rupturing under a strain of forty and four-fifths pounds,' and this greater strength he attributed to the mingling with its muscular belly of tendinous fibres, some of which extend to a bony attachment within the pelvis and thus become actual restraining ligaments when the muscle is fully extended. Its action is to evert the extended, to abduct the partly flexed thigh. Above it is the pyriformis, below it the quadratus femoris. The centre of the head of the femur lies about two inches directly below the anterior inferior spine of the ilium, and at about the same distance downward and outward from the centre of, and in a direction at right angles to, a line drawn from the anterior superior spine of the ilium to the spine of the pubis. When the bones are normal and in place, and the limb is partly flexed, a line drawn across the outer aspect of the thigh from the anterior superior spine of the ilium to the lowest part of the tuberosity of the ischium will cross the upper part of the great trochanter. This is known as Nélaton's, or the Nélaton-Roser, line; its relations to the trochanter have great diagnostic importance. In the child, according to Hueter, the trochanter is brought somewhat higher by the relative shortness of the neck of the femur. The range of motion of the joint has been very carefully studied by Albert; he found that in a preparation consisting of only the bones and ligaments the range of flexion and extension was 140°, and that of abduction and adduction 90° to 100°, of which abduction (from the sagittal plane) was 60°, and adduction 30° or 40°. If the muscles were left in place flexion was diminished 30°, and adduction reduced to 20°. In other words, extension and abduction are checked in the living by the ligaments of the joint, flexion and adduction by the muscles or by the contact of the limb with the abdomen in flexion. The range of abduction and adduction is further modified by the position of the limb as regards its flexion and its rotation about the long axis. The position of the limb in which dislocation of the hip most frequently occurs is that of flexion, adduction, and inward rotation, and the dislocation which then occurs is usually one of the backward forms, although after the head of the bone has left the socket abduction and outward rotation of the limb may lodge it in the obturator foramen. In this position the posterior and inferior portion of the capsule is put upon the stretch and ruptured. By outward rotation and abduction the head may be forced out at the lower and inner part of the capsule below the pubofemoral ligament, toward the obturator foramen; in each case a new centre is found for the exaggerated movement in the more or less direct contact between the neck of the femur and the margin of the acetabulum or in the tension of part of the Y-ligament. The force which produces the dislocation, therefore, almost always acts indirectly, either by moving the limb upon the fixed trunk or by moving the trunk upon the fixed limb. In the great majority of cases the Y-ligament remains untorn, and by the restraint which it exerts upon the movements of the displaced femur it determines in a large measure the character of the secondary displacement, the attitude in which the limb comes to rest, and the manipulations by which the dislocation can be reduced. This influence is so 1 Bigelow: The Hip, 1869, p. 22. 2 Albert: Chirurgie, vol. 4, p. 248. great that Bigelow based upon it the distinction which he made between regular" and "irregular" dislocations, the former including those cases in which the ligament remained untorn and the attitude of the limb was in consequence characteristic; the latter those in which the ligament was more or less torn and the attitude and displacement variable. The distinction has sometimes an important bearing upon the treatment and deserves to be preserved. Statistics. The tables in Chapter I. show that the percentages of dislocation of the hip, compared with all dislocations, vary from 2 per cent. (Krönlein) to 9.76 per cent. (Prahl) and that the percentages in the combined hospital and polyclinic 1432 cases is the same, 8.8 per cent., as in the 964 hospital cases. Agnew says that of 912 dislocations admitted to the Pennsylvania Hospital 89 (9.75 per cent.) were of the hip. Of Krönlein's 8 cases 4 were in patients not more than ten years old, and of Prahl's 41 cases 12 were of the same age, 8 were between eleven and twenty, and 11 were between twenty-one and thirty years old. This preponderance in youth is, however, not found in Agnew's list or in the 41 cases collected by Malgaigne or the 84 cases collected by Hamilton. The latter were divided as follows: Although the numbers are larger in Hamilton's collection than in Prahl's, yet, as the latter are the integral statistics of a single hospital and dispensary, I think its percentages are more likely to represent the actual proportions than those of a collection of published cases are. It is true that the general impression of the profession is that the injury is especially frequent in early middle life, but this impression may have been created by Malgaigne's and Hamilton's statistics. I do not know how to account for the absence from Agnew's list of patients under fifteen years of age. 2 The earliest age at which a dislocation has been reported is six months (Powdrell, Lancet, 1868, i. p. 617), it was a dislocation upon the obturator foramen, and was caused by the fall of a chair in which the child was tied. In the report by W. A. Johnson, of a clinical lecture by Prof. Gross, it is said, "upward of six years ago this child, M. S., aged seven years, had a fall," and received a dorsal dislocation of the hip. The note is entitled "Dislocation of the hip-joint in a child six months of age." Bartels3 reported a dorsal dislocation at eleven months caused by the effort made to put on a shoe. Several others have been reported between the ages of eighteen months and five years. 1 Agnew Surgery, vol. 2, p. 89. 2 Johnson: Phil. Med. Times, 1876-7, vol. 7, p. 5. The oldest patient is one reported by Kennedy,' a woman, aged ninetyone years and five months, who received a dorsal dislocation of the right hip by a fall, while walking across a smooth floor; it was reduced on the twelfth day by manipulation, and two days later the patient died. The autopsy verified the diagnosis. The next oldest patient, eighty-six years, was also a woman (Gauthier, quoted by Malgaigne, loc. cit., p. 805); and the next, a man eighty-one years old, whose dislocation was suprapubic and was verified by autopsy four years later, the neck of the bone was broken by an attempt to reduce while the injury was recent; the case was reported by Verneuil.2 Agnew says he found in the records of the Pennsylvania Hospital five cases between the ages of seventy-five and eighty-five years. They do not appear in the tabulation above quoted. The injury is much more common in males than in females: of Agnew's 89, 11 were women; of 115 cases collected by Hamilton, 104 were males. Concerning the relative frequency of the different varieties it can be said that those in which the head of the femur is found resting upon the lower part of the ilium behind the outer posterior half of the acetabulum, the so-called "iliac" dislocation, to preserve for the moment the old classification, or still lower down on the upper part of the ischium, "ischiatic" dislocations, are much more frequent than those in which it rests in front or on the inner side of the acetabulum, the suprapubic and obturator dislocations. The dislocations upon the dorsum of the ilium are generally thought, on clinical evidence, to be more frequent than the ischiatic, but a comparison of the cases examined after death does not corroborate this view; Malgaigne collected 10 autopsies of ischiatic dislocations, and only 6 of the iliac, one of these being primarily ischiatic, and Lossen,3 taking only cases reported since 1855, found 19 ischiatic, and only 5 iliac. Probably Malgaigne's supposition is correct that many ischiatic cases observed clinically are thought to be iliac; indeed, it will further appear that in many "iliac" dislocations the head of the femur has primarily passed downward and backward, and that its presence upon the dorsum of the ilium is due to a secondary displacement upward. Roser goes so far as to claim that the iliac dislocations, in which the head of the femur has left the cotyloid cavity by its upper posterior portion, are the rarest of all the principal forms. Of the two anterior forms the obturator seems to be more frequent than the suprapubic, but the reported cases are too few to justify a positive assertion. cases. Simultaneous dislocation of both hips has been reported in several Two of them, Boisnot and Schinzinger, have been quoted in Chapter I.; Malgaigne quotes two, and Gibson, Crawford, Steiner, Roberts, James, Jung, Wood, Pollard, Bigelow, Fischer, Kunschert, Barker, Prichard, Allis, Packard, and Bourrienne have each reported one. Compound dislocations are very rare, as might be expected from the thickness of the soft parts, which everywhere cover in the joint. The Kennedy: Cincin. Lancet and Clinic, 1878, i. p. 256. 6 recorded cases are those of Walker,' Bransby Cooper, Macouchy,' Moxon, a German military surgeon,5 Taylor, and Woodward. The first and fifth have been quoted in Chapter III., p. 39. The second is not spoken of by Cooper as a compound dislocation, but the history indicates that it probably was one; the patient, a lad seventeen years old, was run over by a wagon, the wheel passing across the back of his thigh and producing a dislocation forward and inward, the head of the femur lying to the inner side of the great vessels. A rather large lacerated wound was situated just below Poupart's ligament, a little to the inner side of its centre. Profuse suppuration followed, and the patient died on the twentieth day. Macouchy's patient was a boy fourteen years old, who fell from a mast to the deck, a distance of sixty feet, and received, in addition to the dislocation, a fracture of the base of the skull. When seen, he was sitting on the deck with the head of the femur appearing between his legs, through his pilot-cloth trousers, as if protruded from his anus. The head, neck, and great trochanter protruded through the integuments covering the posterior third of the ischium, the head of the bone resting on the posterior part of the tuberosity of the ischium of the opposite side. The head was sawn off, and the shaft replaced. The patient died two days later. Moxon's patient, a railway porter, was injured by a moving train and died shortly afterward in Guy's Hospital. The position of the limb was that of dislocation on the dorsum ilii. There was a large irregular rent in the skin corresponding to the junction of the left sacro-sciatic ligament with the tuber ischii. On passing three or four fingers into the hole a way was found through a pulp of torn muscles and bloodclot, till the fingers rested on the naked head of the thigh bone. The gluteal muscles were much torn up and infiltrated with blood. The head of the thigh bone lay half an inch outside the great sciatic nerve, free under the remains of the glutei. It had escaped through the muscles immediately around the joint by passing between the quadratus femoris and obturator internus. A portion of the head of the bone remained in the socket, attached by the round ligament. Taylor's patient was a lad seventeen years old who was overthrown by a falling tree and received a dislocation into the obturator foramen together with an irregular wound nearly two inches long in the perineum through which the head of the femur could be distinctly felt. Most of the muscles had been separated from the descending ramus of the pubis and the ascending ramus of the ischium. Reduction was made with some difficulty, and the limb immobilized on a long side splint. The wound healed promptly, and at the end of nine weeks the splint was removed, but on the next day inflammatory symptoms appeared on the side of the hip, and an abscess formed and was opened. Eight months later Taylor met the patient riding on horseback. 1 Walker, quoted by Cooper: Loc. cit., p. 80. 6 2 Cooper: Loc. cit., p. 76. Taylor: Lancet, 1881, i. p. 732. 1 Woodward: Boston Med. and Surg. Journ., 1883, vol. 108, p. 129. Woodward's patient, a boy twelve years old, was caught under a freight car and rolled over and over, receiving several fractures in addition to the dislocation. The wound was a longitudinal slit about two inches long on the inner side of the thigh two and a half inches below the angle of the pubes. The limb was abducted, making an angle of nearly 45° with the line of the body, and the foot was everted. The head of the femur, together with the great trochanter entirely stripped of its muscles, projected completely through the opening for about four inches and lay across the scrotum. Its point of exit was just anterior to the adductor longus. No fracture of the femur or pelvis was detected, and the great vessels were uninjured. The patient died in five hours, and after death reduction could not be made. Classification. The classifications adopted by the earlier writers were necessarily faulty and deficient because of the lack of recorded experience and post-mortem examinations. That of Hippocrates, containing four principal forms, outward, inward, forward, and backward, was employed, according to Malgaigne, until the seventeenth or eighteenth century, although the terms do not seem always to have been applied in the same sense. Petit, in the eighteenth century, made two main groups, inward and outward, each with two subdivisions, the four being upward and inward, downward and inward, upward and outward, and downward and outward, but he thought it impossible that the latter form could occur. Verduc, about the same time or a little earlier, sought to substitute a classification based upon the place at which the head of the femur came to rest, and in this he was supported by Duverney and Bertrandi, and thus arose the terms dislocation upon the ilium, upon the ischium, upon the pubes, into the foramen ovale. Sir Astley Cooper gave us dislocations upward, or on the dorsum ilii, downward, or into the foramen ovale, backward, or into the ischiatic notch, and dislocation on the pubes; and Gerdy followed with supra-pubic, sub-pubic, iliac, sacro-sciatic, and ischiatic, the latter being directly downward. Malgaigne was the first to bring to the subject the results of careful study of many pathological specimens; he showed that in the backward dislocations the head of the femur did not go so far as the anatomical terms used in Cooper's classification, for example, would indicate, but that on the contrary it usually remained so near the cotyloid cavity that it partly overlapped it, "incomplete" dislocations, as he called them, and he proposed a classification in four groups, of which the first two were the same as Petit's, though the names are different, as follows: The names ilio-pubic and ischio-pubic were taken from those of corre sponding depressions on the margin of the cotyloid cavity along which the head of the femur was thought to pass, and, acting on the same plan,, |