Distal Femur Fractures
The surgical treatment of supracondylar distal femoral fractures with or without intra-articular involvement (Arbeitsgemunshaft für Osteosynthesefragen/Orthopaedic Trauma Association [AO/OTA] types 33A and 33C) is difficult because of such fracture characteristics as osteoporosis, multiplanar articular injury, a short distal femoral block, associated open wounds, and possible extensor mechanism injuries. Complications are significant and include infection, knee stiffness, malunion, nonunion, and the need for bone grafting.1–3 There has been an evolution in the treatment of distal femoral fractures in the past four decades, as nonoperative methods of treatment were the mainstay in the 1960s and early 1970s. Although the fractures healed without significant difficulty when treated non operatively, there was significant deformity and joint stiffness afterward.4,5
With this experience in mind, surgeons began to utilize techniques of open reduction and rigid internal fixation that were popularized by the AO group in the mid-1970s. During this time, Olerud,6 Wenzl,7 and Schatzker et al8,9 began utilizing the 95-degree angled blade plate, the condylar buttress plate, and the dynamic condylar screw (DCS) for rigid fixation of supracondylar and supracondylar/intercondylar femur fractures. These devices provided sufficient fixation to enable early range of motion, decreased stiffness, and improved mobility of the patient. These early surgical techniques were associated, however, with a significant risk of infection and need for bone grafting. Both of these complications were attributed to the relatively large surgical exposures utilized in the early experience with open reduction and internal fixation of these fractures. Bone grafting rates with classical open reduction and internal fixation ranged between 0% and 87%.1
The concept of biological plating was developed by Mast, Jakob, and Ganz.10,11 It entails the following principles:
Maintenance of soft tissue attachments and vascularity of cortical bone fragments
Anatomic restoration of the articular surface
Restoration of the appropriate length, rotation, and alignment of the metaphyseal/diaphyseal region using indirect methods, without preoccupation with complete anatomic restoration of this region
Bolhofner et al12 demonstrated the efficacy of biological plating for supracondylar femur fractures. In contrast to the early experience with internal fixation, maintenance of the soft tissue viability around the fracture resulted in 100% union. Since then, multiple series have documented the effectiveness of indirect reduction techniques for the repair of supracondylar femur fractures.13–19
Based on the experience with biological plating, surgeons sought ways to even further minimize the exposure of the metaphyseal/diaphyseal component of the fracture. This was accomplished by one of two surgical techniques popularized in the 1990s. The first was the use of retrograde intramedullary nailing.20–27 The results of retrograde nailing of the distal femur fracture are associated with lower rates of infection. The second was the use of sub-muscular plating to maintain the soft tissues around the distal femur fracture.28–30 With submuscular plating, the articular surface of the distal femur fracture can be maximally visualized and fixed while a plate can be slid along the femoral shaft in a submuscular manner. As with retrograde nailing of the femur, the nonunion and infection rates are quite low.13–19,31 However, as expected, whenever the fracture is not directly visualized, malreductions can be problematic.14,32
A significant advance in the evolution of the treatment of distal femur fractures was the utilization of locked internal fixators for the distal femur. Previously, maintenance of reduction of the distal femoral block, especially in the setting of significant osteoporosis or a short distal segment, was a significant concern. The locked plates were developed out of the early experience with Schüli nuts in treating patients with significant osteoporosis and revision fixations33 and also with the utilization of the PC-Fix (Synthes, Paoli, PA) for forearm fractures.34 A biomechanical cadaver study has shown higher axial loads to failure and a lower incidence of loss of distal fixation for locked plating compared with a blade plate and a retrograde intramedullary nail, especially in osteoporotic bone.35 Clinically, the use of locked plates in the distal femur has been helpful in multi-planar articular injuries, osteoporotic fractures, fractures with short distal segments, and fractures above total knee arthroplasty.13–19,31,32,36,37
The goals of treatment of a supracondylar/intercondylar femur fracture are as follows:
Restoration of the articular surface
Restoration of normal alignment of the limb
Full or nearly full range of painless motion
Uneventful healing without need for bone grafting
Return to former activities and a good functional outcome as assessed by modern-day functional outcome instruments
With these goals in mind, the surgeon should be able to classify the fracture, decide on operative versus nonoperative treatment, decide on the mode of treatment, and be able to predict certain outcomes based on the treatment. This chapter explores in detail each of these aspects of the care of these difficult fractures.
Classification
A good classification scheme should help to determine the surgical approach and treatment as well as the prognosis for a particular injury.38 The AO/OTA classification (Fig. 29.1) helps to determine the surgical approach, implant, rehabilitation protocol, and outcome. Fractures are categorized into three types: type A, extra-articular; type B, partial articular; and type C, complete intra-articular with dissociation from the diaphysis.
To use this classification, good quality radiographs are essential. If there is any question regarding the characterization of the injury, the surgeon should obtain anteroposterior (AP), lateral, and oblique traction views. A computed tomography (CT) scan with frontal and sagittal reconstructions may be utilized to characterize the articular injury. Key questions to be answered with the help of these radiographs are the following:
Is there an intercondylar split?
If there is an intercondylar split, is it complex or simple?
Are there separate osteochondral fragments in the intercondylar notch or split?
Is there an associated Hoffa (frontal plane) fracture (best seen on the lateral radiograph)?
The answer to the first question differentiates between a type A and a type C fracture. The answer to the second question differentiates between a type C1/C2 and a type C3 fracture. The answers to the third and fourth questions enable the surgeon to decide if an extensile (lateral parapatellar approach) or less extensile approach (anterolateral approach) is needed. The fourth question is important because Nork et al39 have demonstrated a 38% incidence of Hoffa fractures in type C fractures.
Classification of a fracture as a type B (partial articular) injury is an accurate description of the condyle fracture, whether it is a medial condyle, lateral condyle, or frontal plane fracture. This has significance in terms of the surgical approach and the implant.
Nonoperative Treatment
In their 1967 report on supracondylar femur fractures, Neer et al4 stated, “No category of fracture at this level seemed well suited for internal fixation.” They evaluated 110 patients and reported only 52% satisfactory outcomes with internal fixation compared with 90% satisfactory results with closed treatment. However, the authors did note a significant varus/internal rotation deformity that was commonly seen with nonoperative treatment using functional cast, bracing, or traction. In 1966, Stewart et al5 reported on the treatment of 215 supracondylar femur fractures, and reached a similar conclusion. These observations, however, were made a half-century ago, and it is clear that with appropriate intervention the clinical results of internal fixation have significantly improved since the 1960s.12,13,27,40,41 In addition, it should be recognized that the functional expectations for treatment of a supracondylar femur fracture in the 1960s were relatively low and not in keeping with the expectations of today′s patients. For example, to have a satisfactory Neer score, the patient could still have pain with fatigue, restricted function (for example, needing to climb the stairs sideways), knee motion of only 100 degrees, and up to 5 degrees of angulation or 0.5 cm of shortening.4
With modern techniques at the surgeon′s disposal, the occasions in which nonoperative treatment is the best treatment option are rare. These rare situations might include a nonambulatory patient, a patient with significant comorbidities, and a patient with a very short life expectancy. It is quite challenging in the frail and osteoporotic patient to control the distal femoral block/supracondylar fracture in a cast, even if the surgeon accepts the inherent stiffness. Displacement of the fracture in a frail patient may lead to skin pressure sores from the fractured bone ends themselves.
The surgeon may occasionally encounter a nondisplaced supracondylar femur fracture without intra-articular extension. This fracture may be treated in a hinged brace with early range of motion. In an otherwise healthy patient, immobilization for multiple weeks will result in unacceptable stiffness in a high percentage of cases. In such a case, displacement of the fracture in the hinged brace would represent a surgical indication.
Surgical Treatment
Indications
As noted above, nearly all supracondylar/intercondylar femur fractures should be treated operatively. The basic tenets of articular reconstruction warrant operative intervention for any displaced intra-articular fracture, particularly in a young patient. The foregoing logic also holds for the elderly osteoporotic patient. Medical comorbidities or functional demands might seem to warrant nonoperative treatment, but excessive pain with nonoperative treatment, the inability to mobilize the patient, potential skin breakdown, and fracture displacement would be indications for surgical treatment in these patients.
Surviving the Night
The majority of issues while “on call” regarding supracondylar femur fractures involve treatment of an open injury or an associated vascular injury. Compartment syndrome is extremely rare with a distal femur fracture without other associated fracture or crush injury. The main tool for surviving the night with distal femur fractures is the spanning external fixator.
A high index of suspicion for an associated vascular injury should be present in any patient with a distal femur fracture with significant displacement. The ankle-brachial index (ABI) can be used to compare the systolic blood pressure in the injured leg with that in the arm, and should be done with the injured leg in traction. If the index is less than 0.90, or there are other reasons for concern (e.g., diminished pulses), a CT arteriogram can be obtained. If a vascular injury is present, a spanning eternal fixator is placed, and then the vascular surgeon can proceed with the vascular repair. Definitive fixation of the distal femur fracture can then be done after the vascular repair, or in the ensuing days. The presence of a vascular injury requires emergent surgical treatment.
Although a distal femur fracture can be treated in the acute setting (in the first 24 hours after injury), this should only be done with a well-resuscitated patient without life-threatening injuries, a good understanding of the articular injury, confidence in the quality of debridement of open wounds (if applicable), and an appropriate surgical team. If any of these criteria are not met, a spanning external fixator may be placed across the knee joint. Care is taken to keep the pins relatively high on the femur and low on the tibia, so as not to have the pin sites close to the surgical incision site. Stabilization of the sides of the knee joint with a cylinder splint will add stability to this area, and perhaps provide increased patient comfort.
Surgical Anatomy
An understanding of the osseous anatomy of the distal femur is paramount to understanding distal femur fractures and operative intervention (Fig. 29.2). Both the medial and lateral femoral condyles are convex and articulate with the corresponding medial and lateral tibial plateau, with the medial and lateral meniscus in between.
Key surgical points directly relevant to the surgical anatomy relate to the sloping of the medial and lateral femoral condyles and the insertion site for an intramedullary nail placed through the distal articular surface. The lateral femoral cortex slopes ~ 10 degrees, and therefore a lateral plate must be rotated anteriorly ~ 10 degrees. A common surgical error is to have the posterior aspect of the plate impact upon the posterior aspect of the lateral femoral cortex before the plate is flush with the bone.
The surgeon must also be cognizant of the 25-degree slope of the medial femoral cortex when placing hardware from lateral to medial. For example, if one is placing a screw from lateral to medial in the anterior aspect of the distal femoral condyle, a screw may perforate the medial femoral cortex but appear to be “in” on the AP radiograph. Similarly, when placing a blade plate or DCS, the surgeon must measure the most anterior aspect of the hole drilled for such a device, so that the screw or side plate will not penetrate the medial femoral cortex. If this is not considered, prominent hardware in the medial aspect of the femur will become aggravating for the patient.
Surgical Approaches
There are four common approaches that are utilized in the treatment of distal femur fractures. As already noted in the Classification section, the classification scheme is very helpful in determining the surgical approach (Fig. 29.3; Table 29.1).
Medial Parapatellar Approach: Retrograde Intramedullary Nailing of the Distal Femur Fracture Without Articular Extension
Video 29.1 Retrograde Intramedullary Nail
The patient is placed supine on a radiolucent table with a bump under the hip on the same side as the injury to tilt the pelvis 10 to 15 degrees. The knee can be flexed to 30 to 50 degrees with the use of large towel bumps or a triangular leg support. In the situation of a nonarticular (type A) fracture, an incision 2 to 3 cm long and parallel to the medial aspect of the patellar tendon, inferior to the patella, is made. The plane between the subcutaneous tissue and the patella tendon is developed, the skin and subcutaneous tissue is retracted medially and a medial parapatellar arthrotomy is performed. No attempt is made to directly visualize the articular surface of the distal femur (Fig. 29.4).
Medial Parapatellar Approach: Retrograde Intramedullary Nailing of Distal Femur Fracture with Articular Extension
In the treatment of a type C1/C2 fracture, the articular surface should be visualized to actively reduce the articular surface. Therefore, the medial parapatellar approach is continued cephalad for 2 to 8 cm, depending on the need for further visualization of the articular surface of the distal femur. The incision described earlier for the small percutaneous medial parapatellar approach is then extended proximally through the skin and subcutaneous tissue and through the medial extensor retinaculum. A division in the extensor mechanism 8 to 10 mm medial to the patella is made. In general, for visualization of a simple intra-articular split, eversion of the patella is not necessary. Reduction and fixation of the articular surface as described later can then be performed, after which nailing is completed as already noted. The extensor mechanism is then repaired on the medial aspect of the patella with No. 5 nonabsorbable inverted sutures.
Anterolateral Approach to the Distal Femur: Plate Fixation of Fractures with or Without Simple Articular Extension
The anterolateral approach of the distal femur is utilized for plate fixation of both type A and type C1/C2 fractures. For type A fractures, no attempt is made to visualize the distal articular surface of the femur. In the C1- and C2-type fractures, such visualization is mandatory.
The skin incision for an anterolateral approach of the distal femur begins at the tibial tubercle and then curves toward the anterior one third of the distal femoral condyle and then up the midlateral aspect of the femoral shaft (Fig. 29.5). The distal aspect of the incision is not necessary if the articular surface does not need to be visualized. Dissection is carried down through the skin and subcutaneous tissue sharply to the level of the iliotibial band. The iliotibial band is then divided in line with its fibers. The fibers of the iliotibial band curve anteromedially toward the tibial tubercle. After the iliotibial band is divided, the joint capsule is visualized. Often it is not disrupted even in severely displaced fractures. The joint capsule does not necessarily need to be divided or disrupted in the type A fracture, although doing so may enable the surgeon to accurately assess the plate position on the lateral aspect of the distal femur. For submuscular plating techniques in a type C1/C2 fracture, the skin incision is 10 to 12 cm long, whereas for a type A fracture, it is 8 to 10 cm long.
The surgeon may wish to perform traditional open plating instead of utilizing a submuscular technique. For a formal open biological plating, an anterolateral approach as described earlier for the submuscular techniques is extended proximally up the midlateral aspect of the femur (Fig. 29.5). The iliotibial band is divided. The fascia of the vastus lateralis is then divided roughly between the anterior two thirds and the posterior one third of the vastus lateralis fascia. The muscle belly is then retracted anteriorly with skin rakes while a wood-handled elevator is used to tease the muscle fibers off the posterior aspect of the vastus lateralis fascia and the posterior intramuscular septum, going in a distal to proximal direction. In doing so, multiple perforating arteries are encountered, and they are either ligated or cauterized. No attempt is made to completely strip the lateral aspect of the femur of its periosteum, and certainly no attempt is made to visualize every aspect of the fracture or the anterior/medial aspect of the metaphyseal/diaphyseal component of the fracture. Instead, the muscle fibers are left intact anteriorly over the femoral shaft. Hohmann retractors may be placed anterior to the femur within the quadriceps muscle, approximately 1 cm removed from the anterior surface of the femur, so as not to have these Hohmann retractors strip the muscle belly off the anterior aspect of the femur.
Exposure of the articular surface is performed by dividing the joint capsule from the metaphyseal area down to the level of the lateral meniscus. A Hohmann retractor may be carefully placed over the medial aspect of the femoral condyle so as to enable direct visualization of the articular surface (Fig. 29.5b).
Lateral Parapatellar Approach: Plate Fixation of Fractures with Complex Articular Extension
The lateral parapatellar approach of the distal femur was popularized by Krettek et al,42 and is based on the realization that a medial parapatellar approach (as utilized in total knee arthroplasty) provides excellent visualization of the articular surface of the femur without devitalization of the metaphyseal and diaphyseal component of the distal femur (Fig. 29.6). Its use generally relies on the placement of a plate in a submuscular manner. The rationale for the incision being made lateral rather than medial is that this plate can be relatively easily passed from the same incision. The patient is once again positioned supine, with a buttock bump to tilt the pelvis 15 degrees and a tourniquet utilized as desired. Supracondylar bumps are placed posterior to the distal femur, which aids in neutralizing the hyperex-tension deformity of the distal femur caused by pulling of the gastrocnemius. An incision (15 cm) is then made just lateral to the midline and based over the lateral aspect of the patella (Fig. 29.6b). A full-thickness flap is carried down to the extensor retinaculum. The extensor retinaculum is divided and is later repaired. The quadriceps tendon is divided, separating the lateral 40% from the medial 60%, and this is carried down to the superior pole of the patella. As the arthrotomy is continued around the lateral aspect of the patella, a cuff of extensor mechanism remains on the lateral aspect of the patella (Fig. 29.6c). The incision continues around the distal portion of the patella, finally paralleling the patellar tendon. With the knee in hyperextension, the surgeon can then evert the patella. Care must be taken, especially in osteoporotic individuals, to avoid undue force on the patellar tendon insertion. A common mistake at this juncture is not to release sufficient quadriceps tendon cephalad, which will not enable appropriate eversion of the patella, thereby placing excess force on the patellar tendon.
With varying degrees of flexion and extension of the knee, often with the knee flexed 70 to 90 degrees and the patella everted, excellent visualization of the articular surface can be obtained. Reduction and fixation as described below are then performed for the complex articular injury. Closure of the extensor mechanism is performed with No. 5 nonabsorbable inverted sutures.
In addition to being utilized for these C3 distal femur fractures, the lateral parapatellar approach may be utilized for a complex or very posterior lateral femoral condyle fracture.
Medial Parapatellar Approach: Plate Fixation of Medial Condyle Fractures with Complex Articular Extension
A medial parapatellar approach is performed in an identical way to that described for the lateral parapatellar approach with identical surgical positioning. This approach is quite familiar to most orthopaedic surgeons because it is the approach utilized for a total knee arthroplasty. No significant differences exist from the approach described above other than the incision being made on the medial aspect of the patella. As in the lateral parapatellar approach, its major use is for a complex medial femoral condyle fracture (Fig. 29.7). In the setting of a relatively simple medial femoral condyle fracture, one may utilize a standard anteromedial approach.
Medial/Lateral Posterior Approaches: Plate Fixation of Medial/Lateral Condyle Fractures with Complex Articular Extension (Which Cannot Be Visualized Adequately Through Anterior Approaches)
Occasionally, a medial or lateral condylar frontal plane fracture (Hoffa fracture) may be based so far posterior that there is a concern that the fracture cannot be adequately exposed from an anterior-based approach. In such a case, a posterior-based approach is indicated. The patient is placed in the prone position with the tourniquet high about the thigh with appropriate padding placed underneath the contralateral lower extremity and both upper extremities. A curvilinear midline incision is made over the posterior aspect of popliteal fossa. A full-thickness flap is carried down to the muscle fascia. The sciatic nerve divisions and popliteal artery are identified, and the plane between the medial or lateral gastrocnemius muscle is developed to visualize the femoral condyle. Capsulotomy is then performed with direct visualization of the articular component of the fracture.
Surgical Techniques
As with the surgical approach, the classification of the fracture will determine the appropriate implant and technique for distal femoral fractures (Table 29.2).
Type A or C1/C2 fracture |
Dynamic condylar screw40,43–48 95-degree angled blade plate3,12,48–53 Antegrade femoral nail41,82–84 Retrograde femoral nail16,20–27,85–91 Locked internal fixator (LISS, lateral condylar buttress plate with locked distal screws)13–19,31,32,36,37 |
Type B fracture |
Screw and plate fixation92 |
Type C3 fracture |
Standard condylar buttress plate (nonlocked screws)3,12,40,51,60,94 Locked internal fixator (LISS, lateral condylar buttress plate with locked distal screws)13–19,31,32,36,37 |
Articular Fracture Reduction and Fixation
In simple terms, the treatment of a supracondylar/intercondylar femur fracture can be broken into two steps: (1) articular fracture visualization, reduction, and fixation; and (2) connection of the reconstructed distal femoral articular block to the proximal femur utilizing a plate or retrograde nail. The surgeon must not compromise the first step because of the second step. A common and critical mistake would be to place a retrograde nail or a submuscular plate through a limited approach without appropriate visualization and fixation of the articular injury. Although attempts should be made to avoid nonunions and malunions of the supracondylar region, the reality is that they can be relatively easily addressed if they occur. However, poor reduction of the articular surface is catastrophic and difficult to resolve (Figs. 29.7 and 29.8). Thus the surgeon should carefully assess the articular injury and ensure that the surgical approach will provide appropriate visualization of the articular injury. After the articular injury is exposed, the following reduction aids and techniques for the articular surface may be helpful (Fig. 29.9):
Abbreviations: AO/OTA, Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association; LISS, Less Invasive Stabilization System.
Schanz pins utilized as reduction aids in the medial and lateral femoral condyle to assist in reduction of the intercondylar fracture
Large pointed reduction Weber clamps, or large pelvic reduction clamps, which compress the lateral and medial femoral condyle blocks together
Provisional Kirschner wires (K-wires), which can hold reduction of articular blocks until definitive lag-screw fixation is achieved
Dental picks, which are helpful in fine manipulation of articular segments
After reduction is achieved, multiple 3.5-mm cortical lag screws are utilized in a lateral to medial direction for fixation of intercondylar fractures, or in an anterior to posterior direction for fixation of Hoffa fractures. In general, three lag screws are placed from lateral to medial. Lag screws may then be placed in an anterior to posterior direction. A diagonal screw placed from anterolateral to posteromedial may be helpful to “lock in” the entire distal femoral articular surface in injuries with complex multi-planar involvement (Fig. 29.10). Mini-fragment 2.7-mm lag screws may also be utilized, especially for fixation of small osteochondral fragments in the intercondylar notch. Occasionally, screws may need to be placed through the articular cartilage if fragments are exceedingly small. This should be avoided, however, if possible (Fig. 29.7e). Meticulous attention to detail and surgical patience must be exercised when dealing with complex articular injuries. When there are multiple fragments, provisional fixation of the entire articular surface is advisable before definitive fixation (Fig. 29.7d).
The articular surface reduction is assessed by visual inspection and digital palpation. A common malreduction that can occur is a rotation of one condyle on the other condyle when treating a type C1/C2 injury. This can be avoided with a careful inspection of the superior aspect of the intercondylar fracture as well as the intercondylar notch area around the fracture. Such malrotation will not be appreciated if only an end view of the distal femur is assessed.
Finally, manipulation of severely osteoporotic osseous fragments is a surgical challenge because clamps or Schanz pins tend to crush the bone. In this situation direct manipulation of the osseous fragments may be advisable, utilizing finger pressure.
Blade Plate Fixation of the Distal Femur
The 95-degree angled blade plate is not a commonly used device because it is thought to be a technically difficult device to use. It is utilized for type A and type C1/C2 fractures. Its use in type C3 fractures is limited because of concern of the disruption of the articular surface fixation with introduction of the blade. Its use has been supplanted by the use of locking distal femoral plates, as well as the use of retrograde nails. It is included here for the following reasons:
Multiple surgical series have been documented, along with the DCS (with which it has significant similarities)3,12,40,43–54
The concepts of its use are critical as a foundation for all surgical techniques described below.
It is a device that demonstrates well the concept of indirect reduction of the metaphyseal/diaphyseal component of the fracture. The key concept is that the surgeon must ensure that the blade plate is placed in the distal femur in the appropriate position. If this is properly done, frontal plane (varus/valgus) and sagittal plane (flexion/hyperextension) alignment is ensured.
The blade plate was the first “locked fixator” for the distal femur. The blade provides excellent frontal and sagittal plane control of the distal femoral block.
The key to understanding the blade plate is to recognize which plane of correction is established at each point of the surgical sequence:
The varus/valgus angulation of the distal femur is established by the angle with which the blade goes into the distal femoral block with reference to the joint line in the coronal plane.
The flexion/extension of the distal segment is determined by the amount of flexion or extension with which the blade goes into the distal segment, and is “locked” into place when a second screw is placed in the proximal femoral fragment.
The length and rotation of the femur are determined when the first proximal screw is placed.
After the articular surface undergoes reduction and fixation, the blade is placed. The steps in blade plate placement (Fig. 29.11) are as follows:
Establishment of the varus/valgus angulation of the distal femoral block. A good-quality AP radiograph is obtained. A 4.5-mm drill bit is started at a point 1.5 cm from the distal femoral articular surface at a point between the anterior third and the middle third of the distal femoral condyles (Fig. 29.12). This drill bit (and subsequently the other drill bits, seating chisel, and blade) should be place at a perpendicular orientation to the distal femoral lateral cortex.
A second and third 4.5-mm drill bit is placed in the distal femur utilizing the triple-hole drill guide, which keeps the drill bits parallel to each other. The positions of the second and third drill bits relative to the first drill hole in the distal femur establish the flexion/extension axis that the blade plate will have on the distal femur. At this point, the most anterior hole is measured because this length determines the maximal length of the blade. If the blade is longer than this distance, the anterior aspect of the blade will protrude out of the medial cortex.
A router is used to enlarge the cortical drill holes.
A seating chisel is introduced in the same path as the drill bits. The depth of penetration of the blade is used as a second determinant of the length of the blade to be chosen. When the seating chisel is driven into the distal femoral block, care must be taken to avoid having the blade become incarcerated in bone. This can particularly be a problem in young hard bone. To avoid this, the seating chisel is backslapped after every 10 to 15 mm of forward advancement of the seating chisel.
The seating chisel is replaced by the blade plate. A large amount of force should not be necessary to introduce the blade plate into the distal femoral block, at least for the first half of the blade length, because the blade should be following the path already established by the seating chisel.
The blade plate is then impacted into the bone with an impactor.
The blade plate is secured to the distal segment by additional screws.
The length and rotation of the distal femur are established. This may be aided by the use of an external fixator or femoral distractor. The plate is then held on the proximal fragment with an articulating Verbrugge clamp. One screw in the proximal femur will “lock in” length and rotation.
The lateral radiograph may then be assessed for flexion/extension at the fracture site. The common deformity is hyperextension of the distal segment. This can be minimized through the use of towel bumps posterior to the supracondylar area. Additional screws may be placed in the proximal segment appropriate reduction.
In general, three to four screws in a plate that can accommodate twice that many screws in the proximal segment are utilized for biological plating (Fig. 29.13).
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