neck and fellow limb fractures.
Diagnostic points]
Overview of diagnostic points
It is basically the same as intertrochanteric fracture and can be diagnosed by taking X-ray.
Typing and staging
1. Seinsheimer’s staging Seinsheimer proposed five types according to the number of fracture blocks, location and shape of the fracture line (Figure 1).
Type I: fracture without displacement or displacement <2mm.
Type II: fracture displaced as two fracture blocks. It is further divided into 3 subtypes, IIA transverse fracture under the small coarctation; IIB spiral fracture with the small coarctation in the distal fracture block. IIC spiral fracture with the small coarctation in the distal fracture block.
Type III: there are three fracture blocks, i.e., in addition to the subtrochanteric fracture, IIIA, there is still a small trochanteric fracture, and IIIB has a butterfly-shaped fracture block in the middle of the subtrochanteric fracture.
Type IV: comminuted fracture with 4 fracture blocks or more.
Type V: subtrochanteric fracture with intertrochanteric fracture.
Figure 1 Seinsheimer fracture subtrochanteric fracture type
2. Russell and Taylor typing Russell and Taylor proposed a typing based on the continuity of the lesser trochanter and the posterior extension of the fracture line to the greater trochanter involving the pyriform fossa, two factors affecting treatment.
Type I: the fracture line does not extend posteriorly to the pear-shaped fossa. In type IA fractures, the fracture mass and fracture line extend from the lesser trochanter down to the region of the femoral isthmus, and this region may have various degrees of comminuted bone fragments, including bilateral cortical bone fragments; in type IB fractures, multiple fracture lines and fragments are included in the region from the lesser trochanter to the narrow part.
In type II fractures, the fracture line extends proximally to the greater trochanter and the pear-shaped fossa; in type IIA fractures, the fracture line extends from the lesser trochanter to the pear-shaped fossa via the femoral isthmus, but there is no severe comminution of the lesser trochanter or larger fracture fragments; in type IIB fractures, the fracture line extends to the pear-shaped fossa, along with significant comminution of the medial femoral cortex and loss of continuity of the lesser trochanter.
Complications
1, hip inversion Hip inversion is the most common complication of subtrochanteric fracture. The root cause is the stretching of the femoral fracture by the abductor muscle and the incorrect entry point of the medullary pin. The key to prevention lies in the 1st accurate insertion of the medullary pin entry point. Due to the proximal flexion, abduction and external rotation of the fracture, it is difficult to accurately select the pear-shaped fossa entry point, and the anatomical axis of the femur to open the medulla, which must be confirmed in two planes of C-arm observation in the frontal and lateral position. There are two ways to reduce this difficulty, the
One is to medialize the trunk.
The second is the insertion of a Searle pin in the femoral neck to internalize the proximal end of the fracture. The second reason is incomplete medial femoral cortical structure. In case of incisional repositioning, bone grafting must be performed to reconstruct the medial integrity of the femur, and in case of indirect repositioning, intraoperative attention should be paid to measuring the force line between the anterior superior iliac spine and the 1st and 2nd toes through the midpoint of the patella, which is generally considered acceptable for <10° hip inversion.
2, fracture does not heal Fracture does not heal because of internal fixation failure and fracture, internal fixation fracture and failure occurs in the following three cases.
(1) Proximal locking nail mislocks, especially in postero-lateral femoral fractures, the proximal end of the fracture is displaced forward and the proximal locking nail enters the femoral head from between the posterior fracture lines of the femoral neck, and such locking should be avoided. Proper placement of the proximal locking nail requires fluoroscopic observation of the position of the locking nail in the femoral head. The proximal locking nail should be located in the lower middle third of the femoral head in the frontal position and in the center in the lateral position. Our experience is that when the femoral head is locked, if the 2 screws are not parallel in the frontal and lateral positions, one of the locking nails must be mislocked and should be carefully examined and corrected.
(2) When the medullary pin is not properly dynamized, the static locking can prevent limb rotation and shortening, and the fracture is not healed to remove the distal locking nail, especially in osteoporotic individuals, which must increase the proximal locking nail stress, resulting to proximal locking nail fracture and incurring fracture non-union. Therefore, it is not recommended to power the fracture before it is healed, and the distal locking nail can be removed before the intramedullary pin is taken after the fracture is healed, in order to improve the quality of the bone scab.
(3) Intramedullary pin fracture, intramedullary nail fracture mostly occurs at the proximal locking hole and also at the fracture line, which is caused by the lack of regular review before the fracture heals and the patient’s early complete weight bearing, and the fracture non-healing treatment should be re-internal fixation and bone grafting.
Treatment Overview
1, treatment principles The choice of treatment for subtrochanteric fracture of the femur depends on many factors, generally speaking, the non-operative treatment of traction must be strictly controlled for the indications, at present, the method of indirect repositioning and intramedullary fixation is mostly recommended instead of the previously adopted method of anatomical repositioning and reconstruction of the medial support, the latter angular plate or DHS fixation of subtrochanteric fracture with crushed medial structure, which requires incision and repositioning and bone grafting to reconstruct the medial structure. The injury is large and bleeding is high.
On the contrary, closed reduction with locking medullary pin fixation can avoid the previous incision and reconstruction of the medial structure, less bleeding, less trauma, no bone grafting, faster fracture healing, good quality of bone scab, reduced force arm of internal fixation compared with DHS, reduced stress on internal fixation, closed reduction does not interfere with the blood flow of the bone end to ensure normal fracture healing At the same time, due to the elastic fixation of the intramedullary pin, the quality of the bone scab can prevent complications after lateral plate fixation.
2, non-surgical bone traction method The treatment of subtrochanteric fractures using traction method, the treatment results reported inconsistent, Waddell use non-surgical treatment, to achieve satisfactory results only 36% ~ 50%. Only for inoperable or open fractures, the traction treatment method and precautions are the same as for intertrochanteric fractures, but the healing time is longer than for intertrochanteric fractures.
3.Surgical treatment
(1) Internal fixation characteristics: The commonly used cephalic intramedullary nails include the reconstructive intramedullary nail, γ nail and DHS nail.
The reconstructive intramedullary nail is the 2nd generation intramedullary nail, which is composed of a stainless steel intramedullary nail without a slide groove, and two proximal and two distal interlocking screws. The proximal interlocking screw is partially threaded, thus allowing for sliding and compression within the femoral neck, while the distal interlocking nail is a fully threaded screw that is inserted transversely to fix the distal femur, thus preventing rotation and shortening from occurring. Reconstructive nailing has yielded excellent clinical results for subtrochanteric fractures with minimal nonunion, and it is now a common method of treating high subtrochanteric fractures (Figure 2).
The γ nail has also been used in recent years as a new alternative technique for the treatment of proximal femur fractures. The γ nail was developed by combining the sliding hip screw with the intramedullary nailing technique, which is a strong intramedullary nail, and because the γ nail is closer to the medial side than the standard sliding compression hip screw plate, the patient’s weight is transmitted closer to the femoral spine than with the sliding compression hip screw, which enhances the mechanical strength of the placement. Also mechanically, for subtrochanteric femoral fractures involving medial cortical comminution, the gamma nail avoids the need for fracture anatomical reconstruction and is therefore beneficial in the treatment of retrograde intertrochanteric fractures or subtrochanteric femoral fractures.
There are also the following complications: 1st longitudinal fracture during insertion of the γ intramedullary nail, this medically induced fracture is a major intraoperative complication, designed with a 10° valgus bend at the proximal end of the γ nail, although avoiding the pear-shaped fossa and allowing access from its lateral side, this non-anatomically shaped intramedullary pin into the femoral medullary cavity can increase the stress in the medullary cavity of the femoral stem and lead to a three-point loading and thus potential fracture risk, in order to To prevent medically induced fractures, the proximal femoral medullary cavity should be enlarged by at least 2 mm compared to the chosen intramedullary nail and, in addition, violent hammering into it should be absolutely prohibited.
The intramedullary nail must be inserted by hand; the 2nd tension screw is dislodged in the femoral head, neck, which is caused by the tension screw bias outward or anterior-posterior; the 3rd intramedullary nail distal to the interlocking screw site and the fracture at the tail of the pin, the mechanical load is transmitted down the γ nail and concentrated at the tail of the nail located in the femoral stem, which can lead to a fracture of the femoral stem at the distal end of the intramedullary nail due to stress concentration. To prevent fractures distal to the intramedullary nail Staper recommends the use of custom lengthened γ-nails for the treatment of subtrochanteric femoral fractures with a length of 300-360 mm, which have become an important fixation method for the treatment of complex fractures of the proximal femur due to the mechanical advantages of the γ-nail.