|Year : 2020 | Volume
| Issue : 1 | Page : 1-4
Shortening: The orthopedic theory of relativity
Paley Orthopedic and Spine Institute, West Palm Beach, FL, USA
|Date of Submission||09-Jun-2020|
|Date of Web Publication||30-Jun-2020|
Paley Orthopedic and Spine Institute, 901 45th St., West Palm Beach, FL 33407
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Paley D. Shortening: The orthopedic theory of relativity. J Limb Lengthen Reconstr 2020;6:1-4
In 1985, I started my career path as a limb lengthening and deformity correction surgeon. I was privileged to introduce the Ilizarov techniques to Canada and the US and subsequently played an important role in their introduction to the rest of the world. The idea of being able to gradually correct length and angular deformity was so much less invasive than extensile open surgery. As I applied external fixation distraction methods to every part of the upper and lower limbs for almost every indication, I not only learned the advantages but also experienced the disadvantages and limitations. These related both to the use of external fixation and to the effect of prolonged external fixation upon the muscles and joints. External fixation tethers muscles and fascia, while distraction stiffens muscles and joints and applies indirect pressure to the cartilage of joints and growth plates. The application of locking plates and nails for deformity correction reduced the problems related to tethering of muscles and stiffening of joints and made the rehabilitation easier and faster. Is it preferable to do only a single surgery to achieve limb lengthening with gradual deformity correction versus two independent procedures: deformity correction, first, followed by limb lengthening, second. The latter may offer the joints an advantage. The problem with acute deformity correction was entrapment of nerves and acute stretch of vessels. Therefore, to successfully correct angular deformities acutely, I incorporated nerve decompression to prevent entrapment, and shortening of the bone to prevent neurovascular stretch injury. The bigger the angular deformity, the greater the amount of shortening required to prevent the neurovascular stretch. A good way to think about this is to consider the axial length of the limb segment before correction. After correction with shortening, the axial length remains the same.
In the first 10 years of my practice, preserving length was a basic tenet of limb reconstruction and also of trauma reconstruction surgery. Since 1997, I started using shortening as a means to increase the magnitude and complexity of acute deformity correction. Shortening became one of the steps incorporated into the SUPERhip procedure [Figure 1], SUPERankle procedure [Figure 2], tibial hemimelia reconstruction, ulnarization [Figure 3], congenital pterygium, and knee flexion contracture correction [Figure 4]. We also used shortening to eliminate bone defects instead of bone transport.
|Figure 1: SUPERhip procedure: The severe proximal femoral deformity of congenital femoral deficiency is seen in situ(top left). After soft tissue releases, the femur can be placed so that the neck is in an anatomic position. The blade plate is inserted into the neck (top right). After a subtrochanteric osteotomy, the bone ends are straightened and overlapped. The overlap is due to the tethering soft tissues whose length is shorter than the bone. The level of the second osteotomy for shortening is marked (bottom left). After the shortening, the distal femur is fixed to the plate (bottom right)|
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|Figure 2: SUPERankle procedure: The severe equinovalgus foot deformity of fibular hemimelia is shown from the anteroposterior. There is a malunited subtalar coalition and a maloriented tibial plafond as well as a diaphyseal angulation (left). A supramalleolar osteotomy is performed and the bone ends disengaged and overlapped. This allows the tibia to shorten taking the tension off of the soft tissues. The subtalar coalition is osteotomized, reduced, and pinned, which adds length and soft tissue tension further shortening the limb. The overlap of the bone ends is marked (left middle). The shortening osteotomy is performed (right middle). The bone ends are reduced and pinned with no soft tissue tension due to the shortening (right)|
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|Figure 3: Ulnarization (generation 3): The capsular release is already done according to the ulnarization procedure for treatment of radial club hand deformity of a case of radial aplasia. The scaphoid if present is released and flapped radially to make room for the ulnar head. The hand is shortened due to contracture relative to the length of the ulna (top left). The ulna is osteotomized proximally and telescoped in a shortening direction to overlap the bone ends (top middle). The hand is straightened out of its radial deviation and the carpus is ulnarized by placing the lunate next to the ulnar head and pinning it to the hand. This causes the ulna to telescope further proximal to the necessary level for reduction (top right). An ulnar osteotomy is done with a saw at the level of overlap of the bone ends (red dashed lines) (bottom left). The bone segment created is removed and the overlapped bone ends of ulna reduced and pinned in the shortened position (bottom middle). The ulnar osteotomy is stabilized by plating and rotational stability of the wrist is achieved by adding two more cross wires (bottom right)|
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|Figure 4: Knee flexion contracture with external rotatory subluxation of tibia and dislocated patella after previous femoral lengthening (top). After posterior capsulotomy and relocation of patella, the femur is cut and the bone ends are allowed to overlap as the knee is fully extended. The overlap for extension is marked (middle left). The relocation of the patella tightens the contracted quadriceps. Flexion of the knee further shortens the femur with greater overlap of the bone ends. This greater overlap is marked. This will become the level of shortening required to allow the knee to fully extend and to flex to 90° (middle right). The femur is shortened at the second mark (bottom left). The shortened femur is fixed with a plate. The knee is able to flex to 90° with the patella located (bottom right)|
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We have come full circle from deformity correction with lengthening, to, deformity correction with shortening. There are advantages to each of these methods and both are still useful and valid. Shortening like lengthening is but one more modality available for us use as part of the treatment algorithm. Hence, when is shortening indicated with deformity correction and what are the advantages and disadvantages? What are its consequences and limiting factors?
Acute deformity correction increases length and tension on the concave soft tissues and reduces length and tension on the convex soft tissues. Acute correction stretches muscles, nerves, vessels, and skin on the concave side. To avoid excessive tension on the nerves and vessels, the bone ends are allowed to shorten to maintain the neurovascular length unchanged. Consequently, the muscles on the convex side are not stretched because of the shortening. The muscles on the convex side may in fact be too lax due to the shortening. In most cases, they will readapt. The level of the shortening has a significant effect on this muscle readaptation (e.g., shortening of the distal femur for knee flexion contracture makes the quadriceps muscle length redundant leading to a quads lag. Shortening of the proximal femur has little effect on the quadriceps muscle length and tension since the bulk of the quads is attached distal to the osteotomy and remains anchored to the bone with no change in tension, thus avoiding a quads lag).
Joints like reduced muscle tension. It improves their passive arc of motion by eliminating an extra-articular contracture component. When intra-articular contracture is present, capsular release is also required. When inter-articular adhesions are present, arthrolysis is also added.
What are the limitations of shortening? There are bony limitations and soft tissue limitations. The bony limitations relate to the existing length of the bone. The total length of the bone that needs to be shortened can be too short to allow enough resection needed for full angular correction. We see this in the most severe cases of congenital femoral deficiency (CFD) in which there is >90° angular deformity of the proximal femur combined with a 90° flexion contracture at the knee. The total amount of shortening to fully correct the upper femur and knee deformities can be greater than the length available in the already congenitally short femur. In such cases, the SUPERhip and SUPERknee procedures need to wait until an older age when the bone is longer. The same is true for such severe deformities as congenital pterygium where the bone resection can range from 5 cm to 8 cm.
Soft tissue limitation is not just the length of nerves and vessels. The branches off of the vessels may still tether the vessels and limit the total shortening efficacy. For example, in the distal femur in a young child, one has to be careful to preserve the epiphyseal vessels coming off of the femoral artery and vein before it crosses the knee joint. Therefore, there is a risk of avascular necrosis of the distal femoral epiphysis at the time of posterior capsulotomy and femoral shortening for knee contracture. The second soft tissue limitations are the skin and subcutaneous tissues on the convex side. These tend to bunch up and kink. If the incision is placed on the convex side, it is better to be transverse. Shortening causes a convex side longitudinal incision to pucker open and can even make it impossible to close. The solution sometimes is to combine a transverse and longitudinal incision together. Therefore, L-, Z-, and S-shaped incisions are preferred. One particular incision that was taught to me by our plastic surgeon Dr. Mark Pinsky, is to use a Z-plasty concept in reverse [Figure 5]. A Z-plasty is usually used to lengthen an incision line. The axis of the Z perpendicular to the lengthening shortens. Therefore, a Z placed with its middle line transverse and its other two lines at 60° to the transverse with arms all of equal length will shorten. This concept has been used in the SUPERankle procedure with the middle line of the Z along the ankle joint crease anteriorly.
|Figure 5: Anteroposterior view of fibular hemimelia valgus deformity before correction. The incision will follow a reverse Z-plasty incision (according to Dr. Mark Pinsky) for SUPERankle exposure so that shortening of the anterior skin of the ankle will occur after correction. The middle leg of the Z is across the ankle crease. All legs are the same length with an angle of 60°. The foot is in fixed equinovalgus (left). After correction, the foot is pinned plantigrade and the bone is shortened as in Figure 2. The two triangular skin flaps automatically move into the shortened Z position (middle left). Medial view of fibular hemimelia equinus deformity before correction. Part of the incision can be seen on the medial side (middle right). After correction, the foot is pinned plantigrade and the bone is shortened as in Figure 2. The triangular flap is now reversed from the one seen before the correction (right)|
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Shortening has been particularly instrumental for reconstruction of congenital limb deficiencies since these deformities have neurovascular bundles of restricted length and bones with very severe periarticular deformities. It has allowed us to acutely correct the hip deformity of CFD (SUPERhip), the knee deformity of congenital pterygium of the knee and arthrogryposis, the ankle deformity of fibular hemimelia, the tibial deformity of congenital pseudarthrosis of the tibia, the wrist deformity of radial club hand, and the elbow deformity of congenital pterygium of the elbow and arthrogryposis. This concept is used in the spine for severe kyphosis and scoliosis by performing a vertebrectomy. In trauma, acute shortening allows for immediate closure of soft tissues and less need for flaps.
Shortening is not a new concept for deformity correction. It is a standard part of treated developmental dislocation of the hip (DDH) by doing a femoral shortening in order to reduce the hip into place. Talectomy is another example of shortening to treat clubfoot deformity. What is different is that we are doing it systematically as part of the procedure to allow us to acutely correct deformities without neurovascular injury or embarrassment. Shortening conceptually is not appealing to patients or surgeons. This is because the bone length present is visible physically and on the radiographs, while the soft tissue length is invisible. What is needed is a different way to look at the problem. Instead of thinking of the soft tissues as short, think of the bone as relatively long to the soft tissues. When one looks at it this way, the obvious solution is to shorten the bone so that it matches the length of the soft tissues. This has many benefits including not weakening the muscles. If instead of shortening, the tendons are lengthened, the muscle tendon length ratio is altered, and the muscle strength is reduced. The best example of this is Achilles tendon lengthening. If instead, the bone is shortened and adjusted to the length of the muscle, there is no weakening since the muscle tendon length ratio is preserved.
Hence, what do we do with the leg length discrepancy created by the shortening? This will require limb lengthening in most cases with the short leg. It is much easier to lengthen a bone without complications when the bone and its adjacent joints are straight and stable. We are very good at making more bone by lengthening. We are not good at making a new joint that is damaged by lengthening. Joints and soft tissues heal with scar In contrast bones heal without scar. Therefore, the primary indication for shortening is to prioritize and preserve the joints and soft tissues over the bones. As lengthening techniques become less arduous with lengthening plates and nails it becomes more attractive to consider shortening combined with deformity correction followed by implantable limb lengthening at a later date.
We are only touching the surface with the indications for shortening. We started with the most difficult congenital indications. Other more common indications include spastic patients for both children and adults. Normally, spastic muscles are considered short and are treated by lengthening tendons. What if instead we considered the muscles with normal length, and the bones as being relatively long. I have been using shortening as a method to treat spastic patients instead of tendon lengthenings. For example, combining shortening with bilateral varus derotation osteotomies of the femurs relaxes the hamstrings and adductors helping to treat the knee flexion contracture and hip adduction contracture at the same time without muscle releases. Similarly, shortening the distal tibia treats the equinus contracture without gastrosoleus or Achilles lengthening. If the problem is bilateral, there is no resultant leg length discrepancy. Talectomy for example should be replaced with distal tibial shortening to achieve the same effect.
How much shortening is needed? This is determined by a very simple intraoperative test. The first of the two osteotomies for shortening is performed. The bone ends are disengaged and overlapped in a bayonet position [Figure 1], [Figure 2], [Figure 3]. The amount of overlap with the dislocated joint reduced, the contracted flexed joint extended, and the deformed bone straightened is the amount of shortening required.
From now on as you evaluate deformities, ask yourself whether the soft tissues are short relative to the bone, or is the bone long relative to the soft tissues. This is the orthopedic theory of relativity.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]