Femoral antivalgus opening wedge osteotomy

FEMORAL ANTIVALGUS OPENING WEDGE OSTEOTOMY GIANCARLO PUDDU, MD, and VITTORIO FRANCO, MD

Valgus painful knee is a disabling condition, especially in athletes. To correct this kind of deformity, femoral osteotomy is the most popular surgical procedure among the techniques described in the literature. The authors herein propose a technique of opening wedge osteotomy based on a new system of plates fixation. Furthermore, some special dedicated instruments have been developed that greatly facilitate the performance of the operation. The indications and the limits of osteotomies are briefly considered before introducing the surgical technique, which is described step by step and is well illustrated with many intraoperative pictures. Some principles of rehabilitation conclude the article. KEY WORDS: arthrosis, valgus knee, osteotomy, cartilage

Painful genu valgum is a much less common condition than genu varum, not only in the general population, but also in athletes. Varus osteotomy of the distal femur is infrequently required in both competitive or recreational athletes. A desire to return to vigorous athletic activity is not the only indication for osteotomy; the basic indication for this procedure should be the same for the athlete as for the nonathlete, pain and disability that interfere with activities of daily living. Returning to certain types of sports activities after this operation is related to unpredictable results because absolutely normal knee joint function cannot always be guaranteed, especially from the point of view of some contact sports. The aim of the osteotomy is to prevent or stop the articular degenerative changes, not erase themJ Even with an excellent surgical result, the athlete may not be able to participate in sports as he desires. According to the above mentioned criteria, we consider 4 main categories of conditions for a femur distal osteotomy: 1. Congenital symptomatic femoral valgus less than 15 °. 2. Early cartilage deterioration after a lateral meniscectomy with or without an anterior instability. 3. Lateral compartment arthritis. 4. Slight valgus in symptomatic knee with magnetic resonance imaging (MRI) stress reaction (Fig 1).

PREOPERATIVE PLANNING To assess valgus deformity and the severity of lateral compartment wear, patients are submitted to a routine side-to-side comparative radiographic evaluation in the coronal and sagittal planes with an axial view of the patellofemoral joint. Also, a standing anteroposterior (AP) radiograph of the whole length of the limbs from the hip to the ankle joints and, instead of the standard AP view, a 45 ° From Clinica Valle Giulia, Rome, Italy.

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posteroanterior flexion weight-bearing radiograph of the knee according to the description of Rosenberg and Paulos 2 (Fig 2). We plan the osteotomy by measuring the actual weight-bearing mechanical axis on the long standing radiograph and calculating the correction (degrees of the osteotomy angle and size in millimeters of the wedge base) we need to get a neutral femorotibial axis.

DEDICATED SURGICAL INSTRUMENTATION The object of distal femoral varus osteotomy is to obtain a post-operative neutral mechanical axis, with no, or very little, amount of overcorrectionJ ,s,4 We prefer the opening wedge technique (Fig 3) and, to accomplish better reproducible results with the less technical difficulties as possible in performing the operation, the senior author developed a complete but simple and easy system of dedicated instruments and plates. The plates, specially designed for this osteotomy, are T shaped with 7 holes. Their peculiarity is a spacer, a "tooth" as it were, available in 6 different sizes from 5 to 17.5 mm in thickness. The tooth enters into the osteotomic line holding the position and preventing a later collapse of the bone with the recurrence of the deformity, s The thickness of the chosen spacer must coincide with the desired angle of correction, calculated in advance in the preoperative planning. The 3 holes in the horizontal arm of the plate allow the introduction of cancellous screws and the 4 holes in the vertical arm are cut for the cortical screws (Fig 4). The crucial point of the operation is the opening of the bone after the osteotomy at the desired angle of correction and holding the position to allow the introduction of the plate tooth. A very simple wedge opener greatly facilitates this step. It has 2 wedge-shaped branches, graduated to allow the opening at the correct rate, and a removable handle to allow the positioning of the plate (Fig 5). The other 2 specially dedicated tools are the Homan retractor for vastus lateralis and a long rod guide with an ankle support to check intraoperatively the mechanical femorotibial alignment.

Operative Techniques in Sports Medicine, Vol 8, No 1 (January), 2000: pp 56-60

Fig 3. The osteotomic line. In the lateral opening wedge, the osteotomy should be slightly oblique with an inclination of about 20 ° from lateral to medial.

up opposite the surgeon. The patient is draped as usual in knee surgery; we also prepare the iliac wing and cover the foot using a very fine stockinette and a transparent adhesive drape to minimize the bulging at the ankle so that it will be possible to better realize the femorotibial alignment after the correction. The tourniquet may be inflated.

Step 2: Arthroscopy Fig 1. MRI stress reaction. The (A) MRI can be positive for a stress reaction of the subchondral bone even if the (B) radiographic examination shows only a slight valgus and discrete narrowing of the lateral joint line. SURGICAL

TECHNIQUE

Arthroscopy of the knee is carried out before the osteotomy to assess the relative integrity of the medial compartment and of the patellofemoral joint and to treat any intraarticular pathology: appropriate joint surface debridement, partial meniscectomy, or loose body removal is performed if needed.

Step 1: Patient Position

Step 3: Incision and Exposure

We prefer a normal operating table with the patient in a supine position and the C-arm of an image intensifier set

We expose the lateral aspect of the femur with a standard straight incision through the skin and the fascia 6 starting 2

Fig 2. The Rosenberg radiograph. The comparison between (A) the conventional AP view and (B) the Rosenberg radiograph of the same patient shows, in real terms of severity, the degenerative changes of the arthritic lateral compartment.

OPENINGWEDGEOSTEOTOMY

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Fig 6, Exposure: a longitudinal skin incision of approximately 15 cm is made on the lateral aspect of the distal third of the thigh.

cial dedicated Homan retractor placed ventrally (Fig 7). Perforating vessels are to be expected and should be controlled with ligature or electrocautery. We leave the joint capsule intact. The lateral cortex is now exposed. The procedure is facilitated by flexion of the knee. Step 4: Osteotomy

Fig 4. Femoral plates. (A) T-shaped plates with 7 holes have a tooth acting as a spacer into the osteotomic line and ranging from 5 to 17.5 mm. (B) Four proximal cortical screws and 2 distal cancellous screws fix the plate to the bone safely stabilizing the osteotomy.

fingers breadth distal to the epicondyle and extending the incision about 15 cm proximally (Fig 6).The dissection is carried down to the vastus lateralis, which is retracted from the posterolateral intermuscular septum by the spe-

Fig 5. A very simple tool acts as the wedge opener. It has 2 wedge-shaped branches that are graduated to allow opening at the correct rate, and a removable handle to allow the positioning of the plate.

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The authors' preferred method is when, with the knee in extension and under fluoroscopic guidance, the surgeon drills a guide Steinmann pin keeping a slightly oblique direction (about 20 °) from a proximal point on the lateral cortex, 3 fingers breadth above the epicondyle, to be safely off from the trochlear groove, to a distal point on the medial cortex (Fig 8). The original instrument system also includes an osteotomy cutting guide to facilitate the use of oscillating saw. The guide may be oriented to accommodate variations in size and anatomy and different choices in the inclination of the osteotomy cut in both coronal and sagittal planes are also possible. 7 A second Homan retractor is placed dorsally to prevent soft tissue damage. The

Fig 7. A special femoral retractor: the vastus lateralis is retracted from the posterolateral intermuscular septum by a special adapted Homan placed ventrally.

PUDDUAND FRANCO

Fig 9. The wedge opener: after the osteotomy is completed, a special wedge-shaped tool is inserted into the line to open the bone at the desired angle of correction.

mechanical axis by means of special guide rod, long enough to extend from the center of the femoral head to the center of the ankle, which we check under fluoroscopy at the passage on the knee joint (Fig 10). When the correction is undersized or oversized, we choose a different plate with

Fig 13. (A) The Steinmann guide pin is inserted. (B) Under fluroscopy, the pin is driven into the bone with an inclination of about 20 ° from a point on the lateral cortex, 3 fingers breadth above the epicondyle, to a distal point on the medial cortex. The osteotomy cut is then performed following the oblique direction of the pin.

osteotomy is then performed keeping the blade of an oscillating saw proximal to the guide pin (to prevent an intraarticular fracture), following the direction of it and perpendicularly oriented to the femur in the coronal plane. It is preferable to only start the osteotomy with the saw and stop the blade after the first 3 or 4 cm, then to separate the cancellous bone with an osteotome driven in all directions into the femur, but preserving a medial hinge of aproximately 0.5 cm 4,8 of intact bone.

Step 5: Opening the Wedge The wedge opener is inserted through the osteotomy while the assistant opens the line by forcing the knee in varus stress. This special tool is advanced until the opening corresponds to the planned correction. The surgeon measures the dimension of gap directly on the graduated wedge of the opener and choose the plate (Fig 9).

Step 6: Plate Fixation By removing the handle of the opener, the plate can easily positioned on the lateral cortex of the femur with the spacer tooth introduced into the osteotomic rhyme. If the plate does not fit the femur cortex properly, we must precontour it by modeling with the bending pliers. Before fixing the plate, we make an intraoperative control of the

OPENINGWEDGEOS-[EOTOMY

Fig 10. Checking the axis: (A) a special guide rod, long enough to extend from the center of the hip to the center of the ankle, is used to check the mechanical axis at the knee joint after the correction. (B) Under fluroscopy, the rod position is checked at the hip, knee and ankle joint.

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Fig 11. Internal fixation: the plate is secured to the lateral cortex with 4 proximal screws and 2 distal cancellous screws.

a thicker or thinner tooth as needed. We then fix the plate with 4 cortical screws proximal to the osteotomy and 2 cancellous screws distally (Fig 11). A lateral plate instead of a medial one is r e c o m m e n d e d for an important biomechanical reason. W h e n a n o r m a l knee with a valgus femorotibial angle is l o a d e d in single-leg stance, the lateral f e m u r is the tension side secondary to the extrinsic varus c o m p o n e n t of the b o d y weight. In severe genu valgum, the mechanical axis m o v e s laterally and, therefore, the convex medial side is subjected to tensile forces. After osteotomy, the mechanical axis is again m o v e d medially, which returns the tension side of the knee to the lateral side. To act as a tension band, the plate m u s t be applied to the lateral femur. Application of the plate to the medial f e m u r after the osteotomy, as in the closing w e d g e o s t e o t o m y with the 90 ° angled blade plate, violates this principle and w o u l d be expected to lead to a high incidence of failure. 4,9

Step 7: Bone Grafting With a skin incision extended from the anterosuperior iliac spine 8 to 10 cm above the iliac crest, w e take 2 or 3 cortico-cancellous bone grafts with the same w e d g e shape and thickness of the osteotomic gap. The grafts are press-fit i n t r o d u c e d to fill the gap. It is also possible to use different grafts, such as bone from the bank or synthetic or bovine freeze-dried bone or, according to some other Authors, no grafts at all. The correct position of the plate and grafts is confirmed with AP and lateral radiographs (Fig 12). Two drains, 1 for each incision, are p r e p a r e d and the w o u n d s are closed in a routine fashion.

POSTOPERATIVE REHABILITATION The knee is immobilized with a range-of-motion brace in full extension or at slight flexion of about 10 ° that allows a full range of motion w h e n unlocked. Passive flexionextension in a continuous passive motion device, quadri-

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Fig 12. Postoperatively, radiographic control of the osteotomy is routinely performed in the 2 standard views.

ceps setting, and straight leg raising exercises are started the d a y after surgery. The drains are r e m o v e d 48 hours later. The patients are allowed to walk with no weight bearing on the operated limb, from the second postoperative day and they are dismissed from the hospital in 4 to 5 days. Usually within the first 4 weeks, the patients are able to flex the knee over 100 °. After 6 weeks, functional weight bearing is allowed. To accomplish this objective, the patients wear a special heel orthosis, the Air Cast Whistler (Air Cast, Summit, NJ), which is calibrated o n 15 to 25 kg. This device warns the patient b y whistling each time they exceed the p e r m i t t e d weight. Full weight bearing is normally possible after 8 to 9 weeks w h e n radiographs show satisfactory healing process of the bone.

REFERENCES 1. Sisk TD: Knee realignment and replacement in the recreational athlete, in De Lee JC, Drez D Jr (eds): Orthopaedic Sports Medicine. Philadelphia, PA: Saunders, 1994,pp 1475-1501 2. Rosenberg TD, Paulos LE, Parker RD, et ah The forty-five-degree posteroanterior weight-bearing radiograph of the knee. J Bone Joint Surg Am 70:1479-1483,1988 3. Beaver RJ, Jinxiang-Yu, Sekyi-Otu A, et ah Distal femoral varus osteotomy for genu valgum. A prospective review. Am J Knee Surg 1:9-17,1991 4. Miniaci A, Grossmarm SP, Jakob RP: Supracondylar femoral varus osteotomy in the treatment of valgus knee deformity. Am J Knee Surg 2:65-73, 1990 5. Simmons P: New fixation plate improves tibial, femoral osteotomies. Orthop Today 3:28-29,1999 6. BauerR, Kerschbaumer F, Poiseh Operative zugangswege in othopadie und traumatologie. Berlin, Germany: Thieme Verlag, 1986 7. Puddu G, Fowler PJ, Amendola A: Opening wedge osteotomy system by Arthrex. Surgical technique. Naples, Fh Arthrex Inc, 1998 8. Mains DB: Technique of proximal tibial osteotomy using a guide. Am J Knee Surg 1:15-22,1990 9. Muller ME, Allgower M, Schneider R, et ah Techniques recommended by the AO Group, in ? (editor): Manual of Internal Fixation, ed 2. New York, NY: Springer-Verlag,1979

PUDDU AND FRANCO