Dr. Thomas Schneider
Heinrich Heine University
Dept of Orthopaedic Surgery
40225 Düsseldorf / Germany
Key words: Hip arthroplasty - Early complication - Dislocation
Based on 13 dislocations out of 215 cases with total hip arthroplasties the characteristics of this complication are presented here. Generally the postoperative dislocation following total hip arthroplasty seems to be no serious complication, if it is not due to severe operative failure and if the necessary treatment consisting in plastic cast immobilisation is performed.
Aan de hand van 13 luxaties na 215 heupprothesen-operaties worden de karakteristieke kenmarken van deze komplikatie aangetond. In total schijnt de postoperatieve luxatie van de heupprothese geen erstige komplikatie te zijn, indien ze niet door een zware operatiefout wordt veroorzakt en de postoperatieve immobilisatie konsequent wordt aangehouden.
A propos de 13 luxations apres 215 operations de prothese de hanche les singularites caracteristiques de cette complication sont presentees. En general la luxation postoperative de la prothese de hanche ne presente pas une complication severe si elle n'est pas la suite d'une grave faute operative et si le traitement necessaire d'immobilistion est maintenu.
The postoperative dislocation after total hip arthroplasty is regarded as one of the typical early complications. It occurs with an incidence of 1 - 2% if the case was uncomplicated preoperatively. In case of unfavorable preoperative conditions, e. g. changing of the hip endoprosthesis, the risk of early dislocation can increase up to 25% (7,10,13,14). The late dislocation, occuring years after the implantation of the endoprosthesis has other causes, such as trauma or loosening of the endoprosthesis (1). Compared to early dislocation it represents a different situation requiring other therapeutic strategies.
Generally, the early dislocation after total hip arthroplasty is considered as a controllable complication. Treated adequately it has no effect on the long-term result (1,2,10). However, in case of insufficient therapy it might as well lead to relapsing dislocation of the hip (5,6,7).
Between 1989 and 1993 215 total hip arthroplasties were performed in the orthopaedic department of a hospital in Trier / Germany. This number includes cases with different indications for hip surgery, such as tumor prosthesis, review or previous hip endoprostheses, prosthesis after femoral neck fracture, and others.
The 13 cases of early postoperative dislocation are shown in table 1. 5 men and 8 women were affected. Their age ranged from 27 to 81 years.
The majority of dislocations happened within the first few days after surgery. In 4 cases the dislocation occurred on the day of the operation itself, whereas in one case it happened two weeks after the total hip replacement. Looking at the preoperative conditions, there were 4 patients who needed a replacement of either the shaft and/or the socket of the prosthesis sometimes requiring a spongy reconstruction of the remaining bones. One patient had a dislocation of a Duo-headprosthesis, which was implanted after a femoral neck fracture. 7 patients had idiopathic or secondary osteoarthritis and one had rheumatic coxitis. Different types of endoprostheses were used, such as the conventional cemented hip endoprostheses type Weber - Stühmer, the uncemented type Zweymüller and various combinations of the two systems. The different surgical approaches to the hip joint included the antero-lateral, the postero-lateral and the Bauer-approach. There was no correlation between the number of dislocations and the various surgical approaches mentioned above. 3 patients underwent surgery in spinal anaesthesia and 10 in endotracheal anaesthesia. In two patients an obvious malposition of the socket of the endoprostheses was found. These patients were operated for replacement of the prosthetic socket one week after the total hip replacement and the reposition was performed openly. In all the other patients the reposition was successfully performed conservatively.
After the reposition all the patients were treated with plastic cast immobilisation for at least 3 weeks. Usually, the patient got a plaster cast for the leg with an abduction and internal rotation splint, which was replaced by a Whitman´s plaster of the pelvis and the leg later on. The plaster immobilisation was maintained for an overall period of 6 weeks. The postoperative mobilisation of the patient started after two weeks of wearing the Whitman´s plaster. Patients with dislocation after changing of the endoprosthesis got bed rest for 6 weeks.One patient was additionally provided by an abduction - orthosis for 3 months. We re-examined the patients 1/2-3 years postoperatively. No further dislocations had appeared in the meantime. Compared to patients with an uncomplicated postoperative course there were no differences in any subjective or objective criteria.
Table 2 shows possible reasons for early dislocation after total hip replacement as found in our study and as reported in literature.
Different faults in the operative technique may lead to the dislocation of the hip. Most commonly the reason for dislocation is a malposition of the shaft and/or the socket of the prosthesis. In case of the changing of the prosthesis, a disproportion of the head of the prosthesis and the socket can be a cause. An inappropriate length of the neck and head of the prosthesis may lead to dislocation as well. Other possible reasons for dislocations are bony remains of the medio-caudal part of the acetabulum as well as extents of the Palacos-cement in that particular region, which then works as a hypomochlion. Further reasons are an insufficient refixation of the trochanter major and an over-extended release of the capsule and the muscles.During the postoperative phase too early or too extensive mobilisation may lead to dislocation. Very seldom, traumatic reasons are found.
Generally, the early postoperative dislocation after total hip arthroplasty is regarded as an unproblematic complication with regard to its incidence and its severity. According to the following quotations its incidence is approximately 1% (3,10,11,12 ).
The results from this case study show that if the case was uncomplicated preoperatively, the changing of a hip arthroplasty is the predominant cause of a dislocation. The reasons for early dislocations were mainly due to intraoperative errors. The most common faults are: primary instability after spongy reconstruction of the acetabulum, primary malposition of the socket of the prosthesis, insufficient refixation of the trochanter major, inappropriate length of the neck and head of the prosthesis and bony remains of the medio-caudal part of the acetabulum.
Higher rates of early dislocation after total hip arthroplasty are found in cases with a complicated preoperative course depending on the underlying problem. The rates range from 5% for special prostheses used for coxarthrosis following dysplasia, 20% for regular tumor-prosthesis, 24% for changing of the hip-endoprosthesis up to 35% for special tumor-prostheses ( 4,6,8,13,14 ).
If the case is uncomplicated preoperatively, surgical errors may lead to dislocation. These errors include malposition of the shaft or of the socket or too extended release of the capsule and the muscles. Dislocation may also be caused by other therapeutic, but non-operative errors like too early and too extensive mobilisation.
Generally, the early dislocation following total hip arthroplasty is a controllable complication. A redislocation can be widely avoided by a consequent therapy consisting in plastic cast immobilisation (3,5).
However, a surgical revision is unavoidable if the conservative therapy of early dislocation remains unsatisfactionary or if the dislocation is caused by intraoperative errors (2,4,9,10).