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.
In certain few cases, either from the peculiar character and direction of the primary injury or from an ordinary anterior or posterior luxation becoming subsequently more widely displaced, there result what are known as reversed luxations. They are of two kinds, reversed thyroid and reversed dorsal.
In a thyroid luxation the toes point forward; if now the leg is forcibly twisted until the toes point directly backward a reversed thyroid is produced (Fig. 521). In reducing it the head must be first rotated back to its original thyroid position and then reduced by the usual methods.
In a dorsal luxation the foot is inverted; if now the leg is forcibly twisted outward until the foot is everted, a reversed (or everted) dorsal luxation is produced (Fig. 522). To reduce it the leg must be rotated inward until the head resumes its original position posteriorly and then it may be reduced by the usual dorsal methods. In the production of both these reversed luxations the ligaments are torn still more and the iliofemoral ligament may even be partially detached from its insertion in the femur.
In complete luxations the ligamentum teres is torn but it is not large enough to constitute an obstacle to reduction.
Should the capsule be torn from its attachment to the femur, it may prevent reduction by filling the socket and preventing the entrance of the head. Fragments of muscle may act likewise. To clear the socket Allis advises first, rotation to tighten the Y ligament and pressing the head firmly in; second, to rock the head backward and forward and so clear the obstructing material out.
Fig. 521. - Reversed thyroid luxation. (After Allis).
Fig,. 522. - Reversed dorsal luxation. (After Allis).
If the sciatic nerve is caught around the neck of the femur and cannot be otherwise released, Allis advises extending the leg and cutting down on the nerve at the upper part of the popliteal space. It is then grasped and pulled taut, this releases it from the neck and the thigh can then be flexed and the head replaced: of course, if preferred, an incision can be made directly down on the nerve at the hip.
To accomplish this Allis advises first a trial of the usual direct method of traction and pressure on the head and, if this fails, then while the head is held as near to the socket as possible by an assistant the thigh is brought down and traction is made downward.