Prof. Dr. med. Dietrich Tönnis

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Langzeitergebnisse nach offener Einstellung von Hüftluxationen von einem ventralen Zugang, erst lateral, dann medial des M. Iliopsoas

© Prof. Dr. med. Dietrich Tönnis, Wolfgang Cordier, M.D., Klaus Kalchschmidt, M.D., Klaus Storch, M.D., Bernd Dietrich Katthagen, M.D.

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Einführung

Mit der heutigen Früherfassung von Hüftdysplasien und -luxationen durch das Neugeborenenscreening mit Ultraschall geht die Zahl der operativen Hüftrepositionen zurück und die Erfahrung in diesen Eingriffen verringert sich. Deshalb erscheinen Erfahrungsberichte über ein grösseres Krankengut, verschiedene Operationstechniken, und eine langfristiger Beobachtungszeit wichtig.

Unsere Klinik befasste sich ab 1970 schwerpunktmässig mit der Behandlung von Hüftdysplasien und -luxationen. Die Erfahrungen und Ergebnisse der operativen Hüftluxationseinstellung sollen deshalb hier mitgeteilt werden.

Operatives Vorgehen

Eine tiefe konzentrische Einstellung des Hüftkopfes wird oft durch mediale Anteile der Kapsel und des Labrums am Pfannenrand und durch verspringende Teile des Ligamentum transversum der Pfanne verhindert. Doese Strukturen müssen entfernt oder durchtrennt werden, bis der Hüftkopf tief an den Pfannenboden treten kann. Diese Pfannenanteile sind oft schwer zu identifizieren und von einem lateralen operativen Zugang zu erreichen. Vorsicht ist auch geboten, dass die azetabulare Arterie und Vene am Pfannenboden nicht verletzt werden.

Deshalb haben wir uns von dem antelateralen Zugang zu einem inguinalen von vorn zugewendet (Tönnis 1978). In der Leistenbeuge wird die Faszie unmittelbar unter dem Leistenband durchtrennt. Der Tensor fasciae latae und der Sartorius-Muskel werden an der Spina iliaca superior abgelöst und der M. rectus femoris an der Spina iliaca inferior und mit dem Wundrand nach medial zurückgezogen. Der vordere Rand des M. glutaeus mamimus wird an seinem Vorderrand ein kleines Stück abgelöst in seinem knorpeligen Rand. Das Leistenbandmit der abdorminalen Muskulatur werden auch am Beckenkamm abgelöst und nach cranial gezogen.

Bei Verkürzungsosteotomien lässt sich auch eine subtrochantäre Osteotomie mit Anlagerung einer 4-Lochplatte leichter als eine Varisierung (Abb. 2a, b, c) durchführen. Es wird dann geprüft, ob Luxationsbereitschaft noch besteht wegen der Steilheit des Pfannendaches. Es lässt sich dann auch von hier eine Acetabuloplastik (Abb. 2) durchführen.

Krankengut

Für die Auswertung der operativen Hüfteinstellung wurden nur Kinder einbezogen, bei denen es sich um "typical congenital developmental disclocations" handelte, nicht um "teratological dislocations", und das Alter zwischen O und 4 Jahren lag. Revisionsoperationen von anderernorts vorbehandelten Patienten wurden nicht ausgewertet. Bei der Nachuntersuchung sollte Skelettreife vorliegen. Alle Unterlagen mussten vollständig sein.

Von 87 Patienten kamen dann 86 zur Nachuntersuchung. 70 Patienten waren weiblich, 17 männlich. Bei 31 war die Hüftluxation beidseitig. Damit konnten 117 Gelenke untersucht werden. Das Alter lag zum Zeitpunkt der Operation zwischen 3 Monaten und 4 Jahren, im Mittelwert bei 1 Jahr, 3 Monaten. Die Beobachtungszeit verteilte sich zwischen 10 und 21 Jahren und lag im Mittelwert bei 15 Jahren, 3 Monaten.

Die Schweregrade der Luxation nach Tönnis (2, 16) verteilten sich bei 117 Gelenken wie folgt:

Grad 2 (Kopfkern nur lateralisiert): 0.9%
Grad 3 (Kopfkern auf Höhe des Pfannenerkers): 17.9%
Grad 4 (Kopfkern oberhalb des Pfannenerkers): 81.2%

Die Art der Eingriffe, die bei der Operation verwandt wurden, geht aus Tab. 1 hervor.

Ergebnisse

1. Klinische Befunde

2. Röntgenologische Auswertung

Die Überdachung des operativ reponierten Hüftkopfes ohne und mit Azetabuloplastik wurde durch den seitlichen Überdachungswinkel CE nach Wiberg (17) und den vorderen Überdachungswinkel VCA nach Lequesne and de Sèze (18) beurteilt. Von diesen Autoren werden Winkel über 25° als normal angesehen. Im Mittelwert liegen die Normalwerte allerdings bei 35° im Erwachsenenalter (22), zwischen 8 und 18 Jahren bei 32° (2).

Abb. 1 und 2 zeigen, dass der weitaus überwiegende Teil der Gelenke teils durch spontane Nachreifung und teils durch Azetabuloplastik (siehe Tab.1) voll normalisiert werden konnte, der CE-Winkel in 75,2 % und der VCA-Winkel in 82,6 % auf mehr als 25°, also Normwert, in 17,1 % bzw. 4,1 % auch auf den grenzwertigen Winkel von 20-25°, so dass nur 7,7 % bzw. 13,3 % als Restdysplasien verbleiben, die noch nachzukorrigieren sind. Das darf als sehr gutes Ergebnis angesehen werden.

3. Klinische und röntgenologische Klassifikation der Ergebnisse nach Severin

Um Vergleiche mit anderen Autoren zu ermöglichen, wurden die Hüftgelenke auch nach den Bewertungschemen von Severin (17) klassifiziert. Tab. 3 A zeigt die klinischen Ergebnisse. 82,9% gehörten zur Gruppe A, die symptomfrei ist, 15.4% zur Grppe B, die nur bei grösseren Anstrengungen etwas Beschwerden hat. 1.7% fallen in die Grupen C und D, die ein Hinken oder eine Gehstreckenbegrenzung auf 4-5 km haben.

4. Outcome according to age and type of Operation

It is generally known that outcome is age-dependant. The younger the child the more spontaneous acetabular development will occur (Fig. 4). For this reason Table 6 contains one group in which only surgical reduction and no other additional procedure such as acetabuloplasty or femoral osteotomy was performed. 29 of 32 hips were operated in the first year of life alter the third month and only three in the second year. Mean age was 7 months. In the older age group with a mean age of 17 months, 86 joints were operated at the age of 2 to 4 years and only 20 in the first year of life. In 88% of those hips operated an mainly during the first year of life, a roentgenologic improvement according to Severin's group 1 Gould be achieved (healing) (Tab. 6) whereas only 71% of the hips in whom treatment started in their second to fourth year of life achieved healing, although two thirds of these hips had undergone acetabuloplasty already. Apparently, after the first year of life sufficient spontaneous improvement without additional operative Intervention can not be regularly expected.

5. Complications

Table 7 gives an overview of the complications we observed. Coxa magna was determined by comparing the greatest diameter of the femoral heads of both sides in the horizontal plane at neutral leg position. Gamble et al. (25) considered an increase of more than 15% as coxa magna, whereas Imatani et al. (26) used a limit of 20%. In our investigation we applied the latter value of 20%.

A vascular necrosis of the femoral head was assessed according to the classification of Hirohashi et al. (27). In brief, mild necrosis does not lead to permanent damage, moderate necrosis leads to partial damage and severe necrosis to complete damage. Out of 118 hips 7 (5.9%) presented postoperatively mild avascular necrosis and 2 (1.7%) partial necrosis (Grade 2), which adds up to a total of 9 (7.6%) (Tab. 7).

The surgical technique of shortening osteotomy, often combined with acetabuloplasty, was additionally examined (Tab. 7). This procedure decreases the pressure exerted an the femoral head after reduction from the high dislocation position and an additional levering down of he acetabular roof. In this group no necrosis was observed although the age at operation was averaging 26 months. These children were definitely older than the rest of our patients (average age at operation of 17 months) and shortening osteotomy was performed in grade 4 dislocations only. 6 joints of the first group with shortening osteotomies had an age of one year to one year and six months. The joints of 4 children were operated at the age of two years, four months, to four years, four months.

In 13 hips (11%) redislocation occurred while still in plaster cast. These hips were immediately reoperated. As a result, acetabuloplasty at the time of open reduction was performed more and more often, whereas varus and detorsion osteotomies were given up almost completely (see chapter of indication in the beginning). Neither joint nor deep wound infections were observed. Only in 4% superficial infection occurred.

Discussion

88% of the children who had undergone open reduction mainly within their first year of life achieved grade 1 of the roentgenologic classification of Severin (normal) compared to only 71% of children operated an mainly in the second to fourth year of life (Tab. 6). For the clinical classification of Severin 83% of the cases in both groups reached the standard grade of group A. Considering group A and B as well as 1 and 2 according to Severin together, the values are 98% and 76%, respectively.

Our patients presented with 5.9% grade 1 and 1.7% grade 2% a very low and mild rate of postoperative avasccular necroses when we compare in Table 10 the rate of other approaches to the hip joint. This is certainly due to our anterior approach medial to the iliopsoas muscle which is not touching the vessels of the femoral neck. No necrosis was seen after shortening osteotomies (n=10) (Tab. 9). Since then for all dislocations of higher degrees, reduction was performed sirnultaneously with a subtrochanteric osteotomy (Fig. 2a). The subtrochanteric technique was chosen to avoid damage to the proximal femoral vessels. Additionally, in a child of up to two or three years it is easier to perform a subtrochanteric than an intertrochanteric osteotomy.

Another possible complication that needs to be discussed is redislocation. In the literature (Tab. 8) redislocation occurred in 4% to 12%. For the sake of stabilisation of the femoral head a long girdle-like capsular flap was detached from the craniolateral redundant capsule, pulled anteriorly around the femoral head and sutured together with the previously incised capsule at the medial Joint border (Fig. 3).

If the acetabular angle had a pathological grade 3 and 4 of deviation from normal according to age (Tab. 1) acetabuloplasty with transiliac osteotomy was performed in combination with femoral head reduction in Order to lever the acetabular roof down laterally (Fig. 2 and 4). This way the labrum extends more laterally and distally over the femoral head and offers immediate stabilization.

There are different ways to improve the acetabular roof angle by osteotomies. Salter (28) and Pemberton (29) osteotomize in the anterior- to posterior direction, Wiberg, 1953, (10) in the lateral - to medial direction. In Salters osteotomy the distal pelvic fragment with the acetabulum in total is rotated antero-lateral around an axis passing through the pubic symphysis and the posterior part of the osteotomy. Therefore the improvement of the acetabular angle is limited and the acetabulum obtains a decreased anteversion (30). If this does not remodel, especially towards the end of growth, and the femoral anteversion is low in addition, pain and osteoarthrosis are to be expected (9).

The osteotomy from lateral in medial direction (Fig. 4), which we prefer, has the advantage that an Image intensifier can be used all the way and the chisel is directed exactly as wanted. The anterior part of the osteotomy is visible. Posteriorly we can feel the chisel slightly protruding in the sciatic notch and control it with the finger while it moves medially. The osteotomy ends medially shortly above the posterior end of the triradiate cartilage. In the bone and the anterior- to posterior part of the cartilage zone the acetabular roof can be bent down to the highest degrees (50°). Early fusions of the triradiate cartilage have not been observed (11-14).

In the first years acetabuloplasty was combined with varus-detorsion osteoftomy. We used the femoral bone wedge to support the acetabular roof. Later, when we avoided varus osteotomies as Salter does, xenogenic bone wedges of animals were introduced by Braun Co., Melsungen. Today bone wedges from allergenic femoral necks or femoral heads with a firm cortical rim are carefully examined and tested according to standardized bone bank rules and sterilized at 121°C for 20 min. and then kept deep frozen in the bone bank (31).

Conclusions

As our results show, open reduction of developmental dislocation of the hip can achieve in 92 % normal (CE angle >25°) or almost normal hips (20-25°) at the end of growth. The reduction through a ventral approach first lateral, then medial to the iliopsoas muscle, shortening osteotomy and other preventive measures to avoid ischemic necrosis are important. The advantages of the inguinal approach of Tönnis are:

1. Optimal vision into the acetabulum before and after reduction from anteriorly. When dissecting the medial labrum and transverse ligament, trauma to the acetabular artery and vein is easier to avoid. Also, the deep reduction is better controlled than by lateral approaches.
2. The operation is confined to the acetabulum and the inguinal region. The femoral neck is left covered. The iliopsoas tendon is obliqually dissected at the height of the pubis and acetabulum. Trauma to the medial femoral circumflex artery is avoided this way.
3. Simultaneously a postero-lateral capsulorraphy and acetabular osteotomies can be performed from the same incision. Only subtrochanteric shortening osteotomies need a short lateral incision at the femur. This more distal shortenig does not impede the proximal femoral blond circulation. Detorsion-varus osteotomies have disadvantages (see chapter of technique of open reduction) and became very rare with our transiliac osteotomy technique close to Wiberg 1953.
4. The abductor muscles have not been damaged as the minimal rate of limping shows in the evaluation.
5. Medial approaches have a higher risk of ischemic necroses (16, 33-36) and need a second approach for acetabular osteotomies, which are frequently necessary in the second year of life and later, but sometimes even before. Postero-lateral capsulorraphies which are important for immediate stability cannot be performed from the medial approach.
6. The iliac apophysis and pelvic wing should not be used as a bone wedge for acetabular osteotomies as Pemberton (29) has proposed it. This can result later in pelvic deformities and muscular functional deficiencies.

Simons (36) as well as Gabudza (37) stated that the indication for a certain operative approach should depend on the exact case. However, this does not apply to the approach described in this paper. Also, disadvantages of the ventral approach mentioned by Gabudza are not relevant for the approach laterally and medially to the iliopsoas muscle. Another advantage are the almost invisible scars in the inguinal region.

References

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Authors listed in Table 10

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