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Limb Alignment By Barclay Slocum, DVM and Theresa Devine Slocum, MS Although the success of repairs became improved with perfection of ligament substitution techniques and extracapsular procedures, treatment of the rupture of the cranial cruciate ligament with the Tibial Plateau Leveling Osteotomy technique consistently provided results that provided four characteristics to the patient. The dog regained a full sit, except when permanent bony changes were present preoperatively. The progression of the degenerative joint disease was halted. The musculature of the limb returned to normal, and patients returned to preinjury function. Evaluation of 700 cases revealed a pattern from the small percentage that demonstrated incomplete return to preinjury function as is generally expected by the Tibial Plateau Leveling Osteotomy technique. A review of these cases revealed excessive internal tibial torsion, which would give the dog a bowlegged appearance. This was the beginning of an indepth review and prospective evaluation of cases which had an inadequate limb alignment. The most common malady of limb alignment is the bowlegged appearance of a patient. This corresponds with breeds such as the bullmastiff, rottweiler, pit bull and other bowlegged dogs. In modeling the bowlegged conformation, it was found that bowleggedness occurs from four different sources. The most common bowleggedness seen in Labrador retrievers, and golden retrievers is due to a varus deformity of the distal femur. A varus deformity of the distal femur is often associated with a medial patellar luxation and often rupture of the cranial cruciate ligament due to the internal rotation mechanism. The patella rides high and medial on the trochlear ridge and will often luxate. Treatment of the medially luxating patella by lateral fabella to patella sutures or lateral capsulorrhaphy is doomed to failure, as the alignment of the quadriceps will dictate a medial displacement of the patella, which will stretch any repair provided. Treatment by deepening the trochlear sulcus will also be under pressure to create a medial luxation. The standard lateral tibial tubercle transposition is an enticing treatment as patellar stability is assured. Unfortunately, patellar stability is at the expense of a bowlegged conformation due to an exceptionally lateral tubercle which will cause internal rotation of the stifle and an accentuated bowlegged conformation. In this patient the bowleggedness created by the distal femoral varus has been compounded by internal rotation at the stifle which will accentuate the bowleggedness. The long term effect on the patient is excessive pressure on the medial condyle secondary to the bowleggedness and excessive internal rotation of the stifle which predisposes the rupture of the cranial cruciate ligament. The straightforward and proper treatment of this condition lies in a distal femoral valgus osteotomy for the treatment of femoral varus. Once this limb alignment is corrected, the structures will function normally. Stress will be relieved from the structures attempting to maintain quadriceps alignment as well as the cruciate ligament which was countering the internal rotation of the stifle. If the cruciate ligament is stretched, then a Tibial Plateau Leveling Osteotomy is warranted. The bowlegged patient is often seen to have an unusual gait at the time of weight bearing. When viewed from the rear, if the patient has a lateral projection of the stifle at the instant of weight bearing, then this motion is called a pivot shift. The pivot shift is created by a combination of cranial translation of the tibia combined with internal rotation of the stifle. It is mostly seen with cruciate repairs in stretched cranial cruciate ligament replacement surgery, following failure of the implants or tissues in the patient with bowlegged conformation. It is readily correctable by a Tibial Plateau Leveling Osteotomy plus realigning the limb with an external torsional osteotomy and a distal femoral osteotomy. If left unattended, severe wear of the medial femoral condyle is inevitable. In the rottweiler and bullmastiff, distal femoral varus is often present, but it is also accompanied by internal tibial torsion. This creates a bowlegged appearance from both the femur and the tibia. This type of conformation is often associated with ruptures of the cranial cruciate ligament. Any type of repair will fail unless the alignment is corrected. Almost all revision of failed cranial cruciate ligament repairs by fibular head advancement, over the top technique and lateral capsular sutures are associated with this kind of conformation. Revising such surgeries with larger suture or fishing line will have the same results as the failed surgery. The ideal correction for this condition is a valgus osteotomy of the distal varus femur, which will realign the patella and reduce the stress on the medial condyle of the femur. Correction of the ruptured cranial cruciate ligament by means of a Tibial Plateau Leveling Osteotomy with the associated external torsion osteotomy of the tibia will restore full function. It is important to recognize whether the deviation creating the bowleggedness is in the femur or the tibia, and whether it is created by a varus or a torsion. In order to ascertain the location of the deformity and malalignment, perfect radiographic positioning is necessary. A lateral view of the stifle with the greater trochanter, fibular head, lateral malleolus in on plane will present as superimposed trochlear ridges and condyles in the normal dog. It is important that the knee is a ninety degrees for this positioning. If the lateral femoral condyle is cranial to the medial femoral condyle when the patient is properly positioned, then a distal femoral varus is suspected. Varus of the distal femur can be demonstrated radiographically by an anteroposterior view of the femur. This always requires the patient to be raised vertically to allow the long axis of the femur to be perpendicular to the xray beam. Once this position is accomplished and the patella is located in the trochlear sulcus, it should overlay the medial and lateral walls on the intercondylar notch. Once this position is attained, the varus of the femur can be readily measured. Surgery is recommended when the varus equals or exceeds ten degrees. Internal tibial torsion is best diagnosed on the posteroanterior (caudocranial view) of the stifle, tibia and hock. The radiographic position that is most effective is to place the patient in sternal recumbency, and extend the hip with the stifle and tibia located on the cassette. The stifle is extended and the hock is allowed to be in its extended position, making no attempt to center the calcaneus over the distal tibia. Since the stifle is forced into extension, no rotation at the knee joint is possible. If the stifle is not forced into extension, then errors will occur as the stifle is free to rotate both internally and externally. Perfect position for the stifle places the patella between the medial and lateral walls of the intercondylar notch. When the stifle is in this position, the medial border of the calcaneus should lie at the greatest depth of the talar sulcus. The hock is forced into extension simultaneous with forced extension of the stifle. If the patient is bowlegged due to internal tibial torsion, then the medial border of the calcaneus will be lateral to the talar sulcus. Internal torsion of the femur and varus of the proximal tibia are less commonly seen than the varus of the distal femur and internal torsion of the tibia. If present, these can be corrected by an external torsion osteotomy of the femur and a valgus osteotomy of the tibia. Since these are usually accompanied by rupture of the cranial cruciate ligament, a Tibial Plateau Leveling Osteotomy is a convenient kerf through which alignment correction of the tibia can be made. Failure to gain alignment of the femur and tibia will result in continued medial patellar luxation and the destructive forces of the stifle. The tibial tubercle should be in line with the foot, hock and patella when the dog is under anesthesia in a supine position. The dog is on his back, with the knee flexed at 90 degrees without internal or external rotation of the stifle. If the tibial tubercle is medial to the plane which includes the patella, the hock and foot, then a lateral tibial tubercle transposition is necessary back to that plane. If the alignment of the patella, tibial tubercle, hock and foot are in one plane, and a tibial tubercle is transposed laterally to treat a medially luxating patella, then the long term appearance of this patient will be a bowlegged conformation which predisposes this patient to rupture of the cranial cruciate ligament and excessive wearing of the medial compartment of the stifle. This results in cartilage eburnation. In the field trial springer spaniel, the patient may appear in normal conformation when standing on the exam table or participation in non-working activities. This patient may become bowlegged as a result of a hunting posture specific to this breed. The springer spaniel works and hunts in a very low "vacuum cleaner crouch" in which the hips are externally rotated and the stifles are internally rotated. This seems to lower the center of gravity of the dog. When the patient assumes this posture, the tibial tubercle will be medial to the patella, as the hip is externally rotated and the stifle is internally rotated. This conformation creates a medial patellar luxation. Since the bone structure of this patient is normal, and the posture is desirable, the patient has been genetically engineered for this characteristic. The best correction for this medial patellar luxation is a rectus femoris transfer from the origin to the cervical tubercle. This allows the origin of the quadriceps muscles to be on the proximal femur. Consequently, rotation of the hip does not necessarily dictate abnormal alignment of the patella because all four heads of the quadriceps now originate on the femur. This eliminates the medially directed force on the patella. This is the only function cause of medial luxating patella that I have experienced in clinical practice. All others are associated with anatomical malalignments. The opposite appearance of bowleggedness is the knock kneed conformation. The knock kneed conformation places the stifle medial to the sagittal plane. This should be distinguished from true cow hocked appearance. The cow hocked appearance places the hip, stifle, tibial tubercle, hock and foot in a singular plane with the knee lateral to the sagittal plane. This cow hocked appearance is created by external rotation at the hip. Knock kneed conformation is pathologic because the stifle undergoes external rotation and frequently an anterorotary instability. Anterorotary instability is the desire for the tibia to move cranially and rotate externally. This instability shifts the line of axial rotation of the tibia laterally, and stresses the craniomedial joint capsule which may produce an enlarged knob on the tibia just cranial to the medial collateral ligament. Patients which have knock kneed conformation are German shepherds, great danes, akitas, malamutes or huskies. The first feature to diagnose is the presence or absence of an OCD lesion on the lateral femoral condyle. Sometimes this lesion is subtle and is seen only as a flattened area without loss of cartilage. If an OCD lesion is present on the lateral condyle, then the patient may have laxity within the joint that is caused by a lack of bony spacer which is due to loss of the joint space with the OCD lesion. This laxity is often diagnosed as a rupture of the cranial cruciate ligament, when in fact, the problem exists due to loss of bone. The tibial conformation must be observed as it is usually normal, but may have proximal tibial valgus or external tibial torsion present. The presence of OCD of the lateral femoral condyle, proximal tibial valgus and external tibial torsion causes a stress on the craniomedial joint capsule which leads to craniomedial rotary instability. Correction of the tibial deformities is by proximal tibial varus osteotomy and an internal tibial osteotomy. If the lesion on the femur causes minimal deviation, the latter two osteotomies will shift the weight from the lateral to the medial condyle. The most significant change in alignment comes in the femur for the knock kneed patient. There are two forms seen clinically of distal femoral varus. The first is when the trochlea is in line with the femur, but the supporting condyles are externally rotated around an axis that is perpendicular to the frontal plane. The second form is a distal femoral varus deviation which occurs proximal to the trochlea. The treatments for the first is an osteotomy perpendicular to the sagittal plane which separates the femoral condyles from the trochlea for the patella. Once that separation has occurred, then the distal femur can be relocated in alignment with the trochlea. For distal femoral varus a medial opening wedge or a lateral closing wedge is corrective. If distal femoral valgus is present, then a distal femoral medial closing wedge osteotomy will be curative. Caution should be taken in giant breeds that two plates be utilized at ninety degrees to one another if needed. In addition, bone graft taken in strips from the ilium will enhance the rapidity of healing on these patients. The thin cortices and long limbs predispose dogs such as Great Danes to traumatic fractures without taking these precautions.
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