4 Knee Operative Procedures

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1. Hamstring Lengthening

Indication

Hamstring lengthening is best performed with the child in the supine position, having an assistant elevate the leg through hip flexion. This position allows easy testing of the length of the hamstring with the traditional clini- cal popliteal angle test. Although the exposure is easier when the child is prone, it is impossible to check the amount of hamstring length, which has occurred with the operative procedure. The goal of hamstring lengthening should be to have a popliteal angle between 20° and 40° with only enough force to lift the leg, which causes no rotation of the pelvis. The usual indication for hamstring lengthening includes increasing fixed knee flexion contracture, increased knee flexion at foot contact, increased knee flexion in midstance, and seating difficulties causing sliding out of the wheelchair with supple lumber kyphosis.

Procedure

1. An incision is made midline between the hamstring muscles approximately 4 cm proximal to the knee crease. Excision is extended through the subcutaneous tissue until the fascia is encountered (Figure S4.1.1).

2. By palpation on the medial side with the hip flexed 90° and the knee in maximum extension, the tendon of the semitendinosus is very prominent. A longitudinal incision of the peritenon is performed and the tendon is visualized easily. A transection of the semitendinosus tendon is performed (Figure S4.1.2).

3. After the tenotomy of the semitendinosus, a longitudinal incision is made in the base of the tendon sheath, and the tendon sheath sur- rounding the fascia and tendon of the semimembranosus is encountered. The fascia of the semimembranosus is on the medial side of the thigh, and the muscle belly is toward the midline. With good cleaning of the fascia and excellent retraction, an incision is made circumferentially around the medial side of the semimembranosus, making the first incision as far proximal as possible in the wound. A second circumferential incision then is made around the semimembranosus, approximately 2 to 3 cm distal to the first incision (Figure S4.1.3). The fascia is only present in the medial half of the muscle’s circumference.

The popliteal angle is checked, and if it is 30° or less, foot progression angle is less than 20° external, and the transmalleolar axis-to-thigh

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Knee Operative Procedures

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angle is less than 30° external, no further lengthenings are indicated.

If all these criteria are not met, a biceps femoris lengthening should be performed.

4. The biceps is lengthened by palpation through the same wound on the lateral side, where a longitudinal incision will expose the nice, shiny fascia overlying the biceps. The fascia of the biceps is on the lateral side and tends to have a horizontal component that goes into the muscle, which needs to be incised as well. Again, a proximal fasciotomy is performed first, and then a second, more distal fasciotomy is performed if indicated. Do not dissect to the posterior medial side of the biceps as a way to avoid the common perineal nerve (Figure S4.1.4).

If the popliteal angle is still greater than 40° and the medial side palpation demonstrates that the gracilis is contracted, attention again should be directed to the medial side.

5. The gracilis is palpated by feeling a structure that is more medial and superficial on the medial side. A longitudinal incision in the subcutaneous tissue will expose the gracilis, and a myofascial lengthening can be performed easily (Figure S4.1.5).

956 Surgical Techniques

Figure S4.1.1

Figure S4.1.2

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6. The surgical wound then is closed in two layers, first with a careful closure of the subcutaneous tissue, and then subcuticular closure of the skin. The skin is covered with a watertight dressing. The patient then is placed in knee immobilizers, either in 24 to 48 hours, or immediately at the conclusion of the procedure. Immediate active and passive range of motion is begun 48 hours after the surgical procedure.

Postoperative Care

Soft Velcro-closing knee immobilizers are used postoperatively for 8 to 12 hours per day. The knee immobilizers may be used full time for several days to get the child accustomed to the orthotics; however, active and passive range of motion should be encouraged, and a significant amount of time out of the orthotic is to be encouraged as a mechanism to avoid knee stiffness in extension. Wearing of the knee immobilizer is encouraged at nighttime for 3 months, or as long as the child tolerates the orthotics. The physical therapist should be warned of possible sciatic nerve palsy if the surgeon feels that the release places the nerve at risk. This is most important in revision lengthenings or in those children with severe contractures who gained large lengthenings.

4. Knee Operative Procedures 957

Figure S4.1.3 Figure S4.1.4

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2. Rectus Transfer

Indication

Rectus transfer is indicated to improve toe dragging and stiff knee gait. Spe- cific indications include a complaint of toe drag, increased activity during swing phase of the rectus femoris on EMG, decreased knee flexion in swing phase, and late peak knee flexion in swing phase. The rectus transfer is performed with the child lying in the supine position.

Procedure

1. An incision is made starting distally 2 cm proximal to the patella in the midline. The incision is carried from distal to proximal approximately 30°, and angled to the medial side for 3 cm in length (Figure S4.2.1).

2. The incision is carried through the subcutaneous tissue until the bursa overlying the quadriceps tendon has been opened and the tendon exposed. The quadriceps tendon should be cleanly exposed from the proximal pole of the patella until the muscle belly of the rectus can be seen.

Figure S4.1.5

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3. At the proximal end of the incision, the interval between the vastus medialis and the rectus muscle is identified. A hemostat is passed under- neath the rectus tendon above the vastus intermedius tendon to the lateral border of the rectus. An incision then starts distally just proximal to the patella and is carried proximally. The incision should start 5 to 7 mm off the midline on the medial side and is carried proximally at a depth of 2 to 3 mm, exiting at the junction between the vastus medialis and rectus muscle. This longitudinal incision should not cut into muscle tissue of the vastus medialis but should be entirely within the tendon. A similar incision 5 to 7 mm on the lateral side of the midline is started distally and carried proximally, exiting at the intermuscular septum between the vastus lateralis and the rectus. Neither the medial nor the lateral longitudinal incisions should enter the knee joint (Figure S4.2.2).

4. Now the hemostat can be pulled distally, elevating the rectus muscle until it inserts into the vastus intermedius. Utilizing a knife with sharp dissection, the rectus muscle is freed from its insertion on the vastus intermedius distally to the level of the patella and then is released.

5. Finger palpation of the underbelly of the rectus then is utilized, with the finger stripping distally to make certain that all components of the rectus muscle have been released distally (Figure S4.2.3).

6. Utilizing a slowly absorbable suture, the defect created in the residual quadriceps tendon by removal of the rectus tendon now is closed. This closing involves suturing the tendon of the vastus medialis to the tendon of the vastus lateralis (Figure S4.2.3).

7. Exposure of the sartorius is performed by subcutaneous dissection around the medial side of the thigh, inside the fascia of the vastus medialis. Carrying the dissection through the subcutaneous tissue instead of under the fascia makes the rectus muscle less likely to scar down, but it will be much more prominent, especially in a slender child. As the dissection is carried posterior, the intermuscular septum is encountered. Utilizing a dull instrument, such as a hemostat, the intermuscular septum is opened and stripped proximally and distally. In the subcutaneous tissue, the sartorius muscle and its enveloping fascia can be palpated. The enveloping fascia of the sartorius is opened as well. The

Figure S4.2.1

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sartorius fascia has to be opened proximally, usually by digital dissection, at least into the midthigh to free the muscle and allow easy exposure for the transfer (Figure S4.2.4).

7A. Another alternative is to expose the semitendinosus for transfer to the rectus. This exposure occurs by making a small incision in approximately the midthigh posteriorly, and the semitendinosus is identified. A small incision is made distally just at the level of the knee crease, the tendon is transected through the proximal incision,

Figure S4.2.2

Figure S4.2.3

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and then the tendon is pulled out distally. Next, a tendon passer is introduced from the anterior knee wound into the distal posterior knee wound and the semitendinosus is pulled through the subcutaneous tissue into the proximal wound (Figure S4.2.5).

8. For transfer to the sartorius, the sartorius muscle is identified and a right-angle clamp is placed from medial to lateral, through the mid- substance of the sartorius muscle. The rectus muscle is placed into this clamp and pulled through the opening in the sartorius muscle,

Figure S4.2.4

Figure S4.2.5

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looped back on it, and sutured with absorbable suture (Figure S4.2.6).

Alternatively, the rectus tendon is sutured to the semitendinosus (Fig- ure S4.2.5).

9. The skin is closed, paying particular attention to closing the subcutaneous fascia of the anterior thigh wound. This wound has a tendency to spread, so diligent closure of the subcutaneous tissue and its subcutaneous enveloping fascia is very important.

Postoperative Care

The child’s main problem following rectus transfer is a high rate of severe spasticity in the transferred muscle. Diligent control of spasticity with the use of postoperative diazepam is important. Another option is botulinum toxin injected into the rectus muscle during the procedure, however it will take 2 to 3 days to be effective. No postoperative immobilization is required. Full range of motion and weight bearing are allowed.

3. Posterior Knee Capsulotomy

Indication

Posterior knee capsulotomy is recommended for fixed knee flexion contractures between 10° and 30°. These capsulotomies are performed in combination with hamstring lengthening, which should be performed first. Most capsulotomies can be performed through the medial side alone (Figure S4.3.1). If it is thought that there is not enough release of the posterior capsule from the medial side, a separate lateral incision can also be used (Figure S4.3.2). These incisions and exposures are the same as those used to perform open posterior horn menisectomies, which were common before the advent of arthroscopy.

Figure S4.2.6

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Procedure

1. The incision for posterior knee capsulotomy is made on the medial side with the knee flexed 60°. An incision of 4-cm length is made over the posterior medial corner of the knee at right angles to the knee joint. This incision is the typical incision used for open excision of the posterior horn of the medial meniscus, except some increased distal extension is required for exposure of the medial head of the gastrocnemius (Figure S4.3.1).

2. Opening the subcutaneous tissue distally, and by palpation, the medial head of the gastrocnemius can be identified anterior to the pes anserinus tendons. The enveloping fascia of the gastrocnemius is opened and a myofascial lengthening, or tenotomy if no muscle is encountered on the medial head of the gastrocnemius, is performed. In this exposure, the muscle belly will be superficial and the tendon is deep to the exposure (Figure S4.3.3).

Figure S4.3.1

Figure S4.3.2

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3. The knee joint capsule is opened superior to, and at the posterior medial corner behind, the medial collateral ligament. After opening of the knee capsule, the meniscus is identified inferiorly (Figure S4.3.4).

4. Using a flat elevator, such as a Cobb elevator, the posterior capsule then is cleaned all along its posterior border proximal to the tibia. A

Figure S4.3.3

Figure S4.3.4

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deep retractor is placed into this space, retracting the neurovascular structures and all muscles posterior. Scissors or a knife can be utilized to cut the posterior capsule, making sure that the meniscus is pro- tected inferiorly along the posterior border to the intercondylar notch (Figure S4.3.5).

5. Using a blunt retractor and the Cobb elevator, the posterior capsule of the lateral compartment also can be cleaned, always keeping the knee flexed at least 90° to avoid undue tension on the nerves or ves- sels of the popliteal fossa. After good clean exposure of capsule in the lateral compartment is performed, heavy scissors or a knife is used to perform a posterior capsulotomy in the lateral compartment (Figure S4.3.6). By palpation, one can make sure that the capsule is incised above the meniscus.

6. After this capsular incision, if significant contracture remains, palpation should be utilized to determine whether the contracture is due to cruciate ligaments in the intercondylar notch or to continued contracture on the lateral side. If the contracture is due to cruciate ligaments in the intercondylar notch, a knife is utilized and these are transected.

If the contracture is still thought to be due to posterior lateral capsule, a separate exposure of the posterior lateral corner should be performed (Figure S4.3.2).

7. Exposure of the lateral capsule also is performed by using the exposure typically used as an open exposure of the posterior horn of the lateral meniscus. The capsule again is opened at the posterior lateral corner in the same fascia as was used on the medial side, and using blunt dissection, the soft tissue is stripped off the capsule. The capsule then is excised from the posterior edge of the lateral collateral ligament

Figure S4.3.5

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around into the intercondylar notch. For individuals who are con- cerned, or not very familiar with the anatomy, separate exposure of the peroneal nerve will add an extra level of safety, although this is not routinely necessary.

8. Wound closure is performed by diligent closure of the subcutaneous tissue, but no capsular closure.

Postoperative Care

A bulky dressing should be applied, applying pressure to help control some of the capsular bleeding that occurs postoperatively. A knee extension cast or a knee immobilizer should be applied immediately at the end of the operative procedure. Postoperative management includes careful neurovascular inspection to make sure there is no sciatic nerve palsy. By the third or fourth day, the cast and soft dressing should be removed and active and passive range of motion of the knee initiated. The knee is continued in extension splinting full time except when passive range-of-motion exercises are being performed. Usually, a step-lock knee hinge knee-ankle-foot orthosis (KAFO) is fitted for use for 6 months to prevent recurrent contracture, especially in a child who has a tendency to want to sit with knee flexion.

4. Repair of Dislocation of the Patella

Indication

Surgical correction is recommended for recurrent dislocation of the patella that is causing knee pain for a sitting child or knee instability for an ambu- latory child. The indication for repair and the repair itself are very similar to that which occur in normal adolescence.

Figure S4.3.6

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Procedure

1. An anterior midline incision is made, extending down from the distal pole of the patella 2 or 3 cm proximal to the patella.

2. The lateral side of the patella is exposed and the lateral retinaculum is incised, preventing incision of the underlying synovium. The reti- nacular incision is carried proximally, with some release of the vastus lateralis if necessary, until the patella rests in the midline without any undue tension.

3. The vastus medialis obliquus is elevated from its incision into the patella and distal quadriceps tendon, leaving the medial retinaculum and capsule intact.

4. If a high quadriceps angle is present and the growth plate has closed, the insertion of the tibial tubercle is elevated with an osteotomy (Fig- ure S4.4.1) and fractured distally, then swung to the medial side and fixed with one screw (Figure S4.4.2).

5. If the growth plate is still open, the semitendinosus is detached proximally by making a small incision in the midthigh posteriorly, and an incision also is made distally just distal to the knee joint capsule where the tendon is palpated to cross. The semitendinosus is excised proximally and pulled into the distal wound and is left attached at its ori- gin in the pes anserinus tendon.

6. A tendon passer is passed from the anterior wound in the subcutaneous plane to the distal posterior wound, and the semitendinosus tendon is delivered into the proximal wound. The semitendinosus then is woven into the medial insertion of the patellar ligament and sutured across to the lateral side of the patella.

7. The vastus medialis is advanced medially and distally and sutured to the superior aspect of the patella (Figure S4.4.3). The wound is closed with good subcuticular closure.

8. A leg cylinder cast with the knee in almost full extension is placed, and the knee is kept immobilized in full extension for 4 weeks.

Figure S4.4.1

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Postoperative Care

The postoperative management includes maintaining the knee in a cast al- lowing full weight bearing, and starting active range of motion and strength- ening 6 weeks postoperatively when the cast is removed.

5. Tibial Osteotomy with Cast

Indication

Children who have an open growth plate with significant internal or external tibial torsion that causes problems with gait should have correction. The tibial osteotomy is performed at the distal tibia, and immobilization is done with a pins-in-cast technique.

Figure S4.4.2

Figure S4.4.3

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Procedure

1. A stab incision is made on the medial side of the tibia 1 cm proximal to the distal tibial epiphysis.

2. A 3.2-mm drill bit with a drill sleeve is introduced into the wound, and multiple drillholes are made in the distal tibia in a fanning fashion (Figure S4.5.1).

3. Utilizing an angular bending moment focused at the multiple drillholes, the tibia is fractured. Derotation is performed.

4. If more than 30° of tibial osteotomy is required, this similar technique is used to produce a fracture of the fibula 2 to 4 cm proximal to the tibial osteotomy on the lateral side.

5. A 1.5- or 2-mm drill tip K-wire is introduced in the proximal tibia 2 to 3 cm distal to the tibial epiphysis. This wire is allowed to protrude both medially and laterally.

6. A short-leg cast is applied, incorporating the proximal tibial pin and aligning the foot with the thigh for a zero thigh–foot angle with correction of distal tibial valgus if necessary (Figure S4.5.2).

7. A postoperative radiograph is obtained, and if residual valgus angu- lation is present, the cast should be wedged (Figure S4.5.3).

Postoperative Care

Postoperatively, a sole is applied to the child’s walking cast and the child is allowed to weight bear as soon as tolerated. At 3 to 4 weeks, when radi- ographs demonstrate some visible callus formation, the proximal tibial pin is removed. Typically, the cast is left on for 6 to 8 weeks with the child weight bearing fully. At 6 to 8 weeks, when full healing is demonstrated, the cast is removed and the child is allowed to go to weight bearing as tolerated with full rehabilitation.

Figure S4.5.1

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6. Tibial Osteotomy with Intramuscular Nail

Indication

For individuals whose growth plates have closed and are fully mature and are found to have internal or external tibial torsion that requires correction, tibial osteotomy is performed best utilizing an intramuscular nail. The pins- in-cast technique occasionally yields a delayed union requiring 4 to 6 months of cast wear.

Procedure

1. The osteotomy is performed at the junction of the distal end and middle third of the tibia. This area is visualized under fluoroscopy and a transverse drillhole is placed to fenestrate the tibia.

2. A standard exposure is made to the anterior medial aspect of the tibia for intramedullary nailing. The guidewire is inserted into the tibia, the tibia is reamed in the standard fashion, and an intramedullary nail of the appropriate size is chosen and driven into the tibia just proximal to where the initial drillhole was placed.

3. Utilizing the drill in a fan-shaped fashion, multiple holes are made at this level of the tibia (Figure S4.6.1).

Figure S4.6.1 Figure S4.6.2 Figure S4.6.3

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4. The tibia is fractured with manual force concentrated at this area.

Derotation then is performed.

5. The tibial nail is driven across the osteotomy site and into the distal fragment to just proximal to the tibial plafond. While the tibial nail is introduced, care is taken to make sure that there is no varus or valgus deformity of the distal fragment. Fluoroscopic evaluation is required.

6. Proximal and distal transfixion screws are applied (Figures S4.6.2 and S4.6.3).

7. The wounds are closed in the standard fashion.

Postoperative Care

The wounds are covered with waterproof dressings. The child then is mo- bilized with weight bearing as tolerated, encouraging full weight bearing as quickly as possible. If additional foot procedures or other soft-tissue procedures about the foot were performed, a short-leg walking cast may be needed.

The intramedullary nail or transfixion screws are removed postoperatively only if they cause discomfort.

7. Patellar Advancement

Patellar advancement is primarily an operative procedure that is performed only in combination with distal femoral osteotomy, either concomitantly or, if it has been overlooked, as a follow-up operative procedure. For this reason, patellar advancement is presented as part of the distal femoral osteotomy procedure. However, if the procedure is to be performed as an independent procedure, it can be done through a transverse incision at the distal pole of the patella (Figures S4.7.1 and S4.7.2), with the remaining aspect of the procedure being the same as shown in Figures S4.8.11 and S4.8.12.

Figure S4.7.1

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8. Distal Femoral Osteotomy

Indication

Distal femoral osteotomy is required for knee flexion contractures that are greater than 30°. Derotation and varus-valgus realignment also may be performed at the same time. This osteotomy may be performed with open or closed growth plates, although the fixation is easier if the growth plates are closed.

Procedure

1. The incision is made along the lateral aspect of the distal thigh and carried anterior to the middle of the patellar ligament. The incision needs to extend proximally to approximately the junction of the middle and distal third of the thigh (Figure S4.8.1).

2. The incision is carried down to the knee capsule, which is opened all the way anteriorly to the patellar ligament. The incision then is carried proximally and posteriorly along the edge of the vastus lateralis (Figure S4.8.2). Incision in the periosteum is performed, and subperiosteal dissection allows full exposure of the lateral and anterior femur. Subperiosteal dissection also can be extended circumferentially around the femur in the distal third above the metaphysis. Then, the patella can be dislocated or subluxated to the medial side, exposing the whole distal femur.

3. Insertion of a guidewire at the level of the blade plate is a helpful step. The guidewire is inserted parallel to the distal femoral condyle and parallel to the anterior femur. This guidewire is inserted with visual inspection, but also can be checked with fluoroscopic control (Figure S4.8.3).

4. After insertion of the guidewire, the guidewire should be cut off to allow approximately 3 to 4 cm of wire to be exposed laterally. If the

Figure S4.7.2

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growth plate is open, the wire can be inserted distal to the growth plate. The blade plate chisel then is inserted just proximal to this wire in the plane parallel to the tibia, with the tibia in maximum extension.

5. The chisel for the blade plate is inserted under visual control and can be checked with the fluoroscope. The level of the chisel insertion should be immediately proximal to the growth plate if the child still has an open growth plate, or should be inserted so that it will be just above the notch of the femoral condyles if the growth plate is closed.

Medial lateral insertion should be parallel to the distal femoral

Figure S4.8.1

Figure S4.8.2

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condyles. If varus-valgus correction is desired, the chisel is still inserted parallel to the distal femoral condyles. With the knee in maximum extension, the flat side of the chisel should be at a right angle (Fig- ure S4.8.4, label B) to the long axis of the tibia (Figure S4.8.4, label A).

This angle will correct the flexion contracture. Then, the chisel is introduced from lateral to medial until it just can be palpated on the medial side.

Figure S4.8.3

Figure S4.8.4

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6. Utilizing an oscillating saw, the distal osteotomy is made parallel to the inserted chisel 12 to 15 mm proximal to the chisel (Figure S4.8.5, A).

7. The proximal osteotomy is made transverse to the proximal femur at the level where the distal osteotomy ends (Figure S4.8.5, B). This osteotomy will now remove a significant anterior wedge from the femur (Figure S4.8.6). After removal of this wedge, full extension of the knee should be possible with minimal tension. If full extension is still not possible, additional transverse resections of the proximal femur should be performed. In some severe contractures, an additional several centimeters of resected femur may be required.

8. After the correct amount of femur has been resected, and due to the obliquity of the distal osteotomy, a large posterior spike will be present on the distal fragment. This large posterior fragment can be transected; however, care should be taken not to remove an excessive amount because it will cause weakening of the distal fixation (Figures S4.8.7 and S4.8.8).

9. The chisel is removed and the blade plate will be inserted. Blade plate size typically is chosen as an offset right-angle hip plate. Because of the shortening, the distal femoral osteotomy configuration causes the bone surface on the distal end to be larger than the proximal end.

For most adults, the adult-sized condylar blade plate is preferred.

For adolescents or children in middle childhood, the adolescent-sized plates are ideal. The length of the blade plate is chosen to avoid pen- etration on the medial side, and this can be checked best under fluoroscopic control with the introduction of the chisel, and measuring the depth of chisel insertion (Figure S4.8.7).

10. The osteotomy is reduced, taking care to reduce the anterior surface of the osteotomy so the patellar femoral groove will not develop an offset. With major shortening requirements, the circumference of the

Figure S4.8.5

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Figure S4.8.6

Figure S4.8.7

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proximal fragment sometimes is much less than the circumference of the distal fragment. The reduction should be performed in the midline with the anterior cortices aligned. Then, the osteotomy is com- pressed, using the compression holes and the side plate. The removed bone then can be fragmented and placed alongside the osteotomy to fill in the major defects (Figure S4.8.9).

11. Advancement of the patellar ligaments usually is required because of the significant shortening that has occurred due to correction of major flexion contractures. If the growth plate of the proximal tibia is closed, the patellar ligament insertion on the tibial tubercle can be advanced by utilizing an osteotomy and resecting the tibial tubercle.

The incision has to be extended distally, and this bone block advanced distally to the point where 90° of knee flexion is allowed. The bone is roughened and a screw with a washer is inserted to hold the bone block with the inserted patellar ligament (Figure S4.8.10).

12. If the tibial epiphysis is open, the use of patellar ligament plication is another alternative, and can be used for adults as well. This plication is performed by obliquely transecting the patellar ligament and then overlapping it and suturing the ligament with heavy absorbable sutures so its length is such that the knee can just barely flex to 90°

(Figure S4.8.11).

13. The wounds are closed, being careful to perform a good closure of the lateral capsule.

Postoperative Care

For the child with good stable fixation by patellar advancement and good bony fixation, the knee is immobilized in a knee immobilizer only. Immediate

Figure S4.8.8

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range-of-motion exercises are begun, avoiding knee flexion past 45°. For children who have had patellar ligament plication, or whose bones are less strong, the knee is immobilized in a knee cylinder cast. The knee cast may be split and used as a bivalve cast, which can be removed typically between 2 to 4 weeks, and gentle passive range-of-motion exercises begun. Weight bearing is allowed either immediately postoperatively if the fixation is suffi- ciently stable, or started at 4 to 6 weeks postoperatively. Knee extension splinting is required usually for 6 months, especially at nighttime to prevent recurrent deformity.

Figure S4.8.11