Orthopedics - Oleksa A.P. 2006

Congenital and Acquired Deformities of the Lower Extremity
Congenital Deformities of the Knee Joint
Hyperextended Knee (genu recurvatum)

By the term "hyperextended knee", we understand an axial deformity of the lower limb in the lateral projection (hyperextension at the knee joint). This deformity can be congenital or acquired (Irvin С.Е., 1942; Ishikava Н. et al., 1984; Laura G. et al., 1992; Marczynski W., Pomiema I., 1992, Rappold G., 1992).

Congenital hyperextended knee (genu recurvatum congenitum) typically results from intrauterine fetal compression (Kirmisson Е.), although Ombredanne attributes it to a fetal developmental defect, and Potel to quadriceps dystrophy.

If the hyperextended knee is caused by intrauterine pressure, other associated limb anomalies are also typically present.

Various degrees of knee hyperextension occur — ranging from mild hyperextension (Fig. 171) to anterior subluxation of the Tibia, or even its congenital dislocation.

Diagnosis of this pathology is straightforward, although Aplasia of the thigh flexors and, occasionally, arthromyodysplasia must be ruled out. Treatment consists of the gradual correction of tibial hyperextension at the knee joint using serial plaster casts. As a rule, treatment begins after the newborn is discharged from the maternity hospital. Flexion of the leg is performed without anesthesia, slowly, and within the limits of tissue compliance. During manipulation, care is taken to prevent tibial subluxation; following flexion, a plaster cast is applied in the same position. These flexion maneuvers are repeated every 5–7 days until maximum knee flexion is achieved.

When treating children who are already walking, once full tibial flexion is achieved, an orthosis is prescribed that blocks and prevents tibial hyperextension while allowing full flexion at the knee.

In adults, a hyperextended knee develops As a result of ankle ankylosis with FOOT equinus (Fig. 171), proximal tibial deformity following a fracture, sometimes due to injury to the ligamentous-capsular apparatus of the knee, or a combination of both factors (Moroni A. et аі., 1988; Rappold G., 1992).

Typically, patients complain of pain, a feeling of instability in the knee, and limb weakness. Quite often, a hyperextended knee is accompanied by varus deformity, in which case the lower limb may be slightly (1–2 cm) shorter (Julliard R. et al., 1993).

The degree of knee hyperextension is determined from a lateral radiograph (taken at maximum hyperextension), by drawing the axes of the Femur and tibia and measuring the angle of recurvation, i.e., the angle formed by the long axes of these bones.

Simultaneously, a tangential horizontal line is used to determine the inclination angle of the tibial articular surface relative to its longitudinal axis. Normally, this angle is 96°, meaning that the posterior part of the articular surface lies inferior to the anterior part.

In a hyperextended knee, the posterior part of the articular surface may lie superior to the anterior part, in which case this angle is calculated relative to the normal value (96°). If the hyperextension angle exceeds the inclination angle of the tibial articular surface, it indicates overstretching and insufficiency of the ligamentous-capsular apparatus of the knee, which most commonly occurs as a sequela of poliomyelitis.

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Fig. 171. Hyperextended knee with equinus foot position.

Thus, such measurements provide the basis for selecting the optimal treatment method. Therefore, before surgery, it is necessary to identify the exact factors causing this pathology. Surgical treatment is indicated (Kwiatkowski К. et al., 1999) for a knee recurvation greater than 15° to prevent progression of the deformity. Increased deformity disrupts knee biomechanics, which weakens Muscle strength, increases instability, and leads to Secondary Osteoarthritis (gonarthrosis).

In adults with a hyperextended knee and a normal ligamentous apparatus, surgical treatment is applied in the form of high tibial osteotomy (Bohn С. L. S., 1956; Bowen J. R. et al., 1983; Brett A. L., 1935; Lecuire F. et al., 1980).

Lexer (Lexer F., 1931) was the first to describe wedge-shaped osteotomy above the tibial tuberosity. As Moroni points out, Lecuire and co-authors supplemented this osteotomy by translating the tibial tuberosity to a position that ensures proper patellar placement.

The surgery is performed under general anesthesia and using a tourniquet. Following soft-tissue dissection, the tibial tuberosity is osteotomized and displaced proximally along with the patellar ligament. A high tibial osteotomy is then performed, the inclination angle of the articular end is corrected, and the bone defect resulting from correction is filled with a preserved corticocancellous bone graft (Fig. 172). The fragments are temporarily fixed with percutaneous Kirschner wires (which are removed after three weeks via their ends protruding above the Skin), and the tuberosity is fixed with a screw positioned to ensure correct patellar placement—neither too low nor too high—matching joint biomechanics. The wound is closed, and a plaster cast is applied until bone union occurs. Gradual weight-bearing on the limb begins 6–8 weeks postoperatively.

Fig. 172. Diagram of wedge tibial osteotomy with deformity correction using a bone autograft.

The outcomes of surgery performed in this manner are optimal; they are somewhat less favorable when the osteotomy is performed without transposition of the tibial tuberosity, i.e., without correcting THE POSITION OF the Patella (Kwiatkowski К. et al., 1998).

If knee hyperextension is caused by soft-tissue deficiency, particularly in paralysis resulting from poliomyelitis, reconstructive Procedures on the ligaments and the posterior Joint Capsule, as well as tenodeses, are employed. Arthrorisis is not used in such cases and is considered to be of historical significance only (Irvin С. Е., 1942; Jacguelin Р. et al., 1976; Perry І. et al., 1976).

Based on The Study of long-term surgical outcomes, the majority of orthopedists conclude that timely restoration of the angular relationships of the tibial articular end and correct positioning of the patella are key to preventing the progression of knee recurvation and The Development of gonarthrosis.