Cl inicalfeatures

1 Lateral dislocation of the patella is resisted by the prominent articular

Proximal Femur Shaft Fractures

(c) Popliteal artery Gastrocnemius

Fig. 163 The deformities of femoral shaft fractures. (a) Fracture of the proximal shaft—the proximal fragment is flexed by iliacus and psoas and abducted by gluteus medius and minimus. (b) Fracture of the mid-shaft—flexion of the proximal fragment by iliacus and psoas. (c) Fracture of the distal shaft—the distal fragment is angulated backwards by gastrocnemius—the popliteal artery may be torn in this injury. (In all these fractures overriding of the bone ends is produced by muscle spasm.)

(c) Popliteal artery Gastrocnemius

Fig. 163 The deformities of femoral shaft fractures. (a) Fracture of the proximal shaft—the proximal fragment is flexed by iliacus and psoas and abducted by gluteus medius and minimus. (b) Fracture of the mid-shaft—flexion of the proximal fragment by iliacus and psoas. (c) Fracture of the distal shaft—the distal fragment is angulated backwards by gastrocnemius—the popliteal artery may be torn in this injury. (In all these fractures overriding of the bone ends is produced by muscle spasm.)

Articularis Genu Muscle

Fig. 164 Factors in the stability of the patella: (i) the medial pull of vastus medialis and (ii) the high patellar articular surface of the lateral femoral condyle. These resist the tendency for lateral displacement of the patella which results from the valgus angulation between the femur and the tibia.

Fig. 164 Factors in the stability of the patella: (i) the medial pull of vastus medialis and (ii) the high patellar articular surface of the lateral femoral condyle. These resist the tendency for lateral displacement of the patella which results from the valgus angulation between the femur and the tibia.

surface of the lateral femoral condyle and by the medial pull of the lowermost fibres of vastus medialis which insert almost horizontally along the medial margin of the patella. If the lateral condyle of the femur is underdeveloped, or if there is a considerable genu valgum (knock-knee deformity), recurrent dislocations of the patella may occur (Fig. 164). 2 A direct blow on the patella may split or shatter it but the fragments are not avulsed because the quadriceps expansion remains intact.

The patella may also be fractured transversely by violent contraction of the quadriceps — for example, in trying to stop a backward fall. In this case, the tear extends outwards into the quadriceps expansion, allowing the upper bone fragment to be pulled proximally; there may be a gap of over 2 in (5 cm) between the bone ends. Reduction is impossible by closed manipulation and operative repair of the extensor expansion is imperative.

Occasionally this same mechanism of sudden forcible quadriceps contraction tears the quadriceps expansion above the patella, ruptures the liga-mentum patellae or avulses the tibial tubercle.

It is interesting that following complete excision of the patella for a comminuted fracture, knee function and movement may return to 100% efficiency; it is difficult, then, to ascribe any particular function to this bone other than protection of the soft tissues of the knee joint anteriorly.

Fibula Bone
Fig. 165 The tibia and fibula.

The tibia (Fig. 165)

The upper end of the tibia is expanded into the medial and lateral condyles, the former having the greater surface area of the two. Between the condyles is the intercondylar area which bears, at its waist, the intercondylar eminence, projecting upwards slightly on either side as the medial and lateral intercondylar tubercles.

The tuberosity of the tibia is at the upper end of the anterior border of the shaft and gives attachment to the ligamentum patellae.

The anterior aspect of this tuberosity is subcutaneous, only excepting the infrapatellar bursa immediately in front of it.

The shaft of the tibia is triangular in cross-section, its anterior border and anteromedial surface being subcutaneous throughout their whole extent.

The posterior surface of the shaft bears a prominent oblique line at its upper end termed the soleal line, which not only marks the tibial origin of the soleus but also delimits an area above into which is inserted the popliteus.

The lower end of the tibia is expanded and quadrilateral in section, bearing an additional surface, the fibular notch, for the lower tibiofibular joint.

The medial malleolus projects from the medial extremity of the bone and is grooved posteriorly by the tendon of tibialis posterior.

The inferior surface of the lower end of the tibia is smooth, cartilage-covered and forms, with the malleoli, the upper articular surface of the ankle joint.

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