Irreducible traumatic posterior dislocation of the hip

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Injury,5, 188-193

Irreducible traumatic posterior dislocation of the hip P~ir Sl~tis and Antti Latvala Department of Surgery and Division of Orthopaedic Surgery, Vaasa Central Hospital, Finland Summary Perusal of the literature reveals that on average 2-4 per cent of simple posterior dislocations of the hip require open reduction; the corresponding figure for fracture-dislocations is considerably higher. Two cases are presented in which attempts at closed reduction were unsuccessful; in one owing to interposition of the piriformis muscle, in the other because of avulsion of the origin of the obturator and gemelli muscles which led to interposition of the avulsed muscle mass in the joint cavity. Attention is drawn to the possibility that the torn acetabular labrum may be dislodged into the joint space. If a simple posterior dislocation cannot be reduced under general anaesthesia at the first attempt, operative reduction, and removal of the obstructing tissue, is recommended.

INTRODUCTION

TRAUMATIC dislocations of the hip are divided into two groups, anterior and posterior, according to the position of the femoral head after the injury. Posterior dislocations outnumber anterior dislocations in an average ratio of 10 to 1 (Thompson and Epstein, 1951; Brav, 1962; Lehtonen, 1968; Miller, Gustilo, and Tambornino, 1971). The anterior dislocations are mostly simple extrusions of the femoral head through the front wall of the joint capsule. Reduction is usually straightforward, although occasionally hampered by interposition of the torn capsule (Henderson, 1951; Katznelson, 1962). Posterior dislocation, however, is complicated in more than half the cases by fracture of the hip joint. These bony injuries comprise rim fractures of differing severity, ranging from small chip fractures to large fractures with disintegration of the rim of the acetabulum and gross instability of the joint; to this injury may be added fractures of the head or neck of the

femur (Thompson and Epstein, 1951; Stewart and Milford, 1954). In these instances, fragments of bone, cartilage, and soft tissue tend to be dislodged into the joint cavity and the injury usually defies attempts at closed reduction. There is unanimous agreement that early operative treatment is indicated when instability of the hip joint is due to fracture of the acetabular rim - - t h e presence of a bony fragment in the joint cavity (Urist, 1948; Brav, 1962; Epstein, 1973). There remain simple posterior dislocations of the hip without radiographic evidence of concomitant injury to the acetabulum or the femoral head. In most instances closed reduction is successful, the position is easily retained and the results after early weight-bearing are gratifying (Stewart and Milford, 1954; Lehtonen, 1968; Hunter, 1969; Epstein, 1973). Several authors, however, mention difficulties in connexion with the reposition manoeuvres (Urist, 1948; Miller and others, 1971). Epstein (1973) points out that multiple attempts at closed reduction should not be encouraged, and that operative treatment is preferable if a competent orthopaedic surgeon cannot reduce a dislocated hip at the first attempt. Perusal of the literature reveals that on an average 3 per cent of cases of simple posterior dislocation of the hip need operative reduction. Thompson and Epstein (1951) reported 1 case out of 30, Brav (1962) 3 cases out of 110, Lehtonen (1968) 1 out of 46, Hunter (1969) 1 out of 26, Miller and others (1971) 1 out of 24 patients, and Proctor (1973) 3 out of 100 patients. The reasons for failure to reduce the dislocation are not always given, but a few interesting observations have been made. Thus, Paterson (1957) described partial detachment of the posterior part of the acetabular lip as a cause of obstruction; a similar case was soon reported in an adult by Thompson (1960) and in a child

Sl~tis and Latvala : Posterior Dislocation of the Hip

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by Fordyce (1971). Hunter (1969) reported a case of a buttonhole tear of the posterior capsule entrapping the femoral head. In children, Funk (1962) reported 3 operative reductions in 40 patients; the indication was capsular interposition.

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point exists in the capsule above and below the ischiofemoral ligament in the vicinity of the acetabular lip. The muscles on the dorsal aspect of the hip joint are the piriformis, obturator internus, gemelli, and quadratus femoris (Fig. 1B). The

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Fig. 1.--A, The hip joint seen from behind. The ligaments are thinner on the dorsal than on the ventral aspect. Weak points are noted above and below the ischiofemoral ligament. B, The muscles close to the dorsal aspect of the joint are injured in posterior dislocation. The femoral head extrudes either in a posterosuperior direction (l) or in a posterior direction (2), depending upon the degree of flexion in the hip joint at the moment of impact. The lateral fascicles of the sciatic nerve are apt to be injured by the femoral head or by displaced bony fragments. This report was prompted by experience with 2 cases of posterior dislocation of the hip in which attempts at closed reduction were unsuccessful; in both cases accurate reduction was hampered by interposition of soft tissue.

A N A T O M I C A L CONSIDERATIONS The femoral head forms two-thirds of a sphere and normally lies in the acetabulum. The cupshaped cavity is a hemisphere, but additional stability to the ball-and-socket joint is provided by the acetabular lip. This firm fibrocartilaginous ring is fixed to the rim of the acetabulum in such a way that its inner part fits tightly round the femoral head. Since the aperture at the outer margin of the acetabular lip has a smaller radius than the osseous acetabulum, the lip deepens the socket and narrows the mouth of the cavity. The capsular ligament around the hip joint is exceedingly strong; it is thicker on the anterior aspect and weaker on the posterior aspect (Fig. 1A). Anteriorly the fibres form the iliofemoral ligament, posteriorly the thinner ischiofemoral ligament. The dorsal wall is reinforced by fibres running in the zona orbicularis, which partly encircles the lateral part of the capsule. Thus a weak

sciatic nerve emerges from the infrapiriformic space and crosses the gemelli, the obturator internus, and the quadratus femoris close to the posterior rim of the acetabulum and midway between the ischial tuberosity and the greater trochanter.

CASE REPORTS Case 1

A 45-year-old agricultural worker was sinking a well when earth and stones fell on him from a height of 5 m. and almost buried him. At the moment of impact he was standing almost erect. On admission to the emergency room a fracture-dislocation of the left hip (Fig. 2A), a ruptured spleen, and multiple rib fractures were diagnosed. After apprcpriate resuscitative measures, the hip was manipulated under general anaesthesia, according to Allis and Bigelow. However, the dislocation could not be reduced. The spleen was now removed and then the patient was turned on his right side. The left hip was exposed through a posterior incision. The piriformis muscle was found to be twisted around the femoral neck, blocking the entrance to the acetabulum (Fig. 4B). The belly of the muscle was disengaged from the femoral head, fragments of bone which had been avulsed from the latter were removed from the joint cavity, and the hip was reduced. The capsule was found to be badly ruptured

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with simultaneous detachment of the posterosuperior part of the acetabular lip. The gemellus superior and obturator internus muscles were severely contused and partly torn. The periarticular structures were sutured with non-absorbable material

and the hip immobilized in traction for 3 weeks. The patient made art uneventful recovery. At followup 3 years later, he was doing a full day's work, but had some pain in the left hip after strenuous effort. Radiography (Fig. 2B, C) clearly shows the defect in the femoral head, calcification of the soft parts outside the acetabular lip where the acetabular rim had been detached, and post-traumatic arthritis of the joint. Case 2

A 41-year-old industrial worker sustained posterior dislocation of the left hip in a traffic accident. The hip was reduced under general anaesthesia, but the characteristic clunk was absent and the hip redislocated (Fig. 3A). The following day, several attempts at reduction were made with the Allis, the Bigelow, and the Stimpson manoeuvres (Miller and others, 1971; Epstein, 1973), but without success. Interposition was suspected, and under the same anaesthesia the hip was exposed through a posterior incision. The femoral head was found to have torn the posterior wall of the capsule. The piriformis muscle and the acetabular rim were intact. The joint socket was filled with a lump of muscle which had completely blocked every endeavour to replace the femoral head. The muscle mass was identified as the entire obturator internus, the gemellus superior, and the gemellus inferior muscles which had been torn from their respective origins at the pelvic

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Fig. 2.--Case 1. Art agricultural worker sustained a posterior dislocation of the hip while the joint was almost fully extended. Fragments of bone detached from the femoral head are visible in the radiograph A, closed reduction was unsuccessful and was hampered by interposition of the piriformis muscle hooked around the femoral neck (cf Fig. 4B). In follow-up radiographs taken at B, 3 months and C, 3 years, signs of calcification are visible in the posterosuperior part of the joint, where detachment of the acetabular lip was observed at operation. Post-traumatic arthritis developed, without notable subjective impairment of working ability.

Sl~itis and Latvala : Posterior Dislocation of the Hip

surface of the hip bone, the ischial spine, and ischial tuberosity. The three-headed muscle was still attached by its tendon to the greater trochanter. The tendon was severed and the whole muscle group was removed (Fig. 3B). The hip was reduced, the capsule sutured with non-absorbable sutures, and the hip immobilized in slight traction for 2 weeks. At follow-up 2 years later, the hip was symptom free, had a normal range of movement, and displayed no radiographic evidence of avascular necrosis or post-traumatic arthritis (Fig. 3 C). DISCUSSION

D u r i n g operations for posterior dislocation of the joint, Urist (1948) noted that if the acetabular rim was fractured, the capsule r e m a i n e d essentially intact except for an occasional

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single tear in the posterior capsule. The short external rotator muscles always sustained considerable damage. C o m m i n u t e d fractures of the rim were accompanied by extensive, contused, and lacerated wounds of all posterior soft parts. Paterson (1957), D a m e r o n (1959), and Fordyce (1971) described the torn acetabular labrum as detachment of the posterior acetabular lip, which was conveyed into the joint by the femoral head during attempts to replace it (Fig. 4A). Paterson observed rents in the posterior capsule accompanying the tear in the acetabular lip. The injury inflicted on the soft parts in connexion with traumatic posterior dislocation of the hip is probably dependent on the direction

A

Fig. 3.--Case 2. A, An industrial worker sustained a posterior dislocation of the hip while the joint was flexed. Repeated attempts at closed reduction failed. B,Thejoint was filled by a 3-headed muscle mass formed by the obturator internus and the gemelli (cf. Fig. 4), which was removed. C, At follow-up 2 years later, the hip joint was clinically normal without signs of posttraumatic arthritis or avascular necrosis.

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taken by the femoral head at the moment of impact. If the hip is extended and slightly adducted, the femoral head leaves the socket in an almost posterosuperior direction, above the gemellus superior. In Case 1 the course taken by the femoral head was obviously above even the belly of the piriformis muscle (Fig. 4B). The femoral neck then became hooked on the piriformis muscle, and subsequent attempts at reduction were haJnpered by the muscle crossing the empty acetabular socket. If the hip is flexed and slightly adducted, the femoral head leaves the socket through the dorsal wall and on its way stretches and tears the short external rotators. The sciatic

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may be involved after posterior dislocation: in one, a post-traumatic synovial pouch was found to emerge between the piriformis and gemellus superior muscles, in the other a synovial pouch emerged between the gemellus inferior and quadratus femoris muscles. In both, the labrum had retained its attachment to the acetabular margin, and the sciatic nerve was enclosed in a sheath of fibrous tissue. Posterior dislocation of the hip should be reduced as early as possible. Stewart and Milford (1954) pointed out that the proportion of poor results increases if the reposition manoeuvre is delayed for more than 12 hours after the injury; they advocated the Stimson

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C A B Fig. 4.---Three sources of obstruction to reposition of posterior luxation of the hip joint, not visible in radiographs: A, The torn labrum. The detached part of the acetabular lip, still partly connected to the acetabular rim, is conveyed into the joint by the femoral head during attempts at reduction. B, The hooked piriformis muscle. The muscle becomes twisted around the femoral neck if the femoral head is displaced posterosuperiorly (Case 1). C, The obstructed socket. Detachment of the short rotator muscles at their origin allows displacement of the muscle into the joint cavity (Case 2). nerve, especially its lateral part, is in the danger area and signs of nerve damage are recorded in about 10 per cent of cases. Injury to the nerve in this area is not limited to contusion only. Eisenberg, Sheft, and Murray (1972) have described avulsion of the first sacral root with formation of a meningocele as a result of posterior dislocation of the femoral head. Injury to the muscle is probably a very common feature. However, avulsion of the entire origin of the obturator internus and both gemelli, as in Case 2, has not been described before (Fig. 4C). Recently, Liebenberg and Dommisse (1969) reported their operative findings in 2 cases with recurrent post-traumatic dislocation of the hip, which corroborate the assumption that different parts of the posterior capsule

method of reduction, in which the patient is placed prone on a table with the affected lower limb hanging over the edge. Most authors, however, prefer the Allis method, with the patient supine on the table and the hip flexed to a right angle (Lehtonen, 1968; Epstein, 1973). This method is also advocated in patients with multiple injuries, where the prone position would be harmful (cfi Case 1). We agree with Epstein (1973) that multiple attempts at closed reduction are contra-indicated, that operation should be performed immediately if closed reduction is unsuccessful, and that a posterior approach to the hip is preferable to anterior or anterolateral approaches if torn tissues and fractures need repair in posterior dislocations of the hip joint.

Sl~itis and Latvala : Posterior Dislocation of the Hip

REFERENCES BRAV, E. A. (1962), 'Traumatic dislocation of the hip ', J. Bone Jr Surg., 44A, 1115. DAMERON, T. B., jun. (1959), 'Bucket-handle tear of acetabular labrum accompanying posterior dislocation of the hip ', Ibid., 41A, 131. EISENBERG, K. S., SHEFT, D. J., and MURRAY, W. R. (1972), ' Posterior dislocation of the hip producing lumbosacral nerve-root avulsion ', Ibid., 54A, 1083. EPSTEIN, H. C. (1973), 'Traumatic dislocations of the hip ', Clin. Orthop., 92, 116. FORDYCE, A. J. W. (1971), ' O p e n reduction of traumatic dislocation of the hip in a child ', Br. J. Surg., 58, 705. FUNK, F. J. (1962), 'Traumatic dislocation of the hip of children ', ,/. Bone Jt Surg., 44A, 1135. HENDERSON, R. S. (1951), 'Traumatic anterior dislocation of the hip ', Ibid., 33B, 602. HUNTER, G. A. (1969), 'Posterior dislocation and fracture-dislocation of the hip ', Ibid., 51B, 38. KATZNELSON, A. M. (1962), 'Traumatic anterior dislocation of the hip ', Ibid., 44B, 129.

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LEHTONEN, R. (1968), ' A study of traumatic disloca-

tions of the hip joint and fractures of the acetabulum ', Annls ChiT. Gynaec. Fenn., Suppl. 163, 57. LIEBENBERG, F., and DOMMISSE, G. F. (1969), ' R e current post-traumatic dislocation of the hip', J. Bone Jt Surg., 51B, 627. MmLER, C. H.,GuSTILO, R., and TAMBORNINO,J. (1971 ), ' Traumatic hip dislocation ', Minn. Med., 253. PATERSON, I. (1957), ' T h e torn acetabular labrum ', J. Bone Jt. Surg., 39B, 306. PROCTOR, H. (1973), 'Dislocations of the hip joint (excluding ' central' dislocations) and their complications ', Injury, 5, 1. STEWART, M. J., and MILFORD, L. W. (1954), ' Fracture-dislocation of the hip ', J. Bone Jt Surg., 36A, 315. THOMPSON, S. M. (1960), 'Traumatic dislocation of the hip ', Ibid., 42B, 60. THOMPSON, V. P., and EPSTEIN, H. C. (1951), ' Traumatic dislocation of the hip ', Ibid., 33A, 746. URIST, M. R. (1948), 'Fracture-dislocation of the hip joint ', Ibid., 30A, 699.

Requests for reprints should be addressed to:--P. Sl~.tis, Esq., M.D., ¥aasa Central Hospital, 65 130, Vaasa 13, Finland.