This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The method of treatment to be employed varies according to the character of the injury. When the fracture is from indirect force, means must be employed not only to hold the fragments together, but also to repair the rent in the capsule. Obviously the limb is to be kept in the extended position to relax the quadriceps. The rectus, on account of taking its origin from the pelvis, is also to be relaxed by elevating the limb. A common method of treatment is by open operation. First a flap is raised, exposing the fracture, then the fragments are approximated with wire or other sutures and the rent in the capsule closed with chromic catgut or silk.
In fractures by direct violence, when separation is not marked, the lateral fascial expansion remains untorn and no open operation is necessary; in others, when separation is more marked, and especially if the fracture is compound, a flap may be turned back and the patella surrounded with a strong suture of chromic gut or silk and the fragments thereby drawn together; the suture may also be introduced subcutaneously.
The articular surface of the patella is divided by a longitudinal ridge into an outer and inner part, which articulate with the corresponding condyles of the femur. The outer surface for the external condyle is much the larger. The outer condyle is also much higher than the inner and thus tends to prevent luxations. The lateral fibrous expansions on each side of the patella also help to hold it in place.
Favoring dislocation is the inclination inward of the knee and the oblique pull of the quadriceps. When a person is standing upright with the feet together the femurs diverge from the knee as they approach the hip, the knees forming an angle of 165 degrees with its apex in. When the quadriceps muscle contracts it tends to straighten this angle and so pull the patella out. If the ligaments are normal and the pull not too violent, luxation does not occur. When, however, from long disuse or disease the ligaments become relaxed, then a sudden and perhaps unusual contraction of the quadriceps will dislocate the patella. This also occurs if the outer condyle is abnormally flat or if the muscular contraction lifts the patella off or above the condyles, as occurs when the tendo patellae is too long. In these, as in almost all other cases, the patella is dislocated outward (Fig. 552). Inward dislocation is almost unknown. Direct injury also produces dislocations, practically always outward. The most common form is for the articular surface of the patella to rest on the outer surface of the external condyle. Other forms, which are more rare, are for the inner edge of the patella to rest against the outer surface of the condyle; for the inner edge to be jammed into the upper portion of the intercondyloid notch with its outer edge sticking up; for the patella to be reversed with its articular surface forward and its anterior surface resting on the condyles.
FlG. 551. - Fracture of patella, showing lateral tear of capsule.
For treating the affection in slight cases an elastic knee-cap may be of service, but a cure is probably best achieved by the operation of Goldthwait (Boston Med. and Surg. Journ., Feb. 13, 1904). In this the tendo patellae is split longitudinally and its outer half detached from the tibial tubercle, passed under the remaining half, and sewed fast to the periosteum and expansion of the sartorius at the inner side of the anterior surface of the tibia. This shifts the pull of the quadriceps more inward and the shortening of the tendon holds the outer edges of the patella more firmly against the edge of the external condyle. Simple folding of the inner part of the capsule has been unsuccessful.