1120-7000/215-05$15.00/0

INTRODUCTION

Acetabular dysplasia may present as previously un-diagnosed or as a sequel to treated development dys-plasia of the hip (DDH) in a young adult. We definedacetabular dysplasia as present if the centre-edge angle(CEA) of Wiberg was less than 20 (1, 2). Acetabulardysplasia is recognised to contribute to the devel-opment of osteoarthritis of the hip (3, 4). Innominateosteotomy is described as a primary treatment andalso a prophylactic measure with the aim of delayingthe onset of osteoarthritis in patients with sympto-

matic acetabular dysplasia (5). Innominate osteotomyaims to improve the biomechanical environment ofthe dysplastic hip by restoring a horizontal sourcil,so increasing the area of weightbearing hyaline car-tilage over the femoral head and thereby reducing pres-sure per unit of area (6-8). Although seen as a supero-lateral insufficiency on the plain AP radiograph andas measured by the CEA, the acetabular deficiencyis also located anteriorly (9). This has to be addressedby the osteotomy although over-correcting anteriordefects may lead to posterior insufficiency. There arenumerous described techniques for treatment of

Original Article

Hip International / Vol. 13 no. 4, 2003 / pp. 215-219 Wichtig Editore, 2003

The modified Tonnis triple pelvic osteotomy in the young adult - early results

N. DE ROECK, A. HASHEMI-NEJAD

ABSTRACT: Acetabular dysplasia may present as previously undiagnosed or as a sequel totreated DDH in a young adult, with a natural history of subsequent development of earlyosteoarthritis.Patients with acetabular dysplasia, a normal neck shaft angle, no significant leg lengthinequality and who demonstrate congruency at arthrogram are considered suitable for realign-ment pelvic osteotomy.We report the results of 15 young adults who underwent a modified Tonnis triple osteotomywith a mean 22-month follow-up. The modification was that the ischial osteotomy was per-formed through a groin incision. The only common complication was the requirement of catheterisation post-operatively(60%). There were no infections. There was one delayed union but no non-unions. Onepatient developed a deep vein thrombosis. All patients reported an improvement in theirsymptoms and level of activity, with a mean post-operative Harris hip score of 92. All showedan improved centre-edge angle of 28 (mean increase of 18) and acetabular angle of 37(mean decrease of 13). The early results of this procedure show it to be a safe and useful option to delay the nat-ural history of early osteoarthritis in the young adult. (Hip International 2003; 13: 215-19)

KEY WORDS: Acetabular dysplasia, Osteotomy

Catterall Unit, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore - UK

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acetabular dysplasia in terms of double, triple, peri-acetabular or rotational osteotomy (10-14).

The criteria for undergoing innominate osteotomyin our institution are that patients must have a nor-mal neck shaft angle (120 - 130), leg length inequal-ity of no greater than one centimetre and must demon-strate a congruent, reducible hip. All patients there-fore undergo examination under anaesthetic (EUA)and arthrogram to establish that these criteria aremet.

Tonnis described a triple osteotomy differing fromother innominate osteotomies by the location of thesite of the division of the ischium. This is performedthrough the ischium superior to the ischial tuber-osity, so preserving the sacrotuberous ligament. Thislocation in addition to osteotomies of the pubis andileum is designed to allow greater rotation of theacetabulum and maintain normal tension in thesacrospinous and sacrotuberous ligaments withoutcompromising acetabular vascularity (15). Tonnisdescribed a posterior approach to the ischium, withthe patient in a prone position, necessitating mov-ing the patient during surgery, after completing theischial osteotomy.

The senior author (AHN) performs a modification ofthe Tonnis technique by approaching the ischium througha groin incision to allow the entire procedure to beperformed with the patient supine. The approach alsoallows a more juxta-articular ischial osteotomy allow-ing for greater ease of rotation of the acetabular frag-ment.

The purpose of this study was therefore to assessthe complication rate of this approach and determinethe early clinical and radiographic outcomes ofpatients undergoing modified Tonnis triple osteotomy.

METHODS

A consecutive series of 15 patients with sympto-matic acetabular dysplasia underwent modified Ton-nis triple innominate osteotomy performed by the seniorauthor. All had previously undergone EUA and arthro-gram to establish that the entry criteria described abovehad been met. The pre-operative radiograph was analysedto determine the CEA and also the acetabular angle(AA) of Sharp (16).

Operative technique

The ischial osteotomy, with the modification of theTonnis technique, is performed first. The approach tothe ischium is made via a groin skin crease incisionover adductor longus. The approach passes deep toadductor longus and over adductor brevis after theobturator vessels have been identified. Blunt dissec-tion is continued along the inferior margin of the cap-sule down to the ischium, exposing the ischial spine.

This approach was used following the senior authors experience of performing medial open reductionof the hip for children with developmental dysplasiaof the hip. A wedge-shaped osteotomy is performedunder image-guided control adjacent to the ischialspine, connecting the lesser sciatic notch and the obtu-rator foramen.

Fig. 1 - Single lines demonstrate the site of osteotomies describedby Tonnis. The double line represents the modified ischial osteotomyperformed in this study.

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The iliac and pubic osteotomies are then performed,as in the original description by Tonnis. The ischialapproach allows a more proximal exposure of the ischiumand so a more juxta-articular osteotomy which assists in the correction and rotation that can be achievedwith the acetabular fragment (Fig. 1). When determiningthe final position of the acetabulum it is important toaccount for the three-dimensional deformity. The CEAis assessed along with the position of the anterioracetabular wall, via intra-operative screening, to ensure correct cover and version have been achieved.The acetabulum is stabilised with two or three threaded 4.2 mm pins, inserted proximally to distallyfrom the ilium across the osteotomy into the acetab-ular fragment.

Postoperatively patients spend five days with theaffected limb resting in slings until muscle controlhas been regained. They are then mobilised par-tially weightbearing on crutches for six weeks untiloutpatient clinical and radiographic review. If theradiograph is satisfactory full weightbearing iscommenced.

Patients have remained under annual clinical andradiographic follow-up. Clinical outcome was mea-sured by means of the Harris Hip Score. At the mostrecent follow-up the radiograph was assessed to deter-mine if union had occurred and to measure the CEAand AA. This allowed calculation of the difference com-pared with the pre-operative radiograph.

RESULTS

All 15 patients entered into the study were female,with nine osteotomies performed on the left and sixon the right. The mean age at surgery was 26.9 years,range 17 to 38. The mean follow-up following tripleosteotomy was 22 months, range 9 to 53.

All patients reported an improvement on their pre-operative pain. Pre-operatively the mean Harris HipScore (HHS) was 66, range 60 to 73. The mean HHSat most recent follow-up was 91, range 69 to 100.

One patient had a poor outcome with HHS of 69although this could be confounded by a pre-existinghistory of low back pain.

The mean postoperative centre edge angle was 28and the mean postoperative acetabular angle was 37(Tab. I). Examples of pre-and postoperative radiographsare demonstrated by Figures 2a, b, c and 3a, b.

No neurovascular complications were sustained. Post-operatively nine patients required urinary catheteri-

Fig. 2a, b, c - Pre-operative radiograph, arthrogram showing concentric reduction and postoperative radiograph of a modifiedTonnis triple osteotomy.

TABLE I - CHANGE IN CEA AND AA IN DEGREES

Pre-operative Postoperative Change

Mean CEA 10 28 18CEA Range 0-20 15-40 12-29Mean AA 50 37 13AA Range 40-60 30-52 5-21

a b c

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sation, however eight of these had undergone epi-dural anaesthesia.

All osteotomies achieved union. A single patient sus-tained a femoral vein thrombosis requiring anticoag-ulation and also subsequent delayed union of the iliacosteotomy, which eventually united at 15 months.

DISCUSSION

Triple osteotomy of the pelvis has been shown tooffer good results in terms of pain relief and functionten years postoperatively (17). The theoretical advan-tage of the Tonnis triple innominate osteotomy is theimproved rotation of the acetabulum about thesacrospinous ligament, allowing restoration of the CEA.Tonnis states that ideally this should be between 30and 35, although a wide variation in the normal observedrange has been described (18, 19). The senior authormodified the technique to combine the advantages ofthe anatomical site of the ischial osteotomy descri-bed by Tonnis with a more cosmetic skin crease inci-sion in the groin, which allows the procedure to becompleted without moving the patient. Other authorshave described a subinguinal adductor approach tothe pelvis and ischium at triple osteotomy (20). Wefeel the approach followed by the senior author avoidsthe division of muscle described in other adductorapproaches and allows the ischial osteotomy to beperformed with the benefits Tonnis described.

According to HHS, 93% of patients have achievedgood or excellent results. Direct comparison with clin-ical results in other studies of triple osteotomy is dif-ficult as a variety of assessment methods are described.It is also difficult to apply scoring systems generallyused for assessing hip replacement. Young patientsundergoing pelvic osteotomy for acetabular dyspla-sia usually have a higher level of function than olderpatients undergoing total hip replacement and so theapparent increase in scores may be less marked. Never-theless, we feel the results are satisfactory at this pointalthough the patients require ongoing follow-up to ensurethat comparable long-term results are achieved.

The only potential complication we could attributeto the approach was that nine patients required catheter-isation. The groin incision may have caused perinealswelling, contributing to catheterisation in a female

Fig. 3a, b - Pre- and postoperative radiographs of a modifiedTonnis triple osteotomy.

a

b

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population. It is difficult to draw any conclusion aboutthis however, as eight of those catheterised also receivedan epidural. We did not encounter any other signifi-cant complications.

This preliminary study of the modified triple innom-inate osteotomy shows satisfactory early results interms of clinical and radiographic parameters and noadditional significant complications have arisen. Wetherefore feel we can continue to perform the modi-fied technique with the patients remaining under longterm follow-up.

Address for correspondence:Nick De Roeck, MD39 Glenhurst RoadNorth FinchleyLondon, N12 9UB, UKe-mail: nk@houseofjoy2000.freeserve.co.uk

REFERENCES

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4. Murphy SB, Ganz R, Muller ME. The prognosis in untreateddysplasia of the hip. J Bone Joint Surg (Am) 1995; 77-A: 985-9.

5. Dunn HK, Smith JT, Coleman SS. Pelvic osteotomy: Analternative to total hip replacement in the young adult.Hip 1984: 3-13.

6. Bombelli R. Mechanics of the normal and osteoarthritichip. Clin Orthop 1984; 182: 69-78.

7. Pauwels F. Biomechanics of the normal and diseasedhip. Berlin: Springer-Verlag 1976.

8. Michaelli DA, Murphy SB, Hip JA. Comparison of pre-dicted and measured contact pressures in normal anddysplastic hips. Med Eng Phys 1997; 19: 180-6.

9. Murphy SB, Kijewski PK, Millis MB, Harless A. Acetab-ular dysplasia in the adolescent and young adult. ClinOrthop 1990; 261: 214-23.

10. Steel HH. Triple osteotomy of the innominate bone. JBone Joint Surg (Am) 1973; 55-A: 343.

11. Sutherland DH, Greenfield R. Double innominate

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13. Ganz R, Klaue K, Vinh TS, Mast JW. A new peri-acetab-ular osteotomy for the treatment of hip dysplasias:technique and primary results. Clin Orthop 1988; 232:26-36.

14. Ninomiya S, Tagawa II. Rotational acetabular osteo-tomy for the dysplastic hip. J Bone Joint Surg (Am)1984; 66-A: 430-6.

15. Tonnis D, Behrens K, Tscharani F. A modified techniqueof the triple pelvic osteotomy: Early results. J PediatrOrthop 1981; 1: 241-9.

16. Sharp IK. Acetabular dysplasia: the acetabular angle.J Bone Joint Surg (Br) 1961; 43-B: 268-72.

17. Guille JT, Forlan E, Kumar SJ, MacEwen GD. Triple osteo-tomy of the innominate bone in treatment of develop-mental dysplasia of the hip. J Pediatr Orthop 1992; 12:718-21.

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19. Stulberg SD, Harris WH. Acetabular dysplasia and devel-opment of osteoarthritis of hip. In: The hip. Proceed-ings of the second open scientific meeting of the HipSociety. St Louis: CV Mosby 1974: 82-3.

20. Tachdjian MO. In: Tachdjian MO, ed. Pediatric Ortho-pedics, (2nd ed). Philadelphia: WB Saunders 1990; 493-503.

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