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Problems and solutions of the extensor mechanism
SE
M I N A R S I N
A
R T H R O P L A S T Y
25 (2014) 215–217
Available online at www.sciencedirect.com
www.elsevier.com/locate/semanthroplasty
Problems and solutions of the extensor mechanism Thomas P. Sculco, MD Hospital for Special Surgery, 535 East 70th St, New York, NY 10021
article info
abstra ct
Keywords:
Problems related to the extensor mechanism can be devastating and severely compromise
total knee arthroplasty
the end result of revision knee replacement surgery. Many of these complications can be
extensor mechanism
prevented by careful surgical technique, especially intraoperative avulsion of the patellar tendon. Fractures of the patella in the most extreme forms can lead to prosthetic loosening and disruption of the extensor mechanism. In the most severe cases, complete absence of the extensor mechanism may require allograft extensor mechanisms to restore extensor function. Alterations in rehabilitation and postoperative treatment are often necessary to ensure an excellent result. Along with restoration of bone defects, achieving excellent knee alignment and stability, a functional and aligned extensor mechanism is key to an excellent result in knee revision surgery. & 2014 Published by Elsevier Inc.
The goals to success in revision knee replacement surgery are correction of bone deficits, obtaining satisfactory knee stability, establishment of correct alignment, and a stable and functioning extensor mechanism. Certainly, patellofemoral complications can be devastating after knee replacement surgery and can lead to severe compromise of the end surgical result. This article will review the different types of extensor mechanism problems and what are the prevention and treatments for these potentially devastating complications: patellar tendon avulsion and quadriceps rupture, patella fracture, and completely deficient extensor mechanism. Patellar tendon avulsion is usually a preventable complication. It most commonly occurs intraoperatively, particularly in the stiff knee and more frequently in obese patients. To prevent unrolling at the insertion or an avulsion of the tendon, a pin can be inserted through the patellar tendon extending into the proximal tibia. A lateral release of the patellar retinaculum is also often needed in very obese patients to release tension on the patellar tendon. This will stabilize the tendon when exposing and flexing the knee. Additionally, a radical soft tissue release is performed in
E-mail address: [email protected] http://dx.doi.org/10.1053/j.sart.2014.10.002 1045-4527/& 2014 Published by Elsevier Inc.
those patients with severe knee stiffness. This release is done on the distal femur and proximal femur and extends circumferentially until soft tissue contracture has been relieved, and knee flexion to 901 can be performed without undue tension on the patellar tendon. Additionally, if exposure is still difficult and knee flexion is tight, a lateral quadriceps “snip” can be performed, which will allow eversion of the patella without undue tension on the insertion of the patellar tendon. This release in the quadriceps is then repaired at the conclusion of the procedure. A knee that is extremely tight and has significant reduction in flexion postoperatively, particularly a posttraumatic knee, may be at risk should the knee be manipulated, and complete disruption of the tendon may occur, which severely impacts on the end result of the knee arthroplasty (Fig. 1). In terms of treatment, I have found suture anchors to be very useful in repairing complete or partial patellar tendon avulsions. Two or three multi-suture anchors can be inserted into the proximal tibia and sutured around the patellar tendon. Postoperative flexion is monitored carefully postoperatively, and restriction to 451–601 is maintained for the first 3–4 weeks and then gradually increased.
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T H R O P L A S T Y
Figure 1 – Patellar tendon avulsion after knee manipulation.
If the avulsion happens postoperatively, then often the tendon is in poor condition, and an attempt at primary repair is not possible. Also, significant tension is placed on the primary attempt at repair, and re-rupture may occur. Patients with patella baja and contracture of the patellar tendon are at an increased risk in my experience for both tendon avulsion and quadriceps rupture. Therefore, augmentation of the patellar tendon is necessary and the semitendinosus tendon works well for this reconstruction. The tendon is stripped along its course and is harvested, leaving its distal attachment. A drill hole is made through the inferior pole of the patella, and the semitendinosus tendon is looped back and fixed with sutures into the tibial tubercle. Rehabilitation is handled slowly in these patients with knee flexion held to 451–601 for the first 4–6 weeks. Quadriceps tendon rupture tends to occur in patients with poor tissue integrity, such as diabetic or rheumatoid patients. Patients with severe knee stiffness and morbidly obese patients also are at an increased risk. Quadriceps rupture can result from oversizing of the femoral component, where increased tension due to an increased anteroposterior sizing will lead to increased force in the quadriceps tendon and rupture. Excessive releases of the quadriceps tendon or quad lengthening procedures to achieve flexion in a knee contracted in extension lead to weakness of the quadriceps and can lead to rupture. With multiple injections of cortisone into the quadriceps tendon, the precipitate from these injections may be seen at the rupture site. Treatment for partial ruptures without loss of knee extension power can be treated conservatively by immobilization for 6 weeks. Complete ruptures require repair, and these are generally performed by mobilizing a healthy, viable quadriceps tendon. If tissue is poor and reconstruction is not possible, tendon augmentation should be performed using autograft or allograft tendon.
25 (2014) 215–217
Patellar fractures are treated depending upon whether the extensor mechanism has been disrupted and whether there is prosthetic loosening. If the fracture is minimally displaced, non-operative treatment usually leads to excellent results. Immobilization should be used for 5–6 weeks and then gradual mobilization of the knee. If displacement of the fracture fragments has occurred and there is disruption of the extensor mechanism, then ORIF of the patella should be performed using tension band or other techniques. The quadriceps muscle and tendon should also be repaired. If the fracture is limited to the inferior pole, then excision can be performed with repair of the patellar tendon. In fractures where there is loosening of the patella component, it should be removed, and after ORIF, a new component may be fixed to the patella. If there is significant comminution of the fracture and bone stock is not suitable for a new patella component, then debridement of the patella can be performed and no component is used. In the most extreme cases where comminution does not lend itself to ORIF or reimplantation of the patella component, a patellectomy can be performed with repair of the quadriceps tendon. In the most severe cases of complete extensor mechanism, destruction and absent extensor power in the knee reconstruction with available structures may not be possible. This situation is seen most frequently in an infected knee with
Figure 2 – Multiply operated infected total knee replacement with absent extensor mechanism.
SE
M I N A R S I N
AR
T H R O P L A S T Y
Figure 3 – Allograft extensor mechanism.
multiple reconstructive procedures or in a knee that has had repeated revisions and attempts to repair the extensor mechanism (Fig. 2). In this setting, the only option is to use an allograft of the entire quadriceps tendon, patella, and patellar tendon. The entire remnant of compromised tissue is resected, and a well-vascularized bed of healthy tissue is needed for the allograft. The allograft proximally is attached
25 (2014) 215–217
217
to the remnant of quadriceps tendon and muscle, and distally, the proximal tibial dowel on the allograft is fixed to a trough created in the proximal tibia in proximity to the tibial tubercle. A screw may be used to supplement this bony repair into the proximal tibia. A wiring technique can also be used to fix the allograft distally. The angle at which the allograft is tight will impact significantly the ultimate result of the procedure. If the allograft is too lax, an extensor lag will result, causing impaired function. If the allograft is tensioned too tightly, then knee flexion will be restricted. The graft is best set so that tension is generated in the extensor allograft at 451 of flexion. Rehabilitation proceeds slowly with flexion limited to 601 for 6 weeks postoperatively. A knee brace is used for ambulation to prevent excessive flexion of the knee. Most patients will achieve 901–1001 of flexion and have a minimal extensor lag with this technique (Fig. 3). Extensor mechanism complications can be catastrophic to the end result of the knee arthroplasty. Careful mobilization of the knee intraoperatively and adequate exposure and soft tissue releases to prevent patellar tendon damage are crucial to prevent injury to the tendon. Reconstructions for displaced fracture, disruption of the extensor mechanism, and complete destruction of the extensor are available and can produce satisfactory results, but extensor weakness and dysfunction can still remain after these procedures.
M I N A R S I N
A
R T H R O P L A S T Y
25 (2014) 215–217
Available online at www.sciencedirect.com
www.elsevier.com/locate/semanthroplasty
Problems and solutions of the extensor mechanism Thomas P. Sculco, MD Hospital for Special Surgery, 535 East 70th St, New York, NY 10021
article info
abstra ct
Keywords:
Problems related to the extensor mechanism can be devastating and severely compromise
total knee arthroplasty
the end result of revision knee replacement surgery. Many of these complications can be
extensor mechanism
prevented by careful surgical technique, especially intraoperative avulsion of the patellar tendon. Fractures of the patella in the most extreme forms can lead to prosthetic loosening and disruption of the extensor mechanism. In the most severe cases, complete absence of the extensor mechanism may require allograft extensor mechanisms to restore extensor function. Alterations in rehabilitation and postoperative treatment are often necessary to ensure an excellent result. Along with restoration of bone defects, achieving excellent knee alignment and stability, a functional and aligned extensor mechanism is key to an excellent result in knee revision surgery. & 2014 Published by Elsevier Inc.
The goals to success in revision knee replacement surgery are correction of bone deficits, obtaining satisfactory knee stability, establishment of correct alignment, and a stable and functioning extensor mechanism. Certainly, patellofemoral complications can be devastating after knee replacement surgery and can lead to severe compromise of the end surgical result. This article will review the different types of extensor mechanism problems and what are the prevention and treatments for these potentially devastating complications: patellar tendon avulsion and quadriceps rupture, patella fracture, and completely deficient extensor mechanism. Patellar tendon avulsion is usually a preventable complication. It most commonly occurs intraoperatively, particularly in the stiff knee and more frequently in obese patients. To prevent unrolling at the insertion or an avulsion of the tendon, a pin can be inserted through the patellar tendon extending into the proximal tibia. A lateral release of the patellar retinaculum is also often needed in very obese patients to release tension on the patellar tendon. This will stabilize the tendon when exposing and flexing the knee. Additionally, a radical soft tissue release is performed in
E-mail address: [email protected] http://dx.doi.org/10.1053/j.sart.2014.10.002 1045-4527/& 2014 Published by Elsevier Inc.
those patients with severe knee stiffness. This release is done on the distal femur and proximal femur and extends circumferentially until soft tissue contracture has been relieved, and knee flexion to 901 can be performed without undue tension on the patellar tendon. Additionally, if exposure is still difficult and knee flexion is tight, a lateral quadriceps “snip” can be performed, which will allow eversion of the patella without undue tension on the insertion of the patellar tendon. This release in the quadriceps is then repaired at the conclusion of the procedure. A knee that is extremely tight and has significant reduction in flexion postoperatively, particularly a posttraumatic knee, may be at risk should the knee be manipulated, and complete disruption of the tendon may occur, which severely impacts on the end result of the knee arthroplasty (Fig. 1). In terms of treatment, I have found suture anchors to be very useful in repairing complete or partial patellar tendon avulsions. Two or three multi-suture anchors can be inserted into the proximal tibia and sutured around the patellar tendon. Postoperative flexion is monitored carefully postoperatively, and restriction to 451–601 is maintained for the first 3–4 weeks and then gradually increased.
216
SE
M I N A R S I N
AR
T H R O P L A S T Y
Figure 1 – Patellar tendon avulsion after knee manipulation.
If the avulsion happens postoperatively, then often the tendon is in poor condition, and an attempt at primary repair is not possible. Also, significant tension is placed on the primary attempt at repair, and re-rupture may occur. Patients with patella baja and contracture of the patellar tendon are at an increased risk in my experience for both tendon avulsion and quadriceps rupture. Therefore, augmentation of the patellar tendon is necessary and the semitendinosus tendon works well for this reconstruction. The tendon is stripped along its course and is harvested, leaving its distal attachment. A drill hole is made through the inferior pole of the patella, and the semitendinosus tendon is looped back and fixed with sutures into the tibial tubercle. Rehabilitation is handled slowly in these patients with knee flexion held to 451–601 for the first 4–6 weeks. Quadriceps tendon rupture tends to occur in patients with poor tissue integrity, such as diabetic or rheumatoid patients. Patients with severe knee stiffness and morbidly obese patients also are at an increased risk. Quadriceps rupture can result from oversizing of the femoral component, where increased tension due to an increased anteroposterior sizing will lead to increased force in the quadriceps tendon and rupture. Excessive releases of the quadriceps tendon or quad lengthening procedures to achieve flexion in a knee contracted in extension lead to weakness of the quadriceps and can lead to rupture. With multiple injections of cortisone into the quadriceps tendon, the precipitate from these injections may be seen at the rupture site. Treatment for partial ruptures without loss of knee extension power can be treated conservatively by immobilization for 6 weeks. Complete ruptures require repair, and these are generally performed by mobilizing a healthy, viable quadriceps tendon. If tissue is poor and reconstruction is not possible, tendon augmentation should be performed using autograft or allograft tendon.
25 (2014) 215–217
Patellar fractures are treated depending upon whether the extensor mechanism has been disrupted and whether there is prosthetic loosening. If the fracture is minimally displaced, non-operative treatment usually leads to excellent results. Immobilization should be used for 5–6 weeks and then gradual mobilization of the knee. If displacement of the fracture fragments has occurred and there is disruption of the extensor mechanism, then ORIF of the patella should be performed using tension band or other techniques. The quadriceps muscle and tendon should also be repaired. If the fracture is limited to the inferior pole, then excision can be performed with repair of the patellar tendon. In fractures where there is loosening of the patella component, it should be removed, and after ORIF, a new component may be fixed to the patella. If there is significant comminution of the fracture and bone stock is not suitable for a new patella component, then debridement of the patella can be performed and no component is used. In the most extreme cases where comminution does not lend itself to ORIF or reimplantation of the patella component, a patellectomy can be performed with repair of the quadriceps tendon. In the most severe cases of complete extensor mechanism, destruction and absent extensor power in the knee reconstruction with available structures may not be possible. This situation is seen most frequently in an infected knee with
Figure 2 – Multiply operated infected total knee replacement with absent extensor mechanism.
SE
M I N A R S I N
AR
T H R O P L A S T Y
Figure 3 – Allograft extensor mechanism.
multiple reconstructive procedures or in a knee that has had repeated revisions and attempts to repair the extensor mechanism (Fig. 2). In this setting, the only option is to use an allograft of the entire quadriceps tendon, patella, and patellar tendon. The entire remnant of compromised tissue is resected, and a well-vascularized bed of healthy tissue is needed for the allograft. The allograft proximally is attached
25 (2014) 215–217
217
to the remnant of quadriceps tendon and muscle, and distally, the proximal tibial dowel on the allograft is fixed to a trough created in the proximal tibia in proximity to the tibial tubercle. A screw may be used to supplement this bony repair into the proximal tibia. A wiring technique can also be used to fix the allograft distally. The angle at which the allograft is tight will impact significantly the ultimate result of the procedure. If the allograft is too lax, an extensor lag will result, causing impaired function. If the allograft is tensioned too tightly, then knee flexion will be restricted. The graft is best set so that tension is generated in the extensor allograft at 451 of flexion. Rehabilitation proceeds slowly with flexion limited to 601 for 6 weeks postoperatively. A knee brace is used for ambulation to prevent excessive flexion of the knee. Most patients will achieve 901–1001 of flexion and have a minimal extensor lag with this technique (Fig. 3). Extensor mechanism complications can be catastrophic to the end result of the knee arthroplasty. Careful mobilization of the knee intraoperatively and adequate exposure and soft tissue releases to prevent patellar tendon damage are crucial to prevent injury to the tendon. Reconstructions for displaced fracture, disruption of the extensor mechanism, and complete destruction of the extensor are available and can produce satisfactory results, but extensor weakness and dysfunction can still remain after these procedures.