THE CLASSIC: Complete Replacement Arthroplasty of the Hip by the Ring Prosthesis

Field: Medicine (Health Sciences)

Peter Alexander Ring was born in London in 1922. After his education at University College in London he continued his orthopedic training in a variety of well-known orthopedic centers in and around London. As the Laming Evans Senior Orthopaedic Research Fellow (1956-1959), he studied epiphyseal growth under a variety of conditions and applied the information obtained to the clinical problem of leg length equalization in poliomyelitis patients. In 1959, he appointed surgeon in charge of the Joint Replacement Unit of the Dorking Hospital in Surrey, where he has remained ever since. He rapidly became dissatisfied with the results obtained by using the Austin Moore prosthesis without an acetabular prosthesis in patients with osteoarthritis. He did not bellieve that the use of methylmethacrylate would provide adequate fixation of components over the long term and sought another solution to the problem. His approach was to devise methods of cementless fixation of his two metal components. The results of his work were described in the following paper. The original design was used in the first 25 patients beginning in 1964. A different design featuring a modified cup was used in the remaining 155 patients. The requirements of an arthroplasty of the hip are that it should produce a painless, freely mobile and stable joint. It is apparent that this can be achieved in osteoarthritis only by replacing both the pelvic and femoral components. The success of the intramedullary femoral prosthesis in the treatment of subcapital fractures of the hip lies largely in the way in which the load is transferred through the femoral neck, the stem of the prosthesis serving to locate and maintain this relationship accurately. The results of using the Moore prosthesis in osteoarthritis, however, are relatively poor (Heywood-Waddington 1966) partly because of acetabular erosion. The matching of the arthritic acetabulum to the spherical implant is inaccurate, and can only be improved by some form of acetabular replacement. Progress in the development of the acetabular component has been limited by the difficulties of securing it in the pelvis, and by doubts about the most suitable material for completing the articulation. Charnley (1959) stressed the low-friction characteristics of fluon articulating with stainless steel, but the products of wear in an articulation of this sort are irritant, and produce an inflammatory reaction. The use of high-density polythene may overcome the problem of wear in the cup, but it is doubtful whether low friction is of fundamental importance in the design of a complete joint replacement. Although as early as 1957 McKee reported the use of metal-to-metal articulation, in this case using stainless steel, the suitability of this type of implant rests largely on the work of Scales (1968) who established the superiority of cobalt-chrome over other metals or combinations of metals in the construction of an artificial joint. The Charnley and the McKee-Farrar (McKee and Watson-Farrar 1966) prostheses overcome the problem of fixing the pelvic component by embedding it in acrylic cement. This is a material which does not bond firmly with bone, and may therefore allow the acetabular component to loosen. It may carry with it a slightly increased risk of infection, and is thought occasionally to have produced at the time of insertion an intense and dangerous hypotensive reaction. Because of the uncertainties and risks of using cement for fixation of the prosthesis, the arthroplasty described here has been devised to use two inherently stable components. The acetabular part consists of a cup with a long threaded stem, the former seated well into the acetabulum, and the latter following the weight bearing line of the pelvis. The femoral component is a modified Moore’s prosthesis. Stability is achieved by following the natural lines of weight transmission. No cement is used. The first model embodying these principles used a cup which was little less than a hemisphere, accurately matched to standard 40 millimetres (1⅝ inches) Moore’s prosthesis. Although all but one of the twenty-five that we used have have continued to give satisfactory service, it is clear that the junction of cup and stem was a source of weakness, and that the range of movement was unduly restricted. In the present device the femoral component remains with 40 millimetres head, but this is set medially upon an elongated neck to increase the range of flexion and abduction. The cup is accurately matched to the femoral head, and has a stem 75 millimetres (3 inches) long and 9.5 millimetres (⅜ inch) diameter, with a coarse thread. There are four grooves on its lip, into which an introducer can be fitted, and it is tapered externally to reinforce the junction area and to allow it to be countersunk. Both parts are made of cobalt-chrome alloy. ANATOMICAL PRINCIPLES Weight is transferred from the sacrum to the articular facet of the ilium, and thence through a thick bar of bone which extends down to the upper part of the acetabulum. On its inner surface this bar of bone is represented by the upper part of the ilio-pectineal line. On the outer surface the pelvis is almost flat, and the weight-bearing area tapers into the wing of the ilium. The greater sciatic notch bites into the tapering area of bone, and its constant relationship to the ilio-pectineal line allows it to be used as a landmark. If a cup with a long stem is screwed into the acetabulum so that the stem follows the weight-bearing line, it passes upwards, backwards and medially, about 12 millimetres in front of the greater sciatic notch, and ends just behind and lateral to the sacro-iliac joint. The mouth of the cup faces not only downwards, but also laterally and forwards. The exact plane of the mouth of the cup depends on the height of the acetabulum: in the normal hip it faces about 15 degrees outwards and 15 degrees forwards, but when the acetabulum is dysplastic these angles are increased. To insert the cup correctly it is essential to locate the weight-bearing line. The guide which is used for this purpose has a cannulated head which centres in the acetabulum and a loop which engages in the greater sciatic notch. Because these two points always have a fixed relationship to the weight-bearing line of the pelvis, they can be used to project a guide wire along the correct path. After removal of the guide, a cannulated drill prepares the track for the screw thread. By countersinking the outer surface of the cup, which is tapered, the weight of the body is transferred to the cup over a wide area, and the shearing force at this point merely serves to force the acetabular component more firmly into the ilium. The femoral component has a narrow stem and an elongated neck. These modifications of Moore’s prosthesis permit a greater range of movement. Stability is ensured by a wide flange which must be seated accurately upon the cut femoral neck. Because the curvature of the upper part of the femur tends to throw a straight-stemmed prosthesis backwards, care must be taken to insert the prosthesis with appropriate anteversion. INDICATIONS FOR OPERATION During the development of this procedure patients were selected because they were unsuitable for any other form of operation. Many were grossly disabled, and most were elderly. With increasing experience the indications have broadened a little, and the operation may now be stated to be applicable to the following patients. 1) Adult patients of almost any age with two stiff and painful hips; 2) men over the age of sixty with severe unilateral osteoarthritis, whose work and recreations are largely sedentary; 3) women over the age of fifty with severe unilateral osteoarthritis; 4) patients treated previously but unsuccessfully by cup arthroplasty or intertrochanteric osteotomy provided displacement has been only slight; 5) rheumatoid arthritis. We have continued to advise arthrodesis for men who are actively engaged in heavy work, and for some younger women; the results of sound bony ankylosis in a good position are too satisfactory to abandon this prodecdure lightly (Watson-Jones and Robinson 1956). We have also continued to perform intertrochanteric osteotomy when the changes are early and the joint is still mobile, although femoral displacement has been limited to half a diameter or less to allow arthroplasty to be performed later should the result be unsatisfactory. OPERATION The patient is placed in the lateral position with the hip and knee flexed, and the pelvis is firmly secured by anterior and posterior supports. The whole limb is towelled to permit free movement during the operation. The incision extends from the posterior superior iliac spine to the tip of the greater trochanter and is then angled and extended down the outer side of the thigh. The gluteus maximus is divided in the line of its fibres from well above the acetabulum to its attachment to the ilio-tibial band, and the latter is split for a distance of seven to ten centimetres. The femoral attachment of the gluteus maximus is left undisturbed. The fan of muscles attached to the back of the greater trochanter is displayed, and the piriformis, obturator internus tendon and gemelli, and the upper part of the quadratus femoris are divided close to their insertions. The capsule is resected as widely as possible, and the femoral head is dislocated. If the joint is ankylosed, or if there is central protrusion of the femoral head, it is advisable to devide the femoral neck in the subcapital region before disarticulation to avoid the risk of fracture. With the hip dislocated the femoral head can now be removed and the femur prepared for the femoral component. The line of section should be from the middle of the femoral neck medially to the root of the greater trochanter laterally; it must be made so that the flange of the prosthesis sits firmly throughout its circumference upon the stump of the femoral neck. The division is made with a reciprocating saw. A trial section is usually made at a slightly higher level than that finally required. The leg is rotated medially, and the shaft of the femur is lightly rasped to take the prosthesis. The plane of the rasp is such that the femoral head will lie in about 20 degrees of anteversion. A trial fit with the femoral component is now made, leaving the head about two centimetres proud of the neck, and the final line of neck division is selected. The prosthesis is then withdrawn and the bone division completed. Attention is now turned to the acetabulum. The rest of the capsule and synovial membrane is removed and the flexed limb is allowed to fall forwards over the side of the table to display the acetabulum fully. Osteophytes in the floor of the acetabulum, which tend to interfere with the vertically passing acetabular component, must be removed, but other marginal osteophytes help to seat the cup more firmly and should be preserved. The key to the insertion of the cup and stem lies in relating it to the greater sciatic notch. This is exposed by a subperiosteal clearance of the wing of the ilium, passing a rugine vertically upwards from the acetabulum. A finger can now be inserted, which, after sweeping the gluteal attachments backwards, enters the front of the notch. The vessels and nerves lie behind the finger which, keeping close to the bone, is inserted into the pelvis to free the obturator internus from part of its origin and to allow the thick bar of bone-which is to contain the screw of the acetabular component-to be grasped between finger and thumb. The guide is now introduced, the loop in the deepest part of the greater sciatic notch, and the mushroom in the centre of the acetabulum. The position of the cup is dictated by the relationship of these two fixed points. When the acetabulum is shallow and displaced upwards the mushroom must be seated well medially to counteract this tendency. When it is unduly deep the mushroom should be centred rather laterally in the acetabular roof. When the position is satisfactory the loop is held firmly in the greater sciatic notch and a long guide wire is introduced. The guide can now be dismantled and withdrawn, and the end of the guide wire cut short. The index finger is reinserted into the notch and round into the pelvis to check that the wire is not badly off course, and remains in this position while the track is drilled with a power drill. For normal bone a 6 millimetres cannulated drill is used, but if the bone is very dense the 7.5 millimetres drill is chosen. A drill that is not taking the correct line may be felt by the locating finger in the pelvis. A cone of bone is now removed with the reamer to enable the cup to be countersunk. The amount of bone to be removed depends upon the thickness of the acetabular walls, but should permit half or preferably more of the lateral margin of the cup to be supported. The reamer is turned either by hand with a brace, or in a low-speed drill. The cup is next driven into the track: during its insertion palpation with the finger inserted round the greater sciatic notch should be continued to ensure that the stem is not extruded from the bone. If exposure of the acetabulum has been difficult and incomplete the shaft of the femur tends to throw the cup laterally, and the screw thread off course into the pelvis. This tendency must be corrected by forcing the cup medially during its insertion. A very tight grip should be obtained upon the pelvis by the screw thread, and the cup driven firmly home. Finally the femoral component is introduced and punched firmly home, and the joint reduced. Reduction should be obtained with ease, but if the joint is too tight the femoral part may be adjusted by shortening the neck a little further. Provided reduction is easy, any joint contracture which remains can be ignored because it will disappear with a few days on traction. Tenotomy either of the flexors or adductors is unnecessary. Three or four grammes of chloromycetin are inserted into the wound, which is closed with suction drainage, and skin traction applied. Before the anaesthetic is ended the position of the stem of the socket is checked by antero-posterior and oblique radiographs. Post-operative treatment-Skin traction with the leg on a pillow is maintained for four or five days, but during this time the weight is removed for exercises. Thereafter the limb is left free in bed, and exercises against resistance are commenced, particular attention being paid to the redevelopment of power in the abductors and hip extensors. Walking is permitted as soon as the wound is healed, and most patients leave hospital about three weeks after the operation. When both hips have been operated upon at the same time the patient remains in bed for three weeks rather than two, and in hospital for five or six weeks. Antibiotic cover, usually with a combination of penicillin and streptomycin, is used for about ten days, but anticoagulants have not been given unless there is evidence of deep venous thrombosis. RESULTS This type of complete joint replacement was started in May 1964 and was developed into its present form during the following year. In the last four years we have used 180 of these prostheses, of which 155 have been of the current design. Only one of the 180 hip replacements has required revision. The results in patients whose operations were performed six months or more ago have been analysed in detail. There are 128 patients in this group; of these thirty had operations upon both hips; so there were 158 hips for study. The ages of the patients varied from forty to ninety-seven, with a mean age of sixty-nine. This is not an operation that would usually be selected for a young patient, and those in their forties and early fifties were patients with two stiff hips for whom no satisfactory alternative was available, or those with rheumatoid arthritis. A number of patients in their nineties have been treated with satisfactory results. The vast majority of the hips were disabled with degenerative arthritis, which was usually severe. In three patients cup arthroplasty had been performed, three had had displacement osteotomy, and two had had a Judet prosthesis. Five patients had rheumatoid changes in the hips as well as severe rheumatoid changes elsewhere, and one patient had ankylosing spondylitis. Within these small numbers there was no evidence that the nature of the pre-operative joint changes materially affected the results, and for the purpose of analysis they have been grouped together. All the patients who have been subjected to this operation remain under continuous review, and none has been lost to follow-up. Two patients died soon after operation, one from pulmonary embolus and the other from pneumonia. One patient developed infective arthritis of the shoulder some weeks after discharge and eventually died; at necropsy his hip was also found to be infected and was probably the source of the shoulder infection. This is the only joint infection so far. One patient suffered cerebral thrombosis a few hours after bilateral arthroplasty: he remains severely paralysed and confined to a chair and has been excluded from review. There were three cases of deep venous thrombosis, which subsided with anticoagulant treatment. In patients in this age group there is a steady loss from and from During the in there have been from to the operation. There remain patients for review. and of the hips were free from at all to some form of on No patient had at varied from a of the limb to a well from hip to patients of in the on and occasionally this was with a area over the tip of the stem of the femoral component. the was in the sciatic patients with had a but the range of joint remained In most of these patients to any of the prosthesis. In there was no evidence that either component was Only two changes were with some of the lateral femoral where the tip of the prosthesis to be and of the prosthesis into the femoral shaft following a in the femoral neck at the time of insertion. who of in the first few months after the operation were treated by a few rest in bed by This allowed the to of became less and less as the months and in no patient was to operation. of joint movement was and hips more than a of and only four had less than patients 20 to 25 degrees of joint abduction. were in all but two patients. of the hips in were also studied on The majority of the hips normal and during the weight-bearing was there any of either component. patients with operation on one side well of without the use of a but when both hips had been subjected to operation patients to use one of in some patients to a normal to be to before the operation, with and of the and of these muscles is in the elderly. result has been as when the hip is with more than degrees of and 20 degrees of and the patient is free from and to a or more without a It has been as good when the patient did not this either because he required a of or was by less than degrees of flexion or by All but three of the unilateral cases and two of the bilateral cases into one or other of these The remaining five cases were as because of or upon two No patient was than before the operation. had had in the left hip for ten There was fixed flexion of 40 degrees and fixed of There was throughout the small of movement. replacement arthroplasty was in He was to after one and to his after two He was then free from with a good range of joint but required a The result was as In a and a half after the operation, he of in the left hip and was no to a in the stem of the acetabular component, with of the in the original prosthesis was removed and by an prosthesis of current in the was and he to but died in a six months had a of the femur in developed rheumatoid arthritis which became after a few months but left severe acetabular There was in the hip with some of movement. was to only with two joint replacement was in was maintained for three weeks because of the acetabular The patient now with one and has almost a range of movement. The result was as had had a cup arthroplasty for osteoarthritis in 1964. He was for months when and finally he was only to a few with one of the cup and complete joint replacement was in and the patient left hospital after two weeks. He now with a range of hip and was as an had been confined to his with severe in both He was to a few very with two In bilateral complete replacement arthroplasty was he was in hospital for five weeks. He is now to about half a without using a both hips have degrees of flexion and he was as an This type of complete joint replacement has the of and has been free from There has been only one and only one joint infection, and the and bearing in the age group which has been has been To a satisfactory result a standard of The of the pelvic component depends on the stem firmly in the iliac of bone and countersinking it firmly in the acetabulum. In some patients is and in some the iliac is use of the guide, and during all of with the finger in the greater sciatic notch, are to the correct line. The of the femoral component is no less the cut surface of the femur must seat the flange correctly and the stem must fit very in the shaft of the bone. A good range of joint movement is always In hips which are to degrees of flexion will in those which are more mobile, almost a Joint will after a few days on traction without but of abductors and from joint is to and the pre-operative of tends to for some In to a satisfactory after an arthroplasty it is to the centre of joint movement to its normal and it is that some of the patients who still so because the of joint movement lies behind its natural Although all the patients in this have complete from after the operation, in some there has been a of during the first few weeks after discharge from hospital as and in this has remained as a In these patients it is confined to the weight-bearing and in is It tends to with the of and in no patient has it at a level which would treatment. Provided the has been it is that it in the articulation in the on weight-bearing follows the use of Moore’s prosthesis for fractures of the femoral neck, and it has been that this is to of the stem of the prosthesis in the femoral can be but there is no between this and the either of or under the following 1) When the prosthesis is subjected to from and the tip of the stem into the lateral femoral 2) when the has started to split on the prosthesis, and on weight-bearing the flange tends to into the shaft of the 3) when the femur has been divided too low at the level of the Charnley analysed in some the which from the use of bone cement for the femoral prosthesis in a subcapital but the use of cement in this way is not free from and it has to be that it the of weight-bearing It must be stressed that the majority of those patients in this of have no clinical or evidence on that any movement of either component is During the four years this type of complete replacement has been used there has been no patient any displacement of either component in of the that some of the pelvic components have been inserted in a less position than is of bone round the screw thread has to no more than a of the cup the Although the thread of the screw passes close to the and may occasionally it is that this is a source of Only one hip has been There was no evidence of any wear after a and a and no more than a little from in the around the joint. The in this patient was one of but the replacement by an prosthesis a satisfactory and a well be used in the of any the final of this must upon a of the results which have so been obtained that this is a satisfactory of complete joint replacement which is to the of those patients to whom it has been applied. A complete replacement arthroplasty of the hip is described in which both components are inherently The arthroplasty does not the use of acrylic cement. It is appropriate for the treatment of the severely arthritic hip in which arthrodesis is not and for the of two stiff and painful hips at any It can be performed on both at the same It a and mobile joint in a of and has not to over of to four